JP6922526B2 - How to make methane - Google Patents

Description

The present invention relates to a methane production apparatus capable of efficiently producing methane from a gas containing carbon monoxide, carbon dioxide and hydrogen, such as coke oven gas, from a raw material.

In recent years, many power plants perform so-called combined cycle power generation, which uses the exhaust heat of internal-combustion power generation to generate steam power. Gas turbine engines are mainly used as internal combustion engines, and liquefied natural gas (LNG) is used as the fuel, but LNG is usually cooled to -160 ° C or lower and transported by tanker from the country of origin. , It costs a huge amount of procurement cost. Furthermore, excessive reliance on the use of LNG is considered to pose a difficult phase in the future in order to stably supply raw materials. Therefore, LNG alternative natural gas (SN)
Development of a new manufacturing method of G) is underway.

Although SNG is composed mainly of methane, various studies and improvements have been made on an apparatus and a manufacturing method for synthesizing methane using carbon dioxide, carbon monoxide and hydrogen as raw materials. For example, in Patent Document 1, pretreated coke oven gas is CO-transformed, and then membrane separation is performed to collect non-permeated side gas, so that only coal gas is used without using an expensive carbon source. An apparatus for producing high-calorie gas or SNG using the above as a raw material is disclosed. Further, Patent Document 2 discloses a method for producing a fuel for a gas turbine using a gas containing coke oven gas and having a specific amount of carbon dioxide. Further, Patent Document 3 describes a method for co-producing methane and hydrogen, which comprises a step of reacting a gas containing carbon monoxide and / or carbon dioxide with a catalyst to methaneize, and a hydrogen separation step of permeating and separating hydrogen. Have been described.

Japanese Unexamined Patent Publication No. 2000-104080 JP-A-2015-117312 Japanese Unexamined Patent Publication No. 2016-108256

As mentioned above, there are some reports of devices for synthesizing methane, but there is still room for improvement in the devices for efficient production of methane. In particular, using by-product gas and exhaust gas generated from various industries as a fuel for combined cycle power generation as an alternative to LNG is a good idea.
It is superior in terms of cost and environment, and improvement from this point of view is desired.

An efficient method for obtaining methane is to react hydrogen in the raw material gas with carbon monoxide or carbon dioxide, and react unreacted hydrogen as much as possible to convert it into methane. There are not so many raw materials that contain a large amount of hydrogen, but the gas produced as a by-product in the production of coke, so-called coke oven gas (COG), contains hydrogen, carbon dioxide, carbon monoxide, methane, nitrogen, etc. It is considered promising to do so. In all of Patent Documents 1 to 3, methane is produced from coke oven gas as a raw material, but in the apparatus disclosed in Patent Document 1, the hydrogen composition of the product gas after membrane separation is high, and the gas turbine can be used. Since gas cannot be introduced directly, liquefied petroleum gas (LPG) must be used to adjust the calorific value. Further, in the methods disclosed in Patent Documents 2 and 3, since the composition of nitrogen after the methanation reaction is high, it is necessary to adjust the calorific value.

The present invention uses a gas containing carbon monoxide, carbon dioxide, and hydrogen as a raw material, such as coke oven gas, to efficiently produce methane at a high concentration, and the gas as it is without requiring adjustment of calorific value by LNG or the like. An object of the present invention is to provide a methane production apparatus capable of producing methane that can be used as a fuel for a turbine.

As a result of diligent studies to solve the above problems, the present inventors have developed a reactor as an apparatus for producing methane as a raw material containing at least carbon monoxide, carbon dioxide and hydrogen.
The present invention has been completed by finding that the above problems can be solved by using a separation device and a device having a specific recycling line configuration. That is, the gist of the present invention is as follows.

[1] A reactor having a supply port for supplying a raw material gas containing at least carbon monoxide, carbon dioxide and hydrogen and filled with a methanation reaction catalyst, carbon dioxide remaining as an unreacted component in the reactor. And a separator for separating methane and carbon dioxide from the mixed gas containing at least methane produced in the reactor, and at least a part of the gas containing carbon dioxide separated by the separator into the reactor. A methane production apparatus having a supply recycling line (1).
[2] The methane production apparatus according to [1], wherein a gas turbine is provided after the separation apparatus.
[3] The methane production apparatus according to [2], which has a recycling line (2) for supplying the exhaust gas discharged from the gas turbine to the reaction apparatus.

