Helium extraction from natural gas

Abstract

Provided are a natural gas helium extraction device and a natural gas helium extraction method. The natural gas helium extraction device comprises a primary concentration part, a dehydrogenation and dehydration part, a secondary concentration part, and a final purification part. The primary concentration part comprises a first compressor, a first preheater, and a first membrane separator connected in sequence. The dehydrogenation and dehydration part comprises an oxygen delivery pipe, a mixer, a plurality of dehydrogenation towers connected in parallel, a low-temperature water separator, and a water remover. The secondary membrane separator of the secondary concentration part comprises a permeate gas outlet and a non-permeate gas outlet. The non-permeate gas outlet is connected to the primary concentration part. The final purification part comprises a nitrogen circulating cooling component and a pressure swing adsorption (PSA) device. The PSA device is connected to the permeate gas outlet of the secondary membrane separator and is used to output high-purity helium. The nitrogen circulating cooling component, the PSA device, and the low-temperature water separator form a cooling loop. The natural gas helium extraction device and the natural gas helium extraction method can significantly reduce safety risks and effectively reduce equipment costs.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of helium extraction, in particular to the field of helium extraction from natural gas. BACKGROUND

[0002] Helium is a precious and scarce resource, which is often obtained from natural gas.

[0003] The most important helium extraction process in China at present is still the low-temperature method. The non-condensable gas generated during the liquefaction of natural gas and the evaporation gas generated during the vaporization of LNG are preliminarily separated from methane and helium by low-temperature equipment, or preliminarily purified by rectification tower equipment, and then dehydrogenated, dehydrated and impurity-removed by tower and reactor equipment, and finally liquid helium is extracted by deep cooling liquefaction in a cold box (-268.9℃). The main core of the above process is to separate helium from natural gas by low temperature. The low-temperature environment has high requirements for equipment, and has high equipment cost and energy consumption cost.

[0004] Chinese patent CN219128858U discloses a system for extracting and preparing high-purity helium from natural gas or BOG. The system first separates helium by membrane separation, then catalytically dehydrogenates, and then further purifies. However, the separation process of hydrogen is complex, palladium membrane is used for dehydrogenation, a compressor needs to be added, and the cost and energy consumption of dehydrogenation are high. In addition, during the helium purification process in the membrane separator, the content of hydrogen increases with the increase of helium concentration, which can reach more than 7%, or even more than 25%. At this concentration, the hydrogen is too high, which has an explosion risk in the dehydrogenation process, and is not conducive to the safe and stable operation of the helium extraction device. At the same time, high hydrogen concentration leads to high dehydrogenation reaction temperature, which is not conducive to control. SUMMARY

[0005] An object of the present application is to provide a natural gas helium extraction device which can significantly reduce the safety risk and effectively reduce the equipment cost.

[0006] The natural gas helium extraction device comprises a primary concentration part, a dehydrogenation and dehydration part, a secondary concentration part and a final purification part. The primary concentration part comprises a first compressor, a first preheater and a primary membrane separator connected in sequence. The dehydrogenation and dehydration part comprises an oxygen delivery pipe, a mixer, a plurality of dehydrogenation towers connected in parallel, the dehydrogenation towers are also connected with the preheater, and are used for sending the dehydrogenated gas into the preheater to provide heat, and further comprises a low-temperature water separator and a water remover for receiving the dehydrogenated gas flowing through the preheater. The secondary concentration part comprises a secondary membrane separator, the secondary membrane separator comprises a permeation gas outlet and a non-permeation gas outlet, and the non-permeation gas outlet is connected with the primary concentration part. The final purification part comprises a nitrogen circulation cooling component and a pressure swing adsorption (PSA) device, the PSA device is connected with the permeation gas outlet of the secondary membrane separator, and is used for outputting high-purity helium gas. The nitrogen circulation cooling component, the PSA device and the low-temperature water separator form a cooling loop.

