Natural gas desulfurization process

Abstract

The invention discloses a natural gas desulfurization process and belongs to the technical field of gas desulfurization, fluid in a regeneration tower overflows into a barren liquor tank and then is fed into an absorption tower through a circulating pump, fluid in the absorption tower is conveyed to the downstream regeneration tower in an overflow mode, and a buoyancy valve and a differential pressure self-operated valve are arranged on an overflow pipeline of the absorption tower. The buoyancy valve is used for controlling opening and closing of the overflow channel, a valve element of the buoyancy valve ascends and descends along with liquid level ascending and descending, and therefore the size of the overflow channel is adjusted. The differential pressure self-operated valve is used for controlling the differential pressure of the inlet and outlet of the buoyancy valve, and closing the downstream channel of the buoyancy valve after the differential pressure is greater than a preset value to avoid continuous increase of the differential pressure, so that the buoyancy valve can move upwards to increase the rich liquid flow after the liquid level in the absorption tower rises. The liquid level is controlled through cooperation of the buoyancy valve and the differential pressure self-operated valve, the whole control mechanism can achieve autonomous control, and the unattended requirement is completely met, so that personnel for monitoring the liquid level on site is not needed, only regular inspection is needed, and the operation cost is saved.

Description

Technical Field

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

[0002] Natural gas extracted from the ground usually contains hydrogen sulfide, which is a highly toxic and corrosive substance. Therefore, natural gas needs to be desulfurized.

[0003] Liquid phase redox method is a highly selective, widely applicable, low-investment desulfurization method, and easy to operate. This type of desulfurization device usually includes an absorption tower and a regeneration tower, both of which are bubbling towers. The lean liquid and the sulfur-containing natural gas are in contact in the absorption tower to generate rich liquid and purified natural gas. The rich liquid enters the regeneration tower and mixes with air for regeneration. The lean liquid generated after regeneration overflows into the lean liquid tank, and then is pumped into the absorption tower through the lean liquid pump, thereby realizing liquid circulation. The regeneration tower is a normal pressure tower, and both air and rich liquid flow from bottom to top, and the liquid enters the lean liquid tank by overflow. Since natural gas usually has a certain pressure, such as 0.3MPa, during operation, the pressure of the absorption tower is higher than that of the regeneration tower, and the fluid in the absorption tower enters the regeneration tower by its own pressure. It is necessary to set up regulating valves, liquid level sensors and other equipment to detect and control the liquid level in the absorption tower to balance the liquid levels of the two towers (absorption tower and regeneration tower). This makes the liquid level in each device in the entire circulation system controlled by two factors: the flow rate of the circulation pump and the opening of the regulating valve. The liquid level in each place is prone to fluctuations, so manual monitoring and adjustment of the liquid level are required. It cannot operate autonomously for a long time, thereby 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 of the absorption tower and the regeneration tower by overflow, can automatically balance the liquid level in the main equipment, ensure that the entire system can operate automatically and stably for a long time without external intervention, and save operating costs.

[0005] The specific scheme of the present invention is as follows: A natural gas desulfurization process comprises 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 bubbling towers, the regeneration tower is a normal pressure 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 the 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 regenerated into lean liquid, and sulfur foam is produced as a by-product, the lean liquid in the regeneration tower overflows into the lean liquid tank through an intermediate extraction port, the sulfur foam overflows into the sulfur foam treatment unit and is processed into sulfur, and the process is characterized in that The fluid in the absorption tower is transported downstream by overflow, and a buoyancy valve and a pressure differential self-operated valve are arranged on the overflow pipe of the absorption tower, wherein the buoyancy valve is located upstream of the pressure differential self-operated valve and is used to control the size of the overflow channel, and the valve core of the buoyancy valve rises and falls with the rise and fall of the liquid level, thereby adjusting the flow rate of the rich liquid; the pressure differential self-operated valve is used to control the pressure difference at the inlet and outlet of the buoyancy valve, and closes the downstream channel of the buoyancy valve when the pressure difference is greater than a preset value to prevent the pressure difference from continuing to increase, so that the buoyancy valve can move upward after the liquid level in the absorption tower rises to increase the flow rate of the rich liquid.

