Author Topic: Wood Chip Stove (Read 20218 times)

mustang19432001 · « **on:** November 11, 2007, 09:06:09 AM »

Yet another cornball theory from yours truly.

I have an interesting idea by which one could use plain old wood chips from a wood chipper could be used as fuel in a home made stove.

The idea behind a pellet stove is an auger moving uniform pellets from a storage container to a combustion chamber which combustion is assisted by air flow.

The problem with burning wood chips is the shape and size are very random.

I've been thinking about an idea for an agitator like that of a seed spreader or the use of a conveyor belt to deliver the chips to a tube that would deliver the chips to the combustion chamber.

As for the combustion chamber I'm still thinking about how to make it. I've contemplated taking a 3" diam. iron pipe 120 degrees removed, capped on both ends, and holes drilled to allow air flow as the combustion chamber along with some sort of delivery system.

Another idea for a combustion chamber is a T fitting held as a 45 degree angle. The bottom of the chamber would be a 3" diam. stud with a perforated iron disk welded inside it, then a 45 degree elbow and a pipe connecting to a wind source.

A third idea is to simply weld iron plates to form a tray.

All of the chambers would have the perforated area sealed for the wind flow.

I have seen a boiler that runs on wood chips but the boiler requires someone to "look in on it" periodically. The part that likes to jam is the auger due to the various shapes and sized wood chips can be.

The last part would be to figure out how to extract the heat.

Anyway... Thanks for reading yet another conundrum of mine

Mustang

There are none so empty as those who are so full of themselves.

wdyasq · « **Reply #1 on:** November 11, 2007, 06:58:42 AM »

http://sedorestoves.com/easterncanadaburningnew.html

No electrical power required for this stove.

Ron

dastardlydan · « **Reply #2 on:** November 11, 2007, 07:01:08 AM »

You need to look at a forge, clay

line floor, or a blast furnace

use fire brick .

Steel will burn out real quick.

Forge has clay or furnace cement over steel.

mustang19432001 · « **Reply #3 on:** November 11, 2007, 10:55:29 AM »

Those are wicked... I just can't figure out how it works... I may have to get one of those someday.

mustang19432001 · « **Reply #4 on:** November 11, 2007, 11:16:13 AM »

I see... Clay and firebrick would also make it easier to make... not to mention the fact that it would last notably longer. What would be cool is if I could design it much like a forge or blast furnace. What would also be cool is if I could fire it initially with a bellows then let the draft fire it from there. I know someone with a forge. he uses a hand cranked blower to stoke it. Once it's stoked it takes care of itself. I could male a perforated plate (or make a regular plate then drill small holes in it) to allow air flow. Time to hit the books again... I'll have to do some research on the Sedore stove too to figure out how it works.

wdyasq · « **Reply #5 on:** November 11, 2007, 12:54:24 PM »

The Sedore stove has/had a diagram on the burning. Basically, it is a 'gasifier'. Wood in the hopper area or fine fuel in a hopper basket is gasified and burns at the bottom of the front chamber. A replaceable cast iron baffle separates the gassing chamber from the back chamber.

If I were building a similar stove I would build the back baffle of heavy angle iron, welded. If it worked as I hoped, a replacement baffle of stainless steel would be fabricated. If I lived in a really cold climate, I would have provisions for water heating built in.

I might also build the entire stove taller so I could put more depth of load when using the wood chips I got paid for hauling off from the landscape folks chipping up trees.

Ron

12AX7 · « **Reply #6 on:** November 11, 2007, 09:49:07 PM »

Hello Mustang..

Yours' isn't a "cornball theory". It works.

Back in the 70s I worked for a furniture factory whose boilers had been converted from coal/wood to natural gas. During the early 70s and the energy crunch came along they installed conversions (for backup only) to run on fuel oil (the gas company threatened to cut them off).

This same company produced a lot of wood scrap lots. I mean A LOT. The equipment to burn wood was still there, but hadn't been used for many many years. (took less manpower to run gas than coal or wood) Well, I was very lucky to be at the right place at the right time. They had a collection silo that was over seven stories tall and I'd guess it was about 75 ft. in Di.

(up to that time they paid to have the wood scrap hauled away) An auger dragged the wood to the boiler room, to another auger that fed another three augers (there were three boilers).

I worked with the plants Maint. manager who was new to the company. He was a HANDS on "did it, done it" type man. He and I climbed in and out of the boiler room and (he) figured out the system unused for years.

took a few days, but afterwards we were able to "turn off the gas". and run on 100% wood/sawdust.

The factory was over 400,000 sq. ft. and 0 as in NO insulation. East central wisconsin. I'd be willing to bet that I burned more sawdust/wood splinters / chips in one winter than anyone. Ever.

