Guides for brick and block plant investors and factory managers: clay brick kilns and extruders, sand-lime and fly ash bricks, block machines, standards and plant planning.
Most clay bricks are fired to a peak of around 1,000 °C, depending on the clay: US tunnel kilns run at up to about 1,090 °C (US EPA), and on our reference lines the peak is typically 950–1,050 °C, up to 1,150 °C. Fired too low, a brick stays porous and weak; fired too high, it bloats, distorts or glazes. The whole firing curve takes 10–40 hours (Brick Industry Association).
A vacuum brick extruder mixes prepared clay with water, removes the air from it in a vacuum chamber, and forces it through a die as a dense, continuous column that is then cut into bricks. De-airing makes the column stronger and more uniform, and hollow and perforated bricks must be vacuum-extruded. Its specification follows from your clay, your brick types and your output.
Hoffman kilns and Bull’s trench kilns are both continuous kilns in which the fire moves through stationary stacks of bricks. A tunnel kiln does the opposite: the bricks move on cars past a fixed fire. Bull’s trench kilns are open-topped, seasonal and labor-intensive; Hoffman kilns have a permanent roof and can fire all year; tunnel kilns give the highest output, control and automation.
A tunnel kiln for bricks is a long, fixed tunnel through which bricks travel on kiln cars while the fire stays in place. Each car passes a preheating zone, a firing zone and a cooling zone. Output is set by the kiln’s cross-section and length: on our reference designs, from about 70,000 bricks a day in a 3.3 m wide kiln to 200,000 in a 4.2 m kiln.
Clay bricks are made in eight steps. The raw material is tested, dug and stockpiled, then crushed, ground and mixed with water. A vacuum extruder pushes the mix through a die as a continuous column, which is wire-cut into bricks. The green bricks are set on kiln cars, dried, fired at around 1,000 °C, cooled, unloaded and packed.
