CN114604924A - Low-temperature flash evaporation, concentration and crystallization integrated and zero-discharge process for treating desulfurization wastewater by concentrated solution backflow - Google Patents
Low-temperature flash evaporation, concentration and crystallization integrated and zero-discharge process for treating desulfurization wastewater by concentrated solution backflow Download PDFInfo
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- 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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- 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
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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
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C—CHEMISTRY; METALLURGY
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Abstract
The invention discloses a zero-emission process for treating desulfurization wastewater by integrating low-temperature flash evaporation, concentration and crystallization and refluxing concentrated solution, which comprises a flue gas heat exchange system, a low-temperature multi-effect evaporation system, a condensed water system, a solid-liquid separation system, a filtrate refluxing and electric heating system and a PH (potential of hydrogen) regulation system, wherein the flue gas heat exchange system, the low-temperature multi-effect evaporation system, the solid-liquid separation system, the filtrate refluxing and electric heating system are sequentially connected, the flue gas heat exchange system and the condensed water system are connected with the low-temperature multi-effect evaporation system, and the filtrate refluxing and electric heating system is connected with the low-temperature multi-effect evaporation system. The invention adopts low-temperature flash evaporation, concentration and crystallization integration and a concentrated solution reflux process, cancels the traditional high-temperature flue gas drying process, overcomes the defect of insufficient two-effect and three-effect evaporation capacity of a low-temperature multi-effect flash evaporation system, and also solves a series of problems of high equipment investment cost, high operation and maintenance cost, crystalline salt disposal and the like caused by high-temperature flue gas drying of concentrated water.
Description
Technical Field
The invention relates to the technical field of zero-discharge processes, in particular to a zero-discharge process for treating desulfurization wastewater through low-temperature flash evaporation, concentration and crystallization integration and concentrated solution backflow.
Background
With the gradual maturity of the process for treating the wet desulphurization wastewater of the coal-fired power plant by the low-temperature multi-effect flash evaporation and high-temperature drying zero-discharge technology, the problem that the desulphurization wastewater of the coal-fired power plant cannot be directly discharged after being treated by a neutralization method is solved, the desulphurization wastewater is concentrated by the low-temperature multi-effect flash evaporation, the concentrated water amount is only 1/3-1/10 of the wastewater amount, then the concentrated solution is dried by using high-temperature flue gas, and the dried crystal salt is collected independently or is collected together with fly ash for comprehensive utilization by a power plant.
However, the existing low-temperature multi-effect flash evaporation technology also has certain problems, such as: the first effect evaporation system, the second effect evaporation system and the third effect evaporation system all adopt negative pressure evaporation, the temperature difference between the effects is small, the second effect and the third effect often cannot achieve evaporation design output, and particularly when the temperature of first effect heating steam is low and the steam quantity is insufficient, the third effect even has no evaporation phenomenon. The high-temperature flue gas drying mainly adopts an atomizing spray gun or a rotary atomizer, and the two processes also have respective defects, such as: the atomizing spray gun is not wear-resistant and is easy to block and scale, and the spray gun needs to be replaced regularly; the rotary atomizer process occupies a large area, is not suitable for old plant transformation and the like, and chlorine salt generated by drying enters the fly ash, so that the quality of the fly ash is influenced; the separately collected mixture of the crystalline salts has no economic value, and the disposal cost is not small expense; in addition, the high-temperature flue gas drying also has certain influence on the coal consumption of the boiler, and the more the flue gas quantity is needed, the greater the coal consumption is increased, and the higher the running cost is.
Disclosure of Invention
The invention aims to solve the problem of insufficient secondary-effect and triple-effect evaporation output of a low-temperature multi-effect flash evaporation technology in the prior art and also aims to solve the defects of a high-temperature flue gas drying system, and provides a zero-discharge process for treating desulfurization wastewater through low-temperature flash evaporation, concentration and crystallization integration and concentrated solution backflow.
