A method for removing phosphorus from output wastewater in acetic anhydride production

Abstract

The application discloses a phosphorus removal method for output wastewater in acetic anhydride production, relates to the technical field of phosphorus-containing wastewater treatment, and automatically separates and removes organic phosphorus in wastewater by adopting a mode of a preheating system+one-effect vertical pipe falling film evaporation system+two-effect vertical pipe falling film evaporation system+forced circulation evaporation system+evaporation kettle cooperating with an automatic control system+concentration detection system, converts high-concentration phosphorus-containing wastewater into low-concentration phosphorus-containing wastewater, and then converts the low-concentration phosphorus-containing wastewater into dischargeable liquid which meets the discharge standard through a sewage pool treatment system, so that the pollutants in the wastewater can be effectively removed, the pollution of the organic phosphorus to the environment is prevented, the water quality is improved, the water quality is protected, the healthy development of ecology and society is promoted, and the method has high use value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of phosphorus-containing wastewater treatment, in particular to a phosphorus removal method for wastewater produced in acetic anhydride production. BACKGROUND

[0002] An acetic anhydride plant adopts an acetic acid cracking method to obtain acetic anhydride, and the production principle is that acetic acid is cracked to produce ethylene ketone and water under the catalysis of triethyl phosphate at high temperature, and the ethylene ketone is absorbed by acetic acid to produce acetic anhydride products. The production process is as follows: after the outlet gas phase of the cracking furnace is separated by four-stage quenching, the ethylene ketone is absorbed by acetic acid to produce acetic anhydride products, and the acetic acid and water produced by incomplete reaction form an acetic acid aqueous solution which enters a dilute acetic acid storage tank, the dilute acetic acid enters a dilute acetic acid recovery system, high-purity acetic acid is extracted by acetic acid ethyl ester and azeotropic distillation, and then returned to the cracking system for reuse, and the wastewater produced by separation carries phosphates in the reaction process and needs to be purified to avoid direct discharge and pollution.

[0003] Among them, the selection of the wastewater treatment method needs to consider various factors, and the total phosphorus in the wastewater produced by separation is 1500-2000 mg / l, which has a high concentration. At present, the domestic and foreign wastewater phosphorus removal technologies mainly include chemical method and biological method, the chemical method mainly includes coagulation sedimentation, adsorption and other methods, and is mainly suitable for treating inorganic-state phosphorus-containing wastewater, and the biological method mainly includes A / O, A2 / O and other processes, and is mainly suitable for treating low-concentration organic-state phosphorus-containing wastewater. At present, the research on high-concentration organic phosphorus wastewater treatment has never stopped, but an efficient organic phosphorus treatment method has not been found. SUMMARY

[0004] The purpose of the present application is to solve the problems in the background art, and a phosphorus removal method for wastewater produced in acetic anhydride production is proposed.

[0005] The technical solution adopted by the present application to solve the technical problems is as follows:

[0006] A phosphorus removal method for wastewater produced in acetic anhydride production, comprising the following steps:

[0007] Step one, introducing the material into a preheating system to form hot material;

[0008] Step two, the hot material enters a one-effect vertical tube falling film evaporation system in a forward flow process, and at the same time, primary steam is introduced into the one-effect vertical tube falling film evaporation system as a heat source, the hot material is first formed into primary evaporation material through the one-effect vertical tube falling film evaporation system, and then the primary evaporation material and the primary steam are separated into primary concentrated liquid and secondary steam;

[0009] Step three, the primary concentrated liquid is introduced into the two-effect vertical tube falling film evaporation system through the automatic control system, and the secondary steam is introduced into the two-effect vertical tube falling film evaporation system as a heat source. The primary concentrated liquid is first formed into secondary evaporation material through the two-effect vertical tube falling film evaporation system, and then the secondary evaporation material and the secondary steam are separated into the secondary concentrated liquid, the third steam and the primary condensed liquid through gas-liquid separation.

[0010] Step four, the secondary concentrated liquid is introduced into the forced circulation evaporation system through the automatic control system, and the third steam is introduced into the forced circulation evaporation system as a heat source. The secondary concentrated liquid is first formed into third evaporation material through the forced circulation evaporation system, and then the third evaporation material and the third steam are separated into the third concentrated liquid, the fourth steam and the secondary condensed liquid through gas-liquid separation.

