Ceramic blanket is normally used. Study before you finish the build, I've had 2 finishers, the first was just 16x34" with 2 burners, I think the burners were 6" below the pans. My current finisher has tube burners, they are 8" below the pans. By the way, tube burners work way better. They can be made by drilling gas ports in a black iron pipe. I can get a diameter for propane if you like, just PM me. Then you would need to get the gas valves for each tube with the air inlet adjuster. The main difference, the 2 burner type burned a ring on the bottom right where the flame hit, just like it did back when I had a propane fired bottler. A tube burner spreads the heat better and can do the job easier.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.