Production process of silica bricks used for glass melting furnace

Silica bricks are made of high-purity quartz stone mixed with a small amount of lime milk after being simmered and selected. A part of the aggregate can be used after being crushed by waste silica bricks. High-grade silica brick raw materials are subject to special chemical treatment to remove impurities.

Raw materials and production process of silica bricks

1. Determination of raw material ratio and particle composition

The main raw materials for the production of silica bricks are quartz stone, waste silica bricks, lime, mineralizers and organic binders. Adding waste silica bricks can reduce the firing expansion of the bricks, but also reduce the refractoriness and strength of the products. Therefore, it should be determined according to different situations. The principle is that the larger the unit weight of the product, the more complex the shape, and the more the added amount, which should generally be controlled within 20%. Lime is added in the form of lime milk, which acts as a binder, increases its strength after drying, and acts as a mineralizer during firing. The mineralizer used in production is mainly steel oxide scale. The commonly used organic binder is sulfite pulp waste liquor.

2. Determination of the firing system of silica bricks

Silica bricks undergo a phase change during the firing process, making it difficult to fire. Therefore, the physical and chemical changes of the bricks during the firing process, the shape and size of the green body, and the characteristics of the kiln should be comprehensively considered.

① In the temperature range below 600 °C, the temperature should be raised quickly and evenly.

②In the temperature range of 700-1100 °C, the heating rate can be evenly accelerated compared with the previous stage.

③In the temperature range of 1100-1430℃, the heating rate should be gradually reduced.

④In the high temperature stage, it is fired with a weak reducing flame, and at the same time, the temperature distribution in the kiln is uniform, and the flame impact on the adobe should be avoided. After reaching the maximum firing temperature. There must be enough holding time, which generally fluctuates in the range of 20-48h.

⑤ It can be cooled quickly at above 600℃, and it should be cooled slowly when the temperature is low. Table 10-4 lists the heating rates in different temperature ranges