A liquefaction process for hydrogen purification and nitrogen replenishment in coke oven gas and co-production of LNG.

Abstract

This invention relates to a liquefaction process for hydrogen purification and nitrogen replenishment in coke oven gas and co-production of LNG, comprising the following steps: External coke oven gas undergoes preliminary filtration sequentially through an adsorption tower, a mercury removal tower, and a dust filter; the coke oven gas is then cooled in a main heat exchanger and subsequently passes through a primary separator, a secondary separator, and a dehydrogenation tower for distillation separation. The liquid obtained from the distillation separation is then heated by a subcooling heat exchanger and sent to a denitrification tower equipped with a condenser heat exchanger and a reboiler to obtain a cryogenic liquid and nitrogen-rich gas. The cryogenic liquid is depressurized and becomes LNG for storage; the hydrogen-rich gas obtained from the distillation separation is mixed with liquid nitrogen after heat exchange in a subcooling heat exchanger, and then reheated in the heat exchanger to become nitrogen-hydrogen gas before being discharged; the nitrogen-rich gas is also reheated before being discharged. This invention can efficiently treat coke oven gas to obtain LNG products and tail gas, nitrogen-hydrogen gas, and nitrogen-rich gas that meet emission standards. Simultaneously, by recycling regenerated gas, refrigerant, and nitrogen, it reduces energy waste and improves energy efficiency.

Description

Technical Field

[0001] This invention belongs to the field of coke oven gas treatment, specifically relating to a liquefaction process for hydrogen purification and nitrogen replenishment in coke oven gas and co-production of LNG. Background Technology

[0002] With the increasing stringent environmental protection requirements of the country, the clean utilization of coal resources has become a new development direction. Coke oven gas is a combustible gas produced during the high-temperature dry distillation of coal in a coking oven, along with the production of coke and coal tar. It is a byproduct of the coking industry. Coke oven gas is a mixture, and its yield and composition vary depending on the quality of the coal used for coking and the conditions of the coking process. Generally, 300-350 m³ of coke oven gas (standard conditions) can be produced per ton of dry coal. Its main components are hydrogen (55%-60%) and methane (23%-27%), and it also contains small amounts of carbon monoxide (5%-8%), C2+ unsaturated hydrocarbons (2%-4%), carbon dioxide (1.5%-3%), oxygen (0.3%-0.8%), and nitrogen (3%-7%). Among these, hydrogen, methane, carbon monoxide, and C2+ unsaturated hydrocarbons are combustible components, while carbon dioxide, nitrogen, and oxygen are non-combustible components. Existing methods for treating coke oven gas all involve methanation via hydrogenation during the process, converting carbon monoxide and carbon dioxide into methane and water. However, the methanated coke oven gas still contains trace amounts of CO, hydrogen, and residual methane (10-20 ppm), which not only poisons the ammonia synthesis catalyst but also cannot be directly discharged. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a liquefaction process for hydrogen purification and nitrogen replenishment in coke oven gas and co-production of LNG.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] A liquefaction process for hydrogen purification and nitrogen replenishment in coke oven gas and co-production of LNG includes the following steps:

[0006] S1. The external coke oven gas passes through an adsorption tower, a mercury removal tower and a dust filter arranged in parallel to complete the initial filtration.

[0007] S2. After the coke oven gas has completed the initial filtration, it is sent to the main heat exchanger for cooling and then sequentially passes through the primary separator, the secondary separator, and the dehydrogenation tower for distillation and separation.

[0008] S3. The liquid obtained from the distillation separation at the bottom of the primary separator, secondary separator, and dehydrogenation tower is sent to the denitrification tower equipped with a condenser heat exchanger and a reboiler after heat exchange through a subcooling heat exchanger to obtain cryogenic liquid and nitrogen-rich gas. The cryogenic liquid is depressurized and becomes LNG product for storage.

[0009] S4. The hydrogen-rich gas discharged from the top of the dehydrogenation tower is mixed with liquid nitrogen after being heated by a subcooling heat exchanger. It is then reheated in the heat exchanger to become nitrogen-hydrogen gas before being discharged.

