A natural gas desulfurization process

Abstract

The present invention discloses a natural gas desulfurization process, belonging to the technical field of gas desulfurization. In the regeneration tower, the fluid overflows into the lean liquid tank and then is sent to the absorption tower by a circulation pump. The fluid in the absorption tower is transported to the downstream regeneration tower in an overflow manner. A buoyancy valve and a differential pressure self-acting valve are arranged on the overflow pipeline of the absorption tower. The buoyancy valve is used to control the opening and closing of the overflow channel, and the valve core of the buoyancy valve rises and falls with the liquid level, thereby adjusting the size of the overflow channel. The differential pressure self-acting valve is used to control the differential pressure between the inlet and outlet of the buoyancy valve. After the differential pressure is greater than the preset value, the downstream channel of the buoyancy valve is closed to prevent the further increase of the differential pressure, so that the buoyancy valve can move upward to increase the rich liquid flow rate after the liquid level in the absorption tower rises. The present invention controls the liquid level through the cooperation of the buoyancy valve and the differential pressure self-acting valve. The entire control mechanism can achieve autonomous control and fully meet the requirements of unattended operation. Therefore, there is no need to equip personnel on-site to monitor the liquid level, and only regular inspections are required, thus saving the operation cost.

Description

Technical Field

[0001] The present invention relates to the technical field of gas desulfurization, and particularly to a natural gas desulfurization process. Background Art

[0002] Natural gas extracted from the formation usually contains hydrogen sulfide, which is a highly toxic and strongly corrosive substance. Therefore, it is necessary to desulfurize natural gas.

[0003] The liquid-phase redox method is a desulfurization method with strong selectivity, wide application range, and low investment. Moreover, it is easy to operate. Such desulfurization devices usually include an absorption tower and a regeneration tower, both of which are bubble columns. Lean liquid and sulfur-containing natural gas contact in the absorption tower to generate rich liquid and purified natural gas. The rich liquid enters the regeneration tower and is regenerated by mixing with air. The regenerated lean liquid overflows into the lean liquid tank, and then is sent to the absorption tower through a lean liquid pump, thus realizing liquid circulation. The regeneration tower is an atmospheric tower, and both air and rich liquid flow from bottom to top. The liquid enters the lean liquid tank by overflow. Since natural gas usually has a certain pressure, such as 0.3 MPa, during operation, the pressure of the absorption tower is higher than that of the regeneration tower. The fluid in the absorption tower enters the regeneration tower by its own pressure. It is necessary to set up equipment such as a regulating valve and a liquid level sensor to detect and control the liquid level in the absorption tower to balance the liquid levels in the two towers (absorption tower and regeneration tower). This makes the liquid levels in each device in the entire circulation system controlled by two factors, namely the flow rate of the circulation pump and the opening degree of the regulating valve. The liquid levels at various places are prone to fluctuations. Therefore, it is necessary to monitor and adjust the liquid level manually and cannot operate autonomously for a long time, thus increasing the operating cost. Summary of the Invention

[0004] In view of the above technical problems, the purpose of the present invention is to provide a natural gas desulfurization process, which controls the flow rates of the absorption tower and the regeneration tower by overflow, can automatically balance the liquid levels in the main devices, ensure that the entire system can operate automatically and stably for a long time without external intervention, and can save the operating cost.

[0005] The specific scheme of the present invention is as follows:

