CN111635053A - Desulfurization wastewater zero-discharge treatment system and method - Google Patents

Abstract

The invention discloses a desulfurization wastewater zero-discharge treatment system and a method, wherein the desulfurization wastewater zero-discharge treatment system comprises a regulating tank, an integrated pretreatment device, a microfiltration device, a nanofiltration device, a high-pressure reverse osmosis device, an ultrahigh-pressure reverse osmosis device, a horizontal pipe falling film concentration device and an evaporative crystallization device; the equalizing tank, the integrated pretreatment device, the microfiltration device, the nanofiltration device, the high-pressure reverse osmosis device, the ultrahigh-pressure reverse osmosis device, the horizontal pipe falling film concentration device and the evaporation crystallization device are sequentially connected according to the treatment direction of the desulfurization wastewater. The invention achieves zero discharge of waste water, reduces the scale of an evaporation system, reduces the energy consumption of an evaporation crystallization process, improves the purity of crystallized salt, simplifies the pretreatment process flow and reduces the occupied area and equipment investment.

Description

Desulfurization wastewater zero-discharge treatment system and method

Technical Field

The invention relates to the technical field of wastewater treatment, in particular to a desulfurization wastewater zero-discharge treatment system and a desulfurization wastewater zero-discharge treatment method.

Background

In order to remove sulfur dioxide in flue gas, more than 90% of coal-fired power plants in China adopt a limestone gypsum wet desulphurization process. Various waste water of the power plant is often used as process water of a desulfurization system, so the desulfurization waste water generated by the desulfurization system is tail end waste water of the power plant, and has the characteristics of small water quantity, complex components and difficult treatment. Because the problems of water resource recycling and environmental protection are increasingly prominent, zero discharge of the desulfurization wastewater is more and more necessary.

The main factors influencing the quality of the desulfurization wastewater comprise burning coal types, lime quality, concentrated circulating water, chemical wastewater of a power plant, various agents added in the recycling process and the like. The desulfurization wastewater has the characteristics of weak acidity, large water quality change, high salt content, high calcium and magnesium hardness and multiple heavy metal types, particularly the content of chloride ions reaches 11000-25000 mg/L, wherein NH4⁺The N content is lower, and the COD content is lower.

At present, the desulfurization wastewater zero-discharge treatment process takes an evaporation technology as a core and is divided into two types: the flue gas or steam is used as a heat source, and the flue gas evaporative crystallization process has the defects that the flue gas contacts and exchanges heat with salt to generate mixed salt, and the application of the flue gas evaporative crystallization process is limited due to the problem of product salt treatment. The steam evaporation crystallization process has the defects of large investment and high cost, so that the large-scale popularization of the process is influenced. In recent years, the mainstream steam evaporation technology adopted in engineering is vertical mechanical vapor compression evaporation (MVR), the operation energy consumption of the MVR is less than 10% of that of a multi-effect evaporation (MED) process, evaporation equipment is greatly reduced, the occupied area is greatly reduced, and the problems of high investment and high operation cost still exist. In addition, the wastewater front-end softening pretreatment process has the problems of long flow and more nodes.

Disclosure of Invention

The invention aims to solve the technical problem of providing a desulfurization wastewater zero-discharge treatment system and a desulfurization wastewater zero-discharge treatment method aiming at the defects of the prior art.

The technical scheme adopted by the invention for solving the technical problems is as follows: the utility model provides a desulfurization waste water zero release processing system, including the equalizing basin that inserts desulfurization waste water, carry out the integrated preprocessing device of softening treatment to desulfurization waste water, carry out the micro-filtration device of micro-filtration treatment to the desulfurization waste water after softening, carry out the nano-filtration device of salt purification processing to the desulfurization waste water after micro-filtration, carry out the high pressure reverse osmosis unit and the superhigh pressure reverse osmosis unit of concentration minimizing treatment to the desulfurization waste water after the salt purification, carry out horizontal pipe falling liquid film enrichment facility and the evaporation crystallization device of concentration and crystallization treatment in proper order to the desulfurization waste water after the concentration minimizing;

the equalizing tank, the integrated pretreatment device, the microfiltration device, the nanofiltration device, the high-pressure reverse osmosis device, the ultrahigh-pressure reverse osmosis device, the horizontal pipe falling film concentration device and the evaporation crystallization device are sequentially connected according to the treatment direction of the desulfurization wastewater.

Preferably, the adjusting tank comprises a tank body and a blade stirrer arranged in the tank body.

