Fluorine thermal coupling duplex recovery system and method for phosphoric acid production system

Abstract

The invention discloses a fluorine thermal coupling duplex recovery system and method of a phosphoric acid production system, and the fluorine thermal coupling duplex recovery system of the phosphoric acid production system comprises a washing unit, a waste heat recovery unit and a low-pressure saturated steam production unit. Secondary steam in the washed tail gas enters a waste heat recovery unit for heat release and condensation, after heat conversion is conducted through an organic working medium, the heat of the secondary steam in the tail gas is finally output as high-temperature hot water or enters a low-pressure saturated steam generation unit to be converted into low-pressure saturated steam, and the low-pressure saturated steam is reused in the production link. And after being purified, the fluorine-based compound recovered by washing is conveyed to a downstream fluorine chemical production system to be used as a supplementary raw material for preparing fluorine-series chemical products. Fluorine resources discharged in the prior art are recycled, meanwhile, secondary steam waste heat is recycled for production, the environmental protection problem is solved, waste heat is recycled, energy consumption is reduced, and meanwhile fluorine discharge is reduced.

Description

Technical Field

[0001] This invention relates to a fluorine-thermal coupled dual recovery system and method for phosphoric acid production systems, belonging to the technical field of fluorine and heat energy recovery in phosphoric acid production systems. Background Technology

[0002] The tail gas generated during the phosphoric acid concentration process in a phosphoric acid production system contains a large amount of fluorine and secondary steam. Current phosphoric acid concentration processes typically use water washing to recover fluorine from the tail gas, but the fluorine recovery rate using this method is only 50%–60%, and the fluorine concentration in the tail gas still reaches 140–150 mg / Nm³. 3 All of this fluoride is currently entering the acidic water circulation system and is eventually discharged into the atmosphere through the cooling tower, causing environmental pollution. The secondary steam in the exhaust gas is usually at 50~55℃. The waste heat of the secondary steam in the exhaust gas is directly cooled by the circulating water. While the latent heat of the steam is wasted, fluorides are emitted without organization through the cooling tower.

[0003] Currently, the wet-process phosphoric acid production industry commonly uses inefficient water washing equipment combined with an open-loop cooling system. The heat exchange efficiency of this equipment is less than 30%, resulting in approximately 68% of the fluorine being released in gaseous form during production, with annual fluorine emissions reaching 42,750 tons. This open system lacks waste heat recovery devices, causing a heat loss of approximately 1.2 × 10⁻⁶ tons per ton of product. 9 J. The entire industry suffers a heat loss equivalent to approximately 350,000 tons of standard coal, which is equivalent to half a year's residential heating energy consumption in a medium-sized city. The waste heat utilization rate of wet-process phosphoric acid plants in the industry is less than 5%, and the research and development and engineering application of related waste heat and fluorine recovery technologies are both blank areas. Summary of the Invention

[0004] The purpose of this invention is to provide a dual-stage fluorine recovery system coupled with thermal coupling in a phosphoric acid production system, to solve the technical problems of low fluorine recovery efficiency and waste of secondary steam heat in the tail gas of existing phosphoric acid production systems using water washing. Simultaneously, this invention also provides a method for dual-stage fluorine recovery coupled with thermal coupling in a phosphoric acid production system.

