The purpose and task of non-metallic ore dressing and purification is to separate useful minerals from useless gangue, separate useful minerals coexisting with each other as much as possible and enrich the required concentrates, comprehensively recover valuable components, remove impurities harmful to smelting and other processing processes, improve the quality of concentrates, and make full use of limited mineral resources.
The non-metallic minerals mentioned here include: quartz sand, diatomite, graphite, rutile, wollastonite, sillimanite, kyanite, andalusite, asbestos, kaolin, sepiolite, attapulgite, bentonite, illite, garnet, mica, aluminum oxide, magnesium oxide and other inorganic non-metallic minerals.
So, what is the technological process of non-metallic ore dressing and purification? Compared with metal ore, what characteristics does it have?
Beneficiation is a continuous production process, which consists of a series of continuous operations. No matter how complex the beneficiation method, beneficiation scale and process equipment are, they generally include the following three basic operation processes.
Preparations include ore washing, crushing, screening, grinding and grading. The purpose is to separate useful minerals from gangue minerals and various useful minerals, so as to prepare for the sorting operation. Sometimes it also includes the preparation of dividing the material into several suitable particle sizes.
The beneficiation operation is the key operation (i.e. the main operation) in the beneficiation process. It adopts different beneficiation methods according to the different properties of minerals, such as gravity separation, magnetic separation, electric separation, flotation, etc. This is the key content discussed in this chapter.
This operation mainly includes concentrate dewatering and tailings treatment. Concentrate dewatering usually consists of three stages: concentration, filtration and drying (sometimes required). Tailings treatment usually refers to tailings storage, comprehensive utilization and tailings water treatment.
After beneficiation, ores usually get concentrates, tailings and middlings.
Concentrate is the final product with high content of useful minerals obtained after the raw ore is sorted, which is suitable for smelting or other industrial sectors.
Tailings are minerals with very low content of useful minerals obtained from raw ore after sorting operation, which generally need further treatment or are not suitable for further treatment in terms of current technology and economy.
The middling ore is a semi-finished product (or intermediate product) obtained from the separation of raw ore. The content of useful minerals is lower than that of concentrate and higher than that of tailings. The middling ore generally needs further processing.
Compared with the mineral processing of metal minerals, the main characteristics of non-metallic mineral processing are as follows.
1. The purpose of non-metallic ore dressing is generally to obtain products with specific physical and chemical characteristics, rather than some useful elements in minerals.
2. There are strict requirements and regulations for the physical properties of processed products, such as particle size, fire resistance, loss on ignition, air permeability, whiteness, etc., otherwise it will affect the application of the next higher level.
3. For processed products, not only the content of useful ingredients should meet the requirements, but also the types and content of impurities should be strictly required.
4. The integrity and particle size of useful mineral crystal structure shall be kept as far as possible in the process of non-metallic beneficiation, so as not to affect their industrial use and use value.
5. The calculation of non-metallic mineral processing indexes is generally based on the content of useful minerals, and the ore grade and recovery rate of useful minerals are usually expressed in the form of oxides, rather than the content of certain elements in minerals.
6. The beneficiation and purification of non-metallic ores not only enrich useful minerals and remove harmful impurities, but also grind and classify a series of products with different specifications.
7. Because the same non-metallic mineral can be used in different industrial fields, and different industrial departments have different requirements for product quality, it often brings the particularity, diversity and flexibility of non-metallic mineral processing process.