[0007] In one or more embodiments, the nitrogen circulation cooling component comprises a nitrogen compressor, a nitrogen condenser and a liquid nitrogen buffer tank connected in sequence, the nitrogen compressor is connected with the nitrogen compressor, and the liquid nitrogen buffer tank is connected with the PSA device.

[0008] In one or more embodiments, each of the dehydrogenation towers is independently started and stopped.

[0009] In one or more embodiments, a heat exchanger is arranged between the low-temperature water separator and the water remover, the heat exchanger receives the dehydrogenated gas flowing through the preheater, outputs the gas flowing out of the low-temperature water separator, and exchanges heat between the two parts of the gas.

[0010] In one or more embodiments, a crude helium compressor is further arranged between the water remover and the secondary membrane separator.

[0011] In one or more embodiments, the PSA device comprises a circulation outlet, the circulation outlet is connected with the primary concentration part, and is used for outputting the gas regenerated by the PSA device.

[0012] In one or more embodiments, the primary membrane separator comprises a non-permeation gas outlet, which is used for being connected with a natural gas treatment device.

[0013] In one or more embodiments, the final purification device further comprises a high-purity helium heat exchanger connected with the PSA device.

[0014] Another object of the present application is to provide a natural gas helium extraction method, comprising the following steps:

[0015] S1. initial concentration and methane initial separation of the input initial gas using a primary membrane separator; S2. dehydrogenation treatment and dehydration treatment of the gas obtained in S1, and preheating the dehydrogenated gas to the initial gas input in step S1 before dehydration treatment; S3. secondary membrane separation of the dehydrated gas obtained in S2; S4. nitrogen cooling of the gas output in step S3, and impurity removal treatment of the gas using a pressure swing adsorption (PSA) device, to obtain high-purity helium, while the nitrogen continues to cool the gas in step S2.

[0016] In one or more embodiments, the gas returned from the regeneration of the pressure swing adsorption (PSA) device in step S4 is returned to step S1 to recover helium, and / or the non-permeated gas produced in the secondary membrane separation in step S3 is returned to step S1 to recover helium.

[0017] The natural gas helium extraction device and method described above uses a primary membrane separation device to obtain hydrogen with a suitable concentration, avoids too low or too high hydrogen content, thereby ensuring that the hydrogen concentration is below the explosion limit for oxidative dehydrogenation, ensuring the safety and stability of the device, while also allowing for certain efficiency in hydrogen removal; at the same time, the multiple-stage parallel dehydrogenation towers can flexibly select the number of towers to be opened and closed according to the hydrogen content in the gas, thereby adjusting the dehydrogenation load and improving the dehydrogenation efficiency; at the same time, the nitrogen circulation cooling component, the pressure swing adsorption (PSA) device, and the low-temperature water separator form a cooling loop, which fully utilizes the cold energy. BRIEF DESCRIPTION OF DRAWINGS

[0018] The above and other characteristics, features and advantages of the present application will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the application.

[0019] Figure 1 is a structural schematic diagram of a natural gas helium extraction device;

[0020] Figure 2 is a flowchart of a natural gas helium extraction method. DETAILED DESCRIPTION

[0021] The present application will be further described with reference to the accompanying drawings and specific examples, in which more details are set forth in order to provide a thorough understanding of the application. However, the application is clearly capable of many different embodiments and of being practiced and carried out in various ways, as those skilled in the art will appreciate, and therefore the specifics of the following examples should not be construed as limiting the scope of the application.

[0022] It should be noted that these and other accompanying drawings are merely examples, and are not drawn to scale, and should not be used to limit the scope of protection actually claimed for the present application.

[0023] Helium is a precious and scarce resource, widely used in military, scientific research, petrochemical, refrigeration, medical, semiconductor, pipeline leak detection, superconducting experiment, metal manufacturing, deep-sea diving, high-precision welding, optoelectronic product production, etc. Helium can be used as a low-temperature cold source, and the low boiling point of liquid helium can be used for ultra-low temperature cooling. Helium can also be used for helium testing and analysis, welding protection gas. At the same time, helium can be used as a high-vacuum device, a nuclear reactor, a rocket, a spacecraft, a pressurized gas for transporting liquid hydrogen, liquid oxygen and other liquid propellants. Helium is also used as a cleaning agent for atomic reactors, a mixed gas for breathing in the field of ocean development, and a filling gas for gas thermometers.

