wood gasification and secondary combustion

[machinemaker]

I am starting to design a hot water heating system for my home and shop using wood gasification and secondary combustion. has anyone out there either made or purchased a wood fired furnace that uses this technology? and any ideas?

[JAK]

I would use the Rocket Stove design, modified to heat a replaceable hot water tank rather than a pot. The advantage of this design is that it is very simple and efficient and scalable, and can all be built of inexpensive ceramic except for the hot water tank itself. The low cost insulative but structural ceramic can be made by firing a mixture of sawdust and clay at high temperatures. Another advantage is that it is very vertical so as to take up less floor space. The disadvantage of this design is that the fuel is normally fueled continuously, as for a cooking fire. I think it could be modified however by adding a wood gasification chamber at the bottom, either beneath or surrounding the primary combustion chamber, or perhaps even surrounding the rocket chamber, but such that it vents into the primary combustion chamber. You could also stack the hot water pot on top of a charcoal making pot which vents to the rocket chamber directly underneath it. So you could make charcoal while heating water, and then use the charcoal in the next firing.

Anyhow here is a link to the Rocket Stove Design manual:

http://web.mit.edu/ats/Documents/lesotho%20refresher%20oct%2005.ppt#16

[machinemaker]

JAK,
Thanks for the ideas. I have been scrounging materials for a while and want this to have some mass. I own a machine shop / steel fab shop, and foundry so I am used to working on even a larger scale. I have two vertical steel air tanks that where given to me, one 250 gal. one 125 and about 200' of 3" pipe. I have thought about using the 3' pipe to make the equivalent of a water tube boiler, (but no pressure). I am hoping that with that much storage and lots of insulation I can keep the water hot enough to heat our home and my shop with one large fire every couple of days. I saw a website for a smaller version of what I was thinking about at www.blueforge.com, however they never respond to emails. I am trying to reduce our propane use and be less dependent on gas and electricity. Thought I'd run the pumps off of 12 vac or some other dc voltage. One other concern is that at our elevation water boils at 198 rather than 212, but I doubt that will have too much affect. I have wondered about water treatment to reduce rust. I used to operate boilers and water treatment was a big issue. I have heard and seen rocket stoves and like the idea of a fast efficient burn as opposed to the slow fires we use in our wood stove. I'll look at the site after I'm done here.
Thanks
kent

[jott]

I would consider just using antifreeze, it is available anywhere, it will prevent rust, and it will raise the boiling point. If you talk to some local garages they could probably tell you where to get it by the drum.

[SolarGary]

Hi,
This is just a thought, but you can store water at up to about 170F in an inexpensive EPDM lined tank.
If you make the tank large enough, it could hold enough heat to heat a house for days (depending on the house heat loss).

This is the one I use:
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/Tank/Tank.htm


You have metal working facilities, so the STSS cylinderical EPDM tanks might be more to your liking:
http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm#Storage

just look down the page a ways for STSS. these are just a simple cylinder of sheet metal with an EPDM liner and insulation.

On these types of tanks (if you make them yourself) the insulation is the most expensive part. You might want to consider a way to build the tank such that it could be insulated with cheap insulation (like cellulose).

Gary

[machinemaker]

Thanks for the suggestions. Jott,I figured that I would use some type of antifreeze and my experience is if you can buy an industrial product from an industrial supplier it is always cheaper than buying a consumer product. Gary, thanks for the build solar website, lots of neat stuff. I'll have to spend some time exploring there. I have thought of doing more solar here with our nearly continuous sun shine in the Colorado mountains. I have also wanted to build a wind turbine. We live on a mountain pass at 9500' and have great potential for both solar and wind. Maybe that makes up for our lack of growing season. I figure that I would build everything in a small building with thick walls, tanks and equipment packed in tight and just stuff any open spaces with fiberglass batts.
Thanks again,
kent