JPH038411A - Waste water treatment of wet type desulfurizing device - Google Patents

Abstract

PURPOSE:To treat waste water in a closed circuit by thickening the waste water, returning the recovered water to the stack gas desulfurizing device, adding coal ashes to the concd. water and evaporating the water in the resulted slurry, thereby forming the resulted product of hydration reaction of the dissolved components in the waste water and the coal ashes. CONSTITUTION:The waste water 23 from the stack gas desulfurizing device 11 by a wet type limestone gypsum method applied to treatment of waste combustion gases is thickened by a device 20 and the recovered water is returned to the device 11 by a line 24. The coal ashes 15, 16, 18 are added to the concd. water from the line 25 to prepare the slurry; thereafter, the water in the slurry is evaporated by an evaporation dryer 27 to form the hardened matter 28 contg. the resulted product of hydration reaction of the dissolved components (e.g. halogen compd. dithionic acid, etc.) in the waste water and the coal ashes so that the waste water 23 is not discharged to the outside of the device 11. As a result, the materials, such as halogen compd. and dithionic acid, contained in the waste water from the stack gas desulfurizing device using the wet type limestone gypsum method are recovered as insoluble solids which are easy to handle and have no possibility of reelution.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for treating wastewater discharged from flue gas desulfurization equipment applied to boilers of coal-fired power plants, etc., and particularly to a method for making flue gas desulfurization treatment equipment non-drainage using the wet limestone-gypsum method and its process. The present invention relates to the obtained cured product.

[Conventional technology]

The mainstream of flue gas desulfurization equipment for thermal power generation is the wet limestone-gypsum method, but the problem with this method is that it requires a large amount of wastewater1.For example, the wet limestone-gypsum method in a 1 million kW coal-fired power generation system The amount of water discharged from the desulfurization equipment is approximately 44 tons/
hr, and had the drawback of high wastewater treatment costs. Therefore, recently, studies have been underway to create a closed plant that does not emit waste water around the flue gas desulfurization equipment using the wet limestone-gypsum method.
In the method described in Publication No. 871, the entire amount of wastewater discharged from the desulfurization equipment is sprayed into an exhaust gas flue connected to a dry dust collector, evaporated to dryness, and the resulting solids are collected by the dust collector. ,
A method of creating a drainage-free system that does not discharge wastewater outside the system is being considered. In addition, related publications considering this type of drainage-free system include JP-A-50-72871 and JP-A-5
1-124669, JP-A-52-32896, JP-A-55-97225, JP-A-55-134632,
JP-A-56-155617, JP-A-57-32717
No., JP-A-57-136921, JP-A-59-906
L7, JP-A-60-21220, JP-A-60-22
No. 2135, JP-A-60-235625, JP-A-60
-238121, JP 61-138518, JP 61-178022, JP 61-181519, JP 62-4451, JP 62-117616
Examples include those described in each publication of No. 1971 and Japanese Patent Application Laid-open No. 197130/1983.

[Problems to be solved by the invention]

The above-mentioned conventional technology involves a method in which wastewater is sprayed into the exhaust gas flue line just before the dry precipitator, and the solid matter obtained by evaporation and solidification is collected in the precipitator, and a method in which coal ash and wastewater are mixed together. It can be classified into two types: However, in the former method, in order to evaporate the wastewater sprayed into the flue gas pipe, it is necessary to allow the sprayed wastewater to remain in the flue for a predetermined period of time, which increases the length of the pipe and
Solid matter that has evaporated to dryness adheres to the electrodes of the precipitator, reducing the dust collection efficiency of the precipitator, which may cause problems such as the need for maintenance of the electrodes. Moreover, since the solid material evaporated to dryness is mainly composed of calcium chloride, it is hygroscopic and has problems in handling such as discharge work. In addition, in the latter method, even if coal ash and wastewater are mixed,
When the wastewater is dumped, the ash content simply physically absorbs moisture, so there is a risk that harmful substances in the wastewater may re-elute when the wastewater is dumped. In particular, there was a concern that COD substances such as dithionic acid and halogen compounds contained in the wastewater may be re-eluted. On the other hand, a method has also been proposed in which coal ash and wastewater are mixed and burned at high temperatures, but this method has the disadvantage of making the treatment process quite complicated and increasing the treatment cost. Therefore, the purpose of the present invention is to provide a relatively simple treatment method for removing substances such as halogen compounds and dithionic acid contained in the waste water from flue gas desulfurization equipment using the wet limestone-gypsum method, which is easy to handle and can be re-eluted. To provide a wastewater treatment method in a flue gas desulfurization device using a wet limestone-gypsum method, which recovers the wastewater as a safe insoluble solid and also closes the wastewater so that the separated wastewater is not discharged outside the system.

