# efficient design of homemade OWB



## woodburnerdave (Sep 22, 2011)

Hello all,

I am a total newbie.  I am so new that I thought I sent this thread yesterday and it didn't go through.  I am building an OWB in my backyard out of concrete for my 2 zone heating in my 4,000 foot home with full basement in Virginia.  I'd like to build my boiler as efficiently as possible.  I have been in construction for 35 years and am handy but I am a terrible welder.   I will have an air gap between the firebricked concrete wall housing the boiler and a second concrete wall which is the outside of the building, which I see being about 8' by 10' and 8' high.

Because I cut and load my logs with a bobcat they will be 6' long, so I hope an efficient firebox could be narrow (20"h x 20"w) and long (96"), with preheated combustion air entering near the front door and mixing with coals for 8 feet before passing up to a secondary combustion chamber for the wood gases at 1100F.  In the upper chamber I will plumb 200' of 1" glavanized pipe running at 33 gpm (less pressure loss) for heat recovery.  I will try to stick some water pipes up the flue too.  I bought several books on stove design by Jay W. Shelton which will arrive next week.  Once I find out how hot my flue needs to be I will try to run the exhaust horizontally or with enough water jacket to absorb heat down to this temperature but not so low that it presents a creosote hazard.  

Any ideas how big the secondary upper chamber should be?  An easy length for me would be 96" and an easy width of 20" because it sits on top of the firebox but the height isn't set yet.  How high should this area be and how should it be designed?  Should I baffle it?  I could probably plumb the pipes to act as baffles or (poorly) weld something.   

I may also put heat exchangers at the ceiling of the concrete room for heat recovery.  The water would pass through the cooler ceiling heat exchangers before going through the hotter water and flue jackets.  Inside my home I will have about 300,000 BTUs of heat exchangers and 500' of radiant pipes.  I will first plumb the hot water through a 120,000 BTU heat exchanger on each of my two plenums, then through a water to water heat exchanger for my domestic hot water, then through basement radiators, then through a greenhouse before cycling through the  OWB again.  I am using a Taco 0010 circulating pump at 33 gpm and a 1" line in a close loop system.  I also will drape EPDM rubber in two used 275 gallon fuel oil tanks as heat sinks.  

What am I doing right or wrong?  I really enjoy criticism because I know it will save me manyhours of construction time.  I promise to send at least one joke to everyone that helps out.  Be forewarned, my joke repertoire is limited and dirty!

Thanks for any help you can give.


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## nt30410 (Sep 23, 2011)

This might be of interest to you.



http://logboiler.ca/


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## boatboy63 (Sep 23, 2011)

Welcome Dave. I have been a member here for a little over a year and have learned ALOT. I don't mean to sound like a parent to you or a broken record, but you really need to research this first. To give you an example, I don't think you want to use concrete. It will literally explode if it gets too hot. The firebrick would work, but I would prefer to go with a castable refractory. You buy this in bags just like mortar for masonary work. It will mix and you apply it just like masonary, but it will withstand high heat, is much harder, and won't have cracks in it like you would have between firebricks. 

The next problem I see with your idea is using 6' long logs. If you plan to use this as a gasifier, the wood may be dry enough for your grandchildren. Most of us use split firewood in the 16-24" range and it can take up to a couple of years to season properly. I would about guarantee you that you could take a 6' unsplit log, put it in the dry for 5 years, then cut it in the middle and you would find it was nearly as wet as it was the day you cut it down. Wood cures from the outside ends toward the center. If you did manage to get a fire hot enough to burn these, you would lose half or more of your btu's from the wood just trying to dry the water out. The trick with a gasifier is that the wood has to be truly seasoned and dry.

The last thing I will mention is the use of galvanized pipe in a boiler. I was thinking about using it in mine until I read deeper around here. Someone can correct me if I am wrong, but galvanized can actually create a form of acid when used in a boiler. I don't remember the details of it, but maybe someone will come in and explain.

Don't get frustrated. I have been in the same boat as you. After a year of being around here, I am building a gasser and still having questions as I go. It can be a headache, but a truly rewarding experience when it is done correctly.


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## woodburnerdave (Sep 23, 2011)

nt30410 said:
			
		

> This might be of interest to you.
> 
> 
> 
> http://logboiler.ca/



Holy Cow nt30410, that thing is massive.  It looks like it could heat a small city!


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## woodburnerdave (Sep 23, 2011)

Boatboy63, your advice is great!  Your two minutes of writing just saved me a month of headaches, thanks a lot.  I will get some castable refractory and research how thick to form it.  Hopefully it isn't much more difficult than concrete.

I never thought about the moisture drawback to logs, proving that I am as green as my wood.  I will cut and split my logs asap to get the curing process started.  I thought of galvanized pipe because it's cheap, but instead I could have a buddy weld stainless or carbon steel plate and use a heat transfer liquid that won't cause rust.  I'd guess my system will only be 25 or 30 gallons so any percentage of propylene glycol wouldn't cost much.  If I used plate steel the whole secondary chamber could be a wet sleeve, right?

