John Baymore on mon 23 jun 97
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---------- Forwarded Message ----------
From: John Baymore, 76506,3102
TO: Automatic digest processor, INTERNET:LISTSERV=40LSV.UKY.EDU
DATE: 6/23/97 3:22 AM
RE: Copy of: TOZAN kiln.......... HELP=21=21=21
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=3Csnip=3E ....... HELP=21 The environmental watchdogs here have decided =
that
the Tozan noborigama in Nanaimo, B.C. is putting out too much black smoke,
and the
kiln will have to be shut down until we can install something to clean it
up. ....... =3Cclip=3E
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WOW=21=21=21=21=21=21 Happening in BC, huh? This is scary=21=21=21=21=21
I think that this is just the tip of the iceburg showing=21 The new EPA
particulate proposal here in the US will make all wood kilns without
cyclonic particulate scrubbers (BIG =24) totally illegal. Most already are
overtly exceeding the EPA's simple =22opacity of emissions=22 standard
(without afterburners) and also exceed existing emission standards if
anyone bothered to do actual sampling.
As =22big industry=22 belches TONS AND TONS of junk into the environment on =
an
hourly basis, the =22small guys=22, (and yes.... even with those occasional
billowing clouds of black we are very small polluters) the people with no
=24=24=24=24 in their back pocket, get nailed.
Here in the US, Industry can go and buy things like sulphur dioxide permits
from the government by the TONS. Maybe potters should be able to buy =
=22wood
smoke=22 permits by the ton too?
Less than 1/2 mile away from me is the town recycling center which serves 6
towns. About once a week they (the town) burn, in an open pile, the brush
and (unpainted) wood. They burn more wood a week than I burn in a
year=21=21=21=21=21 And in an open fire the combustion is not really very =
efficient,
particularly since they hose it down to keep the fire burning pretty low.
Add to this the incinerator in which they burn all sorts of plastic, and
other non-recyclable =22combustibles=22....... with the state and EPA's
permission. Bah=21
I am not saying we should go about polluting unthinkingly....... we MUST
take every opportunity to minimize out impacts. I have been starting to
promote the use of afdterburners on wood kilns here in NH just so that we
can do our best to keep the pollution down, and to keep the =22eyes of
officialdom=22 off of us as a group. Wood kilns will only start getting =
shut
down when they become a target of some specific individual's complaint, or
when they become a political =22easy traget=22, because we have become =
=22high
profile=22.
We DO need to keep this in perspective...... we aren't really a huge
problem, and I think that there should be many other things addressed
BEFORE artist potter's kilns get closed down.
I am clearly reminded of how I felt standing at the bottom of Kawii
Kanjiro's climbing kiln in Kyoto last fall.......... a beautiful kiln shut
down forever due to pollution laws. Cobwebs in the flues and doors. A few
bundles of wood sitting around for =22show=22. All the while, all around =
the
Kyoto area I saw lots of other air pollution sources merrily belching =
away=21
Every morning on my way to the train station I walked by numerous Obasan
and Okusan out in their front yards burning the trash in open piles.
But potters don't seem to ever have solid political bases behind them, do
they?
On to the matter at hand....................
I have used afterburner systems on a few smaller (than the Tozan)
noborigama kilns in the past, and can get the visable smoke (off the stack)
to clean up almost completly. With these running, the chimney looks like a
very clean wood stove burning..... light grey mist, not billowing black
clouds. They will pass the 20=25 opacity rule. At the peak of the firing,
flames are coming out the chimney that look like the afterburners on an
F-15...... hard, sharp flames, not lazy, fluffy yellow ones.
This practice does nothing for the smoke leaking off places like the blow
holes, spy ports, and chamber doors. This smoke can be substantial, and
might still be of concern to the =22officials=22. This low-tek =
=22scrubber=22 also
does nothing at all for the emission of particulates (a real issue brewing
here in the US).
Noborigama fireboxes are NOT very efficient, particularly the side stokes
into the chambers (right on the floors). Anagamas are even worse in this
department. Most of the black clouds off the chimney are caused by
unburned gases and particulate carbon compounds, although a little is ash
particulate. The trick is to re-heat the unburned fuel (and partial fuel
air mix) up to ignition temperature, supply enough air to burn it, and
create enough turbulence to mix the air into the somewhat laminar stream of
stack gases. Simple in concept, not so simple in practice. (That's why
God created =22pollution control engineers =3Cg=3E)
You need a burner large enough to heat the effluent stream to ignition
point, an air supply large enough to supply all the necessary air to burn
off the excess fuel, and a flow design that creates turbulence.
It is almost ALWAYS a bigger, more involved system than the typical potter
assumes.
The afterburner system needs to be capable of generating =22EXCESS AIR=22.
This means more air than is required for 100=25 primary areation of the
mixture going thru the burner. This is key. While there are some HP
venturi type mixing units that are very good at entraining primary air,
you will really need a forced air burner........ ie. electrical blower.
With the size of the Tozan kiln (from pictures I have seen), this unit will
be substantial=21 Not having any specifics on the design, and really
=22shooting from the hip=22, I'd guess that the afterburner might want to =
be
in the .5Mil BTU range. That would put a blower for about 125=25 primary at
around 6250 CFH minimum (with the static pressure in the system it'll need
to be be a little bit larger...... maybe 7000 CFH).
If you don't have electrical power on the site, consider a photovoltaic
panel array, batteries, and a DC blower. Expansive, but it might keep the
kiln running.
