A comparison of simple global kinetic models for coal devolatilization with the CPD model

• Simple coal pyrolysis models are needed that are accurate over a range of heating rates in pulverized coal-fired boilers.
• Seven simple forms of pyrolysis models were tested vs. the CPD model at heating rates from 5000 to 106 K/s up to 1600 K.
• Good agreement was found with two different modified forms of the two-step model for the full range of heating rates.

Simulations of coal combustors and gasifiers generally cannot incorporate the complexities of advanced pyrolysis models, and hence there is interest in evaluating simpler models over ranges of temperature and heating rate that are applicable to the furnace of interest. In this paper, six different simple model forms are compared to predictions made by the Chemical Percolation Devolatilization (CPD) model. The model forms included three modified one-step models, a simple two-step model, and two new modified two-step models. These simple model forms were compared over a wide range of heating rates (5 × 103 to 106 K/s) at final temperatures up to 1600 K. Comparisons were made of total volatiles yield as a function of temperature, as well as the ultimate volatiles yield. Advantages and disadvantages for each simple model form are discussed. A modified two-step model with distributed activation energies seems to give the best agreement with CPD model predictions (with the fewest tunable parameters).