[0024] Helium resources are scarce and can only be obtained from natural gas. Most domestic natural gas fields are poor in helium, and the helium content is very low. The cost of directly extracting helium from natural gas is very high. The low-temperature method for extracting helium has the problem of high cost. Moreover, the cold nitrogen gas generated in the low-temperature adsorption process is not reasonably utilized, resulting in loss and waste of cold energy.

[0025] To solve the problem, the present application provides a natural gas helium extraction device and method, which can reasonably utilize cold energy, significantly reduce safety risks, and effectively reduce equipment and maintenance costs.

[0026] Referring to Figure 1 As shown in the figure, the natural gas helium extraction device mainly includes four parts of a primary concentration part A, a dehydrogenation and dehydration part B, a secondary concentration part C and a final purification device D distributed in sequence.

[0027] The primary concentration part A includes a reheater 1, a first compressor 2, a first preheater 3 and a first membrane separator 4 connected in sequence. The low-temperature flash steam E from the top of the LNG storage tank first enters the primary concentration part A, and then enters the BOG first compressor 2 after the reheater 1. In addition, the reheater 1 can also not be used during operation, and the low-temperature flash steam E can be directly reheated by using the high temperature of the exhaust gas of the first compressor 2.

[0028] The gas after pressure increase enters the first preheater 3 through the outlet of the first compressor 2, and the preheated BOG gas enters the first membrane separator 4. The warmed BOG gas can improve the efficiency of the membrane separator and prolong the service life of the membrane separator. Non-permeable gas, i.e. methane, is discharged as tail gas F and enters the downstream natural gas treatment device.

[0029] The main function of the primary concentration part A is to remove part of the methane through the first membrane separator, appropriately increase the concentration of hydrogen, but not too high, so as to avoid a large risk in the subsequent hydrogen-oxygen reaction.

[0030] The permeated gas after the first stage membrane separator enters the dehydrogenation and dehydration section B. The dehydrogenation section of the dehydrogenation and dehydration section includes oxygen delivery pipe G, mixer 5, multiple dehydrogenation towers 6, 7, 8 connected in sequence, and the dehydration section includes low-temperature water separator 10 and water remover 12.

[0031] The multiple dehydrogenation towers 6, 7, 8 are arranged in parallel, and each dehydrogenation tower is arranged to be independently started and stopped, and the number of the dehydrogenation towers to be started and stopped is flexibly selected according to the hydrogen content in the gas, so as to adjust the dehydrogenation load and improve the dehydrogenation efficiency. Compared with the traditional structure with only a single dehydrogenation tower, the multiple dehydrogenation towers arranged in parallel can flexibly adapt to the input gas flow, have higher efficiency, and avoid waste.

[0032] The permeated gas and the oxygen input from the oxygen delivery pipe G enter the static mixer 5 for uniform mixing, and the mixed gas is heated by the dehydrogenation preheater 9 and then enters the dehydrogenation towers 6, 7, 8 for dehydrogenation. The dehydrogenation tower body is provided with a reaction temperature detector, and the amount of feed into each tower is controlled according to the reaction temperature to avoid the danger of over-temperature reaction.

[0033] The dehydrogenation tower is also connected with the first preheater 3, and the gas after dehydrogenation enters the first preheater 3 to provide heat for the initially input BOG gas, that is, the gas after dehydrogenation will return to the preheater in the primary concentration section A to realize full use of heat.