[Means to solve the problem]

In order to achieve the above object, the present invention has been developed as a result of extensive studies, and has been developed through a hydration reaction between coal ash and halogens, dithionic acid, etc. in the waste water discharged from a flue gas desulfurization equipment using the wet limestone-gypsum method. It was discovered that by drying the hydration reaction product, an insoluble cured product could be obtained, and the present invention was completed. That is, the present invention employs the following configuration to achieve the above object. The wastewater from the flue gas desulfurization equipment using the wet limestone-gypsum method applied to flue gas treatment is concentrated, the recovered moisture is returned to the flue gas desulfurization equipment, and after adding coal ash to the concentrated water to form a slurry, The water in the slurry is evaporated to produce a hardened product containing a hydration reaction product between dissolved components in the wastewater and coal ash, and by producing the cured product, the wastewater is removed from the flue gas desulfurization system. The purpose of the present invention is to provide a wastewater treatment method for flue gas desulfurization equipment using the wet limestone-gypsum method, which does not generate wastewater, and to apply this wastewater treatment method to power generation systems.

[Effect]

Table 1 shows typical components contained in the waste water extracted from the flue gas desulfurization equipment using the wet limestone-gypsum method for the combustion flue gas of a power generation boiler. Table 1: This wastewater contains halogen compounds, dithionic acid, etc. After concentrating this wastewater, coal ash is added to make a slurry with a pH of 7 or more, and the coal shown in Table 2 is Among the components of the ash, the main components such as calcium oxide, aluminum oxide, and silicon oxide are eluted. Table 2 Calcium oxide, aluminum oxide, silicon oxide, etc. eluted into this slurry react with halogen ions and dithionate ions in the wastewater, and are then evaporated to dryness or heated with steam to form insoluble water. A cured product is obtained. To promote the formation of hydrated hardened products,
By increasing H, calcium oxide, aluminum oxide, silicon oxide, etc. in coal ash can be eluted into the slurry, and furthermore, halogen compounds, dithionic acid, etc. can be present at high concentrations in the slurry. is valid. Furthermore, by adding lime (slaked lime or quicklime) or gypsum as necessary, for example, chlorine ions of halogen compounds can be removed from Ca0A1203, Si
02,SO+'-,Ca(OH)2CaSO
It reacts with < etc. to produce various double salt hydrates as shown below. m, CaO-^120. -5iOt-n, Ca5O
,-x,,1120s,cao-^120x-nxch
so<-x2. Nz0m3caO-^120. -5iO
z-nrcac+! 2-x3.820m, CaO-81
2oz-n4CaCL-x<, ml in H20 hydrate
,nl, Usually, the hydration reaction is slow, so to accelerate it,
This is carried out using saturated steam, but in the present invention it is evaporated to dryness for ease of handling, or the hydration reaction is accelerated by contact with 8 to 12% of steam contained in the exhaust gas, and a sufficient cured product is produced. I found out that I can get it. Note that A1203 is the main component of coal ash. The method of producing a hardened product by adding slaked lime and gypsum to SiO2, Fe203, etc. and kneading it with water and evaporating the slurry to dryness or heating it with water vapor to produce a hardened product has already been reported in the material chemistry of r-cement. 1 (Dainippon Tosho Publishing). However, in the hydrate of the present invention, components in the wastewater discharged from the wet flue gas desulfurization equipment, such as halogen compounds and dithionic acid, play an important role.
This is different from the hydrate-forming reaction described in the above publication in that it is a hydrate obtained by a hydration reaction. In this way, when the reaction product of coal ash and concentrated wastewater is evaporated to dryness in the exhaust gas downstream of the boiler in an evaporator or the like, or it is brought into direct or indirect contact with the exhaust gas containing water vapor in the exhaust gas flue downstream of the boiler. The moisture generated during the heat treatment is evaporated and introduced into the wet limestone-gypsum desulfurization equipment along with the exhaust gas in the exhaust gas flue.
The separated water that is separated when concentrating the waste water from the desulfurization equipment is collected in the desulfurization equipment, so that virtually no waste water is discharged from the desulfurization equipment, and the wet limestone-gypsum desulfurization equipment No wastewater can be achieved. On the other hand, halogen compounds, dithionic acid, etc. in wastewater are fixed as stable double salts in the cured product through hydration reactions, so the cured product can be treated in the same way as conventional coal ash, and can be disposed of without being dumped. Landfill processing is possible. Furthermore, since the cured product can be made into blocks, it can be used as lightweight aggregate, soft ground improvement material, civil engineering aggregate, or concrete material. By the way, the wastewater from the wet desulfurization apparatus for boiler combustion exhaust gas of the present invention contains 0.8 to 2 wt% of chlorine ions, and this amount of chlorine can be reduced by
-3CaO-A120xCaCNz ・XH, O, etc.), the carbon in the coal ash shown in Table 2 must be
Although it is possible to increase the aO content, if it is necessary to increase the mechanical hardness of the cured product depending on the application,
It is effective to add slaked lime, quicklime, gypsum, or other hardening accelerators from outside the system. In this way lime,
