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co2 temperature and pressure chart for cannabis extraction

Which Cannabis Extraction Method Is Best?

There are many techniques that are applied to separate all the different components of cannabis. Using these extraction techniques, the many different parts of cannabis – all containing different chemicals – can be isolated. This helps in bringing out the more desirable compounds present in cannabis so that they can be used for a wide variety of applications.

There are over 113 cannabinoids that can be separated from the cannabis plant. Of these, the more popular ones are cannabidiol (CBD) and tetrahydrocannabinol (THC). In addition to these, there are many cannabis compounds that include more than one of these cannabinoids and have been referred to as whole plant extracts.

The process isn’t simple. It is an exact science and cannot be likened to cooking. In addition to specific knowledge about the plant, this process requires laboratory equipment and proper safety measures. The process needs to be carried out with great care so that the final product is safe for use by human beings.

Supercritical CO2 extraction is one of the many techniques applied to the extraction of cannabis. Before delving into more details about this form of extraction, it is important to briefly understand the other techniques that are popularly used for cannabis extraction.

Types of Cannabis Extraction Methods

There are many different methods that are commonly used for cannabis extraction. They differ in the type of solvent used, the laboratory conditions, equipment used and so on. Some of the more popular cannabis extraction methods are mentioned below.

Alcohol Extraction

In this technique, the plant material is first soaked in a solvent, most commonly ethanol, before it is removed to filter the liquid.

Once the filtration process is carried out, the alcohol is removed using evaporation. It is important to get rid of the chlorophyll in the plant extract as it can be dissolved by the solvents, giving the remaining product a bitter taste.

The process is carried out under strict monitoring as ethanol – or whichever form of alcohol is used – is extremely flammable. One of the reasons why this method is popular is because the final extract doesn’t have any toxic residual chemicals.

Butane or Propane Extraction

In this method of extraction, solvents like butane or propane are used. If the former is being used, cannabis and liquid butane is placed in a controlled system (both heated and pressurized) where evaporation removes the butane solvent by first turning it into vapor. There are some safety concerns when this method is being used.

For example, butane is highly flammable even in its gaseous phase. If adequate care isn’t taken with regards to the temperature, there can be an explosion. Also, if some butane or propane is left in the extract, it can be very harmful if consumed by humans.

Solvent-Free Extractions

These are more basic techniques when it comes to cannabis extraction, as they don’t utilize any solvents for extracting some of the desirable plant components. Instead, the kief is separated from the cannabis by simply grinding the product and running it through sieves.

Another basic extract of cannabis is hash, also known as hashish. This involves the separation of the trichomes from the rest of the plant material.

This is done because the most amount of desirable compounds are actually in this part. Finally, rosin is another solvent-free extract of cannabis that has become popular over the past few years.

CO2 Extractions

The final technique of extraction to be discussed here, which will be discussed in greater detail throughout the article, is CO2 extractions. Instead of using forms of alcohol, as in the case of other solvent-based extraction techniques, this uses carbon dioxide.

This process of extraction is preferred to others as the yield is higher and less of the desirable compounds are lost through this process. The main issue with this form of extraction is the cost of putting together all the equipment that this technique requires.

What Exactly Is Supercritical CO2?

There are specialized extraction machines that are able to freeze CO2 gas and compress it into a “supercritical” state. In this state, the CO2 takes a cold liquid form.

In order to get the CO2 to this supercritical stage, the compound – which acts as a gas at room temperature and pressure – is turned into liquid after placing it in a machine with the pressure increased to 75 pounds per square inch and the temperature under -69 degrees Fahrenheit.

After the CO2 is in liquid form, the temperature and pressure are increased to make the fluid reach the supercritical stage.

As CO2 is referred to as a “tunable solvent” it can help in the creation of a wide variety of end products, each at a different phase of the process.

As the solubility of CO2 differs at different pressures, the supercritical CO2 allows for the extraction of different compounds at different levels. These levels are the result of small adjustments in the nature of CO2.

This process ensures that you don’t end up with a combination of the different extracts. In addition to this, it is gentler than the other commonly used solvents that can affect the quality of the final product.

Why Is CO2 Used?

Using solvents like ethanol, butane or propane can affect the final product that you achieve at the end of the extraction. With carbon dioxide, however, this is not a problem that you will face. CO2 is known for giving the purest quality of compounds without the presence of any harmful toxins that could be left behind in the final product if any of the other solvents were used for extraction.