[0010] S5. The nitrogen-rich gas is discharged after being reheated by passing through the subcooling heat exchanger and the main heat exchanger in sequence.

[0011] Furthermore, in step S1, a portion of the external coke oven gas is separated as regeneration gas before entering the adsorption towers set in parallel to regenerate the adsorbent in the adsorption towers.

[0012] Furthermore, the aforementioned regeneration includes the following steps:

[0013] S11. The regenerated gas enters the adsorption tower that needs to be regenerated through a programmable valve for cooling and purging;

[0014] S12. The purged coke oven gas enters the regenerated gas heater for heating;

[0015] S13. The heated coke oven gas is returned to the adsorption tower to regenerate the adsorbent.

[0016] S14. After the regenerated coke oven gas is reheated, it is remixed with external coke oven gas and introduced.

[0017] Furthermore, the liquid nitrogen in step S4 is supplied by a nitrogen compressor.

[0018] Furthermore, the aforementioned nitrogen compressor supply steps include:

[0019] S41. The low-pressure nitrogen gas from the outside is pressurized by the nitrogen compressor and sent into the main heat exchanger. In the main heat exchanger, it is cooled into liquid nitrogen. The liquid nitrogen is divided into two streams. One stream is sent into the subcooled heat exchanger, and the other stream is mixed with hydrogen-rich gas through a programmable valve.

[0020] S42. After passing through the subcooling heat exchanger, the liquid nitrogen is divided into two streams. One stream of liquid nitrogen is injected from the top of the dehydrogenation tower as the top reflux liquid of the dehydrogenation tower. It performs mass transfer and heat exchange with the rising coke oven gas in the dehydrogenation tower to wash and absorb the methane and CO in the coke oven gas.

[0021] S43. Another stream of liquid nitrogen, after being pressure-controlled by a process control valve, enters the condenser heat exchanger at the top of the denitrification tower and is used as a cold source;

[0022] S44. Liquid nitrogen discharged from the condenser heat exchanger passes through the subcooling heat exchanger and the main heat exchanger in sequence to be reheated before being sent back to the nitrogen compressor to form a cycle.

[0023] Furthermore, the aforementioned main heat exchanger is supplied with a cold source via a refrigerant compressor.

[0024] Furthermore, the aforementioned steps of providing a cold source using the refrigerant compressor include the following:

[0025] S61. The proportioned mixed refrigerant is sent to the refrigerant compressor for compression and cooling, and then transferred to the refrigerant separator tank;

[0026] S62. The cold liquid discharged from the bottom of the refrigerant separator enters the main heat exchanger to provide cooling capacity for heat exchange in the pre-cooling section of the main heat exchanger;

[0027] S63. The gas separated from the top of the refrigerant separator enters the main heat exchanger and is cooled into a liquid, providing cooling capacity to the cryogenic section of the main heat exchanger for heat exchange.

[0028] S64. The cold liquid in the first two steps is mixed and reheated in the main heat exchanger to form refrigerant, which is then sent back to the refrigerant compressor.

[0029] S65. After being compressed and cooled in the refrigerant compressor, the refrigerant is fed into the refrigerant separator tank.

[0030] Furthermore, in the aforementioned step S1, the coke oven gas purified by the dust filter enters the main heat exchanger for heat exchange and is then sent to the reboiler located at the bottom of the denitrification tower as the heat source required for the distillation of the denitrification tower. The heated coke oven gas returns from the reboiler to the main heat exchanger for cooling.

[0031] Compared with the prior art, the present invention has the following advantages and effects:

[0032] 1) It can efficiently process coke oven gas to obtain LNG products and tail gas, nitrogen-hydrogen gas, and nitrogen-rich gas that meet emission standards;

[0033] 2) The adoption of a recyclable system of regenerated gas, nitrogen, and refrigerant improves energy efficiency and avoids energy waste throughout the process. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the equipment using this liquefaction process in the embodiment.

[0035] Figure 2 This is an enlarged view of the front half of the structural schematic diagram of the equipment using this liquefaction process in the embodiment.