[0011] Step five, the third concentrated liquid is detected for concentration through the concentration detection system. When the concentration of the third concentrated liquid reaches the set value, the automatic control system introduces the third concentrated liquid into the evaporation kettle, and the evaporation kettle performs concentration treatment on the third concentrated liquid to obtain the hazardous waste liquid. At the same time, the fourth steam is introduced into the condenser to form the cooling water with a phosphorus content of ≤50mg / l.

[0012] Step six, the hazardous waste liquid is stored, and the primary condensed liquid, the secondary condensed liquid and the cooling water are treated by electrolysis and flocculation to obtain the dischargeable liquid with a phosphorus content of ≤1mg / l.

[0013] Further, the one-effect vertical tube falling film evaporation system comprises a one-effect tube falling film evaporator, a one-effect vapor-liquid separator, a one-effect falling film circulating pump and a one-effect film distributor.

[0014] The hot material is sent to the top of the one-effect tube falling film evaporator by the one-effect falling film circulating pump, and is made to flow in a film shape from top to bottom in the one-effect tube falling film evaporator by the one-effect film distributor. The hot material absorbs heat in the one-effect tube falling film evaporator and evaporates to form the primary evaporation material. The primary evaporation material and the primary steam enter the one-effect vapor-liquid separator to perform gas-liquid separation and form the primary concentrated liquid and the secondary steam.

[0015] Further, the one-effect film distributor adopts a large-aperture, multi-stage falling film distributor.

[0016] The hot material is pumped into the first-stage material plate of the film distributor by the one-effect falling film circulating pump to realize the first distribution of the material, then enters the film distribution weir of the one-effect film distributor to realize the second distribution, then enters the film distribution disc of the one-effect film distributor to realize the third distribution, and finally falls onto the tube bridge of the heat exchange tube of the heater of the one-effect tube falling film evaporator to realize the fourth distribution. Finally, the material forms a uniform film on the inner wall of the heat exchange tube of the heater of the one-effect tube falling film evaporator and is heated and evaporated.

[0017] Further, the two-effect vertical-tube falling-film evaporation system comprises a two-effect tube falling-film evaporator, a two-effect vapor-liquid separator, a two-effect falling-film circulating pump and a two-effect film distributor.

[0018] The primary concentrated liquid is pumped into the two-effect tube falling-film evaporator by the two-effect falling-film circulating pump, and the hot material is made to flow in a film shape from top to bottom in the two-effect tube falling-film evaporator by the two-effect film distributor, the primary concentrated liquid absorbs heat and evaporates to form secondary evaporation material in the two-effect tube falling-film evaporator, and the secondary evaporation material and secondary steam enter the two-effect vapor-liquid separator to be separated into secondary concentrated liquid, tertiary steam and primary condensed liquid.

[0019] Further, the two-effect film distributor adopts a large-aperture multi-stage falling-film distributor.

[0020] The primary concentrated liquid is pumped into the two-effect tube falling-film evaporator by the two-effect falling-film circulating pump, and the hot material is made to flow in a film shape from top to bottom in the two-effect tube falling-film evaporator by the two-effect film distributor, the primary concentrated liquid absorbs heat and evaporates to form secondary evaporation material in the two-effect tube falling-film evaporator, and the secondary evaporation material and secondary steam enter the two-effect vapor-liquid separator to be separated into secondary concentrated liquid, tertiary steam and primary condensed liquid.

[0021] Further, the forced-circulation evaporation system comprises a tube forced-circulation evaporator, a forced vapor-liquid separator and a forced-circulation pump.

[0022] The secondary concentrated liquid is pumped into the forced-circulation evaporator by the forced-circulation pump, and then is heated and evaporated by the forced vapor-liquid separator to form tertiary concentrated liquid, fourth steam and secondary condensed liquid.

[0023] Further, the concentration detection system is electrically connected with the automatic control system and is used for detecting the concentration of the tertiary concentrated liquid in real time, so that when the concentration detection system detects that the concentration of the tertiary concentrated liquid reaches a set value, the automatic control system controls the forced vapor-liquid separator to open, so that the tertiary concentrated liquid is discharged from the forced vapor-liquid separator.

[0024] Further, the sewage pool treatment system comprises an electrolytic cell, a flocculant and a stirrer.

