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Differences between bauxites
- Aug 27, 2018 -

Differences between bauxites


Bauxite clinker, also known as high aluminum material

Compositions and categorizing

Various high-aluminum bricks made from clinker are widely used in metallurgical industry and other industries for refractory or anti-corrosion materials, especially in electric furnace tops, blast furnaces and hot blast stoves. The fire resistance is very remarkable and the performance is superior to ordinary clay. Refractory bricks.

The main minerals of bauxite clinker are boehmite and high aluminate, and the diaspore content increases with the ratio of alumina to silica. Secondary minerals are rutile, iron ore. Sometimes it also contains a small amount of boehmite and dickite. According to the high aluminum bauxite, there are three grades of bauxite, which can be generally divided into 3 class and 5 grades. The content and color are:

First class premium 85% or more, earth gray color or dark gray color

First-class first grade 75-85%, earth gray color or dark gray color

Second grade 65-75%,  white gray color

Third-class three-level 50-65% blue-gray color

Grade 4 below 50% blue color


High alumina bauxite purity requirements

High alumina bauxite (including more than 35% Al2O3) requires inspection items:

Al2O3:

Refractory grade 85 to 87% or more

Polishing grade 86% or more electric

Welding grade 87% or more

SiO2:  

Refractory grade 6 to 7% or less

Polishing grade 5 to 6% or less

Fe2O3:

Refractory grade 1.6 to 2% or less

Wear resistance grade 2% or less

TiO2:

Refractory grade 3.5 to 4% or less

Polishing grade 4 to 4.5% or less

K2O+Na2O+CaO+MgO:

          Refractory grade 0.5 to 1% or less

Grinding grade 0.5 to 1% or less.

Some of the electric welding grade bauxite also require testing of phosphorus, sulfur, manganese and other projects.

B.D. (bulk density):

Refractory grade 3.10 ~ 3.20g / cm3 or more

Grinding grade, electric welding grade is not required to test the project.

L.O.I (loss on ignition):

All are 0.3% or less.

Moisture:

Generally between 0.5 and 1.5%, if exceed,  deduct weight, or apply other terms.


General bauxite purity requirements

General bauxite (including Al2O3 80% or more) requires inspection items:

Refractory grade:

not less than Al2O3: 80%;

Fe2O3: not more than 2%;

B.D: not less than 2.8g/cm3;

particle size and moisture are determined according to buyer's requirements.

In addition, the particle size of the contract is signed as the fine powder, generally required to be between 100 and 200 mesh, and the pass rate is 85 to 90%.

Iron bauxite purity requirements

Inspection items for iron bauxite:

Al2O3:

not less than 80%;

Fe2O3: 4 to 10%;

TiO2: not more than 4%;

SiO2: not more than 7%,

particle size: according to the buyer's requirements.

Raw bauxite purity requirements

Inspection items for raw bauxite:

Al2O3:

70 to 73%;

Fe2O3: about 1.5%;

TiO2: not more than 4%;

SiO2: not more than 6%;

loss on ignition: 14 to 15%;

K2O + Na2O + CaO + MgO = 0.5 to 1%.


Application of classified bauxite

Premium alumina bauxite use:

(1) Aluminum smelting industry. Used in national defense, aviation, automobiles, electrical appliances, chemicals, daily necessities, etc.

(2) Precision casting. Bauxite Clinker is processed into fine powder and molded into a mold. Used in the military, aerospace, communications, instrumentation, machinery and medical equipment sectors.

(3) For refractory products. The high alumina bauxite clinker has a refractoriness of up to 1780 ° C, strong chemical stability and good physical properties.

(4) Aluminum silicate refractory fiber. It has the advantages of lightweight, high-temperature resistance, good thermal stability, low thermal conductivity, low heat capacity and resistance to mechanical vibration. Used in steel, non-ferrous metallurgy, electronics, petroleum, chemical, aerospace, atomic energy, national defense and other industries. It puts high-alumina clinker into a high-temperature electric arc furnace with a melting temperature of about 2000~2200°C. After high-temperature melting, high-pressure high-speed air or steam blowing and cooling, it becomes a white “cotton” – aluminum silicate. Refractory fiber. It can be pressed into a fiber blanket, a board or a woven fabric instead of a refractory brick lining the industrial high-temperature kiln such as smelting, chemical, and glass. Firefighters can make clothes with refractory fiber cloth.

(5) Using magnesia and bauxite clinker as raw materials, adding appropriate binders is very effective for pouring the whole barrel lining of the steel drum.

(6) Preparation of various compounds for alumina, abrasive materials, ceramics industry, and aluminum for the chemical industry.

Class I high alumina bauxite application:

(1) Raw bauxite, ie bauxite ore (natural sedimentary rock).

(2) Cooked bauxite, after the high-temperature calcination of the raw bauxite (1200 ~ 1700 ° C) is called cooked bauxite.

The high alumina bauxite clinker is classified according to the content of AL2O3 and the content of impurities such as Fe2O3, TiO2, CaO+MgO, K2O+Na2O, clinker bulk density and water absorption.

Calcined bauxite classification

Calcined bauxite classified by kiln:

1 shaft furnace calcined bauxite;

2 converter calcined bauxite;

3 inverted flame kiln bauxite.

Calcined bauxite classified by application:

1 refractory grade bauxite;

2 grinding grade bauxite;

3 electric welding grade bauxite