First RMH In Mongolia

Hello All,

I am working on building the first (AFAIK) RMH in Mongolia. It will also be my first RMH. It will be located in a community center in the Ger District in Ulaanbaatar, with the goal of it being a demonstration model. The Ger District has a poplulation of approximately 800,000 people and growing. It is scattered on the hills to the north of UB proper. The District has no plumbing, no running water, and many homes have are not connected to the grid, which is powered by two sketchy coal plants. The residents of the Ger District are poor, often unemployed, and rely on locally made simple sheet metal stoves. These are essentially a square box with a simple draft and a 4" pipe. During the winter (October through April) the stoves run 24/7 in order to keep the gers (yurts) or small brick homes warm. Most use a bituminous coal as fuel. Wood is not available, and cutting trees is illegal. Some residents are so poor they collect plastic bottles and other trash through the year to use as fuel. Even old tires get cut into chunks and thrown in the stove.

I have a fair amount of masonry experience, as does the guy I'm working with. We will be building a practice stove first, and then the real deal at the Community Center in early June. The build in the Community Center will be an activity in which a group of students from the school I work at will be assisting.

Since coal is the primary fuel of choice I'm thinking that the draft requirments will be different than if wood was being used.

Can anyone comment or have experience building an RMH that will use coal? The available coal is a mixture of grapefruit-sized chunks to dust. Not pretty stuff, but that is what is available.

Ulaanbaatar has the distinction of being the coldest and most polluted captitol city on the planet. Much of this pollution comes from the stoves being used in the Ger District. If the project is viewed by the residents as a success it could have a very positive impact on their lives. I should add that the stoves are also where all the cooking is done, so that must be a consideration. Most of the current stoves in use have a round removable lid, like a cookstove only bigger, so that wok like cooking pots can be placed directly on the fire. I know this won't work with an RMH, but cooking on the barrel top is a must.

Thanks in advance.

I have not buiilt a rocket for coal but I burned coal for my primary heat for the first 5 years that I lived here in Kachemak Bay Alaska as coal washes up on the beach with winter storms. It is nasty stuff but sure does have a bunch of btu's/volume vs. wood and burns for a long time. Bottom air is crucial with a grate and ash pan as the amount of ash is phenomenal (daily emptying a must). If you get into rocket style gas flows, I imagine you will need extra large ashpit fall out after the heat riser too. Figure out what kind of grate material is available because the temps get so hot that they don't last and will need replacing. Firebrick splits that are cut in half lengthwise might be a possible solution. Anyway, sounds like a fun project in a wild scene! canyon

Cooking on the barrel top is easy. As i understand it the food is slow cooked like stews and such? if needed for stir frys you can hammer the bottom into a dish sand it out and put an oil coat on it and it will work just cooking on the top.

you will want to adjust the gap between the heat riser and the barrel for coal; and deal with the ash build up. the stove should perform fine on coal but you will have the problem of it heating to very high temps. use brick heat risers with good insulation so your reburn is as hot as you can get. the stove will need some tweaks for that rich of fuel source.

Why dont folks bring me in to do stuff like this? OK as you build the stove ask questions so i can answer them. detail out the system and give me all the observable symptoms that the stove has. we are traveling currently so it may take a couple days for me to respond.
We will need to think this one through for you to give you better advice. What size system is it and what is going to be the primary building material?

Thanks for the quick replies. We won't be building the practice stove until late April since it will be in an unheated shed, and the hi today was 8, and now at 9:30 pm it is -11. The owner of the garage is hoping the stove will help his vehicle start on those -45 mornings in January.

The available stove pipe is all in centimeters, but is approximately 4" or 8". We will be going with the 8" and a 55 gallon barrel. Good quality clay is available, straw can be had. Firebrick still has to be located.

As an aside, there was a big push in the last two years to develop a more efficient ger stove in order to reduce the air pollution. The lead in the project was the Asian Development Bank, and millions of dollars were spent. In an effort to help I sent them links to several sites that cover the development of efficent cook stoves in developing countries, etc. . . all studiously avoided. Nothing would have it but they had to fund their own research into the matter. Their "new and improved" ger stove was rolled out last year with much fanfare. . . . and was, by all accounts, a near non-starter since the cooking issue had not been addressed. So millions of dollars spent, no forward progress. The stoves had to be manufactured in a factory, were more expensive than the current stoves, didn't work as well, and had to be subsidized in order to entice anybody to buy them. Wouldn't it be great if we made more progress in a couple of weekends and spent like a $100?