In addition to adjusting pH, gypsum also has the effect of improving the mechanical strength of cured products. Figures 6 and 7 show the results of examining the mechanical strength of the cured products obtained by varying the amounts of slaked lime and gypsum added to the wastewater. As shown in FIG. 6, when the amount of slaked lime added to the cured product is increased, the mechanical strength of the resulting cured product increases, and its optimum value is found at around 20 wt% of the amount of slaked lime added. Furthermore, as shown in Figure 7, if the amount of gypsum added to the cured product is increased, the mechanical strength of the cured product can be increased, similar to slaked lime, and its maximum value is seen when the amount of gypsum added is around 8wt%. 0 Although solid gypsum itself may be used as a gypsum source, in flue gas desulfurization equipment that uses the wet limestone-gypsum method, the slurry circulating in the absorption tower system of the desulfurization equipment contains about 10% gypsum. Therefore, by directly extracting a portion of the slurry, using it as a gypsum source, and adding coal ash to this slurry, a cured product with high mechanical strength can be obtained. in this way,
By constantly or intermittently extracting a portion of the slurry containing gypsum from the absorption tower system, adding coal ash to it and bringing it into contact with exhaust gas, it is possible to obtain a hardened product with high mechanical strength. At the same time, it also has the effect of maintaining the halogen compound in the circulating slurry of the desulfurization device at a predetermined amount or less and not reducing the desulfurization performance of the desulfurization device. In addition, it has become clear that controlling the amount of slaked lime and gypsum added is effective in obtaining a high-strength cured product depending on the use and purpose of the cured product.
In addition to gypsum, adding one or more substances that promote the hydration reaction between concentrated wastewater and coal ash, such as cement, quartz, clay, kaolinite, and aluminum sulfate, will prevent impurities from leaching out of the resulting hardened product. A much more stable non-elution treatment can be achieved. Furthermore, in the wet limestone-gypsum method, in order to increase the purity of the by-product gypsum, a dust removal tower may be installed separately from the absorption tower to remove dust contained in the exhaust gas in advance. If a dust removal tower is installed, halogen compounds, dithionic acid, etc. will be concentrated in the waste water inside the dust removal tower, and the pH of the liquid will also be lowered.
When it is used as wastewater downstream of a desulfurization equipment, it is necessary to adjust its pH.For this purpose, coal ash alone or, if necessary, an alkaline substance is added as a pH adjusting agent. It is effective to add inexpensive slaked lime, quicklime, etc. to the wastewater. Further, even if coal ash is added to the waste water having a low pH and the waste water is treated according to the present invention, the above-mentioned desired cured product can be obtained. In an exhaust gas desulfurization device using a wet limestone-gypsum method, when limestone slurry and exhaust gas are brought into contact, sulfur dioxide gas and the like are absorbed into the limestone slurry, and at the same time, halogen compounds and the like are concentrated in the slurry. The absorbed sulfur dioxide gas is oxidized and recovered as gypsum, but among halogen compounds, chlorine has a particularly high solubility, so it is dissolved in the slurry6.According to the results of desulfurization experiments conducted by the present inventors, As shown in Figure 5, when trying to keep the pH constant in order to keep the desulfurization performance of the absorption system constant, the amount of limestone supplied increases as the chlorine ion concentration in the limestone slurry in the absorption tower increases. However, the chlorine ion concentration in the limestone slurry of the absorption system is 8,000 to 20. When it reaches OOOppm, the dissolution rate of limestone decreases, which has a negative effect on the desulfurization performance of exhaust gas by the limestone slurry. Therefore, in order to ensure smooth operation of the wet limestone-gypsum method, it is necessary to constantly or intermittently remove a portion of the slurry containing gypsum in the absorption tower system so that the chlorine concentration in the limestone slurry does not exceed a predetermined concentration. It is necessary to extract it and make up the slurry inside the absorption tower. Therefore, as mentioned above, a part of the slurry circulating in the absorption tower system of the wet limestone-gypsum flue gas desulfurization equipment was extracted.
Using this as a gypsum source for accelerating the hardening of the hydration reaction product of concentrated wastewater and coal ash also has the effect of keeping the chlorine concentration in the limestone slurry in the absorption tower below a predetermined concentration. In addition, even if the concentration of halogen compounds dissolved in the circulating limestone slurry of the desulfurization equipment is high, organic alkali metal salts such as sodium formate and sodium acetate, carboxylic acids such as formic acid, acetic acid, and adipic acid, sodium sulfate, sulfuric acid, etc. If a halogen ion mitigating agent such as an inorganic metal salt such as magnesium is added to the desulfurization equipment, the rate of dissolution of limestone into the slurry will not decrease, as shown in Figure 8. The amount of wastewater discharged can be reduced,
Not only is it possible to reduce the amount of coal ash used, but the burden on the non-drainage equipment installed on the downstream side of the desulfurization equipment is reduced, and the relaxation agent can be fixed in the hardened material. Also,
An absorbent such as an ion exchange resin that selectively absorbs halogen compounds from the coal ash or liquid layer is added to the wastewater discharged from the desulfurization equipment and mixed. After phase separation, the supernatant liquid is returned to the absorption tower and the precipitate is removed. A cured product can also be obtained by evaporation to dryness.

