阅读说明：本技术 一种ro膜后污水的深度处理装置和方法 (Advanced treatment device and method for sewage after RO (reverse osmosis) membrane ) 是由 李彩慧 王建荣 何海平 李光 上官文涛 杜军卫 边俊荣 于 2021-01-29 设计创作，主要内容包括：本发明公开了一种RO膜后污水的深度处理装置及方法,属于污水处理技术领域。包括污水预处理装置、气体预处理装置、除COD及分盐装置、混合盐精制装置；污水预处理装置包括污水储罐、污水加压泵、换热器、电加热器、混合器；气体预处理装置包括压缩机和缓冲罐；除COD及分盐装置反应器、盐沉降罐、第一气液分离器、冷却器、第二气液分离器；混合盐精制装置包括硫酸钾生成釜、氯化钠精制釜；缓冲罐通过减压阀与混合器连接,混合器与反应器连接,反应器的排气口通过管路与换热器连接,硫酸钾生成釜通过管路分别与盐沉降罐和第一气液分离器连接。本发明运行稳定,可显著降低生产成本,出水水质达标,同时可高效回收污水中的混合盐。(The invention discloses a device and a method for advanced treatment of sewage after RO (reverse osmosis) membrane, belonging to the technical field of sewage treatment. Comprises a sewage pretreatment device, a gas pretreatment device, a COD removal and salt separation device and a mixed salt refining device; the sewage pretreatment device comprises a sewage storage tank, a sewage pressure pump, a heat exchanger, an electric heater and a mixer; the gas pretreatment device comprises a compressor and a buffer tank; the system comprises a COD removing and salt separating device reactor, a salt settling tank, a first gas-liquid separator, a cooler and a second gas-liquid separator; the mixed salt refining device comprises a potassium sulfate generating kettle and a sodium chloride refining kettle; the buffer tank is connected with the mixer through a pressure reducing valve, the mixer is connected with the reactor, an exhaust port of the reactor is connected with the heat exchanger through a pipeline, and the potassium sulfate generating kettle is connected with the salt settling tank and the first gas-liquid separator through pipelines respectively. The invention has stable operation, can obviously reduce the production cost, can lead the water quality of the effluent to reach the standard, and can efficiently recover the mixed salt in the sewage.)

1. An advanced treatment device for sewage after RO (reverse osmosis) membrane is characterized by comprising a sewage pretreatment device, a gas pretreatment device, a COD (chemical oxygen demand) removal and salt separation device and a mixed salt refining device;

the sewage pretreatment device comprises a sewage storage tank, a sewage pressure pump, a heat exchanger, an electric heater and a mixer which are sequentially connected through pipelines;

the gas pretreatment device comprises a compressor and a buffer tank which are sequentially connected through a pipeline;

the COD removing and salt separating device comprises a reactor, a salt settling tank, a first gas-liquid separator, a cooler and a second gas-liquid separator which are connected through pipelines, and the salt settling tank is also connected with a coagulant tank;

the mixed salt refining device comprises a potassium sulfate generating kettle and a sodium chloride refining kettle which are sequentially connected through a pipeline;

the buffer tank is connected with the mixer through a pressure reducing valve, the mixer is connected with the reactor, an exhaust port of the reactor is connected with the heat exchanger through a pipeline, and the potassium sulfate generating kettle is respectively connected with the salt settling tank and the first gas-liquid separator through pipelines.

2. An advanced treatment device for sewage after RO membrane as claimed in claim 1, characterized in that, the heat exchanger comprises a first heat exchanger and a second heat exchanger which are connected in sequence, the first heat exchanger is also connected with a third gas-liquid separator and a fourth gas-liquid separator respectively, the third gas-liquid separator is also connected with the second heat exchanger, and the exhaust port of the reactor is connected with the second heat exchanger through a pipeline.

3. An apparatus for advanced treatment of RO membrane sewage as claimed in claim 1 or 2, wherein the mixer is connected to the reactor by a pressure pump.

4. An advanced treatment unit for RO membrane sewage according to claim 1 or 2, characterized in that the mixer is connected with the salt settling tank through a pipeline provided with a salt separating valve.

5. The advanced treatment device for the RO membrane sewage of claim 1 or 2, wherein the mixed salt refining device further comprises a sodium hypochlorite generator, and the sodium chloride refining kettle is connected with the sodium hypochlorite generator through a pipeline.

