Investigation of thermoplastic powder synergizing polymorphic foam to inhibit coal oxidation at low temperature

Abstract

An innovative method involving thermoplastic powder synergizing polymorphic foam (TPPF) is proposed to inhibit the self-heating of coal. The TPPF is synthesized by polycaprolactone, polyethylene, sodium silicate solution, sodium dodecyl sulfate, organic acid and water. It exhibits excellent performance in improving the thermal stability of coal, suppressing the coal self-heating process and extinguishing coal fire. This study includes the preparation process of the TPPF, and differential scanning calorimetry measurements, and a polarizing microscope linked to a thermal station, and simultaneous differential thermogravimetric scanning calorimetric analyzer linked to a mass spectrometer and electron paramagnetic resonance. A preparation device of the TPPF with gas as the sole power source and an optimal working pressure of 0.45 MPa was designed. The TPPF could absorb the heat generated by coal self-heating and was fused simultaneously into a colloid to wrap the coal surface to prevent oxygen ingress, resulting in that the initial reaction of carbon free radicals and methyne reacting with oxygen was controlled; the colloid could maintain extra water vapor to form a multilayer at the surface of coal pores and increase the diffusion resistance for the access of oxygen, leading to the peroxygen content decrease; it could also prevent bridge bonds and branched chain breakage to generate new active hydroxyl and alkyl groups, and consume alkoxy and peroxy radicals generated in the coal low-temperature oxidation process by the hydrogen ions. Therefore, The TPPF could decrease the free radicals concentration of coal and cut off the chain reactions of coal self-heating. The TPPT also decomposed large amounts of water, carbon dioxide and a weight of 80.8% non-flammable residue, mainly consisting of Na2CO3 and SiO2, to choke coal self-heating.