CN116891309B

CN116891309B - High-hardness high-salinity oily sewage treatment system

Info

Publication number: CN116891309B
Application number: CN202310707717.9A
Authority: CN
Inventors: 赵海洋; 姜绪彪; 刘伟; 庞流; 张春志
Original assignee: Huizhou Dayawan Huilu Environment Protection Service Co ltd
Current assignee: Huizhou Dayawan Huilu Environment Protection Service Co ltd
Priority date: 2023-06-14
Filing date: 2023-06-14
Publication date: 2024-05-14
Anticipated expiration: 2043-06-14
Also published as: CN116891309A

Abstract

The sewage treatment system comprises a sewage lifting device, an oil sludge separation device, a divalent cation crystallization separation device, a monovalent ion compensation device, a double-membrane heat balance MVR evaporation concentration device, a secondary denitrification MBR biochemical device, a sterilization and algae removal purification device and a reuse water device in sequence according to the sewage treatment process. The invention firstly removes oil by adopting an oil sludge separating device, secondly removes divalent cations in wastewater by chemical crystallization, and then carries out micro compensation balance on monovalent anions of the wastewater, and then utilizes the physical evaporation characteristic of monovalent ions (sodium salt and potassium salt), concentrates by utilizing an MVR evaporation crystallization system, desalts by a discharging centrifugal device, finally removes COD by denitrification by an MBR biochemical system, finally the system effluent reaches the reuse water standard without the discharge of concentrated liquid, and belongs to the technical field of industrial wastewater treatment in petrochemical industry.

Description

High-hardness high-salinity oily sewage treatment system

Technical Field

The invention relates to the technical field of industrial wastewater treatment in petrochemical industry, in particular to a high-hardness high-salinity oily wastewater treatment system.

Background

In recent years, due to rapid development of market economy, diversification of market demands and diversification of oil extraction processes of crude oil suppliers, partial petroleum companies receive and store crude oil with unfixed varieties, increased salt content in crude oil dehydration (oil tank water cutting), larger fluctuation range of conductivity, and average conductivity of about 4-5 tens of thousands of mu S/cm, and up to about 10 tens of thousands of mu S/cm.

The high-salt-content sewage causes the microorganism inactivation of the traditional sewage treatment biochemical treatment process, the effect of treating the high-conductivity sewage by the traditional sewage treatment facilities (common biochemical process) is poor, and the production and the operation are adversely affected. With the increasing severity of environmental situation, recent pollutant emission standards are continuously exported from the country and place in recent years, and the sewage treated by the common biochemical process cannot meet the recent requirements.

In addition, the conventional sewage treatment process has large occupied area, high energy consumption and uneconomical operation cost, and particularly, the recycling of wastewater treatment cannot be realized in a real sense, so that an demonstration project needs to be established, and a new solution is provided for the high-hardness high-salinity oily sewage. The technical innovation in the water treatment industry needs to be reasonably integrated and developed, and the key points are to overcome the research and development and optimization of high-efficiency energy-saving, high-efficiency biology, low operation cost and various physicochemical biotechnology, and simultaneously, the treatment efficiency and the recycling efficiency are integrally improved. Therefore, the development of an energy-saving efficient high-hardness high-salinity oily wastewater treatment system has very important significance.

Disclosure of Invention

Aiming at the technical problems existing in the prior art, the invention aims at: provides an energy-saving and efficient high-hardness high-salinity oily sewage treatment system.

In order to achieve the above purpose, the invention adopts the following technical scheme: the high-hardness high-salinity oily sewage treatment system sequentially comprises a sewage lifting device, an oil sludge separation device, a divalent cation crystallization separation device, a monovalent ion compensation device, a double-membrane heat balance MVR evaporation concentration device, a secondary denitrification MBR biochemical device, a sterilization and algae removal purification device and a reuse water device according to the sewage treatment process sequence; the sewage lifting device is used for storing and conveying sewage; the oil sludge separating device is used for removing oil sludge in the sewage; the divalent cation crystallization separation device is used for removing divalent cations in the sewage in a chemical crystallization mode; the monovalent ion compensation device is used for supplementing hydrogen ions and chloride ions in the sewage; the double-film heat balance MVR evaporation concentration device is used for evaporating and crystallizing sewage; the secondary denitrification MBR biochemical device is used for denitrifying the sewage; the sterilization and algae removal purifying device is used for sterilizing and algae removal of sewage; the reuse water device is used for storing the treated sewage and conveying the sewage to a user side.

As one preferable mode, the sewage lifting device comprises a sewage storage tank and a sewage lifting pump, and the oil sludge separating device comprises a demulsifier feeder, a polymeric flocculant feeder, a microbubble generator, an oil sludge separator, a first mixer and a second mixer;

The outlet of the sewage storage tank is connected with a sewage lifting pump, the sewage lifting pump and the demulsifier feeder are both connected with the inlet of the first mixer, the outlet of the first mixer and the polymeric flocculant feeder are both connected with the inlet of the second mixer, and the outlet of the second mixer is connected with the microbubble generator;

The upper layer liquid level of the micro-bubble generator is communicated with an oil sludge separator, the oil sludge separator is provided with an oil sludge outlet and a bottom water outlet, the bottom water outlet of the oil sludge separator is communicated with the water outlet of the micro-bubble generator, and the water outlet of the micro-bubble generator is connected with a divalent cation crystallization separation device.

As one preferable, the divalent cation crystallization separation device comprises a sodium carbonate feeder, a sodium hydroxide feeder, an alkalinity regulator, a divalent cation crystal separator, a sludge press filter device, a third mixer, a fourth mixer and a fifth mixer;

the water outlet of the microbubble generator and the sodium carbonate adding device are both connected with the inlet of the third mixer, the outlet of the third mixer and the sodium hydroxide adding device are both connected with the inlet of the fourth mixer, the outlet of the fourth mixer is connected with the alkalinity regulator, the alkalinity regulator and the polymeric flocculant adding device are both connected with the inlet of the fifth mixer, the outlet of the fifth mixer is connected with the divalent cation crystal separator, and the water outlet of the divalent cation crystal separator is connected with the monovalent ion compensation device;

And both the crystal sludge outlet of the divalent cation crystal separator and the sludge outlet of the sludge separator are connected with a sludge filter pressing device.

Preferably, the monovalent ion compensation device comprises a dilute hydrochloric acid feeder, a monovalent ion compensator, a raw liquid pump and an MVR raw liquid storage tank;

The water outlet of the divalent cation crystal separator is connected with a monovalent ion compensator, the dilute hydrochloric acid feeder is connected with the monovalent ion compensator, the monovalent ion compensator is provided with a pH instrument, the monovalent ion compensator is connected with the inlet of a stock solution pump, the outlet of the stock solution pump is connected with an MVR stock solution storage tank, and the MVR stock solution storage tank is connected with a double-film heat balance MVR evaporation concentration device through a feed pump.

