[Stoves] Refractory Brick / ordinary bricks should be fine !

[Kevin Chisholm]

Dear Dean
----- Original Message ----- 
From: "Dean Still" <dstill at epud.net>
To: "'Kevin Chisholm'" <kchisholm at ca.inter.net>; "'adam u partner'" 
<scda1 at t-online.de>; <Stoves at listserv.repp.org>
Sent: Wednesday, May 25, 2005 10:39 AM
Subject: RE: [Stoves] Refractory Brick / ordinary bricks should be fine !


> Dear
>
> Dear Kevin,
>
> Using insulation around a fire helps in many ways, reducing emissions and
> fuel use, improving time to boil, ease in lighting fire.

Right on!! Insulation of the combustion chamber is especially important for 
the primary combustion zone.
>
> Insulation is at least lighter than water.

I am not sure that I understand this, but if you mean that the insulation 
material should have enough voids to give it a "bulk specific gravity of 
less than 1", then this is an excellent practical way to define a "brick" 
that qualifies as "insulating"
>
> Earth and sand bricks are thermal mass not good insulation. Great if 
> that's
> all you have but it is not too hard to make the bricks lighter, full of 
> air
> holes.
>
> A good mix for insulative refractory bricks is:
> 4 parts fine sawdust
> 2 parts dry clay
> 1 part water
>
> Dry the bricks. Fire at 950C. Sawdust burns out.

Sounds very good. One of the problems with insulating refractories is their 
generally poor physical strength. Sometimes it ismpractical to use durable 
tiles that "see the fire and the wood", to protect the porus, weak, and 
sometimes reactive insulation. The trade-off is the extra mass associated 
with the more dense "liner tiles."

Best wishes,

Kevin Chisholm
>
> All Best,
>
> Dean
>
>
> -----Original Message-----
> From: stoves-bounces at listserv.repp.org
> [mailto:stoves-bounces at listserv.repp.org] On Behalf Of Kevin Chisholm
> Sent: Wednesday, May 25, 2005 5:20 AM
> To: adam u partner; Stoves at listserv.repp.org
> Subject: Re: [Stoves] Refractory Brick / ordinary bricks should be fine !
>
> Dear Adam/Chris, and William
> ----- Original Message ----- 
> From: "adam u partner" <scda1 at t-online.de>
> To: <Stoves at listserv.repp.org>
> Sent: Wednesday, May 25, 2005 6:47 AM
> Subject: Re: [Stoves] Refractory Brick / ordinary bricks should be fine !
>
>
>> Dear Wiiliam,
>> In my work in Africa I never used refractory bricks for fire boxes of the
>> community stoves.
>> I made the experience that the great heat in the stove gives extra
>> strength to the bricks, especially if they are not completely burned
>> before.
>
> Actually, a simplistic definition of "refractory brick" could be: "a piece
> of non-metallic material that tends to resist the conditions that are
> applied to it." So, I would suggest that hand made gobs of pre-shaped mud 
> is
>
> a refractory brick, as much as would be a factory made high fired alumina
> refractory brick with 90% Al2O3. I would also suggest that your apparently
> crude "made on site and fired in place" stove liner is indeed a superior
> refractory brick design selection than would be a so-called "factory
> refractory brick."
>
>> For the mortar I used clay-sand mixture, you can also add some cement.
>> I cast a cement plate on the top of the fire box, to hold the bricks
>> together.
>> (Its good to proctect the cement plate from direct contact by fire, by a
>> layer of  brick or brick tiles)
>
> "Hydraulic setting cements" can be very prone to spalling and degradation
> when subjected to temperatures above a certain level. However, it is very
> important to distinguish between the "cement" that is used in the
> manufacture of "concrete" for construction purposes, and "cement" that is
> used to stick fire brick together and provide uniform support and bearing.
> The "cement" used in concrete can also be used in construction of fired
> systems, as long as it is used in areas of the system that are below the
> dehydration temperature for the cement in question.
>
>> That means the design, arrangement of the bricks
>> should be in such a way, that they hold together even if hey are a little
>> loose.
>
> You must have been a Stove Designer in a previous life. ;-) This is
> excellent practise for the design and construction of a durable stove
> system. It allows for expansion and contraction asociated with normal
> operation, and additionally, it usually allows for holding of brick parts 
> in
>
> place after they crack.
>> Regards
>> Chris
>>
>>> Hi.
>>> I have a plan for making a gasifier.
>>> It's going to get hot in there...   so I'd like to line the inside  with
>>> refractory brick.
>
> The term "brick" usually implies "a pre-fired shape." You might  be better
> off with a "Castable Refractory" or a "ramming refractory".
>
>>> Anybody know where to get high-temp bricks?
>
> Do a Google, Yahoo, Mamma, and see what they say.
> You might even Ask Jeeves.:-) Also, look in Yellow Pages
>
> These should be small,
>>> to fit inside a two foot diameter cylinder.
>
> If you use a castable or ramming refractory, size is not a consideration.
> You can form these refractories to virtually any shape and size you want.
>
>>> And I'll need high-temp furnace cement to sock these puppies in place.
>
> Not if you use a castable or ramming refractory!! :-)
>
>>> I'd appreciate some pointers if anyone has related experience.
>>> William
>
> If you are a good listener, it is amazing how helpful Refractory Sales
> people will be.
>
> Please tell us more about your gasifier. What do you mean by "2' diameter
> cylinder?" Is this the throat diameter, or hopper diameter?
>
> Best wishes,
>
> Kevin Chisholm
>
>
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