Process and device for treating high-pressure liquid ammonia tailings in laboratory

Abstract

The invention relates to the technical field of liquid ammonia tailing treatment, and discloses a laboratory high-pressure liquid ammonia tailing treatment device, which comprises a high-pressure absorption tank; the material treatment path conversion device is arranged on the high-pressure absorption tank and is provided with a dilution path and a sampling path, and the dilution path is connected with a tailing pipeline extending towards the inner bottom of the high-pressure absorption tank so as to consume entering liquid ammonia in the high-pressure absorption tank; the discharge pipeline is arranged at the bottom of the high-pressure absorption tank and is connected with a liquid discharge pipeline for discharging diluent outwards, and one end, which is staggered with the tailing pipeline, of the high-pressure absorption tank is connected with a pressure balance device; and the pressure balancing device comprises an absorption pipeline mounted on the high-pressure absorption tank and a gas circulation pipeline connected in parallel to the absorption pipeline. The invention solves the problem of flash evaporation of liquid ammonia in the process of carrying out reduced-pressure flash evaporation on the tailing liquid ammonia to normal pressure and carrying out absorption treatment on the tailing liquid ammonia by water or an acidic aqueous solution in the conventional treatment of the liquid ammonia tailings.

Description

Technical Field

[0001] The invention relates to the technical field of liquid ammonia tailings processing, in particular to a process and a device for processing high-pressure liquid ammonia tailings in a laboratory. Background Art

[0002] Liquid ammonia is extremely volatile. In the process of research and development involving liquid ammonia materials in the laboratory, especially when the ammonia in the outflowing material after the reaction is still in the form of liquid ammonia, the safe handling of the tail material is a difficult point. The conventional treatment method is to reduce the pressure of the tail liquid ammonia and flash it to normal pressure and absorb it with water or acidic aqueous solution. In this process, there will be flash evaporation of liquid ammonia. A large amount of ammonia suddenly changes from liquid to gas, which will cause the material flow rate to increase sharply, and it is necessary to expand the capacity and diameter of the rear end of the reactor. This increases the difficulty of designing laboratory reaction equipment and the demand for physical space. In addition, the emission of a large amount of ammonia will inevitably carry other products and reactants that have not been completely reacted, posing a safety hazard or endangering the health of the experimenters. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a process and device for treating high-pressure liquid ammonia tailings in a laboratory, which solves the problem of flash evaporation of liquid ammonia in the conventional treatment of liquid ammonia tailings, which is to reduce the pressure of the tailing liquid ammonia and flash evaporate it to normal pressure and then absorb it with water or an acidic aqueous solution.

[0004] To achieve the above object, the present invention provides the following technical solution: a laboratory high-pressure liquid ammonia tailings processing device, comprising:

[0005] High pressure absorption tank;

[0006] A material processing path conversion device is arranged on the high-pressure absorption tank and is provided with a dilution path and a sampling path. The dilution path is connected to a tailings pipeline extending to the bottom of the high-pressure absorption tank to consume the liquid ammonia entering the high-pressure absorption tank.

[0007] The discharge pipeline is installed at the bottom of the high-pressure absorption tank and is connected to a discharge pipe for discharging the diluent to the outside.

[0008] In a specific embodiment, the high-pressure absorption tank is staggered at one end of the tailings pipeline and is connected to a pressure balancing device;

[0009] The pressure balancing device comprises an absorption pipeline installed on the high-pressure absorption tank and a gas flow pipeline connected in parallel to the absorption pipeline, which is deviated from the installation position of the absorption pipeline. The high-pressure absorption tank is connected to an input pipeline for injecting inert gas therein, and a pressure gauge is connected to the input pipeline;

[0010] The high-pressure absorption tank comprises a tank body and a plurality of connection ports provided on the tank body. A water ring sleeve surrounds the tank body, a condensed water inlet and a condensed water outlet are provided on the water ring sleeve, and the connection ports penetrate the water ring sleeve and are connected to the tank body.

[0011] The connection port includes a discharge end connected to the drainage pipe and a first end for establishing a passage for the tailings pipe to enter the interior of the tank body. One end of the first end is equipped with a second end and a third end connected to the input pipe and the absorption pipe.

