Kinetic study of the CO2 gasification of manure samples

The influence of the temperature on the gasification of two manure char samples (char Pre and char SW) was evaluated in a thermogravimetric analyser (TG) using CO2 as the gasifying agent. Experimental data were fitted to seven kinetic models in order to reproduce accurately the gasification process. The classic volumetric (VM), shrinking core (SCM) and random pore (RPM) models were considered. In addition, four semi-empirical models based on them (SCM-Emp, RPM1, RPM2 and RPM3) were also tested. For the parameter estimation, a home-made VBA-Excel application was developed. The statistical meaningful of the models and their corresponding parameters were evaluated by using F and t tests, respectively. The best fittings were achieved with SCM (char Pre) and SCM-Emp (char SW) models. A catalytic promotion of the gasification process for char SW was observed, coming from the inorganic matter present in this sample. Consequently, the alkali index (A.I.) for both samples was calculated in order to check the catalytic behaviour of the metallic species contained in the corresponding ashes. As expected, the A.I. value corresponding to char SW was much higher than that of char Pre.