Roles And Controlling Mechanisms Of Additives In Coal Spontaneous Combustion Prevention And Coal Dust Suppression

In order to solve the problem of coal spontaneous combustion and coal dust in the process of storage and transportation. Five different types of additives are selected in this paper,including chloride-calcium chloride,inorganic salt-sodium chloride, organic solution-polyethylene emulsion and glycerin and laboratory-made polymer synthetic agent A. Diluting them with water to different mass fractions solutions. The flame retardant effect of additive on coal sample was investigated by using inhibiting rate determination tester, thermal gravimetric analyzer and blowing-drying box. The dust suppression efficiency of additive on coal sample was investigated by means of wind tunnel device.Research results show that:1) Additive's property of flame retardant on coal should be respectively investigated form the low temperature and medium temperature phase. Driage and Inhibiting rate is related with the additive's property of flame retardant at low temperature stage. The pyrolysis activation energy is related with the additive's property of flame retardant at medium temperature stage.Among five kinds of additives,calcium chloride's flame retardant property is better at low temperature stage and medium temperature phase. Polymer synthesis agent A's flame retardant property is also better at low temperature stage,but at medium temperature stage would promote the coal spontaneous combustion. Sodium triphosphate, polyethylene emulsion and glycerol,both at the low temperature stage or at the middle temperature stage, the flame retardant property are poor. At low temperature phase, water loss rate of coal sample with calcium chloride and Polymer synthesis agent A is smaller and moisturizing property of the two coals is excellent,which are easily leading to a trend that there is a layer of liquid film preventing oxygen reacting with coal on the coal particle surface.Due to the difficulty in the reaction,CO concentrations detected was smaller.The smaller CO concentrations is,The bigger the Inhibiting rate is.For these coals with Sodium triphosphate,polyethylene emulsion and glycerol,the high level at water loss rate,a small quantity of liquid film is on the coal particle surface so that the Inhibiting rate is smaller.At medium temperature stage,other additives reduce the pyrolysis activation energy of coal except for calcium chloride.The bigger the pyrolysis activation energy is,the lower the trend of coal spontaneous combustion is. Calcium chloride reacts with coal particles to generate stable compounds at medium stage,while other additives react with coal particles to generate unstable compounds at medium stage. Compared with other additives, calcium chloride increased the energy barrier before coal combustion.2) Calcium chloride and Sodium triphosphate's effect of dust suppression on coal is week. Glycerol and polyethylene emulsion on the coal dust suppression efficiency change with the solution concentration. The effect of synthesis agent A on coal dust suppression is good, and the dust suppression rate of its four different mass fraction solutions is more than 90%. The large the surface tension of solution is,the worse the wetting property of additives is. It has the worse dispersion in coal.Thus the efficiency of additive on coal dust suppression will be worse.