Eurovent fan was designed specifically for
demanding heavy-duty applications, including hot gasses and fumes, induced
draft, process exhaust and light concentrations of solids in a variety of
We combine the advantages of the radial and backward inclined blades and
replace the traditional light-duty exhauster with a more rugged, longer life
span. It will handle moderate to high pressures and temperatures and has a high
- Induced Draft fans
The Induced Draught fan draws flue gases out of the boiler, through the
air preheater, to maintain furnace conditions at just below atmospheric
pressure. Control of furnace pressure is a critical safety consideration.
- Forced Draught
The Forced Draught fan moves cold air through the air preheater into the
boiler. This air provides the oxygen used in the boiler combustion process. The
FD fans have to supply large quantities of low pressure air to the boiler.
Process characteristics will tend require large diameter, slow running, double
inlet fans, with airfoil profile blades.
- Primary air
On coal and biomass fired boilers the Primary air fan moves air through
the air preheater. The hot air exiting the preheater is mixed with the
pulverized fuel and the air flow conveys this fuel/air mix to boiler combustion
chamber. Oil fired boilers do not require primary air fans. Primary air fans
often have impellers with backward curved plate or aerofoil bladed designs and
as the volume flow requirement is comparatively low they are usually of a
single inlet design. To be able to carry the fuel into the boiler the fan
pressure requirement is relatively high.
- Cold primary air fans operate with
relatively clean ambient air.
The use of cold air means that for a given mass flow of air into the
boiler, the fan does not need to move as high a volumetric flow as a hot PA
fan. This leads to a smaller fan size The process of pressurizing the air in
the preheater encourages leakage of the air into the gas stream. This portion
of the air is lost into the flue gas exiting the plant, which reduces the
- Hot Primary Air fans operate with
hot air coming out of the air heater.
Using a hot primary air fan has the advantage of reducing the leakage of
air into the gas stream within the preheater. As the air is hot, it has a lower
density and the fan will have to move a large volume flow to maintain the mass
flow required by the boiler combustion process. This means the fan needs to be
slightly larger than a cold PA fan Hot primary air fans also have to be
designed to resist abrasion as the hot air will now contain erosive dust
particles that have been carried over into the air by the air heater.
- Secondary air
The secondary air fan takes air from the same sources as the Primary Air
fans, however in this case the air is supplied into the boiler combustion
chamber above the grate. This air creates a turbulent condition over the fuel,
enhancing combustions and providing an additional oxygen source to help
complete the combustion process.
- Gas Recirculation
Gas Recirculation fans are not always fitted to a boiler. This fan
re-circulates combusted flue gas from the back end of the boiler or economizer
through a dust collector and delivers the gas back to the boiler. The
re-circulated gas is introduced either into the immediate vicinity of the
initial burning zone of the boiler to control steam temperature or the gas is
introduced near to the boiler outlet to assist in the control the furnace gas
temperature, in a process known as.