[0006] A natural gas desulfurization process includes an absorption tower, a regeneration tower, a lean liquid tank, a circulation pump, and a sulfur foam treatment unit. Among them, both the absorption tower and the regeneration tower are bubble towers, the regeneration tower is an atmospheric tower, the circulation pump is used to transport the lean liquid in the lean liquid tank to the absorption tower. The lean liquid contacts with sulfur-containing natural gas in the absorption tower to generate rich liquid. The rich liquid is mixed with air and flows upward from the bottom of the regeneration tower and is regenerated into lean liquid, while by-product sulfur foam is produced. The lean liquid in the regeneration tower overflows to the lean liquid tank through the intermediate extraction outlet, and the sulfur foam overflows to the sulfur foam treatment unit to be processed into sulfur. It is characterized in that the fluid in the absorption tower is transported downstream by overflow, and a buoyancy valve and a differential pressure self-acting valve are arranged on the overflow pipeline of the absorption tower. Among them, the buoyancy valve is located upstream of the differential pressure self-acting valve and is used to control the size of the overflow channel. The valve core of the buoyancy valve rises and falls with the liquid level, thereby regulating the flow rate of the rich liquid; the differential pressure self-acting valve is used to control the differential pressure at the inlet and outlet of the buoyancy valve. After the differential pressure is greater than the preset value, the downstream channel of the buoyancy valve is closed to avoid the continuous increase of the differential pressure, so that the buoyancy valve can move upward to increase the flow rate of the rich liquid after the liquid level in the absorption tower rises.

[0007] As a specific embodiment of the present invention, the gas and liquid in the absorption tower are in countercurrent contact, and the overflow of the fluid in the absorption tower to the downstream is controlled by a liquid level control unit, thereby autonomously regulating the liquid level. The liquid level control unit includes:

[0008] An overflow pipe vertically arranged in the absorption tower, the lower end of the overflow pipe is communicated with the liquid outlet of the absorption tower, and is used to transport the rich liquid to the regeneration tower;

[0009] A guide pipe sleeved outside the overflow pipe and spaced a certain distance from the outer wall of the overflow pipe. The lower end of the guide pipe is spaced a certain distance from the bottom of the absorption tower, and the upper end of the guide pipe extends above the upper end of the overflow pipe, so as to guide the rich liquid in the absorption tower to flow from the bottom of the tower to the upper end of the overflow pipe;

[0010] A buoyancy valve located in the overflow pipe, the valve core of the buoyancy valve rises and falls with the liquid level, thereby regulating the flow rate of the rich liquid;

[0011] A differential pressure self-acting valve located downstream of the buoyancy valve, which is used to control the differential pressure at the inlet and outlet of the buoyancy valve. When the differential pressure exceeds the preset value, the downstream channel of the buoyancy valve is closed, so that the buoyancy valve can move upward to increase the flow rate of the rich liquid after the liquid level in the absorption tower rises.

[0012] As a specific embodiment of the present invention, the buoyancy valve includes:

[0013] A valve seat located on the inner wall of the overflow pipe;

[0014] A valve core matching the valve seat;

[0015] A floating body fixedly connected to the valve core;

[0016] Among them, the floating body can float on the liquid surface, thereby driving the valve core to rise and fall with the liquid level.

[0017] As a specific embodiment of the present invention, a cap is provided at the upper end of the diversion pipe, and there is a channel for gas flow between the cap and the upper end of the diversion pipe.

[0018] As a specific embodiment of the present invention, it further includes a flash tank, which is located between the absorption tower and the regeneration tower, and is used to receive the rich liquid from the absorption tower and perform flash evaporation on it. The rich liquid after flash evaporation enters the regeneration tower.

[0019] Furthermore, a liquid level control unit is also provided for the flash tank.

[0020] As a specific embodiment of the present invention, the lean liquid from the regeneration tower overflows and enters the bottom of the lean liquid tank. A gas distributor is provided in the lean liquid tank, and an annular overflow trough is provided at the upper part of the lean liquid tank. The inlet of the circulation pump is communicated with the middle part of the lean liquid tank, and the sulfur foam in the lean liquid tank flows into the sulfur foam treatment unit through the annular overflow trough by itself.

[0021] As a specific embodiment of the present invention, the sulfur foam treatment unit includes a sulfur foam tank, a sulfur foam pump, a filter press, a filtrate collection tank and a filtrate recovery pump. Among them, the sulfur foam from the regeneration tower and the lean liquid tank flows into the sulfur foam tank by itself. The sulfur foam pump is used to send the fluid in the sulfur foam tank to the filter press. After the filter press performs pressure filtration, wet sulfur and filtrate are produced. The filtrate enters the filtrate collection tank by gravity, and the filtrate recovery pump is used to transport the filtrate in the filtrate collection tank.

