CN110723858A - Desulfurization wastewater zero-discharge treatment system and treatment process - Google Patents
Desulfurization wastewater zero-discharge treatment system and treatment process Download PDFInfo
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- CN110723858A CN110723858A CN201911153084.1A CN201911153084A CN110723858A CN 110723858 A CN110723858 A CN 110723858A CN 201911153084 A CN201911153084 A CN 201911153084A CN 110723858 A CN110723858 A CN 110723858A
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- 239000002351 wastewater Substances 0.000 title claims abstract description 113
- 238000006477 desulfuration reaction Methods 0.000 title claims abstract description 108
- 230000023556 desulfurization Effects 0.000 title claims abstract description 108
- 208000028659 discharge Diseases 0.000 title claims abstract description 34
- 238000011282 treatment Methods 0.000 title claims abstract description 29
- 238000000034 method Methods 0.000 title claims abstract description 25
- 238000001694 spray drying Methods 0.000 claims abstract description 56
- 239000010440 gypsum Substances 0.000 claims abstract description 52
- 229910052602 gypsum Inorganic materials 0.000 claims abstract description 52
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 40
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 31
- 239000003546 flue gas Substances 0.000 claims abstract description 31
- 239000012716 precipitator Substances 0.000 claims abstract description 29
- 239000000428 dust Substances 0.000 claims abstract description 28
- 230000003009 desulfurizing effect Effects 0.000 claims abstract description 26
- 239000002002 slurry Substances 0.000 claims abstract description 26
- 238000003860 storage Methods 0.000 claims abstract description 20
- 239000007788 liquid Substances 0.000 claims abstract description 6
- 238000001914 filtration Methods 0.000 claims abstract description 4
- 239000002956 ash Substances 0.000 claims description 18
- 239000010881 fly ash Substances 0.000 claims description 12
- 239000002245 particle Substances 0.000 claims description 12
- 150000003839 salts Chemical class 0.000 claims description 11
- 230000005484 gravity Effects 0.000 claims description 10
- 238000009826 distribution Methods 0.000 claims description 6
- 238000010531 catalytic reduction reaction Methods 0.000 abstract 1
- 239000003814 drug Substances 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 239000000779 smoke Substances 0.000 description 5
- 208000005156 Dehydration Diseases 0.000 description 4
- 235000019738 Limestone Nutrition 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 230000018044 dehydration Effects 0.000 description 4
- 238000006297 dehydration reaction Methods 0.000 description 4
- 239000006028 limestone Substances 0.000 description 4
- 239000010802 sludge Substances 0.000 description 4
- 239000007921 spray Substances 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- 238000005299 abrasion Methods 0.000 description 3
- 239000013043 chemical agent Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
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- 238000011328 necessary treatment Methods 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000002910 solid waste Substances 0.000 description 2
- 239000011398 Portland cement Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
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- 239000003500 flue dust Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- 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
- B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
-
- 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
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/75—Multi-step processes
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- 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
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
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- 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
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
- C02F1/004—Processes for the treatment of water whereby the filtration technique is of importance using large scale industrial sized filters
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/10—Treatment of water, waste water, or sewage by heating by distillation or evaporation by direct contact with a particulate solid or with a fluid, as a heat transfer medium
- C02F1/12—Spray evaporation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/16—Treatment of water, waste water, or sewage by heating by distillation or evaporation using waste heat from other processes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/18—Nature of the water, waste water, sewage or sludge to be treated from the purification of gaseous effluents
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Abstract
The invention discloses a desulfurization wastewater zero-discharge treatment system and a treatment process, wherein the system comprises a boiler, an SCR (selective catalytic reduction) denitration device, an air preheater, a dust remover and a desulfurization tower which are sequentially connected, and further comprises a gypsum cyclone, a vacuum belt dehydrator, a desulfurization wastewater precipitator, a filtering water pit, a desulfurization wastewater buffer storage tank and a spray drying tower; the overflow port of the gypsum cyclone is respectively connected with a slurry pool of the desulfurizing tower and a desulfurizing waste water precipitator; the outlet of the vacuum belt dehydrator and the outlet at the bottom of the desulfurization wastewater precipitator are both connected with a filtered water pit, and liquid in the filtered water pit flows back to the desulfurization tower through a filtered water pit pump; the overflow port of the desulfurization waste water precipitator is connected with a desulfurization waste water buffer storage pool. The spray drying tower is connected with the air preheater in parallel, the flue gas of the spray drying tower is led from the rear flue of the denitration device and returns to the front flue of the dust remover, and the treated desulfurization wastewater is led from the desulfurization wastewater buffer storage pool by the feed pump.
