Fast Co-pyrolysis Of Coal And Biomass In A Free Fall Reactor

Fast pyrolysis and co-pyrolysis of pine sawdust and sub-bituminous coal were conducted in a free fall reactor under nitrogen atmosphere. The pyrolytic characteristic of individual fuel at different temperature ranged from 500℃to 800℃was investigated. The characteristic of the co-pyrolysis of pine sawdust and sub-bituminous coal was also studied in the blending ratio from 0.25 to 0.75 and at temperature between 600℃and 800℃. Attentions were paid on the synergy in the process of co-pyrolysis. Some interesting conclusions were came to through comparing the changes of product distribution and gas composition of pyrolysis and co-pyrolysis. There are some differences between the pyrolytic characteristic of pine sawdust and sub-bituminous. It makes synergy in the co-pyrolysis possible that large amount of hydrogen and methane has been produced in the process of pine sawdust pyrolysis. The results also demonstrated that there is synergy in the co-pyrolysis of pine sawdust and sub-bituminous coal, which could be seen in the increase of liquid product. The gas composition of co-pyrolysis changed noticeably compared to the pyrolysis of individual fuel. The synergy of co-pyrolysis was exhibited more evidently at a higher pine sawdust blending ratio and a lower pyrolysis temperature. The synergy may be attributed to the transfer of hydrogen from biomass to coal.The chemical composition of liquid product from co-pyrolysis was also analyzed. A method based on solvent extraction, chemical treatment and extrography was established for the pre-separation of liquid product, by which the liquid product could be separated into five fractions including water-soluble, acid fraction, aliphatics, aromatics and polar fractions using solvent extraction, chemical treatment and extrography. GC-MS was utilized for quality identification and quantification of compounds in each fraction. The composition of liquid product is complicated and 86 kinds of compound has been identified. Most of these compounds exist in the aliphatics fraction including 52 kinds of hydrocarbon and oxygen-containing heterocyclic compound. There is a large amount of phenolic compounds in the acid fraction. The aromatics fraction is composed of decahydronaphthalene and aromatics hydrocarbon such as naphthalene and biphenylene. Only few of compounds has been identified in the water-soluble and polar fractions.