Novel isothermal bed methanation reactor and methanation process

Abstract

The application belongs to the field of chemical industry and environmental protection technology, and particularly relates to a novel isothermal bed methanation reactor and a methanation process. The reactor comprises coaxially arranged inner and outer cylinders, an upper head and a lower head connected to two ends of the inner cylinder. The inner cylinder is in the shape of a circular truncated cone and is used for loading catalysts and forming a catalyst bed. The inner cylinder has an inner cylinder central passage which is communicated with a head cooling water inlet and a head steam outlet through two bent pipes respectively arranged in the upper head and the lower head. The upper head is provided with a main inlet communicated with a coke oven gas inlet main pipe, and the lower head is provided with a reactor outlet. The application realizes precise temperature control and efficient heat removal for the strong exothermic methanation reaction, completely avoids a large amount of gas circulation in the traditional circulating adiabatic fixed bed process, significantly reduces energy consumption and investment, and improves conversion rate and catalyst life.

Description

Technical Field

[0001] This invention belongs to the fields of chemical and environmental protection technology, specifically relating to a novel isothermal bed methanation reactor and methanation process. Background Technology

[0002] As a reducing agent in blast furnace ironmaking, coke is in huge demand. Its production process generates a large amount of coke oven gas, which has a complex composition. After preliminary purification, the coke oven gas is rich in H2 (55%–60% by volume), CH4 (23%–27%), CO (5%–8%), CO2 (1.5%–3%), N2 (3%–5%), O2 (0.3%–0.5%), and C (2%–3%). n H m It also contains a large number of impurities such as tar, benzene, naphthalene, ammonia, hydrogen cyanide, organic sulfur and inorganic sulfur.

[0003] The composition of coke oven gas shows that it is high in H2 and CH4, and has a high calorific value. However, because many small and medium-sized coking enterprises only coke without processing it, a large amount of coke oven gas is directly released or burned, failing to be fully utilized. The direct combustion and emission of large quantities of coke oven gas into the atmosphere not only results in a significant waste of high-value energy but also poses serious environmental pollution risks. Therefore, the rational, economical, efficient, and clean utilization of coke oven gas is a crucial issue.

[0004] Currently, the methanation process, which utilizes the abundant hydrogen resources in coke oven gas to react with CO and CO2 to generate CH4, thereby increasing the CH4 content and producing synthetic natural gas with hydrogen as a byproduct, is one of the main ways to achieve clean and efficient resource utilization of coke oven gas. In this process, the methanation reactor is the most crucial piece of equipment. The methanation reaction between carbon-containing gas and hydrogen occurs in the reactor packed with a catalyst. The main reactions are as follows: (1) ,

[0005] (2) ,

[0006] As can be seen from the main chemical reactions, this reaction is strongly exothermic, and the process will result in a huge temperature rise (72°C for every 1% increase in CO content; 60°C for every 1% increase in CO2 content). Excessively high reaction temperatures not only affect the chemical equilibrium of the forward reaction and exacerbate side reactions, but also pose significant safety hazards to production.

[0007] To address this issue, various reactors and corresponding processes have been designed in existing technologies. Among these, the adiabatic fixed-bed reactor and the novel isothermal methanation reactor are the two most researched reactors. However, most methanation processes currently in operation employ a circulating adiabatic fixed-bed process, where the product from the first or second reactor is returned to the inlet of the first reactor to dilute the carbon content of the inlet gas. This process has advantages such as simple operation and easy temperature control, but it also suffers from drawbacks such as low reaction rate, large equipment size, and difficulty in removing heat. To remove the heat of reaction, a high-rate gas recirculation is required to control the reactor temperature, necessitating the use of expensive, high-volume circulating gas compressors, making the entire process operation quite complex. The large amount of circulating gas lowers the partial pressure of the reactant gas, leading to a significant increase in compression work and pressure drop, resulting in high equipment investment costs.

