Method for two-stage preparation of methane gas from solid waste

Abstract

The invention discloses a method for two-stage preparation of methane gas from solid waste. The method comprises the following steps: step 10) in a first-stage methanation area, introducing water vapor from the bottom of the area, introducing solid waste and a modified calcium-based ore catalyst from a side edge, and under the action of the water vapor, mixing the solid waste and the modified calcium-based ore catalyst and allowing the mixture of the solid waste and the catalyst to ascend and undergo direct methanation reaction with water vapor to obtain crude methane gas; and step 20) discharging the crude methane gas from the top of the first-stage methanation area, feeding the crude methane gas into a second-stage methanation area, uniformly feeding hydrogen into the second-stage methanation area, pre-regulating the hydrogen-carbon ratio of the crude methane gas, carrying out catalytic methanation reaction on methane gas by using a catalytic methanation catalyst, and preparing high-quality methane gas via the catalytic methanation catalyst under the fluidization action of the hydrogen and the crude methane gas. The method can achieve the effects of high fuel utilization rate, high methane quality and low catalysis cost.

Description

technical field [0001] The invention belongs to the technical field of natural gas preparation by resource utilization of solid waste, and discloses a two-stage method for preparing methane gas from solid waste. Background technique [0002] As an efficient and clean energy source, methane has attracted extensive attention for its synthesis and utilization. The process route of methane preparation can be divided into two categories: indirect methanation and direct methanation. In the indirect methanation process, the raw materials pass through the synthesis gas unit, the cleaning and purification unit, and the catalytic methanation synthesis unit to produce methane in sequence; methane gas. [0003] In the methanation process, fuels such as coal and biomass are widely used, and solid waste, which is also a solid fuel, has a wide range of sources and is rich in hydrogen, so it can theoretically also be used as a raw material for the methanation process. Complicated and not...

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Problems solved by technology

[0003]In the methanation process, fuels such as coal and biomass are widely used, while solid wastes, which are also solid fuels, have a wide range of sources and are rich in hydrogen. It can also be used as a raw material for the methanation process, but it has not been widely used due to its complex components

[0004]The reactor feedstock composition is complex and the temperature uniformity is high, which leads to the competition between gasification reaction, water gas shift reaction and methanation reaction in the methanation process The coupling mechanism is extremely complex

Specifically, the solid waste used as a raw material has heterogeneous and multi-component characteristics, which makes it difficult for the products (coke, volatile matter, tar) in the initial stage of the reaction to have consistent quantitative rules, so that in the subsequent reaction process Due to the difference in the type and quantity of reactants, excessive disproportionation carbon deposition reactions and excessive tar by-products occur, resulting in premature deactivation of the catalyst and a decrease in methane yield.

At the same time, because the temperature difference in the reactor is small, it is difficult to meet the optimal temperature requirements of gasification reaction, water gas shift reaction and methanation reaction at the same time, so there is bound to be a complex competition and coupling relationship among the three reactions. Thus affecting the yield and quality of methane

[0005]The reaction components involved in the solid waste direct methanation process are complex, and the raw materials will also produce sulfur-containing gas, resulting in more gas-solid Heterogeneous catalytic reactions can easily lead to premature deactivation of the catalyst, thereby reducing its service life

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