Characteristics of coal thermodynamics under environmental aqueous chemical erosion conditions

Abstract

Raw and treated coal samples were studied using an X-ray diffractometer, contact angle device, Fourier transform infrared spectrometer and thermogravimetric instrument. The disordered crystalline carbon content of the coal decreased with acid treatment, whereas a contrasting result was found for alkali treatment. Calcite can be removed in acidic solutions, but alkaline solutions can form new minerals with clay minerals. The breakage of aliphatic side chains in coal occurs under both acidic and alkaline treatment. The mass of the coal samples after burnout decreased in the order alkali-treated coal > raw coal > acid-treated coal. In the low-temperature stage, the alkali-treated coal sample had a higher transformation degree than the raw coal or acid-treated coal, and its activation energy was the lowest. The acid-treated coal has higher activation energy, which is beneficial for preventing the spontaneous combustion of coal.