MXPA99003965A - METHOD FOR REDUCING NOx FROM EXHAUST GASES PRODUCED BY INDUSTRIAL PROCESSES - Google Patents

Abstract

Gas-phase methods and systems for reducing NOx emissions and other contaminants in exhaust gases, and industrial processes using the same, are disclosed. In accordance with the present invention, hydrocarbon(s) autoignite and autothermally heat an exhaust gas from an industrial process so that NH3, HNCO or a combination thereof are effective for selectively reducing NOx autocatalytically. Preferably, the reduction of NOx is initiated/driven by the autoignition of hydrocarbon(s) in the exhaust gas. Within the temperature range of about 900-1600°F, the introduced hydrocarbon(s) autoignite spontaneously under fuel-lean conditions of about 2-18%O2 in the exhaust gas. Once ignited, the reactions proceed autocatalytically, heating the exhaust gas autothermally. Under some conditions, a blue chemiluminescence may be visible.

Description

METHOD TO REDUCE THE NITROGEN OXIDES OF THE EXHAUST GASES PRODUCED BY INDUSTRIAL PROCESSES Field of the Invention The present invention relates to the removal of nitrogen oxides or "NOx" from exhaust gases and the like, and more particularly to processes and apparatus for selectively reducing NOx using autothermal, autocatalytic reactions, in a manner that also removes other oxides. exhaust pollutants from the combustion of carbonaceous fuels, and also to industrial processes that use them.

Background of the Invention Without being limited by any particular theory, the background of the present invention will be described by way of a description of the particular problems described in the art and various proposed solutions to such problems. For brevity, several references will be summarized briefly and generally here. A more complete understanding of such a background technique can be obtained by Ref.030163 through a complete review of the documents cited here. What should be understood from the following description is that, despite such previous intense efforts to provide various methods of removal of NO? and the like, there is a continuing need for practical and low cost methods of removing N0X in a variety of industrial processes, which can utilize a variety of commercially available reducing agents. Carbonaceous fuels are burned in internal combustion engines and other equipment such as boilers, furnaces, heaters and incinerators, and the like (that is, in a wide variety of industrial processes). Excess air is often used to supplement the oxidation of combustion byproducts such as carbon monoxide (CO), hydrocarbons and soot. High temperature combustion using excess air, however, tends to generate nitrogen oxides (often referred to as N0X). N0X emissions include nitric oxide (NO) and nitrogen dioxide (N02). The free radicals of nitrogen (N2) and oxygen (02) combine chemically to form mainly NO at high combustion temperatures. This thermal NOx tends to form even when the nitrogen is removed from the fuel. The combustion modifications which reduce the formation of thermal N0X are generally limited by the generation of unwanted by-products. The mobile and stationary combustion equipment are the concentrated sources of N0X emissions. When discharged into the air, NO emissions are oxidized to form N02, which tends to accumulate excessively in many urban atmospheres. In the presence of sunlight, N02 reacts with volatile organic compounds to form ozone at ground level, eye irritants and photochemical smoke. These adverse effects have prompted extensive efforts to control N0X emissions at low levels. Despite advances in combustion and fuel technology, ozone concentrations at ground level still exceed federal regulations in many urban regions. Under the Clean Air Act and its amendments, those ozone-free areas must implement strict N0X emission regulations. Such regulations will require low levels of N0X emissions that are achieved only by after-treatment of the exhaust gases.

Exhaust after-treatment techniques tend to reduce N0X using various chemical or catalytic methods. Such methods are already known in the art and involve non-selective catalytic reduction (NSCR), selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR). Alternatively, NO can be oxidized to N02 for removal by wet scrubbers. Such post-treatment methods typically they require some type of reagent for the removal of N0X emissions. The washing of the N02 wet phase gases produces waste solutions that represent potential sources of water contamination. The wet phase scrubbers are mainly used for N0X emissions from nitric acid plants or for the concurrent removal of N02 with sulfur dioxide (S02). Costs and high complexity generally limit the technology of scrubbers to such special applications. The scrubbers in wet phase are applied to the combustion exhaust gases converting the NO to N02, as described in U.S. Pat. No. 5,047,219. The NSCR method typically uses unburned hydrocarbons and CO to reduce NOx emissions in the absence of 02. Fuel / air ratios must be carefully controlled to ensure a low excess of 02. Both oxidation and oxidation catalysts are needed. of reduction to remove CO and hydrocarbon emissions while also reducing the N0X. The cost of removing the excess 02 excludes the practical applications of the NSCR methods to many exhaust gases containing 02. The combustion exhaust gases containing excess 02 generally require chemical reducing agent (s) ( s) for the removal of N0X. Commercial SCR systems mainly use (NH3) as the reducing agent. Chemical reactions on a solid catalyst surface convert the NOx to N2. These solid catalysts are selective for NOx removal and do not reduce CO emissions and unburned hydrocarbons. The excess NH3 required to achieve low levels of NOx tends to lead to the breakdown or emission of NH3 as an emission of by-products. Normally, large volumes of catalyst are necessary to keep NOx levels low and breakdown or penetration of NH3. The activity of the catalyst depends on the temperature and is reduced with use. Normal variations in catalyst activity are only adapted by enlarging the catalyst volume or limiting the combustion operating range. Catalysts may require premature replacement due to sintering or poisoning when exposed to elevated temperature levels or exhaust contaminants. Even under normal operating conditions, the SCR method requires a uniform distribution of NH3 relative to the NOx in the exhaust gas. However, N0x emissions are frequently distributed unevenly, so that low levels of N0X and NH3 rupture can only be achieved by controlling the distribution of the injected NH3 or by mixing the exhaust gases with a level of N0X uniform. The breakdown of NH3 is alternatively limited by the decomposition of excess NH3 on the surface of a catalyst as described in U.S. Pat. No. 4,302,431. In this case, excess NH3 is catalytically decomposed following an initially equivalent decomposition of N0X and NH3 together. The decomposition of excess NH3, however, reduces the selectivity of the SCR method, increasing the molar ratio of NH3 to N0X by as much as 1.5 or a higher value. In a combination of catalytic and non-catalytic reduction methods, the removal of both N0X and NH3 can be controlled by the SCR following an initial stage of reduction of N0X by the SNCR. In the SNCR method, NOx emissions can be partially reduced without controlling the breakdown of NH3 at a low level. The SCR method can reduce the N0X further while also reducing the NH3 breakdown to an acceptable level. The use of excess NH3 to improve the removal of NOx by the SNCR method is described in detail in U.S. Pat. Nos. 4,978,514 and 5,139,754. With such methods, the injection of the NH3 into the SNCR is controlled so that the NH3 that did not react remains in an amount sufficient for the subsequent catalytic reduction of the NOx at a low level. This injection strategy is based on the use of excess NH3 to reduce N0X to lower levels, as with the SCR method described above. Another method for combining the SNCR and SCR methods is described in U.S. Pat. No. 5,510,092. In this method, the reduction of catalytic N0X is always maximized using a separate NH3 injection grid, and the N0X emissions are reduced not catalytically only when necessary to maintain a low level of final N0X. This method reduces NH3 consumption by minimizing the use of SNCR which removes N0X less selectively than the catalytic method. The low selectivity of the SNCR method and the use of excess NH3 to reduce N0X levels is reported by Lyon, who is believed to have first suggested the non-catalytic reduction of N0X (U.S. Patent No. 3,900,554). In commercial coal burning boiler tests, a 73% reduction of NO with 2.2 ppm of NH3 rupture using a 0.9 molar ratio of NH3 to NO has been reported, while a NO reduction of 86% required 11 ppm of NH3 rupture and a molar ratio of 2.2 with respect to N0X. These results are reported in Environ. Sci. Technol., Vol. 21, No. 3, 1987. In another article (Ind. Eng. Chem. Fundam., Vol. 25, No. 1, 1986), Lyon also reports the inhibitory effect of NH3 on oxidation. of CO This observation in experiments and commercial tests is confirmed by modeling studies. The inhibition has been explained in terms of the competition between NH3 and CO for the reaction with the free OH radical. It is believed that, although NH3 inhibits the oxidation of CO, CO also decreases the selectivity of NO reduction by NH3. This "sacrifice of residual CO oxidation" is described by Lyon as an important limitation of the non-catalytic reduction method. According to these teachings, the injection of NH3 must follow the completion of the oxidation of CO to overcome this limitation. When the NH3 is injected before the complement of the oxidation of the CO, the oxidation of the residual Co tends to diminish, which can lead to greater levels of emissions of CO of by-products. Despite this disadvantage of CO emissions from larger byproducts, many patents teach the use of CO or other auxiliary reducing agents or materials to reduce the effective temperature to decrease NO non-catalytically. For example, the use of CO at a lower temperature for the reduction of NO by the HNCO is described in U.S. Pat. No. 4,886,650 as follows: "Where it is desired to lower the operating temperature to a greater degree, larger amounts of CO or other species generating H atoms or vice versa will be added." This decrease in the effective temperature for NO reduction has been repeated generally in a manner consisting of all the patent literature related to the non-catalytic method. The original discoveries of NH3 (US Pat. No. 3,900,554) and urea (US Pat. No. 4,208,386) as N0X reducing agents in the temperature range of 871.11 to 1093.33 ° C (1600-2000 ° F) both reported the use of auxiliary reducing materials to enable the reduction of non-catalytic NO over the entire temperature range of 704.44 to 1093.33 ° C (1300-2000 ° F). The hydrogen (H2), the CO, and the hydrocarbon (s), including the oxygenated hydrocarbons, have been proposed as auxiliary reducing materials that can reduce the effective temperature for the reduction of non-catalytic NO by NH3 or urea. This use of hydrocarbon (s) and CO is reported to be limited, however, due to incomplete oxidation, leading to the production of air pollutants. Hydrogen has been cited as the preferred reducing material because it does not produce any air pollutant. The use of hydrogen is limited because it decreases the selectivity for the reduction of NO by NH3 or urea. To overcome this limitation, hydrogen can be added in successive multiple stages as described in U.S. Pat. No. 3,900,554. A more detailed description of a multi-step method for the reduction of non-catalytic NO using NH3 and hydrogen is described in U.S. Pat. No. 4,115,515. This multi-stage method typically requires two or more locations along the flow path of the exhaust gas to inject mixtures of the reducing gas. The optimal use of multiple injection stages and mixtures of alternative reducing gases depends on the temperature of the exhaust gas in the vicinity of each injection site. The multi-stage method takes into account the temperature gradients along the gas flow path as well as the variations in temperature at each injection site. In general, according to these teachings, NH3 is injected as the only reducing gas at temperatures in the range of 900 to 1000 ° C (approximately 1650 to 1850 ° F), while mixtures of NH3 and hydrogen are injected at temperatures in the range of 700 to 900 ° C (approximately 1300 to 1650 ° F). By decreasing the concentration of NO in the first stage of injection using only NH3, the less selective reduction of NO in the second stage where the hydrogen is used as the auxiliary reducing material is minimized.

Patents have proliferated on such descriptions of non-catalytic reduction methods. In particular, U.S. Nos. 4,731,231, 4,800,068, 4,886,650 and 4,908,193 have described the decomposition of cyanuric acid, (HNCO) 3 to generate isocyanic acid (HNCO) for the reduction of NO. Also, other patents (for example, US Patents Nos. 4,719,092, 4,751,065, 4,770,863, 4,803,059, 4,844,878, 4,863,705, 4,873,066, 4,877,591, 4,888,165, 4,927,612 and 4,997,631) have described a variety of reducing materials as alternatives for NH3, urea or cyanuric acid, or as enhancers for use with NH3, urea or cyanuric acid. These patents are mainly directed to the acute problems of NH3 rupture and emissions of CO byproduct that are characteristic of the non-catalytic reduction method. In addition to the descriptions of various reducing agents and improvers, other patents (for example, U.S. Patent Nos. 4,777,024, 4,780,289, 4,863,704, 4,877,590, 4,902,488, 4,985,218, 5,017,347 and 5,057,293) describe elaborate control strategies and multi-stage injection methods. Such control strategies and multi-step methods. They are mainly aimed at variations in temperature. The combustion equipment typically operates over a whole load range, and the exhaust gas temperatures generally increase at higher loads. Therefore, local temperatures vary at fixed locations where the reducer (s) and the reducing material (s) are injected into the exhaust gas. Non-catalytic methods do not control the local temperature for the reduction of N0X. With non-catalytic reduction methods, the local temperature is typically used as a means to control the injection of reducing agent (s) and auxiliary reducing material (s). The patents teach the use of reducing material (s) auxiliary (s) to reduce the effective temperature for the reduction of the N0X so that it equals the actual local temperature, which depends only on the production of the exhaust gas . It is important to note that, in such teachings, the auxiliary reducing material (s) is not injected to control the local temperature. The auxiliary reducing material (s) may make it possible to reduce N0X to lower effective temperatures, but may lead to the formation of unwanted by-products. Such teachings tend only to minimize the disadvantages of non-catalytic reduction methods. Such techniques in general do not provide for the concurrent depletion of NH3 and CO emissions. The use of oxygenated hydrocarbons is described in U.S. Pat. No. 4,830,839 as a means to purify the broken NH3 from a previous stage of a non-catalytic NOx reduction. With this method, the evaporated concentrations of the oxygenated hydrocarbons in the range of 2 to 500 ppm are added to the exhaust gas so that their weight ratios relative to NH 3 are in the range of 2 to 200. U.S. Pat. No. 5,047,219, however, subsequently discloses that the oxygenated hydrocarbons are oxidized from NO to N02 at temperatures below about 871.11 ° C (1600 ° F). By decreasing the effective temperature for the non-catalytic reduction below about 926.66 ° C (1700 ° F) the thermal decomposition of the nitrous oxide (N20) as described in U.S. Pat. No. 5,048,432. This patent teaches the reheating of exhaust gases using a burner with a separate source of combustion air. The N20 is thermally decomposed when the high temperature combustion gases of the burner are mixed and reheat the primary exhaust gas above 926.66 ° C (1700 ° F).

