Small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system and process

Abstract

The invention discloses a small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system and process, natural gas and pressurized air are mixed, heated and introduced into a desulfurization reactor A for reaction, H2S is catalytically oxidized into elemental sulfur steam, most of the sulfur steam is gradually condensed and adsorbed in internal pore channels of a catalyst, and the sulfur steam is gradually condensed and adsorbed in the internal pore channels of the catalyst; a small amount of sulfur steam enters the washing tank A along with natural gas to be purified and is cooled, purified gas is obtained, a small amount of gas in the purified gas serves as regenerated gas, is heated and then is introduced into the desulfurization reactor B for regeneration, the sulfur steam can be brought out of the desulfurization reactor B and then enters the sulfur condenser, and a sulfur product is formed in the liquid sulfur tank. Tail gas of the sulfur condenser is introduced into a washing tank B for purification and cooling to obtain fuel gas. According to the present invention, the device is simple, the cost is easily reduced, the H2S conversion approaching 100% and the selectivity not less than 99.3% can be achieved, the high hydrogen sulfide removal rate and the good gas purification performance are provided, and the purity of the obtained sulfur exceeds 99.5%.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas purification technology, and in particular to a small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system and process. Background Art

[0002] Natural gas is stored in underground porous rock formations, including oilfield gas, gasfield gas, coalbed methane, mud volcano gas and biogas, and a small amount is also found in coal seams. It is a high-quality fuel and chemical raw material. In order to ensure sufficient economic efficiency, small-scale natural gas desulfurization must choose a desulfurization process that is as simple as possible. For H2S concentrations less than 1000mg / m 3 The desulfurization of low-sulfur natural gas usually adopts the simple and low-cost solid adsorption method. However, when the H2S concentration increases to 1-30g / m 3 Within the conventional sulfur content range, the solid adsorption method will require frequent replacement of the adsorbent to meet the purification requirements, resulting in a significant decrease in economic efficiency. At this time, the relatively simple complex iron method replaces it as the preferred method for desulfurization of conventional sour natural gas. However, when it comes to direct desulfurization of high-pressure natural gas, the use of complex iron technology is prone to sulfur blockage problems. Therefore, for purification equipment with a potential sulfur content of 1 ton or more, the amine method is traditionally used to remove H2S and CO2, and then complex iron is used to recover acid gas sulfur. Whether using complex iron technology alone or a combination of amine method and complex iron process, it will bring about the complexity of the process, relatively high investment, cumbersome operation, and the problem of substandard sulfur quality. This has always been a long-standing problem that has plagued small and medium-sized natural gas desulfurization.

[0003] H2S can be directly and selectively oxidized to elemental sulfur (SCO) in a single step. This reaction has a large equilibrium constant and can achieve 100% conversion. It is a highly exothermic reaction and can be completed under mild conditions of 130-320°C. Leveraging this sulfur recovery principle while overcoming the drawbacks of high exotherm, the industry has developed the Selectox process for sulfur recovery from low-sulfur gas, including UOP, the TDA process, and the Superclause / Euroclause processes. These processes utilize solid catalysts for direct H2S selective oxidation and sulfur recovery, eliminating the need for solvent separation, resulting in a sulfur product purity of at least 99.5%. These processes can achieve H2S conversions of 95-99.7%, selectivities of 90-99%, and sulfur yields of 90-95%.

[0004] Applying the above-mentioned catalyst and process principles to direct natural gas desulfurization can greatly simplify the natural gas desulfurization process, reduce investment, and avoid the production of undesirable sulfur paste byproducts. Achieving this goal requires overcoming several challenges: first, maintaining high conversion and selectivity for H2S under high pressure; and second, ensuring the smooth separation of sulfur after high-pressure gas desulfurization. In the 1990s, the U.S. Department of Energy (DOE) funded TDA Research, Inc. to develop a catalyst for direct oxidation desulfurization of high-pressure natural gas. In the early 2000s, TDA collaborated with the Gas Technology Institute (GTI) in the United States to complete field validation trials and sign a contract for the first industrial unit. However, subsequent widespread industrial deployment of this unit has been observed. This suggests that issues may exist with catalyst conversion efficiency and process stability during continuous operation. Therefore, a small-scale wellhead high-pressure direct selective oxidation desulfurization process for natural gas based on a highly active and selective H2S selective oxidation catalyst was proposed. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system and process with high conversion rate and high selectivity.

