Tabular Alumina for High Purity Corundum Brick

High purity corundum brick with Al2O3 content above 99% is studied based on tabular alumina and white fused alumina (WFA) as single aggregate and the combination of both. In comparison with Tabular alumina, WFA aggregate has relatively higher SiO2 content of above 0.10% and shows fluctuation on soda content. WFA also has a high open porosity of 8.8%, which very often exists in the form of single large pore or in the form of agglomeration of pores rather than the small closed and evenly distributed pores in tabular alumina. Refractory brick china with different ratio of tabular alumina and WFA have been tested for firing shrinkage, bulk density and apparent porosity, cold and hot strength, thermal shock resistance, and abrasion resistance. Also slag tests with a coal gasifier slag and an oil cracking slag have been conducted. The results from this evaluation conclude that high alumina brick outperforms WFA bricks and importantly gives more balanced performance.

Introduction
High purity corundum brick is widely used as refractory lining for oil cracking unit, coal gasifier, carbon black furnaces, black liquor gasification and other industrial furnaces. This is attributable to the outstanding performance of corundum brickon chemical corrosion resistance, mechanical abrasion resistance and thermomechanical properties like high temperature strength, refractoriness under load and creep resistance, even in environments with corrosive gas or liquid and with high pressure.
Synthetic alumina based aggregates like white fused alumina and tabular alumina are the two main aggregates available for high purity corundum brick. They are selected due to low impurity content (e.g. SiO2), high bulk density and thermomechanical properties, which enables corundum bricks that meet the requirements on thermal, chemical and structural attacks [1] which gasifiers and other furnaces apply in operation.

The different processes for WFA and tabular alumina production (fusion vs. sinter) certainly create differences between the aggregate, which also have an impact on the properties and performance of the corundum brick. Tabular alumina is well received and extensively used in the refractories for steelmaking such as slide gate plate, Al2O3-MgOC brick, castables and pre-cast shapes.

However, for a long period of time, WFA is very commonly used as the aggregate for high purity corundum brick to non-steel applications like gasifier and other industrial furnaces. It is often claimed that WFA aggregate has higher bulk density which consequently increases the density of fire brick China and the corrosion resistance which could enhance the overall performance. However these perceptions should be investigated by an extensive evaluation. This work is designed to evaluate in a comprehensive way the differences on performance of tabular alumina and white fused alumina in respect to aggregate itself and brick properties in order to understand these differences and provide appropriate application guideline for high purity corundum brick.

1. Refractory raw material Almatis global tabular alumina product T60/64 and a common commercial Chinese WFA grade are selected as the aggregate and fine. In the matrix, Almatis’ calcined alumina CT800FG is also used. Sulphite pulp liquor is used as temporary binder for corundum brick making.

2. China refractory brick formulation Five recipes are used in this evaluation. As per the tabular alumina content in aggregate, the formula is named as T100, T75, T50, T25 and T0 and the numbers stand for tabular alumina content in respective brick. Table 1 gives the details with bold highlighted for tabular alumina.

Article Source: refractory fire brick
Company name: Henan Xinmi Changxing Refractory Materials Co.,Ltd
Email: sales1@chinafirebrick.com
Website:http://www.chinafirebrick.com/