An extraction facility is a solvent storage problem and a refrigeration problem before it is anything else. Butane, propane and ethanol have to be stored in quantities the fire code allows, outside the extraction room, and delivered chilled; recovered solvent has to be captured, held and returned; and extraction, winterization, crystallization and cold traps all need chillers that reach minus 40 C and lower and hold there while every extractor in the building runs. Paul Industries installs solvent tank farms and recovery vessels, low-temperature chillers and glycol distribution, and the piping that ties them to extraction and post-processing equipment.
Solvent storage by solvent
| Solvent | Storage | Governing rules | Design points |
|---|---|---|---|
| Butane, propane, blends (LPG) | Cylinders or ASME tanks in a rated outdoor or detached area; recovery tanks at the extractor | NFPA 58, IFC extraction chapter, NFPA 497 classification | Setbacks, relief to safe location, grounding, chilled supply, vapor return |
| Ethanol | Tank farm to NFPA 30 with containment; chilled supply loop | NFPA 30, IFC flammable liquids, C1D1 or C1D2 per quantity | Bonding and grounding, vapor control, low-temperature materials, containment and drainage |
| Carbon dioxide | Bulk cryogenic or high-pressure storage outdoors | ASME code, CGA guidance, asphyxiant monitoring | Vaporizer, pressure regulation, relief, recovery and recycle |
| Recovered solvent | Recovery vessels and receivers at the extractor, returned to storage | Same as the solvent; often the highest-hazard point | Two-phase piping, relief, level control, purity tracking |
The fire code limits how much solvent can be inside the extraction room, so storage goes outside in a rated area and supply comes in by pipe through rated penetrations, which is why the tank farm and the piping are designed together and reviewed with the fire marshal before anything is ordered.
Recovery vessels and relief
Hydrocarbon recovery pulls solvent from the extract by heat and vacuum or by pumping, condenses it and returns it to a recovery tank; ethanol recovery uses falling-film or rotary evaporation with condensers and a receiver. These vessels see temperature and pressure swings every cycle and are where leaks and over-pressure happen, so they are ASME-rated where required, fitted with relief valves piped to a safe outdoor location, instrumented for level and pressure, and installed with the extractor’s listing or peer review in hand. Recovered solvent purity is tracked because water and terpenes accumulate and affect the next extraction.
Cold: what needs it and how cold
| Duty | Temperature | Load character |
|---|---|---|
| Chilled hydrocarbon or ethanol for extraction | Minus 40 C to minus 80 C | Large, continuous during runs; solvent volume and specific heat |
| Winterization (dewaxing) of ethanol extract | Minus 20 C to minus 60 C | Batch cooling of tanks or jacketed vessels; long holds |
| Cold traps and condensers | Minus 40 C to minus 80 C | Continuous during recovery |
| Crystallization (isolate) | Room temperature to minus 20 C | Controlled cooling ramps |
| Jacketed reactors and evaporator condensers | Plus 5 C to minus 20 C | Condensing loads during recovery |
| Formulation and storage | Plus 2 C to plus 20 C | Modest; standard chilled water |
Chillers and distribution
Low-temperature duties use single- or two-stage or cascade refrigeration chillers circulating a heat transfer fluid (silicone oil, low-temperature glycol blends or specialty fluids) at the process temperature, sized for the peak simultaneous load of extractors, traps and winterization tanks rather than the average, with headroom for the extractors the facility plans to add. Fluid selection sets the pump and piping design: viscosity rises sharply at low temperature, lines are insulated with vapor barriers to stop icing, and the loop is balanced so a winterization tank cannot starve an extractor. Immersion chillers and direct-expansion coils serve small tanks; larger facilities run a central low-temperature loop with isolation per user. Heat rejection from the chillers, air- or water-cooled, is a plant utility that is sized with them.
Materials at low temperature and with solvents
Stainless is used for solvent and cold service throughout; carbon steel becomes brittle at low temperature and is avoided on cold lines and vessels; elastomers and seals are chosen for solvent compatibility and cold flexibility (PTFE, FFKM and low-temperature FKM grades); no plastics on solvent lines; and insulation systems are closed-cell with sealed vapor barriers. Vessels for cold service are designed for the thermal cycling and for vacuum where cooling pulls it.
Installation and classification
Tank farms are set on containment pads with setbacks and grounding; chillers are placed outside the classified area or rated for it; glycol and solvent piping enters the extraction room through rated penetrations; relief piping runs to safe locations away from air intakes; and gas detection, ventilation interlocks and emergency shut-offs are tied to the tank farm and the room. The fire marshal’s review covers the tank farm, the relief and the classification drawing together, and the state regulator inspects the facility on top of it.