[0008] Isothermal bed reactors can maintain the stability of the methanation heat system by removing the heat of reaction through cooling devices. Compared with adiabatic reactors, isothermal bed reactors have the advantage of being able to rationally control the flow rate of the cooling medium according to the differences in the catalyst, so that the catalyst activity reaches the optimal reaction temperature and the reaction rate is accelerated. Furthermore, from the perspective of energy conservation, the lower temperature is beneficial to the methanation reaction, eliminating the need for a large amount of circulating gas to re-enter the reactor inlet, thus saving energy and investment. Compared with adiabatic fixed-bed reactors, these advantages are obvious, making it a key direction for future research and development of methanation reactors. Summary of the Invention

[0009] In view of this, the present invention provides a novel isothermal bed methanation reactor and methanation process, which, through its simple process, cost-saving investment, and energy-reducing characteristics, will help the future development and research of methanation reactors.

[0010] To achieve the above objectives, the present invention provides the following technical solution: A novel isothermal bed methanation reactor includes an inner cylinder and an outer cylinder arranged coaxially, and an upper end cap and a lower end cap connected to both ends of the inner cylinder; The inner cylinder has a frustum structure and is used to hold the catalyst and form a catalyst bed. The inner cylinder has a central channel, which is connected to the cooling water inlet and steam outlet of the head through two bends respectively located in the upper and lower heads. The upper end cap is provided with a main inlet connected to the coke oven gas inlet pipe, and the lower end cap is provided with a reactor outlet.

[0011] Furthermore, the outer wall of the inner cylinder has multiple holes corresponding to the catalyst bed position, and is connected to multiple coke oven gas inlet branch pipes through interface flanges to realize segmented lateral gas inlet; The catalyst bed is divided into multiple segments along the axial direction by a number of perforated baffles, and the access position of the coke oven gas inlet branch pipe corresponds to each segment of the catalyst bed.

[0012] Furthermore, the outer cylinder has holes on its wall that correspond to the holes on the inner cylinder's wall, so that the coke oven gas inlet branch pipe can pass through the outer cylinder.

[0013] Furthermore, an annular cooling channel is formed between the outer cylinder and the inner cylinder, which is connected to the cooling water inlet and the steam outlet of the outer cylinder; Two streams of cooling water flow in opposite directions through the central channel of the inner cylinder and the annular cooling channel, respectively, to exchange heat with the reaction gas.

[0014] Furthermore, the cross-sectional area of ​​the inner cylinder gradually increases along the gas flow direction, and the cross-sectional area of ​​the outlet end of the inner cylinder is 1.5 to 4 times the cross-sectional area of ​​the inlet end.

[0015] Furthermore, the outer cylinder is a cylindrical structure, and its interior is provided with a support frame along the axial direction to support the inner cylinder.

[0016] On the other hand, the present invention also provides a methanation process using the novel isothermal bed methanation reactor, comprising the following steps: The purified coke oven gas is fed into the new isothermal bed methanation reactor through multiple channels. One channel enters the inner cylinder directly along the axial direction through the main inlet, while the other channels enter the inner cylinder laterally through multiple coke oven gas inlet branch pipes. After merging with the axial gas, the methanation reaction occurs in the catalyst bed. Two streams of cooling water flow counter-currently into the inner cylinder central channel and annular cooling channel from the lower head cooling water inlet and the outer cylinder cooling water inlet, respectively. After exchanging heat with the reaction gas, they are discharged from the upper head steam outlet and the outer cylinder steam outlet, respectively. After being cooled by the waste heat recovery unit, the reactor outlet stream enters the downstream adiabatic fixed-bed reactor for further reaction of residual CO / CO2. The diversion ratio of the multi-path coke oven gas is axial main path: total of all branches = 2:(1~3); The flow rate ratio of the two cooling water streams is: lower head cooling water inlet: outer cylinder cooling water inlet = 1:(3~4).

[0017] Furthermore, the outlet stream of the adiabatic fixed-bed reactor enters a heat exchanger for cooling. After being cooled to 40°C, it passes through a gas-liquid separator to separate the wastewater, and the product gas enters the next stage.

