Gravity Fed Pellet Burner

Published

Introduction: Gravity Fed Pellet Burner

Hi, 

This is my gravity fed pellet burner.

The air intake and the feeding rate can be adjusted depending on the intensity of heat needed.

Set to the minimum feeding rate,  i get over 8 hrs of heat with a 40 pound bag of wood pellets.

Together the rocket stove and the burner work better then i expected,  

Wood pellet are cheap and easy to find.  

Since wood pellets are made from recycled wood, i guess this is somme kind of green way to heat my garage..


 

Step 1: The Perforated Plate Is the Key to Success

- Pellets will fall on the perforated plate, slide down and form a pile. Fire wil waken the pile and make it crash.  This will allow other pellets to fall into the burner.  This process will continue as long as there are pellets in the container.

- The angle of the perforated plate is about 45 degres.  The holes act in two ways, they allow air to feed the fire and hold the pellets as they fall.  After a few minutes of burning the plate is red hot and every pellet that comes in contact with it quickly ignite.   

- The space between the plate and the interior side of the square tube il about 1/4 inche so air can get in at all time. 

You  can see it work there:

 http://www.youtube.com/watch?v=rEosHNLZJek&feature=g-upl&context=G2e8c2daAUAAAAAAAAAA

This burner could be install on different kind of heat exchanger device, it could just be an extension of the square tube ending to a chimney.  



Any questions???


Step 2: New Burner...

This is the new burner i made.  Bigger holes and less steal.  This model provides a better airflow... 

Step 3: Video

Made this video on how to ignite the pellet burner... 

Cheers!!

https://www.youtube.com/watch?v=jpNxeTdrGXE&feature=g-crec-u

2 People Made This Project!

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34 Discussions

Hi

Have a look at my hobby project. Its a controller unit for biomass.

https://github.com/sedevc/openBC

Hi Seniortrader,

After some consideration I decided to upload this video, which
presents my older burner in action. This design surely violates both Carry and
Wiseway patens, so making a commercial product from this design can be
problematic.

This time I integrated the burner with my house heating
stove. It seems to work pretty well also this way.This is potentially fire-hazardous so I really
do not recommend anyone to do this at home. Certainly this needs continuous monitoring
during the operation, and should not left without it in any circumstances.

1 reply

And typos.... Clarry and Wiseway patents.... and most
probably something else…. How could I
edit my sent replies???

your design is very interesting, it's the answer to the ash problem. Another problem will occur as your burner will work for hours. The pellet intake to the burner is a possible path for the flames. When there is not enough pellets, air can pass trough and the flames will then go both ways, in the heat exchanger and in up in the pellet container. I'm working on a pellet valve design witch will block the pellet intake when the pellet level get to low. Tank you for shearing your design every visitors on this page will apreaciate

Im Finninsh guy nr.2, and im allso building tentstove (sorry my english) i had problems with you burner design, because i think i made it too tight (ari dont pass anywhere else ), pellets bocked "down air intake that size is abut 1cm" and result was great smoke and unburned pellets. Next i make stop vertically longer that pellets stay on that (allso drilled), and cut upper side on the stop about 5mm so air can go over the stop.
I'm using 8mm pellets and 8mm holes 100x100 tube

When i looked your design it's not so tight so air can get sides

2 replies

Hi, be sure to create an air flow through the system by heating the chimney before lighting the wood pellets. I used a propane torch. Simply heat the air inside the chimney to create this stream of air. The burner must receive as much air as possible, adjusting the intensity of the flame is done by adjusting the amount of pellets entering the burner. With some pictures i could help you more! Cheers!

Igniting is no problem... I ment that afther while about 1hour when the holes is blocked by ash and air can't get thru "stop" and my case it can't get sides either.
I think your system works because "stop" is very loose and air can get sides and over" im not sure but i find out today when i make modifications...

Hi,
i would like to make such a stove. But i have a few questions. First, the little holes in the plate (through which the pellet falls), how wide are they (in mm), and how large are the pellets? Also the burner (square tube) where the pellet fall in through the perforated plate, is this burner deep in the chimney and if yes, how deep? What are the dimensions of the burner? Is the burner conected to any tubes inside the chimney, if yes to which tube?
And also is there anything inside the chimney or is it empty? Does the chimney have any isolation inside on the wallas?

It would be great if i could ask you anything else if i need help. Thank you very much.

Best regards,
M.T.

1 reply

Hi, i think most of your questions could find answers on my second instructable the rocket stove mass heater witch is more like a rocket stove without much mass. If you have any questions after viewing this i will be please to help you!