As one preferable mode, the double-film heat balance MVR evaporation concentration device comprises a secondary biphase heat balance regulator, an MVR evaporation crystallizer, a secondary steam purifier, a steam compression device, a double-film forced heat exchanger, a mother liquor baume degree callback device, a discharging centrifugal device and a condensate storage tank, wherein the steam compression device comprises a compressor;

The secondary biphase heat balance regulator is provided with a first inlet, a first outlet, a second inlet, a second outlet, a non-condensable gas outlet and a negative pressure regulating interface, the monovalent ion compensation device is connected with the first inlet, the first outlet is connected with the MVR evaporation crystallizer, the MVR evaporation crystallizer is connected with the double-membrane forced heat exchanger, the double-membrane forced heat exchanger is provided with a condensate outlet, the second inlet of the secondary biphase heat balance regulator is connected with a condensate outlet of the double-membrane forced heat exchanger, the second outlet is connected with a condensate storage tank, and the condensate storage tank is connected with the secondary denitrification MBR biochemical device;

The sewage treated by the monovalent ion compensation device enters the secondary biphase heat balance regulator from the first inlet, exchanges heat by the secondary biphase heat balance regulator, is discharged from the first outlet and enters the MVR evaporation crystallizer;

The MVR evaporation crystallizer is provided with a secondary steam outlet, the secondary steam outlet is connected with a secondary steam purifier, the secondary evaporation purifier is connected with a compressor, and the exhaust end of the compressor is connected with a double-film forced heat exchanger;

The MVR evaporation crystallizer is provided with a crystal mixed liquid outlet, the crystal mixed liquid outlet is connected with a discharging centrifugal device, the discharging centrifugal device is connected with an inlet of a mother liquor baume degree callback device, and an outlet of the mother liquor baume degree callback device is connected with a double-film forced heat exchanger.

As one preferable mode, the MVR evaporation crystallizer comprises an evaporation chamber, a thin material chamber, a thick material chamber and a crystallization chamber, wherein a secondary steam outlet is positioned at the top end of the evaporation chamber, the upper end of the thin material chamber and the upper end of the thick material chamber are both communicated with the evaporation chamber, the crystallization chamber is positioned below the thick material chamber and is communicated with the thick material chamber, and a crystal mixed liquid outlet is positioned at the bottom of the crystallization chamber;

The double-film forced heat exchanger comprises a falling film heat exchanger, a rising film heat exchanger and an axial flow pump, wherein the upper end of the falling film heat exchanger is communicated with a thin material chamber, the lower end of the falling film heat exchanger is communicated with the inlet end of the axial flow pump, the outlet end of the axial flow pump is communicated with the lower end of the rising film heat exchanger, and the upper end of the rising film heat exchanger is communicated with a thick material chamber;

The MVR evaporation crystallizer is provided with a feed inlet pipeline communicated with the thin material chamber, and the feed inlet pipeline is connected with a first outlet of the secondary biphase heat balance regulator.

As one preferable mode, a water outlet of the secondary steam purifier is connected with a purifying circulating pump, and an outlet of the purifying circulating pump is respectively connected with the upper part of the secondary steam purifier and an evaporation chamber of the MVR evaporation crystallizer;

The vapor compression device also comprises a vapor regulating valve; the exhaust end and the air inlet end of the compressor are connected through a steam regulating valve.

Preferably, the mother liquor baume degree callback device comprises a cold crystallization filter, a mother liquor tank and a mother liquor pump;

The mother liquor tank is provided with a mother liquor inlet end, a mother liquor outlet end and a mother liquor reflux end, and the outlet of the cold crystallization filter is connected with the mother liquor inlet end of the mother liquor tank;

the inlet end of the mother liquor pump is connected with the mother liquor outlet end of the mother liquor tank, and the outlet end of the mother liquor pump is respectively connected with the mother liquor reflux end of the mother liquor tank and the lower end of the falling film heat exchanger;

The discharging centrifugal device comprises a discharging pump, a heavy liquid separator and a bipolar pushing centrifugal machine, wherein the upper part of the heavy liquid separator is provided with a clear liquid discharge port, the lower part of the heavy liquid separator is provided with a heavy liquid discharge port, and the bipolar pushing centrifugal machine is provided with a mother liquid discharge port and an industrial salt discharge port;

the inlet of the discharging pump is connected with the crystal mixed liquid outlet of the crystallization chamber, the outlet of the discharging pump is connected with the inlet of the heavy liquid separator, the heavy liquid discharge port of the heavy liquid separator is connected with the inlet of the bipolar pushing centrifugal machine, and the clear liquid discharge port of the heavy liquid separator and the mother liquid discharge port of the bipolar pushing centrifugal machine are both connected with the inlet of the cold crystallization filter.

Preferably, the secondary denitrification MBR biochemical device comprises a micro-carbon source feeder, a blower, a secondary denitrification MBR biochemical reactor and an MBR backwashing device;

the secondary denitrification MBR biochemical reactor comprises an MBR water supply pump, a primary denitrification reaction tank, a primary nitrification reaction tank, a secondary denitrification reaction tank, an MBR membrane tank, an MBR reflux pump and an MBR water producing pump;

The primary denitrification reaction tank, the primary nitrification reaction tank, the secondary denitrification reaction tank and the MBR membrane tank are sequentially communicated, a water outlet pipeline of the MBR membrane tank is connected with an MBR water producing pump, and an outlet of the MBR water producing pump is connected with a sterilizing and algae-killing purifying device and an MBR backwashing device;

An inlet end pipeline of the MBR water supply pump is connected with the condensate storage tank, an outlet end pipeline of the MBR water supply pump is connected with the bottom of the primary denitrification reaction tank, an inlet end pipeline of the MBR reflux pump is connected with the bottom of the MBR membrane tank, and an outlet end pipeline of the MBR reflux pump is connected with the bottom of the primary denitrification reaction tank;

the outlet end pipeline of the micro carbon source feeder is connected to the bottom of the secondary denitrification reaction tank, and the outlet end pipeline of the blower is respectively connected to the bottom of the MBR membrane tank, the bottom of the secondary denitrification reaction tank, the alkalinity regulator and the monovalent ion compensator.

Preferably, the sterilizing and algae-killing purifying device comprises a sterilizing agent feeder and a sterilizing and algae-killing purifier;

the outlet pipeline of the bactericide feeder is connected with the sterilizing and algae-killing purifier and the backwashing device, and the outlet pipeline of the blower is also connected into the sterilizing and algae-killing purifier;

The reuse water device comprises a reuse water storage tank and a reuse water pump, wherein the outlet of the sterilization and algae removal purifier is connected with the inlet of the reuse water storage tank, and the outlet of the reuse water storage tank is connected with the reuse water pump.

The principle of the invention is as follows:

According to the high-hardness high-salinity oily sewage treatment system, firstly, oil is removed, secondly, divalent cations in the wastewater are removed through chemical crystallization, and then, trace compensation balance is carried out on monovalent anions of the wastewater. And then utilizing the physical evaporation characteristic of monovalent ions (sodium salt and potassium salt), concentrating by utilizing an MVR evaporation crystallization system, desalting by utilizing a discharging centrifugal device, finally removing nitrogen and COD by utilizing an MBR biochemical system, and finally enabling the effluent of the system to reach the standard of reuse water without discharging concentrated liquid.

Oil substances have great influence on MVR evaporative crystallization and MBR biochemistry, so oil removal is the first step of the process of the invention.

The high efficiency of the oil sludge separation device requires that the density of the micro bubbles generated by the micro bubble generator is high, the oil particles in the water after demulsification and flocculation reaction are bonded with the raised high density micro bubbles, and the mixture has the specific gravity of less than 0.9 and floats on the liquid surface. Oil is effectively removed from the water by separation in a sludge separator. In this step, the removal rate of oil in water reaches 99%.