[0018] Furthermore, when the gas volume to be processed is large, multiple novel isothermal bed methanation reactors described above are connected in parallel and then connected in series with an adiabatic fixed bed reactor.

[0019] Furthermore, when the amount of coke oven gas suddenly increases beyond the limit (the limit is set adaptively according to the actual operating conditions), the catalyst activity decreases, or the outlet temperature of the new isothermal methanation reactor exceeds 450°C, an additional coke oven gas bypass is added to directly enter the downstream adiabatic fixed-bed reactor to share the load of the new isothermal methanation reactor.

[0020] The beneficial effects of this invention are as follows: This invention, through the unique structural design of a novel isothermal bed methanation reactor (dual-stream counter-current cooling water system, segmented lateral gas inlet, frustum-shaped inner cylinder) and its matching methanation process, achieves precise temperature control and efficient heat removal for the strongly exothermic methanation reaction. This completely avoids the large-scale gas circulation required in traditional circulating adiabatic fixed-bed processes, significantly reducing energy consumption and investment, while simultaneously improving conversion rate and catalyst lifespan. Specific beneficial effects are as follows: 1. More uniform temperature distribution, preventing localized overheating of the bed. The reactor employs a two-stream counter-current cooling water heat exchange system (one stream flows through the central channel of the inner cylinder, and the other flows through the annular gap between the outer and inner cylinders). This system provides a large heat exchange area, a large temperature difference, and high heat exchange efficiency, effectively removing the heat of reaction and resulting in a more uniform temperature distribution in the catalyst bed. This prevents the formation of local hot spots and ensures the long-term safe and stable operation of the reactor.

[0021] 2. Segmented lateral air intake enables precise control of cooling and response levels. Coke oven gas enters the reactor through multiple channels (one main axial inlet and multiple branch pipes for lateral inlets). The cold gas in the later branch pipes cools the already reacted high-temperature gas, while the reacted gas dilutes the carbon component concentration of the subsequent new gas, reduces the local reaction intensity, effectively controls the overall heat release, and further helps maintain the isothermal state of the bed.

[0022] 3. Eliminating atmospheric volume circulation significantly saves energy and investment. Unlike traditional adiabatic fixed-bed processes that require high-rate gas circulation dilution and heat transfer, this invention achieves temperature and reaction control directly through methanation, structural design, and segmented gas intake. It eliminates the need for a circulating compressor, avoiding the compression power consumption, pressure drop loss, and equipment investment associated with large amounts of circulating gas, and significantly reducing operating energy consumption and construction costs.

[0023] 4. The device is more compact and occupies less space. It eliminates the need for large volumes of circulating gas, resulting in higher partial pressure of the gas at the reactor inlet, faster reaction rates, and a significantly smaller reactor volume for the same processing capacity. At the same time, the process flow is simplified, the equipment layout is more compact, and the overall footprint of the unit is significantly reduced, making it easy to retrofit and implement within existing coking plant areas.

[0024] 5. Lower bed temperature improves conversion rate and extends catalyst life. The isothermal bed design allows the reaction to take place in the optimal temperature range of the catalyst (usually at a lower temperature), which is more conducive to the forward shift of the chemical equilibrium of the strongly exothermic methanation reaction and improves the CO / CO2 conversion rate. At the same time, the low temperature significantly inhibits side reactions such as carbon deposition and sintering, slows down catalyst deactivation, extends service life, and reduces the frequency of catalyst replacement and operating costs.

[0025] 6. Optimizing gas space velocity distribution using a frustum-shaped inner cylinder The inner cylinder adopts a frustum structure with a small inlet cross-section and a large outlet cross-section (the outlet cross-sectional area is 1.5 to 4 times that of the inlet). This can compensate for the effect of the increase in gas volume after the methanation reaction, so that the gas space velocity in the front and back sections of the catalyst bed is basically the same, ensuring uniform contact time between the gas and the catalyst, and avoiding the problem of insufficient reaction time in the later stage leading to a decrease in conversion rate.

