The Ultimate Beginners Guide to Closed Loop Butane Extraction: Part 2
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The Ultimate Beginners Guide to Closed Loop Butane Extraction: Part 2

by BVV |


Now that we have covered the proper butane extraction safety protocols and extraction methodologies in Part 1 let's dive deeper into the extraction preparation and actual operation of a closed-loop system.

Butane extraction starts with packing the material column with biomass material and proper assembly of the extractor. During the packing of the material column, botanical biomass is loaded into the material column and packed as evenly as possible to reduce channeling of the solution and tight enough to fit the desired amount of material within the column while still being able to agitate the material by hand. Once the material is loaded into the material column, it is important to remove any debris from the tri-clamp ferrules to ensure a tight seal between the tri-clamp gasket and the endcaps continuing the assembly of the material column.

 Packing Rod for Material Tubes By BVV

Once the material column has been packed and assembled, continue to assemble the remainder of the system. While assembling the extractor, ensure that all high-pressure clamps are tightened with a torque wrench to manufacturer specification (typically 110 inches per sqft). After assembly, prior to initiating a butane extraction, a pre-assembly inspection and testing of the extractor should always be done to ensure safety during extraction. During the inspection, confirm that all gaskets are free of visible wear and ensure all lines and fittings are intact and appropriately tightened before pressure testing the system.

Glycerine Filled Compound Gauge By BVV

After assembly and preinspection of the closed-loop extractor, it is important to pressure test the system to ensure no leaks. A leak within the system can result in butane escaping from the system and being released into the atmosphere. To ensure safety during extraction, it is always recommended to pressure test the system after the reassembly of a closed-loop extraction system. To initiate a pressure test, start by ensuring the outlet to the source solvent tank is closed and then open all process flow valves from the closed source solvent tank to the collection tank and pressurize the system with nitrogen to 100 PSI. Once the system has reached 100 PSI, close the nitrogen input valve and allow the system to be held under pressure for at least 30 minutes prior to extraction to ensure pressure can be held.

BUNA Sanitary Tri-Clamp Screen Gaskets By BVV

If pressure is not held during this time, identify where pressure leaks are coming from by spraying all process connections with soapy water. If the process connection is leaking, it will be observed to create additional bubbles. Once a pressure leak has been identified, depressurize the system and disassemble and reassemble the system as necessary, making sure to replace any parts no longer holding a seal. Once reassembled, proceed to pressure test the system again, and disassemble and reassemble as needed until pressure can be maintained. At BVV, we pressure test every vessel at 100 PSI for 24 hours prior to shipment upon disassembly and reassembly of the unit. The same is always recommended, but a shorter pressure test can be utilized at the discretion of the extractor. 

Once the system has passed the pressure test, prepare the hydrocarbon solvent for extraction by bringing it to the desired extraction temperature. If utilizing fresh solvent, it is always recommended to distill the solvent to eliminate the risk of contamination from the storage solvent tank before bringing it to the desired extraction temperature. At BVV we have exceptional gas quality that results in a clean distillation, but predistillation is always recommended

120LB High Purity Propane tank By BVV

 To distill fresh solvent, start by first bonding the source solvent tank to the grounded extractor and pulling the entire system under vacuum before injecting butane solvent from the source solvent tank into the collection vessel of the pressure tested closed-loop butane extractor. Once loaded, close the valve to the solvent storage tank and proceed to heat the collection with a hot water bath to 38C/100F. During this time, it is important to also chill down the recovery tank to condense the ensuing vapors. Once the collection vessel and recovery tank have reached their operating temperature, open all process connection valves between the collection vessel and the recovery tank and proceed to evaporate the solvent from the collection vessel, recondensing it back into the recovery tank. Once all the solvent has been evaporated from the collection vessel and condensed into the recovery tank, close the vapor valve on the recovery tank, depressurize the closed-loop system, and disassemble the collection vessel. Clean the inside of the collection tank with ethanol to remove any residue from the freshly distilled solvent.

Now that the solvent has been distilled and the collection vessel has been cleaned of any residue, proceed to reassemble the system as normal. This will ensure that the system is assembled to manufacture specification, all high-pressure clamps are torqued to specification, and all process connections are secure and appropriately tightened. After assembly, proceed to pressure test the system again for a minimum of 30 minutes to ensure proper assembly before preparing for the initial extraction.

