An Air Pre-heater is a device designed to heat air before another process (like combustion). Air preheating is done to increase the thermal efficiency of the process. BTL EPC Ltd. manufactures customised Air Pre-heaters based on the clients' requirement. The purpose of the air pre-heater is to recover the heat from the boiler flue gas which increases the thermal efficiency of the boiler by reducing the useful heat lost in the flue gas. It also allows control over the temperature of gases leaving the stack. The Air pre-heater is installed between the economizer and chimney