In order to achieve the purpose, the invention adopts the following technical scheme:
the utility model provides a zero release technology of concentrated crystallization integration of low temperature flash distillation and concentrate backward flow processing desulfurization waste water, includes flue gas heat transfer system, low temperature multiple effect evaporation system, condensate water system, solid-liquid separation system, filtrating backward flow and electric heating system and PH governing system, flue gas heat transfer system, low temperature multiple effect evaporation system, solid-liquid separation system, filtrating backward flow and electric heating system are connected in proper order, flue gas heat transfer system, condensate water system are connected with low temperature multiple effect evaporation system, filtrating backward flow and electric heating system are connected with PH governing system.
Preferably, the flue gas heat exchanger is installed on a flue at the tail part of the boiler, steam generated by the flue gas heat exchanger is connected with the low-temperature multi-effect evaporation system, and one-effect condensed water of the condensed water system is connected with the flue gas heat exchanger.
Preferably, a first-effect forced circulation pump is connected between the first-effect evaporator and the first-effect separator, a second-effect forced circulation pump is connected between the second-effect evaporator and the second-effect separator, a triple-effect forced circulation pump is connected between the triple-effect evaporator and the triple-effect separator, a steam inlet of the single-effect evaporator is connected with the flue gas heat exchanger, the water outlet of the first-effect evaporator is connected with the water inlet of the first-effect separator, the secondary steam outlet of the first-effect separator is connected with the steam inlet of the second-effect evaporator, the water outlet of the second-effect evaporator is connected with the water inlet of the second-effect separator, the secondary steam outlet of the second-effect separator is connected with the steam inlet of the third-effect evaporator, condensed water of the first-effect evaporator, the second-effect evaporator and the third-effect evaporator and secondary steam of the third-effect separator are connected with a condensed water system, and a water outlet of the third-effect separator is connected with a solid-liquid separation system.
Preferably, an extraction opening of the first-effect condensate water tank is connected with a first-effect vacuum pump, a water inlet of the first-effect condensate water tank is connected with a first-effect condenser, the first-effect condenser is connected with a first-effect evaporator condensate water port, a first-effect condensate water pump is connected between the first-effect condensate water tank and the flue gas heat exchanger, second-effect evaporator condensate water is connected with a third-effect evaporator, the third-effect evaporator condensate water is connected with a tail gas condensate water tank, a third-effect evaporator condensate water pipeline is connected with a tail gas vacuum pump air exhaust pipeline, the tail gas condensate water tank is connected with a tail gas condenser, the tail gas condenser is connected with a secondary steam port of a third-effect separator, the extraction opening of the tail gas condensate water tank is connected with a tail gas vacuum pump, and a water outlet on the tail gas condensate water tank is connected with the tail gas condensate water pump.
Preferably, the solid-liquid separation system comprises a thickener, a concentrated solution tank and a dehydrator, an air exhaust port of the first-effect condensed water tank is connected with a first-effect vacuum pump, the water inlet of the first-effect condensed water tank is connected with a first-effect condenser, the first-effect condenser is connected with a condensed water port of a first-effect evaporator, a first-effect condensate pump is connected between the first-effect condensate water tank and the flue gas heat exchanger, condensate water of the second-effect evaporator is connected with the third-effect evaporator, the condensate water of the triple-effect evaporator is connected with a tail gas condensate water tank, the condensate water pipeline of the triple-effect evaporator is connected with an exhaust pipeline of a tail gas vacuum pump, the tail gas condensation water tank is connected with a tail gas condenser, the tail gas condenser is connected with a secondary steam port of the three-effect separator, and an air exhaust port of the tail gas condensate water tank is connected with a tail gas vacuum pump, and an upper water outlet of the tail gas condensate water tank is connected with a tail gas condensate water pump. The thickener water inlet is connected with the triple effect separator water outlet, the water outlet of the thickener is connected with the water inlet of the concentrated solution tank, the air suction port of the thickener is connected with the exhaust pipeline of the tail gas vacuum pump, and the water outlet of the concentrated solution tank is connected with the concentrated solution pump with the dehydrator.