The core technical point of the oil sludge separation device is a micro-bubble generator, which can use an impeller rotating at a high speed (more than 2980 rpm) to shear with air in water at a high strength to generate micro-bubbles, and can also use a mode of completely mixing pressurized air (more than 0.7 MPa) with water to generate micro-bubbles.

Furthermore, since the high-hardness high-salinity oily sewage contains a large amount of ions such as calcium, magnesium, iron, zinc, copper, ammonia, sodium, sulfate radical, chlorine and the like, the evaporation crystallization coefficients of divalent ions and monovalent ions in an MVR evaporation system are inconsistent, and the calcium, magnesium and the like in the divalent ions have the characteristic of easy scaling, the removal of the divalent ions by adopting a chemical crystallization mode is the second step of the process.

The invention uses the chemical crystallization mode of divalent cations, and under certain alkalinity, the divalent cations are separated in a solid-liquid way in a crystal form by precipitation mode, so that the divalent cations are discharged out of the system. The removal rate of divalent cations such as calcium, magnesium, iron, copper and the like in the wastewater in the process is up to 98.5 percent.

Further, since divalent cations are removed, in order to conduct micro-balance on monovalent ions, the concentration of hydrogen ions is controlled to be 1×10 ^-5 to 10 ^-6 mol/L under the adjustment of dilute hydrochloric acid, and carbonate ions (CO ₃ ^-2) in water overflow in the form of carbon dioxide at the same time, and monovalent ions (anions) are compensated. The purpose of this procedure is to ensure stable discharge of sodium or potassium salts from MVR evaporative crystallization systems and to reduce the amount of subsequent mother liquor produced.

The method for removing sodium salt and potassium salt in wastewater by adopting MVR evaporation crystallization is the third step of the process.

Further, the secondary biphase heat balance regulator and the MVR evaporative crystallizer form an MVR evaporative crystallization system, and sewage is evaporated, concentrated and crystallized in the system. The secondary biphase heat balance regulator is driven by a negative pressure regulating pump, condensate and a non-condensable gas pipe network form micro negative pressure, two phases (gas phase and liquid phase) are respectively subjected to heat exchange with MVR feed sewage, on one hand, the feed temperature of an MVR evaporative crystallization system is controlled through the regulation of the negative pressure, and on the other hand, the condensate of the system can be discharged out of the MVR evaporative crystallization system after being cooled. The pipe network pressure is regulated through the negative pressure regulating pump, so that the heat exchange strength and the feeding temperature are regulated, the feeding temperature and the outlet water temperature of the system are balanced, and the feeding sewage is not required to be heated by using steam additionally.

The double-film forced heat exchanger utilizes the evaporation crystallization characteristic of monovalent ions, combines the characteristics of a climbing film type heat exchange process and a falling film type heat exchange process, and carries out circulating forced heating on sewage under the driving of an axial flow pump, so that the maximum efficiency of heat energy transfer is realized, and meanwhile, the scaling in the heat exchanger of the system is reduced.

Further, the secondary steam purifier is used for washing and purifying the secondary steam evaporated by the MVR evaporation crystallization system, and the washing liquid is returned to the MVR evaporation crystallization system again for circulation. The clean steam after washing enters the steam compression device, and the operation condition of the compressor is more stable and efficient.

The vapor compression device uses a high-speed centrifugal compressor to do work, firstly converts electric energy into kinetic energy, rotates through an ultra-high linear speed impeller, recompresses secondary vapor, and converts the kinetic energy into heat energy by using the enthalpy characteristic of the secondary vapor. The secondary steam enters the double-film forced heat exchanger after being heated, the materials of the system are continuously and circularly heated, the materials are continuously evaporated and crystallized, the continuous heating and continuous salt discharging modes are realized, and the system keeps heat balance all the time without utilizing external steam for heat supply.

The discharging centrifugal device is used for separating heavy liquid from crystal mixed liquid in the crystallization chamber, and the bottom heavy liquid of the heavy liquid separator continuously generates industrial salt through continuous operation of the bipolar pushing centrifugal machine, so that sodium salt, potassium salt and the like are discharged out of the system.

The separated light liquid from the bipolar pushing centrifugal machine and the supernatant liquid from the heavy liquid separator are mixed together to form mother liquid, and the mother liquid can be returned to the MVR evaporative crystallization system after being treated by the Baume degree regulator. The mother liquor discharged from the discharging centrifugal device is rapidly cooled (the temperature difference between the mother liquor and the temperature in the discharging centrifugal device is 5-15 ℃), at the moment, impurities in the mother liquor are rapidly crystallized in the cold crystallization filter, and the impurities in the mother liquor are removed. At this time, the Baume degree of the mother solution is matched with that of the material at the front end of the climbing-film heat exchange, and the mother solution enters the MVR evaporation crystallization system again through the middle part (the rear end of the falling film and the front end of the climbing-film) of the double-film forced heat exchanger, and the mother solution and the material (sewage) of the system are circularly evaporated and crystallized together, so that the total recovery of the mother solution is finally realized.

After being treated by the MVR evaporative crystallization system, sodium salt and potassium salt in raw sewage are removed, and the raw sewage continuously and stably works through a discharging centrifugal device, so that the produced industrial salt can be directly sold.

Further, the BOD/COD ratio in the sewage (condensate) after oil removal and desalination treatment is improved, the B/C ratio is improved from about 0.3 to about 0.4, and the biodegradability of the wastewater is improved by about 10-15%. Therefore, the waste water can be continuously treated by a biochemical treatment process, COD and ammonia nitrogen are removed by the biochemical process, the cost is more economical, and secondary concentrate is not generated.

Further, the removal of COD and ammonia nitrogen in wastewater by adopting an MBR biochemical process is the fourth step of the invention.

The invention utilizes the secondary denitrification MBR biochemical device to stably remove the organic matters in the wastewater and has very obvious effect on denitrification. In the primary denitrification reaction tank, an anoxic working condition is created, a condensate water inlet pipeline and a nitrifying liquid backflow pipeline respectively enter from the bottom of the tank, and under the turbulent fluctuation of water flow, the easily degradable BOD carbon source in the condensate and nitrate ions in the backflow nitrifying liquid are subjected to primary denitrification under the action of denitrifying bacteria, so that an agitator is not additionally used. In the secondary denitrification reaction tank, a trace amount of carbon source (methanol, ethanol or glucose and the like) is used as a supplementary denitrification carbon source according to denitrification effect and requirement, and a flow mode entering from the bottom is adopted to perform secondary denitrification on the nitrified liquid in the primary nitrification reaction tank. The secondary denitrification MBR biochemical device is used for treating, the ammonia nitrogen and total nitrogen removal rate in the wastewater respectively reaches more than 95%, the treatment effect is stable, and the problem that algae are easy to breed due to high total nitrogen concentration in conventional reuse water is solved.

MBR membrane used in the secondary denitrification MBR biochemical device can adopt a traditional immersed ceramic membrane or a hollow fiber PVDF curtain membrane, and as most divalent cations in wastewater are removed by pretreatment, monovalent ions are desalted by an MVR evaporation crystallization system, so that an MBR membrane group is not easy to scale. Compared with the traditional process, the back flushing frequency of the MBR system is reduced by 10-20%, the adding amount of back flushing chemical agents is reduced by 20-30%, the MBR system is more stable and economical to operate, and the MBR system can operate with high efficiency for a long period.

