Fine processing of minerals: a book to understand the processing technology of six major mineral materials!

introduction

Mineral material is a natural mineral (primarily non-metallic minerals) as main raw materials and rocks, in order to use its technical physical and chemical properties as the main purpose, the product material with the necessary processing and preparation obtained through its greatest feature It is the main characteristic of the mineral itself.

Natural non-metallic mineral materials differ in their nature, even in the same mineral, due to the complexity of their composition and the state of output. Therefore, mineral materials must be processed to optimize the performance of mineral materials, and to increase their use value and technical economic benefits.

The common processing techniques for non-metallic mineral materials mainly include beneficiation and purification, particle morphology treatment, heat treatment, interface treatment and modification, modification, molding and post-treatment techniques.

1 Non-metallic mineral material beneficiation and purification process

Purification of mineral materials refers to the removal of impurities from mineral materials by some special methods to increase the purity of useful components. At present, the main purification methods are physical methods (such as flotation, magnetic separation, etc.) and chemical methods (such as acid leaching, thermal chlorination, etc.)

At present, the main problems in China's mineral material purification technology are:

(1) High-purity processing technology is relatively backward

Currently mineral processing technology and equipment also difficult to meet the electronics industry, high-tech ceramics or new industrial requirements for non-metallic mineral material, such as quartz, zircon, rutile, high purity aluminum oxide.

(2) The industrial application of fine-grain mineral processing and purification technology is backward

Micro-fine mineral processing and purification technology is one of the important methods for processing high-purity non-metallic mineral products. Since many non-metallic minerals to be separated or sorted have fine grain size, only the superfine pulverization can dissociate the monomers, so the fine-grained minerals Processing and purification technology is an effective technical means for sorting these finely embedded non-metallic minerals. However, the research and development and practical application of micro-fine mineral processing and purification technology in non-metallic mineral processing and purification are far from enough.

(3) The recovery rate of mineral processing and the comprehensive utilization rate of resources are low, which is a common problem in China's small and medium-sized mineral processing enterprises.

2 mineral material particle morphology treatment process

The particle morphology of a mineral refers to characteristics such as the shape and size of the mineral particles, such as the specific surface area of ​​the particles, the particle size, the surface smoothness, and the like. The main purposes of particle morphology treatment of mineral materials are as follows:

The first is to make the particle morphology of the mineral material meet the requirements of the application conditions;

The second is to increase the dispersion of mineral particles in the fluid;

The third is to promote the formation of products.

The key to mineral particle morphology processing is to maximize the protection of the crystal structure of the mineral itself. Different treatment processes are usually used for different crystal forms:

The flake minerals generally adopt the grinding and stripping process;

The fibrous mineral is released by a loosening process;

Granular minerals use an ultrafine pulverization process.

The common processing techniques for the treatment of mineral material particles mainly include grinding and stripping process, release and stripping process, ultrafine grinding process and special treatment processes such as cutting, grinding, polishing and etching.

At present, the ultrafine pulverization process of mineral materials is an important process of mineral granule treatment, including the pulverization of material particles, the prevention of particle agglomeration and the classification of ultra-fine materials.

In general, the grading technology of ultra-fine materials lags behind the ultra-fine pulverization technology, and it is necessary to vigorously carry out development research.

3 heat treatment process of mineral materials

The heat treatment of mineral materials refers to a process of changing the mineral properties by heating, in order to remove the moisture contained in the minerals, to thermally decompose the minerals, or to form and cure the mineral materials.

(1) Calcination

The water contained in minerals is usually three types: free water, adsorbed water and crystal water. The crystallization water is water contained in the mineral crystal molecules, and the heat treatment process for removing the mineral material crystallization water is called calcination.

The montmorillonite begins to remove the water of crystallization at 300 ° C, and the water of crystallization can be completely eliminated at 800 ° C;

After calcination, kaolin has good whiteness and hardness, good optical properties and oil adsorption.

Calcination of attapulgite or sepiolite at 200-500 °C can eliminate a large amount of adsorbed water and crystal water, causing the internal crystal structure of the particle to be broken, becoming slack, multiplying the surface surface, and heating can be converted into a new one. Stable state, can be used to produce high quality adsorbent materials and high performance low density friction materials.

(2) Thermal decomposition

Thermal decomposition refers to the chemical reaction process in which the molecular structure of mineral crystals dissociates during heating. Calcination is usually divided into light burning and reburning.

Light burning refers to the thermal decomposition operation in which the calcination temperature is within the range of mineral decomposition temperature, and the general light burning temperature is about 700-1000 °C.

Reburning refers to a thermal decomposition operation in which the calcination temperature is much higher than the decomposition temperature of the mineral, and the temperature is about 1400 to 1700 ° C. For example, the dolomite clinker used for the refractory material is preferably re-fired.

(3) firing

Firing refers to a calcination operation performed at a temperature far above the thermal decomposition of the mineral. The purpose is to stabilize the physical state of the solid oxide or silicate mineral, making it a stable solid phase. Various oxides formed by thermal decomposition of minerals at lower temperatures generally have poor crystallization, but have high surface activity and can be used as high-performance adsorbent materials.