The formation of N20 as a by-product of non-catalytic reduction is described in U.S. Pat. No. 4,997,631. When the N0X emissions are reduced by the non-catalytic method, a portion of the reduced N0X is converted to N20. As described above, N20 levels are reduced at higher temperatures, but also the reported data suggest a much lower N20 formation when NH3 is used as the chemical reductant. Urea and cyanuric acid reportedly led to higher N20 levels. A different method for staggering the reduction of non-catalytic NO is described in U.S. Pat. No. 3,867,507. It is described that hydrocarbons reduce NO when the molar ratio of 02 to carbon is less than 2.5. Such low levels of 02, however, tend to lead to the formation of undesirable products, including NH3, hydrogen cyanide (HCN), CO and unburned hydrocarbons. Such by-products are removed by oxidation using air added at elevated temperatures, eg, 1100 ° C (approximately 2000 ° F), in a second stage. Similar methods are described for staggering the non-catalytic NOx reduction in U.S. Pat. Nos. 4,851,201 and 4,861,567. With these methods, the reducer (s) are mixed with the exhaust gas and decomposed under fuel-rich combustion conditions in a first stage, and then the N0X is reduced in a second stage with an excess of oxygen. The temperature and oxygen concentration are adjusted between the two stages. The temperature varies for each stage depending on whether the reducer is cyanuric acid instead of NH3 or urea. Another method to lower the effective temperature for the reduction of non-catalytic N0X is described in Int. App. No. PCT / US92 / 07212 (Pub. No. WO 93/03998). It is suggested that the hydrocarbons be injected to create effective stratified mixtures to generate partial oxidation products as auxiliary reducing materials to lower the effective temperature for the reduction of N0X using cyanuric acid. Based on the previous teachings, the reduction of non-catalytic NOx by the hydrocarbon (s) alone (s) tends to be limited to fuel-rich combustion conditions, ie, low levels of 02. In the presence of an excess of 02, the hydrocarbon (s) and the CO are ineffective for NOx reduction but can be used to lower the effective temperature for the reduction of noncatalytic NOx using chemical reductant (s). In such an auxiliary role, such materials are also claimed to reduce NH3 cleavage, but this could only be achieved at the expense of reduced selectivity for the reduction of N0X. Under these conditions, the reduction of non-catalytic N0X tends to be limited because the breakdown of excess NH3 is necessary to achieve low N0X levels, but the oxidation of CO is inhibited by NH3, so that the decrease in the non-catalytic reduction temperature using auxiliary materials tends to increase the by-product CO emissions. Both NH3 and CO are undesirable byproducts of SNCR. In general, even the more elaborate scaling methods and SNCR controls can not exhaust these undesirable byproducts concurrently. In general, such methods only minimize the disadvantageous production of one byproduct at the expense of increasing another. In addition, non-catalytic reduction methods are highly temperature dependent, but tend not to provide a means to control this key condition. Stepping methods and elaborate controls are necessary to maintain an effective temperature for the chemical reducer (s) when the excess 02 is present under the local exhaust conditions. The injection of reducer (s) under fuel-rich, specific combustion conditions, it is also claimed to require a phased introduction of excess air to supplement the combustion of the primary fuel. Despite such elaborate staging methods and controls, NH3 NH3 cleavage is generally depleted only by using a subsequent catalytic method. Such SNCR methods, however, do not remove objectionable byproduct CO emissions from the SNCR without using a separate oxidation catalyst similar to NSCR. Alternatively, this disadvantage of the SNCR can be minimized to a larger extent by limiting the non-catalytic reduction only to maintain a low final N0X level in combination with the SCR as described in U.S. Pat. No. 5,510,092. By relegating the inherent advantages of a gaseous phase method to reduce the N0X to a subordinate role, however, the key disadvantages of using solid catalysts are not minimized. The expensive installation of large volumes of the catalyst adversely affects the combustion equipment. The catalyst beds add a pressure drop, and the vaporization of NH3 can reduce the capacity of the combustion equipment by as much as 2%.

As is well known, solid catalysts tend to become capped and coiled gradually under normal use and require periodic replacement. Premature replacement is necessary when the catalyst is sintered or poisoned due to unusually high temperatures or contaminant levels that result from problems related to combustion or other equipment failures. Similar to SNCR methods, catalytic reduction methods are highly temperature dependent, but do not provide a means to control this key condition. Considering previous lessons and efforts, and in particular in view of the continuing need for numerous applications for effective cost reduction of N0X despite previous intensive efforts, there is a need for new methods for the selective reduction of N0X , which in general combine certain advantages of the previously described methods substantially, but without the disadvantages thereof. As will be described hereinafter, the applicants report that they have discovered such methods. It should be understood that the foregoing description of the background of the present invention, and the detailed description of the present invention given below, are provided for understanding the context and applicability of the present invention, and are provided without being limited to some particular or similar theory. References to patents of particular background or other materials, are for general description purposes only and are based on the understanding of them by the Requesters, and the complete references should be consulted for the actual content of such patents and materials.

Brief Description of the Invention The present invention provides new methods in gas phase to reduce the emissions of N0X and other pollutants in the exhaust gases, and for industrial processes that use it. With the methods according to the present invention, the hydrocarbon (s) automatically self-ignite and heat an exhaust gas so that the NH3, the HNCO or a combination thereof, are effective in reducing N0X autocatalytically. These new autocatalytic methods are distinguished by the self-sustained conversion of the reactants when at least one product of the reaction acts as a catalyst so that the reactions proceed more rapidly with the formation of the catalyst and continue until the reagents are substantially depleted. With the methods according to the preferred embodiments of the present invention, the reduction of N0X is driven by the autothermal heating of the exhaust gas to generate the effective catalytic species for self-maintenance of the reactions until the reagents are substantially depleted. Within the temperature range of approximately 482.22-871.11 ° C (900-1660 ° F), the hydrocarbon (s) are introduced to self-ignite under generally uniform poor fuel conditions with approximately 2-18% O2 in the gas escape Once ignited, the reactions proceed autocatalytically, heating the exhaust gas autothermally. Under some conditions, a blue chemiluminescence may be visible. Such single-stage, autocatalytic methods according to the present invention do not necessarily depend on the order in which the reductant (s) and the hydrocarbon (s) are introduced into the exhaust gas. Contrary to the previous teachings, the autocatalytic methods according to the present invention do not require combustion stages rich in fuel or multiple reaction. The NH3, the HNCO or a combination thereof can be introduced or generated from the reductant (s) before or during the fuel-poor auto-thermal conversion of the hydrocarbon (s) in the exhaust gas. The autocatalytic methods according to the present invention reduce N0X and deplete both CO and NH3 in a substantially concurrent manner. These autocatalytic reactions are self-sustaining by the autothermal heating of the exhaust gas following the substantially uniform self-ignition of the hydrocarbon (s). The gas phase methods according to the present invention can be advantageously applied without a solid catalytic surface. Self-sustained auto-thermal reactions in the gas phase can be used to partially remove other contaminants from the exhaust gas, including hydrocarbons, particulate material and CO. The methods according to the present invention can be considered to combine the advantages of known methods to reduce NOx selectivity, but, unexpectedly, without the disadvantages of solid catalytic surfaces, hazardous waste or by-product emissions, etc., contrary to the foregoing teachings, the autocatalytic methods according to the present invention can use interchangeably reductant (s) consisting of or that are decomposed to generate NH3, HNCO or a combination thereof. In addition, the hydrocarbon (s) which may be used in the embodiments of the present invention may consist of the same liquid, gaseous or vapor phase fuels as those which are burned to produce the exhaust gas containing the N0X in the industrial process. Also contrary to the previous teachings, hydrocarbons and CO do not serve to lower the effective temperature range to reduce NOx by the autocatalytic method. With the autocatalytic methods according to the present invention, the exhaust gas is heated self-thermally both by the partial oxidation of the hydrocarbon (s) to generate the CO and by the oxidation of the CO to C02. The introduction of NH3, NHCO or a combination thereof during this autothermal heating leads to the reduction of N0X, and the hydrocarbon (s), CO and NH3 are depleted together in the same temperature range of about 760-843.33 ° C (1400-1550 ° F). Within this range, the depletion of the hydrocarbon (s), CO and NH3 depends mainly on the final temperature for the autothermal heating of the exhaust gas. Also contrary to the previous teachings, the autocatalytic method is not limited by the inhibition of CO oxidation. Autocatalytic reactions can be self-sustaining while CO and NH3 are depleted together when the hydrocarbon (s) auto-ignite and heat the exhaust gas autothermally to the temperature range of approximately 760-843.33 ° C (1440-1550 ° F) ). In accordance with the present invention, the NH3 can be depleted below 2 ppm concurrently with the removal of CO below about 50 ppm. Also contrary to previous teachings, NOx emissions are reduced to low levels while NH3 is substantially depleted. According to the autocatalytic methods of the present invention, N0X emissions can be reduced approximately 80-90% to approximately 50-200 ppm using NH3 and HNCO almost stoichiometrically. In addition, in the preferred embodiments, NOx emissions can be reduced by as much as 99% for levels both below and approximately 10 ppm by using no more than about twice the stoichiometric ratio of NH3 and HNCO relative to NOx.

Such removal of the concurrent, single gas phase from N0X, NH3, HNCO, hydrocarbon (s) and CO in general is not highly dependent on the chemical reductant (s). Similar results have been obtained according to the present invention using NH3, cyanuric acid, urea or urea decomposition products. Although the conversion of N0X to N20 may depend on the chemical reductant (s)), if desired, the desired by-product N20 emissions may be reduced to low levels using NH3 instead of another reducing (s). (is) chemical (s). In the preferred embodiments of the present invention, the introduction of hydrocarbon (s) is controlled to maintain a final reaction temperature in the range of about 760-843.33 ° C (1400-1550 ° F). The release of autothermal heat increases the temperature of the exhaust gas adiabatically in the absence of heat losses, or alternatively the heat transfer surfaces can recover the heat of the exhaust gas during the autothermal heating. Such recovery of heat, however, should not cool the exhaust gas so excessively that the autothermal reactions are extinguished.

An autothermal heat release equivalent to an increase in adiabatic temperature in the range of about 10-260 ° C (50-500 ° F) is preferably used in the preferred embodiments to achieve an exhaust gas temperature of about 760-843.33. ° C (1400-1550 ° F) to implement the autocatalytic methods according to the present invention. The amount of hydrocarbon (s) introduced depends mainly on the temperature of the initial exhaust gas and on any recovery (recycling) of the heat released by the autothermal reactions. The autocatalytic methods according to the present invention typically use residence times no greater than about 1.5 seconds when the initial exhaust gas temperatures are in the range of 482.22-871.11 (900-1600 ° F). As more fully described elsewhere herein, CO and NH3 are typically depleted faster when thermal heating is initiated at higher temperatures in the range of 565.55-871.11 ° C (1050-1600 ° F). In this case, residence times of the reaction in the range of about 0.02-1.0 seconds may typically be sufficient to deplete both the CO and NH3 substantially. According to the present invention, the highest initial exhaust gas temperatures in the range of about 648.88-871.11 ° C (1200-1600 ° F) make possible the substantial depletion of CO and NH3 within the range of about 0.02- 0.5 seconds According to the present invention, the introduction of hydrocarbon (s) is beneficially reduced when the exhaust gas is preheated to the temperature ranges of approximately 565.55-871.11 ° C (1050-1600 ° F) or approximately 648.88-871.11 (1200-1000). 1600 ° F). In these cases, the release of autothermal heat does not need to exceed an amount equivalent to an adiabatic increase of approximately 10-176.66 ° C (50-350 ° F) or approximately 10-93.33 ° C (50-200 ° F), respectively, since the exhaust gas is heated autothermally to a final temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F). According to the present invention, in certain embodiments this preheating of the exhaust gas can also improve the selectivity of the NOx reduction. With the present invention, the initial exhaust gas temperatures do not depend on how the exhaust gas is preheated or cooled, since the concentration of 0? it is maintained in the range of about 2-18% by volume. The exhaust gas can be heated or cooled initially using heat transfer surfaces, including any of several methods for preheating the exhaust gas by recovering heat after the exhaust gas is treated using autocatalytic methods as mentioned herein. . In the alternative modalities, the exhaust gas is heated directly by the combustion of a supplementary fuel in the exhaust gas. In such alternative modes, the combustion of a supplementary fuel using excess air can also enrich the 02 concentration in an otherwise deficient 02 exhaust gas. In this case, the combustion of the supplementary fuel can serve the dual purpose of preheating of exhaust gas and enrichment of its concentration of 02. The combustion of a supplementary fuel can also serve to preheat a portion of the exhaust gas to ignite more supplementary fuel which is burned directly into the exhaust gas. If the exhaust gas is preheated using fuel-rich combustion, the autocatalytic methods according to the present invention can serve to remove some or substantially all of the additional contaminants from the fuel-rich combustion. In this context, it is important to note that the "supplemental fuel" is burned for the purpose of preheating the exhaust gas, and not to chemically improve the N0X reduction. The autocatalytic methods according to the present invention can be used in combination with various modifications to the combustion process which generates the exhaust gas. In certain embodiments, such modifications can advantageously lower N0X emissions to reduce the introduction of reductant (s) according to the autocatalytic methods of the present invention. In certain embodiments, combustion modifications can beneficially maintain exhaust gas temperatures within the range of approximately 482.22-871.11 (900-1600 ° F) or preferably approximately 648.88-871.11 ° C (1200-1600 ° F) to implement the autocatalytic methods of the present invention. In certain embodiments, the combustion modifications may maintain the concentration of 02 above about 2% by volume to implement the autocatalytic methods of the present invention.

The autocatalytic methods according to the present invention can also be implemented in conjunction with the primary combustion process so that the release of autothermal heat is beneficially recovered. In alternative embodiments, for example, new or existing surfaces in a heat exchange boiler may serve to recover the release of autothermal heat generated in accordance with autocatalytic methods as provided herein. In such modalities, autothermal heating can replace the primary fuel for the purpose of generating steam or fractionating petrochemical substances (as exemplary industrial applications), or autothermal heating can serve to increase the generating capacity of an existing boiler, etc. According to still other modalities, combustion modifications such as secondary air are used to enable the lower N0X emissions of the primary fuel at the same time that 02 is also enriched in the exhaust gas. In the case of boilers that burn coal, the replacement of the primary fuel by the autothermal oxidation can serve to increase the 02 levels of the furnace beneficially with the purpose of reducing the flying ash on the unburned coal. Such benefits of the alternative embodiments of the autocatalytic methods according to the present invention can serve to increase the efficiency of the total boiler while also improving the value of the by-product fly ash, possibly avoiding the generation of a waste in another way. solid. The autocatalytic methods according to the present invention can also beneficially consume the NH 3 breakage of a previous exhaust gas treatment using the SNCR, for example. In such embodiments, the autocatalytic methods according to the present invention can serve to replace the use of SCR as a means to control the breakdown of NH3 from the SNCR. Such uses of the embodiments of the present invention, however, may also preferably apply autocatalytic methods as provided herein in place of SNCR to reduce N0X more selectively. It is recognized that, as an exemplary advantage, the best selectivity of autocatalytic methods as provided herein, can greatly reduce the introduction and cost of reducer (s), while substantially increasing both CO and NH3, and reducing NOx emissions at low levels.