In general, the invention has the following advantages:

(1) According to the invention, the MVR mother liquor is returned to the evaporative crystallization system after the Baume degree is recovered, the mother liquor is not discharged, and the problem of mother liquor treatment of the conventional MVR evaporative crystallization system is solved.

(2) The MVR heat exchange system adopts the double-film forced heat exchanger, breaks the traditional MVR heat exchange mode, has the functions of a falling film type heat exchanger and an up-flow heat exchanger, remarkably enhances the anti-scaling capability, and remarkably improves the heat exchange efficiency.

(3) According to the MVR evaporative crystallization system, the feeding temperature is controlled by using the secondary biphase heat balance regulator, the feeding temperature is controlled and regulated according to the enthalpy balance of the system, external steam is not additionally supplemented under the circulating action of the variable-frequency vapor compression centrifuge, and the system keeps long-period stable operation.

(4) The invention utilizes the secondary steam purifying device to wash and purify the steam generated by MVR evaporation crystallization, can ensure the high-speed stable operation of the steam compression centrifuge, controls the working condition of the centrifuge through the backflow regulating valve of the centrifuge and the frequency converter, saves energy and is efficient, and solves the problems of unstable working condition, high vibration value, easy surge and the like of the steam compression centrifuge in the traditional MVR technology.

(5) In the invention, the equipment model selection surface is wide, the purchase of raw and auxiliary materials is convenient, the MVR evaporation crystallization pretreatment can be carried out step by step in a height difference overflow mode, and the transfer can also be carried out in a pump conveying mode, so that the method is efficient, energy-saving and environment-friendly, is also suitable for upgrading, modifying and upgrading the standard of the traditional sewage treatment station, and has remarkable economy and flexibility.

(6) The traditional MBR membrane technology cannot well solve the problem of membrane scaling due to high conductivity (calcium, magnesium, iron and other ions) in wastewater, and the activity of various aerobic and facultative bacteria is influenced by high salinity, so that the stable operation of the biochemical technology cannot be ensured. After optimization, the method adopts a two-stage denitrification mode, so that the problem that ammonia nitrogen is reduced in the conventional sewage process, but total nitrogen cannot be reduced is solved. The secondary denitrification MVR biochemical reactor is used for denitrification and decarbonization, sterilization, algae removal and purification are carried out, BOD of system effluent is less than or equal to 5mg/L, the number of fecal coliform is less than 40/L, and the quality of recycled water reaches the standard, so that the problem that algae are easy to breed in recycled water recycling is solved.

Drawings

FIG. 1 is a schematic diagram of a high hardness, high salinity oily wastewater treatment system.

FIG. 2 is a process flow diagram of a high hardness, high salinity oily wastewater treatment system.

Wherein, 1 is a sewage lifting device, 2 is an oil sludge separating device, 3 is a divalent cation crystallization separating device, 4 is a monovalent ion compensating device, 5 is a double-membrane heat balance MVR evaporation concentration device, 6 is a secondary denitrification MBR biochemical device, 7 is a sterilization and algae removal purifying device, and 8 is a reuse water device.

11 Is a sewage storage tank, 12 is a sewage lifting pump, 21 is a demulsifier feeder, 2101 is a first mixer, 22 is a polymeric flocculant feeder, 2201 is a second mixer, 23 is a microbubble generator, and 24 is an oil sludge separator.

31 Is sodium carbonate feeder, 32 is sodium hydroxide feeder, 33 is alkalinity regulator, 34 is divalent cation crystal separator, 35 is mud residue filter press device, 3101 is third mixer, 3201 is fourth mixer, 3401 is fifth mixer.

41 Is a dilute hydrochloric acid feeder, 42 is a monovalent ion compensator, 43 is a raw liquid pump, 44 is an MVR raw liquid storage tank, 4401 is a feed pump.

51 Is a secondary biphase heat balance regulator, 52 is an MVR evaporation crystallizer, 53 is a secondary steam purifier, 54 is a steam compression device, 55 is a double-film forced heat exchanger, 56 is a mother liquor baume degree callback device, 57 is a discharging centrifugal device, and 58 is a condensate storage tank.

5101 Is negative pressure regulating pump, 5201 is evaporating chamber, 5202 is thin material chamber, 5203 is dense material chamber, 5204 is crystallization chamber, 5301 is purifying circulating pump, 5401 is compressor, 5402 is steam regulating valve, 5501 is falling film type heat exchanger, 5502 is rising film type heat exchanger, 5503 is axial flow pump, 5601 is cold crystallization filter, 5602 is mother liquid tank, 5603 is mother liquid pump, 5701 is discharge pump, 5702 is heavy liquid separator, 5703 is bipolar pushing centrifuge, 5801 is MBR water feed pump.

61 Is a micro carbon source feeder, 62 is a blower, 63 is a secondary denitrification MBR biochemical reactor, 64 is an MBR backwashing device, 6301 is a primary denitrification reaction tank, 6302 is a primary nitrification reaction tank, 6303 is a secondary denitrification reaction tank, 6304 is an MBR membrane tank, 6305 is an MBR reflux pump, 6306 is an MBR water producing pump, 6401 is a backwashing water tank, 6402 is a backwashing pump, 6403 is a sixth mixer,

71 Is a bactericide feeder and 72 is a sterilizing and algae-killing purifier.

81 Is a reuse water storage tank and 82 is a reuse water pump.

Detailed Description

The invention will be described in further detail with reference to the drawings and the detailed description.

Example 1

The high-hardness high-salinity oily sewage treatment system sequentially comprises a sewage lifting device 1, an oil sludge separation device 2, a divalent cation crystallization separation device 3, a monovalent ion compensation device 4, a double-membrane heat-balance MVR evaporation concentration device 5, a secondary denitrification MBR biochemical device 6, a sterilization and algae removal purification device 7 and a reuse water device 8 according to the sewage treatment process sequence; the sewage lifting device 1 is used for storing and conveying sewage; the oil sludge separating device 2 is used for removing oil sludge in the sewage; the divalent cation crystallization separation device 3 is used for removing divalent cations in the sewage in a chemical crystallization mode; the monovalent ion compensation device 4 is used for supplementing hydrogen ions and chloride ions in the sewage; the double-film heat balance MVR evaporation concentration device 5 is used for evaporating and crystallizing sewage; the secondary denitrification MBR biochemical device 6 is used for denitrifying the sewage; the sterilization and algae removal purifying device 7 is used for sterilizing and algae removal of sewage; the reuse water device 8 is used for storing and delivering the treated sewage to a user side.

