Zigzag firing technology for replacing fixed chimney bull’s trench kiln, comprises of arrangement of bricks in a manner that air is forced to follow a zigzag path. In a zig-zag kiln, powdered coal is fed in small quantities and the fuel feeding zone is longer. this results in cleaner and complete combustion of coal.
Source:http://www.catf.us/resources/publications/files/Brick_Kilns_Performance_Assessment.pdf