[0034] The gas after dehydrogenation is heated by the first preheater 3 and then enters the heat regenerator 11 for further cooling, and at the same time, the gas flowing out of the low-temperature water separator 10 is heated. The gas after heat exchange from the heat regenerator 11 enters the low-temperature water separator 10, which is internally provided with low-temperature coils and liquid distribution plates, and the bottom of the water separator is provided with a filler. The cold nitrogen gas generated in the pressure swing adsorption process enters the coils to cool and separate the water-containing gas in the water separator, and the gas after dehydration is further heated by the heat regenerator 11 and then enters the precision water remover 12 for further dehydration.

[0035] That is, the heat regenerator 11 inputs the gas entering the low-temperature water separator 10 and outputs the gas flowing out of the low-temperature water separator 10, and there is a temperature difference between the two, so the gas entering the low-temperature water separator 10 can be cooled, and the gas flowing out of the low-temperature water separator 10 can be heated, so that the two parts of gas are heat exchanged, the heat and cold are reasonably arranged, and the energy use efficiency is improved.

[0036] The gas after dehydration enters the secondary concentration section C, which includes a second stage membrane separator 14, and in some embodiments, also includes a rough helium compressor 13 arranged between the second stage membrane separator 14 and the precision water remover 12. The gas after dehydration enters the rough helium compressor 13 for pressure increase, and the gas after pressure increase enters the second stage membrane separator 14 to separate most of the methane and nitrogen, thereby reducing the subsequent compression and separation load and reducing equipment cost.

[0037] The secondary membrane separator 14 includes a permeate gas outlet 141 and a non-permeate gas outlet 142, which is connected to the primary enrichment section A, so that the non-permeate gas is recycled back to the inlet of the primary compressor to recover helium. The gas in this section has a higher concentration of helium, so it is necessary to return the non-permeate gas to the primary enrichment section A to recover helium again.

[0038] The permeate gas outlet 141 of the secondary membrane separator 14 leads the permeate gas to the final purification section D. The final purification section D includes a nitrogen circulation cooling unit 21 and a pressure swing adsorption temperature swing adsorber 16. The nitrogen circulation cooling unit 21 includes a nitrogen compressor 17, a nitrogen condenser 18, and a liquid nitrogen buffer tank 19 connected in sequence. The pressure swing adsorption temperature swing adsorber 16 is connected to the permeate gas outlet 141 of the secondary membrane separator 14 and is used to output high-purity helium. The nitrogen circulation cooling unit 21 forms a cooling loop with the pressure swing adsorption temperature swing adsorber 16 and the cryogenic water separator 10.

[0039] Specifically, the permeate gas enters the purification compressor 15, is pressurized, and then enters the pressure swing adsorption temperature swing adsorber 16 after heat exchange in the high-purity helium heat exchanger 20. The pressure swing adsorption temperature swing adsorber 16 removes impurity gases through pressure swing adsorption and low-temperature adsorption. The low-temperature adsorption of impurities is achieved by gasification of liquid nitrogen. Finally, 99.999% high-purity helium is obtained after heat exchange in the high-purity helium heat exchanger 20. The high-purity helium enters the subsequent helium filling or liquefaction unit P.

[0040] The device also recycles energy from the nitrogen gas flowing through the pressure swing adsorption temperature swing adsorber 16. The liquid nitrogen becomes cold nitrogen gas after passing through the pressure swing adsorption temperature swing adsorber 16. The cold nitrogen gas enters the cryogenic water separator 10 of the dehydrogenation and dehydration section B to recycle and utilize the cold energy. Then, the cold nitrogen gas enters the nitrogen compressor 17 through the cryogenic water separator 10, is pressurized, and then enters the nitrogen condenser 18. The condensed liquid nitrogen enters the liquid nitrogen buffer tank 19 and is recycled to the pressure swing adsorption temperature swing adsorber 16.

[0041] Thus, the nitrogen compressor 17 of the nitrogen circulation cooling unit 21 is connected to the cryogenic water separator 10, and the liquid nitrogen buffer tank 19 is connected to the pressure swing adsorption temperature swing adsorber 16. The nitrogen circulation cooling unit forms a nitrogen cooling loop with the pressure swing adsorption temperature swing adsorber and the cryogenic water separator, achieving full utilization of cold energy.

