A high-sulfur natural gas dehydration device and method

Abstract

The application provides a high-sulfur natural gas dehydration device and method, relates to the technical field of natural gas desulfurization and dehydration, and comprises an inlet gas separator, an absorption tower, a flash separation device, a regeneration tower and a dry gas separator. The inlet gas separator is connected with an inlet pipeline, and the inlet gas separator is connected with a gas stripping section of the absorption tower through a first gas feeding pipeline. The regeneration tower is connected with a rectifying section of the absorption tower through a second gas feeding pipeline. The bottom of the absorption tower is connected with the flash separation device through a flash gas feeding pipeline, and a two-stage lean / rich liquid heat exchanger is arranged on the flash gas feeding pipeline. The flash separation device is connected with the regeneration tower through a one-stage lean / rich liquid heat exchanger. The top of the absorption tower is connected with the dry gas separator through a gas outlet pipeline. The high-sulfur natural gas dehydration device and method can realize regeneration of the absorbent, recycling, closed circulation of high-sulfur hydrogen sulfide flash gas, meet the needs of environmental protection and safe operation, and further improve the energy efficiency of the system.

Description

Technical Field

[0001] This invention relates to the field of natural gas desulfurization and dehydration technology, specifically to a dehydration device and method for high-sulfur natural gas. Background Technology

[0002] Hydrogen sulfide in dry natural gas has no corrosive effect on metallic materials; it is only corrosive when dissolved in water (including carbon dioxide). During the gathering and transportation of natural gas in oil fields, the produced materials often contain saturated water, and sometimes even free water. The presence of hydrogen sulfide exposes the equipment and pipelines of the gathering and transportation system to a severely corrosive environment, posing a significant safety risk. Therefore, it is necessary to effectively remove free or saturated water from the natural gas to ensure that no free water exists under gathering and transportation conditions (meeting the water dew point requirement at the gathering and transportation pressure), thus enabling the safe transportation of natural gas with high hydrogen sulfide content. For such oil and gas fields, high-sulfur natural gas from the corresponding blocks can be centrally dehydrated under high pressure before being transported at ambient temperature.

[0003] For carbonate oil and gas reservoirs with high levels of corrosive gases such as hydrogen sulfide and carbon dioxide in the transport medium, the use of traditional gathering and transportation processes presents several problems due to the extremely corrosive nature of the medium: First, if the gas is not treated, high-grade corrosion-resistant alloy steel pipes such as nickel-based alloys are required according to material selection standards, which would increase the investment cost to 2.5 times that of conventional pipes, and the pipeline equipment would be more difficult to maintain in the later stages; Second, if source purification and desulfurization treatment is carried out, there are problems such as the inability to determine the scale of desulfurization, high investment, and long construction period.

[0004] Currently, solvent absorption processes based on triethylene glycol absorbents are widely used in the dehydration of natural gas in oilfields. However, directly applying these processes to the dehydration of high-sulfur natural gas leads to severe equipment corrosion and absorbent degradation, making safe operation impossible. Furthermore, research on solvent absorption methods for dehydrating high-hydrogen-sulfur natural gas is limited, and there is a lack of process methods specifically designed for high-hydrogen-sulfur media. This makes the gathering and transportation of high-sulfur natural gas a major challenge hindering oilfield development.

[0005] Chinese Patent Application No. CN201911402988.3 discloses a system and method for treating high-sulfur natural gas, including a composite solvent desulfurization unit, a triethylene glycol dehydration unit, a Claus flexible split-flow sulfur recovery unit, and a hydrogenation reduction absorption tail gas treatment unit. This invention achieves continuous processing of natural gas with high carbon-to-sulfur ratios and high sulfur content, as well as sulfur recovery from tail gas with low acid gas concentrations, achieving a total sulfur recovery rate of over 99.9%. Furthermore, the Claus split-flow reactor used can increase furnace temperature by controlling split-flow conditions to ensure stable combustion, improve thermal reaction conversion rate, reduce the impact of impurities on downstream catalytic conversion, and enhance the adaptability of the downstream sulfur recovery unit to different acid gas concentrations. Simultaneously, the composite solvent desulfurization unit and the hydrogenation reduction absorption tail gas treatment unit use the same circulating solvent, fully utilizing the solvent's absorption capacity while ensuring natural gas purification and tail gas emission compliance, thus reducing the amount of desulfurization solvent used and regeneration energy consumption. However, this method is mainly for centralized desulfurization of high-sulfur natural gas. The system is complex and requires high investment. It is suitable for large-scale centralized treatment and purification of high-sulfur natural gas, but not for small- to medium-scale gathering, transportation and dehydration of high-sulfur natural gas.

