Hoffman Kiln

1).In a Homan kiln, the re moves through the bricks stacked in an elliptical or rectangular shaped annular circuit (central perimeter 80 – 90 m) which is covered with an arched roof .The kiln structure is usually covered with a shade to protect it from rains.
2).The fre movement is caused by the draught provided by a chimney (25–35 m high) which is located on one side of the kiln.Sometimes a fan is also used to augment the draught.The chimney is connected to the central fue duct of the kiln through an underground duct.
3).There are 3 distinct zones in an operating Hofman kiln:
     3.1 Brick fring zone where the fuel is fed and combustion is happening;
     3.2 Brick preheating zone(in front of the fring zone) where green bricks are stacked and being pre heated by the fue gases;
     3.3 Brick cooling zone (behind the fring zone) where fred bricks are cooled by the cold air fowing into the kiln.
4.1 Air Inlet: Air enters into the kiln from the back end of the cooling zone which is kept open to allow air entrance;
4.2 Seal to guide fue gas: The front end of the preheating zone is sealed to guide the fue gas to the chimney through the fue gas duct system;
4.3 The kiln is connected to the central fue duct through openings provided in the inner wall of the kiln. Openings just before the seal are kept open to allow entrance of fue gases from the kiln to the central fue duct.
5).Feed holes are provided in the kiln roof for feeding of fuels.Solid fuels (mainly frewood or coal) are fed from the feed holes by a single freman standing on the roof of the kiln. Fuel is fed at an interval of every 15-20 minutes and each fuel feeding lasts for 5-10 minutes.
6).The fre travels a distance of around 10 m in 24 hours and fres 10,000 to 20,000 bricks. Daily, fred bricks are unloaded from the back end of the brick cooling zone and an equivalent batch of green bricks is loaded ahead of the brick preheating zone.