Study On Wettability Of Coal And Its Matching Performance With Wetting Dust-fall Agent

In the coal exploiting process, Coal dust is a significant hidden danger andthreatens human health. The basic properties and wettability of different coal typeswere analyzed. According to the wetting effect of different type surfactants on coalparticles, surfactants with better performance were selected out and wetting dust-fallagent was prepared.The basic properties of12types of coal samples was analyzed includingproximate analysis, ultimate analysis, particle size distribution, contact angle etc. inorder to analysis the wettability of the coal samples. Based on basic properties, thechemical dust control technology was introduced that surfactants was added intowater.Determination of surfactant monomers and combination solution, includingsurface tension, contact angle, dust settling experiment, shows that the wetting abilityof water solution on coal dust is greatly improved when suitable surfactants are addedinto water. The critical micelle concentration (CMC) of most of surfactant solutions isabout0.06%. With the increase of solution concentration, the coal dust settling time isreduced and the wetting effect is improved. In addition, the settling time of surfactantcombination solution is below2minutes, which is far less than the time of surfactantmonomers. Nonionic surfactant has the best effect on improving the wetting ability ofcombination solution. And the settling time of combination solution which containsnonionic surfactant is less than1minute. But the cationic surfactant has poor ability.Inorganic salts, including NaCl, CaCl2, Na2SiO3, Na2SO4, were selected assynergists and absorbent agent. The research shows that adding inorganic salts goesagainst dust settling for nonionic surfactant. But the wetting ability of anionicsurfactant is greatly improved as added inorganic salts, and the settling time isreduced from about20minutes to1minute.The ability of inorganic salts to improve thewettability of anionic surfactant is in the following descending order: CaCl2>Na2SiO3>NaCl>Na2SO4。In terms of water retention, four of the inorganic salts can delay theevaporation of water in coal samples. And CaCl2has the best water retention effect,whose moisture content is no less than5.71%，next came NaCl and Na2SiO3. Na2SO4produces poor effect.Orthogonal experiment of four factors and three levels was carried out usingsurfactants and inorganic salts that were selected out. Four formulas of wetting dust-fall agent were obtained, and practicability of formulas was analyzed. Theanalysis results show that four formulas of wetting dust-fall agent show betterdust-fall performance for dust of different coal types and have better effect on coaldust larger than10μm.And they are safe for human body. The cost of spray dust-fallby the wetting dust-fall agent is less than0.2%of coal output, and the growth of tonsof coal cost is about2Yuan. So the economic benefit of the wetting dust-fall agent isconspicious.