System for synthesizing methane from coke oven gas with high carbon hydrogen ratio

Abstract

The utility model provides a system for synthesizing methane from coke oven gas with a high carbon-hydrogen ratio. The system comprises a deep purification unit and a methanation unit, the methanation unit is provided with three stages of methanation reactors; the deep purification unit is connected with a first-stage methanation reactor, the first-stage methanation reactor is connected with a second-stage methanation reactor through a first waste heat boiler, the second-stage methanation reactor sequentially passes through a second waste heat boiler, a coke oven gas preheater and a recycle gas heat exchanger, and the first heat exchanger is connected with a first gas-liquid separator; the first gas-liquid separator is connected with the three-stage methanation reactor through a branch via an inlet and outlet heat exchanger, and is connected with the first-stage methanation reactor through another branch via a recycle gas compressor and a recycle gas heat exchanger in sequence; and a gas outlet of the third-stage methanation reactor is connected to the ammonia washing tower through a second heat exchanger and a second gas-liquid separator for heat exchange at an inlet and an outlet. The system disclosed by the utility model is low in investment, low in energy consumption and low in total content of oxycarbide in a synthesized methane product.

Description

Technical Field

[0001] This utility model relates to the field of industrial methane synthesis, specifically to a system for synthesizing methane from coke oven gas with a high carbon-to-hydrogen ratio. Background Technology

[0002] my country's energy structure is dominated by coal, with oil and natural gas accounting for a relatively small proportion, far below the world average. Natural gas, as a clean energy source, is seeing its market consumption increase year by year, making the entire industry's prospects quite promising.

[0003] Coke oven gas, a combustible gas byproduct produced during coal coking, has seen strong growth in unconventional natural gas projects due to its relatively low cost in LNG production. However, the current global economic climate and the shift in the coal coking industry from incremental market competition to existing market competition necessitate refined management, optimized coal blending technologies, and cost reduction by coking enterprises. This has resulted in higher carbon content and relatively lower hydrogen content in commercially available coke oven gas, leading to a higher carbon-to-hydrogen ratio (high carbon-to-hydrogen ratio coke oven gas) compared to traditional coke oven gas. Traditional coke oven gas contains 8%–12% CO and CO2, while high carbon-to-hydrogen ratio coke oven gas contains over 12%, typically reaching 12%–16%. The methanation reaction of high carbon-to-hydrogen ratio coke oven gas generates more heat and requires more hydrogen. Furthermore, due to the excessive heat release, the circulating gas volume needs to be increased to protect the catalyst and lower the reactor temperature, which in turn increases the system's energy consumption. In addition, when methanating high C / H ratio coke oven gas, in order to ensure that the total CO and CO2 content entering the cryogenic separation unit is less than 50 ppm and increase the product yield, more equipment is required, resulting in higher investment costs.

[0004] Therefore, it is of great significance to provide a system for synthesizing methane from coke oven gas with a high carbon-to-hydrogen ratio, which requires less investment, has low overall energy consumption, and high product yield, in order to produce high methane content gas with a total CO and CO2 content of less than 50 ppm. Utility Model Content

[0005] To solve the above-mentioned technical problems, this utility model provides a system for synthesizing methane from coke oven gas with a high carbon-to-hydrogen ratio. It has the advantages of low investment, low overall energy consumption, and high product yield. The total CO and CO2 content in the obtained high methane gas is less than 50 ppm.

[0006] This utility model provides a system for synthesizing methane from high carbon-to-hydrogen ratio coke oven gas, including a deep purification unit for removing sulfur, naphthalene, benzene and tar impurities from the high carbon-to-hydrogen ratio coke oven gas, and a methanation unit for carrying out the methanation reaction.

[0007] The methanation unit includes a primary methanation reactor, a secondary methanation reactor, and a tertiary methanation reactor. The inlet of the primary methanation reactor is connected to the outlet of the deep purification unit. The outlet of the primary methanation reactor is connected to the inlet of the secondary methanation reactor via a first waste heat boiler. The outlet of the secondary methanation reactor is connected to a first gas-liquid separator via a second waste heat boiler, a coke oven gas preheater, a circulating gas heat exchanger, and a first heat exchanger. The outlet of the first gas-liquid separator is connected to the inlet of the tertiary methanation reactor via a branch line through an inlet and outlet heat exchanger, and to the inlet of the primary methanation reactor via another branch line through a circulating gas compressor and a circulating gas heat exchanger. The outlet of the tertiary methanation reactor is connected to an ammonia washing tower via an inlet and outlet heat exchanger, a second heat exchanger, and a second gas-liquid separator. The outlet of the ammonia washing tower is connected to the cryogenic separation section.