[0005] The phosphoric acid production system fluorine-heat coupled dual recovery system of the present invention adopts the following technical solution: The phosphoric acid production system fluorine-heat coupled dual recovery system includes a washing unit, a waste heat recovery unit, and a low-pressure saturated steam production unit. The washing unit includes a washing tower, a washing liquid circulation tank, and a circulation pump. The circulation pump is used to send the washing liquid in the washing liquid circulation tank into the sprayer of the washing tower. The steam production unit includes a hot water flash tank, which is provided with a water inlet, a steam outlet, a hot water circulation inlet, and a hot water circulation outlet. The waste heat recovery unit includes a high-temperature refrigerant evaporator, a refrigerant compressor, a high-temperature refrigerant condenser, an economizer, and a high-temperature refrigerant cooler. The heat medium inlet and outlet of the high-temperature refrigerant evaporator are respectively connected to... The exhaust gas outlet of the scrubbing tower is connected to the steam condensate pipe. The refrigerant inlet and outlet of the high-temperature refrigerant evaporator are respectively connected to the heat medium outlet of the high-temperature refrigerant cooler and the inlet of the refrigerant compressor. The heat medium inlet of the high-temperature refrigerant condenser is connected to the gas outlet of the refrigerant compressor. The refrigerant inlet and outlet of the high-temperature refrigerant condenser are respectively connected to the hot water circulation inlet and outlet of the hot water flash tank. The heat medium outlet of the high-temperature refrigerant condenser and the liquid outlet of the refrigerant compressor are both connected to the economizer. The outlet of the economizer is connected to the heat medium inlet of the high-temperature refrigerant cooler. The refrigerant in the high-temperature refrigerant evaporator, the heat medium of the high-temperature refrigerant cooler, and the heat medium of the high-temperature refrigerant condenser are all organic working fluids.

[0006] The washing unit includes two or more washing towers, each of which is connected to a washing liquid circulation tank and a circulation pump.

[0007] A pressure-reducing pipe is connected in parallel to the pipeline between the economizer and the high-temperature refrigerant cooler, and a pressure-reducing throttle valve is installed on the pressure-reducing pipe.

[0008] A high-temperature expansion valve is installed on the pipeline between the economizer and the high-temperature refrigerant cooler.

[0009] The hot side of the high-temperature refrigerant evaporator is equipped with a non-condensable gas venting pipe, and a membrane filter is connected to the steam condensate pipe.

[0010] The refrigerant compressor is a screw compressor, and a hot water circulation pump is installed on the pipeline between the refrigerant inlet and the hot water circulation outlet of the high-temperature refrigerant condenser.

[0011] The fluorine-thermal coupling dual recovery method of the phosphoric acid production system of the present invention adopts the following technical solution: The fluorine-thermal coupling dual recovery method of the phosphoric acid production system is carried out by the above-mentioned fluorine-thermal coupling dual recovery system of the phosphoric acid production system, specifically including the following steps: (1) The tail gas of the phosphoric acid production system is introduced into the scrubbing tower, and the scrubbing liquid in the scrubbing liquid circulation tank is sent into the sprayer by the circulation pump. The spray liquid in the sprayer comes into countercurrent contact with the fluorine-containing tail gas and absorbs the fluorine in the tail gas; (2) After the fluorine in the tail gas is absorbed, it is discharged from the tail gas outlet at the top of the spray tower and enters the steam condenser; the tail gas first exchanges heat with the low temperature liquid organic working medium, and the secondary steam in the tail gas is condensed and discharged from the condensate pipe. The low temperature liquid organic working medium absorbs the heat of the secondary steam and then vaporizes to form a low temperature gaseous organic working medium; (3) The low temperature gaseous organic working medium enters the refrigerant compressor and is heated by the refrigerant compressor. After compression, the low-temperature gaseous organic working fluid is compressed to produce high-temperature liquid organic working fluid and high-temperature gaseous organic working fluid. The high-temperature liquid organic working fluid enters the economizer, and the high-temperature gaseous organic working fluid enters the high-temperature refrigerant condenser. (4) In the high-temperature refrigerant condenser, the circulating hot water from the hot water flash tank exchanges heat with the high-temperature gaseous organic working fluid and its temperature rises before returning to the hot water flash tank. The high-temperature gaseous organic working fluid exchanges heat and its temperature drops to form high-temperature liquid organic working fluid which enters the economizer. (5) The liquid organic working fluid in the economizer enters the high-temperature refrigerant cooler and exchanges heat with the circulating water from the boundary area, and its temperature drops. The low-temperature liquid working fluid formed enters the high-temperature refrigerant evaporator. (6) In the hot water flash tank, the hot water that has been heated by the high-temperature refrigerant condenser flashes to form low-pressure saturated steam. The unvaporized saturated liquid hot water returns to the high-temperature refrigerant condenser for heat exchange again.

[0012] There are two or more scrubbing towers. The exhaust gas enters each scrubbing tower in sequence for washing and then enters the waste heat recovery unit.

