Variation of Micropore Structure of Yallourn Brown Coal during Carbonization

Abstract

In order to investigate the influence of carbonization conditions on the formation of microstructure of chars, the adsorption of carbon dioxide by the char samples prepared from Yallourn brown coal was carried out at20°C. The parameter Wo (micropore volume) and n in the Dubinin-Astakhov's equation were estimated from the adsorption isotherms.
As a result, the micropore volume W₀ of chars increased with increasing the heattreatment temperatures up to approximately 850°C. Above 850°C, however, the value of Wo decreased with increasing the heat-treatment temperatures. This seems to be caused by the thermal shrinkage of pores above850°C. The increasing tendency of W₀ was observed with decreasing the heating rates, especially in the temperature range of about 400 to 600°C. Similarly, the char samples, prepared by heating rate of 1°C/min in the temperature range of 200 to 600°C, were obtained in the higher yield. As the conclusion of this study, it seems likely that heating rates is important factor to be required in carbonization, particularly in the temperature range of 200 to 600°C, to make the high W₀ char in the high char yeild.