The Forming Characteristics Of Tiefa Lignite And Optimization To The Press Craft For The Roller

The reserve of lignite resource is very abundant, it is playing an increasing important role in supplying energy. The characteristics of high moisture and easy weathering lignite determine the quality of lignite has to upgrade. However, in the process of lignite quality upgrading there is always accompanied by the conflicts between pressing molding rate not high and strength of the briquette not ideal with high pressure, more binder, and so on. Corresponds with that, the further study on lignite pressing molding characteristics and roll pressing process from different angles and using different methods has become a kind of important subject that people are increasingly getting attention.In this paper, Tiefa lignite was selected as the main research object, and the humic acid sodium was selected as a binder in order to press lignite,added it to Tiefa lignite and press it molding, then discussed lignite molding characteristics from the aspects of microstructure, particle size distribution and intensity. In this paper, a set of pressing and forming die and testing device were designed, and the influence of material parameters such as pressure, particle size ratio and binder content on the forming of lignite were studied. Then based on the optimized parameters of test, using the particle analysis software EDEM to simulate the pressing process of pressure ball machine, based on particle bonding model, established the relationship of three parameters that the rollers diameter,the rollers speed and the feeding rate to achieve a reasonable combination of the three parameters. Finally, with the aid of scanning electron microscope observed before and after the forming of lignite particle morphology and organization structure, discussed the influence of binder, particle size and forming pressure on the intensity of briquette, and gave the corresponding explanation.The research shows that:(1) Binder is a key factor affecting the lignite molding, binder addition amount can neither too little nor too much. Too little of the binder is not enough to make the lignite molding, too much will increase the cost of molding. In the case of proper amount of binder, the hydration of binder will be evenly distributed on the surface of lignite particles, between lignite particles and seep into the pores of lignite particles, forming crystals plate after drying consolidation, they are intertwined to form network, strengthen the interaction forces between lignite particles, lignite strength is higher after the formation; Pressure is the premise of lignite can be molded, but it is not the higher the pressure, the better. Lignite is a low rank coal, the hardness is small, easily crushed under high pressure, which affects the strength of the briquettes; The strength of briquette that wide particle size distribution is better than a single grain of lignite, under the condition of suitable particle size distribution, big size particles act as skeleton of briquettes, small particles agglomerated into body, filled into gaps of big size particles, all sizes of particles are firmly stick together, forming chimerism block, thus strength of briquettes are better.(2) Based on the orthogonal experiment of the ratio of particle size, the molding pressure and binder content, the ratio of particle size is the most important factor affecting the forming lignite, the molding pressure comes second and binder content occupies third. The optimal combination of lignite forming is: the ratio of particle size,3:1:1;The molding pressure,35MPa;Binder content, 10%.(3) From the perspective of the pressure ball machine rollers, the main factor influencing the lignite and forming is the rollers diameter, secondary factor for the feeding rate, the third factor is the rollers speed. The reasonable combination of them is: the rollers diameter,800 mm; feeding rate,3 kg/s; the rollers speed,1.047 rad/s.