[Stoves] Crispin´s kiln-was Re: Traditional Charcoal Making

[Kevin Chisholm]

Dear Crispin

Crispin Pemberton-Pigott wrote:
> Dear Kevin
> 
> Agreed in principle. There will have to be at least 2 kilns minimum at each
> site no matter what because it is probably not possible or worth the risk to
> put 500 stoves in a single kiln at a time.

There is a lot to be said for a multiplicity of smaller systems that 
permit redundancy. For one thing, maintenance can be looked after in a 
way that doesn't cause excessive disruption. The level of operation can 
be set up to track with sales much more easily.

You can think in terms of "parallel production line", where perhaps one 
person can produce clay for 3 potters, and the kiln would be sized to 
take the output from three potters, and another person would be able to 
load, unload and operate three kilns. These people in this "production 
line" would thus have a "self regulating daily production target." This 
production line can be integrated with two or more parallel lines.

Invariably, the people on each line find different ways to do the same 
basic process. Each line can learn from the others, and take the best 
procedures from each line to make a superior process eventually
> 
> I must say that running a continuous operation is really difficult to keep
> going for any length of time in a low tech environment.  I am really
> cautious about recommending it but it definitely is energy efficient.

Don't let energy efficiency become the "design driver," simply because 
"energy efficiency" is fashionable. Optomise the process around what is 
most important to making a consistent quality product at least cost. It 
may turn out that energy efficiency is the key point to optomise, but 
then, it may be that simplicity in operation is more important.
> 
> The Hoffman kilns in Maputo are typically 24 chambers necessitated by the
> long heating and cooling times needed for bricks.  The exit temperature to
> the stack is below 200 C, even as low as 80.  Pretty impressive!

That is very good indeed. However, at the very low end of only 80C, 
exhaust fans would probably be required. Again, it is an optomisation 
process... perhaps it is better to leave gases at say 400 C, and use 
only natural draft, or perhaps it is better to recover heat down to 80C 
and use an exhaust fan.
> 
> In practice I think it will be possible to dry fuel using waste heat, fire
> mostly with biomass and have some form of electric topping off standing by.
> It might be a strange kiln but we are going to build them, not order off the
> shelf so what the heck...

If you focus on function, then you are fundamentally on the right track. 
   However, there is a big difference between "ugly functional", and 
"elegant functional". A little bit of "Lipstick Engineering" can work 
miracles... a stainless steel panel, some paint, some neat temperature 
gages, lighting, access walkways, etc., can turn "ugly" into "elegant." 
Clean and smooth is a big help. Sloppy is ugly.

You can put your Production Process on a spread sheet, and then 
superimpose a Mass and Energy balance on top of it. This will give you 
powerful insights into what is really important.

With dry fuel (say 15% moisture) and good burners (control over primary 
and secondary air, good mixing), you probably have a good chance of 
attaining your desired maximum temperatures. The ideal way to go would 
be if you could set up teh system to run on "biomass only", but with 
provision for supplemental electric "topping heat." Let the system prove 
to you that topping heat is necessary, before you install it.

You have a fascinating project coming up!!

Best wishes,

Kevin


> 
> Thanks
> Crispin
> 
> -----Original Message-----
> From: stoves-bounces at listserv.repp.org
> [mailto:stoves-bounces at listserv.repp.org] On Behalf Of Kevin Chisholm
> 
> If Crispin has a volume market, the best would probably be a Three Kiln 
> System operating in rotation:
> 
> [snip]
> 
> 
> _______________________________________________
> Stoves mailing list
> Stoves at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org
> http://stoves.bioenergylists.org
> http://info.bioenergylists.org
> 
>