The Fred Flintstone Boiler

[Jimxt88]

Here's what Fred told me: I want to transfer heat energy from a combustion chamber to air enclosed in a dwelling. I want to use my existing baseboard hot water pipes as the heat exchanger, exactly as I did when I was heating the house with oil. So now the question is how to get the heat into the water in the baseboard pipes and circulate it. Okay, those are the givens. Now, here's what I'm thinking; dig a hole in the cellar, 6' x 6' x 6'. Line the hole with concrete, sides and bottom. Mortar in a flue collar for a stove pipe exiting this box. This flue collar will hold a stove pipe that will enter my chimney. In the middle of this concrete in-ground box, build a smaller concrete box, say 3' x 3' x 4'. This smaller box will be my combustion chamber. Fill the space between the two boxes with rocks. Install air intake pipes which will pass through the outer box and into the inner box for make up air and combustion oxygen. These air inlets can be closed to extinguish the fire or opened fully to feed the fire. Design the combustion chamber to create an aggressive, hot, cleanburning fire to charge the rocks. The charge should hold for at leat twenty four hours. Exaughst from the combustion chamber will pass through the rocks before exiting the flue collar and going up the chimney. This should cool the gasses considerably and transfer almost all the heat from the exaughst into the rocks. On top of the rocks lay a network of copper tubes looped into the existing baseboard system. Heat absorbed by the rocks will transfer to the water. By thermal siphon, the heated water in the pipes will flow up into the house and be transferred into the air of the rooms above. This water now having given up its heat to the air in the rooms will return to the rock bed loop and be reheated. A sealed lid will cover the combustion chamber during firing. The rocks will absorb and store the heat energy generated in the combustion chamber during aggressive, hot, quick, clean firings.

Barney said, Fred you are assuming that rocks absorb, hold and release thermal energy more effeciently than water. You are assuming the heated water will siphon up to the radiators and back down again. You're assuming the hot water system will work much like a tankless boiler and that having air between the rocks is a better way of holding in the heat than filling the space with water. You are assuming that a horizontal, in-ground fire box insulated by rocks is going to act like a huge heat battery. What makes you thin you can design a gasifying combustion chamber that can burn unsplit wood?

Fred, seek the advice and counsel of people better experienced and more informed about these things than you are.

 

[Nofossil]

It probably would work just about as effectively in the real world as Fred's car ;-)

Rocks hold a LOT less heat than the equivalent volume of water. Passing flue gas through rocks would not work for long. Creosote, fly ash, condensation, CO leakage, and excessive cooling would all be likely problems.

Thermosiphoning is wonderful, but limited in terms of BTU/hr.

Radiant slab, gasifier, and storage is the way to go if you have the option.

Gasifiers have combustion efficiencies near the theoretical maximum for wood. You're not going to do better, but there's lots of opportunity to do worse.

There's still plenty of room to experiment and invent better systems. Plumbing, storage, pumps, valves, controls, heat exchangers - lots of variables.

 

[kuribo]

Among the other issues, concrete will not last long if used as a refractory.....

 

[webbie]

Sounds like what the romans did, so that was a few years after Fred.

Not much new under the sun. As you remember, the Romans never learned about steel nor welding.

 

[Jimxt88]

They were smart. Craig, do you know where I can get my hands on a "build your own gassification combustion chamber" instruction manual. I'm trying figure out the basic principal. What conditions have to exist and how to bring them about. It seems incredibly simple when I look at the combustion chambers in the videos on the diffrent product websites. But, for instance how does the "super heated" secondary air get "super heated". I'd like to have the science explained along with some simple diagrams. There has got to be a "Gasification for Dummies" paper out there somewhere. It is not enough for me to see the videos I want to know why and how it works.

 

[Jimxt88]

Chris, I got you that concrete will not last long if used as a refractory. What would last long? Is it possible to make your own refractory? Is it something I could mix up with limestone mortar for instance. Maybe throw in some flake graphite, or silicone carbide. Is there dry ceramic refractory powder I can buy, add water, mix and cast into bricks or slabs?

 

[slowzuki]

Look up ceramic kiln building info, they sell all the refractory mixes you need.

You sound like you want to make a masonry heater with some water pickup. There are a few challenges to what you have described, I'll try to get back to this thread when I get a chance.

 

[webbie]

I doubt that the "super heated" secondary air is really "super" heated. It moves too quickly through the unit to do that. Certainly, it is pre-heated, but the main thing is to place it into the area where you need it. In the case of the tarm, it is pretty basic and obvious. I assume more other units work in a similar fashion. The air is forced into a 1" (approx) round hole in the refractory, and that hole then leads into a bunch of relatively tiny slots which feed into the center of the refractory. By breaking the air into small pieces and running it through the refractory, you heat it and also spread it out so it feeds into the entire area where the wood gases come down through the grate slot.

There are lots of mixes you can buy. Tarm used to add stainless steel "needles" in order to make it stronger. Tradergordo had a recent post where he named a lot of the mixes.

 

[Eric Johnson]

The EKO has two steel tubes inserted in the refractory that run alongside the nozzle(s), supplying hot air to the nozzle through holes in the pipe. Here's a pic of the secondary "superheated" air inlets on my boiler.

