Device system and method for preparing iron phosphate

Abstract

The present invention relates to the technical field of iron phosphate. Disclosed is a device system for preparing iron phosphate. The device system comprises a mixing tower for preparing a raw material liquid, a filter capable of filtering particulate matter in the raw material liquid, a Venturi-type pre-concentrator capable of evaporating water in the raw material liquid to obtain a concentrated liquid, a roasting furnace capable of decomposing the concentrated liquid at a high temperature, and a cooling conveyor capable of cooling and conveying solid products in the roasting furnace, which are sequentially connected, wherein the roasting furnace is connected to the upper end of the pre-concentrator via a furnace gas pipeline, and the pre-concentrator is also connected to a tail gas treatment device via a pipeline. In this invention, high-purity Fe2O3 powder is dissolved in a mixed solution of hydrochloric acid and phosphoric acid to form a turbid liquid, the turbid liquid is atomized by a two-fluid spray gun and is then calcined, the resulting solid product is iron phosphate, and an iron phosphate powder can be directly prepared, which provides a new method for preparing iron phosphate.

Description

Device system and method for preparing ferric phosphate Technical Field

[0001] The present invention relates to the technical field of iron phosphate, and in particular to a device system and method for preparing iron phosphate. Background Art

[0002] Iron phosphate is widely used in the production of lithium iron phosphate batteries and is known for its safety and reliability. As a precursor material for lithium iron phosphate, iron phosphate is in high demand. Preparation methods for iron phosphate include chemical precipitation, hydrothermal synthesis, sol-gel, fluoride ion synthesis, bio-templated synthesis, microwave-assisted synthesis, and flame spray drying.

[0003] Because the electrochemical activity of FePO4 directly impacts the electrochemical performance of the resulting lithium iron phosphate (LIFP) material, the question of how to utilize commonly used industrial methods to produce high-performance LIFP materials is of great significance. Currently, the main method for synthesizing LIFP materials in industry is precipitation. This method is widely used due to its advantages, including low equipment requirements, low energy consumption, ease of industrialization, and controllable preparation process. This method can produce FePO4 materials with uniform particle size, large specific surface area, and high electrochemical activity. However, it also has certain limitations. The preparation process is relatively cumbersome, typically consisting of slurry mixing, aging, filtration, washing, and drying. The slurry mixing process requires high precision and strict raw material requirements, resulting in completely different preparation processes depending on the raw materials used. Furthermore, the washing process consumes a lot of water, resulting in high wastewater treatment costs. The resulting FePO4 filter cake is relatively viscous, and traditional drying techniques result in uneven drying and high energy consumption. Therefore, vacuum drying is often required to prevent localized overheating.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a device system and method for preparing ferric phosphate. Fe2O3 powder is dissolved in an acid solution mixed with hydrochloric acid and phosphoric acid to form a turbid liquid, the turbid liquid is burned to produce ferric phosphate, and the tail gas is recycled and reused, thus opening up a new method for preparing ferric phosphate and saving energy consumption.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A device system for preparing ferric phosphate comprises a mixing tower for preparing a raw material liquid, a filter capable of filtering particulate matter in the raw material liquid, a venturi-type pre-concentrator capable of evaporating water in the raw material liquid to obtain a concentrated liquid, a roasting furnace capable of pyrolyzing the concentrated liquid, and a cooling conveyor capable of cooling and conveying a solid product in the roasting furnace.

[0008] The roasting furnace is connected to the upper end of the pre-concentrator through a furnace gas pipeline; the pre-concentrator is also connected to the tail gas treatment device through a pipeline.

[0009] Furthermore, the mixing tower and filter are both made of fiberglass, and the interior of the filter is provided with a filter barrel wrapped with a PVDF filter mesh; the cooling conveyor conveys material at a flow rate of 0.0065m / s, a processing capacity of 100 to 10,000kg / h, a cooling area of ​​50 to 600㎡, and a material temperature after cooling of 30-100°C.

[0010] Furthermore, the roasting furnace is in the shape of a vertical cylinder, including an upper cone and a lower cone; the outer shell of the roasting furnace is a steel plate welded structure, the inner side of the outer shell is lined with refractory and acid-resistant bricks, and the outer side of the outer shell is wrapped with an insulation layer; multiple burners are arranged inside the roasting furnace, arranged in a tangential direction on the furnace body; a two-fluid atomizing spray gun made of niobium is provided on the top of the roasting furnace.

