WO2018092894A1 - Fly ash cleaning method - Google Patents

Fly ash cleaning method Download PDF

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Publication number
WO2018092894A1
WO2018092894A1 PCT/JP2017/041531 JP2017041531W WO2018092894A1 WO 2018092894 A1 WO2018092894 A1 WO 2018092894A1 JP 2017041531 W JP2017041531 W JP 2017041531W WO 2018092894 A1 WO2018092894 A1 WO 2018092894A1
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WO
WIPO (PCT)
Prior art keywords
water
fly ash
washing
cleaning
neutralizing agent
Prior art date
Application number
PCT/JP2017/041531
Other languages
French (fr)
Japanese (ja)
Inventor
克義 谷田
昇 宮岡
野下　昌伸
伊藤　正
豊 重森
Original Assignee
株式会社神鋼環境ソリューション
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Application filed by 株式会社神鋼環境ソリューション filed Critical 株式会社神鋼環境ソリューション
Priority to GB1908032.4A priority Critical patent/GB2571048B/en
Priority to MYPI2019002423A priority patent/MY191965A/en
Publication of WO2018092894A1 publication Critical patent/WO2018092894A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
    • B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/38—Removing components of undefined structure
    • B01D53/40—Acidic components
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/68—Halogens or halogen compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/96—Regeneration, reactivation or recycling of reactants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/30—Alkali metal compounds
    • B01D2251/304—Alkali metal compounds of sodium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/30—Alkali metal compounds
    • B01D2251/306—Alkali metal compounds of potassium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/40—Alkaline earth metal or magnesium compounds
    • B01D2251/404—Alkaline earth metal or magnesium compounds of calcium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/20—Halogens or halogen compounds
    • B01D2257/204—Inorganic halogen compounds
    • B01D2257/2047—Hydrofluoric acid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/30—Sulfur compounds
    • B01D2257/302—Sulfur oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0283—Flue gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
    • B09B2101/00—Type of solid waste
    • B09B2101/30—Incineration ashes

Definitions

  • the present invention relates to a fly ash cleaning method for cleaning fly ash generated when waste is incinerated.
  • the fly ash washing facility described in Patent Document 1 includes a fly ash water washing device for washing fly ash and a dehydrator for dehydrating the washed fly ash.
  • the fly ash cleaning equipment is configured such that fly ash and washing water are mixed by a fly ash water washing device to elute salts, neutralizing agents, and the like into the washing water.
  • emitted from the fly ash water washing apparatus is spin-dry
  • the dehydrated cake is put into a cement kiln when it is used as a cement raw material.
  • the wastewater is purified by a wastewater treatment facility and discharged.
  • the drainage is discharged, so every time the fly ash is washed, new washing water must be supplied to the fly ash water washing device, and a large amount of water is washed to wash the fly ash. Wash water is required.
  • the conventional fly ash washing equipment has a problem that a large amount of washing water is required for washing the fly ash, and there is room for improvement.
  • an object of the present invention is to provide a fly ash cleaning method that can suppress the amount of water supplied for cleaning the fly ash.
  • the fly ash cleaning method includes a mixing step of mixing fly ash collected from exhaust gas neutralized with an alkaline neutralizing agent and washing water, and the flying ash obtained in the mixing step.
  • the washed water is reused as at least a part of the washing water so as to be at least 20%.
  • a step of obtaining a concentration of soluble evaporation residue in a mixed solution of the fly ash obtained in the mixing step and the washing water may be provided.
  • the fly ash used in the mixing step may be fly ash collected from the exhaust gas and may be unwashed fly ash.
  • a neutralizing agent containing an alkali metal may be used as the alkaline neutralizing agent.
  • a sodium-based neutralizing agent is used as the neutralizing agent containing an alkali metal, and in the mixing step, a soluble evaporation residue in the mixed solution is 20% or more and 35%.
  • the washed water may be reused as at least part of the washed water so that
  • the fly ash washing method may include a rinsing step of rinsing the dehydrated cake.
  • the rinsed water that rinses the dehydrated cake in the rinsing step may be reused as at least a part of the washing water.
  • FIG. 1 is a configuration diagram of a waste incineration facility, and is a configuration diagram for explaining a flow from generation of fly ash to washing of fly ash.
  • FIG. 2 is a configuration diagram of the fly ash cleaning apparatus.
  • FIG. 3 is a graph showing changes in pH of the wash water with time.
  • FIG. 4 is a graph showing a change in electric conductivity of washing water with time.
  • FIG. 5 is a graph showing the relationship between the liquid-solid ratio between the water used for cleaning the fly ash (the total of the wash water and the rinse water) and the fly ash and the desalting rate.
  • the soluble evaporation residue corresponds to the total amount of dissolved substances in water.
  • the soluble evaporation residue is often expressed as ppm or mg / l as a ratio of dissolved substance to water, but in this embodiment, it is expressed as% as a ratio of dissolved substance to water.
  • the soluble evaporation residue is obtained by heating water (raw water) in which dissolved substances are dissolved at 105 ° C. to evaporate the water, and dividing the weight of the residue by the weight of the raw water or the volume of the raw water. It is calculated by.
  • the soluble evaporation residue is a ratio of dissolved substances to the weight of water, and is obtained by dividing the weight of the residue by the weight of raw water.
  • the fly ash cleaning method of this embodiment includes a mixing step of mixing fly ash collected from exhaust gas neutralized with an alkaline neutralizing agent and cleaning water, and the flying ash obtained in the mixing step.
  • a solid-liquid separation step of obtaining a dehydrated cake and washed water by solid-liquid separation of a mixed solution of ash and the washing water, and in the mixing step, a soluble evaporation residue in the mixed solution
  • the washed water is reused as at least a part of the washing water so as to be at least 20%.
  • the washed water is reused as at least part of the washing water so that the soluble evaporation residue in the mixed solution is 20% or more and 35% or less. May be.
  • the fly ash used in the mixing step may be fly ash collected from the exhaust gas and may be unwashed fly ash.
  • the fly ash cleaning method of the present embodiment includes a rinsing step of rinsing the dehydrated cake, and in the mixing step, the rinsed water rinsed from the dehydrated cake in the rinsing step is at least part of the washing water. May be reused as
  • a neutralizing agent containing an alkali metal is used as the alkaline neutralizing agent (hereinafter referred to as a neutralizing agent).
  • a sodium-based neutralizer is used as the neutralizer containing the alkali metal. The neutralizing agent will be described later.
  • the fly ash cleaning method of the present embodiment is performed, for example, when cleaning fly ash generated in a waste incineration facility 100 as shown in FIG.
  • a waste incineration facility 100 includes an incinerator 1 for incinerating waste, a boiler 2 for heat recovery of exhaust gas discharged from the incinerator 1, and the temperature of water supplied to the boiler 2 by the exhaust gas.
  • the economizer 3 to be raised, the temperature reducing tower 4 for cooling the exhaust gas, the neutralizing agent introduction unit 7 for neutralizing the exhaust gas cooled by the temperature reducing tower 4, and the neutralized exhaust gas are dedusted And a fly ash cleaning device 6 for cleaning fly ash collected from the dust removal device 5.
  • the incinerator 1 for example, a gasification melting furnace, a stoker type incinerator, or a fluidized bed type incinerator can be adopted.
  • the exhaust gas discharged from the incinerator 1 contains acidic gases such as hydrogen chloride (HCl) and sulfur oxide (SOx).
  • the acidic exhaust gas discharged from the incinerator 1 is heat recovered by the boiler 2 and the economizer 3 and sent to the temperature reducing tower 4.
  • the temperature reduction tower 4 is configured to spray water in the tower, for example.
  • the temperature reducing tower 4 cools the acidic exhaust gas by bringing it into contact with the sprayed water, and discharges it outside the tower.
  • the temperature-decreasing tower 4 may be discharged outside the tower after neutralizing the acidic exhaust gas by spraying alkaline water.
  • the neutralizing agent charging unit 7 is provided downstream of the temperature reducing tower 4 and upstream of the dust removing device 5.
  • the neutralizing agent charging unit 7 is connected to a pipe connecting the temperature reducing tower 4 and the dust removing device 5, and is configured to supply the neutralizing agent to the exhaust gas discharged from the temperature reducing tower 4. Yes.
  • the neutralizing agent is supplied to the exhaust gas in a powder, slurry, or liquid state.
  • a neutralizing agent thrown into acidic exhaust gas for example, a neutralizing agent containing an alkaline earth metal such as slaked lime (Ca (OH) 2 ), dolomite (CaMg (CO 3 ) 2 ), or sodium bicarbonate (NaHCO 3).
  • an alkaline earth metal such as slaked lime (Ca (OH) 2 ), dolomite (CaMg (CO 3 ) 2 ), or sodium bicarbonate (NaHCO 3).
  • Caustic soda (NaOH), sodium carbonate (Na 2 CO 3 ), potassium hydrogen carbonate (KHCO 3 ), potassium hydroxide (KOH), potassium carbonate (K 2 CO 3 ) and other neutralizing agents containing alkali metals are used. It is done.
  • the neutralizing agent to be introduced into the acidic exhaust gas one type of neutralizing agent or a mixture of a plurality of types of neutralizing agents may be used.
  • the neutralizing agent containing an alkali metal is preferable.
  • a sodium-based neutralizer is preferable, and sodium bicarbonate is particularly preferable.
  • the acidic exhaust gas is neutralized by introducing a neutralizing agent.
  • a salt such as calcium chloride (CaCl 2 ) or calcium sulfate (CaSO 4 ) is generated by a neutralization reaction between acidic exhaust gas and slaked lime.
  • a salt such as sodium chloride (NaCl) or sodium sulfate (Na 2 SO 4 ) is generated by the neutralization reaction between the acidic exhaust gas and sodium bicarbonate.
  • a salt such as potassium chloride (KCl) or potassium sulfate (K 2 SO 4 ) is generated by a neutralization reaction between acidic exhaust gas and potassium hydrogen carbonate.
  • the neutralizing agent is excessively administered to the acidic exhaust gas so that the neutralization treatment is not unreacted. Therefore, in the fly ash collected by the dust remover 5, the salt generated by the neutralization reaction and the unreacted neutralizer are mixed.
  • the sulfate produced by reacting with the alkaline earth metal is more than the sulfate produced by reacting with the alkali metal.
  • the solubility of calcium sulfate (CaSO 4 ) in 100 ml of water at 20 ° C. is about 0.24 g
  • the solubility of sodium sulfate (Na 2 SO 4 ) in 100 ml of water at 20 ° C. is about 20 g.
  • the solubility of potassium sulfate (K 2 SO 4 ) is about 11 g. Therefore, from the viewpoint of washing fly ash with water, it is preferable to use a neutralizing agent containing an alkali metal as the neutralizing agent, and it is more preferable to use a sodium-based neutralizing agent.
  • the dust removing device 5 for example, a bag filter, a cyclone type dust collector, an electric dust collector or the like can be adopted.
  • the dust removing device 5 of the present embodiment is a bag filter.
  • the fly ash collected by the dust removing device 5 is collected together with the fly ash collected from the boiler 2, the economizer 3, and the temperature reducing tower 4 in the fly ash accumulating part P, and the fly ash cleaning described later Charged into the mixing section 61 of the apparatus 6.
  • the fly ash collected by the dust removing device 5 and the fly ash collected from the boiler 2, the economizer 3, and the temperature reducing tower 4 may be distinguished and washed by the fly ash cleaning device 6.
  • the exhaust gas discharged from the dust removing device 5 is discharged outside the waste incineration facility 100 in a harmless state through a chimney or the like.
  • nitrogen oxides (N ⁇ ⁇ O x) and dioxins (D X N s) are contained in the exhaust gas, a catalyst tower (not shown) is provided downstream of the dust removing device 5, and the exhaust gas contains nitrogen oxides. After (N O x) and dioxins (D X N s) are removed, they are discharged out of the waste incineration facility 100.
  • Reference symbol A represents exhaust gas discharged outside the system.
  • the fly ash cleaning device 6 is configured to wash the fly ash with water and dehydrate the mixture of the fly ash and the wash water. As shown in FIG. 2, the fly ash cleaning device 6 of this embodiment includes a mixing unit 61 for mixing fly ash and cleaning water, and a mixed liquid of fly ash and cleaning water mixed in the mixing unit 61.
  • a solid-liquid separation unit 62 that obtains a dehydrated cake containing fly ash and washed water by solid-liquid separation of W, and a dehydrated cake for discharging the dehydrated cake obtained by the solid-liquid separation unit 62 out of the system
  • a use path 65 and a pump 66 that supplies the mixed liquid W discharged from the mixing unit 61 to the solid-liquid separation unit 62 are provided.
  • the fly ash cleaning apparatus 6 of the present embodiment further includes a rinse water supply path 68 that supplies rinse water for rinsing the dewatered cake.
  • the washing water is water supplied to the mixing unit 61 for washing fly ash, and is used for washing washed water, rinsed water, and fly ash that are reused for washing fly ash.
  • This is a concept including cleaning water and cleaning raw water prepared separately from rinsed water.
  • Washed water is water in a state in which salt mixed in fly ash and unreacted neutralizing agent (hereinafter also referred to as “salts”) are eluted, and water obtained in the solid-liquid separation unit 62 Means.
  • the washed water is water treated as washing water when supplied to the mixing unit 61.
  • the mixing unit 61 includes a mixing tank 611 into which fly ash and washing water are charged, and a stirring unit 612 for stirring the fly ash and washing water in the mixing tank 611.
  • the mixing unit 61 is a part for eluting salts mixed in the fly ash into the wash water.
  • the mixing unit 61 supplies fly ash and washing water into the mixing tank 611 by supplying fly ash into the mixing tank 611 and supplying raw water for cleaning (represented by reference symbol D) or washed water. It is configured to store. In this embodiment, washing of fly ash is performed by batch operation, but may be performed continuously.
