Building a wood chip fueled boiler

In europe there are a lot of chip burners around. The one's I've seen are a little fire brick lined chamber with a blower and chip feed that sits next to a conventional boiler. The combustion products are blown into the old conventional boiler next to it to extract the heat.

BeGreen said:

Moved to the boiler room so the guys with the tatoos and hairy chests can help out. :lol:

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Hey, I resemble that remark!

Here's a couple of European chip burning boilers on display at a recent trade show. They told me that you need chips dry to about 20% moisture content for them to work right. I think getting dry fuel is probably the biggest challenge to successful chip burning.

I would look at your recycled boiler as a heat exchanger and build a separate primary/secondary combustion furnace. The old way of extracting heat from the combustion area is wasteful and polluting. Insulate your combustion area(firebrick most common) and provide adequate air, turbulence and time in the high temp area BEFORE you harvest the heat with your old boiler/heat exchanger. Pre-drying the green chips will be key. I am not sure what the best design is for burning wood chips but I am interested as well. I think a fluidized bed is a common method. Hopefully someone else with experience here can comment.

I agree with canyon. Some sort of gasifier may be the ticket. There was a thread in the Green Room on wood fueled cars, which typically ran on chips I think- generating a combustible gas. There was a link to plans for a gasifier for running an engine- there's no reason it could not be adapted to your purpose.

One issue with drying chips is that air doesn't move through a pile so easily. In the UK they'll compost in a pile before they dry. If at all possible- you might see if you can get whole branches and dry them in a brush pile- so that air will get to all parts first. Then chip and store dry or just before use.

Otherwise- you'll need some place to spread them thin and dry.

They make boilers in Sweden specifically for burning horse manure.

I found this site, and have been emailing him with an idea of buying his plans - http://mysite.verizon.net/vzew10av/id1.html He does not have much info on the site, but tells more in email. For instance he hits 2000 degrees.

This guy has a great concept but he dropped the idea - http://www.sredmond.com/vthr_index.htm I have not been able to get a response from his site.

I'm not finding the webpage right now, but I did find a site that has a government guide for schools/municipalities/hospitals who want to build huge wood chip boilers. But I did not find it very helpfull.

Wood-mizer (American sawmill for small operators) has or had been working on a sawdust burner boiler. They called it Bio-mizer. Forestry forum has 31 pages on this topic http://www.forestryforum.com/board/index.php/topic,23473.0.html They had some discussion on how wet the sawdust can be. Wood chips were too big, but there may be some hints on how to burn bigger chips.

I'm a member of Machine Builders.net, here is one of the members who built a boiler that will burn anything, he is also working on a gengas unit to power an engine. http://www.machinebuilders.net/forum/forum_posts.asp?TID=4367&PN=1

Where's renewablejohn when we need him? He is also in GB and working on something like this . Maybe you can run a pipe up to his plant?

Chiptec makes a gasifier that basically bolts on to a conventional boiler, but they don't do "little" boilers. I haven't heard much chatter about them on here...

http://www.chiptec.com/

Chris

Roger Rug said:

what I have in mind is a big boys version of a smoke re-burning house stove with the boiler/heat xchgr in side the fire box and draw the heat through the spiked section of the boiler and re burn the smoke.

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To "reburn" smoke you need to have the proper amount of air,turbulence and temperature. If you have the heat xchgr in side the fire box you will cool the smoke down and not "reburn" it. Burn it all first and then harvest the heat in your heat xchgr. Maybe something is getting lost in translation?
Bob's your uncle

Redox said:

Where's renewablejohn when we need him? He is also in GB and working on something like this . Maybe you can run a pipe up to his plant?

Chiptec makes a gasifier that basically bolts on to a conventional boiler, but they don't do "little" boilers. I haven't heard much chatter about them on here...

http://www.chiptec.com/

Chris

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Chiptec used to make a small, domestic chip burner called the EnerChip, invented by a guy from White River Junction, Vermont named Cliff Valley. It was a really sweet little chip burner that would burn green chips. I don't know why they don't make them anymore, but as you say, Chiptec is into bigger installations (schools, industry, etc.) these days.