Preferably, the integrated pretreatment device comprises a dosing system, a primary reaction tank, an inclined plate clarification tank, a secondary reaction tank and a concentration tank which are sequentially communicated;

the dosing system comprises a lime dosing device, a sodium carbonate dosing device, an organic sulfur dosing device, a coagulant dosing device and a coagulant aid dosing device; the lime dosing device, the coagulant dosing device and the coagulant aid dosing device are respectively communicated with the primary reaction tank through first dosing pipelines, and the sodium carbonate dosing device, the organic sulfur dosing device, the coagulant dosing device and the coagulant aid dosing device are respectively communicated with the secondary reaction tank through second dosing pipelines.

Preferably, the integrated pretreatment device further comprises a sludge buffer tank and a plate-and-frame filter press;

the inclined plate clarification tank and the concentration tank are respectively connected with the inlet end of the sludge buffer tank through sludge conveying pipelines, and the generated sludge is conveyed to the sludge buffer tank; and the plate-and-frame filter press is connected with the outlet end of the sludge buffer tank to perform filter pressing treatment on the sludge.

Preferably, the high-pressure reverse osmosis device adopts a roll type composite high-pressure reverse osmosis membrane element, and the produced water of the nanofiltration device is subjected to primary concentration and reduction;

the ultrahigh pressure reverse osmosis device adopts a roll type composite ultrahigh pressure reverse osmosis membrane element to perform secondary concentration and reduction on concentrated water from the high pressure reverse osmosis device.

Preferably, the horizontal pipe falling film concentration device comprises a horizontal pipe evaporation tank, a heat exchanger, a steam compression fan and a circulating pump;

the horizontal tube evaporating pot comprises a shell for circulating concentrated water and a plurality of heat exchange tubes which are horizontally arranged in the shell and used for circulating a heating medium, and a feed inlet and a discharge outlet which are communicated with the inner space of the shell are formed in the shell; the cold side inlet end of the heat exchanger is connected with the ultrahigh pressure reverse osmosis device, and the cold side outlet end of the heat exchanger is connected with the feed inlet of the transverse pipe evaporating pot; the hot side inlet end of the heat exchanger is connected with a condensate water outlet of the transverse pipe evaporation tank, and concentrated water output by the ultrahigh pressure reverse osmosis device passes through the heat exchanger and then enters the transverse pipe evaporation tank;

the air inlet end and the air outlet end of the steam compressor are respectively connected with the horizontal pipe evaporating pot through steam pipelines to form a steam loop;

the discharge port of the horizontal tube evaporating pot is connected with the inlet end of the circulating pump, and the outlet end of the circulating pump is connected with the evaporative crystallization device.

Preferably, the outlet end of the circulating pump is also connected with the top of the horizontal tube evaporation tank through a return pipeline to form a concentrated water circulating loop.

Preferably, the desulfurization wastewater zero-discharge treatment system further comprises a normal-pressure reverse osmosis device;

and the normal pressure reverse osmosis device is respectively connected with the high pressure reverse osmosis device and the ultrahigh pressure reverse osmosis device, receives the produced water of the high pressure reverse osmosis device and the ultrahigh pressure reverse osmosis device and carries out normal pressure reverse osmosis treatment.

The invention also provides a desulfurization wastewater zero-discharge treatment method, which comprises the following steps:

s1, introducing the desulfurization wastewater into the regulating tank, and stirring the desulfurization wastewater to ensure that the desulfurization wastewater is uniform in solid and liquid;

s2, conveying the desulfurization wastewater to an integrated pretreatment device for softening treatment to remove colloids, suspended matters, heavy metals and metal ions in the desulfurization wastewater;

s3, sequentially conveying the softened desulfurization wastewater to a microfiltration device and a nanofiltration device, and sequentially performing microfiltration treatment and salt separation purification treatment to obtain nanofiltration product water;

s4, conveying the nanofiltration produced water to a high-pressure reverse osmosis device for primary concentration and reduction treatment;

s5, conveying the concentrated water obtained by the primary concentration and reduction treatment to an ultrahigh pressure reverse osmosis device for secondary concentration and reduction treatment;

s6, conveying the concentrated water obtained after the secondary concentration and reduction to a horizontal tube falling film concentration device for concentration treatment;

and S7, conveying the concentrated product water to an evaporation crystallization device for crystallization treatment to obtain sodium chloride crystal salt and evaporation condensate water.

Preferably, the processing method further comprises the steps of:

and S8, conveying the concentrated water of the high-pressure reverse osmosis device and the ultrahigh-pressure reverse osmosis device to a normal-pressure reverse osmosis device for normal-pressure reverse osmosis treatment to obtain reuse water.

