A gravity back-flushing heat exchange reaction tower and a method for synthesizing hydrogen selenide

Abstract

The present invention relates to the technical field of hydrogen selenide production, and provides a gravity back-blowing heat exchange reaction tower and a method for synthesizing hydrogen selenide. The present invention utilizes the principle of gravity back-blowing. When the heat exchange tower is blocked, a direction-changing valve group is used in conjunction with a membrane press to reverse the direction of the hydrogen selenide product airflow and perform product gas back-blowing. At the same time, a hot oil circulation heater is used to control the temperature of the heat exchanger to above the melting point of selenium. The molten selenium refluxes to the reaction tower under the dual effects of gravity and gas back-blowing. The gravity back-blowing heat exchange reaction tower of the present invention is used to produce hydrogen selenide. While ensuring the removal of selenium impurities in the crude hydrogen selenide product, it can solve the problem of heat exchanger blockage in the production process. No manual disassembly and cleaning is required. The operation and use are convenient and stable. During the production process, pipe unblocking and raw material recycling and reuse can be completed, ensuring stable and continuous production operation, greatly improving the production efficiency of hydrogen selenide, and greatly saving the operation and maintenance costs of the heat exchanger.

Description

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on March 3, 2022, with application number 202210201403.7 and invention name “A gravity back-flushing heat exchange reaction tower and a method for synthesizing hydrogen selenide”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention relates to the technical field of hydrogen selenide production, in particular to a gravity back-flushing heat exchange reaction tower and a method for synthesizing hydrogen selenide. Background Art

[0003] Hydrogen selenide is an electronic gas widely used in the semiconductor industry. It can be produced by directly combining high-purity hydrogen and selenium powder. This method produces high yields and a high-purity product. In chemical production, crude hydrogen selenide products must first be pre-cooled and separated, typically using a heat exchanger with a temperature below the melting point of selenium to remove selenium impurities carried over from the crude product. During production, excess solid selenium can accumulate and adhere to the heat exchanger, potentially blocking the heat exchanger tubes and preventing the product gas from passing through the heat exchanger, thus disrupting continuous production.

[0004] Heat exchangers use the walls of the tube bundle enclosed within a shell as heat transfer surfaces to transfer heat, thereby maintaining the fluid temperature within process specifications. Shell-and-tube heat exchangers are typically cleaned after clogging, primarily through manual or mechanical methods, high-pressure water jet flushing, or chemical descaling. Heat exchanger maintenance and cleaning require specialized personnel, and frequent cleaning significantly shortens their service life and wastes the raw selenium. Summary of the Invention

[0005] In light of this, the present invention provides a gravity backflush heat exchange reaction tower and a method for synthesizing hydrogen selenide. The gravity backflush heat exchange reaction tower provided by the present invention eliminates the need for disassembly and cleaning of the heat exchanger when it becomes clogged, enabling pipe unblocking and raw material recycling during the production process, ensuring stable and continuous production.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A gravity back-flushing heat exchange reaction tower, characterized in that it comprises a reaction tower 1, a heat exchanger 2, a direction-changing valve group 3, a membrane press 4 and a hot oil circulation heater 5;

[0008] The heat exchanger 2 is arranged at the top of the reaction tower 1, and a gas inlet and outlet 8 is provided at the top of the heat exchanger 2;

[0009] The hot oil circulation heater 5 is connected to the shell side inlet and outlet of the heat exchanger 2;

[0010] A backflush port 12 is provided on the side of the reaction tower 1, and the backflush port 12 is connected to the first gas inlet and outlet 9 through a backflush pipeline 16;

[0011] The membrane press 4 is provided with a first gas inlet and outlet 9 and a second gas inlet and outlet 10. The gas inlet and outlet 8 is connected to the first gas inlet and outlet 9 through a main line 13 and a first branch line 14; the gas inlet and outlet 8 is connected to the second gas inlet and outlet 10 through a main line 13 and a second branch line 15; a gas collection line 11 is also branched off from the second branch line 15; a backflush line 16 is also branched off from the first branch line 14, and is connected to the backflush port 12 on the side of the reaction tower 1.

