KR20070113287A - Adsorbent for mercury removal from combustion gases - Google Patents

Abstract

The present invention provides a catalyst adsorbent formed from activated carbon doped with dispersed halide salts. The catalytic adsorbents provided herein are stable and harmless at room temperature and chemically adsorb at typical elevated temperatures for the flue gas stream. The present invention also provides a process for preparing the doped activated carbon adsorbent.

Description

Adsorbent for mercury removal from combustion gases {ADSORBENTS FOR MERCURY REMOVAL FROM FLUE GAS}

The present invention generally relates to a catalyst adsorbent for use in the removal of mercury from a flue gas stream and to a process for preparing said catalyst adsorbent.

Mercury toxicity to humans and the environment has long been known. For example, it is known that mercury exposure can cause neurological damage in humans. A particularly destructive example of the detrimental effects of mercury occurred in Minamata, Japan, in the 1950s, when organic mercury by-products of acetaldehyde production were released into bays in the area. The byproducts were ingested and metabolized by fish. It has been reported that the consumption of fish in the bay has led to widespread neurological damage and birth defects in local populations.

Coal used for power generation often contains about 0.1 ppm of mercury. In the United States alone, about 50 tonnes of mercury are released as steam in the exhaust each year. The mercury can be concentrated thousands of times in fish through chemical and biological processes and enter harmful levels in human food feeds.

Efforts have long been made to remove trace amounts of mercury from air, water, natural gas and other industrial streams, but removing mercury from coal combustion flue gas streams is a very difficult problem.

Prior art of removing mercury from air or hydrocarbons at room temperature has generally been limited to removing mercury from flue gas streams. Mercury has a large atomic weight and adsorption temperature is an important problem. At room temperature, the dispersion interaction with carbon is sufficient to fix mercury atoms. However, at about 300 [deg.] F. (temperature of many flue gas streams), physical adsorption can no longer trap elemental mercury.

In addition, sufficient contact time with fast moving flue gas streams is another problem for mercury removal. The total time of combustion gases from the generation by combustion to the exit through the stack is often less than 10 seconds. As the injected powder, the adsorbent is mixed with the combustion gas and scattered about 2 seconds, or as the filter cake on the bag house bag, the contact time between the activated carbon captured by the filter and the combustion gas is 1 Less than a second.

The reactivity and reaction kinetics required for combustion gas cleanup cannot be adequately tested by conventional packed beds. Conventional packed bed is insufficient for cleaning the flue gas because the cost of compressing it and pushing it through the packed bed is excessive because the volume of the flue gas is too large. In "air adsorption" or "filter adsorption", the contact time with the combustion gases is several times shorter than conventional packed beds. Thus, test results from conventional packed beds are of limited relevance to combustion gases.

Further problems associated with the removal of mercury from flue gases include low levels of mercury in the flue gas stream. In many other industrial processes (eg waste incineration), the concentration of mercury is about mg / m 3, while the concentration of mercury in the flue gas stream is μg / m 3. Very early operations include streams other than coal boilers and emissions containing mercury in the range of 5 μg / m 3 are believed to be fully purified. This is not much lower than the initial mercury concentration in the flue gas.

Above all, the prior art regards the adsorption of mercury as occurring between the adsorbent and mercury. While this is true in air or hydrocarbon streams at room temperature, the flue gas contains very polar and reactive components that can both play a role in preventing and enabling mercury removal. One of the composition models used in the combustion gases is about 6% O ₂ , 12% CO ₂ , 8% H ₂ O, 1600 ppm SO ₂ , 400 ppm NO, 50 ppm HCl, 20 ppm NO ₂ and 12 μg / m 3 Hg It contains an element.

Conventional attempts to remove mercury from combustion gases in coal boilers include a variety of techniques. One approach focuses on adding halogen salts to coal before combustion so that the combustion process produces hydrogen halide gas and then injects powdered carbon downstream into the combustion gas at lower temperatures. Some mercury is captured by the interaction between hydrogen halide gas, activated carbon and mercury. Another approach is to add hydrogen halides or elemental halides with activated carbon to lower temperature combustion gases.

Karlsruhe US Pat. No. 1,984,164 (1934) proposes carbon or silica gel or other adsorbents containing halogen elements for removing mercury from indoor air. Other prior attempts include adding halide salts to coal prior to combustion, since these salts are known to be very stable. The combustion process oxidizes the halide to halogen and further reacts with hydrogen to produce hydrogen halide. For example, US Pat. No. 5,435,980 (1995) to Felsvang et al. Adds chloride or chlorine containing materials to coal prior to or during combustion, or adds HCl upstream of the drying-absorption zone or drying- It is proposed to add to the combustion gases in the absorption zone.

Nelson, Jr., US Patent Application 2004/0003716 A1, discloses a process for removing mercury and mercury-containing compounds from combustion gases by injecting adsorbents into the combustion stream. Adsorbents are prepared by treating a carbonaceous substrate with a gas containing bromine. Bromine gas is known to be very toxic upon inhalation, ingestion or skin contact. HBr is also known to be corrosive. In addition, bromine and HBr compounds are reactive and can be easily added to alkenes. Bromine is also reactive with aromatic compounds.

US Pat. No. 6,533,842 B1 to Maes et al. Discloses a powder containing about 40% carbon, 40% calcium hydroxide, 10% copper chloride and 10% KI ₃ impregnated carbon for removing mercury from a high temperature, high humidity gas stream. Adsorbents are disclosed.

In December 2000, the U.S. Environmental Protection Agency (EPA) made a regulatory decision that it was necessary to regulate mercury emissions from coal-fired power plants.

Thus, in the field of mercury removal from flue gas streams, it would be desirable to provide an adsorbent that has improved adsorbent characteristics over the flue gas temperature range and that can be manufactured economically and efficiently.

Brief summary of the invention

The present invention provides a catalyst adsorbent in which a halide salt is dispersed on activated carbon and the oxidation catalytic activity of the activated carbon promotes the formation of mercury halide. At the same time, the adsorbent quality of activated carbon keeps the mercury halides thus formed. The present invention recognizes that while halide salts are stable and harmless at room temperature, doped activated carbon can form mercury halogen compounds at typical elevated temperatures in the flue gas stream and in the presence of typical reactive components of the flue gas. These mercury halogen compounds are retained on the surface of activated carbon. In addition, increased adsorbent capacity and faster adsorption rates result in the need for smaller amounts of adsorbent compared to the undoped activated carbon formed from the starting materials.

Accordingly, the catalytic adsorbent composition for removing mercury from the flue gas stream comprises activated carbon with a dopant (ie halide salt) dispersed on the activated carbon. The cations of the dopant used in the halide salts according to the invention can be alkali metals, alkaline earth metals or transition metals (eg Na, Ca, Mg, Cu and K). Anions included may be bromide or chloride. Particularly preferred dopants include, but are not limited to, NaCl, CaCl ₂ , CuCl ₂ , CuBr ₂ , NaBr, KBr, CaBr ₂ and MgBr ₂ .