The invention has the beneficial effects that: the desulfurization wastewater is subjected to softening treatment of an integrated pretreatment device, salt separation purification treatment of a nanofiltration device, concentration and reduction treatment of high-pressure and ultrahigh-pressure reverse osmosis, and final concentration and crystallization treatment, so that zero discharge of wastewater is achieved, the scale of an evaporation system is reduced, the energy consumption of an evaporation crystallization process is reduced, the purity of crystallized salt is improved, the pretreatment process flow is simplified, and the occupied area and equipment investment are reduced.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic view of a connection structure of a desulfurization waste water zero-discharge treatment system according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of an integrated pretreatment device in a desulfurization wastewater zero-discharge treatment system according to an embodiment of the present invention;

fig. 3 is a schematic structural view of a horizontal tube falling film concentration device in a desulfurization wastewater zero-discharge treatment system according to an embodiment of the present invention.

Detailed Description

For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

As shown in fig. 1, the desulfurization wastewater zero-discharge treatment system according to an embodiment of the present invention includes a conditioning tank 10, an integrated pretreatment device 20, a microfiltration device 30, a nanofiltration device 40, a high-pressure reverse osmosis device 50, an ultrahigh-pressure reverse osmosis device 60, a horizontal tube falling film concentration device 70, and an evaporative crystallization device 80, which are sequentially connected to each other in the treatment direction of desulfurization wastewater.

Wherein, the equalizing basin 10 is connected with the desulfurization wastewater, and can stir the desulfurization wastewater, so that the desulfurization wastewater is uniform in solid and liquid and is not easy to settle. The integrated pretreatment device 20 is an integrated device, and performs softening treatment on the desulfurization wastewater to remove colloids, suspended matters, heavy metals, metal ions and the like in the desulfurization wastewater. The microfiltration device 30 carries out microfiltration treatment on the softened desulfurization wastewater, thereby canceling the arrangement of a secondary clarification tank of the traditional pretreatment process, reducing process links and reducing the occupied area and equipment investment. The nanofiltration device 40 carries out salt separation and purification treatment on the microfiltration desulfurization wastewater, and improves the purity of sodium chloride in produced water, thereby improving the purity of sodium chloride in subsequent evaporation product salt to 97.5 percent or more. The high-pressure reverse osmosis device 50 and the ultrahigh-pressure reverse osmosis device 60 sequentially perform concentration and reduction treatment on the desulfurized wastewater after the desalination purification. The horizontal tube falling film concentration device 70 and the evaporation crystallization device 80 sequentially perform concentration and crystallization treatment on the desulfurization wastewater after concentration and reduction, and finally obtain sodium chloride crystal salt and evaporation condensate water.

Specifically, the equalizing basin 10 may include a basin body and a paddle agitator disposed in the basin body, and the desulfurization wastewater entering the basin body is agitated by the paddle agitator.

As shown in fig. 1 and 2, the integrated pretreatment device 20 includes a dosing system 21, a first-stage reaction tank 22, an inclined plate clarification tank 23, a second-stage reaction tank 24 and a concentration tank 25 which are sequentially communicated. The dosing system 21, the primary reaction tank 22, the inclined plate clarification tank 23, the secondary reaction tank 24 and the concentration tank 25 are integrated into a whole, so that the floor area of the whole pretreatment device and the pipeline investment in the pretreatment device are reduced.

The dosing system 21 is used for adding corresponding reagents into the primary reaction tank 22 and the secondary reaction tank 24 respectively. The dosing system 21 further comprises a lime dosing device 211, a sodium carbonate dosing device 212, an organic sulfur dosing device 213, a coagulant dosing device 214, and a coagulant aid dosing device 215.

The lime dosing device 211, the coagulant dosing device 214 and the coagulant aid dosing device 215 are respectively communicated with the primary reaction tank 22 through a first dosing pipeline (not shown), and a dosing pump is arranged on the first dosing pipeline. The primary reaction tank 22 is connected with the regulating tank 10 through a delivery pump 210, the delivery pump 210 provides power to deliver the desulfurization wastewater in the regulating tank 10 to the primary reaction tank 22, lime is added into the desulfurization wastewater in the primary reaction tank 22 through a lime dosing device 211, the pH of the desulfurization wastewater is adjusted to be alkaline (such as pH is 11.2), and hard magnesium and hard silicon can be removed; the coagulant adding device 214 and the coagulant aid adding device 215 are respectively used for adding a polyferric solution (coagulant) and a PAM solution (coagulant aid) into the desulfurization wastewater in the primary reaction tank 22, so that the precipitation, flocculation and sedimentation can be promoted.

