Drying induced changes in the molecular properties of six different as-received coals with water contents ranging from 8 to 60 wt % of their wet weight were investigated on the basis of the mobility of the coal hydrogen and the distribution of different types of water. When dried at 303 K, a brown coal releases water in the following order: free water identical to bulk water, bound water that froze at around 226 K, finally, nonfreezable water that never froze even at 123 K. According to 1H NMR criteria, a portion of the coal hydrogen was found to be mobile. The amount of the mobile coal hydrogen (CMH) varied inversely with the amount of the nonfreezable water, while the release of the free and bound water had little effect on the reduction of CMH. For coals with water contents of up to 32 wt %, CMH in the as-received samples agreed well with the hydroxylic hydrogen content, CDH, which was determined by a hydrogen-deuterium exchange technique. However, in coals with higher water content, CMH was approximately twice as great as CDH.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology