Supercritical hydrothermal combustion reactor for recovering salt from organic wastewater and its application

Abstract

The present invention relates to the field of high-salt organic wastewater treatment and resource utilization, and specifically to a supercritical hydrothermal combustion reactor for recovering salt from organic wastewater and its application. The reactor comprises a top cover and a cylindrical cavity surrounded by a pressure-bearing wall; the cylindrical cavity comprises a hydrothermal combustion reaction chamber, a quenching chamber and a subcritical water chamber connected by fluid from top to bottom; the annular gap between the evaporation wall and the pressure-bearing wall of the hydrothermal combustion reaction chamber is an evaporation wall area; a first gas-liquid mixing injection device is installed on the top cover; a purified water outlet is provided on the upper part of the side wall of the hydrothermal combustion reaction chamber, and a second gas-liquid mixing injection device is installed in the middle part of the side wall; the annular gap between the permeable wall and the pressure-bearing wall of the quenching chamber is a cooling water chamber; a high-salt water outlet is provided at the bottom of the subcritical water chamber. The reactor can effectively degrade organic matter in wastewater, and the obtained high-salt water can obtain salt that meets industrial standards after evaporation and crystallization.

Description

Technical Field

[0001] The invention relates to the field of high-salt organic wastewater treatment and resource utilization, and in particular to a supercritical hydrothermal combustion reactor, system and process for recovering salt from organic wastewater. Background Art

[0002] Industrial wastewater is an important part of water pollution control. The discharge of high-salt wastewater in industrial wastewater increases year by year. This type of wastewater has high salt content, complex composition and high toxicity, which brings huge challenges to the current wastewater treatment and recycling. This type of wastewater mainly comes from the production process of chemical industries such as pesticides, chemicals, medicines, printing and dyeing, coal chemical industry and oil and gas extraction industry. In addition, it also includes concentrated brine produced by other wastewater treatment processes such as reverse osmosis, electrodialysis, evaporation and concentration. If high-salt wastewater is discharged directly, the salt in the wastewater will damage the soil environment, increase the salt content in the water body, and waste precious mineral resources.

[0003] In order to achieve salt recovery from high-salt organic wastewater (usually refers to wastewater with a salt content greater than 5% or concentrated by reverse osmosis, electrodialysis, etc.) and make it meet the standards of industrial salt, the industry usually adopts the following practices: (1) First evaporate and crystallize the high-salt organic wastewater to produce solid salt, and then purify the solid salt to remove organic pollutants; (2) Remove organic matter from the high-salt wastewater under a high-salt environment, and then evaporate and crystallize to obtain clean solid salt. Regarding the first method, the industry currently adopts high-temperature incineration, thermal cracking and superheated steam carbonization, but there are problems such as high equipment investment cost and operating cost, and easy to generate secondary pollution. Regarding the second method, since high-salt organic wastewater contains salt and a large amount of toxic, harmful and difficult to biodegrade organic matter, it is difficult to effectively remove it using traditional microbial methods and conventional advanced oxidation technologies (such as Fenton reagent, ozone catalysis, etc.), and it is difficult to make the solid salt after evaporation and crystallization meet the standards of industrial salt.

[0004] Supercritical water oxidation (SCWO, Super Critical Water Oxidation) is an oxidation reaction of organic matter with water and carbon dioxide as the main products under the conditions of temperature and pressure higher than the critical temperature (374.2℃) and critical pressure (22.05MPa) of water, using the characteristics of supercritical water (SCW) to cause the oxidation reaction of organic matter under the homogeneous conditions of supercritical water with water and carbon dioxide as the main products. Due to the problems of thorough reaction and no secondary pollution, supercritical water oxidation has received more and more attention in the industry. In actual engineering applications, SCWO technology is difficult to achieve large-scale application due to the corrosiveness of materials and the blockage caused by the precipitation of salts. In order to solve these two problems, supercritical hydrothermal combustion technology has been developed. Supercritical hydrothermal combustion (SCHC) refers to a new type of combustion method in which fuel or a certain concentration of organic matter and oxidant undergo a violent oxidation reaction in supercritical water (temperature>3740C, pressure>22MPa) to produce a water-heat flame. When a hydrothermal flame is used as the heat source inside the supercritical water oxidation reactor, the reactor inlet material can enter the reactor directly without preheating to the supercritical temperature. The high temperature generated by the supercritical hydrothermal flame is used to directly heat the inlet material to a temperature above the supercritical temperature and the oxidation reaction occurs quickly. Since the inlet material is processed inside the reactor, the corrosion of the pipeline and heat exchanger and the salt deposition problems are reduced. Summary of the invention

[0005] In view of the existing problems in the purification and salt recovery of high-salt organic wastewater, the present invention provides a supercritical hydrothermal combustion reactor and a treatment process thereof, which can effectively degrade organic matter in wastewater under a high-salt environment so that the salt after evaporation and crystallization meets the standards of industrial salt.

[0006] The present invention provides a supercritical hydrothermal combustion reactor for recovering salt from organic wastewater, comprising a top cover 30 and a cylindrical cavity surrounded by a pressure-bearing wall 04, characterized in that:

[0007] The cylindrical cavity includes, from top to bottom, a hydrothermal combustion reaction chamber 05, a quenching chamber 08 and a subcritical water chamber 14 which are fluid-connected;

[0008] The side wall of the hydrothermal combustion reaction chamber 05 includes an outer pressure-bearing wall 04 and an inner evaporation wall 03; the annular gap between the evaporation wall 03 and the pressure-bearing wall 04 is an evaporation wall area 10; the pressure-bearing wall 04 is provided with an evaporation wall area water inlet 06 and an evaporation wall area water outlet 07;

[0009] The top cover 30 is provided with a first gas-liquid mixing injection device 01 for mixing fuel and oxidant and injecting them into the hydrothermal combustion reaction chamber 05; the upper part of the side wall of the hydrothermal combustion reaction chamber 05 is provided with a purified water outlet 15, and the middle part of the side wall is provided with a second gas-liquid mixing injection device 02 for mixing sewage and oxidant and injecting them into the hydrothermal combustion reaction chamber 05;

[0010] The side wall of the quenching chamber 08 includes an outer pressure-bearing wall 04 and an inner permeable wall 09; the annular gap between the permeable wall 09 and the pressure-bearing wall 04 is a cooling water chamber 13; the pressure-bearing wall 04 is provided with a cooling water chamber water inlet 11 and a cooling water chamber water outlet 12;

[0011] A high-salt water outlet 16 is provided at the bottom of the subcritical water chamber 14 .