Preferably, filtrating backward flow and electric heating system include filtrate case, electric heater unit, electric heat tracing device, filtrate pump etc, the last electric heater unit that is equipped with of filtrate case, filtrate water backflow pipeline installs electric heat tracing device additional, one-effect evaporator entry steam conduit links to each other with three-effect evaporator, the water inlet of filtrate case links to each other with hydroextractor filtrating mouth of a river, be equipped with on the three-effect separator with filtrate water backward flow mouth and reserve steam port, filtrate water backflow mouth links to each other on filtrate case's delivery port and the three-effect separator.
Preferably, the PH governing system includes alkali dosing pump, PH adjusting pump etc. alkali dosing tank goes out the medicine mouth and links to each other with the PH adjusting pump, the export of PH adjusting pump links to each other with the filtrate case, install the PH meter on the filtrate case.
A zero-emission process for treating desulfurization wastewater by integrating low-temperature flash evaporation, concentration and crystallization and refluxing concentrated solution comprises the following steps:
step 1, after desulfurization wastewater is subjected to low-temperature multi-effect flash evaporation concentration by a low-temperature multi-effect evaporation system, enabling dissolved salts in the wastewater of a three-effect separator in the low-temperature multi-effect evaporation system to be saturated, and enabling the salts in the concentrated water to be separated out by naturally cooling or forcibly cooling the discharged concentrated water;
step 2, discharging the concentrated water into a concentrated solution box through a thickener, sending the concentrated water into a dehydrator by a concentrated solution pump for solid-liquid separation, taking gypsum, crystal salt and certain concentrated water away from the dehydrated mud cake, and finally balancing the salt in the original wastewater with the salt in the mud cake;
and 3, pumping the steam and the condensed water in the one-effect evaporator into the one-effect condenser through the one-effect vacuum pump, condensing the steam into condensed water through circulating cooling water, collecting the condensed water in the one-effect condensed water tank, and pumping the condensed water through the one-effect condensed water into the flue gas heat exchanger for recycling.
Step 4, condensed water in the second-effect evaporator automatically flows into the third-effect evaporator, after waste heat is utilized, the condensed water and the condensed water in the third-effect evaporator enter a tail gas condensation water tank together, a negative pressure difference is formed by a first-effect, second-effect and third-effect system and is realized through a tail gas vacuum pump, tail gas generated in the third-effect separator enters a tail gas condenser, the tail gas is condensed into condensed water through circulating cooling water, and the condensed water is collected in the tail gas condensation water tank and is pumped to a power plant through a tail gas condensed water pump for recycling;
step 5, collecting the filtrate after solid-liquid separation in a filtrate tank, adding other alkaline substances such as limestone, sodium hydroxide and the like into the filtrate tank, controlling the dosage of the added medicament through a pH adjusting pump to adjust the pH value of the wastewater, and stirring and fully mixing the filtrate water and the added medicament to maintain the pH value of the filtrate water at about 4.5-6;
and 6, additionally arranging an electric heater on the filtrate tank, or additionally arranging electric tracing on a filtrate water backflow pipeline, or supplementing a small amount of steam at the inlet of the one-effect evaporator to enter the three-effect evaporator to perform heating compensation for losing heat, and pumping the heated filtrate into a three-effect separator in the low-temperature multi-effect evaporation system through a filtrate pump.
Has the advantages that:
1. according to the invention, after desulfurization wastewater is concentrated by low-temperature multi-effect flash evaporation, dissolved salts in wastewater in the three-effect separator are saturated, the problems of scaling, hardening and the like easily caused when crystallized salts are separated out in the three-effect evaporator and the three-effect separator are prevented by increasing the discharge amount of concentrated water and the reflux amount of filtrate, the discharged concentrated water is separated out into crystallized salts in a concentrated liquid tank in a natural cooling or forced cooling mode, and then gypsum and crystallized salts in the concentrated water are pressed into mud cakes to be taken away by using a filter press, a screw stacking machine and the like, so that the salt content in the filtrate water is reduced, and finally the salt content brought into a wastewater system and the salt content brought away from the mud cakes are balanced, so that the normal and stable operation of the system is ensured.