The halide salt is inert to mercury and activated carbon at room temperature. At elevated temperatures (eg, 200 ° F. to 570 ° F.) and in the presence of typical flue gas compositions, mercury halogen compounds form and remain on the activated carbon. Without wishing to be bound by any theory, it is believed that any or all or the following combinations may occur. Oxidizers (eg, oxygen or oxidants on activated carbon to form combustion gases) oxidize mercury, and the anion of the dopant provides counter ions for the mercury ions that are oxidized by the oxidant. Alternatively or in addition, the oxidant oxidizes the anion of the salt, which in turn oxidizes mercury to form a mercury halogen compound on the activated carbon. Alternatively or in addition, the acid gases present in the flue gas react with the dopant salt to form hydrogen halides. The hydrogen halide is then oxidized by the oxidant to form halogen species. The halogen species then reacts with mercury to form a mercury halogen compound, which is then adsorbed by activated carbon.

The present invention further provides an economical and safe process for preparing the doped activated carbon adsorbent. The catalyst adsorbent of the present invention can be produced by several methods. In one embodiment, the catalytic adsorbent is placed in an aqueous solution containing a halide salt to form a mixture, the mixture is stirred until a uniform slurry is formed, the activated carbon is dried to evaporate water from the aqueous solution and the halide salt Can be formed by dispersing on the surface of the powdered activated carbon.

The inventors consider that the conditions for burning activated coal to generate power and the conditions for activating carbonaceous feedstock to produce activated carbon are substantially different. For example, the temperature of the boiler in the combustion chamber is very high and there is enough oxygen to oxidize all the carbon present. Thus, the halide salt can be oxidized and undergo a complex reaction to yield hydrogen halides. In contrast, the temperature range during carbon activation is about 1200 ° F. to 2000 ° F., which is much lower than the boiler temperature. A small amount of oxidant is quickly consumed and the surface of the carbon remains reducing. Thus, the halide salt can pass through the activation process in perfect state. Thus, doping of activated carbon can be accomplished by doping coal. Given that the halide salts on the activated carbon in the combustion gas at about 270 ° F. are reactive to mercury, it is surprising to find that activating gases containing oxidants can keep the halide salts intact during the activation process.

In another exemplary method of preparation, the catalyst adsorbent may be prepared by feeding a presoaked and dried mixture of carbonaceous feedstock and halide salt, or a dry mixture of halide salt and carbonaceous feedstock with the activation gas stream to the reaction chamber. When a mixture of halide salts and carbonaceous feedstocks (pre-soaked and dried or dried) is used, the activating gas stream may contain air and / or steam, O ₂ , CO ₂ , N ₂ , CO or mixtures thereof. have. Carbonaceous feedstock and activating gas are injected into the reaction chamber under conditions sufficient to form powdered activated carbon with a halide salt dispersed on the surface of the powdered activated carbon and for a residence time. In this method, the reaction chamber may be a batch reactor such as a tube furnace, mixing chamber or a reactor designed in a continuous manner (eg fluidized bed reactor, burner, etc.). The dopant is formed with an anion selected from cations and bromide and chlorides selected from the group consisting of alkali metals, alkaline earth metals and transition metals (eg, Na, K, Mg, Ca and Cu). In some embodiments, the dopant may be selected from the group consisting of NaCl, KCl, CaCl ₂ , CuCl ₂ , CuBr ₂ , NaBr, KBr, CaBr ₂ and MgBr ₂ .

In this embodiment, a mixture of carbonaceous material and halide salts can be obtained by dipping coal in a salt solution or dry mixing. The two methods are similar except that a dopant is introduced. Doping by dry mixing may be desirable because it can reduce processing costs. Mixing for doping is preferred at the molecular level and considering the coal and salt particles are typically in the micrometer size range (ie, much larger than the molecular level), the degree of efficiency of dry doping was unexpected.

The catalytic adsorbents of the present invention are suitable for use in removing mercury from gas streams containing oxidants and / or acidic gases at elevated temperatures, such as combustion gas streams present in boilers or combustion processes. In this process, the catalytic adsorbent of the present invention is injected into the flue gas stream in an aerial manner of mercury capture. As discussed above, the dopant is inert to mercury at room temperature. However, the dopant effectively removes mercury from the flue gas stream at flue gas temperatures and in the presence of activated carbons, oxidants and / or acid gases. Mercury is retained on the activated carbon in the form of mercury halogen compounds and can be separated from the flue gas stream with blowing ash.

For a more complete understanding of the present invention and its advantages, reference is made to the following detailed description of the invention in conjunction with the accompanying drawings.

1 illustrates one embodiment for the preparation of a catalyst adsorbent according to the present invention.

2 illustrates a method of using a catalyst adsorbent according to the present invention.

3-6 illustrate a graph relating to Example 1. FIG.

7-12 illustrate the graphs related to Example 2. FIG.

13 illustrates a graph relating to Example 3. FIG.

14-20 illustrate the graphs related to Example 4. FIG.

Like numbers refer to like parts in some of the drawings.

The present invention provides a catalytic adsorbent suitable for use in removing mercury from flue gas streams at elevated temperatures. Catalytic adsorbents of the present invention include compositions having activated carbon containing a dopant dispersed on the activated carbon. The dopant is a halide salt. The cations of the dopant may be alkali metals, alkaline earth metals and transition metals, and the anion of the dopant may be bromide or chloride. The catalytic adsorbent of the present invention can be formed from various methods.

The present invention also provides a method of using said composition for mercury capture at elevated temperatures in the presence of acidic and / or oxidizing gases commonly found in flue gas streams produced by coal combustion.

Mercury capture is a synergistic combination of components in the flue gas stream, as well as adsorbent composition, as well as flue gas stream temperature. As will be appreciated from the examples provided below, the activated carbon itself does not adsorb mercury in the nitrogen stream at 2O <0> F. KBr doped silica gel does not adsorb a significant amount of mercury even in the presence of total combustion gases. KBr doped graphite does not adsorb mercury at all. However, bromide salt doped activated carbon is a particularly effective adsorbent for combustion gases because it can remove mercury at extremely low levels. It can also remove some mercury from the nitrogen stream.

As discussed above, alkali metal, alkaline earth metal and transition metal halides are harmless salts and are inert to mercury and activated carbon at room temperature. However, at about 200 ° F. to 570 ° F. (eg, 270 ° F.) and in the presence of acidic and / or oxidizing gases in the combustion gases, these doped activated carbon compositions can capture mercury with high efficiency. Unused halide salts remain in their salt form.