[0011] Furthermore, the exhaust gas treatment device includes an exhaust gas blower connected to the pre-concentrator and capable of extracting the exhaust gas, a first washing tower for washing HCl gas in the exhaust gas with desalted water, and a second washing tower for washing the exhaust gas again with desalted water added with alkali solution; an absorption tower capable of absorbing HCl gas is arranged between the pre-concentrator and the exhaust gas blower, a third washing tower for performing a primary washing of HCl gas in the exhaust gas, and a graphite heat exchanger capable of reducing the exhaust gas temperature to below 40°C.

[0012] Furthermore, the absorption tower is made of FRP or PPH; the interior of the absorption tower is filled with PP structured packing, and there is a PTFE nozzle on the top; the first washing tower and the second washing tower are both packed towers, made of FRP or PPH, with PP corrugated packing inside and a PTFE nozzle on the top; the washing water outlet of the first washing tower is connected to the absorption tower, and the second washing tower is connected to a chimney for discharging exhaust gas; the third washing tower is a post-Venturi type.

[0013] A method for preparing ferric phosphate using any one of the above-described apparatus systems for preparing ferric phosphate comprises:

[0014] S1: Fe2O3 powder is dissolved in a mixing tower with a certain proportion of HCl solution and H3PO4 solution to form a turbid liquid, i.e. raw material liquid; H + with Fe 3+ The molar ratio is 3:1 to 7:1;

[0015] S2: The raw material liquid is filtered in a filter and then transported to a pre-concentrator by a circulation pump to evaporate 25% to 30% of the water to obtain a concentrated liquid, which is then atomized by a spray gun and then fed into a roasting furnace;

[0016] S3: In the roasting furnace, the concentrated liquid decomposes into iron phosphate powder and HCl gas. The iron phosphate powder flows countercurrently with the combustion hot air flow and naturally falls to the cooling conveyor at the bottom of the furnace. The iron phosphate powder is discharged and cooled to below 50°C. The tail gas composed of HCl gas, water vapor, natural gas combustion products, a small amount of iron phosphate powder and excess oxygen is extracted from the top of the furnace and enters the pre-concentrator through the furnace gas pipeline.

[0017] S4: A small amount of iron phosphate powder is absorbed in the pre-concentrator, and the remaining exhaust gas is treated by the exhaust gas treatment device and discharged from the chimney.

[0018] Furthermore, in step S2, the gas temperature in the roasting furnace is 420° C. to 850° C., and the pre-concentrator performs heat exchange with the gas in the roasting furnace to evaporate the water in the raw material liquid.

[0019] Furthermore, the roasting furnace uses natural gas as raw material and air as combustion-supporting gas; in the process of decomposing the concentrated liquid into iron phosphate powder and HCL vapor in step S3, the temperature at the outlet of the lower cone of the roasting furnace is 300-600°C, the temperature at the burner is 1300-1450°C, and the temperature at the furnace top is 450-850°C; the concentrated liquid enters the spray gun and is atomized and sprayed out, the liquid phase flow pressure is 200kPa~400kPa, and the flow rate is 0.3m 3 ~6m 3 The gas atomization wind pressure is 0.3 MPa ~ 1.0 MPa; the temperature of the core reaction zone of the roasting furnace is 650-950 ° C; the droplet particle size sprayed by the spray gun is 3 μm ~ 150 μm.

[0020] Furthermore, in step S4, the cooled tail gas is passed into a third scrubbing tower to initially scrub the HCl gas therein with rinse water, then passed into the first scrubbing tower to scrub the HCl gas again with desalted water, and finally passed into a second scrubbing tower to scrub the residual HCl gas with desalted water added with alkali solution, and the washed tail gas is discharged through a chimney.