[0012] Preferably, the direction-changing valve group 3 is used to control the flow direction of the product gas. When the heat exchanger operates normally, the product gas is controlled to be introduced into the gas collection pipeline 11 through the membrane press 4 for collection; when the heat exchanger is blocked, the product gas flow direction is changed, and the product gas enters the backflush pipeline 16 from the backflush port 12, and is discharged from the second gas inlet and outlet 10, enters the gas inlet and outlet 8 at the top of the heat exchanger through the second branch pipeline 15, and is backflushed into the heat exchanger 2.

[0013] Preferably, a heat exchanger pressure monitoring gauge 7 is provided on the main pipe 13;

[0014] The backflush pipeline 16 is provided with a reaction tower pressure monitoring gauge 6 .

[0015] Preferably, the direction switching valve group 3 includes a first valve 3-1, a second valve 3-2, a third valve 3-3, a fourth valve 3-4 and a fifth valve 3-5;

[0016] The first valve 3-1 and the third valve 3-3 are arranged on the first branch pipe 14, and the third valve 3-3 is arranged at one end close to the first gas inlet and outlet 9;

[0017] The fourth valve 3-4 is provided on the second branch pipe 15;

[0018] The second valve 3-2 is provided on the gas collecting pipeline 11, and the connection point between the gas collecting pipeline 11 and the second branch pipeline 15 is located between the fourth valve 3-4 and the second gas inlet and outlet 10;

[0019] The fifth valve 3 - 5 is provided on the backflush pipeline 16 , and the connection point between the backflush pipeline 16 and the first branch pipeline 14 is located between the first valve 3 - 1 and the third valve 3 - 3 .

[0020] Preferably, the heat exchanger 2 is a vertical shell and tube heat exchanger.

[0021] The present invention also provides a method for synthesizing hydrogen selenide using the gravity back-flushing heat exchange reaction tower described in the above scheme, comprising the following steps:

[0022] Adding selenium and hydrogen into the reaction tower 1 to react and generate crude hydrogen selenide;

[0023] The crude hydrogen selenide product enters the heat exchanger 2, and the temperature of the heat exchanger 2 is controlled below the melting point of selenium by the hot oil circulation heater 5 to separate selenium from the crude hydrogen selenide product. The separated and purified hydrogen selenide gas flows out from the gas inlet and outlet 8;

[0024] The direction of flow of hydrogen selenide gas is controlled by the direction-changing valve group 3 and the membrane press 4, so that the hydrogen selenide gas enters the membrane press 4 from the first gas inlet and outlet 9, and then is introduced into the gas collection pipeline 11 from the second gas inlet and outlet 10 of the membrane press 4 for collection;

[0025] When the heat exchanger 2 is blocked, the hot oil circulation heater 5 is used to control the temperature of the heat exchanger 2 above the melting point of selenium, and the direction conversion valve group 3 and the membrane press 4 are adjusted. The product gas enters the first gas inlet and outlet 9 from the backflush port 12 through the backflush pipeline 16, and is discharged from the second gas inlet and outlet 10, enters the gas inlet and outlet 8 at the top of the heat exchanger through the second branch pipeline 15, and is backblown into the heat exchanger 2; after the heat exchanger is unblocked, the direction conversion valve group 3 and the membrane press 4 are adjusted to collect hydrogen selenide gas.

[0026] Preferably, the circulating medium in the hot oil circulation heater 5 is one of thermal conductivity A, paraffin, dimethyl silicone oil, tetramethyl silicate, solder, triethylene glycol and benzophenone; when collecting hydrogen selenide gas, the temperature of the circulating medium is 100-300°C, and when backflushing is performed, the temperature of the circulating medium is 200-450°C.

