Highly efficient sulfamic acid inhibitor enhanced coal spontaneous combustion prevention through acid corrosion and hydrolysis

Abstract

An amphiphilic sulfamic acid (SA) water-based inhibitor was investigated regarding its inhibiting performance on spontaneous combustion of multi-rank coals. Based on the optimal concentration of the SA water-based inhibitor solution, the free radical changes, weight loss rates, and low-temperature oxidation characteristics, and pore structure parameters of multi-rank coals before and after inhibition treatment were discussed through low-temperature nitrogen adsorption experiments, scanning electron microscopy, programmed heating experiments, thermogravimetric experiments and electron paramagnetic resonance experiments. Results show that 5 wt% SA water-based inhibitor solution can exert superior emulsifying, wetting, and permeating effects. The SA water-based inhibitor solution suppresses coal spontaneous combustion mainly via two pathways: (1) it dissolves inorganic minerals and destroys organic macromolecular structures in coal through acid corrosion, thereby changing its pore structure; (2) it generates incombustible gases and inactivates free radicals though hydrolysis (into salts), thus impeding the coal-oxygen reactions. The SA water-based inhibitor solution has a stronger inhibiting effect on low- and medium-rank coals. The inhibition rates of the SL and DFS coals at 110 °C reach 75.2 % and 85.0 %, respectively. Moreover, their cross-point temperatures are increased by 38 °C and 22.9 °C respectively in comparison to the cross-point temperatures of the raw samples treated with deionized water.