[0036] Figure 3 This is an enlarged view of the latter half of the structural schematic diagram of the equipment using this liquefaction process in the embodiment.

[0037] The accompanying drawings, which are provided to further understand this application and constitute a part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. Detailed Implementation

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0039] Example

[0040] The liquefaction process for hydrogen purification and nitrogen replenishment in coke oven gas and co-production of LNG includes the following:

[0041] S1. The external coke oven gas passes through an adsorption tower, a mercury removal tower, and a dust filter arranged in parallel to complete the initial filtration.

[0042] In step S1, a portion of the external coke oven gas is separated as regeneration gas before entering the parallel-connected adsorption towers to regenerate the adsorbent inside the towers. This regeneration process includes the following steps:

[0043] S11. The regenerated gas enters the adsorption tower that needs to be regenerated through a programmable valve for cooling and purging;

[0044] S12. The purged coke oven gas enters the regenerated gas heater for heating;

[0045] S13. The heated coke oven gas is returned to the adsorption tower to regenerate the adsorbent.

[0046] S14. After the regenerated coke oven gas is reheated, it is remixed with external coke oven gas and introduced.

[0047] S2. After the coke oven gas has completed the initial filtration, it is sent to the main heat exchanger for cooling and then sequentially passes through the primary separator, the secondary separator, and the dehydrogenation tower for distillation and separation.

[0048] S3. The liquid obtained from the distillation separation at the bottom of the primary separator, secondary separator, and dehydrogenation tower is sent to the denitrification tower equipped with a condenser heat exchanger and a reboiler after heat exchange through a subcooling heat exchanger to obtain cryogenic liquid and nitrogen-rich gas. The cryogenic liquid is depressurized and becomes LNG product for storage.

[0049] In step S1, the coke oven gas purified by the dust filter enters the main heat exchanger for heat exchange and is then sent to the reboiler located at the bottom of the denitrification tower as the heat source required for the distillation of the denitrification tower. The heated coke oven gas returns from the reboiler to the main heat exchanger for cooling.

[0050] S4. The hydrogen-rich gas discharged from the top of the dehydrogenation tower is mixed with liquid nitrogen after heat exchange in a subcooling heat exchanger. It is then reheated in the heat exchanger to become nitrogen-hydrogen gas before being discharged.

[0051] The liquid nitrogen in step S4 is supplied by a nitrogen compressor. The nitrogen compressor supply steps include:

[0052] S41. The low-pressure nitrogen gas from the outside is pressurized by the nitrogen compressor and sent into the main heat exchanger. In the main heat exchanger, it is cooled into liquid nitrogen. The liquid nitrogen is divided into two streams. One stream is sent into the subcooled heat exchanger, and the other stream is mixed with hydrogen-rich gas through a programmable valve.

[0053] S42. After passing through the subcooling heat exchanger, the liquid nitrogen is divided into two streams. One stream of liquid nitrogen is injected from the top of the dehydrogenation tower as the top reflux liquid of the dehydrogenation tower. It performs mass transfer and heat exchange with the rising coke oven gas in the dehydrogenation tower to wash and absorb the methane and CO in the coke oven gas.

[0054] S43. Another stream of liquid nitrogen, after being pressure-controlled by a process control valve, enters the condenser heat exchanger at the top of the denitrification tower and is used as a cold source;

[0055] S44. Liquid nitrogen discharged from the condenser heat exchanger passes through the subcooling heat exchanger and the main heat exchanger in sequence to be reheated before being sent back to the nitrogen compressor to form a cycle.

[0056] S5. The nitrogen-rich gas is discharged after being reheated by passing through the subcooling heat exchanger and the main heat exchanger in sequence.

[0057] In the above process, the main heat exchangers all use a refrigerant compressor to provide the cold source. The steps for the refrigerant compressor to provide the cold source include the following:

[0058] S61. The proportioned mixed refrigerant is sent to the refrigerant compressor for compression and cooling, and then transferred to the refrigerant separator tank;

[0059] S62. The cold liquid discharged from the bottom of the refrigerant separator enters the main heat exchanger to provide cooling capacity for heat exchange in the pre-cooling section of the main heat exchanger;

[0060] S63. The gas separated from the top of the refrigerant separator enters the main heat exchanger and is cooled into a liquid, providing cooling capacity to the cryogenic section of the main heat exchanger for heat exchange.

