A Conversation About Wood Smoke from Masonry Heaters

Date: Sat, 30 Jan 2010
From: Alex Chernov <alex_stovemaster(at)yahoo.ca>
Subject: RE: wood smoke
To: Anthony Biundo <abiundo(at)hotmail.com>, Norbert Senf <mheat(at)heatkit.com>

Yep, right, Norbert.
People mistakenly think that contraflow or bell designs have everything set in stone. Lots of different fireboxes were used in different models using contraflow principle, and the same applies to bell heaters, and even more to bell as there is no such thing as one "bell design". It is a principle rather than one drawing.

I have changed firebox designs at least 3 times. I also think that emissions are not affected much by heat exchange portion or its design unless one chokes the system. Emissions depend on firebox design.


--- On Sat, 1/30/10, Norbert Senf <mheat(at)heatkit.com> wrote:

From: Norbert Senf <mheat(at)heatkit.com>
Subject: RE: wood smoke
To: "Anthony Biundo" <abiundo(at)hotmail.com>
Cc: "Alex Chernov" <alex_stovemaster(atyahoo.ca>

Ha ha, Tony, that's funny. It would be nice if it were that simple. Once you actually get into trying to measure this stuff, you find out how complicated it is. But, there is no alternative, otherwise it is basically idle speculation.

I'll cc this to Alex, in case he wants to comment.

After 10+ years of testing, what I have seen so far, is:

- big underfire air grate running down the middle is very, very bad when combined with bottom ignition. Highest PM ever measured in a masonry heater.

- for big fireboxes with big (North American style) loads, big wood can work very well. It has to be dry.

- this is off the scale for anything ever tried in Austria, so it is outside the realm of their experience.

- With big loads and big wood, top or side ignition gives very clean burns, provided you have enough kindling to ignite the main pile without smoldering.

- cold fireboxes burn dirtier than warm fireboxes. The basic idea is to get everything up to temperature, without overamping anything, and then everything burns clean. By the same token, introducing cold outside air directly into the firebox just has to be bad, without even measuring it.

- as long as you don't screw something up, burning clean is fairly simple. As Dave has shown through testing in Alaska, even an ordinary firebrick lined metal stove at high burn rate gives you
1 g/kg.

- possibly, there might be some effect from how low your chimney temperature is, in terms of whether you have enough "oomph" to get the fire going fast enough, not sure. Otherwise, it doesn't seem as if the particulars of the heat exchange system have much effect. If you have a channelled system with too much friction (too long channels), you eventually reach a point where the whole thing chokes. The Austrian calculation system is mainly aimed at finding that point, and not overstepping it. Current thinking is that there is not much point in trying to get too close, because you are only talking about a couple of points of efficiency. Also, with a masonry chimney, you don't want a lot of water condensation in there. With an insulated chimney, you can run a bit lower stack temperature, because you don't have the same chimney losses.


At 09:03 AM 1/30/2010 -0500, Anthony Biundo wrote:
> Norbert; are you seeing any differences, from an emissions stand point between the contraflow and bell designs? On an intuitive level I would guess that the bell may have less particulate due to slower flue gas flow, if indeed that is the case.   Thanks ...   Tony
> > Date: Fri, 29 Jan 2010 09:29:29 -0500
> > To: abiundo(at)hotmail.com
> > From: mheat(at)heatkit.com
> > Subject: Re: wood smoke
> >
> > At 03:54 PM 1/28/2010 -0500, Anthony Biundo wrote:
> > >Hey Norbert: I have two proposals
> > > 1)As they speak in Washington,what
> > > about trying to git the EPA to agree on a
> > > definition of wood smoke that would include a
> > > baseline particulate count that is above
> > > threshold for a heater flue gas emission.It
> > > seems to me that me that wood smoke as defined
> > > i.e something that you can see and smell is the
> > > main cause for complaint from the environs,then
> > > a secondary definition of masonry heaters as
> > > devices that emit below the threshold of wood
> > > smoke as now defined ,would exempt said device
> > > from proposed regulation.so in essence to ask
> > > that wood smoke be regulated not the devices
> > > that may generate it,they then could only be
> > > viewed as in our out of compliance.
> >
What is regulated in North America is PM2.5
- particulate matter below 2.5 microns.
Wood smoke is not something that is very easy to define,
because it is so highly variable in composition.

What we are arguing over is how to do a test to
determine the particulate emissions. That boils
down to, how do you define a standardized method
for fueling a heater, that creates a level
playing field. The argument centers around "real
word", ie., cordwood, vs "repeatability", which
involves standardized "cribs" of dimensioned
lumber. Cribs is the current method, and there is
not a lot of data for masonry heaters, so we are
mostly dealing in the realm of opinions. Alex and
I are currently conducting some research (testing) on cribs............Norbert

Norbert Senf---------- mheat(at)heatkit.com
Masonry Stove Builders
25 Brouse Rd.
RR 5, Shawville------- www.heatkit.com
Québec J0X 2Y0-------- fax:-----819.647.6082
---------------------- voice:---819.647.5092