Why are clay bricks preferred over high-alumina bricks or silica bricks for the coke oven roof area, small flues, and flues?

High-alumina bricks have good resistance to firing and heat, but their thermal insulation properties are relatively poor.

Clay bricks are made from clay (including powders such as shale and coal cinders) as the main raw material, through processes of slurry preparation, molding, drying, and firing. During the Spring and Autumn and Warring States periods, China successively developed square and rectangular bricks. In the Qin and Han dynasties, brick-making technology, production scale, quality, and variety of designs saw significant progress, giving rise to the term \"Qin bricks and Han tiles\". The dimensions of ordinary bricks are 240 mm × 115 mm × 53 mm, and they are classified into 6 strength grades – MU30, MU25, MU20, MU15, MU10, and MU7.5 – based on their compressive strength (in Newtons per square millimeter, N/mm2). Clay bricks are made from locally available materials, are inexpensive, durable, and possess advantages such as fire resistance, heat insulation, sound insulation, and moisture absorption; they are widely used in civil engineering construction. Broken bricks can also be used as aggregate for concrete. To overcome the disadvantages of ordinary clay bricks, such as their small size, heavy weight, and high clay consumption, there is a trend toward developing bricks that are lightweight, high-strength, hollow, and larger in size. Gray sand brick is made by combining lime with quartz sand, sand, or fine sandstone in appropriate proportions, grinding the mixture, adding water, pressing it using a semi-dry method, and then curing it through autoclaving. Fly ash bricks are made using fly ash as the main raw material, with additives such as coal gangue powder or clay serving as binding materials. They are produced through processes of mixing ingredients, shaping, drying, and firing, thereby allowing for the effective utilization of industrial waste residues and saving fuel.

Silicon bricks have three crystal phase transition points, and significant volume changes occur in the vicinity of these transition points. As a result, silicon bricks have poor resistance to sudden temperature changes; therefore, they cannot be used in such areas! !

Clay bricks have good thermal stability, whereas high-alumina bricks or silica bricks may not have the same level of stability in such an environment; this is something that requires special attention.

Silicon bricks have good thermal conductivity, making them suitable for constructing the walls of carbonization chambers. Clay bricks can withstand sudden changes in temperature, which is why they are appropriate for use in small flues

The price of bricks is also a factor to consider.

The operating temperature of these areas, the external conditions, and the properties of the refractory materials determine that silicon bricks are not used in these areas.