CN117427570A - Methane preparation system and methane preparation method - Google Patents

Abstract

The invention provides a methane preparation system and a methane preparation method. The methane preparation system includes: a first heat exchange device, which includes a first heat channel and a first medium channel; a first synthesis device, which is used to perform a methane synthesis reaction to obtain the first post-column gas; a second synthesis device Equipment, used to receive the heated synthesis gas and the cooled first tower post-gas; a second heat exchange equipment, which includes a second heat channel and a second medium channel; a gas-liquid separation equipment, to receive the cooled second gas The gas behind the tower is subjected to gas-liquid separation to separate water; a pressurizing device is provided downstream of the gas-liquid separation device to receive the second post-column gas after water separation and pressurize it to obtain circulating gas; a third synthesis device , to receive circulating gas and supply circulating gas for methane synthesis reaction; cooling and separation equipment to receive the synthesized preliminary methane, cool the preliminary methane and separate gas and liquid to obtain methane products.

Description

Methane preparation system and methane preparation method

Technical field

The present invention relates to the technical field of methane preparation, and in particular to a methane preparation system and a methane preparation method.

Background technique

At present, the synthesis process of methane mainly includes the adiabatic methanation synthesis process with circulation and the isothermal methanation synthesis process without circulation.

In the process of isothermal methanation to synthesize methane, due to the fast methanation reaction speed, the reaction hot spot temperature will be close to the equilibrium temperature. For feed gas with high carbon monoxide and carbon dioxide content, the methanation hot spot temperature will be very high. At this time, the carbon evolution reaction is prone to occur and Cause the methanation catalyst to fail. Although the concentration of carbon monoxide and carbon dioxide in the raw gas can be diluted by directly adding a large amount of steam to the raw gas to control the methanation hot spot temperature, the energy consumption is extremely high due to the need to directly add a large amount of steam. For feed gas with low carbon monoxide and carbon dioxide content, due to the heat transfer in the isothermal reaction, the methanation hot spot temperature is not high, the methanation reaction speed decreases as the temperature decreases, and the catalyst efficiency will decrease.

In the process of adiabatic methanation to synthesize methane, the reacted methane gas is returned to dilute the concentration of carbon monoxide and carbon dioxide in the raw material gas to control the methanation hot spot temperature. Since the temperature after the adiabatic reaction is higher, the equilibrium concentration of carbon monoxide and carbon dioxide in the gas after the reaction is also higher. For feed gas with high carbon monoxide and carbon dioxide content, in order to control the temperature of methanation hot spots, it is necessary to increase the circulation volume and increase the number of adiabatic methanation reactors. At the same time, it is necessary to increase related facilities for recovering high-temperature heat of adiabatic methanation reaction gas, resulting in investment Larger, energy consumption is relatively high.

Contents of the invention

The object of the present invention is to provide a methane preparation system and a methane preparation method with lower energy consumption, so as to solve the problems in the existing technology.

In order to solve the above technical problems, the present invention provides a methane production system, including:

The first heat exchange device includes a first heat channel and a first medium channel that are independent of each other and capable of heat exchange; the inlet of the first medium channel is used to receive external syngas, and the syngas contains (H ₂ - The volume percentage of CO ₂ )/(CO+CO ₂ ) is greater than 3;

A first synthesis device is connected to the outlet of the first medium channel to receive the heated synthesis gas; the first synthesis device is used to perform a methane synthesis reaction to obtain the first post-column gas; the first synthesis device The outlet of the synthesis equipment communicates with the inlet of the first heat channel to provide the gas after the first tower;

The inlet of the second synthesis device is connected to the outlet of the first medium channel and the outlet of the first heat channel at the same time, so as to receive the heated synthesis gas and the cooled first tower post-gas; The second synthesis equipment is used to carry out the methane synthesis reaction to obtain the gas after the second tower;

The second heat exchange device includes a second heat channel and a second medium channel that are independent of each other and capable of heat exchange; the inlet of the second heat channel is connected to the second synthesis device to receive the gas after the second tower. ;The outlet of the second medium channel is connected with the inlet of the first synthesis device;

Gas-liquid separation equipment, which is arranged downstream of the second heat channel to receive the cooled gas after the second tower and perform gas-liquid separation to separate water;

A pressurizing device is provided downstream of the gas-liquid separation device to receive the post-gas from the second tower after water has been separated and pressurize it to obtain circulating gas. The pressurizing device is connected to the inlet of the second medium channel. communicate;

A third synthesis device, which is arranged in parallel with the first synthesis device and is located downstream of the second medium channel to receive the circulating gas and supply the circulating gas for methane synthesis reaction;

Cooling and separation equipment is provided downstream of the third synthesis equipment to receive the synthesized preliminary methane, cool the preliminary methane, and separate gas and liquid to obtain methane products.

