General Introduction: Air Preheater
The plate air preheaters are mostly made of 1.5-4mm thin steel
plates. The steel plate is welded into rectangular boxes, several
boxes are put together in a group, and the entire air preheater
consists of 2-4 boxes. The flue gas passes through the outside of
the box from top to bottom, and the air passes through the inside
of the box horizontally, turns upward in the lower part, and
interacts with the flue gas twice to transfer energy, so that the
flue gas and the air form a reverse flow and obtain a better heat
transfer efficiency.
Working Principle
Taking the rotary air preheater as an example to illustrate the
principle of air preheater, it will rotate slowly during operation,
the flue gas will enter the flue gas side of the air preheater and
then be discharged, and the heat carried in the flue gas will be
absorbed by the heat sink in the air preheater, and then the air
preheater rotates slowly, the heat sink moves to the air side, and
then the heat is transferred to the air before entering the boiler.
The application of air preheater in boiler is mostly
three-compartment type, with fire alarm system, gap adjustment
system and frequency conversion control system. Air preheaters are
easy to use, simple to operate, safe to operate, and can improve
the heat exchange performance of the boiler system, so it is very
commonly used in flue gas boiler systems.
Details
The main heat transfer component of tubular air preheater is
thin-walled steel tube. The tubular air preheaters are mostly
cubic. The steel tubes are arranged vertically and staggered with
each other. Both ends are welded on the upper and lower tube
sheets.The tubular air preheater is equipped with an intermediate
tube sheet in the tube box. The flue gas passes through the
preheater up and down the pipe, while the air passes through the
preheater horizontally to complete heat transfer.
Tubular air preheater is widely used in power station boilers and
industrial boilers because of its advantages of good sealing, high
heat transfer efficiency, easy manufacturing and processing. The
shortcomings of tubular air preheater are large volume, easy ash
plugging of steel tube content, difficult cleaning and easy wear
and tear at flue gas inlet.
Functions
1. Improve and enhance combusion
The air through the air preheater enters the boiler inside, and
speed up the fuel processes of drying, ignition and combusion, and
makes sure the stable combusion inside the bouler, and improve the
combusion effieciency.
2.Enforce heat tranfer
Due to the improvement and enforcement of combusion in the boiler,
as well as the increase of hot wind temperature when entering the
boiler, the average temperature inside is increased, too. This can
enforce the radiation heat transferrring in the boiler.
3.Reduce the boiler loss, decrease the exhaust gas temperature and
improve the thermal efficiency of the boiler.
Because the combusion inside is stable, and the radiation heat
transferring is enhanced, it can reduce the loss caused by chemical
incomplete combusion. On the other hand, the air preheater take the
advantage of gas flue heat to further reduce the exhaust loss,
which thus improves the thermal efficiency. According to
experience, when the air tempeature inside the air preheater is
increased by 1.5 degrees, the temperature of gas flue can be
decreased by 1 degree. If installed, the air preheater can preheat
the air by 150-160 degrees, then can reduce the temperature of gas
flue by 110-120 degrees, and increase the thermal efficiency by
7-7.5% as well as save fuel by 11-12%.
4.the heat air can be the fuel desiccant.
For layer-burning boilers, it is okay to use fuel whose miosture
and ash content is high when preheated air is available. For power
station boilers, hot air is an important desiccant for fat power
system and medium to convey coal powder.
Parameter
| Layout item | Horizontal layout | Vertical layout |
| Tube arrangement | staggered arrangement /
in-line arrangement | staggered arrangement /
in-line arrangement |
| Sealing of pipe and plate | Packing heat- resistant material/
welding | welding |
| Anti-wearing | 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. |
Enamel air preheater products are classified as following by
application
1.Enamel heat exchanger designed for denitration renovation
projects
2.Enamel heat exchanger for circulating fluidized bed boiler and
pulverized coal boilers Heat
exchanger parts for garbage incinerators and biomass boilers
3.Heat exchanger parts for grate furnaces, like chain grate
furnaces4.Heat exchanger parts for gas-fueled boilers, such as
kerosene boilers, coke ovens, etc.
