JP2000262853A - Method and apparatus for treating exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stable exhaust gas treatment method for reducing dioxin in exhaust gas while considering the simplificity of fly ash treatment without using energy wastefully. SOLUTION: An exhaust gas treatment method is adapted to the detoxifying treatment of exhaust gas containing a harmful component and comprises a first process for introducing exhaust gas into an electric precipitator 4 at 200-350 deg.C to remove soot in the exhaust gas, a second process for introducing the exhaust gas from the first process into a denitrating tower 8 and/or a dioxin removing tower to remove nitrogen oxide and/or dioxins in the exhaust gas, a third process for introducing the exhaust gas from the second process into a temp. lowering tower to quench the exhaust gas by water spraying and a fourth process for introducing the exhaust gas from the third process into a reaction bag filter 3 to spray slaked lime into the exhaust gas to remove an acidic component in the exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a municipal solid waste incineration plant,
The present invention relates to a method and an apparatus for detoxifying an exhaust gas containing harmful components such as dioxins discharged from a combustible waste treatment facility, a metal smelting plant, and the like.

[0002]

2. Description of the Related Art Exhaust gas emitted during the process of incineration of municipal solid waste and industrial waste, and the preheating and melting of scrap containing flammable deposits at metal smelting plants, etc. includes soot and hydrogen chloride. And various harmful substances such as organic components, nitrogen oxides, heavy metals such as mercury, and organic halogen compounds such as dioxins and their precursors.
Of these harmful substances, acidic components such as HCl and SOx are often removed by blowing slaked lime powder into the exhaust gas and neutralizing in a dry reaction tower, etc., and removing nitrogen oxides by a denitration tower. Have been.

FIGS. 7 and 8 show a conventional exhaust gas treatment apparatus. 7 and 8, reference numeral 101 denotes a cooling tower;
2a is a first bag filter, 102b is a second bag filter, 106 is a slaked lime sprayer, 107 is a steam reheater, 108 is a denitration tower, and 110 is a neutralization reaction tower. FIG.
Is an example of the above-mentioned conventional technology, in which exhaust gas from an incinerator or a boiler is cooled in a cooling tower 101 as a cooling device, and slaked lime powder is sprayed to a neutralization reaction tower 110 by a slaked lime spraying device 106. The slaked lime is mixed with the exhaust gas in the same device to remove the acidic components in the exhaust gas, and the dust (fly ash) and the neutralization reaction product are collected and removed by the bag filter 102, and then the steam reheater 107 is used. After the temperature of the exhaust gas is raised, the exhaust gas is introduced into the denitration tower 108 to remove nitrogen oxides in the exhaust gas.

[0004] In recent years, dioxins, which are very toxic trace harmful substances that have become a social problem, and organic halogen compounds including them, have been reduced by, for example,
It is treated by controlling generation by controlling the combustion of incinerators, preventing re-synthesis by controlling the temperature of exhaust gas, oxidative decomposition by a catalyst, and removing by adsorption with an adsorbent. In addition, not only dioxin in exhaust gas from garbage incineration facilities but also fly ash discharged from dust collectors such as bag filters contain dioxin, and treatment of dioxin in fly ash has been a major issue in recent years. . Dioxin in fly ash, 3
A method of heat dechlorination at about 00 to 500 ° C., 120
A method of melting at 0 ° C. or higher has been proposed. As a method for removing acidic components such as HCl and SOx and nitrogen oxides such as NOx in exhaust gas, reducing the amount of fly ash which is difficult to treat, and facilitating the melting treatment, for example, the following method is used. Can be mentioned.

FIG. 8 shows another example of the conventional exhaust gas treatment method different from that shown in FIG. 7, in which exhaust gas from an incinerator or a boiler is cooled by a cooling tower 101 as a cooling device, and soot (dust) in the exhaust gas. Fly ash) is removed by the first bag filter 102a, followed by spraying slaked lime as a neutralizing agent into the neutralization reaction tower 110 by the slaked lime spraying device 106, and mixing slaked lime with exhaust gas in the reaction tower. To neutralize the acidic components in the exhaust gas, and then remove the reaction product by the second bag filter 102b, and raise the temperature of the exhaust gas after the dust removal by the steam reheater 107.
This is an exhaust gas treatment method including a step of conducting denitration by introducing the heated exhaust gas to the denitration tower 108. Most of the dust (fly ash) contained in the exhaust gas is removed by the first bag filter 102a, and thus has the effect of reducing the amount of fly ash discharged from the second bag filter 102b, which is sometimes difficult to treat. .

