Influence of CuSO4 initiation additive on kinetic characteristics of coal oxidation and pyrolysis processes

Abstract

Coals oxidation and pyrolysis processes of different metamorphic grades containing 5%wt of initiation additive were studied. The experiment was performed by thermogravimetric analysis method at a heating rate of 2.5°C/min to a maximum temperature of 600°C in an atmosphere of air and nitrogen. Based on the results of TGA, an analytical evaluation of kinetic characteristics of pyrolysis and oxidation processes was conducted. It has been established that addition of CuSO4 initiating agent leads to significant decrease in the initial temperature of oxidation and pyrolysis processes, which promotes the shift of the reaction to a low-temperature region. Change of the initial reaction temperature ΔTi for oxidation process was 30°C, ΔTd for pyrolysis was 45°C. Effect of initiation additive was also expressed in significant reduction of sample residence time within volatile substances sublimation zone: for oxidation Δti was 14 minutes, for pyrolysis Δtd was 18 min. For modified sample characterized by lower stage of metamorphism, the decrease in oxidation time Δtf was the greatest (22 min), which is explained by the high content of volatile substances. According to mass-spectrometric analysis, presence of SO2 (intense peaks at 290°C and 440°C) was recorded in modified samples oxidation products, which is explained by partial hydrolysis of copper sulfate.