Combined Coal/Biomass Pyrolysis

 

As we've suggested to be possible and feasible, experiments are being performed on the co-pyrolysis of coal and biomass, combined, to generate the raw materials for liquid fuels.
 
The development in the case we cite herein is taking place in China, home of the rather extraordinary coal-to-liquids industrialization program we've reported, and where, as we've also reported, they are using agricultural development to consume excess Carbon Dioxide.
 
The excerpt, with comment about their choices of both biomass and coal following: 

" Li Zhang, Shaoping Xu, Wei Zhao and Shuqin Liu

State Key Laboratory of Fine Chemicals, Department of Chemical Engineering, Dalian University of Technology, 158 Zhongshan Road, PO Box 33, Dalian 116012, China 

Abstract

An experimental study on co-pyrolysis of biomass and coal was performed in a free fall reactor under atmospheric pressure with nitrogen as balance gas. The coal sample selected was Dayan lignite, while the biomass used was legume straw. The operation temperature was over a range of 500–700 °C, and the blending ratio of biomass in mixtures was varied between 0 and 100 wt.%. The results indicated that there exist synergetic effects in the co-pyrolysis of biomass and coal. Under the higher blending ratio conditions, the char yields are lower than the theoretical values calculated on pyrolysis of each individual fuel, and consequently the liquid yields are higher. Moreover, the experimental results showed that the compositions of the gaseous products from blended samples are not all in accordance with those of their parent fuels. The CO2 reactivities of the chars obtained from the co-pyrolysis under the higher blending ratio (around 70 wt.%) conditions are about twice as high as those of coal char alone, even higher than those of biomass alone."

First, "straw" would suggest the dried stems of grasses or grains, consisting we would suppose, in large part, of cellulose - which we've previously documented to be compatible with coal as a co-feed for a suitably-designed gasification/liquefaction facility.

Second, the coal they are using is lignite, which will be lower in organic content and higher in ash than West Virginia bituminous, but which will be comparable in some ways to carbonaceous wastes found in some, especially older, WV coal mine spoil accumulations.

Third, the use of combining coal with cellulose appears to be synergistic: The "liquid yields are higher", with lower residual "char".

Finally, the combination is synergistic in another way, as well: The straw, as it grows, consumes the Carbon Dioxide that evolves when the fuel is combusted.