【Example】

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. The embodiment shown in Fig. 1 is a flow sheet in which the wastewater treatment device of the present invention is applied to installing a high temperature collector B 3 (low dust method) as a comprehensive flue gas treatment method in a coal-fired power generation system. is low temperature $! ! An example of a high-dust system in which the air preheater 3 is installed on the downstream side of the air preheater 8 is shown below. A comprehensive flue gas treatment system for a coal-fired power plant shown in FIG. 1 will be explained. Combustion exhaust gas 2 from boiler 1 is high temperature!
The coal ash is guided to a duster 3 and collected, and the combustion exhaust gas is introduced to a denitrification device 6. Ammonia 5 is supplied to the combustion exhaust gas upstream of the denitrification device 6. The combustion exhaust gas 7 on the downstream side of the denitrification device 6 is then led to an air preheater 8, and the exhaust gas temperature is lowered. The combustion exhaust gas at about 120°C exiting the air preheater 8 is guided to the gas-gas heat exchanger 13.
Heat is exchanged with the outlet exhaust gas 12 from the desulfurization device 11 arranged in the downstream part adjacent to the exhaust gas. The exhaust gas 12 from the desulfurizer 11 is heated to a temperature higher than the dew point and is discharged from the chimney. Second
The integrated flue gas treatment system shown in the figure also operates in the same manner as described with respect to FIG. The wastewater treatment apparatus of the present invention installed in FIGS. 1 and 2 operates as follows. Drainage water 23 from the desulfurization equipment 11
is led to a concentrator 20, where halogen compounds, COD substances, metal components, etc. are concentrated. Concentration of wastewater is carried out by evaporation, electrical methods (electrolysis, electrodialysis), crystallization, or chemical methods. An example of an evaporation method using a heat source of exhaust gas will be shown. Moisture after slurry concentration is recovered to the desulfurization device through the line 24, achieving drainage-free wet flue gas desulfurization. Halogen compounds, CO
The wastewater in which the D substance, metal components, etc. are concentrated is then led to one slurry mixer, and the coal ash 15 collected by an electrostatic precipitator 3
．． A portion of 16 is supplied. In addition, slaked lime if necessary.
A hardening accelerator such as gypsum is supplied through line 17. The slurry 26 is then fed to an evaporative dryer 27, where the slurry 26
By evaporating to dryness, a cured product 28 is obtained. As the heat source for evaporation to dryness, it is effective to effectively use the exhaust gas 9 on the upstream side of the desulfurization device. However, the exhaust gas is not limited to the above exhaust gas as long as it is in an atmosphere with a temperature higher than that of the slurry. In the embodiment shown in FIGS. 1 and 2, the air preheater 8
An example is shown in which exhaust gas 9 on the downstream side of is used. Exhaust gas 22 and evaporative dryer 2 used in the concentrator 20
It is effective to return the two exhaust gases used in step 7 to the exhaust gas line 10 on the upstream side of the desulfurization device 11 to close the exhaust gases. At the same time, this is also effective in preventing the water collected from the concentrator 20 and the evaporator 27 from being discharged outside the system. The embodiment shown in FIG. 3 is a method for treating waste water 23 discharged from the wet limestone-gypsum desulfurization equipment in the integrated flue gas treatment system shown in FIGS. 1 and 2, using an exhaust gas line. A detailed explanatory diagram of a concentration method using an evaporation method is shown. In FIG. 3, wastewater 23 discharged from the