[0012] In a specific embodiment, it is specifically described that the tailings pipeline establishes a flow channel for liquid ammonia in the tank body, an end sleeve is provided at the end of the tailings pipeline, the diameter of the end sleeve is larger than the diameter of the tailings pipeline, and a plurality of overflow holes are opened on the end sleeve to increase the instantaneous contact area between the liquid ammonia and the liquid in the pipe body after the liquid ammonia overflows from the end sleeve.

[0013] In a specific embodiment, it is specifically described that the water ring sleeve is wrapped around the side wall of the tank body from a height above the center line of the tank body, and the condensed water outlet and the condensed water inlet are filled into the water ring sleeve to absorb the heat dissipated outward from the tank body.

[0014] In a specific embodiment, the tank body contains an absorption liquid for absorbing liquid ammonia, and one end of the tank body is connected to a filling pipe for replenishing the absorption liquid into the tank body;

[0015] The material processing path conversion device, the discharge pipeline and the pressure balancing device are all provided with a plurality of valves for opening and closing the passages.

[0016] In a specific embodiment, it is specifically described that the material processing path conversion device includes a first passage connected to an external reaction sampling system, a three-way valve is connected to one end of the first passage to establish a conversion point for the material to flow to the reaction sampling system or the tailing material pipeline, and a second passage connected between the three-way valve and the tailing material pipeline establishes a flow path for the material to flow to the tailing material pipeline.

[0017] The present invention also provides a laboratory process for processing high-pressure liquid ammonia tailings, comprising:

[0018] S101: Replenish absorption liquid; check that all valves are in the closed state, check the air tightness of all connection parts, ensure that the pressure gauge shows zero, and replenish absorption liquid;

[0019] S102, pressurizing; inputting inert gas into the tank body so that the pressure reading is 0.6-4MPa, then opening the valves on the absorption pipeline and the gas flow pipeline to absorb the small amount of ammonia that is subsequently volatilized;

[0020] S103, tailing liquid ammonia treatment and sampling; adjust the material processing path conversion device, switch the three-way valve when sampling so that the material is directly connected to the reaction sampling system, and when not sampling, switch the three-way valve so that the material flows to the tailing pipeline, and the material enters the tank through the tailing pipeline;

[0021] S104, waste liquid collection; open the gas circulation pipeline valve to empty the gas in the tank until the indication is zero, then close the gas circulation pipeline valve, open the drain pipeline valve, discharge the waste liquid to the external waste liquid collector, and complete the treatment.

[0022] Compared with the prior art, the present invention provides a process and device for treating high-pressure liquid ammonia tailings in a laboratory, which has the following beneficial effects:

[0023] In the technical solution disclosed in the present invention, liquid ammonia is directly absorbed by water or acid aqueous solution through a pressurized high-pressure absorption tank to form ammonia water and ammonium salt aqueous solution, which reduces the risk of a sharp increase in gas flow rate caused by liquid ammonia flash evaporation and avoids the expansion of the reaction back-end pipeline and the expansion of the pipe diameter. The experimental device can be greatly simplified and the safety of laboratory operators is guaranteed.

[0024] The high-pressure absorption tank is operated in parallel with the reaction sampling and can be switched at any time without affecting each other. The high-pressure absorption tank can be cut out of the system online for emptying and replaced with water or acid aqueous solution for absorption. The high-pressure absorption tank can also be cut into the system online at high pressure without affecting the front-end reaction, thereby improving the overall reaction efficiency and the efficiency and safety of tail liquid ammonia treatment.