Cheers! ST

Hi,

I tried a couple of different stops and I came into same conclusion as you. If the stop is open enough not to form too much ash on the plate, it gives only marginal help during the ignition phase. After about 30 minutes of operation, the stop seems to lose its purpose as you state.

First I used too small diameter for the feeder outlet. That made the feeding unreliable and too pulse-like, which also made the rolling worse. It seems the minimum diameter for reliable feeding is about 57mm with D8mm pellets. That results about 3lbs / h pellet consumption without any air block at the air intake.

Your design just work as it is. It could not be any simpler and still it has all what is needed.

Sure I'll send some pictures once I figure out how to upload them here.

I made a direct copy of your design, and I have to say I'm positively surprised how well it works! So far I have made about ten trial burns with different settings. The movable 45deg angle plate assy seems to be functioning well for adjusting the pellet feeding. I used constant pellet volume, and so far I have been able to variate the burning time between 45mins and 2 hours.

Only disadvantage in the design I can see is the fact that at least in my unit, the pellets seem to roll quite far away from the plate towards the exhaust. Those pellets are not probably burning optimally. Have you considered / tried to make some kind of stopper to the lower edge of the perforated plate to prevent that?

My intention is to integrate the burner to a rocket stove and use it for heating up my 12-person Swedish army tent (In Finland you can get those tents relatively cheap nowadays). In order to make as light construction as possible, I want to leave the mass around the central-pipe away . Does anyone have any opinion does that cause any problems?

1 reply

Hi Finnish-guy,

Glad you like the design! I thought about adding a stop but I immediately had a problem with the ash.

After some time of operation, the ash that accumulates at the bottom of the burner will act as a stop and it will become so hot in there that the pellets that have rolled foreword will burn quickly ..

Youre idea of using the burner in a rocket stove is the main reason why i did it that way. The only thing you have to care about is that this burner will work fine only if the air draft is good enough.

I would realy like to see some pics of that stove you will build.

Cheers!!!

Hy Badjo2,

It will work fine with any solid fuel that will act like wood pellet. It has to be able to flow down from the tank to the burner and form a pile. Corn could be a good fuel. I would like it very much if you could post your prototype even if it does not past the test... i'm working on a new desing to..

Cheers!

+++GREAT JOB+++Perfect 'Add-on"  for many Rocket mass heaters or stoves. Just the airflow gate - cut two 3.2mm (thickness of cutting disc) equal slots on the vertical sides,+-5mm from the edge and insert 3mm plate. Sliding the plate in or out regulates the airflow very fine and you do NOT need to "hold" it in position. Did you try using anything different then wood pallets.  At the moment I am working on "Weld free" 3 pieces "Rocket".- BBQ,oven and stove. I shall post all details as soon as it past the tests.
Cheers 
      Victor

Nice work.I built a similar RMH stove a few years ago. In place of your ramp, I had a wedge shapes stainless steel mesh that the pellets would drop onto. In a 4 car insulated garage, I was hard pressed to burn 40lbs in a 10-14 hr burn. I did not regulate pellets, only the air from below. I am currently working on a smaller version that hopefully won't overheat the space as much.

1 reply

I think the only way to adjust the heat with pellet heating is by ajusting the flow of pellets in the burner. The airflow must be constent and sufficient to obtain the most complete combustion possible. Hope to see pics of your new stove soon!!

Cheers!

I am planning to build a rocket stove mass heater and this looks like an amazing invention to feed your RMH. The only thing is, I would like to have a bit bigger burn chamber for when I am not using pellets. I saw in your other instructable that you basically use the same diameter square 'pipe' but this is a bit small for my liking. All the rest off it seems amazingly well designed! And I like the fact I could get back into welding again, no need for firebricks. Just weld it!

My question is: would it be possible to attach a bigger 'burn chamber' for regular wood? I'm thinking: dumpsterdived cargo-pellets cut up small with a chainsaw.

I would end up making a cob bench though, something like described in here:
http://www.richsoil.com/rocket-stove-mass-heater.jsp

I like the idea of sitting on a heat mass battery, reading a book :)

Thanks for the inspiration!

2 replies

Hi,

The exhaust must be at least the same size as the input and the pipe from the inlet to the end of the central chimney must have the same dimension. Your rocket stove will work best when you put small size peices of dry wood in it. When the fire intensity is not high enough you will get smoke witch is not an environment-friendly way to make heat.

If you make your stove would you be kind enough to send me a link to you're stove.. Thank you!

ST.