For mineral materials having two or more crystal modifications, the purpose of changing the crystallization mode can be achieved by firing. The quartz crystal can be converted into a cristobalite crystal by heating, and can be converted into a tridymite crystal by adding a mineralizer.

(4) Melting

Melting refers to the process by which a mineral material changes from a solid phase to a liquid phase at a temperature at which it reaches the melting point. If pulverized quartz sand is used as a raw material, opaque quartz glass with numerous small bubbles is called fused silica, and the core or hollow product (beads) is a good filler enhancer.

4Interfacial treatment and modification process of mineral materials

The interface treatment and modification process of mineral materials is an important technology in the processing of mineral materials. The purpose is to improve the physical and chemical properties of mineral particles, thereby increasing the use value of mineral materials, or opening up new applications for mineral materials.

(1) Physical processing technology

1 Wetting and impregnation: The mineral material is completely placed in the liquid medium to achieve the purpose of the surface of the mineral particles being wetted by the liquid. The wetting and dipping process is usually also used as an auxiliary work of chemical treatment technology.

2 Surface coating treatment: Coating the surface of mineral particles is a common method to achieve mineral material modification, in order to improve the decorative appearance or oxidation resistance of mineral materials.

The casting sand is coated with a layer of phenolic resin or garnet resin, and the formed molding sand can obtain higher casting production speed and improve the performance of the mold and the core.

Pearl mica is a lithium oxide, chromium oxide, titanium oxide and iron oxide coated mica surface made of a different color pearlescent effect can be obtained by controlling the coating thickness, it is widely used in cosmetics, paints and other products.

3 heat treatment modification: the chemical composition, physical properties, etc. of mineral materials are changed by heating. The kaolin heat treatment modification removes about 14% of the structural water and also removes a portion of the volatiles and organics.

(2) Chemical treatment technology

1 Surface chemical modification: Surface coating modification is a method for modifying the surface of particles by adsorption or chemical reaction of functional groups in the surface of organic surface modifier molecules. It is the most commonly used surface modification of inorganic powder. Sexual approach. (Click to view details: methods, processes, equipment, modifier formulations, evaluation criteria, technological progress and development trends of inorganic powder surface modification)

2 chemical treatment: the use of inorganic or organic chemical reaction methods to process mineral materials.

Acid-base treatment: Treatment of bentonite with mineral acid can enhance the adsorption of bentonite.

Bleaching: When the kaolin is iron-containing, the ferric iron on the surface of the kaolin may be removed by using sodium thiosulfate or sodium sulfite to be reduced to soluble ferrous iron and removed.

Ion exchange: The conversion of calcium-based bentonite to sodium-based bentonite is achieved by utilizing the Na+ exchange capacity higher than that of Ca2+.

Interlayer compounds: Chemical or electrochemical methods are used to insert other chemicals between the crystal lattice layers of these minerals to form new mineral materials with special and excellent use properties, such as mica, graphite , vermiculite , bentonite and the like.

5 modification of mineral materials

The modification of mineral materials refers to the directional change of the properties of mineral rocks after physical or chemical processing of natural or man-made minerals and rock materials. This is the artificial change of mineral materials in composition or structural characteristics. .

Natural zeolite modification: P-type zeolite can be obtained by treating natural zeolite with NaOH; H-type zeolite with high adsorption rate and cation exchange capacity can be obtained by treatment with dilute mineral acid; gas adsorption can be obtained by treatment with Na salt Very strong Na type zeolite.

Modification of montmorillonite: Mg2+ can be used to completely replace Al3+ in montmorillonite octahedron to control the level of layer charge, and at the same time, it can fully hydrate with additives to increase the interlayer spacing of montmorillonite lattice. After dissociation and dissociation, the lattice is dislocated, causing most of the crystal faces to be destroyed, resulting in new breaks and broken bonds, increasing the specific surface and variable charge, and achieving the purpose of changing the colloidal properties of montmorillonite. This modification process is also referred to as "crystal separation technology."

6 Forming and post-treatment of mineral materials

In addition to the application of the mineral material in powder form, the majority of the materials are subjected to a forming process and a post-treatment process to obtain a product having a certain shape and size. Such processes include forming processes, curing processes, and other post-processing processes.

(1) Forming process

Forming is a process in which a mineral material is formed into a product having a certain shape and strength by a mechanical force or other physical chemical force on a certain mold. The mineral material must be designed with the group distribution ratio of the product before forming. According to different materials and production process characteristics, the molding mixture is prepared. The mixture is called mud casting material, paste, blank, suspension and dispersion slurry. Press plastic, material, etc.

Commonly used forming processes include plastic molding, injection molding, molding, rolling, extrusion, spraying, winding, laminating, copying, and granulation forming.

(2) Curing process

The purpose of curing the product is to further improve the mechanical strength of the processed product and obtain various functions required for the product, such as pressure resistance, folding resistance, wear resistance and the like.

The curing method can be divided into two major categories: sintering process and cementing process according to the basic principle of the curing process.

(3) Product post-treatment process

The product post-treatment process refers to a processing process including the appearance quality, structural shape, and the like performed on the manufactured product. Commonly used product post-treatment processes include heat treatment, morphology processing, surface treatment, bonding and coating treatment technologies.