It looks like I need to do some serious reading and I will start now.  Perhaps the fireplace design books would have steered me toward the right path, but perhaps gasification is a recent design innovation.  Thanks again.  If you see some other obvious deficiencies, please point them out.


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## boatboy63 (Sep 23, 2011)

Dave, another thing most of us do is to use an oxygen barrier pex tubing to transfer the hot water. When water gets somewhere around 160 degrees, it keeps the oxygen from releasing and rust will be at a very minimum. The oxygen barrier pex keeps it from entering also. You can use a boiler additive that will also help keep rust away. 

I will give you another warning...the castable refractory I am using is around $50 for a 50 pound bag in my area. This refractory (Mizzou Castable Plus) is one of the best and is recommended for boilers and is rated at 3000 degrees. There are "recipes" on the net for making it, but it isn't rated as hot. Considering a good gasser can burn at 1800-2000 degrees or more, you want to make sure you have something that can handle it.

Stainless is also questionable in the build of these. Many companies have used them in the past, but there is talk about problems. These relate to stainless being more prone to cracking over time. Basic steel will handle the expansion and contraction better.


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## Duetech (Sep 23, 2011)

Hi wodburnerdave, 
boatboy63 is right about the galvanized pipe and the process he refers to is electrolysis. Electrolysis will dissolve stell as fast or faster than aggressive rust. Not a good element for a boiler. Sounds like a big project and I wish the best to you. Many very experienced people frequent this forum and you will learn loads to prevent extending your learning curve. Keep us posted please!


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## woodburnerdave (Sep 23, 2011)

boatboy63, I had planned to use pex everywhere but the hot room.  Good to hear that mild carbon steel is best because it's also the cheapest and maybe I should build a wet sleeve around the whole secondary burn chamber.  I also have 160' of 1.5" ID pipe left from a previous job that would give a lot of surface area.  I will research what thickness to use and check a local company to find out their largest tubes and their bending capacity.  Now that you've explained that long logs won't work, is a long firebox necessary for more complete combustion?  Maybe I should just wait to see what Jay Shelton had to say.   I don't mind the refractory cement cost because it doesn't look like it is very thick, it may even be applied in parge coats over fire brick.  

Cave2k, thanks for the warning about electrolysis, I should have known that --duh.  Mild steel is much easier to work with.  When I figure out the dimensions of the secondary chamber I will let you know.  In the meantime I am open to suggestions.  What's wrong with a very large gasification chamber with a whole lot of steel surface area for absorption?


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## boatboy63 (Sep 23, 2011)

I would beware of using a large diameter pipe for your heat exchanger. If you go too big, you are missing out on what is flowing in the middle of the pipe. I think 1.5" is about right. You also don't want to overdo the amount of pipe for it. You want your flue temp to run at around 300-350 to prevent creosote. If you try to pull too much heat from the exchanger, you will drop your flue temp and have the black soot running back down the pipe. You may also want to research the term "turbulator". It has to do with making the exhaust air circulate and come in contact with the pipe wall to exchange heat better. I have read threads about people using chains to hang down in each pipe to make the exhaust "stir".

As for a longer firebox, I wouldn't go any larger than needed. The way I look at it is with a "smoke dragon" (old school wood burner), you don't really care about the efficiency as long as it burns. With a gasser, you need to keep a consistent burn and it would be easier to regulate in a 24" box as opposed to a 60". The larger the box, the harder it is to keep a consistent amount of air to all areas. The primary burn chamber of the boiler I am building measures 18.5â€ wide by 26â€ deep by 32â€ tall. The secondary chamber is the same length and width, but is only 12" tall. 

Be careful about skimping on the thickness of the refractory. The manufacturer recommends a thickness of 3" or more to prevent it from crackng and to tolerate the impact of the wood entering it.


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## Duetech (Sep 25, 2011)

My EKO uses 2" or the closest metric size to it for the 8 heat exchanger tubes. I have cleaned them several times and built a tool to speed things up. The EKO40 came with built in turbulators in each tube. ie suspended, near diameter blades, mildly twisted (2-4 twists per foot) that run nearly the full length of the tubes attached to a handle that allows you to raise and lower the blades to help keep the tubes cleaned between serious cleanings. Remember I used my EKO without storage so the need for cleaning because of creosote from idling was more prevalent. If a gasifier is working correctly (not bridging, wet wood etc)  the only time you will experience creosote build up is at start up or shut down when there is still viable wood in the primary combustion chamber as secondary combustion will ideally burn any potential creosote. Some with storage have used chains instead of blades to create turbulence as mentioned above and have claimed clean tubes even after a month of standard storage operation.

