[Terrapreta] Let's talk retort materials for a little bit

[MFH]

Greg

I've never used more than 1/8", 3mm. Had mild steel fire boxes last several
years with this material and fires burning 24/365

Warping is a potential problem as the seal on the end or cap. This is where
reinforcement is needed, and where cast iron is best. Steal some manhole
covers.

Yes, line the outer drum with castable refractory. For a pipe shaped firebox
I used 3mm mild steel for the outer and much thinner galvanised steel sheet
as an inner mould, say 1mm. It could be tack-welded at the join and these
ground off after the cement had set, and removed. Or left in place. After a
couple of fires it will distort and pull away from the cement and can be
removed.

Chimney routing - absolutely from the base before rising. Take it
horizontally for a while before rising and use the heat to pr-dry the next
batch.

M




-----Original Message-----
From: terrapreta-bounces at bioenergylists.org
[mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of Greg and April
Sent: Thursday, 15 May 2008 11:51 PM
To: Kevin Chisholm; Terra Preta
Subject: Re: [Terrapreta] Let's talk retort materials for a little bit

I'm willing to put up with a little cost to gain some efficiency and life. 
I don't want to use more than 1/4" of material, since thinner walls improve 
thermal efficiency.    I figure that some warping is fine, and not really 
going to change the overall efficiency.

Temperature will be fairly uncontrolled, unless/until a thermocouple and 
damper is installed.

I am planning on a layer of castable refractory on the inside of the outer 
shell, so it will have a layer of protection and so it can be of lesser ( 
cheaper ) material.

I am thinking about improving thermal efficiency by routing the chimney so 
that it dips below the level of the retort, before going up as it normally 
would - in this way the heat builds up around the inner shell, before 
exiting.


Greg H.


----- Original Message ----- 
From: "Kevin Chisholm" <kchisholm at ca.inter.net>
To: "Greg and April" <gregandapril at earthlink.net>
Cc: "Terra Preta" <terrapreta at bioenergylists.org>
Sent: Wednesday, May 14, 2008 15:07
Subject: Re: [Terrapreta] Let's talk retort materials for a little bit


> Dear Greg
>
> Greg and April wrote:
>> What kind of materials make a good retort?
>>  Titanium?
>> Carbon Steel?
>> Stainless Steel?
>>  What?
>
> There are several answers...
>
> 1: If you want low cost... then carbon steel
> 2: If you want longer life, then use thicker carbon steel
> 3: If you want longer life still:
>    lower the temperature of the metal to hold it to about 700 F
> 4: If you want longer life still, use SS, and limit shell temperature to 
> aprox. 900 F
>
> Enclose the heated surfaces so that they only "see" products of 
> combustion, with minimum possible excess air.
>
> Titanium is very expensive, but would probably be good to a higher 
> temperature. However, it has a significant tenancy to form Nitrides and 
> Carbides.
>
> Hope this is helpful.
>
> Best wishes,
>
> Kevin
>>  Greg H.
>>  ------------------------------------------------------------------------
>
> 


_______________________________________________
Terrapreta mailing list
Terrapreta at bioenergylists.org
http://tech.groups.yahoo.com/group/biochar/
http://terrapreta.bioenergylists.org
http://info.bioenergylists.org