A method and system for recovering tail gas after hydro-reduction of arsenic trichloride

Abstract

The application discloses a recovery method and system of tail gas after hydroreduction of arsenic trichloride, and the recovery method comprises the following steps: carrying out cooling separation treatment on the tail gas to obtain first tail gas, liquid arsenic trichloride and arsenic powder; the first tail gas is introduced into concentrated sulfuric acid to dissolve residual arsenic trichloride vapor in the first tail gas and obtain second tail gas; hydrogen chloride in the second tail gas is absorbed by an absorption liquid, and hydrogen is separated out and discharged or recovered. Through three-stage cooperative treatment, solid arsenic, unreacted liquid arsenic trichloride and gaseous hydrogen chloride in the tail gas are respectively separated and purified for reuse, closed-loop circulation of arsenic and chlorine elements is realized, and safe discharge of the tail gas is achieved.

Description

Technical Field

[0001] This invention relates to the field of recovery technology for tail gas after hydrogenation and reduction of arsenic trichloride, and in particular to a method and system for recovering tail gas after hydrogenation and reduction of arsenic trichloride. Background Technology

[0002] In fields such as semiconductor materials and specialty glasses, the preparation of high-purity arsenic typically involves the hydrogenation reduction process of arsenic trichloride (AsCl3 + 3 / 2 H2 → As + 3HCl). The exhaust gas produced after this reaction is complex, mainly containing unreacted arsenic trichloride, hydrogen chloride (HCl) gas generated in the reaction, excess hydrogen gas, and trace amounts of arsenic powder that precipitate out due to the decrease in temperature.

[0003] Currently, the common method for treating such highly toxic and corrosive exhaust gases is to use ordinary condensers to recover some AsCl3. However, the condensation efficiency is limited, and a large amount of arsenic compounds and HCl remain in the exhaust gas, which cannot meet the requirements for environmental protection emissions and resource recycling. Summary of the Invention

[0004] The technical problem to be solved by this invention is that the tail gas after the hydrogenation and reduction of arsenic trichloride is partially recovered by using a conventional condenser, but the condensation efficiency is limited, and a large amount of arsenic compounds and HCl remain in the tail gas, which cannot meet the requirements of environmental protection emission and resource recycling.

[0005] To address the aforementioned technical problems, this invention provides a method for recovering the tail gas after the hydrogenation and reduction of arsenic trichloride, comprising the following steps: The exhaust gas is cooled and separated to obtain the first exhaust gas, liquid arsenic trichloride, and arsenic powder. The first tail gas is passed into concentrated sulfuric acid to dissolve the residual arsenic trichloride vapor in the first tail gas and to obtain the second tail gas. The hydrogen chloride in the second tail gas is absorbed by the absorbent liquid, and the hydrogen gas is separated for discharge or recovery.

[0006] Furthermore, the cooling and separation process includes: The exhaust gas is cooled to a first temperature, which is lower than the dew point temperature of arsenic trichloride and not higher than the sublimation temperature of the arsenic powder, so that the arsenic trichloride vapor liquefies and the arsenic vapor sublimates into arsenic powder.

[0007] Furthermore, after passing the first tail gas into concentrated sulfuric acid, the process also includes: Discharge the sulfuric acid solution containing arsenic trichloride; The sulfuric acid solution containing the arsenic trichloride was subjected to a static separation treatment to obtain an upper sulfuric acid layer and a lower arsenic trichloride layer. Separate the sulfuric acid layer and the arsenic trichloride layer.

[0008] Furthermore, before allowing the sulfuric acid solution containing arsenic trichloride to stand and separate into layers, the sulfuric acid solution containing arsenic trichloride is stirred.

[0009] Furthermore, the absorbent is pure water.

[0010] This invention also provides a system for recovering the exhaust gas after the hydrogenation and reduction of arsenic trichloride. The system utilizes the method described above for recovering the exhaust gas after the hydrogenation and reduction of arsenic trichloride. The recovery system includes: The condenser includes a condenser body, an outlet end, an inlet end, and a collection end. The outlet end and the inlet end are connected through the condenser body. The end of the inlet end away from the condenser body is connected to the furnace body to allow the exhaust gas to enter the condenser body. The collection end is located at the lower end of the condenser body and is used to collect the arsenic powder and the liquid arsenic trichloride. A sulfuric acid absorption tank, filled with concentrated sulfuric acid, is connected to the outlet end to absorb the first tail gas; and An absorbent container filled with absorbent liquid has one end connected to the sulfuric acid absorption tank and the other end serving as an exhaust port.