The sodium carbonate dosing device 212, the organic sulfur dosing device 213, the coagulant dosing device 214 and the coagulant aid dosing device 215 are respectively communicated with the secondary reaction tank 24 through a second dosing pipeline (not shown), and a dosing pump is arranged on the second dosing pipeline. Sodium carbonate and organic sulfur are respectively added into the desulfurization wastewater in the secondary reaction tank 24 through a sodium carbonate dosing device 212 and an organic sulfur dosing device 213, so that hard calcium ions and heavy metal ions can be respectively removed; the coagulant adding device 214 and the coagulant aid adding device 215 are respectively used for adding a polyferric solution (coagulant) and a PAM solution (coagulant aid) into the desulfurization wastewater in the secondary reaction tank 24, so that the precipitation, flocculation and sedimentation can be promoted.

The inclined plate clarifier 23 is communicated between the first-stage reaction tank 22 and the second-stage reaction tank 24, and clarifies the desulfurization wastewater from the first-stage reaction tank 22, and traps precipitates and the like in the desulfurization wastewater in the inclined plate clarifier 23, and the clarified liquid flows to the second-stage reaction tank 24 to be reprocessed. The desulfurization wastewater is treated in the secondary reaction tank 24 and then is conveyed to the concentration tank 25, passes through the concentration tank 25 and is conveyed to the microfiltration device 30.

Height difference overflow is adopted among the pools in the primary reaction tank 22, the inclined plate clarification tank 23, the secondary reaction tank 24 and the concentration tank 25, only one two delivery pumps 210 for one use are needed to be arranged between the regulating tank 10 and the primary reaction tank 22 to provide water inlet power for the integrated pretreatment device 20, and the arrangement of a plurality of water pumps is omitted.

When the desulfurization waste water passes through the integrated pretreatment device 20, colloid, suspended matters, heavy metals, calcium, magnesium, barium, strontium and other metal ions in the desulfurization waste water are removed through chemical dosing treatment, the calcium hardness of the water discharged from the concentration tank 25 is controlled to be less than 5mg/l, and the magnesium hardness is controlled to be less than 5mg/l, so that a better softening effect is achieved.

In this embodiment, each of the first-stage reaction tank 22, the inclined plate clarification tank 23, the second-stage reaction tank 24, and the concentration tank 25 is a rectangular water tank. The submerged stirrers 221 and 241 are arranged in the first-stage reaction tank 22 and the second-stage reaction tank 24 at opposite angles respectively, have the characteristics of high thrust, low energy consumption and uniform solid-liquid stirring, and are used for uniformly stirring the desulfurization wastewater and the added medicament. The inclined plate clarifier 23 is internally provided with inclined plate filler for filling, thereby improving clarification efficiency and reducing the floor area of the inclined plate clarifier 23. The inside of the concentration tank 25 is provided with a blade stirrer, and the bottom of the concentration tank 25 is conical, so that the sludge accumulation is reduced.

Further, the integrated pretreatment device 20 further comprises a sludge buffer tank 26 and a plate-and-frame filter press 27. The inclined plate clarification tank 23 and the concentration tank 25 are respectively connected with the inlet end of a sludge buffer tank 26 through sludge conveying pipelines, and the generated sludge is conveyed to the sludge buffer tank 26; the sludge conveying pipeline can be provided with a sludge conveying pump for providing power. The plate-and-frame filter press 27 is connected with the outlet end of the sludge buffer tank 26 to perform filter-pressing treatment on the sludge.

The microfiltration device 30 is connected with the concentration tank 25 of the integrated pretreatment device 20 and receives the effluent from the concentration tank 25. The microfiltration device 30 adopts a tubular microfiltration membrane, and has good filtering effect on high-flow and high-suspended matter wastewater, so that the arrangement of a secondary clarification tank of the traditional pretreatment process is cancelled, the process links are reduced, and the occupied area and the equipment investment are reduced.

The produced water of the microfiltration device 30 is conveyed to the nanofiltration device 40 for salt separation and purification treatment. The nanofiltration device 40 adopts a roll type composite membrane element (such as a spiral roll type polypiperazine composite membrane element) with high selectivity, higher monovalent ion transmittance, higher divalent ion and COD interception rate, and the working pressure is 0.6MPa-4 MPa. The pH of the produced water received by the nanofiltration device 40 is 5-10; when the pH is not 5-10, hydrochloric acid is added as required for adjustment. The sodium chloride purity of the produced water is improved through the treatment of the nanofiltration device 40, so that the sodium chloride purity of the subsequent evaporation product salt is improved and can reach 97.5 percent or more.