Description
Technical Field
The invention relates to the field of comprehensive treatment of wastewater, in particular to a zero-discharge treatment system and method for flue gas desulfurization wastewater by a limestone/lime-gypsum method.
Background
The slurry of the limestone/lime-gypsum method desulfurization process is enriched with chloride ions, heavy metals and the like in the continuous circulation process, and in order to maintain the stable operation of a system, certain desulfurization wastewater needs to be discharged periodically, the water quantity is not large, but the property is complex, and the slurry is treated by adopting a materialization method 'triple box' process for a long time and then is discharged according to the standard of 'limestone-gypsum wet method desulfurization wastewater quality control index of thermal power plants' (DL/T997-. However, the triple box process does not remove salt, and the effluent still contains salt with high concentration, especially Cl-The concentration is generally 6000-20000 mg/l, and the direct discharge has harm to water, soil and ecology. With the enhancement of environmental awareness and the gradual promotion of ten national water, the discharge of high-salinity wastewater is gradually concerned and limited, for example, zero discharge of wastewater is required in the project environmental assessment and the national wastewater comprehensive discharge standard of Liaoning, Shanghai and the like has the limit on the concentration of chloride ions. It can be seen that the zero emission of high-salinity wastewater represented by desulfurization wastewater in coal-fired power plants becomes a necessary trend for power plant water development in the future.
In recent years, two end treatment process routes have been developed around "zero emission" of desulfurized waste water: evaporative crystallization and spray evaporative drying, which are seen in national policies and regulations such as the technical policy for pollution control of thermal power plants, the feasible technical guideline for pollution control of thermal power plants (HJ 2301 and 2017), and the design specification for wastewater treatment of power plants (DL/T5046 and 2018). Because evaporative crystallization (salt production) processes usually need complex deep pretreatment and concentration units, and have the problems of long process flow, large maintenance workload, high operation cost of adding medicaments, difficult sludge treatment, difficult crystalline salt absorption and the like, the current spray evaporative drying processes, in particular to the route for treating desulfurization wastewater by utilizing an air preheater bypass high-temperature flue gas spray drying tower, are increasingly popular in the market, however, in order to avoid the problems of blockage, abrasion and the like of an atomizer (an atomizing nozzle of a double-fluid spray gun or an atomizing disc of a centrifugal atomizer), the conventional ' neutralization-sedimentation-flocculation-clarification ' triple box ' or ' integrated ' treatment of desulfurization wastewater is still needed, a certain medicament still needs to be added, and a certain amount of sludge waste needs to be treated.
Disclosure of Invention
The invention aims to provide a desulfurization wastewater zero-discharge treatment system and a treatment process. The system abandons a triple box or an integrated pretreatment system, only carries out simple physical precipitation on the desulfurization wastewater without adding any medicament, and carries out spray drying treatment on the precipitated desulfurization wastewater by utilizing the high-temperature flue gas of the bypass of the air preheater, so that the process is simple, economic and simple, no new solid waste needing to be treated independently is generated, and zero emission is really realized.
In the wet flue gas desulfurization system of the coal-fired power plant in the prior art, a slurry tank of a desulfurization tower periodically discharges a part of slurry to a gypsum cyclone through a gypsum slurry pump, the underflow of the gypsum cyclone is sent to a vacuum belt conveyor for dehydration to produce gypsum, and the overflow of the gypsum cyclone is partially returned to an absorption tower slurry tank through gravity, and certain desulfurization wastewater needs to be periodically discharged.
In order to realize the purpose of zero emission, the technical scheme adopted by the invention is as follows:
a desulfurization wastewater zero-emission treatment system comprises a boiler, an SCR denitration device, an air preheater, a dust remover and a desulfurization tower which are sequentially connected, and further comprises a gypsum cyclone, a vacuum belt dehydrator, a desulfurization wastewater precipitator, a filtered water pit, a desulfurization wastewater buffer storage tank and a spray drying tower;
the inlet of the gypsum cyclone is connected with the slurry pool of the desulfurizing tower through a gypsum discharge pump, the outlet at the bottom of the gypsum cyclone is connected with the vacuum belt dehydrator, and the overflow port of the gypsum cyclone is respectively connected with the slurry pool of the desulfurizing tower and the desulfurizing wastewater precipitator;
the outlet of the vacuum belt dehydrator and the outlet at the bottom of the desulfurization wastewater precipitator are both connected with a filtered water pit, and liquid in the filtered water pit flows back to the desulfurization tower through a filtered water pit pump;
the overflow port of the desulfurization wastewater precipitator is connected with a desulfurization wastewater buffer storage pool;
an opening is arranged on a flue connected between the SCR denitration device and the air preheater and is connected with a spray drying tower; the bottom outlet of the spray drying tower is connected with the inlet of the dust remover;
and the desulfurization wastewater buffer storage pool is connected with an inlet of an upper atomizer of the spray drying tower through a spray drying conveying feed pump.
