JP2008272574A - Method of suppressing elution of hexavalent chromium and thermal power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of suppressing elution of hexavalent chromium which does not require a large amount of equipment investment and can reduce a chemical purchase cost, and to provide a thermal power generation system capable of suppressing elution of hexavalent chromium. <P>SOLUTION: The method of suppressing elution of hexavalent chromium is a method of suppressing the elution of hexavalent chromium from coal ash in the thermal power generation system provided with a combustion boiler 142 of combusting fuel, and a dust collector 164 which is disposed on the downstream of the combustion boiler 142 and collects coal ash in the exhaust gas produced by combustion of coal. The method of suppressing elution of hexavalent chromium comprises: a calcium sulfite producing process S40 of producing calcium sulfite by reacting sulfur oxide in exhaust gas and a calcium compound in a low oxygen environment; and an ash-elution suppressor mixing process S50 of mixing the calcium sulfite produced in the calcium sulfite producing process S40 and the fly ash collected by the dust collector 164. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hexavalent chromium elution suppression method and a thermal power generation system.

  There are various methods for burning coal in a coal-fired power generation system that is an example of a thermal power generation system. Among them, finely pulverized particles of coal are blown into a furnace of a combustion boiler (coal boiler) and burned. The so-called pulverized coal combustion method is mainly adopted. And, from the viewpoint of effective use of resources, some of the coal ash that becomes the residue after coal combustion is used as civil engineering and building materials such as concrete and soil improvement materials, but the surplus is disposed of in landfills .

  By the way, coal used as fuel contains sulfur compounds and nitrogen compounds in addition to carbon, and also contains trace amounts of harmful elements such as boron, fluorine, selenium, arsenic and hexavalent chromium (hereinafter referred to as the above harmful Elements are called "toxic trace elements"). For this reason, in consideration of the environment, the allowable concentration of harmful trace elements from coal ash is regulated by law.

  In particular, hexavalent chromium among harmful trace elements has a great adverse effect on the human body and has been a cause of large-scale soil contamination in the past. For this reason, elution of hexavalent chromium from coal ash (hereinafter referred to as “hexavalent chromium” includes hexavalent chromium compounds) is strictly regulated.

  Therefore, a technique for reducing the elution concentration of hexavalent chromium contained in coal ash to a regulated value or less has been studied.

For example, an elution inhibitor is proposed to suppress the elution of hexavalent chromium from cement by adding artificial zeolite impregnated with one of aqueous solutions of sodium sulfite, sodium bisulfite, and calcium sulfite to cement. (See Patent Document 1).
JP-A-2005-112706

  However, the cost of purchasing sodium sulfite, sodium bisulfite, and calcium sulfite used in the prior art described in Patent Document 1 is high, and in a thermal power plant, these chemicals are actually used to convert hexavalent chromium. It is difficult to suppress elution. In addition, even if an attempt is made to reduce the purchase cost of the drug by providing the above-mentioned drug manufacturing facility, naturally, a large amount of capital investment is required for the installation of the manufacturing facility.

  The present invention has been made in view of the above-mentioned problems, and does not require a large amount of capital investment, and can reduce the cost of drug purchase, and a hexavalent chromium elution suppressing method and hexavalent chromium can be reduced. It aims at providing the thermal power generation system which can suppress elution.

  As a result of intensive studies to solve the above problems, the present inventors have found that elution of hexavalent chromium from combustion ash can be suppressed by mixing calcium sulfite and combustion ash. .

  (1) In the thermal power generation system comprising: a combustion boiler that burns fuel; and a dust collector that is provided downstream of the combustion boiler and collects combustion ash in exhaust gas generated by the combustion of the fuel. A hexavalent chromium elution suppression method for suppressing elution of hexavalent chromium from ash, the sulfur compound in the exhaust gas, and a calcium compound containing at least one selected from the group consisting of quicklime, limestone, and slaked lime, Calcium sulfite production step for producing calcium sulfite by reacting in a low oxygen atmosphere, calcium sulfite produced in the calcium sulfite production step, and combustion ash collected by the dust collector A hexavalent chromium elution suppression method comprising: a mixing step.