2. The effective temperature difference of the low-temperature multi-effect flash evaporation system is only about 40 ℃, the temperature of the first-effect separator and the third-effect separator is reduced by about 20 ℃, the amount of secondary steam generated by the first-effect separator and the second-effect separator cannot reach the designed amount, the insufficient evaporation capacity of the second effect and the third effect is easily caused, and the concentrated solution after solid-liquid separation can cause certain heat loss when the filtrate returns to the third-effect evaporation system due to natural cooling or forced cooling, and if the evaporation capacity of the third effect is not improved, the unsatisfactory evaporation capacity of the third effect is achieved.
3. After dissolved salts in the three-effect system reach saturation, the pH value is low, the salt content is high, the chloride ion concentration is even higher than 200000ppm, and the corrosion capacity to equipment is enhanced.
4. The invention returns the filtrate water to the triple-effect separator, cancel the traditional high-temperature drying system, and only increase the measures such as electrical heating, electric tracing, or supplement of a small amount of one-effect evaporator inlet steam to the filtrate water, not only reduce the high-temperature drying system equipment investment cost, but also not need high-temperature flue gas and can not influence the increase of the thermal efficiency and coal consumption of the boiler, indirectly reduce the operation and maintenance cost and dispose a series of problems such as crystal salt, etc.
Drawings
FIG. 1 is a schematic flow diagram of a zero-discharge process for integrated low-temperature flash evaporation, concentration and crystallization and concentrated solution reflux treatment of desulfurization wastewater provided by the invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
Referring to fig. 1, the zero-discharge process for treating desulfurization wastewater through low-temperature flash evaporation, concentration and crystallization integration and concentrated solution backflow comprises a flue gas heat exchange system, a low-temperature multi-effect evaporation system, a condensed water system, a solid-liquid separation system, a filtrate backflow and electric heating system and a PH regulation system, wherein the flue gas heat exchange system, the low-temperature multi-effect evaporation system, the solid-liquid separation system and the filtrate backflow and electric heating system are sequentially connected, the flue gas heat exchange system and the condensed water system are connected with the low-temperature multi-effect evaporation system, the filtrate backflow and electric heating system is connected with the PH regulation system, the flue gas heat exchange system comprises a flue gas heat exchanger, the low-temperature multi-effect evaporation system comprises a one-effect evaporator, a one-effect separator, a two-effect evaporator, a two-effect separator, a three-effect evaporator, a three-effect separator and a circulating pump, the condensed water system comprises a one-effect condenser, a three-effect separator and a circulating pump, The system comprises an effective condensate water tank, an effective condensate water pump, an effective vacuum pump, a tail gas condenser, a tail gas condensate water tank, a tail gas condensate water pump, a tail gas vacuum pump and the like, wherein a solid-liquid separation system comprises a thickener (containing a stirrer), a concentrated solution tank (containing a stirrer), a dehydrator and the like, a filtrate backflow and electric heating system comprises a filtrate tank (containing a stirrer), an electric heating device, an electric heat tracing device, a filtrate pump and the like, and a PH adjusting system comprises an alkali dosing tank, a PH adjusting pump and the like.