Wherein, the spray drying tower contains an atomizer and an auxiliary system thereof.
Wherein, the upper part in the spray drying tower is provided with an air distribution system.
Wherein, a stirrer is arranged in the filtering water pit and the desulfurization wastewater buffer storage tank.
And an induced draft fan is arranged between the dust remover and the desulfurizing tower.
Wherein, the top outlet of the desulfurizing tower is finally connected with a chimney.
The treatment process of the desulfurization wastewater zero-discharge treatment system specifically comprises the following steps:
a slurry tank of the desulfurizing tower periodically discharges a part of slurry to a gypsum cyclone through a gypsum discharge pump, the underflow of the gypsum cyclone is sent to a vacuum belt dehydrator for dehydration to produce gypsum, one part of the overflow of the gypsum cyclone returns to the slurry tank of the desulfurizing tower through gravity, and the other part of the overflow becomes desulfurization wastewater which is periodically discharged;
the desulfurization wastewater automatically flows to a desulfurization wastewater precipitator for gravity settling; through simple gravity sedimentation without adding any chemical agent, the retention time is about 2-5 hours, and the precipitation separation of larger particles in the wastewater is realized.
The underflow containing larger particles in the desulfurization wastewater precipitator is discharged to a filtered water pit (which is used for collecting the drained water of a vacuum belt conveyor and the like), and the filtered water pit is pumped back to the desulfurization tower by a filtered water pit pump and participates in the circulation of the desulfurization system again, including the further growth of the granular gypsum crystals, so that the granular gypsum crystals can enter the bottom of the gypsum cyclone and flow through the vacuum belt conveyor for dehydration to form gypsum. Since no chemical agent is added in the pretreatment, the bottom flow of the precipitator is returned to the slurry tank of the desulfurization tower without any adverse side effect on the desulfurization system, and instead, the calcium carbonate which may be contained therein and not fully reacted before is recycled.
Meanwhile, the residual fine particles contained in the desulfurization wastewater automatically flow into the desulfurization wastewater buffer storage tank along with the overflow of the desulfurization wastewater precipitator, and the tank is provided with a stirrer to prevent precipitation.
A part of hot flue gas (320-400 ℃) is led to a spray drying tower by a flue connected between the SCR denitration device and the air preheater, and meanwhile, the desulfurization wastewater is sent to an atomizer of the spray drying tower through a spray drying conveying feed pump; the hot flue gas is uniformly distributed into a spray drying tower through a certain air distribution system, the wastewater is fully atomized (the particle size of fog drops is generally 30-60 mu m) through an atomizer and is uniformly sprayed in the spray drying tower, the wastewater and the fog drops are fully contacted in the spray drying tower and rapidly generate heat exchange, and the moisture in the wastewater is evaporated to dryness to form water vapor which enters the flue gas. Because the residual particles of the desulfurization wastewater after gravity settling are finer and the amount of the desulfurization wastewater is also obviously reduced, the problems of blockage, abrasion and the like of an atomizer (a nozzle of a two-fluid spray gun or an atomizing disc of a centrifugal atomizer) are greatly improved, and the system can realize long-term stable and reliable operation.
Dissolved salts or suspended matters in the wastewater are actually mixed with fly ash in the flue gas into a whole after being dried by the hot flue gas, and the collection mode can be designed into one of the following two types according to requirements:
(1) the flue gas outlet of the spray drying tower is arranged at the bottom of the lower cone part of the tower, so that all the ash returns to the main flue behind the air preheater and in front of the dust remover along with the flue gas, and is finally collected uniformly by the dust remover. The mass ratio of the waste water evaporation product to the original fly ash in the flue gas is very small (< 1%), the influence on each component of the fly ash is very small, the fly ash is not influenced to be used as an additive of common concrete, and the fly ash can also be used as a blending material of common Portland cement under the condition of controlling the blending proportion.
