Tabular corundum refractory material is alpha-alumina with sheet-shaped crystals, aluminum oxide feedstock is calcined alumina ground to a fine powder and palletized to balls with an abt diameter of 25 mm. These balls are sintered (fired) at 1750°C in modern shaft kilns and following crushed, milled, and sieved to standard fractions/sizes. Tabular corundum refractory material is a re-crystalline sintered alpha alumina with high density. It consists of large (50 – 200 µm), flat, tablet-shaped corundum crystals.
The main properties of tabular alumina are as follows:
·The concentration of high purity Al2O3 is 99.2%min;
·Very high crystal hardness;
·Low yield, high fracture rate 2-3 times;
·High particle bulk density 3.5-3.6g/cm3
·High melting point : 2000°C
·Good thermal shock resistance
·Excellent volume stability
·High single crystal strength
Tabular Alumina can be used as the main component in aluminium-carbon, aluminium-magnesium-carbon, magnesia-aluminium-carbon, magnesia-spinel and aluminium-chromium refractory bricks. It can also be introduced into high aluminium amorphous refractories as the enriched alumina component. It can be widely used in steel, casting, ceramics and other industries, and its application in iron and steel industry almost covers. The whole process of ironmaking and steelmaking has been completed.Other applications include electrical insulators, kiln furniture and catalyst carriers. Finely ground plate corundum powder is an excellent filler for epoxy or resin systems to achieve the desired high insulation strength, thermal conductivity and wear resistance.
As a large and important raw material in refractory materials, the process of producing sintered slab corundum by high temperature vertical kiln is as follows:
1. Ball mill. The bayer process is used to light burn aluminum oxide powder as raw material for continuous ball milling. The fineness and specific surface area must meet the requirements, which is helpful for sintering and densification of aluminum oxide powder.
2, into the ball. The powder after grinding is made into ball by ball plate or ball barrel. After forming, the blank ball should be strong to avoid breaking in the process of transportation to the dryer. In order to solve the problems of high water content, easy layering and difficult drying, the process optimization design was carried out.
3. After drying, the blank ball is put into the dryer. About 15%(W) of moisture was removed by using hot air against the current in the vertical kiln. However, the temperature in the vertical kiln should be strictly controlled to avoid cracks, delamination, even agglomeration and furnace blocking inside the billet ball. The ball flow is interrupted and the drying quality is decreased.
4. Sintering. After drying, the billet goes into the shaft kiln. The sintering temperature is 1900 '1950°C. By controlling the hot air temperature and flow rate in the vertical kiln, crystal development was obtained. The tabular structure of sintered corundum.
After firing, after cooling, picking up (picking up burnt and under-burned products), inspection (physical and chemical index inspection of sintered products), crushing and screening, products with different particle size can be obtained.