Ceramic / refractory material for combustion baffle

[Eric Johnson]

I'm just trying to get this forum up and running with lots of contributions and ideas for people interested in central heat. So the more the merrier.

I'll really have to hunt down some Tarm guys and get them over here. Tarm makes great boilers and gasifiers and it would be nice to compare notes. There's a small group of Tarm 60 owners over on Yahoo who taught me a lot about storage and gasifiers when I was thinking about getting one. They might want to stop by.

And there's a few Hearth.com members with OWBs, and I hope they'll feel welcome here as well. They do some interesting things with heat exchangers and heating garages and outbuildings that most indoor boiler people don't get into. And in-floor radiant--that's a pretty hot new technology that the "big box burners" seem to know something about. Most OWB's aren't pressurized, which I find interesting, since I've always had closed loop pressurized systems.

Check out nofossil's website if you get the chance. A lot of knowledge and thought obviously went into it. Leaddog has the same boiler I do, and I've already learned a lot from him. And slowzuki's got three of these really cool, obsolete gasifiers that you load vertically and go like the speed of sound, or some such. My boiler has a little electronic controller that's so small the mfg. houses it in a big pyramid on top of the boiler so that it looks impressive. Slowzuki's rig has what looks like a utility substation bolted to a big piece of plywood.

So it's all good.

 

[Nofossil]

I have two fires with the new ceramic baffle now. Definitely faster startup - my last one was six minutes from lighting the match to gasification. It runs with a bypass damper open during startup, and flue temperature measured 24" from the boiler was less than 225F when I switched to gasification mode. Water jacket temp was 30C (86F).

With this setup, I get through startup faster and at lower temperatures than before. Life is good. Thanks for the help.

 

[sled_mack]

Nofossil,

This thread is pretty old. I was hoping for some feedback on how this setup has held up for you? I do like the idea a lot.

I guess the other question is how effective it has been after using it for a while. Zenon told me I should keep the "tunnel" as large as possible for better burning. But your setup is effectively cutting the tunnel in half.

I've also thought of doing something like this, but turned on it's side. Block off the front of the tunnel, forcing all gasses to the rear. Block off the rear, but have an opening to one side (let's say the left). Gasses now have to come back to the front, around the end of the tunnel, then along the other side to the rear.

Just curious what you think if that idea as well.

Thanks.

 

[Nofossil]

Nofossil,

This thread is pretty old. I was hoping for some feedback on how this setup has held up for you? I do like the idea a lot.

I guess the other question is how effective it has been after using it for a while. Zenon told me I should keep the "tunnel" as large as possible for better burning. But your setup is effectively cutting the tunnel in half.

I've also thought of doing something like this, but turned on it's side. Block off the front of the tunnel, forcing all gasses to the rear. Block off the rear, but have an opening to one side (let's say the left). Gasses now have to come back to the front, around the end of the tunnel, then along the other side to the rear.

Just curious what you think if that idea as well.

Thanks.

The lightweight alumina bricks are toast. My current version uses high-density half bricks that are rated for 3000 degrees. Good so far, but the 2300 degree ceramic board is getting eaten. I'm looking for a replacement. If I can't find it. I think I'll just lose the tunnel floor and be happy. I cut the tunnel in half to create more turbulence and a longer 'hot' path before the gases see the cold water jacket.

Works good in that I get gasification reliably in 6 minutes from the match. Since I build a fire almost every day, clean and quick starts are important to me. Others may not care as much.

I'm trying to make sure that I have symmetric flow, so that all the HX pipes get their fair share. My rear panel is about 1 1/2" from the HX tube water jacket so that flow from both sides has a little more chance to get to the center tubes. I'd be worried that you approach would starve the HX tubes on the far side.

Now that I have secondary combustion and flue temp monitoring, I can fiddle and see what makes a difference.

 

[rsnider]

were can you get the ceramic board? thanks ryan

 

[begreen]

eBay, often has some for sale. Search on insulation board.

I see some Marinite in 4 x 8 sheets, $6 per sheet. This looks like it would be a good insulation board. I'm checking with the manufacturer to see if they agree and to get it's insulation values translated into R and/or K units.

http://stores.ebay.com/HIGH-TEMP-REFRACTORY-STORE_W0QQ_trksidZp284Q2em158QQtZkm

 

[Nofossil]

With a 1200 degree rating, it won't last but a few minutes. The board that I bought was from eBay as well. It was rated for 2300 degrees, and it failed too. I'm working on sources and specifications for something with a little more strength at temperature.

 

[begreen]

You're right. The provider in the link might be worth contacting. It looks like they sell a broad range of ceramic insulation products.

 

[swestall]

I do not recall the name of the product, but a few years back I purchased a bag of refractory material through a local company that relines large scale boilers. My application was to reline the inside of an old Antique Oak coal/wood stove where the bottom half has a refractory pot poured in. To make the pot I needed to line the inside of the stove with the cement, using 1/4 inch cage wire, and let it harden.
They told me the interior of the boilers they reline gets to very high temps; so perhaps this type product cast to your need might do the trick.

 

[KeithO]

Mr Nofossil

If you will send me a PM with a mailing address and the size of board that you need, I could send you an alternative material to try that is not very stiff mechanically, but quite erosion resistant, will never crack and will sustain the temperatures you are looking at.

How are the heavier firebricks holding up ?

Keith

With a 1200 degree rating, it won't last but a few minutes. The board that I bought was from eBay as well. It was rated for 2300 degrees, and it failed too. I'm working on sources and specifications for something with a little more strength at temperature.

