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Ceramic / refractory material for combustion baffle

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Nofossil, Oct 5, 2007.

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  1. j.w.young

    j.w.young New Member

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    Yep, kinda tan or mixed tan to darker, I hide it behind firebrick. My Maple arch isn't as fierce flames as a gasifer.

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  2. Brian VT

    Brian VT Minister of Fire

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    So...should I build my VC Everburn box out of 1/2" Kaowool board or not ?
  3. Medman

    Medman Feeling the Heat

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    NoFossil - anything to update here? I would like to make improvements to the secondary chamber as well. What luck have you had with new materials?
  4. Nofossil

    Nofossil Moderator Emeritus

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    Nothing I'd recommend yet. I'll report back when I get done with this round of tests. Life is busy just now.
  5. verne

    verne Member

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    anyone have any updates on this? My curved blocks have cracked after one season. I found high alumina castable refractory rated at 3000 deg. I think the brand was Kaolite.I can get 20 lb bags shipped for about $30. Any thoughts ? thanks scott
  6. Adios Pantalones

    Adios Pantalones Minister of Fire

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    Silicon carbide kiln shelves are a bad bet for this- they do not withstand thermal shock well (I use them in my kiln- need to raise temp slowly). High alumina shelves may work, but buying a bag of castable refractory and just casting them would be cheapest.

    Kaowool boards need to be rigidized with alumina, silica, or ITC100 rigidizer or they are very brittle. ITC100 is great stuff, but pricey. All are available through pottery supply houses- Sheffield pottery, or the Big Ceramics Store.
  7. Nofossil

    Nofossil Moderator Emeritus

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    Interesting that this thread resurfaced just now. I had failure of one of my high alumina / high density 2300 degree firebricks yesterday. I also made a tentative discovery. Due to impending structural failure of various combustion labyrinth component, I had added some additional support which had the effect of increasing the flow restriction in the secondary chamber. I had really pronounced problems with 'puffing' mini-explosions in the primary chamber - something that I generally don't see, and which I had always attributed to excessive gas-generating surface area such as too much kindling.

    I'll be burning tonight with a revised labyrinth that's much simpler and offers virtually no flow resistance. Reports to follow.

    I have a bag of castable refractory that I'll do up if I ever get some spare time to make the forms.
  8. Fred61

    Fred61 Minister of Fire

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    Nofossil,

    I see you're in Addison county. When I had my Woodgun I found a place in Montpelier that sold all kinds of refractory material. I can't recall the name at this time but I do remember they were on Barre Street.

    You could ask these guys some questions: http://www.cotronics.com/vo/cotr/cm_castable.htm
  9. kabbott

    kabbott Member

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    I'll bring this old thread back to life.
    Any news on the castable refractory?
    The choices are bewildering, I assume material for the secondary tunnel that withstands extreme temps would be a poor choice
    for the nozzle itself. I am thinking the nozzle wont be near as hot but will take more mechanical abuse?
    Any thoughts on what to use?
  10. Nofossil

    Nofossil Moderator Emeritus

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    That's a tough one. I've had a very hard time getting real advice on castable materials. My brother got some pretty expensive castable material for the floor of his, and had it kiln-fired (a very long and slow process for a large and heavy piece). It cracked anyway.

    The 2300 degree high density / high alumina firebricks don't hold up indefinitely either.

    The EKO appears to have a cast nozzle that's a different material than the floor of the primary chamber. It's very close-grained - more like ceramic than brick. However, ceramic tiles turn to gravel when used as a flame target. You may be right that the nozzle doesn't see the full fury of the flame, but the bottom side certainly comes close.
  11. KeithO

    KeithO Minister of Fire

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    NoFossil, I didn't send the low densiy alumina material when I read of some of your failures. Doesn't appear to have enough structural properties. Recently found this site: http://www.sentrotech.com/ceramictube.php

    They have no prices online, so don't know what to expect. But the stuff they have is very high grade and super dense (specific gravity of 3.9).

    They DO have silicon carbide products also, but as one poster mentioned one has to reduce thermal shock or it can easily crack due to the high expansion.

    "SentroTech offers Sintered Alpha Silicon Carbide Products. Alpha silicon carbide material is most commonly used in sintered products in industrial application. It is formed by mixing very fine silicon carbide powder with non-oxide sintering additives at sintering temperature between 2000oC to 2600oC under vacuum or inert atmosphere to form very dense products. Silicon carbide parts can be formed by dry press, extrusion, isostatic press and injection moulding. Various complicated shapes can be formed by these process technologies. Due to its very fine gain size and high density, sintered alpha silicon carbide product has excellent surface finishing and tight dimensional control that require non or minimum after-sintering machining."

    There is also this place: http://www.advaluetech.com/alumina-tubes.html Size limited (largest is 3" OD) but price seems OK, depending on how much you need.

    There is also this place : http://www.graphitestore.com/items_list.asp?action=prod&prd_id=348&cat_id=42&curPage=1
    Larger tube sizes available, gets expensive as the diameter and length go up. Maybe the right way to go is a high grade alpha aluminum tube inside the low density insulation (will slow the cooling rate) and then a firebrick "box" around the outside.

    Best regards
    Keith
  12. Nofossil

    Nofossil Moderator Emeritus

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    Thanks for the links - I'll follow up on them as time permits. One problem I have is that none of the high-tech materials places are all that excited about selling 25 pounds to an eccentric like myself. I have to pretend to be authentic, and the strain takes its toll.
  13. fabguy01

    fabguy01 New Member

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    You need to talk to these guy's http://www.indfirebrick.com/ Not only do they know there products but they also have a service department that services the product. they do our furnaces at work and I have nothing but good to say of them
  14. KeithO

    KeithO Minister of Fire

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    [​IMG]
    Outside Diameter: 4" (10.16cm)
    Inside Diameter: 3.625" (9.21cm)
    Length: 24" (60.96cm)
    99.8% Alumina Furnace Tube - Open Both Ends. Inert to hydrogen, carbon and refractory metals; can be used at operating temperatures to 1950°C in both oxidizing and reducing atmospheres. Dimensional Tolerances:+/-4% or +/- .050" min.

    $500 = expensive.

    Not sure whether you need 4" or 2x3" (for path there & back)

    Outside Diameter: 3" (7.62cm)
    Inside Diameter: 2.75" (6.99cm)
    Length: 24" (60.96cm) a mere $345 per 2 ft.

    Don't recall how much you need, but if they have the right dimensions for you and it is better than what ECO sells, it may be the ticket.
  15. KeithO

    KeithO Minister of Fire

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