According to the present invention, methane is efficiently produced at a high concentration by using a gas containing carbon monoxide, carbon dioxide and hydrogen such as coke oven gas as a raw material, and adjustment of calorific value by LNG or the like is not essential. It is possible to provide a methane production apparatus capable of producing methane that can be used as it is as a fuel for a gas turbine.

It is a schematic diagram which shows an example of the methane production apparatus of this invention.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following description, and can be arbitrarily modified and carried out without departing from the gist of the present invention.

[Methane production equipment]
The methane production apparatus of the present invention has a supply port for supplying a raw material gas containing at least carbon monoxide, carbon dioxide and hydrogen, and is a reactor filled with a methaneation reaction catalyst, an unreacted component in the reactor. A separator for separating methane and carbon dioxide from a mixed gas containing at least methane produced in the reactor, and at least one of the gases containing carbon dioxide separated by the separator. It has a recycling line (1) that supplies parts to the reactor.

[Reactor]
The reactor used in the present invention has a supply port for supplying a raw material gas containing at least carbon monoxide, carbon dioxide and hydrogen, and is filled with a methanation reaction catalyst filled with a methanation reaction catalyst. Yes, methane is produced using these raw materials and catalysts.

(Raw material gas)
The raw material gas used in the present invention is not particularly limited as long as it contains at least carbon monoxide, carbon dioxide and hydrogen, and typical examples thereof include coke oven gas and pyrolysis furnace gas. This raw material gas is supplied from the supply port of the reactor and is subjected to a methanation reaction.

<Coke furnace gas>
The coke oven gas means the gas generated from the inside of the coke oven when coke is produced from coal. Specifically, the coke oven gas is a gas generated when coal is heated and carbonized at a temperature of 600 ° C. or higher to produce coke, and has a general composition of 10 to 70% by volume of hydrogen.
Methane 20-70% by volume, hydrocarbons other than methane (olefins such as ethylene) 1-
15% by volume, carbon monoxide 4-9% by volume, carbon dioxide 1-6% by volume, nitrogen 1-13% by volume,
Oxygen 0-0.5% by volume, sulfur compound such as hydrogen sulfide 0.3-1.5% by volume, nitrogen compound such as ammonia 0.3-1.8% by volume, benzols 0.1-1.8% by volume %, And other trace components derived from coal.

As the coke oven gas that can be used in the present invention, the gas having the above composition discharged from the coke oven can be used as it is, but it is preferable to use the pretreated coke oven gas. Specifically, it is preferable to use a coke oven gas that has been refined to reduce sulfur compounds such as hydrogen sulfide, nitrogen compounds such as ammonia, and benzols among the above components.

_{The pretreatment is mainly Fe 2} as a desulfurization catalyst in a dry desulfurization reactor that treats hydrogen sulfide, for example.
Removing hydrogen sulfide at about room temperature (20 ° C.) using O _3. Further, in the hydrogenated desulfurization reactor, Ni-Mo-based, C as a catalyst for converting a sulfur compound other than hydrogen sulfide into hydrogen sulfide.
It can be performed using an o-Mo system or the like. When these catalysts are used, hydrogenation is carried out by hydrogen in the coke oven gas. The pretreatment may be carried out according to a conventional method. For example, the treatment may be carried out under the conditions of a reactor inlet temperature of about 200 to 350 ° C., a reactor internal pressure of about 0.5 to 5.0 MPaG, and a reactor outlet temperature of about 100 to 450 ° C. Just do it. Further, for example, the coke oven gas may be sent to an adsorption desulfurizer to perform adsorption desulfurization with ZnO. The concentration of each component of the pretreated coke oven gas is generally 0.001 to 0.2% by volume of a sulfur compound such as hydrogen sulfide.
, Nitrogen compounds such as ammonia are reduced to 0.01 to 0.2% by volume and benzols are reduced to 0.02 to 0.3% by volume, and the concentrations of components other than these are substantially unchanged before and after the purification treatment.

The raw material gas used in the present invention may be either coke oven gas or pyrolysis furnace gas, but preferably contains at least coke oven gas. The content ratio of coke oven gas in the raw material gas is not limited, but is usually 1% by volume or more, preferably 10% by volume or more.
It is more preferably 50% by volume or more, further preferably 70% by volume or more, and particularly preferably 85% by volume or more. The upper limit of the content ratio of the coke oven gas is not limited, and may be 100% by volume.