If my EKO were 10" or 12" taller in the primary combustion chamber I think I would like it even more than I do. That being said I would suggest shortening the length of the primary combustion chamber and raising the roof for longer burns. 60 ninches is long and will be difficult to to load according to your storage peaking out without getting idling from a fuel overload (more wood than needed which will cause idling). As well an elongated primary combustion chamber may cause loads of bridging and burnouts/cold ineffective fires as a result from unbalanced burns. Look up some of the EKO40/60 threads concerning bridging and you will get an idea of what I mean as some 60 users have even closed off one of the two nozzles in the EKO60 to great effect. By design a shorter length box will force the fuel into the nozzle region for a more consistent burn if designed properly and a taller box will allow you to go for longer burn times with fewer loadings. That may only be 2 cents but in my experience of going for the longest burn times it makes a whole lot of sense. So to cap on your heat needs maybe a 24" box with a single nozzle or up to a 40" box with two nozzles would be more in line with your heat needs. If you go with a longer box and two nozzles I would recommend cutting your wood at 16-18" to frustrate any potential bridging. Getting caught short on time will allow you to buy pre-cut, split and seasoned wood that will fit your boilers design.


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## woodburnerdave (Sep 25, 2011)

boatboy63 said:
			
		

> I would beware of using a large diameter pipe for your heat exchanger. If you go too big, you are missing out on what is flowing in the middle of the pipe. I think 1.5" is about right. You also don't want to overdo the amount of pipe for it. You want your flue temp to run at around 300-350 to prevent creosote.



Thanks for the good advice again.  I'll take the square footage of exposed steel times the temperature difference and figure on 2 BTU's per hour of heat exchange per sq.ft./hr/degree difference F.  This will give me the length of pipe needed to drop the temps down to 300 but no lower.  Of course I have to guess the BTU/hr capacity of the stove but after measuring the exhaust temperature I can adjust the amount of water pipe or horizontal flue until I get it right.  

I'll research the turbulator, I don't know if this is meant for water or air pipes but I will figure it out.  

How many BTUs per hour is your setup?  I'm aiming for 200,000 so I may need a proportional scale up in dimension.  I'll take your advice that a longer firebox doesn't create a more efficient burn.    I will be sure that the refractory cement is a full 3" thick.


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## Duetech (Sep 25, 2011)

"I'll research the turbulator, I don't know if this is meant for water or air pipes but I will figure it out."  

How many BTUs per hour is your setup?  I'm aiming for 200,000 so I may need a proportional scale up in dimension.  I'll take your advice that a longer firebox doesn't create a more efficient burn.    I will be sure that the refractory cement is a full 3" thick.[/quote]

Turbulators work inside the heat tubes to keep creosote and ash from building up on the tubes and robbing them of efficeincy and of course clogging the pipes and sice the tubes are in a water jacket there will always be a tendency for condensation. The chains or blades that act as turbulence devices simply force mor heat to the tube walls as the exhaust gasses escape towards the chimney. Check  www.cozyheat.net and you will get some very helpful information about boiler btu/kwh ratings.

No matter what size you build be sure to stick with your plan to have the secondary combustion chamber in a water jacket to prevent warping your boiler as some have found even very thick refractory or firebrick was not enough insulatoin to protect the steel from warping and ruining their work. It might be labor intensive but a design concept I have is 1/4" or 3/8" fins on the secondary chamber roof and side walls to absorb more heat than a flat surface will transfer. The real trouble with that concept is the eventual effect on the flue temps and of course not making the fins too large or "tall" and too plentiful. To facilitate easier cleaning I would not use fins on the bottom of the secondary chamber. Please keep us posted on your progress.


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## boatboy63 (Sep 25, 2011)

Cave2k said:
			
		

> My EKO uses 2" or the closest metric size to it for the 8 heat exchanger tubes. I have cleaned them several times and built a tool to speed things up. The EKO40 came with built in turbulators in each tube. ie suspended, near diameter blades, mildly twisted (2-4 twists per foot) that run nearly the full length of the tubes attached to a handle that allows you to raise and lower the blades to help keep the tubes cleaned between serious cleanings. Remember I used my EKO without storage so the need for cleaning because of creosote from idling was more prevalent. If a gasifier is working correctly (not bridging, wet wood etc)  the only time you will experience creosote build up is at start up or shut down when there is still viable wood in the primary combustion chamber as secondary combustion will ideally burn any potential creosote. Some with storage have used chains instead of blades to create turbulence as mentioned above and have claimed clean tubes even after a month of standard storage operation.


Cave2k, any idea what the length of each heat exchanger tube is or the total length combined? Also, what about the wall thickness of these? Are they thinner like exhaust pipe on cars as opposed to a thicker pipe? Thanks


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## Duetech (Sep 25, 2011)

boatboy63 said:
			
		

> Cave2k said:
> 
> 
> 
> ...



Without doing a little disassembly work no I can't tell you the exact length of the heat tubes but with a tape measure I came up with an approximate length of 32" per pipe and as I said there are eight of them. If you need me to open up the boiler plate for specifics I can. Wall thickness *is at least the same as regular 2" steel black pipe* but I am inclined to think it is closer to the thickness of steam pipe whick I am inclined to think is called schedule 40. In any event the heavier pipe would seem to provide a longer life expectency for the heat exchanger.


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## benjamin (Sep 26, 2011)

Hi Dave

It sounds like you're not afraid of jumping in head first.

You've gotten plenty of solid advice, but I'll add my two cents more.  