  • the mixed liquid W is stirred for a predetermined time in the mixing tank 611, and when the salts in the fly ash are eluted and the rise of the soluble evaporation residue of the mixed liquid W stops, the mixed liquid W is supplied to the solid-liquid separation unit 62 via the pump 66. Be transported. Therefore, the liquid mixture W discharged
  • the solid-liquid separator 62 is configured to dehydrate the mixed solution W to obtain a dehydrated cake containing fly ash and washed water. That is, the solid-liquid separation unit 62 includes a concentration unit 621 that concentrates the liquid mixture W and accumulates dehydrated cake, and a liquid recovery unit 622 that recovers washed water obtained by concentrating the liquid mixture W.
  • the solid-liquid separation unit 62 of the present embodiment is a filter press machine that separates the mixed liquid W into solid and liquid by, for example, a filter press (squeezing) using a filter cloth.
  • the liquid mixture W obtained in the mixing unit 61 is pumped to the concentration unit 621 by the pump 66, so that the concentration of solid content (fly ash) is higher than that of the liquid mixture W through the filter cloth.
  • the mixed solution W is separated into a dehydrated cake having a high concentration and washed water having a solid content lower than that of the mixed solution W.
  • the solid-liquid separation unit 62 of this embodiment is configured to rinse the dehydrated cake with rinse water in order to reduce the chlorine concentration of the water in the dehydrated cake. That is, the solid-liquid separation unit 62 is configured to be able to supply rinse water to the concentration unit 621. In the present embodiment, the solid-liquid separation unit 62 is configured such that the rinse water is pumped to the concentration unit 621 by the pump 66 and the washed water contained in the dewatered cake in the concentration unit 621 is replaced with the rinse water. . The solid-liquid separation unit 62 is configured to be able to separate the rinsed water from the dehydrated cake.
  • the solid-liquid separation unit 62 is configured to be able to perform the rinsing step, so that the washed water in the dehydrated cake is replaced with rinse water to reduce the chlorine concentration of the dehydrated cake, and the dehydrated cake.
  • the solid-liquid separation unit 62 may be, for example, a belt press machine or a centrifugal dehydrator.
  • the dehydrated cake discharge path 63 is a path for discharging the dehydrated cake concentrated in the solid-liquid separator 62 to the outside of the system.
  • the dehydrated cake discharge path 63 is connected to the concentration unit 621 of the solid-liquid separation unit 62 or configured to receive the dehydrated cake discharged from the concentration unit 621.
  • the dehydrated cake is taken out of the system through the dehydrated cake discharge path 63 and is reused for landfill, cement raw material, and the like.
  • a symbol B represents a dehydrated cake discharged out of the system.
  • the drainage path 64 is a path for draining the washed water and the rinsed water obtained from the solid-liquid separation unit 62 out of the system.
  • the drainage path 64 is connected to the liquid recovery unit 622 of the solid-liquid separation unit 62.
  • the wastewater discharged from the fly ash cleaning device 6 is sent to another purification treatment facility (not shown) via the drainage path 64 and subjected to purification treatment.
  • the symbol C represents washed water or rinsed water that is drained out of the system.
  • the solid-liquid separation unit 62 is configured such that the concentration unit 621 is connected to the dewatered cake discharge path 63 and the liquid recovery unit 622 is connected to the drainage path 64, so Is configured to be discharged out of the solid-liquid separator 62.
  • the reuse path 65 is a path for supplying water that has been washed by the solid-liquid separation unit 62 to the mixing unit 61 as washing water.
  • One end of the reuse path 65 is connected to a storage facility (not shown) such as a tank, and the other end is open to the mixing unit 61.
  • the washed water discharged from the solid-liquid separator 62 is stored in a storage facility such as a tank via the drainage path 64 and is pumped by a separately provided pump (not shown). Water is supplied to the mixing unit 61 via the reuse path 65.
  • the pump 66 transfers the mixed liquid W discharged from the mixing unit 61 to the solid-liquid separation unit 62.
  • the pump 66 is configured to be able to transfer rinse water to the concentration unit 621.
  • the pump 66 is disposed in a transfer pipe 67 that connects the mixing unit 61 and the solid-liquid separation unit 62.
  • the rinse water supply path 68 is a path for supplying rinse water to the concentration unit 621 of the solid-liquid separation unit 62.
  • the rinse water supply path 68 of this embodiment is connected to the transfer pipe 67.
  • the rinse water supply path 68 is connected to an upstream pipe 671 provided on the suction side of the pump 66 in the transfer pipe 67.
  • the rinse water is pumped by the pump 66 and is sent to the solid-liquid separation unit 62 via the downstream pipe 672 provided on the discharge side of the pump 66.
  • tap water, industrial water, ground water, or industrial waste water is adopted as the rinse water.
  • Symbol E represents rinse water introduced into the system.
  • the washed water is reused for the fly ash washing
  • the washed water is reused for the fly ash washing within the range where no precipitate is generated in the mixed solution W, and used for the fly ash washing.
  • a neutralizing agent containing an alkaline earth metal is used as a neutralizing agent for neutralizing fly ash
  • the soluble evaporation residue in the mixed solution W is about 20%
  • precipitates were generated in the mixed solution W.
  • the neutralizing agent containing an alkali metal even if the soluble evaporation residue in the liquid mixture W was 20% or more, it was confirmed that no precipitate was generated.
  • a sodium-based neutralizing agent it was confirmed that no precipitate was formed if the soluble evaporation residue was 35% or less.
  • the fly ash collected in the fly ash accumulating part P is put into the mixing tank 611, and the raw water for washing is supplied to the mixing part 61 so that the liquid-solid ratio between the washing water and the fly ash is 5 to 10 in the mixing tank 611. Is introduced.
  • the stirrer 612 is driven to stir the fly ash and the cleaning raw water for a predetermined time in the mixing tank 611, and the salts mixed in the fly ash are eluted into the cleaning raw water.
  • the mixing of the fly ash and the raw water for washing is referred to as the first washing operation, and the washed water obtained in the solid-liquid separation step after the first washing operation is referred to as first washed water.
  • fly ash before washing contains a larger amount of chloride than sulfate. Since the solubility of chlorides such as calcium chloride (CaCl 2 ), sodium chloride (NaCl), and potassium chloride (KCl) is 15 g or more with respect to 100 ml of water at 20 ° C., at the end of the first washing operation, Usually, the soluble evaporation residue in the mixed solution W is 20% or less.
  • the liquid mixture W is passed through the solid-liquid separation unit 62 for solid-liquid separation (dehydration) to obtain a dehydrated cake containing fly ash and first washed water.
  • the first washed water discharged from the solid-liquid separation unit 62 is returned to the mixing unit 61 via the reuse path 65 or stored in a storage facility such as a tank. Subsequently, the dehydrated cake obtained in the solid-liquid separation unit 62 is transferred to a rinsing process.
  • the rinsing step rinse water is supplied to the concentration unit 621 of the solid-liquid separation unit 62, and the first washed water in the dehydrated cake is replaced with rinse water.
  • the rinsing water is introduced into the concentrating unit 621 via the rinsing water supply path 68 so that the liquid-solid ratio of the rinsing water and the fly ash is 2.5 to 5.
  • the chlorine concentration of the dehydrated cake can be lowered.
  • the chlorine concentration in the cement is preferably 350 ppm or less.
  • the chlorine concentration of the entire dehydrated cake including solids and moisture is preferably 1% or less.
  • the chlorine concentration in the dehydrated cake after drying is more preferably 1% or less.
  • about 3% fly ash can be used as a cement raw material.
  • the moisture content of the dehydrated cake after dehydration is A%
  • the chlorine concentration in the dehydrated cake after rinsing is X%.
  • the concentration of chlorine contained in the solid content of the dehydrated cake is as close to zero as possible, the water in the dehydrated cake before rinsing is washed water with a relatively high soluble evaporation residue, The chlorine concentration in the fly ash after drying may exceed 1%. Therefore, in the present embodiment, the chlorine concentration of the entire dehydrated cake is lowered, and the dehydrated cake is rinsed in the rinsing step so that the chlorine concentration becomes an appropriate cement raw material.
  • the rinsed water discharged from the solid-liquid separation unit 62 is stored in a storage facility (not shown) such as a tank.
  • the process of supplying washed water or rinsed water to the mixing tank 611 is referred to as a reuse process.
  • the reuse step may be performed in parallel with the solid-liquid separation step or the rinsing step, or may be performed after the solid-liquid separation step and the rinsing step are completed.
  • This embodiment demonstrates the case where a reuse process is implemented after a solid-liquid separation process and a rinse process are complete
  • the storage facility in which the first washed water is stored and the storage facility in which the rinsed water is stored are connected to the reuse path 65, and the reuse path 65 is connected to a pump (not shown) from each storage facility. It is configured to be able to pump water through.
  • the rinsed water may be supplied to the mixing tank 611 as washing water.
  • raw water for cleaning can be supplied as cleaning water.
  • the fly ash collected in the fly ash accumulating part P is put into the mixing tank 611 in an empty state, and the mixing ratio is adjusted so that the liquid-solid ratio of the washing water and the fly ash becomes 5 to 10 in the mixing tank 611.
  • the first cleaned water is supplied as cleaning water through the use path 65.
  • the process proceeds to the mixing step, and the fly ash and the wash water as the first washed water are stirred for a predetermined time in the mixing tank 611 as in the first washing operation, and the salts mixed in the fly ash are removed. Elute in wash water.
  • this washing operation as the second washing operation, the washed water obtained in the solid-liquid separation step after the second washing operation is referred to as second washed water.
  • the soluble evaporation residue in the mixed solution W is confirmed. Then, the above washing operation is repeated until the soluble evaporation residue in the mixed solution W reaches 20% (or 35% or less). Since the solid-liquid separation step and the rinsing step after the mixing step are the same as the already described solid-liquid separation step and the rinsing step, the description will not be repeated.
  • the mixing step and the rinsing step are performed with the liquid / solid ratio of washing water and fly ash being 5, and the liquid / solid ratio of rinsing water and fly ash being 2.5, and the mixed solution is obtained at the end of the fifth washing operation.
  • the soluble evaporation residue in W reaches 20%.
  • the cleaning water is used 37.5 times ((5 + 2.5) ⁇ 5) as much as the fly ash.
  • the washed water is reused as washing water in all five washing operations as in this embodiment, it is 17.5 times as much as fly ash (5 + 2.5 ⁇ 5). This means that the washing water was used.
  • a neutralizer containing an alkaline earth metal or a neutralizer containing another alkali metal such as potassium is used. Since the solubility of the salt produced by the sum is high, the washed water can be reused until the soluble evaporation residue in the mixed solution W becomes 20% or more and 35% or less. Therefore, the number of times the washed water can be reused is increased compared to the case of using a neutralizing agent containing an alkaline earth metal or a neutralizing agent containing another alkali metal such as potassium as the neutralizing agent. Can be further saved.
  • the solubility of sodium chloride in 100 ml of water at 20 ° C. is about 36 g
  • the upper limit of the soluble evaporation residue in the mixed solution W is set to 35% in consideration of the presence of sulfate.
  • the washed water after the soluble evaporation residue exceeds 35% is sent to another purification treatment facility such as a neutralization treatment facility via the drainage path 64 and subjected to purification treatment.
  • the washed water after the soluble evaporation residue exceeds 35% may be evaporated and solidified.
  • the thermal energy required for the evaporation and solidification can be suppressed compared with the case where the washed water with a low salt concentration is evaporated and solidified. It is.
  • a sodium-based neutralizing agent (same as a neutralizing agent containing an alkali metal) is used, so the pH of the washed water is higher than that when a neutralizing agent containing an alkaline earth metal is used. Low (see FIG. 3), it can also save the chemicals required for neutralization of washed water.
  • the washed water obtained as a result of mixing fly ash collected from exhaust gas that has been neutralized with an alkaline neutralizing agent with washing water includes a plurality of types of salts, neutralizing agents, heavy metals, etc.
  • the substance was dissolved, it was confirmed that there was no problem even if it was reused for cleaning fly ash.
  • the applicant has determined that if the soluble evaporation residue in the mixed liquid of fly ash and washing water is kept lower than a predetermined concentration, the dissolved substance in the mixed liquid does not precipitate and precipitates. It was confirmed that washed water could be used without problems for washing fly ash because problems such as obstruction of the flow path with objects did not occur easily.
  • the fly ash cleaning method according to the present invention was obtained by the mixing step of mixing the fly ash collected from the exhaust gas neutralized with an alkaline neutralizer and the washing water, and the mixing step.
  • the washed water is reused as at least part of the wash water so that the product is at least 20%.
  • the washed water obtained in the solid-liquid separation step is reused for washing the fly ash.
  • the washed water can be reused as the washing water. The amount of water supply can be reduced.
  • the above embodiment includes a step of obtaining a soluble evaporation residue concentration in a mixed solution of the fly ash obtained in the mixing step and the washing water.
  • fly ash collected from exhaust gas that has been neutralized with an alkaline neutralizer and washing water are mixed, the mixture is in a state where a plurality of substances such as salts and neutralizers are dissolved at high concentrations. Become. If the washed water in which salts are dissolved at a high concentration is used as waste water, a large amount of washing water is required, and the energy required for the purification treatment of the waste water is enormous.
  • the concentration at which the soluble evaporation residue precipitates while monitoring the concentration of the dissolved substance in the mixed solution can be reused for washing the fly ash so that it is at least 20% of the area. Therefore, it can be used while gradually increasing the concentration of washed water, so that washed water that is valuable as washing water is prevented from being drained, and the washed water is used to the maximum extent possible. Can do.
  • the fly ash used in the mixing step is fly ash collected from the exhaust gas, and is unwashed fly ash.
  • the fly ash used in the mixing step is fly ash collected from the exhaust gas and is unwashed fly ash, so the unwashed fly ash obtained in the mixing step.
  • the mixed liquid of ash and washing water is separated into solid and liquid to obtain washed water, and the washed water can be reused as a part of washing water in the mixing step. Therefore, it is possible to dare to use water that contains a large amount of impurities and is usually drained (not suitable for reuse), so the amount of water used for washing fly ash can be reduced.
  • the wastewater treated water can usually be used to the maximum extent possible, so even if a portion of the water is discarded without being reused, the load for treating the discarded water Can be made relatively small.