[0006] The technical solution is as follows: In a first aspect, the present invention provides a small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system, which comprises a desulfurization reactor A and a desulfurization reactor B, wherein the inlets of the desulfurization reactor A and the desulfurization reactor B are both connected to a mixed gas inlet pipe, and a first air intake control valve and a second air intake control valve are respectively provided on the mixed gas inlet pipe near the inlets of the desulfurization reactor A and the desulfurization reactor B;

[0007] The outlets of the desulfurization reactor A and the desulfurization reactor B are both connected to the sulfur condenser through a condenser pipe, and a first condensation control valve and a second condensation control valve are respectively provided on the condenser pipe near the outlets of the desulfurization reactor A and the desulfurization reactor B;

[0008] The outlets of the desulfurization reactor A and the desulfurization reactor B are connected to the water washing tank A through a water washing pipe, and the first water washing control valve and the second water washing control valve are respectively provided on the water washing pipe near the outlets of the desulfurization reactor A and the desulfurization reactor B;

[0009] A regeneration gas pipe is connected between the inlet of the desulfurization reactor A and the desulfurization reactor B and the water washing tank A. A first regeneration control valve and a second regeneration control valve are respectively provided on the regeneration gas pipe near the inlet of the desulfurization reactor A and the desulfurization reactor B.

[0010] Preferably, the mixed gas intake pipe is connected to a natural gas intake pipe and an air intake pipe respectively, a booster pump is provided on the air intake pipe, and the booster pump can make the pressure of the air consistent with the pressure of the natural gas, and a first heater is provided on the mixed gas intake pipe.

[0011] Preferably, the outlet of the sulfur condenser is connected to a water washing tank B via a pipeline, the outlet of the water washing tank B is connected to a fuel gas pipe, and a first air cooler is provided on the fuel gas pipe.

[0012] Preferably, a circulating gas pipe is provided on the fuel gas pipe, one end of the circulating gas pipe is connected to the fuel gas pipe, and the other end is connected to the regeneration gas pipe, and the outlet of the circulating gas pipe is provided in front of the air inlet end of the second heater on the regeneration gas pipe.

[0013] Preferably, the regeneration gas pipe is connected to a purified gas exhaust pipe, and a second air cooler and a second heater are respectively provided on the regeneration gas pipes on both sides of the purified gas exhaust pipe, wherein the second air cooler is located between the second air cooler of the water washing tank A.

[0014] The second aspect of the present invention provides a small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization process, comprising a small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system provided by the first aspect of the present invention, wherein the desulfurization reactor A and the desulfurization reactor B are both filled with a selective oxidation catalyst;

[0015] Wellhead natural gas and air pressurized by a booster pump enter the mixed gas inlet pipe and are mixed in a certain proportion. After being heated by a first heater, the first air inlet control valve is opened to pass the mixed gas into the desulfurization reactor A for reaction, so that H2S in the mixed gas is catalytically oxidized into elemental sulfur vapor. Most of the sulfur vapor is gradually condensed and adsorbed in the pores inside the catalyst. A small amount of sulfur vapor enters the water wash tank A through the first water wash control valve and the water wash pipe to achieve sulfur vapor separation and gas cooling, and is passed into the second air cooler for cooling treatment to obtain purified gas. Most of the purified gas is discharged from the purified gas discharge pipe, and a small amount is passed into the second heater as regeneration gas for heating. After heating, it enters the desulfurization reactor B for regeneration through the second regeneration control valve. After regeneration, it enters the sulfur condenser through the second condensation control valve and the condensation pipe for condensation and separation. The tail gas in the sulfur condenser enters the water wash tank B for purification. After cooling treatment by the first air cooler, fuel gas is obtained, and is discharged through the fuel gas pipe or enters the circulating gas pipe as circulating regeneration gas and enters the regeneration gas pipe.

