Preparation and rheological property of the char-water slurry based on co-pyrolysis of sawdust and lignite

An integrated experimental apparatus for pyrolysis/co-pyrolysis was employed to carry out the upgrading process of sawdust, Yunnan lignite, and their blends. The slurry-ability of the upgraded char was investigated. The results show that the slurry-ability of sawdust and Yunnan lignite is significantly improved via pyrolysis process. Bio-char and semi-coke were prepared at 500 ℃ holding 1.5 h. The solid loadings of the resulting slurry fuels derived from sawdust and lignite were enhanced from 29.21% and 54.63% to 38.57% and 60.19%, respectively. Under the same pyrolysis conditions, the slurry-ability of the char prepared from co-pyrolysis of sawdust and Yunnan lignite is apparently superior to that of the corresponding bio-char/coal char mixture with the same original mass ratio of feedstock. The prepared char-water slurries generally display pseudo-plastic behavior, i.e., the shear press decreases with increasing shear rate. When the mass ratio of sawdust exceeds 50%, the rheological property of char-water slurry tend to be shear thickening, exhibiting strong dilatant behavior at low shear rate, which is similar to the rheological property of biochar-water slurry. The desirable slurry-ability of the char produced from co-pyrolysis could be attributed to the synergistic effect of biomass and coal, which is likely to improve aromaticity of the resulting hybrid char.