Study On Catalytic Cracking Of Tar In Biomass Gasification With Steam In Fluidized Bed

Biomass gasification is an important kind of biomass utilizationtechnology, while the high content of tar has prevented the extensiveapplication of this technology. Based on such background, the cotton stalkwas used in the thermogravimetric experiment and fluidized bed steamgasification experiment. And the effect of alkaline earth oxides catalysts ontar cracking was investigated by quantum chemistry calculation.It was observed that the pyrolysis of cotton stalk was devided into activepyrolysis zone and negative pyrolysis zone during the thermogravimetricexperiment. Both CaO and MgO had catalytic effect in these two zones; andthey improved the pyrolysis characteristics of the cotton stalk; and reducedthe amount of benzene, toluene and phenol in tar.In the gasification experiment, it was found that with the increase ofgasification temperature, the increase of S/B, the decrease of fluidizationnumber, the tar content is reduced. And by changing the gasificationtemperature and S/B, the tar component could be adjusted. The effect ofdolomite on tar catalytic cracking was better than that of olivine.In the quantum chemistry calculation, it was found the toluene radicalcould be adsorbed by the CaO and MgO in four ways. Among them, the wayCaO and MgO was adsorbed side by side and oxygen atom was far awayfrom methyl was easiest. After the toluene radical was adsorbed by the CaOand MgO, the C-C bond Mulliken population in toluene radical was reduced,and in CaO case, it was reduced more.