[0011] Furthermore, the condenser body includes a shell, two coils, and quartz packing. The two coils are spaced apart inside the shell, and the quartz packing fills the gap between the coils and the inner wall of the shell, as well as the gap between the two coils.

[0012] Furthermore, it also includes an empty tank and a first valve body. The empty tank is disposed between the sulfuric acid absorption tank and the absorbent liquid container, and the empty tank is connected to the sulfuric acid absorption tank and the absorbent liquid container through a pipeline, on which the first valve body is disposed.

[0013] Furthermore, it also includes a separation device, which includes a stirrer and a settling separation tank. The settling separation tank is used to receive the sulfuric acid solution containing arsenic trichloride in the sulfuric acid absorption tank, and the stirrer is used to stir the sulfuric acid solution containing arsenic trichloride in the settling separation tank.

[0014] Furthermore, a second valve body is provided on the pipeline between the condenser and the furnace body and / or between the condenser and the sulfuric acid absorption tank.

[0015] Compared with existing technologies, the beneficial effects of the method and system for recovering tail gas after the hydrogenation and reduction of arsenic trichloride in this invention are as follows: This invention embodiment performs three-stage synergistic treatment through the above steps, separating and purifying solid arsenic, unreacted liquid arsenic trichloride, and gaseous hydrogen chloride in the exhaust gas for reuse, realizing a closed-loop cycle of arsenic and chlorine elements, and achieving safe emission of exhaust gas. Among them, arsenic is mainly removed through a stepped method of cooling and condensation and concentrated sulfuric acid absorption, avoiding the risk of AsCl3 directly contacting water to produce highly toxic AsH3. Attached Figure Description

[0016] The present application will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, those skilled in the art will understand that these drawings are drawn only for the purpose of explaining the preferred embodiments and therefore should not be construed as limiting the scope of the present application. Furthermore, unless specifically indicated, the drawings are intended only to conceptually represent the composition or structure of the described objects and may contain exaggerated representations, and the drawings are not necessarily drawn to scale.

[0017] Figure 1 This is a schematic flowchart of the method for recovering tail gas after hydrogenation and reduction of arsenic trichloride provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the tail gas recovery system after hydrogenation and reduction of arsenic trichloride provided in an embodiment of the present invention; In the diagram, 1 is the condenser; 11 is the condenser body; 12 is the outlet; 13 is the inlet; 14 is the collection end; 2 is the sulfuric acid absorption tank; 3 is the absorption liquid container; 4 is the empty tank; 5 is the first valve body; and 6 is the second valve body. Detailed Implementation

[0018] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0019] like Figure 1 As shown, this invention provides a method for recovering the tail gas after the hydrogenation and reduction of arsenic trichloride, in order to recover hydrogen, arsenic trichloride, and arsenic powder, etc., to prevent environmental pollution and resource waste. The recovery method includes the following steps: S110. The exhaust gas is cooled and separated to obtain the first exhaust gas, liquid arsenic trichloride, and arsenic powder. Understandably, the tail gas after the hydrogenation reduction reaction of arsenic trichloride contains unreacted arsenic trichloride vapor, byproducts such as elemental arsenic vapor, hydrogen chloride gas, and hydrogen. This step involves cooling the tail gas, causing most of the arsenic trichloride vapor to liquefy, while some of the reduced arsenic precipitates as solid powder. After cooling, the mixed gas is initially separated into liquid arsenic trichloride, solid arsenic powder, and residual gas (i.e., the first tail gas), which mainly contains hydrogen chloride, hydrogen, and trace amounts of arsenic trichloride vapor. This step can initially separate and recover arsenic trichloride and arsenic powder, reducing the load on subsequent treatment and preventing direct emissions of arsenic compounds that could cause pollution.

[0020] S120. The first tail gas is passed into concentrated sulfuric acid to dissolve the residual arsenic trichloride vapor in the first tail gas and obtain the second tail gas. The first tail gas is passed into concentrated sulfuric acid, which absorbs the trace amount of arsenic trichloride vapor in the first tail gas, thereby further removing the residual arsenic compounds in the first tail gas, ensuring the safety of the first tail gas emission, and with high removal efficiency.

[0021] S130. The hydrogen chloride in the second tail gas is absorbed by the absorbent liquid, and the hydrogen gas is separated for discharge or recovery.