  • a neutralizing agent containing an alkali metal is used as the alkaline neutralizing agent. According to this configuration, since the neutralizing agent containing an alkali metal is used as the alkaline neutralizing agent, the pH of the washed water can be kept low. Therefore, the amount of chemicals required for neutralizing the washed water can be suppressed, and the washed water can be easily neutralized.
  • a sodium-based neutralizing agent is used as the neutralizing agent containing the alkali metal.
  • the soluble evaporation residue in the mixed solution is 20% or more and 35%.
  • the washed water is reused as at least a part of the washing water so as to become the following.
  • the neutralizing agents containing alkali metals among the neutralizing agents containing alkali metals, the salts produced when using sodium-based neutralizing agents are used when using neutralizing agents containing other alkali metals such as potassium. It is more soluble in water than the salts produced (highly soluble in water). Therefore, if the soluble evaporation residue is 35% or less, the fly ash can be washed with washed water with almost no dissolved substance being deposited. Therefore, according to such a configuration, fly ash can be washed in a state where almost no dissolved substances are deposited while increasing the soluble evaporation residue in the mixed solution W, and the washed water is sufficiently reused. be able to.
  • the fly ash cleaning method includes a rinsing step of rinsing the dehydrated cake.
  • the dewatering cake since the dewatering cake is provided with a rinsing step, the dewatering cake can be made into a property suitable for reuse, for example, as a cement raw material.
  • the rinsed water that rinses the dehydrated cake in the rinsing step is reused as at least a part of the washing water.
  • the rinsed water used in the rinsing step can be used for washing the fly ash, so that the rinsed water can be effectively used.
  • the pH of the washed water is lowered as compared with the case of using a neutralizing agent containing an alkaline earth metal as the neutralizing agent. can do.
  • a neutralizing agent containing an alkaline earth metal as the neutralizing agent.
  • FIG. 3 when comparing sodium bicarbonate ash neutralized with baking soda and slaked lime ash neutralized with slaked lime, from the start to the end of stirring, It can be seen that the pH of the wash water (or washed water) is lower than the pH of the slaked lime ash wash water (or washed water).
  • the pH of the washed water can be kept low by using a neutralizing agent containing an alkali metal, so that the amount of chemicals required for neutralizing the washed water can also be reduced. And the burden on the neutralization process is reduced.
  • the liquid-solid ratio is 7.5 (washing water 5 times, rinsing water 2.5 times).
  • a neutralizing agent containing an alkali metal when used as a neutralizing agent, a neutralizing agent made of an alkaline earth metal is used as a neutralizing agent.
  • the dissolution rate of salts in the wash water is fast. Therefore, by using a neutralizing agent containing an alkali metal as a neutralizing agent, the mixing step can be shortened, and the fly ash washing treatment capability can be increased. Specifically, the electric conductivity of washing water (or washed water) of sodium bicarbonate ash exceeds 9 S / m at the same time when stirring is started, and then slightly increases.
  • a desalination rate is improved.
  • a desalination rate is improved.
  • sodium bicarbonate ash and slaked lime ash are washed at the same liquid-solid ratio, and the liquid-solid ratio is 7.5 times (washing water 5 times, rinsing water 2.5 times). Increase 10 times (5 times washing water, 5 times rinse water), 12.5 times (10 times washing water, 2.5 times rinse water), and 15 times (10 times washing water, 5 times rinse water).
  • the desalting rate of baking soda ash was higher than the desalting rate of slaked lime ash, and the baking salt ash had a high desalting rate even when the liquid-solid ratio was low.
  • fly ash cleaning method of the present invention is not limited to the above embodiment. Further, the operational effects of the fly ash cleaning method according to the present invention are not limited to those described above. Furthermore, it goes without saying that various modifications can be made to the fly ash cleaning method according to the present invention without departing from the gist of the present invention.
  • fly ash cleaning method is performed when cleaning the fly ash generated in the waste incineration facility 100 has been described, but the present invention is not limited to this.
  • the fly ash cleaning method can be implemented in various facilities having an incineration process such as a coal-fired power plant.
  • the rinsed water can be reused as rinse water.
  • the washed water and the rinsed water are reused by supplying water to the mixing unit 61 .
  • the present invention is not limited to this.
  • the washed water and the rinsed water may be reused by being supplied to the mixing unit of another fly ash washing apparatus, or may be reused in another waste incineration facility.
  • the mixing unit 61 may include means for measuring the soluble evaporation residue in the mixed solution W, and the soluble evaporation residue in the mixed solution W is predetermined. An operator or the like may be notified when this value is reached.

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Abstract

A fly ash cleaning method according to the present invention comprises: a mixing step for mixing cleaning water and fly ash collected from exhaust gas which has been neutralized with an alkaline neutralizing agent; and a solid-liquid separation step for performing solid-liquid separation of a mixture, of the fly ash and the cleaning water, acquired in the mixing step, and acquiring dehydrated cake and water used for cleaning, wherein, in the mixing step, the water used for cleaning is reused as at least a part of the cleaning water until the proportion of dissolved solids in the mixture reaches at least 20%.

Description

飛灰の洗浄方法How to clean fly ash 関連出願の相互参照Cross-reference of related applications
　本願は、２０１６年１１月１８日出願の日本国特願２０１６－２２４７７８号の優先権を主張し、この出願が引用によって組み込まれる。 This application claims the priority of Japanese Patent Application No. 2016-224778 filed on November 18, 2016, and this application is incorporated by reference.
　本発明は、廃棄物を焼却した際に発生する飛灰を洗浄するための飛灰の洗浄方法に関する。 The present invention relates to a fly ash cleaning method for cleaning fly ash generated when waste is incinerated.
　廃棄物を焼却した際に発生する酸性の排ガスは、そのまま系外に排出することができないため、例えば、特許文献１に記載されているように、アルカリ性の中和剤が吹き込まれて中和された後に飛灰が捕集され、煙突等を介して系外に排出される。上記のような中和処理済みの排ガスから捕集された飛灰には、中和反応により生成した塩類や未反応の中和剤、重金属等様々な有害物質が混入している。該飛灰は、埋め立てやセメント原料に用いられるなど利用価値があるものの、有害物質を含有した状態では利用することができない。そのため、従来から、有害物質が混入された飛灰を洗浄するための飛灰の洗浄設備が種々提案されている。 Since the acidic exhaust gas generated when the waste is incinerated cannot be discharged out of the system as it is, for example, as described in Patent Document 1, an alkaline neutralizing agent is blown and neutralized. After that, fly ash is collected and discharged out of the system through a chimney or the like. Various toxic substances such as salts generated by the neutralization reaction, unreacted neutralizers, and heavy metals are mixed in the fly ash collected from the neutralized exhaust gas as described above. Although the fly ash has utility value such as being used for landfill or cement raw material, it cannot be used in a state containing harmful substances. For this reason, various types of fly ash cleaning equipment have been proposed in the past for cleaning fly ash mixed with harmful substances.
　例えば、特許文献１に記載の飛灰の洗浄設備は、飛灰を洗浄する飛灰水洗装置と、洗浄後の飛灰を脱水する脱水機と、を備える。前記飛灰の洗浄設備は、飛灰水洗装置で飛灰と洗浄水とが混合され、塩類や中和剤等を洗浄水に溶出するように構成されている。そして、飛灰水洗装置から排出された飛灰と洗浄水との混合液が脱水機で脱水され、該混合液は、脱水ケーキと排水とに分離される。 For example, the fly ash washing facility described in Patent Document 1 includes a fly ash water washing device for washing fly ash and a dehydrator for dehydrating the washed fly ash. The fly ash cleaning equipment is configured such that fly ash and washing water are mixed by a fly ash water washing device to elute salts, neutralizing agents, and the like into the washing water. And the liquid mixture of the fly ash and washing water discharged | emitted from the fly ash water washing apparatus is spin-dry | dehydrated with a dehydrator, and this liquid mixture is isolate | separated into a spin cake and waste water.
　上記飛灰の洗浄設備では、脱水ケーキは、セメント原料化される場合にはセメントキルンに投入される。排水は、排水処理設備で浄化処理されて放流される。 In the above fly ash cleaning equipment, the dehydrated cake is put into a cement kiln when it is used as a cement raw material. The wastewater is purified by a wastewater treatment facility and discharged.
日本国特開２００７－８３１４４号公報Japanese Unexamined Patent Publication No. 2007-83144
　上記従来の飛灰の洗浄設備では、排水は放流されてしまうので、飛灰を洗浄する度に飛灰水洗装置に新しい洗浄水を供給しなければならず、飛灰を洗浄するために多量の洗浄水が必要である。このように、上記従来の飛灰の洗浄設備は、飛灰洗浄のために多量の洗浄水が必要になるという問題があり、改善の余地がある。 In the above conventional fly ash cleaning equipment, the drainage is discharged, so every time the fly ash is washed, new washing water must be supplied to the fly ash water washing device, and a large amount of water is washed to wash the fly ash. Wash water is required. As described above, the conventional fly ash washing equipment has a problem that a large amount of washing water is required for washing the fly ash, and there is room for improvement.
　そこで、本発明は、かかる実情に鑑み、飛灰を洗浄するための洗浄水の給水量を抑えることができる飛灰の洗浄方法を提供することを課題とする。 Therefore, in view of such a situation, an object of the present invention is to provide a fly ash cleaning method that can suppress the amount of water supplied for cleaning the fly ash.
　本発明に係る飛灰の洗浄方法は、アルカリ性の中和剤で中和処理済みの排ガスから捕集された飛灰と洗浄水とを混合する混合工程と、前記混合工程で得られた前記飛灰と前記洗浄水との混合液を固液分離して、脱水ケーキと洗浄済み水とを得る固液分離工程と、を備え、前記混合工程では、前記混合液中の溶解性蒸発残留物が少なくとも２０％となるように、前記洗浄済み水を、少なくとも前記洗浄水の一部として再利用する。 The fly ash cleaning method according to the present invention includes a mixing step of mixing fly ash collected from exhaust gas neutralized with an alkaline neutralizing agent and washing water, and the flying ash obtained in the mixing step. A solid-liquid separation step of obtaining a dehydrated cake and washed water by solid-liquid separation of a mixed solution of ash and the washing water, and in the mixing step, a soluble evaporation residue in the mixed solution The washed water is reused as at least a part of the washing water so as to be at least 20%.
　本発明の一態様として、前記混合工程で得られた前記飛灰と前記洗浄水との混合液中の溶解性蒸発残留物濃度を入手する工程を備えてもよい。 As an aspect of the present invention, a step of obtaining a concentration of soluble evaporation residue in a mixed solution of the fly ash obtained in the mixing step and the washing water may be provided.
　本発明の一態様として、前記混合工程で使用される飛灰は、前記排ガスから捕集された飛灰であって、未水洗の飛灰であってもよい。 As one aspect of the present invention, the fly ash used in the mixing step may be fly ash collected from the exhaust gas and may be unwashed fly ash.
　本発明の一態様として、前記アルカリ性の中和剤として、アルカリ金属を含む中和剤を使用してもよい。 As an aspect of the present invention, a neutralizing agent containing an alkali metal may be used as the alkaline neutralizing agent.
　本発明の他態様として、前記アルカリ金属を含む中和剤として、ナトリウム系の中和剤を使用し、前記混合工程では、前記混合液中の溶解性蒸発残留物が２０％以上、且つ３５％以下となるように、前記洗浄済み水を、少なくとも前記洗浄水の一部として再利用してもよい。 As another aspect of the present invention, a sodium-based neutralizing agent is used as the neutralizing agent containing an alkali metal, and in the mixing step, a soluble evaporation residue in the mixed solution is 20% or more and 35%. The washed water may be reused as at least part of the washed water so that
　また、本発明の別の態様として、飛灰の洗浄方法は、前記脱水ケーキをすすぐすすぎ工程を備えていてもよい。 As another aspect of the present invention, the fly ash washing method may include a rinsing step of rinsing the dehydrated cake.
　また、本発明の別の態様として、前記混合工程では、前記すすぎ工程で前記脱水ケーキをすすいだすすぎ済み水を、少なくとも前記洗浄水の一部として再利用してもよい。 Further, as another aspect of the present invention, in the mixing step, the rinsed water that rinses the dehydrated cake in the rinsing step may be reused as at least a part of the washing water.
図１は、廃棄物焼却施設の構成図であって、飛灰の発生から飛灰の洗浄までのフローを説明するための構成図である。FIG. 1 is a configuration diagram of a waste incineration facility, and is a configuration diagram for explaining a flow from generation of fly ash to washing of fly ash. 図２は、飛灰洗浄装置の構成図である。FIG. 2 is a configuration diagram of the fly ash cleaning apparatus. 図３は、洗浄水のｐＨの径時変化を表すグラフである。FIG. 3 is a graph showing changes in pH of the wash water with time. 図４は、洗浄水の電気伝導度の径時変化を表すグラフである。FIG. 4 is a graph showing a change in electric conductivity of washing water with time. 図５は、該飛灰の洗浄に使用した水（洗浄水及びリンス水の合計）と飛灰との液固比と脱塩率との関係を表すグラフである。FIG. 5 is a graph showing the relationship between the liquid-solid ratio between the water used for cleaning the fly ash (the total of the wash water and the rinse water) and the fly ash and the desalting rate.
　本実施形態では、溶解性蒸発残留物（Ｔｏｔａｌ　Ｄｉｓｓｏｌｖｅｄ　Ｓｏｌｉｄ）は、水中の溶存物質の総量に相当する。溶解性蒸発残留物は、水に対する溶存物質の割合として、ｐｐｍ、又はｍｇ／ｌで表記される場合が多いが、本実施形態では、水に対する溶存物質の割合として％で表記している。溶解性蒸発残留物は、溶存物質が溶存した状態の水（原水）を１０５℃で加熱し、水分を蒸発させ、残留物の重さを前記原水の重さ、又は前記原水の容積で除することで算出される。本実施形態では、溶解性蒸発残留物は、水の重さに対する溶存物質の割合となっており、残留物の重さを原水の重さで除したものである。 In this embodiment, the soluble evaporation residue (Total Dissolved Solid) corresponds to the total amount of dissolved substances in water. The soluble evaporation residue is often expressed as ppm or mg / l as a ratio of dissolved substance to water, but in this embodiment, it is expressed as% as a ratio of dissolved substance to water. The soluble evaporation residue is obtained by heating water (raw water) in which dissolved substances are dissolved at 105 ° C. to evaporate the water, and dividing the weight of the residue by the weight of the raw water or the volume of the raw water. It is calculated by. In the present embodiment, the soluble evaporation residue is a ratio of dissolved substances to the weight of water, and is obtained by dividing the weight of the residue by the weight of raw water.