[0027] Preferably, when collecting hydrogen selenide gas, the first valve 3-1, the second valve 3-2 and the third valve 3-3 are opened, and the fourth valve 3-4 and the fifth valve 3-5 are closed; when backflushing is performed, the three valves 3-3, the fourth valve 3-4 and the fifth valve 3-5 are opened, and the first valve 3-1 and the second valve 3-2 are closed.

[0028] Preferably, the judgment standard for whether the heat exchanger 2 is blocked is: the pressure difference between the reaction tower pressure monitoring gauge 6 and the heat exchanger pressure monitoring gauge 7 is 0.5~1.5MPa; the judgment standard for whether the heat exchanger 2 is unblocked is: the pressure difference between the reaction tower pressure monitoring gauge 6 and the heat exchanger pressure monitoring gauge 7 is reduced to below 0.1MPa.

[0029] The present invention provides a gravity back-blowing heat exchange reaction tower, comprising a reaction tower 1, a heat exchanger 2, a direction-changing valve group 3, a membrane press 4 and a hot oil circulation heater 5. The present invention controls the communication mode between the heat exchanger 2 and the membrane press 4, and controls the flow direction of the product gas by setting the direction-changing valve group 3. When the heat exchanger operates normally, the direction-changing valve group 3 is controlled to collect the hydrogen selenide product gas. When the heat exchanger 2 is blocked, the hot oil circulation heater 5 is used to control the temperature of the heat exchanger 2 to melt the solid selenium blocked in the heat exchanger 2. The direction-changing valve group 3 is controlled to cooperate with the membrane press 4 to reverse the flow direction of the hydrogen selenide product gas, so that the hydrogen selenide product gas flows out from the back-blowing port of the reaction tower 1 and enters the heat exchanger 2 from the gas inlet and outlet 8 at the top of the heat exchanger 2, and the molten selenium is back-blown. The selenium blocked in the heat exchanger falls back into the reaction tower 1 under the dual effects of gravity and gas back-blowing, thereby achieving unblocking of the heat exchanger 2.

[0030] The gravity back-flushing heat exchange reaction tower provided by the present invention is used to produce hydrogen selenide, which can ensure the removal of selenium impurities in the crude hydrogen selenide product while avoiding the precipitation and accumulation of selenium in the heat exchanger tube. The gravity back-flushing principle is used to solve the problem of heat exchanger blockage in the production process. No manual disassembly and cleaning is required, the operation and use are convenient, the stability is good, and the operation and maintenance costs of the heat exchanger are greatly saved. The tube dredging and the recycling and reuse of raw materials can be completed during the production process, ensuring stable and continuous production operation, greatly improving the production efficiency of hydrogen selenide, and greatly saving the operation and maintenance costs of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural diagram of a gravity back-flushing heat exchange reaction tower;

[0032] Figure 2 Schematic diagram of the structure of the directional control valve group 3;

[0033] Figures 1-2 In: 1-reaction tower, 2-heat exchanger, 3-direction switching valve group, 4-membrane press, 5-hot oil circulation heater, 6-reaction tower pressure monitoring gauge, 7-heat exchanger pressure monitoring gauge, 8-gas inlet and outlet of heat exchanger, 9-first gas inlet and outlet, 10-second gas inlet and outlet, 11-gas collection pipeline, 12-backflush port, 13-main pipeline, 14-first branch pipeline, 15-second branch pipeline, 16-backflush pipeline, 3-1-first valve, 3-2-second valve, 3-3-third valve, 3-4-fourth valve, 3-5-fifth valve. DETAILED DESCRIPTION

[0034] The present invention provides a gravity back-blowing heat exchange reaction tower, the structural schematic diagram of the gravity back-blowing heat exchange reaction tower is as follows: Figure 1 As shown below, combined Figure 1Provide detailed explanation.

[0035] The gravity backflush heat exchange reaction tower provided by the present invention includes a reaction tower 1. The present invention has no particular requirements for the specific structure of the reaction tower 1, and a reaction tower for producing hydrogen selenide familiar to those skilled in the art can be used. In the present invention, a backflush port 12 is provided on the side of the reaction tower 1. The backflush port 12 is preferably located near the top of the reaction tower 1 and exceeds the position where the maximum amount of reaction raw materials can be added.