[0012] Preferably, the upper end of the first gas-liquid mixing injection device 01 is located outside the hydrothermal combustion reaction chamber 05 and is provided with a fuel inlet and an oxygen inlet, the middle is provided with a mixing chamber for mixing fuel and oxygen, and the lower end is located inside the hydrothermal combustion reaction chamber 05 and is provided with a fuel nozzle opening facing downward.

[0013] Preferably, one end of the second gas-liquid mixing injection device 02 is located outside the hydrothermal combustion reaction chamber 05 and is provided with a sewage inlet and an oxygen-enriched air inlet, and the other end extends into the hydrothermal combustion reaction chamber 05 and is provided with a material nozzle with an opening facing the central axis of the hydrothermal combustion reaction chamber 05.

[0014] Preferably, the evaporation wall zone water inlet 06 is arranged on the pressure-bearing wall 04 at the lower part of the evaporation wall zone 10 , and the evaporation wall zone water outlet 07 is arranged on the pressure-bearing wall 04 at the upper part of the evaporation wall zone 10 .

[0015] Preferably, the cooling water chamber water inlet 11 is arranged on the pressure-bearing wall 04 at the lower part of the cooling water chamber 13 , and the cooling water chamber water outlet 12 is arranged on the pressure-bearing wall 04 at the upper part of the cooling water chamber 13 .

[0016] Preferably, the porosity of the permeable wall 09 increases gradually from top to bottom.

[0017] Preferably, the upper portion of the permeable wall 09 is in an inverted cone shape, and the lower portion is in a cylindrical shape.

[0018] Preferably, two or more evenly arranged first gas-liquid mixing injection devices 01 are provided on the top cover 30 .

[0019] Preferably, at least one layer of second gas-liquid mixing injection device 02 is provided in the middle of the side wall of the hydrothermal combustion reaction chamber 05, and each layer is provided with two or more second gas-liquid mixing injection devices 02 arranged in the form of colliding flows.

[0020] The present invention also provides a system for recovering salt from high-salt organic wastewater, characterized in that it includes any of the supercritical hydrothermal combustion reactors described above, and a fuel pipeline, a first oxidant pipeline, a sewage pipeline and a second oxidant pipeline connected to the reactor.

[0021] Preferably, the fuel pipeline includes a fuel tank 19, a fuel tank auxiliary booster pump 20, a hydraulic jet pump 21 and a first heat exchanger 22 which are connected in sequence through pipelines; the hydraulic jet pump 21 is provided with a fuel inlet, a water inlet and a liquid outlet, the liquid outlet of which is connected to the fuel inlet of the first heat exchanger 22, and the fuel outlet of the first heat exchanger 22 is connected to the fuel inlet of the first gas-liquid mixing injection device 01 of the reactor; the hot water inlet of the first heat exchanger 22 is connected to the purified water outlet 15 of the reactor, and the hot water outlet is connected to the water inlet of the hydraulic jet pump 21;

[0022] The first oxidant pipeline includes a liquid oxygen storage tank 24, a liquid oxygen high-pressure pump 32 and a liquid oxygen vaporizer 25 which are connected in sequence through pipelines; the oxygen outlet of the liquid oxygen vaporizer 25 is connected to the oxygen inlet of the first gas-liquid mixing injection device 01;

[0023] The sewage pipeline includes a sewage regulating tank 17 and a sewage high-pressure pump 18 connected by a pipeline; the outlet of the sewage high-pressure pump 18 is connected to the sewage inlet of the second gas-liquid mixing injection device 02 of the reactor;

[0024] The second oxidant pipeline includes an oxygen-enriched air production device 31, whose oxygen-enriched air outlet is connected to the oxygen-enriched air inlet of the second gas-liquid mixing injection device 02;

[0025] The high-salt water outlet 16 of the reactor is connected to the brine inlet of the second heat exchanger 26 , and the brine outlet of the second heat exchanger 26 is connected to the multi-effect evaporation crystallizer 27 .

[0026] Preferably, the hot water outlet of the first heat exchanger 22 is also connected to the inlet of the steam-water separator 23; the water outlet of the steam-water separator 23 is connected to the water inlet of the condensed water storage tank 28;

[0027] The water outlet of the multi-effect evaporation crystallizer 27 is connected to the water inlet of the condensed water storage tank 28;

[0028] The evaporation wall area water outlet 07 and the cooling water chamber water outlet 12 of the reactor are connected to the water inlet of the condensed water storage tank 28;

[0029] The water outlet of the condensed water storage tank 28 is respectively connected to the inlet of the condensed water high-pressure pump 29 and the cold water inlet of the second heat exchanger 26; the outlet of the condensed water high-pressure pump 29 is respectively connected to the evaporation wall area water inlet 06 of the reactor and the cooling water chamber water inlet 11.

[0030] The present invention also provides a process for recovering salt from high-salt organic wastewater, characterized in that: using any of the above-mentioned supercritical hydrothermal combustion reactors or any of the above-mentioned systems, the steps are as follows:

[0031] The liquid fuel and the first oxidant preheated to the auto-ignition temperature are continuously introduced into the first gas-liquid mixing injection device 01; the sewage and the second oxidant at room temperature are continuously introduced into the second gas-liquid mixing injection device 02;

[0032] The fuel and the first oxidant are fully mixed in the first gas-liquid mixing injection device 01 and then sprayed into the hydrothermal combustion reaction chamber 05 in a supercritical water state, generating a stable supercritical hydrothermal flame; the sewage and the second oxidant are sprayed into the hydrothermal combustion reaction chamber 05 through the second gas-liquid mixing injection device 02, and the atomized sewage particles are rapidly heated to a temperature above the supercritical state by the supercritical hydrothermal flame and an oxidation reaction occurs rapidly, oxidizing the organic pollutants into water and carbon dioxide;

[0033] The salt in the sewage precipitates under the supercritical state and sinks into the quenching chamber 08. The cooling water in the cooling water chamber 13 enters the quenching chamber 08 through the permeable wall 09, quickly cooling the supercritical water to a subcritical state, so that the precipitated salt is redissolved in the water, and the obtained high-salt water is discharged through the high-salt water outlet 16, and the solid salt is recovered through the multi-effect evaporation crystallizer 27.

[0034] Preferably, the first oxidant is oxygen, and the second oxidant is oxygen-enriched air.

[0035] Preferably, the liquid fuel is pressurized by a hydraulic jet pump 21 and then heated by a first heat exchanger 22 before entering the first gas-liquid mixing injection device 01;

[0036] The high-temperature and high-pressure water discharged from the purified water outlet 15 enters the first heat exchanger 22 to heat the liquid fuel; a portion of the high-temperature and high-pressure water after heat exchange enters the hydraulic jet pump 21, where the fuel and water are mixed and pressurized, and another portion of the high-temperature and high-pressure water enters the steam-water separator 23, and the separated water enters the condensed water storage tank 28;

[0037] The high-salt water discharged from the high-salt water outlet 16 is passed through the second heat exchanger 26 to recover heat and then enter the multi-effect evaporation crystallizer 27 to obtain solid salt and condensed water, and the condensed water enters the condensed water storage tank 28;

[0038] The water discharged through the evaporation wall area outlet 07 and the cooling water chamber outlet 12 enters the condensed water storage tank 28;

[0039] A portion of the water in the condensed water storage tank 28 enters the evaporation wall area 10 and the cooling water chamber 13 after being pressurized by the condensed water high-pressure pump 29 , and the other portion of the water enters the second heat exchanger 26 .

