Methanation system for prolonging service life of methanation catalyst

Abstract

The utility model belongs to the technical field of coal gasification, and particularly discloses a methanation system capable of prolonging the service life of a methanation catalyst, which comprises a methanation reactor, a heat exchanger raw material pretreatment device and a cryogenic liquefaction device, an outlet of the heat exchanger is connected with the steam pocket, an outlet of the steam pocket is connected with the steam water segregator, and an outlet of the steam water segregator is connected with an inlet of the methanation reactor; in a methanation reaction process, disproportionation reaction of CO may occur, and generated carbon powder can seal active sites of a catalyst or block pore channels, reduce the activity of the catalyst, even pulverize the catalyst and shorten the service life of the catalyst. According to the methanation reactor, the steam is introduced into the methanation reactor, so that the total mole number of a system is increased, the mole fraction of carbon monoxide is reduced, the partial pressure of the carbon monoxide is reduced, the disproportionation reaction of the carbon monoxide is inhibited, and carbon deposition is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of coal gasification, and particularly relates to a methanation system for prolonging the service life of a methanation catalyst. BACKGROUND

[0002] Methanation refers to a process in which CO and H in synthesis gas undergo chemical reactions to generate CH under the action of a catalyst at a certain temperature and pressure. Methanation is a strong exothermic, volume-reducing reversible reaction, and carbon may be precipitated during the reaction. The temperature rises by 70-72 DEG C for every 1% conversion of CO. Methanation must be carried out under the action of a catalyst, and the catalytic reaction between CO and H is a typical selective catalytic reaction.

[0003] Patent CN116179248A discloses a method and system for preparing natural gas by methanation of coke oven gas. The coke oven gas is subjected to a first-stage isothermal methanation reaction by a catalyst I. The first-stage reaction gas is subjected to first-stage condensation gas-liquid separation to obtain a first-stage gas phase and a first-stage liquid phase. The first-stage gas phase is mixed with carbon dioxide, and the obtained mixed gas is subjected to a second-stage isothermal methanation reaction in the presence of a catalyst II. The second-stage reaction gas is subjected to second-stage condensation gas-liquid separation to obtain a methane product gas and a second-stage liquid phase.

[0004] However, the above methanation reaction process may cause the disproportionation reaction of CO The carbon powder generated may block the active sites of the catalyst or block the pores, reducing the activity of the catalyst and even causing the catalyst to pulverize, thereby reducing the service life of the catalyst. UTILITY MODEL CONTENT

[0005] The utility model aims to provide a methanation system for prolonging the service life of a methanation catalyst to solve the problem of reduced service life of the methanation catalyst caused by carbon deposition during the methanation reaction process.

[0006] To achieve the above-mentioned purpose, the basic scheme provided by the utility model is as follows: a methanation system for prolonging the service life of a methanation catalyst, comprising a methanation reactor, a heat exchanger raw material pretreatment device, and a deep cooling liquefaction device. The outlet of the methanation reactor is connected to the inlet of the heat exchanger shell layer. The outlet of the heat exchanger tube bundle is connected to a steam drum. The outlet of the steam drum is connected to a steam bleeder. The outlet of the steam bleeder is connected to the inlet of the methanation reactor.

[0007] The principle and beneficial effects of the utility model are as follows: the methanation reaction is a strong exothermic reaction. Steam is generated by using the waste heat of the product gas of the methanation reaction through a heat exchanger. The steam is introduced into the methanation reactor, increasing the total number of moles of the system, reducing the mole fraction of carbon monoxide, and thus reducing the partial pressure of carbon monoxide, thereby inhibiting the disproportionation reaction of carbon monoxide Reduces the generation of carbon deposits. Steam may also react with carbon monoxide to form a water-gas shift reaction. This reaction consumes carbon monoxide, further reducing the actual concentration and partial pressure of carbon monoxide. The generated carbon dioxide and hydrogen can participate in other reactions, reducing the possibility of carbon deposition reactions.

[0008] Option 2, a preferred alternative to the basic option, requires the medium-pressure steam discharged from the heat exchanger tube bundle to be at 2.4 MPa. Excessive steam may intensify competition with side reactions such as the water-gas shift reaction, thereby reducing methane selectivity. Therefore, the steam pressure and input rate must be controlled to achieve reaction equilibrium.

[0009] Option 3 is the preferred option of the basic option. The medium-pressure steam delivered by the steam separator is also separated and connected to the inlet of the raw material pretreatment device. A part of the steam is used to remove excess CO in the raw material gas and convert CO into CO2

[0010]

[0011] Option 4, a preferred option over the basic option, includes gas analyzers at the inlet and outlet of the methanation reactor, and a temperature sensor within the methanation reactor. Gas analyzers are installed at the inlet and outlet of the methanation reactor to monitor the concentrations of the feed gas (carbon monoxide and hydrogen) and products (methane, carbon dioxide, etc.) in real time. Catalyst deactivation is determined by calculating the conversion rates of carbon monoxide and hydrogen. However, due to the complex conditions of the methanation reaction, hotspot temperature and temperature fluctuations must be considered to determine whether catalyst activity has decreased. Furthermore, the inlet and outlet gas analyzers can be used to calculate the selectivity of methane in the product (methane selectivity = amount of substance producing methane / amount of substance consuming carbon monoxide in the reaction × 100%) to comprehensively determine changes in catalyst activity. The steam input can be dynamically adjusted based on the catalyst activity.

