JP2012213744A - Apparatus and method for treating exhaust gas and coal upgrading process facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and method for treating an exhaust gas for removing NOx, SOx and Hg in an upgrading exhaust gas generated during a coal upgrading process and a boiler exhaust gas, and to provide a coal upgrading process facility.SOLUTION: The apparatus for treating an exhaust gas includes: a boiler for burning either one or both of an upgrading exhaust gas and carbonization oil; a denitrification means for denitrifying nitrogen oxide containing the boiler exhaust gas; an alkali supply means for supplying either one or both of an alkali metal salt and an alkaline earth metal salt into the boiler exhaust gas; an activated carbon adsorption means for spraying an activated carbon at an upstream side and a downstream side of the alkali supply means and at least one place between those sides to adsorb mercury in the boiler exhaust gas; and a collecting and removing means for collecting and removing the compound generated by the denitrification and the activated carbon adsorbed the mercury.

Description

  The present invention relates to an exhaust gas treatment apparatus and a treatment method for treating boiler exhaust gas generated by burning reformed exhaust gas and dry distillation oil generated when reforming low-grade coal in a boiler, and a coal reforming process facility. .

  Low-grade coal with high water content such as lignite and sub-bituminous coal has high reserves but low calorific value per unit weight and poor transport efficiency, so heat treatment such as drying, dry distillation, and cooling by the coal reforming process Etc., reforming to reformed coal with an increased calorific value per unit weight is performed.

  Conventionally, the treatment of reformed exhaust gas generated from a coal reforming process has a dust collection removal process for removing dust and the like in the reformed exhaust gas, but nitrogen oxide (NOx), sulfur oxide (SOx), mercury ( None have an exhaust gas treatment process for removing Hg) and the like.

  There has been proposed an exhaust gas treatment method including a dust collection step for removing dust and the like in exhaust gas generated from a coal reforming process (see, for example, Patent Document 1). Although this exhaust gas treatment method includes a dust collection step, there is a problem that it does not include a treatment step for removing NOx, SOx, Hg, and the like.

US Pat. No. 5,067,968

There is a large difference in the content of components contained in the exhaust gas between the exhaust gas generated from the coal fired boiler and the reformed exhaust gas generated from the coal reforming process. The reformed exhaust gas generated from the coal reforming process has a water (H ₂ O) concentration of about 3 times, an oxygen (O ₂ ) concentration of about 1/3 times, and a nitrogen oxide ( The NOx) concentration is about 4 to 5 times, and the mercury (Hg) concentration is about 4 times.

  When removing mercury in the reformed exhaust gas by adsorption with activated carbon, mercury removal performance may be reduced due to the influence of coexisting components.

  Since the exhaust gas treatment method described in Patent Document 1 includes only a dust collection process that removes soot and the like in the exhaust gas generated from the coal reforming process, NOx, SOx, Hg in the exhaust gas generated from the coal reforming process is included. Etc. cannot be removed.

  In order to improve the thermal efficiency of the coal reforming process, the reformed exhaust gas containing any one of dry gas, dry distillation gas, and dry distillation off gas generated when reforming low-grade coal and dry coal are dry-distilled. However, there are those that generate the carbonized oil generated by burning in a private power generation boiler, but there is no one that has a treatment device for treating the boiler exhaust gas burned in the boiler.

  Therefore, removal of NOx, SOx, Hg, etc. in the reformed exhaust gas and boiler exhaust gas cannot be prevented simply by removing the dust in the reformed exhaust gas and boiler exhaust gas generated from the coal reforming process. Is desired.

  In addition, in coal reforming process facilities installed in inland areas, it is desired to perform non-drainage treatment to prevent the desulfurization effluent of the wet desulfurization apparatus from being drained to the outside.

  The present invention has been made in view of the above, and it is possible to remove NOx, SOx, and Hg in boiler exhaust gas generated by burning reformed exhaust gas and dry distillation oil generated from a coal reforming process in a boiler. An object of the present invention is to provide an exhaust gas treatment apparatus and treatment method that can be used, and a coal reforming process facility.

  In order to solve the above-mentioned problems and achieve the object, the exhaust gas treatment apparatus according to claim 1 of the present invention is either or both of reformed exhaust gas and dry distillation oil generated when reforming low-grade coal. An exhaust gas treatment apparatus for treating boiler exhaust gas generated by combustion in a boiler, wherein the boiler exhausts one or both of the reformed exhaust gas and the dry distillation oil, and nitrogen oxides contained in the boiler exhaust gas Denitration means for denitrating, alkali supply means for supplying one or both of alkali metal salt and alkaline earth metal salt into the boiler exhaust gas, upstream side and downstream side of the alkali supply means, and their Activated carbon adsorbing means for adsorbing mercury in the boiler exhaust gas by spraying activated carbon at least one of the gap between the activated carbon adsorbing the compound generated by desulfurization and the activated carbon. It characterized by having a a collecting and removing means.