[0025] The primary condensed liquid, the secondary condensed liquid and cooling water are introduced into the electrolytic cell for electrode treatment, then the flocculant is added into the electrolytic cell and high-frequency flocculation stirring is performed by the stirrer, and after static precipitation, the dischargeable liquid with phosphorus content ≤1 mg / l is obtained.

[0026] Further, the one-effect vertical-tube falling-film evaporation system, the two-effect vertical-tube falling-film evaporation system and the forced-circulation evaporation system are respectively provided with a flushing system and a venting opening, when the corresponding pipeline is blocked, the flushing system is started to flush the blockage in the blocked pipeline along the venting opening, so that the smooth operation of the system can be effectively ensured.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] The present application has the advantages of no secondary pollution, high phosphorus removal rate, small occupied area, automatic separation and removal of organic phosphorus in wastewater by using a preheating system + a one-effect vertical tube falling film evaporation system + a two-effect vertical tube falling film evaporation system + a forced circulation evaporation system + an evaporation kettle + a concentration detection system, storage of the produced non-recyclable hazardous waste liquid for handing by an enterprise with a hazardous waste treatment qualification, conversion of high-concentration phosphorus-containing wastewater into low-concentration phosphorus-containing wastewater, and conversion of the low-concentration phosphorus-containing wastewater into dischargeable liquid meeting the discharge standard by a sewage pool treatment system, which can effectively remove pollutants in wastewater, prevent environmental pollution caused by organic phosphorus, improve water quality, protect water quality, and promote the healthy development of ecology and society. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A flowchart of a phosphorus removal method for wastewater produced in acetic anhydride production; DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application. The present application is further described in conjunction with the drawings and embodiments:

[0031] A phosphorus removal method for wastewater produced in acetic anhydride production, comprising the following steps:

[0032] Step one, introducing the material into a preheating system to exchange heat between the material and steam condensate water in the preheating system, thereby increasing the temperature of the material and forming hot material;

[0033] Step two, introducing the hot material into a one-effect vertical tube falling film evaporation system in a co-current process, and introducing primary steam into the one-effect vertical tube falling film evaporation system as a heat source, so that the hot material is first formed into primary evaporation material by the one-effect vertical tube falling film evaporation system, and then the primary evaporation material and the primary steam are separated into primary concentrated liquid and secondary steam by gas-liquid separation;

[0034] Step three, introducing the primary concentrated liquid into a two-effect vertical tube falling film evaporation system by a self-control system, and introducing the secondary steam into the two-effect vertical tube falling film evaporation system as a heat source, so that the primary concentrated liquid is first formed into secondary evaporation material by the two-effect vertical tube falling film evaporation system, and then the secondary evaporation material and the secondary steam are separated into secondary concentrated liquid, tertiary steam and primary condensed liquid by gas-liquid separation;

[0035] Step four, the secondary concentration liquid is introduced into the forced circulation evaporation system through the automatic control system, and the third steam is introduced into the forced circulation evaporation system as a heat source. The secondary concentration liquid is first formed into a third evaporation material through the action of the forced circulation evaporation system, and then the third evaporation material and the third steam are separated into the third concentration liquid, the fourth steam and the secondary condensate through gas-liquid separation;

[0036] Step five, the third concentration liquid is detected for concentration through the concentration detection system. When the concentration of the third concentration liquid reaches the set value, the automatic control system introduces the third concentration liquid into the evaporation kettle, and the evaporation kettle performs concentration treatment on the third concentration liquid to obtain the hazardous waste liquid. At the same time, the fourth steam is introduced into the condenser to form cooling water with a phosphorus content of ≤50 mg / l;

[0037] Step six, the non-recyclable hazardous waste liquid is stored and handed over to an enterprise with hazardous waste treatment qualification for treatment. The primary condensate, the secondary condensate and the cooling water are treated through electrolysis and flocculation to obtain a dischargeable liquid with a phosphorus content of ≤1 mg / l.