(2) The flue gas outlet of the spray drying tower is arranged on the side surface of the lower conical part of the tower, the conical bottom is provided with an independent ash outlet, a part of ash is uniformly collected by the dust remover along with the flue gas in the main flue before returning to the dust remover, most of the ash is settled and collected at the conical bottom of the spray drying tower, and the ash can be pumped to an ash warehouse through an ash conveying bin after passing through the independent ash outlet, and can also be independently collected for necessary treatment.
Compared with the prior art, the invention has the outstanding effects that:
(1) no medicament is added: the wastewater pretreatment only separates larger suspended matters in the wastewater through simple gravity sedimentation; the bottom flow of the precipitator without the addition of the medicament is returned to the slurry tank of the desulfurizing tower, so that the safety is higher, and the worry about any adverse effect on a desulfurizing system is avoided.
(2) The problems of sludge discharge, disposal and the like are solved: the bottom flow of the desulfurization waste water precipitator returns to the slurry tank of the absorption tower by means of the existing filtered water pit, pump and pipeline system of the original desulfurization system, and is added into the circulation of the desulfurization system again (including the growth of gypsum crystals and the final discharge of gypsum); the overflow of the desulfurization waste water precipitator is treated by spray drying, and the contained salts and fine particles are dried and then collected as fly ash by the existing dust remover of the power plant along with the flue gas and dust, so that no additional solid wastes such as sludge and the like are added, and the comprehensive utilization of the fly ash is not influenced.
(3) The process is simple, the system is reliable, the operation and maintenance are economical and simple, and the method is suitable for popularization and application.
The desulfurization wastewater zero-discharge treatment system and the treatment process of the invention are further described with reference to the accompanying drawings and specific examples.
Drawings
FIG. 1 is a schematic flow diagram of a desulfurization wastewater zero-discharge treatment system.
The system comprises a desulfurization tower 1, a gypsum discharge pump 2, a gypsum cyclone 3, a vacuum belt dehydrator 4, a desulfurization wastewater precipitator 5, a filtered water pit 6, a filtered water pit pump 7, a desulfurized wastewater buffer storage pool 8, a spray drying conveying and feeding pump 9, a spray drying tower 10, a boiler 11, an SCR denitration device 12, an air preheater 13, a dust remover 14, an induced draft fan 15 and a chimney 16.
Detailed Description
As shown in fig. 1, a desulfurization wastewater zero-discharge treatment system comprises a boiler 11, an SCR denitration device 12, an air preheater 13, a dust remover 14 and a desulfurization tower 1 which are connected in sequence, and further comprises a gypsum cyclone 3, a vacuum belt dehydrator 4, a desulfurization wastewater precipitator 5, a filtered water pit 6, a desulfurization wastewater buffer storage tank 8 (or a desulfurization wastewater buffer storage tank) and a spray drying tower 10;
an inlet of the gypsum cyclone 3 is connected with a slurry pool of the desulfurizing tower 1 through a gypsum discharge pump 2, a bottom outlet of the gypsum cyclone 3 is connected with a vacuum belt dehydrator 4, and an overflow port of the gypsum cyclone 3 is respectively connected with the slurry pool of the desulfurizing tower 1 and a desulfurizing waste water precipitator 5;
the outlet of the vacuum belt dehydrator 4 and the outlet at the bottom of the desulfurization wastewater precipitator 5 are both connected with a filtered water pit 6, and liquid in the filtered water pit 6 flows back to the desulfurization tower 1 through a filtered water pit pump 7; an overflow port of the desulfurization waste water precipitator 5 is connected with a desulfurization waste water buffer storage pool 8; an opening is arranged on a flue connected between the SCR denitration device 12 and the air preheater 13 and is connected with the spray drying tower 10; the bottom outlet of the spray drying tower 10 is connected with the inlet of a dust remover 14; the desulfurization waste water buffer storage tank 8 is connected with the upper inlet of a spray drying tower 10 through a spray drying conveying feed pump 9.
The spray drying tower 10 contains an atomizer and its auxiliary systems. An air distribution system is arranged at the upper part in the spray drying tower 10.
An induced draft fan 15 is arranged between the dust remover 14 and the desulfurizing tower 1. The top outlet of the desulfurization tower 1 is finally connected to a stack 16. Stirrers are arranged in the filtering water pit 6 and the desulfurization wastewater buffer storage tank 8.
