Characteristics of American coals in relation to their conversion into clean energy fuels. Quarterly technical progress report, October--December 1975

Abstract

The actual coal gasification reaction is controlled diffusionally in the lower part of the bed and kinetically in the upper part of the bed. When closely size-graded pulverized coal particles undergo rapid devolatilization in a laminar flow reactor, the effect of heating-up time on weight loss is negligibly small. All other experimental conditions being equal, the smaller the particle, the greater is the weight loss. Reactivity of a char increases with increase in partial pressure of oxygen in the air-nitrogen mixtures. Reactivities of various chars are determined by rank of the parent coals and their mineral matter content. There is a 170-fold difference in the reactivities of various chars. Char reactivities are maximized by keeping the maximum heat treatment temperature as low as possible, the heating rate to maximum temperature as high as possible, and allowing no soak time at maximum temperature. Therefore, reactivity of a char prepared by rapid devolatilization is appreciably higher than that of a char prepared by heat treatment using slow heating rates. The differential scanning calorimetry technique can be used to characterize carbons in terms of their reactivities. Small angle x-radiation scattering shows promise in characterization of internal porosity in coal chars. Siderite and pyritemore » significantly increase reactivity of Saran carbon to hydrogen. On the other hand, calcite and kaolinite inhibit the hydrogasification reaction. Oil-water-air emulsions have lower thermal efficiency than oil itself; however, the addition of coal to the emulsion increases the efficiency to that of oil. The addition of coal also consistently results in increased heat flux from the flame to the water tubes. (auth)« less