[0061] S64. The cold liquid in the first two steps is mixed and reheated in the main heat exchanger to form refrigerant, which is then sent back to the refrigerant compressor.

[0062] S65. After being compressed and cooled in the refrigerant compressor, the refrigerant is fed into the refrigerant separator tank.

[0063] For ease of understanding, the following describes an equipment structure employing the aforementioned liquefaction process for hydrogen purification and nitrogen replenishment in coke oven gas and co-production of LNG, such as... Figures 1-3 As shown.

[0064] The equipment consists of a preliminary purification unit and a deep purification unit. The preliminary purification unit is used to perform preliminary purification of coke oven gas, removing trace amounts of water, carbon dioxide, trace amounts of mercury, and large particulate dust. This preliminary purification unit includes an inlet pipe 51, adsorption towers 1, 2, and 3 arranged in parallel, a regenerated gas heater 4, a regenerated gas cooler 5, a regenerated gas heat exchanger 6, a cooling unit 7, a regenerated gas separator 8, a mercury removal tower 9, and a dust filter 10. The inlet pipe 51 is connected to the inlets of adsorption tower 1, adsorption tower 2 and adsorption tower 3 respectively. The outlets of adsorption tower 1, adsorption tower 2 and adsorption tower 3 are connected to the inlet of mercury removal tower 9 through connecting pipe 53. The outlet of mercury removal tower 9 is connected to the inlet of dust filter 10. A programmable valve 21 is installed on the inlet pipe 51. Programmable valves 22, 23 and 24 are respectively installed between programmable valve 21 and the inlets of adsorption tower 1, adsorption tower 2 and adsorption tower 3. Programmable valves 25, 26 and 27 are respectively installed between pipe 53 and the inlets of adsorption tower 1, adsorption tower 2 and adsorption tower 3. Specifically, the workflow of the preliminary purification unit includes: after the coke oven gas from the external system enters the preliminary purification unit, it first passes through the inlet pipe 51 and then the pressure is controlled by the programmable valve 21. After that, it enters the corresponding adsorption tower 1, adsorption tower 2, or adsorption tower 3 through the programmable valve 22, programmable valve 23, or programmable valve 24. The adsorption tower 1, adsorption tower 2, or adsorption tower 3 can remove trace amounts of water and carbon dioxide from the coke oven gas. After the purified coke oven gas is discharged from the adsorption tower 1, adsorption tower 2, or adsorption tower 3, it is output to the pipe 53 through the corresponding programmable valve 25, programmable valve 26, or programmable valve 27. It is then sent to the mercury removal tower 9 through the pipe 53 to remove the trace amounts of mercury contained in the coke oven gas. After the mercury removal, the coke oven gas is sent from the mercury removal tower 9 through the pipe 54 to the dust filter 10 to filter out the dust in the coke oven gas, thus obtaining the coke oven gas that has completed the preliminary purification.