[0013] In step (2), after the secondary steam in the exhaust gas is condensed, the non-condensable gas in the exhaust gas is extracted and vented by a vacuum pump, and the condensate produced after the secondary steam in the exhaust gas is condensed is discharged after being defluorinated by a membrane filter.

[0014] The liquid high-temperature organic working fluid is cooled down after passing through the economizer and high-temperature expansion valve, and then enters the high-temperature refrigerant cooler.

[0015] The beneficial effects of this invention are as follows: First, this invention utilizes a scrubbing unit to recover fluorine resources from the exhaust gas. After scrubbing, the secondary steam in the exhaust gas becomes very clean and can then enter the waste heat recovery unit for exothermic condensation. After heat conversion through an organic working fluid, the heat is ultimately output as high-temperature hot water or enters a low-pressure saturated steam generation unit to be converted into low-pressure saturated steam, which is then reused in the production process. The fluorine-based compounds recovered from scrubbing are purified and then transported to the downstream fluorochemical production system as supplementary raw materials for the preparation of fluorine-based chemical products.

[0016] The washing unit employs a circulating washing method. The washing liquid is drawn from the washing liquid circulation tank, pressurized by a circulation pump, and then sent to the washing tower for circulating washing. The secondary steam generated in the washing process enters the high-temperature refrigerant evaporator, where it exchanges heat with the liquid high-temperature organic working fluid, causing the liquid organic working fluid to transform into a gaseous organic working fluid. During this process, the secondary steam releases latent heat and condenses into liquid water, which is then reused in the production system. Residual non-condensable gases are continuously vented through the non-condensable gas venting pipeline and a vacuum pump. The vaporized gaseous organic working fluid undergoes adiabatic compression by the refrigerant compressor, and its temperature and pressure are simultaneously increased before being sent to the high-temperature refrigerant condenser. Here, it undergoes countercurrent heat exchange with circulating hot water, causing the high-temperature gaseous working fluid to transform back into a liquid state. The liquid refrigerant flows through an economizer to recover waste heat, then passes through a high-temperature expansion valve for throttling and pressure reduction, and subsequently enters the high-temperature refrigerant cooler for secondary heat exchange with circulating cooling water, ultimately forming a subcooled liquid that returns to the high-temperature refrigerant evaporator, thus forming a complete closed-loop thermodynamic cycle. The circulating hot water enters the high-temperature refrigerant condenser, where it exchanges heat with the gaseous organic working fluid to raise its temperature. It is then transported to the hot water flash tank for flash evaporation. The low-pressure saturated steam generated during the flash evaporation process is recycled back to the phosphoric acid production unit via a recovery system. The unvaporized saturated liquid hot water is pressurized and transported by the circulating hot water pump back to the high-temperature refrigerant condenser to participate in the heat exchange process again.

[0017] This invention recovers fluorine from the tail gas of wet-process phosphoric acid concentration through a washing unit, achieving a total fluorine recovery rate of nearly 100%. The condensate from the secondary steam in the tail gas can be used as washing water for phosphoric acid filtration, achieving 100% water saving. A waste heat recovery unit enables cascade utilization of thermal energy, with low-pressure saturated steam as a byproduct, resulting in a high steam reuse rate. This invention recovers and utilizes the fluorine resources emitted by existing technologies, while simultaneously recovering the waste heat from secondary steam for reuse in production. This solves environmental problems, recovers waste heat, saves energy, and reduces fluorine emissions. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a fluorine-thermal coupled dual recovery system in a phosphoric acid production system according to an embodiment of the present invention; Figure 2 yes Figure 1 Enlarged view of the medium-pressure waste heat recovery unit and the low-pressure saturated steam production unit.

