Summary:Kaolin is a common clay mineral in nature and a very important non-metallic mineral. Because of its white color, it is also called dolomite. The p
What Is Kaolin
Kaolin is a common clay mineral in nature and a very important non-metallic mineral. Because of its white color, it is also called dolomite. The pure kaolin is white, fine, soft and soft, with good plasticity, fire resistance, suspension, adsorption and other physical properties. The world is rich in kaolin resources, with a total amount of about 20.9 billion tons, which is widely distributed. Countries such as China, the United States, the United Kingdom, Brazil, India, Bulgaria, Australia, Russia and other countries have high-quality kaolin resources. my country's kaolin mineral resources rank among the top in the world, with 267 proven mineral deposits and proven reserves of 2.91 billion tons.
Uses Of Kaolin
With the continuous economic development, the role of kaolin in social production has become increasingly prominent, and it is an essential mineral raw material for national economic construction. It is also widely used in industrial sectors such as rubber, plastics, refractory materials, petroleum refining, and cutting-edge technology in agriculture and national defense.
1. Paper Industry:
Kaolin is used in papermaking, which can give the paper good covering performance and good coating gloss performance. It can also increase the whiteness, opacity, smoothness and printability of the paper, and greatly improve the quality of the paper.
2. Ceramic Industry:
Kaolin is used in the field of ceramics, which is conducive to the formation of mullite and improves its chemical stability and sintering strength.
3. Petrochemical Industry:
Kaolin can be used as a catalyst filler for petroleum cracking, and kaolin has high purity, which is good for making catalyst carriers.
4. Coating Industry:
The main role of kaolin in paint is filler and pigment substitute.
5. Rubber Field:
Nano-grade kaolin can improve rubber's performance in terms of elasticity, flex resistance, dimensional stability, compression deformation and other properties.
6. Agriculture Field:
The application of kaolin aqueous solution in fruit trees, grains, vegetables and other agricultural fields can greatly reduce production costs and reduce the amount of pesticide residues in crops.
Kaolin Powder Making Process
Kaolin Raw Material Composition Analysis Table
Selection Scheme Of Main Machine For Kaolin Pulverizing
|Product specifications (mesh)||Fine powder 325 mesh||Deep processing of superfine powder (600 mesh-2000 mesh)|
|Equipment selection scheme||Vertical mill or Raymond mill|
The First Stage: The Crushing Of Raw Materials
The kaolin bulk material is crushed by the crusher to the fineness (15mm-50mm) that can enter the mill.
The Second Stage: Milling
The crushed small pieces of kaolin are sent to the storage hopper by the elevator, and then sent to the grinding chamber of the mill evenly and quantitatively by the feeder for grinding.
The Third Stage: Classification
The ground material is classified by the classification system, and the unqualified powder is classified by the classifier and returned to the main engine for re-grinding.
The Fourth Stage: The Collection Of Finished Products
The powder that meets the fineness is separated and collected in the dust collector through the pipeline through the airflow. The collected finished powder is sent to the finished product silo by the conveying device through the discharge port, and then is packaged by a powder tanker or an automatic baler.
Kaolin Purification Technologies
The purpose of purifying kaolin, on the one hand, is to remove harmful dyeing impurities such as iron minerals, titanium minerals and organic matter, so as to improve the whiteness of the product; on the other hand, to remove sandy minerals such as quartz and feldspar to improve Improve the quality of kaolin products, and then expand the breadth and depth of its application, and obtain better economic benefits while making full use of kaolin resources.
At present, the purification process of kaolin mainly includes gravity separation, magnetic separation, flotation, leaching, chemical bleaching and roasting.
The gravity separation purification process mainly uses the difference in density and particle size between kaolin and gangue minerals to remove light organic matter and high-density impurities containing elements such as iron, titanium and manganese, so as to achieve the purpose of purifying kaolin and reduce or remove impurities. Negative impact on its whiteness.
2. Magnetic Separation
The magnetic separation process is used to remove weak magnetic dyeing impurities such as hematite, siderite, pyrite and rutile in kaolin. Magnetic separation does not require the use of chemicals and has no pollution to the environment, so it is widely used in the purification process of non-metallic ores. The removal of weakly magnetic impurity particles in kaolin requires a high magnetic induction intensity and magnetic field gradient, and the development of magnetic separation technology and equipment upgrades have enabled the magnetic separation and purification of kaolin and other non-metallic minerals to be effectively realized.
