# Building a wood chip fueled boiler



## Roger Rug (Aug 12, 2008)

Hi, this is my first post on this forium, I am in the south of England (UK)  and run a business that wash's horse rugs. We use a lot of hot water and in the winter our workshop does get a bit chilly! I have aquired from the scrap yard a boiler block from a large gas fired boiler and intend to fire this with wood chippings from a local tree surgeon that has to pay to dispose of these at the land fill site. Does any one know how to make this furnace re-burn its smoke and fumes. Most diagrams that I find on the net are hard to understand and or blurry pics from sales brochures. This will reduce ash and add to the calorific value of the free fuel.  Look forwad to any comments or sugestions  Thanks  Roger


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## Jags (Aug 12, 2008)

Roger, Interesting idea.  I have always found it impossible to keep chips dry (had a big ol' pile for a different reason).  You may find that this tread will be moved to the boiler room.  There are some pretty sharp cookies there, and they are more used to hot water than us "hot air" guys/gals here.


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## begreen (Aug 12, 2008)

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


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## Roger Rug (Aug 12, 2008)

Be Green,  Thanks very much for moving this to the Boiler Room, I suppose the project is a bit industrial At the moment we used bottled LPG for hot water and no winter heating in a 1350 sq/ft work shop, although we dont get the artic winters, here in the UK, that you guys may get, it still gets bloody cold!! and every time the gas bottle man delivers it has gone up in price, but that is the way of it! :-S


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## slowzuki (Aug 12, 2008)

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.


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## Roger Rug (Aug 12, 2008)

This is the boiler block from a big gas fired boiler


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## Roger Rug (Aug 12, 2008)

Another view of boiler


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## Eric Johnson (Aug 12, 2008)

BeGreen said:
			
		

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



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.


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## canyon (Aug 12, 2008)

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.


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## Adios Pantalones (Aug 12, 2008)

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.


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## Roger Rug (Aug 12, 2008)

Thanks for all the interest and replies. 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. I am pretty sure that with the help of a blower it will consume 25% wet chippings. I have a muck heap that has been burning/smouldring since the spring and it is fueled by shavings and shire horse dung every day and the shavings have pee'd on, A beeze keeps it going, so the tought train took me down this road!! So the idea may be a pile of horse **** but I think it might work. Just got to get the design right. Horse dung has a high sugar level and may well become the next fuel experiment!  Any sugestions are welome.


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## Eric Johnson (Aug 12, 2008)

They make boilers in Sweden specifically for burning horse manure.


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## maurice (Aug 13, 2008)

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


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## Redox (Aug 13, 2008)

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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## canyon (Aug 13, 2008)

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.


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


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## Roger Rug (Aug 13, 2008)

Thanks again giuys for all your in put, it all makes sense!  Had re think and am now thinking about making a gassifier furnace much like the Econoburn on the add at the bottom of this page, sure it will have to have a blower but the cost of the electic to run that is minimal. The burning gasses will be directed into the void where the gas burner was sited in side the boiler/heat exchanger.
Looking at running one jet back into the combustion chamer to help the burn, a bit like a charcoal kiln, may try to make a mock up out of a ten gallon drum over the week end.
It is stange that all the re-newable fuel furnaces and home heating systems are either on the other side of the pond or Scandinavian or Europian, the Uk does not seem to be getting thier head round it, just putting gas and electricty prices up by the day.
Bring back horses and heat your home with thier waste product!! oh if it was that simple Will keep you all posted, this is the first forum I have ever joined on line and amazed at the community spirit I have found here  Thanks again Roger


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## Eric Johnson (Aug 13, 2008)

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...
> 
> ...



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.


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## Redox (Aug 13, 2008)

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


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## maurice (Aug 14, 2008)

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?)


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## renewablejohn (Aug 14, 2008)

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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## Redox (Aug 14, 2008)

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


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## leaddog (Aug 18, 2008)

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.
> 
> ...



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


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## Willman (Aug 18, 2008)

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


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