[0019] In the diagram: 1-Washing unit, 1.1-Washing tower, 1.2-Washing liquid circulation tank, 1.3-Circulation pump, 2-Waste heat recovery unit, 2.1-High-temperature refrigerant evaporator, 2.2-Vacuum pump, 2.3-Refrigerant compressor, 2.4-High-temperature refrigerant condenser, 2.5-Economizer, 2.6-High-temperature expansion valve, 2.7-High-temperature refrigerant cooler, 3-Low-pressure saturated steam production unit, 3.1-Hot water flash tank, 3.2-Hot water circulation pump. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 As shown, an embodiment of the phosphoric acid production system of the present invention includes a fluorine-thermal coupled dual recovery system, comprising a washing unit 1, a waste heat recovery unit 2, and a low-pressure saturated steam production unit 3. The washing unit 1 includes a washing tower 1.1, a washing liquid circulation tank 1.2, and a circulation pump 1.3. The circulation pump 1.3 is used to send the washing liquid in the washing liquid circulation tank 1.2 into the sprayer of the washing tower 1.1. The washing unit includes two or more washing towers, each of which is correspondingly connected to a washing liquid circulation tank and a circulation pump.

[0022] The steam production unit 3 includes a hot water flash tank 3.1, which is equipped with a water inlet, a steam outlet, a hot water circulation inlet, and a hot water circulation outlet. The waste heat recovery unit 2 includes a high-temperature refrigerant evaporator 2.1, a refrigerant compressor 2.3, a high-temperature refrigerant condenser 2.4, an economizer 2.5, and a high-temperature refrigerant cooler 2.7. The heat medium inlet and outlet of the high-temperature refrigerant evaporator 2.1 are connected to the exhaust gas outlet of the scrubbing tower 1.1 and the steam condensate pipe, respectively. The refrigerant inlet and outlet of the high-temperature refrigerant evaporator 2.1 are connected to the heat medium outlet of the high-temperature refrigerant cooler 2.7 and the inlet of the refrigerant compressor 2.3, respectively. The heat medium inlet of the high-temperature refrigerant condenser 2.4 is connected to the refrigerant compressor... The gas outlet of compressor 2.3 is connected to the gas outlet of the high-temperature refrigerant condenser 2.4. The refrigerant inlet and outlet of the high-temperature refrigerant condenser 2.4 are connected to the hot water circulation inlet and outlet of the hot water flash tank 3.1, respectively. The heat medium outlet of the high-temperature refrigerant condenser 2.4 and the liquid outlet of the refrigerant compressor 2.3 are both connected to the economizer 2.5. The outlet of the economizer 2.5 is connected to the heat medium inlet of the high-temperature refrigerant cooler 2.7. The refrigerant in the high-temperature refrigerant evaporator 2.1, the heat medium in the high-temperature refrigerant cooler 2.4, and the heat medium in the high-temperature refrigerant condenser 2.7 are all organic working fluids. R245Fa (pentafluoropropane) can be used as the organic working fluid.

[0023] A pressure-reducing pipe is connected in parallel between the economizer 2.5 and the high-temperature refrigerant cooler 2.4, and a pressure-reducing throttle valve 2.8 is installed on the pressure-reducing pipe. A high-temperature expansion valve 2.6 is installed on the pipe between the economizer 2.5 and the high-temperature refrigerant cooler 2.7. A non-condensable gas venting pipe is provided on the hot side of the high-temperature refrigerant evaporator 2.1, and a vacuum pump 2.2 is installed on the non-condensable gas venting pipe. A membrane filter (not shown in the attached figure) is connected to the steam condensate pipe. The refrigerant compressor 2.3 is a screw compressor, and a hot water circulation pump 3.2 is installed on the pipe between the refrigerant inlet and the hot water circulation outlet of the high-temperature refrigerant condenser 2.4.