[0016] Or, wellhead natural gas and air after the booster pump pressurized into the mixed gas inlet pipe mixed in a certain proportion, and through the first heater heating after opening the second inlet control valve, the mixed gas into the desulfurization reactor B reaction, so that the mixed gas H2S is catalytically oxidized into elemental sulfur vapor, most of the sulfur vapor gradually condenses and adsorbs in the internal pore of the catalyst, a small amount of sulfur vapor through the second water washing control valve and water washing pipe into the water washing tank A to realize the separation of sulfur vapor and gas cooling, and into the second air cooler cooling treatment to obtain purified gas, most of which is discharged from the purified gas discharge pipe, and a small amount of it as a regeneration gas enters the second heater for heating, and after heating, it enters the desulfurization reactor A for regeneration through the first regeneration control valve, and after regeneration, it enters the sulfur condenser through the first condensation control valve and the condensation pipe for condensation separation, and the tail gas in the sulfur condenser enters the water washing tank B for purification, and after cooling treatment by the first air cooler, fuel gas is obtained and discharged through the fuel gas pipe or enters the circulating gas pipe as circulating regeneration gas into the regeneration gas pipe.

[0017] Preferably, the selective oxidation catalyst uses alumina as the carrier, and is fused with manganese oxide, titanium oxide and silicon oxide, and the sulfur capacity can reach more than 40% of the weight of the catalyst itself.

[0018] Preferably, the temperature of the catalyst is 150-350℃, the suitable reaction pressure is 1-8MPa, and the space velocity is controlled at 600-3000h -1 .

[0019] Preferably, the natural gas uses conventional sulfur-containing natural gas, and the content of H2S is 1-30g / m 3 .

[0020] Preferably, the mixing oxygen-sulfur ratio of H2S gas in the wellhead natural gas and oxygen in air is 0.5-0.65.

[0021] Compared with the prior art, the process has the following beneficial effects: the device is simple, the double-tower switching mode is used for natural gas desulfurization and regeneration, which helps to reduce the investment and operation cost of small-scale desulfurization devices, and is easy to realize unattended operation, has stronger economic efficiency, can use the selected catalyst to realize nearly 100% conversion of H2S and not less than 99.3% selectivity in the process, has high hydrogen sulfide removal rate and good gas purification performance, the auxiliary water washing tank can ensure that the purified gas finally meets the strict pipeline gas quality standard; small-scale high-pressure wellhead natural gas is directly subjected to selective oxidation desulfurization, avoiding the use of wet method to remove H2S, so that the process is greatly simplified, has cost competitive advantage, and the purity of the obtained sulfur is more than 99.5%. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present application. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0024] like Figure 1 As shown, a small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system includes a desulfurization reactor A1 and a desulfurization reactor B2. The inlets of the desulfurization reactor A1 and the desulfurization reactor B2 are both connected to a mixed gas inlet pipe 9. A first air intake control valve 10 and a second air intake control valve 11 are respectively provided on the mixed gas inlet pipe 9 near the inlets of the desulfurization reactor A1 and the desulfurization reactor B2;

[0025] The outlets of the desulfurization reactor A1 and the desulfurization reactor B2 are both connected to the sulfur condenser 4 through a condenser pipe 12. A first condensation control valve 13 and a second condensation control valve 14 are respectively provided on the condenser pipe 12 near the outlets of the desulfurization reactor A1 and the desulfurization reactor B2;

[0026] The outlets of the desulfurization reactor A1 and the desulfurization reactor B2 are connected to the water washing tank A3 through the water washing pipe 15. The first water washing control valve 16 and the second water washing control valve 17 are respectively provided on the water washing pipe 15 near the outlets of the desulfurization reactor A1 and the desulfurization reactor B2;

[0027] A regeneration gas pipe 26 is connected between the inlets of the desulfurization reactor A1 and the desulfurization reactor B2 and the water washing tank A3. A first regeneration control valve 18 and a second regeneration control valve 19 are respectively provided on the regeneration gas pipe 26 near the inlets of the desulfurization reactor A1 and the desulfurization reactor B2.

[0028] The mixed gas intake pipe 9 is connected to the natural gas intake pipe 20 and the air intake pipe 21 respectively. A booster pump 6 is provided on the air intake pipe 21. The booster pump 6 can make the pressure of the air consistent with the pressure of the natural gas. A first heater 8 is provided on the mixed gas intake pipe 9.

[0029] The outlet of the sulfur condenser 4 is connected to a water washing tank B5 via a pipeline. The outlet of the water washing tank B5 is connected to a fuel gas pipe 22 , and a first air cooler 23 is provided on the fuel gas pipe 22 .

