Tubular Type Air Preheater APH Boiler Industry Waste to Energy Environmental friendly
What is Air Preheater (APH)
An air preheater (APH) is a general term to describe any device designed to heat air before another process (for example, combustion in a boiler) with the primary objective of increasing the thermal efficiency of the process.
They may be used alone or to replace a recuperative heat system or to replace a steam coil.
In particular, this article describes the combustion air preheaters used in large boilers found in thermal power stations producing electric power from e.g. fossil fuels, biomasses or waste.
Purpose of Air Preheaters(APH)
The purpose of the air preheater 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.
As a consequence, the flue gases are also conveyed to the flue gas stack (or chimney) at a lower temperature, allowing simplified design of the conveyance system and the flue gas stack.
It also allows control over the temperature of gases leaving the stack (to meet emissions regulations, for example).
Types of Air Preheaters
There are two types of air preheaters for use in steam generators in thermal power stations: One is a tubular type built into the boiler flue gas ducting, and the other is a regenerative air preheater. These may be arranged so the gas flows horizontally or vertically across the axis of rotation.
1. Tubular Type Air Preheater
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.
Inside the ducting, the hot furnace gases pass around the preheater tubes, transferring heat from the exhaust gas to the air inside the preheater.
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.
2. Rotating-Plate Regenerative Air Preheater
The rotating-plate design (RAPH) consists of a central rotating-plate element installed within a casing that is divided into two (bi-sector type), three (tri-sector type) or four (quad-sector type) sectors containing seals around the element.
The seals allow the element to rotate through all the sectors, but keep gas leakage between sectors to a minimum while providing separate gas air and flue gas paths through each sector.
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