Kinetics of coal drying‐decomposition

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Abstract
A series of seven coals of different ranks and from various locations were heated in an inert atmosphere under relatively mild conditions to measure the rates of gas evaporation. Samples crushed to various fractions in the particle size range −6+50 U.S. mesh were studied at temperatures in the range of 150 to 300°C. The results show that: (1) most water is released at 100°C, evidently an evaporation process, (2) CO2 is evolved at 150°C and above, and (3) CO is evolved at 250°C and above. An interpretive model was developed to fit the CO2 production rate and kinetic constants were obtained. Gas evolution rates are independent of particle size for the most porous coals, but vary among coals, depending on both chemical composition and physical structure. A 15% loss in heating value was incurred during drying and subsequent oxidation when the pretreatment temperature was increased from 150 to 225°C.