Experimental study on the influence of surfactant foam properties on the slow release of gas in coal

In the process of mining coal resources, the abnormal emission of gas associated with coal may lead to serious gas overrun, and trigger problems such as gas disaster or greenhouse effect. Many studies have shown that injecting surfactant solutions into coal seam is one of the effective and important means of gas management. Surfactant mixed with gas is easy to form stable foam. However, there are few studies on the influence of foam properties on gas desorption. Therefore, this paper studied the influence of surfactant foam properties on the slow release law of gas. Two surfactants, sodium dodecyl benzene sulfonate (SDBS) and alkyl glycoside (APG0810), were selected to test the surface tension, viscosity, foaming, stability and foam morphology of solutions. The effects of surfactant foam properties on gas release was investigated using a self-developed experimental apparatus. The experimental results shown that with the increase of surfactant mass fraction, the surface tension of liquid decreased greatly at first, the foaming rate increased obviously, and the foaming stability increased gradually. When approaching the critical micelle concentration, the decrease amplitude of surface tension slowed down, and the foaming and foaming stability increased gently. At a mass fraction of 0.15%, the foaming heights of SDBS and APG0810 after air injection were 44 mm and 40 mm, respectively, and the maximum half-life of SDBS foam was 786.5 s. The slow release effect of solution foam on gas was well correlated with its foaming rate and half-life. At the same mass fraction, SDBS was generally better than APG0810 in the slow release of gas. At a mass fraction of 0.15%, the gas slow release rate of APG0810 and SDBS within 10 min were about 37.4% and 12.7%, respectively, and that of SDBS within 2 h was still about 50.84%. This study can provide a new perspective to investigate the inhibition and its mechanism of gas desorption in coal by surfactants, and also a certain theoretical support for the prevention and control of gas in mines and the green mining of coal.