According to the invention of (1), calcium sulfite is generated from sulfur oxide (sulfurous acid gas (SO ₂ )) in the exhaust gas generated by the combustion of fuel in the thermal power generation system. Since sulfur oxide is contained in the exhaust gas, no sulfur oxide production facility is required. In addition, calcium sulfite can be produced by modifying an existing desulfurization apparatus that is usually provided in a thermal power generation system. Furthermore, since the drug cost is only the purchase cost of a calcium compound containing at least one selected from the group consisting of quick lime, limestone, and slaked lime that is relatively inexpensive and easily available, the drug purchase cost can be kept low. It is.

  As described above, according to the invention of (1), sulfur oxides, which are regulated as harmful substances in the thermal power generation system, are effectively used, a large capital investment is not required, and the purchase cost of the medicine is low. It is possible to suppress elution of hexavalent chromium from combustion ash while reducing costs.

  (2) The hexavalent chromium elution suppression method according to (1), wherein the thermal power generation system is a pulverized coal combustion type power generation system.

  (3) The hexavalent chromium elution suppression method according to (1), wherein the thermal power generation system is a heavy crude oil combustion type power generation system.

  The invention of (2) or (3) specifically defines a thermal power generation system. In the invention of (2) or (3), when the thermal power generation system is a coal thermal power generation system, there are power generation systems such as a fixed bed combustion system, a fluidized bed combustion system, and a pulverized coal combustion system. A power generation system is preferred. Moreover, when the thermal power generation system is an oil thermal power generation system, there are power generation systems such as a heavy crude oil combustion system and a crude oil combustion system, but any power generation system may be used. In addition, as another thermal power generation system, it is applicable also to power generation systems, such as an organic waste combustion system and a waste solid fuel (RDF) combustion system.

  (4) a combustion boiler that burns fuel; and a dust collector that is provided downstream of the combustion boiler and collects combustion ash in the exhaust gas generated by the combustion of the fuel; A thermal power generation system capable of suppressing elution of chromium, wherein the sulfur oxide in the exhaust gas reacts with a calcium compound containing at least one selected from the group consisting of quicklime, limestone, and slaked lime in a low oxygen atmosphere. A heating power comprising: a calcium sulfite generating device that generates calcium sulfite by mixing, a calcium sulfite generated by the calcium sulfite generating device, and a mixing device that mixes the combustion ash collected by the dust collector Power generation system.

  The invention of (4) captures the invention of (1) as a thermal power generation system. The same effect as the invention of (1) is produced.

  According to the present invention, sulfur oxide, which is regulated as a hazardous substance in a thermal power generation system, is effectively used, and a large amount of capital investment is not required. It is possible to suppress elution of hexavalent chromium.

  Hereinafter, an embodiment showing an example of the present invention will be described with reference to the drawings.

<A: Configuration of coal-fired power generation system>
FIG. 1 is a schematic explanatory diagram illustrating a coal-fired power generation system 10 that is an example of a thermal power generation system. Here, as shown in FIG. 1, the coal-fired power generation system 10 processes a coal supply / pulverized coal generation unit 12, a pulverized coal combustion unit 14 that burns pulverized coal, and exhaust gas generated by the combustion of pulverized coal. An exhaust gas treatment unit 16, a calcium sulfite generation unit 18, an ash / elution inhibitor mixing unit 20, and an exhaust gas discharge unit 22.

  In the present embodiment, the thermal power generation system in the present invention is a pulverized coal combustion type power generation system, but may be another thermal power generation system, specifically, heavy crude oil or heavy crude oil using crude oil. It may be a combustion type power generation system.

<A-1: Coal supply / pulverized coal generation unit>
The coal supply / pulverized coal generation unit 12 includes a coal bunker 122 that stores coal supplied from a coal silo (not shown) by a coal transportation facility, and a pulverized coal machine 124. The pulverized coal machine 124 pulverizes the coal supplied from the coal bunker 122 via a coal feeder (not shown) to a fine particle size to form pulverized coal. Then, by mixing the pulverized coal and air, the pulverized coal is preheated and dried to facilitate combustion. Air is blown onto the formed pulverized coal, whereby the pulverized coal machine 124 supplies the pulverized coal to the pulverized coal combustion unit 14.