[0022] As a specific embodiment of the present invention, the outlet of the filtrate recovery pump is communicated with the annular overflow trough of the lean liquid tank for flushing the annular overflow trough.

[0023] As a specific embodiment of the present invention, the bottoms of the regeneration tower, the lean liquid tank and the sulfur foam tank are respectively communicated with the inlet of the sulfur foam pump, and valves are provided on each connecting pipeline, which is convenient for the sulfur foam pump to independently send the liquids in the regeneration tower, the lean liquid tank and the sulfur foam tank to the filter press for pressure filtration.

[0024] Compared with the prior art, it has the following advantages:

[0025] In the present invention, the liquid level is controlled by the cooperation of a buoyancy valve and a differential pressure self-acting valve. The differential pressure self-acting valve is used to control the differential pressure before and after the buoyancy valve, so that the buoyancy valve can be opened smoothly. The buoyancy valve will automatically act with the rise and fall of the liquid level in the absorption tower to adjust the liquid level. The entire control mechanism does not require equipment such as liquid level sensors and controllers and can achieve autonomous control. There is only one power device in the entire liquid circulation system. After the flow rate changes, the liquid levels of the absorption tower and the regeneration tower can be automatically adjusted and balanced by means of overflow, fully meeting the requirements of unattended operation. Therefore, there is no need to equip personnel on site to monitor the liquid level, and only regular inspections are required, thus saving the operation cost. Brief Description of the Drawings

[0026] Figure 1 It is a flowchart of a specific embodiment of the natural gas desulfurization process of the present invention;

[0027] Figure 2 It is Figure 1 a schematic diagram of the overall structure of the absorption tower liquid level control unit in

[0028] Figure 3 It is Figure 2 a schematic diagram of the structure of the buoyancy valve in

[0029] Figure 4 a schematic diagram of the overall structure of the absorption tower liquid level control unit in another specific embodiment;

[0030] Figure 5 It is Figure 1 a partial schematic diagram of the differential pressure self - acting valve in

[0031] Figure 6 a schematic diagram of the overall structure of the absorption tower liquid level control unit in yet another specific embodiment;

[0032] Figure 7 It is a flowchart of another specific embodiment of the natural gas desulfurization process of the present invention;

[0033] Figure 8 It is Figure 7 a schematic diagram of the overall structure of the flash tank liquid level control unit in

[0034] Figure 9 It is a flowchart of yet another specific embodiment of the natural gas desulfurization process of the present invention;

[0035] In the figure, absorption tower 100; regeneration tower 200; lean liquid tank 300; circulation pump 400; flash tank 600; gas distributor 110; second drain pipe 120; valve 210; overflow pipe 510; diversion pipe 520; buoyancy valve 530; differential pressure self - acting valve 540; valve seat 531; valve core 532; floating body 533; cap 521; piston container 541; piston 542; valve rod 543; spring 544; sulfur foam tank 710; sulfur foam pump 720; filter press 730; filtrate collection tank 740; filtrate recovery pump 750; blower 810; air cooler 820; raw gas separator 910; purifier separator 920; purifier coalescer 930. Detailed Description of the Embodiments

[0036] The present invention will be further described in detail below in conjunction with the embodiments and the drawings, but the embodiments of the present invention are not limited thereto.

[0037] Embodiment

[0038] Please refer to Figures 1 to 9 , which shows the structures of multiple specific embodiments of the natural gas desulfurization process of the present invention. The natural gas desulfurization process of the present invention includes an absorption tower 100, a regeneration tower 200, a lean liquid tank 300, a circulation pump 400, and a sulfur foam treatment unit. Among them, both the absorption tower 100 and the regeneration tower 200 are bubble columns, the regeneration tower is an atmospheric tower, the circulation pump 400 is used to transport the lean liquid in the lean liquid tank 300 to the absorption tower 100. In the absorption tower 100, the lean liquid contacts the sulfur-containing natural gas countercurrently to generate rich liquid and purified natural gas, and the purified natural gas is sent out of the device; the rich liquid enters the regeneration tower 200. In the regeneration tower 200, the rich liquid is mixed with air and flows upward from the bottom of the regeneration tower 200 and is regenerated into lean liquid, while by-product sulfur foam is produced; the lean liquid in the regeneration tower 200 overflows to the lean liquid tank 300 through the intermediate extraction port, and the sulfur foam overflows to the sulfur foam treatment unit through the annular overflow trough at the upper part of the regeneration tower 200 and is processed into sulfur. The above-mentioned equipment are all conventional equipment in the industry, and the specific structures will not be described in detail here. The main purpose of the present invention is to set a liquid level control unit for automatically controlling the liquid level of the absorption tower 100, so as to eliminate the need for manual intervention in the liquid level of the absorption tower 100 and reduce the operating cost.

