The use of solid-state NMR techniques for the analysis of water in coal and the effect of different coal drying techniques on the structure and reactivity of coal. Quarterly report, June 1, 1992--August 31, 1992

Abstract

The results of measuring the change in moisture content of the Eagle Butte and Usebelli coals as a function of time are shown in Figure 1. As expected, the measured moisture content increases with time and reaches a maximum after about 8 hours. Two different types of sorbed water are removed sequentially. Free or surface sorbed water is rapidly removed followed by the water in the micropores of the coal as the reagents migrate into the pore structure. There appears to be an induction period of about 4 hours for the Eagle Butte coal before the moisture content increases more rapidly with time due to the reactions of the more ``tightly bound or ``pore`` water with the reagents. The chemical drying experiment was repeated twice for the Usebelli coal. In the first experiment, aliquots of the reaction mixture were removed sequentially, and in the second experiment separate coal samples were prepared and allowed to stand until the appropriate time for the NMR spectrum to be acquired. Excellent reproducibility was obtained. Both cools were thermally dried by heating to 110{degrees}C for 1 hour. The moisture content was determined by weight loss. Using the thermal drying method, the Eagle Butte coal had a moisture content of 16.6 wt % and the Usebelli coal a moisture content of 14.1 wt %. These values are near the moisture content of coal as determined by chemical drying.