Now that the fresh solvent has been distilled, proceed to bring the solvent to the desired extraction temperature while pulling the remainder of the extraction system under vacuum. Pulling the system under vacuum evacuates ambient pressure from the system, creating a low-pressure zone that allows the butane or propane to move through the system more easily and provides a clean atmosphere for the extraction process to be performed. Additionally, pulling an EMPTY recovery tank under vacuum prior to initiating the recovery process creates a low-pressure zone for the solvent vapors to be pushed/pulled towards during recovery.
12CFM Two-Stage Spark Free Vacuum Pump By BVV

Before pulling the system under vacuum, start by ensuring the solvent tank is closed off and no residual vapors are within the system. If butane or propane vapors are pulled into a standard vacuum pump, it could cause ignition of the flammable vapors. Once the solvent tank has been confirmed to be closed, open all process connections from the closed source solvent tank to the collection vessel. Connect the vacuum line from the collection vacuum valve to an explosion proof vacuum pump. Ensure all process connections are tightened appropriately and proceed to turn on the vacuum pump and allow the system to be pulled under vacuum to -29.9hg before closing the vacuum valve and turning off the vacuum pump. Once the system has been pulled under vacuum, isolate each component of the extraction system by closing all input and output valves and allowing the hydrocarbon solvent to reach the desired extraction temperature.

Once the extraction solvent reaches the desired temperature, the extraction can be initiated by transferring the solvent from the solvent tank to the material column. If the solvent is warm, the solvent will have its own inherent pressure that can be utilized to inject the solvent into the material column due to the pressure differential being pulled under a vacuum. While this pressure differential is typically sufficient in the transfer from the solvent tank to the material column, if the solvent is chilled enough to reduce the pressure of the hydrocarbon solvent, then nitrogen can be utilized to push the solvent from the recovery tank into the material column of the system. In both cases, nitrogen can push the solvent into the material column by first pressurizing the solvent tank to the desired injection pressure. While higher pressures can be utilized to inject the solvent, 10-25 PSI is typically sufficient in transferring the solvent into the material column.

Explosion Proof Platform Scale By BVV

Once the solvent tank has been pressurized appropriately, place the LP recovery tank on an explosion-proof scale. Tare the scale and open the process connection valves from the source solvent tank to the material column, injecting the desired amount of solvent into the material column, allowing the biomass material to be saturated. If utilizing a quick wash solvent saturation strategy, ensure the process connection valves from the outlet of the material column to the collection vessel are open, allowing the solvent to drain into the collection vessel upon injection. If utilizing a longer saturation, ensure the material column outlet valve is closed, allowing the material to be completely submerged in a solvent for the desired retention time before draining the extraction solution to the collection vessel. Once the entirety of the extraction solution has made its way into the collection vessel, proceed to initiate the solvent recovery process. If nitrogen was utilized to inject solvent into the system ensure it is purged from the collection vessel prior to apply heat  by venting the nitrogen from the headspace of the collection vessel through a line into the exhaust of your C1D1 Booth.

To initiate the recovery of solvent within a closed-loop butane extractor, start by closing the inlet valve to the collection vessel and then chill down the solvent tank and heat the collection vessel. If the recovery tank is empty, isolate the recovery tank and pull it under vacuum to create a lower pressure zone for vapors to be pulled towards. Depending on the boiling point of the target compounds to be preserved within the botanical extract, more or less heat may be applied to preserve these compounds. Typically the collection vessel will be heated to a temperature range between 20C/68F and 37C/100F to evaporate the hydrocarbon solvent. The application of heat to the collection vessel can be applied by submerging the collection vessel in a hot water bath or recirculating hot water through the jacket of the collection vessel utilizing a heated circulator.
7 Liter heated Circulator By Polyscience

Commonly the solvent tank will be chilled as cold as possible by either submerging the recovery tank and condensing coil in a dry ice/ethanol slurry or circulating chilled fluid through the jacket of the solvent tank utilizing a refrigerated circulator. Once both the collection vessel and the recovery tank have reached the desired temperature, initiate the solvent recovery process by opening all process connection valves between the collection vessel and the recovery tank. If utilizing an active recovery pump, turn it on at this time. During this time, closely monitor the extract within the collection vessel to gauge the solvent recovery process. The solvent recovery process can be continued until the extract completely solidifies. No more boiling is observed, requiring it to be scraped out of the collection vessel. It can also be stopped once only a small amount of the extraction solvent remains to allow the extract to be poured or drained from the collection vessel and purging the remainder of the solvent utilizing a vacuum oven.

Once the solvent recovery process has been performed to the extractors liking, turn off the recovery pump if utilized, isolate the solvent tank and collection vessel, depressurize the closed-loop extractor, and harvest the extract. Once the extract has been harvested, proceed to your vacuum purging procedure.



  1. Purpose

The purpose of this procedure is to provide detailed instructions for closed-loop hydrocarbon extraction.

  1. Scope

This procedure applies to all lab technicians tasked with closed-loop hydrocarbon extraction.

  1. Definitions/Acronyms

Personal Protection Equipment (PPE) Items worn to protect employees from exposure to hazardous materials and prevention of injury.