  The exhaust gas treatment apparatus according to claim 2 of the present invention is the exhaust gas treatment apparatus according to claim 1, wherein the denitration catalyst is a reducing agent that reduces nitrogen oxides contained in the boiler exhaust gas, and an oxidation that oxidizes mercury in the presence of hydrogen chloride. Supply of a chemical agent that reduces nitrogen oxides contained in the boiler exhaust gas with an auxiliary agent and a denitration catalyst, and supplies one or more reducing oxidation assistants that oxidize mercury in the presence of hydrogen chloride into the flue of the boiler. And a reductive denitration apparatus having a denitration catalyst for reducing nitrogen oxide in the boiler exhaust gas with a reducing agent and oxidizing mercury in the presence of hydrogen chloride.

  A coal reforming process facility according to claim 3 of the present invention includes a drying furnace for drying low-grade coal, a carbonization furnace for carbonizing dried dry coal, and an exhaust gas treatment apparatus according to claim 1 or 2. It is characterized by having.

  The exhaust gas treatment method according to claim 4 of the present invention treats boiler exhaust gas generated by burning either or both of reformed exhaust gas and dry distillation oil generated when reforming low-grade coal in a boiler. An exhaust gas treatment method, wherein a boiler that burns one or both of the reformed exhaust gas and the dry distillation oil, a denitration step of denitrating nitrogen oxides contained in the boiler exhaust gas, and the boiler exhaust gas In the boiler exhaust gas by spraying activated carbon at least once before and after the alkali supplying step and supplying the alkali metal salt and / or alkaline earth metal salt, and before and after the alkali supplying step. And an activated carbon adsorption process for adsorbing mercury, and a collection and removal process for collecting and removing the compound produced by desulfurization and the activated carbon adsorbed with mercury.

  Further, the exhaust gas treatment method according to claim 5 of the present invention is the exhaust gas treatment method according to claim 4, wherein the denitration catalyst is a reducing agent that reduces nitrogen oxides contained in the boiler exhaust gas, and an oxidation that oxidizes mercury in the presence of hydrogen chloride. An agent that reduces nitrogen oxides contained in the boiler exhaust gas with an auxiliary agent and a denitration catalyst, and supplies any one or more reducing oxidation assistants that oxidize mercury in the presence of hydrogen chloride into the flue of the boiler. It has a supply process, and the reduction | restoration denitration process which has a denitration catalyst which oxidizes mercury in presence of hydrogen chloride while reducing the nitrogen oxide in the said boiler exhaust gas with a reducing agent, It is characterized by the above-mentioned.

  According to the exhaust gas treatment apparatus and treatment method and coal reforming process facility of the present invention, NOx, SOx, and Hg in boiler exhaust gas generated by burning reformed exhaust gas and dry distillation oil generated from a coal reforming process in a boiler are removed. There is an effect that it can be removed.

FIG. 1 is a configuration diagram of a coal reforming process facility having an exhaust gas treatment apparatus according to the present embodiment. FIG. 2 is a schematic configuration diagram of the exhaust gas treatment apparatus according to the present embodiment.

  Embodiments of a coal reforming process facility having an exhaust gas treatment apparatus according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by the content described in the following Examples. In addition, constituent elements in the following embodiments described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments described below can be appropriately combined.

<Coal reforming process equipment>
A coal reforming process facility having an exhaust gas treatment apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a coal reforming process facility having an exhaust gas treatment apparatus according to an embodiment of the present invention. As shown in FIG. 1, the coal reforming process facility 10 includes a coal reformer 11 and an exhaust gas treatment device 30.

[Coal reformer]
The coal reforming apparatus 11 includes a drying furnace 16 that is a drying means for drying the low quality coal 12, a dry distillation furnace 17 that is a carbonization means for dry distillation of the dry coal 13, and a pulverizer that is a pulverization means for pulverizing the dry distillation coal 14. 18, a molding machine 19 that is a molding means for compressing and molding the pulverized dry-distilled coal 14, and a cooler 20 that cools and inactivates the molded reformed coal 15.

  In the present embodiment, the dry gas 16a, the dry distillation gas 17a, and the dry distillation off gas 17b that are generated when the low-grade coal 12 is reformed by the coal reformer 11 are referred to as reformed exhaust gas 27. Further, the reformed exhaust gas 27 including any one of the dry gas 16a, the dry distillation gas 17a, and the dry distillation off gas 17b generated when the low-grade coal 12 is reformed, and the dry distillation oil 25a generated by dry distillation of the dry coal 13. Exhaust gas generated by combustion in the boiler 28 is referred to as boiler exhaust gas 29.

  A hopper (not shown), which is a coal supply means for supplying the low quality coal 12, is connected to the inlet of the drying furnace 16. The outlet of the drying furnace 16 is connected to the inlet of the dry distillation furnace 17. The outlet of the carbonization furnace 17 is connected to the inlet of the pulverizer 18. The outlet of the pulverizer 18 is connected to the inlet of the molding machine 19. The outlet of the molding machine 19 is connected to the cooler 20. The reformed coal 15 as a product is discharged from the outlet of the cooler 20.