[0039] Please refer to Figure 2 and Figure 6, the liquid level control unit of the present invention includes an overflow pipe 510, a diversion pipe 520, a buoyancy valve 530, and a differential pressure self-acting valve 540. The overflow pipe 510 is vertically arranged in the absorption tower 100. The lower end of the overflow pipe 510 is communicated with the liquid outlet of the absorption tower 100 for transporting rich liquid to the regeneration tower 200. The diversion pipe 520 is sleeved outside the overflow pipe 510 and is spaced from the outer wall of the overflow pipe 510 by a certain distance, so as to form an annular channel between the inner wall of the diversion pipe 520 and the outer wall of the overflow pipe 510 for the rich liquid to flow through. The lower end of the diversion pipe 520 is spaced from the bottom of the absorption tower 100 by a certain distance, and the upper end of the diversion pipe 520 extends above the upper end of the overflow pipe 510, so as to guide the rich liquid in the absorption tower 100 to flow from the bottom of the tower to the upper end of the overflow pipe 510. In this way, after the lean liquid enters the absorption tower 100, it still flows to the bottom of the absorption tower 100, so as to fully contact with the sulfur-containing natural gas. The buoyancy valve 530 is located at the upper end of the overflow pipe 510. The valve core 532 of the buoyancy valve 530 rises and falls with the liquid level, so as to control the flow channel area of the rich liquid flow and adjust the flow rate. The differential pressure self-acting valve 540 is located at the lower end of the overflow pipe 510 and is used to control the differential pressure at the inlet and outlet of the buoyancy valve 530. The greater the differential pressure, the smaller the opening of the differential pressure self-acting valve 540, so as to reduce the flow rate. When the differential pressure is greater than a preset value, such as 40 kPa, the channel downstream of the buoyancy valve is closed to avoid that the buoyancy valve cannot be opened smoothly after being closed due to excessive differential pressure. When the liquid level in the absorption tower 100 is low, the buoyancy valve 530 reduces the flow channel area, and the differential pressure at the inlet and outlet of the buoyancy valve 530 increases. The differential pressure self-acting valve 540 gradually closes, so as to avoid excessive differential pressure at the inlet and outlet of the buoyancy valve 530, so that the buoyancy valve 530 can move upward smoothly again after the liquid level in the absorption tower 100 rises, and then increase the flow channel area of the rich liquid flow and increase the rich liquid flow rate.

[0040] The present invention controls the liquid level through the buoyancy valve 530. The rise and fall of the liquid level will drive the buoyancy valve 530 to automatically act for liquid level adjustment. The entire control mechanism does not require equipment such as liquid level sensors and controllers, and can achieve autonomous control, fully meeting the requirements of unattended operation. Therefore, there is no need to equip personnel on-site to monitor the liquid level, and only regular inspections are required, thus saving operating costs.

[0041] In some embodiments, as Figure 3 shown, the buoyancy valve 530 includes a valve seat 531, a valve core 532, and a floating body 533. Among them, the valve seat 531 is fixed on the inner wall of the overflow pipe 510, and the flow channel of the valve seat 531 is vertically arranged. The valve core 532 is matched with the valve seat 531. The floating body 533 is fixedly connected to the valve core 532 through a connecting rod. The floating body 533 can float on the liquid surface, so as to drive the valve core 532 to rise and fall with the liquid level, and then change the flow channel area of the rich liquid.