I have seen one of their installations at a wood products manufacturer here. It looked like a very well thought out design with VFDs on the fans and material handling end and was controlled by microprocessor. The main gasification chamber was a huge ceramic vault that bolted up to a more or less standard steam boiler. The chief engineer running it said there was a long learning curve before they finally got it tweaked just right, but that they were saving $20k a month in oil for their kilns. They apparently got it to pass MD environmental regs and had been running more or less problem free for about a decade before it finally popped a drive. It even calls out for help when it's not "happy"!

I suspect that it is the learning curve thing that is keeping these devices off the market. We keep looking for "easy" solutions for our problems and high fuel costs are the result. Biomass isn't "easy" enough yet, but the times are a changin! Let's hope we start to see more of these European designs making it across the pond or some good 'ol American ingenuity filtering to the surface.

Chris

As I see it, new inventions comes from those who are not waiting for someone else to invent it.

I can see that a long learning curve can deter selling to the general public. And as with the Vermont chip burner I linked to, there can be problems that show up in a low percentage of burns. (Is this called making it idiot proof?) BUT, for those of us mechanically inclined, I think we can invent some burners.

For instance, I did a very simple crude experiment. From my scrap pile, I dug out a 6" steel pipe about 4 foot long, a riding mower front wheel (no rubber), drilled a 1 inch home in the rim. I set the pipe on the center of the rim, filled it with damp wood chips (from a tree trimming service), started a fire at the bottom, then used an electric leaf blower to "fan the flames". I had to hold the blower to te edge of the hole (not full in the hole) but I was able to burn those chips. Yes, there was ash flying out of the top, but when I "shut it down" with a bucket of water, the steel was how enough to flash some water to steam. Crude - I took no mearsurements yet.

So, if you chose to not worry about gasification just yet, but to get something up and heating, just add enough air to the combustion.

If someone figures something out, I would think there would be a market for selling the plans? (Look at ebay for homebuilt OWB boiler plans - $30 multiplied by 900 sells?)

Roger Rug

I am always scared when people start designing woodchip burners as woodchip has a nasty habit of exploding due to gasification. Fine if it is controlled but scary for the unwary.

For a medium size boiler requirement have a look at

http://www.farm2000.co.uk/refo.htm

This will burn quite wet woodchip but I would always dry my woodchip down to 20%-30% moisture in a polytunnel. Always wear a filter mask as the fungal spores can be a killer. Also keep the woodchip less than 1 metre deep as it can spontaneously combust.

For a larger burner try

http://www.dunsterwoodfuels.co.uk/chippy.html

If you want more advice on using arb waste please PM me

See! I knew he'd show up sooner or later. Howzit going John?

Funny you should mention explosion; there was some kind of explosion in the conveyor system at the aforementioned wood products company that was never explained. It basically blew the covers off the infeed screw but didn't cause any major damage.

That is some interesting equipment you linked to. Once again, it appears that Europe and the UK are ahead of us in figuring this stuff out. One day, we'll get our act together...

Chris

renewablejohn said:

Roger Rug

I am always scared when people start designing woodchip burners as woodchip has a nasty habit of exploding due to gasification. Fine if it is controlled but scary for the unwary.

For a medium size boiler requirement have a look at

http://www.farm2000.co.uk/refo.htm

This will burn quite wet woodchip but I would always dry my woodchip down to 20%-30% moisture in a polytunnel. Always wear a filter mask as the fungal spores can be a killer. Also keep the woodchip less than 1 metre deep as it can spontaneously combust.

For a larger burner try

http://www.dunsterwoodfuels.co.uk/chippy.html


If you want more advice on using arb waste please PM me

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I really like the looks of the refo but they aren't interested in selling them over here. I tried to buy atleast three and they dont' sell here in the states. tobad as I think there is a HUGE market for something here like that.
Leaddog

I see the "Chippy" has an optional humidification feature for burning kiln dried wood waste. It seems that there is such a thing as too dry. Awesome equipment. All we need is somebody building them here beings they don't want to sell to USA. With the pound sterling real strong against the buck one would think they would be all over shipping them west.
Oh well we can still dream right.

Will