[0065] like Figure 1As shown, in the preliminary purification unit, the air inlet pipe 51 is also connected to the air inlets of adsorption tower 1, adsorption tower 2, and adsorption tower 3 via pipe 56. The air outlets of adsorption tower 1, adsorption tower 2, and adsorption tower 3 are also connected to pipes 57 and 58, respectively. The other end of pipe 57 is connected to the inlet of regeneration gas heater 4, and the other end of pipe 58 is connected to the outlet of regeneration gas heater 4. The air inlets of adsorption tower 1, adsorption tower 2, and adsorption tower 3 are also connected to pipe 59, the other end of which is connected to regeneration gas cooler 5. Regeneration gas cooler 5, one heat exchange pipe of regeneration gas heat exchanger 6, air conditioning unit 7, and air inlet of regeneration gas separator 8 are connected in sequence. The top outlet of regeneration gas separator 8 is connected to another heat exchange pipe of regeneration gas heat exchanger 6, which is connected to air inlet pipe 51 via pipe 65. The bottom outlet of regeneration gas separator 8 is connected to sewage pipe 63. Programmable valves 28, 29, and 30 are respectively installed between pipe 56 and the inlets of adsorption towers 1, 2, and 3. Programmable valves 31, 32, and 33 are respectively installed between the outlets of adsorption towers 1, 2, and 3 and pipe 57. Programmable valves 34, 35, and 36 are respectively installed between the outlets of adsorption towers 1, 2, and 3 and pipe 58. Programmable valves 37, 38, and 39 are respectively installed between the inlets of adsorption towers 1, 2, and 3 and pipe 59. Programmable valve 34 is installed between the regeneration gas separator 8 and sewage pipe 63. These structures are used for regenerating the adsorbent in the adsorption towers during non-operational periods in the preliminary purification mechanism. In this embodiment, one operating state is selected for description. In actual use, the operating state is not limited to the following description: When the adsorption tower 2 needs to be regenerated, the programmable valve 23 and programmable valve 26 are closed. A portion of the coke oven gas from the external system will be separated at the inlet pipe 51 and directly enter the adsorption tower 2 through the pipe 56 and programmable valve 29 for cooling and purging. The purged coke oven gas will enter the regeneration gas heater 4 through the programmable valve 32 for heating. The heated coke oven gas will be introduced into the adsorption tower through the programmable valve 35. The adsorbent is heated and regenerated inside tower 2. After the regeneration is completed, the coke oven gas passes through pipeline 59 and then through regeneration gas heat exchanger 6 and cooling unit 7 for further cooling. After being cooled to 5°C, it enters regeneration gas separator 8. Wastewater containing carbon dioxide is separated from the bottom of regeneration gas separator 9. This wastewater is discharged through sewage pipeline 63 via programmable valve 34. The gas discharged from the top of regeneration gas separator 8 is reheated to room temperature through regeneration gas heat exchanger 6 and then sent back to inlet pipeline 51 through pipeline 65, realizing the recycling of coke oven gas in the regeneration gas section.

