Franklin J. Wright

Coal Science: Basic Research Opportunities

More fundamental knowledge of coal (knowledge of its structure and its behavior during conversion processes) is essential before we can generate new technologies necessary for the efficient use of coal in the future. Herein are suggested specific basic research opportunities in the areas of coal characterization, gasification, combustion, and liquefaction, along with an assessment of the impact such research programs could have. Critical characterization needs include qualitative and quantitative determination of the chemical forms of carbon, oxygen, nitrogen, and sulfur and reliable methods for the measurement of surface area, pore volume, and weight-average molecular weights. Mechanistic studies aimed at increasing understanding of the thermal breakdown of the functionalities in coal, the behavior of coal in the presence of molecular and donor hydrogen environments, and carbon gasification and hydrocarbon synthesis reactions starting from carbon monoxide and hydrogen will lay the scientific foundation for the development of new processes for converting coal into clean usable fuels and chemicals.

The Science of Mineral Matter in Coal

Publisher Summary This chapter discusses the modes of occurrence of inorganic elements in coal, both as mineral phases and as organically bonded elements. The effects that highly dispersed elements may have on coal processing are also reviewed in the chapter. Mineral matter plays a variety of important roles in all coal utilization processes. Inorganically bound elements in present-day coals are the result of at least five mechanisms operating at or from the time of initial peat deposition: (1) incorporation of elements from the original plant material; (2) precipitation of elements from aqueous solution; (3) accumulation of airborne detritus; (4) accumulation of waterborne detritus; and (5) epigenetic mineralization, that is, minerals that have formed in cleats and fractures of the coal deposit. Accumulation of detrital mineral particles and the chemical precipitation of dissolved species from aqueous solution are the major processes by which inorganic elements are introduced into the peat deposit from external sources.

The oxidation of soot by O atoms

The oxidation of soot by O atoms has been studied gravimetrically using a sensitive recording balance. At 5 Torr, the rate of the reaction expressed as the number of C atoms leaving 1 cm 2 of geometric surface per sec is a function of the square of O atom concentration over a 5-fold range. This reaction order is independent of temperature between 300°K and 850°K. The rate of oxidation, however, varies in a complex manner with temperature. At a concentration of O atoms of 3.5×10 14 atoms per cc it reaches a maximum of 1.4×10 17 C atoms per cm 2 /sec at 425°K. It then decreases to a rate 1/7 of the above at 650°K. Above this temperature, the rate increases once again in a more normal manner. At 5 Torr, CO 2 is the only reaction product detected. At lower pressures (∼0.05 Torr) CO appears to be formed also. Both the high order of 2 and the preponderance of CO 2 , are rationalized on the basis that the present work was carried out at higher pressures than usual. The rates of oxidation of pyrographite and vitreous carbon by O atoms were also obtained over the same temperature range. Apart from the absence of the sharp maximum at 425°K, these rates showed remarkable general agreement with those obtained for soot and with literature values. The reactivity of O atoms thus appears little affected by the nature or micro-structural features of the carbon. The data available on the reactivity of pyrographite can therefore be used with confidence to infer the behavior of soot. There are now strong reasons to believe that oxygen atoms play an important role in the removal of soot in hydrocarbon flames.