　本実施形態の飛灰の洗浄方法は、アルカリ性の中和剤で中和処理済みの排ガスから捕集された飛灰と洗浄水とを混合する混合工程と、前記混合工程で得られた前記飛灰と前記洗浄水との混合液を固液分離して、脱水ケーキと洗浄済み水とを得る固液分離工程と、を備え、前記混合工程では、前記混合液中の溶解性蒸発残留物が少なくとも２０％となるように、前記洗浄済み水を、少なくとも前記洗浄水の一部として再利用する。具体的には、前記混合工程では、前記混合液中の溶解性蒸発残留物が２０％以上、且つ３５％以下となるように、前記洗浄済み水を、少なくとも前記洗浄水の一部として再利用してもよい。 The fly ash cleaning method of this embodiment includes a mixing step of mixing fly ash collected from exhaust gas neutralized with an alkaline neutralizing agent and cleaning water, and the flying ash obtained in the mixing step. A solid-liquid separation step of obtaining a dehydrated cake and washed water by solid-liquid separation of a mixed solution of ash and the washing water, and in the mixing step, a soluble evaporation residue in the mixed solution The washed water is reused as at least a part of the washing water so as to be at least 20%. Specifically, in the mixing step, the washed water is reused as at least part of the washing water so that the soluble evaporation residue in the mixed solution is 20% or more and 35% or less. May be.
　また、本実施形態の飛灰の洗浄方法は、前記混合工程で使用される飛灰が、前記排ガスから捕集された飛灰であって、未水洗の飛灰であってもよい。この場合には、例えば、前記混合工程で使用する洗浄水の一部として再利用される洗浄済み水から、前記固液分離工程にて得られる前記脱水ケーキを洗浄することにより得られる洗浄済み水などは除外されることとなる。 Further, in the fly ash cleaning method of this embodiment, the fly ash used in the mixing step may be fly ash collected from the exhaust gas and may be unwashed fly ash. In this case, for example, washed water obtained by washing the dehydrated cake obtained in the solid-liquid separation step from washed water reused as part of the washing water used in the mixing step. Etc. will be excluded.
　また、本実施形態の飛灰の洗浄方法は、前記脱水ケーキをすすぐすすぎ工程を備え、前記混合工程では、前記すすぎ工程で前記脱水ケーキをすすいだすすぎ済み水を、少なくとも前記洗浄水の一部として再利用してもよい。 Further, the fly ash cleaning method of the present embodiment includes a rinsing step of rinsing the dehydrated cake, and in the mixing step, the rinsed water rinsed from the dehydrated cake in the rinsing step is at least part of the washing water. May be reused as
　本実施形態では、前記アルカリ性の中和剤（以下、中和剤とする）として、アルカリ金属を含む中和剤を使用している。具体的には、該アルカリ金属を含む中和剤として、ナトリウム系の中和剤を使用している。中和剤については、後述する。 In this embodiment, a neutralizing agent containing an alkali metal is used as the alkaline neutralizing agent (hereinafter referred to as a neutralizing agent). Specifically, a sodium-based neutralizer is used as the neutralizer containing the alkali metal. The neutralizing agent will be described later.
　以下、本発明の一実施形態について、図面を参照しつつ説明する。本実施形態の飛灰の洗浄方法は、例えば、図１に示すような廃棄物焼却施設１００で発生した飛灰を洗浄する際に実施される。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The fly ash cleaning method of the present embodiment is performed, for example, when cleaning fly ash generated in a waste incineration facility 100 as shown in FIG.
　廃棄物焼却施設１００は、廃棄物を焼却するための焼却炉１と、焼却炉１から排出される排ガスの熱回収を行うためのボイラ２と、ボイラ２へ供給される水の温度を排ガスによって上昇させるエコノマイザ３と、排ガスを冷却するための減温塔４と、該減温塔４で冷却された排ガスを中和するための中和剤投入部７と、中和処理済みの排ガスを除塵するための除塵装置５と、ボイラ２、エコノマイザ３、減温塔４、及び除塵装置５から捕集された飛灰を洗浄するための飛灰洗浄装置６と、を備える。 A waste incineration facility 100 includes an incinerator 1 for incinerating waste, a boiler 2 for heat recovery of exhaust gas discharged from the incinerator 1, and the temperature of water supplied to the boiler 2 by the exhaust gas. The economizer 3 to be raised, the temperature reducing tower 4 for cooling the exhaust gas, the neutralizing agent introduction unit 7 for neutralizing the exhaust gas cooled by the temperature reducing tower 4, and the neutralized exhaust gas are dedusted And a fly ash cleaning device 6 for cleaning fly ash collected from the dust removal device 5.
　焼却炉１としては、例えば、ガス化溶融炉、ストーカ式焼却炉、又は流動床式焼却炉
が採用され得る。焼却炉１から排出された排ガス中には、塩化水素（ＨＣｌ）、硫黄酸化物（ＳＯｘ）等の酸性ガスが含まれている。焼却炉１から排出された酸性の排ガスは、ボイラ２及びエコノマイザ３によって熱回収され、減温塔４へと送られる。 As the incinerator 1, for example, a gasification melting furnace, a stoker type incinerator, or a fluidized bed type incinerator can be adopted. The exhaust gas discharged from the incinerator 1 contains acidic gases such as hydrogen chloride (HCl) and sulfur oxide (SOx). The acidic exhaust gas discharged from the incinerator 1 is heat recovered by the boiler 2 and the economizer 3 and sent to the temperature reducing tower 4.
　減温塔４は、例えば、塔内で水を噴霧するように構成されている。減温塔４は、酸性の排ガスを、噴霧された水に接触させることによって冷却し、塔外に排出する。減温塔４は、アルカリ性の水を噴霧することによって、酸性の排ガスを中和処理した後に塔外に排出するものであってもよい。 The temperature reduction tower 4 is configured to spray water in the tower, for example. The temperature reducing tower 4 cools the acidic exhaust gas by bringing it into contact with the sprayed water, and discharges it outside the tower. The temperature-decreasing tower 4 may be discharged outside the tower after neutralizing the acidic exhaust gas by spraying alkaline water.
　中和剤投入部７は、減温塔４の下流であって、除塵装置５の上流に設けられている。本実施形態では、中和剤投入部７は、減温塔４と除塵装置５とを繋ぐ配管に接続され、減温塔４から排出された排ガスに中和剤を供給するように構成されている。中和剤は、粉末状、スラリー状、又は液状の状態で排ガスに供給される。 The neutralizing agent charging unit 7 is provided downstream of the temperature reducing tower 4 and upstream of the dust removing device 5. In the present embodiment, the neutralizing agent charging unit 7 is connected to a pipe connecting the temperature reducing tower 4 and the dust removing device 5, and is configured to supply the neutralizing agent to the exhaust gas discharged from the temperature reducing tower 4. Yes. The neutralizing agent is supplied to the exhaust gas in a powder, slurry, or liquid state.
　酸性の排ガスに投入される中和剤としては、例えば、消石灰（Ｃａ（ＯＨ）２）、ドロマイト（ＣａＭｇ（ＣＯ３）２）等のアルカリ土類金属を含む中和剤や、重曹（ＮａＨＣＯ３）、苛性ソーダ（ＮａＯＨ）、炭酸ナトリウム（Ｎａ２ＣＯ３）、炭酸水素カリウム（ＫＨＣＯ３）、水酸化カリウム（ＫＯＨ）、炭酸カリウム（Ｋ２ＣＯ３）等のアルカリ金属を含む中和剤が用いられる。 As a neutralizing agent thrown into acidic exhaust gas, for example, a neutralizing agent containing an alkaline earth metal such as slaked lime (Ca (OH) 2 ), dolomite (CaMg (CO 3 ) 2 ), or sodium bicarbonate (NaHCO 3). ), Caustic soda (NaOH), sodium carbonate (Na 2 CO 3 ), potassium hydrogen carbonate (KHCO 3 ), potassium hydroxide (KOH), potassium carbonate (K 2 CO 3 ) and other neutralizing agents containing alkali metals are used. It is done.
　酸性の排ガスに投入される中和剤としては、一種類の中和剤であってもよいし、複数種類の中和剤が混合されたものであってもよい。本実施形態では、中和剤としては、アルカリ金属を含む中和剤が好ましい。具体的には、ナトリウム系の中和剤が好ましく、特に、重曹が好ましい。 As the neutralizing agent to be introduced into the acidic exhaust gas, one type of neutralizing agent or a mixture of a plurality of types of neutralizing agents may be used. In this embodiment, as a neutralizing agent, the neutralizing agent containing an alkali metal is preferable. Specifically, a sodium-based neutralizer is preferable, and sodium bicarbonate is particularly preferable.
　酸性の排ガスは、中和剤が投入されることで中和される。例えば、酸性の排ガスと消石灰とが中和反応することによって、塩化カルシウム（ＣａＣｌ２）や、硫酸カルシウム（ＣａＳＯ４）等の塩が生成される。酸性の排ガスと重曹とが中和反応することによって、塩化ナトリウム（ＮａＣｌ）、硫酸ナトリウム（Ｎａ２ＳＯ４）等の塩が生成される。また、酸性の排ガスと炭酸水素カリウムとが中和反応することによって、塩化カリウム（ＫＣｌ）、硫酸カリウム（Ｋ２ＳＯ４）等の塩が生成される。中和剤は、酸性の排ガスに対して、中和処理が未反応状態とならないように過剰に投与される。そのため、除塵装置５で捕集された飛灰中には、中和反応によって生成された塩、及び未反応の中和剤が混入している。 The acidic exhaust gas is neutralized by introducing a neutralizing agent. For example, a salt such as calcium chloride (CaCl 2 ) or calcium sulfate (CaSO 4 ) is generated by a neutralization reaction between acidic exhaust gas and slaked lime. A salt such as sodium chloride (NaCl) or sodium sulfate (Na 2 SO 4 ) is generated by the neutralization reaction between the acidic exhaust gas and sodium bicarbonate. Further, a salt such as potassium chloride (KCl) or potassium sulfate (K 2 SO 4 ) is generated by a neutralization reaction between acidic exhaust gas and potassium hydrogen carbonate. The neutralizing agent is excessively administered to the acidic exhaust gas so that the neutralization treatment is not unreacted. Therefore, in the fly ash collected by the dust remover 5, the salt generated by the neutralization reaction and the unreacted neutralizer are mixed.
　酸性の排ガスと中和剤との中和反応によって生成された硫酸塩のうち、アルカリ土類金属と反応することによって生成された硫酸塩は、アルカリ金属と反応することによって生成された硫酸塩よりも水に対する溶解度が低い。例えば、２０℃の水１００ｍｌに対する硫酸カルシウム（ＣａＳＯ４）の溶解度は、約０．２４ｇであるのに対して、２０℃の水１００ｍｌに対する硫酸ナトリウム（Ｎａ２ＳＯ４）の溶解度は、約２０ｇであり、硫酸カリウム（Ｋ２ＳＯ４）の溶解度は、約１１ｇである。そのため、飛灰を水洗浄する観点から、中和剤として、アルカリ金属を含む中和剤を使用するのが好ましく、中でもナトリウム系の中和剤を使用するのがより好ましい。 Among the sulfates produced by the neutralization reaction between the acidic exhaust gas and the neutralizer, the sulfate produced by reacting with the alkaline earth metal is more than the sulfate produced by reacting with the alkali metal. Has low solubility in water. For example, the solubility of calcium sulfate (CaSO 4 ) in 100 ml of water at 20 ° C. is about 0.24 g, whereas the solubility of sodium sulfate (Na 2 SO 4 ) in 100 ml of water at 20 ° C. is about 20 g. Yes, the solubility of potassium sulfate (K 2 SO 4 ) is about 11 g. Therefore, from the viewpoint of washing fly ash with water, it is preferable to use a neutralizing agent containing an alkali metal as the neutralizing agent, and it is more preferable to use a sodium-based neutralizing agent.
　除塵装置５としては、例えば、バグフィルタ、サイクロン式集塵機、電気集塵機等が採用され得る。本実施形態の除塵装置５は、バグフィルタである。本実施形態では、除塵装置５で捕集された飛灰は、ボイラ２、エコノマイザ３、及び減温塔４から捕集された飛灰と共に飛灰集積部Ｐに集められ、後述する飛灰洗浄装置６の混合部６１に投入される。しかしながら、除塵装置５で捕集された飛灰と、ボイラ２、エコノマイザ３、及び減温塔４から捕集された飛灰とを区別して飛灰洗浄装置６で洗浄してもよい。除塵装置５から排出された排ガスは、煙突等を介して、無害な状態で廃棄物焼却施設１００外に排出される。排ガス中に窒素酸化物（Ｎ Ｏ ｘ）やダイオキシン（Ｄ Ｘ Ｎ ｓ）類が含まれている場合には、除塵装置５の下流に触媒塔（図示しない）を設け、排ガスは、窒素酸化物（Ｎ Ｏ ｘ）やダイオキシン（Ｄ Ｘ Ｎ ｓ）類が除去された後に廃棄物焼却施設１００外へ排出される。符号Ａは、系外に排出される排ガスを表している。 As the dust removing device 5, for example, a bag filter, a cyclone type dust collector, an electric dust collector or the like can be adopted. The dust removing device 5 of the present embodiment is a bag filter. In this embodiment, the fly ash collected by the dust removing device 5 is collected together with the fly ash collected from the boiler 2, the economizer 3, and the temperature reducing tower 4 in the fly ash accumulating part P, and the fly ash cleaning described later Charged into the mixing section 61 of the apparatus 6. However, the fly ash collected by the dust removing device 5 and the fly ash collected from the boiler 2, the economizer 3, and the temperature reducing tower 4 may be distinguished and washed by the fly ash cleaning device 6. The exhaust gas discharged from the dust removing device 5 is discharged outside the waste incineration facility 100 in a harmless state through a chimney or the like. When nitrogen oxides (N 酸化 物 O x) and dioxins (D X N s) are contained in the exhaust gas, a catalyst tower (not shown) is provided downstream of the dust removing device 5, and the exhaust gas contains nitrogen oxides. After (N O x) and dioxins (D X N s) are removed, they are discharged out of the waste incineration facility 100. Reference symbol A represents exhaust gas discharged outside the system.
