Gasification under CO 2 –Steam Mixture: Kinetic Model Study Based on Shared Active Sites

In this work, char gasification of two coals (i.e., Shenfu bituminous coal and Zunyi anthracite) and a petroleum coke under a steam and CO 2 mixture (steam/CO 2 partial pressures, 0.025–0.075 MPa; total pressures, 0.100 MPa) and CO 2 /steam chemisorption of char samples were conducted in a Thermogravimetric Analyzer (TGA). Two conventional kinetic models exhibited difficulties in exactly fitting the experimental data of char–steam–CO 2 gasification. Hence, a modified model based on Langmuir–Hinshelwood model and assuming that char–CO 2 and char–steam reactions partially shared active sites was proposed and had indicated high accuracy for estimating the interactions in char–steam–CO 2 reaction. Moreover, it was found that two new model parameters (respectively characterized as the amount ratio of shared active sites to total active sites in char–CO 2 and char–steam reactions) in the modified model hardly varied with gasification conditions, and the results of chemisorption indicate that these two new model parameters mainly depended on the carbon active sites in char samples.