KAOLIN
1. WHAT IS KAOLIN
Kaolin (derived from the French word kaolin /kaɔlɛ̃/) is a white, flaky, refractory clay, mainly composed of the mineral kaolinite and some other minerals such as illite, montmorillonite, Quartz…
In industry, kaolin is used in many fields, such as ceramics, refractories, abrasives, aluminium production, alum, casting, paint fillers, rubber, paper, and white cement and also used in cosmetic production.
Name history
Kaolin derives its name from Gaoling soil (高岭土, white clay in Gaoling), a hilly area in Jingdezhen, Jiangsu, China. White clay mines here are exploited as a source of raw materials for the production of Chinese porcelain. The name kaolin was introduced to Europe by French Jesuits in the 18th century and when transliterated back into Vietnamese, it became kaolin.
2. PRODUCTION PROCESS OF KAOLIN
In Vietnam, kaolin processing technology is carried out by two main methods including:
Manual filtering method
Kaolin processing method by hydraulic method
For customers to know the kaolin production process using these two methods, we will learn as follows:
2.1. MANUAL FILTERING METHOD
Step 1: Kaolin will be mixed with water in the correct solid-liquid ratio. Workers will use manual stirring or use a stirrer.
Step 2: After stirring, the kaolin slurry will be put into a filtration trench system with an appropriate slope. This process will retain coarse particles in the filter channel, while fine particles will follow the water flow into the tank.
Step 3: After some time, the fine kaolin in the tank will settle to the bottom of the tank. To separate water from kaolin, investors will often use a kaolin plate press to separate the water.
ADVANTAGES OF MANUAL FILTERING TECHNOLOGY
- Simple technology
- Low investment costs
- Applicable to many scales from small to large
DISADVANTAGES OF MANUAL FILTERING TECHNOLOGY
- Low-quality kaolin
- Unstable in capacity and quality
- The loss rate is large
- Time and cycle are long
- Kaolin yield is low
2.2. KAOLIN PROCESSING METHOD BY HYDRAULIC FILTERING
- Step 1: Mining pure kaolin, then it will be beaten with a stirrer or sprayed with plaster. Pure kaolin will go through a preliminary separation system to remove all large soil particles and gravel.
- Step 2: The crushed kaolin part, after removing sand and soil, will be pumped into the hydraulic cyclone system, through the hydrocylon, thanks to centrifugation, the ultra-fine, small-volume particles are separated by the water flow at the bottom. On top of hydroxyl.
- Step 3: In this water, large particles will follow the hydroxyl bottom out. Kaolin slurry after hydroxyl will be put into the atomization system to remove iron ores, then will be transferred to the concentration tank.
- Step 4: Use a specialized pump (Piton pump) and a plate mud press (Kaolin press to form kaolin cake.
ADVANTAGES OF HYDRAULIC FILTERING TECHNOLOGY
- Good quality kaolin
- Minimize loss
- Take advantage of by-products
- High productivity
- Doesn’t consume much human effort
- Environmental protection
DEFECT
- High investment costs
2.3 CLASSIFICATION OF KAOLIN
Kaolin has low elasticity properties. In soft, white soil conditions, a type of Kaolin will form called white Kaolin. The chemical weathering of aluminium silicate minerals such as feldspar forms this substance.
At the same time, in some other places, the kaolin will form in colours such as pink, orange, and red. This is Kaolin formed by iron oxide. And pure clay is usually yellow white or light orange… Because clay is formed from rock weathering, depending on the weathering background, it will be divided into many different types of clay.
3. PROPERTIES OF KAOLIN
Kaolin has a 2-layer 1:1 structure (similar to dickite, nacrite, and halloysite)… with the general formula Al2Si2O5(OH)4.nH2O (n = 0, 2), ingredients include SiO2, Al2O3, H2O, in addition there are small amounts of Fe, Ti, K and Mg impurities.