The sewage lifting device 1 comprises a sewage storage tank 11 and a sewage lifting pump 12, and the oil sludge separating device 2 comprises a demulsifier feeder 21, a polymeric flocculant feeder 22, a microbubble generator 23, an oil sludge separator 24, a first mixer 2101 and a second mixer 2201;

the outlet of the sewage storage tank is connected with a sewage lifting pump, the sewage lifting pump 12 and the demulsifier feeder 21 are both connected with the inlet of the first mixer 2101, the outlet of the first mixer 2101 and the polymeric flocculant feeder 22 are both connected with the inlet of the second mixer 2201, and the outlet of the second mixer 2201 is connected with the microbubble generator 23;

the upper layer liquid level of the micro-bubble generator 23 is communicated with the sludge separator 24, the sludge separator 24 is provided with a sludge outlet and a bottom water outlet, the bottom water outlet of the sludge separator 24 is communicated with the water outlet of the micro-bubble generator 23, and the water outlet of the micro-bubble generator 23 is connected with the divalent cation crystallization separation device 3.

The microbubble generator 23 adopts a high-speed gas dispersion impeller type process or a pressurized gas dissolving type process. The demulsifier in the demulsifier feeder 21 can be any one of ferric trichloride and polyaluminium chloride, the concentration is controlled to be 3-10%, the polymeric flocculant feeder 22 is anionic polyacrylamide, and the concentration is controlled to be 0.5-3 per mill.

The divalent cation crystallization separation device 3 includes a sodium carbonate feeder 31, a sodium hydroxide feeder 32, an alkalinity adjuster 33, a divalent cation crystal separator 34, a sludge press 35, a third mixer 3101, a fourth mixer 3201, and a fifth mixer 3401;

The water outlet of the microbubble generator 23 and the sodium carbonate feeder 31 are both connected with the inlet of the third mixer 3101, the outlet of the third mixer 3101 and the sodium hydroxide feeder 32 are both connected with the inlet of the fourth mixer 3201, the outlet of the fourth mixer 3201 is connected with the alkalinity regulator 33, the alkalinity regulator 33 and the polymeric flocculant feeder 22 are both connected with the inlet of the fifth mixer 3401, the outlet of the fifth mixer 3401 is connected with the divalent cation crystal separator 34, and the water outlet of the divalent cation crystal separator 34 is connected with the monovalent ion compensation device 4;

The crystal sludge outlet of the divalent cation crystal separator 34 and the sludge outlet of the sludge separator 24 are both connected with a sludge press filter device 35.

The alkalinity adjuster 33 is equipped with a pH meter, and the pH value control range in the alkalinity adjuster is 10.5-11.5.

The divalent cation crystal separator 34 is any one of radial flow, horizontal flow, and inclined plate tube precipitation separation processes. The crystal sludge outlet of the divalent cation crystal separator 34 and the sludge outlet of the sludge separator 24 are connected to the sludge press 35 through a sludge pump 3501.

The monovalent ion compensation device 4 comprises a dilute hydrochloric acid feeder 41, a monovalent ion compensator 42, a stock solution pump 43 and an MVR stock solution storage tank 44;

The water outlet of the divalent cation crystal separator 34 is connected with a monovalent ion compensator 42, the dilute hydrochloric acid feeder 41 is connected with the monovalent ion compensator 42, the monovalent ion compensator 42 is provided with a pH meter, the monovalent ion compensator 42 is connected with the inlet of a raw liquid pump 43, the outlet of the raw liquid pump 43 is connected with an MVR raw liquid storage tank 44, and the MVR raw liquid storage tank 44 is connected with a double-film heat balance MVR evaporation concentration device 5 through a feed pump 4401.

The concentration of hydrochloric acid in the dilute hydrochloric acid feeder 41 is controlled to be 10-20%, and the concentration of hydrogen ions in the monovalent ion compensator is controlled to be 1X 10-5 to 10-6mol/L.

The double-film heat balance MVR evaporation concentration device 5 comprises a secondary biphase heat balance regulator 51, an MVR evaporation crystallizer 52, a secondary steam purifier 53, a steam compression device 54, a double-film forced heat exchanger 55, a mother liquor Baume callback device 56, a discharging centrifugal device 57 and a condensate storage tank 58, wherein the steam compression device 54 comprises a compressor 5401; the compressor 5401 is a high-speed centrifugal compressor.

The secondary biphase heat balance regulator 51 is provided with a first inlet, a first outlet, a second inlet, a second outlet, a non-condensable gas outlet and a negative pressure regulating interface, the monovalent ion compensation device 4 is connected with the first inlet, the first outlet is connected with the MVR evaporation crystallizer 52, the MVR evaporation crystallizer 52 is connected with the double-film forced heat exchanger 55, the double-film forced heat exchanger 55 is provided with a condensate outlet, the second inlet of the secondary biphase heat balance regulator 51 is connected with a condensate outlet of the double-film forced heat exchanger 55, the second outlet is connected with a condensate storage tank 58, and the condensate storage tank 58 is connected with the secondary denitrification MBR biochemical device 6;

the negative pressure regulating interface is connected with a negative pressure regulating pump 5101;

The sewage treated by the monovalent ion compensation device 4 enters the secondary biphase heat balance regulator 51 from the first inlet, exchanges heat by the secondary biphase heat balance regulator 51, is discharged from the first outlet and enters the MVR evaporation crystallizer 52;

The MVR evaporation crystallizer 52 is provided with a secondary steam outlet, the secondary steam outlet is connected with a secondary steam purifier 53, the secondary evaporation purifier 53 is connected with a compressor 5401, and the exhaust end of the compressor 5401 is connected with a double-film forced heat exchanger 55;

The MVR evaporation crystallizer 52 is provided with a crystal mixed liquid outlet, the crystal mixed liquid outlet is connected with a discharging centrifugal device 57, the discharging centrifugal device 57 is connected with the inlet of a mother liquor baume degree callback device 56, and the outlet of the mother liquor baume degree callback device 56 is connected with a double-film forced heat exchanger 55.

The compressor 5401 performs inverter control.

The MVR evaporation crystallizer 52 comprises an evaporation chamber 5201, a thin material chamber 5202, a thick material chamber 5203 and a crystallization chamber 5204, wherein a secondary steam outlet is positioned at the top end of the evaporation chamber 5201, the upper end of the thin material chamber 5202 and the upper end of the thick material chamber 5203 are both communicated with the evaporation chamber 5201, the crystallization chamber 5204 is positioned below the thick material chamber 5203 and is communicated with the thick material chamber 5203, and a crystal mixed liquid outlet is positioned at the bottom of the crystallization chamber 5204;

The double-film forced heat exchanger 55 comprises a falling film heat exchanger 5501, a rising film heat exchanger 5502 and an axial flow pump 5503, wherein the upper end of the falling film heat exchanger 5501 is communicated with a thin material chamber 5202, the lower end of the falling film heat exchanger 5501 is communicated with the inlet end of the axial flow pump 5503, the outlet end of the axial flow pump 5503 is communicated with the lower end of the rising film heat exchanger 5502, and the upper end of the rising film heat exchanger 5502 is communicated with a thick material chamber 5203;

The MVR evaporation crystallizer 52 is provided with a feed inlet pipeline communicated with the thin material chamber 5202, and the feed inlet pipeline is connected with a first outlet of the secondary biphase heat balance regulator 51.

The falling film heat exchanger 5501 and the rising film heat exchanger 5502 are provided with a recompression steam inlet at the upper part, and the exhaust end of the compressor 5401 is connected to the recompression steam inlet. The condensate outlet is provided in the lower part of the falling film heat exchanger 5501 and the rising film heat exchanger 5502.

The axial flow pump 5503 is controlled in a variable frequency mode.