[0006]

However, in the processing method shown in FIG. 8, the fly ash discharged from the first bag filter does not contain slaked lime (neutralizing agent), so that the slag has a stable property and the like. It has the advantage of easier processing,
As in the processing method of FIG. 7, the following problems have occurred.
That is, in the conventional method shown in FIGS. 7 and 8, when introducing the exhaust gas into the denitration tower, in order to maintain the activity of the denitration catalyst in the denitration tower, the exhaust gas is introduced into the steam reheater and the temperature is raised. Was needed. That is, there is a disadvantage that extra energy for raising the temperature of the exhaust gas and a steam reheater are separately required. Further, in the method shown in FIGS. 7 and 8, the exhaust gas is cooled in advance to, for example, 200 ° C. or less using a water spray-type cooling tower in order to make the temperature suitable for the bag filter or the temperature at which dioxin is less generated. I needed to.
At this time, since the exhaust gas containing a large amount of dust is sprayed and cooled in the cooling tower, dust in the exhaust gas or dust attached to the inner wall of the tower forms wet dust due to unevaporated water droplets in the cooling tower, and further accumulates. There was often a risk of causing fatal problems, such as difficulty discharging.

In the method shown in FIG. 8, since the neutralization step after removing fly ash by the first bag filter is performed in the reaction tower before the second bag filter, the exhaust gas and the slaked lime powder are mixed. The installation space of the reaction tower to make it work cannot be ignored. In other words, there is a disadvantage that the installation of the reaction tower requires more site. Further, in the method shown in FIG. 8, since the exhaust gas introduced into the first bag filter contains many acidic components such as HCl and SOx, the inside of the first bag filter device becomes acidic, and the moisture in the exhaust gas and the partial Because of the formation of a low-temperature region, there is a possibility that acid corrosion of the inner wall of the apparatus may be induced. The present invention overcomes the above problems and provides a method and an apparatus for treating exhaust gas, which reduces dioxin in exhaust gas while taking into account the simplicity of fly ash treatment, and is stable without wasting energy. is there.

[0008]

SUMMARY OF THE INVENTION The present invention provides a method for detoxifying an exhaust gas containing harmful components.
A first step of introducing the exhaust gas in the temperature range to an electric dust collector to remove soot in the exhaust gas, b) introducing the exhaust gas having passed through the first step into a denitration tower or / and a dioxin tower, A second step of removing nitrogen oxides and / or dioxins in the exhaust gas; c) a third step of introducing the exhaust gas having passed through the second step into a cooling tower and rapidly cooling the exhaust gas by water spraying. Step d) An exhaust gas treatment method comprising a fourth step of introducing the exhaust gas having passed through the third step into a reaction bag filter and removing acidic components in the exhaust gas together with slaked lime spray. In the above-mentioned means 1, in the first step (a), slaked lime is sprayed as an anticorrosive in the exhaust gas before the dust is removed by the electrostatic precipitator or directly in the electric precipitator, and sprayed as the anticorrosive. An exhaust gas treatment method in which the amount of slaked lime to be sprayed is 1/5 or less of the amount of slaked lime sprayed when the acidic component is removed in the fourth step (d) or the equivalent ratio to the acidic component is 0.5 or less. It has been adopted.

Further, according to the present invention, when detoxifying an exhaust gas containing a harmful component, a) an electric dust collector for removing dust in the exhaust gas in a temperature range of 200 to 350 ° C .; A denitration tower and / or a dioxin tower for removing nitrogen oxides and / or dioxins in the exhaust gas; c) a cooling tower for spray cooling the exhaust gas passing through the apparatus; And a reaction bag filter provided with a slaked lime sprayer for removing acidic components in the exhaust gas. Further, in the above means 3, an exhaust gas treatment device comprising a slaked lime spraying device for spraying slaked lime as an anticorrosive directly into the flue upstream of the electric dust collector or the electric dust collector in the above item a).

