Classification of re-election-screw classifiers and three major influencing factors

The spiral classifier is mainly used as an auxiliary equipment for grinding for pre-classification and inspection and classification, and sometimes used for washing the clay-containing ore and de-sludge and dewater the slurry. The spiral classifier can be divided into two types: high-grade and immersed according to the level of the liquid level. The overflow weir of the sorghum classifier is higher than the center of the lower screw axis and lower than the upper edge of the spiral blade. The length of the grading liquid surface is not large, and the liquid surface can directly feel the agitation action of the spiral blade, so it is suitable for grading and grading, and the grading granularity is more than 0.15 mm. The lower end spiral blade of the immersion classifier is completely immersed below the liquid level, and the classification area is large and stable. It is suitable for fine-grain classification, and the classification granularity is below 0.15 mm, and its overflow productivity is high. In addition, there is a low-slung spiral classifier with a lower level liquid level than the lower end spiral bearing, a small liquid surface and a large agitation action, which is mainly suitable for washing with mud ore.

There are many factors affecting the process effect of the spiral classifier, which can be basically divided into three aspects: equipment structure factor, ore property factor and operating condition factor.

(1) Equipment structural factors In terms of structural factors, the size of the grading area in the tank is the determining factor affecting the processing capacity and grading granularity of the classifier. When the working liquid level is stable, the classification area should be proportional to the overflow volume treatment amount and inversely proportional to the classification particle size. The width of the grading tank depends on the diameter of the helix that carries the return sand. The inclination of the bottom of the groove is mainly determined by the necessary lifting height of the sand returning, and the ore is not excessively limited. The speed of the spiral affects the degree of agitation of the liquid surface and the ability to transport sand.

(2) Ore property factors The influence of ore properties on classification is mainly reflected in three aspects: ore density, particle size composition and mud content. The ore density almost indirectly affects the productivity of the classifier by weight; 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 decreases, and the processing ability and classification accuracy are reduced. The classification of the mud-containing and fine-grained ore is preferably carried out at a low concentration, which helps to improve the classification efficiency.

(3) Influencing factors of operating conditions The main influencing factor of the classifier in operation is the concentration of the ore. 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 I critical concentration. The processing capacity of the classifier is maximized at the critical concentration. The critical concentration varies with the density and mud content of the ore and is related to the specified fractional particle size. The higher the ore density, the higher the critical concentration. The mud content increases and the critical concentration decreases. As the classification particle size decreases, the critical concentration decreases, so controlling the ore concentration of the classifier becomes an effective means to control the overflow particle size.

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