Mongolian heat riser...

Greetings from Asia's wild West
Just finished our 3rd RMH experiment (2 8" systems and 1 4" system in a yurt) before the winter gets started. I've made several small adaptations from Ianto's book for using locally available materials and burning coal (thank you Wisners!), but my one MAIN question at this point is:

What could be a good non-manufactured substitute for perlite/vermiculite as the heat riser's insulation?!

In the first two I used coal dust with a clay slip (packed into a sheet metal sleeve around the brick riser, which I left in), and in the 3rd we got a pick-up load of "slag" from the local heating plant - broke up the lighter stuff and packed it in the same way. Any thoughts on which is better, what else might work, or if I should just try to import something fancier?

May be you could usea paper pulp and clay slip mixture. The paper would be burning/consume in the heat riser leaving plenty of air bubbles in the clay.

wood ash?

et al ; Yes. any ash out of the fire plae or downstream from there ! ! BIG AL !

Sawdust is frequently used to make lichtwight refractory brick in cobination whit clay and ash. The sawdust will carbonise creating airpockets and byso isolating
I don't remember if it's used for heatrisers too , it could be there are to many forces to bild it in one round heatriser . you can always use a square one whit bricks made of the licht wicht refractory .

kind regards karl

Hi Jeremy,
I am in mongolia and i am planning to build a RSMH this year. are you still in Mongolia? where are you? I'm in Nalaikh.
can you spare any time to help me? i'm planning to put together a workshop with some people to help with the work.

what is Slag?
can you find clay here? did you find any anywhere? can i find any perlite that is not garden grade? i read where that is not the best to use for this.
And what about the answer from Paul and Allen on this thread? can i really use wood ash? i can start saving that now! i got plenty!

On treeless plains in Russia, bundles of straw, dry reeds and grasses have been used to fire Russian fireplaces. The fast burn would work well with a RMH for those without wood or coal.

According to the OP, all three systems are heating one yurt. . Or, a comma or something may have been left out. That would make for a nice warm yurt.

There has been some recent discussion of using wool (fleece, I believe) mixed in cob as an insulating material. Might be an option?

Thanks for the suggestions!
So far I am getting up to 500F (in the home) and 600F (in the office) on the barrel tops of stoves I built this Fall. I left about a 3" interior gap because I was worried the coal might melt my barrels I hope to try some different heat riser insulation materials this next year to try and get 1000F... but perhaps I am assuming that is a good goal? What is the average top surface heat for a wood burner?!

Jeremy Fields : If you close the gap between your Heat Riser to around 2''/5cm, you may get to 800dF, otherwise i Think you are near your max, but
please come back here and tell use more ! Big AL !

I would not make the barrel-top temperature a design goal... you could push the system to the point where it may warp or damage the barrel without seeing significant improvements in more important factors like fuel efficiency or comfort.

It's useful to target an optimal, quite-hot temperature in the firebox (where it affects clean combustion) - for wood this is between 1000 and 2000 F, I understand coal burns hotter but if you get much above 2400 F you are burning nitrogen from the air and it starts creating a new kind of pollution.
The other goal is to store as much heat as possible in the bench. To that end, you want to move exhaust smoothly from the barrel into the heat-exchange mass without wasting too much heat along the way. But some heat loss in the barrel is useful to induce the exhaust to draft downward. It's all a balancing act.

The only reason I can see wanting an extremely hot barrel top would be for certain kinds of cooking.
There's also been some success with cooking over the firebox feed itself, when using coal, if you can maintain good air flow to keep the fire happy at the same time. See this thread:
https://permies.com/t/13385/wood-burning-stoves/RMH-Mongolia

yours,
Erica W