[Stoves] Fly ash cement, Curiosity.

Sun Feb 8 15:03:30 CST 2015

Dear Richard the Practical

Bricks that are hard and ordinary have an R-factor of about 1 per inch of thickness. ‎It is a lousy conductor.

Anything less dense is better as an insulator. The emissivity is about 0.93 so it re-radiates well‎.

Other things being equal, find the one that has the ‎lowest level of free silica. It will last the longest.

Regards
Crispin in tropical Jakarta rain
From: Richard Stanley
Sent: Monday, February 9, 2015 02:52
To: Discussion of biomass cooking stoves
Reply To: Discussion of biomass cooking stoves
Cc: Venter Kobus
Subject: Re: [Stoves] Fly ash cement, Curiosity.

Crispin, Michael et al,

Interesting coincidence about your discussion re refractory materials as liners. You need Kobus Venter in the conversation as he worked with company in South Africa which was forming a highly efficient material by blasting hi silica sand with high voltage literally popping it apart into a fluffy low density structure then slurrying that into any mold desired. the sleeve Kobus used in his early stoves reflected  heat off a briquette like no other I have ever seen before or since…
Kobus has the details and the prognisis of its use..

Cut to stage left here in the laguna de Apoyo, Nicaragua….  I am just blowing the dust off ,  from just having shaped two broken,otherwise rather  standard  soft red clay construction bricks into a liner for use of 3" dia briquettes in the very popular durable and affrodable Coci Nica stove. ( That stove is being  made and widely distributed through the good efforts of Bryan and Nancy Davis).
Am not sure the bricks offer much thermal insulation and reflectivity, nor am I sure they will withstand the thermal shock of a repeated combustion cycles of a local stove (although they seem to stand up well in the overall stove body)  but they will assure us a concentrated and much better-focused air supply thru the center hole of the briquette, with some room for underflow of what is probably or soon becomes the primary air supply during combustion. The slot below also intended for ash removal.

Thoughts from anybody most welcome as we are happy to co-vent it:  Its a work in progress

Richard
Villa Petra,
Laguna de Apoyo,  Nicaragua

Below; one block on left broke and had to be re-cemented and pegged with a long screw. That plus general cleanup and patching affords us two  blocks which look a bit cleaner than this.

Still, this is  only a first cut.  If we put our heads together we can probably come us with something simpler and more practical but let me first combust a few briquettes in them to see if performance improves …and what further issues need to be addressed to enhance combustion, if any.

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