How Vacuum Impacts Cannabis Processing
If you are processing cannabis sativa in marijuana grade or in hemp grade, you are sure to encounter a number of steps that require vacuum in order to get a good product. In some cases, you want to keep the terpene cocktail that your strain of cannabis has, in other cases, you want all aromatics removed. In both scenarios, you will still be using vacuum pumps as a critical component to your production of oils.
So, which steps require a vacuum and what vacuum equipment is the most appropriate for that particular step?
- Growing cannabis has virtually no steps that require vacuum equipment.
- Decarboxylation of cannabis is simply a step where the temperature of the cannabis is elevated high enough to make a fast reaction. The THC-A or CBD-A is reacted to THC or CBD, exuding carbon dioxide as a waste gas. This step often requires a slight vacuum, maybe a few inches of mercury below atmospheric pressure. An excellent choice of vacuum pump for this step is likely a side channel blower. It is a very simple type pump that uses momentum to drag air from the inlet to the exhaust of the pump along a rotating plate with specially shaped pockets. They are one of the least expensive vacuum pumps for this range of pressures.
- Extraction steps do not generally require vacuum pumps except for oxygen/air removal prior to filling the reaction vessel with the solvent of choice. These include: butane, alcohol, supercritical carbon dioxide, etc.
- Vacuum ovens are used for butane or alcohol removal, post extraction step. These vacuum ovens have had a wide variety of vacuum pumps used to provide the vacuum needed, which generally has a lower pressure limit of 1 torr, which is the same thing as 1mm of mercury. This is an absolute pressure meaning that it is measured up from absolute zero pressure rather than down from atmospheric pressure. It will never be shown as “negative” pressure and can have a number of different types of units, such as: mbar, torr, pascal, microns, etc.
Oil free (dry) vacuum pumps seem to have the longest durability and least maintenance burden so far. They are often scroll pumps, which have some limitations to consider. Read more about scroll pumps here.
Lately, there are some new small air cooled dry screw pumps, like the Leybold Varodry 65, that are being introduced to the market with very impressive success and durability. These dry pumps tend to cost more than equivalent oil filled vacuum pumps but they do not have any oil in the vacuum generating region, so there are no concerns about vacuum oil contaminating your product. Additionally, there are no concerns with terpenes and other sticky oils contaminating the vacuum pump oil, which destroys the pump over a fairly short period of time and immediately causes loss of performance. Oil free is far superior in this way. The increased production will justify the extra cost associated with implementing a dry pump. See Your Vaccum Pump May Be Costing More Than You Think
- Rotary Vaporizers require vacuum pumps with reasonably high capacity and base pressure between 1 torr and 25 torr. There are a number of choices here. The original standard pump used is a multi-stage diaphragm pump. For the size and maintenance burden, these are not the best choice of pump. However, a solution like air cooled small screw vacuum pumps would be a very good choice for this pump. It will allow for alcohol recovery and give you long durability and up time. Additionally, the higher pumping capacity will allow you to move your bulk oil through faster, raising your productivity. Our Varodry 65 should be at the top of your short list for vacuum pumps for this equipment.
- Short path distillation is the most vacuum intensive process currently used in cannabis oil production processing. The pressures required are a factor of 10 to 100 times lower than what is required for any other process, and the oil fractions that end up in the pumps can pose some challehttps://www.vacuumscienceworld.com/blog/alba-synchrotron-uhv-vacuum-pumps?hs_preview=hGodFXgK-42215711354nges. For quite a while, oil filled rotary vane vacuum pumps, like the Leybold D16B or D65B have been widely used in short path distilling plants. Many of the industry’s major distilling plant manufacturers provide these pumps with their systems. However, the oil filled rotary vane pump has all the same issues previously mentioned, particularly contamination of the pump oil, and back migration of vacuum pump oil into your product. Again, the dry scroll pump for very small plants and the larger screw pumps for larger plants are becoming the new way to pump out these oils. With new pump opportunities come some challenges.
Reaching some of the required operating pressures needed for final THC or CBD distillate passes requires a secondary pump to improve the base pressure performance. These secondary pumps can come in three forms, the diffusion pump, the turbomolecular pump, and the mechanical booster pump (blower). All three have some advantages and all three have some limitations.
