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Mullite Application and Powder Processing Equipment

Source:nclirik Posted:2022-12-20

What is mullite?

Mullite also named aluminum silicate. It is a mineral formed by aluminosilicate at high temperature, and mullite will be formed when aluminosilicate is artificially heated.

Mullite-Aluminum silicate
Mullite-aluminum silicate

Natural mullite crystals are elongated needles in radial clusters. Mullite ore is used to produce high temperature refractory materials.

It is mostly used as a thermal barrier coating in composite materials and is widely used.

Mullite is a binary solid solution that is stable under normal pressure in the Al2O3-SiO2 elemental system. There are very few natural mullites with the chemical formula AI2O3-SiO2, and they are usually synthesized artificially by sintering or electric melting.

Properties of mullite

Mullite is a high-quality refractory raw material, which has the characteristics of uniform expansion, excellent thermal shock stability, high load softening point, low high temperature creep value, high hardness, and good chemical corrosion resistance.
At present, there are mainly high-purity fused mullite, ordinary fused mullite, all-natural bauxite concentrate sintered mullite and lightly burned mullite.

Mullite powder

Mullite powder is made of mullite raw materials through high-temperature roasting, crushing, screening, Raymond, iron removal and other machining processes. It has high aluminum, low iron content, high hardness, small thermal expansion coefficient, high refractoriness, and thermal Excellent mullite series sand and powder with stable chemical properties.

Mullite powder
Mullite Powder

Product use: Mainly used as molding materials for fusion film casting, V-method molding of gypsum filler and vacuum suction casting, as well as refractory materials for large, medium and small steel castings, copper castings, furnace linings, and also for manufacturing water glass and refractory products , concrete materials, etc. Widely used in machinery, aviation, weapons, metallurgy, petroleum, heat preservation, sintering, construction and other industries.

Mullite use

Mullite powder1. Mullite can be used in refractory materials, ceramics, metallurgy, casting, electronics and other industries. It has the characteristics of high temperature resistance, high strength, low thermal conductivity, and remarkable energy saving effect.

2. Mullite is suitable for the lining of petroleum cracking furnaces, metallurgical hot air furnaces, ceramic roller kilns, tunnel kilns, electric porcelain drawer kilns, glass crucible kilns and various electric furnaces, and can directly contact the flame.

Technical parameters of mullite

Physical index

Item Indicator
Melting point(℃) 1850
Maximum operating temperature(℃) 1800
Bulk density(g/cm3 ≥2.65
Coefficient of linear expansion(20—1000℃) 5.3×10-6

Chemical indicators

Item High-purity fused mullite Ordinary fused mullite All natural sintered mullite light burnt mullite
Al2O3% 72.6 71.7 74.1 68.2
SiO2% 25.6 22.0 26.2 25.3
Fe2O3% 0.01 0.65 0.81 0.95
TiO2% 0.01 2.81 2.05 2.13
CaO% 0.17 0.15 0.28 2.30
MgO% 0.08 0.20 0.25 0.29
K2O% 0.01 0.19 0.21 0.25
Na2O% 0.19 0.05 0.15 0.13
Body dense g/cm 3.02 2.84 2.86 2.75
Apparent porosity 2.1 9.4 5 10
Specification Main chemical composition %
Al2O3 Fe2O3 SiO2 Na2O
RS-M70 68—73 ≤1.0 22—25 ≤0.25
RS-M60 58—62 ≤1.0 35-38 ≤0.30
RS-M45 42—45 ≤1.0 49-55 ≤0.4

How to produce mullite powder?

The mullite grinding process can be divided into two parts - crushing and grinding

1. Crushing: The purpose of crushing is to crush the large pieces of mullite into a suitable grinding particle size. The size of the mined mullite can be several meters, but in order to meet the feeding requirements of different mills, it is usually broken to tens of millimeters.

2. Milling: The purpose of milling is to produce products. According to the different requirements of product fineness, choose the appropriate type of milling machine. Generally, Raymond milling machine and ultra-fine milling machine are used.

What equipment is needed for mullite powder production?

1. Crusher
Crushing is the forefront stage of mullite production. First, the jaw crusher is used for coarse crushing to break large pieces of material into small pieces, and then the impact crusher is used to break it into smaller particles again.

Jaw crusher
Jaw Crusher

2. Mill
There are many milling equipments on the market that can grind mullite powder, but it is recommended to use Raymond mill. The output particle size of Raymond mill is between 80-325 mesh. The hardness is below grade 7. Firstly, the small pieces of material are pulverized, and the over-coarse powder is collected again, and returned to the pulverizer for re-grinding.

Raymond mill
Raymond Mill
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