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIGS. 1 to 3 are diagrams showing an embodiment in which the exhaust gas treatment method and apparatus of the present invention are adopted in a refuse incineration facility. FIG.
FIG. 6 to FIG. 6 are elevation views of the reaction bag filter illustrating the installation position of the powder blowing port when spraying powder such as slaked lime or a stripping agent onto the reaction bag filter. Here, 1 is a cooling tower, 3 is a reaction bag filter, 3a is a slaked lime spray device attached to the reaction bag filter, 4 is an electric dust collector, 5 is a fly ash treatment device, 6
Is an anticorrosive (slaked lime) spray device, 8 is a denitration tower, 8a is an ammonia spray device attached to the denitration tower, 9 is a dioxin tower,
11 is an exhaust gas introduction duct, 12 is a filter cloth, 13 is a fly ash discharge section, 14 is an exhaust gas discharge duct, 15 is a pulse jet type backwashing device, 16a to c are powder supply ducts, 17 is a reaction bag filter body (baghouse). ). Hereinafter, an outline of the exhaust gas treatment flow will be described with reference to FIG.

FIG. 1 is a diagram for mainly explaining the invention according to claim 1. 20 discharged from incinerators and boilers
The exhaust gas at 0 to 350 ° C. is introduced into the electric dust collector 4, and dust (fly ash) in the exhaust gas is collected and removed. Electric dust collector 4
The exhaust gas which has passed through is introduced into the denitration tower 8, and the ammonia sprayed by the ammonia spraying device 8a and the denitration catalyst in the denitration tower 8 convert nitrogen oxides in the exhaust gas into harmless nitrogen and remove them. Next, the exhaust gas that has passed through the denitration tower 8 is
And fine water droplets are sprayed by a spray nozzle (not shown) to rapidly cool the exhaust gas to a predetermined temperature. At this time, dioxin remaining in the exhaust gas is efficiently removed by the quenching effect of the water spray. Subsequently, the exhaust gas quenched in the cooling tower is introduced into the reaction bag filter 3 and slaked lime is slaked with the slaked lime spray device 3 attached to the reaction bag filter.
a, the slaked lime as a neutralizing agent and the acidic component in the exhaust gas undergo a neutralization reaction in the reaction bag filter 3, and the acidic component in the exhaust gas is removed. The clean exhaust gas that has passed through the reaction bag filter 3 is released to the atmosphere from the chimney. On the other hand, fly ash discharged from the electric dust collector 4 and the reaction bag filter 3 is separately rendered harmless by the fly ash treatment device 5. In FIG. 1 and the like, the description of an attraction fan for inducing exhaust gas, slaked lime silo, and other peripheral devices is omitted.

Next, an embodiment of the present invention will be described in detail with reference to FIG.
A description will be given based on FIG. The dust collection temperature at the time of collecting dust by the electric dust collector 4 is 200 to 350 ° C., and the exhaust gas in this temperature range is obtained by heating the combustion exhaust gas through a heat recovery means such as a boiler. When the temperature is 200 to 350 ° C., the temperature does not exceed the heat-resistant temperature of the electric dust collector 4 and the reduction of the dust collecting efficiency due to the low temperature of 200 ° C. or less can be avoided. Exhaust gas of 200 to 350 ° C. that has passed through a boiler or the like is separated by an electrostatic precipitator without dust and neutralization reaction, so that dust (fly ash) containing dioxins and heavy metals is separated from the exhaust gas. The ash has a low content of salts and calcium, and thus becomes fly ash suitable for an electric resistance type melting process and a cement solidification process, which are examples of the fly ash treatment device 5.

