[Stoves] Mongolian traditional clay stove

Mon May 25 21:56:14 CDT 2020

Dear Ron

In Tajikistan I was told the agriculture people are very concerned that so much Dung is used for fuel, usually necessitated by poverty. What I observed is that there is a great deal of work required to prepare,  dry and store (meaning move twice) the fuel.

In the traditional stoves, there is prey poor combustion for two reasons: the fire is not hot, and the combustion efficient is terrible.

A stove was developed specifically for burning dung more effectively. This was classed as the Model 2 in later iterations during the Kyrgyz stove project. The final version for heating above 10,000 ft is the KG2.5. It is larger, the kind of stove that would be used in Pamir in Tajikistan.

When the fuel is burned badly, it produces a great deal of dung-char. You might be surprised to learn that. Chunks or slabs might be heated off-gas but not burn well at all. There is a large amount of char that goes to the fuel with the ash. The ash is mineral-rich of course.

The new stoves are operated in a very different manner - end-lit crossdraft style as per the MM2 from Ulaanbaatar.

The result is a controllable flame, very much better combustion efficiency, higher temperatures and better CO combustion. The fuel saving is large - maybe 50%. The KG2.5 is about 88+90% efficient (LHV).

So the agriculture people are very happy about this. The fuel use drops by half, and the dung is available to be returned to the fields.

The question you might ask is: does adding char from badly burned dung bring more benefit to the ecosystem than returning a higher fraction of the original material to the soil?

I think the Ag people think that dung is a better offer.  If only half the work is needed for fuel preparation and it provides faster cooking, a more controllable fire, less chimney cleaning and less 50% transport, it is a good choice.

As for the Mongolian vs Tibetan aspect, historically these two are strongly connected populations, 600 years ago the Mongolian leaders invited Tibetan Buddhists to take over the country and establish a system of empire-wide administration which they did. The populations are largely indistinguishable. You will recall the various head Lamas like the Dalai Lama are often found in the Mongolian population. Six to eight thousand years ago when the Earth was much warmer than today, the Gobi Desert was fertile grazing land, like the Sahara. It is possible there is no cultural difference between the two groups. It was a Turkic Empire in the 6th century so I think it is fair to call the stove and the clay dung burner "Mongolian" and risk being correct.

Later the leaders invited Russia to come to Mongolia to establish communism throughout the country - the only country to join the Soviet Union by choice. It is an interesting place.

Regards
Crispin
From: rongretlarson at comcast.net
Sent: May 25, 2020 9:18 PM
To: stoves at lists.bioenergylists.org; crispinpigott at outlook.com
Cc: ajheggie at gmail.com; info at sun24.solar
Subject: Re: [Stoves] Mongolian traditional clay stove

Crispin,  Andrew, List. Adding Kevin

See a few inserts below - especially on the added information about the tray.   Note the material with the video says Tibet, not Mongolia.

On May 25, 2020, at 11:15 AM, Crispin Pemberton-Pigott <crispinpigott at outlook.com<mailto:crispinpigott at outlook.com>> wrote:

Dear Andrew

I presume the shot at the end showing the smoky modern metal stove against the clean flame from the newly built clay stove was to tell us something.

The metal stove is a traditional model in used for about 120 year. It is ultimately based on a Russian design. It is a great wood stove though not a very good dung burning stove.  All stoves that burn dung, save a few, are smoky, because they are not idealized.

The metal one in the video is the unit we are trying to get rid of in Ulaanbaatar.  Owners take a pretty good wood stove and line it with bricks to prevent excessive heat damage, then fuel it with coal for which it is hopelessly inappropriate. Lignite actually.

Tell me if the fibres in the dung are to give the clay strength as it dries presumaby once it's fired they severe no further purpose ...

As explained very briefly in the vide, the fibres prevent or largely prevent cracking during drying.  As you can see, the plates are assembled as soon as they can be stood up - this is far from ideal.  It would be better if they were sub-baked and heated to 500-600 C in a pit using grass for fuel.

...and the clay is held together as earthenware byt the point contact partial vitrification?
[RWL:   My guess is that this is totally unfired.  One of the workers was still adding clay as a first fire was lit.  If any Tibetans are listening, I hope they add some charcoal to the raw clay next time - likely to be stronger - and a better insulator.

Yes.  Similar cookers can be made using termite mounds where the inside gets vitrified but the outside never gets hot enough to change at all.

The curious extra piece that the author doesn't know about is possibly one of two things: an air guide which means that the stove is probably built in a way that the piece is headed into or away from the wind, or it may have a spiritual function and always faces East, or South.

The tray on which the yak dung is pre-loaded is most interesting.  Is it the first time people have seen such a device attached to a stove?
[RWL:  Yes - for me - first time.  And clever.   Not looking closely one might think also that the two low holes are there for adding fuel.  Not so - maybe not even so important for air supply -  they are there for ash removal.

The bottom holes can’t be used for adding fuel because of the type of fuel - light and fluffy - not stick-like.

I bring this up because Kevin McLean has been developing a stove also for light material - and is also feeding (in his pre-loading much but adding the extras) from the top.  Corn cobs and corn stalks, at least - but there are plenty of other non-wood options that are going to waste.

Kevin’s interest of course is in making char.  He is calling this an AgWa stove (for Ag Waste).  This Tibetan stove wouldn’t qualify (char production not being obvious to me).

I hope people/places that have other fuels will not turn to burning any sort of dung - Yak or otherwise.  Much better to pyrolize it - and make money off the char (and combine with other fresh dung in a compost operation).

I’m afraid I don’t see a way yet to turn this stove into a char-maker.  But this use of an upper tray is certainly intriguing.

Also the use of flat plates in a triangle shape is great to see.  Not your usual 45-45-90 or 60-60-60 triangle - but looks close to 40-70-70.  This caused by the needed tray.

The other thing that most impressed me, was that the makers/users were obviously very proud of their stove.  Plenty of extra flourishes you don’t see in many locally made stoves.  All in all a very well thought out design in all respects - obviously not a research project.  I’d like to know if this goes back centuries.   A BIG improvement over 3-stones!.  Efficiency over 15%?

Ron

Ps.  Thanks to the video producers - who normally are into nomad architecture - not stoves.  I hope they can find other unusual nomad stoves.  Note this was a 2020 release.

 It allows the fuel to be metered into the chamber "at will" and will provide a certain amount of drying (hence the metal).

Yak dung is a widely used fuel.  In the Pamir region of eastern Tajikistan, it is the only fuel, save a little oily bush.

Regards
Crispin

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