Experimental study on fast pyrolysis of free-falling millimetric biomass particles between 800 ℃ and 1000 ℃

摘要

Pyrolysis experiments were performed between 800 ℃ and 950 ℃ on wood particles with diameters from 350 to 800 μm in a lab-scale drop tube reactor to reproduce surface heat flux representative of gas-ifiers conditions. It was shown that particle size affected the required pyrolysis time but changed neither gas/tar/char mass yields nor composition of the products at the end of pyrolysis. The initial particle size also affected the resulting char morphology: the larger the biomass particles, the more fibrous the char. Temperature had influence neither on gas/tar/char mass yields nor on gas and solid elemental composition at the end of pyrolysis, but significantly changed the yields of individual gas species. Whatever the conditions tested, a significant shrinkage could be observed on particles during pyrolysis. These experimental results confirm the strong coupling between chemical reactions, particle geometrical properties and heat transfers during pyrolysis under these conditions.