[0025] The water-passing ring is connected to the side wall of the tank in an embracing manner so that the heat generated by the absorption of liquid ammonia in the tank can be released in time through the infusion of condensed water in the water-passing ring. The uninterrupted infusion of condensed water can prevent the tank from operating stagnant due to the internal temperature, and the cooling operation of the internal temperature of the tank can be transferred to the outside of the tank, thereby reducing the factors affecting the stagnation of the work inside the tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the overall structure of a laboratory device for processing high-pressure liquid ammonia tailings according to the present invention;

[0027] Figure 2 This is a schematic diagram of the overall cross-sectional structure of a laboratory device for processing high-pressure liquid ammonia tailings according to the present invention;

[0028] Figure 3 This is a schematic diagram of the operation of a laboratory device for processing high-pressure liquid ammonia tailings according to the present invention;

[0029] Figure 4 It is a working schematic diagram of a pressure balancing device of a laboratory device for processing high-pressure liquid ammonia tailings of the present invention;

[0030] Figure 5 It is a working schematic diagram of a material processing path conversion device of a laboratory high-pressure liquid ammonia tailings processing device of the present invention;

[0031] Figure 6 The present invention is a schematic diagram of the workflow of a laboratory process for processing high-pressure liquid ammonia tailings.

[0032] Numbers in the figure:

[0033] 1. High-pressure absorption tank; 11. Tank body; 12. Connection port; 121. Discharge terminal; 122. First terminal; 123. Second terminal; 124. Third terminal; 13. Water ring; 14. Condensate water inlet; 15. Condensate water outlet; 16. Liquid filling pipe;

[0034] 2. Material processing path conversion device; 21. Dilution path; 22. Sampling path; 23. Tailing material pipeline; 24. End sleeve; 25. Overflow hole; 26. First passage; 27. Three-way valve; 28. Second passage; 29. ​​Tailing material inlet valve;

[0035] 3. Discharge pipeline; 31. Drain pipe; 32. Waste liquid discharge valve;

[0036] 4. Pressure balancing device; 41. Absorption pipeline; 42. Gas circulation pipeline; 43. Input pipeline; 44. Pressure gauge; 45. Tail gas discharge valve; 46. Back pressure valve; 47. Manual pressure relief valve; 48. Automatic safety pressure relief valve; 49. Inert gas replenishing valve; 410. Normal pressure absorption tank. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] See also Figure 1-Figure 6Liquid ammonia is very volatile, especially when the ammonia in the outflow material after the reaction still exists in the form of liquid ammonia, the safe treatment of the tail material is a difficult point. The conventional treatment method is to reduce the pressure of the tail liquid ammonia flash to normal pressure and absorb it with water or acidic aqueous solution. In this process, there will be flash evaporation of liquid ammonia. A large amount of ammonia suddenly changes from liquid to gas, which will cause a sharp increase in the material flow rate. It is necessary to expand the capacity and diameter at the rear end of the reactor, which increases the difficulty of laboratory reaction device design and the demand for physical space. In addition, the emission of a large amount of ammonia will inevitably carry other products and incompletely reacted reactants, which may pose a safety hazard or endanger the health of the experimenters. Taking this laboratory reaction as an example, ethanolamine (MEA) and liquid ammonia are used as raw materials, reacting in a hydrogen atmosphere, and the reaction pressure is 15-25MPa. When MEA: NH3 = 1: 4 (MEA = 1.50mL / min), according to the conversion rate, the remaining liquid ammonia emission is 5.66mol / h. If it is directly discharged as gas, the emission rate can reach 136.4L / h, and the ammonia emission is large. Therefore, adopting a simple, safe and efficient liquid ammonia tail material treatment process and device is an important solution, which is of great significance to the safe development of laboratory research and development. Based on the above, this scheme describes a laboratory high-pressure liquid ammonia tail material treatment device, which directly absorbs liquid ammonia with an absorption liquid through a pressurized high-pressure absorption tank 1. When the absorption liquid is specifically a water or acid aqueous solution, it encounters liquid ammonia to form ammonia water and ammonium salt aqueous solution, which reduces the danger of a sharp increase in gas flow rate caused by liquid ammonia flash evaporation, and avoids the expansion of the capacity and diameter of the rear-end pipeline of the reaction. It can greatly simplify the experimental device and ensure the safety of laboratory operators. The high-pressure absorption tank 1 is operated in parallel with the reaction sampling, which can be switched at any time without affecting each other. The high-pressure absorption tank 1 can be cut out of the system online for emptying, and replaced with water or acid aqueous solution for absorption. The high-pressure absorption tank 1 can also be cut into the system online at high pressure without affecting the front-end reaction, which improves the overall reaction efficiency and the efficiency and safety of the tail liquid ammonia treatment.

