How Does an Air Preheater Work?

How Does an Air Preheater Work?

An Air Preheater (APH) is a device used to increase the thermal efficiency of a boiler system. Its main function is to utilise the waste heat in the flue gases discharged from the boiler, use this heat to preheat the air, and then feed the preheated air into the boiler for combustion. This preheating process helps to reduce fuel consumption and increase the thermal efficiency of the entire system. The following is the basic working principle of air preheater:

Flue gas heat exchange: The boiler produces flue gases while burning fuel. These flue gases contain high temperature heat. The air preheater is usually installed in the flue gas discharge channel of the boiler. As the flue gases pass through the air preheater, they come into contact with the heat exchange surfaces inside the preheater (usually tubes or fins) and transfer the heat from them to the surface of the preheater.

Air preheating: At the same time, the boiler requires large amounts of fresh air to support the combustion process. This air flows through the air preheater on the other side. On this side, the cold fresh air comes into contact with the heat exchange surfaces inside the preheater and absorbs the heat transferred from the flue gases. This allows the air to be preheated before it enters the boiler, increasing the efficiency with which the boiler burns the fuel.

Improved Combustion Efficiency: Preheated air enters the boiler combustion chamber, mixes with the fuel and participates in combustion. Since the air has been preheated, the fuel burns more fully, resulting in improved combustion efficiency. This means that the boiler can provide more heat under the same fuel conditions.

Energy saving and emission reduction: By utilising the waste heat in the flue gas, the air preheater lowers the temperature of the flue gas and raises the temperature of the air at the same time, thus realising the recovery and reuse of heat energy, thus reducing the consumption of fuel and lowering the cost of energy, and at the same time, reducing the emission of pollutants produced in the process of combustion, making it an energy-saving and environmentally friendly device.