In the embodiment, the flue gas heat exchanger is arranged on a flue at the tail part of a boiler, and a condensed water inlet and a steam outlet of the flue gas heat exchanger are respectively connected with a condensed water system and a low-temperature multi-effect evaporation system; a first-effect forced circulation pump is connected between the first-effect evaporator and the first-effect separator, a second-effect forced circulation pump is connected between the second-effect evaporator and the second-effect separator, a third-effect forced circulation pump is connected between the third-effect evaporator and the third-effect separator, a steam inlet of the first-effect evaporator is connected with the flue gas heat exchanger, a water outlet of the first-effect evaporator is connected with a water inlet of the first-effect separator, a secondary steam outlet of the first-effect separator is connected with a steam inlet of the second-effect evaporator, a water outlet of the second-effect evaporator is connected with a water inlet of the second-effect separator, a secondary steam outlet of the second-effect separator is connected with a steam inlet of the third-effect evaporator, a water outlet of the third-effect evaporator is connected with a water inlet of the third-effect separator, and a water outlet of the third-effect separator is connected with the solid-liquid separation system; the condensate system comprises an effective condensate system, an exhaust condensate system and a circulating cooling water system, wherein an air suction port of an effective condensate water tank is connected with an effective vacuum pump, a water inlet of the effective condensate water tank is connected with a condensate water port of an effective condenser, an inlet of the effective condenser is connected with a condensate water port of an evaporator, the effective condensate water pump is connected between the effective condensate water tank and the flue gas heat exchanger, a water inlet of the exhaust condensate water tank is connected with a condensate water port of the exhaust condenser, an inlet of the exhaust condenser is connected with a secondary steam outlet of the triple effect separator, an air suction port of the exhaust condensate water tank is connected with an exhaust vacuum pump, the exhaust condensate water tank is connected with an exhaust condensate water pump, and condensate water is pumped to a power plant for recycling through the exhaust condensate water; the solid-liquid separation system comprises a thickener (comprising a stirrer), a concentrated solution tank (comprising the stirrer) and a dehydrator, wherein a water inlet of the thickener is connected with a water outlet of the three-effect separator, an air exhaust port of the thickener is connected with an air exhaust pipeline of a tail gas vacuum pump, a water outlet of the thickener is connected with a water inlet of the concentrated solution tank, a water outlet of the concentrated solution tank is conveyed to the dehydrator through a concentrated solution pump for dehydration, dehydrated mud cakes are treated uniformly by a power plant, and dehydrated filtrate enters a filtrate backflow and electric heating system; the filtrate backflow and electric heating system comprises a filtrate box (comprising a stirrer), electric heating (electric tracing), a filtrate pump and the like, wherein a water outlet of the filtrate box is connected with the three-effect separator, an electric heater and a PH meter are installed on the filtrate box, the electric heater is additionally installed on the filtrate box, or electric tracing is additionally installed on a filtrate water backflow pipeline, or a small amount of steam at the inlet of the one-effect evaporator is led to a standby steam port of the three-effect evaporator; the PH adjusting system comprises an alkali dosing tank, a PH adjusting pump and the like, wherein the inlet of the PH adjusting pump is connected with the medicine outlet of the alkali dosing tank, and the inlet of the PH adjusting pump is connected with the filtrate tank.
In the embodiment, after desulfurization wastewater is concentrated by low-temperature multi-effect flash evaporation, dissolved salts in wastewater in a three-effect separator are saturated, the problems of scaling, hardening and the like easily caused when crystallized salts are separated out in a three-effect evaporator and the three-effect separator are prevented by increasing the discharge amount of concentrated water and the reflux amount of filtrate, the discharged concentrated water is separated out of crystallized salts in a concentrated liquid tank in a natural cooling or forced cooling mode, gypsum and crystallized salts in the concentrated water are pressed into mud cakes by using a filter press, a stacked screw machine and other dewaterers, so that the salt content in the filtrate water is reduced, finally the salt content in the wastewater system is balanced with the salt content in the mud cakes, an electric heater is additionally arranged on the filtrate tank, or electric heat is additionally arranged on a filtrate water return pipeline, or a small amount of steam at an inlet of a one-effect evaporator is introduced to a spare steam port of the three-effect evaporator, and the like, so as to heat and compensate heat loss caused by temperature reduction, and then the heated filtrate is sent to a three-effect separator in a low-temperature multi-effect evaporation system.