[0040] The supercritical hydrothermal combustion reactor of the present invention preferably uses liquid oxygen as an oxygen source, and the liquid oxygen is heated into oxygen by a liquid oxygen vaporizer and enters the first gas-liquid mixing injection device 01 after reaching the auto-ignition temperature of the fuel. The fuel and a portion of the high-temperature and high-pressure water discharged from the purified water outlet 15 are mixed and pressurized by a jet device, and then heated to the auto-ignition temperature of the fuel by a heat exchanger and enter the first gas-liquid mixing injection device 01. The fuel and oxygen are fully mixed in the first gas-liquid mixing injection device 01 and reach the auto-ignition temperature, and then sprayed into the hydrothermal combustion reaction chamber 05 in a supercritical water state through the nozzle at the lower end of the first gas-liquid mixing injection device 01, generating a stable supercritical hydrothermal flame. The initial supercritical water state in the hydrothermal combustion reaction chamber 05 is formed by heating and pressurizing deionized water to a supercritical state and entering the hydrothermal combustion reaction chamber 05 through the second gas-liquid mixing injection device 02, and after a stable supercritical water state is formed in the hydrothermal combustion reaction chamber 05, it is gradually replaced with sewage.

[0041] The sewage can be at room temperature or lower temperature (if there is excess heat available), and is mixed with oxygen-enriched air through the second gas-liquid mixing injection device 02 and then sprayed into the hydrothermal combustion reaction chamber 05 in an atomized state. The atomized sewage particles are rapidly heated to a temperature above the supercritical state by the high temperature formed by the supercritical hydrothermal combustion flame, and an oxidation reaction occurs rapidly in the presence of oxygen, with a reaction time of less than 1 second, rapidly oxidizing the organic pollutants in the sewage into water and carbon dioxide. Most of the salt in the sewage precipitates under the supercritical state and sinks into the quenching chamber 08. The cooling water in the cooling water chamber 13 enters the quenching chamber 08 through the permeable wall 09, and quickly cools the supercritical water to a subcritical state (temperature <374°C), so that most of the precipitated salt is redissolved in the water to prevent salt deposition and clogging of the pipeline. The obtained high-salt water is discharged from the high-salt water outlet 16 at the bottom of the subcritical water chamber 14, and after heat exchange and heat recovery by the heat exchanger, it can directly enter the multi-effect evaporation crystallizer with mature technology to obtain salt that meets the industrial salt standards, realizing the resource utilization of salt.

[0042] In the reactor of the present invention, low-temperature water enters the evaporation wall area 10 through the evaporation wall area water inlet 06, which can balance the pressure of the reaction fluid on the evaporation wall 03 in the hydrothermal combustion reaction chamber 05, and at the same time penetrates into the reactor through the porous evaporation wall 03 and forms a subcritical water film on the inner surface of the evaporation wall 03, preventing the weak acid generated by the oxidation reaction of the pollutants from contacting the wall surface and dissolving the inorganic salts precipitated in the reaction area, thereby solving the corrosion and salt deposition problems in the reactor.

[0043] The present invention makes full use of the characteristics of inorganic salts precipitating in supercritical water state, and sets the purified water outlet 15 at the upper part of the hydrothermal combustion reaction chamber 05, so as to obtain high-temperature and high-pressure salt-free deionized water, and realize the following resource utilization:

[0044] ① The deionized water discharged from the purified water outlet 15 is reused as fuel additive water, eliminating the need for a traditional deionized water production device (such as a reverse osmosis device), thereby saving equipment cost and operating cost.

[0045] ② The high-temperature water discharged from the purified water outlet 15 is used to heat the fuel through the first heat exchanger 22 to reach the auto-ignition temperature, thereby omitting the traditional method of using an external heat source and saving energy consumption.

[0046] ③ Using the high-pressure water discharged from the purified water outlet 15 and using a jet pump to pressurize the fuel can achieve the dual functions of mixing and pressurizing the fuel and water. This saves the traditional method of using a high-pressure plunger pump to pressurize the fuel. The jet pump is simple, has no complicated accessories, operates reliably, and at the same time recovers the pressure energy of the system, achieving the purpose of energy saving and reducing energy consumption.

[0047] ④ The remaining high-pressure water enters the steam-water separator 23, and the separated water is recovered into the condensed water storage tank 28 for recycling.

[0048] The present invention uses sewage at room temperature and oxygen-enriched air, avoiding the serious corrosion problem of the heat exchanger, pipelines and accessories and the salt deposition problem caused by the traditional supercritical water oxidation system using a heat exchanger to heat sewage to a supercritical temperature (such as sodium chloride at a temperature of 500-550°C and a pressure of 22-25MPa, the solubility is about 31.4-101mg / kg, while the saturated solubility of sodium chloride in water at room temperature and pressure is 25000mg / kg), reducing the complexity of the system and enhancing the reliability and safety of the system. In addition, the use of oxygen-enriched air reduces the operating cost of the system.

[0049] The present invention can adjust the appropriate position of the first gas-liquid mixing injection device 01 in the reactor according to the designed sewage treatment capacity, the specific form of the reactor and the distribution of the supercritical hydrothermal combustion flame, so as to ensure that the atomized sewage and oxygen-enriched air can be quickly heated to the designed temperature. One or more first gas-liquid mixing injection devices 01 can be set according to the amount of sewage to be treated and the heat required for the reaction, and evenly arranged on the top cover 30 of the reactor. The distance L1 between the top of the hydrothermal combustion reaction chamber 05 and the nozzle opening at the lower end of the first gas-liquid mixing injection device 01 can be optimized and adjusted according to the distribution of the supercritical hydrothermal combustion flame, that is, the position of the nozzle opening at the lower end of the first gas-liquid mixing injection device 01 in the hydrothermal combustion reaction chamber 05 can be adjusted.

[0050] The present invention can determine the fuel and the required amount of oxygen based on the amount of sewage to be treated and the heat required to heat the sewage to the designed reaction temperature, while ensuring the flame stability of the supercritical hydrothermal combustion. According to the amount of sewage to be treated and the content of organic matter in the sewage, the content of the imported fuel (such as the proportion of fuel is 8% to 16%, and the rest is deionized water) and the injection speed of the first gas-liquid mixing injection device 01 can be adjusted.