[0042] In some embodiments, the pressure swing adsorption temperature swing adsorber 16 includes a circulation outlet 160 connected to the primary enrichment section A to output the gas regenerated by the pressure swing adsorption temperature swing adsorber. The regenerated gas is returned to the inlet of the primary compressor 2 and is recycled to recover helium.

[0043] The above device has the following advantages:

[0044] (1) Compared with the multi-stage membrane separator arranged continuously, the device uses a first-stage membrane separation device to obtain hydrogen with a suitable concentration, avoids excessively low or high hydrogen content, ensures that the hydrogen concentration is below the explosion limit for oxidative dehydrogenation, guarantees the safety and stability of the device, and enables the hydrogen removal to have a certain efficiency;

[0045] (2) The oxidative dehydrogenation reactor is arranged between the first-stage membrane and the second-stage membrane, the use of expensive palladium membrane and other dehydrogenation equipment is avoided, the equipment cost is reduced, the multi-stage dehydrogenation reactor is connected in parallel, the dehydrogenation system load can be flexibly adjusted according to the hydrogen content fluctuation of the raw gas, the operation flexibility is improved, and the energy consumption is reduced;

[0046] (3) The low-temperature water separator is arranged at the rear end of the dehydrogenation system, the water after dehydrogenation is removed, the coil pipe and the multi-stage liquid blocking plate are used in the water separator, the low-temperature nitrogen gas input by the final-stage purification part D is used for heat exchange and cooling, the nitrogen gas circulating cooling part, the pressure swing coupling temperature swing purifier and the low-temperature water separator form a cooling loop, the nitrogen gas cold energy is fully utilized, the efficiency of the low-temperature dehydration of the gas after dehydrogenation is improved, the dew point of the crude helium gas is reduced, which is beneficial to the subsequent purification, and the waste of resources is avoided;

[0047] (4) The heat exchangers are arranged at the inlet of the first-stage membrane separation, the outlet of the low-temperature water separator and the outlet of the pressure swing coupling temperature swing purifier, the internal energy of the device is fully utilized, the energy consumption of the device is reduced, and the heat of the gas after dehydrogenation output by the dehydrogenation tower is used for heat recovery, and the energy utilization rate is further improved.

[0048] (5) The device uses the primary concentration part to preliminarily remove methane, realizes dehydrogenation, and then removes nitrogen, methane and other impurities through secondary concentration, the process design is reasonable, the energy consumption and equipment cost can be effectively reduced on the premise of obtaining high-purity helium, and the purpose of energy saving and environmental protection is achieved.

[0049] In combination with the introduction of the above natural gas helium extraction device, a natural gas helium extraction method can also be understood.

[0050] As shown in Figure 2 , the method comprises the following steps: S1. using a first-stage membrane separator to preliminarily concentrate and separate methane from the input initial gas such as BOG gas or natural gas; S2. performing dehydrogenation treatment and dehydration treatment on the gas obtained in S1, and preheating the gas after dehydrogenation treatment to the initial gas input in step S1 before performing dehydration treatment; S3. performing second-stage membrane separation on the gas after dehydration treatment in S2 to separate methane and nitrogen; S4. using nitrogen to cool the gas output in step S3, and using a pressure swing coupling temperature swing purifier to perform impurity removal treatment on the gas by low-temperature adsorption to obtain high-purity helium, and meanwhile making the nitrogen continue to cool the gas under dehydration treatment in step S2.

[0051] To ensure that the helium in the flash vapor can be fully recovered, the gas produced in the pressure swing coupling temperature swing purifier in step S4 can also be returned to step S1 to collect helium again, and / or the non-permeate gas produced in the secondary membrane separation in step S3 can be returned to step S1 to collect helium again.

[0052] It should be noted that the above content uses the words "first", "second", etc. to limit the parts, which is only for the convenience of distinguishing the corresponding parts. If there is no further declaration, the above words have no special meaning, and therefore cannot be understood as a limitation on the scope of protection of the present application.