Since autocatalytic methods according to the present invention can reduce N0X emissions below most regulatory requirements, the application of the present invention can replace the need for costly catalysts altogether. Such autocatalytic activity to remove NH3 and CO in the company of N0X can be self-sustained and conducted in a manner that does not deteriorate with use similar to solid catalysts. As a result, autocatalytic methods according to the present invention can avoid the need to replace the existing catalysts poisoned by the exhaust pollutants. If the emissions regulations require additional N0X reductions, then the autocatalytic methods according to the present invention can serve to improve the SCR applications while minimizing the catalyst volume. In addition to reducing the N0X before the SCR, the autocatalytic methods as provided herein can also decrease contaminants such as hydrocarbons and soot which can foul the catalytic surfaces. In such modalities that utilize a combination of treatments, the autocatalytic methods as provided herein may make possible the use of more efficient or effective catalyst beds in terms of the cost due to both the removal of contaminants and the control of gas temperatures. escape. In a preferred combination of catalytic and autocatalytic reduction methods, the autothermal heating can continuously decrease the hydrocarbon and soot pollutants while controlling the temperature of the exhaust gas with respect to the catalyst. The N0X emissions can be maintained at a desired level by using a separate injection of NH3 beyond the catalyst to minimize the reductant (s) introduced to the catalytic method. Since the need for N0X reduction autocatalytically does not exceed about 80-90%, the reductant (s) can be consumed almost stoichiometrically, and the CO emissions can be depleted substantially in the shortest possible time. Accordingly, it is an object of the present invention to solve the problems, limitations and disadvantages of the prior techniques of NOx reduction of exhaust gases produced by a variety of industrial processes.

It is another object of the present invention to provide practical and low cost methods of N0X removal in a variety of industrial processes, which can utilize a variety of commercially available reducing agents. It is another object of the present invention to provide practical and low cost methods for the removal of N0X in a variety of industrial processes, which can deplete NH3 and CO in a substantially concurrent manner. It is still another object of the present invention to provide N0X reduction methods which do not require solid catalytic surfaces or hazardous materials. It is a further object of the present invention to provide methods for the removal of N0X which can be selective and conducted almost stoichiometrically in the gas phase. Finally, it is an object of the present invention to provide N0 reduction methods: autocatalytic, autothermal, in a wide variety of industrial processes, and also to various systems and apparatuses to carry them out.

Brief Description of the Drawings The features, objects, and concomitant advantages of the present invention, mentioned above, can be better appreciated and understood when considered in relation to the appended drawings, wherein: Figures 1 (a) through (c) are reproduced graphs of "Chemical Reaction Engineering" by Octave Levenspiel, John Wiley and Sons, Inc., 1962, p. 228 (Library of Congress Catalog Card Number: 62-15185), and which serve to illustrate the distinctive characteristics of self-sustained autothermal reactions as used in accordance with the embodiments of the present invention; Figure 2 illustrates the effects of NH3 and HNCO on the release of autothermal heat and self-ignition of the hydrocarbon (s) under the conditions of poor fuel in an exhaust gas initially containing approximately 10% of 02; Figure 3 illustrates the selective reduction of N0X by HNCO while self-igniting and self-heating heat is introduced from the hydrocarbon (s), to an exhaust gas containing in the range of approximately 5-9% of 02; Figure 4 illustrates the substantially concurrent depletion of CO and NH3 by self-sustained autocatalytic reactions in an exhaust gas according to the embodiments of the present invention, wherein the auto-ignition and autothermal heat of the hydrocarbon (s) to the gas exhaust under poor fuel conditions containing in the range of approximately 5-9% O2; Figure 5 illustrates the increase in CO depletion in the presence of NH3 at higher temperatures in the range of about 751.66-773.88 ° C (1385-1425 ° F); Figure 6 compares the selective reduction of N0X using cyanuric acid powder and aqueous urea solutions as an alternative reductant (s) for the generation of NH3 and HNCO to reduce N0X autocatalytically according to the embodiments of the present invention. Figure 7 is a diagram illustrating the embodiments of the present invention in which the hydrocarbon (s) are introduced to self-ignite and autothermally heat an exhaust gas while the reducer (s) are introduced to generate NH3, HNCO or a combination thereof, so that N0X is selectively reduced while CO and NH3 are both substantially depleted, as can be carried out in a single stage treatment under poor fuel conditions where the exhaust gas contains at least about 1% of 02; Figure 8 is a diagram illustrating an embodiment of the present invention wherein a single-stage exhaust gas treatment such as that illustrated in Figure 7 is incorporated with the production of the exhaust gas by the combustion equipment, and additionally it may include heat recovery, preheating or enrichment of 02 in the embodiments in which the present invention serves to control N0X emissions while producing petrochemical products, electricity is generated or mobile machinery or equipment is operated. Figure 9 is a diagram illustrating an embodiment of the present invention wherein a single-stage exhaust gas treatment such as that illustrated in Figure 7 is incorporated with a heat exchange boiler so that the heat released in the implementation of the present invention to control NOx emissions is recovered in conjunction with the production of petrochemical products or the generation of electricity by the heat exchange boiler, and the combustion of the fuel in the heat exchange boiler can be modified additionally to control the composition of N0X and initial 0 of the exhaust gas for the implementation of the present invention.

Detailed Description of the Preferred Modalities The present invention will now be described in greater detail with reference to the particular alternative and preferred embodiments. Such a description is for a more complete understanding of the background, utility and application of the present invention, and is not intended to be limited by any particular theory or the like. Referring to Figures 1 (a) to 1 (c), the material balance curves illustrate the characteristic relationship between temperature and conversion of reactants for irreversible, exothermic reactions. The alternative energy balance lines in Figures 1 (a), (b), and (c) illustrate the release of potential adiabatic heat starting from the same initial temperature T. As will be understood in the art, the current conversion and the Heating depends on the satisfaction of the material and energy balances simultaneously as represented by the points of the intersection, which can be described as follows. In Figure 1 (a), the initial temperature and the amount of reagents are insufficient for self-sustained adiabatic heating beyond the point of intersection. The extent of the reaction remains negligible because the heating required to sustain the reaction exceeds the potential amount of heat release from the reaction. In Figure 1 (b), the largest amount of heat release makes the virtually complete conversion possible from the same initial temperature. In this case, a high final temperature necessarily results from the release of high heat from a temperature lower than the ignition temperature as described below. Figure 1 (c) illustrates the meaning of ignition as a limiting condition for self-sustained adiabatic heating using less heat release. At any initial temperature lower than the ignition condition, the heating required to sustain the reaction exceeds the heat release, so that the reaction can never proceed adiabatically beyond the Mr point, similar to Figure 1 (a). The appreciable conversion is self-sustaining only when the reagents are first turned on; then, the same heat release can self-sustain the almost complete conversion as illustrated by point M '. "The hydrocarbon (s) and CO are known to be oxidized by irreversible, exothermic reactions. These reactions can self-sustain the conversion of fuels into the combustion equipment, such combustion using excess air produces exhaust gases at elevated temperatures where the reagent fuel and 02 are typically preheated above the ignition temperature using a stabilized flames Such hot oxidant gases, however, generate NOx emissions thermally and convert the nitrogen in the fuel, including NH3 and HNCO, to form NOx, such oxidizing conditions are avoided by limiting the conversion of reagents into the previous teachings related to NOx reduction not catalytically According to such teachings, the conversion is imitated by a deficiency of either 02 or auxiliary reducing material. Referring again to Figures 1 (a) to 1 (c), it can be understood that any of these deficiencies limits both the release of heat and the self-sustained conversion of the reactants. The limited conversion, however, tends to necessarily lead to the production of air pollutants as previously described. Such teachings, for example, generally correspond to the introduction of NH3, the HNCO or the hydrocarbon (s) in the fuel-rich gas, deficient in 02 or the use of stratified fuel mixtures to generate partial oxidation products. According to such teachings, the partial oxidation products reduce N0X directly under the fuel-rich conditions, deficient in 02 or lower the effective temperature for the selective N0X reduction by NH3 and HNCO in the presence of 02 in excess. As previously explained, according to these teachings: "Where it is desired to reduce the operating temperature to a greater degree, larger quantities of CO or other species generating the H atom or vice versa will be added". As described in relation to Figures 1 (a) to 1 (c), however, the larger quantities of auxiliary reducing materials must be incompletely converted to lower the operating temperature. Similarly, the reported inhibition of CO oxidation by NH3 and HNCO must necessarily decrease the adiabatic heating of an exhaust gas containing 02 in excess. According to such teachings, the production of by-product air pollutants is avoided only by removing the CO prior to the injection of NH3 or HNCO. Such teachings, however, tend to require higher temperatures in the range of 871.11-1093.33 ° C (1600-2000 ° F) for the reduction of N0X non-catalytically unless the hydrogen is used as the auxiliary reducing material. Although hydrogen can lower the effective temperature to reduce NOx non-catalytically without producing other air pollutants, this technique is limited as previously described. Such prior teachings do not seem to appreciate the possibility of an ignition condition for self-sustaining gas phase reactions, to selectively reduce NOx. Contrary to such previous teachings, NH3, HNCO or a combination thereof, can be used for effective autocatalytic N0X reduction when the hydrocarbon (s) self-ignite and heat the exhaust gas autothermally under poor fuel conditions wherein the exhaust gas contains at least about 1% of 02. Such characteristics, aspects and unique attributes of the present invention will become more apparent to those skilled in the art from the following detailed description, which refers to the Figures and the tables described later. Figure 2 illustrates the autothermal heating of an exhaust gas containing about 10% of 02 and 155 ppm of NOx at an initial temperature of about 493.33 ° C (920 ° F). The exhaust gas was produced by a high speed, work or heavy load diesel engine. The continuous line in Figure 2 shows the temperature profile when the diesel fuel was only injected to auto-ignite and auto-heat the exhaust gas. Temperatures measured using type K thermocouples coated with stainless steel along the flow path never reached 760 ° C (1400 ° F) when the diesel fuel was injected alone. The composition of the final exhaust gas contained approximately 7.6% O2, and the initial NOx level was not appreciably reduced by the injection of diesel fuel at this high 02 level. The continuous rectangles in Figure 2 illustrate the temperatures measured when the cyanuric acid was injected in addition to the diesel fuel. The cyanuric acid was injected to decompose and generate HNCO at a molar ratio of approximately 1.4 with respect to the initial N0X in the exhaust gas. Lower temperatures compared to diesel fuel at residence times of less than about 0.4 seconds indicate that the introduction of HNCO slowed the initial autothermal heating of the exhaust gas using the same amount of diesel fuel. Further introduction of HNCO eventually led to a higher temperature in excess of 760 ° C (1400 ° F) after approximately 0.4 seconds, indicating greater autothermal heating than that of diesel fuel alone. In addition, NOx emissions were reduced by more than 90%, and the final CO concentration was increased from approximately 185 ppm to approximately 520 ppm. As illustrated in Figure 2, the introduction of the HNCO increased the final temperature for the autothermal heating of the exhaust gas compared to the injection of the same amount of diesel fuel alone. Since the HNCO contributed up to 2000 ppm of the CO reagent, the much smaller increase of only 335 ppm in the final CO concentration showed a larger conversion of CO compared to the same introduction of the diesel fuel alone. These results demonstrate a uniquely larger conversion of both N0X and CO concurrently in accordance with the present invention. The lower temperatures initially with the generation of HNCO illustrated in Figure 2 far exceed any cooling effects related to decomposition and vaporization of cyanuric acid. These lower temperatures reflect an initially slower rate of heat release from diesel fuel due to the generated HNCO. This initial inhibition of autothermal heating did not last more than about 0.4 seconds. After this initial inhibition, the exhaust gas was heated faster at temperatures above 760 ° C (1400 ° F), and both NOx and CO were depleted substantially as a result of the generation of HNCO during autothermal heating. These experimental results support a solely autocatalytic NOx reduction distinctly different from the previous teachings. As described by Levenspiel, the autocatalytic reactions are distinguished by the self-sustained conversion of the reagents which start slowly as illustrated in Figures 1 and 2. In these reactions, at least one product of the reaction acts as a catalyst. Reactions proceed more quickly with catalyst formation and continue until the reagents are substantially depleted. When the N0X emissions are reduced autocatalytically, the reductant (s) and the hydrocarbon (s) are both substantially converted by the reactions which release heat autothermally as illustrated in Figures 1 and 2. The temperature of the exhaust gas is increased by adding either more reductant (s) or more hydrocarbon (s). This is contrary to previous teachings where larger quantities of auxiliary reducing materials are added to lower the temperature for N0X reduction or where the reducer (s) are added under fuel-rich conditions, deficient in 02, etc. Similar one-stage experiments were performed using an exhaust gas from another diesel engine.This exhaust gas was pretreated in the range of approximately 593.33-704.44 ° C (1100-1300 ° F) by the combustion of the fuel The supplemental fuel was completely burned off so that the engine exhaust gas, pretreated, virtually did not contain CO, and approximately 8.7% O2 and 700 ppm NOx.

NOx emissions were reduced autocatalytically by introducing diesel fuel and cyanuric acid after the pretreatment of the exhaust gas. By pretreating the exhaust gas, less diesel fuel was needed for self-ignition and autothermal heating to the final temperatures in the range of approximately 751.66-773.88 ° C (1385-1425 ° F). Using less diesel fuel compared to the results illustrated in Figure 2, the selectivity of the N0X reduction was actually increased as illustrated in Figure 3. Figure 3 illustrates the selectivity and levels of NOx reduction in these treatments single stage autocatalytic when the exhaust gas was pretreated in the range of approximately 671.11-687.77 ° C (1240-1270 ° F). The initial NOx level of about 700 ppm was reduced as much as about 95% to as low as about 31 ppm. The N0X was reduced approximately 80-90% almost stoichiometrically, and this selectivity of almost 100% declined only gradually when more HNCO was added to reduce the additional NOx. For the molar ratios of HNCO to NOx in the range of about 0.8-1.6, the CO and NH3 were depleted in a substantially concurrent manner as illustrated in Figure 4. The extent of this concurrent depletion was increased by introducing more fuel diesel so that the exhaust gas was heated autothermally to a higher temperature in the range of approximately 751.66-773.88 ° C (1385-1425 ° F). This attempt at temperature is illustrated in Figure 5. Contrary to the previous teachings, the amount of diesel fuel does not change the operating temperature for the reduction of selective N0x. The autothermal heating of approximately 248.88 ° C (480 ° F) in Figure 2 was reduced to the range of approximately 37.77-148.88 ° C (100-300 ° F) for the experimental results illustrated in Figures 3-5. Substantial depletion of CO and NH3 confirmed the almost complete conversion of reagents, and the final operating temperature for NOx removal remained at almost 760 ° C (1400 ° F). As can be understood from the discussion related to Figures 1 (a) to 1 (c), the auto-ignition of the reactants makes possible the almost complete conversion to approximately the same final temperature, without taking into account the initial temperature. The higher initial temperatures above the ignition condition decrease the release of autothermal heat which is necessary for self-maintenance of almost the same conversion of the reactants. The aforementioned comparisons of the experimental results in Figures 2-5 are indicative of the characteristics of the autocatalytic reactions. Self ignition and autothermal heating represent the requirements / conditions for reducing N0X autocatalytically according to the present invention. Without these key conditions, NH3 and HNCO reduce NOx non-catalytically. Previous teachings for N0x reduction do not catalytically prevent or omit any one-step method to overcome the limiting inhibition of CO oxidation by NH3 and HNCO, as may be understood from the previous description or a review of such teachings previous The experimental results provided herein, however, clearly demonstrate different conditions of self-ignition and autothermal heating advantageously used in accordance with the present invention to reduce NOx autocatalytically. These inventively new conditions for the reduction of autocatalytic N0X do not depend on the solid surfaces to catalyze the reactions. Contrary to the previous teachings, the final operating temperature for autocatalytic reactions in the gas phase do not change in general with the use of the alternative reductant (s) or different amounts of hydrocarbon (s). These autocatalytic N0X reduction characteristics according to the present invention are further evidenced by the comparison of the test results in Table 1 given below.