[0051] The present invention can arrange multiple layers of second gas-liquid mixing injection devices 02 on the side wall of the hydrothermal combustion reaction chamber 05 according to the concentration of organic matter in the sewage. Preferably, two or more second gas-liquid mixing injection devices 02 are arranged on each layer in the form of a collision flow. Preferably, four second gas-liquid mixing injection devices 02 are arranged on each layer, and every two second gas-liquid mixing injection devices 02 are arranged in the form of a coaxial horizontal collision flow.

[0052] The present invention can design a suitable porosity of the permeable wall 09 of the quenching chamber 08 according to the heat generated by the reactor, so as to conveniently control the amount of cooling water entering the quenching chamber 08, reduce the supercritical water to the subcritical water state, and ensure that there is no problem of salt precipitation and salt deposition. In some embodiments of the present invention, the permeable wall 09 is set to different porosities in a stepped manner according to the required cooling amount to control the permeability at different positions of the permeable wall 09, so as to achieve the purpose of gradual cooling. For example, the permeable wall 09 is divided into two parts, the upper and lower parts, and the permeability of the upper half of the permeable wall 09 is different from that of the lower half.

[0053] The present invention can use a temperature automatic control system to calculate and automatically control the temperature and amount of cooling water entering the quenching chamber 08 according to the heat balance of the reactor, thereby controlling the solubility of the salt. The solubility of inorganic salts in supercritical water can be calculated using the following formula:

[0054] logC NaCI,ppm =7772+3.866log(ρ w / g.cm -3 )-1233.4 / (T / K),

[0055] The conditions for using this formula are: temperature 450~550℃, pressure 10~25MPa, where ppm is expressed as mg(NaCI)·(kgSCW) -1 .

[0056] Under subcritical conditions (temperature: 350-374°C, pressure: 19.0-30.5MPa), the solubility of salt (C / mg / kg) can be estimated by the following formula (taking sodium sulfate as an example):

[0057] LnC=-1047-27550 / T+(4805 / T)Lnρ H2O .

[0058] The system and process provided by the present invention purifies high-salt organic wastewater and recovers salt based on a supercritical hydrothermal combustion reactor. After the sewage is purified by the supercritical hydrothermal combustion reactor, a high-salt water with high temperature and high pressure in a subcritical state is obtained, which is discharged from the high-salt water outlet 16, and after pressure relief and heat exchange in a heat exchanger, part of the heat of the high-salt water is recovered, and the obtained steam can be used for heating and power generation; the high-salt water after heat exchange directly enters the multi-effect evaporation crystallizer 27 to produce solid salt that meets the industrial salt standard, thereby realizing salt recovery; the condensed water of the evaporated crystallization enters the condensed water storage tank 28, and the condensed water is deionized water, which can be pressurized by the condensed water high-pressure pump 29 and enter the evaporation wall area 10 and the cooling water chamber 13 through the evaporation wall area water inlet 06 and the cooling water chamber water inlet 11, thereby realizing recycling.

[0059] Compared with the prior art, the advantages of the present invention include:

[0060] (1) High-salinity organic wastewater is fed at room temperature, thus avoiding the traditional method of using a heat exchanger to heat the high-salinity wastewater to a temperature above the supercritical temperature, which causes serious corrosion of the heat exchanger, pipes and accessories, as well as pipeline blockage caused by salt deposition.

[0061] (2) The use of oxygen-enriched air reduces the technical requirements, equipment investment and operating costs of oxygen production equipment.

[0062] (3) By adopting the purified water outlet at the top of the supercritical water thermal combustion reactor, deionized water can be easily obtained and used for direct mixing and heating of the fuel. The deionized water produced at the top of the reactor can also be directly reused in the evaporation wall water system.

[0063] (4) The high-temperature and high-pressure purified water discharged from the upper part of the reactor is used to pressurize the fuel through a jet pump, which recovers the pressure energy and reduces the energy consumption of the system. There is no need for a high-pressure pump such as a plunger pump to pressurize the fuel, which reduces the system cost and improves the reliability of the system operation.

[0064] (5) A quenching chamber is set up in the reactor, which cooperates with the permeable wall and the cooling chamber water circulation system. The water temperature can be flexibly controlled according to the thermal balance in the reactor and the control of the permeation volume of the cooling water, so that the precipitated salt can be quickly dissolved into the water, thereby avoiding the problem of salt deposition and pipeline blockage.

[0065] (6) The high-temperature characteristics of the high-salt water outlet of the reactor are fully utilized. After heat exchange and heat energy recovery in the heat exchanger, it can directly enter the technically mature multi-effect evaporation crystallizer to obtain salt that meets industrial salt standards. The condensed water produced by evaporation and crystallization can be directly reused or discharged.

[0066] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0067] The term "pressure-bearing wall" used herein refers to the pressure-bearing outer shell of the reactor, which is made of a material capable of withstanding high pressure, such as stainless steel. The term "annular gap" used herein refers to the annular cavity formed between the inner shell and the outer shell of a cylindrical or tubular cavity, and the difference between the outer diameter and the inner diameter of the annular cavity can be large or small, thereby forming a wide annular gap and a narrow annular gap.

[0068] The term "quenching" as used herein refers to the technology of using low-temperature and high-heat-capacity water to rapidly cool the liquid after the supercritical hydrothermal combustion reaction. The inner wall of the "quenching chamber" of the present invention is a permeable wall, and cold water enters the quenching chamber from the cooling water chamber through the permeable wall to achieve gradual cooling of the high-temperature brine.

[0069] The term "supercritical water" used herein refers to water whose temperature and pressure exceed the critical point. The critical temperature of water is T = 374.2 ° C, and the critical pressure is P = 22.05 MPa. "Subcritical water" refers to water with a temperature between 100 ° C and 374 ° C, a sufficiently large pressure, and maintained in a liquid state.

[0070] The term "evaporation wall" used herein refers to the porous inner shell in the reactor, which can be a layered plate lining structure or a porous material element. The layered plate lining structure is a structure in which small holes with certain rules are engraved on multiple layers of stainless steel sheets by etching technology, and the small holes on each layer of the sheets are different in shape, and then these sheets are pressed together and rolled into a porous inner tube of the reactor. The porous material element includes a porous sintered iron-aluminum intermetallic compound, etc.

[0071] The term "permeable wall" used herein refers to the porous material inner shell of the quench chamber, whose porosity is greater than the porosity of the porous material of the evaporation wall. The porous material can be an iron-aluminum intermetallic compound.

