Date: Mon, 21 Nov 2005 20:49:01 -0500
            From: David Gordon <>
         Subject: Re: wood kiln ventilation
          Dear Steve,
          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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