This 1986 study has been provoking some interesting discussions in another thread. In the interest of keeping that one on topic, I'm starting a new one here. The study in question is here: http://www.arb.ca.gov/research/apr/past/a3-122-32.pdf
Continuing with our discussion already in progress...
[quote author="Battenkiller" date="1294357162"]Yes, the green wood needed more air to achieve maximum burn rates, he even says so in the text. However, the overall efficiency numbers don't lie. There was not a significant loss of sensible heat up the flue due to the extra air being introduced. Yes, some dilution effect is evident, especially is the open stove, but that doesn't support anecdotal evidence of massive amounts of creosote deposition in residential chimneys venting stoves burning green wood. Just the opposite is reported here, and the dilution effect is clearly aiding this... to the benefit of green burners everywhere. [/quote]
True. And I think I found the reason why the "green" oak burned better than expected (in addition to what you wrote further down about the moisture content being less than what we might think of as green), with less air than one would expect. Look at table 5-2, Summary of Fuel Load Properties, see the Avg. Piece Mass. For the green oak it hovers around 1.1kg, or 2.4 lbs. That is a very small piece of wood. Most here would consider that large kindling. It would be in the same size range as a 2x4. In the airtight stove, the load was six of these pieces. Put pieces that small on a live 20% charcoal bed and it is not going to be difficult to burn a 38%MC load like that.
The largest pieces were used in the Blaze King - about 2.5kg, or 5.5 lbs. All the other stoves burned pieces half that weight, four to six pieces at a time. I'd bet my boots than almost nobody on this forum regularly loads their stove only with pieces that small - we're talking maybe a 3" diameter round or split. That's about the size of wood I use in the X33, because the firebox is very shallow.
I think much of that too is explained by the piece size. Also, the thing I find most significant about the Oregon weighting is not so much the uncertainty factor, but the heavy weighting of lower burn rates. Throw out the lowest burn rate tests, and results improve dramatically for all of the non-cats.
I didn't know the rarer metals could be recovered in recycling. Is it a high percentage recovery?
There's no denying the effectiveness of cats, especially for round-the-clock burners. They're not well suited to my heating needs so I've never used one - odd, perhaps, in 30+ years of burning, but true.
There's a place for both in the scheme of things. It's a pleasure to be able to delve in to the depths of things with you.
Continuing with our discussion already in progress...
[quote author="Battenkiller" date="1294357162"]Yes, the green wood needed more air to achieve maximum burn rates, he even says so in the text. However, the overall efficiency numbers don't lie. There was not a significant loss of sensible heat up the flue due to the extra air being introduced. Yes, some dilution effect is evident, especially is the open stove, but that doesn't support anecdotal evidence of massive amounts of creosote deposition in residential chimneys venting stoves burning green wood. Just the opposite is reported here, and the dilution effect is clearly aiding this... to the benefit of green burners everywhere. [/quote]
True. And I think I found the reason why the "green" oak burned better than expected (in addition to what you wrote further down about the moisture content being less than what we might think of as green), with less air than one would expect. Look at table 5-2, Summary of Fuel Load Properties, see the Avg. Piece Mass. For the green oak it hovers around 1.1kg, or 2.4 lbs. That is a very small piece of wood. Most here would consider that large kindling. It would be in the same size range as a 2x4. In the airtight stove, the load was six of these pieces. Put pieces that small on a live 20% charcoal bed and it is not going to be difficult to burn a 38%MC load like that.
The largest pieces were used in the Blaze King - about 2.5kg, or 5.5 lbs. All the other stoves burned pieces half that weight, four to six pieces at a time. I'd bet my boots than almost nobody on this forum regularly loads their stove only with pieces that small - we're talking maybe a 3" diameter round or split. That's about the size of wood I use in the X33, because the firebox is very shallow.
Considering the stated +/-25% uncertainty in the Oregon weighted averages, the only really significant fuel factors across all the tests and burn cycles was for the production of elemental carbon (soot), and NOx production (assumed… based solely the performance of the Blaze King - a catalytic stove commonly thought to produce high NOx anyway). The major contributing factor in this study was the appliance effect. The better stoves burned both cleaner and more efficiently regardless of the fuel type - green oak, seasoned oak, or doug fir. Seeing as how that was what was being investigated to begin with, we have a clear winner:
The stove is much more important than the quality of the wood… at least in this study.
I think much of that too is explained by the piece size. Also, the thing I find most significant about the Oregon weighting is not so much the uncertainty factor, but the heavy weighting of lower burn rates. Throw out the lowest burn rate tests, and results improve dramatically for all of the non-cats.
Add in to that a basic discomfort about the sourcing of the elements used in catalysts.
I hear you, mate, but we are pretty much stuck using precious metals as long as the population continues to increase and the technology necessary to reduce our contribution to pollution lags behind. The fact is that catalysts are a crude but highly effective club that can be applied after the fact to cleanup the mess left behind from inferior design. As long as financial motives are the driving force behind scientific development, industry will continue to use whatever crude and inelegant solution they come up with providing that it satisfies the bottom line. The nice thing about the metals themselves is that they are recoverable once the appliance craps the bed. The combustors and converters themselves decline in efficacy with use, but the metals themselves can be largely recovered during recycling of the spent devices.
I didn't know the rarer metals could be recovered in recycling. Is it a high percentage recovery?
There's no denying the effectiveness of cats, especially for round-the-clock burners. They're not well suited to my heating needs so I've never used one - odd, perhaps, in 30+ years of burning, but true.
Anyway, keep working on your projects, they may lead to the next breakthrough in this technology. Me… I’m more of a thinker than an inventor. I like to know how things work, but leave it to the smarter guys to figure out how to make them work better.
There's a place for both in the scheme of things. It's a pleasure to be able to delve in to the depths of things with you.