KINETICS OF THE ALKALI CARBONATE CATALYZED GASIFICATION OF CARBON .3. H2O GASIFICATION

The rates of the alkali catalysed water-gas shift reaction (WGS) and steam gasification of carbon have been studied at 1.5 x 10(5) Pa total pressure as a function of temperature (800-1000 K), feed composition (pure H2O or mixtures of H2O with either CO2, H-2 or CO), alkali metal (Na, K, Rb, Cs) and K2CO3 loading (0-25 wt%). A four step kinetic model is selected which describes the observed temperature dependency of the reaction rates and inhibition by CO, H-2 and CO2. Only beyond 950-1000 K is the catalysed WGS oxygen exchange at thermodynamic equilibrium. In H2O atmospheres, with low CO2 or CO contents, the various alkali elements exhibit similar activities due to high dispersion. At higher CO2 concentrations the H2O gasification rate is strongly lowered, while CO can completely inhibit H2O gasification, and only the WGS reaction takes place. The effect of potassium loading on the H2O gasification activity is similar to that observed for gasification in CO2.