Dan Hill on tue 2 nov 10
Hi All
I am contemplating rejigging the floor of my downdraft soda kiln. Currently
I have a flue collection trough running the whole length of the kiln floor
and leading to the exit flue at the back. The exit flue and chimney with
the 2 forced air propane burners on either side facing the door opening.
After looking at many other kilns including the MFT it would seem that the
need for this trough is unnecessary and I would gain 3 or 4" of stacking
space, save some fuel and maintain even heat distribution.
My question is what is the usual height off the floor for the first layer o=
f
kiln shelves as well as the spacing at the front and back between the
shelves and and kiln wall to allow for good heat distribution etc. I read
somewhere that 2" may be a good spacing off of the floor. If 2" is the case
then that first shelf would divide the flue opening. Is that O.K.?
My kiln is a sprung arch with inside dimensions of 40.5" X 40.5" X 46" H.
The flue exit is 32 cu.in. with the burner ports slightly below the level o=
f
the flue. Chimney is 12' high with a 9" X 9" inside dimension.
Sorry for the long winded message but any input from other downdrafters
would be helpfull.
Dan Hill
Hill Pottery
^6 Soda fired porc. and stoneware
Soda firng workshops
Vince Pitelka on wed 3 nov 10
Hi Dan -
I think that the kind of kiln design that you have (burners on either side
of the chimney pointing forwards towards the door, with the flame passing
along the inner side walls) is probably the design that benefits least from
a flue channel, because with such a design you rarely have any problem
getting heat to the lower front of the chamber (since the burners are
pointing in that direction). I have always felt that flue channels are
primarily an advantage in kilns that are deeper than they are wide.
Another consideration - if you stack the bottom layer of shelves at least 2=
"
above the floor and place them pretty close to the flue opening at the
center back, then the flue suction will pull significantly from beneath the
bottom shelf, and that will act at least partially like a flue channel,
pulling heat to the lower front. If you want to accentuate that effect, yo=
u
can lay old pieces of kiln furniture or cut pieces of hardbrick along the
floor beneath the bottom shelf from front to back to create even more of a
flue channel effect. With this method you would be able to eliminate your
current flue channel and gain that extra kiln space, and still have some
flue channel effect.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
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