[0072] The "collision flow" used in this article refers to the collision of two fluids flowing towards each other at high speed, reaching an extremely high relative speed at the moment of collision, causing the dispersed phase particles to perform reciprocating oscillatory permeation motion between the two opposing fluids. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 . A schematic diagram of a supercritical hydrothermal combustion reactor in a typical embodiment of the present invention;

[0074] Figure 2 . Figure 1 AA cross-sectional view of the supercritical hydrothermal combustion reactor shown;

[0075] Figure 3 . A system for recovering salt from high-salinity organic wastewater in a typical embodiment of the present invention;

[0076] Reference numerals: first gas-liquid mixed injection device (01), second gas-liquid mixed injection device (02), evaporation wall (03), pressure wall (04), hydrothermal combustion reaction chamber (05), evaporation wall area water inlet (06), evaporation wall area water outlet (07), quenching chamber (08), permeation wall (09), evaporation wall area (10), cooling water chamber water inlet (11), cooling water chamber water outlet (12), cooling water chamber (13), subcritical water chamber (14), purified water outlet (15), high salt water outlet Port (16), sewage regulating tank (17), sewage high-pressure pump (18), fuel tank (19), fuel tank auxiliary booster pump (20), hydraulic jet pump (21), first heat exchanger (22), steam-water separator (23), liquid oxygen storage tank (24), liquid oxygen vaporizer (25), second heat exchanger (26), multi-effect evaporation crystallizer (27), condensate storage tank (28), condensate high-pressure pump (29), top cover (30), oxygen-enriched air production device (31), liquid oxygen high-pressure pump (32).

[0077] Figure 1 In the figure, L1 is the distance between the top of the hydrothermal combustion reaction chamber (05) and the nozzle opening at the lower end of the first gas-liquid mixing injection device (01); L2 is the distance between the nozzle opening at the lower end of the first gas-liquid mixing injection device (01) and the central axis of the second gas-liquid mixing injection device (02); and L3 is the distance between the central axis of the second gas-liquid mixing injection device (02) and the bottom of the hydrothermal combustion reaction chamber (05). DETAILED DESCRIPTION

[0078] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the following embodiments are only for explanation and illustration and are not intended to limit the scope of the present invention. Modifications and variations made by ordinary technicians in this field based on the technical solution of the present invention fall within the protection scope of the present invention.

[0079] like Figure 1As shown, the present invention provides a supercritical hydrothermal combustion reactor for recovering salt from organic wastewater, comprising a top cover 30, and a cylindrical cavity surrounded by a pressure-bearing wall 04, characterized in that: the cylindrical cavity comprises a fluid-connected hydrothermal combustion reaction chamber 05, a quenching chamber 08 and a subcritical water chamber 14 from top to bottom; the side wall of the hydrothermal combustion reaction chamber 05 comprises an outer pressure-bearing wall 04 and an inner evaporation wall 03; the annular gap between the evaporation wall 03 and the pressure-bearing wall 04 is an evaporation wall area 10; the pressure-bearing wall 04 is provided with an evaporation wall area water inlet 06 and an evaporation wall area water outlet 07; the top cover 30 is provided with a nozzle 06 for mixing fuel and The first gas-liquid mixing injection device 01 for mixing sewage and oxidant and spraying them into the hydrothermal combustion reaction chamber 05; a purified water outlet 15 is provided on the upper part of the side wall of the hydrothermal combustion reaction chamber 05, and a second gas-liquid mixing injection device 02 for mixing sewage and oxidant and spraying them into the hydrothermal combustion reaction chamber 05 is installed in the middle of the side wall; the side wall of the quenching chamber 08 includes an outer pressure-bearing wall 04 and an inner permeable wall 09; the annular gap between the permeable wall 09 and the pressure-bearing wall 04 is a cooling water chamber 13; a cooling water chamber water inlet 11 and a cooling water chamber water outlet 12 are provided on the pressure-bearing wall 04; a high-salt water outlet 16 is provided at the bottom of the subcritical water chamber 14.

[0080] In some preferred embodiments, the upper end of the first gas-liquid mixing injection device 01 is located outside the hydrothermal combustion reaction chamber 05 and is provided with a fuel inlet and an oxygen inlet, the middle is provided with a mixing chamber for mixing fuel and oxygen, and the lower end is located in the hydrothermal combustion reaction chamber 05 and is provided with a fuel nozzle opening facing downward.

[0081] In some preferred embodiments, one end of the second gas-liquid mixing injection device 02 is located outside the hydrothermal combustion reaction chamber 05 and is provided with a sewage inlet and an oxygen-enriched air inlet, and the other end extends into the hydrothermal combustion reaction chamber 05 and is provided with a material nozzle with an opening facing the central axis of the hydrothermal combustion reaction chamber 05.

[0082] In some preferred embodiments, the evaporation wall zone water inlet 06 is arranged on the pressure-bearing wall 04 at the lower part of the evaporation wall zone 10 , and the evaporation wall zone water outlet 07 is arranged on the pressure-bearing wall 04 at the upper part of the evaporation wall zone 10 .

[0083] In some preferred embodiments, the cooling water chamber water inlet 11 is arranged on the pressure-bearing wall 04 at the lower part of the cooling water chamber 13 , and the cooling water chamber water outlet 12 is arranged on the pressure-bearing wall 04 at the upper part of the cooling water chamber 13 .

[0084] In some preferred embodiments, the porosity of the permeable wall 09 increases gradually from top to bottom.

[0085] In some preferred embodiments, the upper portion of the permeable wall 09 is in an inverted cone shape, and the lower portion is in a cylindrical shape.

[0086] In some embodiments, a first gas-liquid mixing injection device 01 is provided on the top cover 30 .

[0087] In other embodiments, the top cover 30 is provided with two or more evenly arranged first gas-liquid mixing injection devices 01 .

[0088] In some preferred embodiments, at least one layer of second gas-liquid mixing injection device 02 is provided in the middle of the side wall of the hydrothermal combustion reaction chamber 05, and each layer is provided with two or more second gas-liquid mixing injection devices 02 arranged in the form of colliding flows.

[0089] In some embodiments, four second gas-liquid mixing injection devices 02 arranged in the form of impinging flows are provided in the middle of the side wall of the hydrothermal combustion reaction chamber 05 .

[0090] In other embodiments, two or more layers of second gas-liquid mixing injection devices 02 are provided in the middle of the side wall of the hydrothermal combustion reaction chamber 05, and each layer is provided with four second gas-liquid mixing injection devices 02 arranged in the form of colliding flows.

[0091] In some embodiments, the bottom end of the evaporation wall 03 is connected to the top end of the permeation wall 09 .

[0092] The present invention also provides a system for recovering salt from high-salt organic wastewater, characterized in that it includes any of the supercritical hydrothermal combustion reactors described above, and a fuel pipeline, a first oxidant pipeline, a sewage pipeline and a second oxidant pipeline connected to the reactor.