[0039] The present embodiment provides a laboratory device for processing high-pressure liquid ammonia tailings, specifically, a high-pressure absorption tank 1 and a material processing path conversion device 2 installed on the high-pressure absorption tank 1 are provided, wherein a dilution path 21 and a sampling path 22 are differentiated on the high-pressure absorption tank 1 to cut the high-pressure absorption tank 1 into or out of the reaction system with liquid ammonia. After the high-pressure tank is cut into the reaction system, a pressure balancing device 4 arranged on the high-pressure absorption tank 1 is used to balance the internal pressure of the high-pressure absorption tank 1 and assist in absorbing the ammonia gas overflowing from the high-pressure absorption tank 1. After the high-pressure absorption tank 1 completes the absorption of liquid ammonia, the high-pressure absorption tank 1 is separated from the high-pressure absorption tank 1 through the discharge pipeline 3, thereby achieving the purpose of processing the liquid ammonia tailings.

[0040] The dilution path 21 is connected to a tailings pipeline 23 extending to the bottom of the high-pressure absorption tank 1 to consume the liquid ammonia entering the high-pressure absorption tank 1. The material processing path conversion device 2 includes a first passage 26 connected to an external reaction sampling system. A three-way valve 27 is connected to one end of the first passage 26 to establish a conversion point for the flow of materials to the reaction sampling system or the tailings pipeline 23. A second passage 28 connected between the three-way valve 27 and the tailings pipeline 23 establishes a flow path for the material to the tailings pipeline 23. A tailings liquid inlet valve 29 is installed on the second passage 28. The material is released into the reaction sampling system or released into the tank body 11 through the three-way valve 27 for absorption of liquid ammonia.

[0041] The high-pressure absorption tank 1 includes a tank body 11 and a plurality of connection ports 12 opened on the tank body 11. The tank body 11 contains an absorption liquid for absorbing liquid ammonia. In this specific embodiment, the absorption liquid can be water or an acid aqueous solution. One end of the tank body 11 is connected to a filling pipe 16 for replenishing the absorption liquid into the tank body 11. The tank body 11 is surrounded by a water ring 13. The water ring 13 is provided with a condensed water inlet 14 and a condensed water outlet 15. The side or lower part of the water ring 13 can be used as a condensed water outlet. The water inlet 14 is located at the side of the water ring 13, and the condensed water outlet 15 is located at the side of the water ring 13. Based on the height difference, the condensed water is flooded into the water ring 13 to fully exchange heat with the tank body 11. The connection port 12 passes through the water ring 13 and is connected to the tank body 11. The water ring 13 is encircled on the side wall of the tank body 11 from a height above the center line of the tank body 11. The condensed water outlet 15 and the condensed water inlet 14 are poured into the water ring 13 to absorb the heat dissipated from the tank body 11 to the outside. In order to timely release the heat generated by the absorption of liquid ammonia in the tank body 11 through the condensed water flowing in the water ring 13, the uninterrupted pouring of condensed water can prevent the tank body 11 from stagnating due to the internal temperature, and the cooling operation of the internal temperature of the tank body 11 is transferred to the outside of the tank body 11, reducing the factors affecting the stagnation of the internal operation of the tank body 11. In order to establish a connection between the pressure balancing device 4, the discharge pipeline 3 and the dilution path 21 and the tank body 11, a tail material pipeline 23 is established through the first end 122 included in the connecting port 12 to enter the internal passage of the tank body 11, and one end of the first end 122 is installed with a second end 123 and a third end 124 that are connected to the input pipeline 43 and the absorption pipeline 41.

[0042] The discharge pipeline 3 is installed at the bottom of the high-pressure absorption tank 1 and is connected to a discharge pipe 31 for discharging the dilution liquid outward. The discharge pipe 31 is connected to the tank body 11 through a discharge terminal 121. The discharge pipe 31 is connected to a waste liquid discharge valve 32, and the discharge pipe 31 is connected to an external waste liquid collection container.

