The Road to Manono, page-1030

LPG is also by far the most cost effective heating agent. I have seen kilns operating with gas heaters on the discharge end and air drawn countercurrent to the slow flow of calcined product down the kiln shell. The burners have to be outside the shell because of the incredibly corrosive nature of the sulphuric acid but 275 degrees is easily achieved with gas.

There are also several microwave oven tests going on at the moment, and I believe the OPEX is even lower than gas. I will also try to discover where the 11MW/ton hydroxide comes from (this is more than 1MW/ton of SC6)