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

ABSTRACT

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, Na₂S₂O₃$\cdot$5H₂O, CaCl₂$\cdot$6H₂O, MgCl₂$\cdot$6H₂O and their compound inhibitors, were used to inhibit coal samples in this study. Inhibited coal samples were heated in a programmed heating device, and Fourier transform infrared spectra of coal samples before and after the treatment were made. The results show that the inhibition mechanisms of crystalliferous water-containing mineral salts are a combination of physical and chemical ones, and CaCl₂$\cdot$6H₂O is the most effective inhibitor among the crystalliferous water-containing mineral salt inhibitors selected in this study. Compared to the raw coal sample, not only does CaCl₂$\cdot$6H₂O reduce the amount of CO generated from heated coal samples, but also it prevents functional groups of coal from being oxidized in the process of oxidation. Furthermore, from the perspective of functional groups, the inhibitory and catalytic effects of MgCl₂$\cdot$6H₂O on coal were interpreted. Among compound inhibitors, the one made of Na₂S₂O₃$\cdot$5H₂O, CaCl₂$\cdot$6H₂O and MgCl₂$\cdot$6H₂O with a mass ratio of 1: 1: 1 is the most effective. The coal sample treated with the compound inhibitor released less CO, but lots of functional groups (–OH,–CH₂–, etc.) are converted into the C–O group. Finally, the analysis reveals that CaCl₂$\cdot$6H₂O has the best inhibitory effect.

KEYWORDS:

• Crystalliferous Water-Containing Mineral Salts
• Programmed Heating
• Infrared Spectrum
• Inhibition Mechanism
• Function Groups

Acknowledgments

This work is supported by the Fundamental Research Funds for the Central Universities (2018GF12), the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

Additional information

Funding

This work is supported by the Fundamental Research Funds for the Central Universities (2018GF12), the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).