Table 1 Engine Output Test 1 Test 2 Test 3 Test 4 Diesel Initial Temperature ° C 501. 11 672. 77 693. 88 713.33 NOx, ppm 1550 700 700 700 Exit Treatment Tempera-ture Final ° C 784. 44 799. .44 776. 11 805.55 02,% 8.0 6.2 7.8 4.5 NOx, ppm 64 46 52 54 CO, ppm 98 18 93 54 Reducer (Source Mix CYA CYA Urea of HNCO) Molar Ratio 1.1 1.1 1.1 0.8 (HNCO / NOx) Residence Time 0.7 0.4 0.7 0.4 Reaction, sec. Coating SS SS CF CF Reaction Chamber SS = Stainless Steel; CF = Ceramic Fiber Test 1 was carried out using the same exhaust gas and the reaction chamber corresponding to the results illustrated in Figure 2. This reaction chamber is coated with stainless steel and contains stainless steel deflectors. Tests 2-4 were performed using the same exhaust gas and the reaction chamber corresponding to the results illustrated in Figures 3-5. This reaction chamber is coated with ceramic fiber insulation and contained internal stainless steel fittings which were removed only for Runs 3 and 4. The cyanuric acid powder (CYA) was pneumatically injected in Runs 2 and 3 as the source of HNCO. An aqueous solution containing approximately 25% by weight of urea was injected as the source of HNCO in Test 4. A pulverized product of the decomposition of urea (Mix) was injected pneumatically in Test 1. This mixed source of HNCO was estimated that it contains approximately 25% of cyanuric acid in the company of 75% biuret and urea to calculate the molar ratio of HNCO to NOx.

Tests 1-4 were all performed almost adiabatically using diesel fuel injection to control the final temperature of the autothermal heating. The injection of diesel fuel was decreased in Tests 2-4 where the exhaust gas of the engine was preheated prior to the introduction of the diesel fuel and the reducer (s). The final 02 concentrations reflect the differences in the pneumatic transport of the sprayed reducer (s) and the preheating of the exhaust gas as well as the amount of diesel fuel injected to auto-ignite and heat the exhaust gases autothermally. Despite the differences in the composition of the exhaust gas and the preheating, the materials of the reaction chamber and the residence times, and the chemical composition of the reducer (s), the NOx and CO emissions were always reduced in a substantially concurrent manner. Higher final temperatures in the narrow range of approximately 760-816.55 ° C (1400-1500 ° F) converted the reactants to similarly low levels over a wide range of initial NOx concentrations and autothermal heat releases.

As illustrated by the data in Table 1, the highest final temperatures for autothermal heating mainly depleted the reagents in shorter residence times. This depletion of the reagents included NH3 even when the NH3 was generated in large quantities by the thermal decomposition of the urea. In effect, the results of Test 4 demonstrated the reduction of N0X in excess of the HNCO generated from urea, indicative that high NH3 levels can be effective in reducing N0X autocatalytically according to the present invention. The comparisons in Table 1 are based on the molar ratio of the HNCO to the NOx because of the uncertainty in the estimation of the NH3 generation from the mixture of the urea decomposition products. This uncertainty is removed when urea and cyanuric acid are compared directly in Figure 6. For this comparison, the molar ratios are based on the generation of equal amounts of NH3 and HNCO from urea, as reported in Combust, Sci, and Tech., Vol. 65, 1989. On this basis, NH3 reduces NOx autocatalytically less selectively than HNCO as illustrated in Figure 6. The data in Figure 3 are repeated in Figure 6 for direct comparison of similar experiments. The urea was tested in place of the cyanuric acid by injecting an aqueous solution containing about 25% by weight of the urea. Although the mixture generated of NH3 and HNCO reduced the N0X less selectively than the HNCO alone, the N0X was reduced autocatalytically at the same low level using urea or cyanuric acid interchangeably. An independent source contractor analyzed the engine exhaust gas both before and after Test 1 in Table 1. These analyzes for typical combustion byproducts are summarized in Table 2 below. As illustrated by these results, the reduction of the autocatalytic N0X according to the present invention does not produce any significant amount of typical contaminants in the combustion exhaust gas. In effect, autothermal reactions with the autocatalytic methods for NOx reduction as provided herein, can actually decrease other typical exhaust contaminants in addition to NOx.

Table 2 Engine Exhaust Results of the Baseline of the Subproducts of Test 1 CO, ppm 210 98 CH4, ppm 3.2 2.6 HCN, ppm 0.079 0.087 MW solid, g / dscf 0.0099 0.0096 total ppm, f / dscf 0.0167 0.0139 organic, ppm 0.5 0.5 (different from CH4) Similar results are obtained in the application of the autocatalytic methods of NOx reduction according to the present invention with respect to a preheated exhaust gas of a diesel electric generator with an average speed of 4000 bhp with a capacity of approximately 2.8 MW. In this case, the engine exhaust occurred at temperatures below 315.55 ° C (600 ° F) and was preheated above about 537.77 ° C (1000 ° F) using a heat exchanger. The final temperature of the autoattatic N0X reduction was maintained at approximately 760 ° C (1400 ° F) by controlling the introduction of diesel fuel into the preheated exhaust gas. The heat exchanger cooled the treated exhaust gas by preheating the engine exhaust gas. The supplemental fuel was burned in a burner to preheat the engine exhaust gas initially as a means of starting the heat recovery. The preheated exhaust gas was introduced into the reaction chamber through a round conduit with an internal diameter of 36 inches. Diesel fuel and pulverized cyanuric acid were introduced into this conduit. The diesel fuel was dispersed in the exhaust gas using pressure atomization from a single liquid spray nozzle. The cyanuric acid powder was introduced pneumatically. In this particular example, the exhaust gas of the preheated engine contained more than about 13.5% of 02 at temperatures above about 537.77 ° C (1000 ° F). Under these conditions, the stratified ignition was prevented by swirling at the total exhaust gas flow rate which totaled almost 13,000 dscfm. Self ignition and uniform autothermal heating were visually verified by the appearance of a chemiluminescence with a substantially uniform blue color as the exhaust gas introduced into the open reaction chamber. The reaction chamber consisted of a round open vessel covered with a ceramic fiber insulation. The internal diameter of the insulation coating was approximately 2.13 m (7 ft.). Blue chemiluminescence was observed to appear in the large open gas space. The surfaces exposed in the large open container were negligible to catalyze any of the reactions. The residence time for the gas phase reactions in the open container was approximately 1.3 seconds. The emissions source tests were carried out by an independent contractor. These measurements confirmed the previous test results as illustrated in Table 3. In the relatively long residence time of approximately 1.3 seconds, the NH3 break was exhausted down to about 2 ppm, while the CO was exhausted down to about 50. ppm at the final temperature of approximately 760 ° C (140C ° F). In addition, particulate emissions were decreased concurrently by about 70%.

Table 3 Exhaust Gas Exhaust Gas The treated batch base line of 4000 bhp 2.8 MW Fuel of 611.5 621.07 Engine, kg / h Gas Exhaust of 292.77 315 Engine, ° F Gas Exhaust 563.33 Pretreated, ° F Final Reaction, ° F 760 Cyanuric Acid, 35.91 kg / h Flow Speed 12,974 12,970 Exhaust, dscfm 02,% 13.78 11.5 C02,% 5.15 7.0 N0X, (15% 02) ppmc 481 45.7 CO, ppm 47.0 49.2 NH3, ppm 1.8 Particles, g / dscf 0.0196 0.0061 The treated N0X levels were measured before the cooled exhaust gas was discharged to the atmosphere. The rate of introduction of the cyanuric acid was controlled to maintain a treated NOx level. This level of N0x was maintained over a range of engine loads based on both the N0x and load measurements. N0X emissions were maintained below a level of regulatory compliance using these measurements either individually or collectively. These consistent results using different reactor configurations confirm the distinctive characteristics of the N0x reduction by the gas phase autocatalytic reactions according to the present invention. Contrary to previous teachings, all of the reagents including NH3, HNCO, CO and hydrocarbon (s) can be depleted in a substantially concurrent manner in a single step treatment. Also, the autocatalytic treatment according to the present invention can substantially reduce the levels of typical contaminants in the combustion exhaust gases. The concurrent exhaustion of the reagents is clearly indicative of an autocatalytic mechanism as described by Levenspiel. The key ignition condition for self-sustained autocatalytic reactions is visually supported by the appearance of a substantially uniform chemiluminescence. Contrary to previous teachings, such autocatalytic reaction conditions in the presence of O2 in excess do not necessarily oxidize NH3 or HNCO to form N0x. The experimental results produced by the Applicants indicate that NH3, HNCO or a combination thereof may be effective for the reduction of autocatalytic N0x according to the present invention when the hydrocarbon (s) self-ignite and heat a gas exhaust autothermally under poor fuel conditions where the exhaust gas contains at least about 1% of 0. Under such conditions, reagents including N0X, NH3, HNCO, CO, hydrocarbon (s) and other typical exhaust contaminants, can be reduced in a substantially concurrent manner. This concurrent conversion of the reactants is in conflict with the previous teachings for the reduction of non-catalytic NOx. According to these teachings, the oxidation of CO is limited by the inhibitory effects of NH3 or HNCO. This limited conversion of reagents is previously described as producing air pollutants unless hydrogen is used as the auxiliary reducing material to lower the effective temperature to selectively reduce NOx, etc. According to the present invention, both NH3 and CO can be depleted together when autocatalytic reactions are self-sustained at a final temperature in the range of about 760-843.33 ° C (1400-1550 ° F). Unexpectedly, the NH3 can be depleted down to even 2 ppm concurrently with the removal of the CO below about 50 ppm. The concurrent removal of NH3 and CO is illustrated in Figure 4 and is unique to the autocatalytic reaction method. Based on this characteristic relationship, CO measurements can be used to reliably indicate the level of NH3 breakdown, and in certain preferred embodiments a CO measurement is used in an industrial process to determine if the NH3 breakdown is occurring and / or is exceeding a predetermined level. Higher final temperatures in the range of 760-843.33 ° C (1400-1550 ° F) primarily deplete reagents autocatalytically in a shorter residence time when the exhaust gas is preheated above approximately 482.22 ° C (900 ° F). ). A maximum residence time of approximately 1.5 seconds is decreased below approximately 1.0 seconds by preheating the exhaust gas above approximately 565.55 ° C (1050 ° F). Also, the residence time is decreased below approximately 0.5 seconds by preheating the exhaust gas above approximately 648.89 ° C (1200 ° F). The autocatalytic reactions described here, unexpectedly, can be effective in reducing the selectivity of N0X when the exhaust gas is heated autothermally to the temperature range of approximately 760-843.33 ° C (1400-1550 ° F). This range of final temperatures is not highly dependent on the "amount of hydrocarbon (s) introduced to auto-ignite and heat the exhaust gas autothermally." This is in conflict with previous teachings, where the largest quantities of auxiliary reducing materials are additives to decrease the effective temperature for the reduction of NOx by NH3 and HNCO In accordance with the present invention, N0X emissions are reduced approximately 80-90% to approximately 50-200 ppm using NH3 and HNCO almost stoichiometrically. In addition, N0X emissions can be reduced by as much as 99% to levels as low as approximately 10 ppm by using no more than about twice the stoichiometric ratio of NH3 and HNCO to N0X. The NOx emissions can be selectively reduced using a molar ratio of NH3 and HNCO together with respect to the N0x in the range of about 0.5-2.0. Contrary to the previous teachings, cyanuric acid, urea and NH3 can be used in a substantially exchangeable manner to reduce NOx autocatalytically. When the hydrocarbon (s) self-ignite and heat the exhaust gas autothermally at temperatures in the range of approximately 760-843.33 ° C (1400-1550 ° F), the reducer (s) that generates (n) ) NH3, HNCO or a combination thereof, can be effective to reduce NOx to a low level according to the present invention. The uniform distribution of NOx, hydrocarbon (s) and reducer (s) is preferred to maintain poor fuel conditions for auto-ignition, autothermal heating and selective N0X reduction. Contrary to the previous teachings, stratified fuel blends or other methods or escalation of fuel-rich combustion do not benefit the selective N0X reduction.