[0036] The gravity backflush heat exchange reaction tower provided herein includes a heat exchanger 2. In the present invention, the heat exchanger 2 is disposed at the top of the reaction tower 1 and is provided with a gas inlet and outlet 8. The heat exchanger 2 is preferably a vertical shell-and-tube heat exchanger. In the present invention, the heat exchanger 2 is used to solidify and separate the selenium impurity carried by the crude hydrogen selenide product produced by the reaction tower 1.

[0037] The gravity back-flushing heat exchange reaction tower provided by the present invention includes a direction-changing valve group 3, which is used to control the flow direction of the product gas so that the product gas is collected or enters the heat exchanger 2 for back-flushing. Specifically, when the heat exchanger is operating normally, the product gas is controlled to pass through the membrane press 4 and then enter the gas collection pipeline 11 for collection; when the heat exchanger is blocked, the product gas is controlled to pass through the membrane press 4 and then enter the heat exchanger 2 from the gas inlet and outlet 8; the valve setting method of the direction-changing valve group will be described in detail later.

[0038] The gravity backflush heat exchange reaction tower provided by the present invention includes a membrane press 4. The present invention has no special requirements for the membrane press (i.e., diaphragm compressor); any membrane press commonly used in chemical production can be used. The membrane press 4 is used to reverse the flow direction of the product gas in conjunction with the direction-reversing valve assembly 3. The membrane press 4 is provided with a first gas inlet and outlet 9 and a second gas inlet and outlet 10.

[0039] In the present invention, the gas outlet 8 is preferably connected to the first gas inlet and outlet 9 through a main line 13 and a first branch line 14; the gas outlet 8 is preferably connected to the second gas inlet and outlet 10 through a main line 13 and a second branch line 15; a gas collection line 11 is also branched off from the second branch line 15; a backflush line 16 is also branched off from the first branch line 14, which is connected to the backflush port 12 on the side of the reaction tower 1.

[0040] In the present invention, the main pipe 13 is preferably provided with a heat exchanger pressure monitoring gauge 7, specifically, at an end near the gas outlet 8; and the backflush pipe 16 is preferably provided with a reaction tower pressure monitoring gauge 6, specifically, at an end near the backflush port. In the present invention, the heat exchanger pressure monitoring gauge 7 and the reaction tower pressure monitoring gauge 6 are used to monitor the pressures of the heat exchanger 2 and the reaction tower 1, and the blockage and unblocking of the heat exchanger 2 are determined based on the pressure difference between the heat exchanger pressure monitoring gauge 7 and the reaction tower pressure monitoring gauge 6.

[0041] In the present invention, the direction conversion valve group 3 preferably includes a first valve 3-1, a second valve 3-2, a third valve 3-3, a fourth valve 3-4 and a fifth valve 3-5; the first valve 3-1 and the third valve 3-3 are preferably arranged on the first branch pipeline 14, and the third valve 3-3 is preferably arranged at one end close to the first gas inlet and outlet 9; the fourth valve 3-4 is preferably arranged on the second branch pipeline 15; the second valve 3-2 is preferably arranged on the gas collection pipeline 11, and the connection point between the gas collection pipeline 11 and the second branch pipeline 15 is located between the fourth valve 3-4 and the second gas inlet and outlet 10; the fifth valve 3-5 is arranged on the backflush pipeline 16, and the connection point between the backflush pipeline 16 and the first branch pipeline 14 is located between the first valve 3-1 and the third valve 3-3. Figure 2 Schematic diagram of the structure of the direction conversion valve group 3.

[0042] The gravity backflush heat exchange reaction tower provided by the present invention includes a hot oil circulation heater 5 , which is connected to the shell-side inlet and outlet of the heat exchanger 2 and is used to control the temperature of the medium in the shell-side of the heat exchanger 2. The present invention has no particular requirements for the specific method of connecting the hot oil circulation heater 5 to the heat exchanger 2, and methods familiar to those skilled in the art can be used.