Ernie, June is a great time of year here. We can offer a nice bedroom, good company and an interesting experience. . . . .I can shake a few bushes and see if an NGO or other organization would bring you in.

Thanks Again

I've been told that when you burn coal in a regular stove, it sets on a steel grate so that air can get to the underside of the coal. I believe it will help to have a removable steel grate that will hold your coal up off the bottom so air can get under the coal. Also, can you post videos?

We have been trying to get things moving in the cold places for several years now and at every turn have been blocked by the cook stove folks. Erica and I would love to see RMH's in Mongolia as well as be in on the building/testing them for that environment. Mongolia sounds and has sounded wonderful for so many years to us. We cant see june this year but we could see it next year. We will try to guide you on your first stove from here.

8Inch is the way to go. if you have a choice build the first stove under the advisement of an actual elder (not many left but well worth finding). they can usually tell you where to build so the folks who will want one can see it. Invite them to come to the build site and give them a warm place to sit. either with a rocket bench or a nice rumford fire place, maybe a pocket rocket. no pressure needs be applied just tea and a warm spot will usually take things along at a merry enough clip.

Take your time, i have heard thousands of accounts of introducing stoves into new cultures and almost all fail due to folks trying to hurry the population into adopting the tech.

Best thing about rocket stoves is that the folks who want a stove will adjust it to fit the need and you dont have to fight it to get folks adopting the stove. a warm but and a nice place to cook can change minds better than any argument or subsidy.

you might want to look at the local bed size and make one bed shaped and sized (one partner will like a warm bed and then you have the partners that build things in a great hurry to make a warm bed) Sides it would give you twice the practice before you build in someones home. Above all take the time the stove needs to get folks excited. this is the tortoise and the hair race slow and study wins the race.

only other thing is make the folks in workshops pay something, Eggs, milk, chickens, what have you. (dont demand cash cause some folks dont have cash) its all about value and free is not valuable. but to much dont work either it needs to be accepting something small that the folks can afford to pay. just dont follow the failed stoves by trying to give them to folks or sell them for a profit. neither path can work.


alright get to work and let us know what we need to do to help.

Right. . . .must get to work. . . will update as progess is made. Any ideas on the design of the feed tube/grate/draft will be cheerfully accepted.

Andy,

I understand that Ernie may be none too fond of him, but, Crispin Pemberton-Pigott has been working in UB for a few years now and has done some excellent work in improving the traditional Mongolian stove. I think his collaboration would be particularly beneficial in dealing with the local coal. You can review what he has done at <http://www.newdawnengineering.com/website/library/Stoves/shatalt/>. I would recommend that you repeat your question on the Stoves List, <stoves@lists.bioenergylists.org>.

Do they burn straw in Mongolia? Straw burning masonry stoves were popular in the steppes of Russia and among Mennonite immigrants in North America.


Good Luck

Andrew Parker

I was sure this subject had come up on the Stoves list before and sure enough it had. Here is an excerpt from the thread, in reverse order:
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Dear Crispin and all,

Relating to Crispin's comments:
1. I had forgotten about the condensation. A difficulty to solve, but an advantage of gaining back all that latent heat.

2. BECAUSE the TLUD is a batch operation, (and can even be rigged to have a small alarm that says when the batch is about over), therefore the total fire is removed and the dampers and doors on the high mass heater can be tightly closed without any fears of further emissions from lingering regular fires.

3. Thanks for the target numbers of 12 to 25 kW.

Is this the energy content of the fuel? or is it the amount of thermal energy that is captured and is useful in the household?

What does this translate into as kg of common wood (or Mongolian dung or other fuels)?

Paul
--
Paul S. Anderson, PhD
Known to some as: Dr. TLUD Doc Professor
Phone (USA): 309-452-7072 SKYPE: paultlud Email: psanders@ilstu.edu
www.gtz.de/de/dokumente/giz2011-en-micro-gasification.pdf (Best ref.)
---------------------------------------------------------------------------------
Quoting Crispin Pemberton-Pigott <crispinpigott@gmail.com>:

Dear Massive Friends

There is a strong preference to put mass walls into homes in Mongolia as spare income becomes available. Something like 60% of people who used to live in a ger (yurt) have built permanent structures and many of the small homes have a mass wall in them.