In one embodiment, a first flow regulating valve is provided between the first medium channel and the first synthesis device; and/or,

A second flow regulating valve is provided between the first medium channel and the second synthesis device.

In one embodiment, a steam superheater is further provided between the first synthesis equipment and the first heat channel. The steam superheater includes a heating pipe, and the inside of the heating pipe is used for steam to pass through. The steam absorbs the heat of the gas after the first tower to form superheated steam. The outlet of the heating pipe is connected with the inlet of the second synthesis equipment to input the superheated steam to the second synthesis equipment.

In one embodiment, a first steam generator is further provided between the second synthesis device and the second heat exchange device, and the first steam generator includes a first water supply pipe for water supply circulation, The second post-column gas is used to provide heat to the water in the first water supply pipe to convert the water into steam. The outlet of the first water supply pipe is connected to the heating pipe of the steam superheater.

In one embodiment, a first cooling device is further provided between the second heat exchange device and the gas-liquid separation device.

In one embodiment, the cooling and separation equipment includes a second steam generator and a gas-liquid separator;

The second steam generator includes a second water supply pipeline for water supply circulation, the preliminary methane is used to provide heat to the water in the second water supply pipeline to convert the water into steam, and the gas-liquid separator is used to The preliminary methane after cooling is received and gas-liquid separation is performed to obtain a methane product.

In one embodiment, a second cooling device is provided between the second steam generator and the gas-liquid separator.

In one embodiment, the first synthesis device is filled with a nickel catalyst, the second synthesis device is filled with a nickel catalyst, and the third synthesis device is filled with a nickel catalyst.

In one embodiment, the first synthesis device, the second synthesis device and the third synthesis device are all axial-radial adiabatic synthesis reactors.

The invention also provides a method for preparing methane, which includes the following steps:

Providing synthesis gas, the volume percentage of (H ₂ -CO ₂ )/(CO + CO ₂ ) in the synthesis gas is greater than 3;

The synthesis gas is heated up through heat exchange and then enters the first synthesis equipment and the second synthesis equipment respectively;

A methane synthesis reaction is performed in the first synthesis equipment to obtain the first post-column gas;

The gas after the first tower and the synthesis gas enter the second synthesis equipment after being cooled by heat exchange. The gas after the first tower and the synthesis gas jointly perform methane synthesis in the second synthesis equipment. Reaction to obtain the second column back gas;

The gas after the second tower is cooled and then subjected to gas-liquid separation to separate the water in the gas after the second tower;

The gas after the second tower after separated water is pressurized to form a circulating gas. The circulating gas exchanges heat with the gas after the second tower and is heated up before entering the first synthesis equipment and the third synthesis equipment. A methane synthesis reaction is carried out in the third synthesis device to obtain preliminary methane;

After the preliminary methane is cooled and separated from gas and liquid, the product methane is obtained.

In one of the embodiments, the following steps are also included:

Adjust the amount of the synthesis gas entering the first synthesis device so that the molar percentage of the synthesis gas in the first synthesis device and the total carbon oxides in the circulating gas is 3.0 to 5.0%; and /or,

Adjust the amount of the synthesis gas entering the second synthesis equipment so that the molar percentage of the synthesis gas in the second synthesis equipment and the total carbon oxides in the gas after the second tower is 3.0 to 10.0 %.

In one of the embodiments, before heat exchange between the second column back gas and the circulating gas, the following steps are further included:

The gas after the second tower exchanges heat with water, releasing heat to convert the water into steam. The cooled gas after the second tower exchanges heat with the circulating gas, and the steam interacts with the gas after the first tower. heat exchange.

In one of the embodiments, before heat exchange between the first column back gas and the synthesis gas, the following steps are further included:

The gas after the first tower exchanges heat with the above-mentioned steam, releasing heat to convert the steam into superheated steam. The steam enters the second synthesis equipment as the superheated steam, and the cooled gas after the first tower and the above-mentioned steam are The synthesis gas exchanges heat.

In one embodiment, the synthesis gas and the circulating gas enter from the top of the first synthesis equipment, and pass through the nickel-based catalyst bed from top to bottom, at a pressure of 1 to 12 MPa and a temperature of 250 to 500°C. Under, the first column post-gas is obtained through catalytic reaction; and/or,

The synthesis gas and the gas after the first tower enter from the top of the second synthesis equipment, pass through the nickel-based catalyst bed from top to bottom, and are catalyzed at a pressure of 1 to 12 MPa and a temperature of 250 to 550°C. React to obtain the second column back gas; and/or,

The circulating gas enters from the top of the third synthesis equipment, passes through the nickel-based catalyst bed from top to bottom, and undergoes a catalytic reaction to obtain the preliminary methane at a pressure of 1 to 12 MPa and a temperature of 250 to 300°C.