  The gas discharge port of the carbonization furnace 17 is connected to a gas inlet of an oil scrubber 25 that separates and recovers the gaseous carbonization oil 25a generated from the dry coal 13 by carbonization from the carbonization gas 17a, and is a fuel supply means for carbonization. It is connected to the gas inlet of the circulation blower 24. The gas outlet of the circulation blower 24 is connected to a heating gas supply path of a dry distillation combustion furnace 22 which is a dry distillation combustion gas generating means. The dry distillation oil 25a recovered by the oil scrubber 25 is supplied to the dry distillation combustion furnace 22, the dry combustion furnace 21, and the private power generation boiler 28. The gas outlet of the oil scrubber 25 is connected to a mist separator 26 that separates the mist-like dry distillation oil 25a. A part of the dry distillation off gas 17 b separated by the mist separator 26 is supplied to the dry distillation combustion furnace 22 and the drying combustion furnace 21. Others are supplied to the private power generation boiler 28. The private power generation boiler 28 is connected to a private power generation device (not shown) provided with a steam turbine or the like.

  A gas discharge port of the drying furnace 16 is connected to a gas receiving port of a circulation blower 23 which is a drying fuel supply means. The gas outlet of the circulation blower 23 is connected to the private power generation boiler 28 and to the heating gas supply path of the drying combustion furnace 21 which is a drying combustion gas generating means.

  The boiler exhaust gas 29 after burning in the private power generation boiler 28 is discharged from the chimney 36 after NOx, SOx, Hg, etc. in the boiler exhaust gas 29 are removed by the exhaust gas treatment device 30 of the coal reforming process facility 10. Hereinafter, the reformed exhaust gas treatment apparatus of the coal reforming process facility 10 may be referred to as “exhaust gas treatment apparatus”.

  In the coal reforming process facility 10 according to the present embodiment, when the low quality coal 12 is introduced into the hopper, the hopper supplies the low quality coal 12 to the drying furnace 16 in a fixed amount. The low quality coal 12 supplied to the drying furnace 16 is heated with a drying heating gas (about 150 ° C. to 350 ° C.) from the drying combustion furnace 21 to remove moisture, thereby becoming dry coal 13. And transferred to the dry distillation furnace 17. The dry charcoal 13 transferred to the dry distillation furnace 17 is heated by dry distillation combustion gas (about 350 ° C. to 550 ° C.) from the dry distillation combustion furnace 22 to be dry distilled, whereby the dry distillation gas 17a, the dry distillation oil 25a, etc. These components are removed and the carbonized carbon 14 is transferred to a pulverizer 18. The pulverized dry distillation coal 14 is transferred to a molding machine 19. The dry distillation coal 14 transferred to the molding machine 19 becomes a reformed coal 15 having a briquette shape or the like by being compression-molded. The reformed coal 15 thus formed is cooled by the cooler 20 and is subjected to an inactivation treatment to become a product reformed coal 15.

  On the other hand, a part of the dry distillation gas 17 a generated in the dry distillation furnace 17 is sent to the heated gas supply path of the dry distillation combustion furnace 22 by the circulation blower 24. A part of the dry distillation oil 25a recovered by the oil scrubber 25 and the gaseous dry distillation oil (dry distillation off gas: about 300 ° C. to 350 ° C.) 17b separated by the mist separator 26 are fed to the combustion furnace 22 for dry distillation. By being burned, the combustion gas for dry distillation (about 350 ° C. to 550 ° C.) is supplied to the dry distillation furnace 17.

  On the other hand, a part of the dry distillation oil 25a and a part of the dry distillation off gas 17b are supplied to the drying combustion furnace 21 and burned to become a drying combustion gas (about 150 ° C. to 350 ° C.). 16 is supplied. Part of the combustion gas used for drying in the drying furnace 16 (dry gas 16a, about 90 ° C. to 150 ° C.) is sent again to the drying furnace 16 together with the combustion gas from the drying combustion furnace 16 by the circulation blower 23. The other dry gas 16 a is supplied to the private power generation boiler 28.

  A part of the dry distillation off gas 17b is supplied to the private power generation boiler 28 as the reformed exhaust gas 27. A part of the carbonized oil 25a is supplied to the private power generation boiler 28. The reformed exhaust gas 27 and the dry distillation oil 25a are combusted as fuel and introduced into the exhaust gas treatment device 30 as a boiler exhaust gas 29. Then, NOx, SOx, Hg, etc. are removed and discharged out of the system. On the other hand, the steam generated in the private power generation boiler 28 is supplied to a private power generation device (not shown), and power is generated by moving the steam turbine. The electric power generated by the private power generation apparatus is used by the power usage equipment in the coal reforming process facility 10 and the surplus is sold.

[Exhaust gas treatment equipment]
Next, the configuration of the exhaust gas treatment apparatus 30 according to the present embodiment will be described. FIG. 2 is a schematic configuration diagram of an exhaust gas treatment apparatus for a coal reforming process facility according to the present embodiment. As shown in FIG. 2, the exhaust gas treatment apparatus 30 according to the present embodiment uses a reformed exhaust gas 27 generated from the coal reforming apparatus 11 and a dry distillation oil 25 a generated by dry distillation of the dry coal 13 as a private power generation boiler ( This is an exhaust gas treatment device 30 that removes NOx, SOx, and Hg contained in the boiler exhaust gas 29 generated by combustion in the boiler 28). The boiler exhaust gas 29 discharged from the boiler 28 was purified through the processes in the reduction denitration device 32, the air preheater 33, the spray dryer (alkali supply means) 34, and the bag filter (collection removal means) 35. After that, it is discharged from the chimney 36 outdoors.