There is a significant risk with these devices and that is the problem of controlling the air flow through them once the fire dies down. The amount of heat lost up the chimney can be very significant when the wall is hot and there are open holes. It is not possible to close the chimney completely because it is never certain that a fire is completely out so CO would get into the home if the ventilation of the wall is blocked.

When checking the excess air ratio of a couple of these ?wall stoves? as they call them, I found a lot of air is being pulled through, driven by the retained heat. It is not only possible, but a surety that the thermal efficiency drops below 0% under late-fire and fire-out conditions. There are a few things one can do with the design, but keep in mind that having an episodic fire instead of a continuous one exacerbates the problem. A continuous fire for a long time is inevitably going to have different firepower at different stages so it is not a complete cure either.

The big advantage of a mass wall is not that it smooths the heat delivery (which is does) but that it will deliver heat throughout the night. That is the biggest issue. 10 hours of heating. No one wants to get up on the night and tend a stove.

There is a lot of work needing to be done on this to get systems that drain water effectively (there is a huge amount of condensation inside such devices) and to work out the best mass. I did a little work with (then) GTZ modelling this and we arrived at a number of 500 bricks as being the minimum number to be effective in that climate. Maybe 1-2 tons.

The brick layout determines the effectiveness at picking up heat so possibilities abound. It is expected that these devices will approach the efficiency of a high efficiency condensing natural gas furnace (92%). At present there are huge issues with the condensation because it appears not to have been seriously considered when building them. The amount of water to be handled is large: perhaps 450 litres per month. Only some of it passes through as water vapour.

I look forward to seeing this application applied with rigour.

We tested a double TLUD stove in Ulaanbaatar made by a local artisan. It worked in sequence so there was always a fire going. Whether the fire is continuous or episodic, there is still a large advantage to a well-build mass wall: it turns the stove into a condensing heat exchanger! That is a gain of at least 15% in efficiency, more likely 60% compared with the baseline devices. The downside risk is that the chimney will run all the heat out of the system by pulling cold air into the home and shoving it up the chimney when the fire is out, or nearly out, at a (negative) efficiency of -250% or even more. What we know for sure is that people who have a heating wall use about 1.5 times as much fuel as those who do not (for a complex of reasons).

If you want to build suitable ones in which we would be interested, go for 12 and 25 kW sizes.

It may surprise you to know that the major application of new stoves this year (season starting Aug 2011) is TLUD stoves from ?Silver? being installed on heating walls. The market is sometimes ahead of the stovers! They are installing a couple of thousand a week, many connected to heating walls.

Regards

Crispin
+++++++++
Alex: I believe the most appropriate answer to your final question below ("What do you see as the advantages of combining these two approaches?") is one you gave yourself: ("...a desire for char ...").

The beauty of high mass heaters is that they mesh well with a batch process - the main (only?) drawback of char-making stoves.

Ron
++++++
Paul,
The TLUD configuration has it's advantages and disadvantages, like any system. One advantage is it's steady state energy release. High mass heaters strive for a similar result. It seems a bit redundant to pair the two. Perhaps it depends on other considerations like a desire for char or an available particulate fuel supply.

There are some folks doing fine work at the Masonry Heater Association.
http://mha-net.org/
They have done a lot on emissions, efficiency and durability. They have looked into Down feed rocket configurations.
I'm not sure if they have quantified losses between firings, or seasonal efficiency.

Its a simple concept with lots of technical details.

What do you see as the advantages of combining these two approaches?

Alex
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Sorry for the monologue, but I was considering what Crispin mentioned about massive heat loss from the necessity of leaving the damper open to exhaust CO. Could the masonry heat sink be isolated from the combustion area and chimney? Ernie, didn't you have a setup like that for testing one of your RMH's. The Mennonite straw burning stoves I read about last week showed a double chamber fuel feed with the chimney rising above the first chamber. Could that have been the purpose, to isolate the mass of masonry while venting gas from dying embers?