The water outlet of the secondary steam purifier 53 is connected with a purifying circulating pump 5301, and the outlet of the purifying circulating pump 5301 is respectively connected with the upper part of the secondary steam purifier 53 and the evaporation chamber 5201 of the MVR evaporation crystallizer 52;

vapor compression device 54 also includes a vapor regulator valve 5402; the discharge end and the intake end of the compressor 5401 are connected to each other by a steam control valve 5402.

The steam control valve 5402 is any one of an electric control valve and a pneumatic control valve.

The mother liquor baume degree callback device 56 comprises a cold crystallization filter 5601, a mother liquor tank 5602 and a mother liquor pump 5603;

the mother liquor tank 5602 is provided with a mother liquor inlet end, a mother liquor outlet end and a mother liquor reflux end, and the outlet of the cold crystallization filter 5601 is connected with the mother liquor inlet end of the mother liquor tank 5601;

An inlet end of the mother liquor pump 5603 is connected with a mother liquor outlet end of the mother liquor tank 5602, and an outlet end of the mother liquor pump 5603 is respectively connected with a mother liquor reflux end of the mother liquor tank 5602 and a lower end of the falling film heat exchanger 5501;

the discharging centrifugal device 57 comprises a discharging pump 5701, a heavy liquid separator 5702 and a bipolar pushing centrifugal machine 5703, wherein a clear liquid discharge port is arranged at the upper part of the heavy liquid separator 5702, a heavy liquid discharge port is arranged at the lower part of the heavy liquid separator 5702, and the bipolar pushing centrifugal machine 5703 is provided with a mother liquid discharge port and an industrial salt discharge port;

An inlet of the discharge pump 5701 is connected with a crystal mixed liquid outlet of the crystallization chamber 5204, an outlet of the discharge pump 5701 is connected with an inlet of the heavy liquid separator 5702, a heavy liquid discharge port of the heavy liquid separator 5702 is connected with an inlet of the bipolar pushing centrifugal machine 5703, and a clear liquid discharge port of the heavy liquid separator 5702 and a mother liquid discharge port of the bipolar pushing centrifugal machine 5703 are both connected with an inlet of the cold crystallization filter 5601.

The secondary denitrification MBR biochemical device 6 comprises a micro-carbon source feeder 61, a blower 62, a secondary denitrification MBR biochemical reactor 63 and an MBR backwashing device 64;

The secondary denitrification MBR biochemical reactor 63 comprises an MBR water feed pump 5801, a primary denitrification reaction tank 6301, a primary nitrification reaction tank 6302, a secondary denitrification reaction tank 6303, an MBR membrane tank 6304, an MBR reflux pump 6305 and an MBR water producing pump 6306;

The primary denitrification reaction tank 6301, the primary nitrification reaction tank 6302, the secondary denitrification reaction tank 6303 and the MBR membrane tank 6304 are sequentially communicated, an outlet pipeline of the MBR membrane tank 6304 is connected with an MBR water producing pump 6306, and an outlet of the MBR water producing pump 6306 is connected with a sterilizing and algae-killing purifying device 7 and an MBR backwashing device 64;

an inlet end pipeline of the MBR water feed pump 5801 is connected with the condensate storage tank 58, an outlet end pipeline of the MBR water feed pump 5801 is connected with the bottom of the primary denitrification reaction tank 6301, an inlet end pipeline of the MBR reflux pump 6305 is connected with the bottom of the MBR membrane tank 6304, and an outlet end pipeline of the MBR reflux pump 6305 is connected with the bottom of the primary denitrification reaction tank 6301;

The outlet end pipeline of the micro carbon source feeder 61 is connected to the bottom of the secondary denitrification reaction tank 6303, and the outlet end pipeline of the blower 62 is connected to the bottom of the MBR membrane tank 6304, the bottom of the secondary denitrification reaction tank 6303, the alkalinity adjuster 33 and the monovalent ion compensator 42 respectively.

The upper openings of the primary denitrification reaction tank 6301, the primary nitrification reaction tank 6302, the secondary denitrification reaction tank 6303 and the MBR membrane tank 6304 are communicated through the upper openings, and the upper openings of the primary denitrification reaction tank 6301, the primary nitrification reaction tank 6302, the secondary denitrification reaction tank 6303 and the MBR membrane tank 6304 are sequentially arranged from high to low, so that sewage flows sequentially through the height difference.

The sterilizing and algae-killing purifying device 7 comprises a sterilizing agent feeder 71 and a sterilizing and algae-killing purifier 72;

The outlet pipeline of the bactericide feeder 71 is connected with a sterilizing and algae-killing purifier 72 and a backwashing device 64, and the outlet pipeline of the blower 62 is also connected into the sterilizing and algae-killing purifier 72;

The reuse water device 8 comprises a reuse water storage tank 81 and a reuse water pump 82, wherein the outlet of the sterilization and algae removal purifier 72 is connected with the inlet of the reuse water storage tank 81, and the outlet of the reuse water storage tank 81 is connected with the reuse water pump 82.

The MBR backwash device 64 includes a backwash water tank 6401, a backwash pump 6402 and a sixth mixer 6403, wherein an outlet of the MBR water producing pump 6306 is connected to an inlet of the backwash water tank 6401, an outlet of the backwash water tank 6401 is connected to the backwash pump 6402, and an outlet of the backwash pump 6402 and an outlet pipe of the bactericide feeder 71 are both connected to an inlet of the sixth mixer 6403, and an outlet of the sixth mixer 6403 is connected to the MBR water producing pump 6306.

By adopting the system to treat sewage of a certain crude oil depot, the system effluent is detected to reach the open type circulating cooling water supplementing standard in the environmental assessment requirement of the fire water standard in the urban sewage recycling urban miscellaneous Water quality GT/T18920-2020 and the urban sewage recycling-Industrial Water quality GB/T19923-2005. The following are the system implementation parameters.

Treatment scale: daily treatment water amount: 132t/d (5.5 t/h).

Water quality of inlet water:

COD	Conductivity of	NH3-N	Total hardness of	Chlorides (CPS)
					516mg/L	7.8×10⁴μs/cm	83.2	6.79×10³mg/L	3×10⁴mg/L

Water quality of reuse water:

COD

BOD

pH

NH₃-N

TDS

Total phosphorus

Coli bacterium

18mg/L

1.6mg/L

6.7

0.077mg/L

538mg/L

0.18mg/L

40/Liter

Design temperature rise of high-speed centrifugal compressor: 22 ℃.

Double-film heat balance MVR evaporation concentration device control: setting the liquid level of the evaporating chamber to 40 percent, and starting the feeding pump to set the frequency to 40HZ. When the liquid level in the evaporating chamber is higher than 35HZ, the axial flow pump is started, and when the liquid level in the evaporating chamber reaches 18%, the feeding pump is stopped.

MVR stock control: the feeding pump is started, the secondary heat exchange biphase heat balance regulator is manually started, the secondary heat exchange biphase heat balance regulator is slowly started from 5% -10% -15% -20% -30%, and when the steam regulating valve is fully opened by 100%, the set temperature is 101 ℃.

