BOG helium extraction device with self-circulation guarantee

Abstract

The utility model discloses a BOG helium extraction device with self-circulation guarantee. The BOG helium extraction device comprises a catalytic dehydrogenation unit, a crude helium extraction unit, a low-temperature helium purifier and a helium filling device, the catalytic dehydrogenation unit comprises a raw material gas BOG storage tank, a circulating compressor and a catalytic dehydrogenation device, and the raw material gas BOG storage tank is connected with the circulating compressor and the catalytic dehydrogenation device; the circulating compressor is connected with the oil separator, the oil separator is connected with the heat exchanger, the heat exchanger is connected with the second electric heater, the second electric heater is connected with the catalytic dehydrogenation device, the catalytic dehydrogenation device is connected with the heat exchanger, the heat exchanger is connected with the cooling tower, the cooling tower is connected with the first electric heater, and the first electric heater is connected with the crude helium extraction unit. The crude helium extraction unit is connected with the low-temperature helium purifier, and the low-temperature helium purifier is connected with the helium filling device. The helium extraction device disclosed by the utility model can be used for producing helium by utilizing enriched helium-containing BOG during operation, and the technology is high in helium enrichment concentration, small in investment, quick in equipment installation and flexible in operation.

Description

Technical Field

[0001] The utility model belongs to the technical field of helium extraction equipment, and particularly relates to a BOG helium extraction device with self-circulation guarantee. Background Technique

[0002] Helium, as a non-renewable scarce resource, is widely used in the fields of national defense, aerospace, nuclear industry, scientific research, medical treatment, industry, etc. Helium mainly exists in natural gas. China is a poor helium natural gas field with extremely low helium content. Moreover, the cost of directly extracting helium from natural gas is extremely high. Industrial helium basically depends entirely on imports, with a very high degree of foreign dependence.

[0003] BOG refers to the cryogenic flash steam generated during the storage and transportation of LNG, that is, Boil Off Gas (BOG). The daily evaporation rate of the LNG storage tank is about 0.8‰. In natural gas liquefaction facilities, through a specific process, helium will be effectively enriched in the flash steam (BOG). The main component ratios from high to low are methane, helium, nitrogen, hydrogen, etc. Therefore, recovering helium from BOG has become a method with significant economic benefits. Currently, the main methods for extracting helium from BOG include cryogenic method, membrane separation method, adsorption method, absorption method, diffusion method, etc. The investment in the cryogenic process is relatively high, generally applicable to large-scale helium extraction devices. The technology is mature, but the economy is not good when using cryogenic equipment for too small scales. The membrane separation process has a simple flow, is easy to operate, has low energy consumption, high cost performance, and stable operation, and is applicable to medium and small-scale helium extraction devices, but currently, there are relatively few membrane components involved. The adsorbent method is limited by the adsorption capacity of the adsorbent and is generally applicable to the purification of crude helium with an impurity content of less than 10%. The absorption method is generally applicable to occasions with a relatively high helium content and is usually used together with PSA. The helium extracted by the diffusion method has a quite high purity, but the process is complex, the cost is high, and it needs to be operated under high temperature and high pressure difference, and has not been applied industrially yet. Content of the Utility Model

[0004] The purpose of the utility model is to provide a BOG helium extraction device with self-circulation guarantee, which can recover the helium enriched in the BOG of a natural gas liquefaction plant and avoid the waste of rare gases.

[0005] The technical solution adopted by the present utility model is a BOG helium extraction device with self-circulation guarantee, which includes a catalytic dehydrogenation unit, a crude helium extraction unit, a low-temperature helium purifier and a helium filling device; the catalytic dehydrogenation unit includes a raw gas BOG storage tank, a circulating compressor and a catalytic dehydrogenation device, and the raw gas BOG storage tank is respectively connected to the circulating compressor and the catalytic dehydrogenation device; the circulating compressor is connected to an oil separator, the oil separator is connected to a heat exchanger, the heat exchanger is connected to a second electric heater, the second electric heater is connected to the catalytic dehydrogenation device, the catalytic dehydrogenation device is connected to the heat exchanger, the heat exchanger is connected to a cooling tower, the cooling tower is connected to a first electric heater, and the first electric heater is connected to the crude helium extraction unit; the crude helium extraction unit is connected to the low-temperature helium purifier, and the low-temperature helium purifier is connected to the helium filling device.

