Cannabis / Hemp Solvent Recovery
Solvents are used in initial extraction, winterization, isolation, and other key steps in the processing chain. This solvent must be separated from the cannabis oil prior to consumption.
The Importance of Solvent Recovery
Solvent recovery is one of the more overlooked steps in the processing chain. It’s a simple process, but it can often become a bottleneck for many processors. Even though the process of solvent recovery may be straightforward, the systems that achieve solvent recovery often use large amounts of power to achieve high efficiency. This means processors must be aware of the amount spent on electricity consumption and select solvent recovery systems that match the needs of the other downstream processing systems in the facility.
Ethanol Recovery
Solvent recovery is often performed after the initial extraction step when using ethanol as the extraction solvent. Solvent recovery is also performed after the winterization step to separate crude oil from the solvent used during winterization.
Prior to performing distillation, isolation, or further cannabis crude oil refinement beyond winterization, the solvent must be separated from the cannabis oil. Solvent recovery systems are designed to purify the solvent in the process of recovery. What this means is that you can reuse that solvent to perform further extractions, winterization, or other post-processing techniques. This saves valuable capital, as solvent is one of the more expensive consumable items that cannabis processing facilities use.
Types of Solvent Recovery Systems
Rotary Evaporators
One of the most common types of solvent recovery systems is a rotary evaporator. Rotary evaporators are specifically designed to recover a wide range of solvents and are used in many types of laboratories beyond the cannabis industry.
Their ability to recover a variety of solvents makes them extremely useful. Rotary evaporators come in a variety of sizes to match the needs of your solvent recovery process. Rotary evaporators usually fit into laboratory-scale operations but can be scaled by adding multiple systems. As you will see, there are some solvent recovery systems that can handle much larger volumes than rotary evaporators.
Rotary evaporators make use of a rotating flask that causes the solution inside to become agitated. The rotating flask also sits in a heated water bath. The combination of heat, agitation, and the reduction in pressure by a vacuum pump causes the solvent to evaporate. The solvent vapor is pulled by the vacuum pump into a condenser within the rotary evaporator. This condenser is attached to a chiller which circulates liquid through it. The temperature differential of the condenser causes the vapor solvent to condense back into a liquid where it is collected and re-used for further processing.
Falling Film Systems
If you need to recover more solvent than a rotary evaporator can handle, a falling film solvent recovery system is the next best option.
A single falling film can handle the same volume as several of the largest-sized rotary evaporators. Falling films are especially useful when performing ethanol extraction, as the amount of solvent generated from this type of extraction method is very large. It is more efficient and cost-effective to use a falling film system to recover solvents. Some falling film systems are limited to certain solvents only, which means you may need a falling film system for your ethanol recovery as well as a rotary evaporator to perform other processes like isolation. Isolation typically involves different solvents, such as heptane or pentane.
Falling films operate on a similar principle to rotary evaporators, except they have much greater evaporation and condensation surface area. Falling films operate by feeding the solvent solution into a heat exchanger, which heats the solution and causes the solvent to evaporate and become a vapor. This vapor is pulled into the condensation area of the system by a vacuum pump, where the vapor recondenses and can be re-used for further processing. Falling films have very large heat exchangers that maximize the evaporation surface area, allowing more solution to be fed into the system than a standard rotary evaporator.
Membrane Recovery Systems
Membrane solvent recovery systems are a special type of solvent recovery system that have membrane filters to separate the solvent from the cannabis crude oil.
Membrane filters have similar recovery rates to falling films, but they consume much less power. Membrane systems are often fully automated as well, making them highly efficient at reducing solvent in the solution to minimal levels. Membrane recovery systems must be used in tandem with a falling film, as they cannot fully reduce the solvent levels of the solution to a level that would allow for further processing.
Membrane recovery systems have the advantage of minimal power consumption (compared to traditional falling film systems), so if you are in need of multiple falling film systems to achieve sufficient recovery, it may be best to purchase a single membrane recovery system paired with a single falling film. This would ideally recover the same amount as multiple falling film evaporators, while reducing the footprint, power consumption, and capital required to purchase and operate multiple systems.
Your Solvent Recovery System
Don’t let solvent recovery become the bottleneck in your cannabis processing operation. Precision experts can help properly size the solvent recovery solution needed for your operation. Schedule your free consultation today.
