Black heart is an easy phenomenon in aluminum brick production. The causes and conditions of black heart are as follows
The main impurity oxides in high alumina brick are Fe2O3 and TiO2, which are the conditions for producing black heart. However, when iron and titanium oxides coexist alone, they have different effects on the coloring of products. When titanium ions exist alone, the coloring is not significant, and the products appear slightly blue, while when iron ions exist alone, the products appear brown. However, the coexistence of iron and titanium can increase the coloring of products even in an oxidizing atmosphere. In a reducing atmosphere, the coexistence of iron and titanium ions alone can produce black centers in the coloring of products
Ways to avoid black centers in high alumina bricks:
1) The high titanium bauxite raw material is subject to strong magnetic iron removal to minimize the coexistence of titanium and iron ions
2) Change the kiln charging method of high alumina bricks, the fire path is large and smooth, and the sand cushion between bricks is full
3) Increase the amount of hot air to create an oxygen enriched atmosphere
4) During cooling,Slow cooling to avoid decolorization due to re oxidation of iron and titanium ions