[0006] Chinese patent application CN201821410422.6 discloses a TEG dehydration device for high-sulfur natural gas. This device includes a TEG absorption tower, a dry gas / lean liquid heat exchanger, a TEG reboiler, a TEG rich liquid flash stripping separator, a mechanical / activated carbon filter, and a TEG lean / rich liquid heat exchanger. All components are connected by pipelines, and control valves and other control devices are installed on the pipelines to regulate process parameters. This invention uses a TEG rich liquid flash stripping process to flash and strip the TEG rich liquid. The hydrogen sulfide extracted by the flash stripping is pressurized and returned to the feed gas, preventing it from entering the regeneration gas. This reduces the load on the subsequent TEG reboiler, alleviates corrosion in the TEG regeneration system, and reduces the hydrogen sulfide content in the regeneration gas, ensuring that the regeneration gas meets the national first-class emission standard after combustion. This invention is small in size, has low equipment investment, low operating costs, and can guarantee long-term stable operation, resulting in significant economic benefits. This device is suitable for TEG dehydration of sulfur-containing and high-sulfur natural gas. However, this device performs post-treatment of the sulfur-containing regeneration gas generated at the top of the regeneration tower by burning. Although it can reduce the emission of sulfur compounds in the tail gas to a certain extent compared with traditional processes, the sulfur-containing compounds after burning will still cause pollution to the environment.

[0007] However, the aforementioned dehydration processes have the following drawbacks: they are suitable for processing scales that are either too large or too small; they lack the function of dehydrating natural gas separately during gathering and transportation; or they lack the closed-loop processing capability for regenerated gas or flash vapor, which is not conducive to the dehydration treatment of natural gas in oilfields during gathering and transportation. In summary, to solve these problems, it is necessary to provide a dehydration process suitable for gathering and transportation in oilfields with high hydrogen sulfide content. Summary of the Invention

[0008] Based on the above problems, the purpose of this invention is to provide a dehydration device and method for high-sulfur natural gas.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] This invention provides a dehydration device for high-sulfur natural gas, comprising an inlet separator, an absorption tower, a flash separator, a regeneration tower, and a dry gas separator;

[0011] The air intake separator is connected to the air intake pipe, and the air intake separator is connected to the air stripping section of the absorption tower through the first air supply pipe.

[0012] The regeneration tower is connected to the rectification section of the absorption tower via a second gas supply pipe;

[0013] The bottom of the absorption tower is connected to the flash separator via a flash gas delivery pipe, and a two-stage lean / rich liquid heat exchanger is provided on the flash gas delivery pipe.

[0014] The flash separator is connected to the regeneration tower via a primary lean / rich liquid heat exchanger.

[0015] The top of the absorption tower is connected to the dry gas separator via an outlet pipe, and a dry gas / lean liquid heat exchanger is installed on the outlet pipe.

[0016] Preferably, the second gas delivery pipeline passes sequentially through the primary lean / rich liquid heat exchanger, the secondary lean / rich liquid heat exchanger, and the dry gas / lean liquid heat exchanger.

[0017] Preferably, the second gas delivery pipe carries a lean absorbent solution.

[0018] Preferably, filters are provided on the flash separator and the secondary lean / rich liquid heat exchanger.

[0019] Preferably, the top of the regeneration tower is connected to the air inlet pipe via a first reflux pipe.

[0020] Preferably, the flash separator is provided with a second reflux pipe, which is connected to the first reflux pipe.

[0021] Preferably, the regeneration tower is further provided with a stripping gas delivery pipeline for supplying stripping gas into the regeneration tower.

[0022] This invention also provides a method for dehydrating high-sulfur natural gas, using the high-sulfur natural gas dehydration device as described in any one of the above claims for dehydration and desulfurization, specifically as follows:

[0023] The raw gas passes through the inlet pipe and undergoes preliminary separation by the inlet separator to produce dry gas, which then enters the absorption tower. The dry gas reacts with the lean glycol solution from the regeneration tower. The dehydrated dry gas produced by the reaction passes through a dry gas / lean liquid heat exchanger and then enters the dry gas separator. The rich glycol solution produced by the reaction passes through a flash gas supply pipe from the bottom of the tower, passes through a secondary lean / rich liquid heat exchanger, and then enters the flash separator for flash evaporation treatment. The flash-evaporated rich glycol passes through a primary lean / rich liquid heat exchanger and then enters the regeneration tower for regeneration.