[0006] The characteristics of the present utility model also lie in that

[0007] The crude helium extraction unit includes a membrane separator and a booster compressor. The first electric heater is connected to the membrane separator, the membrane separator is connected to the booster compressor, the booster compressor is connected to a PSA pressure swing adsorption device, the PSA pressure swing adsorption device is connected to a buffer tank, and the buffer tank is connected to the low-temperature helium purifier.

[0008] The helium filling device is also connected to a helium filling truck.

[0009] An air-operated proportional regulating valve is configured outside the booster compressor, and 2 manual valves are connected in series at the front and rear ends of the air-operated proportional regulating valve.

[0010] A pressure reducing valve and an air-operated proportional regulating valve are configured outside the helium filling device.

[0011] The beneficial effects of the present utility model are as follows

[0012] (1) For the BOG helium extraction device with self-circulation guarantee of the present utility model, taking the BOG of a natural gas liquefaction plant as the raw gas, diluting and boosting it through a circulating compressor, then purifying it through catalytic dehydrogenation, and then extracting crude helium through a membrane separation + PSA pressure swing adsorption process, and finally producing refined helium through low-temperature heat exchange and then filling helium, it can recover the helium enriched in the BOG of the natural gas liquefaction plant, avoid the waste of rare gases, and is relatively environmentally friendly and economical;

[0013] (2) For the BOG helium extraction device with self-circulation guarantee of the present utility model, it can produce helium by using the enriched helium-containing BOG during the production and operation of the natural gas liquefaction plant. Compared with extracting helium from low-helium natural gas, this technology has a high helium enrichment concentration, small investment, fast installation of skid-mounted equipment, and flexible operation;

[0014] (3) The BOG helium extraction device with self - circulation guarantee of the present utility model enters the self - circulation mode for each unit when the upstream gas source is interrupted. It has a large load adjustment range, can achieve self - circulation operation for a long time, avoid the situation that the compressor idles and is damaged due to gas interruption, avoid the loss of the device caused by frequent startup and shutdown due to unstable gas source, and at the same time reduce the waste of natural gas resources during startup and shutdown. Brief Description of the Drawings

[0015] Figure 1 is a schematic structural diagram of the BOG helium extraction device with self - circulation guarantee of the present utility model;

[0016] Figure 2 is a schematic structural diagram of the crude helium extraction unit in the BOG helium extraction device with self - circulation guarantee of the present utility model;

[0017] Figure 3 is a schematic structural diagram of the catalytic dehydrogenation unit in the BOG helium extraction device with self - circulation guarantee of the present utility model.

[0018] In the figure, 1. Raw gas BOG storage tank, 2. Circulation compressor, 3. Catalytic dehydrogenation device, 4. First electric heater, 5. Membrane separator, 6. Booster compressor, 7. PSA pressure swing adsorption device, 8. Buffer tank, 9. Low - temperature helium purifier, 10. Helium filling device, 11. Oil separator, 12. Heat exchanger, 13. Second electric heater, 14. Cooling tower, 15. Helium filling truck. Detailed Embodiments

[0019] The present utility model will be described in detail below in conjunction with the drawings and specific embodiments.

[0020] Embodiment 1

[0021] The BOG helium extraction device with self - circulation guarantee of the present utility model, as Figure 1 shown, includes a catalytic dehydrogenation unit, a crude helium extraction unit, a low - temperature helium purifier 9 and a helium filling device 10;

[0022] The catalytic dehydrogenation unit includes a raw gas BOG storage tank 1, a circulation compressor 2, and a catalytic dehydrogenation device 3. The raw gas BOG storage tank 1 is respectively connected to the circulation compressor 2 and the catalytic dehydrogenation device 3; as Figure 3 shown, the circulation compressor 2 is connected to the oil separator 11, the oil separator 11 is connected to the heat exchanger 12, the heat exchanger 12 is connected to the second electric heater 13, the second electric heater 13 is connected to the catalytic dehydrogenation device 3, the catalytic dehydrogenation device 3 is connected to the heat exchanger 12, the heat exchanger 12 is connected to the cooling tower 14, the cooling tower 14 is connected to the first electric heater 4, and the first electric heater 4 is connected to the crude helium extraction unit;

