Chimney
A steam boiler assembly, be it any fuel (solid/liquid/gaseous) used for combustion, the flue gases coming out of the Induced draft fan, coming from air preheaters and dust collectors, enters the chimney to conclude this process before getting released to the atmosphere.Self-supported type Chimneys can be provided suiting the boiler size. It can be designed and manufactured as per IS-6533 standard to ensure compliance.
Industrial Chimney |
Working
The
chimney’s working is based on the natural draft or stack effect. As we
know, the density of a gas reduces, with rising in its temperature, so
because of this reason when the flue gases enter the chimney, the
buoyancy forces of air come into action and help in carrying the flue
gases out of the chimney. In the case of a Boiler assembly employing an
Induced Draft Fan, the flue gases are brought to the chimney by this fan
and then buoyancy forces deliver them to the atmosphere. These buoyancy
forces depend upon the weight of the air displaced by the flue gases in
the chimneys. Greater the weight, greater are the buoyancy forces
present. And this weight can be increased by increasing the height of
the chimney. Back in time, when Lancashire Boilers were in fashion,
induced draft fans were not used. The reason was the extremely high
temperature of flue gases at the chimney inlet, this high temp. of flue
gases reduced the density of flue gases to a great extent. Now they were
even lighter and the buoyancy forces produced were of greater
magnitude. This removal of flue gases in the chimneys created a vacuum
at the chimneys inlet. So, because of this vacuum (pressure difference
between boiler furnace and chimney inlet), the flue gases traveled all
the way from the boiler to the chimneys, eliminating the need for an Induced Draft Fan.Buoyancy forces produced, are given by relation as given below:
Fb = (Pa – Pf )xgxh
where
Fb = Buoyancy force (N)
Pa = Density of Ambient Air (kg/m3)
Pf = Density of Flue gases at chimney inlet temperature (kg/m3)
g = Acceleration due to gravity (m/s2)
h = Height of chimney (m)
We, at thermodyne have successfully designed, manufactured, supplied and erected both structure and self-supported Chimneys in compliance with IS-6533 (part-1&2) to many of our clients.
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