Study on the influence of surfactant on wettability and gas desorption properties of coal

In order to study the influence law of surfactants on the wettability and gas desorption performance of coal, the wetting characteristics of six surfactant solutions on six different coal samples with different metamorphic degrees were analyzed; the inhibition effect of surfactants on gas desorption in coal was studied by using water injection test equipment after gas adsorption/desorption. The results showed that: with the increase of volatiles, the contact angles of the solutions with different mass fractions on the coal surface all show an inverse U-shaped trend, and the contact angles of sodium diethylhexyl solfosuccinate (rapid penetrant T), primary alcobol ethoxylate (AEPO-9) and coconutt diethanol amide (6501) solutions on the coal surface under the same conditions are smaller, indicating that the three solutions have better wettability for different coal samples. With the increase of the mass fraction of surfactant solution, the spreading coefficient is positively correlated and the adhesion tension is negatively correlated, which is related to the wetting spreading effect and adhesion effect of water molecules on the coal surface changed by the addition of surfactant. The initial and ultimate desorption amount of gas in coal has a good negative exponential relationship with the mass fraction of the solution, which reflects the significant weakening effect of surfactant solution on the desorption ability of gas in coal. It is analyzed that this is mainly related to the wetting enhancement effect of the solution on the coal, the capillary resistance effect of the solution on the coal microporous fissures, and the expansion and compression effect of the coal adsorption of water on the pores.