In the embodiment, after the dissolved salt in the triple-effect system is saturated due to the backflow of the filtrate, the pH value is reduced, the salt content is increased, the concentration of chloride ions is even higher than 200000ppm, the corrosion capacity of the equipment is enhanced, 2507 alloy or titanium material with better corrosion resistance is selected as the equipment material of the triple-effect system, in addition, alkaline substances such as limestone and sodium hydroxide are added into the filtrate tank, the pH value of the wastewater in the triple-effect system is maintained at 4.5-6, and the corrosion resistance of the equipment is improved.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (8)
1. The utility model provides a zero release technology of integration of low temperature flash distillation concentration crystallization and concentrate backward flow processing desulfurization waste water, includes flue gas heat transfer system, low temperature multiple-effect evaporation system, condensate water system, solid-liquid separation system, filtrating backward flow and electric heating system and PH governing system, its characterized in that: the system comprises a flue gas heat exchange system, a low-temperature multi-effect evaporation system, a solid-liquid separation system, a filtrate reflux and electric heating system and a PH regulation system.
2. The low-temperature flash evaporation, concentration and crystallization integrated and concentrated solution reflux desulfurization wastewater zero-emission process as claimed in claim 1, wherein the flue gas heat exchanger system is characterized in that: the flue gas heat exchanger is arranged on a flue at the tail part of the boiler, steam generated by the flue gas heat exchanger is connected with the low-temperature multi-effect evaporation system, and one-effect condensed water of the condensed water system is connected with the flue gas heat exchanger.
3. The low-temperature flash evaporation, concentration and crystallization integrated and concentrated solution backflow desulfurization wastewater zero-emission process according to claim 1, wherein the low-temperature multi-effect evaporation system is characterized in that: a first-effect forced circulation pump is connected between the first-effect evaporator and the first-effect separator, a second-effect forced circulation pump is connected between the second-effect evaporator and the second-effect separator, a triple-effect forced circulation pump is connected between the triple-effect evaporator and the triple-effect separator, a steam inlet of the single-effect evaporator is connected with the flue gas heat exchanger, the water outlet of the first-effect evaporator is connected with the water inlet of the first-effect separator, the secondary steam outlet of the first-effect separator is connected with the steam inlet of the second-effect evaporator, the water outlet of the second-effect evaporator is connected with the water inlet of the second-effect separator, the secondary steam outlet of the second-effect separator is connected with the steam inlet of the third-effect evaporator, the condensed water of the first-effect evaporator, the second-effect evaporator and the third-effect evaporator and the secondary steam of the third-effect separator are connected with a condensed water system, and a water outlet of the third-effect separator is connected with a solid-liquid separation system.
4. The low-temperature flash evaporation, concentration and crystallization integrated and concentrated solution backflow desulfurization wastewater zero-emission process according to claim 1, wherein the condensed water system is characterized in that: the extraction opening of an effect condensate tank is connected with an effect vacuum pump, the water inlet of an effect condensate tank is connected with an effect condenser, an effect condenser is connected with an effect evaporator condensate outlet, an effect condensate pump is effective between an effect condensate tank and the flue gas heat exchanger, two-effect evaporator condensate water links to each other with three-effect evaporator, three-effect evaporator condensate water links to each other with tail gas condensate tank, three-effect evaporator condensate water pipeline links to each other with tail gas vacuum pump exhaust pipe, tail gas condensate tank links to each other with tail gas condenser, tail gas condenser is connected with the secondary steam mouth of three-effect separator, tail gas condensate tank's extraction opening is connected with the tail gas vacuum pump, the delivery port is connected with tail gas condensate pump on the tail gas condensate tank.
5. The low-temperature flash evaporation, concentration and crystallization integrated and concentrated solution backflow desulfurization wastewater zero-emission process according to claim 1, wherein the solid-liquid separation system is characterized in that: the thickener water inlet is connected with the triple effect separator water outlet, the water outlet of the thickener is connected with the water inlet of the concentrated solution tank, the air suction port of the thickener is connected with the exhaust pipeline of the tail gas vacuum pump, and the water outlet of the concentrated solution tank is connected with the concentrated solution pump with the dehydrator.