The biggest trick.. to run it so hot that the wood would spontaneously combust and not exceed max boiler pressure (a bad thing).

I also have a extensive background in packaging. Which includes "product" handling and control.

With all this in mind, I too have been thinking/planning a "pellet/biomass" type stove/heater.

The auger in a pellet/corn stove is a "Volumetric" type system. Screw size/pitch vers. RPM determine how many pellets are fed. This is a poor system at best. Bulk density and "compaction" or how the pellets enter the flights of the screw can very greatly. Not to mention the issues of chance of auger jams or "bridging" of the chips in a hopper. I think a conveyor to feed fuel will not work.

Another way to feed fuel would be a "true volumetric" filler. Rather than an auger a spinning disk with a "cup" spins under a hopper fills the cup, then rotates and drops the fuel into a tube that feds the burn pot/chamber back under the hopper.. ect ect..

I've never seen one but I think this is how the Bixby (sp?) stove works. and I think this system has a better chance than an auger.

I'd plan on a very hot fire chamber. lots of fire brick and a well controlled power draft. also plan on dealing with ash. Lots of it if the fire burns cool.

Don't extract the heat at the point of fire, plan on how the system will deal with the moisture. Many other issues to deal with, like not burning down the house (might be a part of wife appeal). L

lots of other ideas/opinions but it's getting late.

Have fun, and don't burn your fingers!

Mary B · « **Reply #7 on:** November 12, 2007, 08:35:43 PM »

The Bixby does use a cup system. From the descriptions and a couple of pictures I have seen it is a ferris wheel arrangement that dumps one cup at a time into the burn pot. The Bixby's have issues with different sized fuels because the varying sizes amount to more or less fuel in each cup. If the fuel source was first fed into a grinder that made it all a similar size it would work.

zap · « **Reply #8 on:** November 12, 2007, 10:40:50 PM »

It is a ferris wheel but not really a 'cup' but more of a slot as seen in the following link.

http://www.hinkletown.com/brochure.html

12AX7 · « **Reply #9 on:** November 13, 2007, 12:41:13 AM »

it seems others have been looking into the makings of pellet/corn stoves....

BrianK · « **Reply #10 on:** November 13, 2007, 07:01:19 AM »

I also have been looking into pellet stoves. I went to a local farm store, and checked out as much as I could into the stoves they had on display. The one I looked at had the 45deg auger the basic concept that I got lokks like it augers the pellets up then drops them into a thick steal box tube that drops them into the fire pot. The fire pot looked to be about 4in by 4in perferated stainless. My thought was how do you keep from setting all the hopper full of pellets on fire because I didnt see anything that would stop heat from getting back up to the top of the auger. It does have me thinking about trying to just build one. The one I looked at had a $1000 price tag and I think for that kind of money I could about build at least 2 of them.

.

Shadow · « **Reply #11 on:** November 13, 2007, 09:03:02 PM »

You got most of it right, the auger spits out about 6-10 pellets at a time that tumble down a tube/shoot into the fire box. So theres really no way the fire can go back up the tube to catch fire. I think if one or two pellets ever did catch fire they would be knocked back in when the auger turned again.And it seems to need alot of forced air to keep this thing burning. Which isnt available in the auger.I know as soon as you shut off the exhaust fan it shuts down real quick, the only air it gets is forced air.

As for Wood chip stoves, I wonder if a chain drive feed system might work? I know on some of the Mix-Mills used on farms to grind grain and bales etc used a chain conveyor with a couple up-right teeth every 12 inches or so to pull the bales into the grinder. Bale elevators also have them. The type used for putting hay bales up in the barn loft. Most of them are chain drive, driven by an electric motor.

Mary B · « **Reply #12 on:** November 13, 2007, 10:07:39 PM »

I have a Corn Flame 30,000 BTU stove. It is a very simple design that uses the auger to drop tube feed. One of the issues burning corn is storage and there are many different ways to store and move corn. I built a vacuum system for mine, pictures are here http://s226.photobucket.com/albums/dd248/maryalanab/

12AX7 · « **Reply #13 on:** November 13, 2007, 10:46:47 PM »

Over the last few years I've "looked" at several different pellet stoves.

All of them had the ability to adjust the btu output.

Some of them had two augers, some dropped the pellets into the fire pot from above and there were a few that "pushed" the pellets into the fire pot (this type is suppose to push the ash up over and out of the fire pot). I've seen a few demo's (county fairs and such). I was VERY surprised at the amount of heat being sent outside.

Over the last few years I've seen the prices go up and the quality... not.

My "opinion" is the heat chamber (what the fire pot sits inside of) are too small.

Not enough area for heat exchangers, remember that "high forced draft" that's needed.