[0021] Furthermore, the operating temperature of the absorption tower is 60-105°C, the absorption water in the absorption tower flows in the countercurrent direction to the tail gas, and the regenerated acid formed by the absorption water absorbing HCl gas can be mixed with the Fe2O3 powder in step S1 to prepare a turbid liquid; the water condensed from the graphite heat exchanger enters the water collecting tank and then flows to the absorption tower for reabsorption; the weak acid solution formed by the washing water of the first washing tower and the third washing tower absorbing the HCl gas in the tail gas enters the absorption tower through a plastic pump; the washing wastewater after the second washing tower absorbs the HCl gas is discharged into the sewage station for treatment.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention dissolves high-purity Fe2O3 powder in a mixture of hydrochloric acid and phosphoric acid to form a turbid liquid, atomizes it with a two-fluid spray gun, and then burns it. The resulting solid product is ferric phosphate, which can be directly prepared from ferric phosphate powder without the need for slurry mixing, aging, washing, drying, etc. The preparation process is simple, and a new method for preparing ferric phosphate has been opened up.

[0024] (2) The tail gas generated in the present invention is treated by the tail gas treatment device and then discharged into the atmosphere, and the tail gas treatment device can recycle and reuse the hydrochloric acid, thereby reducing the acid discharged into the atmosphere and achieving waste gas recycling and reuse, thus saving energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a schematic diagram of the device system of the present invention;

[0026] FIG2 is a process flow chart of the present invention.

[0027] Among them, the names corresponding to the figure numbers are: 1-mixing tower, 2-filter, 3-pre-concentrator, 4-calciner, 5-absorption tower, 6-graphite heat exchanger, 7-third washing tower, 8-exhaust gas fan, 9-first washing tower, 10-second washing tower, 11-cooling conveyor, 12-furnace gas pipeline. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and examples. The embodiments of the present invention include but are not limited to the following examples.

[0029] As shown in FIG1 , this embodiment provides a device system for preparing ferric phosphate, comprising a mixing tower 1 , a filter 2 , a pre-concentrator 3 , a calciner 4 , and an exhaust gas treatment device connected to the pre-concentrator 3 , which are connected in sequence.

[0030] The mixing tower 1 is made of glass fiber reinforced plastic and is used to prepare the raw material liquid. Fe2O3 powder and a certain proportion of HCl solution and H3PO4 solution are dissolved in the mixing tower to form a turbid liquid, i.e. the raw material liquid. + with Fe 3+ The molar ratio is 3:1 to 7:1.

[0031] Filter 2 is also made of fiberglass. The raw material liquid in mixing tower 1 is pumped into filter 2 through a plastic pump. A filter barrel wrapped with a PVDF filter mesh is provided inside filter 2 to filter out impurities such as particulate matter in the raw material liquid.

[0032] The filtered raw material liquid is transported to the pre-concentrator 3 through a circulation pump. The pre-concentrator 3 is a Venturi type and is connected to the upper end of the roasting furnace 4 through a furnace gas pipe 12. The high-temperature gas (gas temperature is 420-850°C) in the roasting furnace 4 enters the pre-concentrator 3 through the furnace gas pipe for heat exchange, evaporating 25%-30% of the water in the raw material liquid to obtain a concentrated liquid, which is atomized by a spray gun and enters the roasting furnace 4.

[0033] The roasting furnace 4 is the main reaction device, which is a vertical cylindrical body and includes an upper cone and a lower cone. The shell of the roasting furnace 4 is a steel plate welded structure, the inner side of the shell is lined with refractory acid-resistant bricks, and the outer side of the shell is wrapped with an insulation layer. There are multiple burners inside the roasting furnace 4, which are arranged tangentially on the furnace body. A niobium-made double-fluid atomizing spray gun is set on the top of the roasting furnace 4. The concentrated liquid in the pre-concentrator enters the roasting furnace 4 through the double-fluid atomizing spray gun and is decomposed into iron phosphate powder and HCL vapor. The iron phosphate powder is in countercurrent with the combustion hot air flow, and the iron phosphate powder naturally falls to the lower furnace. The cooling conveyor 11 at the bottom cools the material while conveying it. The conveyor has a material flow rate of 0.0065 m / s, a processing capacity of 100 to 10,000 kg / h, a cooling area of ​​50 to 600 m2, and a temperature of 30-100°C after cooling. Tail gas consisting of HCl vapor, water vapor, natural gas combustion products, a small amount of iron phosphate powder, and excess oxygen is extracted from the furnace top through the furnace gas pipe 12 and enters the pre-concentrator 3, where the small amount of iron phosphate powder is absorbed.