 

[Adios Pantalones]

Castable refractory cement will withstand very high temps. I got mine from Cutter Atlantic refractories- Woburn, MA. I have cast a number of shapes that withstand good temps (2300 F). I know folks that add metal fiber to give it crack resistance, but I cast a 1" thick 22x22" kiln chimney cap that has withstood 4 firings without it, and know folks that cast larg portions of high fire kilns with it.

Ceramic fiber board is held together with a starch. You can add rigidizer- silica or alumina based, that holds to higher temps. You could also treat it with ITC100 and it will rigidize, withstand higher temps, and withstand erosion better. The material and coatings are available from a number of pottery supply sores- Sheffield pottery, MA is a good starting place.

Super duty brick will withstand well over 2600F sustained and is high alumina. It's available in a number of configs- 2" thick fire tile, 9x4.5x2.5 straight brick, 9x4.5x1.25" splits, and several custom sizes. Check refractory suppliers.

 

[steam man]

My woodstove has castable ceramic plates. The top plate gets blasted by the flames. Its about 1.5" thick and is only supported by the edges. Its been on there for 18 years with no problem and its the hottest stove going. I've made castable stuff for industrial boilers. Typically styrofoam forms are used to make odd shapes. I think you can get the 3000 deg stuff and reinforcing stainlees "needles" on ebay. I think you just need to leave some expansion by making it out of separate pieces. It has to fire slowly to get the moisture out or it will disintegrate. If you can find a kiln oven..........

Mike

 

[Nofossil]

This thread is back from the dead!

KiethO, sent you a PM - thank very much. The new firebricks are holding up quite well.

Mike and AP: Thanks for the encouragement. I know there has to be something out there that will work.

 

[Brian VT]

Ok if I revive this thread again ? You guys seem to know your materials.
I'd like to make a replacement "everburn" secondary combustion box for my woodstove rather than pay $250 for the o.e.m. replacement.
I was just at a local HVAC supply house and saw Kaowool boards 1/2"x18"x36" that I could work with. Do you think this would be suitable for my purpose ?
The salesman said it is commonly used where a flame from an oil burner contacts it directly so he thought it’d be fine for my application. There’s no specs. on the manufacturer’s website (Lynn). What about adding these coatings you refer to ? Would those help or even be necessary ? I don't know what temps. occur in this box.

 

[trehugr]

NoFo, I was a ladle maker in a foundry years ago. We used a product called coral plastic. It has a consistency like modeling clay. We lined all ladles with it. Its tough stuff. (broken link removed to http://www.refwest.com/index.asp?PageAction=VIEWPROD&ProdID=75) It withstood 3000 + for long periods of time. ( we poured armor for the M1 tank ) Just a thought.

 

[trehugr]

Data Sheet for Coral Plastic
(broken link removed to http://www.hwr.com/products/datasheetsv1/CORAL_PLASTIC_28-82_ADTECH.pdf)

 

[Gooserider]

Ditto... I'm going to be trying to make it through the winter on my existing refractory box that I've tried to patch back together with stainless wire and refractory cement, but wouldn't mind finding suitable stuff to make a new one out of come spring...

Gooserider

 

[Nofossil]

Wow - more materials! This is great!

I just got some castable material as a free sample from a local industrial boiler service outfit. I'll try anything. I'd love to get a durable solution that's also easy to clean ashes from.

 

[j.w.young]

I get ceramic fiberboard from my Maple syrup equipment supplirs. They will sell a box or 1 sheet at a time, about $10 per 1"x12"x36" We use it to insulate behind the firebricks in the eaporators. Easy to cut with a construction box knife. Google Maple syrup equipment supplies for a great list of places, yes they will sell to anyone.

 

[Nofossil]

I get ceramic fiberboard from my Maple syrup equipment supplirs. They will sell a box or 1 sheet at a time, about $10 per 1"x12"x36" We use it to insulate behind the firebricks in the eaporators. Easy to cut with a construction box knife. Google Maple syrup equipment supplies for a great list of places, yes they will sell to anyone.

Thanks - I think that's the type of ceramic board that I have now. A bit soft and crumbly before firing?

It gets eaten away where the flames touch it, and it gets very brittle after firing. Probably good for insulation if protected by firebrick, but not strong enough for my application.

 

[Brian VT]

It gets eaten away where the flames touch it, and it gets very brittle after firing.

Is that the Kaowool board I asked about ? Kinda tan in color ?

 

[Nofossil]

It gets eaten away where the flames touch it, and it gets very brittle after firing.

Is that the Kaowool board I asked about ? Kinda tan in color ?

I'd say more like off-white. Rated for 2300 degrees.

 

[DaveBP]

Nofossil, have you looked at kiln furniture? The shelves and posts that are stacked in ceramic pottery kilns to hold all those bowls and mugs. Some of those things are fired to 2300F and higher with all that weight on them. Silicon Carbide and alumina are used. Try googling "Nitride Bonded Silicon Carbide Kiln Shelves" and you'll get lots of brags about tough and hot. Some pottery is fired closer to 2500F and some kilns are run on wood. I used to mess with that stuff but that was 30 years ago.

 

[Nofossil]

I don't know the actual temperatures in the flame zone. Ruined an inconel jacketed type K thermocouple - the signal went screwy after the indicated temp hit about 2500. The research I've done suggests that the max temp is right around that, and in the flame zone it oscillates between reducing and oxidizing as the gases swirl around. Hadn't thought about kiln shelving - sounds worth pursuing.

 

[Nofossil]

Did a little research on 'ash fusion' - the temperature at which ash residue starts to fuse and clump together. Looks like that's around 2700 degrees. I'm definitely seeing a bit of that phenomenon.