Coalpail.com Forum

Hi all. My father and brother both invested this summer in an outdoor pellet/corn boiler back when we all thought heating oil was going to $5/gallon. They considered coal as well, but the fact is that as potato farmers, they always have some sort of grain they grew as a rotation crop. And, with the low prices they have gotten historically for the grain, they thought they might as well burn it. A business acquaintance bought one of these last year, and has been burning all sorts of things in it with success... rye, barley, cherry pits. Basically, anything he could get for free or cheap, that was granular enough to go through the machine seemed to burn OK.

This is the unit:
http://www.maximheat.com/

Here's a few pictures I took of my father's unit during Christmas.

They put their units in their garages. Why trudge through the snow?


A 43-bushel hopper and auger saves constant filling. They bring oats in old oil drums in the back of the pickup. Takes 7 to fill the hopper. (The internal hopper is only 7 bushels.)


Inside the unit more oats trickle in.
**Broken Image Link(s) Removed**

Pex to the house. The unit uses propane to light up your fuel.


Here's the burn chamber, heat exchangers off to the left.


Burning. Dad's is pretty dirty. Needs regular cleaning.. just scraping. My brother's is cleaner... with a bigger house and 3 kids and their showers, his unit runs at full blast much more often. Dad's unit has to idle sometimes.



Ashes are pushed forward by incoming fuel and by the agitator. The agitator is there to aerate the burning matter and break up clinkers. Dad scoops out the ashes with a grain scoop into an oil drum. Seems to run about 15 drums oats = 1 drum ashes. Oat ash is interesting, you are left with little black oats.

Interesting--thanks for posting. Good pics.

Is that oat residue (oatmeal?) on the inside surfaces of the burn chamber? How many pounds do they burn per day?

Potato skins are next!

Thanks for sharing. Free fuel is good fuel. If you can find a way to stay warm in the Northern part of the state you've done well.

Interesting....
looks pretty messy...also, what the propane tank for?

The unit uses electricity to light the propane, and the propane flame ignites your fuel. While wood pellets light well electrically, it is very hard to get corn to light with just a hot element. Even harder to get a pile of grain to start burning.

How many pounds per day? That's a bit trickier. They have never really measured it, nor run the hopper dry. Dad believes it to be about 120 pounds per day, average. My brother's burns about 150. With oats, like other biomass, you can use a rule-of-thumb that 20 pounds = 1 gal oil. (For reference, Dad used to burn about 1000 gal annually.) The house is warmer than when they burned oil. Knowing that their money is no longer going into Arab pockets, Mom and Dad feel free to turn up the thermostat!

Dad's unit was dirty, but it wasn't cold around Christmas, so he had to idle a lot. Curiously, the smoldering oats make the garage smell vaguely of pot. It has been colder lately, so he has burning hotter for longer periods of time. The inside is much cleaner now. My brother's house demands more heat, so his unit has always been cleaner.

I would also note they are burning oats as harvested. There is chaff and bits of straw in the mix. Were one buying hulled grain or shelled corn, they would get a cleaner burn. But, my father and brother would be growing some sort of grain for rotation, even if just to plow in under.... so their fuel is essentially free.

Does it smell like toasted oats or anything?

At full blast, there is no smell. As I mentioned above, at low burn, the smoldering oats make Dad's garage smell vaguely of pot.

I had read that these fuels are often highly acidic and the maintenance costs are really high due to this fact. Many of the bio-fuels are much more acidic than coal (cherry pits for example)

Any thoughts on this?

thx

neat!

av8r wrote:I had read that these fuels are often highly acidic and the maintenance costs are really high due to this fact. Many of the bio-fuels are much more acidic than coal (cherry pits for example)

Any thoughts on this?

thx

This concern puzzles me, since biomass ashes can be used as a liming agent. Corn ash has a pH of around 10, oak ashes have a pH around 13.7. In fact, you can make lye by leaching wood ashes. Biomass fuel before burning won't be highly acidic. Although cherries are slightly acidic, that is the actual fruit. I can't imagine the pits are acidic enough to be a concern. That covers before burning and after burning. What about during the burn?