[0043] The present invention also provides a method for synthesizing hydrogen selenide using the gravity back-flushing heat exchange reaction tower described in the above scheme, comprising the following steps:

[0044] Adding selenium and hydrogen into the reaction tower 1 to react and generate crude hydrogen selenide;

[0045] The crude hydrogen selenide product enters the heat exchanger 2, and the temperature of the heat exchanger 2 is controlled below the melting point of selenium by the hot oil circulation heater 5 to separate selenium from the crude hydrogen selenide product. The separated and purified hydrogen selenide gas flows out from the gas inlet and outlet 8;

[0046] The direction of flow of hydrogen selenide gas is controlled by the direction-changing valve group 3 and the membrane press 4, so that the hydrogen selenide gas enters the membrane press 4 from the first gas inlet and outlet 9, then flows out from the second gas inlet and outlet 10 of the membrane press 4, and is introduced into the gas collection pipeline 11 for collection;

[0047] When the heat exchanger 2 is blocked, the hot oil circulation heater 5 is used to control the temperature of the heat exchanger 2 above the melting point of selenium, and the direction conversion valve group 3 and the membrane press 4 are adjusted. The product gas enters the first gas inlet and outlet 9 from the backflush port 12 through the backflush pipeline 16, and is discharged from the second gas inlet and outlet 10, enters the gas inlet and outlet 8 at the top of the heat exchanger through the second branch pipeline 15, and is backblown into the heat exchanger 2; after the heat exchanger is unblocked, the direction conversion valve group 3 and the membrane press 4 are adjusted to collect hydrogen selenide gas.

[0048] The present invention has no special requirements for the addition ratio of the hydrogen and selenium, and a ratio well known to those skilled in the art can be used. In the present invention, the selenium is specifically selenium particles. The hydrogen and selenium react in the reaction tower 1 to generate hydrogen selenide. The chemical reaction equation is as follows:

[0049] H2+Se=H2Se

[0050] In the present invention, the circulating medium in the hot oil circulation heater 5 is preferably one of Thermal Conductivity A, paraffin, dimethyl silicone oil, tetramethyl silicate, solder, triethylene glycol and benzophenone; when collecting hydrogen selenide gas, the temperature of the circulating medium is preferably 100-300°C, and when backflushing is performed, the temperature of the circulating medium is preferably 200-450°C.

[0051] In the present invention, when collecting hydrogen selenide gas, it is preferred that the first valve 3-1, the second valve 3-2 and the third valve 3-3 are opened, and the fourth valve 3-4 and the fifth valve 3-5 are closed; when backflushing is performed, it is preferred that the three valves 3-3, the fourth valve 3-4 and the fifth valve 3-5 are opened, and the first valve 3-1 and the second valve 3-2 are closed.

[0052] In the present invention, the criterion for judging whether the heat exchanger 2 is blocked is preferably: the pressure difference between the reaction tower pressure monitoring gauge 6 and the heat exchanger pressure monitoring gauge 7 is 0.5-1.5 MPa; the criterion for judging whether the heat exchanger 2 is unblocked is preferably: the pressure difference between the reaction tower pressure monitoring gauge 6 and the heat exchanger pressure monitoring gauge 7 is reduced to below 0.1 MPa, specifically 0-0.1 MPa, preferably 0.05 MPa. In the present invention, the blockage and unblocking of the heat exchanger are judged by monitoring the pressure difference between the reaction tower pressure monitoring gauge 6 and the heat exchanger pressure monitoring gauge 7; in a specific embodiment of the present invention, the process of unblocking the heat exchanger by backblowing can be repeated, that is, normal production can be resumed after unblocking is completed. When the heat exchanger 2 is blocked again, the direction conversion valve group 3 and the membrane press 4 are adjusted again, and unblocked by backblowing. After unblocking is completed, normal production can be resumed. This cycle is repeated to achieve continuous and stable production of hydrogen selenide.

