Steam gasification or pyrolysis of biomass was conducted at heating rates of 1, 10, and 100 K
s-1 using a thermobalance reactor. Three kinds of biomass samples (cellulose, lignin, and bagasse)
were used. Time profiles of weight change of biomass samples during steam gasification and
pyrolysis were measured at 973 K. Char obtained in steam gasification of lignin was analyzed
with a scanning electron microscope and a CHNS elemental analyzer. The effect of the heating
rate on final conversion and reaction rate of char was investigated. It was found that a higher
heating rate substantially increased the reaction rate of lignin char in steam gasification because
porous char was produced during devolatilization due to rapid evolution of volatiles. A higher
heating rate also increased final conversion of biomass. The heating rate showed no pronounced
influence on elemental composition of char.
Evolution rates of low-molecular-weight gas products (H 2 , CH 4 , CO, and CO 2 ) in pyrolysis and steam gasification of biomass (cellulose and lignin) were studied using thermogravimetric-mass spectrometric (TG-MS) analysis. Total gas yields were measured with a TCD-micro gas chromatograph (micro GC) at heating rates of 1, 10, and 100 K s -1 . Steam gasification of biomass demonstrated heating rate effects on gas evolution: 81 wt % of cellulose was converted into tar in pyrolysis; also, slow heating and steam gasification of nascent char occurred above 700 K, evolving H 2 . Rapid heating significantly enhanced secondary pyrolysis of cellulose tar to yield H 2 , CO, and CH 4 . In contrast, char formation at 500-773 K was dominant in lignin pyrolysis. Evolution of H 2 and CO 2 were significantly increased by steam gasification of char. Insignificant influence of heating rate on carbon and hydrogen yield of lignin was observed. Over 70% of lignin's chemical energy was converted into gas, especially hydrogen.
The pyrolysis of cellulose was studied using a novel CCDR in which tar and gases can be fractionated according to the reaction time. Similar trends of evolution behavior were observed for both tar and lowmolecular-weight gases in the pyrolysis of cellulose at 673 K. The evolution of tar and low-molecular-weight gases achieve a peak at 20-30 s, converting depolymerizing cellulose to nascent char. The dehydration of nascent char produced by depolymerization and devolatilization was found to take place after the devolatilization is completed.
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