Burning Wood Pellets in the DF520

Using only the short burner tube and worm, I experimented burning hardwood wood pellets in the stoker. Neither I, nor anybody at efm, is recommending that you try this.

The first test used the open pot. The eventual feed rate was full open, 11 teeth, and 1 on the air. Everything went well. The ash volume after one 40# bag of pellets was about a coffee cup full. At the low air setting, the fire was smoky. One bag lasted about 4 hours. The boiler maintained about 140 degrees and was able to run two of the Modines full time in this warmer weather. Each Modine is rated at 92K. In any event, even using coal, the boiler is too small to heat the building, which probably needs 400-500K BTUH.

In order to add more air to the fire, a small cone was made for the center of the pot, to block off the lower air holes in the plates and to keep a 3" supply of pellets in the tube and is shown below. In a few minutes, 2 sheer pins were broken.

A new cone was made to hold 1 1/2" of pellets in the vertical cone and this worked with no problem. The feed was set at 11 teeth and the air at 5. There was no smoke in the fire and the boiler performed as in the first test. The fire burned in the middle of the pot and the air holes in the plates above the fire eliminated the smoke.

The same result could probably be had if I just sealed up all the bottom holes in the plates.

I removed the sheer pin to stop the feed, but left the fan running, to see if the air from the fan would cause the pellets to burn down the pipe to the supply bin. The fire did burn down to the bottom of the pot and then went out after about two hours of smoldering, which might possibly be long enough to hold a fire until the timer kicks in.

Next test is corn.

Very interesting to see pellets and corn discussed in this appliance! I don't see why you won't be sucsesful - the design has been for others. The key ( as I have lamented in the past is cost of fuel per BTU produced )

Here is a link for a boiler that burns coal but this operator is burning corn and barley - note his modifications to make it work better. Do a search and you will find more in the link too.

http://forum.iburncorn.com/viewtopic.php?t=86

I found -- and this is just me - that pellets burn faster than corn - thus you can produce more usable BTU's in a higher load than you can corn. Corn burning is limited by the amount of air you can get into the pot ( corn takes not more air and different delivery of it for best combustion or it burns cold) BUT when you combine / mix two parts pellets to one part corn ---- the BTU production goes way up in my burn pot. I built a two bin holding system and a pre mix delivery to the appliance bin last year to support that. As I stated its all about cost of fuel - This year pellets are Hi and corn is reasonable in Wisconsin - so I am modifying the mix system and am going to deliver 1 part pellets to 2 parts corn this year - or almost straight corn in the early weeks of heating

Pictures to follow - but you can find some of the old system here.

http://forum.iburncorn.com/viewtopic.php?t=8170

Hope to hear more of your experiments - anything a amateur can do to help????? Let me know please!

Kind Regards
Sting

stoker-man wrote: The eventual feed rate was full open, 11 teeth, and 1 on the air. The ash volume after one 40# bag of pellets was about a coffee cup full.
Next test is corn.

Sounds like a great summertime project. Did you use Hardwood pellets, or Junk-wood pellets? I would be concerned the feedrate is at its max, and may need to be faster for Junk-wood pellets.

Hardwood pellets from VA.

The feed rate is maximum because I'm trying to run 5 modines with a capacity of 450K BTUH with only a boiler capable of 188K

I'm going to apply refractory cement to the bottom half of the burner plate's holes and try again tomorrow.

I do believe that a pellet fire would smolder long enough to be maintained by the stoker's timer.

Farmers currently use corn mixed with coal successfully and 100% corn was tried in the '70s and worked as long as it was 24/7 burning.

My timer will maintain an idle fire on a 8 or a 16 minute off cycle - depending on draft.

yes close up those lower holes for pellets and open them for corn - others ( folks burning the LDJ corn boiler ) have simply used sheet metal screws to plug lower combustion air holes and bring the wood pellet fire higher in the pot.

I couldn't get the bagged feed corn to ignite. Even tried 50/50 with pellets and that failed too. I'll try corn/coal today.

I hand fill my pot with pellets soaked with charcoal lighter ( mineral spirits or anything you would use to start a fireplace or the coal boiler) and light

That gets combustion going - and then it will support a mix or even straight corn, but you need a pot of pellets to get the corn to melt and pool into a burning cake or mass - then that will idle fire and burn the new fuel as introduced.

The corn has to be low in moisture content - pinch a seed in the jaw of a pliers - it must shatter into bits - if is just sort of "smooches" into a mass - it may be at a storage moisture but won't but with a robust fire.

You didn't close off to many of the low pot combustion holes ????

Today I was able to burn 50/50 corn/pellets without any trouble. The fire and combusted fuel stayed low in the pot. Then I put pure corn in the worm feed and the fire went out.

I'm going to seal off the holes at the top of the plates and force more air into the burning mass, since all that air is blowing over the top of the fire. I'll try that on Monday.

The picture below is 50/50 corn/pellet. There is alot of wasted air over the fire that could be used lower in the pot and Monday I'll test the same mixture with all the upper plate air holes closed. And then, pure corn again.

The corn shatters easily when crushed.

Tried 1/3 corn and 2/3 pellets today with good success. Official testing next week.

Was able to burn up to 50/50, but that's about all I can get out of it. Combustion efficiency was 82% no matter what combo I used. 250-300 degree stack temperatures no matter what combo. Shut down for lunch and it fired right back up after 35 minutes. Will try to determine the AFUE rating on Tuesday.