　飛灰洗浄装置６は、飛灰を水洗浄すると共に、飛灰と洗浄水との混合液を脱水するように構成されている。図２に示すように、本実施形態の飛灰洗浄装置６は、飛灰と洗浄水とを混合するための混合部６１と、混合部６１で混合された飛灰と洗浄水との混合液Ｗを固液分離して、飛灰を含有した脱水ケーキと洗浄済み水とを得る固液分離部６２と、固液分離部６２で得られた脱水ケーキを系外へ排出するための脱水ケーキ排出経路６３と、固液分離部６２で得られた洗浄済み水を排水する排水経路６４と、固液分離部６２で得られた洗浄済み水を洗浄水として混合部６１に給水するための再利用経路６５と、混合部６１から排出された混合液Ｗを固液分離部６２に供給するポンプ６６と、を備える。本実施形態の飛灰洗浄装置６は、脱水ケーキをすすぐためのリンス水を供給するリンス水供給経路６８を更に備える。 The fly ash cleaning device 6 is configured to wash the fly ash with water and dehydrate the mixture of the fly ash and the wash water. As shown in FIG. 2, the fly ash cleaning device 6 of this embodiment includes a mixing unit 61 for mixing fly ash and cleaning water, and a mixed liquid of fly ash and cleaning water mixed in the mixing unit 61. A solid-liquid separation unit 62 that obtains a dehydrated cake containing fly ash and washed water by solid-liquid separation of W, and a dehydrated cake for discharging the dehydrated cake obtained by the solid-liquid separation unit 62 out of the system A discharge path 63, a drain path 64 for draining the washed water obtained in the solid-liquid separation unit 62, and a re-flow for feeding the washed water obtained in the solid-liquid separation unit 62 to the mixing unit 61 as washing water. A use path 65 and a pump 66 that supplies the mixed liquid W discharged from the mixing unit 61 to the solid-liquid separation unit 62 are provided. The fly ash cleaning apparatus 6 of the present embodiment further includes a rinse water supply path 68 that supplies rinse water for rinsing the dewatered cake.
　洗浄水とは、飛灰を洗浄するために混合部６１に供給される水であり、飛灰の洗浄のために再利用される洗浄済み水、すすぎ済み水、及び飛灰を洗浄するために洗浄済み水及びすすぎ済み水とは別に準備された洗浄用原水とを含めた概念である。洗浄済み水とは、飛灰に混入している塩、及び未反応の中和剤等（以下、塩類ともいう）が溶出した状態の水であって、固液分離部６２で得られた水を意味するものである。洗浄済み水は、混合部６１に供給される場合には、洗浄水として扱われる水である。 The washing water is water supplied to the mixing unit 61 for washing fly ash, and is used for washing washed water, rinsed water, and fly ash that are reused for washing fly ash. This is a concept including cleaning water and cleaning raw water prepared separately from rinsed water. Washed water is water in a state in which salt mixed in fly ash and unreacted neutralizing agent (hereinafter also referred to as “salts”) are eluted, and water obtained in the solid-liquid separation unit 62 Means. The washed water is water treated as washing water when supplied to the mixing unit 61.
　混合部６１は、飛灰と洗浄水とが投入される混合槽６１１と、該混合槽６１１内で飛灰と洗浄水とを撹拌するための撹拌部６１２とを備える。混合部６１は、飛灰に混入している塩類を洗浄水中に溶出させる部分である。混合部６１は、混合槽６１１に飛灰が投入され、洗浄用原水（符号Ｄで表される）や、洗浄済み水が供給されることで、混合槽６１１内に飛灰と洗浄水とを貯留するように構成されている。本実施形態では、飛灰の洗浄はバッチ操作によって実施されるが、連続式で実施されてもよい。 The mixing unit 61 includes a mixing tank 611 into which fly ash and washing water are charged, and a stirring unit 612 for stirring the fly ash and washing water in the mixing tank 611. The mixing unit 61 is a part for eluting salts mixed in the fly ash into the wash water. The mixing unit 61 supplies fly ash and washing water into the mixing tank 611 by supplying fly ash into the mixing tank 611 and supplying raw water for cleaning (represented by reference symbol D) or washed water. It is configured to store. In this embodiment, washing of fly ash is performed by batch operation, but may be performed continuously.
　混合液Ｗは、混合槽６１１内で所定時間撹拌され、飛灰中の塩類が溶出して混合液Ｗの溶解性蒸発残留物の上昇が止まると、ポンプ６６を介して固液分離部６２に移送される。そのため、混合部６１（混合槽６１１）から排出された混合液Ｗは、塩類が除去された洗浄飛灰と、塩類が溶存した洗浄済み水とが混合された状態のものである。 The mixed liquid W is stirred for a predetermined time in the mixing tank 611, and when the salts in the fly ash are eluted and the rise of the soluble evaporation residue of the mixed liquid W stops, the mixed liquid W is supplied to the solid-liquid separation unit 62 via the pump 66. Be transported. Therefore, the liquid mixture W discharged | emitted from the mixing part 61 (mixing tank 611) is a state in which the washing | cleaning fly ash from which salts were removed, and the washed water in which salts were dissolved were mixed.
　固液分離部６２は、混合液Ｗを脱水して、飛灰を含有した脱水ケーキと洗浄済み水とを得るように構成されている。即ち、固液分離部６２は、混合液Ｗを濃縮して脱水ケーキを集積する濃縮部６２１と、混合液Ｗを濃縮することで得られる洗浄済み水を回収する液回収部６２２とを有する。本実施形態の固液分離部６２は、例えば、濾布を用いたフィルタープレス（圧搾）によって混合液Ｗを固液分離するフィルタープレス機である。例えば、フィルタープレス機は、混合部６１で得られた混合液Ｗがポンプ６６によって濃縮部６２１に圧送されることで、濾布を介して、混合液Ｗよりも固形分（飛灰）の濃度が高い脱水ケーキと、混合液Ｗよりも固形分の濃度が低い洗浄済み水とに混合液Ｗを分離するように構成されている。 The solid-liquid separator 62 is configured to dehydrate the mixed solution W to obtain a dehydrated cake containing fly ash and washed water. That is, the solid-liquid separation unit 62 includes a concentration unit 621 that concentrates the liquid mixture W and accumulates dehydrated cake, and a liquid recovery unit 622 that recovers washed water obtained by concentrating the liquid mixture W. The solid-liquid separation unit 62 of the present embodiment is a filter press machine that separates the mixed liquid W into solid and liquid by, for example, a filter press (squeezing) using a filter cloth. For example, in the filter press, the liquid mixture W obtained in the mixing unit 61 is pumped to the concentration unit 621 by the pump 66, so that the concentration of solid content (fly ash) is higher than that of the liquid mixture W through the filter cloth. The mixed solution W is separated into a dehydrated cake having a high concentration and washed water having a solid content lower than that of the mixed solution W.
　本実施形態の固液分離部６２は、脱水ケーキ中の水の塩素濃度を下げるために脱水ケーキをリンス水ですすぐように構成されている。即ち、固液分離部６２は、濃縮部６２１にリンス水を供給可能に構成されている。本実施形態では、固液分離部６２は、リンス水がポンプ６６によって濃縮部６２１に圧送され、濃縮部６２１中の脱水ケーキに含水した洗浄済み水をリンス水で置換するように構成されている。また、固液分離部６２は、脱水ケーキから、該脱水ケーキをすすいだすすぎ済み水を分離可能に構成されている。このように、固液分離部６２は、すすぎ工程を実施し得るように構成されることで、脱水ケーキ中の洗浄済み水をリンス水で置換して脱水ケーキの塩素濃度を下げ、該脱水ケーキをセメント原料に利用可能な性状にすることができる。固液分離部６２は、例えば、ベルトプレス機や遠心脱水機であってもよい。 The solid-liquid separation unit 62 of this embodiment is configured to rinse the dehydrated cake with rinse water in order to reduce the chlorine concentration of the water in the dehydrated cake. That is, the solid-liquid separation unit 62 is configured to be able to supply rinse water to the concentration unit 621. In the present embodiment, the solid-liquid separation unit 62 is configured such that the rinse water is pumped to the concentration unit 621 by the pump 66 and the washed water contained in the dewatered cake in the concentration unit 621 is replaced with the rinse water. . The solid-liquid separation unit 62 is configured to be able to separate the rinsed water from the dehydrated cake. In this way, the solid-liquid separation unit 62 is configured to be able to perform the rinsing step, so that the washed water in the dehydrated cake is replaced with rinse water to reduce the chlorine concentration of the dehydrated cake, and the dehydrated cake. Can be used as a cement raw material. The solid-liquid separation unit 62 may be, for example, a belt press machine or a centrifugal dehydrator.
　脱水ケーキ排出経路６３は、固液分離部６２で濃縮された脱水ケーキを系外に排出する経路である。脱水ケーキ排出経路６３は、固液分離部６２の濃縮部６２１に接続されているか、又は濃縮部６２１から排出された脱水ケーキを受けるように構成されている。脱水ケーキは、脱水ケーキ排出経路６３を介して系外に持ち出され、埋め立て、セメント原料等に再利用される。符号Ｂは、系外に排出される脱水ケーキを表している。 The dehydrated cake discharge path 63 is a path for discharging the dehydrated cake concentrated in the solid-liquid separator 62 to the outside of the system. The dehydrated cake discharge path 63 is connected to the concentration unit 621 of the solid-liquid separation unit 62 or configured to receive the dehydrated cake discharged from the concentration unit 621. The dehydrated cake is taken out of the system through the dehydrated cake discharge path 63 and is reused for landfill, cement raw material, and the like. A symbol B represents a dehydrated cake discharged out of the system.
　排水経路６４は、固液分離部６２から得られた洗浄済み水やすすぎ済み水を系外に排水する経路である。排水経路６４は、固液分離部６２の液回収部６２２に接続されている。飛灰洗浄装置６から排出された排水は、排水経路６４を介して図示しない他の浄化処理設備に送られ、浄化処理される。符号Ｃは、系外に排水される洗浄済み水又はすすぎ済み水を表している。 The drainage path 64 is a path for draining the washed water and the rinsed water obtained from the solid-liquid separation unit 62 out of the system. The drainage path 64 is connected to the liquid recovery unit 622 of the solid-liquid separation unit 62. The wastewater discharged from the fly ash cleaning device 6 is sent to another purification treatment facility (not shown) via the drainage path 64 and subjected to purification treatment. The symbol C represents washed water or rinsed water that is drained out of the system.
　即ち、固液分離部６２は、濃縮部６２１が脱水ケーキ排出経路６３に接続され、液回収部６２２が排水経路６４に接続されていることで、固液分離後の脱水ケーキと洗浄済み水とを、固液分離部６２の外に排出できるように構成されている。 That is, the solid-liquid separation unit 62 is configured such that the concentration unit 621 is connected to the dewatered cake discharge path 63 and the liquid recovery unit 622 is connected to the drainage path 64, so Is configured to be discharged out of the solid-liquid separator 62.
　再利用経路６５は、固液分離部６２で得られた洗浄済み水を洗浄水として混合部６１に給水する経路である。再利用経路６５は、一端がタンク等の貯留設備（図示しない）に接続され、他端が混合部６１に対して開放されている。具体的には、固液分離部６２から排出された洗浄済み水は、排水経路６４を介してタンク等の貯留設備に貯留され、別途設けられたポンプ（図示しない）によって圧送されることで、再利用経路６５を介して混合部６１に給水される。 The reuse path 65 is a path for supplying water that has been washed by the solid-liquid separation unit 62 to the mixing unit 61 as washing water. One end of the reuse path 65 is connected to a storage facility (not shown) such as a tank, and the other end is open to the mixing unit 61. Specifically, the washed water discharged from the solid-liquid separator 62 is stored in a storage facility such as a tank via the drainage path 64 and is pumped by a separately provided pump (not shown). Water is supplied to the mixing unit 61 via the reuse path 65.
　ポンプ６６は、混合部６１から排出された混合液Ｗを固液分離部６２に移送する。また、ポンプ６６は、リンス水を濃縮部６２１に移送可能に構成されている。ポンプ６６は、混合部６１と固液分離部６２とを接続する移送配管６７内に配されている。 The pump 66 transfers the mixed liquid W discharged from the mixing unit 61 to the solid-liquid separation unit 62. The pump 66 is configured to be able to transfer rinse water to the concentration unit 621. The pump 66 is disposed in a transfer pipe 67 that connects the mixing unit 61 and the solid-liquid separation unit 62.
　リンス水供給経路６８は、固液分離部６２の濃縮部６２１にリンス水を供給する経路である。本実施形態のリンス水供給経路６８は、移送配管６７に接続されている。具体的には、リンス水供給経路６８は、移送配管６７のうちのポンプ６６の吸込み側に設けられた上流配管６７１に接続されている。リンス水は、ポンプ６６によって圧送され、ポンプ６６の吐出側に設けられた下流配管６７２を介して固液分離部６２に送られる。例えば、リンス水として、水道水や工業用水、地下水、工業排水が採用される。符号Ｅは、系内に導入されるリンス水を表している。 The rinse water supply path 68 is a path for supplying rinse water to the concentration unit 621 of the solid-liquid separation unit 62. The rinse water supply path 68 of this embodiment is connected to the transfer pipe 67. Specifically, the rinse water supply path 68 is connected to an upstream pipe 671 provided on the suction side of the pump 66 in the transfer pipe 67. The rinse water is pumped by the pump 66 and is sent to the solid-liquid separation unit 62 via the downstream pipe 672 provided on the discharge side of the pump 66. For example, tap water, industrial water, ground water, or industrial waste water is adopted as the rinse water. Symbol E represents rinse water introduced into the system.
