Co-pyrolysis of biomass and coal in a free fall reactor

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.