Kaolin is a non-metallic mineral composed mainly of kaolinite and other minerals. It is widely used in ceramics, paper, rubber, plastics and refractory industries due to its excellent processabilities. There are two main processes for processing kaolin ore - dry and wet processes. The dry process produces hard kaolin while the wet process produces soft kaolin. The wet process involves several stages including ore preparation, beneficiation to remove impurities using methods like magnetic separation, flotation or flocculation, and product processing. High gradient magnetic separation is commonly used to remove iron-titanium impurities. The beneficiated kaolin is then dewatered using processes like filtration or

1. Kaolin
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10. Kaolinite
Kaolinite is a non-metallic mineral, mainly composed of kaolinite,
halloysite, hydromica, illite, montmorillonite and quartz, feldspar and
other minerals, often mixed with pyrite, limonite, anatase, quartz,
chalcedony, alum, etc.
Kaolin is widely used in ceramics, paper, rubber, plastics and refractory
industries due to its excellent processabilities such as plasticity,
cohesiveness, sinterability and fire resistance.
There are three main types of the genesis of kaolin deposits: weathering,
sedimentary and hydrothermal alterations.
The processing of kaolin ore depends on the nature of the ore and the
end-use of the product. There are two processes used in industrial
production: the dry process and wet process. Usually, hard kaolin is
produced by the dry process, and soft kaolin is produced by a wet
process.

11. Kaolin dry beneficiation process
The kaolinite dry mining process is a simple and economical process. The ore is crushed to
25.4mm by a hammer crusher and fed into the cage mill to reduce the particle size to 6.35mm.
The hot air in the cage mill reduces the moisture of the kaolin from about 20% to 10%.
The crushed ore is further ground by a blown-type Raymond mill equipped with a centrifugal
separator and a cyclone. This process removes most of the sand and the product is commonly
used in low-cost fillers in the rubber, plastics and paper industries. When used in the paper
industry, the product can be used as a filler in the filler layer with an ash content of less than
10% or 12%. At this time, the brightness of the product is not high.
When the dry beneficiation method requires high whiteness of the product, the product
produced by Raymond mill must be dry iron removed. The dry process has the advantages of
eliminating the dehydration and drying process, reducing the loss of ash powder, short process
flow, low production cost, and is suitable for drought and water shortage areas. However, it is
necessary to rely on the wet beneficiation process to obtain high-purity kaolin.

12. Kaolin wet beneficiation process
The wet process includes three stages of ore preparation, ore beneficiation processing and product processing.
The beneficiation stage may include hydraulic grading, flotation, selective flocculation, magnetic separation, chemical
treatment (bleaching), etc. to remove different impurities.
The prepared slurry pulp is first desanded by the rake type washing box, floating tank classifier or cyclone, and then
divided into two grades of coarse and fine by the continuous centrifuge, hydraulic cyclone, hydraulic separator or
vibrating fine sieve (325 mesh).
The fine-grained grade of the classifier is fed into HGMS (high-gradient magnetic separator) to remove iron-titanium
impurities. The product is detached by stirring and scouring and then leached by iron oxide. The clay which is high
enough in brightness and has good coating properties can be magnetically removed. Stripped and sent directly to the
leaching operation. After leaching, alum is added to the slurry to coagulate the clay minerals to facilitate dehydration.
The bleached clay is dewatered using a high-speed centrifuge, a rotary vacuum filter or a filter press. Dewatering by filter
or filter press. The filter cake is redispersed into a slurry of 55% to 65% solids and then spray dried to make a loose dry
product. Part of the dry product was mixed into the dispersed slurry to make 70% solids and shipped to the paper mill.
The final product, which is not selected, has low brightness and can only be obtained by magnetic separation, froth
flotation or selective flocculation in the process. However, these independent operations have their own advantages and
disadvantages, so the industry usually uses a combined process of two or three of these processes for the comprehensive
utilization of clay resources

13. Kaolin production process

14. High gradient magnetic separator

15. Superconducting magnetic separators
In recent years, superconducting magnetic separators have been successfully
applied to kaolin sorting, which not only reduces energy consumption, but also
greatly increases the field strength, and the quality of kaolin concentrate is also
higher. The Eriez superconducting magnetic separator features a rapid magnetic
lift, achieving the highest design field strength (5T) in 60 seconds, while the
degaussing time is short, which greatly reduces the time required to flush
magnetic impurities from the magnet during the load cycle. Its energy
consumption is low, about 80% less than conventional magnetic separator, and
the processing capacity is large, up to 100t/h.
The United Kingdom has tested a reciprocating helical superconducting
magnetic system that is similar in design to a conventional can magnetic filter,
except that it retains the superconducting magnet in an excited state during the
duty cycle without switching control. Continuous operation. The 3048mm
superconducting high gradient magnetic separator designed by Humboldt of
Germany has simple structure, low operation and maintenance cost and good
stability.

