Factors Affecting the Process Effect of Spiral Classifier
The spiral classifier is one of the important beneficiation equipment. Many factors are affecting the process effect of the spiral classifier, which can be divided into three aspects: equipment structure factor, ore property factor and operating condition facto
In terms of equipment structural factors, the size of the grading area in the tank is a decisive factor affecting the processing capacity and grading granularity of the classifier. Increasing the width of the groove, increasing the height of the weir or reducing the angle of inclination can increase the graded area. The width of the grading tank depends on the helix diameter of the return sand (ie the size of the classifier) and is 100 - 200 mm larger than the diameter of the helix. The bottom inclination of the groove is mainly determined by the necessary lifting height of the sand returning, and the ore is not excessively limited. The structural parameters that can be changed in production are mainly the weir height, but this factor is rarely determined at the initial stage of production. The weir height is customarily referred to as the slope height from the centerline of the screw shaft to the top of the weir, 400 - 800 mm for the sorghum classifier and 930 - 2000 mm for the immersion classifier.
The speed of the spiral affects the degree of agitation of the liquid surface and the ability to transport sand. The number of revolutions is related to the diameter of the helix, in the range of 1.5-10 r/min. The influence of ore properties on classification is mainly reflected in three aspects: ore density, particle size composition and mud content. The ore density affects the productivity of the classifier by weight almost in proportion; the effect of the ore size composition and the mud content is mainly reflected in the slurry viscosity. The viscosity increases, the sedimentation velocity of the ore particles is small, and the processing ability and classification accuracy are reduced. Therefore, in the case of a lot of ancient mud in the mine, it is necessary to remove the mud in advance. However, it is not harmful to contain a small amount of mud in the feed of the mechanical classifier, and sometimes it is advantageous. Because the clay can increase the viscosity of the slurry, the development of the slurry turbulence can be inhibited, and the ore particles can be stably settled, and the graded particle size will not be excessively sensitive. The classification of mud-containing and fine-grained ores is preferably carried out at low concentrations, which helps to improve the classification efficiency.
The chemicals added to the grinding cycle at the flotation plant and the agents brought by the same water have an impact on the classification process and even the grinding operation. The dispersing agent and the coagulating medicinal agent cause a large difference in the sedimentation rate of the particles. This problem is often overlooked in actual work, but its impact is quite large. The main regulator of the grader in operation is the feed concentration. The concentration not only affects the graded particle size, but also affects the processing capacity at that particle size. At a certain critical volume concentration, the amount of precipitation reaches a maximum, and the weight concentration corresponding to this value is called the critical concentration. The throughput of the classifier is maximized at critical concentrations.
The density of the critical concentration tunnel ore varies with the amount of mud and is related to the specified graded particle size. The higher the ore density, the higher the critical concentration by weight. However, as the mud content increases, the critical concentration will decrease. The effect of the graded particle size on the critical concentration is the same as the mud content, ie the critical concentration decreases as the fractional particle size decreases.
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