In one embodiment, the space velocity of the circulating gas entering the third synthesis device is smaller than the space velocity of the synthesis gas and the first tower post-gas entering the second synthesis device. The space speed of the third synthesis device is less than the space speed of the synthesis gas and the circulating gas entering the first synthesis device, and the space speed of the synthesis gas and the circulating gas entering the first synthesis device is greater than Or equal to the space velocity at which the synthesis gas and the gas after the first tower enter the second synthesis equipment.

It can be seen from the above technical solutions that the advantages and positive effects of the present invention are:

The first synthesis equipment, the second synthesis equipment and the third synthesis equipment in the present invention are arranged in series and parallel processes to make the reaction balance of the synthesis gas more thorough, and to maximize the single-pass methane conversion rate, and to reduce the compression power consumption. , the energy heat recovery is more concentrated, which reduces the energy consumption of the entire methane preparation system.

The methane preparation method in the present invention has high conversion rate, small cycle ratio, flexible and controllable temperature of methanation synthesis equipment, large production capacity adjustment range, more reasonable system heat exchange, low energy consumption, high energy heat recovery, and high energy recovery. The steam quality is high.

Description of the drawings

Figure 1 is a schematic diagram of the liquid carbon dioxide preparation system in the present invention.

The reference symbols are explained as follows:

1. First heat exchange equipment; 2. First synthesis equipment; 3. Second synthesis equipment; 4. Second heat exchange equipment; 5. Gas-liquid separation equipment; 6. Pressurization equipment; 7. Third synthesis equipment; 8. First flow regulating valve; 9. Steam superheater; 10. Steam regulating valve; 11. Second flow regulating valve; 12. First steam generator; 13. First cooling equipment; 14. Second steam generator ; 15. Gas-liquid separator; 16. Second cooling equipment.

Detailed ways

Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments, without departing from the scope of the present invention, and the description and illustrations are essentially for illustration, not limitation. this invention.

In order to further illustrate the principle and structure of the present invention, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

It should be noted that the synthesis reaction equation of methane is as follows:

CO+3H ₂ =CH ₄ CO ₂ +4H ₂ =CH ₄ +2H ₂ O.

The synthesis reaction of methane is an exothermic reaction, and low temperature can increase the probability of H ₂ synthesizing methane. Therefore, the lower the temperature, the more the synthesis shifts towards _CH4 .

The invention provides a methane preparation system, which can control the temperature of synthesis gas containing hydrogen, carbon monoxide and carbon dioxide to synthesize methane, and has low energy consumption.

Figure 1 shows a schematic diagram of a methane production system. Referring to Figure 1, the methane production system includes a first heat exchange device 1, a first synthesis device 2, a second synthesis device 3, a second heat exchange device 4, and a gas-liquid separation device 5. , pressurizing equipment 6, third synthesis equipment 7 and cooling and separation equipment.

The first heat exchange device 1 includes a first heat channel and a first medium channel that are independent of each other and capable of heat exchange. The inlet of the first medium channel is used to receive syngas from the outside, that is, the inlet of the first medium channel is used to communicate with the outside world.

Among them, the main components of syngas are hydrogen (H ₂ ), carbon monoxide (CO) and carbon dioxide (CO ₂ ). The volume percentage of (H ₂ -CO ₂ )/(CO + CO ₂ ) in the synthesis gas used in this application is greater than 3, that is, according to the synthesis reaction of methane, the content of hydrogen in the synthesis gas is such that it reacts with carbon monoxide and carbon dioxide. Time is sufficient and abundant.

The synthesis gas undergoes heat exchange in the first heat exchange device 1, and the synthesis gas absorbs heat to increase its temperature.

The first synthesis device 2 is connected to the outlet of the first medium channel to receive the heated synthesis gas. The first synthesis equipment 2 is used to perform a methane synthesis reaction to obtain the first post-column gas. Among them, in the first synthesis device 2, before the circulating gas is generated, the synthesis gas undergoes a methane synthesis reaction. After the circulating gas enters the first synthesis device 2, the synthesis gas and the circulating gas jointly perform a methane synthesis reaction.

Specifically, the first synthesis device 2 is an axial-radial type adiabatic synthesis reactor. The first synthesis device 2 is filled with a nickel catalyst. The first synthesis equipment 2 is designed with separate outer shell and internal parts. The outer shell can withstand external pressure and the temperature is consistent with the inlet air temperature, thus saving materials. The internal parts bear the role of gas distribution and catalyst reaction heat, but do not bear pressure. The overall structure of the first synthesis equipment 2 is safe and reliable.