In addition, the catalytic adsorbent of the present invention performs well in flue gas streams produced by burning low chloride coal (e.g., Powder River Basin (PRB) coal from Wyoming), but Norit Current adsorbents such as FGD carbon do not function efficiently.

Thus, the present invention disperses the halide salt on the activated carbon so that the salt remains chemically inert at room temperature but reacts with mercury in a hot combustion gas to provide a nonvolatile mercury halide. More particularly, at temperatures ranging from about 200 ° F. to 570 ° F. and in the presence of acidic and / or oxidizing gases from the flue gas, the halide salt reacts with mercury and releases mercury where activated carbon is present at very low concentrations in the flue gas stream. Helps to capture. The catalytic adsorbent of the present invention uses very rapid kinetics at elevated temperatures to optimize both chemical adsorption as well as physical adsorption. Thus, the reactivity of halide salts as used herein is a cooperative phenomenon.

As discussed below, the catalytic adsorbents of the present invention can be prepared by a variety of methods. Adsorbents can be prepared from commercially available powdered activated carbon (PAC) or raw carbonaceous materials. Exemplary PACs suitable for use in the present invention include FGD (commercially available from Norit America, Inc.), ash-free activated carbon powders and rayon fibers made from refined petroleum coke. Carbon fiber powders prepared by carbonization include, but are not limited to. It will also be appreciated that other activated carbon may be used in the present invention.

The catalytic adsorbent of the present invention can be prepared by various techniques. In one embodiment of the invention, the adsorbent may be prepared by dipping activated carbon in an aqueous solution of a halide salt. This approach is an economical and safe process compared to treating activated carbon with hydrogen halide or halogen gas.

In this embodiment, the minimum amount of water needed to prepare the salt solution is used. The cations of the dopant may be alkali metals, alkaline earth metals and transition metals. Anions included may be bromide or chloride. Thus, suitable salts for use in the present invention include, but are not limited to, NaCl, CaCl ₂ , CuCl ₂ , CuBr ₂ , NaBr, KBr, CaBr ₂ and MgBr ₂ . In some embodiments KBr, NaBr or CaBr ₂ may be preferred, and in some embodiments NaBr or KBr may be the most preferred salt.

The PAC, preferably in powder form, is placed in an aqueous solution and the mixture is stirred until it is a uniform slurry, so that there is sufficient contact time between the salt solution and the PAC so that the salt solution is dispersed on the PAC. Those skilled in the art will understand that the solution and halide salts will be dispersed in the PAC since the PAC has porosity.

In this approach, the amount of salt required for the aqueous solution is determined based on the amount of PAC desired for the particular adsorbent and the ratio of salt to PAC (ie, the dopant level in the desired PAC determines the concentration of the salt solution). In some embodiments, the ratio of dopant level to PAC level is 1: 10,000 to 30: 100. In a more preferred embodiment, the ratio of dopant to PAC is from 1: 4000 to 10: 100 and in other embodiments, the ratio of dopant to PAC is from 0.1: 100 to 7: 100.

The salt solution containing the PAC is sufficiently dried to allow the PAC to flow freely after being immersed. During this time, water is evaporated and the salt enters the pore volume of the PAC and is dispersed on the surface of the PAC. After the PAC is dried, it is in powder form. It can be ground and passed through a desired mesh of the appropriate size. It should not be construed as limited, but the PAC can pass through 200 mesh. In this method, PACs can be used for mercury removal in materials less than 200 mesh or equivalent to 200 mesh. Those skilled in the art will appreciate that the adsorbent may be processed to a suitable size depending on the intended use of the adsorbent. For example, in some applications a smaller mesh (eg 400 mesh) may be desirable.

It is believed that the catalytic adsorbent of the present invention will perform good mercury removal from the flue gas stream at elevated temperatures, given the salts dispersed on the surface of the PAC. Without wishing to be bound by any theory, it is believed that the salts are inert to mercury elements at room temperature and at high temperatures (ie, in the range of the combustion zone). However, mercury in the flue gas stream may be oxidized at elevated temperatures of about 200 ° F. to 570 ° F. (eg, at about 270 ° F. to 300 ° F.) and in the presence of oxidizing and / or acidic gases and doped activated carbon in the flue gas. And can be effectively removed from it.

An alternative to immersing the PAC in aqueous solution as described above is to spray water droplets containing the desired halide salt on the PAC in such a way that the halide salt is dispersed as discussed above. This approach is described in U.S. Patent Application No. 11 / 078,517 (filed March 14, 2005), entitled "Production of Activated Char Using Hot Gas" and entitled "Production of Activated Char Using Hot Gas." U.S. Patent Application by Bool et al. It may be used in connection with the activated carbon produced in the same application (the same application), the two documents are incorporated herein by reference in their entirety.

Another method for producing a catalyst adsorbent suitable for use in the present invention is shown in FIG. 1. In this embodiment, the catalyst adsorbent may be prepared by presoaking the prepulverized carbonaceous feedstock in an aqueous solution of an alkali metal, alkaline earth metal or transition metal halide salt. Alternatively, the prepulverized carbonaceous feedstock may be immersed in an alcohol (eg ethanol) solution containing an alkali metal, alkaline earth metal or transition metal halide salt. The presoaked feedstock is then exposed to an oxidizing gas mixture such as air and steam at elevated temperature in the reaction chamber to produce a catalyst adsorbent and exhaust gas.

Catalyst adsorbents prepared directly from a carbonaceous feedstock can save significant costs over the process for preparing activated carbon first and then doping the activated carbon to produce a catalytic adsorbent. Instead of preimmersion, catalytic adsorbents may also be prepared by dry mixing alkali metal, alkaline earth metal or transition metal halide salt powders with the prepulverized carbonaceous feedstock. It is preferable that the mixing action is thorough, that is, as close to the molecular mixing as possible. For example, NL Ai Alpr. Mixers such as NPP Alfr. Andersoen as multivector fluidization techniques or flow mixers with a tip action by Scott Equipment Co. Can be used. At the bench top level, mixing was achieved by grinding into a mortar and pestle on a very small scale.

The dry mixed feedstock is then added to an activating gas mixture containing components such as air, steam, O ₂ , N ₂ , H ₂ O, CO ₂ , CO or mixtures thereof at elevated temperatures such as 1200 to 2000 ° F. The exposure produces a catalyst adsorbent and exhaust gas. The activating gas mixture may be highly oxidizing or highly reducing or intermediate. The chemical composition of the carbonaceous material determines the requirements of the oxidizing power of the activating gas mixture, which in turn determines the composition of the activating gas mixture. For example, high grade (high carbon content) coal may require a mixture of high oxidative capacity to provide an active surface. In the case of lignite or other high oxygen content carbonaceous materials, gases with low oxidative capabilities are required to provide activated carbon products in high yields.