<Pyrolysis furnace gas>
Pyrolysis furnace gas means gas generated when coal is pyrolyzed in a pyrolysis furnace. The composition of the pyrolysis furnace gas used in the present invention is not limited, but usually hydrogen, carbon dioxide, carbon monoxide, etc.
Contains methane, nitrogen, etc.

In the present invention, coke oven gas and pyrolysis furnace gas may be used in combination as the raw material gas. Even when the coke oven gas and the pyrolysis furnace gas are used in combination, it is preferable that the raw material gas in which both are mixed contains hydrogen, carbon dioxide, and carbon monoxide. The coke oven gas and the pyrolysis oven gas in the present invention do not necessarily have to be formed in a perfect gas state, and may be aerosols such as dust, fume, smoke, and mist, and these may be contained in the gas. It may contain the one in the state. Furthermore, it also includes liquid or solid substances formed by agglomeration or coagulation of gas.

<Other raw materials>
Any raw material can be used in combination with the coke oven gas and / or the pyrolysis furnace gas of the present invention (hereinafter, the raw materials other than the coke oven gas and the pyrolysis furnace gas may be referred to as "other raw materials"). The other raw material may be a gas, a solid or a liquid, but is preferably a gas in a state of being mixed with the coke oven gas and / or the pyrolysis furnace gas (including the state shown above). ..

(Methaneation reaction catalyst)
The methanation reaction catalyst charged in the reaction apparatus is not limited as long as it is a catalyst capable of reacting carbon monoxide and / or carbon dioxide with hydrogen to produce methane, but is generally known as a metanation reaction catalyst. Known catalysts can be used without limitation. Specifically, a nickel-based catalyst, a platinum group metal-based catalyst, another noble metal-based catalyst, or the like is used, and is particularly preferable from the viewpoint of good reaction efficiency and low cost of the nickel catalyst.

The methanation reaction in the present invention uses the above-mentioned raw material gas in the presence of a methanation reaction catalyst.
Substantially the following reactions are performed as the main reaction.
CO + 3H ₂ → CH ₄ + H ₂ O
CO ₂ + 4H ₂ → CH ₄ + 2H ₂ O

[Separator]
The separation device used in the present invention is a device for separating methane from a mixed gas containing at least carbon dioxide remaining as an unreacted component in the reaction device and methane produced in this reaction device. Further, the methane production apparatus of the present invention preferably has a line for supplying at least a part of the carbon dioxide-containing gas separated by the separation apparatus to the above-mentioned reaction apparatus. Examples of the separating device include a device using a separating material, a device using a chemical absorbent, a device using a physical adsorbent, and the like, but a device using a separating material or a device using a chemical absorbent is preferable. be. In addition, these devices may be used in combination as appropriate.

In the case of a separation device using a separation material, the separation material is not limited as long as it can separate carbon dioxide and methane, but it is preferable to use a separation membrane. Generally, examples of the gas separation / purification method include a membrane separation method, an adsorption separation method, an absorption separation method, a distillation separation method, a deep cold separation method, and the like, but the membrane separation method using a separation membrane has separation selectivity. It is suitable because the separation rate is high, there is almost no phase change during separation, and the equipment is inexpensive and compact.

The material of the separating material is not limited, but the types include organic polymer materials such as polyimide, polyaramid, polyamide, polycarbonate, polyether sulfone, polypropylene, and polyethylene, and zeolite, silicon, silicon carbide, silicon nitride, palladium, and silica. -Examples include oxides such as alumina, polyimide and zirconia, and inorganic materials such as composite oxides thereof. Here, the polyaramid refers to a total aromatic polyamide obtained by using an aromatic dicarboxylic acid and an aromatic diamine as main raw materials. Among these, polyimide, polyaramid, polyamide or zeolite is preferable as the material of the separation membrane.

In addition, the shape of the separating material is not limited, but specifically, a flat film shape, a hollow thread shape, a spiral shape, etc.
Tubular shape and the like can be mentioned. Of these, when an organic polymer material is used as the separating material, it is preferably in the form of a hollow thread because the permeation area can be increased.

In the case of a separation device using a chemical absorption liquid, examples of the chemical absorption liquid include aqueous ammonia, an alkanolamine solution, and monoethanolamine. These may be used in combination as appropriate.

In the case of a separation device using a physical adsorbent, examples of the physical adsorbent include activated carbon and zeolite. These may be used in combination as appropriate.

It is preferable that the separating device is provided with a mechanism for controlling the temperature from the viewpoint of the permeation rate. The temperature inside the device is usually 0 to 100 ° C, preferably 30 to 70 ° C.