[0053] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0054] Example 1

[0055] use Figure 1 The gravity back-flushing heat exchange reaction tower shown in the figure produces hydrogen selenide, and the specific steps are as follows:

[0056] Selenium particles and high-purity hydrogen are reacted in the reaction tower 1.

[0057] The crude hydrogen selenide product generated by the reaction is passed from reaction tower 1 to heat exchanger 2. A hot oil circulation heater 5 controls the temperature of heat exchanger 2 between 100°C and 300°C. Selenium impurities carried over from the product are converted to a solid state and separated by the heat exchanger. The first, second, and third valves 3-1, 3-2, and 3-3 of directional control valve assembly 3 are opened, while the fourth and fifth valves 3-4, 3-5 are closed. The hydrogen selenide product gas is then directed from membrane compressor 4 to a gas collection device.

[0058] As the reaction proceeds, the pressure differential between the reaction tower pressure monitoring gauge 6 and the heat exchanger pressure monitoring gauge 7 continues to increase. When the pressure differential reaches 1.0 MPa, the hot oil circulation heater 5 controls the temperature of the heat exchanger 2 to a range of 200-450°C, melting the solid selenium impurities clogged in the heat exchanger 2. The third valve 3-3, the fourth valve 3-4, and the fifth valve 3-5 in the directional control valve group open, while the first valve 3-1 and the second valve 3-2 close. The membrane compressor 4 controls the flow of hydrogen selenide product gas from the backflush port 12 on the side of the reaction tower 1. After passing through the membrane compressor 4, it enters the gas inlet and outlet 8 at the top of the heat exchanger 2 and is backflushed into the heat exchanger 2. The selenium clogged in the tube side of the heat exchanger 2 flows back into the reaction tower 1 under the action of gravity and gas backflush.

[0059] When the pressure difference between the reaction tower pressure monitoring gauge 6 and the reaction tower pressure monitoring gauge 7 gradually decreases to 0-0.1 MPa, the heat exchanger is unblocked. The direction-switching valve group 3 and the membrane press 4 are controlled to change the direction of the product gas flow, and normal chemical production resumes. The above backflush steps can be repeated to achieve continuous and stable production of hydrogen selenide.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A gravity back-flushing heat exchange reaction tower, characterized in that: It comprises a reaction tower (1), a heat exchanger (2), a direction switching valve group (3), a membrane press (4) and a hot oil circulation heater (5); The heat exchanger (2) is arranged at the top of the reaction tower (1), and a gas inlet and outlet (8) is provided at the top of the heat exchanger (2); The hot oil circulation heater (5) is in communication with the shell-side inlet and outlet of the heat exchanger (2); A backflush port (12) is provided on the side of the reaction tower (1), and the backflush port (12) and the first gas inlet and outlet (9) are connected via a backflush pipeline (16); The membrane press (4) is provided with a first gas inlet and outlet (9) and a second gas inlet and outlet (10); the gas inlet and outlet (8) is connected to the first gas inlet and outlet (9) through a main pipeline (13) and a first branch pipeline (14); the gas inlet and outlet (8) is connected to the second gas inlet and outlet (10) through a main pipeline (13) and a second branch pipeline (15); a gas collection pipeline (11) is further branched from the second branch pipeline (15); a backflush pipeline (16) is further branched from the first branch pipeline (14) and is connected to a backflush port (12) on the side of the reaction tower (1); The direction-changing valve group (3) is used to control the flow direction of the product gas. When the heat exchanger operates normally, the product gas is controlled to be introduced into the gas collection pipeline (11) through the membrane press (4) for collection. When the heat exchanger is blocked, the direction of the product gas flow is changed, and the product gas enters the backflush pipeline (16) from the backflush port (12), and is discharged from the second gas inlet and outlet (10), enters the gas inlet and outlet (8) at the top of the heat exchanger through the second branch pipeline (15), and is backflushed into the heat exchanger (2). The direction conversion valve group (3) comprises a first valve (3-1), a second valve (3-2), a third valve (3-3), a fourth valve (3-4) and a fifth valve (3-5); The first valve (3-1) and the third valve (3-3) are arranged on the first branch pipeline (14), and the third valve (3-3) is arranged at one end close to the first gas inlet and outlet (9); The fourth valve (3-4) is arranged on the second branch pipeline (15); The second valve (3-2) is arranged on the gas collecting pipeline (11), and the connection point between the gas collecting pipeline (11) and the second branch pipeline (15) is located between the fourth valve (3-4) and the second gas inlet and outlet (10); The fifth valve (3-5) is arranged on the backflush pipeline (16), and the connection point between the backflush pipeline (16) and the first branch pipeline (14) is located between the first valve (3-1) and the third valve (3-3).