Dry doping can also further simplify the process of preparing the catalyst adsorbent of the present invention. It is desirable because it eliminates the drying step required to prepare the doped carbonaceous feedstock for activation.

In this embodiment the final concentration of the halide salt in the catalyst adsorbent is measured as in the previous embodiment, except that the weight loss of the carbonaceous material due to combustion in the reaction chamber is measured (ie the ratio of dopant to activated carbon). Is measured in advance to determine the concentration of the salt solution). Therefore, the weight loss due to activation can be accounted for by measuring the concentration based on the yield of the final product.

Halide salts are essential for sufficient mercury removal, but excess halide salts may be undesirable and incur additional manufacturing costs. Very good catalyst adsorbents of the present invention can be prepared with a halide salt to coal in a ratio of about 1: 1000 (weight).

As shown in FIG. 1, a carbonaceous feedstock 16 is injected into the reaction chamber 10. Carbonaceous feedstock 16 has not yet been activated and can be selected from various types of feedstock such as coal or biomass material. Although not intended to be limiting, suitable coals for use in the present invention include, but are not limited to, lignite, sub-bituminous coal, bituminous coal or anthracite coal. The feedstock may be premilled, for example, to a suitable size of about 5 to 200 micrometers.

Prior to injection into the reaction chamber 10 with the solution containing the preferred halide salt, the carbonaceous feedstock 16 may be premixed by dry mixing or pre-soaking with the solution containing the preferred halide salt as discussed above. Can be. In preimmersion embodiments, water may be preferred, but the solution may be formed from water or ethanol.

Activation gases 12 and 14 (eg, air 12 and steam 14) are injected into the reaction chamber 10 simultaneously with or almost simultaneously with the carbonaceous feedstock 16. Preferably, the steam is preheated and injected at a temperature of about 1800 ° F. Some of the feedstocks (such as lignite) are more responsive to oxygen to improve the activated carbon yield, and the activating gas may also be only steam and / or nitrogen. At very high temperatures, such as 2000 ° F., water can react with carbon and become an oxygen source for the surface of activated carbon. The activating gas may also comprise a mixture of O ₂ , N ₂ , H ₂ O, CO ₂ , CO and the composition of the mixture may be used to adjust the gas mixture reducing capacity to meet the requirements of the feedstock.

The reaction chamber 10 is a single batch reactor (eg tube furnace), or gas temperature, composition, in which the feedstock is fluidized or stratified (eg suspended on a filter medium) and the reactant gas passes through the feedstock. And a continuous reactor (eg fluidized bed reactor) in which the feedstock residence time can be controlled for optimal conditions. The feedstock may be fluidized with a fluidizing device (for continuous processes), such as an activating gas or a flow mixer available from Scott Equipment Company.

Heating of the reaction chamber 10 may be provided from various sources, for example the reaction chamber may be heated electrically or with a flame. Alternatively or in addition to such heating, reaction chamber 10 may be heated from the heat of reaction between the feedstock and the air. Those skilled in the art will appreciate that the desired temperature of the reaction chamber depends on various factors including the stoichiometric ratio of oxygen or oxidizing gas to the feedstock, the contact time and the reactivity of the feedstock. Heating may be provided from any source sufficient to generate combustion gas 18 and adsorbent 19. Typically, the temperature in the furnace will be about 1450 to 2700 degrees Fahrenheit, more preferably about 1650 to 2200 degrees Fahrenheit. If the stoichiometric ratio of oxygen to the feedstock is greater than 1, the contact time between the oxidizing gas and the feedstock becomes more important because more feedstock can potentially be consumed and affect product yield. If the stoichiometric ratio is less than 1, the contact time will be less important.

The residence time in the reaction chamber 10 of the carbonaceous feedstock 16, the reactive activating gas (such as air 12 and steam 14) is generated by the combustion gas 18 and the adsorbent 19 in the chamber 10. Long enough to be. The residence time of carbon is independent of the gas and can be controlled independently. This can be important because it requires enough time to liquefy and partially oxidize the feedstock. The residence time can be short, but it is important that it is long enough to properly activate the carbon. In some embodiments, the residence time can be about several minutes, but can also be as short as milliseconds. It will be appreciated that too long residence time or too much oxygen or steam will adversely affect the adsorbent yield.

The adsorbent 19 is removed from the reaction chamber 10 and ready for use as a mercury removal adsorbent from the combustion gas stream at elevated temperature. Combustion gas 18 typically includes combustible gases such as CO ₂ , CO, N ₂ and H ₂ O. Any unreacted, partially combusted (eg CO) gas in the gas stream 18 can be further combusted.

Another alternative embodiment for preparing catalytic adsorbents for use in accordance with the present invention is described in U.S. Patent Application, such as Boul et al. Entitled "Production of Activated Char Using Hot Gas", which is incorporated by reference in its entirety. No. 11 / 078,517 (filed March 14, 2005) and US Pat. Appl. No. 11 / 224,590 (filed September 12, 2005), such as the fire entitled "Production of Activated Char Using Hot Gas." have.

In this embodiment, the feedstock is presoaked with aqueous or ethanol solution as discussed above. Subsequently, activated carbon is prepared by treating the pre-soaked feedstock as discussed in US Patent Application Nos. 11 / 078,517 and 11 / 224,590 entitled "Production of Activated Char Using Hot Gas."

The catalyst adsorbent of the present invention may also be formed by dry mixing the prepulverized raw carbonaceous material with a halide salt powder. In this embodiment, the raw carbonaceous material and the halide salt powder are mixed together in dry form. The product can then be injected as shown in US Patent Application Nos. 11 / 078,517 and 11 / 224,590 entitled "Production of Activated Char Using Hot Gas." The temperature in the reaction zone will be above the melting point of the halide salt such that the halide salt melts and wets the surface of the carbonaceous material. Finally, the salt can be dispersed in the carbonaceous material.

Referring now to FIG. 2, an exemplary system for using the catalytic adsorbent of the present invention is shown. Combustion gas 22 is formed as a result of combustion in a furnace or boiler 20. The combustion gases 22 may vary in composition and temperature, but the model composition is 6% O ₂ , 12% CO ₂ , 8% H ₂ O, 1600 ppm SO ₂ , 400 ppm NO, 50 ppm Of HCl, 20 ppm of NO ₂ , and 12 μg / m 3 of Hg element, and a temperature range of about 200 to 570 ° F. after passing through various heat exchangers before being released into the air. A catalyst adsorbent 30a that can be formed from any of the methods described above can be injected upstream of the particulate collection device (PCD) 24. The particulate collection device 24 is typically a bag house or an electrostatic precipitator (ESP). Adsorbent 30a is injected into the combustion gas stream 22 upstream of the PCD 24 so that the residence time is sufficient for the catalytic adsorbent to capture the combustion gas 22 and remove mercury therefrom.