[0093] like Figure 3As shown, in some preferred embodiments, the fuel pipeline includes a fuel tank 19, a fuel tank auxiliary booster pump 20, a hydraulic jet pump 21 and a first heat exchanger 22 connected in sequence through pipelines; the hydraulic jet pump 21 is provided with a fuel inlet, a water inlet and a liquid outlet, and its liquid outlet is connected to the fuel inlet of the first heat exchanger 22, and the fuel outlet of the first heat exchanger 22 is connected to the fuel inlet of the first gas-liquid mixing injection device 01 of the reactor; the hot water inlet of the first heat exchanger 22 is connected to the purified water outlet 15 of the reactor, and its hot water outlet is connected to the water inlet of the hydraulic jet pump 21; the first oxidant pipeline includes a liquid oxygen storage tank 24, a water inlet and a liquid outlet connected in sequence through pipelines. A liquid oxygen high-pressure pump 32 and a liquid oxygen vaporizer 25; the oxygen outlet of the liquid oxygen vaporizer 25 is connected to the oxygen inlet of the first gas-liquid mixing injection device 01; the sewage pipeline includes a sewage regulating tank 17 and a sewage high-pressure pump 18 connected by a pipeline; the outlet of the sewage high-pressure pump 18 is connected to the sewage inlet of the second gas-liquid mixing injection device 02 of the reactor; the second oxidant pipeline includes an oxygen-enriched air production device 31, whose oxygen-enriched air outlet is connected to the oxygen-enriched air inlet of the second gas-liquid mixing injection device 02; the high-salt water outlet 16 of the reactor is connected to the brine inlet of the second heat exchanger 26, and the brine outlet of the second heat exchanger 26 is connected to the multi-effect evaporation crystallizer 27.

[0094] In some preferred embodiments, the hot water outlet of the first heat exchanger 22 is also connected to the inlet of the steam-water separator 23 ; and the water outlet of the steam-water separator 23 is connected to the water inlet of the condensed water storage tank 28 .

[0095] In some preferred embodiments, the water outlet of the multi-effect evaporation crystallizer 27 is connected to the water inlet of the condensed water storage tank 28 .

[0096] In some preferred embodiments, the evaporation wall area water outlet 07 of the reactor and the cooling water chamber water outlet 12 are connected to the water inlet of the condensate storage tank 28; the water outlet of the condensate storage tank 28 is connected to the inlet of the condensate high-pressure pump 29, and the outlet of the condensate high-pressure pump 29 is respectively connected to the evaporation wall area water inlet 06 of the reactor and the cooling water chamber water inlet 11.

[0097] In some preferred embodiments, a water outlet of the condensed water storage tank 28 is connected to a cold water inlet of the second heat exchanger 26 .

[0098] In some preferred embodiments, the hot water outlet of the first heat exchanger 22 is also connected to the inlet of the steam-water separator 23; the water outlet of the steam-water separator 23 is connected to the water inlet of the condensate storage tank 28; the water outlet of the multi-effect evaporation crystallizer 27 is connected to the water inlet of the condensate storage tank 28; the evaporation wall area water outlet 07 and the cooling water chamber water outlet 12 of the reactor are connected to the water inlet of the condensate storage tank 28; the water outlet of the condensate storage tank 28 is respectively connected to the inlet of the condensate high-pressure pump 29 and the cold water inlet of the second heat exchanger 26; the outlet of the condensate high-pressure pump 29 is respectively connected to the evaporation wall area water inlet 06 and the cooling water chamber water inlet 11 of the reactor.

[0099] The present invention also provides a process for recovering salt from high-salt organic wastewater, characterized in that: using any of the above-mentioned supercritical hydrothermal combustion reactors or any of the above-mentioned systems, the steps are as follows: continuously introducing liquid fuel and a first oxidant preheated to the auto-ignition temperature into a first gas-liquid mixing injection device 01; continuously introducing sewage at room temperature and a second oxidant into a second gas-liquid mixing injection device 02; the fuel and the first oxidant are fully mixed in the first gas-liquid mixing injection device 01 and then sprayed into a hydrothermal combustion reaction chamber 05 in a supercritical water state to generate a stable supercritical hydrothermal flame; the sewage and the second oxidant are sprayed into a supercritical water state. The sewage is sprayed into the hydrothermal combustion reaction chamber 05 through the second gas-liquid mixing injection device 02, and the atomized sewage particles are rapidly heated to a temperature above the supercritical state by the supercritical hydrothermal flame and an oxidation reaction occurs rapidly, oxidizing the organic pollutants into water and carbon dioxide; the salt in the sewage precipitates out under the supercritical state and sinks into the quenching chamber 08, and the cooling water in the cooling water chamber 13 enters the quenching chamber 08 through the permeable wall 09, rapidly cooling the supercritical water to a subcritical state, so that the precipitated salt is redissolved in the water, and the obtained high-salt water is discharged through the high-salt water outlet 16, and the solid salt is recovered through the multi-effect evaporation crystallizer 27.

[0100] In some preferred embodiments, the first oxidant is oxygen, and the second oxidant is oxygen-enriched air.

[0101] In some preferred embodiments, the liquid fuel is pressurized by a hydraulic jet pump 21, and then heated by a first heat exchanger 22 before entering the first gas-liquid mixing injection device 01; the high-temperature and high-pressure water discharged from the purified water outlet 15 enters the first heat exchanger 22 to heat the liquid fuel; a portion of the high-temperature and high-pressure water after heat exchange enters the hydraulic jet pump 21, where the fuel and water are mixed and pressurized by the hydraulic jet pump 21, and another portion of the high-temperature and high-pressure water enters the steam-water separator 23, and the separated water enters the condensate storage tank 28; the high-salt water discharged through the high-salt water outlet 16 recovers heat through the second heat exchanger 26 and then enters the multi-effect evaporation crystallizer 27 to obtain solid salt and condensed water, and the condensed water enters the condensate storage tank 28; the water discharged through the evaporation wall area outlet 07 and the cooling water chamber outlet 12 enters the condensate storage tank 28; a portion of the water in the condensate storage tank 28 enters the evaporation wall area 10 and the cooling water chamber 13 after being pressurized by the condensate high-pressure pump 29, and another portion of the water enters the second heat exchanger 26.

[0102] In some preferred embodiments, the salt-free high-temperature and high-pressure water passes through the purified water outlet 15, and after heating the fuel to the auto-ignition temperature through the first heat exchanger 22, part of the high-pressure water enters the hydraulic jet pump 21 to increase the pressure of the inlet fuel to meet the inlet pressure requirement of the first gas-liquid mixing injection device 01. After the remaining high-pressure water enters the steam-water separator 23, the water is recovered into the condensed water storage tank 28 for recycling.

