Air Curtain Burners, also called
FireBoxes, were
designed principally as a pollution control device. The primary
objective of an air curtain machine is to reduce the particulate matter
(PM) or smoke, which results from burning clean wood waste. It is
sometimes hard to visualize without seeing a machine in operation, but
the machines do not burn anything, rather they control the results of
something burning.
You could look at it as a pollution control device
for open burning. Clean wood waste is loaded into the FireBox, and
an accelerant such as Diesel fuel is poured onto the wood and the pile is ignited.
This is very similar to starting a campfire. The air curtain is not engaged
until the fire has grown in strength or the air curtain may blow the
fire out. Once the fire has reached suitable strength, usually in 15 to 20
minutes, the air curtain is engaged. The air curtain then runs at steady
state throughout the burn operation and the waste wood is loaded at
a rate consistent with the rate of burn. Our smallest machine will burn
at a rate of 1 to 2 ton per hour, our largest machine can burn in
excess of 10 tons per hour.
Principle
The
purpose of the air curtain is to stall or slow down the smoke particles on
their way out of the FireBox. In doing this the particles are subjected
to the highest temperatures in the FireBox. Stalling the smoke particles
in this region just under the air curtain causes them to re-burn,
further reducing their size to an acceptable limit. The result is a very
clean burn with opacities well under 10% per EPA Method 9 Testing (as
compared to open burning which typically can run at 80% to 100% opacity).
Operation
 The picture to the right
shows an Air Burners FireBox S-327 completely full and burning while in the background a pile of wood is open burned.
The wood pile that is open burning continued to burn for several days. That
entire pile could have been eliminated with the FireBox in less than 2
hours.
For proper operation, the air
curtain machine has to be designed to provide a curtain of air over the
fire that has a mass flow and velocity that are in balance with the
potential mass flow and velocity of the burning wood waste. If the
air curtain velocity is too high, the FireBox can become over
pressurized and over agitated. The higher pressure will lift the curtain
and cause it to become ineffective. The over-agitation will cause embers
and ash to be blown out of the FireBox or pit past the ineffective air curtain
at a significantly higher rate than normal. If the mass flow of the
curtain is too low then the unburned particles (smoke) will penetrate
the curtain on the high velocity of the hot gasses being generated from
the burning wood.
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Air Curtain Burners do not
burn anything.
They are Pollution Control Devices for Open Burning.
They control the results of
something burning.
"The Wood Waste is the Fuel" |
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| 1 |
Air
curtain machine manifold and nozzles directing high velocity air
flow over and into refractory lined fire box. |
| 2 |
Refractory
lined wall of FireBox..
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| 3 |
Wood waste material
to be burned.
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| 4 |
Initial
airflow forms a high velocity “air curtain” over fire.
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| 5 |
Continued
air flow over-oxygenates the fire keeping temperatures high. Higher
temperatures provide near 100% combustion efficiency and that
results in a cleaner and more complete burn.
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Video Clip of an
Operating FireBox
Video Clip of operating FireBox on |
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Rev. 12.2012AU
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