[0006] 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, so as to autonomously adjust the liquid level. The liquid level control unit includes: An overflow pipe is vertically arranged in the absorption tower, the lower end of which is connected to the liquid outlet of the absorption tower and is used to transport rich liquid to the regeneration tower; A draft pipe is sleeved outside the overflow pipe and spaced a certain distance from the outer wall of the overflow pipe, the lower end of the draft pipe is spaced a certain distance from the bottom of the absorption tower, and the upper end of the draft pipe extends above the upper end of the overflow pipe, thereby guiding the rich liquid in the absorption tower to flow from the bottom of the tower to the upper end of the overflow pipe; The buoyancy valve located in the overflow pipe, the valve core of the buoyancy valve rises and falls with the liquid level, thereby adjusting the flow of rich liquid; The differential pressure self-acting valve located downstream of the buoyancy valve is used to control the differential pressure at the inlet and outlet of the buoyancy valve. When the differential pressure exceeds a 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.

[0007] As a specific embodiment of the present invention, the buoyancy valve comprises: A valve seat located on the inner wall of the overflow pipe; A valve core matched with a valve seat; A floating body fixedly connected to the valve core; The floating body can float on the liquid surface, thereby driving the valve core to rise and fall with the rise and fall of the liquid level.

[0008] As a specific embodiment of the present invention, a cap is provided at the upper end of the flow guide tube, and a channel for gas flow is provided between the cap and the upper end of the flow guide tube.

[0009] As a specific embodiment of the present invention, a flash tank is also included. The flash tank is located between the absorption tower and the regeneration tower and is used to receive the rich liquid from the absorption tower and flash evaporate it. The rich liquid after flash evaporated enters the regeneration tower.

[0010] Furthermore, the flash tank is also equipped with a liquid level control unit.

[0011] As a specific embodiment of the present invention, 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 on the upper part of the lean liquid tank, and the inlet of the circulation pump is connected 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.

[0012] 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 collecting tank and a filtrate recovery pump, wherein the sulfur foam in the regeneration tower and the lean liquid tank flows into the sulfur foam tank by gravity, the sulfur foam pump is used to send the fluid in the sulfur foam tank into the filter press, the filter press produces wet sulfur and filtrate after filtration, the filtrate enters the filtrate collecting tank by gravity, and the filtrate recovery pump is used to transport the filtrate in the filtrate collecting tank.

[0013] As a specific implementation of the present invention, the outlet of the filtrate recovery pump is connected to the annular overflow groove of the lean liquid tank for flushing the annular overflow groove.

[0014] 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 connected to the inlet of the sulfur foam pump, and valves are provided on each connecting pipeline to facilitate the sulfur foam pump to independently deliver the liquid in the regeneration tower, the lean liquid tank and the sulfur foam tank to the filter press for filtration.

[0015] Compared with the existing technology, it has the following advantages: The present invention controls the liquid level by cooperating with a buoyancy valve and a pressure differential self-operated valve. The pressure differential self-operated valve is used to control the pressure difference before and after the buoyancy valve, so that the buoyancy valve can be opened smoothly. The buoyancy valve automatically moves to adjust the liquid level as the liquid level in the absorption tower rises and falls. The entire control mechanism does not require equipment such as a liquid level sensor and a controller, 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 overflow, which fully meets the unmanned operation requirements. Therefore, there is no need to equip the site with personnel to monitor the liquid level, and only regular inspections are required, thereby saving operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart of a specific embodiment of the natural gas desulfurization process of the present invention; Figure 2 for Figure 1 Schematic diagram of the overall structure of the liquid level control unit of the middle absorption tower; Figure 3 for Figure 2 Schematic diagram of the structure of the middle buoyancy valve; Figure 4 It is a schematic diagram of the overall structure of the absorption tower liquid level control unit in another specific embodiment; Figure 5 for Figure 1 Schematic diagram of the partial structure of the medium pressure differential self-acting valve; Figure 6 It is a schematic diagram of the overall structure of the absorption tower liquid level control unit in another specific embodiment; Figure 7 A flow chart of another specific embodiment of the natural gas desulfurization process of the present invention; Figure 8 for Figure 7 Schematic diagram of the overall structure of the liquid level control unit of the flash tank; Fig. 9 This is a flow chart of another specific embodiment of the natural gas desulfurization process of the present invention; In the figure, there are an absorption tower 100; a regeneration tower 200; a lean liquid tank 300; a circulation pump 400; a flash tank 600; a gas distributor 110; a second liquid discharge pipe 120; a valve 210; an overflow pipe 510; a guide pipe 520; a buoyancy valve 530; a differential pressure self-operated valve 540; a valve seat 531; a valve core 532; a floating body 533; a cap 521; a piston container 541; a piston 542; a valve stem 543; a spring 544; a sulfur foam tank 710; a sulfur foam pump 720; a filter press 730; a filtrate collecting tank 740; a filtrate recovery pump 750; a fan 810; an air cooler 820; a raw gas separator 910; a purifier separator 920; and a purifier coalescer 930. DETAILED DESCRIPTION

