Study On Process Intensification Of Scarce Difficult-to-float Coal

There are full ranges of coal resources in China, but the distribution is unbalanced. The coking coal and fat coal reserves account for less than6%and3%respectively of the identified coal resources in China, which belong to scarce types. With the development of economy in our country, the consumption gap between high quality coke and fat coal is very large, while the amount of import has been increasing year by year. By2009, the amount of imported coking coal in China has reached to34.49million tons. On the other hand, the separation recovery of main coke and fat coal production is low, which causes tremendous waste of resources. Take Kailuan group for example. The total amount of concentrate accounts for about one third of the washed coal. However, the yield of the concentrate is less than50%of coal slime separated and carrying high ash content, which has seriously hampered the development of coal industry. Scare coking coal, especially those difficult-to-float coals, has not only become a problem, but also become the bottleneck of resources in coking coal industry as well as coal chemical industry.Improving the efficiency of high quality coal separating is of vital significance at the face of the actual demand due to scare coal resources. In terms of the limitations and deficiencies of process intensification and flotation efficiency at home and abroad, and by means of experimental and analytical approaches, the surface properties of scarce coal slime separation process and process intensification was focused on in this paper, the association between mineral dissemination and variation during floatation process. It also emphasizes establishing a process flow for two-stage-column flotation that conforms to physical changes in flotation process and the associated two-stage-column flotation and middlings fine grind disaggregation, with the former serves as the main base for compulsory adjustable pulp. With the help of Mlm photomicrometer, infrared spectrometer and scanning electron microscope, our experiments systematically analyzed the essential quality of scarce coal sample surfaces and mineral properties, through the combination of multi-component collector, fine ball mill grind disintegration and two-stage-column type flotation, and obtained the natural characteristics and reagent mechanism between the major function groups of coal, as well as fine grinding of coal and characteristic parameters of the two-stage-column flotation process. The combination between two-stage-column flotation process and industrial application disintegration of coal was firstly proposed in this paper. Based on these researches, this paper proposes and establishes a process flow of combination compulsory adjustable pulp, with two-stage-column flotation and middlings fine grind disintegration, and carries out half industrial practice verification. The results show that the process can further improve the efficiency of scarce coal flotation. The research has achieved the results and insights as follows:(1) The paper has studied on the surface properties of difficult-to-separate coal slurry, and the existing problems of the traditional reagents in difficult-to-separate coal separating process was analysed. It has also introduced multi-component reagent compounding system to deal with the serious problem of difficult-to-separate, high ash content, difficult to float, low selectivity and high percentage of fine particles and middlings. Aromatic ring, ether oxygen keys, carboxyl and hydroxyl were play a major part in functional groups of multi-composition reagent. Moreover, it also carried extensive researches on multi-component reagent intensification mechanism by means of infrared spectrum analysis and ξ, potential analysis.(2) Pulp strengthening process had been studied by adopting dispersant and high-speed shear in the paper. The result has shown that adding dispersant can increase the partial surface potential absolute value, enhance the dispersion of particles, decreases the fine particle adhesion, while at the same time, the fine grained surface of slime has been raised as well as the competition for collector adsorption has been reduced. High-speed shear also improved particle surface adhesion, offered fresh surface for reagent compounding effect, improved the slime in hydrophobicity, and provided necessary mineral conditions for efficient separation of fine-grained coal.(3) The separation craft with middlings grinding was established. It proposed that the scare coal flotation process would yield with high percentage of middlings, i.e., adopting middlings grinding would ensure the separation between combustible composition and gangue, which provided technical support for the realization of efficient flotation of high quality scare coal. It made use of the density distribution of flotation product rate to determine the content of slime middlings, and established a reasonable coal slime fine grind process according to the flow of the middlings. Finally, it established the last step of process flow by using middlings fine grind disintegration after coal classification as the main body of the flotation. Middlings fine grind flotation process coal flotation extracted59.47%of-0.074mm fineness of the material content, finely ground alone after the coal flotation, and integrated coal combustible body of the final recoveries accounted for76.42%, yield rate for65.20%and with the remaining ash content of11.63%. Through the remaining coal classification, without changing the original production rate, the combustible recovery has increased by10%or more by means of middlings disintegration.(4) New two-stage-column flotation process was put forward that matched with the changing rule of difficult-to-separate coal separation properties, i.e., according to the characteristics of difficult-to-separate slime, adopting efficient surfaced mechanism of easily floating grain satirized, hard-to-beneficiate microgranular coal, efficient micro bubble mineralization, high turbulence, strong vortex and high-energy state powerful separation mechanism of two-stage-column flotation process, which has achieved hard-to-beneficiate slime sorting efficiency and recovery enhancement. The process provides new conception for the flotation of coal, other metal and non-metallic minerals. With bubbles and particle collisions mineralization as the basis, establishing two-stage-column flotation speed constant model and particle retention time model. The calculated results have shown that two-stage-column floatation speed constant is about5times of the one-stage floatation speed constant. When dealing with50m3·h-1, the particle retention time is4.9min. According to the recovery axial diffusion model, the results obtained shown that the two-stage-column flotation process recovery rate is apparently much higher than that of one-stage-column. According to the above experimental results, half industrial separation test system of two-stage-column flotation process was established, and a large number of tests have been carried out on this system with optimized parameters. It also validated the theoretical basis of two-stage-column floatation.A novel combination of compulsory adjustable pulp and two-stage-column flotation and middlings fine grind as main approach in flotation process was puts forward in this paper, combined with the enhanced role of collectors to improve the surface properties of coal slime, solved the existing problem of higher ash, high fine clay content, and the high content of the middlings in difficult-to-separate coal slime. The system has separated Qianjiaying difficult-to-separate coal, and obtained the concentrate ash up to12.01%, and combustible recovery was83.75%. With Qianjiaying field production flotation index, combustible recovery has increased more than10percentage under12%concentrate ash.