[0008] In one manner, the outlet of the deep purification unit is divided into two paths: the first path is connected to the other branch of the first gas-liquid separator, and the second path is connected to the pipeline connecting the outlet of the first-stage methanation reactor to the inlet of the second-stage methanation reactor.

[0009] In one approach, the hydrogen-rich gas obtained from the cryogenic separation section is circulated to the inlet of the secondary methanation reactor via a pressurization device, or it is connected to the second-stage inlet of the compressor that pressurizes the coke oven gas without a pressurization device.

[0010] In one embodiment, the deep purification unit comprises a pre-hydrogenation reactor, a primary hydrogenation reactor, a first solid desulfurization catalyst reactor, a secondary hydrogenation reactor, and a second solid desulfurization catalyst reactor connected in sequence; a high carbon-to-hydrogen ratio coke oven gas feed device is connected to the inlet of the pre-hydrogenation reactor via a compressor and a coke oven gas preheater; the outlet of the second solid desulfurization catalyst reactor is divided into two paths, the first path connecting to the other branch of the first gas-liquid separator, and the second path connecting to the pipeline connecting the outlet of the primary methanation reactor to the inlet of the secondary methanation reactor.

[0011] In one approach, the upper part of the ammonia washing tower is equipped with an inlet connected to the demineralized water conveying device, the top is equipped with an air outlet, and the bottom is equipped with a liquid outlet.

[0012] In one approach, the condensate outlet at the bottom of the second gas-liquid separator is connected to either the plant's circulating water system or the plant's wastewater treatment system.

[0013] As one approach, the outlet at the bottom of the ammonia washing tower is connected to the plant's wastewater treatment system.

[0014] Compared with the prior art, this utility model has the following advantages:

[0015] 1. This utility model provides a system for synthesizing methane from coke oven gas with a high carbon-to-hydrogen ratio. This system requires less investment, has low overall energy consumption, and high product yield, producing a high methane content gas product with a total CO and CO2 content of less than 50 ppm.

[0016] 2. In the high C / H ratio coke oven gas to methane synthesis system provided by this utility model, the coke oven gas does not need to undergo cooling and heating heat exchange in the fine desulfurization process. The raw gas directly enters the methanation process after high-temperature fine desulfurization, which simplifies the operation process and reduces investment. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the technical solution of this utility model and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solution of this utility model and do not constitute a limitation on the technical solution of this utility model.

[0018] Figure 1 This is a schematic diagram of the system for synthesizing methane from high carbon-to-hydrogen ratio coke oven gas as described in this utility model.

[0019] Marked in the image:

[0020] 1. Pre-hydrogenation reactor; 2. Primary hydrogenation reactor; 3. First solid desulfurization catalyst reactor; 4. Secondary hydrogenation reactor; 5. Second solid desulfurization catalyst reactor; 6. Primary methanation reactor; 7. First waste heat boiler; 8. Secondary methanation reactor; 9. Second waste heat boiler; 10. Coke oven gas preheater; 11. Circulating gas heat exchanger; 12. First heat exchanger; 13. First gas-liquid separator; 14. Circulating gas compressor; 15. Inlet and outlet heat exchangers; 16. Tertiary methanation reactor; 17. Second heat exchanger; 18. Second gas-liquid separator; 19. Ammonia washing tower. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the described embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0022] Example 1

[0023] A system for synthesizing methane from coke oven gas with a high carbon-to-hydrogen ratio, such as Figure 1 As shown, it includes a deep purification unit for removing sulfur, naphthalene, benzene and tar impurities from high carbon-to-hydrogen ratio coke oven gas, and a methanation unit for carrying out methanation reaction.

[0024] The methanation unit includes a primary methanation reactor 6, a secondary methanation reactor 8, and a tertiary methanation reactor 16. The inlet of the primary methanation reactor 6 is connected to the outlet of the deep purification unit. The outlet of the primary methanation reactor 6 is connected to the inlet of the secondary methanation reactor 8 via a first waste heat boiler 7. The outlet of the secondary methanation reactor 8 is connected to the first gas purification unit via a second waste heat boiler 9, a coke oven gas preheater 10, a circulating gas heat exchanger 11, and a first heat exchanger 12. Liquid separator 13; the outlet of the first gas-liquid separator 13 is connected to the inlet of the third-stage methanation reactor 16 via a branch line through the inlet and outlet heat exchanger 15, and is connected to the inlet of the first-stage methanation reactor 6 via another branch line through the circulating gas compressor 14 and the circulating gas heat exchanger 11; the outlet of the third-stage methanation reactor 16 is connected to the ammonia washing tower 19 via the inlet and outlet heat exchanger 15, the second heat exchanger 17, and the second gas-liquid separator 18; the outlet of the ammonia washing tower 19 is connected to the cryogenic separation section.