These previous teachings appear to adversely extinguish the conversion of the reactants, which tends to lead to the production of other air pollutants in addition to reducing the selectivity of the N0X reduction compared to the new single-stage autocatalytic methods described herein. As illustrated in Figure 7, the autocatalytic methods according to the present invention can be implemented in a single step. The hydrocarbon (s), reducer (s) and exhaust gas can be mixed together for auto-ignition, thermal heating and selective N0X reduction. Preferably, the exhaust gas should contain about 2-18% of 02 at a temperature in the range of about 482.22-871.11 ° C (900-1600 ° F) for spontaneous ignition and autothermal heating to exhaust the substantially generated reagents. The sinuous arrows in Figure 7 depict the mixing or other dispersion of the reagents to maintain poor fuel conditions where the exhaust gas contains at least about 1% of 02. Mixing of the exhaust gas may begin before or after the introduction of the hydrocarbon (s) and the reductant (s), and the mixing can be extended through a portion, or even all, of the autothermal heating. The baffles or stirring blades can modify the flow path of the exhaust gas to be mixed with the reactants. One or more spray nozzles may disperse the hydrocarbons and reducing agent (s) substantially through the cross section of the exhaust gas flow path. Preferably, mixing, dispersion or a combination thereof should establish a substantially uniform exhaust gas composition prior to the appearance of a chemiluminescence. According to the present invention, the reductant (s) may comprise material (s) selected from the group consisting of NH 3, HNCO, urea, urea decomposition products, cyanuric acid or a tauromer of cyanuric acid, compounds which are decomposed to produce NH3 as a by-product, ammonium salts of organic acids, hydrocarbon amines or combinations of the above, either pure compounds or mixtures, such as solids, liquid melts, emulsions, suspensions or solutions in water, alcohols , hydrocarbons or oxygenated hydrocarbon solvents. In general, only the selectivity of the reduction of N0X and the conversion of N0X to N20 significantly depends on the chemical reductant (s). Although the reduction of N0X by NH3 generates less byproduct N20 emissions, the HNCO removes N0X more selectively. In any case, preferably a molar ratio of NH3 and HNCO together in the range of about 0.5-2.0 with respect to N0X can be used for the effective reduction of NOx as much as 99% at levels in the range of about 10-200 ppm . The introduction of the reductant (s) is preferably controlled to maintain a level of N0X reduction or a level of final NOx emissions in the treated exhaust gas. In certain preferred embodiments, continuous measurements of N0X emissions are used to increase or decrease the introduction of the reducer (s) as a part of a feedback control system to maintain a final NOx emission level ( set to a predetermined, desired level, for example). Alternatively, testing of the source of NOx emissions can establish characteristic relationships between the operating conditions for the combustion equipment and the introduction of the reducer (s) necessary for a desired level of N0X reduction. Based on these relationships, the continuous verification of the operating conditions can be used to control the advance of the feed of the reduction of the N0X emissions. As well, feedback control and feed advance combinations can reliably maintain final N0X emission levels despite variations in the exhaust gas flow velocity and N0X levels of the baseline during air operations. combustion. The hydrocarbon (s) used in accordance with the embodiments of the present invention may comprise material (s) selected from the group consisting of mixtures of hydrocarbons such as natural gas, liquefied petroleum gas, alcohols, gasoline, diesel fuel, aviation turbine fuel, various oxygenated hydrocarbons, hydrocarbon amines or any fraction of such mixtures, including purified components such as carbon monoxide, methane, propane, methanol and ethanol, introduced either as liquids or vapors. In addition, the hydrocarbon (s) may include the same liquid, gaseous or vapor phase fuels that are burned to produce the exhaust gas containing N0X. The autocatalytic methods according to the present invention generally do not depend on the order in which the reductant (s) and the hydrocarbon (s) are introduced into the exhaust gas. Within the temperature range of approximately 482.22-871.11 ° C (900-1600 ° F), the introduced hydrocarbon (s) self-ignite under poor fuel conditions of approximately 2-18% of 02 in the exhaust gas. NH3, HNCO or a combination thereof may be introduced or generated from the reductant (s) at any time or during the fuel-poor auto-thermal conversion of the hydrocarbon (s) and CO in the exhaust gas. Self-sustaining reactions in the gaseous phase as used here tend not to be adversely affected by other exhaust gas contaminants, including gaseous organic substances, particulate matter or CO. Indeed, such autothermic reactions can serve to remove at least partially these typical exhaust contaminants. This conversion of contaminants can reduce unwanted emissions which decreases the amount of hydrocarbon (s) required to maintain a final temperature for CO depletion and NH3 breakdown substantially in a concurrent manner. In preferred embodiments, the introduction of hydrocarbon (s) is controlled to maintain a final temperature in the range of about 760-843.33 ° C (1400-1550 ° F). The release of autothermal heat increases the temperature of the exhaust gas adiabatically in the absence of heat losses, or in alternative modes the surfaces for the heat transfer can recover the heat of the exhaust gas during the autothermal heating. In general, heat recovery must not cool the exhaust gas so excessively that it extinguishes the autothermal reactions before the complement of the NOx removal and the CO depletion and the NH3 breakdown. An autothermal heat release at an adiabatic temperature increase in the range of 10-26 ° C (50-500 ° F) is used in the preferred embodiments to achieve a fine exhaust gas temperature in the range of about 760 ° C. 843.33 ° C (1400-1550 ° F) to implement such autocatalytic methods. The amount of the introduced hydrocarbon (s) depends mainly on the temperature of the initial exhaust gas and any recovery of the heat released by the autothermal reactions. Autocatalytic methods according to the preferred embodiments typically require residence times not greater than about 1.5 seconds. In general, CO and NH3 are depleted faster when autothermal heating is initiated at higher temperatures in the range of approximately 565.55-871.11 ° C (1050-1600 ° F). With such modalities, the residence times of the reaction in the range of about 0.02-1.0 seconds may be sufficient to deplete both the CO and NH3 substantially. The initial higher exhaust gas temperatures in the range of approximately 648.88-871.11 (1200-1600 ° F) make possible the depletion of CO and substantial NH3 within the range of about 0.02-0.5 seconds. The introduction of hydrocarbon (s) decreases beneficially when the exhaust gas is preheated to the temperature ranges of approximately 565.55-871.11 (1050-1600 ° F) or approximately 648.88-871.11 ° C (1200-1600 ° F). In these cases, the release of the autothermal heat does not need to exceed an amount equivalent to an adiabatic increase of approximately 10-176.66 ° C (50-350 ° F) or 10-93.33 ° C (50-200 ° F), respectively, since that the exhaust gas is heated autothermally to a final temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F). This preheating of the exhaust gas also improves the selectivity of the NOx reduction. In general, the temperatures of the initial exhaust gas do not depend on how the exhaust gas is preheated or cooled since the concentration of the 02 is maintained in the range of about 2-18% by volume. The exhaust gas can be heated or cooled initially using heat transfer surfaces, including any of several methods for preheating the exhaust gas by recovering the heat after the exhaust gas is treated using the autocatalytic methods as provided. here. Alternatively, the exhaust gas can be heated directly by the combustion of a supplementary fuel in the exhaust gas. The combustion of a supplementary fuel using excess air also serves to enrich the 02 concentration in an otherwise deficient 02 exhaust gas. In this case, the combustion of the supplementary fuel can serve the dual purpose of preheating the escape and enrich its concentration of 02. The combustion of a supplementary fuel can also serve to preheat a portion of the exhaust gas to ignite more supplementary fuel which is burned directly into the exhaust gas. If the exhaust gas is pretreated using a fuel-rich combustion, the autocatalytic methods as provided herein can partially remove the additional contaminants from the fuel-rich combustion. The autocatalytic methods according to the present invention can be used in combination with various modifications to the combustion process, to produce the exhaust gas. Such modifications can beneficially decrease the N0x emissions and maintain the exhaust gas temperatures within the range of approximately 482.22-871.11 ° C (900-1600 ° F), or preferably approximately 648.88-871.11 ° C. (1200-1600 ° F), for autocatalytic methods as provided herein, since the concentration of 02 remains above about 2% by volume. Such modifications may also beneficially decrease the introduction of both the reductant (s) and the hydrocarbon (s) in such autocatalytic methods. Autocatalytic methods such as those illustrated in Figure 7 are implemented in alternative embodiments using any of several techniques to incorporate after-treatment of the exhaust gas with the combustion equipment as illustrated in Figures 8 and 9. Autocatalytic methods in accordance with The present invention can also be implemented in conjunction with the primary combustion process so that the release of autothermal heat is beneficially recovered as illustrated in Figure 9. For example, new or existing surfaces in a heat ange boiler are used in certain embodiments to also recover the release of autothermal heat produced with autocatalytic methods as provided here to replace the primary fuel, and may be used, for example, for the purpose of generating steam and / or electricity, or for fractionating substances petrochemicals, or heating to autothermal can serve to increase the capacity of generation of an existing boiler, etc., as illustrated. In such modalities, mechanical work is carried out, petrochemical substances are fractionated or otherwise processed, steam and / or electricity are generated, steam recovered, etc., which can be carried out under conditions that in general are optimized for the primary process. The use of the autocataiitic methods according to the present invention effectively make possible the reduction of the N0X that is to be dissociated from the primary process, and by means of this make it possible for the primary process to be carried out in a more optimal manner. . Combustion modifications such as overburning air can be used to make possible lower N0X emissions from the primary fuel while 02 is also enriched in the exhaust gas. In the case of boilers that burn coal, the replacement of the primary fuel by the autothermal heating can serve to increase the 02 levels of the furnace beneficially with the purpose of reducing the unburned coal on the fly ash. Such benefits of the autocatalytic methods as provided herein, can serve to increase the overall efficiency of the boiler, while also improving the value of the fly ash byproduct, possibly avoiding the generation of an otherwise solid waste. The ato-catalytic methods according to the present invention can also beneficially consume the NH3 breakage of a previous exhaust gas treatment using the SNCR. In such embodiments, autocatalytic methods can replace the use of SCR as a means to control NH3 cleavage from SNCR. Autocatalytic methods, however, can be preferentially applied in place of SNCR to reduce N0X more selectively. The best selectivity of autocatalytic methods as provided herein, can greatly reduce the consumption and cost of the reducer (s), while exhausting both the CO and NH3 in a substantially common manner, and reducing emissions from N0X to lower levels. Autocatalytic methods according to the present invention can reduce N0X emissions below most regulatory requirements, and the present invention typically supersedes the need for costly catalysts together. The autocatalytic activity for removing NH3 and CO in the presence of NOx in accordance with the present invention can be self-sustained and in a manner that does not deteriorate with the use of similar solid catalysts. As a result, the autocataitic methods that are provided here can avoid the need to replace the existing catalysts poisoned by the exhaust pollutants. If emission regulations require additional NOx reductions, then autocatalytic methods as provided herein can serve to improve SCR applications while minimizing catalyst volume. In addition to reducing NOx before SCR, autocatalytic methods can also decrease contaminants such as hydrocarbons and soot which can foul catalytic surfaces. In the modalities using such a combination of treatments, autocatalytic methods can make possible the use of more efficient or effective catalyst beds in terms of the cost due both to the removal of contaminants and to the control of exhaust gas temperatures. In a preferred combination of the autocatalytic and catalytic reduction methods, the autothermal heating continuously decreases the soot and hydrocarbon contaminants while controlling the temperature of the exhaust gas with respect to the catalyst. NOx emissions are maintained at the required level using a separate injection of NOx beyond the catalyst to minimize the reductant (s) used with the autocatalytic method. In many such situations, the reduction of the autocatalytic N0X need not exceed approximately 80-90%, so that the reductant (s) are converted almost stoichiometrically and the CO emissions are substantially depleted in the shortest possible time. The substantial depletion of both NH and CO makes possible in a unique way the autocatalytic reduction of non-uniform NOx and CO distributions. Similar to catalytic methods, autocatalytic methods can remove excess NH3 while reducing NOx at low levels. As a result, the non-uniform distributions of the N0X in the exhaust gases tend to only decrease the selectivity of the N0X reduction by the autocatalytic methods. By reducing both N0X and NH3 to uniformly low levels, autocatalytic methods can replace the need for exhaust gas mixing, especially when such autocatalytic methods are combined with the SCR to achieve ultra-low emission levels. The autocatalytic methods, as provided herein, are uniquely suited for combination with the elements of the catalytic air heater. Such catalytic elements replace existing heat transfer surfaces in rotary regenerative air heaters, such as those described in U.S. Pat. Nos. 4,602,673, 4,678,643, 4,719,094 and 4,867,953. Using autocatalytic methods to control temperature as well as uniform N0X levels beyond the catalyst, it greatly improves the ability to remove both N0X and NH3 within the limited volume for installation of catalytic elements in existing air heaters. In the modes of the heat exchange boiler, the replacement of the elements of the air heater can also improve the recovery of the heat released with autocatalytic methods. The increase in exhaust gas temperatures improves heat recovery by all existing surfaces downstream of the heat release, but this improvement does not generally recover the full release of the autothermal heat. Full recovery of the autothermal heat release usually requires the installation of some new heat transfer surfaces. The replacement of the air heating elements with improved surfaces can be conveniently used to complement the recovery of the autothermal heat release. This replacement of the air heating elements can uniquely complement the recovery of the autothermal heat release while catalytic surfaces are also provided to achieve ultra low levels of both NOx and NH3. In certain modalities, such modifications can still make improvements to the efficiency of the boiler possible by reducing the temperatures of the flue gas. The efficiency of the boiler can be further improved when implementing catalytic methods in combination with combustion modifications to reduce the unburnt carbon on the fly ash.

In such diverse applications, autocatalytic methods such as those provided herein are implemented by controlling the final temperature of the autothermal heating at a level in the range of about 760-843.33 ° C (1400-1550 ° F). This controlled condition is preferably achieved by using one or more injection nozzles for the introduction of hydrocarbon (s) and reducing agent (s). Such nozzles may inject the hydrocarbon (s) and the reductant (s) separately or concurrently, as mixtures, solutions, emulsions, suspensions or combined chemical structures, using combinations of solids, liquids, and gases. In addition, the introduction of hydrocarbon (s) and reductant (s) may involve the use of pressurized gas to transport or atomize the injected material (s). The pressurized gas may consist of steam, air, exhaust gas or gaseous or vapor forms of hydrocarbon (s) or reductant (s). When compressed air is used to transport or atomize any of the injected material (s), the compressed air can beneficially enrich the 02 concentration in the exhaust gas. In certain embodiments, one or more injection nozzles are distributed in various ways since the distribution of the hydrocarbon (s) and the reducing agent (s) in the exhaust gas is sufficiently uniform to prevent localized heating beyond the temperature range of approximately 760-843.33 ° C (1400-1550 ° F). The distribution and mixing of the injected material (s) may include various uses of vanes or screens for the exhaust gas to swirl or to generate turbulent mixing eddies. Such methods or combinations thereof must disperse the injected hydrocarbon (s) in a substantially uniform manner before the appearance of a chemiluminescence. The location of such agitation screens or blades before or after the injection locations can make possible the continuous mixing of the exhaust gas through a portion, or even the whole, of the flow path during the autothermal heating. Any such modifications to the flow path preferably extend over its entire cross-section. The use of such methods for the mixing of the exhaust gas can also make possible the introduction of the hydrocarbon (s) and the reductant (s) using a variety of convenient nozzle configurations such as wall nozzles or injection grilles. In certain embodiments, the use of injection grids can avoid the need to modify the gas flow path. In such embodiments, a multiplicity of nozzles are preferably used to distribute the hydrocarbon (s) and reducer (s) over the cross section of the gas flow path. Such injection grids can be likened to the well-known practice of NH3 distribution pre-weighted ahead of the solid catalysts in the SCR methods. Alternatively, the injection grids may consist of liquid nozzles that use either the pressure or the atomization of the gas. When the hydrocarbon (s) or reductant (s) are introduced as liquids, the preferred atomization depends on the degree of mixing of the exhaust gas. In certain embodiments, no atomization is necessary if the exhaust gas is well mixed by turbulent flow conditions. For example, the autocatalytic methods according to the present invention can be implemented in conduits as large as C.9144 meters (three feet) or more in diameter using only a single injector when the exhaust gas is swirled sufficiently to mix the vaporized hydrocarbon (s) and the reducer (s). The drops atomized in the range of approximately 20-500 microns, however, they are preferred in the modalities where the mixing depends mainly on the dispersion. The hydrocarbon (s) and the reductant (s) are preferably introduced in their most concentrated form. By using mixtures or concentrated solutions, the hydraulic load losses due to the latent and sensible heats of the carrier liquids or gases tend to be minimized. The dilution of the injected material (s), however, can improve its dispersion in some cases. For example, aqueous solutions of urea may require dilution to provide a multiplicity of nozzles needed for adequate dispersion or to decrease the size of the remaining reducing particles after evaporation of the water from the atomized droplets. In such embodiments, commercial aqueous solutions containing about 50% by weight of urea are diluted down to a concentration of 35% which is typically used to prevent crystallization in storage tanks and other distribution equipment.