In addition to this, industries are investing in the commercial processing abilities of CO2 as it works out to be cheaper in the long run because of the relatively safe processing and low number of post-processing steps. When other solvents are used, the post-processing takes a lot of time and effort.

CO2 works in a more efficient manner. While there is a good amount of initial investment required for the equipment, CO2 extractions work out to be inexpensive in the long run. Most importantly, CO2 is considered as a solvent that can be tuned to fit your requirements. It works to separate the different constituents of cannabis in the process of extraction.

Finally, CO2 acts like a sanitizing agent, which will keep the resulting cannabis compounds clean. It can also be used for extracting other plants like hops or organic crops.

Difference between Supercritical and Subcritical CO2 Extraction

The prerequisites for the CO2 to be considered supercritical have been mentioned earlier. While extractions using supercritical CO2 are the more popular ones, it isn’t the only method to carry out extractions using CO2. The other type of CO2 extraction utilizes subcritical CO2, which will be discussed in greater detail below.

Supercritical CO2 Extractions

The more popular type of CO2 extraction is the one that uses supercritical CO2. Here, the pressure is very high and the temperature is kept at 88 degrees Fahrenheit. These high pressure and high temperature conditions affect the process of extraction by damaging most of the terpenes and heat sensitive chemicals that are a part of the plant matrix.

This method, however, is popular as it is faster and can extract the larger molecules of lipids, waxes, as well as the chlorophyll from the plant.

Subcritical CO2 Extractions

From the supercritical stage, if the temperature and pressure are both lowered, the CO2 will reach a subcritical stage. Extractions can be carried out even in this stage but the amount of time that it takes will increase by quite a bit. In addition to this, the yield is also lesser than supercritical extractions. The advantage of subcritical CO2 extractions, however, is that they hold on to the more sensitive chemicals in the plant, in addition to terpenes and essential oils.

There are also mid-critical extractions that take place between the range of supercritical and subcritical but they will not be discussed here.

How Is Supercritical CO2 Used for Cannabis Extraction?

The process starts with liquid CO2, which has to be converted to its supercritical form for the best results. In order to facilitate this, the temperature of the CO2 is increased using a heater and the pressure is increased using a compressor. The increase in pressure and temperature converts the liquid CO2 into its supercritical form, which is then passed through good quality cannabis.

This cannabis is stored in an extractor and on coming in contact with the CO2, all the trichomes, terpene oils and waxes are removed from the plant material. The solution – with all the desirable compounds of cannabis – is moved through a separator. In this step of the process, compounds like trichomes, terpenes and others are pulled apart to be placed in a collection vessel.

The supercritical CO2 moves through a specialized condenser, which turns it into a liquid again. This liquid moves back into the storage tank where the process was started so that the cycle can be repeated again and again.

The best part about using supercritical CO2 for this method of extraction is that you don’t have to worry about any remaining CO2 that could have been left behind in the final extract that you have collected. Once the pressure is removed, the liquid CO2 converts into the gaseous form and evaporates without leaving a trace.

This means that you can get rid of any residual CO2 by just leaving the extract at room temperature for a brief amount of time. The CO2, in its gaseous form, will just evaporate into the atmosphere. If the supercritical CO2 extraction machine is more sophisticated – as is the case with industrial-level machinery – it will be able to recapture the residual CO2 and reuse it at the end of the extraction process.

CO2 System Considerations for Cannabis Extraction

Supercritical CO2 extraction is one of the best methods of extracting chemical compounds from the plant matrix. In order to conduct the entire process with greater efficiency, the machinery that is being used is of critical importance. The most important factors that control this efficiency are the pressure conditions, the temperature considerations and maintenance of these factors throughout the process.

First, the maximum pressure rating will be able to ensure that there is enough pressure in the vessel to push the CO2 into its supercritical format. Pressure is only the first out of two important considerations to keep the CO2 in its supercritical form.

The second factor is temperature. This can be divided into two distinct verticals. First, you will have to ensure that the temperature of the carbon dioxide can be measured. Here, it is important that the temperature of the gas is being monitored and not the temperature of the vessel containing it.

After this, there is a need for high wattage heaters to be present within the machine so that the temperature – which was measured earlier – can be increased or decreased according to the needs of the extraction.

