Clay brick manufacturing process Part three
Drying of bricks
In the brickmaking process, the clay is refined and water is added in order to mould the brick. Before the bricks can be fired, they must be dried properly: the moisture content has to be reduced to 8% of volume for the clamp kiln.
In South Africa, there is adequate sun for the dr ying operation and most clamp kiln brickmakers make full use of this free source of energy by placing the bricks on open hacklines. This operation has the disadvantage that it may make the process timeconsuming, especially in the rainy season. To reduce the drying cycle, brickmakers have introduced some mechanical means of drying. The two most common methods are tunnel or chamber driers. The energy (heat) for the dr ying is produced in a supplementary coal heater or recycled off the kiln and the heated air is fed into the driers. These methods work as follows:
Tunnel driers: The bricks are produced and then offset on flat rail trolleys or kiln cars. The cars are pushed through the tunnel. This operation can take up to 40 to 50 hours, from green to dry.
Chamber driers: Patented chamber driers are large rooms where bricks are packed onto pallets. The chambers may have a capacity of 50 000 to 60 000 bricks. Hot air is fed into the chamber. Drying time is between 30 and 45 hours – much quicker than the 14 to 21 days needed for solar dr ying.