Q: Your company makes several different products. What is a good solvent recovery system?
RVL: A lot of what I’ve done in TruSteel is because I was trying to replace what’s called a rotovap, which is essentially a giant glass ball that you fill up with solvent. It sits in a warm heating bath and spins around. As you heat it up, the solvent evaporates off; there’s a glass condenser where it’s converted back to a liquid so that you can collect it and reuse it. These things are glass and so if you just look at them the wrong way they’ll break. They’re very hard to maintain and service; a lot of them come from overseas, so there are quality issues and it’s sometimes hard to get replacement parts for them. I started out running one back in 2015 and I hated it. We were getting three quarters of a gallon per hour of solvent back, and to be anywhere on a commercial scale you need at least tens of gallons per hour, so I set out to invent something different. I started reading up on industrial solvent recovery and came across the falling film evaporator. It seemed like the technology that would work perfectly for us, so I started buying parts here and there as I was importing stuff from overseas. I was importing lab equipment for my own personal lab, so every time I would order something I’d also order a piece for the falling film because we couldn’t afford the entire unit to start.
The falling film evaporator is much more efficient. It’s probably the most ideal solvent recovery system, at least for ethanol recovery in the cannabis industry, and the way it works is rather simple. You have a cluster of tubes that’s inside a larger tube, called the shell. Heating fluid is run to the outside of that cluster of tubes, and as your product falls down the inside tubes, it’s heated up and the volatiles evaporate off, leaving your product behind, and recovering your solvent for reuse on the other side. The tube and shell heat exchanger I described is far superior to the rotary evaporator, you can cram a lot more evaporation surface area into a smaller space.
Our AutoVap 30 takes up roughly three by four feet of floor space; that’s about the size of one rotary evaporator. A rotary evaporator that size would get you about two gallons per hour. The AutoVap 30 can do upwards of 40 gallons per hour in the same footprint.
Q: Do you need a pump for solvent recovery equipment?
RVL: Yes. Because it’s a continuously fed machine, you’re not filling it up and waiting for it to run out of liquid before you refill it like a rotary or batch evaporator. It has a feed pump that pumps the solution from a feed tank into the evaporator, and then it has two discharge pumps, one to discharge the residue (or concentrate), which can be anything from cannabis oil, to fragrances, dyes, food products, and pharmaceutical compounds, and the other to pump out your condensed solvent, known as distillate (or condensate).
Q: What would be considered an efficient solvent recovery rate?
RVL: That’s an excellent question! Efficiency is really a metric of how much solvent is left in your end product when you’re finished with your solvent recovery steps. There are what I would consider inefficient falling film evaporators out there that leave 15% or more of the input solvents in the residue. I’ve had issues with this in the past where a client buys a different company’s falling film and then they buy our DR-10, which is intended for decarboxylation. They throw 50/50 residue and solvent in and completely overload the condenser and experience extended periods of time to run what should be a quick process, since it was designed to be paired with our AutoVap systems. I would consider 95% and up more an efficient rate. You should really be shooting for 99%, and again, this is based off the input stream. So, for example, if you have 100 gallons of solvent with 5 gallons of oil in it, you should be getting somewhere between 95 and 99 gallons of clean solvent back.
Q: In your method, what is the best solvent recovery system for liquids?
RVL: Absolutely the AutoVap!