[Gasification] Gasifiers at China workshop

[Paul S. Anderson]

Report on stove technology at ARECOP 2006 workshop in China (final part)

[Sorry, no photos at this time in this document.  I will try to get them to Tom
Miles for posting.]

1.  The theme of the workshop was gasifiers for thermal applications for cottage
and small industry, so few things were seen or discussed about traditional /
standard combustion.

2.  The sources of information:
	a.  Chinese stoves (8 or 10 different models) at Mr. Hao¡¦s factory
	b.  Reports on Chinese stoves from the competition sponsored by the Shell
Foundation.  I did NOT have access to the final results and I only had brief
access to a small set of photos (4 or 5 photos ¡V one of each of 9 stoves - on
2 photocopy pages) and some descriptive comments.
	c.  Two stoves at a factory that actually handles biogas installations,
	d.  My own 2 gasifier stoves (or parts of stoves) that I took to China.
	e.  Discussions during the workshop, including Alexis Belonio¡¦s PowerPoint
presentations that show his gasifiers.
	f.  Some stoves seen in rural Chinese homes visited on the field trip (and by
me on a separate morning outing.).

3.  Loose classifications (by me, not by the workshop) and notes:
	a.  Traditional burning:  Not discussed much and not seen except in the home
visits.  Mr Hao had one unit that turned out to be a solidly built central
channel (ala the sawdust burners)  cookstove.  It had several controls for
primary air, leading toward being a quasi-gasifier.

	b.  We saw some of the 200 million  improved cook stoves (ICS).  Large (for
large wok pot), solid, built into the kitchens, with chimney.  An LPG 2-burner
stove was frequently also in the kitchen.  The ICS seemed to have a metal
insert to enhance the combustion under the pot.  (more comments below).  These
are not gasifiers, but might be ¡§semi-gasifiers¡¨.

	 c.  Semi-gasifier or quasi-gasifier.  Terms are not well defined.  These
reminded me of Crispin¡¦s Vesto Stove that has a ¡§bucket grate¡¨ (a deep
(maybe 30 cm) chamber for the fuel, air in from the bottom, and with side holes
in the bucket).  But the Vesto has MUCH larger side holes.  The Chinese ones at
Mr. Hao¡¦s factory had small holes.  When ignited, these burned very strongly. 
They did not seem to have much ability to be turned down for simmering, except
to let the fuel run low.  Dean Still presented a report (still draft??) about
one of these stoves that was tested at Aprovecho.  I will not repeat that
report (I hope it is posted when appropriate), but remember the comments that
there were some CO and PM (carbon monoxide and particulate matter) emissions
that rose when much additional fuel was put in, but had fewer emissions
problems when the fuel was gradually and frequently added to the fire (meaning
more user attention was needed frequently).  Mr. Hao actually calls some of his
stoves ¡§quasi-gasifiers¡¨.  From what I could tell from the limited information
from the Shell Foundation evaluations, many of the candidates were/are quasi- or
semi-gasifiers.  I found no indication of true up-draft or true down-draft
gasifiers in these small and medium cookstoves.  Comments about T-LUD pyrolytic
gasifiers are later in this document.

	d.  ¡§Tibetan Stove¡¨:  Mr. Hao had 2 impressive large cookstoves on display,
one was ignited, designed for Tibet conditions (cold, people sit near the low
stove).  Probably measured 80+ cm across and 1.2 m length, with a nifty
(distinctive, impressive, functional) oven/box/bain-marie at the end where the
chimney begins.  The box was sealed from the flue gases, and had two
pot-openings on the top.  So if filled with water, the water would boil and
give the double-boiler/bain-marie function.  But if dry, the box was like an
oven.  They cooked some ¡§fried bread¡¨?? in it for eating while there.  The
combustion in the Tibet stove was (to me) something like a Rocket elbow, but
with more air control (but I do not know how effective the air control is). 
The size of the stove allowed the long sticks (maybe 60 cm??) to be pushed in
horizontally, and the outside door to the fuel entry could be closed, meaning
no air was entering in the same channel as the sticks.  It used much larger
diameter sticks than what are recommended for the metered-fuel of the Rocket
stoves.  The tips could burn in the Tibetan stove, but also wood seemed to fall
into the fuel chamber that is perhaps 15 cm deep.  The primary air was coming up
from the bottom, as in a Rocket.  But this stove did not have much of an
internal chimney (combustion chimney below the pot).  Instead it had what
looked to me to be like the combustion inserts seen in the Chinese ICS
mentioned above in ¡§3.b¡¨.  (description below).

