Self-hardening thermoplastic foam for the inhibition of coal oxidation at low temperatures

ABSTRACT

Self-hardening thermoplastic foams (STFs), as an innovative technology mainly synthesized using 1 wt. % auxiliary agent (organic acid and polycaprolactone) and 99 wt. % foaming solution (polyethylene oxide, sodium silicate solution, sodium dodecyl sulfate, and water), were proposed to inhibit the self-oxidation of coal. When gas was injected into the synthetic solution using the self-made device with gas as the single power source, due to the synergistic action of the surfactant and polyethylene oxide, an aqueous foam with an excellent wetting ability was initially formed, followed by organic acids gradually reacting with sodium silicate, with the sol-gel foam and STF obtained after 180 and 220 s, respectively. The thermal characteristics of STF inhibiting the self-heating of coal were analyzed by differential scanning calorimetry, X-ray photoelectron spectroscopy, electron paramagnetic resonance, and Fourier transform infrared spectroscopy. After the STF absorbed the heat generated by coal self-heating, it was fused into a colloid in the range of 42–93°C. The colloid could seal coal gaps and cracks as a thin whole colloid layer from oxygen ingress, thus, the initial reactions of carbon free radicals and methyne with oxygen were controlled. The colloid could destroy the active functional groups, leading to an obvious decrease in the relative content of C-O. The colloid could keep the allowed water to maintain the moisture of the coal body, resulting in a peroxygen content decrease. The colloid could prevent cycloalkanes and bridge bond breakage from generating new alkyl groups. The colloid also provided hydrogen ions that could destroy peroxy, alkoxy, and hydroxyl radicals. Therefore, the STF could cut off the free radical chain reaction of coal and prevent its further oxidation.

KEYWORDS:

• Coal oxidation
• Extinguishing fire
• Foaming device
• Self-hardening thermoplastic foams
• Thermoplastic powder

Acknowledgments

This work was supported partly by the “National Natural Science Funds of China (Grant No.51304146),” partly by “131 Innovative Talents Cultivation Engineering for Tianjin Province, China,” partly by “Training Program for Innovative Research Team in Tianjin Institutions of Higher Education (Grant No.TD13-5021) and partly by “Tianjin City High School Science & Technology Fund Planning Project (Grant No. 20140526).”

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the 131 Innovative Talents Cultivation Engineering for Tianjin Province, China; Tianjin City High School Science & Technology Fund Planning Project [20140526]; Training Program for Innovative Research Team in Tianjin Institutions of Higher Education [TD13-5021]; National Natural Science Funds of China [51304146].