The distribution of the hydrocarbon (s) or reducer (s) to the injectors should prevent the degradation of the material (s) prior to injection. Such degradation can lead to plugging of the distribution networks or orifices of the nozzle. Although heating or vaporization of some material (s) can improve its injection without degradation, other material (s) may require a means to prevent such heating or vaporization. In embodiments where the latter could occur, the atomization gas can also serve as a cooling medium or insulating boundary to prevent degradation prior to injection. Chemical additives can also help prevent the formation of scale or plugging in distribution networks prior to the injection of the hydrocarbon (s) or reducer (s). Such chemical additives may comprise any of the formulations commercially available for this purpose. The use of distilled or deionized water for aqueous solutions can prevent the formation of scale in storage tanks, pipes or other equipment or instrumentation used to pressurize, dose, transport, distribute and inject the chemical reducer (s) ( s) such as NH3 or urea. In addition, slag and corrosion formation are minimized by selecting the appropriate construction materials through all of these systems, depending on the injected material (s). What can be understood from the above is as follows. According to the present invention, a wide variety of methods to reduce the N0X of industrial exhaust gases are provided, which may comprise the autothermal heating of the exhaust gas using one or more hydrocarbons in the presence of NH3, HNCO or a combination thereof, wherein the autothermal heating is under effective conditions to selectively reduce the N0X autocatalytically. Such methods may consist of the steps of: controlling the temperature and initial composition of an exhaust gas in the ranges of approximately 482.22-871.11 ° C (900-1600 ° F) and approximately 2-18% of 02, respectively, effective for the self-ignition of hydrocarbon (s); control the introduction of the hydrocarbon (s) to self-ignite and release heat autonomously, effective to self-sustain autocatalytic reactions under poor fuel conditions where the exhaust gas contains at least about 1% of 02 and is heated to a final temperature in the range of about 760-843.33 ° C (1400-1550 ° F); introducing the NOx reductant (s) into the exhaust gas where the NH3, the HNCO or a combination thereof are generated from the reductant (s); wherein the NOx is selectively reduced, and the NH3, the HNCO and the hydrocarbon (s), including the byproduct CO, are substantially depleted. As will be appreciated from the foregoing description, other methods according to the present invention include the following. A method for auto-thermally heating the exhaust gases using hydrocarbon (s) so that NH3, HNCO or a combination thereof is effective to selectively reduce NOx autocatalytically. A method for auto-thermally heating the exhaust gases to temperatures in the range of approximately 760-843.33 ° C (1400-1550 ° F) using hydrocarbon (s) to remove the CO so that the NH3, the HNCO or a combination of the They are effective concurrently to selectively reduce NOx autocatalytically. A method that includes the steps of: controlling the initial temperature and composition of an exhaust gas, effective for the self-ignition of the hydrocarbon (s); control the introduction of hydrocarbon (s) to auto-ignite and release the effective heat autothermally to self-sustain the autocatalytic reactions under poor fuel conditions, where the exhaust gas contains at least about 1% oxygen; introducing the reducer (s) for the N0X into the exhaust gas where the NH3, the HNCO or a combination thereof are generated from the reductant (s); wherein the N0X is selectively reduced, and the NH3, the HNCO and the hydrocarbon (s), including the byproduct CO, are substantially depleted. Other methods according to the present invention include the following. A method to heat the exhaust gases using the hydrocarbon (s), so that the NH3, the HNCO or a combination of them are effective to selectively reduce the nitrogen oxides A method to selectively reduce the oxides of nitrogen in an exhaust gas using NH3, HNCO or a combination thereof while the hydrocarbon (s) self-ignite and heat the exhaust gas autothermally.A method to selectively reduce oxides of nitrogen in a gas exhaust gas using NH3, HNCO or a combination thereof while the hydrocarbon (s) auto-ignite and heat the exhaust gas autothermally, substantially depleting the residual concentrations of the unburned hydrocarbons, the CO, the HNCO and NH3 - A method for selectively reducing oxides of nitrogen in an exhaust gas by using NH3, HNCO or a combination thereof s that the hydrocarbon (s) auto-ignite and heat the exhaust gas autothermally at a temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F). A method for selectively reducing oxides of nitrogen in an exhaust gas by using NH3, HNCO or a combination thereof, while the hydrocarbon (s) auto-ignite and heat the exhaust gas autothermally at a temperature in the exhaust gas. range of approximately 760-843.33 ° C (1400-1550 ° F), substantially depleting the residual concentrations of unburned hydrocarbons, CO, HNCO and NH3. A method for automating the exhaust gases using the hydrocarbon (s) so that the NH3, the HNCO or a combination thereof are effective in selectively reducing oxides of nitrogen while the residual concentrations of the hydrocarbons are not burned, the CO, the HNCO and the NH3 are substantially depleted. Still other methods according to the present invention include the following. A method for automatically heating exhaust gases to a temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F) using hydrocarbon (s) so that NH3, HNCO or a combination thereof is effective to selectively reduce oxides of nitrogen. A method for automatically heating the exhaust gases to a temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F) using the hydrocarbon (s) so that the NH3, the HNCO or a combination of they are effective in selectively reducing nitrogen oxides while the residual concentrations of unburned hydrocarbons, CO, HNCO and NH3 are substantially depleted. A method for the self-ignition of the hydrocarbon (s) in the exhaust gases so that the NH3, the HNCO or a combination thereof is effective to selectively reduce the nitrogen oxides while the exhaust gas is heated autothermally. A method for the self-ignition of the hydrocarbon (s) in the exhaust gases so that the NH3, the HNCO or a combination thereof is effective to selectively reduce the nitrogen oxides while the exhaust gas is heated autothermally to exhaust substantially the residual concentrations of unburned hydrocarbons, CO, HNCO and NH3. A method for the self-ignition of the hydrocarbon (s) in the exhaust gases so that the NH3, the HNCO or a combination thereof is effective to selectively reduce the nitrogen oxides while the exhaust gas is heated autothermally at a temperature in the range of about 760-843.33 ° C (1400-1550 ° F). Still other methods according to the present invention include the following. A method of self-ignition of the hydrocarbon (s) in the exhaust gases so that the NH3, the HNCO or a combination thereof are effective to selectively reduce nitrogen oxides while the exhaust gas is heated autothermally at a temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F), substantially depleting the residual concentrations of unburned hydrocarbons, CO, HNCO and NH3. A method of generating the NH3, the HNCO or a combination thereof from the chemical reductant (s) so that the nitrogen oxides in an exhaust gas are selectively reduced while the exhaust gas is reduced. heated autothermally by the hydrocarbon (s). A method of generating the NH3, the HNCO or a combination thereof from the chemical reductant (s) so that the nitrogen oxides in an exhaust gas are selectively reduced while the gas in the exhaust gas is reduced selectively. The exhaust is heated autothermally by the hydrocarbon (s) to substantially deplete the residual concentrations of the unburned hydrocarbons, CO, HNCO and NH3. A method of generating NH3, HNCO or a combination thereof from chemical reductant (s) so that the nitrogen oxides in an exhaust gas are selectively reduced while the exhaust gas is heated autonomously by the hydrocarbon (s) at a temperature in the range of about 760-843.33 ° C (1400-1550 ° F). A method of generating the NH3, HNCO or a combination thereof from the chemical reductant (s) so that the nitrogen oxides in an exhaust gas are selectively reduced while the exhaust gas is heated autothermally by the hydrocarbon (s) at a temperature in the range of about 760-843.33 ° C (1400-1550 ° F), substantially depleting the residual concentrations of the unburned hydrocarbons, the CO, the HNCO and and NH3. Still other methods according to the present invention include the following. A method for concurrent removal of nitrogen oxides and carbon monoxide from an exhaust gas using NH3, HNCO or a combination thereof while the hydrocarbon (s) self-ignite and heat the exhaust gas autothermally. A method for concurrent removal of the nitrogen oxides and carbon monoxide from an exhaust gas using NH3, HNCO or a combination thereof while the hydrocarbon (s) auto-ignite and heat the exhaust gas autothermally, exhausting substantially the residual concentrations of unburned hydrocarbons, HNCO and NH3. A method for concurrent removal of nitrogen oxides and carbon monoxide from an exhaust gas using NH3, HNCO or a combination thereof while the hydrocarbon (s) self-ignite and heat the exhaust gas autothermally at a temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F). A method for concurrent removal of nitrogen oxides and carbon monoxide from an exhaust gas using NH3, HNCO or a combination thereof while the hydrocarbon (s) self-ignite and heat the exhaust gas autothermally at a temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F), substantially depleting the residual concentrations of unburned hydrocarbons, HNCO and NH3. A method to treat an exhaust gas to remove the oxides of nitrogen in the company of carbon monoxide and other combustible pollutants using NH3, HNCO or a combination thereof while the hydrocarbon (s) self-ignite and heat the gas. escape autothermally. A method to treat an exhaust gas to remove the oxides of nitrogen in the company of carbon monoxide and other combustible pollutants using NH3, HNCO or a combination thereof while the hydrocarbon (s) self-ignite and heat the gas escape autothermally, 'substantially depleting the residual concentrations of HNCO and NH3. A method to treat an exhaust gas to remove the oxides of nitrogen in the company of carbon monoxide and other combustible pollutants using NH3, HNCO or a combination thereof while the (ios) hydrocarbons (s) self-ignite and heat the gas of leak autothermically at a temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F). Other methods according to the present invention include the following. A method to treat an exhaust gas to remove the oxides of nitrogen in the company of carbon monoxide and other combustible pollutants using NH3, HNCO or a combination thereof while the hydrocarbon (s) self-ignite and heat the gas. exhaust autothermically at a temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F), substantially depleting the residual concentrations of HNCO and NH3. A method for the treatment of an exhaust gas to remove unburned hydrocarbons, CO and other combustible pollutants using hydrocarbon (s) to auto-ignite and heat the exhaust gas autothermally so that the NH3, the HNCO or a combination of the They are also effective in selectively reducing the nitrogen oxides in the exhaust gas. A method for the treatment of an exhaust gas to remove unburned hydrocarbons, CO and other combustible contaminants while concurrently exhausting the residual HNCO and NH3 using hydrocarbon (s) to auto-ignite and heat the exhaust gas autothermally so that the NH3, the HNCO or a combination thereof are also effective in selectively reducing the nitrogen oxides in the exhaust gas. A method for the treatment of an exhaust gas to remove unburned hydrocarbons, CO and other combustible pollutants using hydrocarbon (s) to auto-ignite and heat the exhaust gas autothermally at a temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F) so that NH3, HNCO or a combination thereof are also effective in selectively reducing nitrogen oxides in the exhaust gas. A method for the treatment of an exhaust gas to remove unburned hydrocarbons, CO and other combustible contaminants while concurrently exhausting the residual HNCO and NH3 using hydrocarbon (s) to auto-ignite and heat the exhaust gas autothermally to a temperature in the range of about 760-843.33 ° C (1400-1550 ° F) so that NH3, HNCO or a combination thereof are also effective in selectively reducing the nitrogen oxides in the exhaust gas. A method that includes the steps of: introducing reducer (s) for the nitrogen oxides in the exhaust gas so that the reductant (s) generate NH3, HNCO or a combination thereof; introducing the hydrocarbon (s) into an exhaust gas containing about 2-18% oxygen at a temperature in the range of about 482.22-871.11 ° C (900-1600 ° F) so that the hydrocarbon (s) self-ignite in the exhaust gas; wherein the nitrogen oxides are selectively reduced while the exhaust gas is heated autothermally by self-sustained autocatalytic reactions. As can also be understood from the foregoing, according to the embodiments of the present invention: the N0X in the exhaust gas can be reduced almost stoichiometrically by as much as 80-90%; the N0X in the exhaust gas can be selectively reduced as much as about 99%; the N0X in the exhaust gas can be reduced to a level in the range of about 10-200 ppm; and NH3 and HNCO together may be in the range of about 0.5-2.0 or 0.5-4.0 of the molar to N0X ratio in the exhaust gas. The highest molar ratios of NH3 and HNCO together to approximately 4.0 (eg, from 0.5 to 4.0, C.75 to 4.0, from 0.75 to 3.5, approximately 3.0, approximately 3.5, approximately 4.0, etc.) with respect to NOx, they can generally increase the N0X reduction without appreciably increasing NH3 cleavage using the autocatalytic methods according to the present invention, but the cost effectiveness of such higher molar ratio modalities decrease when NH3 and HNCO, etc. ., are used at levels in excess of twice the stoichiometric ratio with respect to the NOx levels of the baseline. Additionally: the selective NOx reduction and the depletion of the residual NH3 and the HNCO can contribute to the heating of the exhaust gas; the oxidation of combustible pollutants in the exhaust gas can contribute to the heating of the exhaust gas; the temperature of the exhaust gas may initially be in the range of about 482.22-871.11 ° C (900-1600 ° F) and the exhaust gas may initially contain 02 in the range of about 2-18%, the release of autothermal heat can be initiated by self-ignition of the hydrocarbon (s) in the exhaust gas; the exhaust gas can be substantially uniformly heated by the self-ignition of the hydrocarbon (s) and the self-sustained heat release of autocatalytic reactions; autocatalytic reactions can be self-sustained in the auto-heated exhaust gas even when a portion of the heat released is recovered by the surfaces for heat transfer, the heat release can be equivalent to a uniform adiabatic increase of approximately 10-260 ° C (50-500 ° F) at the temperature of the exhaust gas; The exhaust gas can be heated within approximately 0.02-1.5 seconds to a final temperature; the exhaust gas can be heated to a final temperature in the range of about 760-843.33 ° C (1400-1550 ° F), the exhaust gas can contain at least about 1% of 02 at a final temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F); the residual concentrations of hydrocarbons, CO, NH3 and HNCO can be substantially depleted at a final temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F); the CO can be oxidized below a residual concentration of approximately 2000 ppm; the CO can be oxidized below a residual concentration of approximately 500 ppm; the residual concentration of CO can be maintained at a level below about 500 ppm by controlling the temperature of the final exhaust gas to be in the range of approximately 760-843.33 ° C (1400-1550 ° F); and the residual concentration of NH3 can be maintained at a level below about 20 ppm by controlling the temperature of the final exhaust gas in the range of about 760-843.33 ° C (1400-1550 ° F), or by controlling and / or verifying the CO level. Additionally: residual concentrations of CO and NH3 can be decarbonized together in the exhaust gas at a final temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F); the final temperature can be controlled in the range of about 760-843.33 ° C (1400-1550 ° F) to maintain the residual CO