　廃棄物焼却施設１００についての説明は以上である。以下、飛灰の洗浄方法について、更に具体的に説明する。 This completes the explanation of the waste incineration facility 100. Hereinafter, the fly ash cleaning method will be described more specifically.
　洗浄済み水を飛灰の洗浄のために再利用するにあたって、混合液Ｗ中に析出物が生じない範囲内で洗浄済み水を飛灰の洗浄に再利用することとし、飛灰の洗浄に使用される洗浄水を大幅に削減するに至った。具体的には、飛灰を中和処理する中和剤として、アルカリ土類金属を含む中和剤を使用した場合には、混合液Ｗ中の溶解性蒸発残留物が２０％程度となると、混合液Ｗに析出物が発生することを確認した。また、アルカリ金属を含む中和剤を使用した場合には、混合液Ｗ中の溶解性蒸発残留物が２０％以上であっても析出物が生じないことを確認した。更に、ナトリウム系の中和剤を使用した場合には、溶解性蒸発残留物が３５％以下であれば、析出物が生じないことを確認した。 When the washed water is reused for the fly ash washing, the washed water is reused for the fly ash washing within the range where no precipitate is generated in the mixed solution W, and used for the fly ash washing. This has led to a significant reduction in the amount of washing water used. Specifically, when a neutralizing agent containing an alkaline earth metal is used as a neutralizing agent for neutralizing fly ash, when the soluble evaporation residue in the mixed solution W is about 20%, It was confirmed that precipitates were generated in the mixed solution W. Moreover, when the neutralizing agent containing an alkali metal was used, even if the soluble evaporation residue in the liquid mixture W was 20% or more, it was confirmed that no precipitate was generated. Further, when a sodium-based neutralizing agent was used, it was confirmed that no precipitate was formed if the soluble evaporation residue was 35% or less.
　飛灰集積部Ｐに集められた飛灰を混合槽６１１に投入し、混合槽６１１内で洗浄水と飛灰との液固比が５～１０となるように、混合部６１に洗浄用原水を導入する。混合工程では、撹拌部６１２を駆動して、混合槽６１１内で、飛灰と洗浄用原水とを所定時間撹拌し、飛灰に混入していた塩類を洗浄用原水に溶出させる。飛灰と洗浄用原水との混合を１回目の洗浄操作として、該１回目の洗浄操作後の固液分離工程で得られた洗浄済み水を第１洗浄済み水と称する。１回目の洗浄操作が終了した時点で、混合液Ｗ中の溶解性蒸発残留物を確認する。 The fly ash collected in the fly ash accumulating part P is put into the mixing tank 611, and the raw water for washing is supplied to the mixing part 61 so that the liquid-solid ratio between the washing water and the fly ash is 5 to 10 in the mixing tank 611. Is introduced. In the mixing step, the stirrer 612 is driven to stir the fly ash and the cleaning raw water for a predetermined time in the mixing tank 611, and the salts mixed in the fly ash are eluted into the cleaning raw water. The mixing of the fly ash and the raw water for washing is referred to as the first washing operation, and the washed water obtained in the solid-liquid separation step after the first washing operation is referred to as first washed water. When the first washing operation is completed, the soluble evaporation residue in the mixed solution W is confirmed.
　一般的に、洗浄前の飛灰には、塩化物が硫酸塩よりも多量に含有されている。塩化カルシウム（ＣａＣｌ２）、塩化ナトリウム（ＮａＣｌ）、及び塩化カリウム（ＫＣｌ）等の塩化物の溶解度は、２０℃の水１００ｍｌに対して１５ｇ以上であるため、１回目の洗浄操作終了時点では、通常、混合液Ｗ中の溶解性蒸発残留物が２０％以下となる。 In general, fly ash before washing contains a larger amount of chloride than sulfate. Since the solubility of chlorides such as calcium chloride (CaCl 2 ), sodium chloride (NaCl), and potassium chloride (KCl) is 15 g or more with respect to 100 ml of water at 20 ° C., at the end of the first washing operation, Usually, the soluble evaporation residue in the mixed solution W is 20% or less.
　混合工程後、固液分離工程に移行する。固液分離工程では、混合液Ｗを固液分離部６２に通して固液分離（脱水）し、飛灰を含有した脱水ケーキと第１洗浄済み水とを得る。固液分離工程後、固液分離部６２から排出された第１洗浄済み水を、再利用経路６５を介して混合部６１に戻すか、タンク等の貯留設備に貯留しておく。続いて、固液分離部６２で得られた脱水ケーキをすすぐすすぎ工程に移行する。 後 After the mixing process, move to the solid-liquid separation process. In the solid-liquid separation step, the liquid mixture W is passed through the solid-liquid separation unit 62 for solid-liquid separation (dehydration) to obtain a dehydrated cake containing fly ash and first washed water. After the solid-liquid separation step, the first washed water discharged from the solid-liquid separation unit 62 is returned to the mixing unit 61 via the reuse path 65 or stored in a storage facility such as a tank. Subsequently, the dehydrated cake obtained in the solid-liquid separation unit 62 is transferred to a rinsing process.
　すすぎ工程では、固液分離部６２の濃縮部６２１にリンス水を供給し、脱水ケーキ中の第１洗浄済み水をリンス水で置換する。すすぎ工程では、リンス水と飛灰との液固比が２．５～５となるように、リンス水供給経路６８を介して濃縮部６２１にリンス水を導入する。脱水ケーキをリンス水ですすぐことによって、脱水ケーキの塩素濃度を下げることができる。具体的には、セメント中の塩素濃度は、３５０ｐｐｍ以下であることが好ましく、脱水ケーキをセメント原料に利用する場合には、脱水ケーキ中の塩素濃度を極力下げる必要がある。例えば、固形分及び水分を含めた脱水ケーキ全体として塩素濃度が１％以下であることが好ましい。また、乾燥後の脱水ケーキ中の塩素濃度が１％以下であることがより好ましい。脱水ケーキ中の塩素濃度を下げた結果、例えば、乾燥後の脱水ケーキ中の塩素濃度が１％まで下がった場合には、約３％の飛灰をセメント原料として使用できるようになる。 In the rinsing step, rinse water is supplied to the concentration unit 621 of the solid-liquid separation unit 62, and the first washed water in the dehydrated cake is replaced with rinse water. In the rinsing step, the rinsing water is introduced into the concentrating unit 621 via the rinsing water supply path 68 so that the liquid-solid ratio of the rinsing water and the fly ash is 2.5 to 5. By rinsing the dehydrated cake with rinse water, the chlorine concentration of the dehydrated cake can be lowered. Specifically, the chlorine concentration in the cement is preferably 350 ppm or less. When the dehydrated cake is used as a cement raw material, it is necessary to reduce the chlorine concentration in the dehydrated cake as much as possible. For example, the chlorine concentration of the entire dehydrated cake including solids and moisture is preferably 1% or less. The chlorine concentration in the dehydrated cake after drying is more preferably 1% or less. As a result of lowering the chlorine concentration in the dehydrated cake, for example, when the chlorine concentration in the dehydrated cake after drying is reduced to 1%, about 3% fly ash can be used as a cement raw material.
　脱水後の脱水ケーキの含水率をＡ％とし、すすぎ後の脱水ケーキ中の塩素濃度をＸ％とする。セメント原料となる乾燥した脱水ケーキ中の塩素濃度をＹ％とすると、Ａ、Ｘ、及びＹには以下の関係がある。
　Ｙ　＝　１００・Ｘ／（１００－Ａ）
　即ち、すすぎ工程では、乾燥した脱水ケーキ中の塩素濃度の目標値を定め、脱水ケーキの含水率から、すすぎ後の脱水ケーキに対してどの値まで塩素濃度を下げる必要があるかを算出し、脱水ケーキ中の塩素濃度が該値以下となるように、脱水ケーキをすすぐ。 The moisture content of the dehydrated cake after dehydration is A%, and the chlorine concentration in the dehydrated cake after rinsing is X%. When the chlorine concentration in the dried dehydrated cake used as a cement raw material is Y%, A, X, and Y have the following relationship.
Y = 100 · X / (100-A)
That is, in the rinsing step, the target value of the chlorine concentration in the dried dehydrated cake is determined, and from the moisture content of the dehydrated cake, the value to which the chlorine concentration needs to be reduced relative to the dehydrated cake after rinsing is calculated, Rinse the dehydrated cake so that the chlorine concentration in the dehydrated cake is below this value.
　例えば、脱水ケーキの固形分に含まれた塩素濃度が限りなくゼロに近い場合でも、すすぎ前の脱水ケーキ中の水分は、溶解性蒸発残留物が比較的高い状態の洗浄済み水であるので、乾燥後の飛灰中の塩素濃度が１％を超えてしまう場合がある。そのため、本実施形態では、脱水ケーキ全体としての塩素濃度を下げ、セメント原料として適切な塩素濃度となるようにすすぎ工程で脱水ケーキをすすぐ。すすぎ工程後、固液分離部６２から排出されたすすぎ済み水を、タンク等の貯留設備（図示しない）に貯留しておく。 For example, even if the concentration of chlorine contained in the solid content of the dehydrated cake is as close to zero as possible, the water in the dehydrated cake before rinsing is washed water with a relatively high soluble evaporation residue, The chlorine concentration in the fly ash after drying may exceed 1%. Therefore, in the present embodiment, the chlorine concentration of the entire dehydrated cake is lowered, and the dehydrated cake is rinsed in the rinsing step so that the chlorine concentration becomes an appropriate cement raw material. After the rinsing step, the rinsed water discharged from the solid-liquid separation unit 62 is stored in a storage facility (not shown) such as a tank.
　次に、混合工程で、洗浄済み水を再利用する方法について説明する。以下、洗浄済み水又はすすぎ済み水を混合槽６１１に給水する工程を再利用工程と称する。再利用工程は、固液分離工程又はすすぎ工程と平行して実施されてもよく、固液分離工程及びすすぎ工程が終了してから実施されてもよい。本実施形態では、固液分離工程及びすすぎ工程が終了した後に、再利用工程が実施される場合について説明する。第１洗浄済み水が貯留された貯留設備及びすすぎ済み水が貯留された貯留設備は、それぞれ再利用経路６５に接続されており、再利用経路６５は、それぞれの貯留設備から、図示しないポンプを介して水を汲み上げ可能に構成されている。再利用工程では、洗浄済み水が不足した場合に、すすぎ済み水を洗浄水として混合槽６１１に給水してもよい。また、再利用工程では、洗浄水として、洗浄用原水を給水することもできる。 Next, a method for reusing washed water in the mixing step will be described. Hereinafter, the process of supplying washed water or rinsed water to the mixing tank 611 is referred to as a reuse process. The reuse step may be performed in parallel with the solid-liquid separation step or the rinsing step, or may be performed after the solid-liquid separation step and the rinsing step are completed. This embodiment demonstrates the case where a reuse process is implemented after a solid-liquid separation process and a rinse process are complete | finished. The storage facility in which the first washed water is stored and the storage facility in which the rinsed water is stored are connected to the reuse path 65, and the reuse path 65 is connected to a pump (not shown) from each storage facility. It is configured to be able to pump water through. In the reuse process, when the washed water is insufficient, the rinsed water may be supplied to the mixing tank 611 as washing water. In the reuse process, raw water for cleaning can be supplied as cleaning water.
　空の状態の混合槽６１１内に、飛灰集積部Ｐに集められた飛灰を投入し、混合槽６１１内で洗浄水と飛灰との液固比が５～１０となるように、再利用経路６５を介して第１洗浄済み水を洗浄水として給水する。続いて混合工程に移行し、１回目の洗浄操作と同様に、混合槽６１１内で飛灰と第１洗浄済み水としての洗浄水とを所定時間撹拌し、飛灰に混入していた塩類を洗浄水に溶出させる。この洗浄操作を２回目の洗浄操作として、該２回目の洗浄操作後の固液分離工程で得られた洗浄済み水を第２洗浄済み水と称する。２回目の洗浄操作が終了した時点で、混合液Ｗ中の溶解性蒸発残留物を確認する。そして、混合液Ｗ中の溶解性蒸発残留物が２０％となるまで（又は３５％以下となるように）上記の洗浄操作を繰り返す。混合工程後の固液分離工程、及びすすぎ工程についてはすでに説明した固液分離工程及びすすぎ工程と同様であるため、説明は繰り返さない。 The fly ash collected in the fly ash accumulating part P is put into the mixing tank 611 in an empty state, and the mixing ratio is adjusted so that the liquid-solid ratio of the washing water and the fly ash becomes 5 to 10 in the mixing tank 611. The first cleaned water is supplied as cleaning water through the use path 65. Subsequently, the process proceeds to the mixing step, and the fly ash and the wash water as the first washed water are stirred for a predetermined time in the mixing tank 611 as in the first washing operation, and the salts mixed in the fly ash are removed. Elute in wash water. With this washing operation as the second washing operation, the washed water obtained in the solid-liquid separation step after the second washing operation is referred to as second washed water. When the second washing operation is completed, the soluble evaporation residue in the mixed solution W is confirmed. Then, the above washing operation is repeated until the soluble evaporation residue in the mixed solution W reaches 20% (or 35% or less). Since the solid-liquid separation step and the rinsing step after the mixing step are the same as the already described solid-liquid separation step and the rinsing step, the description will not be repeated.
　例えば、洗浄水と飛灰との液固比を５、リンス水と飛灰との液固比を２．５として混合工程及びすすぎ工程を実施し、５回目の洗浄操作の終了時点で混合液Ｗ中の溶解性蒸発残留物が２０％に達したとする。この場合、５回の洗浄操作の全てにおいて洗浄用原水を使用した場合には、飛灰に対して３７．５倍（（５＋２．５）×５）の洗浄水を使用したこととなる。これに対して、本実施形態のように、５回の洗浄操作の全てにおいて洗浄済み水を洗浄水として再利用した場合には、飛灰に対して１７．５倍（５＋２．５×５）の洗浄水を使用したこととなる。このことからも明らかなように、洗浄済み水を再利用することで、飛灰に対して約２０倍もの水を節約することができる。 For example, the mixing step and the rinsing step are performed with the liquid / solid ratio of washing water and fly ash being 5, and the liquid / solid ratio of rinsing water and fly ash being 2.5, and the mixed solution is obtained at the end of the fifth washing operation. Assume that the soluble evaporation residue in W reaches 20%. In this case, when the raw water for cleaning is used in all of the five cleaning operations, the cleaning water is used 37.5 times ((5 + 2.5) × 5) as much as the fly ash. On the other hand, when the washed water is reused as washing water in all five washing operations as in this embodiment, it is 17.5 times as much as fly ash (5 + 2.5 × 5). This means that the washing water was used. As is clear from this, by reusing the washed water, it is possible to save about 20 times as much water as the fly ash.