[0030] A circulating air pipe 27 is provided on the fuel air pipe 22, one end of the circulating air pipe 27 is connected to the fuel air pipe 22, and the other end is connected to the regeneration air pipe 26. The outlet of the circulating air pipe 27 is provided in front of the air inlet end of the second heater 25 on the regeneration air pipe 26, and a fan 28 is also provided on the circulating air pipe 27.

[0031] The regeneration gas pipe 26 is connected to the purified gas exhaust pipe 24, and the second air cooler 7 and the second heater 25 are respectively provided on the regeneration gas pipe 26 on both sides of the purified gas exhaust pipe 24, wherein the second air cooler 7 is located between the second air cooler 7 of the water washing tank A3.

[0032] An online hydrogen sulfide analyzer and an online flow meter are also installed on the natural gas inlet pipe 20. A tail gas residual oxygen analyzer linked to the booster pump 6 is also provided at the outlet of the water wash tank B5. The outlets of the water wash tank A3, the sulfur condenser 4 and the water wash tank B5 are all connected to a discharge pipe, which is connected to the liquid sulfur tank.

[0033] A small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization process includes the small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system described above. The direct selective oxidation of hydrogen sulfide is a highly exothermic reaction. Excessively high H2S concentration in natural gas will lead to a significant exothermic effect. Under high-pressure conditions, H2S is easily catalytically converted into elemental sulfur vapor. The high sulfur vapor partial pressure will also lead to an increase in the sulfur dew point. Once sulfur vapor is generated during the reaction in desulfurization reactor A1 or desulfurization reactor B2, it will inevitably condense and adsorb in the pores inside the catalyst, causing the catalyst activity in the reactor to gradually decrease.

[0034] Therefore, the process design takes into account the practical problem of liquid sulfur condensation when the catalyst bed in the reactor is operated below the sulfur dew point during desulfurization. When the catalyst surface is covered with liquid sulfur condensation, the condensed liquid sulfur can be evaporated and removed from the catalyst by increasing the bed temperature to above the sulfur dew point and maintaining it for a certain period of time. Therefore, a dual-tower switching mode is adopted for natural gas desulfurization and regeneration. Desulfurization reactors A1 and B2 are simple adiabatic fixed-bed reactors that can withstand a natural gas pressure of 8MPa. The specific process is as follows:

[0035] The desulfurization reactor A1 and the desulfurization reactor B2 are both filled with a selective oxidation catalyst;

[0036] The wellhead natural gas and the air pressurized by the booster pump 6 enter the mixed gas inlet pipe 9 and are mixed in a certain proportion. After being heated by the first heater 8, the first air intake control valve 10 is opened to pass the mixed gas into the desulfurization reactor A1 for reaction, so that the H2S in the mixed gas is catalytically oxidized into elemental sulfur vapor. Most of the sulfur vapor gradually condenses and adsorbs on the internal pores of the catalyst. A small amount of sulfur vapor enters the water washing tank A3 through the first water washing control valve 16 and the water washing pipe 15 to achieve sulfur vapor separation and gas cooling, and then passes into the second air cooler 7 for cooling treatment and purification. Gas, most of which is discharged from the purified gas discharge pipe 24, and a small amount is passed into the second heater 25 as regeneration gas for heating. After heating, it enters the desulfurization reactor B2 through the second regeneration control valve 19 for regeneration. After regeneration, it passes through the second condensation control valve 14 and the condenser pipe 12 to enter the sulfur condenser 4 for condensation and separation. The tail gas in the sulfur condenser 4 enters the water washing tank B5 for purification. After cooling treatment in the first air cooler 23, fuel gas is obtained, and is discharged through the fuel gas pipe 22 or enters the circulating gas pipe 27 as circulating regeneration gas and enters the regeneration gas pipe 26;