6. The method for advanced treatment of sewage after RO membrane by using the device of any one of claims 1-5, characterized by comprising the steps of: inputting sewage after RO membrane into a sewage pretreatment device, preheating by a heat exchanger and supplementing heat by an electric heating device, mixing with mixed gas of carbon dioxide and oxygen from a gas pretreatment device, pressurizing, then entering a COD (chemical oxygen demand) and salt separating device, forming a water/carbon dioxide two-phase subcritical state in a reactor, removing COD in the sewage, simultaneously separating out mixed salt in the sewage in the reactor, precipitating into a salt settling tank under the action of gravity, adding a coagulant in the settling tank, cooling, decompressing and dehydrating the solution to obtain a saturated solution of mixed salt of sodium sulfate and sodium chloride, feeding the saturated solution into a mixed salt refining device, respectively preparing potassium sulfate and sodium chloride, and recovering the generated potassium sulfate.

7. The method for advanced treatment of sewage after RO membrane by using the device of claim 5 is characterized by comprising the following steps:

(1) pumping the sewage subjected to the RO membrane from a sewage storage tank through a sewage pressurizing pump, sending the sewage into a first heat exchanger for heat exchange with steam generated by a third gas-liquid separator, then entering a second heat exchanger for heat exchange with high-temperature high-pressure produced water in a reactor, heating the sewage to 230 ℃ for heat supplement through an electric heater, and entering a mixer after the heat exchange of the high-temperature sewage with the temperature increase value of 260 ℃ and 285 ℃;

(2) the recycled carbon dioxide and oxygen are compressed by a compressor and then stored in a buffer tank 11, and then enter a mixer through a pressure reducing valve, and the carbon dioxide gas and the oxygen are dissolved in high-temperature high-pressure sewage and then pumped into a reactor through a pressure pump;

(3) the high-temperature high-pressure sewage and the carbon dioxide gas in the solution reach a sewage/carbon dioxide two-item subcritical/supercritical state in the reactor, oxygen dissolved in water is utilized to remove COD in the solution, meanwhile, salts such as sodium chloride, sodium sulfate and the like in the sewage are separated out and are precipitated at the bottom of the reactor, and a salt separating valve is opened to enrich the salts in a salt settling tank by utilizing the action of gravity;

(4) the produced water of the reactor is cooled by a second heat exchanger, the pressure of the produced water is reduced in a third gas-liquid separator, steam generated by pressure reduction enters a first heat exchanger to preheat sewage, the steam is cooled and then subjected to gas-liquid separation in a fourth gas-liquid separator, the generated carbon dioxide is dried and then enters a compressor to be recycled, and the generated water is used as circulating water for water supplement;

(5) enriching separated salt in a salt settling tank, closing a salt separating valve, leading the salt settling tank to release pressure through a first gas-liquid separator, adding a CL-III coagulant into the salt settling tank to promote the separation of salt and the growth of salt crystals, simultaneously evaporating partial steam, cooling the steam by a cooler, recovering carbon dioxide in the gas by the gas-liquid separator in a fourth gas-liquid separator, drying, and then entering a compressor for recycling, wherein the separated water is used as water supplement of a circulating cooling system;

(6) generating nearly saturated liquid of sodium chloride and sodium sulfate in a salt settling tank after pressure relief, flowing into a potassium sulfate generating kettle through liquid level difference, reacting for 2 hours at 40 ℃ by adding a certain amount of potassium chloride, obtaining agricultural potassium sulfate through centrifugal separation, sending mother liquor into a sodium chloride refining kettle, and refining in the sodium chloride refining kettle to obtain sodium chloride with the content of more than 94%;

(7) sodium chloride is prepared into industrial grade sodium hypochlorite by a sodium hypochlorite generator.

Technical Field

The invention belongs to the technical field of sewage treatment, and particularly relates to an advanced treatment device and method for sewage after RO (reverse osmosis) membrane treatment.

Background

At present, after biochemical treatment and advanced treatment are carried out on sewage treatment in the industries of metallurgy, coking, medicine, printing and dyeing, electric power and the like in China, concentrated water behind an RO (reverse osmosis) membrane has high COD (chemical oxygen demand) content, TDS (total dissolved solids) content is about 10-20g/L, main salts are sodium chloride and sodium sulfate, and a small amount of Ca (calcium) is contained²⁺、Mg^2+、Fe²⁺And (3) plasma.

At present, the part of concentrated water after RO membrane is mainly treated by the processes of evaporation, concentration, crystallization and salt separation, the process has the defects of high consumption and high treatment cost, the separated sodium chloride and sodium sulfate have high impurity content, low additional value and poor economic benefit, and the technology for recycling and comprehensively utilizing the sodium chloride and the sodium sulfate does not exist in China at present. Taking a coking plant producing 130 million tons of coke annually as an example, the amount of the high-salinity sewage behind the membrane is about 200 tons/day, if an evaporation technology is adopted, about 160 tons/d of steam is consumed, salt generated by evaporation crystallization is also solid waste and cannot be treated, and meanwhile, in the evaporation process, COD in the sewage enters the reclaimed water along with the steam, so that the COD in the reclaimed water can exceed the national reclaimed water standard.