[0034] When the roasting furnace 4 is working, natural gas is used as raw material and air is used as combustion-supporting gas. The temperature at the outlet of the lower vertebral body is 300-600℃, the temperature at the burner is 1300-1450℃, and the temperature at the top of the furnace is 450-850℃. The concentrated liquid enters the spray gun and is atomized and sprayed out. The liquid phase flow pressure is 200kPa~400kPa and the flow rate is 0.3m 3 ~6m 3 , the gas phase atomizing air pressure is 0.3 MPa ~ 1.0 MPa; the temperature of the core reaction zone of the roasting furnace is 650-950 ° C; by adjusting the pressure ratio of the liquid phase to the gas phase and matching the size of the different spray gun nozzles, products of different particle sizes can be produced. In this embodiment, the droplet size sprayed by the spray gun is 3 μm ~ 150 μm.

[0035] The tail gas treatment device includes an absorption tower 5, a graphite heat exchanger 6, a third scrubber 7, an exhaust fan 8, a first scrubber 9, and a second scrubber 10, which are arranged in this order. The exhaust fan 8 is the main power device for gas phase flow, generating a total pressure of 5 to 20 kPa. It is used to extract the exhaust gas generated by the roasting furnace 4, and then pass it through the first scrubber 9 and the second scrubber 10 before being discharged from the chimney.

[0036] In this embodiment, absorption tower 5 is connected to pre-concentrator 3. Exhaust gas extracted by exhaust blower 8 first absorbs some HCl gas in absorption tower 5. It is then cooled to below 40°C by graphite heat exchanger 6 and scrubbed by third scrubber 7 before entering first scrubber 9 and second scrubber 10. Absorption tower 5 is constructed of FRP or PPH and filled with PP structured packing. A PTFE nozzle at the top evenly distributes the spray liquid across the packing. The spray liquid flows countercurrently with the exhaust gas containing HCl vapor, absorbing the HCl to form regenerated acid. The operating temperature is 60-105°C. The condensed water from graphite heat exchanger 6 enters a sump and flows to absorption tower 5 for reabsorption. Third scrubber 7 is a post-Venturi type, using rinse water to scrub some HCl gas from the exhaust gas. The first washing tower 9 and the second washing tower 10 are both packed towers made of FRP or PPH materials, with PP corrugated packing inside and PTFE nozzles installed on the top. The washing water of the first washing tower 9 is desalted water, and its outlet is connected to the absorption tower 5. The washing water is sprayed down to absorb the HCl in the exhaust gas, and the generated weak acid solution enters the absorption tower 5 through a plastic pump. The second washing tower 10 is connected to a chimney for discharging exhaust gas. The washing water is desalted water with alkali added, and the washing water after washing is discharged into the sewage station for treatment.

[0037] The process for preparing ferric phosphate using the above-mentioned device is shown in FIG2 and includes the following steps:

[0038] S1: Fe2O3 powder is dissolved in a mixing tower with a certain proportion of HCl solution and H3PO4 solution to form a turbid liquid (raw liquid); H + with Fe 3+ The molar ratio is 3:1 to 7:1;

[0039] S2: The raw material liquid is filtered in a filter and then transported to a pre-concentrator by a circulation pump. The gas temperature in the roasting furnace is 420℃~850℃. The pre-concentrator and the gas in the roasting furnace perform heat exchange to evaporate 25%~30% of the water in the raw material liquid to form a concentrated liquid. The concentrated liquid is atomized by a spray gun and then enters the roasting furnace;

[0040] S3: The concentrated liquid decomposes into iron phosphate powder and HCl vapor in the roasting furnace. The reaction equation is as follows: FeCl3+H3PO4=FePO4↓+3HCl↑

[0041] The iron phosphate powder flows countercurrently to the combustion hot air flow and naturally falls to the cooling conveyor at the bottom of the furnace. During the discharge process, the temperature of the iron phosphate powder is reduced to below 50°C. The tail gas composed of HCl gas, water vapor, natural gas combustion products, a small amount of iron phosphate powder and excess oxygen is extracted from the top of the furnace and enters the pre-concentrator through the furnace gas pipeline. In the pre-concentrator, a small amount of iron phosphate powder is absorbed.

