The reasons of Black heart of Refractory brick

Black heart is a high alumina brick production is prone to a phenomenon. The characteristics of this brick, brick profile color gradually changes from the surface of the yellow-green to the internal gray-black transition. If this black heart brick in the oxidizing atmosphere to re-calcined, black heart can be re-burn white part.

(1) the reasons and conditions of black heart

   The main impurity in the high alumina brick is Fe203, Ti02. From the oxidizing atmosphere under the re-burning black heart brick white facts can be speculated that the cause of black heart is iron, titanium impurity oxide, the atmosphere is a black heart conditions.

However, iron, titanium oxide coexistence and existence, respectively, on the brick color has a different role. Titanium ion alone, the color is not significant, brick body was blue, and iron ions exist alone, the brick was orange-brown. However, iron and titanium coexist, even in the oxidizing atmosphere, can increase the coloring and sintering of alumina to produce black heart.

In the reduction of atmospheric conditions, iron, titanium ions exist alone and coexistence can make brick black heart. But iron and titanium coexist deeper than the presence of color alone. Therefore, the reduction of the atmosphere than the oxidation of the atmosphere easier to make brick color, especially iron, titanium ions coexist in the reduction atmosphere, especially the black heart.

(2) to avoid high black brick black heart of the way

    From the above, we can see that the formation of high black brick black and white has two processes: one is high temperature and reducing the atmosphere to iron, titanium ions to restore coloring, one is at low temperatures, low iron, titanium ions re-oxidation and decolorization. Accordingly, the following methods can be used to avoid coloring:

① high titanium bauxite raw materials using strong magnetic separation iron, try to avoid iron and titanium ions coexist;

    ② change the way of high alumina brick kiln;

    ③ increase the amount of hot air, resulting in oxygen-rich operation, to avoid the reduction of the atmosphere;

    ④ in the cooling process, slow cooling, so that low-cost iron, titanium ions re-oxidation and decolorization.