After a minute of reading the search results for the author you mentioned I found one solid fuel encyclopedia from 1982 and a book on homeopathy.  I won't touch the homeopathy, but the early 80's was the dark ages of a lot of american technology, so I'd take the books with your 70's sun glasses on.

If you want to do a gasifer, then Professor Hill and his research is required reading.  Specifically, he states somewhere that a water jacketed PRIMARY chamber is required to keep the wood from burning too fast.  

The garn is another great example that you should understand.  It's big, but in some ways simpler than "true gasifiers", it manages this by using the storage to not have to idle.  

Also don't be afraid to use firebrick and masonry, coal burning boilers used them for centuries, and they'll work fine for a wood burner if you figure out how to do it right.  I can't point you in any direction for wood boilers built with fire brick, but you could look up some antique books on coal boilers and translate that knowledge over to wood boilers.  

Also, you might want to consider adapting a junk boiler to your purposes rather than building from scratch.  I have a small commercial cast iron boiler core that I've used on top of a firebrick combustion chamber, it has serious drawbacks but when I finally abandon it I can haul it to the scrap yard and get my $50 back.  A steel fire tube boiler could be adapted to a gasifer easily enough if you could scrounge something like that.


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## DoubleClutch (Sep 26, 2011)

benjamin said:
			
		

> If you want to do a gasifer, then Professor Hill and his research is required reading.  Specifically, he states somewhere that a water jacketed PRIMARY chamber is required to keep the wood from burning too fast.



Benjamin,

Can you give me more info on this person and his research, and where I might find it ... specifically, Hill's full name and the titles of any of his publications? I would be interested in reading this material.

TIA.

DC


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## tom in maine (Sep 26, 2011)

Dick's paper is here:

http://hotandcold.tv/wood furnace.html

Make sure you use the whole line since this website seems to not underline the whole thing.


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## DoubleClutch (Sep 26, 2011)

Thank you, Tom. That looks like a valuable paper with a wealth of information. Looking forward to reading it...

Edited to Add: It appears that pages 10 and 11 are missing from the pdf ... does anyone have them or know where to get them, by any chance?

Edit #2: I found another version of the file containing the missing pages at 

http://www.vtwoodsmoke.org/pdf/Hill-79.pdf


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## woodburnerdave (Sep 27, 2011)

Thanks Benjamin, I'm not afraid of jumping right in but I'd rather copy an efficient design from anybody in the 200,000 BTU/hr range.  I am not sophisticated enough to build a high tech gasifier, but I think my construction skills can make a functional one.  I will also look up the guy you recommend.  I got a book on rocket mass fireplaces, but this does not look like the direction I want to go.  

I'll look into the Hill guy you recommend, although I think I can run enough pipe through the secondary combustion chamber to transfer heat.  The theory you mention is different from the theory to keep the firebox hot for greater efficiency, but I don't know enough to weigh in the debate.  I'm just learning a lot.    

Am I right in thinking that people are talking about a wet sleeve with 2" pipes for the exhaust with turbulators.  I think I can do something like this but the homemade turbulators may be very crude.   

I'll look around for a used boiler.  Good idea.


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## woodburnerdave (Sep 27, 2011)

OK, so I read it and it looks like a very good paper.  The problem is that I probably absorbed about 20%, the burn theories are a little complicated for me.  I seem to be stuck on a traditional firebox with the secondary chamber above it.  These designs with a pipe connecting two seperated chambers just look more challenging.  But it appears that the secondary chamber is twice the size of the firebox, maybe I should increase it's size.


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## benjamin (Sep 28, 2011)

I misunderstood your description.  I thought you were talking about copying a typical gasifer with different materials and on a larger scale.

I think what your talking about resembles a larger version of a greenwood/adobe/? at least as far as a firebrick main combustion chamber and a relatively simple water tube boiler section in a separate chamber.  

I agree that the precision and control needed to make a gasifier work aren't always worth the effort.  The garn is a simpler alternative.  There is at least one thread here of a homemade boiler that is based on the garn, and many garn installations.  

It's actually really simple to burn wood efficiently, just split it really small and feed another piece every couple of minutes.  It gets more complicated when you try to load it up and make it the heat last, and that is why we're so obsessed with storage and gasification.


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## berlin (Sep 29, 2011)

If you want to do it right, you won't waste time with logs. Get a wood chippper and a stoker boiler designed for wood chips and you won't have any smoke or a smoldering mess. Something such as: http://www.youtube.com/watch?v=IR5-KHOnihQ


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## peakbagger (Sep 29, 2011)

Dicks Hill's paper is an early version of his design. After he had sold the rights for household units, he developed a much larger version for a Maine Forest Service Nursery in Greenbush Maine. It looked the same but was much larger. If I remember correctly, at full fire it required 40 pounds of wood every 20 minutes. The wood was standard splits. I do not know if there was a paper published. 

Trying to combust a whole log effciently is very difficult, the logs tend to be wetter and the log can form a char layer on its exterior slowing the burn. There were several outdoor boilers that advertised they could burn green logs, in theory they could but most of the heat went up the stack as CO and creosote with a lot of water vapor. Most states have banned them.