Next, the exhaust gas that has passed through the electric precipitator 4 is introduced into a denitration tower 8 in FIG. 1 and into a dioxin tower 9 in FIG.
Thereafter, each is introduced into the cooling tower 1. The denitration tower 8 and the deoxin tower 9 are composed of, for example, a denitration catalyst and a deoxin catalyst. The denitration catalyst and the dioxin catalyst are
For example, it is composed of one or more oxides of vanadium, titanium, and tungsten, and if necessary, cobalt, manganese, platinum and the like are added, and generally functions as an oxidation catalyst. In the case of denitration, an ammonia spraying device 8a is separately required. As a method in which no catalyst is used in the de-dioxin tower 9, for example, a packed tower of activated coke and other adsorbents is used.

Since the exhaust gas maintained at a temperature of 200 to 350 ° C. that has passed through the electric precipitator 4 is introduced into the denitration tower 8 and / or the dioxin tower 9, the denitration catalyst of the denitration tower 8 and / or the dioxin tower 9 and / or Efficient denitration and / or dioxin removal of exhaust gas is possible without impairing the activity of the de-dioxin catalyst and without clogging the device with dust in the exhaust gas.
If the temperature is higher than 350 ° C., the ammonia added in the denitration tower is oxidized to form nitrogen oxides and the denitrification effect is lowered, and if it is lower than 200 ° C., the activity of the catalyst is remarkably lowered. That is, 200 to 350
Since the range of ° C. is suitable for the denitration catalyst and / or the dioxin catalyst, the exhaust gas introduced into the electrostatic precipitator and the subsequent catalytic device (8 and / or 9) is 200 to
A range of 350 ° C. is desirable. At the same time, 200-350 ° C
Therefore, it is not necessary to raise the temperature of the exhaust gas introduced into the denitration tower 8 and / or the dioxin tower 9 again in order to increase the activity of the apparatus. There is an advantage that no separate reheating means is required, and no extra energy for reheating is required. The spray amount of the ammonia spray device 8a is determined according to the concentration of nitrogen oxide to be treated or the treatment level, and the spray amount is controlled by feedback control, feed forward control, or a control method combining these. .

Next, the exhaust gas subjected to denitration and / or dioxin introduction is introduced into the cooling tower 1 and the exhaust gas is rapidly cooled by spraying water from a spray nozzle (not shown).
Dioxin remaining in the exhaust gas can be efficiently removed. At this time, since the exhaust gas introduced into the cooling tower 1 has already removed dust, at the time of water spray cooling, the dust in the exhaust gas or the dust attached to the inner wall of the tower forms wet dust due to unevaporated water droplets, Further, it is possible to avoid the possibility of causing a fatal problem such as accumulation and dust discharge difficulty. The temperature at which the exhaust gas is cooled in the cooling tower 1 is not particularly limited. For example, if the temperature is 130 to 180 ° C., the resynthesis of dioxin is not performed, and while avoiding the acid dew point, the temperature of the reaction bag filter 3 in the subsequent stage is reduced. It is more preferable because the acid gas removal performance is enhanced. If the cooling tower 1 is a water spray type, it is preferable because the exhaust gas can be rapidly cooled.
Other than that, even if the temperature is reduced by heat recovery or the like, rapid cooling can be achieved. In the case of performing water spraying in the cooling tower 1, it is preferable to employ a two-fluid system or a pressurized one-fluid system as a spray method because fine water droplets can be obtained and the quenching effect can be more remarkably obtained. Next, since the exhaust gas cooled in the cooling tower 1 is introduced into the reaction bag filter 3 and sprayed with slaked lime, acid gases such as HCl and SOx remaining in the exhaust gas can be efficiently removed.

The reaction bag filter 3 is a device that neutralizes and removes acidic gases and removes reaction products by spraying slaked lime, and is characterized by a form in which dust is collected immediately after the neutralization reaction, and a neutralization after dust collection. That is, a complex type reaction in which a reaction is performed and a dust collection and neutralization reaction are simultaneously performed occur almost simultaneously in a manner that cannot be clearly distinguished. Therefore, a method must be distinguished from a method in which the neutralization reaction is substantially completed by the neutralization reaction tower upstream of the bag filter, and then the reaction products are removed. The blowing port for slaked lime in the reaction bag filter 3 may be installed in the exhaust gas introduction duct (FIG. 4) or on the outer wall of the bag house (FIGS. 5 and 6). A reaction bag filter is configured including the entire backwashing device.

