Development of Bench Scale Techniques for coal Reactivity Characterisation at Elevated Pressure

Bench-scale methods have been developed that enable volatile yield and intrinsic char reactivity data to be generated at elevated pressures. These data are in a form that can be used in mathematical process models to assess coal performance in high intensity coal utilisation technologies such as emerging entrained flow coal gasification technologies.

There are two stages to the technique: coal volatile yields are measured under high heating rate and high pressure conditions in a wire-mesh reactor (WMR); and char reactivity parameters (such as reaction rates, orders and activation energies) are measured at elevated pressures in a pressurised thermogravimetric analyser.

Both of the apparatus were thoroughly characterised in this work. The WMR was used to measure volatile yields as a function of pressure and the TGA was used to characterise char samples (including those produced in the WMR) in terms of the kinetic parameters for the reactions with CO2, H2O and O2. It was concluded that the WMR technique is a useful alternative to large and expensive flow reactors for determining coal volatile yields at high heating rates and elevated pressures and that the TGA method is extremely useful for characterising the heterogeneous char-gas reactions at increased pressures in terms of reaction rates, activation energies and reaction orders. The data generated using the TGA were combined with measured char structural parameters to demonstrate their application in estimation of gasification rates of chars at high temperatures and pressures.