It is preferable to have a mechanism for controlling the pressure of the mixed gas introduced into the separation device, and it is preferable to have a mechanism for controlling the pressure of carbon dioxide separated by the separation device. The pressure of the mixed gas introduced into the separation device is usually 0 to 5 MPaG in gauge pressure, and the pressure of the separated carbon dioxide is usually 0 to 10 MPaG in gauge pressure.

(Mixed gas)
When methane is separated by the separation device used in the present invention, a mixed gas containing at least carbon dioxide remaining as an unreacted component in the reaction device and methane produced in this reaction device is used.

As described above, a mixed gas containing at least carbon dioxide and methane is introduced into the separator, and these [volume of carbon dioxide]: [volume of methane] are preferably 80:20 to 1.
: 99, more preferably 70:30 to 5:95. In the mixed gas, it is preferable that these volume ratios are in the above range from the viewpoint of methane production efficiency.

Further, the mixed gas may contain other gases other than carbon dioxide and methane.
Other gases include carbon monoxide, nitrogen, oxygen, sulfur compounds, naphthalene, benzene,
Examples thereof include aromatic hydrocarbon compounds such as toluene and xylene. These are usually derived from coke oven gas and the like and are included in the mixed gas. On the other hand, when a separating material as described later is used in the separating device, it is preferable that the ratio of other gases in the mixed gas is small from the viewpoint of preventing deterioration of the separating material. Therefore, the other gas is usually 20% by volume or less, preferably 10% by volume or less, and more preferably 5% by volume or less with respect to the total mixed gas.
More preferably, it is 1% by volume or less. Therefore, it is preferable that the methane production apparatus of the present invention is provided with a mechanism for removing other gases in advance before introducing the mixed gas into the separation apparatus.

[Recycling line (1)]
The methane production apparatus of the present invention has a recycling line (1) for supplying at least a part of carbon dioxide-containing gas to the reaction apparatus in the separation apparatus. By recycling the gas containing carbon dioxide separated by the separation device in this way, carbon dioxide that is stoichiometrically efficient as a raw material for the methanation reaction is supplied as a raw material, and the reaction efficiency of the methanation reaction itself. Not only does it improve the purity of the resulting methane. As a result, it can be used as it is as a fuel for a gas turbine that can be used as an alternative to LNG without requiring mixing of the obtained methane with another gas.

[gas turbine]
In the methane production apparatus of the present invention, it is preferable that a gas turbine is provided after the above-mentioned separation apparatus. Here, the gas turbine is not particularly limited as long as it has a mechanism for rotating the turbine by burning methane to generate steam to generate electricity. By providing a gas turbine, electric power can be generated by using methane obtained by a methane production apparatus as fuel.

[Recycling line (2)]
The methane production apparatus of the present invention preferably has a recycling line (2) for supplying the exhaust gas discharged from the above-mentioned gas turbine to the above-mentioned reaction apparatus. Recycling line (2)
By providing the above, hydrogen in the raw material gas can be consumed, which has an advantage of improving the production efficiency of methane. When the methane production apparatus of the present invention has both a recycling line (1) and a recycling line (2), these lines may be connected to the reaction apparatus as independent lines, or these lines may be connected to the reaction apparatus. May merge and be connected to the reactor.

Here, the exhaust gas emitted from the gas turbine usually contains carbon dioxide.
Other gas components that can be contained in the exhaust gas include carbon dioxide, carbon monoxide, and the like. The exhaust gas may contain only one type of gas component, but as described above,
It is usually a mixture of two or more gas components. It is preferable to further recover only carbon dioxide in the exhaust gas, transfer it to the reactor, and recycle it.

Claims (3)

A method for producing methane from a raw material gas, which is a combination of a reactor filled with a methanation reaction catalyst and a separator for separating methane and carbon dioxide produced in the reactor.
The raw material gas contains coke oven gas and
The raw material gas is supplied to the reactor, the mixed gas containing at least methane produced in the reactor is supplied to the separator, and at least a part of the gas containing carbon dioxide separated by the separator is recycled. A method for producing methane, which is supplied to the reactor through (1). The method for producing methane according to claim 1, wherein the carbon dioxide concentration of the raw material gas is 6% by volume or less. The method for producing methane according to claim 1 or 2, wherein the methane separated by the separation device is supplied to the gas turbine, and the exhaust gas discharged from the gas turbine is supplied to the reaction device through the recycling line (2).

Images