The produced water of the nanofiltration device 40 is transferred to a high pressure reverse osmosis device 50. The working pressure of the high-pressure reverse osmosis device 50 is 6MPa to 8 MPa. The high-pressure reverse osmosis device 50 adopts a high-pollution-resistant roll-type composite high-pressure reverse osmosis membrane element (such as a spiral roll-type polyamide composite thin film element) to perform primary concentration and reduction on the produced water of the nanofiltration device 40. The high pressure reverse osmosis device 50 receives product water from the nanofiltration device 40 at a pH of 5 to 10.

The concentrated water output by the high-pressure reverse osmosis device 50 is conveyed to the ultrahigh-pressure reverse osmosis device 60; the pH of the outgoing concentrated water is preferably 5-10. The working pressure of the ultrahigh-pressure reverse osmosis device 60 is 8MPa to 12 MPa. The ultra-high pressure reverse osmosis device 60 employs a wide flow passage, anti-pollution roll type composite ultra-high pressure reverse osmosis membrane element to perform secondary concentration and reduction on the concentrated water from the high pressure reverse osmosis device 50. The treatment scale of a subsequent evaporation system is reduced by further concentrating and reducing the concentrated water.

The desulfurization wastewater zero-discharge treatment system also comprises a normal-pressure reverse osmosis device 90. The normal pressure reverse osmosis device 90 is connected with the high pressure reverse osmosis device 50 and the ultrahigh pressure reverse osmosis device 60 respectively, receives the produced water (reverse osmosis produced water, different from concentrated water) of the high pressure reverse osmosis device 50 and the ultrahigh pressure reverse osmosis device 60 and carries out normal pressure reverse osmosis treatment, and the treated produced water can be collected as recycled water for a power plant to be reused. The normal pressure reverse osmosis device 90 employs an anti-pollution polyamide composite membrane element.

The concentrated water after the secondary concentration and reduction is conveyed to a horizontal tube falling film concentration device 70 from the ultrahigh pressure reverse osmosis device 60 for concentration treatment.

Referring to fig. 1 and 3, in the present embodiment, the horizontal tube falling film concentrating apparatus 70 includes a horizontal tube evaporator 71, a heat exchanger 72, a vapor compression fan 73, and a circulation pump 74.

The heat exchanger 72 is a plate heat exchanger, the cold side inlet end of the heat exchanger is connected with the ultrahigh pressure reverse osmosis device 60 to receive concentrated water output by the ultrahigh pressure reverse osmosis device 60, and the cold side outlet end of the heat exchanger is connected with the feed inlet of the horizontal pipe evaporation tank 71; the hot side inlet end of the heat exchanger 72 is connected with the condensed water outlet of the horizontal tube evaporator tank 71. The concentrated water output by the ultrahigh-pressure reverse osmosis device 60 passes through the heat exchanger 72 and then enters the horizontal tube evaporation tank 71, and in the heat exchanger 72, the concentrated water and the condensed water entering the heat exchanger 72 exchange heat, so that the waste heat of the condensed water is fully utilized to preheat the concentrated water, and the power consumption is reduced.

The horizontal tube evaporator tank 71 can comprise a shell and a plurality of heat exchange tubes horizontally arranged in the shell; the plurality of heat exchange tubes are distributed from top to bottom to form a plurality of layers. The level setting of heat exchange tube, traditional standpipe setting relatively can reduce the total height of whole device, reduces and maintains the degree of difficulty, reduces the factory building height, reduces the quantity of steel construction, reduces the requirement of ground.

In the horizontal tube evaporator tank 71, the shell is used for circulating concentrated water from the ultrahigh pressure reverse osmosis device 60, and the heat exchange tube is used for circulating a heating medium. The shell is provided with a feed inlet and a discharge outlet which are communicated with the inner space of the shell, and is also provided with a condensed water inlet and a condensed water outlet which are communicated with the heat exchange tube. Concentrated water preferably enters from a feed inlet at the middle position of the top of the shell, liquid film flow is uniformly formed outside the layer-by-layer heat exchange tubes, and a heating medium (steam) circulates in the heat exchange tubes and exchanges heat with the concentrated water in the shell; the concentrated water is heated and vaporized by the heating medium in the heat exchange tube to form secondary steam, and the secondary steam enters the condenser to be condensed and discharged or enters the steam compression fan 73 to be recycled. Compared with the traditional vertical pipe with concentrated water arranged in the heat exchange pipe, in the horizontal pipe evaporation tank 71, the film of the concentrated water outside the heat exchange pipe is thinner, the effective heat exchange area is larger, and the liquid film needs to be redistributed for heat exchange once after passing through one layer of heat exchange pipe, so that the flow speed is reduced, the flow time is increased, and the evaporation efficiency is improved.