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## woodburnerdave (Oct 3, 2011)

OK guys, I have redesigned the firebox and secondary burn chamber and I will cast them out of refractory cement.  The firebox and the gasifier will each be 24" by 26" and the gasifier will have the 1" pipes laid out as alternating up and down columns to act as baffles.  I'm thinking that the baffles will be about 6" apart, does this sound too close or too far away?  They'll be created by turning the 24" pipes 180 degrees with two elbows at the end and running them back.  Twelve or 15 will create a wall for a baffle and I'll weld a thin piece of flat steel to them so the air has to flow the hard way instead of between the pipe.  

If you see any major flaws with this design please advise me now.  I will take a picture in a week once it is formed up from plywood.


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## woodburnerdave (Oct 3, 2011)

The cheapest refractory cement I've found is 25 pounds of premix for $17.  I would guess that 3/4 of this is sand, which means that I'm paying about $3 per pound for cement.  Does anyone know a cheaper source in the mid-atlantic area?


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## tom in maine (Oct 3, 2011)

Dickâ€™s paper is here:

http://hotandcold.tv/wood furnace.html

Make sure you use the whole line since this website seems to not underline the whole thing. 

We found the missing pages.

Castable refractory needs to be cured. Either it sits for about 30 days unfired or it is slowly fired for longer periods at relatively low temps.
Read the labels if you purchase it.


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## kuribo (Oct 3, 2011)

good castable refractory is not cheap. I wouldn't waste my time with the low budget variety if you hope to get any longevity at all out of it....


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## tom in maine (Oct 4, 2011)

peakbagger said:
			
		

> Dicks Hill's paper is an early version of his design. After he had sold the rights for household units, he developed a much larger version for a Maine Forest Service Nursery in Greenbush Maine. It looked the same but was much larger. If I remember correctly, at full fire it required 40 pounds of wood every 20 minutes. The wood was standard splits. I do not know if there was a paper published.
> 
> Trying to combust a whole log effciently is very difficult, the logs tend to be wetter and the log can form a char layer on its exterior slowing the burn. There were several outdoor boilers that advertised they could burn green logs, in theory they could but most of the heat went up the stack as CO and creosote with a lot of water vapor. Most states have banned them.





I actually inherited one of the Greenbush boilers. Sold it to a farmer who never paid for it in full.
I was glad to get rid of it since it was quite large.
Dick said that the guys who had to pitch the wood into it would try to mess it up since they did not like pitching wood into it all day long.

Apparently, they did work okay. I still have an ID fan for one of the units. It was big.


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## boatboy63 (Oct 4, 2011)

kuribo said:
			
		

> good castable refractory is not cheap. I wouldn't waste my time with the low budget variety if you hope to get any longevity at all out of it....


I will vouch for that. I paid about $1 per pound for Mizzou Castable Plus refractory. Bought it in 50# bags, but it is rated for 3000 degrees. I actually have more money spent in the refractory than any other item in my boiler. I recently saw a listing on ebay for refractory that was sold by the pallet in 5 gallon buckets for around $200. It consisted of about (10) 5 gallon buckets, but they were out of date. There is a recipe for making your own refractory here. https://www.hearth.com/econtent/index.php/forums/viewthread/54155/ I don't know the rating for it and that is the primary reason why I went ahead and bought something rated. When I finish my boiler, I don't want to stand back and say, "If only I had bought the good stuff."


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## peakbagger (Oct 4, 2011)

One saturday during college, I got to feed the Greenbush boiler for a few hours. It was a nice design but it really needed an automatic stoker unless there were prisoners (or college students) available to feed it.


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## woodburnerdave (Oct 4, 2011)

boatboy63 said:
			
		

> I will vouch for that. I paid about $1 per pound for Mizzou Castable Plus refractory. Bought it in 50# bags, but it is rated for 3000 degrees. ."



I agree with you, but need a clarification.  If your castable refractory for $1 per pound was pure cement this is a cheap price.  I'm looking at 80 cents a pound for a mix that is probably 75% sand, which puts pure cement in the price range of $2.40 per pound, which is expensive.  Does anyone have an idea where I can pick up castable refractory cement for less than this price?


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## boatboy63 (Oct 4, 2011)

