System for purifying helium in tail gas with high carbon dioxide content

Abstract

The invention discloses a system for purifying helium in tail gas with high carbon dioxide content, which comprises a carbon dioxide purifying unit, a vacuum cold box unit is arranged at the downstream of the carbon dioxide purifying unit, and a first pressure swing adsorption unit, a second pressure swing adsorption unit and a third pressure swing adsorption unit are arranged at the downstream of the vacuum cold box unit. A catalytic dehydrogenation unit is arranged at the downstream of the third pressure swing adsorption unit, the catalytic dehydrogenation unit is provided with a low-temperature purification unit, and a helium collection unit is arranged at the downstream of the low-temperature purification unit. The system for purifying helium in tail gas with high carbon dioxide content can effectively utilize helium in natural gas, effectively improves the development and comprehensive utilization efficiency of resources, is high in helium purity, and has good economic benefits.

Description

Technical Field

[0001] The invention relates to a natural gas processing device, more specifically, to a system for purifying helium from tail gas containing high carbon dioxide content. Background Art

[0002] A small amount of helium components have been found in the deep carbon dioxide gas fields in the Huangqiao area. After passing through the carbon dioxide purification device, the helium content in its non-condensable tail gas is about 0.2% to 0.24%, the tail gas emission is stable at 1000Nm3 / h, and the pressure is 4.0MPa. It has good development and utilization prospects. The tail gas can be separated and recovered to improve the development and comprehensive utilization efficiency of resources. However, there is currently no device for extracting helium from natural gas. Summary of the invention

[0003] Based on this, it is necessary to provide a system for purifying helium from tail gas with high carbon dioxide content in order to solve the above technical problems.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: A system for purifying helium from tail gas with a high carbon dioxide content, characterized in that the system for purifying helium from tail gas with a high carbon dioxide content comprises a carbon dioxide purification and refining unit, a vacuum cold box unit is provided downstream of the carbon dioxide purification and refining unit, a first pressure swing adsorption unit, a second pressure swing adsorption unit and a third pressure swing adsorption unit are provided downstream of the vacuum cold box unit, a catalytic dehydrogenation unit is provided downstream of the third pressure swing adsorption unit, the catalytic dehydrogenation unit is provided with a low-temperature purification unit, and a helium collection unit is provided downstream of the low-temperature purification unit.

[0005] As a preferred embodiment of the present invention, the first pressure swing adsorption unit, the second pressure swing adsorption unit and the third pressure swing adsorption unit are arranged in series.

[0006] As a preferred embodiment of the present invention, a return pipeline is provided between the vacuum cold box unit and the carbon dioxide purification unit.

[0007] As a preferred embodiment of the present invention, the outlet temperature of the carbon dioxide purification unit is -20 degrees Celsius, and the outlet pressure is 4 MPa. The outlet temperature of the vacuum cold box unit is -20 degrees Celsius, and the outlet pressure is 4 MPa. The outlet temperature of the first pressure swing adsorption unit is 38 degrees Celsius and the outlet pressure is 3.95 MPa, and the outlet temperature of the second pressure swing adsorption unit is 40 degrees Celsius and the outlet pressure is 2 MPa.

[0008] As a preferred embodiment of the present invention, the temperature of the low-temperature purification unit is 77K.

[0009] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a system for purifying helium from tail gas with high carbon dioxide content. After the carbon dioxide from the gas well passes through the carbon dioxide purification and refining unit, the discharged non-condensable tail gas contains 0.2% to 0.24% helium. After entering the vacuum cold box unit, a large amount of carbon dioxide and high-boiling impurity gas are separated and returned to the existing carbon dioxide purification and refining unit for reuse. The helium-containing component enters the first pressure swing adsorption unit to remove the remaining carbon dioxide, enters the second pressure swing adsorption unit to remove a large amount of methane and nitrogen, and then enters the third pressure swing adsorption unit to remove methane, nitrogen and a small amount of carbon dioxide, purifies the helium to more than 99%, and then enters the catalytic dehydrogenation unit to remove hydrogen in the helium, and finally enters the low-temperature purification unit to reduce the helium to 77K, purifies the helium to 99.999%, and collects it in the helium collection unit 8. The system for purifying helium from tail gas with high carbon dioxide content can effectively utilize the helium in natural gas, effectively improve the development and comprehensive utilization efficiency of resources, has high helium purity, good economic benefits, and strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the scheme of the present invention, a brief introduction is given below to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0011] Figure 1 It is a structural schematic diagram of the system for purifying helium from tail gas with high carbon dioxide content of the present invention; The markings in the figure are as follows: 1. Carbon dioxide purification and refining unit; 2. Vacuum cold box unit; 3. First pressure swing adsorption unit; 4. Second pressure swing adsorption unit; 5. Third pressure swing adsorption unit; 6. Catalytic dehydrogenation unit; 7. Low temperature purification unit; 8. Helium collection unit. DETAILED DESCRIPTION