Mercury-containing particulates and adsorbents are removed from PCD 24 by stream 28. Thus, the combustion gas 26 has a lower mercury content than the combustion gas 22 and can be sent to the stack.

In some embodiments, it may be desirable to inject a catalytic adsorbent into the combustion gas downstream of the PCD. This process is currently being studied in other fields.

As discussed above, it is contemplated that the catalytic adsorbents of the present invention provided with salts dispersed on the surface of the PAC will be widely used for mercury removal from the flue gas stream at elevated temperatures.

As shown below, the physical adsorption of PAC at about 27O <0> F is not sufficient to retain the element of mercury in the absence of HCl as promoter. In contrast, doped PACs function well in the absence of HCl. However, the presence of HCl, O ₂ and / or SO ₂ acts as an accelerator for the doped PAC.

In some examples, three types of commercial PACs were treated to produce doped PACs. In another example, doped PACs were prepared by activating halide salt treated coal.

The first commercial PACs used were Norit America, Inc. FGD carbon available from Norit America, Inc. It is made from Texas lignite and contains about 30% ash by weight. In powder form, it is widely tested and accepted as a reference for activated carbon to remove mercury from combustion gases. The second PAC is Carbon Resource Inc. Ash-free activated carbon available from Carbon Resource Inc. It is typically prepared from refined petroleum pitch and contains trace amounts of ash. It is usually sold in bead form. In the following examples, about 400 mesh portions were used by grinding and sieving for mercury removal. The third PAC used was activated carbon fiber ACF-1300 / 200, which is also available from Carbon Resource Inc. It is made from rayon and is typically provided in the form of a cloth. This material was ground and sieved through a 400 mesh sieve before use.

To prepare halide salt doped PACs from coal, coal was immersed in an aqueous or ethanol halide salt solution or coal and salt were ground together in a mortar with pestle. Doped coal was activated in a stream of oxygen, nitrogen, and steam in the temperature range of about 1800 ° F to about 2070 ° F.

Different coals corresponded to activating gases with different and significantly different degrees. For example, lignite from Beulah, North Dakota, USA is easy to oxidize and can provide activated carbon in lower yield than sub-bituminous coal from Powder River Basin (PRB) from Wyoming, USA. . This indicates that different activation conditions may be needed for different feedstocks.

Different ranges of dopant levels were taken into account as well as different halide salts. Doping was not expected to perform well at as low a ratio as 1: 1000 (doping agent to coal), but the results were good compared to activated carbon (not inactivated coal) doped with 7-15% halides.

Adsorbents were evaluated using two tests, a fixed bed test and a retention chamber test. In the fixed bed test, a fixed bed consisting of 150 mg of adsorbent was supported on a quartz filter about 63.5 mm in diameter. Details of the test setup are described in the literature published by the EERC, for example, as disclosed in the "DOE Mercury Control Technology R & D Program Review Meeting" held August 12-13, 2003 in Pittsburgh, Pennsylvania, USA. have. The gas stream containing mercury as well as the components of the flue gas were passed through a thin layer. Mercury break through was monitored and the spent adsorption bed was collected and analyzed.

In the residence time chamber test, slip streams from power plants in Pleasant Prairie, Wisconsin, and Pueblo, Colorado, were passed through chambers of different lengths. Adsorbent was injected at one end of the chamber to float with the flue gas stream. At the other end of the chamber, the adsorbent was separated from the flue gas stream and the clean flue gas was analyzed for Hg content to determine the efficiency of the adsorbent. The chamber length was used to determine the contact time between the flue gas and the adsorbent. In "air adsorption", strong adsorption affinity and fast adsorption kinetics are required for high mercury removal efficiency. Details of the residence time chamber device (designed by the Electric Power Research Institute (EPRI)) can be found in the published literature ("Combined Power Plant Air Pollutant Control Mega Symposium" (2004, Washington, DC, USA). (Assessment of Low Cost Novel sorbents for Coal Fired Power Plant Mercury Control).

Example  One

This example demonstrated that at room temperature, undoped PAC is a good adsorbent for elemental mercury and accelerators do not provide additional benefits. However, at 270 ° F. physical adsorption was overwhelmed by kinetic energy, so in the absence of promoter, adsorption by undoped PAC was not appropriate.

A fixed bed test was performed on four samples in a stream containing nitrogen and about 13 μg / m 3 element of mercury. Test conditions and results are summarized in Table 1 and FIGS. 3 to 6. Undoped FGD carbon samples were tested at room temperature and 100% mercury removal was achieved for more than 15 hours without signal of mercury emissions. For samples tested at 270 ° F., all three types of activated carbon immediately reached nearly 100% emissions (0% removal).

Sample number Sample name Sample processing Test temperature Test gas composition and sequence Description of the test results FGD Carbon Untreated 72 ℉ N ₂ + Hg 100% Hg removal for 15 hours, no signal of emissions 17297-89 FGD Carbon Vacuum activation at 1000 ° F 270 ℉ N ₂ + Hg Ejected immediately 17343-13 Carbon fiber 6N HCl extraction and heating at 1800 ℉ at N ₂ 270 ℉ N ₂ + Hg Ejected immediately 17297-99 Ashless carbon 6N HCl extraction and heating at 1800 ℉ at N ₂ 270 ℉ N ₂ + Hg Ejected immediately

6 traces of ash were removed using 6 N HCl extraction in Sample Nos. 17343-13 and 17297-99. The heating at 1800 ° F. at N ₂ was to remove the oxidized species on the commercially available PAC so that the oxygen species could be introduced at the selected time. None of the treatments changed the mercury adsorption properties of the PACs. These samples were exposed at 27 ° F. to a test gas containing nitrogen as well as nitrogen and mercury. Data is recorded in the examples below. Oxygen in the test gas alone was not sufficient for PAC to adsorb mercury.

Example  2

This example demonstrated how the halide salt as the dopant alters the combustion gas, mercury and carbon interactions to promote mercury adsorption from the combustion gas stream. In this example, a thin fixed layer of PAC sample was sequentially exposed to different gas mixtures. All experiments started with nitrogen and mercury (about 13 μg / cm 3). Continuous or sequential combinations of the combustion products of the other components were 6% O ₂ , 12% CO ₂ , 8% H ₂ O, 1600 ppm SO ₂ , 400 ppm NO, 20 ppm NO ₂ , 50 ppm HCl, Hg of 12-14 μg / m 3 and the remaining amount of N ₂ were added to the stream towards the model composition of the synthesis flue gas.

Two types of PAC (without ash and FGD) and three dopants (KBr, NaBr and NaCl) were used in the following experiments. The details and results of the experiments are summarized in Table 2. Emission curves are shown in Figures 7-12. The results demonstrate that the composition of the gas plays an important role in mercury adsorption.

