Further insights into the effect of the mass transfer limitations on the reaction order of the char-CO2 reaction
2019
Geng, Ping | Zhang, Yan | Liu, Zhiyi | Liao, Lei | Liu, Rui | Zheng, Jinhao
In this study, the reaction order of the char-CO2 gasification in the char conversion range of 0.1 to 0.8 is measured using a flat alumina disc (FAD) and cylindrical alumina crucibles (CCs) in thermogravimetric analysis (TGA). The height of the crucible sidewall and the layer number of char bed are used as indirect estimation for the external and inter-particle diffusion limitations, respectively. The results indicate that the CO2 partial pressure exponent in the nth order equation is a reasonable representative of the intrinsic reaction order when the bed thickness is below three layers, regardless of the existence or absence of the external diffusion. For thick-bed configurations with more than three layers, the exponent is always equivalent to the intrinsic order at the initial stage of the reaction that corresponds to the surface-layer reaction at x ≤ 0.3. The inter-particle diffusion has apparent effect on the reaction order.
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