Experiment and Field Application of Inhibitior Liquid in Spontaneous Combustion Process of Coal Based on Thermogravimetric Analysis

Abstract

Abstract An effective way to slow down the process of coal spontaneous combustion (CSC) is by injecting inhibitor liquid into the coal body. Research on inhibitors has achieved good effects, but many have occurred only under laboratory conditions; for applications in actual underground coal mines, there may be many limitations. In this paper, MgCl2, CaCl2, and NH4H2PO4 are selected, and they are prepared as inhibitor liquids and injected into coal samples from three coal mines to obtain inhibitor coal samples. Industrial analysis (IA) and thermogravimetric analysis (TGA) of raw and inhibitor coal samples were carried out under laboratory conditions. Finally, MgCl2 was selected as the inhibitor to carry out a field test in a coal mine working face. The results show that the volatile content, fixed carbon content, and calorific value decrease and the ash content increases after injection of the inhibitor. NH4H2PO4 has the greatest influence on coal, which is more obvious in the Nantun coal samples. MgCl2 and CaCl2 have stronger inhibitory effects in the temperature range of 0–200 °C, and the inhibitory effects decrease in the high-temperature stage. This is due to the evaporation of water and the loss of active components under high temperature. The inhibitory effect of NH4H2PO4 at high temperature is stronger than those of MgCl2 and CaCl2. The CO concentration was significantly reduced after injection of the inhibitor liquid in an underground field, which delays the oxidation process of coal for approximately 10 days and greatly reduces the risk of CSC.