Silica brick for coke oven

Silica brick for coke oven

Silica bricks for coke ovens are siliceous refractory products used for building coke ovens with tridymite as the main crystal phase. Coke oven silica bricks are used to build regenerator walls, ramps, combustion chambers, carbonization chambers and furnace roofs of coke ovens. Silica brick is an acid refractory material with good resistance to acid slag erosion. The softening temperature under load is as high as 1640-1670 °C, and the volume is relatively stable in long-term use at high temperature.

A modern coke oven is a large thermal equipment built with tens of thousands of tons of refractory materials of nearly 1,000 types of bricks, of which the amount of silica bricks accounts for 60% to 70%. Coke oven silica bricks are used to build regenerator walls, ramps, combustion chambers, carbonization chambers and furnace roofs of coke ovens.

The properties and process of silica bricks are closely related to the crystal transformation of SiO2. Therefore, the true specific gravity is an important quality indicator of silica bricks. The general requirement is below 2.38, and the high-quality silica brick should be below 2.35. The true specific gravity is small, which reflects that the amount of tridymite and cristobalite in the brick is large, and the amount of residual quartz is small, so the residual linear expansion is small, and the strength drop in use is also small. Silica has seven crystalline variants and one amorphous variant. These variants can be divided into two major categories: the first class variants are quartz, tridymite and cristobalite, which are very different in crystal structure and transform slowly between each other; the second class variants are subspecies of the above variants- ─αβ and γ types, their structures are similar, and they can be converted quickly to each other

Coke oven silica bricks should have the following characteristics:

(1) The softening temperature under load is high. The coke oven silica brick is required to withstand the dynamic load of the coal loading truck on the top of the furnace at high temperature, and requires long-term use without deformation, so the coke oven silica brick is required to have a high softening temperature under load.

(2) High thermal conductivity. Coke is made of coking coal by conduction heating by the wall of the combustion chamber in the carbonization chamber, so the silica bricks used to build the combustion chamber wall should have high thermal conductivity.

(3) Good thermal shock resistance. Since the coke oven needs to periodically charge coal and discharge coke, the temperature of the silica bricks on both sides of the combustion chamber wall changes drastically, so the coke oven silica bricks are required to have good thermal shock resistance.

(4) High temperature volume stability.

Although the refractoriness of silica brick is not very high, the softening temperature under load is high, the high-temperature structural strength is high, and it has good stability when used for a long time above 600 ℃, and can resist the erosion of acid slag. Therefore, it is currently mainly used for masonry glass furnaces and coke ovens. The coke oven carbonization chamber partition wall is built with silica brick, which has good stability and air tightness at high temperature, and its service life can reach 10-15 years, and if used properly, it can reach more than 25 years. Silica bricks were used as lining bricks for acid converters. The top of the electric furnace, the vault of the reverberatory furnace, the regenerator and the slag chamber were also widely built with silica bricks in the past, and now they have been gradually replaced by high-alumina bricks and magnesia-alumina bricks.