6. The low-temperature flash evaporation, concentration and crystallization integrated and concentrated solution backflow desulfurization wastewater zero-emission process according to claim 1, wherein the filtrate backflow and electric heating system is characterized in that: the electric heater device is additionally arranged on the filtrate tank, the electric heat tracing device is additionally arranged on the filtrate water backflow pipeline, the steam pipeline at the inlet of the first-effect evaporator is connected with the third-effect evaporator, the water inlet of the filtrate tank is connected with the filtrate water inlet of the dehydrator, the third-effect separator is provided with a filtrate water backflow port and a standby steam port, and the water outlet of the filtrate tank is connected with the filtrate water backflow port on the third-effect separator.
7. The low-temperature flash evaporation, concentration and crystallization integrated and concentrated solution backflow desulfurization wastewater zero-emission process according to claim 1, wherein the pH adjusting system is characterized in that: the alkali dosing box is characterized in that a medicine outlet is connected with a PH adjusting pump, an outlet of the PH adjusting pump is connected with a filtrate box, and a PH meter is installed on the filtrate box.
8. The low-temperature flash evaporation, concentration and crystallization integrated and concentrated solution backflow process for zero emission of desulfurization wastewater as claimed in claims 1-7, characterized in that: the method comprises the following steps:
step 1, after desulfurization wastewater is subjected to low-temperature multi-effect flash evaporation concentration by a low-temperature multi-effect evaporation system, enabling dissolved salts in the wastewater of a three-effect separator in the low-temperature multi-effect evaporation system to be saturated, and enabling the salts in the concentrated water to be separated out by naturally cooling or forcibly cooling the discharged concentrated water;
step 2, discharging the concentrated water into a concentrated solution tank through a thickener, sending the concentrated water into a dehydrator by using a concentrated solution pump for solid-liquid separation, taking gypsum, crystallized salt and certain concentrated water away from the dehydrated mud cake, and finally balancing the salt brought into the original wastewater with the salt brought away from the mud cake;
step 3, pumping steam and condensate water in the first-effect evaporator into a first-effect condenser through a first-effect vacuum pump, condensing the steam into condensate water through circulating cooling water, collecting the condensate water in a first-effect condensate water tank, and pumping the condensate water through a first-effect condensate water pump into a flue gas heat exchanger for recycling;
step 4, condensed water in the second-effect evaporator automatically flows into the third-effect evaporator, after waste heat is utilized, the condensed water and the condensed water in the third-effect evaporator enter a tail gas condensation water tank together, a negative pressure difference is formed by a first-effect, second-effect and third-effect system and is realized through a tail gas vacuum pump, tail gas generated in the third-effect separator enters a tail gas condenser, the tail gas is condensed into condensed water through circulating cooling water, and the condensed water is collected in the tail gas condensation water tank and is pumped to a power plant through a tail gas condensed water pump for recycling;
step 5, collecting the filtrate after solid-liquid separation in a filtrate tank, adding other alkaline substances such as limestone, sodium hydroxide and the like into the filtrate tank, controlling the dosage of the added medicament through a pH adjusting pump to adjust the pH value of the wastewater, and stirring and fully mixing the filtrate water and the added medicament to maintain the pH value of the filtrate water at about 4.5-6;
and 6, additionally arranging an electric heater in the filtrate tank, or additionally arranging electric tracing in a filtrate water return pipeline, or supplementing a small amount of steam at the inlet of the one-effect evaporator to enter the three-effect evaporator, performing heating compensation for losing heat, and pumping the heated filtrate into a three-effect separator in the low-temperature multi-effect evaporation system through a filtrate pump.
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|---|---|---|---|---|
| CN115321626A (en) * | 2022-07-28 | 2022-11-11 | 温州市金榜轻工机械有限公司 | Multi-effect continuous energy-saving forced circulation crystallization evaporator |
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2022
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115321626A (en) * | 2022-07-28 | 2022-11-11 | 温州市金榜轻工机械有限公司 | Multi-effect continuous energy-saving forced circulation crystallization evaporator |
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