The job of the afterburner is to raise the temperature of the unburned
gases above the ignition point, and to mix in some additional air to help
burn the unburned effluent. In addition, you will need to add more air
into the high temperature stream because the burner will probably not be
able to supply all the additional O2 necessary for all that crap coming out
of the kiln. This can be accomplished by creating a few ports into the
chimney just above the entry point of the afterburner. A number of smaller
ports is preferable to one large one due to the quenching (cooling) action
of the cold air stream.
If you can design the air flow so that this air is drawn for a good
distance across hot refractories or in the hot ehaust gas flow to warm it
(thru stainless pipes inserted into the lower flue?) before going into the
chimney, so much the better. You can pre-heat the p. air for the burner in
a similar way.... but if you attempt this also, contact me via e-mail for
important safety considerations.
These air ports will also act like passive dampers...... air let into the
chimney will decrease the =22draw=22 downstream on the kiln side of the =
system.
The output of the burner will also act like this. So you might have to
increase the carrying capacity of the chimney to accomodate for this
additional gas passage. Increase in XC or height or both. Some draft
INCREASE will be evidenced by the higher stack temperatures caused by the
combustion in the chimney. It might offset the losses, but I don't think
so. Since the kiln is a noborigama, the chimney is probably more just to
get the effluent up in the air and away from people, than a major source of
draft...... so this might be easier than for a regular downdraft kiln.
The burner will need to have a burner block / retention head custom made
for it at the entry point. You'll have to modify the chimney at this point
to create the port, which will be quite large. This nozzle head can be
cast out of something like APG Mizzou castable, with a stainless steel pipe
fitting embedded into the cast for connection to the burner mixing unit's
output. (Size to match the burner's pipe thread diameter.) The casting
(with stainless pipe embedded) needs to be fired to at least red heat
before installing. Don't go too hot, or you'll rust the stainless a lot.
The head should create a =22fan=22 of flame that pretty much covers the =
entire
cross section of the flue (or at least close). The head should resemble a
=22ring burner=22 on a gas stove in that it is a monolithic cast (to act as =
a
retention nozzle via quenching mode) with a lot of small holes scattered
across it. These small holes also slow the gas/air mixture so that the
flame front can burn back toward the source at an adequate rate and keep
the flame seated on the nozzle. The holes need to be designed to =22fan=22 =
the
flame across the chimney XC. If the XC is really large, you might consider
two or more smaller burners.
The afterburner should have both gas and air controls on it....... the
settings will vary throughout the firing. It should have flame safety,
but that is difficult in the location without resorting to ultraviolet
detectors (and lots of =24=24=24=24) Have calibrations on your =
controls.....
guages and/ or speed controls. You will have to install a small port which
can be opened to light the afterburner. This can have a plug that goes in
and out. Conversely, you can set up an electrical ignition system using a
special spark plug and a transformer.
JUST (and I mean JUST) below the burner block and the additional air ports
you will want to place a couple of refractory =22bars=22 across the flue =
cross
section to create turbulence in the flow. The longer the straight chimney
run before the location of the afterburner, the more the gases will tend to
run smoothly in a stream (laminar flow). You want to brake this nice neat
flow up to achieve mixing of the air with the gases. A great place to
locate the afterburner is just AFTER a right angle turn in the flue flow
channel.
These bars should be good refractories..... maybe old scrap silicon carbide
element bars from a glo-bar kiln, or whatever. Not too many so that they
close off the chimney XC...... just a few to break up the flow. They
should be in close proximity to the =22splatter=22 of the afterburner flame =
so
that they get good and hot.
The quality of the refractories in the chimney might be a concern in the
afterburner area. This area will now be closer to resembling a firebox in
a gas kiln. The grades of refractories will have to be higher to withstand
the temperature and the reduction effects. The hotter you can get it here,
the better...... so an IFB lining is a real desirable characteristic to cut
smoke. Might be worth rebuilding the entire chimney, since it is probably
pretty short on a nobodigama. Also the chimney cold face temperature will
go UP SUBSTANTIALLY if you con't change the construction. Watch out for
the proximity of combustables near the chimney. Particularly the roof
penetration point.
You might want to put a good thick insulation layer on the chimney from the
exit point from the last chamber on to the top. This will keep the flue
gases hotter.... making it easier to raise the ignition temperature and
burn things off. It also will help with the hotter cold face created by
the action of the afterburner.
If you are in real danger of being shut down for good, you might want to
contact a pollution engineering company in your area. They CAN solve this
for sure, but it will be very expensive. They might be willing to =
=22grant=22
you some of the design cost if you give them really positive press for
their efforts into helping out =22the arts=22. You might get a grant from =
the
local arts groups to help fund keeping this unique kiln =22on-line=22 for
future generations.
So........ hopefully this is of some help. I'd hate to see this happen.
It bodes poorly for all of us who fire with wood. Let me know if I can be
of any help........ us woodfirer's need to stick together.
Best,
......................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086
603-654-2752
JBaymore=40Compuserve.com
=22First started firing with wood in 1969.=22
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=22New Hampshire Woodfire Potters=22 exhibition opens this weekend.
June 27, 1997 - August 31, 1997
Manchester Institute of Art
148 Concord Street
Manchester, NH
Reception: June 28, 1997 5PM
Featured artists are Sam Azzaro, John Baymore, Dave Ernster, and Jon
Keenan, and includes works by Bob Chase, Dan Comte, Rosti Eismont, Tom
Flavin, Al Jaeger, Linda Fletcher, Scot Montagnino, Rand O'Brien, Barbara
Sansing, Teresa Taylor, and Gerry Williams.
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