<A-2: Pulverized coal combustion section>
The pulverized coal combustion unit 14 includes a combustion boiler 142 that burns coal, which is an example of fuel. The combustion boiler 142 burns the pulverized coal supplied from the pulverized coal machine 124 together with the forcibly supplied air. By burning pulverized coal, coal ash such as clinker ash, cinder ash, and fly ash, which are examples of combustion ash, is generated, and sulfur dioxide (sulfurous acid gas, SO ₂ ) and sulfur trioxide (SO ₃ ). Exhaust gases such as sulfur oxide (SOx) and nitrogen oxide (NOx) are generated. The combustion boiler 142 is connected to a denitration device 162 of the exhaust gas treatment unit 16 through an exhaust passage.

  Here, the clinker ash falls to the furnace bottom of the combustion boiler 142 and is collected, and is also referred to as bottom ash. Clinker ash is porous and has drainage (water permeability) and breathability. Cinder ash is combustion ash that falls when the exhaust gas of the combustion boiler 142 passes in the vicinity of the economizer or air preheater. Further, fly ash is the remaining soot and is collected (collected) by a dust collector 164 described later.

<A-3: Exhaust gas treatment unit>
The exhaust gas treatment unit 16 includes a denitration device 162, a dust collection device 164 that is provided downstream of the combustion boiler 142 and collects fly ash (dust) in the exhaust gas generated by combustion of coal, and a desulfurization device 166.

  The denitration device 162 disposed on the exhaust passage removes nitrogen oxides in the exhaust gas. In other words, ammonia gas is injected as a reducing agent into exhaust gas at a relatively high temperature (300 ° C. to 400 ° C.), and nitrogen oxides in the exhaust gas are decomposed into harmless nitrogen and water vapor by the action of a denitration catalyst. A catalytic reduction method is preferably used. The exhaust gas is cooled by exchanging heat with combustion air by an air preheater (AH) (not shown), recovered by a gas heater (not shown), and then sent to the dust collector 164.

  The dust collector 164 is a device that collects fly ash from the coal ash in the exhaust gas. The dust collector 164 is preferably provided in a plurality of stages. The fly ash collected by the dust collector 164 is collected by the fly ash collection device 174. The exhaust gas that has passed through the dust collector 164 is guided to the desulfurizer 166.

  The dust collector 164 may be any device that collects fly ash. Specifically, an electrostatic dust collector (EP) that collects fly ash with an electrode, a bag filter, or the like. Such as filtration dust collector, gravity dust collector that separates by gravity sedimentation of fly ash gravity, inertial force acting on fly ash, centrifugal force, electrostatic force, etc. and diffusion movement of particles etc. on obstacles It may be an obstacle type dust collector, a centrifugal dust collector or the like to be separated.

  The desulfurization device 166 removes sulfur oxide in the exhaust gas. That is, the desulfurization device 166 absorbs and oxidizes sulfur oxide contained in the exhaust gas by spraying a mixed liquid (lime slurry) of limestone, quicklime, slaked lime, dolomite, and the like and water on the exhaust gas, thereby gypsum slurry. Is generated. The desulfurization device 166 generates gypsum (calcium sulfate) by dehydrating the gypsum slurry. Part of the desulfurization effluent discharged from the desulfurization device 166 is circulated, and the rest is sent to a wastewater treatment facility. The generated gypsum is sent to the gypsum warehouse.

  The coal-fired power generation system 10 includes a limestone silo 172 and a fly ash recovery device 174.

  The limestone silo 172 is a device that sends a calcium compound containing at least one or more selected from the group consisting of stored quicklime, limestone, and slaked lime to the desulfurization device 166 and the calcium sulfite generation unit 18 described later.

  The fly ash collection device 174 is a device that collects the fly ash collected by the dust collection device 164 and further sends the collected fly ash to the ash / elution inhibitor mixing unit 20 described later. Note that the fly ash collection device 174 may be omitted. That is, the fly ash collected by the dust collector 164 may be sent directly to the ash / elution inhibitor mixing unit 20.

<A-4: Calcium sulfite production part>
The calcium sulfite generation unit 18 includes a calcium sulfite generation device 182, and a part of the exhaust gas that has passed through the exhaust gas treatment unit 16 is led here. As shown in Formula (1), the calcium sulfite generator 182 reacts sulfite gas in exhaust gas with a calcium compound containing at least one selected from the group consisting of quicklime, limestone, and slaked lime in a low oxygen atmosphere. a device for generating calcium sulfite (sulfite _{gypsum, CaSO 3 · 1 / 2H 2} O) as the elution inhibitor by.