[0023] As Figure 2As shown, the crude helium extraction unit includes a membrane separator 5 and a booster compressor 6. The first electric heater 4 is connected to the membrane separator 5, the membrane separator 5 is connected to the booster compressor 6, the booster compressor 6 is connected to a PSA pressure swing adsorption device 7, the PSA pressure swing adsorption device 7 is connected to a buffer tank 8, the buffer tank 8 is connected to a cryogenic helium purifier 9, the cryogenic helium purifier 9 is connected to a helium filling device 10, and the helium filling device 10 is connected to a helium filling vehicle 15;

[0024] Example 2

[0025] The booster compressor 6 and the helium filling device 10 are both diaphragm machines. A manual reflux valve is provided on the main body, and a pneumatic proportional regulating valve is added on the outside. The compressor inlet and outlet pneumatic valves are closed, and the reflux valve is used for control to ensure the normal operation of the compressor.

[0026] The boost compressor 6 is externally provided with a pneumatic proportional control valve to control the flow and return pressure. Two manual valves are connected in series at the front and rear ends of the pneumatic proportional control valve. The load can be adjusted manually with a stop valve or automatically with the pneumatic proportional control valve. The load is 0-100%. The outlet temperature is reduced when the load is reduced, and the pressure remains unchanged.

[0027] The helium filling device 10 is externally equipped with a pressure reducing valve and a pneumatic proportional regulating valve. The pressure reducing valve first reduces the pressure to control the reflux pressure, and the pneumatic proportional regulating valve then controls the flow rate. Two manual valves are connected in series at the front and rear ends of the pneumatic proportional regulating valve. The load can be manually adjusted by a stop valve or automatically adjusted by a pneumatic proportional regulating valve. The load is 0-100%. The outlet temperature is reduced when the load is reduced, and the pressure remains unchanged.

[0028] The leakage rate of circulating compressor 2 is 10-6pa.m 3 / s, which is very small. The 12.5L / 2.4L gas volume in the inlet buffer tank is used for reflux circulation to achieve non-stop operation of the compressor. Therefore, the booster compressor and the charging compressor will not be affected if they are not stopped within 2 hours.

[0029] Catalytic dehydrogenation process: The operating load is 30% to 110%. The load can be reduced in a short period of time without affecting the operation of the equipment. The catalytic dehydrogenation compressor and the catalytic dehydrogenation device can be programmed to establish an internal cycle without releasing gas. The catalytic dehydrogenation device is a static device and can be programmed to release gas.

[0030] The PSA pressure swing adsorption device is a static device. When there is no raw gas, the device can be suspended. The cryogenic helium purifier is a static device. When there is no raw gas, a one-way valve is added to the inlet of the device to prevent the device from losing pressure. There is a back pressure valve at the outlet end, so no additional valve is required.

[0031] The helium filling device 10 is a membrane press, a dynamic device, and the frequent opening and closing is minimized. At this time, no raw gas enters, and an external pneumatic proportional regulating valve and a ball valve are required to perform reflux internal circulation to avoid frequent starting and stopping of the equipment.

[0032] Example 3

[0033] For the BOG helium extraction device with self-circulation guarantee of the utility model, its specific working principle is as follows:

[0034] The raw material gas BOG is pressurized to 1.6 MpaG by the circulation compressor 2, and after oil-gas separation, it enters the catalytic dehydrogenation device 3. The hydrogen is removed by the method of oxygen-added catalytic oxidation. The catalyst reacts with hydrogen through oxygen to generate water under the conditions of a pressure of 1.6 MPaG and a temperature of 140 °C, and the hydrogen is removed to below 0.02 ppm. The reacted gas contains a large amount of water vapor, and after being cooled and separated from the condensed water by the cooling tower 14, it enters the first electric heater 4 for drying.

