| In the recent 20 years,the demand for large-scale flotation equipment is increased strongly with mineral grade reduce and ore processing capacity increase,and the flotation machine scaling up has become an important trend.In 2019,the world's largest 680m3 air-forced flotation machine was put into production.However,based on scaling up method of geometric similarity and dynamic similarity,pulp was considered as homogeneous,the rapid increase of transport area and the differences between coarse and fine particles in pulp were ignored and,which results in poor flotation performance of coarse particles in large-scale flotation machine.In view of this,in the paper,the laboratory scale and industrial scale flotation machine were taken as the research object and studied with CFD simulation,3D-PIV,online flotation detector.The suspension behavior of coarse particles,the movement characteristics of coarse particles on the mineralized bubbles and the structural characteristics of the transport area were tested and then the design method of large-scale flotation machine to strengthen the recovery of coarse particles was carried out,the following research results were obtained:The coarse particles suspension characteristics and influencing factors in different scales flotation machines were studied.Based on the laboratory scale flotation machine suspension test system,the factors influencing the critical speed of impeller suspension from the bottom were studied,and the structural influence coefficient Ks and the air flow rate influence coefficient Ka of the critical speed of impeller suspension from the bottom of flotation machine were determined.The effects of particle size,impeller speed,pulp concentration and aeration rate on the different suspension of coarse and fine particles are analyzed.It is found that the particle size and pulp concentration have significant effects on the suspension of coarse particles,and the difference is that the particle size and impeller speed have significant effects on the fine particles suspension.The suspension characteristics of solid particles in five industrial scale flotation machines in three flotation processes are studied.It is found that the differential suspension of coarse and fine particles is common in the upper of the flotation machine.With the increase of the volume of the flotation machine,the suspension difference of the coarse and fine particles in the upper of the flotation machine increases.Under high concentration separation condition,the suspension mutation of the coarse particles in the transport area of the flotation machine occurs,in the same flotation machine,the particle weight suspension and metal suspension have different variation characteristicsThe distribution of turbulence intensity in flotation machine and the variation of loaded coarse particles on mineralized bubbles were studied.A laboratory scale test system and an industrial scale CFD calculation model for the turbulence intensity of liquid flow in a flotation machine are established.The results show that the turbulence intensity in the upper of the flotation machine increases with the increase of rotating speed.From the bottom to the top of cell,the turbulence intensity first increases and then decreases at low rotating speed,first increases and then decreases and then increases at high rotating speed;The structure of a push bubble cone and a tapered tank in an industrial scale flotation machine changed the flow direction of the liquid in the upper region and produced strong turbulence intensity between the center of the flotation machine and the middle of the cell wall,which was quite different from the laboratory scale.The test system of industrial scale flotation machine's bubble load was established.The results show that the change regulation of bubble weight load capacity in the upper area of flotation machine in roughing and scavenging operation is inconsistent.During the process of bubble floatation in roughing operation flotation machine,its weight load capacity first decreases and then increases,while in scavenging operation,it gradually decreases;+0.125mm coarse particle yield carried on the bubble in roughing operation floatation decrease gradually in rougher,The change trend of bubble weight load capacity in scavenging operation is just the opposite.It is suggested that the separation effect of coarse particles can be improved by reducing the floating distance of the bubble particle aggregate and the turbulence intensity in the upper part of the impeller.The structural characteristics of the transport area of the air forced mechanical agitated flotation machine are described.The PIV test system of laboratory scale flotation machine has been established.The research shows that the transport area is in a circulation flow field,and its geometric characteristics are clear and nearly trapezoid.The transportation area is symmetrical in the center section of the flotation machine,and there is an upper and lower boundary line near the impeller and the overflow weir.The inner boundary near the center area is connected by two oblique lines with opposite movement direction and the zero velocity point of the circulation flow field,and the outer boundary is close to the tank wall side.The method of adjusting the upper and lower boundaries of the transport area by increasing the impeller position and the impeller jet angle is put forward,and the effectiveness of improving the recovery rate of coarse-grained minerals is verified by the laboratory beneficiation test.The design principle of large-scale flotation machine for strengthening coarse particle recovery with the control of transportation area as the core is put forward.The design methods of distance between impeller and bottom,tube and bottom flow strengthening device are developed.This paper studies and designs a flotation machine with a capacity of 160m3 to strengthen the recovery of coarse particles,and establishes an industrial test system of coarse apatite flotation composed of two 160 m3 flotation machines,and carries out industrial tests.The results show that the recovery of P2O5 is about 14 percentage points higher than that of 40 m3 coarse particle flotation machine,in which the recovery of-0.15+0.074mm particle is about 13 percentage points higher,the recovery of-0.25+0.15mm particle is about 12 percentage points higher,the recovery of+0.25mm particle is about 10 percentage points higher,and the recovery of coarse particle is much higher.The above research shows that the dynamic environment of 160m3 flotation machine with enhanced coarse particle recovery is suitable for the separation of coarse particle minerals,which proves the correctness of flotation machine design.In this paper,a variety of analysis and test methods are used to reveal the suspension characteristics of coarse particle minerals in pulp and the load change rule of coarse particle minerals on mineralized bubbles during the process of floatation;to clarify the structural characteristics of the transport area of air-forced mechanical agitated flotation machine;to develop the design method of large-scale flotation machine to strengthen the recovery of coarse particle minerals.The research results of this paper enrich the basic theory of flotation equipment application,improve the deficiencies in the research of coarse particle recovery of large-scale mechanical agitation flotation machine in China,and improve the technology level of flotation equipment in China. |
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