[0103] In some preferred embodiments, the first gas-liquid mixing injection device 01 includes a cylindrical tube body, in which a fuel inlet pipe and an oxidant inlet pipe independent of each other are arranged; a mixing chamber is arranged in the middle inner cavity of the cylindrical tube body; the upper end of the fuel inlet pipe is a liquid fuel inlet, which is arranged at the top of the cylindrical tube body, and its lower end outlet faces the mixing chamber; the upper end of the oxidant inlet pipe is an oxidant inlet, which is arranged at the top of the cylindrical tube body, and its lower end outlet faces the mixing chamber; the bottom end outlet of the mixing chamber is arranged at the lower end of the cylindrical tube body; and an atomizing nozzle is arranged at the lower end of the cylindrical tube body.

[0104] like Figure 2 As shown, in some embodiments, the second gas-liquid mixing injection device 02 includes a cylindrical tube body, in which independent sewage introduction pipes and oxygen-enriched air introduction pipes are arranged; the inlet of the sewage introduction pipe and the inlet of the oxygen-enriched air introduction pipe are arranged at the inlet end of the cylindrical tube body located outside the hydrothermal combustion reaction chamber 05; the outlet of the sewage introduction pipe and the outlet of the oxygen-enriched air introduction pipe are arranged at the outlet end of the cylindrical tube body located inside the hydrothermal combustion reaction chamber 05; the outlet end is provided with an atomizing nozzle.

[0105] Application Examples

[0106] The process of the invention is used to purify high-salt organic wastewater and recover salt.

[0107] The high-concentration organic wastewater to be treated has a COD value of 80,000 mg / L and a salt content of 100,000 mg / L.

[0108] The amount of sewage treated is: Q = 1m 3 / h, the sewage inlet temperature is 20℃, and oxygen-enriched air with an oxygen content of 95% is used as the oxidant. The amount of oxygen-enriched air required to completely oxidize the organic matter in the sewage (COD is 80000mg / L) is 101.05kg / h (the excess oxygen coefficient is 1.2).

[0109] The liquid fuel used is methanol, with a mass fraction of 12-22%, and a fuel flow rate of 4-20 kg / h. Liquid oxygen is used as an oxidant. Methanol and oxygen are heated to 460-490°C (reaching the auto-ignition temperature) and then enter the first gas-liquid mixing injection device 01. After being fully mixed, they are sprayed into the hydrothermal combustion reaction chamber 05, generating a stable hydrothermal combustion flame in the supercritical water in the reactor. The required amount of liquid oxygen can be determined by the chemical reaction equation of methanol and oxygen:

[0110]

[0111] The sewage and oxygen-enriched air at room temperature are sprayed into the hydrothermal combustion reaction chamber 05 where a stable supercritical hydrothermal combustion flame has been generated through the atomizing nozzle of the second gas-liquid mixing injection device 02. Under the heating of the hydrothermal combustion flame, the temperature is rapidly raised to a supercritical state (the temperature can reach 600-800°C) and an oxidation reaction occurs rapidly, releasing a large amount of heat. The heat generated by the complete oxidation reaction of organic matter in the sewage of this embodiment is 1.176×10 6 kJ / h.

[0112] The total water flow rate through the evaporation wall 03 is 30-70% of the total flow rate entering the supercritical hydrothermal combustion reactor, and the permeability coefficient K of the evaporation wall 03 is 0.17; the permeability coefficient K of the permeation wall 09 is 0.20-0.30. The permeation amount is calculated according to Darcy's Law: Q=KAΔh / δ, where K is the permeability coefficient, A is the permeation wall area, Δh is the pressure difference, and δ is the permeation wall or evaporation wall thickness.

[0113] In the high temperature (600-800°C) area of ​​the hydrothermal combustion reaction chamber 05, the sewage and oxygen-enriched air injected by the second gas-liquid mixing injection device 02 are fully atomized and rapidly heated (reaction time is less than 1 second), and a complete oxidation reaction occurs. The precipitated salt is cooled and dissolved in the quenching chamber 08 and then enters the subcritical water chamber 14.

[0114] Subcritical water enters the second heat exchanger 26 through the high-salt water outlet 16 to recover heat (generating high-temperature and high-pressure steam), and then directly enters the multi-effect evaporation crystallizer 27. The evaporated condensed water enters the condensed water storage tank 28 (this is deionized water), and after cooling, it is pressurized by the condensed water high-pressure pump 29 and enters the evaporation wall area 10 and the cooling water chamber 13 through the evaporation wall area water inlet 06 and the cooling water chamber water inlet 11 for recycling. The salt produced by evaporation and crystallization is a resource-usable salt that meets the national industrial salt standards.

Claims

1. A supercritical hydrothermal combustion reactor for recovering salt from organic wastewater, comprising a top cover (30) and a cylindrical cavity surrounded by a pressure-bearing wall (04), characterized in that: The cylindrical cavity comprises, from top to bottom, a hydrothermal combustion reaction chamber (05), a quenching chamber (08) and a subcritical water chamber (14) which are fluidically connected; The side wall of the hydrothermal combustion reaction chamber (05) comprises an outer pressure-bearing wall (04) and an inner evaporation wall (03); the annular gap between the evaporation wall (03) and the pressure-bearing wall (04) is an evaporation wall area (10); the pressure-bearing wall (04) is provided with an evaporation wall area water inlet (06) and an evaporation wall area water outlet (07); The top cover (30) is provided with a first gas-liquid mixing injection device (01) for mixing fuel and oxidant and injecting the mixture into the hydrothermal combustion reaction chamber (05); the upper portion of the side wall of the hydrothermal combustion reaction chamber (05) is provided with a purified water outlet (15), and the middle portion of the side wall is provided with a second gas-liquid mixing injection device (02) for mixing sewage and oxidant and injecting the mixture into the hydrothermal combustion reaction chamber (05); The side wall of the quenching chamber (08) comprises an outer pressure-bearing wall (04) and an inner permeable wall (09); the annular gap between the permeable wall (09) and the pressure-bearing wall (04) is a cooling water chamber (13); the pressure-bearing wall (04) is provided with a cooling water chamber water inlet (11) and a cooling water chamber water outlet (12); the upper portion of the permeable wall (09) is in an inverted cone shape and the lower portion is in a cylindrical shape, and the porosity of the permeable wall (09) gradually increases from top to bottom; A high-salt water outlet (16) is provided at the bottom of the subcritical water chamber (14).

