First forced-air wood kiln firing

Earlier on this blog I wrote about a kiln I designed and built, here and here.

Yesterday I fired this kiln as a forced-air (with blower) for the first time, using my improvised firebox.

It worked incredibly well.  I have never fired an easier, faster more efficient wood kiln.  What normally takes 3 days was done in less than 8 hours.  It took less than a face cord of firewood to reach temperature (~1,800 F, bisque firing).  It normally takes around 5 - 10 times that much wood.

I used a Ward burner, hooked up to propane to candle the start-up.  After It had warmed up to around 350 degrees F, I lit the wood and turned off the propane.  The blower from the burner provided the forced air.

Here's a short video showing me stoking the kiln.  It is burning just wood (no propane).

Preparing a Forced-air Wood Kiln

Here's a short video showing my wood kiln, which is almost ready to fire for the first time.  This is the first forced-air wood kiln I've ever seen.  Forced-air means that a fan is used to create the draft.  Normally a wood fired kiln does not use a fan, but instead relies on a tall chimney to create a suction or draft through the convection process of heat rising through the tall chimney.

The fire box is set slightly off-center (to the right) which was done to creat a swirling vortex.  This vortex extends the flame path through the firing space, providing more complete combustion and more even temperatures.

Initially this kiln was a gas-fired forced air kiln, built as a prototype under a grant I received from the New York State Energy Research & Development Authority (NYSERDA).  Originally it had 3 burners, each capable of producing 750,000 Btu per hour.  I built another conventional rectangular kiln of the same size, same wall thickness, same burners, etc., for the purpose of comparison.  My kiln proved to be 37% more efficient than the rectangular kiln, which is really quite an improvement.  This kiln is a downdraft, meaning that the hot flue gas vents at the bottom center of the kiln.

I adapted the original gas-fired design to a wood-fired configuration simply to see if it would work.   This is one big experiment: if it works well, it should fire faster than a conventional wood kiln.  A conventional wood firing usually takes around 3 days.  I'm hoping to cut that time substantially.  We'll see!