High speed centrifugal compressor control: when the material temperature of the concentrated material chamber reaches 101 ℃, the negative pressure in the secondary steam purifier is about minus 0.015 to minus 0.025 MPa. The high-speed centrifugal compressor was inspected, and the opening degree of the steam adjusting valve was set to 100%. Starting the high-speed centrifugal compressor, setting the pressure frequency to 5HZ, setting the starting step length to 5HZ, and gradually and slowly increasing the frequency from 5-10-15-20-25-30-32-34-36-38-39-40. When the current of the high-speed centrifugal compressor reaches 350A, the steam regulating valve is closed, and is fully closed from 100% -80% -60% -40% -20%, and the current is kept between 340A and 380A through the frequency lifting of the high-speed centrifugal compressor. When the high-speed centrifugal compressor runs normally, the purifying circulating pump is started, the negative pressure regulating pump is started and is switched to be automatic, the feeding pump is started and is switched to be automatic, and the discharging pump is started. Recording related data once per hour according to the requirement of a recording table, sampling and measuring the concentration of materials, and observing the crystallization condition. The above process maintains the high speed centrifugal compressor current between 370A-420A.

Discharging control of the double-film heat balance MVR evaporation concentration device: when 15% of crystals are separated out from the sampled and observed material, the stirring motor of the heavy liquid separator is started, and the discharge pump is started. When the liquid level of the heavy liquid separator reaches 80%, the bipolar pusher centrifuge is started. And (5) observing the discharging speed and slowly adjusting.

And (3) controlling a secondary denitrification MBR biochemical device: the condensate after pretreatment is continuously treated by biochemistry, so as to remove the dissolved COD and ammonia nitrogen in the water. The dissolved oxygen in the water of the primary nitrification reaction tank is controlled to be 1-3mg/L, condensate and reflux nitrifying liquid enter from the bottom of the primary denitrification reaction tank, and wastewater subjected to denitrification treatment overflows from the upper part of the primary denitrification reaction tank to the primary nitrification reaction tank. The sewage after the aeration treatment of the primary nitrification reaction tank overflows to the secondary denitrification reaction tank, at the moment, the activated sludge slowly precipitates from top to bottom, and the micro carbon source enters from the bottom of the secondary denitrification reaction tank and flows from bottom to top. The wastewater of the secondary denitrification reaction tank overflows to the MBR membrane tank, the aeration of the module is controlled, so that the muddy water forms cross flow on the outer surface of the membrane filaments, water is produced by a single group of membranes for 8 minutes, the water is stopped for 2 minutes, 10 minutes is a water production period, the 6 water production periods are backwashed for one time, and chemical backwashing is carried out in 24 backwashing periods.

And (3) cleaning reuse water: and after the MBR produced water is purified by the sterilization and algae removal purifier, the MBR produced water is conveyed to a reuse water storage tank, the water quality of the reuse water is monitored every day, and the reuse water pump makeup water is started according to the production/fire protection system requirements.

The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.

Claims

1. A high hardness high salinity oily sewage treatment system which is characterized in that: the sewage treatment device sequentially comprises a sewage lifting device (1), an oil sludge separation device (2), a divalent cation crystallization separation device (3), a monovalent ion compensation device (4), a double-membrane heat balance MVR evaporation concentration device (5), a secondary denitrification MBR biochemical device (6), a sterilization and algae removal purification device (7) and a reuse water device (8) according to the sewage treatment process sequence;

The sewage lifting device (1) is used for storing and conveying sewage;

the oil sludge separating device (2) is used for removing oil sludge in the sewage;

The divalent cation crystallization separation device (3) is used for removing divalent cations in the sewage in a chemical crystallization mode;

the monovalent ion compensation device (4) is used for supplementing hydrogen ions and chloride ions in the sewage;

the double-film heat balance MVR evaporation concentration device (5) is used for evaporating and crystallizing sewage;

the secondary denitrification MBR biochemical device (6) is used for denitrifying the sewage;

the sterilization and algae removal purifying device (7) is used for sterilizing and algae removal of sewage;

the reuse water device (8) is used for storing the treated sewage and conveying the sewage to a user side;

The sewage lifting device (1) comprises a sewage storage tank (11) and a sewage lifting pump (12), and the oil sludge separating device (2) comprises a demulsifier feeder (21), a polymeric flocculant feeder (22), a microbubble generator (23), an oil sludge separator (24), a first mixer (2101) and a second mixer (2201);

the outlet of the sewage storage tank (11) is connected with a sewage lifting pump (12), the sewage lifting pump (12) and the demulsifier feeder (21) are both connected with the inlet of the first mixer (2101), the outlet of the first mixer (2101) and the polymeric flocculant feeder (22) are both connected with the inlet of the second mixer (2201), and the outlet of the second mixer (2201) is connected with a microbubble generator (23);

The upper layer liquid level of the micro-bubble generator (23) is communicated with an oil sludge separator (24), the oil sludge separator (24) is provided with an oil sludge outlet and a bottom water outlet, the bottom water outlet of the oil sludge separator (24) is communicated with the water outlet of the micro-bubble generator (23), and the water outlet of the micro-bubble generator (23) is connected with a divalent cation crystallization separation device (3);

the divalent cation crystallization separation device (3) comprises a sodium carbonate feeder (31), a sodium hydroxide feeder (32), an alkalinity regulator (33), a divalent cation crystal separator (34), a sludge press filter device (35), a third mixer (3101), a fourth mixer (3201) and a fifth mixer (3401);

The water outlet of the microbubble generator (23) and the sodium carbonate feeder (31) are both connected with the inlet of the third mixer (3101), the outlet of the third mixer (3101) and the sodium hydroxide feeder (32) are both connected with the inlet of the fourth mixer (3201), the outlet of the fourth mixer (3201) is connected with the alkalinity regulator (33), the alkalinity regulator (33) and the polymeric flocculant feeder (22) are both connected with the inlet of the fifth mixer (3401), the outlet of the fifth mixer (3401) is connected with the divalent cation crystal separator (34), and the water outlet of the divalent cation crystal separator (34) is connected with the monovalent ion compensation device (4);

The crystal mud outlet of the divalent cation crystal separator (34) and the oil mud outlet of the oil mud separator (24) are both connected with a mud residue filter pressing device (35); the monovalent ion compensation device (4) comprises a dilute hydrochloric acid feeder (41), a monovalent ion compensator (42), a stock solution pump (43) and an MVR stock solution storage tank (44);

The water outlet of the divalent cation crystal separator (34) is connected with a monovalent ion compensator (42), the dilute hydrochloric acid adding device (41) is connected with the monovalent ion compensator (42), a pH instrument is arranged on the monovalent ion compensator (42), the monovalent ion compensator (42) is connected with the inlet of a stock solution pump (43), the outlet of the stock solution pump (43) is connected with an MVR stock solution storage tank (44), and the MVR stock solution storage tank (44) is connected with a double-film heat balance MVR evaporation concentration device (5) through a feed pump (4401);

The double-film heat balance MVR evaporation concentration device (5) comprises a secondary biphase heat balance regulator (51), an MVR evaporation crystallizer (52), a secondary steam purifier (53), a steam compression device (54), a double-film forced heat exchanger (55), a mother liquor Baume degree callback device (56), a discharging centrifugal device (57) and a condensate storage tank (58), wherein the steam compression device (54) comprises a compressor (5401);