Kaolin is white, grey-white, dense or light-coloured ground-like blocks, small scales, and hexagonal crystal units linked into small, thin sheets, about 0.2-12 µm in diameter. , density is about 2.1-2.6 g/cm3, hardness is 1-2.5, has a cation exchange capacity of about 2–15 meq/100g and depends heavily on the size of the particle, but the reactions The cation substitution reaction occurs at a very high rate [].
When soaked in water, it is flexible but does not stretch. This is the earliest known property of kaolin, people used it in paste form to shape and sinter to create ceramics. Melting temperature of kaolin: 1,750-1,787⁰C. When heated, kaolin has an endothermic effect, the peak at 510-600⁰C is related to the loss of crystallization water and the amorphous phenomenon of the mineral. The two exothermic peaks from 960 to 1,000 and 1,200⁰C are related to the militarization of amorphous kaolin products, with the 1,200⁰C peak being the crystallization of amorphous silicon oxide to form cristobalite.
MAIN APPLICATION
Kaolin is widely used in many industrial fields such as ceramics, paper, paint, rubber, fibreglass, plastics, construction materials, refractory bricks, and as a catalyst for oil refining technology. … Thanks to its special ability to absorb not only fats and proteins but also viruses and bacteria, kaolin in is used in both medical and pharmaceutical fields. , cosmetics….
Paper production industry
In the paper industry, kaolin is used as a filler to create a smoother surface for paper, increase tightness, reduce light transparency and increase ink absorption to the best level.
Regular paper contains 20% kaolin, some contain up to 40%. Normally, one ton of paper requires 250-300 kg of kaolin.
The quality of kaolin used to make paper is determined by the whiteness, dispersion and uniformity of the particle groups
Ceramic production industry
Porcelain production industry, civil ceramics, fine art ceramics, laboratory instruments, insulating ceramics, sanitary ceramics, etc. All use kaolin as the main material;
The adhesive material is white, flexible fire clay. The quality of kaolin is very demanding and must control colouring oxides (Fe2O3 and TiO2).Fe2O3 content should not be more than 0.4-1.5%; TiO2 not more than 0.4-1.4%; CaO not more than 0.8% and SO3 not more than 0.4%.
Production of refractory materials
In the refractory materials industry, people use kaolin to produce refractory bricks, semi-acid bricks and other refractory items.
In the ferrous metallurgy industry, refractory bricks made of kaolin are mainly used to line blast furnaces, iron furnaces, and hot wind furnaces.
Other industries need refractory bricks in smaller quantities, mainly for lining furnaces and boilers in non-ferrous metallurgy and the chemical industry, in oil refineries, in the glass and porcelain industry, and at home. Cement machines and lime kilns.
Glass fibre manufacturing
Another field where kaolin use also increases rapidly every year is as an input material for fibreglass production.
Kaolin contains both silica and alumina, substances found in fibreglass. Kaolin is used concurrently with small amounts of iron and titanium.
The reason for the increased demand for kaolin in this field is because of restrictions on the use of asbestos, a substance harmful to health. Filler field: kaolin is widely used in the field of paper, plastic, rubber, flavouring fillers, etc.
Kaolin has the effect of increasing the hardness, elasticity, insulation, and durability of rubber. Increases hardness and reduces product costs of plastics such as PE, PP, PVC… In the production of artificial leather (faux leather), kaolin has the effect of increasing durability and elasticity.
In fertilizer production
Kaolin is used as a filler and coating agent,
which is very important in preserving and improving fertilizer quality.
OTHER APPLICATIONS
Nguyen Vinh Holdings is located in Hanoi City, Vietnam, known as the “Northern porcelain capital”, is a professional export company of all kinds of minerals, and raw materials specializing in the production of ceramic, paint, coatings, plastics, new resistant materials, was founded in 2007.
Since the founding of the company, the company has always adhered to the business philosophy of “quality first, based on integrity, efficiency, mutual benefit and win-win”, and established good cooperation and long-term with upstream and downstream enterprises, creating a spread of domestic and foreign sales channels and marketing networks, building reputation and good credit in the industry.