The air inlet end and the air outlet end of the steam compressor 73 are respectively connected with the horizontal pipe evaporation tank 71 through a steam pipeline 731 to form a steam loop. Steam formed by heating and vaporizing the concentrated water enters a steam pipeline 731, passes through a steam compressor 73 and then flows back into the horizontal tube evaporation tank 71. The vapor compressor 73 may employ a centrifugal fan or a roots fan.

The inlet end of the circulating pump 74 is connected with the discharge hole of the horizontal tube evaporation tank 71, the outlet end of the circulating pump 74 is connected with the evaporative crystallization device 80, and concentrated water after concentration treatment is conveyed to the evaporative crystallization device 80 through the circulating pump 74.

Furthermore, the outlet end of the circulating pump 74 is also connected to the top of the horizontal tube evaporator 71 through a return pipe 741 to form a concentrated water circulation loop, so that the concentrated water output from the discharge port of the horizontal tube evaporator 71 can flow back into the horizontal tube evaporator 71 through the return pipe 741 to be re-concentrated, and is conveyed to the evaporative crystallization device 80 after being circulated for one or more times, thereby further improving the concentration of the produced water. A valve is arranged on a pipeline between the outlet end of the circulating pump 74 and the evaporative crystallization device 80 for on-off switching.

The overall height of the cross-tube falling film concentrator 70 can be reduced by preferably using a low-lift (lift less than 10m) circulation pump 74, so that the energy consumption of the circulation pump 74 is reduced by 60% compared with that of a circulation pump of a vertical evaporator.

In addition, for the horizontal tube evaporator 71, the horizontal arrangement of the heat exchange tubes is preferably a thin-walled tube compared with the vertical arrangement, because the axial stress at the joint of the heat exchange tubes and the tube plates is only the pressure difference between the inside and the outside of the tubes, and the stress is small. In the embodiment, the heat exchange tube adopts the titanium tube with the thickness of 0.7mm, so that the cost can be reduced, and the heat transfer effect is enhanced by about 10 percent; and compared with the vertical arrangement, the vertical heat exchanger can preferably adopt a pipeline with a smaller diameter, adopts higher filling density and can improve the heat exchange efficiency by about 10 percent.

The joint of the heat exchange tube is preferably connected only in an expansion joint mode, so that the installation cost is saved. The concentrated water side is in the shell pass, the medium at the joint of the heat exchange tube is steam or condensed water, and the tube pass side at the joint always has water flow from top to bottom, so that the phenomenon of local crystallization does not exist, and the pressure is reduced.

The lower flow velocity and the extremely thin liquid film enable the horizontal tube evaporating pot 71 to have higher requirements on the quality of inlet water, and the hardness content needs to be strictly controlled. The hardness requirement of the outlet water of the front end concentration tank 25 is strictly controlled, the calcium hardness of the inlet water of the horizontal pipe evaporation tank 71 is less than 5mg/l, and the magnesium hardness is less than 5 mg/l.

The evaporative crystallization device 80 receives the produced water from the horizontal tube falling film concentration device 70, and carries out evaporative crystallization treatment on the produced water to obtain sodium chloride crystal salt and evaporative condensed water.

The evaporative crystallization device 80 can select a multi-effect evaporative crystallizer or an MVR evaporative crystallizer, and the generated evaporative condensed water meets the requirements of GBT50050-2017 'design specification for industrial circulating cooling water treatment' on indirect cooling open type circulating cooling water and can be reused in a power plant; the crystallized salt is dehydrated and dried to obtain sodium chloride product salt which meets the secondary (97.5%) standard of industrial salt (GB/T5462-.

The desulfurization wastewater zero-discharge treatment method is realized by adopting the treatment system. Referring to fig. 1-3, the processing method may include the steps of:

s1, the desulfurization wastewater is introduced into the regulating tank 10, and the desulfurization wastewater is stirred to be uniform in solid and liquid.

And S2, conveying the desulfurization wastewater to the integrated pretreatment device 20 for softening treatment, and removing colloids, suspended matters, heavy metals and metal ions in the desulfurization wastewater.

And the desulfurization wastewater sequentially passes through a primary reaction tank 22, an inclined plate clarification tank 23, a secondary reaction tank 24 and a concentration tank 25 in combination with the integrated arrangement of all the water tanks of the integrated pretreatment device 20, and the treatment of all the water tanks can be specifically referred to the relevant description of the system.