[0022] This step uses an absorbent to absorb hydrogen chloride and generate hydrochloric acid, thereby removing and recovering hydrogen chloride from the second tail gas. The remaining gas is mainly hydrogen, which is insoluble in water and chemically stable. It can be separated and recycled by a gas-liquid separation device or safely discharged.

[0023] This embodiment employs a three-stage synergistic treatment process, as described above, to separate and purify solid arsenic, unreacted liquid arsenic trichloride, and gaseous hydrogen chloride from the exhaust gas for reuse. This achieves a closed-loop cycle of arsenic and chlorine elements, ensuring safe emission of the exhaust gas. Arsenic removal is primarily achieved through a tiered process of cooling and condensation followed by absorption with concentrated sulfuric acid, avoiding the risk of arsenic trichloride reacting directly with water to produce highly toxic AsH3.

[0024] Understandably, the arsenic powder recovered in the above steps of this embodiment can be directly used for processing or purified into products, while the liquid arsenic trichloride can be returned to the hydrogenation reduction process of arsenic trichloride in the previous step, reducing raw material consumption. The recovered hydrochloric acid can also be reused in production, reducing raw material costs. In addition, the concentrated sulfuric acid can also be recycled after treatment, reducing the need for concentrated sulfuric acid replenishment in the above steps, thereby achieving maximum recycling of arsenic and chlorine elements within the production system, significantly reducing hazardous waste treatment costs, and reducing the production cost of the main product through the high-value recovery of by-products.

[0025] Furthermore, the cooling and separation process includes: cooling the exhaust gas to a first temperature, which is lower than the dew point temperature of arsenic trichloride and not higher than the sublimation temperature of arsenic powder, so that the arsenic trichloride vapor liquefies and the arsenic vapor sublimates into arsenic powder.

[0026] This embodiment utilizes the difference in physical properties between the two substances to achieve selective phase change separation through a single cooling step. The process is simple and has low energy consumption. The first temperature must meet two conditions: firstly, it must be lower than the dew point temperature of arsenic trichloride to liquefy the arsenic trichloride vapor; secondly, it must not be higher than the sublimation temperature of arsenic to condense the arsenic vapor into solid arsenic powder. This allows for the simultaneous phase change separation of the two different substances, preventing the direct emission of toxic arsenic trichloride and arsenic vapor into the atmosphere and reducing environmental pollution.

[0027] Furthermore, after the first tail gas is passed into concentrated sulfuric acid, the process also includes: S140. Discharge the sulfuric acid solution containing arsenic trichloride; After the first tail gas is introduced into concentrated sulfuric acid, some arsenic trichloride vapor is absorbed into the concentrated sulfuric acid, forming a sulfuric acid solution containing arsenic trichloride. This step is to discharge the liquid from the device and enter the next processing unit to realize material transfer and prepare for subsequent separation.

[0028] S150. The sulfuric acid solution containing arsenic trichloride is subjected to a static layering treatment to obtain an upper sulfuric acid layer and a lower arsenic trichloride layer. By utilizing the differences in density and poor miscibility, the liquids are allowed to naturally separate into layers under static conditions, providing conditions for the subsequent recycling of different materials.

[0029] S160, separate the sulfuric acid layer and the arsenic trichloride layer.

[0030] Using a separating funnel, a separatory tank, or an automatic separating device, the upper layer of sulfuric acid and the lower layer of arsenic trichloride are collected separately. The recovered sulfuric acid can be recycled for the first tail gas absorption, reducing costs. The recovered arsenic trichloride can be used as a high-purity arsenic source for hydrogenation reduction reaction in the previous process, avoiding the direct discharge of arsenic-containing waste acid.

[0031] The above steps in this embodiment realize the recovery of arsenic trichloride and the regeneration and reuse of sulfuric acid, thereby reducing operating costs.

[0032] Furthermore, before allowing the sulfuric acid solution containing arsenic trichloride to stand and separate into layers, the sulfuric acid solution containing arsenic trichloride is stirred.

[0033] Understandably, during the absorption of the first exhaust gas, problems such as gas agitation or interfacial tension may make it difficult to separate into layers, and moderate stirring can actually help with sedimentation.

[0034] Furthermore, the absorbent is pure water.

[0035] In this step, the second tail gas containing hydrogen chloride is passed into pure water. The hydrogen chloride will dissolve rapidly and form a hydrochloric acid solution, while the hydrogen gas is almost insoluble in water and will escape in the form of bubbles, which can be collected by a gas-liquid separation device.

