In zigzag kilns, bricks are arranged to allow hot air to travel in a zigzag path. The length of the zigzag air path is about three times that of a straight line, and this improves the heat transfer from the flue gases to the bricks, making the entire operation more efficient. In addition, better mixing of air and fuel allows complete combustion, reducing coal consumption to about 20 percent.
- The zigzag design also ensures uniform distribution of heat, increasing the share of Class I bricks to about 90 percent. It also reduces emissions considerably.
- The zigzag technology has two sub-types: natural and induced. The induced draft uses fans to regulate air While the natural draft has a chimney. The operational cost of the induced draft includes the cost of diesel and the maintenance of a generator to run the fan, which comes up to about Rs 250,000 a season. This cost is eliminated in the natural model, but it requires an initial investment in building a chimney