Study on a novel high-temperature carbonizing intumescent gel foam with excellent coal spontaneous combustion inhibitory and extinguishing properties based on expandable graphite and DOPO

The fire accidents caused by coal spontaneous combustion seriously endanger the safety of mine production, and gel foam has been utilized to control coal spontaneous combustion. However, most gel foams exhibit a tendency to rupture under high-temperature conditions, which limit their fire extinguishing efficiency. To address this issue, a novel high-temperature carbonizing intumescent gel foam (ETPSGF) was prepared by introducing an intumescent flame retardants system (ED) based on expandable graphite (EG) and 9,10-Dihydro-9-oxa-10-phospha-phenanthrene-10-oxide (DOPO). The results show that ED was successfully incorporated into the gel foam system, with the foam expansion volume reaching 6.3 times and the half-life increasing to 19 days. Furthermore, the ETPSGF can form a foam film with the thickness of 1.52 cm, and it also can form a worm-like intumescent char layer under high-temperature condition. The CO inhibition efficiency of the ETPSGF-treated coal at 200 °C reaches 70.5 %, and the crossing point temperature delayed by 23.6 °C. In the fire extinguishing test, the ETPSGF-treated coal is rapidly cooled from 700 °C to 35 °C within 60 min with no re-ignition phenomenon, indicating that ETPSG exhibits fire extinguishing efficiency under high-temperature conditions. This work provides a new idea for the design of high-performance gel foam, and promotes the development of gel foam technology for preventing and controlling coal spontaneous combustion.