  That is, the calcium sulfite generation device 182 is a facility for reacting the sulfurous acid gas in the exhaust gas discharged from the desulfurization device 166 in the mixed solution of calcium compound and water (slurry of calcium compound). Specifically, the calcium sulfite generator 182 includes a water tank that stores a slurry of calcium compound, and the exhaust gas is dispersed in bubbles in the water tank. The produced calcium sulfite is sent to the ash / elution inhibitor mixing unit 20 as an elution inhibitor. The air treated by the calcium sulfite generator 182 is sent to the exhaust gas discharge unit 22.

  In the present embodiment, the calcium sulfite generation device 182 employs a bubble dispersion method in which the exhaust gas guided to the water tank storing the calcium compound slurry is dispersed, but the present invention is not limited to this. That is, the calcium sulfite generating apparatus may be any apparatus as long as it can react the sulfurous acid gas in the exhaust gas with the calcium compound in a low oxygen atmosphere.

<A-5: Ash / elution inhibitor mixing part>
The ash / elution inhibitor mixing unit 20 includes a mixing device 202. The mixing device 202 is a device that mixes (kneads) the calcium sulfite produced by the calcium sulfite producing device 182 and the fly ash collected by the dust collecting device 164. Specifically, the mixing apparatus 202 has a kneader in which calcium sulfite and further water are supplied to fly ash to knead them.

  The mixing device 202 has a kneader that mixes fly ash and calcium sulfite. However, any mixing device 202 may be used as long as it has a function of sufficiently mixing fly ash (combustion ash) and calcium sulfite. It may be anything.

<A-6: Exhaust gas emission part>
The exhaust gas discharge unit 22 includes a chimney 222. The chimney 222 discharges the exhaust gas treated by the exhaust gas treatment unit 16 and / or the calcium sulfite generation unit 18 to the atmosphere.

<B: Hexavalent chromium elution suppression method of the present invention>
The hexavalent chromium elution suppression method of the present invention includes a combustion boiler that burns fuel, and a dust collector that is provided downstream of the combustion boiler and collects combustion ash in exhaust gas generated by combustion of the fuel. In the thermal power generation system, a hexavalent chromium elution suppression method for suppressing elution of hexavalent chromium from the combustion ash, at least selected from the group consisting of sulfur oxides in the exhaust gas, quick lime, limestone, and slaked lime Calcium sulfite producing step for producing calcium sulfite by reacting a calcium compound containing one or more in a low oxygen atmosphere, calcium sulfite produced in the calcium sulfite producing step, and dust collection by the dust collector An ash / elution inhibitor mixing step of mixing the burned ash with the combustion ash. It will be described with reference to power generation system 10. The hexavalent chromium elution suppression method of the present invention is carried out in a calcium sulfite production step and an ash / elution inhibitor mixing step.

  Each step of the coal-fired power generation system 10 includes a coal supply / pulverized coal generation step S10 for pulverizing supplied coal to generate pulverized coal, a pulverized coal combustion step S20 for burning the pulverized coal, and combustion of pulverized coal Exhaust gas treatment step S30 for treating the exhaust gas generated by the reaction, a sulfur oxide in the exhaust gas, and a calcium compound containing at least one selected from the group consisting of quicklime, limestone, and slaked lime in a low oxygen atmosphere Ash / elution suppression for mixing calcium sulfite generation step S40 for generating calcium sulfite by mixing, calcium sulfite generated by the calcium sulfite generation step S40, and the combustion ash collected by the dust collector Including an agent mixing step S50 and an exhaust gas releasing step S60 for releasing the treated exhaust gas to the atmosphere. Each step includes a coal supply / pulverized coal generation unit 12, a pulverized coal combustion unit 14, an exhaust gas treatment unit 16, a calcium sulfite generation unit 18, an ash / elution inhibitor mixing unit 20, respectively, of the coal-fired power generation system 10 described above. This is performed in the exhaust gas discharge unit 22. And calcium sulfite production | generation process S40 and ash / elution inhibitor mixing process S50 which are the characteristics of this invention are performed in said calcium sulfite production | generation part 18 and ash / elution inhibitor mixing part 20. FIG.