Therefore, since the neutralization reaction by slaked lime spray and dust removal of the reaction product are performed in one reactor, that is, the reaction bag filter 3, the neutralization reaction tower 110 for mixing the exhaust gas and the slaked lime powder is used. There is no need to separately install the sum means, so that the site can be saved and there is an advantage that the structure is compact. The blowing position will be described with reference to the drawing. For example, slaked lime is provided with a powder supply duct 16a on the outer wall of the bag filter main body 17 above the exhaust gas introduction duct 11 of the bag filter main body 17, as shown in FIG. The slaked lime is sprayed on the bag filter main body 17 or, as shown in FIG. 6, a powder supply duct 16b is installed at the introduction portion of the exhaust gas introduction duct 11 of the bag filter main body 17 to spray slaked lime on the bag filter main body 17. Alternatively, as shown in FIG. 6, the powder supply duct 16c branched into a plurality of pieces is installed on the outer wall of the bag filter main body 17, and slaked lime is sprayed. But,
The slaked lime only needs to effectively reach the surface of the filter cloth, and is not limited to the blowing method shown in FIGS. 4 to 6.

The temperature of the exhaust gas introduced into the electric precipitator 4 in the present invention is 200 to 350 ° C., but the use of the electric precipitator 4 in this temperature range usually promotes the resynthesis of dioxin and increases the dioxin concentration. It is reported that the temperature range is disadvantageous. However, the present invention has ascertained the following as a result of a diligent search and has led to the present invention. That is, dioxins can be reduced only by rapidly cooling the exhaust gas temperature to, for example, 200 ° C. or lower, but chlorobenzene and chlorophenol, which are referred to as precursors, hardly decrease at this time. The precursor which does not decrease becomes a main cause of inducing re-synthesis of dioxins again in a subsequent exhaust gas treatment process, for example, in a temperature rise process of 200 ° C. or more for denitration treatment, and ensures that dioxins in the exhaust gas are reduced. Cannot be reduced. In the present invention, the exhaust gas is introduced into the electric precipitator 4 in a temperature range in which the resynthesis of dioxins is considered to be large, whereby the dioxins are temporarily increased by resynthesis, and the increased dioxins are removed from the dedioxin tower 9 or / In addition, a measure was taken to rapidly reduce the temperature by rapidly cooling the cooling tower 1. In other words, since the resynthesis of dioxins is actively carried out, the precursors involved in dioxins resynthesis are extremely reduced, and the advantage that the possibility of resynthesis of the dioxins is significantly reduced and the temporary increase is also observed. The present inventors have found that the higher the concentration of dioxins, the higher the concentration, the higher the dioxin removal effect by quenching in the de-dioxin tower 9 or the cooling tower 1 and the lower the emission concentration. Have determined. As described above, the temporary increase of dioxins in the electrostatic precipitator 4 does not pose a problem, but rather enhances the dioxin removal effect in the subsequent stage, and finally achieves a high level of dioxin reduction effect.

FIG. 3 is a diagram mainly for explaining the invention according to claim 2, and the description of the same components as those in FIGS. 1 and 2 will be omitted. Exhaust gas at 200 to 350 ° C. from an incinerator or a boiler is introduced into the electric precipitator 4. At this time, slaked lime as an anticorrosive agent is discharged into the flue gas upstream of the electric precipitator 4 or directly into the electric precipitator 4. Sprayed. Since slaked lime is sprayed as an anticorrosive, HCl,
It is possible to prevent acid corrosion of the inner wall of the device due to acidic components such as SOx. Slaked lime sprayed as an anticorrosive
Some of the slaked lime that has reached the inner wall of the device or flue is coated on the inner wall while reaching the dust collecting section in the electric dust collector, and the slaked lime that has reached the inner wall is formed by acidic components and partial dew condensation in the exhaust gas. Erosion of the inner wall metal can be prevented. At this time, the sprayed amount of slaked lime is one of the slaked lime sprayed amount used as a neutralizing agent in the subsequent reaction bag filter.
/ 5 or less or an equivalent ratio to the acidic component of 0.5 or less. When the ratio is 1/5 or more (or the equivalent ratio to the acidic component is 0.5 or more), the neutralization reaction is positively performed in the preceding electrostatic precipitator, and the reaction products and unreacted slaked lime discharged from the electric precipitator are removed. Increasing the amount of fly ash contained, that is, the amount of waste disposal, and the disadvantage that the disposal of fly ash becomes difficult as described below.

