| To reduce the coarse particle losses in flotation, and solve the problem of uncontrollable size constitution in flotation tailings, flotation is integrated with classification and gravity concentration is united into flotation, which brings about the construction of new Gravity&Flotation Separator with Double-Tailing Discharge (GFS). The GFS utilizes flotation and gravity concentration to discharge fine and coarse tailings separately. The successful construction of it provides a new efficient method for fine coal separation, and show significance for improving the overall separation efficiency and shortening the treating process of flotation tailings.A classification device with inner overflow was developed, which can be arranged inside a flotation column. The effects of the flow-rate and the underflow proportion on the underflow partition curves were studied. The results show that the classification device with inner overflow can discharge1/2-2/3of-0.074mm slimes of high ash. On the basis of experimental data, a mathematical model with a single size variable for partition curve was constructed and showed good fitness for "fish-hook" partition curves. By analyzing the relationship between model parameters and experiment parameters, a multi-variable mathematical model was established involving size d, feeding rate Q, underflow split rate Rf and feeding concentration C. The model indicates that feeding rate and the concentration decide the goodness of classification process, while the underflow proportion mainly influences the entrainment. The establishment of this multi-variable model has a positive significance for predicting the classification result under certain conditions, pre-determining proper classification conditions, and realizing the controlling of process through operation variable adjusting.A classification device with outer overflow, which can be arranged at the bottom of flotation column, was developed. The effect of structure parameters and operation parameters on the classification performance of-1mm was studied.The results show that the partition size increases with the increasing of feeding rate. The fine entrainment in the underflow is proportional to the under proportion Rf. It showed much improvement in decreasing both the coarse loss into the overflow and entrapment in the underflow and can meet the classification requirements in GFS.An independent industrial classifier unit was designed and manufactured, and successfully applied in Shuguang Coal Preparation Pant. It was used to classify the flotation tailings, accompanied with a three-product cyclone. It realized separate application of GFS. The industrial operation data show that in a limited space, the classifier unit played a role of deslime and classification, reducing the coarse content into the thickener and showed significance for recovering coarse coal particles of low ash.Based on the models of the outer overflow classification devices of a tube-type and a peripheral-type, the influence of structural parameters including feeding rate, underflow proportion, sedimentary cone and the height of inner column on the flow field was investigated. The multi-phase simulation results show that:1) The concentration of the overflow is significantly lower than that of the underflow.2) The particles are concentrated in the area of the bottom cone and ultimately settle down onto the bottom surface to form a layer of sedimentation.3) The coarse particles mainly deposit on the surface of the bottom cone while the fine particles are mainly thickened and suspend inside the bottom cone. 4) The turbulence at the lower part of the classification device is relatively high, which is helpful for particle suspension and layering. By contrast, the turbulence in the upward ring area is relatively low, which is much useful for the particles to settle down.5) The partition size increases with the increasing of feeding rate, which agrees with the experimental results.A Cyclonic Separator and Aerator (CSA) of Φ150mm was developed and aerating experiments both in water and coal slurry were carried out. Taking aerating amount, air-water ratio and critical water column height as the comparison indexes, the effect of the lane, the feeding pressure and the structure parameters on the aerating performce was investigated. The experimental results prove that the lane is the critical element strenghening the aerating performance of CSA and increased the aerating amount by over50%. The aerating amount increases with the increasing of feeding pressure. They seem to have a linear relationship.The gravity concentration performance of CSA was investigated for-1mm coal. It was found that the lane may help decrease the separation density and improve separation efficiency, which provides a new idea of controlling separation density on line.The flow field simulation of CSA is carried out employing Reynolds Stress Model and VOF Multiphase model. The effects of feeding pressure, the vane, and the structure parameter on the flow field were investigated. The results show that:1) The air phase and the water phase in CSA have a distinct interface from all flow field varieties, involving the phase volume fraction, the static pressure contours, the velocity contours and the turbulence contours. The lane show more significant influence on the air phase rather than on the water phase.2) The air core in CSA is much like a column but has different diameter from down to top. The diameter of the vortex finder influences the diameter of the air core. Larger vortex finder means greater air core diameter. The diameter of the air core is about34-35mm in a0150mm CSA. The air core is not stable when going through CSA and larger vortex finder seems to cause the air core less stable.3) The significant increase in the axial velocity and negative pressure value is the critical reason why the lane has increased the aerating amount of CSA so much. The increasing mode of air flux and water flux with the feeding pressure agrees with that obtained in the experiments.4) The lane decreases the axial velocity of the internal vortex, which may have caused the decrease in ash content of the clean coal.An experimental model machine of GFS with a Φ400mm flotation column was made and experimented in flowsheet. The results show that GFS has good separation performance for-lmm coal and can realize the separate discharge for the fine and the coarse tailings, with ash content of54.93.%and56.54%, respectivley. The classification and gravity experiments show that the classification (first tailing-discharge) device can discharge90%of-0.044mm slimes, which can effectively avoid the null circulation and re-treatment of fine particles with high ash. The gravity concentration (second tailing-discharge) device realized the scavenging of the classification underflow after de-sliming and discharged coarse tailings after scavenging.A movable experimental system of GFS was ultimately designed and fabricated with supporting facilities and control system, which established the foundation of further industrialization of GFS. |
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