[0017] The present invention will be further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0018] Example Please refer to Figures 1 to 9, which shows the structure 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, wherein the absorption tower 100 and the regeneration tower 200 are both bubbling towers, the regeneration tower is a normal pressure 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 and the sulfur-containing natural gas are countercurrently contacted 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 regenerated into lean liquid, and sulfur foam is produced as a by-product; the lean liquid in the regeneration tower 200 overflows into the lean liquid tank 300 through the intermediate extraction port, and the sulfur foam overflows into the sulfur foam treatment unit through the annular overflow trough at the top of the regeneration tower 200 and is processed into sulfur, the above equipment are all conventional equipment in the industry, and the specific structure is not described in detail here. The main purpose of the present invention is to provide a liquid level control unit for automatically controlling the liquid level of the absorption tower 100, thereby eliminating the need for manual intervention in the liquid level of the absorption tower 100 and reducing operating costs.

[0019] Please refer to Figure 2 and Figure 6The liquid level control unit of the present invention comprises an overflow pipe 510, a guide pipe 520, a buoyancy valve 530 and a pressure differential 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 connected to the liquid outlet of the absorption tower 100, and is used to transport the rich liquid to the regeneration tower 200. The guide pipe 520 is sleeved outside the overflow pipe 510 and is spaced a certain distance from the outer wall of the overflow pipe 510, so that an annular channel is formed between the inner wall of the guide pipe 520 and the outer wall of the overflow pipe 510 for the rich liquid to flow. The lower end of the guide pipe 520 is spaced a certain distance from the bottom of the absorption tower 100, and the upper end of the guide pipe 520 extends to the upper end of 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, the lean liquid still flows to the bottom of the absorption tower 100 after entering the absorption tower 100, so as to fully contact with the sulfur-containing natural gas. 30 is located at the upper end of the overflow pipe 510, and the valve core 532 of the buoyancy valve 530 rises and falls with the rise and fall of the liquid level, thereby controlling the flow channel area of ​​the rich liquid flow and adjusting the flow rate; the pressure difference self-operated valve 540 is located at the lower end of the overflow pipe 510, and is used to control the pressure difference at the inlet and outlet of the buoyancy valve 530. The greater the pressure difference, the smaller the opening of the pressure difference self-operated valve 540, thereby reducing the flow rate. When the pressure difference is greater than the preset value, such as 40kPa, the channel downstream of the buoyancy valve is closed to prevent the buoyancy valve from being unable to open smoothly after closing due to excessive pressure difference. When the liquid level in the absorption tower 100 is low, the buoyancy valve 530 reduces the flow channel area, the pressure difference at the inlet and outlet of the buoyancy valve 530 increases, and the pressure difference self-operated valve 540 is gradually closed, thereby preventing the pressure difference at the inlet and outlet of the buoyancy valve 530 from being too large, so that the buoyancy valve 530 can move upward smoothly again after the liquid level in the absorption tower 100 rises, thereby increasing the flow channel area for the rich liquid flow and increasing the rich liquid flow rate.

[0020] 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 operate 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, fully meeting the unmanned requirements. Therefore, there is no need to deploy personnel on site to monitor the liquid level, only regular inspections are required, thereby saving operating costs.

[0021] In some embodiments, Figure 3 As shown, the buoyancy valve 530 includes a valve seat 531, a valve core 532 and a floating body 533, wherein the valve seat 531 is fixed to the inner wall of the overflow pipe 510, and the flow channel of the valve seat 531 is arranged vertically, the valve core 532 is matched with the valve seat 531, and the floating body 533 is fixedly connected to the valve core 532 via a connecting rod. The floating body 533 can float on the liquid surface, thereby driving the valve core 532 to rise and fall with the liquid level, thereby changing the flow channel area of ​​the rich liquid.

