I started building my new unit this past weekend. I'm using a 100 lb propane cylinder and a grill tank for a catch tank. I ran my other one between 450 and 600 degrees depending upon how heavy a weight of oil I wanted. There is no pressure. I run all the vacuum my pump will pump. Small changes in vacuum make a big difference in the oil's boiling point. This unit has a 100 lb propane cylinder for a main dirty oil tank, a modine hot water furnace coil with a fan as a condenser, and a 20 lb grill tank for the finished oil to run into. I don't need such big tanks since the PLC will control the fluid levels, heat, vacuum, purge pressure, and the solenoid valves on the 2 tanks. I scored 500 gallons of pretty clean oil today at a local garage. The oil disposal company charges him $300 to dispose of it otherwise. I'd like to get several thousand gallons ahead for the tractor, dozers, and heat this coming winter.
WARNING
BTW, if you decide to build one of these by all means use a NEW cylinder. I had a used 100 lb cylinder that I emptied, filled with water, emptied, and held a 29" vacuum on for 3 weeks. I cut a hole in the side with a holesaw for the heating element. When I waved a propane torch over the hole to check for safety the darn thing still exploded and shot flames 50 feet into the air. It didn't damage anything but my hearing. It DID scare the hell out of me! Don't try this with used cylinders, it just isn't worth it. Besides, a new cylinder won't have the propane "stink".