Project:RMH,horizontal feed Batchbox model 6",

[dvawolk]

And regarding the helpful thread link.
My heat riser are insulative boards and OUTSIDE dimensions are not more than 23 x 23cm. I put heatriser on one side of the drum (diameter of barrel is 55cm) so i have more than half of empty barrel in one piece. The exhaust hole will be on the bottom of the drum (the same as the hole for heat riser). The exhaust hole has no obstructs up to the top of the barrel. The gap between drum and heat riser is 25cm.
I would say that this situation has more in common with a first bell and not so much with a original RMH system. Sketch attached.

If i stick the exit flue in this round hole - is just the original csa enough or not? I understand the extra why exit chamber should be larger with ordinary RMH. But i just can't see the same scenario here.

[Donkey]

Huh... That's a very good question. I suppose it would depend on the temperature of the stuff you are trying to cram through the hole.
I want to say that my gut reaction is that it would be fine... On the other hand, my little shoulder meanie wants to know why I would ever think that..
You'll just need to try it and see.

[dvawolk]

I agree that the larger the bell= the lower exhaust temperature=the closer is CSA of exhaust opening to system CSA.

But do imagine that exhaust gases can come to this exit hole from sides also and they may interfere with "direct " exhaust gases path...

[dvawolk]

So after i tried the burner WO drums it stayed smokeless.
(Below are the images. They don't show here-i dont know why. But when clicking on them you can see it)
TODAY i tested it with two drums stacked as the sketch shows:


I measured inside temperature on points A B and C (this one is 10cm above the exhaust hole)
I DRIED my wood this time. There was no bubbles forming on the back of the sticks when burning. So it was far more dry than any test before.
This is how it looks:



Inside the drum:


Outside Temperature 5°C Humidity near 100%. No sun at all. Hardly any wind.
6kg of beech hardwood (5cm below the top of batchbox)

15:06
Lighting my fire my fire. Draft is obvious:


15:08
After that i added more wood and partly closed the window (second video). No problems with draft from the begining on. Very minimal smoke (the difference between dry wood and previous wood was very obvious)
TEMPERATURES : 205°C (A),190°C (B),110°C (C)



15:15
Smokeless operation:272°C (A),250°C (B),153°C (C). I closed the window and the primary air intake is now 25 to 30 square cm + p-channel

15:20
Smokeless operation:315°C (A),290°C (B),185°C (C)

15:23
Flash over started. Here the "A" temperature has risen from 330°C to 400°C very quickly. Through exhaust flue i saw flames of flashover. And then just a minute or so after start of flashower all at once started to smoke like mad. Thick browny smoke with bad smell of unburned gasses. From here on the "A" temperature dropped to 255°C.

15:28
Smoke smoke smoke. Thick smoke:255°C (A),226°C (B),170°C (C)


15:35
Still thick smoke but slowly it is disappearing. The temperature is rising again.
300°C (A),272°C (B),188°C (C)


15:38
Still smoky but less than in previous step
312°C (A),280°C (B),196°C (C)

15:42
Low smoke but not smokeless.
342°C (A),316°C (B),215°C (C)


15:44
367°C (A),341°C (B),230°C (C)
Flashower again, smokeless.

15:53


15:55
Last flames seen
321°C (A),300°C (B),216°C (C)

16:07
End of flames. Just coals now.
235°C (A),220°C (B),165°C (C)

16:10
Coals...
220°C (A),205°C (B),155°C (C)


I was so happy when the flashover started. But then smoke, smoke, smoke. I cleaned my drums and even if thin film of oil remained on them i am pretty sure smoke did not come from it. FIRST it was flash over and after that SMOKE. And smoke pretty much ruined the most powerfull part of burning. When the main part of burning started to end also the smoking ended and there was just enough power to get to flashover for last few minutes. If all was okay that flashover should last from 15:23 to 15:45.But in this case it lasted a minute in the beginning and few minutes at the end of this interval.

And here you can see those handles of clamps. At the beginning they were vivid red. Not it is carbon over them -from that smoke on, of course.


What could be the reason(s) for this appearing? Too small exhaust hole (it was 17cm DIA) and heat riser is 16x16cm square! I am desperate for answers as i am out of clue. WTF happened?!

Please, help...
Klemen

[grizbach]

dvawolk, There is not enough oxygen for a full burn.
Placing a vertical stack on it will help the draft tremendously and bring in more oxygen!
If it is still not enough, start opening up the intake. You definitely need a stack first though.

[dvawolk]

Feb 26, 2013 10:12:43 GMT -8 grizbach said:

There is not enough oxygen for a full burn.
Placing a vertical stack on it will help the draft tremendously and bring in more oxygen!