[0037] Alternatively, the wellhead natural gas and the air pressurized by the booster pump 6 enter the mixed gas inlet pipe 9 and are mixed in a certain proportion. After being heated by the first heater 8, the second air intake control valve 11 is opened to pass the mixed gas into the desulfurization reactor B2 for reaction, so that the H2S in the mixed gas is catalytically oxidized into elemental sulfur vapor. Most of the sulfur vapor gradually condenses and adsorbs on the internal pores of the catalyst. A small amount of sulfur vapor enters the water washing tank A3 through the second water washing control valve 17 and the water washing pipe 15 to achieve sulfur vapor separation and gas cooling, and then passes into the second air cooler 7 for cooling treatment to obtain clean sulfur vapor. Most of the purified gas is discharged from the purified gas discharge pipe 24, and a small amount is passed into the second heater 25 as regeneration gas for heating. After heating, it enters the desulfurization reactor A1 through the first regeneration control valve 18 for regeneration. After regeneration, it passes through the first condensation control valve 13 and the condenser pipe 12 into the sulfur condenser 4 for condensation and separation, and the tail gas in the sulfur condenser 4 enters the water washing tank B5 for purification. After cooling treatment by the first air cooler 23, fuel gas is obtained, and is discharged through the fuel gas pipe 22 or enters the circulating gas pipe 27 as circulating regeneration gas and enters the regeneration gas pipe 26.

[0038] Desulfurization reactor A1 and desulfurization reactor B2 are switchable. The reaction mode of desulfurization reactor A1 and the regeneration mode of desulfurization reactor B2 can be switched to the reaction mode of desulfurization reactor B2 and the regeneration mode of desulfurization reactor A1. The switching period can be flexibly adjusted according to process requirements and can generally be set to 12 hours or 24 hours. The temperature in the reaction mode is 150-250°C, and the temperature in the regeneration mode is 250-350°C.

[0039] The selective oxidation catalyst uses aluminum oxide as a carrier and is integrated with manganese oxide, titanium oxide, and silicon oxide metal oxides. Its sulfur capacity reaches more than 40% of the catalyst's own weight. The selected catalyst has good stability and can ensure a service life of 3-5 years. This is of great benefit in preventing frequent replacement of catalysts in remote areas and increasing labor intensity. It can also reduce the operating costs of the device.

[0040] The catalyst has an adaptable temperature of 150-350°C, a suitable reaction pressure of 1-8 MPa, and a space velocity of 600-3000 h -1 .

[0041] The direct oxidation of hydrogen sulfide is a highly exothermic reaction. Excessive H2S concentration in natural gas will lead to a significant exothermic effect, excessive temperature rise in the catalyst bed, and difficulty in controlling the temperature, which in turn affects the desulfurization selectivity. Therefore, the natural gas used is conventional sour natural gas, in which the H2S content is 1-30g / m 3 .

[0042] The booster pump 6 is equipped with a flow regulating valve. The hydrogen sulfide online analyzer and the online flow meter can cooperate with the flow regulating valve and adjust the air ratio of natural gas and air in a timely manner to ensure that it always meets the stoichiometric relationship, that is, the mixed oxygen-sulfur ratio of the H2S gas in the wellhead natural gas and the oxygen in the air is 0.5-0.65.

[0043] Monitoring bed temperature is crucial for the selective catalytic oxidation of hydrogen sulfide to sulfur production. It not only affects hydrogen sulfide conversion and selectivity, but also impacts process equipment safety. Thermocouples are installed at the top, middle, and bottom of the reactor bed to monitor changes in bed temperature. This temperature can be controlled by controlling the feed gas preheat temperature, air distribution ratio, and space velocity.

[0044] Whether it is mixed gas or regenerated gas, before entering the desulfurization reactor A1 or the desulfurization reactor B2, the gas needs to be properly heated by the first heater 8 or the second heater 25 to meet the conditions for desulfurization reaction and regeneration. The provision of a heater helps to simplify the process flow. If energy saving is required at the production site, energy saving can also be achieved by heat exchange between materials before and after the reactor, or by using the low-pressure water vapor produced as a by-product of the sulfur condenser to preheat the raw gas.

[0045] The water scrubber A3 and water scrubber B5 are both filled with a certain volume of soft water for cooling the natural gas and capturing trace sulfur vapor, which is then cooled and converted into solid sulfur particles for discharge. Alkaline substances are also added to the water scrubber A3 to absorb trace amounts of H2S or SO2 in the natural gas. The gas purified by the water scrubbers A3 and B5 is guaranteed to meet strict pipeline quality standards.

[0046] Because high-temperature gas is always passed through the water washing tank A3 and the water washing tank B5, the water temperature in the tank is high, and the water is easy to evaporate into water vapor loss, in addition, the temperature of the gas after passing through the water washing tank A3 and the water washing tank B5 is close to 100 DEG C, in order to reduce the loss of water in the water washing tank, while ensuring the safe transportation and use of the purified gas and fuel gas, the second air cooler 7 and the first air cooler 23 are arranged to reduce the gas temperature to about 50 DEG C.