	e.  The combustion inserts seemed to be double-walled hollow ¡§donuts¡¨ of
quite solid steel (no tincanium was seen).  Total diameter about 25 to 30 cm,
with the inner diameter about 15 to 20 cm (leaving about 5 cm of gap for air to
be inside the ¡§donut¡¨.  The air would come out of numerous holes (maybe 2 to 5
mm diameter) into the inner chamber, being secondary air jets.  The heat of the
fire would make the metal donut hot, so the secondary air was pre-heated.

	f.  Steam box:  Mr. Hao is the originator (unless prior art is shown) of the
steam box that shoots 3 very tiny jets of steam (I think it is mainly ¡§dry
steam¡¨, that is, not misty or ladened  with water vapor.)  The streams of
steam are directed horizontally into the vertical mid-point of the combustion
area of the gases, NOT into the area of solid fuels.  The impact seems to be
the resulting turbulence, which is substantial and clearly audible.  On the
Stoves list serve we have already discussed the possibility of the H2O having
contact with methane or carbon-black in the gases, resulting in fire-enhancing
chemistry.  That topic remains open for scientific testing.
	The main type of steam box has a cap with a spring-loaded disk to allow release
of the pressure if the holes become plugged.  That is also how you add water. 
(Another steam box has no cap.  It becomes hot, then is placed holes-down into
water, upon which the cooling causes water to be sucked into the steam box,
which can then go back to the fire to expel the steam.  I have one and it works
quite nicely.)
	Crispin sent me a message and photo of a many-decades-old steam-ejecting device
seen in Dakar, plus cautions about possible explosions.  That device is so very
much larger than Mr. Hao¡¦s.   I believe the only pressure in Mr. Hao¡¦s steam
box comes from the resistance by the 3 tiny holes.    But if the holes become
blocked, well............   Needs some study and/or comments from Mr. Hao¡¦s
experience.  Unfortunately, Mr. Hao does not understand English, and all
contacts with him by me and by others was via an interpreter.  So, information
flows are limited at present.
	I have assured Mr. Hao that I would emphasize to all readers that he should be
recognized as the originator and the stimulator of steam-box efforts of the
style that I have described.  He has a patent in China for his invention.  If
you (or anyone you see) are going to do steam box research and possible
inclusion of it in your stoves, please be sure to acknowledge that Mr. Hao was
your starting point.  If Hao-type steam boxes become meaningful in the stoves
efforts, he should not only be recognized, but appropriately rewarded.  5 or 10
units, no problem, just name him as the starting point of your work.  But if you
get to producing hundreds or thousands or more, he deserves some financial
reward.  Interestingly, he is as concerned about the Western World ripping off
his invention as the stovers of the Western World are concerned about China
copying the Western innovations.  He and I chuckled when I said his invention
might be called the     Hao2 steam box.    Get it??   ¡§How to steam box.¡¨

	g.  T-LUD (Top-Lit UpDraft) pyrolytic gasifiers:  Perhaps, maybe, possibly, one
of the candidate stoves in the Shell-sponsored 9-stove evaluations might be a
T-LUD.  The description mentioned charcoal making.  I have asked David Pennise
to help clarify this question.  I do not remember the name of the stove
company, but it was not Mr. Hao¡¦s company.
	I went to Mr. Hao¡¦s factory 3 times:  Before the workshop for a half day, no
lighting of fires; during the workshop with the other participants, for about 5
hours there (not counting when we went to lunch and all ate delicious ¡§crossing
the bridge noodles¡¨, a specialty of Kunmimg and region) when we did ignite
about 5 of his stoves; and after the workshop I went with the interpreter for
about 6 hours, and we did ignite 2 stoves.  It was at this final session when I
showed Mr. Hao the simple pieces of the T-LUD that I brought to the workshop.  I
asked if he had ever done top-lighting as in the T-LUD type.  He said yes, I was
surprised because that stove was not seen at the earlier meetings.  His men
brought in a stove that is about 75 cm tall and almost 40 cm in diameter. 
Bottom half is for the fuel and the top half is for the combustor and the pot
holder.  It is a T-LUD (or close enough to be one with a few special features),
but it is his only prototype of that stove.  The bottom (fuel area) had an inner
cylinder maximum 20 cm tall and about 15 cm diameter for short stick-wood fuel
(but not using chip-size fuel, so his fire did rather-quickly move to the
bottom for some bottom-burning.)   Between the inner cylinder and outside wall
was a cylindrical area in which they stuffed grasses/straw.  The heat from the
inner cylinder was pyrolyzing the outer ring of grasses, giving continual
¡§smoke¡¨ that went to the central outlet and was consumed by the flames and in
the combustor chamber.  Interesting, but not totally impressive because the
smoldering did not seem to end except when opened, resulting in much smoke at
that time.  Good as a prototype, but needs work, and he agreed with my opinion.
	But the combustor!!!!   That is a different story.  Think of it as like the
combustor I described for the Tibet stove, except that it is taller (about 25
cm) and more narrow (about 15 cm outside diameter, with 3 cm sealed air gap,
then the inner cylinder about  7 cm diameter from which the flames and heat
come out.  The inside cylinder has side air holes at 4 levels, and of course, a
steam box that has its own sealed-sided ¡§window¡¨ that gives it access to the
inner cylinder.  Heavy.  Real steel.  Holds the heat, and heats some of the
secondary air.  The major secondary air enters through lateral holes in the
bottom 5 cm of the combustor.
	I now have this stove in America.  Mr. Hao and I traded stoves (more story
below).  The combustor is slick.  I will bring it to Stove Camp.  It really
makes my T-LUD fuel chamber (the bottom part of a T-LUD) perform very well.  We
will measure its emissions at camp.