Dave, I don't know if it will help you or not, but I am attaching the .pdf for my refractory. I also noticed when I dug up the email, I paid $48 for a 55# bag of this.
Edit, can't post .pdf so I will c/p the file.
II I
Product Data 02/09: 5976
Page 1 of 2
MIZZOUÂ® CASTABLE PLUS
Description: 3000Â°F High-Alumina Castable
Features: â€¢ Excellent resistance to numerous slags.
â€¢ Resists vitrification.
â€¢ Shows expansion rather than shrinkage at high temperatures.
â€¢ Superior resistance to spalling.
â€¢ High strength throughout its entire temperature range.
Uses: â€¢ Combustion chambers.
â€¢ Low-temperature incinerators.
â€¢ Air heaters, boilers, and burner blocks.
â€¢ Aluminum furnace upper sidewalls and roof regions.
â€¢ Forge furnaces and iron foundry ladles.
Chemical Analysis: Approximate (Calcined Basis)
Silica (SiO2) 32.6%
Alumina (Al2O3) 60.6%
Iron Oxide (Fe2O3) 1.2%
Titania (TiO2) 2.2%
Lime (CaO) 2.6%
Magnesia (MgO) 0.3%
Alkalies (Na2O+K2O) 0.5%
Physical Data (Typical)
Maximum Service Temperature 3000Â°F (1650Â°C)
Material Required 141 lb/ft3 (2.26 g/cm3)
Bulk Density
After 220Â°F (105Â°C)
After 1500Â°F (815Â°C)
lb/ft3 (g/cm3)
145 (2.32)
141 (2.26)
Modulus of Rupture
After 220Â°F (105Â°C)
After 1500Â°F (815Â°C)
After 2000Â°F (1095Â°C)
After 2500Â°F (1370Â°C)
lb/in.2 (MPa)
1,200 (8.3)
800 (5.5)
600 (4.1)
1,100 (7.6)
Cold Crushing Strength
After 220Â°F (105Â°C)
After 1500Â°F (815Â°C)
After 2000Â°F (1095Â°C)
After 2500Â°F (1370Â°C)
lb/in.2 (MPa)
5,500 (37.9)
3,500 (24.1)
3,000 (20.7)
4,000 (27.6)
Permanent Linear Change
After 220Â°F (105Â°C)
After 1500Â°F (815Â°C)
After 2000Â°F (1095Â°C)
After 2500Â°F (1370Â°C)
After 2900Â°F (1595Â°C)
-0.1%
-0.2%
-0.2%
+0.9%
+2.8%
Product Data
Page 2 of 2
MIZZOUÂ® CASTABLE PLUS
Thermal Conductivity
At 400Â°F (205Â°C)
At 800Â°F (425Â°C)
At 1200Â°F (650Â°C)
At 1600Â°F (870Â°C)
At 2000Â°F (1095Â°C)
At 2400Â°F (1315Â°C)
BtuÎ‡in/hrÎ‡ft2Î‡Â°F (W/mÎ‡Â°C)
7.8 (1.12)
7.7 (1.11)
7.6 (1.10)
7.5 (1.08)
7.4 (1.07)
7.4 (1.07)
Particle Size
Maximum Grain Size 4 Mesh (Tyler)
Less than 5%
Note: The test data shown are based on average results on production samples and are subject to normal variation on individual tests. The test
data cannot be taken as minimum or maximum values for specification purposes. ASTM test procedures used when applicable.
Mixing and Using Instructions (Water calculated at 8.337 lb/gallon) 55 lb bag 1000 lb bag 1500 lb bag
Water Requiredâ€”Vibration Casting (Weight 8.6%)
Pounds
Gallons
Liters
4.7
0.6
2.1
86.0
10.3
39.0
129.0
15.5
58.5
Water Requiredâ€”Hand Casting/Pouring (Weight 9.1%)
Pounds
Gallons
Liters
5.0
0.6
2.3
91.0
10.9
41.2
136.5
16.4
61.9
Working Time 20 minutes
For detailed mixing and using instructions, contact your ANH representative or visit www.anhrefractories.com.
Heatup/Dryout Schedule
See ANH Dryout Schedule 2â€”PLUS Rated Castables and Gunning Castables.
Installation Guidelines
See ANH Installation Guidelines CC-1â€”Conventional Castablesâ€”Standard.
Shelf Life (Under Proper Storage Conditions) 365 days


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## Duetech (Oct 5, 2011)

woodburnerdave said:
			
		

> boatboy63 said:
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Here are a couple links for castable refractory
http://www.ebay.com/itm/130343615133?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

http://www.ebay.com/itm/130343614933?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649


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## boatboy63 (Oct 6, 2011)

Cave2k said:
			
		

> woodburnerdave said:
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Shipping to my location is $77 for 1 bag. Dave lives 1 state north of me so I don't see where it would be worth it. Check out this link http://www.ebay.com/itm/130427938990?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 For $200, you could get over 1000 pounds of the stuff and have a nice roadtrip too. :>


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## bigburner (Oct 6, 2011)

Didn't read whole post, but I looked for a long time for fire brick and castable. I ended up finding a company that did boiler work [big stuff] and they had a warehouse full of products [there are hundreds] and a bunch of information on the use of the ones I wanted. My vote is there is one of these companies in every major city [still lots of boilers out there] I would search this route. I do remember buying fire brick at less then half the old price, units were a custom size but that didn't matter to me I was just piling them up any way.


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## woodburnerdave (Oct 9, 2011)

boatboy63 said:
			
		

> Check out this link http://www.ebay.com/itm/130427938990?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 For $200, you could get over 1000 pounds of the stuff and have a nice roadtrip too. :>



What a great link!!  I will drive up to this place next week and pick up the half ton.  That's only 20 cents a pound for the mix whereas the best local price I could find was about 75 cents a pound.  Now I can pour my boiler 4" or 5" thick instead of 3".  I intended to put some high strength reinforcing steel in the mix (either 6x6, #10 gauge or #3 rebar), but now I can cast this stuff thick enough that the reinforcement won't be necessary.  

