I have in my possession a
Lytron LL820G12 heat exchanger that I got off eBay. It's a 20 plate model, stainless steel plates, and is copper-brazed. It's supposed to be able to transfer over 64000 BTU/hr, or 19000 W. I suspect that this heat exchanger should have little trouble heating up a water/ethanol mix at about 150 grams/min to 90 C from whatever ambient temperature is.
It's a long sucker, about 330 mm long. And it apparently had been used in to past to do something with oils or grease, so I got to figure some way to decontaminate it. I've washed it as much as I could with pressurized water from my shower-based waterpik, so I'll probably follow up with denatured ethanol or something.
This, along with my ShurFlow pump that I dug out of storage, and an E-85 capable fuel injector that I have left over from my engine project of last year, will provide the backbone of my system.