Experimental study on the inhibitory effects and mechanisms of crystalliferous water-containing mineral salts

In underground collieries, wide application of traditional inhibitors needs a large quantity of water, and there is a problem on getting water nearby. A sloping terrain leads to an uneven distribution of inhibitor solution concentration because of its fluidity. With the loss of water, traditional inhibitors are out of effect. To solve the above three issues, crystalliferous water-containing mineral salts, Na(2)S(2)O(3)5H(2)O, CaCl(2)6H(2)O, MgCl(2)6H(2)O and their compound inhibitors, were used to inhibit coal samples in this study. Inhibited coal samples were heated in a programmed heating device, and Fourier transform infrared spectra of coal samples before and after the treatment were made. The results show that the inhibition mechanisms of crystalliferous water-containing mineral salts are a combination of physical and chemical ones, and CaCl(2)6H(2)O is the most effective inhibitor among the crystalliferous water-containing mineral salt inhibitors selected in this study. Compared to the raw coal sample, not only does CaCl(2)6H(2)O reduce the amount of CO generated from heated coal samples, but also it prevents functional groups of coal from being oxidized in the process of oxidation. Furthermore, from the perspective of functional groups, the inhibitory and catalytic effects of MgCl(2)6H(2)O on coal were interpreted. Among compound inhibitors, the one made of Na(2)S(2)O(3)5H(2)O, CaCl(2)6H(2)O and MgCl(2)6H(2)O with a mass ratio of 1: 1: 1 is the most effective. The coal sample treated with the compound inhibitor released less CO, but lots of functional groups (-OH,-CH2-, etc.) are converted into the C-O group. Finally, the analysis reveals that CaCl(2)6H(2)O has the best inhibitory effect.