Thank you both for the information.
I'm trying to evaluate costs, etc, but the furnace may well be completely experimental.
The French seem to be very experienced in modern combustion technologies, using bio-fuels,
and I hope to be able to build a furnace (using some of that technology), that can be fired by wood from sustainable sources.
Sourcing refractory materials should not be a problem, as locally we have a village of small potteries, who as a collective, have built a Japanese kiln for ceramics, also wood-fired.
Regards,
Marcus