[0026] In summary, this invention achieves efficient, clean, and economical utilization of coke oven gas methanation process while maintaining process simplicity, safety, and reliability. Compared with existing adiabatic cycle processes, it has significant technical and economic advantages and is the preferred direction for reactor development in the field of coke oven gas resource utilization.

[0027] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the structure of the novel isothermal bed methanation reactor in this invention; Figure 2 This is a schematic diagram of a methanation process in Example 1; Figure 3 This is a schematic diagram of a methanation process in Example 2.

[0029] Figure reference numerals: 1-Coke oven gas inlet main pipe; 2-Coke oven gas inlet branch pipe; 3-Outer cylinder cooling water inlet; 4-Head cooling water inlet; 5-Reactor outlet; 6-Head steam outlet; 7-Outer cylinder steam outlet; 8-Outer cylinder; 9-Catalyst bed; 10-Lower head; 11-Perforated baffle; 12-Bend; 13-Inner cylinder; 14-Upper head; 15-Inner cylinder central channel. Detailed Implementation

[0030] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0031] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0032] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0033] like Figure 1 As shown, this is a novel isothermal bed methanation reactor. The reactor mainly consists of an inner cylinder 13 with a coaxial frustum structure, an outer cylinder 8 with a cylindrical structure, an upper head 14, and a lower head 10. The upper head 14 and the lower head 10 are connected to the upper top surface and the lower bottom surface of the inner cylinder 13, respectively. The top of the upper head 14 is equipped with an interface flange to connect to the coke oven gas inlet main pipe 1, and the bottom of the lower head 10 has an opening as the reactor outlet 5 and is equipped with an interface flange to connect to the outlet pipe. Specifically, the cross-sectional area of ​​the inner cylinder 13 gradually increases along the gas flow direction, and the cross-sectional area of ​​the outlet end of the inner cylinder 13 is 1.5 to 4 times the cross-sectional area of ​​the inlet end.

[0034] Both the upper end cap 14 and the lower end cap 10 are equipped with bent pipes 12 that connect to the outside. The two ends of the bent pipe 12 in the upper end cap 14 are connected to the inner cylinder central channel 15 and the end cap steam outlet 6, respectively. The two ends of the bent pipe 12 in the lower end cap 10 are connected to the inner cylinder central channel 15 and the end cap cooling water inlet 4, respectively. The inner cylinder 13 is the area for holding the catalyst, that is, the reaction site for the methanation of coke oven gas. Along the axial direction (from top to bottom), there is a perforated baffle 11, which divides the inner cylinder 13 into multiple sections. The catalyst bed 9 is placed on the perforated baffle 11. Multiple holes are made in the outer wall of the inner cylinder 13 so that the area in the inner cylinder 13 that holds the catalyst can be connected to the outside through the side wall. Interface flanges are installed in the holes to connect with the coke oven gas inlet branch pipe. Holes are made in the outer cylinder 8 corresponding to the holes in the inner cylinder 13 so that the coke oven gas inlet branch pipe can pass through the outer cylinder 8. Furthermore, the outer cylinder 8 is provided with an outer cylinder steam outlet 7 and an outer cylinder cooling water inlet 3 at its upper and lower ends, respectively, so as to connect cooling water between the outer cylinder 8 and the inner cylinder 13; The coke oven gas flows axially through the inner cylinder 13 containing the catalyst. After undergoing a methanation reaction, it is transformed into methane-rich outlet gas. Two streams of cooling water also flow axially, passing through the inner cylinder flow channel formed by the outer cylinder 8 and the bend 12 and the central channel 15 of the inner cylinder, respectively. After exchanging heat with the coke oven gas, they are transformed into water vapor. The cooling water flows in the opposite direction to the coke oven gas flow to obtain a larger heat exchange temperature difference.

