Biscuit ovens normally consists of 4-5 stacks in an oven . These stacks are there to release flue gases due to combustion in the fire tubes.
Biscuit manufacturing involves high temperatures for baking .Various type of ovens are available for baking bakery products . Heat recovery can be done for biscuit oven which has 5 - 6 zones basically in indirect Oven .As temperatures are very high ( 400-500degc) on infeed end these stacks are then joined to a common duct which collects heat from these stacks with help of blower and then these flue gases is passed onto the last zone which requires low temperature . This temperature is as low as 180- 200 degc can be attained by circulating flue gases collected in common duct from these stacks .This eleminates need of one burner all together at coloring zone or last zone .
Fuel is saved by implementing this kind of arrangement . 15 ltrs-20ltrs /hr can be saved