wet limestone-gypsum desulfurization equipment 11 is composed of coal ash 15 collected in the first [A and blood collector 3 shown in FIG. 2] and separately prepared lime (slaked lime, Alternatively, it is kneaded with quicklime (or quicklime) or gypsum 17 in a slurry mixer 19 to form a slurry. The Kei coal ash 15, lime 17, and wastewater 23 are made into a slurry of appropriate viscosity, and the slurry 26 is then sent to a molding machine 30 (not shown in FIGS. 1 and 2). The molded product 26 is then sent to an evaporator dryer 27, where it is brought into direct contact with the exhaust gas from the exhaust gas line 21 shown in FIGS. 1 and 2, and the molded product 26 is evaporated to dryness. , an endless conveyor 40 moving in a direction intersecting the exhaust gas line 21 within the evaporative dryer 27 as shown in the figure.
The molded product 26 is placed thereon, and during the process of being evaporated to dryness by the combustion exhaust gas 21 while moving on the conveyor 40, a hydration reaction progresses and a cured product 28 is formed. Although not shown, the molded product 26 may be introduced into a boiler exhaust gas flue installed between the boiler 1 and the desulfurization device 11, and brought into direct or indirect contact with the exhaust gas to generate a cured product. At this time, the hydration reaction is promoted by the heat treatment using water vapor in the exhaust gas. Moisture in the slurry is entrained in the exhaust gas and collected in the boiler exhaust gas flue, achieving zero drainage here as well. Instead of being evaporated to dryness using boiler exhaust gas as a heat source, the slurry exiting the slurry kneader 19 can be used as a heat source other than boiler exhaust gas, boiler steam as a water vapor source, or factory waste if the temperature is higher than the temperature of the slurry. It can also be made into a cured product using heat-utilizing steam or the like. In this way, the obtained cured product 28 is transferred to the evaporator dryer 2.
It is extracted out of the system from the bottom of 7. FIG. 4 shows the results of X-ray diffraction of the cured product 28 extracted from the evaporator dryer 27 shown in FIGS. 1 and 2 to confirm how chlorine compounds are incorporated as double salts. show. As is clear from Fig. 4, chlorine in the wastewater is converted into β-3CaO-Al 20. due to a hydration reaction with added coal ash, slaked lime, etc. -CaC12-10H2
It is stably fixed as a hydrate such as 0. In addition, the chlorine concentration in the above wastewater was set to 1,000.10.00.
0.50,000.100,000 and 200. OO
Oppm, the wastewater slurry is mixed with coal ash to form a hardened product, and the temperature is 120.150.200 and 350.
A curing test was conducted by evaporating to dryness at ℃. The results are shown in Table 3 (a) and (b). Table 3 (a) Table 3 (b) As shown in Table 3 (a), it can be said that the higher the chlorine concentration in the waste water, the more effective it is for solidification treatment. Further, it can be said that an effective evaporation temperature is around 100 to 150°C. In order to reduce the amount of wastewater to the wastewater-free treatment process, the concentration of halogen compounds, dithionic acid, etc. in the wastewater 23 from the desulfurization equipment 11 is temporarily concentrated, that is, the desulfurization equipment 11 shown in FIGS. 1 and 2. It becomes effective to provide a device 20 for concentrating the waste water from. Table 4 and Figure 9 (a )~
Not shown in (c). (Margins below) Table 4: Components contained in the cured product (unit: mg/e) From these results, the cured product is a stable halogen substance. It has been revealed that it fixes dithionic acid and other substances, and can be disposed of in landfills similar to industrial waste. In particular, dithionic acid and fluorine ions among halogens were found to be easily fixed.