[0038] Specifically, for step two, the primary vertical tube falling film evaporation system specifically comprises:

[0039] The primary vertical tube falling film evaporation system comprises a primary tube falling film evaporator, a primary vapor-liquid separator, a primary falling film circulating pump and a primary membrane distributor. The hot material is sent into the top of the primary tube falling film evaporator by the primary falling film circulating pump, and the hot material flows from top to bottom in the form of a film in the primary tube falling film evaporator through the action of the primary membrane distributor. The hot material absorbs heat and evaporates in the primary tube falling film evaporator to form a primary evaporation material. The primary evaporation material and the primary steam enter the primary vapor-liquid separator for gas-liquid separation to form a primary concentration liquid and a secondary steam.

[0040] In the primary vertical tube falling film evaporation system, the primary membrane distributor adopts a large-aperture, multi-stage falling film distributor to uniformly distribute the material liquid to the inner wall of the heat exchange tube of the primary tube falling film evaporator in the form of a uniform film, and to ensure that the primary membrane distributor is not blocked. The hot material is pumped into the first stage of the membrane distributor by the primary falling film circulating pump to realize the first distribution of the material, then enters the membrane weir of the primary membrane distributor for the second distribution, and then enters the membrane disc of the primary membrane distributor for the third distribution, and finally falls onto the tube bridge of the heat exchange tube of the primary tube falling film evaporator for the fourth distribution. Finally, the hot material forms a uniform film on the inner wall of the heat exchange tube of the primary tube falling film evaporator and is heated and evaporated, completing the whole membrane distribution process.

[0041] In step three, the automatic control system specifically comprises:

[0042] The automatic control system is used to control the feeding node. When the secondary vertical tube falling film evaporation system, the forced circulation evaporation system or the evaporation kettle needs to be fed, the automatic control system starts the corresponding feeding action.

[0043] Wherein, for step three, the two-effect vertical-tube falling-film evaporation system specifically comprises:

[0044] The two-effect vertical-tube falling-film evaporation system comprises a two-effect tube falling-film evaporator, a two-effect vapor-liquid separator, a two-effect falling-film circulating pump and a two-effect film distributor. The primary concentrated liquid is sent into the top of the two-effect tube falling-film evaporator by the two-effect falling-film circulating pump, and the hot material is made to flow in a film shape from top to bottom inside the two-effect tube falling-film evaporator by the action of the two-effect film distributor. The primary concentrated liquid absorbs heat and evaporates to form secondary evaporation material inside the two-effect tube falling-film evaporator. The secondary evaporation material and secondary steam enter the two-effect vapor-liquid separator to be separated into gas and liquid and form secondary concentrated liquid, tertiary steam and primary condensed liquid.

[0045] Wherein, for the two-effect vertical-tube falling-film evaporation system, the two-effect film distributor adopts a large-aperture, multi-stage falling-film distributor to make the material liquid uniformly distributed onto the inner wall of the heat exchange tube of the two-effect tube falling-film evaporator in a uniform film shape, and to ensure that the two-effect film distributor is not blocked. The primary concentrated liquid is pumped into the two-stage material plate of the film distributor by the two-effect falling-film circulating pump to realize the first distribution of the material, then enters the film distribution weir of the two-effect film distributor to realize the second distribution, then enters the film distribution disc of the two-effect film distributor to realize the third distribution, and finally falls onto the tube bridge of the heat exchange tube of the two-effect tube falling-film evaporator to realize the fourth distribution, and finally forms a uniform film on the inner wall of the heat exchange tube of the two-effect tube falling-film evaporator to be heated and evaporated, completing the whole film distribution process.

[0046] Wherein, for step four, the forced circulation evaporation system specifically comprises:

[0047] The forced circulation evaporation system comprises a tube forced circulation evaporator, a forced vapor-liquid separator and a forced circulation pump. The secondary concentrated liquid is sent into the heating chamber of the forced circulation evaporator by the forced circulation pump to be heated and circulated, and then evaporated and separated by the forced vapor-liquid separator to form tertiary concentrated liquid, fourth steam and secondary condensed liquid.

[0048] Wherein, for step five, the concentration detection system specifically comprises:

[0049] The concentration detection system is electrically connected with the automatic control system and is used for real-time detection of the concentration of the tertiary concentrated liquid. When the concentration detection system detects that the concentration of the tertiary concentrated liquid reaches a set value, the automatic control system controls the forced vapor-liquid separator to be opened, so that the tertiary concentrated liquid is discharged from the forced vapor-liquid separator.