According to market research, the amount of high COD and high salinity sewage in various domestic industries is large at present, and the vanadium-titanium alloy smelting industry is about 500 million tons/year; about 15-25 million tons/year in the printing and dyeing industry; about 2000 million tons/year in the metallurgical coking industry; the industries of pesticides, medicines, medicine intermediates and pesticide intermediates are about 1500 ten thousand tons/year. Therefore, how to obtain high COD and high salt in sewage is an urgent problem to be solved in the field of sewage treatment.

In order to solve the problems in the industries, the invention develops an advanced treatment process of sewage after RO (reverse osmosis) membrane, which utilizes water/CO₂Treatment of high COD by using two-term sub-supercritical principleAnd salt separation, the quality of the treated effluent can meet the requirement of using the regenerated water as the water supplement of a circulating cooling system, and meanwhile, agricultural potassium sulfate and industrial sodium hypochlorite are byproducts, so that the comprehensive utilization of waste salt resources is realized.

Disclosure of Invention

The invention provides an advanced treatment device and method for sewage after an RO (reverse osmosis) membrane, aiming at solving the problems of high energy consumption and high operation cost in the existing sewage treatment after the RO membrane and high impurity content of sodium chloride and sodium sulfate obtained by separation.

The invention is realized by the following technical scheme:

an advanced treatment device for sewage after RO (reverse osmosis) membrane comprises a sewage pretreatment device, a gas pretreatment device, a COD (chemical oxygen demand) removal and salt separation device and a mixed salt refining device;

the sewage pretreatment device comprises a sewage storage tank, a sewage pressure pump, a heat exchanger, an electric heater and a mixer which are sequentially connected through pipelines;

the gas pretreatment device comprises a compressor and a buffer tank which are sequentially connected through a pipeline;

the COD removing and salt separating device comprises a reactor, a salt settling tank, a first gas-liquid separator, a cooler and a second gas-liquid separator which are connected through pipelines, and the salt settling tank is also connected with a coagulant tank;

the mixed salt refining device comprises a potassium sulfate generating kettle and a sodium chloride refining kettle which are sequentially connected through a pipeline;

the buffer tank is connected with the mixer through a pressure reducing valve, the mixer is connected with the reactor, an exhaust port of the reactor is connected with the heat exchanger through a pipeline, and the potassium sulfate generating kettle is respectively connected with the salt settling tank and the first gas-liquid separator through pipelines.

Further, the heat exchanger comprises a first heat exchanger and a second heat exchanger which are sequentially connected, the first heat exchanger is further respectively connected with a third gas-liquid separator and a fourth gas-liquid separator, the third gas-liquid separator is further connected with the second heat exchanger, and an exhaust port of the reactor is connected with the second heat exchanger through a pipeline.

The mixer was connected to the reactor by means of a pressure pump.

The mixer is connected with the salt settling tank through a pipeline provided with a salt separating valve.

The mixed salt refining device further comprises a sodium hypochlorite generator, and the sodium chloride refining kettle is connected with the sodium hypochlorite generator through a pipeline.

Furthermore, the invention also provides a method for advanced treatment of sewage after RO membrane by using the device, which comprises the following steps: inputting sewage after RO membrane into a sewage pretreatment device, preheating by a heat exchanger and supplementing heat by an electric heating device, mixing with mixed gas of carbon dioxide and oxygen from a gas pretreatment device, pressurizing, then entering a COD (chemical oxygen demand) and salt separating device, forming a water/carbon dioxide two-phase subcritical state in a reactor, removing COD in the sewage, simultaneously separating out mixed salt in the sewage in the reactor, precipitating into a salt settling tank under the action of gravity, adding a coagulant in the settling tank, cooling, decompressing and dehydrating the solution to obtain a saturated solution of mixed salt of sodium sulfate and sodium chloride, feeding the saturated solution into a mixed salt refining device, respectively preparing potassium sulfate and sodium chloride, and recovering the generated potassium sulfate.

Preferably, the potassium sulfate is recycled, and the sodium chloride is prepared into industrial sodium hypochlorite through a skid-mounted sodium hypochlorite generator.