[0066] like Figure 1As shown, the deep purification unit is used to further process the pre-purified coke oven gas to obtain LNG products and water and gas that meet emission standards. The deep purification system includes a main heat exchanger 11, a subcooling heat exchanger 12, a primary separator 13, a secondary separator 14, a reflux tank 15, a dehydrogenation tower 16, a denitrification tower 17, a nitrogen compressor 20, a nitrogen pipeline 78, an LNG storage tank 98, a tail gas pipeline 96, and a nitrogen-hydrogen pipeline 93. The main heat exchanger 11 contains heat exchange pipelines 11A, 11B, 11C, 11D, 11E, and 11H. The subcooling heat exchanger 12 contains subcooling pipelines 12A, 12B, 12C, 12D, 12E, and 12F. The denitrification tower 17 contains a condenser heat exchanger 99 and a reboiler 12. The dust filter 10 has an outlet, heat exchange pipeline 11E, and a primary... The air inlet of separator 13 is connected in sequence to the top outlet of primary separator 13, subcooling pipe 12E, and the air inlet of secondary separator 14. The top outlet of secondary separator 14 is connected to the air inlet of dehydrogenation tower 16. Nitrogen pipe 78, nitrogen compressor 20, and heat exchange pipe 11D are connected in sequence. Heat exchange pipe 11D and subcooling pipe 12D are connected via connecting pipe 81. Subcooling pipe 12D is connected to the air inlet of dehydrogenation tower 16 via connecting pipe 84. The bottom liquid outlet of primary separator 13, the bottom liquid outlet of secondary separator 14, and the bottom liquid outlet of dehydrogenation tower 16 are connected to one end of subcooling pipe 12F. The other end of subcooling pipe 12F is connected to the inlet of denitrification tower 17. The bottom liquid outlet of denitrification tower 17, heat exchange pipe 11H, and LNG storage tank 98 are connected in sequence. The top outlet of the denitrification tower 17, the reflux tank 15, the subcooling pipe 12A, the heat exchange pipe 11A, and the tail gas pipe 96 are connected in sequence; the top outlet of the dehydrogenation tower 16, the subcooling pipe 12C, the heat exchange pipe 11C, and the nitrogen-hydrogen pipe 93 are connected in sequence; the connecting pipe 84 is connected to one end of the condensing heat exchanger 99 via the connecting pipe 86, and the other end of the condensing heat exchanger 99, the subcooling pipe 12B, and the heat exchange pipe 11B are connected in sequence, with the other end of the heat exchange pipe 11B connected to the nitrogen pipe 78 via the connecting pipe 89. A circulation pipe 70 is connected in the middle of the heat exchange pipe 11E, and the circulation pipe 70 is connected to the reboiler 12. The connecting pipe 81 and the heat exchange pipe 11C are connected via the connecting pipe 82, and a programmable valve 41 is installed on the connecting pipe 82. A programmable valve 40 is installed between heat exchange pipeline 11H and LNG storage tank 98; a programmable valve 37 is installed between primary separator 13 and pipeline 12F; a programmable valve 38 is installed between secondary separator 14 and pipeline 12F; a programmable valve 39 is installed between dehydrogenation tower 16 and pipeline 12F; a programmable valve 43 is installed between reflux tank 15 and subcooling pipeline 12A; and a programmable valve 42 is installed between connecting pipeline 86 and condensing heat exchanger 99.The workflow of this deep purification mechanism includes: the pre-purified coke oven gas discharged through the outlet of the dust filter 10 enters the main heat exchanger 11 for heat exchange and cooling, and then is sent to the reboiler 12 located at the bottom of the denitrification tower 17. This coke oven gas can provide the heat source required for the distillation of the denitrification tower 17. The coke oven gas sent from the reboiler 12 returns to the main heat exchanger 11 for further cooling and then enters the primary separator 13. The gas discharged from the top of the primary separator 13 enters the subcooling heat exchanger 12, and after further cooling, enters the secondary separator 14. The gas discharged from the top of the secondary separator 14 enters the dehydrogenation tower 16 for distillation separation. The liquid discharged from the bottom of the dehydrogenation tower 16 is sent to the subcooling heat exchanger 12 after the pressure is controlled by the process control valve 39. The liquid discharged from the bottom of the secondary separator 14 is sent to the subcooling heat exchanger 12F via the subcooling pipe 12F. The liquid discharged from the bottom of the primary separator 13 is also sent to the subcooling heat exchanger 12F via the subcooling pipe 12F, after the pressure is controlled by the process control valve 37. After being reheated in the subcooling heat exchanger 12, the liquid is then discharged into the denitrification tower 17 for distillation to separate impurities such as nitrogen and CO. On one hand, the liquid discharged from the bottom of the denitrification tower 17 enters the main heat exchanger 11, where it is cooled to a cryogenic liquid. This cryogenic liquid is then depressurized by the control valve 40 and stored as LNG in the LNG storage tank 98. On the other hand, the nitrogen-rich gas discharged from the top of the denitrification tower 17 passes through the reflux tank 15. After pressure control via programmable valve 43, the nitrogen-rich gas is sent to subcooling heat exchanger 12 for reheating. The reheated nitrogen-rich gas is further reheated via main heat exchanger 11, and then discharged to the outside via tail gas pipe 96. Low-pressure nitrogen is introduced via nitrogen pipe 78, and after being pressurized by nitrogen compressor 20, it enters main heat exchanger 11, where it is cooled into liquid nitrogen. The liquid nitrogen enters subcooling heat exchanger 12 via pipe 81. The liquid nitrogen exiting subcooling heat exchanger 12 is divided into two streams. One stream is sprayed from the top of dehydrogenation tower 16 via connecting pipe 84, serving as the top reflux liquid of dehydrogenation tower 16. This liquid nitrogen undergoes mass transfer and heat exchange with the rising coke oven gas inside dehydrogenation tower 16, washing and absorbing methane and CO from the coke oven gas, resulting in a liquid stream exiting dehydrogenation tower 16. The liquid discharged from the bottom of column 6 is methane liquid containing nitrogen and CO; another stream of liquid nitrogen enters the top of denitrification tower 17 through connecting pipe 86 and pressure controlled by process control valve 42, serving as the cold source for the top condenser heat exchanger 99 of denitrification tower 17. After being discharged from condenser heat exchanger 99, this liquid nitrogen passes through subcooler heat exchanger 12 and main heat exchanger 11 in sequence for reheating before being sent back to nitrogen pipeline 78 to complete nitrogen circulation; while the liquid discharged from the top of dehydrogenation tower 16 is hydrogen-rich gas. The methane and CO content in the hydrogen-rich gas can be controlled by the injection rate through connecting pipe 84. This hydrogen-rich gas is sent to subcooler heat exchanger 12, serving as the cold source for heat exchange, and then introduced into main heat exchanger 11 for mixing and reheating to become nitrogen-hydrogen gas before being discharged from nitrogen-hydrogen pipeline 93.The programmed valve 41 is used to adjust the ratio of nitrogen to hydrogen in the nitrogen-hydrogen gas discharged from the nitrogen-hydrogen pipeline 93. Liquid nitrogen can be mixed into the hydrogen-rich gas through the programmed valve 41 to make the nitrogen-hydrogen ratio 1:3.