[0025] In one manner, the outlet of the deep purification unit is divided into two paths: the first path is connected to the other branch of the first gas-liquid separator 13, and the second path is connected to the pipeline connecting the outlet of the first-stage methanation reactor 6 to the inlet of the second-stage methanation reactor 8.

[0026] In one approach, the hydrogen-rich gas obtained from the cryogenic separation section is circulated to the inlet of the secondary methanation reactor 8 via a pressurization device, or it is connected to the second-stage inlet of the compressor that pressurizes the coke oven gas without a pressurization device.

[0027] In one embodiment, the deep purification unit comprises a pre-hydrogenation reactor 1, a primary hydrogenation reactor 2, a first solid desulfurization catalyst reactor 3, a secondary hydrogenation reactor 4, and a second solid desulfurization catalyst reactor 5, connected in sequence. The high carbon-to-hydrogen ratio coke oven gas feed device is connected to the inlet of the pre-hydrogenation reactor 1 via a compressor and a coke oven gas preheater 10. The outlet of the second solid desulfurization catalyst reactor 5 is divided into two paths: the first path is connected to the other branch of the first gas-liquid separator 13, and the second path is connected to the pipeline connecting the outlet of the primary methanation reactor 6 to the inlet of the secondary methanation reactor 8.

[0028] In one approach, the upper part of the ammonia washing tower 19 is provided with an inlet connected to the demineralized water conveying device, the top is provided with an air outlet, and the bottom is provided with a liquid outlet.

[0029] The condensate outlet at the bottom of the second gas-liquid separator 18 is connected to the plant's circulating water system or the plant's wastewater treatment system.

[0030] The liquid outlet at the bottom of the ammonia washing tower 19 is connected to the plant's wastewater treatment system.

[0031] The basic steps and processes of the above system operation are as follows:

[0032] Coke oven gas, after being desulfurized, denaphthalene-free, benzene-free, and detar-free, is pressurized by a compressor and then preheated in a deep desulfurized coke oven gas preheater 10. It then sequentially enters a pre-hydrogenation reactor 1 and a primary hydrogenation reactor 2 for a primary hydrogenation reaction of organic sulfur and unsaturated hydrocarbons in the coke oven gas. After that, it enters a first solid desulfurization catalyst reactor 3 for the first removal of hydrogen sulfide, and then enters a secondary hydrogenation reactor 4 for a secondary hydrogenation reaction of organic sulfur. Finally, it enters a second solid desulfurization catalyst reactor 5 for a secondary removal of hydrogen sulfide. The resulting deeply purified coke oven gas (with H2S content less than 0.1 ppm) enters the methanation process.

[0033] The deeply purified coke oven gas is divided into two streams. The first stream, along with the circulating gas from the outlet of the secondary methanation reactor 8, pressurized by the circulating gas compressor 14, enters the primary methanation reactor 6 for reaction. After recovering heat in the first waste heat boiler 7, the outlet gas is mixed with the second stream of coke oven gas and enters the secondary methanation reactor 8 for further reaction. The outlet gas from the secondary methanation reactor 8 first recovers heat in the second waste heat boiler 9, then exchanges heat with the coke oven gas feedstock gas that will enter the deep desulfurization process in the coke oven gas preheater 10, and then reacts with the gas in the circulating gas heat exchanger 11. The recirculated gas, after being pressurized by the recirculated gas compressor 14, undergoes heat exchange and is finally cooled by the first heat exchanger 12 before entering the first gas-liquid separator 13. After water separation in the first gas-liquid separator 13, the gas exiting is divided into two streams. One stream is pressurized by the recirculated gas compressor 14 and then exchanges heat with the process gas output from the outlet of the secondary methanation reactor 8. This process gas then mixes with a deeply purified coke oven gas stream and enters the inlet of the primary methanation reactor 6. The other stream exchanges heat with the gas output from the outlet of the tertiary methanation reactor 16 in the inlet and outlet heat exchangers 15 before entering the tertiary methanation reactor 16 for reaction. In this configuration, the outlet gas of the tertiary methanation reactor 16 first exchanges heat with the inlet gas to recover heat, is cooled by the second heat exchanger 17, and then enters the second gas-liquid separator 18 to separate water before entering the ammonia washing tower 19. The ammonia washing tower 19 uses demineralized water to wash away trace amounts of ammonia and other impurities from the gas before it proceeds to the cryogenic separation process.

