High temperature combustion of pulverized coal

During recent years there has been mounting interest in the combustion of coal under conditions of high heating rates and high final temperatures. This has resulted from the national interest in coal utilization due to the present energy crisis.

This research was conducted in conjunction with a magnetohydrodynamics (MHD) coal combustor development program conducted at The University of Tennessee Space Institute. During the course of this development program, studies were made on the effects of mixing rate and residence time on the combustion of bituminous coal. Nominal heating rates of 105 degrees K per second with final combustion temperatures on the order of 3000°K characterized the typical test conditions. The stoichiometry was nominally 0.90 with oxygen concentrations in the oxidant above 55%. The experimental results were compared to a theoretical coal combustion model involving a one-step, first order Arrhenius reaction rate constant. This model proved to be adequate for the test conditions being studied.

Conclusions were reached as to the behavior of pulverized coal under flame conditions such as those that might be experienced in an MHD coal combustor. Qualitative information is presented as to the behavior of the coal particles during combustion and subsequent burn-out of the carbon.

Recommendations for further work are presented along with recommendations for improving the coal combustion model.