[0067] like Figure 1 As shown, the deep purification mechanism also includes a refrigerant compressor 19 and a refrigerant separator 18. The main heat exchanger 11 is also equipped with heat exchange pipes 11F, 11G, and 11I. The outlet of the refrigerant compressor 19 is connected to the inlet of the refrigerant separator 18. The top outlet of the refrigerant separator 18, heat exchange pipes 11G and 11F, and the inlet of the refrigerant compressor 19 are connected in sequence. The bottom outlet of the refrigerant separator 18, heat exchange pipes 11I and 11F are connected in sequence. A programmable valve 361 is installed between heat exchange pipes 11G and 11F, and a programmable valve 351 is installed between heat exchange pipes 11I and 11F. The aforementioned structures serve as the cold source for the main heat exchanger 11. Specifically, the workflow of these structures is as follows: the proportioned mixed refrigerant is fed into the refrigerant compressor 19 for compression and cooling. The compressed high-pressure refrigerant enters the refrigerant separator 18. The liquid discharged from the bottom of the refrigerant separator 18 enters the heat exchange pipe 11I in the main heat exchanger 11. After being pre-cooled to a certain temperature in the main heat exchanger 11, it is throttled and depressurized by the process control valve 35 and then sent back into the main heat exchanger 11 to provide cooling capacity for the pre-cooling section of the main heat exchanger 11 for heat exchange. The top of the refrigerant separator 18... Part of the separated gas enters the main heat exchanger 11, where it is cooled and liquefied within the heat exchange pipe 11G. The refrigerant exiting the main heat exchanger 11 is throttled and depressurized by the process control valve 36, then returns to the heat exchange pipe 11F within the main heat exchanger 11 to provide cooling for the cryogenic section of the main heat exchanger 11. Inside the main heat exchanger 11, it mixes with the refrigerant passing through the process control valve 35. The mixed refrigerant then provides cooling for the pre-cooling section of the heat exchanger before being discharged. The reheated refrigerant is then sent back to the refrigerant compressor 19, achieving refrigerant cycle compression and refrigeration. In this embodiment, the aforementioned mixed refrigerant consists of methane, ethylene, propane, isopentane, and nitrogen, and the refrigerant compressor 19 is a centrifugal compressor.

[0068] The above description is merely illustrative of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not depart from the content of this specification or exceed the scope defined by the claims, all of which should fall within the protection scope of this invention.