[0043] The pressure balancing device 4 is connected to the tank body 11 and is offset at one end of the tailings pipe 23. The tailings pipe 23 establishes a flow channel for liquid ammonia in the tank body 11. An end sleeve 24 is provided at the end of the tailings pipe 23. The diameter of the end sleeve 24 is larger than the diameter of the tailings pipe 23. A plurality of overflow holes 25 are provided on the end sleeve 24 to increase the instantaneous contact area between the liquid ammonia and the liquid in the pipe body after the liquid ammonia overflows from the end sleeve 24. The pressure balancing device 4 includes an absorption pipeline 41 installed on the high-pressure absorption tank 1 and a gas circulation pipeline 42 connected in parallel to the absorption pipeline 41. The absorption pipeline 41 is connected with a tail gas discharge valve 45 and a back pressure valve 46. The rear end of the back pressure valve 46 is connected to a normal pressure absorption tank 410. The normal pressure absorption tank 410 is filled with an aqueous solution. The water or acid in the high-pressure absorption tank 1 can absorb the volatilized ammonia. A manual pressure relief valve 47 and an automatic safety pressure relief valve 48 are installed on the gas circulation pipeline 42. The automatic safety pressure relief valve 48 can automatically release pressure to the fume hood when the pressure exceeds the set value. The manual pressure relief valve 47 can release pressure to normal pressure when the high-pressure absorption tank 1 does not perform liquid ammonia treatment. It deviates from the installation position of the absorption pipeline 41. The high-pressure absorption tank 1 is connected with an input pipeline 43 for injecting inert gas therein, and the input pipeline 43 is connected with a pressure gauge 44 and an inert gas replenishing valve 49 for controlling the flow rate of inert gas in the input pipeline 43.

[0044] like Figure 6 As shown, this embodiment also provides a laboratory process for processing high-pressure liquid ammonia tailings, including:

[0045] S101: Replenish the absorption liquid; check that all valves are in the closed state, check the air tightness of all connecting parts, ensure that the reading of the pressure gauge 44 is zero, and then replenish the absorption liquid.

[0046] In this embodiment, the absorption liquid can be water or an acid aqueous solution. In the absorption liquid replenishment stage, the absorption liquid replenishment source is first connected, and water is injected into the high-pressure absorption tank 1 using a peristaltic pump. The absorption liquid replenishment valve is opened to inject deionized water into the high-pressure absorption tank 1. After the absorption liquid is replenished, the peristaltic pump is turned off to complete the absorption liquid replenishment step.

[0047] S102, pressurizing; inputting inert gas into the tank 11 so that the pressure gauge 44 shows 0.6-4MPa, then opening the valves on the absorption pipe 41 and the gas flow pipe 42 to absorb the small amount of ammonia that is subsequently volatilized;

[0048] First, open the tail gas discharge valve 45, close the back pressure valve 46, open the external inert gas replenishment source valve, and open the inert gas replenishment valve. The inert gas is filled into the high-pressure absorption tank 1 and when the pressure gauge 44 shows between 0.6-4MPa, close the inert gas replenishment source valve and open the back pressure valve 46 until bubbles emerge in the normal pressure absorption tank 410.

[0049] S103, tailing liquid ammonia treatment and sampling; adjust the material processing path conversion device 2, switch the three-way valve 27 when sampling so that the material is directly connected to the reaction sampling system, and when not sampling, switch the three-way valve 27 so that the material flows to the tailing pipeline 23, and the material enters the tank body 11 through the tailing pipeline 23;

[0050] S104, waste liquid collection; open the gas flow pipeline valve to empty the gas in the tank 11 to zero reading, then close the gas flow pipeline valve, open the drain pipe 31 valve, discharge the waste liquid to the outside waste liquid collector, and complete the treatment.

[0051] The control method of the electrical components appearing in this article is to automatically control through a controller. The control circuit of the controller can be implemented by simple programming by technicians in this field. The provision of power is also common knowledge in this field. The present invention is mainly used to protect mechanical devices, so the present invention will no longer explain the control method and circuit connection in detail.