I've talked to a few pellet stove owners, the number one issue they had/have is that the "fire goes out sometimes"

Another "opinion" of mine is their taking heat away to "early".

Ever burn wood in a wood stove thats had it's fire brick removed?

An auger feed system tends to "jam". it's the nature of the beast. However if one spends any time working out the "details" of the "transition" point. Where your trying to push pellets (or woodchips) into a small tube/hole and prevent any air flow from the same). I don't know how one would do this with an chain or a conveyor belt.

A properly designed "volumetric" (I'm not real keen on bixbys term "fairies wheel) system is another "proven" method.

The comment about pre-grinding the woodchips is very good idea as long as you don't spend a lot of money/time doing it. course, same is true with making wood chips. If their FREE.. that's something else!

in the end.. it's gotta be safe. can you sell it to your insurance company?

I've thought an outdoor biomass/boiler. (no pressure in the boiler)

Don't let the family sing to you.. "burnin down the house"

and have fun!

12AX7 · « **Reply #14 on:** November 13, 2007, 10:55:40 PM »

Hello MaryAlana,

one quick question. Are you using vacuum to transfer the corn from outside to inside?

I've thought a bit on this idea and I worry about the amount of "cold" air being brought into the house.

I'm thinking of using a "spiral" something like an auger. just the volume of fuel with it's surrounding air bing brought inside.

BigBreaker · « **Reply #15 on:** November 14, 2007, 01:22:56 PM »

One solution to fuel feed is to use a gasification style furnace.

Gasification uses a two step process. First wood is pyrolized into wood gas and second the wood gas is burned. It's pretty easy to regulate the gas and the pyrolization step is not especially sensitive to variations in the feed rate. Many gasifiers are batch fed for a days heating. Normally they use an electric blower, a negative.

Mary B · « **Reply #16 on:** November 14, 2007, 03:26:42 PM »

The inside container is sealed and has to hold a vacuum. I use a 6.5hp shop vac to pull the corn in and it is also used to transfer corn from the trailer to the big square tanks. The shop vac seems to heat the air a bit but as soon as I find the right connector for my shop vac and am going to vent the dust back outside and run without filters. The room I have the inside barrel in isn't heated other than what seeps in from the rest of the house so a bit of cold air isn't a problem either. Keep in mind you only pull corn in about every 4-7 days depending on outside temps. www.cornvac.com is where I bought my corn cleaner and http://forum.iburncorn.com/index.php has a wiki link at the top of the page for another corn cleaner that is made from pvc pipe. Lots of good ideas there also for corn/pellet storage.

Mary B · « **Reply #17 on:** November 14, 2007, 03:35:00 PM »

Exhaust temps vary from design to design. Mine runs about 190 degrees. But one thing you don't want in a corn burner is condensing flue gas, they are extremely corrosive and will eat stainless in a year from the chlorine and sulpher content. The heat exchanger designs have to be designed around those limitations and some of the stoves are approaching 90% efficiency. As soon as someone finds a material that will stand up to the corrosive gas I expect to see better efficiencies and the use of PVC as a vent pipe. The active fire is also very small compared to a wood stove so the comparison can't be used. In my stove there is maybe a cup of corn burning at a time compared to having several logs burning. Auger jams happen but I haven't had one yet this year and I have been burning corn for 6 weeks already.

wdyasq · « **Reply #18 on:** November 15, 2007, 08:22:00 AM »

MaryAlana,

You may want to look for a vacuum motor by itself to put on top of your corn bin. 5 years ago they were $15-20. If noise is a problem, the Fein Vacuum is very quiet.

Proper tubing runs can increase efficiency if that is desired and be aware the material moving against any plastic pipe can create a static charge. Discharge of this charge can cause an explosion.

Nice setup, thanks for posting.

Ron

mustang19432001 · « **Reply #19 on:** November 15, 2007, 10:17:54 AM »

an Ingenious idea.

It seems possibly that the wheel design could be modified have holes in for the wood chips and a plate behind it to hold them in place until the serving "cup" meets the hole, where the chips would fall down a tube to the burn pot.

TomW · « **Reply #20 on:** November 15, 2007, 11:22:47 AM »

That wheel setup is a dead ringer for planter plates like they used in old JD planters to use different size seed. It would not be too hard to make it tunable for different volumes, either.

Cheers.