concentration below about 50 ppm while the residual NH3 is depleted below about 2 ppm; the hydrocarbon (s) may consist of material (s) selected from the group consisting of mixtures of hydrocarbon (s) such as natural gas, liquefied petroleum gas, alcohols, gasoline, fuel diesel, aviation turbine fuel, various oxygenated hydrocarbons, hydrocarbon amines, or any fraction of such mixtures, including purified components such as carbon monoxide, methane, propane, methanol, and ethanol, either as liquids or vapors; the hydrocarbon (s) may consist of the same material (s) as the liquid, gaseous, or vapor phase fuel used to produce or otherwise heat the exhaust gas initially in the range of temperature of approximately 482.22-871.11 ° C (900-1600 ° F); the hydrocarbon (s) can be introduced into the exhaust gas substantially throughout the cross section or around a perimeter of the exhaust gas flow path using one or more nozzles, including a multiplicity thereof; the hydrocarbon (s) can be introduced as liquid droplets with diameters in the range of about 20-500 microns; the hydrocarbon (s) can be introduced into the exhaust gas using a carrier or atomization gas such as steam, compressed air, pressurized exhaust gas, gaseous hydrocarbon (s) or vapor phase or any other compositions of NH3 gas or vapor phase; the hydrocarbon (s) and any atomizing carrier or gas can be distributed to an array of one or more nozzles, including a multiplicity thereof, and the hydrocarbon (s) and any atomizing carrier or gas they can be distributed in ways that prevent the formation of carbon or that improve the uniformity of self-ignition and autothermal heating. Additionally: the hydrocarbon (s) and any atomizing carrier or gas can be pressurized and / or dosed; a final temperature can be measured at one or more locations throughout the cross section of the exhaust gas flow path and the amount of the introduced hydrocarbon (s) can be controlled to maintain the (s) temperature (s) measured (s) at a level in the range of approximately 760-843.33 ° C (1400-1550 ° F); the final CO concentration can be measured at one or more places across the entire cross section of the exhaust gas flow path downstream of the temperature measurement (s); the final CO measurement (s) can be used to verify a level of CO depletion corresponding to the final temperature (s) to control the introduction of the hydrocarbon (s); NH3, HNCO or a combination thereof can be introduced into the exhaust gas; NH3, HNCO or a combination thereof may be generated by the evaporation, decomposition or catalytic conversion of the reductant (s) which may consist of the selected material (s) from the group consisting of NH3, HNCO, cyanuric acid or a tautomer of cyanuric acid, urea, the decomposition products of urea, the compounds which decompose to produce NH3 as a by-product, the ammonium salts of the acids organic, hydrocarbon amines, or combinations of the above, either as pure compounds or as mixtures, as solids, liquid molten substances, emulsions, suspensions, or solutions in water, alcohols, hydrocarbons, or oxygenated hydrocarbon solvents; NH3, HNCO or a combination thereof - may be generated prior to the introduction of the hydrocarbon (s); and NH3, HNCO or a combination thereof can be generated after the introduction of the hydrocarbon (s); the NH3 the HNCO a combination thereof may be generated concurrently with the hydrocarbon (s). Additionally: the reducer (s) can be injected directly to vaporize or decompose in the exhaust gas; the reducer (s) can be injected prior to the introduction of the hydrocarbon (s); the reducer (s) can be injected after the introduction of the hydrocarbon (s); the reducer (s) may be injected concurrently with the hydrocarbon (s) introduced as mixtures, solutions, emulsions, suspensions, atomization gases, atomized liquids or combined chemical structures; the reducer (s) may be injected substantially throughout the cross section or around a perimeter of the exhaust gas flow path using one or more nozzles, including a multiplicity thereof; the reducer (s) can be injected using a carrier or atomizing gas such as steam, compressed air, pressurized exhaust gas, gaseous (s) or vapor phase hydrocarbon (s) or any gaseous NH3 compositions or vapor phase; the reducer (s) are atomized to form liquid droplets with diameters in the range of about 20-500 microns; the reducer (s) and any atomizing carrier or gas can be distributed to an array of one or more nozzles, including a multiplicity thereof; the reducer (s) and any atomizing carrier or gas can be distributed in ways that prevent the accumulation of solid deposits and improve the consistent introduction of NH3, HNCO or a combination thereof into the exhaust gas; the reducing agent (s) may consist of a concentrated aqueous solution consisting of NH3, urea or combinations thereof in water containing dissolved nitrogen in the range of about 15-30% by weight; a concentrated aqueous solution of reductant (s) can be diluted with water, and the reductant (s), the dilution water and any atomizing carrier or gas can be pressurized and / or dosed. Additionally: the N0X levels of the baseline in the exhaust gas can be measured with respect to an operating condition of the combustion equipment that produces the exhaust gas and the amount of the reducer (s) injected to maintain a the predetermined level of NOx reduction or a predetermined final NOx level in the exhaust gas can be controlled throughout the range of operation of the combustion equipment; an operating condition of the combustion equipment can be verified to provide a basis for estimating NOx emissions from the baseline throughout the operating range of the combustion equipment, either continuously or on a periodic basis; the amount of the injected reductant (s) can be controlled to generate NH3 and HNCO together at a level in the range of about 0.5-2.0 of the molar ratio to the N0X of the baseline depending on a measurement of the operating condition for the combustion equipment; The final NOx level can be measured in one or more locations throughout the cross section of the exhaust gas flow path downstream of the autothermal heating and any temperature measurement (s) can be used to control the introduction of the ( of the) hydrocarbon (s), the final NOx levels (es) can be used to verify the effectiveness of the selective N0X reduction corresponding to an amount of the NH3 and the introduced HNCO or an amount of the ) reducer (s) injected (s) to generate the NH3, the HNCO or a combination thereof; the amount of NH3 and HNCO introduced or the amount of reducer (s) injected (s) can be controlled to maintain a predetermined final N0X level in the exhaust gas; and the amount of the NH3 and the HNCO introduced together or the amount of the injected reductant (s) can be increased or decreased depending on the need to raise or lower, respectively the final NOx level measured with respect to a desired final level of the N0X in the exhaust gas. Additionally: the dilution water and any atomization carrier or gas can be treated to prevent the formation of deposits or scale in the equilibrium chamber, the pipeline, and other equipment or instrumentation used to pressurize, dose, transport, distribute, and inject the dilution water, the carrier gas, the atomization gas, the concentrated aqueous solutions consisting of NH 3, urea, or combinations thereof, can be formulated and / or prepared in water containing dissolved nitrogen in the range of about 15%. -30% by weight; the concentrated aqueous solution can be prepared using distilled or deionized water to prevent the formation of deposits or scale in the equilibrium chambers, the pipe and other equipment or instrumentation used to pressurize, declassify, transport, distribute, and inject the reducer (is) dissolved (s) as solutions concentrated or diluted in water; the concentrated aqueous solution may contain chemical additives to prevent the formation of deposits or scale in the storage tanks, the pipeline, and other equipment or instrumentation used to pressurize, dose, transport, distribute and inject the dissolved reductant (s) as solutions concentrated or diluted in water. Additionally: the exhaust gas can be preheated or precooled to a temperature in the range of about 482.22-871.11 ° C (900-1600 ° F) before the introduction of the hydrocarbon (s); the exhaust gas can be preheated or precooled to a temperature in the range of about 565.55-871.11 ° C (1050-1600 ° F) so that the exhaust gas is heated autothermally in about 0.02-1.0 seconds at a final temperature in the interval of approximately 760-843.33 ° C (1400-1550 ° F) for a heat release equivalent to an adiabatic increase of approximately 10-176.66 ° C (50-350 sF) effective to improve the selectivity of the autocataitic N0X reduction; the exhaust gas can be pre-cooled or precooled to a temperature in the range of about 648.88-871.11 ° C (1200-1600 ° F) so that the exhaust gas is heated autothermally in about 0.02-0.5 seconds to a final temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F) for a heat release equivalent to an adiabatic increase of approximately 10-93.33 ° C (50-200 ° F) effective to improve the selectivity of the NOx reduction autocatalytic; the temperature of the exhaust gas can be controlled at a level in the range of about 482.22-871.11 ° C (900-1600 ° F) before the introduction of the hydrocarbon (s); and the heat can be recovered from the autothermally heated exhaust gas using heat transfer surfaces to preheat the exhaust gas in the temperature range of approximately 482.22-732.22 ° C (900-1350 ° F). Additionally: the temperature of the auto-heated exhaust gas can be controlled at a level in the range of about 760-843.33 ° C (1400-1550 ° F) to maintain the temperature of the preheated exhaust gas in the range of about 482.22-732.22 ° C (900-1350 ° F) using a heat exchanger; a supplementary fuel can be burned to preheat the exhaust gas in the temperature range of approximately 482.22-732.33 ° C (900-1350 ° F), a supplementary fuel can be burned directly into the exhaust gas; the exhaust gas can be preheated by mixing it with the combustion products of the supplementary fuel and the air; a supplementary fuel can be burned directly into the exhaust gas after a portion of the exhaust gas is preheated by mixing with the products of the combustion of the supplemental fuel and the air; the supplemental fuel may consist of the same hydrocarbon (s) which self-ignite and maintain the release of autocatalytic heat in the exhaust gas; the supplementary fuel may consist of the same material (s) used to produce the exhaust gas; and the exhaust gas can be enriched to contain in the range of about 2-5% of 02 using excess air for the combustion of the supplemental fuel. Additionally: the trajectory of the exhaust flow can be modified to mix the injected material (s) as well as the composition of the exhaust gas; the flow path of the exhaust gas can be modified before the introduction of the hydrocarbon (s); the flow path of the exhaust gas can be modified after the introduction of the hydrocarbon (s), the flow path of the exhaust gas can be modified before and after the introduction of the hydrocarbon (s) ); the effects of mixing can extend substally throughout the cross section of the exhaust gas flow path and can continue to mix the exhaust gas composition for a portion, or even all, of the autothermal heating; blades can be used to swirl the flow path, either as a single swirl flow or as a multiplicity of swirling mixing flows; screens can be used to generate a multiplicity of turbulent mixing eddies; and the introduced hydrocarbon (s) can be mixed in a substally uniform manner before the appearance of a visible chemiluminescence. Additionally: the heat can be recovered from the auto-heated exhaust gas using heat transfer surfaces between the exhaust gas and the heat recovery fluid; the heat can be recovered from the exhaust gas to heat another fluid such as steam, water, combustion air or a petrochemical composition; a petrochemical composition can be fractionated; the steam can be generated; and steam can be coupled to a turbine and operate machinery or generate electricity. Additionally: the production of the exhaust gas containing the N0X can be modified to maintain a temperature in the range of about 482.22-871.11 ° C (900-1600 ° F) and to contain in the range of about 2-18% of 02; the production of the exhaust gas can be modified by staggering the primary combustion using secondary air or overburning air to reduce the formation of N0X; the fuel consumed to produce the exhaust gas can be reduced by an amount of heat release less than or equal to the heat released by the autocatalytic reactions in the exhaust gas; 02 enrichment of the primary combustion can decrease the formation of combustible contamin in the exhaust gas, including gaseous organic substances, soot, and unburnt carbonaceous materials or particulate matter; and the enrichment of 02 of the combustion of the mineral coal can decrease the unburned carbon on the fly ash. Additionally: a fuel can be burned in a heat exchange boiler and the exhaust gas can be cooled before the introduction of the hydrocarbon (s) which self-ignite and maintain the release of autocatalytic heat in the gas escape; a petrochemical composition can be fractionated; the steam can be generated; The steam can be coupled to a turbine and operate the machinery or generate electricity; a fuel can be burned in an internal combustion machine; The internal combustion engine can be coupled to an electric generator, and electricity can be generated; The internal combustion engine can be coupled to a pump or compressor, and the pressure and / or fluid flow can be generated using the pump or the compressor, the internal combustion engine can be coupled to the machinery, and the machinery can be operated to produce mineral resources; the internal combustion engine can be coupled to mobile power equipment, and personnel, materials, products or minerals can be transported and / or processed; and the waste can be burned in a waste for the thermal incinerator, and the waste of the fuel can be discarded. Additionally: NH3 cleavage can be generated from a previous non-catalytic process to selectively reduce N0X, and N0x can be reduced non-catalytically at temperatures above 871.11 ° C (1600 ° F) prior to the heating of the exhaust gas Autothermal and autocatalytic N0X reduction; a portion of the remaining N0X can be reduced catalytically using a solid catalytic surface and additional generation of NH3, HNCO or a combination thereof after heating of the autothermal exhaust gas; the exhaust gas can be heated autothermally to control the temperature for the subsequent catalytic N0X reduction using a solid catalytic surface; the first stage of the autocatalytic N0X reduction in gas phase can reduce the input N0X level for the solid catalytic surface; the first stage of the autothermal heating can reduce the contaminants of the exhaust gas such as hydrocarbons, soot, CO and particulate matter; and the solid catalytic surface can serve the dual purpose of lowering the final N0X level and recovering a portion of the autothermal heat release. In addition, the reducer (s) can be injected or generated increasingly when the exhaust gas is heated autothermally. The staggering of the injection or the generation of the reducer (s) filling NH3, HNCO, or a combination thereof in the exhaust gas as the reagents, are consumed for the reduction of N0X. This staggering is effective for the reduction of N0X since autocatalytic reactions continue to heat the exhaust gas. The injection of the reducer (s) may be stepped using one or more nozzles, including a multiplicity thereof, along the exhaust gas flow path. Alternatively, the NH3, the HNCO, or a combination thereof may be increasingly generated by the decomposition or vaporization of the reductant (s) which are injected as solids, liquid molten substances, emulsions, suspensions, or solutions. This alternative stepping may involve different reducing agent (s), solution concentrations, and spray droplet sizes to modify the generation of NH3, HNCO, or a combination thereof during the autothermal heating of the exhaust gas. For this step, the reducer (s) may consist of a dilute aqueous solution consisting of NH 3, urea, or a combination thereof in water containing the dissolved nitrogen in the range of about 2-15% by weight . From the foregoing, it will be understood and appreciated by those skilled in the art that the embodiments of the present invention can be used in a wide variety of applications and in modified and similar configurations. Although several preferred embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and / or substitutions are possible without departing from the scope and spirit of the present invention as described in the claims.