  The exhaust gas treatment apparatus 30 according to this embodiment includes a denitration means (not shown), a chemical supply unit 40, a reduction denitration apparatus 32, an air preheater (AH) 33, a spray dryer (alkali supply means) 34, and a bag filter. (Collecting / removing means) 35 and activated carbon adsorbing means (activated carbon spraying device) 38.

(Drug supply department)
The chemical supply unit 40 includes an oxidation aid solution supply unit (not shown), a reducing agent solution supply unit (not shown), and a reduction oxidation aid supply unit (not shown). The oxidation aid solution supply means supplies an HCl solution containing hydrogen chloride (HCl) as the oxidation aid 41. The reducing agent solution supply means supplies an NH ₃ solution containing ammonia (NH ₃ ) as the reducing agent 42. The oxidation-reduction aid supply means supplies an NH ₄ Cl solution containing ammonium chloride (NH ₄ Cl) as the reduction oxidation aid 43.

The chemical supply unit 40 supplies an HCl solution, an NH ₃ solution, and an NH ₄ Cl solution, each solution adjusted to a predetermined concentration in the solution tank, to the upstream side of the reductive denitration device 32 on the downstream side of the boiler 28. It supplies in the flue 31 which is a side.

In this embodiment, the reduction oxidation aid 43 functions as an oxidation aid used to oxidize metallic mercury (Hg ⁰ ) in the presence of an oxidizing gas and a reducing agent that reduces NOx with the reducing gas. Say what you do. In this embodiment, HCl gas is used as the oxidizing gas, and NH ₃ gas is used as the reducing gas. The reducing agent 42 refers to a denitration catalyst that reduces NOx contained in the boiler exhaust gas 29. In addition, the oxidation assistant 41 is an agent that oxidizes (Hg ⁰ → Hg ²⁺ ) metal mercury (Hg ⁰ ) contained in the exhaust gas in the presence of HCl gas on the denitration catalyst.

The boiler exhaust gas 29 discharged from the boiler 28 is supplied with an HCl solution from an oxidizing aid solution supply means (not shown). The HCl solution supply means sprays the HCl solution on the boiler exhaust gas 29 in a liquid state, and oxidizes Hg ⁰ contained in the boiler exhaust gas 29 (Hg ⁰ → Hg ²⁺ ).

The droplets of the HCl solution sprayed from the nozzle head of the spraying device into the flue 31 are evaporated and vaporized by the high-temperature ambient temperature of the boiler exhaust gas 29, and HCl gas can be supplied into the flue 31. HCl gas oxidizes Hg as shown in the following formula (1).
Hg + 1 / 2O ₂ + 2HCl → HgCl ₂ + H ₂ O (1)

  In the exhaust gas treatment apparatus 30 according to the present embodiment, HCl is used as the oxidation aid 41. However, the present embodiment is not limited to this, and the oxidation aid 41 generates an oxidizing gas when vaporized. Anything can be used. Examples thereof include hydrogen halides such as hydrogen bromide (HBr) and hydrogen iodide (HI). Moreover, although the oxidation auxiliary agent 41 was demonstrated as a liquid, it is not restricted to this, You may supply gas (for example, hydrogen chloride gas).

Further, the boiler exhaust gas 29 discharged from the boiler 28 is supplied with NH ₃ solution from a reducing agent solution supply means (not shown). The NH ₃ solution supply means sprays the NH ₃ solution on the boiler exhaust gas 29 in a liquid state to reduce NOx contained in the boiler exhaust gas 29.

The droplets of the NH ₃ solution sprayed from the nozzle head of the spraying device into the flue 31 are evaporated and vaporized by the high-temperature ambient temperature of the boiler exhaust gas 29, and NH ₃ gas can be supplied into the flue 31. The NH ₃ gas reduces and denitrifies NOx as shown in the following formula (2) on the denitration catalyst filled in the denitration catalyst layer filled in the reductive denitration device 32.
4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O (2)

In the exhaust gas treatment apparatus 30 according to the present embodiment, NH ₃ is used as the reducing agent 42, but the present embodiment is not limited to this, and the reducing agent 42 generates reducing gas when vaporized. Anything can be used. For example, urea ((NH ₂ ) ₂ CO) can be used. Moreover, although the reducing agent 42 was demonstrated as a liquid, you may supply gas (for example, ammonia gas), without being restricted to this.

Further, the boiler exhaust gas 29 discharged from the boiler 28 is supplied with an NH ₄ Cl solution from a reduction oxidation aid supply means (not shown). The NH ₄ Cl solution supply means sprays the NH ₄ Cl solution onto the boiler exhaust gas 29 in a liquid state, and is included in the boiler exhaust gas 29 on the denitration catalyst filled in the denitration catalyst layer filled in the reduction denitration device 32. NOx is reduced and Hg ⁰ is oxidized.