[0024] Preferably, the sulfur-containing flash vapor generated in the regeneration tower and the flash separator is introduced into the inlet pipe through the first reflux pipe and the second reflux pipe, respectively.

[0025] Preferably, stripping gas is also introduced into the regeneration tower to purify the lean glycol solution.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] This invention provides a high-sulfur natural gas dehydration device and process. The raw gas passes through an inlet pipe and undergoes preliminary separation by an inlet separator to generate dry gas, which then enters an absorption tower. This dry gas reacts countercurrently with a lean glycol solution from a regeneration tower. The resulting dehydrated dry gas is then heated by a dry gas / lean liquid heat exchanger before entering a dry gas separator and then a subsequent processing unit. The absorbent rich solution containing water and hydrogen sulfide obtained at the bottom of the tower undergoes flash evaporation and enters a rich solution regeneration tower. The regenerated lean absorbent solution is returned to the absorption tower for recycling, achieving a closed-loop circulation of high-hydrogen sulfide flash vapor. This meets the needs of environmental protection and safe operation, further improving system energy efficiency. Compared to the traditional triethylene glycol dehydration process where the preheating coil is placed inside the regeneration tower, this method solves the problems of easy corrosion and difficulty in maintenance and replacement of the built-in preheating coil (due to the smaller diameter of the regeneration tower). Furthermore, the separate lean / rich liquid heat exchanger facilitates subsequent maintenance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a high-sulfur natural gas dehydration device according to the present invention;

[0029] Figure label:

[0030] 1-Inlet separator, 2-Absorption tower, 3-Flash separator, 4-Regeneration tower, 5-Dry gas separator

[0031] 6-Dry gas / lean liquid heat exchanger, 7-First-stage lean / rich liquid heat exchanger, 8-Second-stage lean / rich liquid heat exchanger, 9-Filter,

[0032] 10-Intake pipe, 11-First air supply pipe, 12-Stripping gas supply pipe, 13-Outlet pipe.

[0033] 14-Subsequent pipeline, 15-Second gas supply pipeline, 16-Flash gas supply pipeline, 17-Second return pipeline.

[0034] 18-Regeneration pipe, 19-First return pipe. Detailed Implementation

[0035] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0036] In the description of this application, it should be understood that the terms "length", "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0037] like Figure 1 As shown, the present invention provides a dehydration device for high sulfur-containing natural gas, comprising an inlet separator 1, an absorption tower 2, a flash separator 3, a regeneration tower 4, and a dry gas separator 5;

[0038] The inlet separator 1 is connected to the inlet pipe 10, which supplies raw gas to the inlet separator 1. The inlet separator 1 is connected to the gas stripping section of the absorption tower 2 via the first gas supply pipe 11. After the raw gas undergoes gas-liquid separation in the inlet separator 1, the resulting dry gas is further supplied to the gas stripping section of the absorption tower 2 via the first gas supply pipe 11. The regeneration tower 4 is connected to the rectification section of the absorption tower 2 via the second gas supply pipe 15. The second gas supply pipe 15 carries lean absorbent solution and passes sequentially through the primary lean / rich solution heat exchanger 7, the secondary lean / rich solution heat exchanger 8, and the dry gas / lean solution heat exchanger 6. Therefore, after the lean absorbent solution enters the rectification section of the absorption tower 2, it comes into countercurrent contact with the rising dry gas in the absorption tower 2, and after sufficient reaction, dehydrated dry gas and rich absorbent solution are produced.

[0039] Absorption tower 2 can be a plate tower or a packed tower, with the tower containing 3 to 5 theoretical plates. The absorption operating conditions are: natural gas feed temperature 25–40°C, absorbent feed temperature 3–8°C higher than the gas temperature, and pressure 5–9 MPa. Regeneration tower 4 is a packed tower, consisting of a stripping column and a distillation column. The packing material is one of ceramic, metal, or plastic, and can be packaged in bulk or in a pre-assembled form. The operating pressure is 0.1 MPa, the distillation column top temperature is 85–100°C, and the reboiler temperature is 170–205°C.