[0022] In some embodiments, a cap 521 is provided at the upper end of the flow guide pipe 520 to block the lean liquid sprayed from the top to prevent it from falling into the upper end of the flow guide pipe 520 and being directly discharged, which would not fully exert the desulfurization effect. The cap 521 is supported on the upper end of the flow guide pipe 520 by a support rod, thereby forming a gap between the cap 521 and the upper end of the flow guide pipe 520, through which the gas flows, so that the liquid levels inside and outside the flow guide pipe 520 are flush.

[0023] In some embodiments, Figure 6 As shown, the gas distributor 110 in the absorption tower 100 is an annular tubular structure. In this case, there is no other equipment at the central axis of the absorption tower 100, and the guide pipe 520 can be directly installed at the center of the absorption tower 100; in other embodiments, such as Figure 2 As shown, a gas distributor 110 is provided on the central axis of the absorption tower 100. At this time, the guide pipe 520 is arranged in the central pipe of the gas distributor 110, the upper end of the guide pipe 520 passes through the central pipe of the gas distributor 110 and is sealed therewith, and the lower end of the guide pipe 520 extends to below the gas outlet of the gas distributor 110.

[0024] In some embodiments, Figure 4 As shown, a second drain pipe 120 is provided at the bottom of the absorption tower 100 to completely drain the liquid in the absorption tower 100 during inspection and maintenance. The lower end of the overflow pipe 510 passes through the side wall of the second drain pipe 120 and is sealed therewith.

[0025] In some embodiments, the pressure differential self-actuated valve 540 is Figure 5 As shown, the pressure differential self-acting valve 540 includes a piston container 541, a piston 542, a valve stem 543 and a spring 544. The piston 542 is connected to the inner wall of the piston container 541 in a sliding and sealing manner, thereby dividing the interior of the piston container 541 into two upper and lower cavities, wherein the lower cavity is connected to the overflow pipe 510 downstream of the buoyancy valve 530, and the upper cavity is connected to 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 to move in the direction of reducing the volume of the upper cavity. When the pressure difference 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 pressure differential self-acting valve 540, and adjusting the flow rate. When the pressure difference increases, the valve stem 543 moves downward to reduce the flow rate, and vice versa, the valve stem 543 moves upward to increase the flow rate. The specific controlled pressure difference can be selected as needed, such as 0.1MPa, and the set pressure difference can also be adjusted by adjusting the length of the spring 544.

[0026] In some embodiments, if the natural gas pressure is high, such as 1 MPa, a certain amount of natural gas is dissolved in the rich liquid. Figure 7As shown, a flash tank 600 is provided between the absorption tower 100 and the regeneration tower 200 for flashing the rich liquid, and the rich liquid after flashing enters the regeneration tower 200. The natural gas after flashing is processed as required, such as being pressurized and sent to the purified natural gas or directly sent to the flare. When sent to the flare, the flash tank 600 can be operated at normal pressure, and the bottom of the flash tank 600 is directly connected to the bottom of the regeneration tower 200. 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 is generally maintained in the flash tank 600, such as 0.2 MPa. At this time, the flash tank 600 also needs to be equipped with a liquid level control unit, such as Figure 8 shown.

[0027] In some embodiments, a gas-liquid separation device is also provided to separate the gas entering and exiting the absorption tower 100 from the gas-liquid. Figure 7 and Fig. 9 As shown, a raw gas separator 910 is provided to remove liquid from sulfur-containing natural gas; a purifier separator 920 and a purifier coalescer 930 are also provided in series to remove liquid from purified natural gas. The liquid level in these separators rises slowly, and a two-position program-controlled valve can be used to control the liquid level. When 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 human supervision.

[0028] In some embodiments, the lean liquid of the regeneration tower 200 overflows and 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 groove is provided on the top of the lean liquid tank 300, so that the lean liquid tank 300 continues to be used as a regeneration place, and the inlet of the circulating pump 400 is connected to the middle part of the lean liquid tank 300, and the fluid in the annular overflow groove in the lean liquid tank 300 flows into the sulfur foam treatment unit by gravity.

[0029] 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, wherein the sulfur foam of the regeneration tower 200 enters the sulfur foam tank 710, an agitator is provided in the sulfur foam tank 710, and the sulfur foam is broken by stirring. The sulfur foam pump 720 is used to send the fluid in the sulfur foam tank 710 into the filter press 730. After filtration, the filter press 730 produces wet sulfur and filtrate. The filtrate enters the filtrate collection tank 740 by gravity and is sent into the lean liquid or rich liquid through the filtrate recovery pump 750 to continue circulation.