And S3, sequentially conveying the softened desulfurization wastewater to a microfiltration device 30 and a nanofiltration device 40, and sequentially performing microfiltration treatment and salt separation purification treatment to obtain nanofiltration water.

The microfiltration device 30 employs a tubular microfiltration membrane to filter the softened desulfurization wastewater. The nanofiltration device 40 adopts a roll-type composite membrane element (such as a spiral roll-type polypiperazine composite membrane element) with high selectivity, higher monovalent ion transmittance, higher divalent ion and COD interception rate to carry out salt separation and purification treatment on the produced water of the microfiltration device 30, thereby improving the purity of the produced water, namely sodium chloride.

And S4, conveying the nanofiltration produced water to the high-pressure reverse osmosis device 50 for primary concentration and reduction treatment.

And S5, conveying the concentrated water obtained by the primary concentration and reduction treatment to the ultrahigh pressure reverse osmosis device 60 for secondary concentration and reduction treatment.

And S6, conveying the concentrated water obtained after the secondary concentration and reduction to a horizontal tube falling film concentration device 70 for concentration treatment. The concentration treatment can be referred to in connection with the above-mentioned system.

And S7, conveying the concentrated product water to an evaporative crystallization device 80 for crystallization to obtain sodium chloride crystal salt and evaporative condensed water.

Further, the processing method of the invention also comprises the following steps:

and S8, conveying the produced water of the high-pressure reverse osmosis device 50 and the ultrahigh-pressure reverse osmosis device 60 to the normal-pressure reverse osmosis device 90 for normal-pressure reverse osmosis treatment to obtain recycled water which can be used in a power plant.

In conclusion, the invention adopts the integrated pretreatment softening hardness removal, nanofiltration salt separation purification, concentration and decrement of high-pressure reverse osmosis and ultrahigh-pressure reverse osmosis, horizontal tube falling film concentration and evaporative crystallization to perform zero discharge treatment on the desulfurization wastewater, and finally generates reverse osmosis water, evaporative condensate water and sodium chloride crystal salt. The integrated pretreatment device is combined with microfiltration, so that the pretreatment process flow is simplified, and the floor area and equipment investment are reduced; the purity of the crystallized salt is improved through nanofiltration; the MVR evaporation concentration is replaced by the ultrahigh-pressure reverse osmosis concentration, so that the scale and the investment of an evaporation system are further reduced; the horizontal pipe falling film concentration device with special design reduces the energy consumption of the evaporative crystallization process, reduces the investment of process equipment, realizes zero discharge treatment of desulfurization waste water, and has considerable economic benefit and environmental protection benefit.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (10)

1. The desulfurization wastewater zero-discharge treatment system is characterized by comprising an adjusting tank, an integrated pretreatment device, a microfiltration device, a nanofiltration device, a high-pressure reverse osmosis device, an ultrahigh-pressure reverse osmosis device, a transverse pipe falling film concentration device and an evaporation crystallization device, wherein the adjusting tank is connected with desulfurization wastewater, the integrated pretreatment device is used for softening the desulfurization wastewater, the microfiltration device is used for carrying out microfiltration on the softened desulfurization wastewater, the nanofiltration device is used for carrying out salt separation and purification treatment on the microfiltration wastewater, the high-pressure reverse osmosis device and the ultrahigh-pressure reverse osmosis device are used for carrying out concentration and reduction treatment on the desulfurization wastewater after salt separation and purification, and the transverse pipe falling film concentration device and the;

the equalizing tank, the integrated pretreatment device, the microfiltration device, the nanofiltration device, the high-pressure reverse osmosis device, the ultrahigh-pressure reverse osmosis device, the horizontal pipe falling film concentration device and the evaporation crystallization device are sequentially connected according to the treatment direction of the desulfurization wastewater.

2. The desulfurization wastewater zero-emission treatment system of claim 1, wherein the conditioning tank comprises a tank body and a paddle agitator arranged in the tank body.

3. The desulfurization wastewater zero-discharge treatment system of claim 1, wherein the integrated pretreatment device comprises a dosing system, a primary reaction tank, an inclined plate clarification tank, a secondary reaction tank and a concentration tank which are sequentially communicated;

the dosing system comprises a lime dosing device, a sodium carbonate dosing device, an organic sulfur dosing device, a coagulant dosing device and a coagulant aid dosing device; the lime dosing device, the coagulant dosing device and the coagulant aid dosing device are respectively communicated with the primary reaction tank through first dosing pipelines, and the sodium carbonate dosing device, the organic sulfur dosing device, the coagulant dosing device and the coagulant aid dosing device are respectively communicated with the secondary reaction tank through second dosing pipelines.