[0035] Example 1 Processing capacity of coke oven gas: 30,000 Nm³ 3 / h (using one of the novel isothermal bed methanation reactors described in this invention) The purified coke oven gas (temperature 270℃) enters the new isothermal bed methanation reactor in three streams. One stream of gas enters the reactor directly along the axial direction through the coke oven gas inlet main pipe connected to the upper head 14 of the reactor. The other two streams of gas enter the reactor in sections through branch pipes on the coke oven gas inlet main pipe and merge with the coke oven gas that enters the reactor directly. The gas flow ratio of the three streams is 2:1:1. The methanation reaction occurs at the catalyst bed, and then the stream leaves through the reactor outlet. Two streams of cooling water (approximately 20°C, total volume 3600 kg / h) are used. One stream enters the bend pipe 12 through the cooling water inlet 4 at the lower head 10, and then enters the inner cylinder central channel 15. After exchanging heat with the coke oven gas undergoing reaction, it is converted into steam and enters the steam pipe through the steam outlet 6 at the upper head 14 via the bend pipe 12. The other stream of cooling water enters the space between the outer cylinder 8 and the inner cylinder 13 through the outer cylinder cooling water inlet 3 at the outer cylinder 8. After exchanging heat with the coke oven gas undergoing reaction, it is converted into steam and enters the steam pipe through the steam outlet 7 at the outer cylinder 8. The ratio of the two streams of cooling water is 1:4. The effluent stream (approximately 400°C) from the novel isothermal bed methanation reactor enters a waste heat boiler / heat exchanger, where it is cooled to 230°C before entering an adiabatic fixed-bed reactor to react and remove residual CO / CO2, ensuring that the stream composition meets technical requirements. Afterward, the effluent stream from the adiabatic fixed-bed reactor enters a heat exchanger, where it is cooled to 40°C before passing through a gas-liquid separator to separate wastewater. The product gas then enters the next stage.

[0036] Example 2 Processing capacity of coke oven gas: 50,000 Nm³ 3 / h (using two novel isothermal bed methanation reactors from this invention arranged in parallel); The purified coke oven gas (temperature 290℃) is first divided into two streams, which enter two parallel new isothermal bed methanation reactors respectively; The coke oven gas entering the new isothermal bed methanation reactor is then divided into three streams. One stream of gas enters the reactor directly along the axial direction through the main coke oven gas inlet pipe connected to the upper head 14 of the reactor. The other two streams of gas enter the reactor in sections through branch pipes on the main coke oven gas inlet pipe and merge with the coke oven gas that enters the reactor directly. The gas flow ratio of the three streams is 2:1.5:1.5. The methanation reaction occurs at the catalyst bed, and then the stream leaves through the reactor outlet. Two streams of cooling water (approximately 20°C, total volume 3900 kg / h) are used. One stream enters the bend pipe 12 through the cooling water inlet 4 at the lower head 10, and then enters the inner cylinder central channel 15. After exchanging heat with the coke oven gas undergoing reaction, it is converted into steam and enters the steam pipe through the steam outlet 6 at the upper head 14 via the bend pipe 12. The other stream of cooling water enters the space between the outer cylinder 8 and the inner cylinder 13 through the outer cylinder cooling water inlet 3 at the outer cylinder 8. After exchanging heat with the coke oven gas undergoing reaction, it is converted into steam and enters the steam pipe through the steam outlet 7 at the outer cylinder 8. The ratio of the two streams of cooling water is 1:3. The effluent stream (approximately 380°C) from the novel isothermal bed methanation reactor enters a waste heat boiler / heat exchanger, where it is cooled to 220°C before entering an adiabatic fixed-bed reactor to react and remove residual CO / CO2, ensuring that the stream composition meets technical requirements. Afterward, the effluent stream from the adiabatic fixed-bed reactor enters a heat exchanger, where it is cooled to 40°C before passing through a gas-liquid separator to separate wastewater. The product gas then enters the next stage.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A novel isothermal bed methanation reactor, characterized in that, It includes an inner cylinder (13) and an outer cylinder (8) arranged coaxially, and an upper end cap (14) and a lower end cap (10) connected to both ends of the inner cylinder (13); The inner cylinder (13) has a frustum structure and is used to hold the catalyst and form a catalyst bed (9). The inner cylinder (13) has an inner cylinder central channel (15), which is connected to the head cooling water inlet (4) and the head steam outlet (6) through two bends (12) respectively provided in the upper head (14) and the lower head (10); The upper end cap (14) is provided with a main inlet connected to the coke oven gas inlet pipe (1), and the lower end cap (10) is provided with a reactor outlet (5).