The method for advanced treatment of the sewage after RO membrane by using the device comprises the following specific steps:

(1) pumping the sewage subjected to the RO membrane from a sewage storage tank through a sewage pressurizing pump, sending the sewage into a first heat exchanger for heat exchange with steam generated by a third gas-liquid separator, then entering a second heat exchanger for heat exchange with high-temperature high-pressure produced water in a reactor, heating the sewage to 230 ℃ for heat supplement through an electric heater, and entering a mixer after the heat exchange of the high-temperature sewage with the temperature increase value of 260 ℃ and 285 ℃;

(2) the recycled carbon dioxide and oxygen are compressed by a compressor and then stored in a buffer tank 11, and then enter a mixer through a pressure reducing valve, and the carbon dioxide gas and the oxygen are dissolved in high-temperature high-pressure sewage and then pumped into a reactor through a pressure pump;

(3) the high-temperature high-pressure sewage and the carbon dioxide gas in the solution reach a sewage/carbon dioxide two-item subcritical/supercritical state in the reactor, oxygen dissolved in water is utilized to remove COD in the solution, meanwhile, salts such as sodium chloride, sodium sulfate and the like in the sewage are separated out and are precipitated at the bottom of the reactor, and a salt separating valve is opened to enrich the salts in a salt settling tank by utilizing the action of gravity;

(4) the produced water of the reactor is cooled by a second heat exchanger, the pressure of the produced water is reduced in a third gas-liquid separator, steam generated by pressure reduction enters a first heat exchanger to preheat sewage, the steam is cooled and then subjected to gas-liquid separation in a fourth gas-liquid separator, the generated carbon dioxide is dried and then enters a compressor to be recycled, and the generated water is used as circulating water for water supplement;

(5) enriching separated salt in a salt settling tank, closing a salt separating valve, leading the salt settling tank to release pressure through a first gas-liquid separator, adding a CL-III coagulant into the salt settling tank to promote the separation of salt and the growth of salt crystals, simultaneously evaporating partial steam, cooling the steam by a cooler, recovering carbon dioxide in the gas by the gas-liquid separator in a fourth gas-liquid separator, drying, and then entering a compressor for recycling, wherein the separated water is used as water supplement of a circulating cooling system;

(6) generating nearly saturated liquid of sodium chloride and sodium sulfate in a salt settling tank after pressure relief, flowing into a potassium sulfate generating kettle through liquid level difference, reacting for 2 hours at 40 ℃ by adding a certain amount of potassium chloride, obtaining agricultural potassium sulfate through centrifugal separation, sending mother liquor into a sodium chloride refining kettle, and refining in the sodium chloride refining kettle to obtain sodium chloride with the content of more than 94%;

(7) sodium chloride is prepared into industrial grade sodium hypochlorite by a sodium hypochlorite generator.

The invention relates to a method for preparing high-salt sewage and mixed gas, which achieves a subcritical/supercritical state of water/carbon dioxide in a reactor, COD in the sewage is decomposed under the state, salt is hardly dissolved in water, thereby achieving the purposes of removing COD and separating salt, the slow stirring of a stirrer in the reactor can prevent the separated salt from depositing on the wall of the reactor in a large amount but depositing at the bottom of the reactor, the salt is enriched in a salt settling tank through a pipeline, a proper amount of CL-coagulant III is added to promote the separation of salt and the growth of salt crystals, the mixed salt is cooled, decompressed and dehydrated through a gas-liquid separator to reach a near saturated solution, the mixed salt enters a mixed salt refining system, a proper amount of potassium chloride is added into a potassium sulfate generating kettle of the mixed salt near saturated solution, agricultural potassium sulfate can be obtained through centrifugal separation, mother liquor enters a sodium chloride refining kettle, and can prepare over 94 percent of sodium chloride, and then the industrial grade sodium hypochlorite is prepared by a sodium hypochlorite generator, and the water quality of the system effluent can reach the national standard of reclaimed water as the water supplement of a circulating cooling system and is used as the water supplement of circulating water.

In conclusion, the invention can lead the water quality of the effluent water of the high-COD and high-salt membrane to reach the national standard of using the reclaimed water as the water supplement of the circulating cooling system, and can comprehensively utilize the mixed salt in the sewage to obtain the agricultural potassium sulfate and the industrial sodium hypochlorite.

Drawings

FIG. 1 is a schematic structural view of the present invention;

in the figure: 1-sewage storage tank, 2-sewage pressure pump, 3-first heat exchanger, 4-second heat exchanger, 5-electric heater, 6-mixer, 7-pressure pump, 8-third gas-liquid separator, 9-fourth gas-liquid separator, 10-compressor, 11-buffer tank, 12-pressure reducing valve, 13-reactor, 14-salt separating valve, 15-salt settling tank, 16-first gas-liquid separator, 17-coagulant tank, 18-cooler, 19-second gas-liquid separator, 20-potassium sulfate generating kettle, 21-sodium chloride refining kettle and 22-sodium hypochlorite generator.