The major source of acid in combustion would be from sulfur in the fuel. Burning sulfur will produce sulfur dioxide which can combine with water to form sulfuric acid. Should this condense out of your exhaust gases, you have the potential for corrosion. The solution, as always, is to maintain a flue temperature high enough to avoid condensation. Coal has some sulfur content, which I imagine varies greatly from vein to vein, so would have the same issues. (You also get nitric oxides forming nitric acid, but with a boiling point of 83 degrees C [181 degrees F], it is less likely to condense out. Sulfuric acid boils at 290 degrees C [554 degrees F], so is the condensing culprit.)

I've never seen an elemental analysis of such crops as corn and oats, but I can refer to how much sulfur these crops need.
A 160-bushel-per-acre corn crop (8480 lbs) pulls 12 pounds of sulfur per acre from the soil.
A 50-bushel-per-acre winter wheat crop (3000 lbs) pulls about 4 pounds of sulfur from the soil.
Oats aren't sulfur hungry... in sandy soils, you might add only 10 lbs per acre.

Here's an article where a coal power plant added oat hulls to the combustion in order to lower acid emissions. (I know... most likely bituminous coal.. more sulfur than anthracite.)
http://www.facilities.uiowa.edu/CoalPowerFall2006.pdf

Interesting. I'll try to find where I read this. I was looking at biomass stuff a few years ago and I could swear I either read this or was told this by someone....hmmmm

I know corn ash is very acidic. It will eat away stainless steel. I does not do much damage until it gets a little moisture in it. So just like coal you must clean your appliance in the off season or you will get a lot of rust and corrosion.

gambler wrote:I know corn ash is very acidic. It will eat away stainless steel. I does not do much damage until it gets a little moisture in it. So just like coal you must clean your appliance in the off season or you will get a lot of rust and corrosion.

I do not say this just to be argumentative, but corn ash is not acidic. It has a high pH meaning it is alkaline.

Stainless steel is merely corrosion resistant, it is not impervious to corrosion. It is still susceptible to galvanic corrosion. It is especially susceptible to salts, as the chlorine ion disrupts the passivation layer (the chromium oxide layer that forms on the surface, which is what protects stainless steel), and allows the steel to rust. Abrasion is also a problem, as the passivation layer is constantly rubbed away and exposes the steel. Stainless steel can also become pitted, often because foreign matter has adhered to the surface, cutting off the oxygen and preventing the formation of the chromium oxide layer at the spot. As the pits become ever larger, the stainless steel becomes weak as corrosion penetrates throughout the metal. Know how they recommend solving this? Cleaning the stainless steel with acid! The acid removes the debris, the chromium oxide layer has a chance to reform, and your steel is stainless once more.

So, those stainless steel parts you thought were being eaten by the corn ash? A regular acid bath would have prevented the problem nicely.

Now, corn ash would be really hard on aluminum. Aluminum too has a passivation layer, it is protected by a layer of aluminum oxide... essentially sapphire. This layer does not behave well in high pH , so the aluminum will corrode.

Just for fun... mercury destroys aluminum. Check this Popular Science article: a little mercury paste on an I-beam, a scratch to get the mercury past the passivation layer, and..... bye-bye I-beam.
http://www.theodoregray.com/PeriodicTable/Popular ... .small.jpg

OK, Sounds logical enough. I can't argue with you on the reason corn ash attacks metal venting systems. All I know is from first hand experience that burning corn causes even stainless steel to become pin holed in a couple of years if ash is allowed to remain on the surface of the stainless through the summer. I have also heard but can not personally verify that corn exhaust will degrade the mortar between the tiles of a clay lined chimney. So for what ever reason the corn ash is hard on venting systems to the point that most venting mfg will not warrant claims when used with a corn burning appliance. Many have gone to using AL29-4C grade stainless to combat the corrosion issue.

http://www.brownmetals.com/downloads/AL29-4CTechSheet.pdf

BUMP ^^^^^^^

An interesting read...and full of some facts that may be good to be aware of...