That is, if a large amount of unreacted slaked lime or calcium chloride or other reaction products is contained, a large amount of calcium chloride melt is generated when the fly ash is melted and solidified by an electric resistance method. Forming a molten salt layer, the current flowing between the electrodes is concentrated on the molten salt layer,
The operation of the melting furnace is significantly impaired. In addition, when performing cement solidification treatment as fly ash disposal treatment, calcium chloride in the solidified material is dissolved after the solidified material is discarded, and the solidified material gradually disintegrates, so harmful heavy metals etc. May be leaked. In these cases, it was confirmed that stable processing and stable operation were generally possible when the slaked lime blowing rate was about 1/5 (or the equivalent ratio to the acidic component was about 0.5).

For the above reasons, the amount of slaked lime is desirably 1/5 or less (or equivalent ratio to acidic component 0.5 or less) of the amount of slaked lime used in the subsequent reaction bag filter. In addition, the equivalent ratio of slaked lime sprayed to neutralize acidic components in waste incineration facilities is usually about 2 to 4,
One-fifth of this value corresponds to an approximately equivalent ratio of 0.5. The equivalent ratio is calculated from the following chemical reaction formula or the like.
H) The ratio to the theoretical requirement of 2). 2HCl + Ca (OH) 2 → CaCl2 + 2H2OSO2 + Ca (OH) 2 → CaSO3 + H2OSO3 + Ca (OH) 2 → CaSO4 + H2O If a known agent other than slaked lime is used as an anticorrosive,
It has the disadvantage that an extra drug silo is required and that it does not actively react with the acidic components in the exhaust gas when sprayed, so the burden of removing the acidic components in the subsequent reaction bag filter cannot be reduced. I have. Therefore, by using slaked lime used in the reaction bag filter as the anticorrosive, the anticorrosion effect can be more easily obtained. FIG.
In the above, the slaked lime spray position as the anticorrosive was set as the upstream flue of the electric dust collector 4, but the slaked lime blowing position of the reaction bag filter shown in FIGS. It may be installed in a duct (FIG. 4) or on the outer wall of the electric precipitator (FIGS. 5 and 6), and the blowing position is appropriately selected.

As the slaked lime spraying device 3a and the slaked lime spraying device 6 as an anticorrosive used in the present invention, a known powder supply device may be used. For example, the supply amount of powder is adjusted by using an air-conveying table feeder or the like. It is preferable that it can be made and supply fluctuation is small. Further, the slaked lime spraying device may branch the line 6 for spraying as an anticorrosive and the line 3a for spraying as a neutralizing agent to the reaction bag filter, or separate the slaked lime cutting portion of the slaked lime spraying device into two lines. Spraying may be carried out on a transport line, and these measures are made at any time in operation. As the electric dust collector 4 used in the present invention, a known dust collecting device using corona discharge is used, and if it can be used at 200 to 350 ° C., a charging type, a dry type, a wet type, a material of a dust collecting electrode, and the like are used. Does not matter.

The reaction bag filter 3 used in the present invention may be a known bag filter using a woven fabric, a nonwoven fabric, a felt, or the like as a filter cloth. The backwashing method may be any of a backwind type, a pulse jet type, and the like. The effect is the same. In addition, an auxiliary agent such as diatomaceous earth may be sprayed together with slaked lime in order to improve the backwashing efficiency of the reaction bag filter 3, and these are appropriately adopted for the convenience of operation. The cooling tower used in the present invention,
Although it is a water spray type device using a spray nozzle, if the exhaust gas can be rapidly cooled to a predetermined temperature, the same effect can be obtained even with an economizer, other heat recovery means, or a cooling means using cold air or other heat medium. In the case of a water spray type cooling tower, a two-fluid spray nozzle that can obtain fine water droplets,
When a pressurized spray nozzle is used, the quenching effect can be more reliably obtained, and the dioxin reduction effect can be more reliably obtained. In the present invention, as another measure for reducing dioxin in exhaust gas to a higher degree, for example, an activated carbon spraying device may be attached to the reaction bag filter 3, May be impregnated with water and sprayed, and these are used as appropriate.