[0036] Understandably, pure water has a strong dissolving power for hydrogen chloride, which can effectively remove it from the mixed gas and prevent hydrogen chloride from being released into the atmosphere, causing corrosion or environmental pollution. In addition, the pure water solution obtained after absorption is a hydrochloric acid solution of a certain concentration. The quality of hydrochloric acid is stable and controllable, and it can be further purified or used in other processes to realize the resource utilization of waste.

[0037] like Figure 2 As shown, the present invention also provides a system for recovering the tail gas after the hydrogenation and reduction of arsenic trichloride. The system utilizes the method described above for recovering the tail gas after the hydrogenation and reduction of arsenic trichloride. The recovery system includes a condenser 1, a sulfuric acid absorption tank 2, and an absorption liquid container 3, wherein: The condenser 1 includes a condenser body 11, an outlet end 12, an inlet end 13, and a collection end 14. The outlet end 12 and the inlet end 13 are connected through the condenser body 11. The end of the inlet end 13 away from the condenser body 11 is connected to the furnace body a so that the exhaust gas is introduced into the condenser body 11 for cooling and separation. The collection end 14 is located at the lower end of the condenser body 11 and is used to collect arsenic powder and liquid arsenic trichloride so that the arsenic powder and arsenic trichloride can be reused and raw material loss can be reduced.

[0038] The sulfuric acid absorption tank 2 is filled with concentrated sulfuric acid and is connected to the gas outlet 12 to absorb the first tail gas and the residual arsenic trichloride vapor in the first tail gas.

[0039] The absorbent container 3 is filled with absorbent liquid. One end is connected to the sulfuric acid absorption tank 2, and the other end is the exhaust end, which treats the second tail gas that may still contain hydrogen chloride after the first two steps of treatment.

[0040] This embodiment achieves cascaded arsenic removal by combining condenser 1 with sulfuric acid absorption tank 2, avoiding the risk of arsenic trichloride directly contacting water to produce highly toxic AsH3. The entire system operates in a closed loop to prevent the leakage of toxic gases, and most of the generated substances can be recycled, resulting in low amounts of wastewater and waste residue.

[0041] It should be noted that the absorbent container 3 in this embodiment can be a pure water absorption tank, a falling film absorption tower, or a spray absorption tower.

[0042] Furthermore, the condenser body 11 includes a shell, two coils, and quartz packing. The shell is used to accommodate other components, such as coils and packing, and forms a gas flow channel. Cooling medium (such as cooling water or chilled brine) is introduced into the coils. The two coils are spaced apart inside the shell. This embodiment adopts a double-coil structure, which can increase the heat exchange area and improve the condensation efficiency. The quartz packing fills the gap between the coil and the inner wall of the shell, as well as the gap between the two coils, which can provide a larger surface area, allowing the airflow to disperse and form a thin film, extending the contact time for better liquefaction or sublimation. It can also better intercept dust carried in the exhaust gas.

[0043] Furthermore, it also includes an empty tank 4 and a first valve body 5. An empty tank 4 is provided between the sulfuric acid absorption tank 2 and the absorbent liquid container 3, and the empty tank 4 is connected to the sulfuric acid absorption tank 2 and the absorbent liquid container 3 through a pipeline. A first valve body 5 is provided on the pipeline for opening or cutting off the fluid passage between the empty tank 4 and the upstream and downstream equipment (i.e., the sulfuric acid absorption tank 2 and the absorbent liquid container 3).

[0044] Understandably, in this embodiment, the empty tank 4 is a hollow container without any internal filling or absorbent liquid. It does not directly participate in the chemical reaction or absorption process, but serves as a temporary channel or buffer space for gas or liquid. When the system shuts down, pressure fluctuates, or negative pressure is generated in the absorbent liquid container 3, the absorbent liquid may be backflowed into the sulfuric acid absorption tank 2, causing the concentrated sulfuric acid to be diluted and reducing the absorption efficiency. The empty tank 4, as a gas seal or buffer isolation section, can block the direct backflow path of the liquid and improve safety.

[0045] In addition, the flow rate or pressure of the exhaust gas may fluctuate when it passes through multiple treatment stages. Empty tank 4 can act as a buffer and stabilizer to prevent airflow impact from causing the absorbent liquid to splash or the absorption efficiency to decrease.

[0046] Furthermore, it also includes a separation device, which includes a stirrer and a settling separation tank. The settling separation tank is used to receive the sulfuric acid solution containing arsenic trichloride in the sulfuric acid absorption tank 2, and the stirrer is used to stir the sulfuric acid solution containing arsenic trichloride in the settling separation tank.