2. The gravity back-flushing heat exchange reaction tower according to claim 1, characterized in that: The main pipe (13) is provided with a heat exchanger pressure monitoring gauge (7); the backflush pipe (16) is provided with a reaction tower pressure monitoring gauge (6).

3. The gravity back-flushing heat exchange reaction tower according to claim 2, characterized in that: The heat exchanger (2) is a vertical shell and tube heat exchanger.

4. A method for synthesizing hydrogen selenide using the gravity back-flushing heat exchange reaction tower according to claim 2 or 3, characterized in that: The following steps are involved: Adding selenium and hydrogen into a reaction tower (1) to react and generate crude hydrogen selenide; The crude hydrogen selenide product enters the heat exchanger (2), and the temperature of the heat exchanger (2) is controlled below the melting point of selenium by using a hot oil circulation heater (5), so that selenium is separated from the crude hydrogen selenide product, and the separated and purified hydrogen selenide gas flows out from the gas inlet and outlet (8); The direction of flow of hydrogen selenide gas is controlled by a direction conversion valve group (3) and a membrane press (4), so that the hydrogen selenide gas enters the membrane press (4) from a first gas inlet and outlet (9), and then is introduced into a gas collection pipeline (11) from a second gas inlet and outlet (10) of the membrane press (4) for collection; When the heat exchanger (2) is clogged, the temperature of the heat exchanger (2) is controlled to be above the melting point of selenium by using a hot oil circulation heater (5), and the direction conversion valve group (3) and the membrane press (4) are adjusted, so that the product gas enters the first gas inlet and outlet (9) from the backflush port (12) through the backflush pipeline (16), and is discharged from the second gas inlet and outlet (10), enters the gas inlet and outlet (8) at the top of the heat exchanger through the second branch pipeline (15), and is backflushed into the heat exchanger (2); after the heat exchanger is unblocked, the direction conversion valve group (3) and the membrane press (4) are adjusted to collect hydrogen selenide gas.

5. The method according to claim 4, characterized in that The circulating medium in the hot oil circulation heater (5) is one of thermal conductivity A, paraffin, dimethyl silicone oil, tetramethyl silicate, solder, triethylene glycol and benzophenone; when collecting hydrogen selenide gas, the temperature of the circulating medium is 100-300°C, and when backflushing is performed, the temperature of the circulating medium is 200-450°C.

6. The method according to claim 4, characterized in that When hydrogen selenide gas is collected, the first valve (3-1), the second valve (3-2) and the third valve (3-3) are opened, and the fourth valve (3-4) and the fifth valve (3-5) are closed; when backflushing is performed, the third valve (3-3), the fourth valve (3-4) and the fifth valve (3-5) are opened, and the first valve (3-1) and the second valve (3-2) are closed.

7. The method according to claim 4, characterized in that The criterion for judging whether the heat exchanger (2) is blocked is that the pressure difference between the reaction tower pressure monitoring gauge (6) and the heat exchanger pressure monitoring gauge (7) is 0.5-1.5 MPa; the criterion for judging whether the heat exchanger (2) is unblocked is that the pressure difference between the reaction tower pressure monitoring gauge (6) and the heat exchanger pressure monitoring gauge (7) is reduced to below 0.1 MPa.

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