Abstract: Our principal accomplishments in the physical property studies of low-rank coals are the determination of their: (A) relative amounts of tightly and loosely bound moisture, (B) porosity and pore size distribution, (C) mechanical and thermal friabilities, and (D) surface areas. The occurrence of moisture in low-rank coals involves at least two fundamentally different mechanisms for binding the water to the coal matrix. The first type of moisture behaves as if it were ''free''; the vapor pressure versus temperature behavior is similar to that of pure water. The second type occurs at sites where it is bound more tightly, resulting in a lowering of the corresponding vapor pressure. A dielectric-relaxation-spectroscopic investigation of a North Dakota lignite and a subbituminous coal provides direct evidence for the existence of the two types of moisture. Lignite incorporates 80% of its moisture in a loosely-bound form which freezes to ice and the remaining 20% is present possibly chemically bound to inorganic moieties. The subbituminous coal contains only the latter type of bound moisture. Small angle scattering has proven to be a useful and convenient method of studying the pore structure of coal, and yields information related to pore size, pore size distribution, specific surface areamore » and specific volume. Calculation of values for these parameters must be made in terms of some model; a pore model developed at the University of Missouri has proven to be quite useful. The objective in friability studies is to determine the shift in particle size distribution as a result of tumbling or heating. 6 figs., 2 tabs.« less
Publication Year: 1985
Publication Date: 1985-07-01
Language: en
Type: article
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Cited By Count: 4
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