Some people (and governments) get really emotional about this subject. There is a great fear of people having a means to isolate flow through their mass stoves in case they choose to do this when there is a fire producing CO that will back up and sneakily poison the occupants. Certainly a justified concern, but IMHO not a reason to outlaw it for everyone. In my experience it is very easy to guage when it is appropriate to shut off the flow through the mass when one is burning hot "episodic" fires. I am grateful for my homebuilt bypass damper (diverter) that allows me to divert flow from the mass but after building and using a "guillitine" for another rocket that actually positively shuts the flow (except a very small 5/8"hole for residual co) , I will be adding one to mine and others. IF there happens to be a few very small coals left in the ash of the unit, the small amount of co can make it up the 5/8" hole. Plus, with good wood and hot turbulent fire, there is not much left to pollute in the residuals. I have tested with the Testo for ambient CO after corking off the flow for some time and not seen anything coming back out of the unit. If someone did shut the thing too early, smoke becomes visible coming back out. I do realize that there is that period where smoke would not be present and CO is (CO is clear, odorless), my experience has shown me that it is not hard to have a feel for how long that period is. While it is very important for stove operators to be aware of what is going on and the potential dangers and such, it can save a lot of heat with educated use of flue isolation devices and they should at least be allowed! There is a good look at this subject in David Lyle's masonry stove book worth reading. Canyon

Yes we put bricks over the feed tube. lets a little flow in and clears the stove of what little CO is in the system. not that it matters much cause we hardly have a CO problem in the first place.

Look in any discussion about nomads living in permanent housing you always get the same thing "the nomads are stupid so we must protect them from themselves" this is patently bullshit. those have the same brains as everyone else and the same not wanting to die. shoving a stove, house or power plant down there throats is going to result in the same things. resistance from the elders and stupidity from the youth.

I am so sick and tired of these idiot crats saying the people they serve are morons I could spit. let the people see a good idea and they will decide in there own time. I understand that upper mongolia seems to be on island time and so should anyone bringing them new ideas. trying to make a schedule with folks who dont have schedules is fool hardy.

Bah!!! this subject makes me furious every time.
the idiots running this stuff have pet projects and nothing will stop them from forcing these on everyone. there is no way to get through unless you are one of these assholes friends and have a shit turtle neck to prove it.

Greeting Friends of RMH's

I was introduced to the RMH by Roger Lehet some time ago and read the books/material I was able to locate. I am delighted that someone is trying to build one in UB (Ulaan Baatar). It believe the construction of the heat exchange, at least in princple, has great potential for increasing the system efficiency well above the baseline stoves (which is 53% as presently determined).

A couple of updates for those who follow the developments from some distance and might not get news easily:

The laboratory build by the Asian Development Bank operated almost continuously for about 1 year which was enough time to test a few dozen proposed improved stoves. Significant reductions in smoke were attained with a maximum thermal efficiency increase of 30% (to 83%) for a few. This is still not a condensing system, which I believe Ianto has achieved on the long bench systems. Great. The WB and ADB do not develop stoves so those which are hitting the market since about August 2011 are what projects have decided to promote. The main projects are MCC, XacBank, GIZ (ex-GTZ) and a company owned by a large mining company that wants to work on the air quality problem. There are about 30 local manufacturers of stoves.

The major project at the moment is the MCC (Millenniun Challenge Corp, Washington) which is subsidizing portable top-lit updraft coal stoves made from cast iron nad sheet metal. They have placed about 72,000 in the past 7 months which is about 50% of the ger-dwellers' stoves. There has been some leakage into the rural areas which I was encouraged to hear although not part of the plan. It means wider adoption of a new technology - not always something easy.

XacBank is providing finance to really poor people and as the payback on saved fuel is a matter of a few weeks, and given they have 2 years to pay, it is a no brainer for those needing to save money. The typical ger-dweller uses 4.5 tons of coal a year. They can cut that in half.

I have recent news from Prof Lodoysamba that the refuelling issue (TLUD's are hard to refuel if you are not careful about when it is done) has been succesfully resolved with widespread understanding that is has to be a fairly large refuel (with wet lignite which cooled the chamber) followed by immediate re-lighting. This allows 24/7 operation. The technique was developed at the ADB lab and shared with the trainers - it seems to have been completely transmitted to the general population so it won't be lost.

Anecdotal reports of better quality air in the city were received but I want to see it before I believe it. There are lots of sources of smoke and dust. Let's hope it is working. The PM2.5 emissions from the new stove are dramatically lower than the traditional ones, primarily because of the elimination of the smoky start-up cycle. That accounted for more than 85% of the smoke from any burn.

Back to the RMH. The possiblity of a condensing system for town-based gers and of course the thousands of small fixed dwellings is very attractive. As people can afford it, they build something permanent and that tends to drive up their coal consumption and emissions. Little attention is paid to solar orientation so lots of work needed there. Insulation is well understood but considered expensive. The RMH could easily be added to the thermal mass walls that are popular, though not exactly optomised.

