During normal boiler operation, the hot slag (about 850℃) falling from the cold ash hopper drops onto the conveying steel belt of the steel belt slag conveyor through the boiler bottom slag discharge device and moves slowly with the steel belt.

Under the negative pressure of the boiler, a certain amount of cold air enters through the ventilation holes around the shell of the steel belt slag conveyor. The hot slag is gradually cooled and re-combusted on the conveying steel belt, completing heat exchange between cold air and high-temperature slag.

The cold air absorbs waste heat from the slag and heat released by the re-combustion of combustibles, heats up to 400-500℃ and returns to the furnace. After being conveyed and cooled by the slag conveyor, the slag temperature drops below 200℃ and enters the next conveying equipment.