　また、中和剤として、ナトリウム系の中和剤を使用した場合には、アルカリ土類金属を含む中和剤やカリウム等のその他のアルカリ金属を含む中和剤を使用した場合よりも、中和によって生成される塩の溶解度が高いため、混合液Ｗ中の溶解性蒸発残留物が２０％以上、且つ３５％以下となるまで洗浄済み水を再利用できる。そのため、中和剤として、アルカリ土類金属を含む中和剤やカリウム等のその他のアルカリ金属を含む中和剤を使用した場合よりも、洗浄済み水を再利用できる回数が増えるので、洗浄水を一層節約することができる。 Further, when a sodium-based neutralizer is used as a neutralizer, a neutralizer containing an alkaline earth metal or a neutralizer containing another alkali metal such as potassium is used. Since the solubility of the salt produced by the sum is high, the washed water can be reused until the soluble evaporation residue in the mixed solution W becomes 20% or more and 35% or less. Therefore, the number of times the washed water can be reused is increased compared to the case of using a neutralizing agent containing an alkaline earth metal or a neutralizing agent containing another alkali metal such as potassium as the neutralizing agent. Can be further saved.
　ここで、ナトリウム系の中和剤によって中和処理済みの飛灰中には、塩化ナトリウムが多量に存在する。２０℃の水１００ｍｌに対する塩化ナトリウムの溶解度が約３６ｇであるが、硫酸塩の存在も考慮して、混合液Ｗ中の溶解性蒸発残留物の上限を３５％とした。 Here, a large amount of sodium chloride is present in the fly ash that has been neutralized with a sodium-based neutralizer. Although the solubility of sodium chloride in 100 ml of water at 20 ° C. is about 36 g, the upper limit of the soluble evaporation residue in the mixed solution W is set to 35% in consideration of the presence of sulfate.
　溶解性蒸発残留物が３５％を超えた後の洗浄済み水は、排水経路６４を介して中和処理設備等の他の浄化処理設備に送られ、浄化処理される。又は、溶解性蒸発残留物が３５％を超えた後の洗浄済み水は、蒸発固化されてもよい。この場合、塩濃度が高い洗浄済み水を蒸発固化するので、塩濃度が低い洗浄済み水を蒸発固化する場合と比較して、蒸発固化に要する熱エネルギーを抑えることができ、エネルギー的にも有利である。本実施形態ではナトリウム系の中和剤（アルカリ金属を含む中和剤に同じ）を使用しているので、洗浄済み水のｐＨは、アルカリ土類金属を含む中和剤を使用した場合よりも低く（図３参照）、洗浄済み水の中和処理に必要な薬剤も節約することができる。 The washed water after the soluble evaporation residue exceeds 35% is sent to another purification treatment facility such as a neutralization treatment facility via the drainage path 64 and subjected to purification treatment. Alternatively, the washed water after the soluble evaporation residue exceeds 35% may be evaporated and solidified. In this case, since the washed water with a high salt concentration is evaporated and solidified, the thermal energy required for the evaporation and solidification can be suppressed compared with the case where the washed water with a low salt concentration is evaporated and solidified. It is. In this embodiment, a sodium-based neutralizing agent (same as a neutralizing agent containing an alkali metal) is used, so the pH of the washed water is higher than that when a neutralizing agent containing an alkaline earth metal is used. Low (see FIG. 3), it can also save the chemicals required for neutralization of washed water.
　本実施形態の飛灰の洗浄方法は、上記のように構成されているので、以下の利点を有するものである。 Since the fly ash cleaning method of the present embodiment is configured as described above, it has the following advantages.
　出願人は、アルカリ性の中和剤で中和処理済みの排ガスから捕集された飛灰を洗浄水と混合した結果得られる洗浄済み水には、塩類、中和剤、重金属等、複数種類の物質が溶存しているものの、飛灰の洗浄に再利用しても不具合が生じないことを確認した。
　具体的には、出願人は、飛灰と洗浄水との混合液中の溶解性蒸発残留物が所定の濃度よりも低く保たれていれば、混合液中の溶存物質が析出せず、析出物が流路を塞ぐなどの不具合が生じ難いので、洗浄済み水を飛灰の洗浄に問題無く使用できることを確認した。
　即ち、本発明に係る飛灰の洗浄方法は、アルカリ性の中和剤で中和処理済みの排ガスから捕集された飛灰と洗浄水とを混合する混合工程と、前記混合工程で得られた前記飛灰と前記洗浄水との混合液を固液分離して、脱水ケーキと洗浄済み水とを得る固液分離工程と、を備え、前記混合工程では、前記混合液中の溶解性蒸発残留物が少なくとも２０％となるように、前記洗浄済み水を、少なくとも前記洗浄水の一部として再利用する。 Applicants have decided that the washed water obtained as a result of mixing fly ash collected from exhaust gas that has been neutralized with an alkaline neutralizing agent with washing water includes a plurality of types of salts, neutralizing agents, heavy metals, etc. Although the substance was dissolved, it was confirmed that there was no problem even if it was reused for cleaning fly ash.
Specifically, the applicant has determined that if the soluble evaporation residue in the mixed liquid of fly ash and washing water is kept lower than a predetermined concentration, the dissolved substance in the mixed liquid does not precipitate and precipitates. It was confirmed that washed water could be used without problems for washing fly ash because problems such as obstruction of the flow path with objects did not occur easily.
That is, the fly ash cleaning method according to the present invention was obtained by the mixing step of mixing the fly ash collected from the exhaust gas neutralized with an alkaline neutralizer and the washing water, and the mixing step. A solid-liquid separation step for obtaining a dehydrated cake and washed water by solid-liquid separation of the mixed solution of the fly ash and the washing water, and in the mixing step, soluble evaporation residue in the mixed solution The washed water is reused as at least part of the wash water so that the product is at least 20%.
　本実施形態の飛灰の洗浄法によれば、固液分離工程で得られた洗浄済み水を飛灰の洗浄に再利用すると洗浄済み水が濃縮されていくものの、上記構成の飛灰の洗浄方法は、混合液Ｗ中の溶解性蒸発残留物が少なくとも２０％になるように、洗浄済み水で飛灰を洗うため、洗浄済み水を洗浄水として再利用することができるので、洗浄水の給水量を抑えることができる。 According to the fly ash washing method of the present embodiment, the washed water obtained in the solid-liquid separation step is reused for washing the fly ash. In the method, since the fly ash is washed with the washed water so that the soluble evaporation residue in the mixed solution W is at least 20%, the washed water can be reused as the washing water. The amount of water supply can be reduced.
　また、上記実施形態では、前記混合工程で得られた前記飛灰と前記洗浄水との混合液中の溶解性蒸発残留物濃度を入手する工程を備える。アルカリ性の中和剤で中和処理済みの排ガスから捕集された飛灰と洗浄水とを混合すると、混合液は、塩類、中和剤等の複数種類の物質が高濃度で溶存した状態となる。そして、塩類が高濃度で溶存した洗浄済み水を排水とすると、洗浄水を多量に要することとなり、排水の浄化処理に要するエネルギーも膨大となる。しかしながら、かかる構成によれば、混合液中の溶解性蒸発残留物濃度を入手する工程を備えているので、混合液中の溶存物質の濃度を監視しながら、溶解性蒸発残留物が析出する濃度域である少なくとも２０％となるように、洗浄済み水を飛灰の洗浄に再利用することができる。そのため、洗浄済み水の濃度を除々に上昇させつつ使用することができるので、洗浄水として利用価値のある洗浄済み水が排水されるのを防止して、洗浄済み水を最大限有効利用することができる。 In addition, the above embodiment includes a step of obtaining a soluble evaporation residue concentration in a mixed solution of the fly ash obtained in the mixing step and the washing water. When fly ash collected from exhaust gas that has been neutralized with an alkaline neutralizer and washing water are mixed, the mixture is in a state where a plurality of substances such as salts and neutralizers are dissolved at high concentrations. Become. If the washed water in which salts are dissolved at a high concentration is used as waste water, a large amount of washing water is required, and the energy required for the purification treatment of the waste water is enormous. However, according to such a configuration, since the step of obtaining the concentration of the soluble evaporation residue in the mixed solution is provided, the concentration at which the soluble evaporation residue precipitates while monitoring the concentration of the dissolved substance in the mixed solution. The washed water can be reused for washing the fly ash so that it is at least 20% of the area. Therefore, it can be used while gradually increasing the concentration of washed water, so that washed water that is valuable as washing water is prevented from being drained, and the washed water is used to the maximum extent possible. Can do.
　また、上記実施形態では、前記混合工程で使用される飛灰は、前記排ガスから捕集された飛灰であって、未水洗の飛灰である。かかる構成によれば、前記混合工程で使用される飛灰が、前記排ガスから捕集された飛灰であって、未水洗の飛灰であるので、前記混合工程で得られる前記未水洗の飛灰と洗浄水との混合液を固液分離して洗浄済み水を得て、該洗浄済み水を混合工程における洗浄水の一部として再利用することができる。そのため、不純物が多量に含まれ、通常は排水処理される（再利用には適さない）水を敢えて使用することができるので、飛灰の洗浄に使用される水の量を削減することができる。また、通常は排水処理される水を最大限有効利用することができるので、このような水の全てを再利用せずに一部を廃棄する場合であっても、廃棄する水を処理する負荷を比較的小さくすることができる。 In the above embodiment, the fly ash used in the mixing step is fly ash collected from the exhaust gas, and is unwashed fly ash. According to this configuration, the fly ash used in the mixing step is fly ash collected from the exhaust gas and is unwashed fly ash, so the unwashed fly ash obtained in the mixing step. The mixed liquid of ash and washing water is separated into solid and liquid to obtain washed water, and the washed water can be reused as a part of washing water in the mixing step. Therefore, it is possible to dare to use water that contains a large amount of impurities and is usually drained (not suitable for reuse), so the amount of water used for washing fly ash can be reduced. . In addition, the wastewater treated water can usually be used to the maximum extent possible, so even if a portion of the water is discarded without being reused, the load for treating the discarded water Can be made relatively small.
　また、上記実施形態では、前記アルカリ性の中和剤として、アルカリ金属を含む中和剤を使用している。かかる構成によれば、アルカリ性の中和剤として、アルカリ金属を含む中和剤を使用するので、洗浄済み水のｐＨを低く抑えることができる。そのため、該洗浄済み水を中和処理する際に必要な薬剤の量も抑えられ、洗浄済み水の中和処理を行い易い。 In the above embodiment, a neutralizing agent containing an alkali metal is used as the alkaline neutralizing agent. According to this configuration, since the neutralizing agent containing an alkali metal is used as the alkaline neutralizing agent, the pH of the washed water can be kept low. Therefore, the amount of chemicals required for neutralizing the washed water can be suppressed, and the washed water can be easily neutralized.
　また、上記実施形態では、前記アルカリ金属を含む中和剤として、ナトリウム系の中和剤を使用し、前記混合工程では、前記混合液中の溶解性蒸発残留物が２０％以上、且つ３５％以下となるように、前記洗浄済み水を、少なくとも前記洗浄水の一部として再利用している。かかる構成によれば、アルカリ金属を含む中和剤のうち、ナトリウム系の中和剤を使用した際に生成される塩類は、カリウム等のその他のアルカリ金属を含む中和剤を使用した際に生成される塩類よりも水に溶けやすい（水への溶解度が高い）。そのため、溶解性蒸発残留物が３５％以下であると、溶存物質がほとんど析出することなく洗浄済み水で飛灰を洗浄することができる。そのため、かかる構成によれば、混合液Ｗ中の溶解性蒸発残留物を高くしつつも、溶存物質がほとんど析出しない状態で飛灰を洗浄することができ、洗浄済み水を十分に再利用することができる。 In the above embodiment, a sodium-based neutralizing agent is used as the neutralizing agent containing the alkali metal. In the mixing step, the soluble evaporation residue in the mixed solution is 20% or more and 35%. The washed water is reused as at least a part of the washing water so as to become the following. According to this configuration, among the neutralizing agents containing alkali metals, the salts produced when using sodium-based neutralizing agents are used when using neutralizing agents containing other alkali metals such as potassium. It is more soluble in water than the salts produced (highly soluble in water). Therefore, if the soluble evaporation residue is 35% or less, the fly ash can be washed with washed water with almost no dissolved substance being deposited. Therefore, according to such a configuration, fly ash can be washed in a state where almost no dissolved substances are deposited while increasing the soluble evaporation residue in the mixed solution W, and the washed water is sufficiently reused. be able to.
　また、上記実施形態では、飛灰の洗浄方法は、前記脱水ケーキをすすぐすすぎ工程を備えている。かかる構成によれば、脱水ケーキをすすぐすすぎ工程を備えているので、脱水ケーキをセメント原料にするなど、再利用に適した性状にすることができる。 In the above embodiment, the fly ash cleaning method includes a rinsing step of rinsing the dehydrated cake. According to such a configuration, since the dewatering cake is provided with a rinsing step, the dewatering cake can be made into a property suitable for reuse, for example, as a cement raw material.
　また、上記実施形態では、前記混合工程では、前記すすぎ工程で前記脱水ケーキをすすいだすすぎ済み水を、少なくとも前記洗浄水の一部として再利用している。かかる構成によれば、すすぎ工程で使用されたすすぎ済み水を飛灰の洗浄に使用することができるので、すすぎ済み水を有効利用することができる。 In the embodiment, in the mixing step, the rinsed water that rinses the dehydrated cake in the rinsing step is reused as at least a part of the washing water. According to such a configuration, the rinsed water used in the rinsing step can be used for washing the fly ash, so that the rinsed water can be effectively used.