[0034] Among them, supplementary hydrogen-rich gas (with a hydrogen volume fraction of 70%~80%) is added at the inlet of the second stage cylinder of the compressor for coke oven gas pressurization or at the inlet of the second stage methanation reactor 8.

[0035] Valves or other auxiliary components for control pipeline closure and branch switching not specifically listed in this system are all conventionally purchased products. Technical personnel can make conventional selections without affecting the basic operation of this system.

[0036] Although the embodiments disclosed in this utility model are as described above, the content described is only for the purpose of facilitating understanding of this utility model and is not intended to limit this utility model. Any person skilled in the art to which this utility model pertains may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in this utility model, but the patent protection scope of this utility model shall still be determined by the scope defined in the appended claims.

Claims

1. A system for the synthesis of methane from high carbon-to-hydrogen ratio coke oven gas, characterized in that, The deep purification unit comprises a deep purification unit for removing sulfur, naphthalene, benzene and tar impurities in high carbon hydrogen ratio coke oven gas, and a methanation unit for carrying out a methanation reaction. The methanation unit comprises a first-stage methanation reactor (6), a second-stage methanation reactor (8) and a third-stage methanation reactor (16); the gas inlet of the first-stage methanation reactor (6) is connected to the gas outlet of the deep purification unit, the gas outlet of the first-stage methanation reactor (6) is connected to the gas inlet of the second-stage methanation reactor (8) through a first waste heat boiler (7), the gas outlet of the second-stage methanation reactor (8) is sequentially connected to a first gas-liquid separator (13) through a second waste heat boiler (9), a coke oven gas preheater (10), a circulating gas heat exchanger (11) and a first heat exchanger (12); the gas outlet of the first gas-liquid separator (13) is connected to the gas inlet of the third-stage methanation reactor (16) through an inlet-outlet heat exchanger (15) in one branch and connected to the gas inlet of the first-stage methanation reactor (6) through a circulating gas compressor (14) and the circulating gas heat exchanger (11) in another branch; the gas outlet of the third-stage methanation reactor (16) is connected to an ammonia washing tower (19) through the inlet-outlet heat exchanger (15), a second heat exchanger (17) and a second gas-liquid separator (18); the gas outlet of the ammonia washing tower (19) is connected to a deep cooling separation section.

2. The system for synthesis of methane from high carbon to hydrogen coke oven gas according to claim 1, characterized in that, The gas outlet of the deep purification unit is divided into two branches, one branch is connected to the other branch of the first gas-liquid separator (13), and the other branch is connected to the pipeline connecting the gas outlet of the first-stage methanation reactor (6) to the gas inlet of the second-stage methanation reactor (8).

3. The system for synthesis of methane from high carbon to hydrogen coke oven gas according to claim 2, characterized in that, The hydrogen-rich gas obtained from the deep cooling separation section is connected to the gas inlet of the second-stage methanation reactor (8) through a pressurizing device or connected to the second inlet of the compressor for pressurizing the coke oven gas without the pressurizing device.

4. The system for synthesis of methane from high carbon to hydrogen coke oven gas according to claim 2, characterized in that, The deep purification unit comprises a pre-hydrogenation reactor (1), a first-stage hydrogenation reactor (2), a first solid desulfurization catalyst reactor (3), a second-stage hydrogenation reactor (4) and a second solid desulfurization catalyst reactor (5) connected in sequence; the high carbon hydrogen ratio coke oven gas is connected to the gas inlet of the pre-hydrogenation reactor (1) through a compressor and a coke oven gas preheater (10); the gas outlet of the second solid desulfurization catalyst reactor (5) is divided into two branches, one branch is connected to the other branch of the first gas-liquid separator (13), and the other branch is connected to the pipeline connecting the gas outlet of the first-stage methanation reactor (6) to the gas inlet of the second-stage methanation reactor (8).

5. The system for synthesis of methane from high carbon to hydrogen coke oven gas according to claim 1, characterized in that, The upper part of the ammonia washing tower (19) is provided with a liquid inlet connected to a desalted water delivery device, the top is provided with a gas outlet, and the bottom is provided with a liquid outlet.

6. The system for synthesis of methane from high carbon to hydrogen coke oven gas according to claim 1, characterized in that, The condensate outlet at the bottom of the second gas-liquid separator (18) is connected to a plant circulating water system or a plant sewage treatment system.

7. The system for synthesis of methane from high carbon to hydrogen coke oven gas according to claim 5, characterized in that, The liquid outlet at the bottom of the ammonia washing tower (19) is connected to a plant sewage treatment system.

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