| Biomass can be used as substitutes for fossil fuel to generate energy,chemicals and bio-carbons for its renewability, abundant in resources and environmental friendly. Biomass pyrolysis liquefaction technology is a very promising thermo-chemical conversion technology, and has drawn more attention from the academic world and industry. Based on the recent development in the biomass pyrolysis liquefaction technology, it is proposed in the study to design and fabricate a fixed bed reactor to study the influences of different biomass materials and pyrolysis temperature on the bio-oil composition, which is essential for understanding the mechanism of biomass fast pyrolysis liquefaction.In order to achieve the test purpose, a set of fixed bed biomass pyrolysis liquefaction equipment was designed and fabricated. The equipment consisted of an inert carrier gas supply system, a fixed bed reactor, a heating unit, a temperature controller, data acquisition system, a quenching unit and bio-oil collecting vessel. Preliminary experimental results indicated that the equipment had a good stability and reliability, and could meet the requirement of pyrolysis completely. Then biomass pyrolysis experiments were carried out on the equipment, and the effects of biomass materials species and pyrolysis temperature on the bio-oil composition was investigated.Variables investigated were biomass type(corn stalk, wheat straw and cotton stalk with an average particle size of 0.925 mm) and pyrolysis temperatures(400℃, 450℃, 500℃ and 550℃). The experiments were conducted on the fixed-bed reactor with a constant flow rate of nitrogen.The pyrolysis products properties including bio-oil chemical composition and moisture content, the ultimate analysis of char and its morphologies structure were analyzed then. Conclusions could be drawn as following.(1) For the pyrolysis of the maize stalk, wheat straw and cotton straw powder, 500℃ was the optimal temperature for obtaining the highest average bio-oil yield.(2) Pyrolysis temperature had a significant influence on thecomposition of bio-oil. And each kind of bio-oil has their unique content and their content has a certain difference. Biomass type has a significant effect on the composition and content of bio-oil. The amount of ketones was riched in bio-oil derived from corn stalk, followed by acids. While, the major compounds in bio-oil derived from wheat straw and cotton stalk were acids, and ketones next to acids are the second largest substance.(3) Pyrolysis char had high concentration of carbon, and the char surface cracks became larger as temperature increased. Some pyrolytic carbon particles embedded in the structure were also observed at higher temperature. |
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