The outlet of the first synthesis device 2 communicates with the inlet of the first heat channel to transport the gas after the first tower. That is, in the first heat exchange equipment 1, the gas after the first tower and the syngas exchange heat. The gas after the first tower releases heat and cools down, and the syngas absorbs heat and heats up.

Further, a first flow regulating valve 8 is provided between the first medium channel and the first synthesis device 2 . The opening of the first flow regulating valve 8 is adjustable, thereby adjusting the amount of synthesis gas entering the first synthesis device 2 . By adjusting the amount of synthesis gas entering the first synthesis device 2 and adjusting the volume percentage of the total carbon oxides in the synthesis gas and the circulating gas in the first synthesis device 2, the reaction degree of methane synthesis is adjusted, thereby controlling the third synthesis gas. A temperature rise within the synthesis equipment 2.

Preferably, a steam superheater 9 is also provided between the first synthesis equipment 2 and the first heat channel. The steam superheater 9 includes a heating pipe, and the heating pipe is used for steam to pass through, and the steam absorbs the heat of the gas after the first tower to form superheated steam. In this embodiment, a cylinder is provided outside the heating pipe, and there is a space between the cylinder and the heating pipe for the gas after the first tower to pass, that is, the gas after the first tower passes outside the heating pipe and provides heat to the steam.

The outlet of the heating pipe communicates with the inlet of the second synthesis device 3 to input superheated steam into the second synthesis device 3 .

Specifically, a steam regulating valve 10 is disposed between the steam superheater 9 and the second synthesis equipment 3 , that is, the steam regulating valve 10 is disposed between the heating pipe and the second synthesis equipment 3 to regulate the flow into the second synthesis equipment 3 the amount of superheated steam.

The inlet of the second synthesis device 3 is connected to the outlet of the first medium channel and the outlet of the first heat channel at the same time, for receiving the heated synthesis gas and the cooled first tower post-gas.

The heated synthesis gas and the cooled first post-column gas react in the second synthesis device 3 to obtain the second post-column gas.

When the methane synthesis reaction occurs in the second synthesis device 3, the speed of the methane synthesis reaction is controlled by introducing superheated steam to avoid the reaction being too fast. Moreover, the entry of superheated steam can also reduce the temperature rise within the entire second synthesis equipment 3 .

Specifically, the second synthesis device 3 is an axial-radial type adiabatic synthesis reactor. The second synthesis device 3 is filled with a nickel catalyst. The second synthesis equipment 3 is designed with separate outer shell and internal parts. The outer shell can withstand external pressure, and the temperature is consistent with the inlet air temperature, thus saving materials. The internal parts bear the role of gas distribution and catalyst reaction heat, but do not bear pressure. The overall structure of the second synthesis equipment 3 is safe and reliable.

Further, a second flow regulating valve 11 is provided between the second synthesis device 3 and the first medium channel. The opening of the second flow regulating valve 11 is adjustable, thereby adjusting the amount of synthesis gas entering the second synthesis device 3 .

The second heat exchange device 4 includes a second heat channel and a second medium channel that are independent of each other and capable of heat exchange. The inlet of the second heat channel is connected to the second synthesis device 3 to receive the gas after the second tower, that is, the gas after the second tower releases heat and is cooled. The outlet of the second medium channel is connected with the inlet of the first synthesis device 2 .

Furthermore, a first steam generator 12 is provided between the second synthesis device 3 and the second heat exchange device 4 . Specifically, the first steam generator 12 is connected with the inlet of the second heat channel. The first steam generator 12 includes a first water supply pipe for water supply circulation. The second tower back gas is used to provide heat to the water in the first water supply pipe to convert the water into steam. The outlet of the first water supply pipe is connected to the steam superheater. The heating pipe of device 9 is connected.

The water inlet of the first water supply pipe is used to communicate with the outside world. In this embodiment, the water in the first water supply pipe is boiler water.

After water enters the first water supply pipe, it absorbs heat and is converted into steam, and then enters the steam superheater 9 and is converted into superheated steam and enters the second synthesis device 3 .

The gas-liquid separation equipment 5 is arranged downstream of the second heat channel to receive the cooled gas after the second tower and perform gas-liquid separation to separate water.

Furthermore, a first cooling device 13 is provided between the second heat exchange device 4 and the gas-liquid separation device 5 . The first cooling device 13 is used to further cool the gas after the second tower. In this embodiment, the first cooling device 13 may be a circulating water cooling device or a desalted water heat exchange device.

Specifically, the temperature of the gas after the second tower is reduced to 30-80°C after passing through the first evaporator, the second heat exchange device 4 and the first cooling device 13.

The pressurizing device 6 is disposed downstream of the gas-liquid separation device 5 to receive the gas after the second tower after water separation and pressurize it to obtain circulating gas. In this embodiment, the boosting equipment 6 is a circulation machine.

