Study on Combustion Characteristics of Bituminous Coal Modified by Typical Inorganic Acids

Abstract

In order to cooperate with the application of acid fracturing technology in coal mines, this article focuses on the effects of HF, HCl, and HNO₃ solutions on coal combustion characteristics. Combining FTIR analysis, TG-DTA analysis, and thermal analysis kinetics, a mechanism analysis method from microstructure and combustion parameters to combustion kinetics is proposed. The research results show that inorganic acid will destroy the C=O in coal, especially the carbonyl group in the HNO₃ coal sample completely disappears. In addition, inorganic acid is remarkable for enhancing the reaction rate and thermal effect of the combustion stage and improving the comprehensive combustion characteristics of coal. Among them, the improved efficiency is exposed as HF>HNO₃ >HCl. The combined effect of inorganic acid on the chemical modification of coal molecular structure and the physical modification of pore structure changed the mechanism function in the initial weight loss stage. As well as, it had different degrees of influence on the activation energy and pre-exponential factor in each stage. Hydrofluoric acid and hydrochloric acid reduce the activation energy in the weight gain stage of coal oxidation and increase the spontaneous combustion tendency of coal.

Keywords: Corrosion ratio, FTIR, Bagchi method, Apparent activation energy, Spontaneous combustion tendency