Griz, thank you for your reply. I tried opening the intake when the smoke was there. It didn't help. So i'll try a vertical pipe in the end.

Before flashover it was smokeless. That would mean that at flashover mode the thing needs more oxygen.
The second that comes to my mind is that when flashing over it produces much more heat than prior to that. And hotter gasses are harder to push down compared to cooler gasses- that may also be the case why it started smoking a minute after flashower started...
I'll try vertical stack ofcourse but do you think that i am thinking into the right direction?

Thanks again for helpful opinion!

Klemen

[peterberg]

Feb 26, 2013 8:17:12 GMT -8 dvawolk said:

I am desperate for answers as i am out of clue. WTF happened?!

I know, I know, you won't believe me. But I'll try again.

You are using a fresh cleaned barrel on top. There has been oil in there and unless you cleaned it with lots of petrol or another solvent over and over again, it's still there. In fact, you have to burn the oil out, it's that simple. May I remind you that wood smoke in anyone's experience isn't brownish at all?

The other possibility, less likely than the first, is the absence of a vertical stack. The speed of the gases should get higher and higher and a stack could help with that. In order to rule things out: change one thing at the time.

My advice: run the thing a couple of times, every time the top of the uppermost drum reach a new temperature height it will smoke again. Eventually this will stop and I fully expect it will stay smokeless until the paint start burning off.

Waittaminute! Most 55 gallon oil barrels have got a clear coating on the inside, did you check that? Others are painted yellow, blue, white or red on the inside.

[pinhead]

The only times my Peterburg stove has ever smoked was when it was wet and when the flame port was half-full of ash.

You say it doesn't smoke at all with no barrel? I'd add a vertical chimney and see how it performs. I'd be willing to bet with the chimney assisting with draft there will be enough air to eliminate the smoke.

I may have overlooked this detail... But does the stove have a P-Channel?

[matthewwalker]

I'm with Peter on this. I've never built a new stove that didn't smoke like crazy with each successive increase in temperature. Burn the heck out of it a half dozen times, it'll clear up. Oil in the barrel, binders in the vermiculite board, and is that tape I see on the riser? Lots of stuff to burn off.

[dvawolk]

Phew...
I googled for motor oil and found that flash point is from 200 to 250°C. Then i checked again my temperatures reached in my drum:
flashover got the inside temperature to 400°C. This was measured 10cm below the top of the drum and the probe was about 10cm long. On a few i measured temperature of the drum surface temperature (IR noncontact).
When the inside temperature was 315°C, then the surface temperature was 160°C. I would agree that when inside got to 400°C the surface was above 200°C reaching the smoldering of oil.

GAWD.... this oil is RELENTLESS!


Oh, some conections between temperatures inside drum (10cm away from walls) and outside temperature.
For me it's interesting.
inner °C...... surface °C.... difference
321............ 170.............. 151
315............ 160.............. 155
312............ 155.............. 157
300............ 155.............. 145
290............ 137.............. 153
280............ 158.............. 122
216............ 90.............. 126

I'll report new discoveries!
Thanks for now, everyone

Klemen

[dvawolk]

Peter:
inner coating is clear...

[morticcio]

I had a similar problem with my 8" stove. The 205 litre barrel had gearbox oil in it so was very viscous. I burnt off as much as I could before installing it on the stove. I thought it was clean but there was still a small amount of oil weeping from the seam at the end of the barrel whenever I tipped it over and it was still oily to the touch. Needless to say it smoked for a short while!

How is your vermiculite riser coping with the heat? Can you take any temperature readings from inside the lower part of the riser?

[Donkey]

Wow.. I burn the barrels out COMPLETELY before I use them.

One way is to turn the 55 gallon barrel into an 8 inch pocket rocket and get it going with wood, when it's hot I pour in waste vegetable oil. The entire barrel will glow cherry red and burn the paint and oil off in a huge toxic cloud. Ernie and Ericha (at permies.com stove forums) use this method with one addition, they cover the barrel with newspaper dipped in clay slip. This paper/clay coating is supposed to catch a lot of the toxins released. I don't know how well this works, though it makes sense to me that it might help.

After the fact, since your barrel is already installed, you could pour waste veggie oil into your running and hot rocket stove. The temperature should sky-rocket inside and it should finish the job in your barrel.

[dvawolk]

Morticcio: i will check with the supplier. They said it is not vermicuite board but something else?! I 'll check again
I will measure the temperature at that point in the next firing.

Donkey: you mean pour veggie oil into the batchbox? on the wood? Where would be the best option to pour oil? Just before the port?

Klemen

[Vortex]

Needs a chimney stack.