<Coal supply and pulverized coal production process>
First, in the coal supply / pulverized coal generation step S10, the coal stored in the coal bunker 122 is supplied to the pulverized coal machine 124 by a coal feeder (not shown). The coal supplied to the pulverized coal machine 124 is specifically bituminous coal, subbituminous coal, lignite, or the like, but is not limited to these coals and may be any coal that can perform pulverized coal combustion. Good. The supplied coal is pulverized by the pulverized coal machine 124, thereby generating pulverized coal. The generated pulverized coal is supplied to the combustion boiler 142. At this time, the average particle size of the pulverized coal formed in the pulverized coal generation step may be a particle size range generally used in pulverized coal combustion, and generally 74 μm under 80 wt% or more. The degree of pulverization. This range can also be applied when combustion ash is added.

<Pulverized coal combustion process>
Next, in the pulverized coal combustion step S <b> 20, the pulverized coal generated by the pulverized coal machine 124 is burned by the combustion boiler 142. The combustion temperature at this time ranges from 1300 ° C to 1500 ° C. Among the coal ash produced by the combustion, the clinker ash is discharged at the lower part of the combustion boiler 142, and the fly ash is sent to the next process together with the exhaust gas. Thereafter, the fly ash is sent to a subsequent denitration device 162 and a dust collector 164. The coal ash produced in this pulverized coal combustion process is usually in the form of a powder having an average particle size in the range of 1 μm to 100 μm.

<Exhaust gas treatment process>
The exhaust gas treatment step S30 is a step in which the exhaust gas generated by the combustion of pulverized coal is sequentially sent to the denitration device 162, the dust collector 164, and the desulfurization device 166 and processed. The exhaust gas treated by the desulfurization device 166 is sent to the calcium sulfite generation device 182.

<Calcium sulfite production process>
The calcium sulfite generation step S40 generates calcium sulfite by reacting sulfur oxide in the exhaust gas with a calcium compound containing at least one selected from the group consisting of quicklime, limestone, and slaked lime in a low oxygen atmosphere. It is a process. Preferably, in the calcium sulfite generation step, the exhaust gas discharged from the desulfurization device 166 by the calcium sulfite generation device 182 is a mixed solution of calcium compound and water containing at least one selected from the group consisting of quicklime, limestone, and slaked lime. Calcium sulfite is produced by dispersing bubbles in (a calcium compound slurry).

  As described above, the calcium compound of the present invention is a slurry obtained by adding water to a calcium compound containing at least one selected from the group consisting of quicklime, limestone, and slaked lime, sent from the limestone silo 172. Is preferred. The calcium compound of the present invention may contain dolomite. The produced calcium sulfite is sent to the mixing device 202.

  In the present embodiment, in the calcium sulfite generation step, calcium sulfite is generated by reacting the sulfur oxide in the exhaust gas treated in the exhaust gas treatment step S30 with the calcium compound slurry. You may make it produce | generate calcium sulfite by making the waste gas before processing by process process S30, ie, the sulfur oxide before processing by the desulfurization apparatus 166, and the slurry of a calcium compound react.

<Ash / elution inhibitor mixing process>
The ash / elution inhibitor mixing step S50 is a step of mixing the calcium sulfite generated in the calcium sulfite generation step S40 and the fly ash collected by the dust collector 164.

  Specifically, the ash / elution inhibitor mixing step S50 is a step of adding fly ash and water to the mixing device 202 and adding and mixing (kneading) calcium sulfite almost simultaneously. The fly ash to which calcium sulfite is added is sent to a coal ash storage.

  The timing of adding fly ash and calcium sulfite to the mixing device 202 may be a timing when both are reliably mixed. For example, fly ash and calcium sulfite may be simultaneously input to the mixing device 202. . Water may be added at an appropriate amount and timing, and water may not be added.

When calcium sulfite having a reducing action and fly ash are mixed, hexavalent chromium (Cr ⁶⁺ ) in the fly ash is reduced to produce trivalent chromium (Cr ³⁺ ). For this reason, it is possible to suppress the elution of harmful hexavalent chromium.

  It is preferable to add 0.1 to 100 parts by mass of calcium sulfite with respect to 100 parts by mass of fly ash. When the amount of calcium sulfite input is less than 0.1 parts by mass, hexavalent chromium cannot be sufficiently reduced to trivalent chromium, and thus elution of hexavalent chromium from fly ash cannot be prevented. Even if the input amount of calcium sulfite exceeds 100 parts by mass, no significant improvement is observed in the reduction effect of trivalent chromium. The upper limit of the input amount of calcium sulfite is more preferably 50 parts by mass and particularly preferably 10 parts by mass.