You just saved me a lot of money, this is just a few hours from me.  Thanks so much.


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## Gasifier (Oct 9, 2011)

Hi wodburnerdave, 
boatboy63 is right about the galvanized pipe and the process he refers to is electrolysis. Electrolysis will dissolve stell as fast or faster than aggressive rust. Not a good element for a boiler. Sounds like a big project and I wish the best to you. Many very experienced people frequent this forum and you will learn loads to prevent extending your learning curve. Keep us posted please! 

Quick question for you guys about galvanized. My boiler installers used a 24 gage galvaized flue pipe to go from my Wood Gun's exhaust to my S.S. chimney inside my basement. Would this cause any problems? Should I switch that to regular black exhaust pipe? We filled cracks with that red/orange high temp. caulk. What do you think? If it is going to create a problem I will change it. Thanks for your time.


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## Duetech (Oct 12, 2011)

Gasifier said:
			
		

> Hi wodburnerdave,
> boatboy63 is right about the galvanized pipe and the process he refers to is electrolysis. Electrolysis will dissolve steel as fast or faster than aggressive rust. Not a good element for a boiler. Sounds like a big project and I wish the best to you. Many very experienced people frequent this forum and you will learn loads to prevent extending your learning curve. Keep us posted please!
> 
> Quick question for you guys about galvanized. My boiler installers used a 24 gage galvaized flue pipe to go from my Wood Gun's exhaust to my S.S. chimney inside my basement. Would this cause any problems? Should I switch that to regular black exhaust pipe? We filled cracks with that red/orange high temp. caulk. What do you think? If it is going to create a problem I will change it. Thanks for your time.



My experience with galvanized and exhaust says pull out the galvanized as it is very prone to corrosion where creosote is invlolved. 24 ga is so thin you could be leaking exhaust gases in a single season. 16 or 18 ga black would definitely be a better choice.


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## boatboy63 (Oct 14, 2011)

woodburnerdave said:
			
		

> boatboy63 said:
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Glad I could be of assistance. Would have replied sooner, but computer took a crap Saturday morning and had to get another. Don't know if it makes any difference, but in the 3rd pic, it does say on the outside that it is supposed to be used by 3/18/11. Don't really know if it will make any difference or not, but just wanted you to know. Guess that is why it is so cheap.


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## maple1 (Oct 14, 2011)

Cave2k said:
			
		

> Gasifier said:
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I'd also consider or check out stainless flue pipe - if it's a short run it won't cost all that much, then you should be set for a long time. I think 24ga. galvanized is the last thing I would put in.


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## Duetech (Oct 15, 2011)

+1 stainless (but remeber stainless does not mean it won't rust...creosote and water are very agressive and exhaust is often laden with steam)


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## benjamin (Oct 15, 2011)

woodburnerdave said:
			
		

> boatboy63 said:
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I haven't followed the whole thread but I wanted to point out that the buckets of mortar are for laying up firebrick and are probably premixed.  Not sure if they would/could word for casting or not.


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## sixmenn (Feb 4, 2012)

Hey all.  I know it's been a while since this thread was active, but I'm very curious as to the status of your project, woodburner.  

I have had a very similar project in the works for some time.  In case it isn't too late to chime in:

1. Instead of using poured concrete (spalling issues; too much moisture near too much heat), my plan was to lay concrete blocks as the walls, and at any structural bearing points to fill the voids in the blocks with poured concrete.  I'd then fill the rest of the voids with sand (cheap) and line the inside of the building with firebrick.  I found firebrick to be expensive, though, so like you I've looked into other alternatives like refractory cement, which as you know is also very expensive.  Recently I stumbled onto ceramic fiber board and am wondering whether it might be both less expensive and easier to install.  Check it out here (some companies I researched will even custom-form sizes and shapes for you):

http://www.ceramaterials.com/ceramicfiberboards.html

2. I'd like to make a gasification unit, but fear I'll spend far too much time and money trying to get it to work right.  My idea instead is to have the exhaust exit  the burn room through the rear of the burn room through an opening in the burn room near the floor.  My thinking is that a) this will allow the unburned fuel to rise in the refractory-lined burn room where it will ignite in the vicinity of the suspended water tanks (see point #3 below), thereby realizing at least some gain from the burning of the gases, and b) only the coolest exhaust in the burn room will exit the burn room.  

3. For water tanks (see attachment), my plan was to support three 120 gallon vertical-style propane tanks inside the block building at the ceiling, giving me 360 gallons of water to heat, and approximately 141 sq ft of surface area on the tanks ( Central Boiler claims their 393 gallons of water in their system is exposed to 119 sq ft of heat).  Propane tanks are between 3/16 and 1/4 inches thick and already have numerous openings in them for plumbing.  The water path would circulate from one to the other, then the other before exiting the structure.  Also similar to you, I was first going to route my return water through 2" steel pipes criss-crossed in the room in the rear where the exhaust goes prior to venting out through the chimney.  In order to "fine-tune" it, I was going to install shutoffs so I could either bypass this room with my return water, or gate it back as necessary.  