4. The desulfurization wastewater zero-discharge treatment system of claim 3, wherein the integrated pretreatment device further comprises a sludge buffer tank and a plate-and-frame filter press;

the inclined plate clarification tank and the concentration tank are respectively connected with the inlet end of the sludge buffer tank through sludge conveying pipelines, and the generated sludge is conveyed to the sludge buffer tank; and the plate-and-frame filter press is connected with the outlet end of the sludge buffer tank to perform filter pressing treatment on the sludge.

5. The desulfurization wastewater zero-emission treatment system of claim 1, wherein the high-pressure reverse osmosis device adopts a roll-type composite high-pressure reverse osmosis membrane element to perform primary concentration and reduction on the produced water of the nanofiltration device;

the ultrahigh pressure reverse osmosis device adopts a roll type composite ultrahigh pressure reverse osmosis membrane element to perform secondary concentration and reduction on concentrated water from the high pressure reverse osmosis device.

6. The desulfurization waste water zero emission treatment system of claim 1, wherein the horizontal tube falling film concentration device comprises a horizontal tube evaporation tank, a heat exchanger, a vapor compression fan and a circulating pump;

the horizontal tube evaporating pot comprises a shell for circulating concentrated water and a plurality of heat exchange tubes which are horizontally arranged in the shell and used for circulating a heating medium, and a feed inlet and a discharge outlet which are communicated with the inner space of the shell are formed in the shell; the cold side inlet end of the heat exchanger is connected with the ultrahigh pressure reverse osmosis device, and the cold side outlet end of the heat exchanger is connected with the feed inlet of the transverse pipe evaporating pot; the hot side inlet end of the heat exchanger is connected with a condensate water outlet of the transverse pipe evaporation tank, and concentrated water output by the ultrahigh pressure reverse osmosis device passes through the heat exchanger and then enters the transverse pipe evaporation tank;

the air inlet end and the air outlet end of the steam compressor are respectively connected with the horizontal pipe evaporating pot through steam pipelines to form a steam loop;

the discharge port of the horizontal tube evaporating pot is connected with the inlet end of the circulating pump, and the outlet end of the circulating pump is connected with the evaporative crystallization device.

7. The desulfurization waste water zero-emission treatment system as claimed in claim 6, wherein the outlet end of the circulating pump is further connected with the top of the horizontal tube evaporation tank through a return pipeline to form a concentrated water circulating loop.

8. The desulfurization wastewater zero-emission treatment system of claim 1, further comprising an atmospheric reverse osmosis device;

and the normal pressure reverse osmosis device is respectively connected with the high pressure reverse osmosis device and the ultrahigh pressure reverse osmosis device, receives the produced water of the high pressure reverse osmosis device and the ultrahigh pressure reverse osmosis device and carries out normal pressure reverse osmosis treatment.

9. A desulfurization wastewater zero-discharge treatment method is characterized by comprising the following steps:

s1, introducing the desulfurization wastewater into the regulating tank, and stirring the desulfurization wastewater to ensure that the desulfurization wastewater is uniform in solid and liquid;

s2, conveying the desulfurization wastewater to an integrated pretreatment device for softening treatment to remove colloids, suspended matters, heavy metals and metal ions in the desulfurization wastewater;

s3, sequentially conveying the softened desulfurization wastewater to a microfiltration device and a nanofiltration device, and sequentially performing microfiltration treatment and salt separation purification treatment to obtain nanofiltration product water;

s4, conveying the nanofiltration produced water to a high-pressure reverse osmosis device for primary concentration and reduction treatment;

s5, conveying the concentrated water obtained by the primary concentration and reduction treatment to an ultrahigh pressure reverse osmosis device for secondary concentration and reduction treatment;

s6, conveying the concentrated water obtained after the secondary concentration and reduction to a horizontal tube falling film concentration device for concentration treatment;

and S7, conveying the concentrated product water to an evaporation crystallization device for crystallization treatment to obtain sodium chloride crystal salt and evaporation condensate water.

10. The desulfurization waste water zero-discharge treatment method as claimed in claim 9, further comprising the steps of:

and S8, conveying the concentrated water of the high-pressure reverse osmosis device and the ultrahigh-pressure reverse osmosis device to a normal-pressure reverse osmosis device for normal-pressure reverse osmosis treatment to obtain reuse water.

Images