16. Kaolinfrothflotationprocess
The purpose of the flotation operation is to float titanium impurities from the kaolin. Since the impurity
particles are extremely fine, a carrier flotation process is usually employed. The carrier mineral may be calcite or
silica sand (-325 mesh), and the amount of the carrier mineral is generally 10% to 20% by weight of the kaolin, and a
part of the carrier may be reused after being recycled.
The agents used in the flotation process include dispersant sodium silicate, pH adjuster amine hydroxide and caustic
soda collector Tal oil, fatty acid and calcium petroleum sulfonate. However, flotation has many disadvantages. The
hydrophobization of the carrier requires a large number of chemicals. The flotation process can only be effective at a
lower concentration of the slurry, thereby increasing the cost of dewatering. The loaded body must be removed from
the clay product as much as possible. Recycling in the product for recycling.
Chemicals and carrier minerals remaining in the clay are detrimental to the final product. Cundy and Yong et al.
studied a flotation process that does not require a carrier and floats anatase directly from kaolin, which is
characterized by the presence of dispersants (such as sodium silicate) and pH adjusters (usually amine hydroxide).
Under high conditions, high pulp concentration (40% to 60% solids) is scrubbed to remove surface contaminants. At
the same time, scrubbing also disintegrates anatase and hematite from kaolin minerals, and then traps a small number
of activators and fatty acids. The slurry is added together with the slurry, and the anatase covered by the collector
forms selective agglomeration under high shear stirring conditions, so that the particle size is significantly increased,
and the slurry after high shear stirring and slurry is diluted to 15%~ Flotation is carried out with 20% solids, and alum
in kaolin can also be removed by flotation.a
You may interest in buying flotation machine, 7 Factors Affecting Froth Flotation

17. At pH 8~11, selective agglomeration of iron-titanium impurities was observed by adding
alkaline earth metal ions such as Ca2+ and Mg2+ to the kaolin slurry, and then selective
flocculation was carried out with a weak anionic polyelectrolyte. The process requires a slurry
concentration of less than 20%, so a large amount of moisture must be removed in
subsequent operations, and the residual flocculant also affects the quality of the final product.
Selective flocculation of kaolin with high-molecular flocculant, the kaolin particles flocculate
to the bottom, and the iron-titanium impurities are reddish-brown in the suspension in the
upper part due to the fine particles, and the upper suspension can be removed. Most of the
iron-titanium impurities are removed and processed by other operations (such as magnetic
separation) to obtain high-quality kaolin. Suzhou Kaolin Company has achieved good
indicators using a new process of selective flocculation. The use of selective flocculation and
high gradient magnetic separation to treat kaolin also obtained satisfactory indicators.

18. Leaching is carried out in the presence of a weakly acidic
solution (pH 3 to 4) in the presence of a reducing agent
(NaS2O4) to keep the dissolved iron in the Fe2+ state,
avoiding the formation of Fe(OH)3, and washing it with water
to separate it from the kaolin. In order to remove the dark
organic matter, it can be bleached with a strong oxidizing
agent (hydrogen peroxide, sodium hypochlorite, etc.), and
the Suzhou Kaolin Company has obtained high-quality kaolin
products by oxidative bleaching. It has been reported that
the treatment of kaolin with microorganisms can significantly
improve the quality of the product.

19. The selected clay is stored in a slurry tank for 6-8 hours, and the pH is adjusted to 3-4, which is close to the zero points of
the clay, so that the clay particles are easily agglomerated. The addition of alum to the pulp helps the agglomeration of
the clay particles and promotes dehydration. The cylinder filter is a commonly used dewatering device which increases
the slurry concentration to 55% to 60%. One of the important functions of the filtration operation is to remove chemicals
from the clay.
To enhance this work, the water spray is often used. Spray drying has become a very effective process in the clay industry,
but it is expensive. In recent years, a new filtration process utilizing the electrophoretic properties of charged particles in
an electric field has emerged. The kaolin particles are negatively charged at pH > 3 and are surrounded by an oppositely
charged ion mist to form an electric double layer.
In the electric field, the clay particles move toward the anode, and the counterions in the ion mist move toward the
cathode. When the particles reach the anode, they are used to protect the filter cake formed on the anode film of the
electrode. The anode filter cake is further dehydrated by electroosmosis, and the excess water is pumped out through
the negatively charged filter cake capillary by the electroosmotic principle.
The dehydrating agent is used to agglomerate the kaolin particles into large particles, which can accelerate the
precipitation rate of the particles, facilitate the dehydration, and reduce the kaolin loss of the fine particles. Therefore,
the development of new high-efficiency dehydrating agent for kaolin is also one of its research directions

20. Kaolinprocessingtechniqueconclusion
1 The carrier flotation process makes it possible to select fine-grained kaolin. The advantage is that the kinetic
energy of the particles is increased, but the consumption of the agent is high, and the use and processing cost
of the carrier mineral is further increased.
2 The activation of polyvalent cations without a carrier can also cause anatase to float, but the consumption of
fatty acid-matched collectors is higher than that of other industrial minerals, which may be due to the large
surface area of ​​the particles.
3 High-shear agitation plays a two-fold role in the flotation. One is to dissociate the anatase from the kaolinite,
and the other is to induce shear flocculation between the anatase particles covered by the collector.
4 High-gradient magnetic separation technology has greatly changed the appearance of the kaolin industry.
Especially the vibration high-gradient magnetic separation can effectively remove the iron-titanium impurities
in kaolin, but has little effect on the particle size composition and physical and chemical properties of the
product. Produce high-quality kaolin products. Dry high gradient magnetic separation treatment of hard kaolin
can eliminate product dehydration and reduce product loss, which is suitable for dry and low water areas. The
superconducting high gradient magnetic separator has low energy consumption and large processing capacity.
The product purity is high and will be widely used in the kaolin industry.
5 oxidative leaching and microbial treatment of kaolin products can greatly improve product quality.
6 Electrophoresis/electroosmosis dehydration process to increase the slurry concentration to about 70%, and
the production cost is much lower than spray drying.
The combination of 7 kinds of operations and the final product are the main features of the kaolin mineral
processing process
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