[0047] Understandably, in this embodiment, the sulfuric acid layer and the arsenic trichloride layer are separated by stirring with a stirrer and settling in a settling separation tank. The separated upper sulfuric acid layer or lower arsenic trichloride layer can then enter different processing flows.

[0048] Furthermore, a second valve body 6 is installed on the pipeline between condenser 1 and furnace body a and / or between condenser 1 and sulfuric acid absorption tank 2. During equipment maintenance, malfunction, or emergency shutdown, closing the second valve body 6 can cut off the material flow. In addition, the second valve body 6 can be used to regulate flow rate or pressure, optimizing the efficiency of processes such as condensation and absorption.

[0049] The working principle of the exhaust gas recovery system after the hydrogenation and reduction of arsenic trichloride is as follows: The high-temperature exhaust gas from the hydrogenation reduction reaction is passed into condenser 1. Condenser 1 uses a low-temperature cooling medium (such as chilled brine) for heat exchange, rapidly reducing the exhaust gas temperature below the dew point of arsenic trichloride and the sublimation temperature of arsenic powder. Under these conditions, most of the unreacted arsenic trichloride vapor is condensed into liquid, while the arsenic powder entrained in the exhaust gas is captured and condensed on the coil wall and at collection end 14, forming the first exhaust gas. The arsenic powder is collected periodically by staff and can be sucked out using a vacuum cleaner at the outlet of collection end 14.

[0050] The first tail gas, after condensation, still contains trace amounts of gaseous arsenic trichloride. This first tail gas is then passed into sulfuric acid absorption tank 2. Arsenic trichloride comes into contact with concentrated sulfuric acid and is absorbed and dissolved by the concentrated sulfuric acid. However, hydrogen chloride has extremely low solubility in concentrated sulfuric acid, and most of it is not absorbed and passes through, thus deeply removing the residual arsenic compounds in the first tail gas and forming the second tail gas.

[0051] The second tail gas after absorption by concentrated sulfuric acid mainly consists of hydrogen chloride gas and excess hydrogen gas. This second tail gas is passed into a pure water absorption tank (or falling film absorption tower), where the hydrogen chloride is absorbed by the pure water to produce hydrochloric acid. Since the preceding steps have almost completely removed arsenic impurities, the arsenic content in the resulting hydrochloric acid can be strictly controlled to less than 1 ppm, resulting in extremely high quality. It can be directly returned to the production line for reuse (such as for the synthesis of arsenic trichloride or other processes). The hydrogen gas, as an inert carrier gas, can be directly discharged or reused after testing.

[0052] Workers periodically drain the sulfuric acid solution rich in arsenic trichloride from sulfuric acid absorption tank 2, and after stirring, allow it to settle and separate into layers. Due to the different densities and limited miscibility of arsenic trichloride and sulfuric acid, the solution forms two distinct layers: an upper layer mainly composed of sulfuric acid and a lower layer mainly composed of arsenic trichloride. After separation, the lower layer of arsenic trichloride can be returned to the hydrogenation reduction reaction section for reuse; the upper layer of sulfuric acid can be replenished and returned to sulfuric acid absorption tank 2 for continued recycling.

[0053] The following describes the recovery of the tail gas after the hydrogenation reduction of arsenic trichloride using the above-described method, as illustrated in Examples 1-3. The tail gas originates from the same type of vertical hydrogenation reduction reactor, and the typical initial tail gas composition is: HCl ~35 vol%, H2 ~60 vol%, unreacted AsCl3 ~4 vol%, and entrained arsenic powder ~1000 mg / Nm³. The relevant condition parameters for each example are shown in Table 1. Table 1 After the exhaust gas recovery system following the hydrogenation reduction of arsenic trichloride operated continuously and stably for 168 hours (one week), key nodes of each embodiment were sampled and analyzed. The results are shown in Table 2. Table 2 Conclusions: Example 1 achieved excellent overall performance under conditions of -15℃ and 92% concentrated sulfuric acid, producing arsenic hydrochloride with a content far below 1 ppm, making it the optimal choice for economic efficiency. Example 2 exhibited extreme purification effects under even lower temperatures and higher sulfuric acid concentrations, suitable for scenarios with extremely high requirements for the purity of the byproduct hydrochloric acid. Example 3, under relatively relaxed conditions, still ensured a final arsenic hydrochloride content of <1 ppm, demonstrating the effectiveness of the present invention over a wide range of parameters.

