A simple kinetic analysis to determine the intrinsic reactivity of coal chars

The intrinsic oxidn. reactivity in air of an activated carbon char derived from bituminous coal was investigated using a new thermogravimetric anal. (TGA) method. Applying the new method, values of the Arrhenius activation energy E and pre-exponential factor A were estd. from TGA data obtained via heating samples at different const. rates. A novel statistical criterion was subsequently used to det. the heating rate at which optimum values of E and A were obtained. This is a valuable development, for in conventional non-isothermal TGA, while Arrhenius parameters vary with heating rate, there is no formal method for selecting one rate (and hence one set of values of E and A) over another. Using this new method, the following optimum values were obtained for the carbon at a heating rate of 25 Deg min-1: E=129.4 kJ mol-1 and ln(A//s)=10.4. These results are similar to those calcd. for the same material using more time consuming and less accurate isothermal TGA methods. It is therefore proposed that this new anal. method might be an improvement on conventional techniques to det. the intrinsic oxidn. reactivity in air of coal chars. [on SciFinder (R)]