[0012] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0013] like Figure 1 As shown, the system for purifying helium from high-carbon dioxide tail gas comprises a carbon dioxide purification and refining unit 1, a vacuum cold box unit 2 is provided downstream of the carbon dioxide purification and refining unit 1, a first pressure swing adsorption unit 3, a second pressure swing adsorption unit 4 and a third pressure swing adsorption unit 5 are provided downstream of the vacuum cold box unit 2, a catalytic dehydrogenation unit 6 is provided downstream of the third pressure swing adsorption unit 5, the catalytic dehydrogenation unit 6 is provided with a low-temperature purification unit 7, and a helium collection unit 8 is provided downstream of the low-temperature purification unit 7.

[0014] In addition, a return pipeline 23 is provided between the vacuum cold box unit 2 and the carbon dioxide purification and refining unit 1 .

[0015] The vacuum cold box unit 2 includes a vacuum cold box 21 and a gas-liquid separator 22 .

[0016] The first pressure swing adsorption unit 3, the second pressure swing adsorption unit 4 and the third pressure swing adsorption unit 5 are arranged in series.

[0017] It should be noted that the outlet temperature of the carbon dioxide purification unit 1 is -20 degrees Celsius and the outlet pressure is 4 MPa, and the outlet temperature of the vacuum cold box unit 2 is -20 degrees Celsius and the outlet pressure is 4 MPa. The outlet temperature of the first pressure swing adsorption unit 3 is 38 degrees Celsius, and the outlet pressure is 3.95 MPa. The outlet temperature of the second pressure swing adsorption unit 4 is 40 degrees Celsius, and the outlet pressure is 2 MPa.

[0018] In addition, the temperature of the low-temperature purification unit 7 is 77K.

[0019] The working mode of the system for purifying helium from tail gas containing high carbon dioxide content is described below.

[0020] After the carbon dioxide from the gas well S passes through the carbon dioxide purification unit 1, the discharged non-condensable tail gas contains 0.2% to 0.24% helium. After entering the vacuum cold box unit 2, a large amount of carbon dioxide and high-boiling point impurity gases are separated and returned to the existing carbon dioxide purification unit 1 through the return pipeline 23 for reuse. The helium-containing component enters the first pressure swing adsorption unit 3 to remove the remaining carbon dioxide, and enters the second pressure swing adsorption unit 4 to remove a large amount of methane and nitrogen. The analyzed methane and nitrogen enter the existing incineration device for combustion, and the heat generated is used to boil water to supply surrounding areas.

[0021] Next, the gas enters the third pressure swing adsorption unit 5 to remove methane, nitrogen and a small amount of carbon dioxide, purifies the helium to more than 99%, and then enters the catalytic dehydrogenation unit 6 to remove hydrogen from the helium. Finally, it enters the low-temperature purification unit 7 to reduce the helium to 77K, purifies the helium to 99.999%, and is collected in the helium collection unit 8.

[0022] It should be noted that after the non-condensable tail gas enters the vacuum cold box 21, it uses its own high pressure characteristics to reduce pressure and throttle through the throttle valve at the bottom outlet of the gas-liquid separator 22 to generate cold capacity until it drops to -35°C, liquefying most of the carbon dioxide and high-boiling point gases, and the helium-containing non-condensable gas is discharged from the top of the gas-liquid separator 22 and enters the vacuum cold box 21 to exchange heat with the raw gas to -20°C, and then enters the first pressure swing adsorption unit 3 at the rear end. The liquid carbon dioxide discharged from the bottom of the gas-liquid separator 22 is throttled and cooled to enter the vacuum cold box 21, and the cold box temperature is reduced to provide cold capacity for the raw gas, and then it is reheated to -20°C and returned to the carbon dioxide purification and refining unit 1 for compression and liquefaction for sale.

[0023] The interior of the vacuum cold box 21 is a multi-stage heat exchange structure. The raw gas first exchanges heat with the helium-containing gas discharged from the top of the gas-liquid separator 22, and then exchanges heat with the throttled carbon dioxide coming out from the bottom to reduce the temperature to -35°C and liquefy before entering the gas-liquid separator 22.

