Ken Peavey wrote:Used as an insulator, DE is close to fiberglass in effectiveness, however the weight would be an issue to consider in wall and ceiling structures.
I recently came back from doing some field visits to fired clay brick manufacturers, where I found that DE is being used as an insulator in kiln walls and ceilings with very good results. Its obviously raw mined unprocessed DE, not food grade, so it probably contains other minerals as well.
Here is a photo of the raw mineral:
I got this sample of a clay stabilized DE (or as it is called here: diatomite) brick:
It is a solid (no holes) brick and weighs about 1/3 of a standard solid fired clay brick of the same dimentions made by the same manufacturer. The manufacturer is highly empirical so he kept no record of the proportions of clay/DE used to make this one, but he claims that you could put an acetylene torch to one side of the brick while holding it with your hand and not get burned (he didn't mention for how long though
). This is by no means a real insulation test but you see what he was trying to get at.
One advantage of having the DE stabilized with clay is that it can act as a refractory/insulative material at the same time. The manufacturer also claims that he overhauled the vault ceiling on one of his batch kilns (pictured below) using this type of brick and it reduced the amount of coal needed for every batch burn by about 30%, which is quite a lot without making any adjustments to the combustion itself.
Another brick manufacturer is building a tunnel kiln (continuous operation as opposed to batch, pictured below) in which they are adding the raw DE as filler in between the refractory bricks and between the refractory bricks and ceramic fiber insulation in the ceiling of the kiln, which is expected to increase the insulation compared to just the layers of refractory brick and ceramic fiber.
This got me thinking that DE might be used for rocket mass heater cores. Particularly when making a cast riser where diatomite might be more easily available and/or cheaper than perlite or pumice, or when building the riser out of bricks if one can get hold of bricks like the one I have shown.
Some online sources cite a temperature resistance of up to 900 ºC
, which I believe could be raised even higher using the right mix of DE/clay/other refractory minerals (like alumina), and thermal conductivity values from 0.06 W/mK for DE
and 0.12 W/mK for Diatomite
Should I move this post to the RMH forum?