The pressurizing device 6 communicates with the inlet of the second medium channel, that is, it delivers circulating gas to the second medium channel of the second heat exchange device 4 . The circulating gas exchanges heat with the gas after the second tower in the second heat exchange device 4. The circulating gas absorbs heat and increases its temperature, while the gas after the second tower releases heat and cools down.

The third synthesis device 7 is arranged in parallel with the first synthesis device 2 and is located downstream of the second medium channel to receive the circulating gas and supply the circulating gas for methane synthesis reaction.

Specifically, the third synthesis device 7 is an axial-radial type adiabatic synthesis reactor. The third synthesis device 7 is filled with nickel catalyst. The third synthesis equipment 7 is designed with separate outer shell and internal parts. The outer shell can withstand external pressure, and the temperature is consistent with the inlet air temperature, thus saving materials. The internal parts bear the role of gas distribution and catalyst reaction heat, but do not bear pressure. The overall structure of the third synthesis device 7 is safe and reliable.

The cooling and separation equipment is arranged downstream of the third synthesis equipment 7 to receive the synthesized preliminary methane, cool the preliminary methane, and separate gas and liquid to obtain methane products.

Specifically, the cooling and separation equipment includes a second steam generator 14 and a gas-liquid separator 15 .

The second steam generator 14 includes a second water supply pipe for circulation of water supply. The preliminary methane is used to provide heat to the water in the second water supply pipe to convert the water into steam. After the preliminary methane releases heat, the temperature decreases.

Specifically, the second steam generator 14 is connected to the outlet of the third synthesis device 7 to receive preliminary methane.

The outlet of the second water supply pipe outputs low-pressure saturated steam, which can be saved and utilized or sold.

The gas-liquid separator 15 is used to separate water from preliminary methane.

Further, a second cooling device 16 is provided between the second steam generator 14 and the gas-liquid separator 15 .

Specifically, after the preliminary methane is cooled by the second steam generator 14 and the second cooling device 16, the temperature is lowered to 30-50°C, and then separated by the gas-liquid separator 15, the methane product is output.

In the methane production system of this embodiment, the first heat exchange heat equipment, the first synthesis equipment 2, the second synthesis equipment 3, the second heat exchange equipment 4, the steam superheater 9, the first steam generator 12, the first cooling The equipment 13 and the gas-liquid separation equipment 5 form an open circulation loop.

In the above-mentioned open circulation loop, the first synthesis device 2 and the second synthesis device 3 exist both in series and in parallel. The synthesis gas is divided into two paths and enters the first synthesis device 2 and the second synthesis device respectively. When equipment 3 is used, the two are connected in parallel. When the gas after the first tower is cooled and then enters the second synthesis equipment 3, the two are connected in series.

The series and parallel combination of the first synthesis equipment 2 and the second synthesis equipment 3, the distribution of synthesis gas flow and the design of superheated steam control temperature rise ensure the appropriate reaction temperature and at the same time achieve a high conversion rate and stability. Operating characteristics.

In the above-mentioned open circulation loop, the first synthesis device 2 is an auxiliary reactor and the second synthesis device 3 is the main reactor. The second synthesis device 3 is a device for adjusting the output of the entire methane preparation system. Specifically, the production capacity and circulation ratio of the entire preparation system are adjusted by adjusting the amount of superheated steam entering the second synthesis device 3 . Therefore, the entire methane production system has a wide production capacity control and adjustment range and strong adaptability.

The third synthesis equipment 7 is connected in series with the above-mentioned open circulation loop and receives circulating gas. Therefore, the third synthesis equipment 7 mainly conducts deep purification reactions. The reaction temperature is close to a constant temperature. There is almost no carbon and oxygen in the preliminary methane produced. compound.

After the syngas passes through the first synthesis device 2 and the second synthesis device 3, the content of carbon oxides (CO+CO ₂ ) is greatly consumed, that is, the content of carbon oxides in the gas after the second tower is relatively low. . After the circulating gas passes through the third synthesis device 7, the content of carbon oxides (CO+CO ₂ ) is deeply purified, that is, there is almost no carbon oxides in the preliminary methane formed.

The series and parallel process deployment makes the reaction balance of the syngas more thorough, and can maximize the single-pass methane conversion rate, with low compression power consumption, concentrated energy and heat recovery, higher quality and high recovery volume of by-product steam, More economical.

The invention also provides a method for preparing methane, which includes the following steps:

S1. Provide synthesis gas. The volume percentage of (H ₂ -CO ₂ )/(CO + CO ₂ ) in the synthesis gas is greater than 3.

The synthesis gas can be obtained by biomass gasification yourself or purchased from outside.

