Research On The Theory And Technology For Dust Control By Foam In Underground Coal Mines

Mine dust, one of the major hazards in coal mines, not only makes quantities of coal miners suffering from pneumoconiosis, but also results in serious dust explosion incidents and enormous economic losses. At present, many coal mines use the water spraying dust suppression technology, which is ineffective and easy to block nozzles, consumes a large amount of water. In 1950s, some researchers firstly proposed the foam dust control technique, with high efficiency and water resource saving, but there were many defects in application for the technology. In view of this situation, the author carried out related research on the theory and techniques for dust control by foam, then developed a set of technology and equipment, and a series of achivements were obtained,such as the mechanism and characteristics of dust capture by foam,foaming agents,the related equipment, the application process in underground mines and so on .In the thesis, in order to provide theoretical fundamentals for producing and utilizing of the foam. The author studied the mechanism for dust removal and the fundamental characteristics of the foam. By establishing the model for analyzing the dust capture process in microcosmic view, the model describes the regimes of the reaction between foam and dust in detail, then depicted comprehensively that the foam has a high efficiency in dust capture. When spraying on the dust generating points, the foam will cover these points without gaps; When spraying into the air with dust, foam has large volume and area; The foam film contains special foaming agents can increase the rate of wetting for dust; The foam with good viscosity, will quickly be adhered to sediment.The characteristic of foam'rheological dynamics was tested by rotary viscosimeter, it was pointed out that foam is shear-thinning non-Newtonian pseudoplastic fluid, then the constitutive equation of foam was derivated; The fluidal characteristics were studied by establishing mathematical model. Based on the state equations of the foam, the author deduced the expansion multiples in the outlet of pipelines, the compression coefficient ,and the quantitative relationship between the volume and pressure before and after the expansion; On the basis of direct proportion between elasticity and non-deformability of foam, a new testing method for elasticity was invented, then studied the elasticity of foam combining experiment and thory; Self-designed apparatus was used to study the effect of different multiples and dust particle sizes on the foam drainage.Inorder to inhence the efficiency of dust control by foam, the author worked out the high efficiency foaming agent. By using the Ross-Miles method and water film flotation method,which were combined with two main factors,foaming and wetting properties, the author screened and built foam agent from quantities of surfactantst, and worked out its adding proportion.The author designed the new application process and related equipment for dust control by foam. After analyzing of the foam generator around the world, the author put forward a new kind of foam generator, and used CFD to simulate and optimize the key parameters inside the generator. The generator has many merits such as strong mixing intensity, maintenance conveniently and nonclogging; Take the roadway head for example, the author studied on the dust generation and spread mechanism, and gave the application process principle, "Generate foam together, and remove dust in different points"; Based on a large number of experiments, it was concluded that the nozzle should avoid suddenly internal change, the smooth border line was used to change flow lines, as well as the expansion to make the foam spread. The internal structure of generator was also studied, with method been proposed to determine the key parameters of the nozzle, as a result, the nozzles, can get uniform distribution, with wide spread angle, and great flow rate.Building a laboratory experimental system which can simulate the conditions in underground mines, to test the performances of foam agent, foam generator and nozzle, then high-performance foams were produced. The foam dust control technology was applied in Zaozhuang Coal Mining Group Xinyuan 12,211 roadway head, the results showed that ,foam dust removal efficiency were 2.11 times and 1.72 times higher than water spray respectively, the new technology reduced dust concentration effectively, with great significance in dust control. Now the technology has been applied for six patents, three of which have been authorized.