Coal oxidation at low temperatures: oxygen consumption, oxidation products, reaction mechanism and kinetic modelling

Coal oxidation at low temperatures (i.e. <100 °C) is the major heat source responsible for the self-heating and spontaneous combustion of coal and is an important source of greenhouse gas emissions. This review focuses on the chemical reactions occurring during low-temperature oxidation of coal. Current understanding indicates that this process involves consumption of O 2, formation of solid oxygenated complexes, thermal decomposition of solid oxygenated complexes and generation of gaseous oxidation products. Parameters, such as mass change, heat release, oxygen consumption, and formation of oxidation products in the gas or solid phase, have been used to qualitatively and quantitatively describe the oxidation process. Reaction mechanisms have been proposed to explain the characteristics of consumption of O2, and formation of oxidation products in the gas and solid phases. Various kinetic models have also been developed to describe the rate of oxygen consumption and the rates of formation of gaseous oxidation products in terms of the rate parameters of the relevant reactions, oxidation time, temperature, and initial concentration of oxygen in the oxidising medium. Further research emphasis should be placed on the formation of the complete reaction pathways proceeding in the oxidation process and on the development of kinetic models applicable for predicting the self-heating and gas emission in a coal seam or stockpile.

Coal oxidation at low temperatures: oxygen consumption, oxidation products, reaction mechanism and kinetic modelling, Pages 487-513

Coal fires in China over the last decade: A comprehensive review

Reaction pathway of coal oxidation at low temperatures: a model of cyclic chain reactions and kinetic characteristics

Chemical changes of Chinese lignite upon drying in superheated steam, microwave, and hot air have been studied in this paper using the Fourier transform infrared (FTIR) spectroscopy technique. The infrared (IR) spectra of raw and dried samples were curve-fitted to a series of bands in aliphatic hydrogen (3000–2800 cm–1) and carbonyl absorption (1850–1500 cm–1) zones. It has been found that aliphatic hydrogen absorbance decreased slightly with an increasing temperature during superheated steam drying, while absorption of carboxyl (COOH) and carbonyl (C═O) groups decreased drastically, indicative of the loss of oxygen functionalities with an increasing drying temperature. During steam drying, aromatic carbon and aromatic ring stretch absorption remained relatively unchanged up to 250 °C and decreased significantly thereafter because of some pyrolysis reactions that took place at higher drying temperatures. Microwave heating of lignite resulted in a significant decrease in the concentration of oxygen-contain...

Saurabh Bhat

Papers

Low-temperature oxidation of coal. 1. A single-particle reaction-diffusion model

The effect of moisture condensation on the spontaneous combustibility of coal