Influence of metal nitrates on the process of coal oxidation of various metamorphism stages

Abstract

The process of oxidation of lignite and bituminous coal modified with metal nitrates (Cu, Ce, Na, Co, Fe) in the amount of 5 wt.% is studied. Application of additives to the coal samples is carried out by the method of incipient wetness impregnation with preliminary dissolution of the additive in an aqueous-alcohol solution with a volume ratio of C2H5OH/H2O=50/50. Reactivity of the samples is studied by thermogravimetric analysis in the oxidation mode at a heating rate of 2.5 °C/min in the temperature range 25–600°C at atmospheric pressure. It has been found that application of activating additives contributes to reduction of the initial temperature of intensive oxidation (Ati=5–97°C) and to a shift of the process to the low-temperature region as a whole. According to the results obtained, the greatest activity is specific for addition of Cu(NO3)2. It is manifested in a decrease in the temperature of the beginning of intensive oxidation ti and an increase in the average reaction rate wav. The Coats-Redfern method is used to calculate activation energy of the oxidation process in the presence of activating additives. Maximum decrease in Eais observed for a copper nitrate-modified coal sample.