If you want to see a step-by-step photo essay on building a downdraft gasifier (EKO knockoff), check this out:

http://server.cedarlakedesign.com/pictures/buzz/Nofossil/

We also have a guy who built his own Garn. Pretty darn impressive workmanship on both.

https://www.hearth.com/talk/threads/11262/

 

[Nofossil]

Gasifiers are deceptively simple. It's like looking at a turbine blade: simple piece of gray metal, tapered with a little twist, and a bit thicker on one edge. How complicated could it be?

There's a lot of analysis and engineering that goes into 'simple'. I wouldn't discourage anyone from trying, but understand that there is hard science involved in getting it right. If you're willing to study and learn to do the analysis that's required, you too could make a deceptively simple model that works quite well. If the word 'stoichiometric' isn't in your vocabulary yet, then the learning phase might be a bit longer.

For me, just learning about the range of refractory materials has been daunting. Trial and error is really out of the question - far more expensive than buying a commercial unit.

There are studies, test reports, and thesis papers out there. I haven't personally seen detailed plans that I place much faith in.

 

[Willman]

There are studies, test reports, and thesis papers out there. I haven’t personally seen detailed plans that I place much faith in.

Fred Seton has plans for his boiler available. He has been building them for years. Seems to be a fairly trouble free rig. I will be finding out for myself.
Will

 

[canyon]

Jimxt88 check out the rocket mass heaters book by Ianto Evans and Leslie Jackson. Do a search online. It is a design build manual for a particular homebuilt but explains many things that you are concerned with.

 

[Jimxt88]

Thank you all for your suggestions and referrals. I have and will check out all of your referrals. I will look for and find the rocket mass heaters book.

The photo and description of the nozzle and pipe for super heated air didn't explain much to me. It appears that the pipe openings shown projecting from what I assume is the back of the boiler are covered by the round metal discs attached to the back panel when the panel is in place, which would block air from entering the pipes. Where those pipes go once they enter the refractory is still a mystery to me.

The step-by-step photo essay on building a downdraft gasifier (EKO knockoff), was impressive but without text to describe what I am looking at, it is only awe inspiring and not educational. Same for the Garn photos. What a beast. Is the combustion chamber encased in a holding water tank? I mean, is that the water storage tank that holds the heat energy for distribution to the radiant heating system long after the fire has been extinguished. What are the blue tubes? The hole thing looks like a giant shell and tube heat exchanger. I tried to reach someone at Garn today but no call back or email.

Of the many things I like about the GARN: the combustion chamber is concave. That is so smart. The secondary chamber for emissions burning is not above or below the primary combustion chamber but on the same plane, and behind it. This is what tells me that there is alot of flexibility in gasification chamber design so long as basic principles are complied with. Also, both chambers are round tubes, the primary chamber larger than the secondary chamber - but just two ceramic pipes laid end to end and centered. Why does the vent from the secondary chamber appear to wrap around and come out the front? I really would like to understand this monster.

The refractory masonry referrals will surely come in handy. But I wonder if anyone is selling molds for a ceramic gasifying fire box. Molds would be alot lighter and less expensive to ship than the cast pieces.

 

[Jimxt88]

I'd like to share this video with those interested in the "simplicity" of gasification: What do you think, Nofossil? [youtube]<object width="425" height="355"><param name="movie" value="http://www.youtube.com/v/OYA-Er2zmbE&rel=1"></param><param name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/OYA-Er2zmbE&rel=1" type="application/x-shockwave-flash" wmode="transparent" width="425" height="355"></embed></object>[/youtube]

 

[Eric Johnson]

Actually, that's the front of the boiler shown in the pic. Here's the other ones from that series. Those discs move in and out on threaded rods and are the secondary air control. The pipes go into the refractory all the way to the back, with the two nozzles (the EKO 60 has 2) in between the pipes. Air is drawn into the area behind the plate holding the blowers and is then channeled into the primary combustion chamber as well as the secondary tubes.

 

[Jimxt88]

Erik, this helps a lot. So the ECO is a down draft system. Is that right? The lower door of the boiler opens to the gasifiying chamber. The fans are covered by the grill with the air holes. The yellow nuts open or close the discs that cover the holes in the ends of the pipes entering the refractory. The fans are sucking oxygen to the area around the openings controlled by the disks but the fans are not directly over the pipe ends. The pipes enter the fire box where nozzles release oxygen and then those same pipes turn 90 degrees and enter the secondary lower burn chamber providing the "super heated" oxygen described in the promotional videos. The pipes are not making a straight run but teeing off to reach the lower chamber and in that space are perferated along their length.

Sorry about that last post with the youtube URL. I don't know how to make the link to a post yet. I'll try again when the Administrator gets back to me.

 

[Eric Johnson]

Very good except that the secondary air tubes are just straight pipes that go right into the refractory and to the back of the boiler, supplying air to the nozzles in the process. Combustion air enters the firebox through the steel sliders in the upper corners of the opening shown in the third pic. Combustion air enters there, and is pushed DOWN to the base of the firebox through square steel tubes welded inside the firebox, where it feeds the fire. I believe this to preheat the primary combustion air before it reaches the primary air flame.

 

[Jimxt88]

This took the mystery out of building a gassifier. Disclaimer: I am not affiliated in anyway with Knowledge Publicatons.

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[Jimxt88]

The above video is first in a series of videos on gasification by the person who made it. It is entertaining and informative. If you're interested in watching more demonstrations by this person, you will find them on Youtube, search under "sodacan" and "gasification".