High Heat Exchange Performance Boiler Air Preheater for Coal-Fired
Power Station Boilers
General Introduction: Air Preheater
Air preheater is a kind of preheating equipment that improves the
heat exchange performance of the boiler and reduces heat loss. It
can conduct the heat carried in the flue gas discharged from the
flue at the tail of the boiler to the air before entering the
boiler through the heat sink to preheat the air to a certain
temperature.
Air preheater is mostly used in coal-fired power station boilers.
It can be divided into two types: tube box type and rotary type, of
which the rotary type is divided into two types: wind hood rotary
type and heating surface rotary type. Power station boilers often
use rotary preheaters on the heating surface. The application in
boilers is generally two-bin, three-bin, and four-bin, of which
four-bin is more commonly used in circulating fluidized bed
boilers.
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.
Function
1.Improve and intensify combustion
The air after passing through the waste heat collector enters the
furnace, which accelerates the drying, ignition and combustion
process of the fuel, ensures the stable combustion in the boiler,
and improves the combustion efficiency.
2. Strengthen heat transfer
Radiative heat transfer in the furnace is enhanced due to the
improved and intensified combustion in the furnace and the increase
in the temperature of the hot air entering the furnace, which
increases the average temperature level in the furnace.
3. Reduce the loss in the furnace, reduce the exhaust gas
temperature, and improve the thermal efficiency of the boiler
Due to the stable combustion in the furnace and the intensification
of radiant heat exchange, the loss of chemical incomplete
combustion can be reduced;On the other hand, the air preheater uses
the waste heat of flue gas to further reduce the exhaust gas loss,
thus improving the thermal efficiency of the boiler.According to
experience, when the air is raised by 1.5 °C in the preheater, the
exhaust gas temperature can be reduced by 1 °C. After the air
preheater is installed in the boiler flue, if the air waste heat
can be reduced by 150-160 °C, the exhaust gas temperature can be
reduced by 110-120 °C, which can increase the boiler thermal
efficiency by 7%-7.5%. It can save 11%-12% of fuel.
For laminar furnaces, there is hot air that can be used with fuel
with higher moisture and ash content, and for power station
boilers, hot air is an important desiccant and pulverized coal
conveying medium for pulverizing systems.
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.
