Spiral classifier It is one of the key pieces of equipment in the ore-dressing process. Its working principle relies on the differences in settling velocities of solid particles in a solution to achieve particle classification. The classification efficiency of the spiral classifier directly affects the proportion of qualified products in the returned sand, thereby influencing the efficiency of the grinding operation.

In the grading process, the factors that affect the grading performance of a classifier include the following three aspects: feed supply to the classifier, classifier structure, and classifier operating mode. Next, we will analyze in detail how these three factors impact the grading performance of spiral classifiers.

1. Feeding the spiral classifier

At the feeding stage of the classifier, there are two main factors that affect the classification performance of the classifier: one is the powder content in the feed to the classifier, and the other is the particle size distribution.

The higher the powder content or the greater the proportion of fine particles in the graded feed, the higher the viscosity of the slurry will be, and the slower the mineral particles will settle in the slurry. This, in turn, leads to a broader particle size distribution in the overflow product. Under such circumstances, to ensure that the overflow particle size meets the required standards, it is advisable to appropriately increase the make-up water supply, thereby reducing the slurry concentration. On the other hand, if the feed contains little powder or has already undergone sludge dewatering, every effort should be made to increase the slurry concentration, thus minimizing the carryover of excessive fine particles in the returned sand.

2. Construction of the spiral classifier

The structure of the classifier itself mainly comprises three factors that influence its classification efficiency: the inclination angle of the classifier’s trough, the height of the overflow weir, and the rotational speed of the screw.

The inclination angle of the classifier’s trough can affect the overall settlement of the classifier equipment’s foundation. However, since the spiral classifier’s trough is fixed and cannot be altered once installed, the inclination angle of the classifier’s trough must be adjusted to an appropriate value during installation. Generally, an inclination angle between 16° and 18° is suitable for classifier assembly.

If the inclination angle is too large, the total area of foundation settlement decreases, sandy materials tend to settle more easily, and the overflow particle size becomes coarser. However, the proportion of sandy materials in the returned sand will decrease accordingly. Conversely, if the inclination angle is too small, the foundation settlement area expands, the overflow particle size becomes finer, and the proportion of sandy materials in the returned sand increases. Therefore, when designing a mineral processing plant, the inclination angle should be determined comprehensively based on the material properties, classification particle size, and other relevant factors.

The more common classifiers mainly include high-weir classifiers and submerged classifiers. Spiral classifier Among these, the high-weir spiral classifier is suitable for classifying sand-sized particles, with the particle size of the overflow typically exceeding 0.15 mm; the submerged classifier, on the other hand, is suitable for classifying fine sand, with the particle size of the overflow generally below 0.15 mm. The common feature of both classifiers lies in the fact that the relative height of the overflow weir affects the total area of foundation settlement.

The overflow weir has been widened, the total area of foundation settlement has increased, the capacity of the classifier equipment has been expanded, and the particle size of the overflow has become narrower. Generally, after the relative height of the overflow weir is adjusted appropriately during the initial stage of manufacturing, it seldom changes under normal operating conditions. For high-weir classifiers, the relative height of the overflow weir typically remains within the range of 400–800 mm, whereas for submerged spiral classifiers, the relative height of the overflow weir usually falls between 930 and 2000 mm.

3. Practical Operation of Spiral Classifiers

In terms of practical operation, the grading machine here primarily refers to the pulp concentration and the uniformity of the feed grade.

The pulp concentration is an indispensable adjustment parameter. In the actual production process, the pulp concentration significantly affects the particle size of the overflow from the classifier. As the pulp concentration decreases, the overflow particle size becomes narrower; conversely, as the concentration increases, the overflow particle size gradually widens. Therefore, maintaining a certain overflow particle size at an appropriate concentration level can yield better quality indicators. The optimal pulp concentration for achieving the critical separation particle size can be determined through mineral processing tests.

The feed rate of the spiral classifier must be kept uniform and stable, without sudden fluctuations. Otherwise, it can easily lead to unstable classification concentrations and frequent variations in classification particle size, thereby affecting the quality indicators of the subsequent process.

Overall, Spiral classifier The actual effectiveness of classification is influenced by many factors, including the feeding process of the classifier, the structural design of the classifier itself, and the operational aspects of the classifier. According to mining machinery technology experts: when selecting a spiral classifier, be sure to choose a reputable mining machinery manufacturer to ensure equipment quality. In addition, during routine production, classifier operators must pay close attention, rationally analyze any abnormal phenomena, and take appropriate corrective measures. This will help guarantee the safe operation of the classifier and achieve optimal classification results.