[0047] In the process front end, the gas amount of H2S and O2 is ensured to react in proportion, and after passing through the reaction bed, the actual H2S conversion effect may change slightly due to the fluctuation of the operation condition, causing either excess H2S in the tail gas or excess SO2. Regardless of which kind of sulfur-containing substance is excessive, it will cause sulfur loss and affect the quality of natural gas. Therefore, the tail gas residual oxygen analyzer connected with the booster pump 6 is arranged to monitor the oxygen concentration in the tail gas in real time, so as to judge the efficiency of the oxidation reaction, and take this value as the basis for feedback, used for fine tuning the opening of the air booster pump 6 valve, so that the air distribution ratio is real-time perfect, and the efficient gas purification goal is realized to the maximum extent.

[0048] The hydrogen sulfide online analyzer, the online flow meter, the flow regulating valve on the booster pump 6 and the tail gas residual oxygen analyzer cooperate with each other to realize linkage and automatic control, not only can control the flow meter air distribution ratio of natural gas and air, but also can control the temperature of the bed in the reactor, and more easily realize unattended operation, and the economy is stronger, and can be applied to remote well station natural gas desulfurization.

[0049] Finally, it should be noted that the above description is only the preferred embodiment of the present application, and those skilled in the art can make various similar expressions under the inspiration of the present application without departing from the purpose and claims of the present application, and such changes fall within the protection scope of the present application.

Claims

1. A small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system, characterized in that: The invention comprises a desulfurization reactor A (1) and a desulfurization reactor B (2), wherein the inlets of the desulfurization reactor A (1) and the desulfurization reactor B (2) are both connected to a mixed gas intake pipe (9), and a first intake control valve (10) and a second intake control valve (11) are respectively provided on the mixed gas intake pipe (9) near the inlets of the desulfurization reactor A (1) and the desulfurization reactor B (2); The outlets of the desulfurization reactor A (1) and the desulfurization reactor B (2) are both connected to the sulfur condenser (4) via a condenser pipe (12), and a first condensation control valve (13) and a second condensation control valve (14) are respectively provided on the condenser pipe (12) near the outlets of the desulfurization reactor A (1) and the desulfurization reactor B (2); The outlets of the desulfurization reactor A (1) and the desulfurization reactor B (2) are both connected to the water washing tank A (3) via a water washing pipe (15), and a first water washing control valve (16) and a second water washing control valve (17) are respectively provided on the water washing pipe (15) near the outlets of the desulfurization reactor A (1) and the desulfurization reactor B (2); A regeneration gas pipe (26) is connected between the inlets of the desulfurization reactor A (1) and the desulfurization reactor B (2) and the water washing tank A (3), and a first regeneration control valve (18) and a second regeneration control valve (19) are respectively provided on the regeneration gas pipe (26) near the inlets of the desulfurization reactor A (1) and the desulfurization reactor B (2).

2. A small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system according to claim 1, characterized in that: The mixed gas intake pipe (9) is respectively connected to a natural gas intake pipe (20) and an air intake pipe (21); a booster pump (6) is provided on the air intake pipe (21); the booster pump (6) can make the pressure of the air consistent with the pressure of the natural gas; and a first heater (8) is provided on the mixed gas intake pipe (9).

3. A small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system according to claim 1 or 2, characterized in that: The outlet of the sulfur condenser (4) is connected to a water washing tank B (5) via a pipeline. The outlet of the water washing tank B (5) is connected to a fuel gas pipe (22). A first air cooler (23) is provided on the fuel gas pipe (22).

4. A small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system according to claim 3, characterized in that: A circulating gas pipe (27) is provided on the fuel gas pipe (22), one end of the circulating gas pipe (27) is connected to the fuel gas pipe (22), and the other end is connected to the regeneration gas pipe (26), and the outlet of the circulating gas pipe (27) is provided on the front side of the air inlet end of the second heater (25) on the regeneration gas pipe (26).