The amount of hydrogen in the synthesis gas makes the synthesis gas in a surplus state during the methane synthesis reaction. That is, when carbon monoxide and carbon dioxide react with hydrogen, according to theoretical calculations, the amount of hydrogen can ensure that carbon monoxide and carbon dioxide completely react to generate methane.

S2. After the synthesis gas is heated up through heat exchange, it enters the first synthesis equipment 2 and the second synthesis equipment 3 respectively.

The synthesis gas is divided into two paths and enters the first synthesis device 2 and the second synthesis device 3 respectively. At this time, the first synthesis device 2 and the second synthesis device 3 can be understood as being arranged in parallel.

Preferably, the amount of syngas entering the first synthesis device 2 can be adjusted. The amount of syngas entering the first synthesis device 2 is adjusted so that the molar percentage of the total carbon oxides in the syngas in the first synthesis device 2 and the circulating gas is 3.0 to 5.0%. Specifically, a first flow control valve 8 is provided between the first synthesis device 2 and the first heat exchange device 1 , and the amount of synthesis gas entering the first synthesis device 2 is achieved by adjusting the first flow control valve 8 .

Furthermore, the amount of syngas entering the second synthesis device 3 is also adjusted so that the molar percentage of the total carbon oxides in the syngas in the second synthesis device 3 and in the gas after the second tower is 3.0 to 10.0%.

Specifically, a second flow regulating valve 11 is provided between the second synthesis device 3 and the first heat exchange device 1 , and the amount of synthesis gas entering the second synthesis device 3 is achieved by adjusting the second flow regulating valve 11 .

S3. Carry out methane synthesis reaction in the first synthesis equipment 2 to obtain the first column post-gas.

Specifically, the synthesis gas and the subsequently generated circulating gas enter from the top of the first synthesis equipment 2, pass through the nickel-based catalyst bed from top to bottom, and undergo a catalytic reaction at a pressure of 1 to 12 MPa and a temperature of 250 to 500°C. After getting the first tower.

Among them, in the first synthesis device 2, 75 to 85% of the carbon oxides are catalytically converted to generate methane.

Part of the reaction heat generated by the methane synthesis reaction in the first synthesis equipment 2 enters the steam superheater 9 and releases the heat to the steam, and the other part is integrated into the circulating gas.

S4. The gas after the first tower and the synthesis gas enter the second synthesis device 3 after being cooled by heat exchange. The gas after the first tower and the synthesis gas jointly perform a methane synthesis reaction in the second synthesis device 3 to obtain the second gas after the tower. .

Specifically, the synthesis gas and the gas after the first tower enter from the top of the second synthesis equipment 3, and pass through the nickel-based catalyst bed from top to bottom, and undergo a catalytic reaction at a pressure of 1 to 12 MPa and a temperature of 250 to 550°C to obtain The second tower is behind the gas.

Further, before the heat exchange between the gas after the first tower and the synthesis gas is carried out, the following steps are also included:

The gas after the first tower exchanges heat with the steam, releasing heat to convert the steam into superheated steam. The cooled gas after the first tower exchanges heat with the synthesis gas, and the superheated steam enters the second synthesis equipment 3.

S5. After the gas after the second tower is cooled, gas-liquid separation is performed to separate the water in the gas after the second tower.

S6. After water separation, the gas after the second tower is pressurized to form circulating gas. The circulating gas exchanges heat with the gas after the second tower and is heated up before entering the first synthesis equipment 2 and the third synthesis equipment 7. The third synthesis equipment The methane synthesis reaction is carried out within 7 days to obtain preliminary methane.

Specifically, the circulating gas and the synthesis gas enter from the top of the third synthesis equipment 7 and pass through the nickel-based catalyst bed from top to bottom. At a pressure of 1 to 12 MPa and a temperature of 250 to 300°C, a preliminary reaction is obtained through a catalytic reaction. Methane.

S7. After the preliminary methane is cooled and separated from gas and liquid, the product methane is obtained.

In the above preparation method, the space velocity of the circulating gas entering the third synthesis device 7 is controlled to be smaller than the space velocity of the synthesis gas and the gas after the first tower entering the second synthesis device 3, and the space velocity of the circulating gas entering the third synthesis device 7 is smaller than the space velocity of the synthesis gas. The space velocity of the syngas and the circulating gas entering the first synthesis device 2 is greater than or equal to the space velocity of the syngas and the gas after the first tower entering the second synthesis device 3 .

Among them, the space velocity of each synthesis equipment is achieved by controlling the loading amount of the catalyst. Specifically, by controlling the catalyst loading amount, the gas is guided through the catalyst bed at the required space velocity.