[0040] The bottom of the absorption tower 2 is connected to the flash separator 3 via a flash gas supply pipe 16. A two-stage lean / rich liquid heat exchanger 8 is installed on the flash gas supply pipe 16, and a filter 9 is installed on both the flash separator 3 and the two-stage lean / rich liquid heat exchanger 8. The absorbent rich liquid containing water and hydrogen sulfide produced by the reaction passes through the flash gas supply pipe 16 at the bottom of the tower, sequentially through the two-stage lean / rich liquid heat exchanger 8 and the filter 9, undergoes multi-stage filtration in the filter 9, and finally enters the flash separator 3 for flash evaporation treatment. The flash separator 3 is connected to the regeneration tower 4 via a regeneration pipe 18 through a first-stage lean / rich liquid heat exchanger 7. Therefore, the absorbent rich liquid after flash evaporation enters the regeneration tower 4 for regeneration after heat exchange in the first-stage lean / rich liquid heat exchanger 7. The rich absorbent solution collected from the bottom of the absorber tower 2 and the separator is filtered and then enters the secondary lean / rich solution heat exchanger for preheating. It then enters the flash separator 3 to remove dissolved natural gas. After secondary filtration and heat exchange in the primary lean / rich solution heat exchanger 7, it enters the regeneration tower 4 for dehydration. The absorbent solution that has passed the dehydration test enters the storage tank.

[0041] The top of the absorption tower 2 is connected to the dry gas separator 5 via an outlet pipe 13, and a dry gas / lean liquid heat exchanger 6 is installed on the outlet pipe 13. The dehydrated dry gas generated in the reaction inside the absorption tower 2 enters the dry gas separator 5 from the top of the tower through the outlet pipe 13, passes through the dry gas / lean liquid heat exchanger 6, and then enters the subsequent processing unit through the subsequent pipe 14 after further liquid separation in the dry gas separator 5.

[0042] The top of the regeneration tower 4 is connected to the inlet pipe 10 through the first reflux pipe 19. The flash separator 3 is provided with a second reflux pipe 17, which is connected to the first reflux pipe 19. At the same time, the flash separator 3 is also equipped with a compressor. The sulfur-containing flash vapor generated by the regeneration tower 4 and the flash separator 3 is returned to the inlet pipe 10 after being pressurized by the compressor.

[0043] The regeneration tower 4 is also equipped with a stripping gas delivery pipeline 12 for supplying stripping gas into the regeneration tower 4. The stripping gas can be one of purified dry gas, CNG, LNG, etc.

[0044] The absorbent used in this embodiment is triethylene glycol absorbent. Triethylene glycol dehydration solvent has the advantages of being widely available, pollution-free, regenerable, stable in performance, and having a low loss rate.

[0045] The intake separator 1 and the dry air separator 5 can be one or more of the following: gravity separator, cyclone separator, and filter separator.

[0046] This invention also provides a method for dehydrating high-sulfur natural gas, using the aforementioned high-sulfur natural gas dehydration device for dehydration and desulfurization. The specific method is as follows:

[0047] The raw gas passes through the inlet pipe 10 and undergoes preliminary separation in the inlet separator 1 to produce dry gas, which then enters the absorption tower 2. This dry gas reacts with the lean glycol solution from the regeneration tower 4. The resulting dehydrated dry gas is then heated by the dry gas / lean liquid heat exchanger 6 before entering the dry gas separator 5. The resulting rich glycol solution is introduced from the bottom of the tower through the flash gas supply pipe 16, and after being heated by the secondary lean / rich liquid heat exchanger 8, it enters the flash separator 3 for flash evaporation. The flash-evaporated rich glycol is then heated by the primary lean / rich liquid heat exchanger 7 before entering the regeneration tower 4 for regeneration. Stripping gas is also introduced into the regeneration tower 4 to purify the lean glycol solution. By employing dry gas / lean liquid heat exchange preheating and secondary lean / rich liquid heat exchange preheating to exchange heat between dry gas and lean / rich liquid at different temperatures, the energy efficiency of the system can be further improved. Compared with the traditional triethylene glycol dehydration process where the preheating coil is placed inside the regeneration tower 4, this method can solve the problem of easy corrosion and difficulty in maintenance and replacement of the built-in preheating coil (the regeneration tower 4 has a smaller diameter). Furthermore, the separate setting of lean / rich liquid heat exchangers for the preheating process facilitates subsequent maintenance.