[0012] Option 5, a preferred alternative to the basic option, connects the heat exchanger shell outlet to the condenser inlet. Steam and product gas have different liquefaction temperatures, and the condenser separates water from the product gas, ensuring the purity of the product gas.

[0013] Option 6, which is the preferred option of the basic option, connects the outlet of the condenser to the inlet of the heat exchanger tube bundle. The condensed water returns to the heat exchanger to heat the supplementary steam and recycle the water. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a structural schematic diagram of a methanation system for increasing the service life of a methanation catalyst according to the present invention;

[0015] Figure 2This is a structural schematic diagram of a methanation reactor in a methanation system for improving the service life of a methanation catalyst according to the present invention. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below through specific implementation methods:

[0017] The reference numerals in the drawings of the specification include: 1-methanation reactor, 2-heat exchanger, 3-raw material pretreatment device, 4-cryogenic liquefaction device, 5-steam drum, 6-steam water separator, 7-gas analyzer, 8-condenser, 9-temperature sensor.

[0018] Example

[0019] like Figure 1 and Figure 2 As shown, the raw gas first passes through the raw material pretreatment device 3 for desulfurization and decarbonization. The outlet of the raw material pretreatment device 3 is connected to the inlet of the methanation reactor 1, which is connected to the shell inlet of the heat exchanger 2, which is connected to the steam drum 5, which is connected to the steam separator 6, which is connected to the inlet of the methanation reactor 1. Gas analyzers 7 are installed at the inlet and outlet of the methanation reactor 1. A temperature sensor 9 is installed inside the methane reactor 1. The shell outlet of the heat exchanger 2 is connected to the inlet of the condenser 8, which is connected to the tube bundle inlet of the heat exchanger 2. A branch pipe branches from the outlet of the steam separator 6 and is connected to the raw material pretreatment device 3.

[0020] The implementation method of this embodiment is as follows: the raw gas passes through the raw material pretreatment device 3 to remove impurities such as sulfur and benzene, and then enters the methanation reactor 1. During the operation of the methanation reactor 1, a large amount of heat is generated. This heat enters the heat exchanger 2 along with the product gas. The steam generated by the heat exchanger 2 is stored in the steam drum 5. The steam in the steam drum 5 is separated from the liquid water by the steam separator 6, and the steam is transported to the methanation reactor 1. At the same time, a part of the steam is transported to the raw material pretreatment device 3 to assist the shift reaction. The product gas from heat exchanger 2 enters condenser 8, where it is separated from the water and product gas. The condensed water is then fed back into heat exchanger 2 to replenish the steam water. A gas analyzer 7 and temperature sensor 9 calculate the carbon monoxide and hydrogen conversion rates, the selectivity of methane in the product, and temperature fluctuations, comprehensively assessing changes in catalyst activity and dynamically adjusting the steam input based on the catalyst's activity.

[0021] The above only is the embodiment of the present application, and the well-known specific structure and characteristics and other common knowledge in the scheme are not described too much here. It should be pointed out that, for those skilled in the art, without departing from the structure of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application, and these will not affect the effect and practicality of the present application. The protection scope claimed in the present application should be subject to the content of its claims, and the specific implementation mode and the like recorded in the specification can be used to explain the content of the claims.

Claims

1. A methanation system for improving the service life of a methanation catalyst, comprising a methanation reactor (1), a heat exchanger (2), a raw material pretreatment device (3), and a cryogenic liquefaction device (4), characterized in that: The outlet of the methanation reactor (1) is connected to the shell inlet of the heat exchanger (2), the tube bundle outlet of the heat exchanger (2) is connected to the steam drum (5), the outlet of the steam drum (5) is connected to the steam water separator (6), and the outlet of the steam water separator (6) is connected to the inlet of the methanation reactor (1).

2. A methanation system for increasing the service life of a methanation catalyst according to claim 1, characterized in that The medium-pressure steam discharged from the tube bundle of the heat exchanger (2) has a pressure of 2.4 MPa.

3. The methanation system for increasing the service life of a methanation catalyst according to claim 1, characterized in that: The steam water separator (6) is connected to the inlet of the raw material pretreatment device (3).

4. The methanation system for increasing the service life of a methanation catalyst according to claim 1, characterized in that: The inlet and outlet of the methanation reactor (1) are provided with a gas analyzer (7), and a temperature sensor (9) is provided inside the methanation reactor (1).

5. The methanation system for increasing the service life of a methanation catalyst according to claim 1, characterized in that The shell outlet of the heat exchanger (2) is connected to the inlet of the condenser (8).

6. The methanation system for increasing the service life of a methanation catalyst according to claim 5, characterized in that: The outlet of the condenser (8) is connected to the inlet of the tube bundle of the heat exchanger (2).

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