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High-Temperature Gasification Reactivity with Steam of Coal Chars Derived under Various Pyrolysis Conditions in a Fluidized Bed

2009; American Chemical Society; Volume: 24; Issue: 1 Linguagem: Inglês

10.1021/ef9004994

1520-5029

Hao Liu, He Zhu, Mashhiro Kaneko, Shigeru Kato, Toshinori Kojima,

Granular flow and fluidized beds

In a unique fluidized-bed reactor, the gasification reactivity with steam of chars derived under various conditions was investigated at elevated temperatures. It was revealed that, similar to char-CO2 gasification, even at elevated temperatures, the gasification rates in steam were very different between different coals. The gasification rate of char with steam was very different from that of raw coal. A longer pyrolysis time led to lower reactivity of char during char gasification with steam. No significant influence of pyrolysis time on the temperature dependence of gasification reactivity (i.e., activation energy for a char) was identified. The reaction rate for coal had a tendency to level off at a high temperature for simultaneous pyrolysis/gasification experiments, which was probably caused by the ash fusion in a reducing atmosphere. Generally, the activation energy of char gasification with steam, was lower than that with CO2 gasification. Moreover, the former activation energy in the low-temperature range was not significantly different from that in the high-temperature range. At elevated temperatures, the rate of char gasification with steam was not necessarily much higher than that of char-CO2 gasification.