System for preparing natural gas from coke oven gas
By designing a coke oven gas-made natural gas system including multi-stage purification and liquefaction devices, the problem of insufficient area of the cold box design heat exchanger is solved, the methane content in liquefied natural gas is improved, the nitrogen content is reduced, the product quality is improved, and energy consumption is reduced.
Patent Information
- Application Number
- CN202420508769.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-15
- Publication Date
- 2025-03-04
- Estimated Expiration
- 2034-03-15
AI Technical Summary
In the existing coke oven gas-made liquefied natural gas system, the area of the cold box designed heat exchanger is insufficient, resulting in excessive methane content in nitrogen-rich gas and the nitrogen content in liquefied natural gas exceeding 1%, affecting product quality.
A coke oven gas-making natural gas system including raw gas compressor, purification device, synthesizer, synthesis device, liquefaction purification device, liquefaction device, LNG storage tank, BOG gasifier and blower was designed. By optimizing the purification and liquefaction process, the heat exchange efficiency of the cold box is improved and the nitrogen content in the liquefied natural gas is reduced.
It has achieved the improvement of methane content in liquefied natural gas, reduced nitrogen content in liquefied natural gas, improved product quality, and reduced energy consumption, ensuring that the CH4 content in LNG exceeds 99%, the methane content in nitrogen-rich gas is low, the nitrogen content is less than 1%, and the methane recovery rate reaches more than 98%.
Smart Images
Figure CN222556889U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of preparing liquefied natural gas, in particular to a system for preparing natural gas from coke oven gas. Background Art
[0002] In the prior art, the area of all heat exchangers in the cold box design of the coke oven gas to natural gas system is designed according to the nitrogen component in the preliminary design, which will result in insufficient heat exchange area of the cold box, and more methane will be taken away in the nitrogen-rich gas (resulting in a CH4 content of >2% in the nitrogen-rich gas). If the methane content in the nitrogen-rich gas is to be reduced, the evaporation rate of the reboiler at the bottom of the low-pressure tower needs to be reduced, resulting in a N2 content of >1% in the LNG coming out of the tower bottom. If the CH4 content in the LNG is to be >99%, the heat exchange area of the low-pressure tower needs to be increased. In fact, due to the insufficient heat exchange area of the low-pressure tower, the cooling capacity of the nitrogen-rich gas at the top of the tower is insufficient, and methane cannot be condensed, resulting in a methane content of >1% in the nitrogen-rich gas.
[0003] The existing coke oven gas to liquefied natural gas system has the problem that the nitrogen content of the coke oven gas components in actual operation is higher than the designed coke oven gas components. The high nitrogen content in the coke oven gas will directly lead to a high nitrogen content in the liquefied natural gas, making the methane (CH4) in the liquefied natural gas less than 99mol% and the nitrogen (N2) greater than 1mol%, while at the same time making the methane content in the nitrogen-rich gas between 1% and 2mol%. Utility Model Content
[0004] The technical problem to be solved by the utility model is to provide a natural gas production system of coke oven gas with high LNG product quality.
[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is: it includes a raw gas compressor, a purification device, a synthesis gas compressor, a synthesis device, a liquefaction purification device, a liquefaction device, an LNG storage tank, a BOG gasifier and a blower; the inlet of the raw gas compressor is connected to the coke oven gas pipeline, and the outlet of the raw gas compressor is connected to the purification device and the synthesis gas compressor and then connected to the inlet of the synthesis device; the outlet of the synthesis device is connected to the inlet of the liquefaction device, and the liquefied natural gas outlet of the liquefaction device is connected to the inlet of the LNG storage tank; the gas phase outlet at the top of the LNG storage tank is connected to the inlet of the BOG gasifier, and the outlet of the BOG gasifier is connected to the nitrogen-rich gas pipeline through a blower.
[0006] Furthermore, the purification device includes a 1# purification device and a 2# purification device; the 1# purification device and the 2# purification device are respectively connected to the inlet and outlet ends of the synthesis gas compressor.
[0007] Furthermore, the liquefaction device includes a refrigerant compressor and a cold box.
[0008] Furthermore, the hydrogen-rich gas outlet of the cold box is connected to the hydrogen-rich gas pipeline, and the nitrogen-rich gas outlet is connected to the nitrogen-rich gas pipeline.
[0009] The beneficial effects of adopting the above technical solution are: the utility model can improve the problem that the components of coke oven gas under the actual working conditions of producing liquefied natural gas from coke oven gas are inconsistent with the components of coke oven gas in the original design, increase the content of methane components in liquefied natural gas, reduce the content of nitrogen components in liquefied natural gas, and generally improve the quality of liquefied natural gas, while making the methane content in nitrogen-rich gas lower. The utility model also has the characteristics of low energy consumption, high LNG product quality, CH4 content in LNG> 99%, low methane content in nitrogen-rich gas, N2 content < 1%, and methane recovery rate ≥ 98%. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The utility model is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0011] Figure 1 It is a structural schematic diagram of the utility model.
