Studies On Low Temperature Dryness Technology And The Effect On Characters Of Low Rank Coal

Low temperature convective dryness technology of high moisture contently low rank coal was investigated using hot air and nitrogen as the medium. The coal in the experiments was obtained from Shenhua Group Jinfeng Coal Colloery in Inner Mongolia. Characters of the coal are high water content, high volatile, low net calorific value and easily spontaneous combustion. The purpose of this study is to find out optimum conditions of low temperature fast dryness techonology to enhance it's quality. At the same time, samples of the coal before and after drying were determined by FTIR, SEM, TGA, XPS, and BET to compare the effect of low temperature dryness on the functional group constitute, surface morphology, specific surface area, surface carbon valence states and oxidation kinetic parameters.Result of the experiments indicates that the fast convective dryness process was carried out under hot air and it is flowed 2000L/min 170℃hot air is reduced the moisture from 30% to less than 15% within the 10min, the net calorific value of the coal was raised to 23.51MJ/kg, and there is no organic pollutants on dyrness exhaust gas and the process didn't increase risk of coal dust explosion. As the hot air temperature enhanced and the drying time extended, more moisture was removed. The detection result of FTIR, SEM, TGA, XPS and BET indicated that if the hot air exceeded 170℃and drying time was more than 10min, the coal would be oxidized and a series of changes in the coal would happen, such as the bridge bond and lateral chain structure oxidation, surface micro structure was powdered and the oxidation degree of the coal surface carbon was deepened. All these changes will lead to increasing tendency of spontaneous combustion.Experiment studies of nitrogen as the medium have shown that: the nitrogen dryness effect is better than hot air and the oxidation extents of coal surface has been reduced. However, the nitrogen couldn't be low-cost unlimited use and development of the high proportion nitrogen cycle low temperature drying technology is the fundamental solution.