Whatever is built, it has to be able to cook as well as the current technology. This is not going to be traded away unless there is an alternative cooking system (electric or bottled gas). These are popular among people with a bit of money so if they are cooking that way, an RMH cold be added to the house.

It is very important that the combustion process, above all the ignition sequence, be tailored to reduce the possiblity of roading cold fuel on a hot fire. This is the source of the vast emissions of smoke from the traditional stove. The regular box (well described above) is actually a Russian wood stove that has pretty good performance if the front door is kept closed. Radiant heat from the sides is strongly desired as knee level or else the top of the get is warm and the floor where the kids are is freezing. Some people burn wood (pallets especially) all winter but not the majority by far.

For those who want to work on a coal fired RMH the characterisation of the fuel wil be important. It is approx 25% moisture. Of that which remains it is 50% volatiles (easily lit) and 50% carbon. That is approximately the same analysis as wet wood. The desired burn rate is about 0.75 to 1.25 kg per hour for a heat output of 4 kW to 10 kW or so. Remember that there will be a desire to have less heat from the drum and more heat invested in the mass storage so it averages what can be a flaring fire followed by a slow burn. A flaring fire can easily overheat the home. The fuel tends to 'take off' once it gets a chance to burn. The coal from Baganuur (further away but even cheaper that Nalaikh) is worse actually with oil detectable in it.

Any advice on how to reduce the direct heating from the chimney while retain the draft system (which I like a lot) and increasing the storage in thermal mass will be shared with any and everyone.

Last point re cooking, plan to have to boil 4 sheeps heads at a time in a 20 litre wok. Milk is pasturised in 20 litre batches. You can thus see there is a heck of a lot of power required by many families. The traditional stove can be stoked to that level (25 kW) but that does not mean all stoves must do it. It is just that is the sort of question people ask when kicking the tires.

Best regards
Crispin

There is a significant risk with these devices and that is the problem of controlling the air flow through them once the fire dies down. The amount of heat lost up the chimney can be very significant when the wall is hot and there are open holes. It is not possible to close the chimney completely because it is never certain that a fire is completely out so CO would get into the home if the ventilation of the wall is blocked.

It's generally better to close the gas path on the inlet end rather than the outlet end as it's seen as safer, and you don't get a surprise puff of smoke coming back. As Ernie said, cover the feed tube.

Thanks. Robert van der Plas and I have discussed refusing to subsidise any stove that creates a positive pressure in it because of the obvious risk from leaky, artisanal stoves. The cast iron tops are a particular concern as they have (often) multiple rings. The finish is 'as cast' and has zero resistance to internal pressure.

The placing of air entry controls is standard advice at the lab. A lot of design info is shared there because we can show directly on the screen what the effect is - very convincing.

At present I would at least consider a damper that was partial. Still open-minded in case an innovation pops up. Dampers are widely used - a sheet metal slider. But a traditional stove with a well run damper tops out at about 60% eff which is well below target. We have to have more radical designs.

A few points i would like cleared up and then i need to bow out due to being a moderator and the water already passed.

1. direct heated chimney? Are you referring to the heat riser?

2. damper? a bit of steel is better than a brick in some way?

3. internal pressure? where do you see this as a problem?

4. you subsidizing the RMH? Who has asked you to do this thing?

Hi Ernie

Pleased to meet you.

>A few points i would like cleared up and then i need to bow out due to being a moderator and the water already passed.

I am not following the 'water already passed'. Is the thread so old no one is interested any more? That happens....

>1. direct heated chimney? Are you referring to the heat riser?

Is that a reference to another post? I am not sure what a direct heated chimney is - I was trying to describe the traditional stoves as presently used. They have a steel pipe which is often fairly loose on a very short (way too short) stub on the back right (usually) corner of the heat exchanger. The heat exchanger on the traditional stove is a rectangular box behind the combustion chamber.

As for the RMH the central riser is what I presume you meant by the heat riser, yes?

>2. damper? a bit of steel is better than a brick in some way?

I was describing what they use. The common practise is to make a cut with a hacksaw in the chimney and insert a piece of approx 0.6mm flat galv sheet. In virtually all cases I have seen the damper is not capable of closing off the chimney completely. Many stoves have no control on the chimney but do use the ash drawer as a controller epecially during ignition. In general the ash drawers are too loose and do not seal well enough to limit the excess air entering the stove. This leads to two common problems: runaway burning in the first 45 minutes and a negative thermal efficiency in the last 90 minutes. A typical burn is 4-5 hours.