5. A small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system according to claim 4, characterized in that: The regeneration gas pipe (26) is connected to a purified gas discharge pipe (24), and a second air cooler (7) and a second heater (25) are respectively provided on the regeneration gas pipe (26) on both sides of the purified gas discharge pipe (24), wherein the second air cooler (7) is located between the second air cooler (7) of the water washing tank A (3).

6. A small-scale direct selective oxidation desulfurization process for high-pressure natural gas at the wellhead, characterized in that: The small-scale wellhead high-pressure natural gas direct selective oxidation desulfurization system according to claim 5 is provided, wherein the desulfurization reactor A (1) and the desulfurization reactor B (2) are both filled with a selective oxidation catalyst; Wellhead natural gas and air pressurized by a booster pump (6) enter a mixed gas inlet pipe (9) and are mixed in a certain proportion. After being heated by a first heater (8), the first air inlet control valve (10) is opened, and the mixed gas is passed into the desulfurization reactor A (1) for reaction, so that H2S in the mixed gas is catalytically oxidized into elemental sulfur vapor. Most of the sulfur vapor is gradually condensed and adsorbed in the pores inside the catalyst. A small amount of sulfur vapor enters the water washing tank A (3) through the first water washing control valve (16) and the water washing pipe (15) to achieve sulfur vapor separation and gas cooling, and is passed into the second air cooler (7) for cooling treatment to obtain purified gas. Most of the chemical gas is discharged from the purified gas discharge pipe (24), and a small amount is passed into the second heater (25) as regeneration gas for heating. After heating, it enters the desulfurization reactor B (2) through the second regeneration control valve (19) for regeneration. After regeneration, it enters the sulfur condenser (4) through the second condensation control valve (14) and the condensation pipe (12) for condensation and separation. The tail gas in the sulfur condenser (4) enters the water washing tank B (5) for purification. After cooling treatment in the first air cooler (23), fuel gas is obtained, and is discharged through the fuel gas pipe (22) or enters the circulating gas pipe (27) as circulating regeneration gas and enters the regeneration gas pipe (26); Alternatively, the wellhead natural gas and the air pressurized by the booster pump (6) enter the mixed gas inlet pipe (9) and are mixed in a certain proportion. After being heated by the first heater (8), the second air inlet control valve (11) is opened, and the mixed gas is passed into the desulfurization reactor B (2) for reaction, so that H2S in the mixed gas is catalytically oxidized into elemental sulfur vapor. Most of the sulfur vapor is gradually condensed and adsorbed in the pores inside the catalyst. A small amount of sulfur vapor enters the water washing tank A (3) through the second water washing control valve (17) and the water washing pipe (15) to achieve sulfur vapor separation and gas cooling, and is passed into the second air cooler (7) for cooling treatment to obtain purified gas. Most of the purified gas is discharged from the purified gas discharge pipe (24), and a small amount is passed into the second heater (25) as regeneration gas for heating. After heating, it enters the desulfurization reactor A (1) through the first regeneration control valve (18) for regeneration. After regeneration, it enters the sulfur condenser (4) through the first condensation control valve (13) and the condensation pipe (12) for condensation and separation. The tail gas in the sulfur condenser (4) enters the water washing tank B (5) for purification. After cooling treatment in the first air cooler (23), fuel gas is obtained, and is discharged through the fuel gas pipe (22) or enters the circulating gas pipe (27) as circulating regeneration gas and enters the regeneration gas pipe (26).

7. A small-scale direct selective oxidation desulfurization process for natural gas according to claim 6, characterized in that: The selective oxidation catalyst uses aluminum oxide as a carrier and is infused with metal oxides such as manganese oxide, titanium oxide and silicon oxide. The sulfur capacity of the catalyst is more than 40% of the weight of the catalyst itself.

8. A small-scale direct selective oxidation desulfurization process for natural gas according to claim 7, characterized in that: The catalyst has an adaptable temperature of 150-350°C, a suitable reaction pressure of 1-8 MPa, and a space velocity of 600-3000 h -1 .

9. A small-scale direct selective oxidation desulfurization process for natural gas according to claim 6, characterized in that: The natural gas used is conventional sulfur-containing natural gas, wherein the H2S content is 1-30g / m 3 .

10. A small-scale direct selective oxidation desulfurization process for natural gas according to claim 6, characterized in that: The mixed oxygen-sulfur ratio of the H2S gas in the wellhead natural gas and the oxygen in the air is 0.5-0.65.

Images