Sample number Sample name Sample description Test gas composition and sequence Description of the test results 17297-99 Ashless carbon 6N HCl extraction and heating at 1800 ℉ at N ₂ N ₂ + Hg, 6% O ₂ + 8% H ₂ O added, 3. 1600 ppm SO ₂ added 4. 50 ppm HCl added Hg removed only after HCl is added to the test gas 17297-99 Ashless carbon 6N HCl extraction and heating at 1800 ℉ at N ₂ N ₂ + Hg, 50 ppm HCl added, 3. 1600 ppm SO ₂ added HCl promotes Hg adsorption, SO ₂ reduces Hg removal 17343-15 KBr doped ashless carbon 15: 100 (KBr: Carbon) N ₂ + Hg, 6% O ₂ addition, 8% H ₂ O addition, 4. 1600 ppm SO ₂ addition Adsorbs Hg in N ₂ stream, both O ₂ and SO ₂ promote Hg removal 17297-89 FGD carbon Vacuum activation at 1100 ° F N ₂ + Hg, 8% H ₂ O + 50 ppm HCl added, 6% O ₂ added, 4. Complete combustion product added Hg removed only after adding HCl to the test sample 17297-93 NaBr doped FGD 15: 100 (NaBr: carbon) N ₂ + Hg, 8% H ₂ O + 12% C0 ₂ + 6% O ₂ , 1600 ppm SO ₂ , 4. Complete combustion Adsorbs Hg in N ₂ stream, both O ₂ and SO ₂ promote Hg removal 17297-91 NaCl doped FGD 15: 100 (NaBr: carbon) N ₂ + Hg, 2. + 8% H ₂ O + 12% C0 ₂ + 6% O ₂ addition, 1600 ppm SO ₂ addition, complete combustion product addition, 5. 50 ppm HCl removal CO ₂ and SO ₂ are weak promoters, the presence of HCl is important for Hg removal

Example  3

This example demonstrated that physical adsorbents, such as silica gel doped with KBr, did not remove mercury from combustion gases.

The same thin fixed bed method was used in this example as in Examples 1 and 2. Details of sample preparation, test conditions and results are shown in Table 3 and FIG. 13.

Sample number Sample name Sample description Test gas composition and sequence Description of the test results 17297-69 KBr doped silica gel KBr: Silica gel = 15: 100 (weight ratio) O ₂ CO ₂ + 6% 1. 12% H ₂ O + SO ₂ + 8% + 1600 ppm NO 400 ppm HCl + 50 ppm + 20 ppm NO ₂ + Hg + 14 ㎍ N ₂ (complete combustion synthesis) The decrease in Hg concentration is less than 10%

Example  4

In this example, the effectiveness of various halide salts as dopants was analyzed. Doped ash-free carbon was tested in a thin fixed bed process in the synthetic combusted as in Examples 1-3. The results were similar to undoped FGD.

The thin fixed bed test simulated the function of the back house in the power plant. The efficiency of the adsorbent was analyzed by percent mercury removal from the flue gas.

Both thin fixed bed and air adsorption are highly dependent on adsorption kinetics, but the thinner fixed bed is the more important of the adsorption capacity. All molecules in the stream of the second fraction have the opportunity to pass through the densely packed adsorbent powder of mm thickness. However, the adsorbent remains in effect for mercury until removed from the stream.

All doped samples have better mercury removal than undoped FGD carbon. The results are shown in Table 4 below. Emission curves are shown in FIGS. 14-20.

Sample number Sample name Sample description Test gas composition and sequence Description of the test results 17343-02D KCl doped ashless carbon 15: 100 (KCl: carbon) _{1. O 2 6% + CO 2} 12% + H 2 O 8% + SO 2 1600 ppm + NO 400 ppm + HCl 50 ppm + NO 2 20 ppm + Hg 14 ㎍ / ㎥ + N 2 ( complete combustion) Very good removal at around 95% 17343-01C NaCl doped ashless carbon 15: 100 (NaCl: carbon) _{1. O 2 6% + CO 2} 12% + H 2 O 8% + SO 2 1600 ppm + NO 400 ppm + HCl 50 ppm + NO 2 20 ppm + Hg 14 ㎍ / ㎥ + N 2 ( complete combustion) Very good removal at around 93% 17343-02A NaBr doped ash-free carbon 15: 100 (NaBr: carbon) _{1. O 2 6% + CO 2} 12% + H 2 O 8% + SO 2 1600 ppm + NO 400 ppm + HCl 50 ppm + NO 2 20 ppm + Hg 14 ㎍ / ㎥ + N 2 ( complete combustion) Very good removal at around 98% 17297-75A KBr: Carbon = 15: 100 15: 100 (KBr: Carbon) _{1. O 2 6% + CO 2} 12% + H 2 O 8% + SO 2 1600 ppm + NO 400 ppm + HCl 50 ppm + NO 2 20 ppm + Hg 14 ㎍ / ㎥ + N 2 ( complete combustion) Very good removal at about 100% level 17343-02B CaBr ₂ doped ash-free carbon 15: 100 (CaBr ₂ : carbon) _{1. O 2 6% + CO 2} 12% + H 2 O 8% + SO 2 1600 ppm + NO 400 ppm + HCl 50 ppm + NO 2 20 ppm + Hg 14 ㎍ / ㎥ + N 2 ( complete combustion) Very good removal at about 100% level 17343-02C MgBr ₂ doped ash free carbon 15: 100 (MgBr ₂ : carbon) _{1. O 2 6% + CO 2} 12% + H 2 O 8% + SO 2 1600 ppm + NO 400 ppm + HCl 50 ppm + NO 2 20 ppm + Hg 14 ㎍ / ㎥ + N 2 ( complete combustion) Very good removal at around 95% 17297-62 FGD carbon Control (North America) _{1. O 2 6% + CO 2} 12% + H 2 O 8% + SO 2 1600 ppm + NO 400 ppm + HCl 50 ppm + NO 2 20 ppm + Hg 14 ㎍ / ㎥ + N 2 ( complete combustion) Very good removal at around 90%

Example  5

This example demonstrated the efficiency of bromide salt doped PAC in "air adsorption" using a residence time chamber test and the quality of the PAC was prepared by direct activation of bromide salt doped coal.

Dwell Time Chamber Test: The dwell time chamber used in this example was an 8 inch diameter tube setup as discussed above. It was developed by the Electric Power Research Institute (EPRI). A slip stream of 30 acfm of combusted product was withdrawn from the coal combustible boiler duct flowing through the tube. Adsorbent was injected at one end of the tube. In each of the middle region and the outlet end of this tube, there was an outlet sampling tube which made it possible to measure at two different residence times. The mercury removal efficiency of the adsorbent was measured by measuring the mercury concentration at the inlet as well as at the sampling outlet.