Detailed Description

The invention is further illustrated by the following figures and examples.

The advanced treatment device for sewage after RO membrane shown in FIG. 1 comprises a sewage pretreatment device, a gas pretreatment device, a COD removal and salt separation device and a mixed salt refining device;

the sewage pretreatment device comprises a sewage storage tank 1, a sewage pressure pump 2, a first heat exchanger 3, a second heat exchanger 4, an electric heater 5 and a mixer 6 which are sequentially connected through pipelines;

the gas pretreatment device comprises a compressor 10 and a buffer tank 11 which are sequentially connected through a pipeline;

the COD removing and salt separating device comprises a reactor 13, a salt settling tank 15, a first gas-liquid separator 16, a cooler 18 and a second gas-liquid separator 19 which are connected through pipelines, wherein the salt settling tank 15 is also connected with a coagulant tank 17;

the mixed salt refining device comprises a potassium sulfate generating kettle 20, a sodium chloride refining kettle 21 and a sodium hypochlorite generator 22 which are sequentially connected through a pipeline;

buffer tank 11 be connected with blender 6 through relief pressure valve 12, blender 16 is connected with reactor 13 through force (forcing) pump 7, reactor 13 and third vapour and liquid separator 8 are connected respectively to second heat exchanger 4, third vapour and liquid separator 8 and fourth vapour and liquid separator 9 are connected respectively to first heat exchanger 3, potassium sulphate generate cauldron 20 be connected 16 with salt settling tank 15 and first vapour and liquid separator respectively through the pipeline.

When in operation, sewage is pumped out of the sewage storage tank 1 through the sewage pressurizing pump 2, sent into the first heat exchanger 3, subjected to heat exchange with steam generated by the third gas-liquid separator 8, then sent into the second heat exchanger 4, subjected to heat exchange with high-temperature high-pressure produced water in the reactor 13, subjected to heat exchange with the sewage at a heating value of 200-; the recycled carbon dioxide gas and a small amount of oxygen gas are compressed by a compressor 10 and then stored in a buffer tank 11, then enters a mixer 6 through a pressure reducing valve 12, carbon dioxide gas and oxygen are dissolved in the high-temperature high-pressure sewage, then pumped into a reactor 13 by a pressure pump 7, the sewage and the carbon dioxide gas in the solution reach a sewage/carbon dioxide two-item subcritical/supercritical state in the reactor 13, the COD in the solution is removed by utilizing the oxygen dissolved in the water, simultaneously, under the two subcritical/supercritical states of sewage/carbon dioxide, sodium chloride and sodium sulfate in the sewage are separated out, and the separated-out salt can be prevented from being deposited on the wall of the reactor in a large amount by slowly stirring the stirrer in the reaction process, but is precipitated at the bottom of the reactor, a salt separating valve 14 is opened, and the salt is enriched in a salt settling tank 15 by utilizing the gravity action; when the salt in the salt settling tank 15 is enriched to a certain degree, closing the salt separating valve 14 to ensure that the salt settling tank 15 is decompressed through the first gas-liquid separator 16, adding a proper amount of CL-III coagulant into the salt settling tank 15, wherein the CL-III coagulant can promote the salt to be separated out and salt crystals to grow up, simultaneously evaporating partial water vapor, cooling the water vapor through the cooler 18, recovering carbon dioxide in the gas through the gas-liquid separator in the second gas-liquid separator 19, drying the carbon dioxide, and then entering the compressor 10 for recycling, wherein the water quality of the water separated by the second gas-liquid separator 19 can reach the national standard of reclaimed water as recycled water of a circulating cooling system and is used as recycled water; the salt settling tank 15 after pressure relief is a nearly saturated liquid of sodium chloride and sodium sulfate, the nearly saturated liquid flows into a potassium sulfate generating kettle 20 through liquid level difference, a certain amount of potassium chloride is added into the sodium sulfate generating kettle, the mixture reacts for 2 hours at the temperature of 40 ℃, agricultural-grade potassium sulfate is obtained through centrifugal separation, mother liquor is sent into a sodium chloride refining kettle 21, sodium chloride with the content of over 94 percent is obtained through refining in the sodium chloride refining kettle 21, and the sodium chloride at the moment passes through a sodium hypochlorite generator to prepare an industrial-grade sodium hypochlorite solution which can be used by oneself or sold outside.

The foregoing description of the invention is illustrative and not restrictive, and it will be understood by those skilled in the art that many changes, modifications and equivalents may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.