COKING PROPERTY OF THE UPGRADED COAL FROM LOW RANK COAL

摘要

Effective utilization process of the low rank coal has not yet been established due to its high moisture, low heating value, spontaneous ignition behavior and larger generation of carbon dioxide by direct combustion. Some of the reports on the industrial study of the upgrading of low rank coal, such as KFx, LFC and SynCoal processes, by mild gasification and low temperature pyrolysis at the temperature ranging 220 -600℃ have already been published. In these existing processes, the moisture content was significantly reduced and the heating value of the upgraded solid fuel was greatly enhanced to the comparable level with bituminous coal. Spontaneous ignition property of the upgraded solid product was also treated by briquetting, partial oxidation using carefully controlled airflow or/and covering active surface sites by heavy tar fraction. However these present treatment for spontaneous ignition is not enough to prove long distance transportation of the upgraded coal with safety. We proposed the liquid-phase upgrading of low rank coal in the presence of t-decalin at 380-440℃ under 2MPa of initial nitrogen pressure. Heating value of the upgraded solid product from Buckskin (USA subbituminous) coal increased to 30 MJ/kg as compared with 25 MJ/kg of the dry raw coal and the spontaneous ignition behavior was greatly improved. From the XRD patterns, measured by X-ray diffractometry for the upgraded solid product, stacking layer number (N) of aromatic components shifted to larger N and spread much widely. This suggests the possibility to produce value-added clean solid fuel and chemicals by the liquid-phase upgrading. In this work, we studied liquid -phase upgrading of low-rank coals in the presence of solvent at 380-440℃ under nitrogen atmosphere. Characterization of the upgraded solid product was evaluated in terms of heating value, ignition temperature for fuel use and XRD patterns by X-ray diffractometry and fluidity measurement by gieseler plastmeter for cokes use.