Fire clay bricks are special refractory bricks made from fire clay – a type of clay that is high in alumina and silica content which makes it resistant to high temperatures. Additionally, fireclay brick represents an inexpensive yet durable option for lining and insulating industrial furnaces, kilns and combustion chambers that operate at high temperatures. These bricks are used in applications that require heat resistance, thermal insulation, and chemical stability at high working temperatures.
Properties Of Fire Clay Bricks
The main properties that make clay fire brick manufacturing suitable for high temperature uses are:
• High refractoriness – Fire clay bricks remain hard and stable at temperatures up to 2,800°F and above due to their high alumina and silica content. This allows them to withstand the intense heat generated in industrial furnaces and kilns.
• Thermal shock resistance – The dense microstructure of fire brick clay allows them to resist thermal shock from rapid temperature changes without crumbling or cracking. This is important for furnace applications with large temperature fluctuations.
• Low thermal conductivity – The closed-cell structure of fire clay bricks, along with the presence of small pores, gives them a high insulative quality with low thermal conductivity. This helps keep the heat contained within furnaces and kilns.
• Chemical stability – clay fire bricks exhibit high resistance to chemical attack from molten metals, metal oxides and flue gases due to their non-basic chemistry and low porosity. This allows them to maintain their structural integrity in corrosive environments.
• Abrasion resistance – The dense and hard surface of fire clay bricks provides good resistance to wear and erosion from movement of materials within industrial furnaces.
Fire Clay Brick Applications
Some common applications of fire clay bricks include:
• Furnace and kiln linings – Fire clay bricks are used extensively in linings for industrial furnaces and kilns including plate kilns, reverbatory furnaces, rotary kilns and blast furnaces. They protect the walls from the intense heat generated inside.
• Ladle and tundish linings – The ability of fire clay bricks to withstand high temperatures, thermal shock and chemical attack makes them suitable for lining ladles and tundishes that contain and transport molten metals in steel plants.
• Combustion chamber linings – Fire clay bricks can withstand the high heat and erosive environment inside industrial combustion chambers used to burn fuels for heat generation.
• Foundry coping – In foundries, fire clay bricks are used as coping (also called capping) to line the top portions of furnaces that receive damage from ladling and pouring of molten metal.
• Insulation and back-up lining – Fire clay bricks serve as a back-up or secondary lining behind more expensive refractory materials like low cement castables, insulating firebricks and monolithic refractories in high temperature applications.
Manufacturing of Fire Clay Bricks
Fire clay bricks are manufactured using naturally occurring fire clays by the following process:
• Fire clay is mined from deposits and crushed into fine particles.
• Calcined fire clay is mixed with water and additives like sand for workability.
• The wet clay mixture is extruded or molded into brick shapes and dried.
• The green (or dried) bricks are fired in kilns at high temperatures ranging from 2,100°F to 2,300°F to achieve maximum refractoriness and strength.
• The fired fire clay bricks are then graded, inspected and stored for use.