Power plant boiler petrochemical industry condensing gas boiler air preheater
Boiler auxiliary air preheater Introduction
1. Air pre-heater is a heat transfer surface in which air temperature is raised by transferring heat from other media such as flue gas .Hot air is necessary for rapid combustion in the furnace and also for drying coal in milling plants. So an essential boiler accessory which serves this purpose is air pre-heater.
2. The air pre-heater are not essential for operation of steam generator, but they are used where a study of cost indicates that money can be saved or efficient combustion can be obtained by their use. The decision for its adoption can be made when the financial advantages is weighed against the capital cost of heater in the present paper we have taken up the operation and performance and also air heater leakage, corrected gas outlet temperature and finally gas efficiency has been calculated
Air Preheater Pros
2 pass design to extract maximum waste heat from flue gases leaving the boiler.
It is used to extract waste heat from the flue gases leaving the boiler exhaust thereby increasing the efficiency of a boiler by 2-3 %.
It is used to preheat the fuel which further increases the boiler efficiency.
Payback time is less.
Air Preheater Cons
Adding and equipment or accessory in the path of flue gases increases flue gas pressure drop down the line, so the size of Induced Draft Fan increases.
Working of Air Preheaters(APH)
1. Air Preheaters have a shell and tube type construction where exhaust heat from the flue gases is transferred to the air when they come in indirect contact with each other.
2. Air Preheaters consist of a shell where tubes are arranged in a square or triangular pitch and are welded to a tube plate. Depending upon the type of operation and ease of cleaning, flue gases & air can be allowed to travel either shell side or tube side interchangeably.
Tubular type Air Preheater
1. Tubular preheaters consist of straight tube bundles which pass through the outlet ducting of the boiler and open at each end outside of the ducting.
2. Inside the ducting, the hot furnace gases pass around the preheater tubes, transferring heat from the exhaust gas to the air inside the preheater.
3. Ambient air is forced by a fan through ducting at one end of the preheater tubes and at other end the heated air from inside of the tubes emerges into another set of ducting, which carries it to the boiler furnace for combustion.
staggered arrangement /in-line arrangement
staggered arrangement /
Sealing of pipe and plate
Packing heat- resistant material/
a,when gas scours external tube, welcoming smoke tubes have protective tile
b,when gas scours inside tube,wear casing pipes are installed in gas inlet