[0042] S4: The tail gas is extracted from the exhaust gas blower and passes through an absorption tower to absorb part of the HCl gas. It is then cooled to below 40°C by a graphite heat exchanger. The cooled tail gas is passed through a third scrubber to initially scrub the HCl gas with rinse water. The tail gas is then passed through a first scrubber to scrub the HCl gas again with desalted water. Finally, the tail gas is passed through a second scrubber to scrub the remaining HCl gas with desalted water containing alkali. The scrubbed tail gas is discharged through a chimney.

[0043] S5: The regenerated acid formed by the absorption water in the absorption tower absorbing HCl gas is transported to the hydrochloric acid preparation station, and the prepared HCl can be mixed with the Fe2O3 powder in step S1 to prepare the raw material liquid; the water condensed from the graphite heat exchanger enters the water collection tank and then flows to the absorption tower for reabsorption; the washing water of the first washing tower and the third washing tower absorbs the HCl gas in the tail gas to form a weak acid solution and enters the absorption tower through a plastic pump; the washing wastewater after the second washing tower absorbs the HCl gas is discharged into the sewage station for treatment.

[0044] The above-mentioned process for preparing ferric phosphate is used to produce ferric phosphate. 1000g of Fe2O3 powder can produce 1887.5g of ferric phosphate.

[0045] The present invention dissolves high-purity Fe2O3 powder in a mixture of hydrochloric acid and phosphoric acid to form a turbid solution, atomizes it with a two-fluid spray gun, and then calcines it. The resulting solid product is ferric phosphate, which can be directly prepared into ferric phosphate powder without the need for slurry mixing, aging, washing, or drying, resulting in a simple preparation process. The exhaust gas generated in the present invention is treated by an exhaust gas treatment device and then discharged into the atmosphere. The exhaust gas treatment device can also recover and reuse the hydrochloric acid, thereby reducing acid emissions into the atmosphere while achieving waste gas recovery and reuse.

[0046] The above embodiment is only one of the preferred implementation methods of the present invention and should not be used to limit the scope of protection of the present invention. Any changes or modifications that have no substantive meaning made to the main design concept and spirit of the present invention, as long as the technical problems solved are still consistent with the present invention, should be included in the scope of protection of the present invention.

Claims

1. A device system for preparing iron phosphate, characterized in that: The invention comprises a mixing tower (1) for preparing a raw material liquid, a filter (2) capable of filtering particulate matter in the raw material liquid, a venturi-type pre-concentrator (3) capable of evaporating water in the raw material liquid to obtain a concentrated liquid, a roasting furnace (4) capable of high-temperature decomposing the concentrated liquid, and a cooling conveyor (11) capable of cooling and conveying a solid product in the roasting furnace (4); The roasting furnace (4) is connected to the upper end of the pre-concentrator (3) via a furnace gas pipeline (12); the pre-concentrator (3) is also connected to a tail gas treatment device via a pipeline.

2. The device system for preparing ferric phosphate according to claim 1, characterized in that: The mixing tower (1) and the filter (2) are both made of glass fiber reinforced plastics, and a filter barrel wrapped with a PVDF filter mesh is arranged inside the filter (2); the cooling conveyor (11) has a material conveying flow rate of 0.0065 m / s, a processing capacity of 100 to 10,000 kg / h, a cooling area of ​​50 to 600 m2, and a material temperature after cooling of 30 to 100°C.

3. The device system for preparing ferric phosphate according to claim 1, characterized in that: The roasting furnace (4) is in the shape of a vertical cylinder, comprising an upper cone and a lower cone; the outer shell of the roasting furnace (4) is a steel plate welded structure, the inner side of the outer shell is lined with refractory acid-resistant bricks, and the outer side of the outer shell is wrapped with an insulation layer; a plurality of burners are arranged inside the roasting furnace (4) and arranged in a tangential direction on the furnace body; a dual-fluid atomizing spray gun made of niobium is arranged on the top of the roasting furnace (4).

4. The device system for preparing ferric phosphate according to claim 1, characterized in that: The tail gas treatment device comprises an exhaust gas blower (8) connected to a pre-concentrator (3) and capable of extracting the tail gas, a first washing tower (9) for washing HCl gas in the tail gas with desalted water, and a second washing tower (10) for washing the tail gas again with desalted water added with alkali liquid; an absorption tower (5) capable of absorbing HCl gas, a third washing tower (7) for initially washing the HCl gas in the tail gas, and a graphite heat exchanger (6) capable of reducing the temperature of the tail gas to below 40°C are arranged between the pre-concentrator (3) and the exhaust gas blower (8).