>3. internal pressure? where do you see this as a problem?

If the fire is running well and the damper on the chimnmey is closed enough, the stove is under a positive pressure as gases build up in it and leak into the room. This is so common a phenomenon that people are careful to avoid the condition because when it happens it kills everyone in the house, or makes them very sick. It is not just the CO, there are a lot of poorly burned volatiles in a stove that is choked on the chimney side unless the coal is completely coked by then.

>4. you subsidizing the RMH?

Not me that's for sure. I have no money. But I can train people. In order to have any stove subsidised it has to be tested for emissions and thermal efficiency. I believe the RMH will easily pass the % efficiency rating. To my knowledge there is no unit available in UB for testing for emissions. Was the one mentioned above completed?

Very briefly, the emissions test is the measurement of the CO and PM2.5 emitted during an ignition, a burn until 90% of the burnable mass has gone, then a refuelling and a similar burn. The result is expressed in PM mass per megajoule delivered into the home. That takes care of the thermal efficiency number in the same calculation. Basically it is a measure of how much pollution per unit of heat gained by the house. The current target is an 80% reduction in PM 2.5 relative to the baseline (which is 788 mg/Net MJ). The best stoves are in the 3 nines range (99.9% better than the baseline). The 72,000 MCC sponsored TLUD's are in that range.

>Who has asked you to do this thing?

No one. Just looked like a really good idea. I don't want to estimate the uptake, but a demo is probably warranted. Roger pointed me to the USA work and it seemed to have (parts of it at least) a good fit in some circumstances. I will raise it as a possible design if and when I can, to local producers to see what the uptake is. They are a very easy people to introduce new technologies to. Adoption can be quite rapid. So is rejection. Cooking capability is a big issue and if the women don't like it they won't use something even if it is free. There are strong relationships between the families and their stoves. Second hand stoves are rarely sold outside the extended family.

I believe the RNH will be more applicapable to the many thousands of people who are building fixed housing than gers (because it is a nomadic, temporary house). The use of thermal mass walls is widespread in fixd housing though they obviosuly suffer from not having a proper method for dealing with the condensation. The combination of fuel moisture and combustion moisture is on the order of 450 litres per month condensing inside the wall. Lots of issues. The RMH will have to deal with that too if it is a condensing unit (which I believe from what I read, the best ones are). Handing condensate when it is -40 outside is an issue.

Regards......

Crispin and all,

Focusing on the original question about burning coal in an RMH, if one retained the J-tube Rocket configuration, what adaptations must be made to deal with burning coal?

Would one keep the downdraft configuration, or would a crossdraft or a dasifier/pasifier work better?

Is there still a risk of runaway burning?

Would one need to inject secondary air at some point, heated or otherwise?

I would guess that a refractory combustion chamber would be a requirement. Would cast refractory be sufficient, or would kiln fired material be necessary?

Is the startup time for coal significantly longer than wood? If so, would some sort of draft inducer be necessary to maintain draft until the system is heated up?

Addressing the issue of condensation, would a feasible solution be to make sure the flue in the bench, or whatever the mass is shaped like, is sloped to drain with a trap placed inside the heated structure at the bottom of the chimney, or before the exhaust vent perforates the exterior wall?

Addressing cooking, I get the feeling that making a single combo stove for the cold extremes of Mongolia may become a case of "Jack of all Trades, Master of Nothing." While the barrel over the internal chimney of a heating stove may be used to make or warm tea, or slow cook, I don't know that it will be able to cook a meal in a 20 liter wok without some major alterations.

Could a cooking top be fabricated to fit the barrel, something that would lift the wok above the chimney to maximize heat at the top of the barrel, and make a good airtight seal at both the barrel and the wok?

Would it be safer to put the cooking unit ahead of the internal chimney?

Would it be simpler to just buy one stove to cook with and another to heat with?

Dear Andrew'n'All

YOu are really hitting the nails on the heads with that post. Congrats.

>Focusing on the original question about burning coal in an RMH, if one retained the J-tube Rocket configuration, what adaptations must be made to deal with burning coal?

The original downdraft stove was a J stove. With a flat J Iguesss you could say. So far there is not an available downdraft stove though I taught several artisans to make them. One surprised me by calling it a Russian name and he knew how to light it, andreally loved the performance. He got a 13 hours burn from a single load by putting a choke ring in the chimney. So they are known in Mongolia.