[0024] In addition, the helium-containing gas discharged from the top enters the pressure swing adsorption device to reduce carbon dioxide to below 5000ppm, and then enters the second pressure swing adsorption unit 4 to remove a large amount of methane and nitrogen. The analyzed methane and nitrogen enter the existing incineration device for combustion, and the heat generated is used to boil water to supply the surrounding areas; the pressure swing adsorption device is a multi-tower replacement work. After the adsorption of tower A is saturated, it switches to tower B for adsorption and tower A for analysis, and the analyzed gas enters the exhaust gas treatment system.

[0025] The system for purifying helium from tail gas with high carbon dioxide content has the following advantages: 1. This process uses the vacuum cold box device to utilize its own throttling liquefaction separation to remove a large amount of carbon dioxide. It does not need to introduce other refrigerants, does not generate energy consumption, reduces the processing capacity of the back-end pressure swing adsorption device, has low energy consumption, and is economically feasible; 2. At present, helium extraction from natural gas mostly uses membrane separation technology to remove methane and nitrogen. However, carbon dioxide has a strong plasticizing effect on membrane materials, which reduces the service life of membrane materials. Compared with this process, the use of pressure swing adsorption devices can remove methane and nitrogen without being affected by carbon dioxide concentration, and has a long service life; 3. This process uses a cryogenic purifier to use its own throttling to concentrate helium to 99.999%, without introducing liquid nitrogen as a refrigerant, reducing on-site storage risks and being economically feasible; 4. This process comprehensively considers the utilization of multiple resources, separates the carbon dioxide in the non-condensable tail gas and returns it to the existing carbon dioxide purification device for reuse, and purifies the helium to 99.999% to increase the company's profits while also reducing the waste of helium resources; the analysis gas of the pressure swing adsorption device is mostly methane and nitrogen, and the calorific value generated by its combustion can produce hot water to supply surrounding enterprises / residents to generate benefits.

[0026] Obviously, the embodiments described above are only part of the embodiments of the present application, rather than all the embodiments. The drawings provide preferred embodiments of the present application, but do not limit the patent scope of the present application.

Claims

1. A system for purifying helium from tail gas containing high carbon dioxide, characterized in that: The system for purifying helium from tail gas with a high carbon dioxide content comprises a carbon dioxide purification unit (1); a vacuum cold box unit (2) is provided downstream of the carbon dioxide purification unit (1); a first pressure swing adsorption unit (3), a second pressure swing adsorption unit (4) and a third pressure swing adsorption unit (5) are provided downstream of the vacuum cold box unit (2); a catalytic dehydrogenation unit (6) is provided downstream of the third pressure swing adsorption unit (5); the catalytic dehydrogenation unit (6) is provided with a low-temperature purification unit (7); and a helium collection unit (8) is provided downstream of the low-temperature purification unit (7).

2. The system for purifying helium from tail gas containing high carbon dioxide according to claim 1, characterized in that: The vacuum cold box unit (2) comprises a vacuum cold box (21) and a gas-liquid separator (22).

3. The system for purifying helium from tail gas containing high carbon dioxide according to claim 2, characterized in that: The first pressure swing adsorption unit (3), the second pressure swing adsorption unit (4) and the third pressure swing adsorption unit (5) are arranged in series.

4. The system for purifying helium from tail gas containing high carbon dioxide according to claim 3, characterized in that: A return pipeline (23) is provided between the vacuum cold box unit (2) and the carbon dioxide purification unit (1).

5. The system for purifying helium from tail gas containing high carbon dioxide according to claim 4, characterized in that: The outlet temperature of the carbon dioxide purification unit (1) is -20 degrees Celsius and the outlet pressure is 4 MPa. The outlet temperature of the vacuum cold box unit (2) is -20 degrees Celsius and the outlet pressure is 4 MPa. The outlet temperature of the first pressure swing adsorption unit (3) is 38 degrees Celsius and the outlet pressure is 3.95 MPa, and the outlet temperature of the second pressure swing adsorption unit (4) is 40 degrees Celsius and the outlet pressure is 2 MPa.

6. The system for purifying helium from tail gas containing high carbon dioxide according to claim 5, characterized in that: The temperature of the low-temperature purification unit (7) is 77K.

7. The system for purifying helium from tail gas containing high carbon dioxide according to claim 6, characterized in that: The first pressure swing adsorption unit (3), the second pressure swing adsorption unit (4) and the third pressure swing adsorption unit (5) are all double-tower structures.

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