[0053] Meanwhile, specific words are used in the present application to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" means a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that the "one embodiment" or "one alternative embodiment" mentioned in different positions in the specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be properly combined.

[0054] Although the present application is disclosed with the preferred embodiments as above, it is not intended to limit the present application, and any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present application. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, which does not deviate from the technical solution of the present application, falls within the protection scope defined by the claims of the present application.

Claims

1. A natural gas helium extraction device, characterized in that: include: The primary concentration section includes a first compressor, a first preheater and a first-stage membrane separator connected in sequence; a dehydrogenation and dehydration section, comprising an oxygen delivery pipe, a mixer, and a plurality of dehydrogenation towers connected in sequence, the plurality of dehydrogenation towers being arranged in parallel, the dehydrogenation towers being further connected to the first preheater for feeding the dehydrogenated gas into the first preheater to provide heat, and further comprising a low-temperature water separator and a water remover for dehydration, for receiving the dehydrogenated gas flowing through the first preheater; A secondary concentration part, comprising a secondary membrane separator, wherein the secondary membrane separator comprises a permeate gas outlet and a non-permeate gas outlet, and the non-permeate gas outlet is connected to the primary concentration part; as well as The final purification section includes a nitrogen circulation cooling component and a voltage-coupled temperature-variable purifier. The voltage-coupled temperature-variable purifier is connected to the permeate outlet of the secondary membrane separator and is used to output high-purity helium. The nitrogen circulation cooling component, the voltage-coupled temperature-variable purifier, and the low-temperature water separator form a cooling loop. The nitrogen circulation cooling component includes a nitrogen compressor, a nitrogen condenser and a liquid nitrogen buffer tank connected in sequence, the nitrogen compressor is connected to the low-temperature water separator, and the liquid nitrogen buffer tank is connected to the voltage-variable coupled temperature-variable purifier; The pressure-coupled temperature-variable purifier includes a circulation outlet, which is in communication with the primary concentration section and is used to output gas regenerated by the pressure-coupled temperature-variable purifier; The primary membrane separator comprises a non-permeate gas outlet for connection to a natural gas processing device.

2. The natural gas helium extraction device according to claim 1, characterized in that: Each of the dehydrogenation towers is configured to be opened and closed independently.

3. The natural gas helium extraction device according to claim 1, characterized in that: A regenerator is provided between the low-temperature water separator and the water remover. The regenerator receives the dehydrogenated gas flowing through the first preheater, outputs the gas flowing out of the low-temperature water separator, and enables the two parts of gas to undergo heat exchange.

4. The natural gas helium extraction device according to claim 1, characterized in that: A crude helium compressor is further provided between the water remover and the secondary membrane separator.

5. The natural gas helium extraction device according to claim 1, characterized in that: The final stage purification part also includes a high-purity helium heat exchanger connected to the voltage-variable coupled temperature-variable purifier.

6. A method for extracting helium from natural gas, characterized in that: Using the natural gas helium extraction device according to any one of claims 1 to 5, the method comprises the following steps: S1. Using a primary membrane separator to initially concentrate the input initial gas and perform initial methane separation; S2 dehydrogenation and dehydration of the gas obtained in S1, and the dehydrogenation of the gas after the initial gas input in step S1 is preheated and then dehydrated; S3 obtains in S2 dehydration gas secondary membrane separation; S4. The gas output from step S3 is cooled with nitrogen and subjected to low-temperature adsorption to remove impurities using a pressure-coupled temperature-variable purifier to obtain high-purity helium. Meanwhile, the nitrogen continues to cool the gas under dehydration treatment in step S2.

7. The method according to claim 6, wherein Returning the gas regenerated from the pressure-coupled temperature-switching purifier in step S4 to step S1 to recollect the helium, and / or The non-permeate gas generated during the secondary membrane separation in step S3 is returned to step S1 to collect helium again.

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