As described above, in the coal thermal power generation system 10, calcium sulfite is generated using sulfur oxide (sulfurous acid gas (SO ₂ )) in exhaust gas generated by coal combustion as a raw material. Since the sulfur oxide is contained in the exhaust gas, the coal-fired power generation system 10 does not require a sulfur oxide production facility. Calcium sulfite can also be produced by improving the existing desulfurization device 166 provided in the coal-fired power generation system 10. Furthermore, since the drug cost is only the purchase cost of a calcium compound containing at least one selected from the group consisting of quick lime, limestone, and slaked lime that is relatively inexpensive and easily available, the drug purchase cost can be kept low. It is.

  As described above, according to the present invention, the sulfur oxide that is regulated as a harmful substance in the coal-fired power generation system 10 is effectively used, so that a large amount of capital investment is not required and the cost of purchasing the medicine is low. It is possible to suppress the elution of hexavalent chromium while achieving the conversion.

  In the present invention, fly ash is used as the combustion ash to be mixed with calcium sulfite. However, the present invention is not limited to this. That is, the combustion ash mixed with calcium sulfite may be clinker ash or cinder ash. In addition, when the thermal power generation system is a heavy crude oil combustion system, the combustion ash refers to heavy crude ash that is heavy oil or a combustion residue of crude oil. When the thermal power generation system is an organic waste combustion system, combustion ash refers to the combustion residue of organic waste. As an example of the organic waste, there is a chip made of thinned wood.

<Exhaust gas emission process>
The exhaust gas release step S60 is a step of releasing the exhaust gas processed in the exhaust gas treatment step S30 and passing through the calcium sulfite generation step S40 from the chimney 222 to the atmosphere.

  The present invention can reduce the harmfulness (environmental load) of combustion ash discharged from a combustion boiler such as a thermal power plant, and thus is a technology that enables further effective use and safe disposal of combustion ash.

It is a schematic block diagram which shows the coal-fired power generation system which shows one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Coal thermal power generation system 12 Coal supply and pulverized coal production | generation part 14 Pulverized coal combustion part 16 Exhaust gas treatment part 18 Calcium sulfite production | generation part 20 Ash and elution inhibitor mixing part 22 Exhaust gas discharge part 122 Coal bunker 124 Pulverized coal machine 142 Combustion boiler 162 Denitration equipment 164 Dust collector 166 Desulfurization equipment 182 Calcium sulfite production equipment 202 Mixing equipment 222 Chimney S10 Coal supply and pulverized coal production process S20 Pulverized coal combustion process S30 Exhaust gas treatment process S40 Calcium sulfite production process S50 Ash and elution inhibitor mixing process S60 Exhaust gas release process

Claims (4)

A thermal power generation system comprising: a combustion boiler that burns fuel; and a dust collector that is provided downstream of the combustion boiler and collects combustion ash in exhaust gas generated by combustion of the fuel. A hexavalent chromium elution suppression method for suppressing hexavalent chromium elution,
A calcium sulfite production step for producing calcium sulfite by reacting the sulfur oxide in the exhaust gas and a calcium compound containing at least one selected from the group consisting of quicklime, limestone, and slaked lime, in a low oxygen atmosphere;
A hexavalent chromium elution suppression method comprising: a mixing step of mixing calcium sulfite generated in the calcium sulfite generation step and combustion ash collected by the dust collector.   The hexavalent chromium elution suppression method according to claim 1, wherein the thermal power generation system is a pulverized coal combustion type power generation system.   The hexavalent chromium elution suppression method according to claim 1, wherein the thermal power generation system is a heavy crude oil combustion type power generation system. Elution of hexavalent chromium from the combustion ash, comprising: a combustion boiler that burns fuel; and a dust collector that is provided downstream of the combustion boiler and collects combustion ash in exhaust gas generated by combustion of the fuel A thermal power generation system capable of suppressing
A calcium sulfite generator for generating calcium sulfite by reacting the sulfur oxide in the exhaust gas and a calcium compound containing at least one selected from the group consisting of quicklime, limestone, and slaked lime, in a low oxygen atmosphere;
A thermal power generation system comprising: a mixing device that mixes calcium sulfite generated by the calcium sulfite generation device and combustion ash collected by the dust collector.

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