Method for preparing high-quality bio-oil based on microwave activation and pyrolysis gas recycling

Abstract

The invention discloses a method for preparing high-quality bio-oil based on microwave activation and pyrolysis gas recycling. The method includes: based on obvious differences of main chemical component structure of biomass and unique functions of the microwave activation, firstly subjecting biomass raw materials to microwave activation pretreatment on a microwave pyrolysis reactor, selectively decomposing hemicellulose components in the biomass raw materials to reduce formation of moisture and carbonyl compound during a quick pyrolysis stage, activate cellulose components and improve conversion efficiency of the cellulose at the quick pyrolysis stage, subjecting the pretreated products to quick pyrolysis reaction in a fluidized bed, changing composition of pyrolysis products by recycling pyrolysis gas to provide reactive atmosphere, further reducing formation of the carbonyl compound during the quick pyrolysis process, and simultaneously subjecting pyrolysis steam to in situ filtering for removal of solid particles in the pyrolysis steam. The finally obtained bio-oil is lower in content of water, the carbonyl compound and the solid particles, good in storage stability and high in heat value.

Description

technical field [0001] The invention relates to a method for producing bio-oil based on microwave activation and pyrolysis gas recycling, that is, a method for producing high-quality bio-oil through microwave activation pretreatment of biomass raw materials and recycling pyrolysis gas generated by rapid pyrolysis . technical background [0002] Biomass rapid pyrolysis technology is carried out at medium temperature, high heating rate and short residence time. Bio-oil has high energy density, is easy to store and transport, and contains many valuable chemicals and chemical intermediates. This technology has considerable development potential and application prospect. [0003] Rapid pyrolysis conditions are very harsh, and the chemical components of bio-oil are very complex. The moisture and carbonyl compounds in it mainly come from hemicellulose and cellulose in biomass. High moisture content not only reduces the calorific value of bio-oil, but also easily Stratification of...

AI Technical Summary

Problems solved by technology

CN1432626A discloses a method for catalytic cracking and refining of bio-oil. In the catalytic cracking reactor, HZSM-5 is used as a catalyst to carry out catalytic cracking of bio-oil to remove oxygen in bio-oil to improve its quality, but there is a catalyst in the catalytic upgrading process. Easy to deactivate, complex operation and other issues

However, in the pyrolysis process of the spiral pyrolysis reactor, due to the slow heat transfer rate under the conventional heating method, the raw material is heated unevenly, the cellulose is prone to cross-linking and carbonization, the coking reaction of lignin is intensified, and the thermal selectivity is poor.

At present, the reaction process control of fast pyrolysis technology mainly optimizes the process conditions of fast pyrolysis, including feed rate, fluidization gas velocity, reaction temperature and residence time, which can increase the yield of bio-oil, but the quality of bio-oil cannot be obtained. In addition, the solid particles produced in the pyrolysis process have a greater impact on the quality of bio-oil. In the rapid pyrolysis process, cyclone separation is often used to remove solid particles in the pyrolysis steam, but cyclone separation cannot effectively separate them. Small-sized solid particles (below 2-3μm) lead to a high content of solid particles in bio-oil. Due to the high viscosity of bio-oil, direct liquid phase filtration is difficult and complicated to operate.

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