Jedd Haas Posted April 7, 2011 Share Posted April 7, 2011 I am considering different ideas for a stripping still in the range of 55 to 200 gallons. I've looked into steam, and the evidence suggests it's a good option. But maybe heat transfer fluids are more cost-effective? Propylene glycol goes up to 370 F, but here is a heat transfer fluid http://www.therminol.com/pages/products/xp.asp that goes up to 600 F. (It's mineral oil.) So here the question is whether having a larger heat differential will speed up operation (boiling of the wash) enough to justify its use. The glycol costs around $700 per drum, while the Therminol is $1,150. Of course, it's probably best to not heat either fluid up close to the max temperature, both for longevity, and for safety. But let's say you took either one up to 300 F, how would it perform, relative to steam? While the temperature differential is one point, I've seen some postings that suggest that the heat-transfer function is still inferior to steam for various other reasons. I visited a facility today that uses glycol, (for chilling, not heating) and they mentioned that they have slight losses in their system. They weren't sure if the problem was a leak, or maybe the stuff sublimates, very slowly? Or maybe the fluid breaking down causes it to shrink? Bottom line, you would probably need to consider it a consumable. Now the question of direct heat vs. running thermal fluid in a loop. This seems to be the area where the fluid has an advantage, as you can likely use smaller pipe sizes. Maybe 1" black steel for a system the size I mentioned, which is a lot more fun (haha) than 3" black steel for steam. I considered one design for direct heat. This would be a 200 gallon still with an outer shell holding 20-50 gallons of glycol, depending on fill level. The contact area would be at least 10 square feet, and could go as high as 35 square feet, depending on the fill level. Let's say you heated that with 8x 5.5kW immersion heaters, going around the outside, equidistant. That sounds pretty good until you calculate that at 110v, you'd be pulling 400 amps at max power! (Of course, you could have a variety of series-parallel selections to vary the power by steps. Now it could be I'm overestimating the power requirement (or worse, underestimating it). Either way, 400 amps, or even 200, doesn't come cheap. So gas makes more sense. It seems that direct firing a jacketed setup like this, I'd have to build my own firebox. Not sure if that would pass inspection, so the glycol loop seems more attractive. Definitely more modular, for adding more equipment; I also like the safety factor of removing an ignition source from the immediate vicinity of the still. Does anyone have experience with a system like this? Link to comment Share on other sites More sharing options...
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