[0042] In some embodiments, a cap 521 is provided at the upper end of the diversion pipe 520 to block the lean liquid sprayed from the top and prevent it from falling into the upper end of the diversion pipe 520 and being directly discharged, so that the desulfurization effect cannot be fully exerted. The cap 521 is supported at the upper end of the diversion pipe 520 by a support rod, so that a gap is formed between the cap 521 and the upper end of the diversion pipe 520, and the gas flows through this gap, so that the liquid levels inside and outside the diversion pipe 520 are flush.

[0043] In some embodiments, as Figure 6 shown, the gas distributor 110 in the absorption tower 100 is an annular tubular structure. At this time, there is no other equipment at the central axis of the absorption tower 100, and the diversion pipe 520 can be directly installed at the center of the absorption tower 100; in other embodiments, as Figure 2 shown, a gas distributor 110 is provided on the central axis of the absorption tower 100. At this time, the diversion pipe 520 is arranged in the central pipe of the gas distributor 110. The upper end of the diversion pipe 520 passes through the central pipe of the gas distributor 110 and is sealedly connected thereto, and the lower end of the diversion pipe 520 extends below the gas outlet of the gas distributor 110.

[0044] In some embodiments, as Figure 4 shown, a second drain pipe 120 is provided at the bottom of the absorption tower 100 to facilitate the complete discharge of the liquid in the absorption tower 100 during inspection, repair and maintenance. The lower end of the overflow pipe 510 passes through the side wall of the second drain pipe 120 and is sealedly connected thereto.

[0045] In some embodiments, the differential pressure self-acting valve 540 is as Figure 5 shown. The differential pressure self-acting valve 540 includes a piston container 541, a piston 542, a valve stem 543 and a spring 544. The piston 542 is slidably and sealingly connected to the inner wall of the piston container 541, thereby dividing the interior of the piston container 541 into upper and lower cavities. Among them, the lower cavity is communicated with the overflow pipe 510 downstream of the buoyancy valve 530, the upper cavity is communicated with the absorption tower 100, the valve stem 543 is fixedly connected to the piston 542, and the spring 544 is used to push the piston 542 in the direction of reducing the volume of the upper cavity. When the differential pressure between the upper and lower cavities changes, the piston 542 will move synchronously, thereby driving the valve stem 543 to move, changing the flow channel of the differential pressure self-acting valve 540, and adjusting the flow rate. When the differential pressure increases, the valve stem 543 moves downward to reduce the flow rate. On the contrary, the valve stem 543 moves upward to increase the flow rate. The differential pressure for specific control can be selected as needed, such as 0.1 MPa, or the set differential pressure can be adjusted by adjusting the length of the spring 544.

[0046] In some embodiments, if the natural gas pressure is relatively high, such as 1 MPa, then a certain amount of natural gas is dissolved in the rich liquid. Therefore, as Figure 7As shown, a flash tank 600 is provided between the absorption tower 100 and the regeneration tower 200 for flashing the rich liquid. The flashed rich liquid enters the regeneration tower 200. The flashed natural gas is processed as needed. For example, it is sent into the purified natural gas after boosting or directly sent into the flare. When sent into the flare, the flash tank 600 can operate at atmospheric pressure. The bottom of the flash tank 600 is directly connected to the bottom of the regeneration tower 200, and the liquid level in the flash tank 600 can be controlled by overflow. When the flashed natural gas needs to be recovered, a certain pressure, such as 0.2 MPa, is generally maintained in the flash tank 600. At this time, a liquid level control unit also needs to be provided for the flash tank 600, such as Figure 8 as shown.

[0047] In some embodiments, a gas-liquid separation device is also provided for gas-liquid separation of the gas entering and leaving the absorption tower 100, such as Figure 7 and Figure 9 as shown. A raw gas separator 910 is provided to remove the liquid in the sulfur-containing natural gas; a purifier separator 920 and a purifier coalescer 930 in series are also provided to remove the liquid in the purified natural gas. The liquid level in these separators rises relatively slowly, and a two-position programmable valve can be used to control the liquid level. After the liquid level reaches a certain height, the valve is opened to drain the liquid, and then closed after the drainage is completed, without the need for manual attendance.