The droplets of the NH ₄ Cl solution sprayed into the flue 31 from the nozzle head of the spraying device are evaporated and vaporized by the high-temperature ambient temperature of the boiler exhaust gas 29 to generate fine NH ₄ Cl solid particles. As shown in formula (3), it decomposes into HCl and NH ₃ and sublimates. Therefore, the NH ₄ Cl solution sprayed from the spray device is decomposed to generate HCl and NH ₃ , and NH ₃ gas and HCl gas can be supplied into the flue 31.
NH ₄ Cl → NH ₃ + HCl (3)

HCl gas oxidizes Hg as shown in equation (1) above. The NH ₃ gas reduces and denitrates NOx as shown in the above equation (2) on the denitration catalyst filled in the denitration catalyst layer filled in the reductive denitration device 32.

Further, in the exhaust gas treatment apparatus 30 according to the present embodiment, NH ₄ Cl is used as the reduction oxidation aid 43, but this embodiment is not limited to this, and the reduction oxidation aid 43 is vaporized. Any material that generates an oxidizing gas and a reducing gas can be used. An ammonium halide other than NH ₄ Cl, such as ammonium bromide (NH ₄ Br), ammonium iodide (NH ₄ I), or the like may be used as the reduction oxidation aid 43, and a solution dissolved in water may be used. Further, a mixed solution of NH ₄ Cl and aqueous ammonia or hydrochloric acid may be used. Moreover, although the reduction oxidation aid 43 has been described as a liquid, the present invention is not limited to this, and a gas (for example, hydrogen chloride gas and ammonia gas) may be supplied.

As a means for supplying the HCl solution, the NH ₃ solution, and the NH ₄ Cl solution into the flue 31 of the boiler 28, for example, a two-fluid nozzle or the like may be used. In addition, a present Example is not limited to this, You may use the injection nozzle for normal liquid spraying. The supply amounts of the HCl solution, NH ₃ solution, and NH ₄ Cl solution can be arbitrarily adjusted.

  Although the temperature of the boiler exhaust gas 29 in the flue 31 depends on the combustion conditions of the boiler 28, for example, it is preferably 320 ° C. or higher and 420 ° C. or lower, more preferably 320 ° C. or higher and 380 ° C. or lower, and further 350 ° C. or higher and 380 ° C. or lower. preferable. This is because NOx denitration reaction and Hg oxidation reaction can be efficiently generated on the denitration catalyst in these temperature zones.

In the present embodiment, any one or more of an oxidation assistant (HCl solution) 41, a reducing agent (NH ₃ solution) 42, and a reducing oxidation assistant (NH ₄ Cl solution) 43 are provided on the downstream side of the boiler 28. Thus, the air is fed into the flue 31 on the upstream side of the reducing denitration device 32. For example, when the HCl component is insufficient in the NH ₄ Cl solution depending on the content of the boiler exhaust gas 29 component, two NH ₄ Cl solution and HCl solution may be supplied, or the HN ₃ component is insufficient For example, two of NH ₄ Cl solution and NH ₃ solution may be supplied. Further, two of an HCl solution and an NH ₃ solution may be supplied. Further solution _of NH ₄ Cl, HCl solutions, may be supplied with three NH ₃ solution. Further, NOx only supply of the reducing oxidizing aid (NH ₄ Cl solution) 43, SOx, if possible removal of Hg is, ₍₄ Cl solution NH) reducing oxidizing aid 43 one may supply. Therefore, in the exhaust gas treatment apparatus according to the present embodiment, each supply amount of the HCl solution, the NH ₃ solution, and the NH ₄ Cl solution is obtained by determining the contents of NOx, SOx, and Hg contained in the boiler exhaust gas 29. , Can be adjusted by its value. FIG. 2 shows a configuration in which an oxidation assistant (HCl solution) 41, a reducing agent (NH ₃ solution) 42, and a reducing oxidation assistant (NH ₄ Cl solution) 43 are supplied. However, the present invention is not limited to this, and the above three solutions may be mixed and supplied. In addition to the HCl solution, the NH ₃ solution, and the NH ₄ Cl solution, a solution in which the reducing oxidation aid 43 is dissolved, a solution in which the reducing agent 42 is dissolved, and an oxidizing agent (mercury chlorinating agent) 41 are dissolved. Further, a plurality of solutions may be mixed and supplied.

(Reduction denitration equipment)
The reductive denitration device 32 has a denitration catalyst (not shown) that reduces NOx in the boiler exhaust gas 29 with NH ₃ gas and oxidizes metallic mercury (Hg ⁰ ) in the presence of HCl gas. As shown in FIG. 2, the boiler exhaust gas 29 contains, for example, HCl gas and NH ₃ gas generated from droplets of the NH ₄ Cl solution sprayed into the flue 31 from the NH ₄ Cl solution supply means 43. The reduced denitration device 32 is fed. In the reductive denitration device 32, NH ₃ gas generated by decomposition of NH ₄ Cl is used for NOx reductive denitration, and HCl gas is used for Hg oxidation, and NOx and Hg are removed from the boiler exhaust gas 29.