TomW

Mary B · « **Reply #21 on:** November 15, 2007, 05:18:42 PM »

I have the tubing grounded, I doubt I get enough dust for an explosion but the static shocks can be pretty nasty. The shop vac moves a lot of air which is what is needed, I doubt a vacuum pump would provide the needed airflow to make it work. I have 1 1/2 inch pvc, the people at Cornvac recommend 1 1/4 on long runs or 1 1/2 on short. My longest run is 30 feet which is pretty short. Some are moving corn over 100 feet.

wdyasq · « **Reply #22 on:** November 15, 2007, 05:43:26 PM »

The "Vacuum motor" I would recommend is the type used in 'shop-vacs'. By eliminating bends and all kinds of other stuff you can get more air-flow. All it would do is free the shop-vac and move the corn faster. The next step up gets pretty industrial.

Ron

12AX7 · « **Reply #23 on:** November 15, 2007, 08:07:26 PM »

Hello MaryAlana..

another quick question, The 55gal. barrel, it holds a 4-7 day supply of corn? and it's (about) 4 days running at full 30000 btu output? and is that 24/7?

Mary B · « **Reply #24 on:** November 16, 2007, 10:49:25 AM »

Yes, thats running 24/7. On warmer days I turn the stove down so usage varies. Different stoves might use less or more. The Corn Flame is a very basic no frill stove, the more modern ones with computer control are more efficient but that comes with a much higher price tag. I have seen the same stove I have for $599 on eBay.

Mary B · « **Reply #25 on:** November 16, 2007, 10:52:53 AM »

loosen one screw and I have use of the shop vac for other things so it isn't a big issue. The way my storage is setup I can't eliminate any bends but I used 45 degree bends to keep the jamming to a minimum. It is possible to move the corn to fast and lose effectiveness on cleaning it also. The cleaner the corn is the fewer problems you have with auger jams and general buildup in the stove.

12AX7 · « **Reply #26 on:** November 16, 2007, 08:03:29 PM »

MaryAlana..

The issue with "toxic gases" developed if "too much" heat is extracted before venting outside, Living in WI. where the deep winter temps may be -25f Sending out 190f outside just seems sinful.j Room for improvement? if so any ideas how?

Have you "automated" the fill to your corn stove? Any chance of a few pics of your stove setup?

About the plugging problems you have re the 45degs. If you haven't already tried, an adjustable "vent" hole at the 45 may help this (if it is a) problem. The added air flow my help "string out" the corn as it passes though lessening the chance of "bridging".

Not to high jack this thread completely, on the same subject.. I don't think this style "transfer" system would work very well with wood chips. I think that their rough edges may cause them to "nest" together. Kinda like velcro.

Also, grinding up the wood chips is a subject worthy of further discussion. (I'm looking for "other" ideas) I'm thinking it's possible that the "pulverizing" act may cause more "bulk", causing further storage problems.

Mary B · « **Reply #27 on:** November 16, 2007, 09:47:01 PM »

My stove is a no frills model, I use a 5 gallon bucket to fill it :-) I have seen pictures of setups that dump directly into a hopper of the stove or furnace. I have add air valves at the last bin. Adjust added air to get good flow versus cleaning.

I was thinking of using the ground chips in a system that blows them into the fire pot. The air not only moves them but it supplies the power draft for the burn. There are several people using that method to clean and load corn into bins. Forced air draft to the fire pot will result in higher temps to use for heat.

If someone can find a high tech ceramic or plastic that is also a good heat transfer medium I see no reason a corn stove couldn't be made 90+% efficient. Until then there is the problem of corrosion.

No pictures of the stove but it is the Corn Flame 3000 www.cornflame.net very basic with minimal electronics. Room blower speed and a timer for the auger.

ghurd · « **Reply #28 on:** November 17, 2007, 06:01:23 AM »

"If someone can find a high tech ceramic or plastic"

Pyrex type glass?

G-

Mary B · « **Reply #29 on:** November 17, 2007, 11:07:07 AM »

It would be tricky to mold it for a heat exchanger. And cost is another issue. My vent is rated for corn and after 1 season it is showing some signs of corrosion.

12AX7 · « **Reply #30 on:** November 17, 2007, 02:52:42 PM »

MaryAlana,

The corrosion problem in the vent, is it the whole length of the vent?

Is there also a corrosion problem with the heat exchanger, or is it that you would expect corrosion if one were to extract more heat?

Mary B · « **Reply #31 on:** November 17, 2007, 03:09:05 PM »

Any area that gets cool enough to allow the exhaust gas to condense corrodes. There is some internal corrosion to the stove also but it isn't anywhere near as bad. Another thing is that any heat exchanger design has to be able to pass fly ash and have some method to clean the inside.

mustang19432001 · « **Reply #32 on:** November 19, 2007, 07:00:29 AM »

Only in the case of wood chips I may want to either run the chips through a chipper and have a simple 1"deep 1"wide hole or use a place where the holes are 1.5"-2" diameter by 1" deep... much like a revolver cylinder.

News:

Author Topic: Wood Chip Stove (Read 20218 times)