[0048] The sulfur-containing flash vapor generated in the regeneration tower 4 and the flash separator 3 is respectively introduced into the inlet pipe 10 through the first return pipe 19 and the second return pipe 17. The flash separator 3 is also equipped with a compressor. The sulfur-containing flash vapor generated in the flash separator 3 is pressurized by the compressor and returned to the inlet pipe. The flash vapor pressurization and recovery process using the compressor can realize the recovery of flash natural gas containing small amounts of hydrocarbon vapor and hydrogen sulfide. Traditionally, flash vapor without hydrogen sulfide can be collected through pipelines and discharged or burned in the reboiler fuel gas system. However, such treatment of flash vapor with high hydrogen sulfide content will lead to environmental pollution and safety risks. The recovery process of this invention can achieve a closed-loop circulation of flash vapor with high hydrogen sulfide content, meeting the needs of environmental protection and safe operation.

[0049] The above are merely some embodiments of the present invention, described in a relatively specific and detailed manner, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these obvious substitutions all fall within the protection scope of the present invention.

Claims

1. A dehydration device for high-sulfur natural gas, characterized in that: It includes an intake separator, an absorption tower, a flash separator, a regeneration tower, and a dry gas separator; The air intake separator is connected to the air intake pipe, and the air intake separator is connected to the air stripping section of the absorption tower through the first air supply pipe. The regeneration tower is connected to the rectification section of the absorption tower via a second gas supply pipe; The bottom of the absorption tower is connected to the flash separator via a flash gas delivery pipe, and a two-stage lean / rich liquid heat exchanger is provided on the flash gas delivery pipe. The flash separator is connected to the regeneration tower via a primary lean / rich liquid heat exchanger. The top of the absorption tower is connected to the dry gas separator via an outlet pipe, and a dry gas / lean liquid heat exchanger is provided on the outlet pipe. The top of the regeneration tower is connected to the air inlet pipe via a first reflux pipe; The flash separator is provided with a second reflux pipe, which is connected to the first reflux pipe, and a compressor is provided inside the flash separator; The second gas delivery pipeline passes sequentially through the primary lean / rich liquid heat exchanger, the secondary lean / rich liquid heat exchanger, and the dry gas / lean liquid heat exchanger.

2. The high-sulfur natural gas dehydration device as described in claim 1, characterized in that: The second gas delivery pipe carries a lean absorbent solution.

3. The high-sulfur natural gas dehydration device as described in claim 1, characterized in that: A filter is installed on the flash gas supply pipeline between the flash separator and the secondary lean / rich liquid heat exchanger.

4. The high-sulfur natural gas dehydration device as described in claim 1, characterized in that: The regeneration tower is also equipped with a stripper gas delivery pipeline for supplying stripper gas into the regeneration tower.

5. A method for dehydrating high-sulfur natural gas, characterized in that: The dehydration and desulfurization are carried out using the high-sulfur natural gas dehydration device as described in any one of claims 1-4, and the specific method is as follows: The raw gas passes through the inlet pipe and undergoes preliminary separation by the inlet separator to produce dry gas, which then enters the absorption tower. The dry gas reacts with the lean absorbent solution from the regeneration tower. The dehydrated dry gas produced by the reaction passes through a dry gas / lean solution heat exchanger and then enters the dry gas separator. The rich absorbent solution produced by the reaction passes through a flash gas supply pipe from the bottom of the tower, passes through a secondary lean / rich solution heat exchanger, and then enters the flash separator for flash evaporation treatment. The flash-evaporated rich absorbent solution passes through a primary lean / rich solution heat exchanger and then enters the regeneration tower for regeneration. The regenerated lean absorbent solution is returned to the absorption tower for recycling. The sulfur-containing flash vapor generated in the regeneration tower is introduced into the inlet pipe through the first reflux pipe; The sulfur-containing flash vapor generated in the flash separator is introduced into the inlet pipe through the second reflux pipe and the first reflux pipe.

6. The method for dehydrating high-sulfur natural gas as described in claim 5, characterized in that: Stripping gas is also introduced into the regeneration tower to purify the lean absorbent solution.

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