- The diffusion pump is an oil filled pump that runs hot enough to boil the oil inside of it. It tends to operate adequately for small batch processing, but it cannot get pressures in most short path stills less than 10 mtorr to 20 mtorr. If that is the pressures you are comfortable running with, it is a pretty inexpensive and durable pump, though the special oil can be quite pricy. There are very limited choices of manufacturers in this small diffusion pump realm.
- The turbomolecular pump can reach better pressures than the diffusion pump, and models like the Leybold Turbovac 90i or Turbovac 350i have no oil inside, so they can be mounted in any orientation. This makes them more resistant to the accumulation of condensed cannabinoid oils inside the pump, which can lead to pump failure. These are pumps that run at up to 60,000 rpm, so condensing oil can be an issue to watch out for. If the pump is mounted the right way, these issues can be mitigated, but the placement of a good cold trap (which are devilishly hard to find in the market) with good vacuum conductance will help protect the pump, and more importantly, protect your up-time.
- The mechanical blower can deliver pressures in the single digit mtorr range and are about as bulletproof as you can get with regard to durability. They are bulky, require separate mounting structure, and if air cooled can be a little bit noisy. If you plan to do high volume short path distillation, you should ask your OEM about this option. Some have it, some don’t. A very good choice of mechanical blower for this application is the Leybold WH700FC blower. It is the smallest blower available with a giant pumping speed (1400 cubic meters per hour). If you get a water cooled blower, like the WH700, your factory will be quieter and less likely to have overloaded HVAC systems.
- Vacuum systems are often connected to the distilling systems improperly for the best terpene extraction steps. Leybold has been working closely with many of these equipment manufacturers to help them change their designs to operate more efficiently, make a better product, improve feed rates, and have the best equipment durability. See “The Future of Cannabis Processing” to read more about how systems will get better in the future.
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Saving Time & Money in Your Cannabis Distillation Process
In all factory production, (let’s be honest cannabis is no different) time really is money. That is, less time is more money. For now, the market value of refined THC oil or CBD oil is pretty high. Though it has already come down from its lofty beginnings, the value of a kilogram of product is still counted in the thousands of dollars, and a single production line can now make multiple kilograms per hour resulting in a total production value per production line in the tens of thousands per hour. Whenever you have a production scenario where the value is this high, any efforts to raise the output rate of a production line usually have a very short return on investment. This is why we see short path distillation equipment getting larger and capable of up to 50kg/hr.
A key component to the production throughput of a short path still centers around the vacuum system. The pumps are getting larger, but more importantly, the system design is improving with help from companies like Leybold. For example, the first pass (or terpene cut) requires a higher pumping speed and pressure than the final pass (cannabinoid cut). By designing the piping and instrumentation properly, and by adding the right kind of cold traps in the right locations, the feed rates for the first pass can be pushed higher, which is worth a great deal of money over the course of a year.
Consider this, if you're still is producing 40K worth of refined oil per hour (easily possible with new equipment) and if you cut one minute off a one hour cycle, you will raise your revenue in a year by over $5M (if you are running 24 x 7 operation and are getting 8000 hours of production time per year). This is great news because you can do easy upgrades to your still that can dramatically improve your oil throughput, and the cost of the upgrade will be paid for in the first week it is operating.
Consider also, that every hour that you spend changing the oil in your vacuum pump(s) is an hour of lost production. At Leybold, we have been meeting with lab equipment operators who tell us they change the oil once a week or more to keep their pump from crashing. It probably takes a minimum of one hour to change the oil in the pump and get back up and running, which means you lose 52 hours of production per year in order to save a few thousand dollars on the cost of the vacuum pump. At four thousand dollars per hour production rate, that is over 200K in lost production. You are tripping over dollars to save pennies.
Do your factory and your company a favor, buy the more expensive dry vacuum pump, like the Varodry 65 from Leybold. The cost of the pump will be paid for in the first two weeks. Then your equipment operators can focus on keeping the other critical parts of the production line operating smoothly.