It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following

Claims (60)

1. A method for reducing the NOx of an exhaust gas, characterized in that it comprises autothermally heating the exhaust gas using one or more hydrocarbons in the presence of NH3, HNCO or a combination thereof, wherein the autothermal heating is under effective conditions for reduce NOx autocatalytically.

2. The method according to claim 1, characterized in that the N0X in the exhaust gas is reduced almost stoichiometrically by as much as 80-90%.

3. The method according to claim 1, characterized in that the NOx in the exhaust gas is selectively reduced as much as about 99%.

4. The method according to claim 1, characterized in that the NOx in the exhaust gas is reduced to a level in the range of about 10-200 ppm.

5. The method according to claim 1, characterized in that the NH3 and the HNCO together are in the range of about 0.5-2.0 of the molar to NOx ratio in the exhaust gas.

6. The method according to claim 1, characterized in that the temperature of the exhaust gas is initially in the range of 482.22-871.11 ° C (900-1600 ° F) and the exhaust gas initially contains the 02 in the range of about 2. -18%.

7. The method according to claim 1, characterized in that the release of autothermal heat is initiated by the self-ignition of the hydrocarbon (s) in the exhaust gas.

8. The method according to claim 1, characterized in that the autocatalytic reactions are self-sustained in the autothermally heated exhaust gas even when a portion of the heat released is recovered by the heat transfer surfaces.

9. The method according to claim 1, characterized in that the heat release is equivalent to a uniform adiabatic increase of about 10-260 ° C (50-500 ° F) at the temperature of the exhaust gas.

10. The method according to claim 1, characterized in that the exhaust gas is heated within about 0.02-1.5 seconds to a final temperature.

11. The method according to claim 1, characterized in that the exhaust gas is heated to a final temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F).

12. The method according to claim 1, characterized in that the exhaust gas contains at least about 1% of 02 at a final temperature in the range of about 760-843.33 ° C (1400-1550 ° F).

13. The method according to claim 1, characterized in that the residual concentrations of hydrocarbons, CO, NH3 and HNCO are substantially depleted at a final temperature in the range of about 760-843.33 ° C (1400-1550 ° F) .

14. The method according to claim 1, characterized in that the CO is oxidized below a residual concentration of approximately 2000 ppm.

15. The method according to claim 1, characterized in that the CO is oxidized below a residual concentration of approximately 500 ppm.

16. The method according to claim 1, characterized in that the residual concentration of CO is maintained at a level below about 500 ppm by controlling a final exhaust gas temperature in the range of about 760-843.33 ° C (1400-1550 ° F). ).

17. The method according to claim 1, characterized in that the residual concentration of NH3 is maintained at a level below about 20 ppm by controlling a final exhaust gas temperature in the range of about 760-843.33 ° C (1400-1550 ° F). ).

18. The method according to claim 1, characterized in that the residual concentrations of CO and NH3 are depleted together in an autocatalytic manner in the exhaust gas at a final temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F). ).

19. The method according to claim 1, characterized in that the final temperature is controlled in the range of about 760-843.33 ° C (1400-1550 ° F) to maintain the residual CO concentration below about 50 ppm while the Residual NH3 below about 2 ppm.

20. The method according to claim 1, characterized in that the hydrocarbon (s) comprises (s) material (s) selected from the group consisting of mixtures of hydrocarbons such as natural gas, liquefied petroleum gas , alcohols, gasoline, diesel fuel, aviation turbine fuel, various oxygenated hydrocarbons, hydrocarbon amines or any fraction of such mixtures, including purified components such as carbon monoxide, methane, propane, methanol and ethanol, either as liquids or vapors.

21. The method according to claim 1, characterized in that the hydrocarbon (s) is (are) introduced (s) substantially throughout the cross section or around a perimeter of the exhaust gas flow path using one or more nozzles, including a multiplicity of them.

22. The method according to claim 1, characterized in that the hydrocarbon (s) is (are) introduced as liquid droplets with diameters in the range of about 20-500 microns.

23. The method according to claim 1, characterized in that the hydrocarbon (s) is (are) introduced into the exhaust gas using a carrier or atomizing gas such as steam, compressed air, pressurized exhaust gas , gaseous or vapor phase hydrocarbon (s) or any gaseous or vapor phase NH3 compositions.

24. The method according to claim 1, characterized in that it further comprises the steps of measuring a final temperature in one or more locations throughout the cross section of the exhaust gas flow path and controlling the amount of the hydrocarbon ( s) input (s) to maintain the measured temperature (s) at a level in the range of approximately 760-843.33 ° C (1400-1550 ° F).

25. The method according to claim 24, characterized in that it also comprises the step of measuring a final CO concentration in one or more places er. The entire cross-section of the fiow path of the exhaust gas downstream of the measured temperature (s).

26. The method according to claim 25, characterized in that it also comprises the step of using the final CO measurement (s) (es) to verify a level of CO depletion corresponding to the temperature (s) final (s) to control the introduction of the hydrocarbon (s).

27. The method according to claim 1, characterized in that it further comprises the step of generating NH3, HNCO or a combination thereof by vaporization, decomposition, or catalytic conversion of the reductant (s) which comprises any of the the) material (s) selected from the group consisting of NH 3, HNCO, cyanuric acid or a tautomer of cyanuric acid, urea, decomposition products of urea, compounds which decompose to produce NH 3 as a by-product, salts of ammonium of organic acids, hydrocarbon amines, or combinations of the above, if the pure compounds or mixtures, such as solids, liquid molten substances, emulsions, suspensions or solutions in water, alcohols, hydrocarbons, or oxygenated hydrocarbon solvents.

28. The method according to claim 27, characterized in that the NH3, the HNCO or a combination thereof are generated prior to the introduction of the hydrocarbon (s).

29. The method according to claim 27, characterized in that the NH3, the HNCO or a combination thereof are generated after the introduction of the hydrocarbon (s).

30. The method according to claim 27, characterized in that the NH3, HNCO or a combination thereof are generated concurrently with the hydrocarbon (s).

31. The method according to claim 27, characterized in that the NH3, the HNCO, or a combination thereof are increasingly generated during the autothermal heating of the exhaust gas.

32. The method according to claim 27, characterized in that the generated NH3, the HNCO, or a combination thereof, are increasingly injected during the autothermal heating of the exhaust gas.

33. The method according to claim 27, characterized in that it also comprises the step of injecting reducer (s) directly so that they vaporize or decompose in the exhaust gas.

34. The method according to claim 33, characterized in that the reducer (s) is (are) injected prior to the introduction of the hydrocarbon (s).

35. The method according to claim 33, characterized in that the reducer (s) are injected after the introduction of the hydrocarbon (s).

36. The method according to claim 33, characterized in that the reducer (s) are injected concurrently with the hydrocarbon (s) introduced as mixtures, solutions, suspensions, atomization gases, atomized liquids or structures. combined chemicals.

37. The method according to claim 33, characterized in that the reducing agent (s) comprises (n) a concentrated aqueous solution consisting of NH3, urea or combinations thereof in water containing dissolved nitrogen in the range of about 15%. -30% by weight.

38. The method according to claim 33, characterized in that the reducer (s) comprise a dilute aqueous solution consisting of NH 3, HNCO, or a combination thereof in the water containing dissolved nitrogen in the range of about 2. -fifteen%.

39. The method according to claim 38, characterized in that the dissolved reducer (s), the concentration of the solution, and the size of the spray droplets are selected to generate the NH3, HNCO, or a combination of them increasingly during the autothermal heating of the exhaust gas.

40. The method according to claim 33, characterized in that it further comprises the steps of measuring the NOx levels of the baseline in the exhaust gas with respect to an operating condition of the combustion equipment that produces the exhaust gas and controlling the amount of the exhaust gas. [of the] reducer (s) is injected to maintain a level of N0X reduction or a final N0X level in the exhaust gas throughout the operating range of the combustion equipment.

41. The method according to claim 40, characterized in that it further comprises the step of verifying an operating condition of the combustion equipment to provide a basis for estimating NOx emissions from the baseline throughout the operating range of the combustion equipment, whether continuous or frequently.

42. The method according to claim 41, characterized in that the amount of the injected reductant (s) is controlled to generate the NH3 and the HNCO together at a level in the range of about 0.5-2.0 of the molar ratio with respect to the NOx of the baseline depending on a measurement of the operating condition for the combustion equipment.

43. The method according to claim 33, further comprising the step of measuring a final NOx level at one or more locations throughout the cross section of the exhaust gas flow path downstream of the autothermal heating and any of the (s) temperature measurement (s) used to control the introduction of the hydrocarbon (s).

44. The method according to claim 43, characterized in that it also comprises the step of using the final level (s) of N0X (s) to verify the effectiveness of the selective NOx reduction corresponding to an amount of the NH3 and the HNCO introduced or an amount of the injected reductant (s) to generate the NH3, the HNCO or a combination thereof.

45. The method according to claim 44, characterized in that it further comprises the step of controlling the amount of the introduced NH3 and HNCO or the amount of the injected reductant (s) to maintain a final NOx level in the exhaust gas.

46. The method according to claim 1, characterized in that it further comprises either an alternative preheating or pre-cooling step of the exhaust gas at a temperature in the range of approximately 482.22-732.22 ° C (900-1600 ° F) before the introduction of the hydrocarbon (s).

47. The method according to claim 46, characterized in that the exhaust gas is preheated or precooled to a temperature in the range of about 565.55-871.11 (1050-1600 ° F) so that the exhaust gas is heated autothermally at 0.02- 1.0 seconds to a final temperature in the range of approximately 760-843.33 ° C (1400-1550 ° F) for an equivalent of heat release for an adiabatic increase of approximately 10-176.66 ° C (50-350 ° F) effective to improve the selectivity of autocatalytic NOx reduction.

48. The method according to claim 46, characterized in that the exhaust gas is pre-cooled or precooled at a temperature in the range of approximately 648.88-871.11 ° C (1200-1600 ° F) so that the exhaust gas is heated autothermally in 0.02-5.0 seconds at a final temperature in the range of approximately 760-843.33 ° C '1400-155C ° F) for an equivalent of heat release for an adiabatic increase of approximately 10-93.33 ° C (50-200 ° F) effective to improve the selectivity of autocatalytic N0X reduction.

49. The method according to claim 1, characterized in that it further comprises the step of burning a supplementary fuel to preheat the exhaust gas in the temperature range of about 482.22-732.22 ° C (900-1350 ° F).

50. The method according to claim 49, characterized in that a supplementary fuel is burned directly in the exhaust gas.

51. The method according to claim 1, characterized in that the introduced hydrocarbon (s) is (are) substantially uniformly mixed before the appearance of a visible inquisition.

52. The method according to claim 1, characterized in that it further comprises the recovery step of the auto-thermally heated exhaust gas using heat transfer surfaces between the exhaust gas and the fluid for heat recovery.

53. The method according to claim 52, characterized in that the heat is recovered from the exhaust gas to heat another fluid such as steam, water, combustion air or a petrochemical composition.

5 . The method according to claim 52, characterized in that it also comprises the step of fractionating a petrochemical composition.

55. The method according to claim 52, characterized in that it also comprises the step of generating steam.

56. The method according to claim 55, characterized in that it also comprises the steps of acclining the steam to a turbine and operating machinery or generating electricity.

57. method of compliance with the reivín; characterized because it also includes '- i S C generate the breakdown of NH3 from a previous non-catalytic method to selectively reduce N0X, the method also includes the non-catalytic reduction of N0X at temperatures above 871.11 ° C (1600 ° F) prior to the heating of the autothermal exhaust gas and the reduction of autocatalytic NOx.

58. The method according to claim 1, characterized in that it further comprises the step of catalytically reducing a portion of the remaining NOx using a solid catalytic surface and the further generation of NH3, HNCO, or combinations thereof after heating of the autothermal exhaust gas .

59. The method according to claim 58, characterized in that the exhaust gas is heated autothermally to control the temperature for the subsequent catalytic NOx reduction, using a solid catalytic surface. 60. The method according to claim 56, characterized in that the first stage of the autocatalytic N0X reduction in gas phase decreases the input N0X level for the solid catalytic surface. 61. The method according to claim 58, characterized in that the first stage of the autothermal heating reduces the pollutants of the exhaust gas such as hydrocarbons, soot, CO and particulate matter. 62. The method according to claim 58, characterized in that the solid catalytic surface serves the dual purpose of reducing the level of N0X fines and recovering a portion of the heat release "autothermal." 63 63. A method, characterized in that it comprises the steps of: controlling the temperature and the initial composition of an exhaust gas in the intervals of 20 approximately 482.22-871.11 ° C (900-1600 ° F) and approximately 2-18% of 02, respectively, effective for self-ignition of hydrocarbons; control the introduction of hydrocarbons for autcencenaer and release the effective autothermal heat "< < to self-sustain the autocatalytic reactions under poor fuel conditions, wherein the exhaust gas contains at least 1% of 02 and is heated to a final temperature in the range of approximately 760-843.33 ° C (1400-1400). 1550 ° F), introduce one or more reducer (s) for the N0X in the exhaust gas where the NH3, the HNCO or a combination thereof are generated from the reductant (s); NOx is reduced, and NH3, HNCO and hydrocarbons, including any byproduct CO, are substantially depleted.

60. A method for selectively reducing nitrogen oxides in an exhaust gas by using NH3, HNCO or a combination thereof while the hydrocarbon (s) self-ignites and heats the exhaust gas autothermally at a temperature in the range of about "'60 -843.33 ° C (1400-1550 ° F), substantially depleting the residual concentrations of the burned hydrocarbons, CO, HNCO and NH3.