(418bz) Elucidation of the Reaction Mechanism during Coal Pyrolysis

Recently Integrated coal Gasification Combined Cycle (IGCC) has been attracting great attention as a means of highly efficient power generation. As a previous step of coal gasification, volatiles and char are generated from coal pyrolysis. Tar, one of the volatiles, causes problems such as pipeline plugging, defluidization in fluidized bed reactor, reduction in thermal efficiency, and inhibition of char gasification. Therefore, it is necessary to reduce the production of tar or to separate tar from char in order to overcome these problems. Thus, it is essential to elucidate the reaction mechanism of tar production in coal pyrolysis for improvement in the controllability and thermal efficiency of the coal gasification process.

In many previous studies, both pyrolysis and steam gasification of some kinds of coals, such as bituminous coal or brown coal, were investigated with rapid heating or slow heating using a thermobalance reactor, micro GC and mass spectrometer. It was found that time profiles of weight change of coal samples and the evolution of low molecular weight gases (H₂, CH₄, CO and CO₂). To understand concretely the reaction mechanism of tar production, it is necessary to further investigation about the online time profile of tar evolution and componential analysis.

In this study, the time profiles of gas, tar and char evolution, and tar componential analysis during coal primary pyrolysis and secondary pyrolysis were investigated for elucidating the reaction mechanism of volatiles, in particular tar, production. From this result, tar problems will be overcome and thermal efficiency of IGCC will be improved.