That is, NH ₃ gas reduces and denitrates NOx as shown in the following equation (4) on the denitration catalyst packed in the denitration catalyst layer filled in the reduction denitration device 32, and HCl gas expresses the following equation (5). Hg is oxidized (chlorinated) as shown in FIG.
4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O (4)
Hg + 1 / 2O ₂ + 2HCl → HgCl ₂ + H ₂ O (5)

  The reduction denitration device 32 includes one denitration catalyst layer, but the present embodiment is not limited to this, and the reduction denitration device 32 appropriately changes the number of denitration catalyst layers according to the denitration performance. be able to.

  The boiler exhaust gas 29 passes through an air preheater 33 that recovers heat in the boiler exhaust gas 29 after NOx reduction and Hg oxidation in the boiler exhaust gas 29 are performed in the reductive denitration device 32, and then a spray dryer (alkali supply means). ) 34 and desulfurized.

  In the present embodiment, the above-described reduction denitration device 32 may not be provided, and a configuration having denitration means may be employed. In the case of the configuration having the denitration means, examples of the denitration means include a low NOx burner, a low NOx operation, and in-furnace denitration. Examples of the low NOx operation include two-stage combustion, exhaust gas recirculation combustion, and low air ratio combustion. By controlling the supply amount of combustion air and combustion exhaust gas, the oxidation-reduction atmosphere and combustion temperature in the boiler 28 can be controlled, and the generation of NOx can be suppressed. Note that the denitration means is not limited to this, and a conventional denitration technique capable of reducing NOx to suppress the generation of NOx can be applied.

(Spray dryer)
The spray dryer (alkali supply means) 34 removes SOx in the boiler exhaust gas 29 by reacting with an alkali metal salt or an alkaline earth metal salt, for example, slaked lime slurry (Ca (OH) ₂ slurry) 37. . Examples of the alkali metal salt include sodium bicarbonate NaHCO ₃ and caustic soda NaOH as sodium salts. Examples of the alkaline earth metal salt include calcium hydroxide Ca (OH) ₂ , CaO, CaCO _{3 and the} like. The spray dryer (alkali supply means) 34 supplies either one or both of an alkali metal salt and an alkaline earth metal salt. As shown in FIG. 2, in the spray dryer, the boiler exhaust gas 29 is brought into gas-liquid contact with the slaked lime slurry 37 sprayed into the spray dryer 34 from the slaked lime slurry 37 supply means, and is oxidized with SOx in the boiler exhaust gas 29. A part of mercury (HgCl ₂ ) is absorbed in the slaked lime slurry 37. Then, the generated gypsum and calcium sulfite are collected by a bag filter (collecting / removing means) 35 on the downstream side, separated and removed from the boiler exhaust gas 29, and the boiler exhaust gas 29 is purified. The boiler exhaust gas 29 purified by the slaked lime slurry 37 is discharged out of the system from the chimney 36 as a purified boiler exhaust gas 29a.

The slaked lime slurry 37 used for the desulfurization reaction of the boiler exhaust gas 29 is supplied to the spray dryer 34 from the slaked lime slurry 37 supply line 37a. The slaked lime slurry 37 is generated by mixing water with quick lime (CaO). By spraying the slaked lime slurry 37 into the spray dryer 34, the SOx in the boiler exhaust gas 29 undergoes the desulfurization reaction and the drying of lime as shown in the following formulas (6) and (7) simultaneously, and gypsum (CaSO _4. 2H ₂ O) and calcium sulfite (CaSO ₃ .0.5H ₂ O) mixed particles. The particles are collected and collected by a collection / removal means (bag filter) 35 on the downstream side.
Ca (OH) ₂ + SO ₂ → CaSO ₃ .0.5H ₂ O + 0.5H ₂ O (6)
CaSO ₃ · 0.5H ₂ O + 0.5O ₂ + 1.5H ₂ O → CaSO ₄ · 2H ₂ O (7)

In this way, SO _x in the boiler exhaust gas 29 is captured in the form of gypsum (CaSO ₄ .2H ₂ O) or calcium sulfite (CaSO ₃ .0.5H ₂ O) in the spray dryer 34. At this time, since mercury chloride (HgCl ₂ ) in the boiler exhaust gas 29 is water-soluble, a part of mercury chloride (HgCl ₂ ) is transferred to the slaked lime slurry 37 side. As the spray dryer 34 as the alkali supply means 34, a conventional spray dryer can be used.

The mixed particles of gypsum (CaSO ₄ · 2H ₂ O) and calcium sulfite (CaSO ₃ · 0.5H ₂ O) generated by the desulfurization reaction in the spray dryer 34 are sent to the bag filter 35 together with the boiler exhaust gas 29 and collected. Removed. Gypsum, calcium sulfite, dust and the like collected and collected by the bag filter 35 are treated as waste. Examples of the detoxification treatment of waste include a cement solidification treatment. A conventional bug filter can be used as the bag filter 35 as the collecting and removing means 35.

