Study on CMC-Based Suppressant for Coal Dust and Spontaneous Combustion Control

Underground coal mining faces coupled hazards from respirable coal dust and spontaneous coal combustion. This study developed a dual-function flame-retardant dust suppressant comprising carboxymethyl cellulose (CMC), polycarbodiimide (PCDI), ammonium polyphosphate (APP), and zinc borate (ZB). A four-factor, three-level orthogonal design was used to screen formulations by penetration depth, followed by rheological, water-scour, simulated-roadway, temperature-programmed oxidation, contact-angle, Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscope (SEM) analyses. CMC and PCDI significantly affected penetration, whereas APP and ZB showed no significant effects within the tested ranges. The selected formulation (1% CMC, 12% APP, 3.5% ZB, and 1.5% PCDI) showed stable viscosity development and the lowest mass loss under repeated water scour. In simulated-roadway tests, the stock solution achieved an average dust-suppression efficiency of 59.7%. At 170 °C, a 10% treatment reduced CO release by 40.0% and increased the mean apparent activation energy of coal oxidation by 29.73%. Rapid wetting, intermolecular interactions, and formation of a continuous porous crosslinked film supported dust consolidation and oxidation inhibition. The developed material therefore offers a potential integrated approach for controlling coal dust and spontaneous combustion risks in underground mines.