2. The supercritical hydrothermal combustion reactor according to claim 1, characterized in that: The upper end of the first gas-liquid mixing injection device (01) is located outside the hydrothermal combustion reaction chamber (05) and is provided with a fuel inlet and an oxygen inlet, the middle portion is provided with a mixing chamber for mixing fuel and oxygen, and the lower end is located inside the hydrothermal combustion reaction chamber (05) and is provided with a fuel nozzle opening facing downward; And / or one end of the second gas-liquid mixing injection device (02) is located outside the hydrothermal combustion reaction chamber (05) and is provided with a sewage inlet and an oxygen-enriched air inlet, and the other end extends into the hydrothermal combustion reaction chamber (05) and is provided with a material nozzle with an opening facing the central axis of the hydrothermal combustion reaction chamber (05).

3. The supercritical hydrothermal combustion reactor according to claim 1, characterized in that: The evaporation wall area water inlet (06) is arranged on the pressure-bearing wall (04) at the lower part of the evaporation wall area (10), and the evaporation wall area water outlet (07) is arranged on the pressure-bearing wall (04) at the upper part of the evaporation wall area (10); And / or the cooling water chamber water inlet (11) is arranged on the pressure-bearing wall (04) at the bottom of the cooling water chamber (13), and the cooling water chamber water outlet (12) is arranged on the pressure-bearing wall (04) at the top of the cooling water chamber (13).

4. The supercritical hydrothermal combustion reactor according to claim 1, characterized in that: The top cover (30) is provided with two or more evenly arranged first gas-liquid mixing injection devices (01); And / or at least one layer of second gas-liquid mixing injection devices (02) is provided in the middle of the side wall of the hydrothermal combustion reaction chamber (05), and each layer is provided with two or more second gas-liquid mixing injection devices (02) arranged in the form of colliding flows.

5. A system for recovering salt from organic wastewater, characterized in that: A supercritical hydrothermal combustion reactor comprising any one of claims 1 to 4, and a fuel pipeline, a first oxidant pipeline, a sewage pipeline and a second oxidant pipeline connected to the reactor; The fuel pipeline comprises a fuel tank (19), a fuel tank auxiliary booster pump (20), a hydraulic jet pump (21) and a first heat exchanger (22) which are connected in sequence through the pipeline; the hydraulic jet pump (21) is provided with a fuel inlet, a water inlet and a liquid outlet, the liquid outlet of which is connected to the fuel inlet of the first heat exchanger (22), and the fuel outlet of the first heat exchanger (22) is connected to the fuel inlet of the first gas-liquid mixing injection device (01) of the reactor; the hot water inlet of the first heat exchanger (22) is connected to the purified water outlet (15) of the reactor, and the hot water outlet is connected to the water inlet of the hydraulic jet pump (21); The first oxidant pipeline comprises a liquid oxygen storage tank (24), a liquid oxygen high-pressure pump (32) and a liquid oxygen vaporizer (25) which are connected in sequence through pipelines; the oxygen outlet of the liquid oxygen vaporizer (25) is connected to the oxygen inlet of the first gas-liquid mixing injection device (01); The sewage pipeline comprises a sewage regulating tank (17) and a sewage high-pressure pump (18) connected by a pipeline; the outlet of the sewage high-pressure pump (18) is connected to the sewage inlet of the second gas-liquid mixing injection device (02) of the reactor; The second oxidant pipeline comprises an oxygen-enriched air production device (31), the oxygen-enriched air outlet of which is connected to the oxygen-enriched air inlet of the second gas-liquid mixing injection device (02); The high-salt water outlet (16) of the reactor is connected to the salt water inlet of the second heat exchanger (26), and the salt water outlet of the second heat exchanger (26) is connected to the multi-effect evaporation crystallizer (27); The hot water outlet of the first heat exchanger (22) is also connected to the inlet of the steam-water separator (23); the water outlet of the steam-water separator (23) is connected to the water inlet of the condensed water storage tank (28); The water outlet of the multiple-effect evaporation crystallizer (27) is connected to the water inlet of the condensed water storage tank (28); The evaporation wall area water outlet (07) and the cooling water chamber water outlet (12) of the reactor are connected to the water inlet of the condensed water storage tank (28); The water outlet of the condensed water storage tank (28) is respectively connected to the inlet of the condensed water high-pressure pump (29) and the cold water inlet of the second heat exchanger (26); the outlet of the condensed water high-pressure pump (29) is respectively connected to the evaporation wall area water inlet (06) of the reactor and the cooling water chamber water inlet (11).

6. A process for recovering salt from organic wastewater, characterized in that: Using the system described in claim 5, the steps are as follows: The liquid fuel and the first oxidant preheated to the auto-ignition temperature are continuously introduced into the first gas-liquid mixing injection device (01); and the sewage at room temperature and the second oxidant are continuously introduced into the second gas-liquid mixing injection device (02); The fuel and the first oxidant are fully mixed in the first gas-liquid mixing injection device (01) and then injected into a hydrothermal combustion reaction chamber (05) in a supercritical water state, thereby generating a stable supercritical hydrothermal flame; the sewage and the second oxidant are injected into the hydrothermal combustion reaction chamber (05) via the second gas-liquid mixing injection device (02), and the atomized sewage particles are rapidly heated to a temperature above the supercritical state by the supercritical hydrothermal flame and an oxidation reaction occurs rapidly, thereby oxidizing the organic pollutants into water and carbon dioxide; The salt in the sewage precipitates under the supercritical state and sinks into the quenching chamber (08). The cooling water in the cooling water chamber (13) enters the quenching chamber (08) through the permeable wall (09), rapidly cooling the supercritical water to a subcritical state, so that the precipitated salt is redissolved in the water. The obtained high-salt water is discharged through the high-salt water outlet (16), and the solid salt is recovered through the multi-effect evaporation crystallizer (27).

7. The process according to claim 6, characterized in that: The liquid fuel is pressurized by a hydraulic jet pump (21), and then heated by a first heat exchanger (22) before entering a first gas-liquid mixing injection device (01); The high-temperature and high-pressure water discharged from the purified water outlet (15) enters the first heat exchanger (22) to heat the liquid fuel; a portion of the high-temperature and high-pressure water after heat exchange enters the hydraulic jet pump (21), where the fuel and water are mixed and pressurized by the hydraulic jet pump (21), and another portion of the high-temperature and high-pressure water enters the steam-water separator (23), and the separated water enters the condensed water storage tank (28); The high-salt water discharged from the high-salt water outlet (16) is passed through the second heat exchanger (26) to recover heat and then enters the multi-effect evaporation crystallizer (27) to obtain solid salt and condensed water, and the condensed water enters the condensed water storage tank (28); The water discharged through the evaporation wall area water outlet (07) and the cooling water chamber water outlet (12) enters the condensed water storage tank (28); A portion of the water in the condensed water storage tank (28) enters the evaporation wall area (10) and the cooling water chamber (13) after being pressurized by the condensed water high-pressure pump (29), and another portion of the water enters the second heat exchanger (26).

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