[0024] An embodiment of the present invention provides a method for the dual-stage fluorine thermal coupling recovery of a phosphoric acid production system, which utilizes the aforementioned dual-stage fluorine thermal coupling recovery system for the phosphoric acid production system, and specifically includes the following steps: (1) The tail gas of the phosphoric acid production system is fed into the scrubbing tower. The scrubbing liquid in the scrubbing liquid circulation tank is sent into the sprayer by the circulating pump. The spray liquid in the sprayer comes into countercurrent contact with the fluorine-containing tail gas and absorbs the fluorine in the tail gas. In this embodiment, the scrubbing tower has two tail gases that enter each scrubbing tower in sequence and then enter the waste heat recovery unit. (2) After the fluorine in the tail gas is absorbed, it is discharged from the tail gas outlet at the top of the spray tower and enters the steam condenser. The tail gas first exchanges heat with the low-temperature liquid organic working medium. After the secondary steam in the tail gas is condensed, it is discharged through the condensate pipe. The low-temperature liquid organic working medium absorbs the heat of the secondary steam and then vaporizes to form a low-temperature gaseous organic working medium. After the secondary steam in the tail gas is condensed, the non-condensable gas in the tail gas is extracted by the vacuum pump and vented. The condensate produced after the secondary steam in the tail gas is condensed is discharged after defluorination by the membrane filter. (3) The low-temperature gaseous organic working medium enters the refrigerant compressor and is compressed. After compression, high-temperature liquid organic working fluid and high-temperature gaseous organic working fluid are generated. The high-temperature liquid organic working fluid enters the economizer, and the high-temperature gaseous organic working fluid enters the high-temperature refrigerant condenser. (4) In the high-temperature refrigerant condenser, the circulating hot water from the hot water flash tank exchanges heat with the high-temperature gaseous organic working fluid and returns to the hot water flash tank after the temperature rises. The high-temperature gaseous organic working fluid exchanges heat and cools down to form high-temperature liquid organic working fluid, which enters the economizer. The liquid high-temperature organic working fluid passes through the economizer and the high-temperature expansion valve and then enters the high-temperature refrigerant cooler. (5) The liquid organic working fluid in the economizer enters the high-temperature refrigerant cooler and exchanges heat with the circulating water from the boundary area and then cools down. The low-temperature liquid working fluid formed enters the high-temperature refrigerant evaporator. (6) In the hot water flash tank, the hot water that has been heated by the high-temperature refrigerant condenser flashes to form low-pressure saturated steam. The unvaporized saturated liquid hot water returns to the high-temperature refrigerant condenser for heat exchange again.

[0025] The washing unit can be adapted to the actual product structure of the fluorochemical production plant. The washing liquid system configuration includes, but is not limited to, the following system types: sodium sulfate solution system required for sodium fluorosilicate preparation, potassium sulfate solution system required for potassium fluorosilicate preparation, potassium hydroxide solution system corresponding to potassium fluoride synthesis, and ammonia solution system required for ammonium fluoride / ammonium bifluoride production. The number of washing towers in the washing unit can be adapted to the actual product structure of the fluorochemical production plant, employing either single-stage or two-stage washing.

[0026] The present invention has the following advantages: (1) This invention is for wet-process phosphoric acid concentration tail gas (fluorine content 140~150 mg / Nm³). 3At a temperature of 50-55℃, a two-stage cascade washing (water + salt) coupled waste heat recovery and total condensation process is used to achieve a fluorine recovery rate of nearly 100%. In the first-stage water washing tower, the water washing process can efficiently recover more than 70% of the fluorides and prepare an 18% concentration fluorosilicic acid solution. The fluoride concentration in the treated tail gas can be reduced to 145 mg / Nm³. In the second-stage water washing tower, a sodium sulfate salt washing process is used to achieve a deep recovery of 90% of the fluorides, ultimately reducing the fluoride concentration in the exhaust gas to ≤10 mg / Nm³, and simultaneously producing high-purity sodium fluorosilicate (Na2SiF6) byproduct with a purity of ≥98%. The residual fluorides are returned with the condensate to the washing process of the phosphoric acid filtration system and the water replenishment process of the grinding system, thus constructing a complete closed-loop fluorine element recycling system and realizing the full resource recovery of fluorides.