The huge advantage of a downdraft is that when burning high volatiles coal like Nalaikh (which is about 2/3 of domestic consumption in UB) it deals really well with the volatiles and the refuelling emissions which are horrificon a traditional stove. Remember the trad stove is a wood stove with bricks in it.

>Would one keep the downdraft configuration, or would a crossdraft or a dasifier/pasifier work better?

I have seen some pretty wild things tried in UB so I remain open to anything that will burn. I put a video on YouTube about the stove with the rotating grate - that was off-the-wall crazy and partly worked. Would have been better if it was made to tighter tolerances. Thermal eff was 35% tho.

>Is there still a risk of runaway burning?

I really think not. The coal burns pretty much like wood - you have to restrict the primary air to slow it down which is a problem with the trad stoves because of the poor fit of the ash drawrs, as I said.

>Would one need to inject secondary air at some point, heated or otherwise?

That is really likely. As the primary air is necessarly restricted because of the high volatiles, secondary air is needed. With hte GTZ 7 series stoves this was provided by running it through the grate at the low-level end where the coke is. It is an odd way to do it but it sure worked well. Very little additional secondary air is needed on top of that. As others have suggested above, restricting hte primary air at the entrance of the RMH will provide negative pressure in the firebox limiting the chance that anything will leak out.

>I would guess that a refractory combustion chamber would be a requirement. Would cast refractory be sufficient, or would kiln fired material be necessary?

To avoid a general discussion, yes and in the case of Ulaanbaatar, I suggest using the widely available (meaning three outlets or more) of the Chinese boiler liners. They are about $1.25 each and are really well made, can take tremendous thermal shock and are cheaper than the Russian ones. Mentioned above was the need to deal with higher temperatures. Quite right. Metal does not last when exposed to the coal fires at high revs, so to speak.

>Is the startup time for coal significantly longer than wood?

Definitely, especially as the fuel is 25% moisture. It is often frozen like a popsicle when it put in.

>If so, would some sort of draft inducer be necessary to maintain draft until the system is heated up?

In short yes, but what kind? The nest answer seen so far is the heat exchanger bypass which is a hole approx 40 x 50mm leading directly to the chimney bypassing the heating box. The box is made slightly larger to compensate for the heat bleed. It brings the stoves up to temp quickly and has been adopted by several manunfacturers. This is of course not necessary on the RMH.

>Addressing the issue of condensation, would a feasible solution be to make sure the flue in the bench, or whatever the mass is shaped like, is sloped to drain with a trap placed inside the heated structure at the bottom of the chimney, or before the exhaust vent perforates the exterior wall?

I was hoping Ianto or someone with experience would comment on this aspect. How is the condensation dealth with? Is it drained outside or pooled and evaporated later?

>Addressing cooking, I get the feeling that making a single combo stove for the cold extremes of Mongolia may become a case of "Jack of all Trades, Master of Nothing."

Yeah, a serious possiblity. The thing is, the population is in a state of flux and there are definite market segments for specialised products which the RMH might be one. In its favour is that they are used to mass walls which they call heating walls. I have heard one report of a fixed heating wall in a portable ger.

>While the barrel over the internal chimney of a heating stove may be used to make or warm tea, or slow cook, I don't know that it will be able to cook a meal in a 20 liter wok without some major alterations.

The cooking height is a non-negotiable so this has to be considered. Possible cooking locations are the horizontal portion between the firebox and the vertical hot chimney, or on top of the chimney which is too high for short women to put 10 litres of soup. Woks slosh easily.

>Could a cooking top be fabricated to fit the barrel, something that would lift the wok above the chimney to maximize heat at the top of the barrel, and make a good airtight seal at both the barrel and the wok?

The problem is still going to be the height. Making tea might fly.

>Would it be safer to put the cooking unit ahead of the internal chimney?


Exactly. Possible, as they say.

>Would it be simpler to just buy one stove to cook with and another to heat with?

We have available at least some social anthropoligical survey material (American, Cecil Cook) indicating that above a certain income level there is a strong preference for electric hotplate cooking, like a rice cooker and so forth. People also cook with bottled gas if they can afford it. This is also the group that a) has more money and b) probably lives in a house that the RHM could heat.

