Device and process for preparing natural gas by virtue of double-fluidization bed gasification of biomass

Abstract

The invention provides a device and a process for preparing natural gas by virtue of double-fluidization bed gasification of a biomass. The device comprises a burning carrier heating unit, a pyrolysis gasification unit, a biological carbon/carrier separation and conveying unit and a methane synthesis and tar returning unit, wherein the pyrolysis gasification unit is connected with the burning carrier heating unit, the biological carbon/carrier separation and conveying unit and the methane synthesis and tar returning unit. The other components are converted into methane gas as much as possible while the biological carbon is obtained, the content of methane in a pyrolysis product is about 10%, the pressure for subsequent synthesis is reduced, the tar in hydrolysis gas is used as a fuel for a double-fluidization bed, and the problems that combustion cannot be stabilized at a low temperature and alkali metals causes scorification in a high-temperature state when other double-fluidization beds adopt biological carbon combustion can be avoided to ensure that the temperature of a combustion furnace can be controlled very flexibly. The device and the process provided by the invention fully use different pyrolysis products of the biomass, can realize treatment of various biomasses, and are wide in raw material application range.

Description

technical field [0001] The invention relates to the technical field of biomass gas, in particular to a biomass double fluidized bed gasification device and process for producing natural gas. Background technique [0002] my country has huge reserves of agricultural and forestry biomass resources, and the use of biomass gasification synthetic fuels to replace increasingly depleted fossil fuels has broad market prospects. Biomass gasification is an efficient and clean conversion technology. With the help of gasification agent, biomass conversion can be used to obtain gas or syngas whose main combustible components are CO, H2, CO2 and CH4. Gasification technology is combined with subsequent processes. It can be used to generate electricity, heat or synthesize chemicals. Biomass gasification can convert biomass raw materials with large volume, low energy density, non-combustibility or low combustion efficiency into natural gas or other gaseous or liquid fuels with high energy d...

AI Technical Summary

Problems solved by technology

Since the dual fluidized bed gasification technology adopts the method of heat transfer from the combustion furnace to the pyrolysis gasification furnace through the heat carrier, the temperature of the combustion furnace needs to be higher than that of the pyrolysis gasification furnace, while the current dual fluidized bed combustion furnace uses Biochar (semi-coke) is used as the fuel of the combustion furnace, and the ignition temperature of biochar is about 700°C, which requires that the temperature of the combustion furnace should not be lower than 700°C, and many high-alkaline biomass raw materials (wheat straw, straw, etc.) The ash melting point is also around 700°C. Therefore, when using high-alkaline biomass raw materials, the traditional double fluidized bed method cannot operate, and the raw materials can only be limited to high ash melting point biomass such as wood and rice husks. Therefore, it is urgent to develop raw materials to adapt to Wide range of dual fluidized bed technology, so that it can be widely used in grain husks, wood processing scraps, papermaking waste and various crop straw waste utilization and treatment, as a way to save energy, protect the environment, reduce production costs and improve efficiency effective means

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