[Stoves] pellet gasifier

Paul Olivier paul.olivier at esrla.com
Sat Jul 27 17:38:48 CDT 2013


Today I ran the small pellet gasifier again.
https://dl.dropboxusercontent.com/u/22013094/150%20Gasifier/Short/Photos/IMG_1568.JPG
The net reactor height of this unit is only 8 inches (200 mm).

Here you see it in operation on rice hull pellets of a diameter of 8 mm:
https://dl.dropboxusercontent.com/u/22013094/150%20Gasifier/Short/Photos/MVI_1574.MOV
But in this experiment I put a layer of rice hulls on top of the pellets.
Note the beautiful blue flame.

I ran the same unit without the layer of rice hulls on top:
https://dl.dropboxusercontent.com/u/22013094/150%20Gasifier/Short/Photos/MVI_1607.MOV
Note that the flame in this case is not as blue as previously.
It seems that a layer of rice hull char helps a lot in cracking/filtering
the gas.
The Pyrex pot used in this experiment was a bit too small.

There are three problems here.

The first is in lighting the pellets. We soaked some pellets in paraffin:
https://www.dropbox.com/s/vwejx8vvu0t4kvg/IMG_1600.JPG
We put these paraffin-coated pellets on top of the uncoated pellets.
Still it took too long to light the pellets.

We then soaked some loose rice hulls in paraffin, and put a thin layer of
these paraffin-coated rice hulls on top of the pellets. This seems to work
much better. When paraffin burns, it does not smell. We will now experiment
with making paraffin coated wafers of a diameter of about 140 mm to place
on top of the pellets. Perhaps wood pellets would not be as difficult to
light as rice hull pellets.

The second problem is the size of the pellets. I would much prefer to work
with pellets of a diameter of 6 mm and of a fairly uniform length. The 8 mm
pellets that we were using vary in length quite a bit. Hopefully with the
smaller 6 mm pellets we will not have to put a layer of rice hulls on top
of the pellets to get the blue flame.

The third problem is the power of the fan. The fan that we used in this
experiment has an air resistance of 0.40 InAq. This needs to be reduced to
about 0.15 InAq. Such a weak fan would cost a lot less, and it would give a
lot more control over flame height. The amount of electricity used with
such a weak fan surely would not be greater than about 1 watt. Some might
argue: then why use a fan?

We are very close here to a natural draft. But even when the reactor of a
height of 8 inches is filled with only 4 inches of pellets, it does not go
into natural draft mode. If the height of the reactor were extended to
create natural draft conditions, a lot more heat would be loss through the
wall of the reactor. Also the unit would no longer be as small and
lightweight, and the cost would go up quite a bit, since I insist on using
high quality stainless steel. Also in lighting the pellets, we need a lot
more air than in normal operation - air that I believe only a fan could
deliver. Finally a fan gives rapid and easy control over flame height and
turn-down ratio.

This pellet gasifier is the same as the gasifier I designed for loose
biomass, except for two things: the height of the reactor and the power of
the fan. But there is a big difference in the amount of heat that the two
put out. The pellet gasifier runs much hotter.

I really like the biochar that is produced by a pellet gasifier:
https://www.dropbox.com/s/hm66yhk90x5wj7r/IMG_1610.JPG
The biochar pellets have just about the same volume as the original pellets.

Thanks.
Paul Olivier

-- 
Paul A. Olivier PhD
26/5 Phu Dong Thien Vuong
Dalat
Vietnam

Louisiana telephone: 1-337-447-4124 (rings Vietnam)
Mobile: 090-694-1573 (in Vietnam)
Skype address: Xpolivier
http://www.esrla.com/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20130728/22466565/attachment.html>


More information about the Stoves mailing list