The secondary biphase heat balance regulator (51) is provided with a first inlet, a first outlet, a second inlet, a second outlet, a non-condensable gas outlet and a negative pressure regulating interface, the monovalent ion compensation device (4) is connected with the first inlet, the first outlet is connected with the MVR evaporation crystallizer (52), the MVR evaporation crystallizer (52) is connected with the double-film forced heat exchanger (55), the double-film forced heat exchanger (55) is provided with a condensate outlet, the second inlet of the secondary biphase heat balance regulator (51) is connected with the condensate outlet of the double-film forced heat exchanger (55), the second outlet is connected with the condensate storage tank (58), and the condensate storage tank (58) is connected with the secondary denitrification MBR biochemical device (6);

The sewage treated by the monovalent ion compensation device (4) enters the secondary biphase heat balance regulator (51) from the first inlet, exchanges heat by the secondary biphase heat balance regulator (51), is discharged from the first outlet and enters the MVR evaporation crystallizer (52);

the MVR evaporation crystallizer (52) is provided with a secondary steam outlet, the secondary steam outlet is connected with a secondary steam purifier (53), the secondary evaporation purifier (53) is connected with a compressor (5401), and the exhaust end of the compressor (5401) is connected with a double-film forced heat exchanger (55);

The MVR evaporation crystallizer (52) is provided with a crystal mixed liquid outlet, the crystal mixed liquid outlet is connected with a discharging centrifugal device (57), the discharging centrifugal device (57) is connected with the inlet of a mother liquor baume degree callback device (56), and the outlet of the mother liquor baume degree callback device (56) is connected with a double-film forced heat exchanger (55);

The MVR evaporation crystallizer (52) comprises an evaporation chamber (5201), a thin material chamber (5202), a thick material chamber (5203) and a crystallization chamber (5204), wherein a secondary steam outlet is formed in the top end of the evaporation chamber (5201), the upper end of the thin material chamber (5202) and the upper end of the thick material chamber (5203) are both communicated with the evaporation chamber (5201), the crystallization chamber (5204) is located below the thick material chamber (5203) and is communicated with the thick material chamber (5203), and a crystal mixed liquid outlet is formed in the bottom of the crystallization chamber (5204);

The double-film forced heat exchanger (55) comprises a falling film type heat exchanger (5501), a rising film type heat exchanger (5502) and an axial flow pump (5503), wherein the upper end of the falling film type heat exchanger (5501) is communicated with a thin material chamber (5202), the lower end of the falling film type heat exchanger (5501) is communicated with the inlet end of the axial flow pump (5503), the outlet end of the axial flow pump (5503) is communicated with the lower end of the rising film type heat exchanger (5502), and the upper end of the rising film type heat exchanger (5502) is communicated with a thick material chamber (5203);

a feed inlet pipeline communicated with the thin material chamber (5202) is arranged on the MVR evaporation crystallizer (52), and is connected with a first outlet of the secondary biphase heat balance regulator (51);

the water outlet of the secondary steam purifier (53) is connected with a purifying circulating pump (5301), and the outlet of the purifying circulating pump (5301) is respectively connected with the upper part of the secondary steam purifier (53) and the evaporation chamber (5201) of the MVR evaporation crystallizer (52);

the vapor compression device (54) further comprises a vapor regulating valve (5402); the exhaust end and the air inlet end of the compressor (5401) are connected through a steam regulating valve (5402);

the mother liquor baume degree callback device (56) comprises a cold crystallization filter (5601), a mother liquor tank (5602) and a mother liquor pump (5603);

The mother liquor tank (5602) is provided with a mother liquor inlet end, a mother liquor outlet end and a mother liquor reflux end, and the outlet of the cold crystallization filter (5601) is connected with the mother liquor inlet end of the mother liquor tank (5601);

The inlet end of the mother liquor pump (5603) is connected with the mother liquor outlet end of the mother liquor tank (5602), and the outlet end of the mother liquor pump (5603) is respectively connected with the mother liquor reflux end of the mother liquor tank (5602) and the lower end of the falling film heat exchanger (5501);

the discharging centrifugal device (57) comprises a discharging pump (5701), a heavy liquid separator (5702) and a bipolar pushing centrifugal machine (5703), wherein a clear liquid discharge port is arranged at the upper part of the heavy liquid separator (5702), a heavy liquid discharge port is arranged at the lower part of the heavy liquid separator (5702), and a mother liquid discharge port and an industrial salt discharge port are arranged on the bipolar pushing centrifugal machine (5703);

an inlet of the discharging pump (5701) is connected with a crystal mixed liquid outlet of the crystallization chamber (5204), an outlet of the discharging pump (5701) is connected with an inlet of the heavy liquid separator (5702), a heavy liquid discharge port of the heavy liquid separator (5702) is connected with an inlet of the bipolar pushing centrifugal machine (5703), and a clear liquid discharge port of the heavy liquid separator (5702) and a mother liquid discharge port of the bipolar pushing centrifugal machine (5703) are both connected with an inlet of the cold crystallization filter (5601);

The secondary denitrification MBR biochemical device (6) comprises a micro-carbon source feeder (61), a blower (62), a secondary denitrification MBR biochemical reactor (63) and an MBR backwashing device (64);

The secondary denitrification MBR biochemical reactor (63) comprises an MBR water feed pump (5801), a primary denitrification reaction tank (6301), a primary nitrification reaction tank (6302), a secondary denitrification reaction tank (6303), an MBR membrane tank (6304), an MBR reflux pump (6305) and an MBR water producing pump (6306);

The primary denitrification reaction tank (6301), the primary nitrification reaction tank (6302), the secondary denitrification reaction tank (6303) and the MBR membrane tank (6304) are sequentially communicated, an outlet pipeline of the MBR membrane tank (6304) is connected with an MBR water producing pump (6306), and an outlet of the MBR water producing pump (6306) is connected with a sterilizing and algae-killing purifying device (7) and an MBR backwashing device (64);

an inlet end pipeline of an MBR water feed pump (5801) is connected with a condensate storage tank (58), an outlet end pipeline of the MBR water feed pump (5801) is connected with the bottom of a primary denitrification reaction tank (6301), an inlet end pipeline of an MBR reflux pump (6305) is connected with the bottom of an MBR membrane tank (6304), and an outlet end pipeline of the MBR reflux pump (6305) is connected with the bottom of the primary denitrification reaction tank (6301);

an outlet end pipeline of the micro carbon source feeder (61) is connected to the bottom of the secondary denitrification reaction tank (6303), and an outlet end pipeline of the blower (62) is connected to the bottom of the MBR membrane tank (6304), the bottom of the secondary denitrification reaction tank (6303), the alkalinity regulator (33) and the monovalent ion compensator (42) respectively;

the sterilizing and algae-killing purifying device (7) comprises a sterilizing agent feeder (71) and a sterilizing and algae-killing purifier (72);

An outlet pipeline of the bactericide feeder (71) is connected with a sterilizing and algae-killing purifier (72) and an MBR backwashing device (64), and an outlet pipeline of the blower (62) is also connected into the sterilizing and algae-killing purifier (72);

the reuse water device (8) comprises a reuse water storage tank (81) and a reuse water pump (82), wherein the outlet of the sterilization and algae removal purifier (72) is connected with the inlet of the reuse water storage tank (81), and the outlet of the reuse water storage tank (81) is connected with the reuse water pump (82).