Mercury atoms must collide with adsorbent particles in order to be adsorbed. For the retention chamber test, the adsorbent particles may have the opportunity to collide with mercury molecules only in the chamber during suspension. Due to the short residence time (about 2 to 4 seconds), adsorption access to the adsorbent is extremely limited. At the outlet of the chamber, the capacity of the adsorbent was not exhausted. The fact that mercury was removed at a high percentage is evidence of the fast kinetics and strong adsorption affinity of the catalyst adsorbent, that is to say that collisions in the reaction pathway are very effective.

Since the residence time chamber simulates the situation of a power plant with only an electrostatic precipitator (ESP), mercury removal depends on air adsorption. Typical airtime is about 2 seconds. In an example, the sampling outlet allows for a residence time of about 2-4 seconds.

Three groups of adsorbents were tested. Samples of the first group were prepared by doping FGD PAC with an aqueous bromide salt solution. A second group of samples was prepared by activating halide salt doped coal in a stream containing oxygen, nitrogen and water at 1650 ° F to 2000 ° F in a tube furnace. With or without additional steam activation at 1800 ° F., as in US patent application Ser. No. 11 / 078,517 (filed March 14, 2005), such as the fire entitled "Production of Activated Char Using Hot Gas." Without steam activation, halide salt doped coal was activated by a burner to prepare a third group of samples.

Undoped FGD carbon samples were also tested to serve as controls. The test results are shown in Table 5 below. The percentage of Hg removal was calculated by dividing the outlet mercury concentration by the inlet mercury concentration. Since there is no way to measure how much mercury is removed by the cylinder wall, the recorded value is the sum of the air removal and wall removal effects.

Adsorbents from all three groups performed better than commercial FGD carbon.

Example  6

Chemical Form of Dopant in PAC. Activation of the bromide salt doped coal was performed at a temperature near 1800 to 2000 ° F. This amplified the question as to whether the bromide salt remained in its ionic form. The chemical analysis of bromide salt doped coal before and after activation is shown in Table 6. The bromide salt remained in its inactive ionic form. This can be particularly advantageous because bromination of carbon can produce unknown and undesirable organic bromide compounds. It is therefore desirable to avoid the formation of such compounds.

The data in Table 6 also showed that there was an ion exchange reaction between the salt in the coal and NaBr after immersion in NaBr solution. Br ions associate with cations in coal (coal is a complex mixture) and Na associates with anions in coal. Coal was better to carry the new bromide salt than the new sodium salt. During evaporation of the water, the sodium salt remained in the aqueous phase. Once the evaporation was complete, some of the sodium salt eventually attached to the vessel. In the doped coal, the sodium ion concentration was lower than bromide. This necessitated the need to maintain complete uniformity of dopant levels in the wet doping embodiments.

In dry doping by mixing, it was not possible for such salt separation to be present, indicating that the sodium ion concentration in coal is always higher than bromide, as in the data in Table 6.

Sample number Sample name Sample description Ionic Bromine mmol / gm Total bromine mmol / gm Na mmol / gm 17343-85A NaBr doped PRB coal NaBr: PRB coal = 5: 100 (before activation) 0.43 0.48 0.17 17343-85B 17343-85A after activation Tube furnace at 1800 ° F, purged with 10% O ₂ , 90% N ₂ , saturated with steam at 194 ° F 0.65 0.70 0.26 17343-88A NaBr doped PRB coal NaBr: PRB coal = 5: 100 (before activation) 0.09 0.08 0.03 17343-88B 17343-88A after activation Tube furnace at 1800 ° F, purged with 10% O ₂ , 90% N ₂ , saturated with steam at 194 ° F 0.11 0.12 0.05 17390-06A NaBr Dry Mixed Doped PRB Coal NaBr: PRB coal = 1.5: 100 (before activation) 0.11 0.34 17390-06B 17390-06A after activation Tube furnace at 1958 ° F, purged with air, saturated with water vapor at 212 ° F 0.15 0.16 0.45

Example  7

For wet doping, it is necessary to dry the wet coal prior to activation. Therefore, additional costs associated with this drying step are needed. On the other hand, dry mixing using grinding was predicted to be difficult to achieve molecular level mixing. It will be expected that molecular level dispersion of the dopant will be important to prepare catalyst adsorbents having a large surface area. We set out to solve this dilemma, and unexpectedly, even when the dopant level is very low at 0.1% by weight, as shown in the retention chamber data in Table 7, the adsorbent with the same or better wet doping was found. Found to yield. This suggests that the activation step provides a mechanism to achieve sufficient mixing at the molecular level.

Doping level. Another parameter that needs to be measured is the dopant level. It is desirable to use as low dopant levels as possible. The test results of the samples prepared with NaBr to PRB coal ratios of 1.5: 100 and 0.1: 100 are shown in Table 7 below. Performance didn't deteriorate even at the 0.1% level.

Example  8

Coal reactivity and activation conditions.

Activated carbon was a large surface area material with active functional groups on its surface. The reaction between coal and active gas facilitated this process. Lignite is known to be reactive. We conducted a series of activation experiments on North Dakota (ND) lignite from Buera, North Dakota, USA. The results in Table 8 show that in order to produce activated carbon with equivalent capacity for mercury removal, activating gas mixtures with low oxidation activity and low activation temperature and short activation time can significantly increase the yield of the activation process.

The results of the first two samples indicated that at 1800 ° F. water can oxygenate and volatilize the carbon, and increasing the activation time by 5 minutes significantly varies the activated carbon yield. A comparison of the results of the second and third samples showed that air was more effective at volatilizing carbon than water. The results of the fourth sample showed that the breaking ability of air can be mitigated by reducing the activation time. The results of the fifth sample showed a relaxing effect of low activation temperature.

These results showed the importance of the oxidizing power of the activating gas. From pure oxygen to CO ₂ to CO, they only have a wider range of oxidative power by choosing air and water. These results also showed the advantage of an activation process that allows better control of gas composition, temperature and time.

Those skilled in the art should appreciate that they may readily utilize the specific embodiments disclosed above as criteria for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also understand that such equivalent structures do not depart from the spirit and scope of the invention as described in the claims.

