Application of microbial foaming agent in gel foam to prevent coal spontaneous combustion

In order to solve the problem that coal in goaf is prone to spontaneous combustion when contacting with oxygen, a new type of gel foam based on microbial foaming agent was proposed. The effect of glutamic acid (GLU) on microbial foaming performance was studied through foaming height, half-life, and dynamic evolution of bubbles. The results showed that GLU could improve the foaming performance of microorganisms, and the stability of foam increased with the increase of GLU concentration. When the GLU concentration was 20 g/L, the half-life of foam reached the maximum of 4.01 h. The mechanism of microbial foaming was explored using Fourier Transform Infrared Spectrophotometer (FTIR) and Liquid Chromatography-Mass Spectrometry (LC-MS). It was found that the microorganism surfaces showed negative charges and were able to produce various small molecules and peptides during growth, generating more hydrophilic and hydrophobic groups to promote the foaming of microbial solutions. Besides, GLU could also promote the generation of metabolites, which was beneficial for foaming. At the same time, the prepared microbial gel foam could also delay the generation of CO, promote the release of CO2, and show good flame retardancy. The new microbial gel foam can provide a theoretical basis for the prevention and control of coal spontaneous combustion.