Influence of particle size, reactor temperature and gas phase reactions on fast pyrolysis of beech wood

Abstract : In the present work, a drop tube reactor (DTR) and a horizontal tubular reactor (HTR) were used to study the pyrolysis behaviour of beech wood particles of different sizes under the conditions encountered in industrial fluidized bed gasifiers, namely high external heat flux (105-106 W.m 2) and high temperature (800-1000 C). The influence of the reactor temperature (800 and 950 C), of particle size (from 350 µm to 6 mm), and of gas residence time (from 1 to 10 s) were examined. Under the explored conditions, when pyrolysis is finished, more than 80 wt.% of virgin wood is converted into gas and less than 13 wt.% remains in solid. In the gas phase, CO is the main gaseous product (50 wt.% of virgin wood), followed by H 2 (molar ratios of H 2 /CO are between 0.35 to 0.55), H 2 O, CO 2 and CH 4. Species C 2 H 2 , C 2 H 4 , C 2 H 6 and C 6 H 6 are present in much lower amounts. The increase of temperature increases the rate of solid devolatilization and favours the cracking reactions of hydrocarbons. The increase of particle size increases the required time for completing pyrolysis. Meanwhile, the results obtained at 950 C show that the final products distribution at the end of pyrolysis is almost the same for the particles between 350 and 800 µm. The increase of the particle size from 800 µm to 6 mm seems to have some influence on the final products distribution. The gas phase reactions mainly change the yields of light hydrocarbons and H 2 : the increase of gas residence time favours the cracking reactions of hydrocarbons and thus leads to a higher H 2 yield.
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Li Chen, Capucine Dupont, Sylvain Salvador, Guillaume Boissonnet, Daniel Schweich. Influence of particle size, reactor temperature and gas phase reactions on fast pyrolysis of beech wood. International Journal of Chemical Reactor Engineering, De Gruyter, 2010, 8, p.1-19. ⟨10.2202/1542-6580.1922⟩. ⟨hal-01846914⟩

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