  The supply method of the slaked lime slurry 37 can use the two-fluid nozzle which injects the slaked lime slurry 37 and air into the spray dryer 34 simultaneously mentioned above. In addition, a present Example is not limited to this, You may use the injection nozzle for normal liquid spraying. The method is not limited to the method in which the nozzle is jetted in the horizontal direction downstream from the nozzle with respect to the flow of the boiler exhaust gas 29. For example, the nozzle may be jetted in the horizontal direction upstream so as to face the flow of the boiler exhaust gas 29.

(Activated carbon adsorption means)
The activated carbon spraying device 38 is an activated carbon adsorbing means for adsorbing and removing oxidized mercury in the boiler exhaust gas 29. As shown in FIG. 2, in the activated carbon spraying device (activated carbon adsorption means) 38, at least one of the upstream side and the downstream side of the spray dryer (alkali supply means) 34 and between them, Activated carbon is sprayed to adsorb oxidized mercury (HgCl ₂ ). The activated carbon that has adsorbed oxidized mercury is collected by a bag filter (collecting / removing means) 35 on the downstream side, separated and removed from the boiler exhaust gas 29, and the boiler exhaust gas 29 is purified. The boiler exhaust gas 29 purified by activated carbon is discharged out of the system from the chimney 36 as purified gas.

  For example, the above-described two-fluid nozzle may be used as the activated carbon supply method. It is not limited to the method of spraying in the horizontal direction downstream of the flow of the boiler exhaust gas 29 from the nozzle. For example, it may be sprayed in the horizontal direction upstream so as to face the flow of the boiler exhaust gas 29. Further, the spray may be made to flow down from the upper side of the apparatus to the lower side. In addition, about the spraying method of activated carbon, it is not restricted to this, The conventional method can be used. As the supply position of the activated carbon, the flue 31 on the upstream side 39a of the spray dryer 34, the inside 39b of the spray dryer 34, and the flue on the downstream side 39c of the spray dryer 34 on the upstream side of the bag filter 35 are provided. 31 is supplied to any one of the interior of the bag 31 and the front chamber of the bag filter 35. Alternatively, the adsorption / removal rate of oxidized mercury can be improved by supplying any two or more. The activated carbon to be supplied is more preferably used in combination of two or more types having different properties. This is because by using a combination of a plurality of types of activated carbon, it is possible to adsorb other substances such as SOx, NOx, and harmful components simultaneously with the removal of mercury.

  Activated carbon, dust, and the like collected and collected by the bag filter (collecting / removing means) 35 are treated as waste. Examples of the detoxification treatment of waste include a cement solidification treatment. A conventional bug filter can be used as the bag filter as the collecting and removing means 35.

Further, the boiler exhaust gas 29 of the coal reforming process facility 10 to be treated in the present embodiment has a water concentration (H ₂ O) of about three times and an oxygen concentration (O ₂ ) of about 1 as compared with the exhaust gas of the coal fired boiler. / 3 times, the nitrogen oxide (NOx) concentration is about 4 to 5 times, and the mercury (Hg) concentration is about 4 times. When the water concentration (H ₂ O) is high and the oxygen concentration (O ₂ ) and the hydrogen chloride concentration (HCl) are low, the mercury removal performance by activated carbon may be reduced due to the coexisting components.

Thus, in this embodiment, the concentration of HCl (HCl) sprayed into the flue 31 on the upstream side of the reductive denitration device 32 is increased in order not to lower the mercury removal performance by activated carbon. In this embodiment, the concentrations of the HCl solution and NH ₄ Cl solution supplied by the oxidation assistant solution supply means and the reduction oxidation assistant supply means (ammonium chloride (NH ₄ Cl) solution supply means) are increased. Note that HCl gas may be supplied. The concentration of hydrogen chloride supplied into the flue 31 is preferably in the range of 1 ppm to 1000 ppm, more preferably 10 ppm to 200 ppm. If the hydrogen chloride concentration is within the above range, mercury contained in the reformed exhaust gas 27 can be adsorbed and removed by the activated carbon spray device (activated carbon adsorption means) 38.

