Mineral Processing Handbook, Volume 2, Part 1

Author: Chief Editor: Shen Zhicheng et al
Publisher:
Publish Date: 1999-06-01
Features:
Fragment: With the development of science and technology, metallurgical, chemical, building materials, and other industrial sectors that use mineral raw materials as their source not only require high quality but also stable quality. For example, although the specific conditions of various mineral processing plants in China differ, each has its own requirements for the grade of the ore. Steel companies require that the iron grade of magnetic concentrate be greater than 65%, with a grade fluctuation range of ±0.5 to ±1.0%. Copper smelting plants for non-ferrous metals demand that copper concentrate quality be priced based on grade and strictly limit impurity content for each grade. In summary, all mineral products have requirements for quality and quality index fluctuations. To meet the high and stable quality requirements of mineral processing products, blending and uniform treatment of ores are necessary. The processed ores significantly stabilize mineral processing production, improve processing indicators, and reduce costs. If the quality of ores fluctuates greatly and frequently, it forces mineral processing production to make corresponding frequent adjustments, and these adjustments are always lagging behind the fluctuations in ore properties, leading to abnormal production, low quality of concentrate products, and decreased recovery and output. Mineral processing plants adopting ore blending and uniform facilities play a positive role in coordinating the production of mines and mineral processing plants. It reduces the impact of faults in one production process on the other, improving equipment operation rates. Blending and uniform treatment of ores before mineral processing are aimed at stabilizing the quality indicators of ores' grade, hardness, particle size, and other physical properties, as well as improving ore quality and stabilizing concentrate quality. This has recently attracted attention. As early as the 1970s, some countries, such as the Bong iron ore mine in Liberia, adopted blending and uniform treatment due to the significant changes in ore properties (iron grade of 33–45%, magnetite content of 15–70%), which then met mineral processing requirements. The Novokryvorogetsk Mining and Processing Company in the Soviet Union blended ores according to their selectability and fed them through silos, achieving a standard deviation of 0.22% in concentrate iron grade (average per shift). The Dong'anshan iron ore mine and the Dong'anshan Sintering Plant in Ansteel adopted simple blending and uniform measures, resulting in balanced and stable mineral processing production. In recent years, the construction of blending and uniform facilities for newly built mineral processing plants and cement plants has increased, especially in countries with scarce mineral resources that rely on external ore purchases. Some mineral processing plants in China have also adopted this approach. Ore blending and uniform treatment are closely related to ore quality indicators. When the differences in ore quality indicators are significant and affect mineral processing production indicators, blending and uniform treatment are necessary. When the changes in ore quality indicators are minor and have little impact on mineral processing production indicators, blending and uniform treatment is not necessary. Therefore, not every mineral processing plant needs to perform ore blending and uniform treatment. Ore grade, the types and content of harmful impurities, mineral composition, dissemination particle size, and physicochemical properties are all important quality indicators for ore blending and uniform treatment. However, in practice, it is impossible to consider all these quality indicators. Currently, most mineral processing plants only blend and uniformly treat ore grade, and other quality indicators are also improved accordingly during the blending and uniform treatment of ore grade. This allows ore quality indicators to remain stable for a longer period, creating favorable conditions for stable mineral processing operations. However, in certain cases, when all or part of the ore is externally purchased, the quality of ore batches varies due to different origins, and ore quality indicators cannot be maintained stably in the long term. In such situations, only a batch of ore is blended and uniformly treated to maintain stable ore quality indicators within a certain period. This period is called the batch cycle, and the cycle should not be less than one day. Blending and uniform treatment are interrelated, with blending serving as the foundation for uniform treatment, and uniform treatment further ensuring the uniformity of ore quality. There are two common methods for blending and uniform treatment: one is to perform blending and uniform treatment simultaneously, which is known as a uniform material yard; the other is to perform blending and uniform treatment separately, which is typically referred to as a simple blending and uniform facility. When strict requirements are placed on ore quality indicator fluctuations, the former method can be chosen, but it has high initial investment, large land area, and complex management. When the requirements for ore quality indicator fluctuations are less strict, the latter method is more economical and practical. The choice of blending and uniform treatment method should be determined through technical and economic arguments before plant construction, based on the results of the evaluation.