The flue gas of the boiler 11 is discharged after passing through the SCR denitration device 12, the air preheater 13 for recovering waste heat and reducing the temperature, the dust remover 14, the draught fan 15 and the desulfurizing tower 1. A desulfurization system adopting a limestone/lime-gypsum method periodically discharges certain limestone slurry through a gypsum discharge pump 2, larger-particle gypsum in the slurry is primarily separated through a gypsum cyclone 3, and a concentrated solid-liquid mixture discharged from the bottom is sent to a vacuum belt conveyor 4 for secondary dehydration to produce gypsum; except for one part of the overflow of the gypsum cyclone 3 which automatically flows back to the slurry tank of the absorption tower through gravity, a certain amount of waste water needs to be discharged outside the desulfurization system at regular intervals, namely the desulfurization waste water.
The specific discharge amount of the desulfurization waste water can be adjusted by an adjusting valve according to the chloride ion concentration control index in the desulfurization tower slurry pool.
The desulfurization wastewater zero discharge treatment system is realized by the following steps:
(1) the desulfurization wastewater automatically flows into a desulfurization wastewater precipitator 5, the hydraulic retention time is about 2-5 hours, precipitation separation of larger particles in the desulfurization wastewater is realized through simple gravity settling without adding any chemical agent, the underflow containing the larger particles is discharged to a filtered water pit 6, the filtered water pit pump 7 sends the filtered water pit and the collected drainage of a vacuum belt dehydrator 4 back to the desulfurization tower 1 to participate in the circulation of the desulfurization system again, including further growth of the granular gypsum crystals, so that the underflow can enter a gypsum cyclone 3 to be dehydrated by a vacuum belt dehydrator 4 to form gypsum.
(2) The fine particles contained in the desulfurization waste water automatically flow into the desulfurization waste water buffer storage tank 8 along with the overflow of the precipitator 5, and the tank is provided with a stirrer to prevent the precipitation of suspended particles.
(3) A part of hot flue gas (320-; the hot flue gas is uniformly distributed by an air distribution system at the upper part of the spray drying tower 10 and enters the spray drying tower 10 from top to bottom.
(4) Meanwhile, the desulfurization wastewater is delivered to an atomizer of a spray drying tower 10 through a spray drying delivery feeding pump 9, and is fully atomized by the atomizer (the particle size of fog drops is generally 30-60 mu m) and is uniformly sprayed from top to bottom in the spray drying tower 10.
(5) The two phases of gas and liquid flow downward in the spray drying tower 10, fully contact and rapidly generate heat exchange: the water (fog drop) in the waste water is evaporated to dryness to form water vapor which becomes a part of the smoke, the dissolved salts or suspended matters in the waste water are dried by the hot smoke and then mixed with the fly ash in the original smoke into a whole, the smoke returns to the main flue behind the air preheater 13 and in front of the dust remover 14 along with the smoke, and finally the fly ash mixed with the dried matters is uniformly and uniformly collected by the dust remover 14.
If necessary, a flue gas outlet and an independent ash outlet can be respectively arranged at the bottom of the spray drying tower 10, a part of the ash is uniformly collected by the dust remover along with the flue gas in the main flue before returning to the dust remover, most of the ash is settled and collected at the conical bottom of the spray drying tower 10, and the ash can be pumped to an ash warehouse through an ash conveying bin after passing through the independent ash outlet, and can also be independently collected for necessary treatment.
The resistance of the spray drying tower 10 and the flue system thereof is provided by the pressure difference between the front and the rear of the air preheater 13, and a booster fan is not required to be additionally arranged generally; the design of the spray drying tower 10 combines with the type selection of the atomizer and fully considers the characteristics of desulfurization waste water and dust contained in flue gas, so that the fog drops are fully dried without the problems of wet walls or dust deposition and the like in the tower; the material selection of the atomizer overflowing piece fully considers the corrosion and abrasion characteristics of the desulfurization waste water.
The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention by those skilled in the art should fall within the protection scope defined by the claims of the present invention without departing from the spirit of the present invention.