The case where the embodiment of the present invention is applied to a refuse incineration facility has been described above in detail, but the present invention includes an acid gas such as HCl and dioxin in exhaust gas discharged due to combustion or heating. The same applies to exhaust gas emitted from combustible waste such as industrial waste and other combustion equipment in general, and exhaust gas emitted when preheating and melting scrap in metal smelting plants. So that it can be applied. In addition, the organic halogen compounds described in the present specification are dioxins specified by the Ministry of Health and Welfare to guidelines for waste cleaning plants based on toxic conversion values, dioxin precursors, and chlorobenzene and chlorophenol referred to as related substances. , PCB and the like, and these chemical substances partially substituted by halogen elements other than chlorine. Further, dioxins are a general term for polydibenzoparadioxin and polydibenzofuran, and are usually evaluated based on toxic equivalent concentrations. Also, in this specification, the author refuse to simply refer to dioxin in some cases for simplicity.

[0025]

EXAMPLE An example showing the effect of the present invention obtained by applying the exhaust gas treatment method according to the present invention to a refuse incineration facility will be described. Table 1 examines the equivalent concentrations of dioxins in the exhaust gas of the three examples of Example 1 and Example 2 implemented based on claim 1 of the present invention and Comparative Example according to the prior art for comparison. It is a table showing a result. Examples 1 and 2 are based on the device configuration corresponding to FIGS. 1 and 2, respectively, and Comparative Example is based on the device configuration of FIG.
In Example 1 of the present invention, a titanium-vanadium-based catalyst was used as a catalyst for a denitration tower, and in Example 2, a catalyst in which a noble metal was supported on a titanium-vanadium-based catalyst was used as a catalyst for a dedioxin tower. For comparison, the exhaust gas treatment amount, operating conditions of the incinerator (description omitted), and the like were substantially the same in both the examples and the comparative examples.

[0026]

[Table 1]

According to Table 1, in Examples 1 and 2 in which the present invention was implemented, compared with the comparative example, at the outlet of the electric dust collector,
Since the dust collection temperature was between 250 and 300 ° C., the dioxin concentration was high, but on the other hand, the value was sufficiently low at the chimney inlet. In particular, Example 2 employing a de-dioxin tower
Was able to achieve an extremely low value of 0.03 ng / Nm3. Although not shown in the table, as a result of spraying a small amount of slaked lime as an anticorrosive, the fly ash discharged from the electrostatic precipitator contained a little calcium, but was discharged from the electric precipitators of Examples 1 and 2. Like the fly ash, it was subjected to electric resistance type melting treatment and cement solidification treatment, and it was confirmed that the treatment could be performed without any problem.

[0028]

According to the exhaust gas treatment method of the present invention, after a dust collection treatment in an electric dust collector in a temperature range disadvantageous to dioxin, a treatment with a denitration or a dioxin removal catalyst,
Next, by rapid cooling, it became possible to achieve a dioxin reduction exceeding the conventional level. Further, according to the configuration of the exhaust gas treatment apparatus of the present invention, it is possible to omit the conventionally required exhaust gas reheater for denitration, and it is possible to discharge fly ash that can be easily post-processed such as electric resistance melting processing. It became. Furthermore, since rapid cooling by water spray is performed after dust collection, stable exhaust gas treatment capable of avoiding the danger of wet dust accumulation and the like induced by unevaporated water droplets in the water spray process has become possible.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a case in which Embodiment 1 of the present invention is employed in a refuse incineration facility.

FIG. 2 is a diagram illustrating a case where the second embodiment of the present invention is adopted in a refuse incineration facility.

FIG. 3 is a diagram illustrating a case where the third embodiment of the present invention is employed in a refuse incineration facility.

FIG. 4 is an elevational view of a bag filter illustrating a powder inlet for spraying powder onto a bag filter or a reaction bag filter.