One must be careful when interviewing because if you ask about stoves, they tell you things that relate to the importance of 'storing heat' (which most stoves do poorly) and portability, even if it is in a fixed installation. It is a hangover from being nomads. We found the same in South Africa. What people think about stoves (which drives their purchases) is different from their use of them and the cost of using them.

People mistake a small smouldering fire as the stove 'storing heat'. The thermal mass of the stove is not large at all but this capacity rates highly on surveys.The reason is they have such a flash-in-the-pan massive fire followed by some smouldering coals. They mostly have never seen a stove that has continuous heat for a long time like Roger Lehet's vertical masterpiece. Have you seen it BTW? Mother Earth has picked it up as a promo technology through their fairs, somehow. He deserves the victory.

Incidentally I met with Adam Perry of Cob House fame together with Cecil Cook at the East London airport on Wednesday. We didn't talk RMH - no time - but got to see each other. He is examining the spread of soil-cement building technology in the old Transkei where is has displaced cinder blocks in low income housing in some towns. Cecil is an adjunct prof at the Univ of Fort Hare and Adam is studying there. There is a strong AT connection in there too I expect.

Stay well

Success! The first RMH build in Mongolia is complete and was well received! Based on the available stove pipe having a 15 cm diameter (5.9 inches) it is essentially a 6" system. Namkhai, the Mongolian from our school who was assisting us, thinks the door in the ger will be open for much of the winter since the heater will give off too much heat! He is already planning on building one in his countryside house. The Mongolian ladies from the community laughed with delight when they sat on the bench today and felt the warmth on their butts. That was the best moment of the entire experience. The second best was when I had the idea to place one of their round bottomed cooking pots in the feed tube ring. Earlier I had cobbed in a brick to reduce the CSA of the feed tube. The pot rested perfectly on the brick, and allowed the right amount of air to pass between the pot rim and the feed tube ring. So tea and soup on the barrel and hot cooking in the feed tube ring!

Pictures to follow when they get forwarded to me from the students involved in the build.

I've spent every night this week re-reading the book and mining this site for threads that contained the nuggets of wisdom I needed to meet the challenges faced of elbows and T's being unknown in the country, fire brick not being available at the time of the build, figuring out the cob proportions etc. . . . My thanks . . . . you know who you are.

Best,

Andy

Congratulations Andy

Great achievement.

>Based on the available stove pipe having a 15 cm diameter (5.9 inches) it is essentially a 6" system.

Do you think this is adequate? People think pipes are expensive so cost matters a lot. There is a pipe making machine at GIZ in the West end (they have a rented workshop). There is a bending break with a cutter attached, a roller and a seaming machine, all hand op. The chimney pipes are made locally so you can get any size you need by asking them for it. The common sizes at the market are 95, 108 and then the big one. Elbows can be sourced locally. The Korean TLUD briquette stoves with a heat exchanger beside them have a 90 elbow at the bottom of the stack.

>The Mongolian ladies from the community laughed with delight when they sat on the bench today and felt the warmth on their butts.

That is very comfirming. The lower portion of the ger is space that is lived in!

>...I had the idea to place one of their round bottomed cooking pots in the feed tube ring.

Were you burning wood or coal?

I have a list of retailers/importers selling firebricks, both of Chinese and Russian origin, stuffed away somewhere. Let me know if you need it. Some keep a little stock. Some don't. Expect them to be in the Tg1400-1600 range each.

A stove development and training cnetre is about to get started and it would be good if you could give either a class or field demonstration (or both) to the staff of that centre-to-be. The idea is to work with people who are doing-the-doing on the ground to offer them theoretical and practical back-up, product testing and social science impact assessments. The latter as we all know is often missing from 'technical development'. User acceptance, opinions on the fueling, functions, cost, flexibility and durability must be part of the hardward development. That means bringing the formal sector producers into more contact with the users. A very helpful study was done by Cecil Cook the American about a year ago that raised some eyebrows and legitimate issues. It seems old hippies can still make a contribution and get attention.

Would the RMH benefit from a cast iron top where the pot sits? CI is quite cheap. It would be easy to produce at the artisanal level by one of the township foundries. Ditto for the grate.

I wish you success in the coming season.
Crispin

Nothing spells success quite like having to leave your door open in crazy cold temps because your house is too warm!

Andy, Ernie or anyone else who's part of this
Do you have any update on what has been happening with this and any other rocket mass heaters in Mongolia? I have recently moved to Mongolia and would like to meet with any of the people involved in this or other similar projects that have been happening, or just hear about where this has gone.