Study On The Process Strengthen Mechanism And Energy Consumption Of Flotation Column Based On Middlings

Although coal resources are abundant in china,the quantity and the distribution of coal resources are extremely uneven.Coking coal and fat coal are scarce resources,which deposits are relatively less than 22%.A large number of middlings products are discharged through the process of coal preparation,which makes these scarce coal resources waste greatly.Further deep desulfurization and ash reduction on middlings would improve the utilization of scarce coal resources.The structure,mineral impurities,surface properties and inbuilt state of middlings are more complex,they should be dissociated and released the organic components first through the fine grinding process and then through flotation separating.Flotation column has unique advantages in the field of separating fine particles.Improving the separation efficiency and quality of flotation minerals and reducing the energy consumption of floatation are the key points in the research of flotation column.Xinyu middlings were researched in this paper through flotation columns which had different structures,strengthen mechanisms and energy dissipations.The main conclusions showed:The size composition,density,composition of coal macerals and floating characteristics of Xinyu middling were studied first.The floatation conditions and drug system were studied for Xinyu middlings through flotation machine.The results showed: Xinyu middlings had reclaiming value;floatability of fine particles of Xinyu middlings was better.The floatability was much sensitive to the change of the operating conditions,such as the concentration of pulp,the amount of gas and the speed of the operation.The increase of foaming agent,collector and the volume of floatation would lead to the phenomenon of entrainmente;the recoveries of the middling would be not enough when the amount of the agent was reduced.Average gas holdup,local gas holdup,average residence time of gas and decay rules of the swirling flow were studied in the flotation column with different swirling structures.The influence of structural parameters and operating parameters on the uniformity and stability of the phase distribution in a flotation column were analyzed.The results show that:The swirl structure had significant influence on the local gas holdup of the flotation column,and was sensitive to the change of the operating conditions.Attenuation of swirl flow affected the flotation column separation zone stability significantly;the more quickly the swirl flow decayed,the more energy dissipation concentrated,and the disturbance to static separation column was smaller.The non-swirl structure column had better adaptability to the changes of operating conditions than that with rotating structure.The average residence time of the gas was prolonged by the swirling flow intensity in some conditions.When the swirl flow was proper,the cyclone would accelerate the gas escape,residence time would be shorted,which could enhance recovery efficiency.The swirling structure was more conducive to the average distribution of gas phase in flotation columns in a certain ratio range of gas to liquid.Flow patterns,the rules of flow transformation and the energy dissipation law in different sections of the column with with different gas-intake structures were studied.The results showed: Flow patterns in pipe regions,swirl-flow regions,and flotation regions influenced each other;The effect on the breaking bubbles was weak in the non-swirl structure column,which was not conducive to the refinement of the bubbles.Swirl flow could make bubbles refinement and could also cause serious bubble coalescence when ratio of gas to liquid was large which would destroy the static stability of the static separation.The study on energy dissipation laws of flotation column showed that: strong swirl flow would aggravate the energy dissipation in small spaces,which was beneficial to the process of mineralization process strengthen in the swirling section.But too strong swirl would deteriorate the static separation.The factors which affected the stable operation of column flotation equipment were studied.The operation equation of the flotation column was obtained.The performance diagram of the operation load of the flotation column was drawn and the restrictive factor was pointed out.Flotation on Xinyu middlings in flotation columns with different flow structures were caught,the results showed that strong swirl structure was conducive to the improvement of Xinyu coal recovery rate,but too strong swirl flow disturbance would cause entrainment.Separation process for Xinyu middlings rewash were discussed and analyzed: strong swirl(coarse floatation)+ non-swirl(re-floatation)structure column flotation process was put forward for Xinyu middlings.Xinyu middlings flotation experiments showed that: strong swirl roughing recovery rate was 66.67%,non-swirl cleaning operation coal ash was 10.31%.