In the above methane preparation method, the space velocity and large ventilation volume in the first synthesis equipment 2 and the second synthesis equipment 3 can effectively avoid the local heat accumulation phenomenon in the catalyst bed, which is beneficial to reducing the hot spot temperature of the catalytic reaction and slowing down the methane production. The catalyst excessively releases heat in a local area under high hydrogen and high carbon partial pressure, causing more than 80 to 90% of the reaction area of the catalyst bed to be in a high temperature (350 to 550°C) and high conversion rate reaction temperature zone. Therefore, the catalyst improves overall efficiency and service life.

The space velocity in the third synthesis equipment 7 is low. The low space velocity and low carbon partial pressure make the reaction bed temperature more uniform, and the catalyst bed is in a low temperature 250-300°C, high conversion depth reaction temperature zone, which is beneficial to improving the single-pass synthesis loop. The conversion rate is favorable and meets the requirements for deep purification of methane gas.

In the first synthesis device 2, the synthesis gas and the circulating gas react at high space velocity and appropriate carbon oxide (CO+CO ₂ ) content (3.0-5.0%), so that the catalyst does not suffer from local overtemperature. In the second synthesis equipment 3, the synthesis gas and the gas after the first tower react at a relatively high space velocity, with external superheated steam, and a carbon oxide (CO+CO ₂ ) content (3.0-10%), and the reaction is controlled by The temperature rise of the bed and the single-pass methane production prevent local overtemperature of the catalyst.

That is, the methane preparation method in this application has a high conversion rate, a small cycle ratio, flexible and controllable temperature of the methanation synthesis equipment, a large capacity adjustment range, more reasonable system heat exchange, low energy consumption, and high energy heat recovery. The quality of the received steam is high.

While the present invention has been described with reference to several exemplary embodiments, it is to be understood that the terms used are illustrative and exemplary rather than limiting. Since the present invention can be embodied in various forms without departing from the spirit or essence of the invention, it should be understood that the above-described embodiments are not limited to any foregoing details, but are to be construed broadly within the spirit and scope defined by the appended claims. , therefore all changes and modifications falling within the scope of the claims or their equivalents shall be covered by the appended claims.

Claims (15)

1. A methane production system, comprising:

a first heat exchange device including a first heat channel and a first medium channel which are independent of each other and capable of heat exchange; the inlet of the first medium channel is used for receiving outside synthesis gas, and the inlet of the first medium channel is used for receiving outside synthesis gas (H ₂ -CO ₂ )/(CO+CO ₂ ) Is greater than 3 volume percent;

a first synthesizing device connected to an outlet of the first medium channel; the first synthesis equipment is used for carrying out methane synthesis reaction to obtain first tower post gas; the outlet of the first synthesis device communicates with the inlet of the first heat channel to provide the first column off-gas;

the inlet of the second synthesis equipment is connected with the outlet of the first medium channel and the outlet of the first heat channel at the same time and is used for receiving the synthesis gas after temperature rise and the first tower post gas after temperature reduction; the second synthesis equipment is used for carrying out methane synthesis reaction to obtain second tower post gas;

a second heat exchange device including a second heat channel and a second medium channel which are independent of each other and capable of heat exchange; the inlet of the second heat channel is connected with the second synthesis equipment to receive the second post-tower gas; the outlet of the second medium channel is communicated with the inlet of the first synthesis equipment;

the gas-liquid separation device is arranged at the downstream of the second heat channel and used for receiving the cooled second tower post gas and performing gas-liquid separation to separate water;

the pressurizing device is arranged at the downstream of the gas-liquid separation device and is used for receiving the second tower post gas after water is separated and pressurizing to obtain circulating gas, and the pressurizing device is communicated with the inlet of the second medium channel;

a third synthesis device disposed in parallel with the first synthesis device and downstream of the second media path to receive the recycle gas and provide the recycle gas for methane synthesis reactions;

the cooling and separating device is arranged at the downstream of the third synthesizing device to receive the synthesized primary methane and cool the primary methane and separate gas from liquid to obtain a methane product.

2. The methane production system of claim 1, wherein a first flow regulating valve is disposed between the first media channel and the first synthesis device; and/or the number of the groups of groups,

and a second flow regulating valve is arranged between the first medium channel and the second synthesizing equipment.

3. The methane production system of claim 1, wherein a steam superheater is further disposed between the first synthesis plant and the first heat channel, the steam superheater comprising a heating conduit for passing steam inside, the steam absorbing heat from the first post-column gas to form superheated steam, an outlet of the heating conduit communicating with an inlet of the second synthesis plant to input the superheated steam to the second synthesis plant.

4. A methane production system according to claim 3, wherein a first steam generator is further provided between the second synthesis plant and the second heat exchange plant, the first steam generator comprising a first feed water conduit for water circulation, the second post-column gas being adapted to provide heat to water in the first feed water conduit for conversion of water to steam, the outlet of the first feed water conduit being in communication with the heating conduit of the steam superheater.

