burning pellet

[alexis]

hello,

has anyone tried to burn pellet in their rocket mass heater. I don't know if it would be possible, maybe filling an empty bathroom paper cylinder with pellet... or making a small pouch with a newspaper and pellets

pellets are inexpensive, store easily and can be kept for a long time

thanks

Alexis

[canyon]

I think the biggest advantage of pellets are the ability to have automatic feeding of fire. They also can reduce mess and on the spot labor considerably. It is more complicated to burn however. They need a tight grate of sort or a "fluidized bed". As you mention, one could just toss them in some sort of burnable container of course (paper sack etc.) but they need to spread out so the gasses can mix with air (O2). The tight clump will burn smoky for awhile and the smoke is mostly burnable waste. With my inventive mind I could see a hopper and auger set up that automatically feeds a downdraft rocket with an angled grate at the bottom of the feed tube. Once dialed in and with a bed of coals built up initially the pellets could then be slowly fed in with the auger at a steady rate and efficiently burn without operator attention. Good for busy people who want to burn wood efficiently without much mess or effort. There is opportunity there for a manufactured commercial unit.

At a wood energy conference I attented a couple of years ago there was a Swedish gentleman who educated me about the most efficient way known to burn the pellets which is to powderize them with a hammer mill and then pump the powder through burner jets like oil or gas! They are doing this on the extreme scale with large power plants and some smaller scale. For info on pellets we need to look to northern Europe where there is lots of experience!

[Donkey]

Dunno, good question.
So, I'll just give my stock answer... Try it and see, post your results here.

I've often wondered at using pellets or wood chips or biofuel chunks, etc..
One possible issue that comes to mind is that pellets would tend to either pack together, keeping air out or scatter apart, becoming too disorganized for a good burn. Seems like some kind of metal (or brickwork?) basket could be made to keep the pellets together and allow airflow all round.

It seems to me that some kind of automatic feed could be made (my preference would be an un-powered one, I don't like moving parts) that could keep the stove topped up for a time and reduce the need to fiddle with it. Like a hopper that could be filled and would guarantee a known duration of trouble free fire.

[Donkey]

HA!
Canyon beat me to it!
Two approaches, one with motorized auger, one looking for no moving parts..
The auger would be an almost sure bet, though against my personal preference..
IMHO, a commercialized rocket pellet stove gizmo would use a thermocouple to power the auger. No plugs, off the grid action.

[canyon]

Donkey,
Just to clarify, you and I come from the same angle with preference for the advantages of simpler non motorized natural. I do try and keep an open mind (not that you don't!) and allow for the advantages of the technical approach. I do however personally work leaning on the non linear side.

[rectifier]

This is reviving a year old post, but today I was forwarded a commercial gravity-feed, apparently rocket-inspired pellet stove design by some hunting boys, and thought it might inspire some thought as to how to feed pellets.

There is an operation video at:
www.clarrypelletstove.com/pages/operation.html

Edit: Skip to 2:40 for lighting demonstration and a view of the internal chute during the burn. This stove looks very easy to light compared to many rockets because of the grate system.

The same site has pictures of the stoves but it's easier to get an idea of internal structure from the operation video.

So, if you watch the video, you will see this is basically an uninsulated riser side-feed rocket stove that feeds a 40lb hopper of pellets down a chute onto a grate (at 5lb/hr gives an estimate of ~44kbtu/hr for a total 8hr burn, though with this design it looks like most of the heat goes up the chimney). Air is provided from below/behind the burn zone.

8hrs is a loooong unattended burn for a rocket stove! This type of system looks easy to retrofit onto a standard RMH feed, too. Pellets burn very clean even in non-rocket systems and produce very little fine ash. I use them in gasifier experiments as a standardized fuel. Plus around here they are cheaper than purchased cordwood, being made of mill waste...