[0052] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0053] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A laboratory device for processing high-pressure liquid ammonia tailings, characterized in that: include: High pressure absorption tank; A material processing path conversion device is arranged on the high-pressure absorption tank and is provided with a dilution path and a sampling path. The dilution path is connected to a tailings pipeline extending to the bottom of the high-pressure absorption tank to consume the liquid ammonia entering the high-pressure absorption tank. The discharge pipeline is installed at the bottom of the high-pressure absorption tank and is connected to a discharge pipe for discharging the diluent to the outside.

2. A laboratory high-pressure liquid ammonia tailings processing device according to claim 1, characterized in that: The high-pressure absorption tank is staggered at one end of the tailings pipeline and is connected to a pressure balancing device; The pressure balancing device comprises an absorption pipeline installed on the high-pressure absorption tank and a gas flow pipeline connected in parallel to the absorption pipeline, which is deviated from the installation position of the absorption pipeline. The high-pressure absorption tank is connected to an input pipeline for injecting inert gas therein, and a pressure gauge is connected to the input pipeline; The high-pressure absorption tank comprises a tank body and a plurality of connection ports provided on the tank body. A water ring sleeve surrounds the tank body, a condensed water inlet and a condensed water outlet are provided on the water ring sleeve, and the connection ports penetrate the water ring sleeve and are connected to the tank body. The connection port includes a discharge end connected to the drainage pipe and a first end for establishing a passage for the tailings pipe to enter the interior of the tank body. One end of the first end is equipped with a second end and a third end connected to the input pipe and the absorption pipe.

3. A laboratory high-pressure liquid ammonia tailings processing device according to claim 1, characterized in that: The tailings pipeline establishes a flow channel for liquid ammonia in the tank body, an end sleeve is provided at the end of the tailings pipeline, the diameter of the end sleeve is larger than the diameter of the tailings pipeline, and a plurality of overflow holes are opened on the end sleeve to increase the instantaneous contact area between the liquid ammonia and the liquid in the pipe body after overflowing from the end sleeve.

4. A laboratory high-pressure liquid ammonia tailings processing device according to claim 2, characterized in that: The water-passing ring sleeve is encircled on the side wall of the tank body starting from a height above the center line of the tank body, and the condensed water outlet and the condensed water inlet are filled into the water-passing ring sleeve to absorb the heat dissipated outward from the tank body.

5. A laboratory high-pressure liquid ammonia tailings processing device according to claim 2, characterized in that: The tank body contains an absorption liquid for absorbing liquid ammonia, and one end of the tank body is connected to a filling pipe for replenishing the absorption liquid into the tank body; The material processing path conversion device, the discharge pipeline and the pressure balancing device are all provided with a plurality of valves for opening and closing the passages.

6. A laboratory high-pressure liquid ammonia tailings processing device according to claim 1, characterized in that: The material processing path conversion device includes a first passage connected to an external reaction sampling system, a three-way valve connected to one end of the first passage to establish a conversion point for the material to flow to the reaction sampling system or the tailings pipeline, and a second passage connected between the three-way valve and the tailings pipeline to establish a flow path for the material to flow to the tailings pipeline.

7. A laboratory process for processing high-pressure liquid ammonia tailings, characterized in that: include: S101, replenish absorption liquid; check that all valves are in the closed state, check the air tightness of all connection parts, ensure that the pressure gauge shows zero, and replenish absorption liquid; S102, pressurizing; inputting inert gas into the tank body so that the pressure reading is 0.6-4MPa, then opening the valves on the absorption pipeline and the gas flow pipeline to absorb the small amount of ammonia gas that is subsequently volatilized; S103, tailing liquid ammonia treatment and sampling; adjust the material processing path conversion device, switch the three-way valve when sampling so that the material is directly connected to the reaction sampling system, and when not sampling, switch the three-way valve so that the material flows to the tailing pipeline, and the material enters the tank through the tailing pipeline; S104, waste liquid collection; open the gas circulation pipeline valve to empty the gas in the tank until the indication is zero, then close the gas circulation pipeline valve, open the drain pipeline valve, discharge the waste liquid to the external waste liquid collector, and complete the treatment.

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