Evaluation of the effect of a palm acid oil coating on upgrading low rank coal

Abstract

Indonesian low rank coal (LRC) was upgraded by the addition of palm acid oil (PAO), and the efficiency of the inhibition of spontaneous combustion, as well as the resistance to moisture readsorption, was compared with raw coal. Fluorescence microscopy images revealed that PAO was well distributed in the coal matrix during the drying process. The PAO coating the surface of coal decreased the pore volume and the surface area of the upgraded coal and improved its stability. The upgraded LRCs had higher heat calorimetry values, greater resistance to moisture readsorption, and a reduced tendency toward spontaneous combustion when compared to raw coal. In upgraded coal briquettes, PAO was present in the form of a network-like structure, which led to an increase in the compressive strength by binding the coal particles. The upgraded LRCs showed less susceptibility to isothermal oxidation due to the PAO coating on the coal particles, which suppressed the reaction of active functional groups with oxygen in the air.