rael - 31-5-2007 at 00:29
There's a fascinating thread here at https://sciencemadness.org/talk/viewthread.php?tid=2396,
but it's very long, and I wanted to share with others, my own burner construction, as it works quite marvelously
I use a paint stripping heat gun as my blower, and diesel for my fuel.
The paint stripping gun preheats both the intake air and the diesel, however I still need a fire starter cube or equivalent to get the diesel fully
vaporised and burning. If not fully vaporised, it will soak into the furnace lining, and burn/smoke out at a perhaps inconvenient time, also there can
be micro pitting of the refractory liner if unburnt droplets are allowed to hit hot surfaces prior to vaporisation.
However, with my heatgun on maximum, there is a strong air flow, and according to the manual, 500 deg Celcius output temperature. This boosts the
output temperature, and with the high calorific value of diesel, which is also relatively cheap compared to many other fuels, it gets very hot inside.
Last firing, my portland cement/silica sand/perlite/vermiculite lining got very melty 
, I will be looking for some fire clay for next rebuild.
gnitseretni - 31-5-2007 at 11:26
if it happened to me i would brush two or more thin layers of portland cement on the inside of the furnace, letting each layer dry before brushing on
the next layer.
The portland cement alone oughta withstand the heat, unlike your mixture, which, with the perlite and vermiculite in it, has a lower melting point??
Someone correct me if i'm wrong.
My 2 cents.
12AX7 - 31-5-2007 at 15:09
Yes, portland cement is the worst offender, while perlite and vermiculite themselves aren't particularly fond of refractoriness. Clay and sand are
all you really need.
Tim