[0050] Wherein, for step five, the sewage pool treatment system specifically comprises:

[0051] The sewage tank treatment system comprises an electrolytic cell, a flocculant and a stirrer, the primary condensate, the secondary condensate and the cooling water are introduced into the electrolytic cell for electrode treatment, the difficult biodegradable organic matters are decomposed into small molecular organic matters, and the organic phosphorus is converted into inorganic phosphorus, then the flocculant is added into the electrolytic cell, and the high-frequency stirring flocculation treatment is carried out through the stirrer, and the dischargeable liquid with the phosphorus content of less than or equal to 1 mg / l is obtained after static precipitation.

[0052] A phosphorus removal method for output wastewater in acetic anhydride production, which adopts a preheating system + a one-effect vertical tube falling film evaporation system + a two-effect vertical tube falling film evaporation system + a forced circulation evaporation system + an evaporation kettle cooperating with an automatic control system + a concentration detection system to automatically separate and remove organic phosphorus in the wastewater, convert high-concentration phosphorus-containing wastewater into low-concentration phosphorus-containing wastewater, and then convert the low-concentration phosphorus-containing wastewater into dischargeable liquid meeting the discharge standard through a sewage tank treatment system.

[0053] In the implementation process, since the material to be evaporated contains less impurities and has clean water quality, no solid is precipitated in the early concentration process, the risk of overall system blockage and scaling is small, and at a higher temperature, the material has low viscosity and still has good fluidity, therefore, in the early concentration stage, the preheating system + the one-effect vertical tube falling film evaporation system + the two-effect vertical tube falling film evaporation system are selected.

[0054] In the later evaporation stage, the material precipitates crystals, and if the flow speed of the crystals is too slow, the crystals will adhere to the heat exchange surface of the system to form crystal scars and block the system, therefore, the forced circulation evaporation system is adopted; the material is ensured to have a high flow speed under the action of external force, and does forced and intense turbulent flow in the heating chamber of the forced circulation evaporation system, which can increase the heat transfer coefficient and form a scouring effect on the heat exchange surface of the forced circulation evaporation system; and a height difference is formed between the heater and the separator of the forced circulation evaporation system, an appropriate static pressure head is formed through the height difference, the phase change in the heater is prevented, the vaporization only occurs in the separator, and the scaling period of the heater is prolonged.

[0055] After the transformation, the phosphorus-containing wastewater in the acetic anhydride workshop meets the discharge requirements, the total phosphorus content is less than or equal to 1 mg / l, the pollutants can be effectively removed, the pollution of organic phosphorus to the environment is prevented, the water quality is improved, the water quality is protected, and the healthy development of the ecology and the society is promoted.

[0056] In addition, considering that some key pipelines in the one-effect vertical tube falling film evaporation system, the two-effect vertical tube falling film evaporation system and the forced circulation evaporation system are prone to blockage, therefore, a flushing system and a venting opening provided with a valve are arranged in the one-effect vertical tube falling film evaporation system, the two-effect vertical tube falling film evaporation system and the forced circulation evaporation system respectively, when the corresponding pipeline is blocked, the flushing system is started to flush the blockage out of the blocked pipeline along the venting opening, which can effectively ensure smooth operation of the system.