[0054] In summary, the embodiments of the present invention provide a method and system for recovering tail gas after hydrogenation reduction of arsenic trichloride. Through the above-mentioned three-stage synergistic treatment, solid arsenic, unreacted liquid arsenic trichloride, and gaseous hydrogen chloride in the tail gas are separated, purified, and reused, realizing a closed-loop cycle of arsenic and chlorine elements and achieving safe emission of tail gas. Among them, arsenic is mainly removed through a stepped method of cooling and condensation and concentrated sulfuric acid absorption, avoiding the risk of arsenic trichloride directly contacting water to produce highly toxic AsH3.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for recovering tail gas after the hydrogenation and reduction of arsenic trichloride, characterized in that, Includes the following steps: The exhaust gas is cooled and separated to obtain the first exhaust gas, liquid arsenic trichloride, and arsenic powder. The first tail gas is passed into concentrated sulfuric acid to dissolve the residual arsenic trichloride vapor in the first tail gas and to obtain the second tail gas. The hydrogen chloride in the second tail gas is absorbed by the absorbent liquid, and the hydrogen gas is separated for discharge or recovery.

2. The method for recovering the tail gas after the hydrogenation and reduction of arsenic trichloride according to claim 1, characterized in that, The cooling and separation process includes: The exhaust gas is cooled to a first temperature, which is lower than the dew point temperature of arsenic trichloride and not higher than the sublimation temperature of the arsenic powder, so that the arsenic trichloride vapor liquefies and the arsenic vapor sublimates into arsenic powder.

3. The method for recovering the tail gas after the hydrogenation and reduction of arsenic trichloride according to claim 1, characterized in that, After passing the first tail gas into concentrated sulfuric acid, the process also includes: Discharge the sulfuric acid solution containing arsenic trichloride; The sulfuric acid solution containing arsenic trichloride is subjected to a static layering treatment to obtain an upper sulfuric acid layer and a lower arsenic trichloride layer. Separate the sulfuric acid layer and the arsenic trichloride layer.

4. The method for recovering the tail gas after the hydrogenation and reduction of arsenic trichloride according to claim 1, characterized in that, Before allowing the sulfuric acid solution containing arsenic trichloride to stand and separate into layers, the sulfuric acid solution containing arsenic trichloride is stirred.

5. The method for recovering the tail gas after the hydrogenation and reduction of arsenic trichloride according to claim 4, characterized in that, The absorbent is pure water.

6. A system for recovering tail gas after the hydrogenation and reduction of arsenic trichloride, characterized in that, The tail gas after hydrogenation and reduction of arsenic trichloride is recovered using the method for recovering tail gas after hydrogenation and reduction of arsenic trichloride as described in any one of claims 1-5, wherein the recovery system comprises: The condenser includes a condenser body, an outlet end, an inlet end, and a collection end. The outlet end and the inlet end are connected through the condenser body. The end of the inlet end away from the condenser body is connected to the furnace body to allow the exhaust gas to enter the condenser body. The collection end is located at the lower end of the condenser body and is used to collect the arsenic powder and the liquid arsenic trichloride. A sulfuric acid absorption tank, filled with concentrated sulfuric acid, is connected to the outlet end to absorb the first tail gas; and An absorbent container filled with absorbent liquid has one end connected to the sulfuric acid absorption tank and the other end serving as an exhaust port.

7. The tail gas recovery system after the hydrogenation and reduction of arsenic trichloride according to claim 6, characterized in that, The condenser body includes a shell, two coils and quartz packing. The two coils are spaced apart inside the shell, and the quartz packing fills the gap between the coils and the inner wall of the shell, as well as the gap between the two coils.

8. The tail gas recovery system after hydrogenation and reduction of arsenic trichloride according to claim 6, characterized in that, It also includes an empty tank and a first valve body. The empty tank is provided between the sulfuric acid absorption tank and the absorbent liquid container, and the empty tank is connected to the sulfuric acid absorption tank and the absorbent liquid container through a pipeline. The first valve body is provided on the pipeline.

9. The tail gas recovery system after hydrogenation and reduction of arsenic trichloride according to claim 6, characterized in that, It also includes a separation device, which includes a stirrer and a settling separation tank. The settling separation tank is used to receive the sulfuric acid solution containing arsenic trichloride in the sulfuric acid absorption tank, and the stirrer is used to stir the sulfuric acid solution containing arsenic trichloride in the settling separation tank.

10. The tail gas recovery system after hydrogenation and reduction of arsenic trichloride according to claim 6, characterized in that, A second valve is installed on the pipeline between the condenser and the furnace body and / or between the condenser and the sulfuric acid absorption tank.

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