　以上より、本実施形態によれば、飛灰を洗浄するための洗浄水の給水量を抑えることができる飛灰の洗浄方法を提供することができる。 As described above, according to the present embodiment, it is possible to provide a fly ash cleaning method capable of suppressing the amount of water supplied for cleaning water for cleaning fly ash.
　上記実施形態において、中和剤としてアルカリ金属を含む中和剤を使用した場合、中和剤としてアルカリ土類金属を含む中和剤を使用する場合と比較して、洗浄済み水のｐＨを低くすることができる。具体的には、図３に示すように、重曹によって中和処理された重曹灰と、消石灰によって中和処理された消石灰灰とを比較すると、撹拌を開始してから終了するまで、重曹灰の洗浄水（若しくは洗浄済み水）のｐＨが、消石灰灰の洗浄水（若しくは洗浄済み水）のｐＨよりも低いことが分かる。図３からも明らかなように、アルカリ金属を含む中和剤を使用することによって、洗浄済み水のｐＨを低く抑えることができるので、洗浄済み水の中和処理に要する薬剤量も抑えることができ、中和処理に係る負担が軽減される。尚、図３では、液固比は７．５（洗浄水５倍、リンス水２．５倍）としている。 In the above embodiment, when a neutralizing agent containing an alkali metal is used as the neutralizing agent, the pH of the washed water is lowered as compared with the case of using a neutralizing agent containing an alkaline earth metal as the neutralizing agent. can do. Specifically, as shown in FIG. 3, when comparing sodium bicarbonate ash neutralized with baking soda and slaked lime ash neutralized with slaked lime, from the start to the end of stirring, It can be seen that the pH of the wash water (or washed water) is lower than the pH of the slaked lime ash wash water (or washed water). As apparent from FIG. 3, the pH of the washed water can be kept low by using a neutralizing agent containing an alkali metal, so that the amount of chemicals required for neutralizing the washed water can also be reduced. And the burden on the neutralization process is reduced. In FIG. 3, the liquid-solid ratio is 7.5 (washing water 5 times, rinsing water 2.5 times).
　また、図４に示すように、上記実施形態において、中和剤としてアルカリ金属を含む中和剤を使用した場合、中和剤としてアルカリ土類金属から成る中和剤を使用する場合と比較して、塩類の洗浄水への溶解速度が速い。そのため、中和剤としてアルカリ金属を含む中和剤を使用することで、混合工程を短くすることができ、飛灰の洗浄処理能力を上げることができる。具体的には、重曹灰の洗浄水（若しくは洗浄済み水）の電気伝導度は、攪拌を開始すると略同時に９Ｓ／ｍを超え、その後、わずかに上昇する。このことから、重曹灰を洗浄する場合には、攪拌と略同時にほとんどの塩類が溶出することがわかる。これに対して、消石灰灰の洗浄水（若しくは洗浄済み水）の電気伝導度は、攪拌後２０分間で徐々に上昇している。このことから、消石灰灰を洗浄する場合には、塩類の溶出に時間がかかることがわかる。このように、アルカリ金属系の塩類は、アルカリ土類金属系の塩類よりも水に対して早く溶解するため、中和剤としてアルカリ金属を含む中和剤を使用した場合、混合工程を短くすることができる。 In addition, as shown in FIG. 4, in the above embodiment, when a neutralizing agent containing an alkali metal is used as a neutralizing agent, a neutralizing agent made of an alkaline earth metal is used as a neutralizing agent. In addition, the dissolution rate of salts in the wash water is fast. Therefore, by using a neutralizing agent containing an alkali metal as a neutralizing agent, the mixing step can be shortened, and the fly ash washing treatment capability can be increased. Specifically, the electric conductivity of washing water (or washed water) of sodium bicarbonate ash exceeds 9 S / m at the same time when stirring is started, and then slightly increases. This shows that when sodium bicarbonate ash is washed, most of the salts are eluted almost simultaneously with stirring. On the other hand, the electrical conductivity of the slaked lime ash washing water (or washed water) gradually increases in 20 minutes after stirring. From this, it can be seen that when slaked lime ash is washed, it takes time to elute the salts. In this way, alkali metal salts dissolve faster in water than alkaline earth metal salts, so when a neutralizer containing an alkali metal is used as a neutralizer, the mixing step is shortened. be able to.
　更に、上記実施形態において、中和剤としてアルカリ金属を含む中和剤を使用することによって、中和剤としてアルカリ土類金属を含む中和剤を使用する場合と比較して、脱塩率を高くすることができる。具体的には、図５に示すように、重曹灰と消石灰灰とを同じ液固比で洗浄すると共に、該液固比を７．５倍（洗浄水５倍、リンス水２．５倍）、１０倍（洗浄水５倍、リンス水５倍）、１２．５倍（洗浄水１０倍、リンス水２．５倍）、及び１５倍（洗浄水１０倍、リンス水５倍）と上昇させた結果、全ての液固比において、重曹灰の脱塩率が消石灰灰の脱塩率よりも高く、且つ重曹灰は液固比が低くとも脱塩率が高いことが分かった。図５からも明らかなように、重曹灰を使用した場合、液固比が小さくても高い脱塩率を得られるので、混合槽６１１のサイズを小さくすることができる。本実施形態では、脱塩率Ｚ％は、洗浄前の飛灰の塩素濃度をＢ％、洗浄後の飛灰の塩素濃度をＣ％として、以下の式で算出される。
　Ｚ　＝　（（Ｂ－Ｃ）／Ｂ）・１００ Furthermore, in the said embodiment, compared with the case where the neutralizing agent containing an alkaline-earth metal is used as a neutralizing agent by using the neutralizing agent containing an alkali metal as a neutralizing agent, a desalination rate is improved. Can be high. Specifically, as shown in FIG. 5, sodium bicarbonate ash and slaked lime ash are washed at the same liquid-solid ratio, and the liquid-solid ratio is 7.5 times (washing water 5 times, rinsing water 2.5 times). Increase 10 times (5 times washing water, 5 times rinse water), 12.5 times (10 times washing water, 2.5 times rinse water), and 15 times (10 times washing water, 5 times rinse water). As a result, it was found that the desalting rate of baking soda ash was higher than the desalting rate of slaked lime ash, and the baking salt ash had a high desalting rate even when the liquid-solid ratio was low. As apparent from FIG. 5, when sodium bicarbonate ash is used, a high desalting rate can be obtained even if the liquid-solid ratio is small, so that the size of the mixing tank 611 can be reduced. In the present embodiment, the desalination rate Z% is calculated by the following equation, where B is the chlorine concentration of the fly ash before cleaning, and C% is the chlorine concentration of the fly ash after cleaning.
Z = ((BC) / B) .100
　尚、本発明の飛灰の洗浄方法は、上記実施形態に限定されるものではない。また、本発明に係る飛灰の洗浄方法による作用効果は、上記したものに限定されるものでもない。更に、本発明に係る飛灰の洗浄方法に、本発明の要旨を逸脱しない範囲内において種々変更を加え得ることは勿論である。 Note that the fly ash cleaning method of the present invention is not limited to the above embodiment. Further, the operational effects of the fly ash cleaning method according to the present invention are not limited to those described above. Furthermore, it goes without saying that various modifications can be made to the fly ash cleaning method according to the present invention without departing from the gist of the present invention.
　上記実施形態では、飛灰の洗浄方法が、廃棄物焼却施設１００で発生した飛灰を洗浄する際に実施される場合について説明したが、これに限定されるものではない。飛灰の洗浄方法は、例えば、石炭火力発電プラント等、焼却プロセスを有する各種の施設で実施することができる。 In the above embodiment, the case where the fly ash cleaning method is performed when cleaning the fly ash generated in the waste incineration facility 100 has been described, but the present invention is not limited to this. The fly ash cleaning method can be implemented in various facilities having an incineration process such as a coal-fired power plant.
　上記実施形態では特に言及するものではないが、すすぎ済み水をリンス水として再利用することも可能である。 Although not specifically mentioned in the above embodiment, the rinsed water can be reused as rinse water.
　上記実施形態では、洗浄済み水及びすすぎ済み水を混合部６１に給水することによって再利用する場合について説明したが、これに限定されるものではない。洗浄済み水及びすすぎ済み水は、他の飛灰洗浄装置の混合部に給水されることで再利用されたり、他の廃棄物焼却施設で再利用されたりしてもよい。 In the above embodiment, the case where the washed water and the rinsed water are reused by supplying water to the mixing unit 61 has been described. However, the present invention is not limited to this. The washed water and the rinsed water may be reused by being supplied to the mixing unit of another fly ash washing apparatus, or may be reused in another waste incineration facility.
　上記実施形態では特に言及するものではないが、混合部６１は、混合液Ｗ中の溶解性蒸発残留物を測定する手段を備えていてもよく、混合液Ｗ中の溶解性蒸発残留物が所定の値に到達した時点で作業者等に通知するようにしてもよい。 Although not particularly mentioned in the above embodiment, the mixing unit 61 may include means for measuring the soluble evaporation residue in the mixed solution W, and the soluble evaporation residue in the mixed solution W is predetermined. An operator or the like may be notified when this value is reached.
　１００…廃棄物焼却施設、１…焼却炉、２…ボイラ、３…エコノマイザ、４…減温塔、５…除塵装置、６…飛灰洗浄装置、７…中和剤投入部、６１…混合部、６１１…混合槽、６１２…撹拌部、６２…固液分離部、６２１…濃縮部、６２２…液回収部、６３…脱水ケーキ排出経路、６４…排水経路、６５…再利用経路、６６…ポンプ、６７…移送配管、６７１…上流配管、６７２…下流配管、６８…リンス水供給経路、Ａ…排ガス、Ｂ…脱水ケーキ、Ｃ…洗浄済み水又はすすぎ済み水、Ｄ…洗浄用原水、Ｅ…リンス水、Ｐ…飛灰集積部 DESCRIPTION OF SYMBOLS 100 ... Waste incineration facility, 1 ... Incinerator, 2 ... Boiler, 3 ... Economizer, 4 ... Temperature-reduction tower, 5 ... Dust removal apparatus, 6 ... Fly ash washing apparatus, 7 ... Neutralizer input part, 61 ... Mixing part 611 ... Mixing tank, 612 ... Agitation unit, 62 ... Solid-liquid separation unit, 621 ... Concentration unit, 622 ... Liquid recovery unit, 63 ... Dehydrated cake discharge path, 64 ... Drainage path, 65 ... Reuse path, 66 ... Pump , 67 ... Transfer piping, 671 ... Upstream piping, 672 ... Downstream piping, 68 ... Rinsing water supply path, A ... Exhaust gas, B ... Dehydrated cake, C ... Washed water or rinsed water, D ... Raw water for washing, E ... Rinse water, P ... Fly ash accumulation part

Claims (7)

  1. 　アルカリ性の中和剤で中和処理済みの排ガスから捕集された飛灰と洗浄水とを混合する混合工程と、前記混合工程で得られた前記飛灰と前記洗浄水との混合液を固液分離して、脱水ケーキと洗浄済み水とを得る固液分離工程と、を備え、前記混合工程では、前記混合液中の溶解性蒸発残留物が少なくとも２０％となるように、前記洗浄済み水を、少なくとも前記洗浄水の一部として再利用する飛灰の洗浄方法。 A mixing step of mixing the fly ash collected from the exhaust gas neutralized with an alkaline neutralizer and the washing water, and a mixture of the fly ash obtained in the mixing step and the washing water are solidified. A solid-liquid separation step for liquid separation to obtain a dehydrated cake and washed water, wherein the washing step is performed so that the soluble evaporation residue in the mixed solution is at least 20%. A method for cleaning fly ash, wherein water is reused at least as part of the cleaning water.
  2. 　前記混合工程で得られた前記飛灰と前記洗浄水との混合液中の溶解性蒸発残留物濃度を入手する工程を備える、
    　請求項１に記載の飛灰の洗浄方法。     Obtaining a soluble evaporation residue concentration in a mixed liquid of the fly ash obtained in the mixing step and the washing water,
    The method for cleaning fly ash according to claim 1.
  3. 　前記混合工程で使用される飛灰は、前記排ガスから捕集された飛灰であって、未水洗の飛灰である、
    　請求項１または２に記載の飛灰の洗浄方法。     Fly ash used in the mixing step is fly ash collected from the exhaust gas, and is unwashed fly ash.
    The method for cleaning fly ash according to claim 1 or 2.
  4. 　前記アルカリ性の中和剤として、アルカリ金属を含む中和剤を使用する、請求項１～３の何れか１項に記載の飛灰の洗浄方法。 The fly ash washing method according to any one of claims 1 to 3, wherein a neutralizing agent containing an alkali metal is used as the alkaline neutralizing agent.
  5. 　前記アルカリ金属を含む中和剤として、ナトリウム系の中和剤を使用し、前記混合工程では、前記混合液中の溶解性蒸発残留物が２０％以上、且つ３５％以下となるように、前記洗浄済み水を、少なくとも前記洗浄水の一部として再利用する、請求項４に記載の飛灰の洗浄方法。 As the neutralizing agent containing the alkali metal, a sodium-based neutralizing agent is used, and in the mixing step, the soluble evaporation residue in the mixed solution is 20% or more and 35% or less. The method for washing fly ash according to claim 4, wherein the washed water is reused as at least a part of the washing water.
  6. 　前記脱水ケーキをすすぐすすぎ工程を備える、請求項１～５の何れか１項に記載の飛灰の洗浄方法。 The method for cleaning fly ash according to any one of claims 1 to 5, further comprising a rinsing step of the dehydrated cake.
  7. 　前記混合工程では、前記すすぎ工程で前記脱水ケーキをすすいだすすぎ済み水を、少なくとも前記洗浄水の一部として再利用する、請求項６に記載の飛灰の洗浄方法。 The method for washing fly ash according to claim 6, wherein in the mixing step, the rinsed water rinsed from the dehydrated cake in the rinsing step is reused as at least a part of the washing water.
PCT/JP2017/041531 2016-11-18 2017-11-17 Fly ash cleaning method WO2018092894A1 (en)

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