[0035] The dried gas is crude helium, containing helium, nitrogen, oxygen, and trace impurities such as methane and neon. The dried gas is sent to the membrane separation equipment in the crude helium extraction unit at a pressure of 1.5 MpaG. When the gas passes through the membrane separator 5, helium is enriched on the permeate side of the membrane separator 5. The pressure of the gas on the permeate side is about 0.1 MpaG, and the purity of helium reaches more than 80%. The membrane separation permeate gas is pressurized to 1.4 MpaG by the booster compressor 6 and then enters the PSA pressure swing adsorption device 7. The raw material gas at a temperature of 40 °C enters the adsorption tower that is in the adsorption state (one adsorption tower is in the adsorption state). Under the sequential selective adsorption of various adsorbents, impurities such as C1, CO, and N2 are adsorbed, and the unadsorbed helium flows out from the top of the tower as a product. After being stabilized by the pressure regulating system, it is sent out of the boundary area to the helium purification unit. The purity of helium in the product is greater than 99.0%, and the pressure is greater than 1.2 MPa (G).

[0036] The helium purification unit is a low-temperature helium purifier 9, and its working principle is to adopt a medium-pressure, low-temperature condensation adsorption separation process, using liquid nitrogen as the low-temperature cold source. The low-temperature helium purifier 9 internally contains a subcooling heat exchanger, an adsorption cylinder, etc., all immersed in liquid nitrogen. The crude helium gas enters the low-temperature helium purifier 9, and first is further cooled by the subcooling heat exchanger immersed in liquid nitrogen, making the gas temperature closer to the liquid nitrogen temperature. Under medium-pressure and low-temperature conditions, impurities such as nitrogen in the gas are supercooled and saturated and precipitated due to their boiling points being higher than the liquid nitrogen temperature. The crude helium gas enters the adsorption cylinder filled with activated carbon, and using the adsorption characteristics of activated carbon in a low-temperature environment, the remaining impurity components are adsorbed, so that the purity of helium is increased to 99.999%. The maximum outlet pressure of the helium purification device is 1.4 MPa. The high-purity helium gas first passes through the filling compressor for pressurization and then enters the helium filling device 10 for loading trucks.

Claims

1. The BOG helium extraction device with self-circulation guarantee is characterized in that It includes a catalytic dehydrogenation unit, a crude helium extraction unit, a cryogenic helium purifier (9) and a helium filling device (10); the catalytic dehydrogenation unit includes a raw gas BOG storage tank (1), a recycle compressor (2), and a catalytic dehydrogenation device (3), and the raw gas BOG storage tank (1) is respectively connected to the recycle compressor (2) and the catalytic dehydrogenation device (3); the recycle compressor (2) is connected to an oil separator (11), the oil separator (11) is connected to a heat exchanger (12), the heat exchanger (12) is connected to a second electric heater (13), the second electric heater (13) is connected to the catalytic dehydrogenation device (3), the catalytic dehydrogenation device (3) is connected to the heat exchanger (12), the heat exchanger (12) is connected to a cooling tower (14), the cooling tower (14) is connected to a first electric heater (4), and the first electric heater (4) is connected to the crude helium extraction unit; the crude helium extraction unit is connected to the cryogenic helium purifier (9), and the cryogenic helium purifier (9) is connected to the helium filling device (10).

2. The BOG helium extraction device with self-circulation guarantee as described in claim 1, wherein, The crude helium extraction unit includes a membrane separator (5) and a booster compressor (6), the first electric heater (4) is connected to the membrane separator (5), the membrane separator (5) is connected to the booster compressor (6), the booster compressor (6) is connected to a PSA pressure swing adsorption device (7), the PSA pressure swing adsorption device (7) is connected to a buffer tank (8), and the buffer tank (8) is connected to the cryogenic helium purifier (9).

3. The BOG helium extraction device with self-circulation guarantee according to claim 1, characterized in that, The helium filling device (10) is also connected to a helium filling truck (15).

4. The BOG helium extraction device with self-circulation guarantee according to claim 2, characterized in that, An air-operated proportional regulating valve is arranged outside the booster compressor (6), and 2 manual valves are connected in series at the front and rear ends of the air-operated proportional regulating valve.

5. The BOG helium extraction device with self-circulation guarantee according to claim 1, characterized in that A pressure reducing valve and an air-operated proportional regulating valve are arranged outside the helium filling device (10).

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