Cannabis Distillation - Pump Types & Benefits
D8B Rotary Vane Pump: 8 cubic meters per hour, 3mtorr base pressure (at zero flow)
- Small pump good for pilot equipment, proof of concept
- Capable of backing small diffusion pump
- Too small for adequate feed rates on the first pass (terpene cut)
- Has small oil volume, gets severely contaminated quickly, needs a frequent oil change
D16B Rotary Vane Pump
- Larger capacity of oil
- Larger pumping capacity
- Reasonable feed rates on smallest short path stills on terpene cut
- Needs frequent oil change
SC15Plus Scroll Type Dry Vacuum Pump
- Equivalent speed and pressure to D16B
- No oil to change
- Very simple to clean on site
- Too small for larger production, but good for smallest short path stills
- Higher uptime than any oil filled pump.
- Need special variant to be compatible with volatile organic hydrocarbons like terpenes.
Varodry 65 Dry Screw Vacuum Pump, Aluminum Body and Rotors
- 65 cubic meters per hour, 10 mtorr base pressure (at zero flow)
- Very durable construction
- Aluminum pump runs cooler than equivalent steel screw pumps, important for pumping sticky hydrocarbons
- Capable of pumping on terpene cut with medium feed rates (in the range of 10 kg per hour)
- No oil changes, no downtime
- Three phase power required
- Air cooled
- Very durable
- Very good pumping speed
- Can mount large mechanical blowers on this pump for very high pumping speeds
- Years of trouble free pumping
- Cleanable on site
- Requires three phase power
Turbovac 350i Turbomolecular Pumps
- Replaces diffusion pumps for high vacuum processing (final THC or CBD cut)
- Much higher gas throughput (3 to 20 times more than small diffusion pump) keeps pressure lower during processing
- A dry vacuum pump, so no oil.
- Requires valve at the inlet to optimize system performance and turbo protection.
- Capable of pumping speeds as high as 10,000 cubic meters per hour
- Very rugged industrial pumps, not harmed by cannabinoid oil carryover
- Requires three phase power
- Requires a roughing pump like D65B, Varodry 65, or SP630 to pump downstream of it.
Impacts of Oil Contamination in the Cannabis Distillation Process
Two distinct challenges arise with oil vapors that evolve from bulk cannabis oil during the refining process.
- The light, aromatic hydrocarbon oils that need to be removed to make a pure final product have two distinct challenges of their own.
- They stink, well some of them can smell nice, but usually they really stink.
- This can be mitigated if you use an odor capturing filter on the exhaust of your vacuum pumps. Ask Leybold for information on these filters if you have more odor than you can deal with.
- These light hydrocarbons have very low viscosity, which in terms of oil means they have very low lubricating capability. If you have a rotary vane vacuum pump, as the vacuum pump oil (which has good viscosity) gets loaded with the aromatics from your bulk oil, the internal moving parts will lose lubrication and fail after a pretty short life.
- There are two ways to overcome this challenge, good cold traps or use a dry pump.
- The heavier hydrocarbon oils are sticky. This can become a real problem in your vacuum system and can be a particular challenge if you have a dry pump that runs hot. This means that equipment choices can make a huge difference in your equipment durability. Heavier oils can coat turbo pump blades, they can burn on to high temperature areas, and they can contaminate rotary vane pump oils very quickly.
- To best mitigate the issues with heavy hydrocarbons, use a good cold trap to protect your high vacuum pump (turbo or diffusion pump) by shutting a valve at the inlet when you are not actively using the pump.
At the end of the day, the real issue with oil contamination is the lost production time, which can have huge monetary consequences, see "5 Maintenance tips to Optimize Productivity"
The Future of Cannabis Processing
Drying & Freeze Drying – Pump Types and Benefits
Vacuum drying and freeze drying will be coming to cannabis processing facilities in the future. The reasons for this are quite simple, less time is more money as described above. The price of cannabis bulk plant material, whether flower or stem and leaf is too high to let it sit around and dry slowly with traditional hot air blowers.
Vacuum drying speeds up the process tremendously while keeping the plant material and the oils they contain cool enough to preserve all the qualities you want. It is a cash flow problem, millions of dollars tied up in unprocessed inventory is a killer to your cash flow. So check into this idea sooner rather than later and plan your next factory upgrade with this in mind. Leybold is one of the primary suppliers of vacuum equipment to the vacuum drying and freeze drying industries for some very good reasons. Make sure you ask us for details about how to maximize your dryer effectiveness by choosing the best vacuum solutions.
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