[0048] In some embodiments, the lean liquid after overflow in the regeneration tower 200 enters the bottom of the lean liquid tank 300. A gas distributor 110 is provided in the lean liquid tank 300, and an annular overflow trough is provided at the top of the lean liquid tank 300, so that the lean liquid tank 300 can continue to be used as a regeneration site. The inlet of the circulation pump 400 is connected to the middle of the lean liquid tank 300, and the fluid in the annular overflow trough in the lean liquid tank 300 flows by gravity into the sulfur foam treatment unit.

[0049] In some embodiments, the sulfur foam treatment unit includes a sulfur foam tank 710, a sulfur foam pump 720, a filter press 730, a filtrate collection tank 740, and a filtrate recovery pump 750. Among them, the sulfur foam from the regeneration tower 200 enters the sulfur foam tank 710. A stirrer is provided in the sulfur foam tank 710 to break the sulfur foam through stirring. The sulfur foam pump 720 is used to send the fluid in the sulfur foam tank 710 into the filter press 730. The filter press 730 produces wet sulfur and filtrate after filtration. The filtrate enters the filtrate collection tank 740 by gravity and is sent into the lean liquid or rich liquid by the filtrate recovery pump 750 for continuous circulation.

[0050] There may be a situation where relatively large sulfur particles deposit in the regeneration tower 200 and the lean liquid tank 300. These particles will deposit at the bottom of the corresponding containers. If not discharged for a long time, it is easy to cause caking and blockage of the bottom discharge port of the container, which is not conducive to draining the liquid during later maintenance. Therefore, it is necessary to regularly discharge the fluid at the top of the regeneration tower 200 and the lean liquid tank 300. In some embodiments, such asFigure 9 As shown, the bottoms of the regeneration tower 200, the lean liquid tank 300, and the sulfur foam tank 710 are respectively connected to the inlet of the sulfur foam pump 720, and valves 210 are provided on each connecting pipeline, facilitating the sulfur foam pump 720 to independently send the liquids in the regeneration tower 200, the lean liquid tank 300, and the sulfur foam tank 710 to the filter press 730 for filtration.

[0051] In some embodiments, the sulfur foam pump 720 sends the filtrate into the annular overflow trough of the lean liquid tank 300. There is less sulfur foam in the lean liquid tank 300. Using the filtrate to wash the annular overflow trough can accelerate the flow of sulfur foam and prevent it from depositing and scaling on the annular overflow trough. Of course, the filtrate can also be sent to the annular overflow trough of the regeneration tower 200.

[0052] In some embodiments, the air can be provided by an external air source. In other embodiments, a blower 810 can also be provided for air supply. An air cooler 820 is arranged at the outlet of the blower 810 to reduce the temperature of the air.

[0053] As described above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be covered within the protection scope of the present invention.

Claims

1. A natural gas desulfurization process, including an absorption tower, a regeneration tower, a lean liquid tank, a circulation pump, and a sulfur foam treatment unit, wherein, The absorption tower and the regeneration tower are both bubble columns. The regeneration tower is an atmospheric column. The circulation pump is used to transport the lean liquid in the lean liquid tank to the absorption tower. The lean liquid contacts with the sulfur-containing natural gas in the absorption tower to generate rich liquid. After the rich liquid is mixed with air, it flows upward from the bottom of the regeneration tower and is regenerated into lean liquid, while by-product sulfur foam is produced. The lean liquid in the regeneration tower overflows to the lean liquid tank through the intermediate outlet, and the sulfur foam overflows to the sulfur foam treatment unit to be processed into sulfur. It is characterized in that the fluid in the absorption tower is transported downstream by means of overflow. A buoyancy valve and a differential pressure self-operated valve are arranged on the overflow pipeline of the absorption tower. Among them, the buoyancy valve is located upstream of the differential pressure self-operated valve and is used to control the size of the overflow channel. The valve core of the buoyancy valve rises and falls with the liquid level, so as to adjust the flow rate of the rich liquid. The differential pressure self-operated valve is used to control the differential pressure between the inlet and outlet of the buoyancy valve. The greater the differential pressure, the smaller the valve opening. After the differential pressure is greater than the preset value, the downstream channel of the buoyancy valve is closed to avoid the continuous increase of the differential pressure, so that the buoyancy valve can move upward to increase the rich liquid flow rate after the liquid level in the absorption tower rises.