2. The novel isothermal bed methanation reactor according to claim 1, characterized in that, The outer wall of the inner cylinder (13) has multiple holes corresponding to the catalyst bed position, and is connected to multiple coke oven gas inlet branch pipes (2) through interface flanges to realize segmented lateral gas inlet; The catalyst bed (9) is divided into multiple segments along the axial direction by multiple perforated baffles (11), and the access position of the coke oven gas inlet branch pipe (2) corresponds to each segment of the catalyst bed.

3. The novel isothermal bed methanation reactor according to claim 2, characterized in that, The outer cylinder (8) has holes on its wall corresponding to the holes on the inner cylinder (13) so that the coke oven gas inlet branch pipe (2) can pass through the outer cylinder (8).

4. The novel isothermal bed methanation reactor according to claim 2, characterized in that, An annular cooling channel is formed between the outer cylinder (8) and the inner cylinder (13), which is connected to the cooling water inlet (3) of the outer cylinder and the steam outlet (7) of the outer cylinder; Two streams of cooling water flow in opposite directions through the central channel (15) of the inner cylinder and the annular cooling channel, respectively, to exchange heat with the reaction gas.

5. The novel isothermal bed methanation reactor according to claim 4, characterized in that, The cross-sectional area of ​​the inner cylinder (13) gradually increases along the gas flow direction, and the cross-sectional area of ​​the outlet end of the inner cylinder (13) is 1.5 to 4 times the cross-sectional area of ​​the inlet end.

6. The novel isothermal bed methanation reactor according to any one of claims 4-5, characterized in that, The outer cylinder (8) is a cylindrical structure, and its interior is provided with a support frame along the axial direction to support the inner cylinder (13).

7. A methanation process, characterized in that, The novel isothermal bed methanation reactor according to any one of claims 4-6 comprises the following steps: The purified coke oven gas enters the new isothermal bed methanation reactor through multiple channels. One channel enters the inner cylinder directly along the axial direction through the main inlet, while the other channels enter the inner cylinder laterally through multiple coke oven gas inlet branch pipes (2) in sections. After merging with the axial gas, the methanation reaction occurs in the catalyst bed. Two streams of cooling water flow counter-currently into the inner cylinder center channel and annular gap cooling channel from the lower head cooling water inlet (4) and the outer cylinder cooling water inlet (3), respectively. After exchanging heat with the reaction gas, they are discharged from the upper head steam outlet (6) and the outer cylinder steam outlet (7), respectively. After being cooled by the waste heat recovery unit, the reactor outlet stream enters the downstream adiabatic fixed-bed reactor for further reaction of residual CO / CO2. The diversion ratio of the multi-path coke oven gas is axial main path: total of all branches = 2:(1~3); The flow rate ratio of the two cooling water streams is: lower head cooling water inlet: outer cylinder cooling water inlet = 1:(3~4).

8. The methanation process according to claim 7, characterized in that, The outlet stream of the adiabatic fixed-bed reactor enters a heat exchanger for cooling. After being cooled to 40°C, it passes through a gas-liquid separator to separate the wastewater, and the product gas enters the next stage.

9. The methanation process according to claim 7, characterized in that, When processing large volumes of gas, multiple novel isothermal methanation reactors described above are connected in parallel and then connected in series with an adiabatic fixed-bed reactor.

10. The methanation process according to claim 7, characterized in that, When the amount of coke oven gas suddenly increases beyond the limit, the catalyst activity decreases, or the outlet temperature of the new isothermal methanation reactor exceeds 450°C, an additional coke oven gas bypass is added to directly enter the downstream adiabatic fixed-bed reactor to share the load of the new isothermal methanation reactor.

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