[0027] (2) The secondary steam, after two stages of fluorine scrubbing, at 70-50℃, enters the refrigerant evaporator. Through heat exchange with the liquid refrigerant, the liquid refrigerant is transformed into a gaseous working fluid. During this process, the secondary steam releases latent heat and condenses into liquid fluorinated water, which is then reused in the production system. Residual non-condensable gases are extracted using a vacuum pump. The condensate is then defluorinated (membrane filtration, fluorine residue ≤1mg / L) and reused as washing water for phosphoric acid filtration, achieving a 100% water saving rate. (3) The vaporized refrigerant is adiabatically compressed by the refrigerant compressor, and its temperature and pressure are simultaneously increased before being sent to the refrigerant condenser. Here, it undergoes countercurrent heat exchange with the circulating hot water, and the high-temperature gaseous refrigerant changes back to a liquid state. The liquid refrigerant flows through the economizer to recover waste heat, and then passes through the high-temperature expansion valve for throttling and pressure reduction. It then enters the refrigerant cooler to undergo secondary heat exchange with the circulating cooling water, and finally forms a subcooled liquid that returns to the refrigerant evaporator, thus forming a complete closed-loop thermodynamic cycle. The circulating hot water enters the refrigerant condenser, and after exchanging heat with the gaseous organic refrigerant to increase its temperature, it is sent to the hot water flash tank for flash evaporation. The low-pressure saturated steam generated during the flash evaporation process is recycled back to the phosphoric acid production unit itself through the recovery system, while the unvaporized saturated liquid hot water is pressurized and transported by the circulating hot water pump and returned to the refrigerant condenser to participate in the heat exchange process again. The waste heat from the secondary steam (50~55℃) of wet-process phosphoric acid concentration is processed by an organic working fluid screw compressor unit, producing 1.7t / t P2O5 of 0.1MPa saturated steam as a byproduct, with a steam reuse rate of ≥90%.

[0028] This invention can be applied to the flash cooling unit and concentration section of the wet-process phosphoric acid reaction. In the wet-process phosphoric acid concentration section, relying on the latent heat of vaporization contained in the 50°C secondary steam, energy is converted through a screw compressor unit, achieving a byproduct of 1.7 tons of 0.1 MPa low-pressure steam per ton of phosphorus pentoxide production. This steam is recycled back to the wet-process phosphoric acid concentration section in a closed loop, forming a thermal energy recycling system. The annual production of wet-process phosphoric acid is approximately 18 million tons (P2O5 equivalent), which can reduce fluorine emissions by 55,002 tons annually and reduce acid rain pollution area by 2.25 million hectares; steam recovery is 30.6 million tons / year, saving 737,000 tons of standard coal and reducing carbon emissions by 2.376 million tons / year.

[0029] This invention recycles and utilizes resources, while also recovering the waste heat from secondary steam for reuse in production. This solves environmental problems, recovers waste heat, saves energy, and reduces fluorine emissions.

Claims

1. A fluorine-thermal coupled dual recovery system for phosphoric acid production systems, characterized in that: It includes a washing unit, a waste heat recovery unit, and a low-pressure saturated steam production unit. The washing unit includes a washing tower, a washing liquid circulation tank, and a circulation pump. The circulation pump is used to send the washing liquid in the washing liquid circulation tank into the sprayers of the washing tower. The steam production unit includes a hot water flash tank, which has a water inlet, a steam outlet, a hot water circulation inlet, and a hot water circulation outlet. The waste heat recovery unit includes a high-temperature refrigerant evaporator, a refrigerant compressor, a high-temperature refrigerant condenser, an economizer, and a high-temperature refrigerant cooler. The heat inlet and outlet of the high-temperature refrigerant evaporator are respectively connected to the exhaust gas outlet of the washing tower and the steam condensate pipeline. The refrigerant inlet and outlet of the refrigerant evaporator are connected to the heat medium outlet of the high-temperature refrigerant cooler and the inlet of the refrigerant compressor, respectively. The heat medium inlet of the high-temperature refrigerant condenser is connected to the gas outlet of the refrigerant compressor. The refrigerant inlet and outlet of the high-temperature refrigerant condenser are connected to the hot water circulation inlet and outlet of the hot water flash tank, respectively. The heat medium outlet of the high-temperature refrigerant condenser and the liquid outlet of the refrigerant compressor are both connected to the economizer. The outlet of the economizer is connected to the heat medium inlet of the high-temperature refrigerant cooler. The refrigerant in the high-temperature refrigerant evaporator, the heat medium of the high-temperature refrigerant cooler, and the heat medium of the high-temperature refrigerant condenser are all organic working fluids.

2. The fluorine-thermal coupled dual recovery system for phosphoric acid production according to claim 1, characterized in that: The washing unit includes two or more washing towers, each of which is connected to a washing liquid circulation tank and a circulation pump.