Advantages of Supercritical CO2 Extraction Across Fields

The use of supercritical CO2 extraction isn’t just limited to cannabis. It can be applied to a wide variety of products as it is quite cheap and environment friendly, because of its recyclable nature. As opposed to the other harmful solvents like butane, propane and ethanol, supercritical CO2 will not have a detrimental effect on safety of the entire exercise.

Some of the other processes that utilize supercritical CO2 are the creation of high-quality vanilla, coffee, tea, fruit extracts, nut aromas and extracts, omega-3 oils, fragrances and perfumes, hop extraction for beer, algae based oil extractions and so on.

The process of cannabis extraction can be quite complicated and should not be attempted by people who do not have experience in the field. The more sophisticated techniques, like supercritical CO2 extraction, require a great amount of raw materials – like liquid CO2 – and a sound technological system, which cannot be accessed if you are not professionally involved in this field. While the process can sound complicated, it is the best way to extract the different compounds of cannabis effectively.

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Looking to get the most out of your flower? There are multiple ways of varying quality and in this article we explain why using CO2 is the best.

Temperature Control: CBD/THC Processes

Temperature Control for CBD/THC Extraction and Distillation

The legalization of the hemp cannabis derivative CBD and of marijuana and its THC derivative for medical and recreational purposes in many US states and all of Canada has led to significant economic growth in the CBD/THC extraction and distillation equipment sector. Many of the manufacturers of these two categories of equipment have been in business for a number of years, and the processes used for extraction and distillation have been refined over decades since they are used to extract and purify many different organic substances, chemical, petrochemical and alcoholic beverages. However, hemp and marijuana have their own unique characteristics, and the processes to extract and purify CBD and THC from their respective plant sources are still being fine-tuned by processors and original equipment manufacturers (OEMs).

There are quite a few different approaches to extraction and distillation of CBD/THC products, and each has certain benefits as well as some less desirable side effects; but they all have in common these parameters that need to be controlled: temperature, pressure or vacuum, source material throughput volume, and for extraction, solvent feed rate.

Extraction Process – Temperature control considerations

Current extraction processes include CO2, butane or propane, and ethanol. In each of these methods, the extraction agent is cooled down to temperatures that can reach -80°C (-176°F) and then compressed until it is liquefied. The temperature reduction is achieved using a chiller, which can be a standard piece of equipment or a custom unit designed to meet unique temperature profile requirements.

In commercial systems, extraction is typically performed in a jacketed vessel. Water, oil or other liquids are circulated within the jacket by a temperature control unit (TCU) which maintains consistent vessel wall and extraction chamber temperatures.

Temperature control is necessary throughout all the steps in the process, but precise extraction chamber temperature control is absolutely essential to managing final product quality and characteristics. This high level of control must also be replicable from one batch to another and in fact on a continuing basis over a large number of batches. Controlling temperature to within .275°C (.5 °F) is a standard that permits a consistent finished product. It is also important to note that repeatability, in addition to accuracy is extremely important for producers as it allows them to replicate the process over time, and thus insure consistent product quality.

For example, increasing the extraction temperature from the initial agent temperature can:

  • decrease the concentration of terpenoids in the extract
  • risk denaturing the final CBD/THC product
  • increase wax/resin extraction and overall volume, but yield a lower quality product

Similarly, decreasing extraction temperature can lead to:

  • increase the concentration of oil in the extract
  • reduce the wax proportion of the extract

For these reasons, having equipment that is capable of consistent and accurate temperature control is very important to producers; and as there is demand for many variations of this extraction process’ final product, chilling equipment and temperature control units with high precision, closed loop controls are critical.

Once the extraction process is complete a processor is left with “crude extract” that is 55-75% cannabinoid and that may in some instances, be sold without any further processing. For the majority of processors however, further separation of the remaining elements is necessary to obtain fully purified, high value CBD/THC oil.

The next step in the purification process is to remove waxes by cooling the extract down to approximately -20°C (-4°F) in a chiller-driven jacketed vessel. This “winterization” process precipitates some of the undesired elements out of the solution which after filtering, leaves oil made up of cannabinoids, chlorophyll and terpenes. Decarboxylation is an important step that may be performed either before or after the winterization process. It is used to activate CBD/THC components and is accomplished by carefully heating an extracted solution to release the carboxyl ring group (COOH).