[0012] In the figure: raw gas compressor 1, 1# purification device 2, synthesis gas compressor 3, 2# purification device 4, synthesis device 5, liquefaction purification device 6, refrigerant compressor 7, cold box 8, LNG storage tank 9, BOG gasifier 10, blower 11, hydrogen-rich gas pipeline 12, nitrogen-rich gas pipeline 13. DETAILED DESCRIPTION
[0013] Figure 1 As shown, the coke oven gas to natural gas system comprises a raw gas compressor 1, a purification device, a synthesis gas compressor 3, a synthesis device 5, a liquefaction purification device 6, a liquefaction device, an LNG storage tank 9, a BOG gasifier 10 and a blower 11. The purification device comprises a 1# purification device 2 and a 2# purification device 4, and the liquefaction device comprises a refrigerant compressor 7 and a cold box 8. The inlet of the raw gas compressor 1 is connected to the coke oven gas pipeline, and the outlet of the raw gas compressor 1 is connected to the 1# purification device 2, the synthesis gas compressor 3 and the 2# purification device 4 in sequence, and then connected to the inlet of the synthesis device 5. The outlet of the synthesis device 5 is connected to the inlet of the liquefaction device, and the liquefied natural gas outlet of the liquefaction device is connected to the inlet of the LNG storage tank 9; the gas phase outlet at the top of the LNG storage tank 9 is connected to the inlet of the BOG gasifier 10, and the outlet of the BOG gasifier 10 is connected to the nitrogen-rich gas pipeline 13 through the blower 11; the hydrogen-rich gas outlet of the cold box 8 is connected to the hydrogen-rich gas pipeline 12, and the nitrogen-rich gas outlet is connected to the nitrogen-rich gas pipeline 13. The blower 11 is preferably a Roots blower.
[0014] The cold box is equipped with refrigeration heat exchanger A, refrigeration heat exchanger B, high pressure tower, low pressure tower, and low pressure tower matching reboiler. Conventional system, due to the actual coke oven gas components change - become larger, and when SNG is liquefied into LNG, the heat exchange area inside the cold box can no longer be changed, which will lead to N2 content in LNG> 1mol% and CH4 content in nitrogen-rich gas> 1mol%; this system is not a conventional coke oven gas to natural gas system, and there is no need to change the heat exchange area inside the cold box, that is, it can solve the problem of high nitrogen content in the coke oven gas components.
[0015] Figure 1 As shown in the figure, the use process of the coke oven gas to natural gas system is:
[0016] a. The coke oven gas is pressurized from 4 to 6 kPa to 0.45 MPa by the raw gas compressor 1, and then the tar, naphthalene and hydrogen sulfide in the coke oven gas are removed by the 1# purification device 2;
[0017] b. The synthesis gas is then pressurized to 2.45 MPa by the synthesis gas compressor 3, and the organic sulfur in the coke oven gas is converted into inorganic sulfur-hydrogen sulfide and removed to form purified gas by the 2# purification device 4;
[0018] c. The purified gas is methanized by the synthesis device 5 to become product gas, and then passes through the liquefaction purification device 6 to remove ammonia, mercury and saturated water from the product gas;
[0019] d. The product gas is liquefied into liquefied natural gas through the refrigerant compressor 7 and the cold box 8 and enters the LNG storage tank 9;
[0020] e. The gas phase components at the top of the LNG storage tank 9 are mainly methane and nitrogen. The gas phase becomes flash gas after being reheated by the BOG gasifier 10, and is pressurized by the blower 11 and transported to the nitrogen-rich gas pipeline 13; the temperature of the flash gas after being reheated by the BOG gasifier 10 is room temperature; the flow rate of the blower 11 should correspond to the maximum volume generated by the LNG storage tank 9 (this volume corresponds to the pressure of the LNG storage tank 9), that is, it corresponds to the minimum liquid level of the LNG storage tank 9 and the pressure of the LNG storage tank 9 reaches the tripping pressure of the safety valve.
[0021] f. The gas coming out of the cold box 8 includes nitrogen-rich gas 12 and hydrogen-rich gas 13. The pressure of the hydrogen-rich gas is 1.55 MPa, which is reduced to 8-10 kPa by a pressure reducing device and then delivered to other coking users through the hydrogen-rich gas pipeline 12 and the nitrogen-rich gas pipeline 13 respectively.
Claims
1. A system for producing natural gas from coke oven gas, characterized in that: The invention comprises a raw gas compressor (1), a purification device, a synthesis gas compressor (3), a synthesis device (5), a liquefaction purification device (6), a liquefaction device, an LNG storage tank (9), a BOG gasifier (10) and a blower (11); the inlet of the raw gas compressor (1) is connected to a coke oven gas pipeline, the outlet of the raw gas compressor (1) is connected to the purification device and the synthesis gas compressor (3) and then to the inlet of the synthesis device (5); the outlet of the synthesis device (5) is connected to the inlet of the liquefaction device, and the liquefied natural gas outlet of the liquefaction device is connected to the inlet of the LNG storage tank (9); the gas phase outlet at the top of the LNG storage tank (9) is connected to the inlet of the BOG gasifier (10), and the outlet of the BOG gasifier (10) is connected to a nitrogen-rich gas pipeline (13) through a blower (11).
2. A system for producing natural gas from coke oven gas according to claim 1, characterized in that: The purification device comprises a 1# purification device (2) and a 2# purification device (4); the 1# purification device (2) and the 2# purification device (4) are respectively connected to the inlet and outlet ends of the synthesis gas compressor (3).
3. A system for producing natural gas from coke oven gas according to claim 1 or 2, characterized in that: The liquefaction device comprises a refrigerant compressor (7) and a cold box (8).
4. A system for producing natural gas from coke oven gas according to claim 3, characterized in that: The hydrogen-rich gas outlet of the cold box (8) is connected to a hydrogen-rich gas pipeline (12), and the nitrogen-rich gas outlet is connected to a nitrogen-rich gas pipeline (13).