Date: Mon, 21 Nov 2005 20:49:01 -0500
From: David Gordon <email@example.com>
Subject: Re: wood kiln ventilation
It appears from your literature, that you have a gas fired "afterburnern of
sorts that heats the stack to 1800 degrees F. The best way to eliminate
combustible smoke is by afterburning so you are on the right track. The
trick is to keep the flue gas at the temperature for a mini~ of 0.3
seconds and preferably 0.5 seconds before being releaSed to the atmosphere.
This means that you need a large diameter stack so that the flue gases will
travel slowly through it. The smaller the stack diameter, the faster the
flue gas will pass through it and you won't get your 0;5 second residence
In addition, you have to preheat the exhaust stack to a minimum of 1500
degrees F prior to lighting up the wood so that the stack is at afterburner
temperature when the wood lights up. I imagine that the beginning of the
run must be the smokiest time and preheating the stack will burn that smoke.
An afterburner could be fitted onto any wood fired apparatus. A heavy
gauge, removable screen would block the large embers. The afterburner will
only oxidize the nsmoken and it will need the screen as a prefilter. The
screen will have to be cleaned after each firing. There is no way to create
an oxygen rich atmosphere except by feeding oxygen into the stack, but that
could be very dangerous. You could burn out the stack just like an
oxy-acetylene torch could do.
If the kiln is under positive pressure and I imagine that it is based on
your description, a vent system can be designed to efficiently control the
emissions. These could be quite toxic because where there is smoke, there
is carbon monoxide.
Whatever you do, the control systems (afterburner and exhaust system) should
be custom designed for each kiln size and capacity.
Hope this has been some help. By the way, the latest Ceramics Monthly has a
photograph of a system that I designed in Minnesota.
David Gordon, PE, CIH, QEP
Gordon Air Quality Consultants, Inc..
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