Distillation Process – Temperature control consideration

A distillation process is then conducted to complete the separation of the remaining elements and produce the purest possible CBD or THC oil. It is worth noting that even though a source material has been winterized, as much as 40% of the remaining feedstock may consist of undesirable materials. Also, in the case of ethanol extraction, ethanol must then be evaporated to separate it from CBD/THC components.

As in the extraction process, the distillation process that is used to fully purify CBD/THC oils requires closely controlled temperature, pressure and source material feed rates to ensure that the necessary interactions produce a high-quality finished product with characteristics that generate the highest possible value.

The most common pieces of equipment are wiped film, molecular short-path stills. In this approach, the feedstock of oil is fed into a jacketed vessel that is often heated with an oil circulating TCU to achieve temperatures up to 343°C (650°F), though the typical distillation temperature range is 130 -180°C (266-356°F). In these systems, the feed stock is distributed on the evaporation chamber wall with a special wiper. The resulting thin film allows the more volatile terpenes to evaporate through the top of the chamber into their own external collection vessel, while the CBD/THC is collected along a TCU controlled central condenser unit which is cooler (typically 60-70°C / 140-158°F) than the evaporation chamber and serves to attract the cannabinoid vapor. The final step in the process is solvent removal, which is accomplished in a separate, external cold trap, which is also temperature controlled with a chiller.

Certain OEMs offer wiped film molecular short-path distilling equipment that integrates the removal of heavier materials directly into their distilling process. In this instance, chlorophyll, waxes and other heavier residue (up to 40% of the feed stock) descend the outer wall of the distillation vessel and are collected in their designated container.

In certain cases, a final separation step is taken to separate THC from CBD. Crystallization is a common method. A reactor vessel is filled with feedstock and a solvent which is chilled slowly from 60°C to -20°C. A slurry results and that is transferred to a Nutsche filter dryer to produce pure, dried crystals. The Nutsche filter is a jacketed vessel whose temperature is controlled with a circulating hot oil unit. The process results in a 98% or higher purity of the CBD or THC product.

Delta T Systems – Your partner in Pure Temperature Control

Delta T Systems has worked with extraction and distillation equipment manufacturers as well as end user engineering groups for over 25 years. The products we offer are designed to specifically address customers’ production needs. That is why so many customers return to us and choose our equipment over and over again as their production needs expand. We offer industry leading design, efficiency and service.

Delta T Systems has developed a broad range of industry leading product features and capabilities that make our TCUs and chillers the best on the market:

Chillers

  • Capabilities from 1-60 tons (higher capacities offered as custom designs)
  • Variable speed design that can cut energy usage up to 50%
  • Standard operating range from -18°C to 27°C (0°F to 80°F)
  • Highly accurate closed loop temperature control to .275°C (.5°F)
  • Data logging with remote control and analysis tools
  • Industry 4.0 ready
  • Long life heat exchange materials and low maintenance design

Temperature Control Units (TCUs)

  • Water Circulating Temperature Control Units (TCU) will perform in processes up to 300°F (149°C)
    • ¾ to 7 ½ HP Pump, 25 to 150 GPM
    • 9 to 144 KW Low Watt Density Heater
    • 149°C (300°F) Fluid Operating Temperature
  • Oil units up to 343°C/650°F
    • 6, 12, 18, 24 or 36 KW Heaters, or special designs up to 360 KW
    • Maximum Operation Temperature up to 343°C (650°F)
    • 10 to 150 GPM Pumping Capacity
    • Heating Only or Heating with Cooling Capabilities
  • Dual circuit combination TCU/Chiller units

Custom engineered product development and designed solutions are our specialty

  • Made to address customers’ unique needs
  • Custom design chillers and TCUs available for greater capacities

For CBD or THC extraction and distillation temperature control, Delta T Systems has the experience, expertise and capability to give processors and OEM equipment manufacturers standard or custom equipment to meet all aspects of the process’ requirements. All systems are designed for process repeatability. Our equipment lowers production costs, improves temperature accuracy, and delivers long lived quality and ease of maintainability.

Dan Brandenburg, Director of Sales & Marketing at Delta T Systems can be contacted for more information (262) 628-0331.

Controlling the temperature for CBD and THC extraction and distillation is absolutely essential to managing final product quality and characteristics.