FIG. 5 is an elevational view of a bag filter illustrating a powder inlet for spraying powder onto a bag filter or a reaction bag filter.

FIG. 6 is an elevational view of a bag filter illustrating a powder inlet for spraying powder onto a bag filter or a reaction bag filter.

FIG. 7 is a diagram showing an example of a conventional exhaust gas treatment device.

FIG. 8 is a diagram showing another example of a conventional exhaust gas treatment device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 cooling tower 3 reaction bag filter 3 a slaked lime spraying device 4 electric dust collector 5 fly ash treatment device 6 anticorrosive (slaked lime) spraying device 8 denitration tower 8 a ammonia spraying device 9 dedioxin tower 11 exhaust gas introduction duct 12 filter cloth 13 fly ash discharge Unit 14 Exhaust gas exhaust duct 15 Pulse jet type backwashing device 16a-c Powder supply duct 17 Reaction bag filter body (baghouse) 101 Cooling tower 102a First bag filter 102b Second bag filter 106 Slaked lime spraying device 107 Steam re-heating Heater 108 Denitration tower 110 Neutralization reaction tower

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 53/56 B01D 53/34 129Z 53/68 134A 53/86 53/36 G 53/94 102C B01J 23 / 22 B01J 23/64 102A 23/648 B03C 3/01 B B03C 3/013 (72) Inventor Toru Shioman 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Japan Nihon Kokan Co., Ltd. (72) Inventor Atsushi Hirayama 1-1-2, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Masaru Ayukawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. F-term (reference) 4D002 AA02 AA12 AA19 AA21 AA29 AC04 AC10 BA03 BA12 BA13 BA14 CA01 CA07 CA11 CA13 DA05 DA07 DA12 DA35 DA41 DA63 EA02 GA01 GA02 GA03 GB02 GB03 GB06 HA06 HA10 4D048 AA06 AA11 AB02 AB03 BA07X BA23X BA30Y BA31Y BA32Y BA33Y BA34Y CA03 CD03 4D054 AA02 CA20 EA02 EA21 EA22 EA24 EA27 EA30 4D058 JA04 QA05 SA20 TA02 TA06 UA03 UA10 4G069 BC32B BC33B BC50B BC54B BC69B CA02 CA08 CA10 CA13 CA19 DA05

Claims (4)

[Claims] When detoxifying an exhaust gas containing harmful components, a) a first step of introducing exhaust gas in a temperature range of 200 to 350 ° C. into an electric dust collector to remove dust in the exhaust gas; A) introducing the exhaust gas that has passed through the first step into a denitration tower and / or a dioxin tower to remove nitrogen oxides and / or dioxins in the exhaust gas; A third step of quenching the exhaust gas by water spray by introducing the exhaust gas through the step into a cooling tower,
D) A method for treating exhaust gas, comprising a fourth step of introducing the exhaust gas having passed through the third step into a reaction bag filter and spraying slaked lime to remove acidic components in the exhaust gas. 2. A slaked lime spray in which, in the first step of (a), slaked lime is sprayed as an anticorrosive and sprayed into flue gas before dust removal by an electrostatic precipitator or directly into the electric precipitator. The amount is set to 1/5 or less of the slaked lime spray amount to be sprayed when the acidic component is removed in the fourth step (d), or the equivalent ratio to the acidic component is 0.5 or less. 2. The exhaust gas treatment method according to item 1. (3) When detoxifying an exhaust gas containing harmful components, (a) an electric precipitator for removing dust in the exhaust gas in a temperature range of 200 to 350 ° C., and (b) an electric precipitator in the exhaust gas passing through the electric precipitator. A denitration tower or / and / or a dioxin tower for removing nitrogen oxides and / or dioxins; c) a cooling tower which spray-cools the exhaust gas passing through the device; and d) a cooling tower in the cooled exhaust gas. A reaction bag filter provided with a slaked lime spray device for removing acidic components. 4. The exhaust gas treatment according to claim 3, further comprising a slaked lime spraying device for spraying slaked lime as an anticorrosive directly into the flue upstream of the electric dust collector or into the electric dust collector of the above item a). apparatus.