As described above, the exhaust gas treatment device 30 according to the present embodiment includes the oxidation auxiliary agent 41, the reducing agent 42, the reduction agent in the flue 31 that is the downstream side of the boiler 28 and the upstream side of the reducing denitration device 32. A chemical supply unit 40 for supplying any one or more of the oxidation assistants 43, a reductive denitration device 32 for reducing NOx in the boiler exhaust gas 29 with NH ₃ gas and oxidizing Hg ⁰ in the presence of HCl gas; A spray dryer (alkaline supply means) 34 that removes part of SOx and oxidized divalent Hg ^{2+ in} the reductive denitration device 32, and an activated carbon spray device (activated carbon that adsorbs and removes mercury (HgCl ₂ ) oxidized by activated carbon. (Adsorption means) 38 and a bag filter (collection removal means) 35 for collecting and removing gypsum and calcium sulfite produced by desulfurization and activated carbon adsorbing oxidized mercury. As described above, according to the exhaust gas treatment device 30 according to the present embodiment, NOx contained in the boiler exhaust gas 29 generated by combustion in the boiler 28 is removed by the reduction denitration device 32, and oxidation is performed in the SOx and reduction denitration device 32. The reformed exhaust gas 27 is obtained by removing the divalent Hg ²⁺ by a spray dryer (alkaline supplying means) 34, an activated carbon spraying device (activated carbon adsorbing means) 38, and a bag filter (collecting and removing means) 35. In addition, NOx, SOx, and Hg contained in the boiler exhaust gas 29 can be removed. Further, in the present embodiment, in the case where the reduction denitration device 32 is not provided, NOx can be denitrated by having a denitration means. Furthermore, since a wet desulfurization apparatus is not required, it is possible to provide a coal reforming plant that does not discharge desulfurization wastewater to the outside and that does not discharge wastewater.

DESCRIPTION OF SYMBOLS 10 Coal reforming process equipment 11 Coal reformer 12 Low grade coal 13 Dry coal 14 Carbonized carbon 15 Carbonated coal 16 Drying furnace 16a Drying gas 17 Carbonation furnace 17a Carbonation gas 17b Carbonization off gas (gaseous carbonization oil)
18 Crusher 19 Molding machine 20 Cooler 21 Combustion furnace (drying combustion furnace)
22 Combustion furnace (combustion furnace for dry distillation)
23, 24 Circulating blower 25 Oil scrubber 25a Distilled oil (CDL)
26 Mist separator 27 Reformed exhaust gas 28 Private power generation boiler 29 Boiler exhaust gas 29a Purification boiler exhaust gas 30 Exhaust gas treatment device 31 Flue 32 Reductive denitration device 33 Air preheater (air heater: AH)
34 Spray dryer (alkali supply means)
35 Bug filter (collection removal means)
36 Chimney 37 Slaked lime slurry (Ca (OH) ₂ slurry)
38 Activated carbon spray device (activated carbon adsorption means)

Claims (5)

An exhaust gas treatment apparatus for treating boiler exhaust gas generated by burning one or both of reformed exhaust gas and dry distillation oil generated when reforming low-grade coal in a boiler,
A boiler that burns one or both of the reformed exhaust gas and the carbonized oil; and
Denitration means for denitrating nitrogen oxides contained in the boiler exhaust gas;
An alkali supply means for supplying one or both of an alkali metal salt and an alkaline earth metal salt into the boiler exhaust gas;
Activated carbon adsorbing means for adsorbing mercury in the boiler exhaust gas by spraying activated carbon on at least one of the upstream side and the downstream side of the alkali supply means and between them;
A collection and removal means for collecting and removing the activated carbon that has adsorbed the compound produced by desulfurization and mercury;
An exhaust gas treatment apparatus comprising: A reducing agent that reduces nitrogen oxides contained in the boiler exhaust gas with a denitration catalyst, an oxidation aid that oxidizes mercury in the presence of hydrogen chloride, and a nitrogen oxide contained in the boiler exhaust gas with a denitration catalyst and chlorinated. A chemical supply section for supplying any one or more reduction oxidation assistants that oxidize mercury in the presence of hydrogen into the boiler flue;
A reduction denitration apparatus having a denitration catalyst for reducing nitrogen oxides in the boiler exhaust gas with a reducing agent and oxidizing mercury in the presence of hydrogen chloride;
The exhaust gas treatment apparatus according to claim 1, wherein A drying furnace for drying low-grade coal;
A carbonization furnace for carbonizing dried dry coal;
The exhaust gas treatment device according to claim 1 or 2,
A coal reforming process facility characterized by comprising: An exhaust gas treatment method for treating boiler exhaust gas generated by burning one or both of reformed exhaust gas and dry distillation oil generated when reforming low-grade coal in a boiler,
A boiler that burns one or both of the reformed exhaust gas and the carbonized oil; and
A denitration step of denitrating nitrogen oxides contained in the boiler exhaust gas;
An alkali supply step of supplying one or both of an alkali metal salt and an alkaline earth metal salt in the boiler exhaust gas;
An activated carbon adsorption step of spraying activated carbon to adsorb mercury in the boiler exhaust gas at least once before and after the alkali supply step and during the step;
A collection and removal step of collecting and removing the activated carbon having adsorbed the compound produced by desulfurization and mercury;
An exhaust gas treatment method characterized by comprising: A reducing agent that reduces nitrogen oxides contained in the boiler exhaust gas with a denitration catalyst, an oxidation aid that oxidizes mercury in the presence of hydrogen chloride, and a nitrogen oxide contained in the boiler exhaust gas with a denitration catalyst, A chemical supply step for supplying any one or more reducing oxidation assistants that oxidize mercury in the presence of hydrogen chloride into the boiler flue;
A reduction denitration step having a denitration catalyst for reducing mercury oxide in the boiler exhaust gas with a reducing agent and oxidizing mercury in the presence of hydrogen chloride;
The exhaust gas treatment method according to claim 4, comprising:

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