Claims (9)
1. A desulfurization waste water zero release processing system which characterized in that: the device comprises a boiler (11), an SCR denitration device (12), an air preheater (13), a dust remover (14) and a desulfurizing tower (1) which are connected in sequence, and further comprises a gypsum cyclone (3), a vacuum belt dehydrator (4), a desulfurizing wastewater precipitator (5), a filtered water pit (6), a desulfurizing wastewater buffer storage pool (8) and a spray drying tower (10);
an inlet of the gypsum cyclone (3) is connected with a slurry pool of the desulfurizing tower (1) through a gypsum discharge pump (2), a bottom outlet of the gypsum cyclone (3) is connected with the vacuum belt dehydrator (4), and an overflow port of the gypsum cyclone (3) is respectively connected with the slurry pool of the desulfurizing tower (1) and the desulfurizing wastewater precipitator (5);
the outlet of the vacuum belt dehydrator (4) and the outlet at the bottom of the desulfurization wastewater precipitator (5) are both connected with a filtered water pit (6), and liquid in the filtered water pit (6) flows back to the desulfurization tower (1) through a filtered water pit pump (7);
an overflow port of the desulfurization wastewater precipitator (5) is connected with a desulfurization wastewater buffer storage pool (8);
an opening is arranged on a flue connected between the SCR denitration device (12) and the air preheater (13) and connected with the spray drying tower (10); the bottom outlet of the spray drying tower (10) is connected with the inlet of a dust remover (14);
and the desulfurization wastewater buffer storage pool (8) is connected with an upper inlet of the spray drying tower (10) through a spray drying conveying feeding pump (9).
2. The desulfurization waste water zero-discharge treatment system according to claim 1, characterized in that: the spray drying tower (10) contains an atomizer and its auxiliary systems.
3. The desulfurization waste water zero-discharge treatment system according to claim 2, characterized in that: an air distribution system is arranged at the upper part in the spray drying tower (10).
4. The desulfurization waste water zero-discharge treatment system according to claim 3, characterized in that: stirrers are arranged in the filtering water pit (6) and the desulfurization wastewater buffer storage pool (8).
5. The desulfurization waste water zero-discharge treatment system according to claim 4, characterized in that: and an induced draft fan (15) is arranged between the dust remover (14) and the desulfurizing tower (1).
6. The desulfurization waste water zero-discharge treatment system according to claim 5, characterized in that: and the top outlet of the desulfurizing tower (1) is finally connected with a chimney (16).
7. The treatment process of the desulfurization wastewater zero-discharge treatment system of claims 1 to 6, characterized in that: a slurry pool of the desulfurizing tower (1) periodically discharges a part of slurry to a gypsum cyclone (3) through a gypsum discharge pump (2), the underflow of the gypsum cyclone (3) goes to a vacuum belt dehydrator (4) to be dehydrated to produce gypsum, one part of the overflow of the gypsum cyclone (3) returns to the slurry pool of the desulfurizing tower (1) through gravity, and the other part becomes desulfurization waste water to be periodically discharged;
the desulfurization wastewater automatically flows to a desulfurization wastewater precipitator (5) for gravity settling; the underflow containing larger particles in the desulfurization wastewater precipitator (5) is discharged to a filtered water pit (6), and the filtered water pit is pumped by a filtered water pit pump (7) and sent back to the desulfurization tower (1); the desulfurization wastewater precipitator (5) overflows and automatically flows into a desulfurization wastewater buffer storage pool (8);
a part of hot flue gas is led to a spray drying tower (10) by a flue connected between the SCR denitration device (12) and the air preheater (13), and meanwhile, desulfurization wastewater is sent to an atomizer of the spray drying tower (10) through a spray drying conveying feeding pump (9); the hot flue gas is uniformly distributed into the spray drying tower (10) through a certain air distribution system, the waste water is fully atomized by the atomizer and is uniformly sprayed in the spray drying tower (10), the waste water and the waste water are fully contacted in the spray drying tower (10) and rapidly generate heat exchange, and the moisture in the waste water is evaporated to dryness to form water vapor which enters the flue gas.
8. The process of claim 7, wherein: the flue gas outlet of the spray drying tower (10) is positioned at the bottom of the lower cone part of the tower: dissolved salts or suspended matters in the wastewater are dried by hot flue gas and then returned to a main flue behind the air preheater (13) and in front of the dust remover (14) along with the flue gas, and the dissolved salts and particulate matters in the desulfurization wastewater and fly ash in the flue gas are uniformly collected by the dust remover.
9. The process of claim 7, wherein: the flue gas outlet of the spray drying tower (10) is arranged on the side surface of the lower cone part of the tower: part of the fly ash mixed with the salt dry particles is uniformly collected by the dust remover along with the flue gas in the main flue before returning to the dust remover (14), and most of the fly ash mixed with the salt dry particles is settled and collected at the bottom of the tower, passes through a separate ash outlet at the cone bottom, can be pumped to an ash silo through an ash conveying bin, and can also be separately collected for necessary disposal.
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