Experimental study on foaming properties of anion-cation compound foaming agent to prevent coal spontaneous combustion

In this study, an anion-cation compound foaming agent (ACFA) was proposed based on the synergistic mechanism, so as to realize efficient production of low-concentration foam for preventing coal spontaneous combustion. The foaming and coal spontaneous combustion prevention properties of ACFA and anion compound foaming agent (AFA) were investigated by using Foamscan and the coal spontaneous combustion testing system, respectively. The results show that foaming speeds of the two agents both increase with the rise of concentration. The critical micelle concentrations of ACFA and AFA are 1 parts per thousand and 4 parts per thousand, respectively. Compared with AFA, ACFA can reach the required foam volume faster. Besides, the foam produced by ACFA can stabilize 115% longer and maintain its effect longer, because ACFA contains more liquid than AFA at the critical micelle concentration. Moreover, the densely and uniformly distributed foam produced by ACFA can more effectively prevent oxygen from feeding the coal. Since coal samples treated with ACFA and AFA both boast high inhibition rates, they can serve as foam fire-extinguishing agents to prevent coal spontaneous combustion in underground mines, but ACFA is more efficient and economical.