Reasons for "black heart" of high alumina brick

September 15, 2018

Reasons for "black heart" of high alumina brick

High alumina “black heart” brick products not only affect the appearance, but also reduce the quality to varying degrees. Therefore, it is necessary to find out the reasons for the black core of high alumina bricks. Next, let's take a closer look at the following aspects.

1, raw materials

The main raw material for the production of high alumina bricks is bauxite. The higher the content of Al2O3 in high alumina bricks, the higher the grade of bauxite selected, that is, the first or super bauxite. However, the content of iron oxide and dioxins in bauxite with high grade tend to be high. The iron ion is a colored ion. The presence of iron and compound impurities makes it possible to produce a "black heart" in high alumina bricks. The higher the content of impurities, the greater the possibility of producing "black core" in high alumina brick products. In addition, the presence of low-melting materials in the raw materials reduces the firing temperature of the products, promotes the sintering of the products, and increases the amount of liquid phase during the firing of the products, thereby causing unreasonable factors at lower temperatures. It speeds up the movement of the iron ion and promotes the coloring reaction, which accelerates the production of the product "black heart".

2, code brick method

The loading position and method of high alumina bricks also have an impact on the degree of "black heart". If the loading position of high alumina brick is near the combustion chamber designed by the tunnel kiln, that is, close to the flame part, the flame will be heated rapidly to the product, and the local heating rate is faster, thereby aggravating the coloring reaction of the iron ion.

3, firing atmosphere and heating rate

The firing atmosphere and heating rate are very important conditions for the "black heart" of high alumina bricks. If the content of Fe2O3, FeO and TiO2 in the raw material is high, and the temperature rises too fast during the firing, that is, the temperature and oxidation atmosphere in the pre-tropical post-zone and pre-firing zone are very strong, then the "black heart" of the high-aluminum brick is produced. The degree will increase.

In addition, practice has proved that the bricks are not completely dried, the dry billet has a high water content, and the conditions of heating up too quickly after entering the kiln also increase the degree of "black heart" of the products.