[0030] There may be large sulfur particles deposited in the regeneration tower 200 and the lean liquid tank 300. These particles will be deposited at the bottom of the corresponding container. If they are not discharged for a long time, they will easily become hardened and block the bottom discharge port of the container, which is not conducive to the drainage during the 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 as Fig. 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 each connecting pipeline is provided with a valve 210, so that the sulfur foam pump 720 can independently send the liquid in the regeneration tower 200, the lean liquid tank 300 and the sulfur foam tank 710 to the filter press 730 for filtration.

[0031] In some embodiments, the sulfur foam pump 720 sends the filtrate to the annular overflow tank of the lean liquid tank 300. There is less sulfur foam in the lean liquid tank 300. Flushing the annular overflow tank with the filtrate can accelerate the flow of sulfur foam and prevent it from being deposited on the annular overflow tank and scaling. Of course, the filtrate can also be sent to the annular overflow tank of the regeneration tower 200.

[0032] In some embodiments, air may be provided by an external air source. In other embodiments, a fan 810 may be provided to supply air, and an air cooler 820 may be provided at the outlet of the fan 810 to reduce the temperature of the air.

[0033] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field 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, comprising 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 bubbling towers. The regeneration tower is a normal pressure tower. The circulating pump is used to transport the lean liquid in the lean liquid tank to the absorption tower. The lean liquid contacts the 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 regenerates into lean liquid. At the same time, sulfur foam is produced as a by-product. The lean liquid in the regeneration tower overflows into the lean liquid tank through the intermediate extraction port. The sulfur foam overflows into the sulfur foam treatment unit and is processed into sulfur. The fluid in the absorption tower is overflowed by the overflow. The liquid is transported downstream in the form of a flow, and a buoyancy valve and a pressure differential self-operated valve are arranged on the overflow pipe of the absorption tower, wherein the buoyancy valve is located upstream of the pressure differential self-operated valve, and is used to control the size of the overflow channel, and the valve core of the buoyancy valve rises and falls with the rise and fall of the liquid level, thereby adjusting the flow rate of the rich liquid; the pressure differential self-operated valve is used to control the pressure difference between the inlet and outlet of the buoyancy valve, and the larger the pressure difference, the smaller the valve opening, and the downstream channel of the buoyancy valve is closed when the pressure difference is greater than the preset value to prevent the pressure difference from continuing to increase, so that the buoyancy valve can move upward after the liquid level in the absorption tower rises to increase the flow rate of the rich liquid.

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, and 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 which is connected to the liquid outlet of the absorption tower and is used to transport rich liquid to the regeneration tower; A guide pipe is 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, thereby guiding 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 rise and fall of the liquid level, thereby adjusting the flow area in the overflow pipe; The differential pressure self-acting valve located downstream of the buoyancy valve is used to control the differential pressure at the inlet and outlet of the buoyancy valve. The greater the differential pressure, the smaller the valve opening. 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 after the liquid level in the absorption tower rises to increase the rich liquid flow rate.

3. A natural gas desulfurization process according to claim 2, characterized in that: The buoyancy valve comprises: a valve seat located on the inner wall of the overflow pipe; A valve core matched with the valve seat; A floating body fixedly connected to the valve core; The floating body can float on the liquid surface, thereby driving the valve core to rise and fall with the rise and fall of the liquid level.

4. A natural gas desulfurization process according to claim 2, characterized in that: A cap is provided at the upper end of the flow guide tube, and a channel for gas flow is provided between the cap and the upper end of the flow guide tube.

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, and the rich liquid after flashing 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 on the upper part of the lean liquid tank. The inlet of the circulating pump is connected 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 collecting tank and a filtrate recovery pump, wherein the sulfur foam in the regeneration tower and the lean liquid tank flows into the sulfur foam tank by gravity, the sulfur foam pump is used to send the fluid in the sulfur foam tank into the filter press, the filter press produces wet sulfur and filtrate after filtration, the filtrate enters the filtrate collecting tank by gravity, and the filtrate recovery pump is used to transport the filtrate in the filtrate collecting 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 groove of the lean liquid tank for flushing the annular overflow groove.

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

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