The flotation purification process can effectively remove iron, titanium and carbon impurities in kaolin, and realize the recovery and reuse of low-grade kaolin resources such as coal series kaolin. Kaolin has finer particles and is more difficult to float than gangue minerals. Therefore, reverse flotation is often used in the kaolin flotation purification process to achieve a better effect of removing impurities, such as reverse flotation carbon removal, desulfurization and iron removal. Kerosene is used as a collector, pine oil is used as a foaming agent, and water glass is used as an inhibitor. The flotation purification process is mostly used to treat kaolin raw ore with more impurities and lower whiteness, so as to realize the comprehensive utilization of low-grade kaolin resources.
Leaching is a method of selectively dissolving and removing certain impurity components in kaolin through appropriate leaching agents, such as acid leaching and microbial leaching using hydrochloric acid or sulfuric acid. The leaching process is simple, energy-saving, can reduce production costs, and has good development potential. Using sulfuric acid with a concentration of 25% to acid-leach hard kaolin with high iron content for 5 hours, the iron removal rate can reach 37.67%. Because most of the iron in the raw ore exists in the form of pyrite, in order to achieve a better iron removal effect, oxidative acid leaching is carried out with H2O2 as the oxidizing agent. Coal series kaolin contains impurities such as pyrite, limonite and hematite. During the calcination process, pyrite will be oxidized into dark brown iron oxides, which will reduce the whiteness of kaolin. Thiobacillus ferrooxidans can decompose pyrite through catalytic oxidation, so it can be used to remove pyrite from kaolin.
Compared with the currently commonly used purification process, the leaching purification process is simple, which can significantly reduce production costs, enable the effective development and utilization of low-grade kaolin, and have higher development potential. When using microbial leaching, more stringent environmental assessment and economic benefit assessment must be carried out.
5. Chemical Bleaching
Ferric ions and their oxides are the main dyeing impurities that reduce the whiteness of kaolin. The method of removing these harmful impurities through chemical reagents is called chemical bleaching. The chemical bleaching method of kaolin is divided into oxidation method, reduction method and oxidation-reduction combined method.
The principle of the oxidation bleaching method is to oxidize the harmful coloring impurities in the reduced state into soluble substances, and then remove them. For example, oxidize pyrite into soluble ferrous sulfate, and then oxidize the organic matter and remove it by washing with water. Commonly used strong oxidants include sodium hypochlorite, potassium permanganate and hydrogen peroxide. The bleaching effect is affected by pH value, temperature, chemical dosage, pulp concentration and bleaching time.
The principle of the reduction bleaching method is to reduce the insoluble ferric oxide to soluble ferrous salt, so that the harmful element iron is converted into a soluble phase for dissolution, and then removed through the washing process. Commonly used reductive bleaching agents include sodium dithionite (Na2S2O4) and thiourea dioxide (HO2SC(NH)NH2).
Roasting is also an important purification process to improve the whiteness of kaolin. Kaolin can remove carbon-containing impurities in it through roasting process, such as removing magnetic impurities through magnetization roasting and magnetic separation, and removing certain metal impurities through chlorination roasting.
Low-temperature roasting can remove surface and interlayer hydroxyl groups without destroying the kaolinite structure, and at the same time effectively decompose carbon-containing organic matter, so that the low-grade coal-measure kaolin can meet the requirements of glass fiber raw materials, and effectively realize the low-grade coal-measure kaolin resources. use.
Magnetization roasting converts iron-containing impurities in kaolin into strong magnetic or strong magnetic iron-containing minerals, and then removes impurities by magnetic separation. The purification effect of magnetization roasting on kaolin is better than that of traditional chemical bleaching methods.
Chlorination roasting is the addition of chlorinating agents during kaolin roasting to convert certain metal oxides and sulfide impurities into volatile chlorides to achieve the purpose of removing the metal elements.
7. Combined Purification Technology
It is difficult to obtain high-quality kaolin products by a single purification process, especially when dealing with low-grade coal-measure kaolin with large reserves in my country and kaolin with complex mineral composition. Different types of kaolin treatment processes are different, among which soft kaolin treatment process includes crushing, pulping, cyclone, selective flocculation, bleaching, centrifugation, peeling, magnetic separation; hard kaolin treatment process includes crushing, pulping, Cyclone, centrifuge, flaking, bleaching or crushing, roasting, pulping, cyclone, flaking, centrifuge; sandy kaolin treatment process includes pulping, spiral classifier, sedimentation, centrifuge, flaking, bleaching or raw ore , Pulping, Gravity Desanding, Blending, Flotation.
The peeling is divided into mechanical peeling and chemical peeling. It is an important process in the deep processing process. It is necessary to peel kaolin into extremely thin sheets. After magnetic separation, iron removal and bleaching to meet the requirements of low wear and high whiteness, it is widely used in papermaking, Cosmetics, medicine, etc.
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