Improvement of Devolatilization and Control of Low-temperature Oxidation by Vacuum Drying and Tar Coating Treatments of Low-rank Coal

Abstract

Upgrading of low-rank coal by means of a combined process of vacuum drying and tar coating has been conducted in order to suppress low-temperature oxidation and spontaneous combustion of coal. Some advantages on improvement of devolatilization and control of low-temperature oxidation have been observed. This upgrading technique was able to produce the upgraded coals comparable to bituminous coal particularly in moisture, volatile matter and carbon contents. Total weight loss and devolatilization significantly increased with an increase of the upgrading temperature, from 29.5 and 10.5%, respectively at 200°C to 36.5 and 21.9%, respectively, at 300°C. Moreover, upgraded coals showed a lower propensity to oxygen attack and low-temperature oxidation.