[0057] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for removing phosphorus from waste water produced in acetic anhydride production, comprising the following steps: Step 1: introducing materials into a preheating system to form hot materials; Step 2: introducing the hot materials into a first vertical falling film evaporation system in a forward flow process, and introducing primary steam into the first vertical falling film evaporation system as a heat source, so that the hot materials are first formed into primary evaporation materials by the first vertical falling film evaporation system, and then the primary evaporation materials and the primary steam are separated into primary concentrated liquid and secondary steam; Step 3: introducing the primary concentrated liquid into a second vertical falling film evaporation system by a self-control system, and introducing the secondary steam into the second vertical falling film evaporation system as a heat source, so that the primary concentrated liquid is first formed into secondary evaporation materials by the second vertical falling film evaporation system, and then the secondary evaporation materials and the secondary steam are separated into secondary concentrated liquid, tertiary steam and primary condensed liquid; Step 4: introducing the secondary concentrated liquid into a forced circulation evaporation system by the self-control system, and introducing the tertiary steam into the forced circulation evaporation system as a heat source, so that the secondary concentrated liquid is first formed into tertiary evaporation materials by the forced circulation evaporation system, and then the tertiary evaporation materials and the tertiary steam are separated into tertiary concentrated liquid, quaternary steam and secondary condensed liquid; Step 5: detecting the concentration of the tertiary concentrated liquid by a concentration detection system, and introducing the tertiary concentrated liquid into an evaporation kettle by the self-control system when the concentration of the tertiary concentrated liquid reaches a set value, so that the evaporation kettle is used to concentrate the tertiary concentrated liquid to obtain hazardous waste liquid, and the quaternary steam is introduced into a condenser to form cooling water with a phosphorus content of ≤50 mg / l; Step 6: storing the hazardous waste liquid, and treating the primary condensed liquid, the secondary condensed liquid and the cooling water by electrolysis and flocculation to obtain dischargeable liquid with a phosphorus content of ≤1 mg / l. The first vertical falling film evaporation system comprises a first falling film evaporator, a first vapor-liquid separator, a first falling film circulating pump and a first membrane distributor. The hot materials are pumped into the first falling film circulating pump, distributed on the first membrane plate of the first membrane distributor, then distributed on the membrane weir of the first membrane distributor, and then distributed on the membrane disc of the first membrane distributor, and finally fall on the tube bridge of the heat exchange tube of the heater of the first falling film evaporator to form a uniform film on the inner wall of the heat exchange tube of the heater of the first falling film evaporator. 2.A method for removing phosphorus from waste water produced in acetic anhydride production according to claim 1, wherein the second vertical falling film evaporation system comprises a second falling film evaporator, a second vapor-liquid separator, a second falling film circulating pump and a second membrane distributor. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The primary concentrated liquid is pumped into the top of the double-effect tubular falling film evaporator by the double-effect falling film circulating pump, and the hot material flows from top to bottom in the form of film in the double-effect tubular falling film evaporator by the action of the double-effect film distributor. The primary concentrated liquid absorbs heat and evaporates to form secondary evaporated material in the double-effect tubular falling film evaporator. The secondary evaporated material and secondary steam enter the double-effect vapor-liquid separator for gas-liquid separation to form secondary concentrated liquid, tertiary steam and primary condensed liquid.

3. The method according to claim 2, wherein: The double-effect film distributor uses large-aperture, multi-stage falling film distributors; The primary concentrated liquid is pumped into the secondary plate of the double-effect film distributor to realize the first distribution of the material, then enters the distribution weir of the double-effect film distributor for the second distribution, and then enters the distribution disc of the double-effect film distributor for the third distribution, and finally falls onto the tube bridge of the heat exchange tube of the double-effect tubular falling film evaporator heater for the fourth distribution, and finally forms a uniform film on the inner wall of the heat exchange tube of the double-effect tubular falling film evaporator heater before being heated and evaporated.

4. The method according to claim 2, wherein: The forced circulation evaporation system includes a tubular forced circulation evaporator, a forced vapor-liquid separator and a forced circulation pump; The secondary concentrated liquid is pumped into the heating chamber of the forced circulation evaporator by the forced circulation pump for circulating heating, and then evaporates and separates in the forced vapor-liquid separator to form tertiary concentrated liquid, fourth steam and secondary condensed liquid.

5. The method according to claim 4, wherein: The concentration detection system is electrically connected with the automatic control system and is used for real-time detection of the concentration of the tertiary concentrated liquid, so that when the concentration detection system detects that the concentration of the tertiary concentrated liquid reaches a set value, the automatic control system controls the forced vapor-liquid separator to open to allow the tertiary concentrated liquid to be discharged from the forced vapor-liquid separator.

6. The method according to claim 1, wherein: The sewage pool treatment system includes an electrolytic cell, a flocculant and a stirrer; The primary condensed liquid, the secondary condensed liquid and cooling water are introduced into the electrolytic cell for electrode treatment, then the flocculant is added into the electrolytic cell and high-frequency flocculation stirring is performed by the stirrer, and after static sedimentation, a dischargeable liquid with phosphorus content ≤1 mg / l is obtained.

7. The method according to claim 1, wherein: A flushing system and a vent are respectively arranged in the single-effect vertical tube falling film evaporation system, the double-effect vertical tube falling film evaporation system and the forced circulation evaporation system, and when the corresponding pipeline is blocked, the flushing system is started to flush the blockage in the pipeline out of the vent.

Images