5. The methane production system according to claim 1, wherein a first cooling device is further provided between the second heat exchange device and the gas-liquid separation device.

6. The methane production system of claim 1, wherein the cooling and separation apparatus comprises a second steam generator and a gas-liquid separator;

the second steam generator comprises a second water supply pipeline for water supply circulation, the primary methane is used for providing heat for water in the second water supply pipeline so as to enable the water to be converted into steam, and the gas-liquid separator is used for receiving the primary methane after temperature reduction and performing gas-liquid separation to obtain methane products.

7. The methane production system of claim 6, wherein a second cooling device is further disposed between the second steam generator and the gas-liquid separator.

8. The methane production system of claim 1, wherein the first synthesis apparatus is charged with a nickel catalyst, the second synthesis apparatus is charged with a nickel catalyst, and the third synthesis apparatus is charged with a nickel catalyst.

9. The methane production system of claim 1, wherein the first synthesis apparatus, the second synthesis apparatus, and the third synthesis apparatus are all shaft radial adiabatic synthesis reactors.

10. A method for producing methane, comprising the steps of:

providing synthesis gas, wherein (H) ₂ -CO ₂ )/(CO+CO ₂ ) Is greater than 3 volume percent;

the synthesis gas is heated by heat exchange and then enters into first synthesis equipment and second synthesis equipment respectively;

methane synthesis reaction is carried out in the first synthesis equipment to obtain first tower post gas;

the first post-tower gas and the synthesis gas enter the second synthesis equipment after heat exchange and temperature reduction, and the first post-tower gas and the synthesis gas jointly perform methane synthesis reaction in the second synthesis equipment to obtain second post-tower gas;

cooling the second tower post gas, and then performing gas-liquid separation to separate water from the second tower post gas;

pressurizing the second tower gas after water separation to form circulating gas, carrying out heat exchange and heating on the circulating gas and the second tower gas, and then entering the first synthesis equipment and the third synthesis equipment, and carrying out methane synthesis reaction in the third synthesis equipment to obtain primary methane;

and cooling and gas-liquid separating the primary methane to obtain the product methane.

11. The method for producing methane according to claim 10, further comprising the steps of:

adjusting the amount of the synthesis gas entering the first synthesis equipment to make the mole percentage of the total carbon oxides in the synthesis gas and the recycle gas in the first synthesis equipment be 3.0-5.0%; and/or the number of the groups of groups,

the amount of the synthesis gas entering the second synthesis equipment is regulated so that the mole percentage of the total carbon oxides in the synthesis gas and the second post-tower gas in the second synthesis equipment is 3.0-10.0%.

12. The method for producing methane according to claim 10, further comprising the steps of, before the second post-column gas exchanges heat with the recycle gas:

and the second post-tower gas exchanges heat with water, releases heat to convert the water into steam, exchanges heat with the circulating gas after cooling, and exchanges heat with the first post-tower gas.

13. The method of producing methane according to claim 12, further comprising the steps of, before the first post-column gas exchanges heat with the synthesis gas:

and the first post-tower gas exchanges heat with the steam, releases heat to convert the steam into superheated steam, and the superheated steam enters the second synthesis equipment, and exchanges heat with the synthesis gas.

14. The method for producing methane according to claim 10, wherein the synthesis gas and the recycle gas enter from the top of the first synthesis equipment and pass through a nickel-based catalyst bed from top to bottom, and are subjected to catalytic reaction at a pressure of 1 to 12MPa and a temperature of 250 to 500 ℃ to obtain the first post-tower gas; and/or the number of the groups of groups,

the synthesis gas and the first tower post gas enter from the top of the second synthesis equipment, pass through a nickel-based catalyst bed layer from top to bottom, and are subjected to catalytic reaction at the pressure of 1-12 MPa and the temperature of 250-550 ℃ to obtain the second tower post gas; and/or the number of the groups of groups,

the recycle gas enters from the top of the third synthesis equipment, passes through a nickel-based catalyst bed layer from top to bottom, and undergoes catalytic reaction at the pressure of 1-12 MPa and the temperature of 250-300 ℃ to obtain the primary methane.

15. The method of producing methane according to claim 10, wherein the space velocity of the recycle gas entering the third synthesis apparatus is less than the space velocity of the synthesis gas and the first post-column gas entering the second synthesis apparatus, the space velocity of the recycle gas entering the third synthesis apparatus is less than the space velocity of the synthesis gas and the recycle gas entering the first synthesis apparatus, and the space velocity of the synthesis gas and the recycle gas entering the first synthesis apparatus is greater than or equal to the space velocity of the synthesis gas and the first post-column gas entering the second synthesis apparatus.