Safety Data Sheet (SDS) Provides useful information on chemicals, describing the hazards the chemical presents, and giving information on handling, storage, and emergency measures in case of an accident.

  1. Safety

  1. SDS Sheets: Butane SDSPropane SDSTri-Blend SDS

  2. PPE: The following should be worn by all lab personnel during this refinement procedure:

    1. Protective eyewear

    2. Lab coat/Anti-static clothing

    3. Nitrile Gloves

5. Hazard Identification
  1. Preparation and Use:
    Target compounds will be extracted from biomass material utilizing hydrocarbon solvent.

    1. Concentration- Use  high purity n-Butane or Propane (BVV)

    2. Quantity-  3-5lb of hydrocarbon solvent per 1lb of biomass

    3. Frequency- An initial volume of solvent is used, no more is added.

    4. Location- Hydrocarbon extraction occurs within a C1D1 environment,  inside of a closed-loop hydrocarbon extractor (BVV). 

  2. Potential Hazards and Risks

    See hydrocarbon solvent SDS for detailed risks.

6. Preparation

  1. Load the material column with the desired amount of biomass material packing the material tightly and evenly.
  2. Clear any excess biomass from the tri-clamp ferrules and fully assemble the remainder of the material column ensuring that all high-pressure clamps are torqued to manufacture specification.
  3. Proceed to assemble the remainder of the system ensuring all clamps are torqued to manufacturer specifications and all process connection hoses are secured and tightened properly.
  4. Once the hydrocarbon system assembly is complete proceed to pressure test the system by first ensuring the source solvent tank is closed and all process connections are open from the closed solvent tank to the collection vessel.
    1. Proceed to inject nitrogen into the injection manifold of the extractor pressurizing the system to 100 PSI before isolating the system.
    2. Allow the system to remain under pressure for a minimum of 30 minutes to ensure the system is assembled correctly with no leaks.
    3.  If the pressure within the system drops below 100PSI proceed to spray all process connections with soapy water to identify where the leak is coming from. If bubbling is observed at a process connection, a pressure leak has been identified.
    4. Once the pressure leak has been identified, depressurize the system and disassemble and reassemble as necessary before repressurizing the system again and disassembling and reassembling the system as needed until pressure is maintained. 
    5. Once pressure is held within the system for a minimum of 30 minutes proceed to depressurize the system and proceed to pull the system under vacuum.
  5. Ground the extractor system ensuring all connections are stable.
  6.  Attach a spark-free vacuum pump to the collection base of the closed-loop system and open all process flow valves from the collection vessel to the closed source solvent tank ensuring the source solvent tank valve is fully closed.
  7. Turn on the spark-free vacuum pump and allow adequate time for the entire system to be pulled under vacuum. Once the system has reached  -29.9mmHg close the vacuum valve, turn off the spark-free pump, and close all processing flow valves on the system isolating each component.
  8. Proceed to bond the solvent and recovery tanks and transfer 3-5 lbs of distilled hydrocarbon solvent for every 1lb of biomass you plan to extract into the solvent recovery tank of the closed-loop extraction system and proceed to chill the solvent recovery tank to the desired temperature through the use of dry ice or an appropriately sized chiller.
  9. Once the solvent has reached the desired injection temperature, proceed to start your initial extraction.

7. Procedure

  1. Pressurize the recovery solvent tank with nitrogen to the desired injection pressure 10-25PSI and open all processing valves from the recovery solvent tank to the material column saturating the material column at a 3-5:1 ratio (solvent: material).
  2. After the desired saturation of the material column has been achieved, open all processing valves from the material column to the collection vessel allowing the entirety of botanical extract solution to flow into the collection vessel. 
  3. Once the entirety of the solution has been transferred into the collection vessel close the collection vessel inlet valve.
  4. Proceed to initiate solvent recovery by submerging the collection base in a hot water bath or turning on the heated recirculator setting the temperature to the desired solvent recovery temperature and proceeding to chill the recovery tank to the desired temperature using a dry ice/ethanol slurry or an appropriate refrigerated circulator.
  5. Once the collection vessel and solvent recovery tank have reached the desired solvent recovery temperatures open the process connections between the collection vessel and the recovery tank to start the solvent recovery process.
  6. Proceed to recover the hydrocarbon solvent until only extract remains, isolate the recovery tank, depressurize the closed-loop system, and drain or harvest the botanical extract into a clean receptacle.
  7. Once the botanical extract has been harvested proceed to the vacuum purging procedure. 

Disassembly and cleaning

  1. Depressurize the closed-loop system to ambient pressures by opening the input/output valves on the material column and collection base.
  2. Once each gauge reads 0PSI proceed to disassemble the system by removing the high-pressure clamps and disposing of the spend biomass material.
  3. Proceed to clean and sanitize all parts with 200 proof ethanol to remove any particulate, oil, or other contaminants.