homemade gasifier wood boiler

[Jvagle]

I am looking to start the process of building a gasifying wood boiler to be placed in my shop. I know that the fireboxes have to withstand temperatures of at least 2000 degrees. I have found a supplier relatively close that can supply me with castable refractory mortar that can be used to make the floor of my firebox. I am wondering if anyone has good pictures of the "inside" of a gasifier? I would like to see how the firebox is supported and what materials are used.

Thanks in advance for your input and help

Joel

 

[Nofossil]

I am looking to start the process of building a gasifying wood boiler to be placed in my shop. I know that the fireboxes have to withstand temperatures of at least 2000 degrees. I have found a supplier relatively close that can supply me with castable refractory mortar that can be used to make the floor of my firebox. I am wondering if anyone has good pictures of the "inside" of a gasifier? I would like to see how the firebox is supported and what materials are used.

Thanks in advance for your input and help

Joel

It's a great project, but you'll want to spend a good deal of time really studying a gasifier. There's a lot more technology than meets the eye. If you search a bit you'll find threads that discuss home-made gasifiers. Some have been successful (my brother made an interesting one) and some have not worked out well. Materials is part of it, control systems are another, and gasification science is another. The ratio of primary and secondary air, the air flow rates vs. nozzle area, excess oxygen percentage - all these are important and difficult to get right.

 

[Singed Eyebrows]

What Nofossil said. I was going to build one & have the fabricating skills to do this, however, when I added up the cost of good boiler plate, etc etc etc I was within about $1000 of buying one. There was also after spending a lot of money & time, no assurance it would work. I would help you with my Atmos if I could, there are passages, heat exchanger, that are all welded in with no way to look at much less measure, Randy

 

[Jvagle]

If I cave a fully ceramic firebox and combustion chamber will I still need to use boiler steel? My plan was to use 2.5" thick fire brick for the front, back, and sides and then pour castable refractory cement for the top and bottom. I would then make a frame out of 1/4" x 3" angle iron for a support system and then use 1/4" steel for a divider between the firebox and the heat exchanger. The design I am going for is similar to the EKO gasifier.

Thanks
Joel

 

[Nofossil]

The temperature gradients get pretty intense. I've turned 2500 degree high alumina firebrick into gravel in the combustion chamber. You'll also need to think about the floor of the upper chamber. It's relatively cool on the top and REALLY hot on the bottom, and it has to hold up the weight of the firewood. It also needs to hold the nozzle and the air passages that feed the nozzle.

The nozzle itself probably needs to be ceramic - it takes a thermal beating.

 

[Singed Eyebrows]

If I cave a fully ceramic firebox and combustion chamber will I still need to use boiler steel? My plan was to use 2.5" thick fire brick for the front, back, and sides and then pour castable refractory cement for the top and bottom. I would then make a frame out of 1/4" x 3" angle iron for a support system and then use 1/4" steel for a divider between the firebox and the heat exchanger. The design I am going for is similar to the EKO gasifier.

Thanks
Joel

Joel, You need to have a separate primary & secondary chamber & I'm not sure you understand this. The nozzle separates the 2 chambers. As the Mod says you need to feed air to the nozzle & this needs to be heated air. You also need primary air into the top chamber to give a measure of pyrolosis, this cannot be just "any amount" of air. After the nozzle isn't a big deal, you just duct this to your firetube exchanger, 6 vertical tubes around 3" dia should be close for around 125,000 btu. You are concentrating on using a lot of ceramic & while gassers have some it is not just "covering everything up". Are you going to use forced draft or induced draft? Induced draft is preferable if unit is inside home. Why don't you draw something up & post a pic or 2 maybe we can help some that way, Randy

 

[tom in maine]

I think it is imperative to have a secondary containment (boilerplate or something like it) between the firebrick or refractory and the outside.
I, too, have destroyed high temperature refractories and had them turn to dust or gravel.

A good burning wood fire can hit 3000F, without warning.

The little boiler we have posted on Youtube has 3" of vermiculite cement insulation and 1" ceramic fiber and the surface temperature is too hot
to touch after a couple hours.

 

[Jvagle]

I definitely will have two separate compartments one for fuel and a nozzle at the bottom going to the second bottom chamber. I am a High School shop teacher so I am going on break for Christmas and hopefully I can get something drawn up that I can post so those of you giving me feedback and info can see what I am thinking.

Thanks for all of your suggestions thus far!

Joel