5. The device system for preparing ferric phosphate according to claim 4, characterized in that: The absorption tower (5) is made of FRP or PPH material; the absorption tower (5) is filled with PP structured packing inside, and has a PTFE nozzle on the top; the first washing tower (9) and the second washing tower (10) are both packing towers, made of FRP or PPH material, filled with PP corrugated packing inside, and have a PTFE nozzle on the top; the washing water outlet of the first washing tower (9) is connected to the absorption tower (5), and the second washing tower (10) is connected to a chimney for discharging exhaust gas; the third washing tower (7) is a rear Venturi type.

6. A method for preparing iron phosphate using any one of the apparatuses for preparing iron phosphate as claimed in claims 1 to 5, characterized in that: include: S1: Dissolve Fe2O3 powder in a mixing tower with a certain proportion of HCl solution and H3PO4 solution to form a turbid liquid, i.e., the raw material liquid; + with Fe 3+ The molar ratio is 3:1 to 7:1; S2: filtering the raw material liquid in a filter and then conveying it to a pre-concentrator by a circulating pump to evaporate 25% to 30% of the water to obtain a concentrated liquid, and then atomizing the concentrated liquid through a spray gun and then entering a roasting furnace; S3: In the roasting furnace, the concentrated liquid is decomposed into iron phosphate powder and HCL gas. The iron phosphate powder is in countercurrent with the combustion hot air flow. The iron phosphate powder naturally falls to the cooling conveyor at the bottom of the furnace, and the iron phosphate powder is output while being cooled to below 50°C; the tail gas composed of HCL gas, water vapor, natural gas combustion products, a small amount of iron phosphate powder and excess oxygen is extracted from the top of the furnace and enters the pre-concentrator through the furnace gas pipeline; S4: A small amount of iron phosphate powder is absorbed in the pre-concentrator, and the remaining exhaust gas is treated by the exhaust gas treatment device and discharged from the chimney.

7. A method for preparing ferric phosphate according to claim 6, characterized in that: In step S2, the gas temperature in the roasting furnace is 420° C. to 850° C., and the pre-concentrator performs heat exchange with the gas in the roasting furnace to evaporate the water in the raw material liquid.

8. A method for preparing ferric phosphate according to claim 7, characterized in that: The roasting furnace uses natural gas as raw material and air as combustion-supporting gas; in the process of decomposing the concentrated liquid into iron phosphate powder and HCL vapor in step S3, the temperature at the outlet of the lower vertebral body of the roasting furnace is 300-600°C, the temperature at the burner is 1300-1450°C, and the temperature at the furnace top is 450-850°C; the concentrated liquid enters the spray gun and is atomized and then sprayed out, the liquid phase flow pressure is 200kpa~400kpa, and the flow rate is 0.3m 3 ~6m 3 , gas phase atomization wind pressure is 0.3 MPa ~ 1.0 MPa; the temperature of the core reaction zone of the roasting furnace is 650-950 ° C; the droplet particle size sprayed by the spray gun is 3 μm ~ 150 μm.

9. A method for preparing ferric phosphate according to claim 8, characterized in that: In step S4, the tail gas after cooling is passed into the third washing tower to initially wash the HCl gas therein with rinsing water, then passed into the first washing tower to wash the HCl gas again with desalted water, and finally passed into the second washing tower to wash the residual HCl gas with desalted water added with alkali solution, and the washed tail gas is discharged from the chimney.

10. A method for preparing ferric phosphate according to claim 9, characterized in that: The operating temperature of the absorption tower is 60-105° C. The absorption water in the absorption tower flows in the opposite direction to the tail gas. The regenerated acid formed by the absorption water absorbing HCl gas can be mixed with the Fe2O3 powder in step S1 to prepare a turbid liquid; the water condensed from the graphite heat exchanger enters the water collecting tank and then flows to the absorption tower for reabsorption; the washing water of the first washing tower and the third washing tower absorbs the HCl gas in the tail gas to form a weak acid solution and enters the absorption tower through a plastic pump; the washing wastewater after the second washing tower absorbs the HCl gas is discharged into the sewage station for treatment.

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