Complete the sentence: "The function of the ___________ is to increase the temperature of air before it enters the furnace".

Explanation:

Air Preheater

• An air preheater is a heat exchanger device used in the thermal power generation process to increase the temperature of the air before it enters the furnace. Its primary function is to recover heat from the flue gases (exhaust gases) exiting the boiler and utilize this heat to preheat the incoming air required for combustion. By doing so, it improves the overall efficiency of the boiler and reduces fuel consumption.

Working Principle: The air preheater works on the principle of heat exchange. It extracts heat from the hot flue gases leaving the boiler and transfers it to the incoming air. This heated air is then supplied to the furnace for combustion. The preheating of air enhances the combustion process, resulting in better fuel efficiency and reduced emissions.

Air preheaters can be of two main types:

• Regenerative Air Preheater: In this type, a rotating matrix or regenerative element is used to transfer heat from flue gases to air.
• Tubular Air Preheater: In this type, heat transfer occurs through tubes where hot flue gases and air flow separately.

Advantages of Air Preheaters:

• Improves boiler efficiency by recovering waste heat from flue gases.
• Reduces fuel consumption as preheated air facilitates efficient combustion.
• Helps in reducing the emission of harmful pollutants by ensuring complete combustion.
• Enhances the overall thermal performance of the power plant.

Additional InformationSuper heater

• A superheater is used to increase the temperature of steam, not air. It is a device in the boiler system that heats the saturated steam produced by the boiler to a higher temperature, converting it into superheated steam. This superheated steam is then used in turbines for power generation.

Injector

• An injector is a device used to feed water into the boiler using steam pressure. It works by creating a vacuum that draws water into the boiler without the need for a mechanical pump.

Economizer

• An economizer is a device used to preheat feedwater entering the boiler by recovering heat from the flue gases. Its function is to improve the efficiency of the boiler by reducing the amount of heat required to convert water into steam.