Claims (53)

A catalyst adsorbent composition for removing mercury from a flue gas stream at elevated temperature comprising activated carbon having a halide salt having a cation and an anion, dispersed on the activated carbon. The catalyst adsorbent composition of claim 1 wherein the cation is selected from the group consisting of alkali metals, alkaline earth metals and transition metals. The catalyst adsorbent composition of claim 2 wherein the cation is selected from the group consisting of Na, Mg, Ca, Cu and K. The catalyst adsorbent composition of claim 1 wherein the anion is selected from the group consisting of bromide and chloride. The catalyst adsorbent composition of claim 1 wherein the halide salt is selected from the group consisting of NaCl, KCl, CaCl ₂ , CuCl ₂ , CuBr ₂ , NaBr, KBr, CaBr ₂ , MgBr ₂ and mixtures thereof. The catalyst adsorbent composition of claim 5 wherein the halide salt is NaBr, KBr or mixtures thereof. Putting powdered activated carbon into an aqueous solution containing a halide salt having a cation and an anion to form a mixture; Stirring the mixture until a uniform slurry is formed; And Drying the powdered activated carbon to evaporate water from the aqueous solution and dispersing the halide salt on the surface of the powdered activated carbon A method of making a catalytic adsorbent for use in adsorption of mercury from a combustion gas stream at elevated temperatures. 8. A process according to claim 7, wherein the cation is selected from the group consisting of alkali metals, alkaline earth metals and transition metals. The method of claim 8, wherein the cation is selected from the group consisting of Na, Mg, Ca, Cu, and K. 10. 8. A process according to claim 7, wherein the anion is selected from the group consisting of bromide and chloride. 8. The process according to claim 7, wherein the halide salt is selected from the group consisting of NaCl, CaCl ₂ , CuCl ₂ , CuBr ₂ , NaBr, KBr, CaBr ₂ , MgBr ₂ and mixtures thereof. The process of claim 11 wherein the halide salt is NaBr, KBr or mixtures thereof. Injecting the pre-soaked carbonaceous feedstock into the reaction chamber; Injecting one or more oxidizing gases into the reaction chamber; And Injecting steam into the reaction chamber Injecting a carbonaceous feedstock, air, and steam into the reaction chamber under conditions sufficient to form an activated carbon having a halide salt with cations and anions, dispersed on the surface of the activated carbon, and for a residence time, A process for preparing a catalytic adsorbent for use in adsorption of mercury from a combustion gas stream at elevated temperatures. The method of claim 13, wherein the oxidizing gas comprises air, oxygen, steam, nitrogen, or a combination thereof. The method of claim 13, wherein the reaction chamber is a tube furnace. The process of claim 13, wherein the reaction chamber is a fluidized bed reactor. The method of claim 13, wherein the cation is selected from the group consisting of alkali metals, alkaline earth metals and transition metals. 18. The method of claim 17, wherein the cation is selected from the group consisting of Na, Ca, Cu, and K. The method of claim 13, wherein the anion is selected from the group consisting of bromide and chloride. The method of claim 13, wherein the halide salt is selected from the group consisting of NaCl, KCl, CaCl ₂ , CuCl ₂ , CuBr ₂ , NaBr, KBr, CaBr ₂ , MgBr ₂ and mixtures thereof. The method of claim 19, wherein the halide salt is NaBr, KBr or a mixture thereof. Injecting a dopant with cations and anions and a catalyst adsorbent containing activated carbon into the gas stream; Adsorbing mercury on the catalytic adsorbent; And Removing the mercury-containing catalyst adsorbent from the gas stream A method for removing mercury from a gas stream at elevated temperatures comprising a. The method of claim 22, wherein the gas stream contains oxidizing gas, acidic gas or combinations thereof. The method of claim 22, wherein the gas stream contains an inert gas. The method of claim 24, wherein the inert gas comprises nitrogen. Dry mixing the carbonaceous feedstock with a halide salt; Injecting the mixed carbonaceous feedstock into the reaction chamber; And Injecting one or more activating gases into the reaction chamber Injecting the carbonaceous feedstock and the one or more activating gases into the reaction chamber under conditions sufficient for forming an activated carbon having a halide salt with cations and anions, dispersed on the surface of the activated carbon, and for a residence time. A process for producing a catalytic adsorbent for use in adsorption of mercury from a combustion gas stream at elevated temperatures. The method of claim 26, wherein the one or more activating gases comprises air, oxygen, steam, nitrogen, CO ₂ , CO, or a combination thereof. The method of claim 27, wherein the combination of one or more activating gases and the mixed carbonaceous feedstock and halide salts is selected according to the reactivity of the carbonaceous feedstock. The method of claim 26, wherein the reaction chamber is a furnace. The method of claim 26, wherein the reaction chamber is a fluidized bed reactor. 27. The method of claim 26, wherein the cation is selected from the group consisting of alkali metals, alkaline earth metals and transition metals. 32. The method of claim 31 wherein the cation is selected from the group consisting of Na, Ca, Mg, Cu and K. The method of claim 26, wherein the anion is selected from the group consisting of bromide and chloride. The method of claim 26, wherein the halide salt is selected from the group consisting of NaCl, KCl, CaCl ₂ , CuCl ₂ , CuBr ₂ , NaBr, KBr, CaBr ₂ , MgBr ₂ and mixtures thereof. The method of claim 34, wherein the halide salt is NaBr, KBr or a mixture thereof. The method of claim 26, wherein the carbonaceous feedstock comprises coal. 37. The process of claim 36, wherein the coal comprises sub-bituminous coal. 37. The process of claim 36, wherein the coal comprises bituminous coal. 37. The method of claim 36, wherein the coal comprises lignite coal. Wet mixing the carbonaceous feedstock with a halide salt; Drying the mixture of carbonaceous feedstock and halide salts; Injecting the mixed carbonaceous feedstock into the reaction chamber; And Injecting one or more activating gases into the reaction chamber Injecting the carbonaceous feedstock and the one or more activating gases into the reaction chamber under conditions sufficient for forming an activated carbon having a halide salt with cations and anions, dispersed on the surface of the activated carbon, and for a residence time. A process for producing a catalytic adsorbent for use in adsorption of mercury from a combustion gas stream at elevated temperatures. The method of claim 40, wherein the one or more activating gases comprise air, oxygen, steam, nitrogen, CO ₂ , CO, or a combination thereof. 42. The process of claim 41, wherein the combination of one or more activating gases and the mixed carbonaceous feedstock and halide salt is selected according to the reactivity of the carbonaceous feedstock. The method of claim 40, wherein the reaction chamber is a furnace. 41. The process of claim 40, wherein the reaction chamber is a fluidized bed reactor. 41. The method of claim 40, wherein the cation is selected from the group consisting of alkali metals, alkaline earth metals and transition metals. The method of claim 45, wherein the cation is selected from the group consisting of Na, Ca, Mg, Cu, and K. 46. The method of claim 40, wherein the anion is selected from the group consisting of bromide and chloride. The method of claim 40, wherein the halide salt is selected from the group consisting of NaCl, KCl, CaCl ₂ , CuCl ₂ , CuBr ₂ , NaBr, KBr, CaBr ₂ , MgBr ₂ and mixtures thereof. The method of claim 48, wherein the halide salt is NaBr, KBr or a mixture thereof. 41. The process of claim 40, wherein the carbonaceous feedstock comprises coal. 51. The process of claim 50, wherein the coal comprises sub-bituminous coal. 51. The process of claim 50, wherein the coal comprises bituminous coal. 51. The method of claim 50, wherein the coal comprises lignite.

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