【Effect of the invention】

According to the present invention, halogen compounds and CO in the wastewater discharged from the flue gas desulfurization equipment using the wet limestone-gypsum method
Substance D, metals, etc. are fixed with coal ash, an insoluble cured product is obtained, and a desulfurization device can be made drain-free. In addition, the concentration of halogen compounds in the slurry in the absorption tower of the exhaust gas desulfurization equipment using the wet limestone-gypsum method can be maintained below a predetermined concentration, so the solubility of limestone in the slurry does not become higher than necessary. The absorption tower can operate smoothly and the amount of limestone used can be reduced. Furthermore, halogen substances, COD substances, metals, etc. can be fixed as stable hydrates in the hardened material, so they can be treated in the same manner as industrial waste, and can be disposed of in landfills or other forms of disposal in the same way as coal ash.
As such, it can also be used as lightweight aggregate, soft ground improvement material, etc. Furthermore, if slaked lime, quicklime, gypsum, or other hardening accelerator is added to the concentrated wastewater in addition to coal ash, the mechanical strength of the cured product will be improved and a more chemically stable cured product will be obtained. Furthermore, even if the concentration of halogen compounds dissolved in the circulating limestone slurry of the desulfurization device is high, if a halogen ion moderator is added in the desulfurization device, the rate of dissolution of limestone into the slurry will not be reduced. Therefore, in this case, the amount of wastewater discharged from the desulfurization equipment is reduced, and the relaxation agent can be fixed to the cured product, reducing the burden on the wastewater-free equipment. If the energy unit required for wastewater treatment in a conventional process without wastewater treatment is 100, then the energy unit required for the wastewater treatment of wastewater from the desulfurization apparatus of the present invention is about 63. Furthermore, in the case of the conventional method of obtaining solids by combining the wastewater with coal ash without concentrating it, the concentration of the wastewater is so low that even if coal ash is added to it, a slurry cannot be obtained; therefore, in order to obtain solids, A large amount of coal ash was required in proportion to the amount of wastewater, but since the method of the present invention concentrates the wastewater, slurry can be easily obtained by simply adding coal ash to the concentrated wastewater. In contrast, traditional methods
Approximately 43 t/h of coal ash was required to obtain solids, but in the method of the present invention, the wastewater amount was 44 t/h.
(containing about 7,500 ppm of halogen compounds), for example, when concentrating to 11 t/h, about 30
．． Contains OOOppm of halogen compounds. ),
The amount of coal ash used can be reduced to 100-200g/h.