	h.  The T-LUD gasifiers of Alexis Belonio were only seen in the PowerPoint
presentations, but they got substantial attention.  He is sending photos and
comments for posting on the Bioenergylists.org website, where you can also find
his ¡§Rice Husk Gas Stove Handbook¡¨  This is an important document if you have
T-LUD interests (and you should have T-LUD interests!! ļ).  Alexis and I are
encouraging each other.  I encourage him to do more with gasifiers, and he
encourages me to work on rice husks as a promising fuel for millions of people.

	i.  The T-LUD emphasis by Prof. Mukunda in his presentations was a pleasant
surprise for me, and was well received by the workshop participants. 
Calculations were made for the T-LUDs for 6 cottage industry applications that
were discussed earlier.  I would have liked to have seen some photos of the
T-LUDs made at IISc.

	j.  One true gasifier was seen.  I brought a 15 cm diameter continuous feed
gasifier that is named ¡§Macula¡¨.  The good news is that it operated quite
nicely on my final visit to Mr. Hao¡¦s factory.  We discussed it at length, and
he accepted it in trade for his prototype T-LUD.   The bad news is that on the
day of the visit by the workshop participants, there was a significant smoke
problem, for which I take responsibility as ¡§operator error with too little
chimney, wrong-sized fuel, and different blower.¡¨  Thankfully, Dean Still
pointed out that I violated a major rule:  ¡§Never light your stove in the
presence of anyone else.¡¨  That got a good laugh, and helped me to ¡§save
face¡¨ with my friends who all indicated that they had experienced similar
difficulties.  A different unit will be taken to Stove Camp where it will
compete for the coveted ¡§Kirk Smith Cat Pee Award¡¨.

	k.  There were also many discussions of stove designs by the workshop
participants.  Some conversations were ¡§off the record¡¨, so we must wish them
well and wait for disclosures by them at later dates.

Conclusion:
	The ARECOP 2006 workshop on gasifiers for thermal applications for cottage
industry was a major success.  Never before have I been in the presence of so
many people for so long and all focused on small gasifiers.  Nobody has yet
produced the truly great small gasifier that should be made and distributed by
the millions, but we are getting close.  This workshop emphasized the larger
sizes of small gasifiers (that is, for cottage industry), thereby stimulating
an additional dimension of the small gasifier efforts.  At the same time, there
was much discussion of the cookstove aspects of small gasifiers.  The coming 12
months will be exciting times.  The presentation of the results of the
application efforts by the workshop participants is to be in Bangalore, India,
probably in July 2007.  Perhaps the sponsors (ARECOP and its donors) and the
hosts (Dr. Mukunda¡¦s IISc) might find extra funding and extra attendance if
additional thermal gasifier-related presentations could be made along with the
results of applications by the workshop participants.  I plan to be there.  I
hope many of you can also attend.

-- 
Paul S. Anderson, Ph.D., Geography professor - Emeritus
Telephone:  USA-309-452-7072 (residence and office)
Internet site:  www.ilstu.edu/~psanders
For my gasifier stoves info, go to:
http://bioenergylists.org/contributors#Paul_Anderson





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