2. A natural gas desulfurization process according to claim 1, characterized in that, The gas and liquid in the absorption tower are in countercurrent contact. The overflow of the liquid in the absorption tower to the downstream is controlled by a liquid level control unit, and the liquid level control unit includes: An overflow pipe vertically arranged in the absorption tower. The lower end of the overflow pipe is communicated with the liquid outlet of the absorption tower and is used to transport the rich liquid to the regeneration tower. A diversion pipe sleeved outside the overflow pipe and spaced a certain distance from the outer wall of the overflow pipe. The lower end of the diversion pipe is spaced a certain distance from the bottom of the absorption tower, and the upper end of the diversion pipe extends above the upper end of the overflow pipe, so as to guide the rich liquid in the absorption tower to flow from the bottom of the tower to the upper end of the overflow pipe. A buoyancy valve located in the overflow pipe. The valve core of the buoyancy valve rises and falls with the liquid level, so as to adjust the flow area in the overflow pipeline. A differential pressure self-operated valve located downstream of the buoyancy valve, which is used to control the differential pressure between the inlet and outlet of the buoyancy valve. The greater the differential pressure, the smaller the valve opening. After the differential pressure exceeds the preset value, the downstream channel of the buoyancy valve is closed, so that the buoyancy valve can move upward to increase the rich liquid flow rate after the liquid level in the absorption tower rises.

3. A natural gas desulfurization process according to claim 2, characterized in that, The buoyancy valve includes: A valve seat located on the inner wall of the overflow pipe; A valve core matching with the valve seat; A floating body fixedly connected with the valve core; Among them, the floating body can float on the liquid surface, so as to drive the valve core to rise and fall with the liquid level.

4. A natural gas desulfurization process according to claim 2, characterized in that, A cap is arranged at the upper end of the diversion pipe, and there is a channel for gas flow between the cap and the upper end of the diversion pipe.

5. A natural gas desulfurization process according to claim 2, characterized in that, It also includes a flash tank, which is used to receive the rich liquid from the absorption tower and flash it. The flashed rich liquid enters the regeneration tower.

6. A natural gas desulfurization process according to claim 5, characterized in that, The flash tank is also equipped with a liquid level control unit.

7. A natural gas desulfurization process according to claim 2, characterized in that, The lean liquid of the regeneration tower overflows and enters the bottom of the lean liquid tank. A gas distributor is arranged in the lean liquid tank. An annular overflow groove is arranged at the upper part of the lean liquid tank. The inlet of the circulation pump is communicated with the middle part of the lean liquid tank. The sulfur foam in the lean liquid tank flows into the sulfur foam treatment unit through the annular overflow groove.

8. A natural gas desulfurization process according to claim 7, characterized in that, The sulfur foam treatment unit includes a sulfur foam tank, a sulfur foam pump, a filter press, a filtrate collection tank, and a filtrate recovery pump. Among them, the sulfur foams from the regeneration tower and the lean liquid tank flow by gravity into the sulfur foam tank. The sulfur foam pump is used to send the fluid in the sulfur foam tank into the filter press. After the filter press performs pressure filtration, wet sulfur and filtrate are produced. The filtrate enters the filtrate collection tank by gravity. The filtrate recovery pump is used to transport the filtrate in the filtrate collection tank.

9. A natural gas desulfurization process according to claim 8, characterized in that, The outlet of the filtrate recovery pump is communicated with the annular overflow trough of the lean liquid tank for flushing the annular overflow trough.

10. A natural gas desulfurization process according to claim 9, characterized in that, The bottoms of the regeneration tower, the lean liquid tank, and the sulfur foam tank are respectively communicated with the inlet of the sulfur foam pump, and valves are provided on each connecting pipeline.

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