3. The fluorine-thermal coupled dual recovery system for phosphoric acid production according to claim 1, characterized in that: A pressure-reducing pipe is connected in parallel to the pipeline between the economizer and the high-temperature refrigerant cooler, and a pressure-reducing throttle valve is installed on the pressure-reducing pipe.

4. The fluorine-thermal coupled dual recovery system for phosphoric acid production according to claim 1, characterized in that: A high-temperature expansion valve is installed on the pipeline between the economizer and the high-temperature refrigerant cooler.

5. The fluorine-thermal coupled dual recovery system for phosphoric acid production according to claim 1, characterized in that: The hot side of the high-temperature refrigerant evaporator is equipped with a non-condensable gas venting pipe, and a membrane filter is connected to the steam condensate pipe.

6. The fluorine-thermal coupled dual recovery system for phosphoric acid production according to claim 1, characterized in that: The refrigerant compressor is a screw compressor, and a hot water circulation pump is installed on the pipeline between the refrigerant inlet and the hot water circulation outlet of the high-temperature refrigerant condenser.

7. A dual-mode fluorine thermal coupling recovery method for phosphoric acid production systems, characterized in that, It is carried out using the fluorine-thermal coupled dual recovery system of the phosphoric acid production system according to any one of claims 1 to 7, and specifically includes the following steps: (1) The tail gas of the phosphoric acid production system is fed into the scrubbing tower. The scrubbing liquid in the scrubbing liquid circulation tank is sent into the sprayer by the circulating pump. The spray liquid in the sprayer comes into countercurrent contact with the fluorine-containing tail gas and absorbs the fluorine in the tail gas. (2) After the fluorine in the tail gas is absorbed, it is discharged from the tail gas outlet at the top of the spray tower and enters the steam condenser. The tail gas first exchanges heat with the low-temperature liquid organic working medium. After the secondary steam in the tail gas is condensed, it is discharged from the condensate pipe. The low-temperature liquid organic working medium absorbs the heat of the secondary steam and then vaporizes to form a low-temperature gaseous organic working medium. (3) The low-temperature gaseous organic working medium enters the refrigerant compressor and is compressed. After the low-temperature gaseous organic working medium is compressed, it produces a high-temperature liquid organic working medium and a high-temperature gaseous organic working medium. The working fluid enters the economizer, and the high-temperature gaseous organic working fluid enters the high-temperature refrigerant condenser; (4) In the high-temperature refrigerant condenser, the circulating hot water from the hot water flash tank exchanges heat with the high-temperature gaseous organic working fluid and its temperature rises and returns to the hot water flash tank. The high-temperature gaseous organic working fluid exchanges heat and its temperature drops to form a high-temperature liquid organic working fluid that enters the economizer; (5) The liquid organic working fluid in the economizer enters the high-temperature refrigerant cooler and exchanges heat with the circulating water from the boundary area and its temperature drops. The low-temperature liquid working fluid formed enters the high-temperature refrigerant evaporator; (6) In the hot water flash tank, the hot water that has been heated by the high-temperature refrigerant condenser flashes to form low-pressure saturated steam. The unvaporized saturated liquid hot water returns to the high-temperature refrigerant condenser for heat exchange again.

8. The method for dual-linked fluorine thermal recovery in a phosphoric acid production system according to claim 7, characterized in that: There are two or more scrubbing towers. The exhaust gas enters each scrubbing tower in sequence for washing and then enters the waste heat recovery unit.

9. The method for dual-linked fluorine thermal recovery in a phosphoric acid production system according to claim 7, characterized in that: In step (2), after the secondary steam in the exhaust gas is condensed, the non-condensable gas in the exhaust gas is extracted and vented by a vacuum pump, and the condensate produced after the secondary steam in the exhaust gas is condensed is discharged after being defluorinated by a membrane filter.

10. The method for dual-linked fluorine thermal recovery in a phosphoric acid production system according to claim 7, characterized in that: The liquid high-temperature organic working fluid is cooled down after passing through the economizer and high-temperature expansion valve, and then enters the high-temperature refrigerant cooler.

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