Claims

1. A liquefaction process for cogeneration of hydrogen purification and nitrogen make-up in coke oven gas and LNG, characterized in that, The method comprises the following steps: S1. External coke oven gas is sequentially filtered by an adsorption tower, a mercury removal tower and a dust filter in parallel; S2. The coke oven gas filtered in step S1 is sent into a main heat exchanger, cooled and then sequentially passed through a first separator, a second separator and a dehydrogenation tower for rectification and separation; S3. The liquid obtained from the first separator, the second separator and the bottom of the dehydrogenation tower is sent into a de-nitrogenation tower provided with a condensing heat exchanger and a reboiler after heat exchange in a supercooling heat exchanger, to obtain low-temperature liquid and nitrogen-rich gas, and the low-temperature liquid is depressurized to become LNG product for storage; S4. The hydrogen-rich gas discharged from the top of the dehydrogenation tower is mixed with liquid nitrogen after heat exchange in the supercooling heat exchanger, and is rewarmed in the heat exchanger to become nitrogen-hydrogen gas and is then discharged; S5. The nitrogen-rich gas is sequentially rewarmed by the supercooling heat exchanger and the main heat exchanger and then discharged.

2. The process for co-production of LNG and nitrogen by hydrogen purification and make-up in coke oven gas according to claim 1, characterized in that: In step S1, a part of the external coke oven gas is separated as regeneration gas to regenerate the adsorbent in the adsorption tower before entering the adsorption tower.

3. The process for co-production of LNG and nitrogen from coke oven gas according to claim 2, wherein, The regeneration comprises the following steps: S11. The regeneration gas is introduced into the adsorption tower to be regenerated through a process control valve for cooling and purging; S12. The coke oven gas after purging is heated in a regeneration gas heater; S13. The heated coke oven gas is returned to the adsorption tower to heat and regenerate the adsorbent; S14. The coke oven gas after regeneration is rewarmed and mixed with the external coke oven gas for introduction.

4. The process for co-production of LNG and nitrogen by hydrogen purification and make-up in a coke oven gas according to claim 1, characterized in that: The liquid nitrogen in step S4 is provided by a nitrogen compressor.

5. The process for co-production of LNG and nitrogen by hydrogen purification and make-up in a coke oven gas according to claim 4, characterized in that, The gas supply step of the nitrogen compressor comprises: S41. The external low-pressure nitrogen gas is pressurized by the nitrogen compressor and then sent into the main heat exchanger to be cooled into liquid nitrogen, and the liquid nitrogen is divided into two parts, one of which is sent into the supercooling heat exchanger, and the other is mixed with the hydrogen-rich gas through a process control valve; S42. The liquid nitrogen after the supercooling heat exchanger is divided into two parts, one of which is sprayed into the top of the dehydrogenation tower as the top reflux liquid of the dehydrogenation tower, and the other is introduced into the condensing heat exchanger at the top of the de-nitrogenation tower as a cold source; S43. The liquid nitrogen discharged from the condensing heat exchanger is sequentially rewarmed by the supercooling heat exchanger and the main heat exchanger and then sent back to the nitrogen compressor to form a cycle; The main heat exchanger is provided with a cold source by a refrigerant compressor.

6. The process for co-production of LNG and nitrogen by hydrogen purification and make-up in a coke oven gas according to claim 1, characterized in that: The cold source providing step of the refrigerant compressor comprises the following steps:

7. The process for co-production of LNG and nitrogen from coke oven gas according to claim 6, wherein, S61. The mixed refrigerant with a proper ratio is sent into the refrigerant compressor for compression and cooling, and then into a refrigerant separation tank; S62. The cold liquid discharged from the bottom of the refrigerant separation tank is introduced into the main heat exchanger to provide cold energy for the pre-cooling section of the main heat exchanger for heat exchange; S63. The gas separated from the top of the refrigerant separation tank is introduced into the main heat exchanger to be cooled into liquid, which provides cold energy for the deep cooling section of the main heat exchanger for heat exchange; S64. The cold liquid in the previous two steps is mixed and rewarmed in the main heat exchanger to form refrigerant which is sent back to the refrigerant compressor again; S65. The refrigerant is compressed and cooled in the refrigerant compressor and then input into the refrigerant separation tank. ​ 8. The process for co-production of LNG and nitrogen from coke oven gas according to claim 1, wherein: In step S1, the coke oven gas purified by the dust filter enters the main heat exchanger for heat exchange, and then enters the reboiler at the bottom of the denitration tower as a heat source required for the rectification of the denitration tower. The heated coke oven gas returns to the main heat exchanger for cooling.

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