Like woodburner, I'd love to hear whether my ideas have merit or I'm totally out to lunch.  Please feel free to shoot holes in my project!

Colin


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## bigburner (Feb 4, 2012)

You have several issues, as drawn. First the heat HX is going to cool the fire, second open the door for reload, smoke will poor out the door with out a bypass, third there needs to a re burn chamber/dome. That said up draft glassifiers work well, not many many moving parts. The heat transfer for you tanks will be poor [like an OWB] At a glance look at the "green-wood" fire box its all refractory, the draw back with the design is the HX, now take your tanks and add some fire tubes in two of them route the flue gases out of the fire box and threw the tanks then out the chimney. There will lots opinion here, this is mine. I currently run a system that has a very large fire box like yours, it's 40 inches wide 60 deep and 84 inches tall, the top is arched refractory and the flue gases burn up there, then the exhaust travels threw the back wall down into refractory tubes 12x12 on either side [by pass in the middle] then travels threw a fire tube HX. I use a fan on a timer for reloads, It will bring the fire box back up to temp, when it shuts off is when the magic happens, burns like a forage [super hot] I obliviously can put big pieces in there and to see a 24" round glowing to a point to where you think you could see threw it. Amazing, it's pretty cool.  It's all about the refractory! Research will show you that all the big boys use lots of it.


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## bigburner (Feb 4, 2012)

Sorry I for got to mention the concrete, my boiler is setting on poured concrete with the fire box inside, I inch air gap between the concrete and fire brick it did not spall, because it was baked slowly and the moisture escaped. It will get to 500F on the out side, that's sound warm but bad things don't happen until over a 1000 if cured correctly and heated and cooled slowing. Mine is a monster[boiler] and weight is about 20,000 lbs, I traded the wall for hunting privileges. doing it again I would build my fire box first. then a steel frame to set the fire tubes tanks on then frame the whole thing with steel studs and lot of rock wool insulation, pole bard steel if it's out side. None of this is cheap, might better just buy a Garn.


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## sixmenn (Feb 5, 2012)

bigburner said:
			
		

> You have several issues, as drawn. First the heat HX is going to cool the fire, second open the door for reload, smoke will poor out the door with out a bypass, third there needs to a re burn chamber/dome. That said up draft glassifiers work well, not many many moving parts. The heat transfer for you tanks will be poor [like an OWB] At a glance look at the "green-wood" fire box its all refractory, the draw back with the design is the HX, now take your tanks and add some fire tubes in two of them route the flue gases out of the fire box and threw the tanks then out the chimney. There will lots opinion here, this is mine. I currently run a system that has a very large fire box like yours, it's 40 inches wide 60 deep and 84 inches tall, the top is arched refractory and the flue gases burn up there, then the exhaust travels threw the back wall down into refractory tubes 12x12 on either side [by pass in the middle] then travels threw a fire tube HX. I use a fan on a timer for reloads, It will bring the fire box back up to temp, when it shuts off is when the magic happens, burns like a forage [super hot] I obliviously can put big pieces in there and to see a 24" round glowing to a point to where you think you could see threw it. Amazing, it's pretty cool.  It's all about the refractory! Research will show you that all the big boys use lots of it.



Thanks for the reply.  I appreciate your insights.  I have a few questions to make sure I understand what you're saying:

1. What does HX stand for and how will it cool the fire?
2. I've looked at a few boilers and don't remember seeing a bypass on them to prevent smoke coming out the door.  Won't opening the door just introduce fresh air and kindle the fire?  With fresh air coming in, won't the smoke naturally escape out the chimney due to the draft effect?
3. Do you have plans for your design?  Can you post pics?
4. How often do you lhave to load your boiler?

Thanks again!


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## sixmenn (Feb 5, 2012)

bigburner said:
			
		

> Sorry I for got to mention the concrete, my boiler is setting on poured concrete with the fire box inside, I inch air gap between the concrete and fire brick it did not spall, because it was baked slowly and the moisture escaped. It will get to 500F on the out side, that's sound warm but bad things don't happen until over a 1000 if cured correctly and heated and cooled slowing. Mine is a monster[boiler] and weight is about 20,000 lbs, I traded the wall for hunting privileges. doing it again I would build my fire box first. then a steel frame to set the fire tubes tanks on then frame the whole thing with steel studs and lot of rock wool insulation, pole bard steel if it's out side. None of this is cheap, might better just buy a Garn.



When you say 500F on the outside, is that the outside of the concrete, on in the air space?

The building method you describe sounds similar to what I plan to do.  You're saying you would first build the firebox (out of steel and refractory??), then support the fire tubes and tanks on a steel frame (can you describe the tube/tank design a bit?), then build the insulating and cosmetic shell around the outside.  Is that right?

Thanks again, bigburner


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