SELECTED OBSERVATIONS ON THE COMBUSTION OF CHARCOAL BRIQUETS UTILIZED FOR THE OUTDOOR PREPARATION OF FOOD V. DETERMINATION ON THE REACTION RATE CONSTANTS FOR FIRST ORDER KINETICS

摘要

This manuscript presents the experimental data and the resultant computations required to determine the First Order reaction kinetics correlations for the combustion of charcoal briquets normally utilized for the preparation of foods. A Weber covered cooking kettle served as an assumed semi-batch reactor in which the reaction was a batch of "Kingsford" charcoal briquets combusting in a stream of fresh air entering through inlet ports in the bottom of the kettle. Experimental data included the initial weight of the briquets, the ambient climatological conditions, and the weight loss of the briquets and the kettle internal temperature as functions of time. These data provided input to appropriate mathematical relationships for computation of the weight fraction of volatiles, the weight fraction of charcoal consumed as a function of time, and the First Order conversion function. Subsequent linear regression analyses of the natural logarithm of the incremental kinetic rate constant versus the reciprocal of the absolute temperature yielded the Arrhenius frequency factor and the activation energy E_a/R for ten individual experiments. The average value of our activation energy was 2433 K; by way of contrast, the activation energy for a wood charcoal of unspecified properties from the literature was 3488 K. Considering caveats in our work and the unknowns about this wood charcoal, we concluded that the two values were in agreement. The manuscript concludes with recommendations for additional experiments (1) to further investigate the ignition process with the goal of better defining the role of the volatiles in the combustion reaction, and (2) to directly measure the combustion temperature of the charcoal briquets themselves in order to obtain more credible values of the activation energy.