[Gasification] Wood heating in the UK - whole log gasification

Jason urepedese at gmail.com
Sat Dec 28 02:57:07 CST 2013


Mark,

I am thinking back to an early email exchange with Doug where he told me
that an absence of visible smoke doesn't necessarily mean clean combustion.
My experience at the Decathlon has reinforced that comment. I am very much
still learning but it seems to me that low emission combustion of wood is
still seen as dirty by legislators so it needs to get much cleaner.

In New Zealand, and from what I read also the USA, emission laws are
getting tougher and bans on wood burners still being seen and implemented
as a solution. I listened to one air scientist here apply the term
"decommissioning" and this was the only solution he offered. In the long
run the battle I face for retrofits is against this type of thinking, I can
only hope my zero emission result starts to make waves in official circles.

Knowing what I now know I don't think a vitreous shield is sufficient,
better techniques to maintain flame temperature are necessary. I certainly
haven't found it an advantage with a retrofit anyway.

So yes I do think heat recovery on the exhaust is the way forward, get the
combustion complete before any heat is removed.

Of course the holy grail of long burn times is always a goal that
complicates matters, in particular engineering that into a simple low cost
system. It is going to be hard to beat automated feed systems to achieve
that along with zero emissions but a jet stream type water jacket may make
it possible. I will certainly give it a go when I have the R&D resources
available to me.

I think low emissions and greater efficiency is always a relevant topic and
useability quite an appropriate discussion also :-)

Cheers

Jason

PS. I have one aquaintance in New Zealand that is challenging the science
around respiratory disease and emissions from wood smoke. He says the link
is tenuous and the early bogus studies keep getting repeated and used as
justification to ban wood stoves.


On Sat, Dec 28, 2013 at 8:33 PM, Mark Ludlow <mark at ludlow.com> wrote:

> Hi Jason,
>
>
>
> Using a vitreous shield (Dick Gallien’s solution) seems functionally
> sensible but it confuses the heat-transfer analysis a bit. If this is a
> stove (rather than a char producer or gasifier) where we idealize a clean
> exhaust, robbed of all of it sensible heat. Hmmm… Are heat recovery coils
> or perhaps plate heat-exchangers on the exhaust the only way to go?
> Naturally, all of this deviates a bit from pyrolysis and gasification…
>
> I like your targeting of retrofits!
>
>
>
> Best, Mark
>
>
>
> *From:* Gasification [mailto:gasification-bounces at lists.bioenergylists.org]
> *On Behalf Of *Jason
> *Sent:* Friday, December 27, 2013 10:48 PM
>
> *To:* Discussion of biomass pyrolysis and gasification
> *Subject:* Re: [Gasification] Wood heating in the UK - whole log
> gasification
>
>
>
> To all,
>
> my experience with top feeding systems is keeping the upper ends of the
> fuel from pyrolysing too early. A water jacket is a logical solution so the
> link to the jetstream is interesting for me as I have not come across that
> before.
>
> When taking a look at some of the alternate designs at the bottom of that
> wikipedia page I am reminded of one discussion with a judge at the wood
> stove decathlon. He advised of the terrible pollution problem from poorly
> designed boilers, something I had seen discussed but had not explored in
> depth. The Alliance For Green Heat is in the thick of combating the
> problem. When the problem of combustion chambers surrounded by water
> jackets was explained the problem was immediately apparent, the combustion
> just doesn't get hot enough or for long enough to be complete. So yes a
> water jacket but its integration into the design has to be carefully
> considered. The plans for an ultra clean design are in my head now as a
> consequence of that discussion :-)
>
> Jason
>
>
>
>
>
>
>
> On Sat, Dec 28, 2013 at 2:10 PM, Tom Miles <tmiles at trmiles.com> wrote:
>
> Alex,
>
>
>
> I was thinking of Dick’s Jetstream. He employed a lot of good combustion
> principles to stick wood burning at a time when we were just migrating from
> the “tin wonder” wood stoves.
>
>
>
> I didn’t realize that there was a Wikipedia page on it.
>
>
>
> Thanks
>
>
>
> Tom
>
>
>
> *From:* Gasification [mailto:gasification-bounces at lists.bioenergylists.org]
> *On Behalf Of *Alex English
> *Sent:* Friday, December 27, 2013 4:41 PM
> *To:* Discussion of biomass pyrolysis and gasification
>
>
> *Subject:* Re: [Gasification] Wood heating in the UK - whole log
> gasification
>
>
>
> Ken,
>
>
>
> If you haven't already heard of the Jetstream
> The wood was loaded into a vertical tube which passed through the water
> jacket into a refractory lined combustion chamber. In this chamber the
> burning took place and was limited to the ends of the logs. The water
> jacket prevented the upper parts of the logs from burning so they would
> gravity feed as the log was consumed.
>
> http://en.wikipedia.org/wiki/Jetstream_furnace
>
> Not a chimney powered stove.
>
> Alex
>
>
> On 27/12/2013 6:47 PM, Jeff Davis wrote:
>
> Hi Ken,
>
>
>
> Thanks for the interest!
>
>
> This is my main unknown as yet,  how would a split log combust and
> pyrolise, if presented to the ember bed, cut end first.  I suspect that
> there would be little penetration of heat axially, directly through the
> end, because the ring structure presents a tough barrier. Therefore, most
> burning would have to come radially, and so air nozzles would have to be
> positioned to act radially on the sides of the log.
>
>
> OK, I should try cutting the wood at 45 deg instead of 90. Interesting!
>
>
> In your design, it looks similar to a Rocket, but with the fuel container
> near vertical.  However, the top loading hatch looks fairly airtight?  - so
> unlike a rocket, there is no air drawn through fuel.
>
>
> The next test run will be at almost vertical and more distance between the
> tube and grate.
>
> This has only run for short periods of time but once it's burning OK I
> have been leaving it up. In the middle of the door is an adjustable air
> inlet. It's rusted open because of the nasty acidic coal that was burned in
> it for a few years.
>
>
> Nevertheless it appears to burn well and produces a healthy amount of good
> sized charcoal.  I would be very interested to know how it copes with a
> larger log. Perhaps by way of experiment, one could be loaded, instead of
> the 2" material, to see how it fairs - this would be very useful
> information.
>
>
>
> In due time.
>
>
>
>
> Best wishes,
> Jeff
>
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