[Brief explanation of drawings]

Figures 1, 2, and 3 are schematic diagrams of an embodiment of the drainage-free desulfurization system of the present invention, Figure 4 is the X-ray diffraction results of the cured product, and Figure 5 is the wet limestone-gypsum system. Figure 6.7 shows the limestone concentration and equilibrium limestone concentration when the pH in the slurry in the absorption tower is kept constant, Figure 6.7 shows the amount of limestone and gypsum added and the strength of the cured product, and Figure 8 shows the halogen concentration. A diagram showing the relationship between the solubility of CaC○ in the slurry and the desulfurization rate in the case of deafness to which an ion relaxant has been added. It is a drawing showing the results of the test. Boiler, 3... Dust collector, 6... Denitrification device,... Air preheater, 13... Gas-gas heat exchanger tfA device, 1... Desulfurization device, 20... Concentration! Equipment, 7...slaked lime, gypsum, etc.
15.16.18...Coal ash, 9...Slurry kneading machine,
27・Evaporator dryer 3-・Drainage from desulfurization equipment, 28・
...Cured product Fig. 3 Fig. Chlorine ion concentration (ppm) Fig. 6 Addition amount of slaked lime (it%) Fig. Fig. Addition amount of gypsum (vt%) Fig. (1))

Claims (9)

[Claims] (1) Drainage from the flue gas desulfurization equipment using the wet limestone-gypsum method applied to combustion exhaust gas treatment was concentrated, the recovered water was returned to the flue gas desulfurization equipment, and coal ash was added to the concentrated water to form a slurry. After that, water in the slurry is evaporated to produce a hardened product containing a hydration reaction product between dissolved components in the wastewater and coal ash, thereby preventing the wastewater from exiting the flue gas desulfurization system. A wastewater treatment method for flue gas desulfurization equipment using the wet limestone-gypsum method. (2) In addition to coal ash, a hydration reaction promoter is added to the concentrated wastewater discharged from the flue gas desulfurization equipment to promote the hydration reaction between dissolved components in the wastewater and coal ash. A wastewater treatment method for a flue gas desulfurization device according to claim 1. (3) The wastewater treatment method for a flue gas desulfurization device according to claim 2, wherein a portion of the slurry circulated in the absorption tower of the flue gas desulfurization device is extracted and used as a hydration reaction accelerator. (4) Claims 1 to 3, characterized in that a halogen ion mitigating agent is added to the absorption tower circulation slurry of the flue gas desulfurization equipment.
Wastewater treatment method for flue gas desulfurization equipment described. (5) Dissolved components in the wastewater obtained by evaporating the water in the slurry consisting of a mixture of concentrated wastewater and coal ash discharged from a flue gas desulfurization equipment using the wet limestone-gypsum method applied to combustion flue gas. A hardened product containing a hydration reaction product with coal ash. (6) In addition to coal ash, a hydration reaction accelerator is added to the concentrated wastewater discharged from the flue gas desulfurization equipment to promote the hydration reaction between dissolved components in the wastewater and coal ash. The cured product according to claim 5. (7) The cured product according to any one of claims 5 to 6, wherein a portion of the slurry circulated in an absorption tower of a flue gas desulfurization equipment is extracted and used as a hydration reaction accelerator. (8) The cured product according to claim 6, wherein the hydration reaction accelerator is one or more substances selected from the group consisting of lime, cement, clay quartz, kaolinite, gypsum, and aluminum sulfate. (9) In a flue gas desulfurization treatment method for a power generation system in which boiler exhaust gas from a combustion boiler is desulfurized after denitrification treatment, dust collection treatment, etc., coal ash is added to the concentrated wastewater from the wet limestone-gypsum desulfurization equipment. The slurry is dried to form a hardened product, and the halogen compounds and CO contained in the wastewater are removed.
A wastewater treatment method for a flue gas desulfurization treatment device for a power generation system, characterized by fixing substance D and metal components in a cured product.