Property of upgraded solid product from low rank coal by thermal reaction with solvent

The upgrading process for the production of clean solid fuel from subbituminous and brown coals is receiving current attention. We propose upgrading of low rank coal with solvent at 350–450 °C under 2 MPa of initial nitrogen atmosphere. Upgrading of German Fortuna brown coal (heating value: 25.4 MJ/kg, daf) at 440 °C in the presence of t-decalin gave 66 wt.% of solid products with heating value of 35.4 MJ/kg, daf. Gaseous product consisted of mainly carbon dioxide (80 wt.%) and methane. Therefore, cracking of carboxylic functional group took place effectively in this condition. Ignition temperature of the upgraded solid product, measured by thermogravimetry under airflow, increased to higher than 400 °C, while raw brown coal showed corresponding temperature of 290 °C. From the XRD patterns by X-ray diffractometry for the upgraded product, distribution of aromatic stacking layer number (N) shifted to larger N by upgrading with solvent. It is obvious that the effective carbonization occurs under these conditions. This suggests the possibility to produce value-added solid fuel or carbonaceous liquid and solid chemicals, from low rank coal, whose quality is comparable to the bituminous coal.