What Paul Industries installs
Hydrocarbon, ethanol and CO2 storage and tank farms with containment, grounding and relief; recovery vessels and receivers with relief and instrumentation; low-temperature chillers, heat transfer fluid loops, insulation and balancing; immersion and direct-expansion cooling for tanks; heat rejection; solvent and glycol piping through rated penetrations; and coordination of the classified-area design with the electrical contractor and the fire marshal.
Standards referenced: NFPA 30 · NFPA 58 · NFPA 497 · ASME BPVC · ASME B31.3
Frequently asked questions
Where is solvent stored at an extraction facility?
Outside the extraction room in a rated area: LPG in cylinders or ASME tanks in an outdoor or detached enclosure to NFPA 58, ethanol in a tank farm with containment to NFPA 30, and CO2 in bulk storage outdoors, with supply piped into the extraction room through rated penetrations. The fire code limits the quantity inside the room, which is why storage is designed with the piping and reviewed by the fire marshal first.
What chiller temperature does cannabis extraction need?
Minus 40 C is the common target for chilled hydrocarbon and ethanol extraction and cold traps, with some processes at minus 60 to minus 80 C; winterization runs at minus 20 to minus 60 C; crystallization and condensers at warmer set points. Low-temperature chillers with cascade or two-stage refrigeration and a heat transfer fluid rated for the temperature serve these duties.
How are extraction chillers sized?
For the peak simultaneous load: every extractor, cold trap and winterization tank running together at the warmest ambient the plant sees, plus headroom for planned extractors, rather than the average. Chiller capacity is the utility most often undersized as extractors are added, and undersizing shows as slow cool-downs and drifting extraction temperatures.
What heat transfer fluid is used for low-temperature extraction loops?
Silicone oils, low-temperature glycol blends or specialty synthetic fluids rated for the loop’s temperature, chosen for viscosity at temperature (which rises sharply below minus 30 C), pump compatibility, freezing margin and safety. Standard propylene glycol at high concentration is too viscous for the coldest duties; the fluid sets the pump and pipe sizing.
What is a recovery vessel and why is it a hazard point?
The vessel where solvent pulled from the extract is condensed and collected before returning to storage: it sees pressure and temperature swings every cycle, holds flammable solvent, and is where over-pressure and leaks occur. It is ASME-rated where required, fitted with relief piped to a safe outdoor location, instrumented for level and pressure, and covered by the extractor’s listing or peer review.
What materials are used for solvent and cold service?
Stainless steel for solvent and cold lines and vessels; no carbon steel on cold service because it embrittles; no plastic on solvent lines; PTFE, FFKM or low-temperature FKM seals chosen for solvent compatibility and cold flexibility; and closed-cell insulation with sealed vapor barriers to prevent icing. Vessels are designed for thermal cycling and vacuum.
How does the fire code limit solvent quantities?
By setting maximum allowable quantities per control area for flammable gases and liquids, depending on occupancy, sprinklers and construction, and by requiring storage above those quantities to be in rated storage areas or outdoors. The hazard analysis the fire marshal reviews fixes the quantities, and the tank farm and piping are designed to them.
What is winterization and what cold does it need?
Chilling an ethanol extract, typically to minus 20 to minus 60 C, and holding it so fats and waxes precipitate and can be filtered out. It needs jacketed tanks or a cold room on the low-temperature loop with long holds, and it is often the largest batch cooling load in the facility, competing with the extractors for chiller capacity.
How is relief piping designed for extraction equipment?
Relief valves on recovery vessels, solvent tanks and CO2 systems are sized for the relieving case and piped to a safe outdoor location away from ignition sources, air intakes and people, with the discharge route shown on the drawings the fire marshal reviews. Relief that vents into the room is a common finding on facilities built without a piping engineer.
Can a chiller be located inside the extraction room?
Only if it is rated for the room’s electrical classification, which most are not, so chillers are located outside the classified area with the heat transfer fluid piped in through rated penetrations. The chiller’s electrical and mechanical equipment is then outside the hazard and the room contains only the cold loop.
How is ethanol stored and supplied?
In a tank farm to NFPA 30 with secondary containment, bonding and grounding, vapor control and setbacks, supplied through a closed, chilled loop to the extraction equipment and returned from recovery, with proof and water content tracked because recovered ethanol accumulates water and terpenes. Tank farm size is set by the code’s quantity limits and the delivery schedule.
What is different about CO2 storage and supply?
CO2 is stored outdoors in bulk cryogenic or high-pressure tanks under the ASME code and CGA guidance, vaporized and regulated to the extractor’s supply pressure, recovered and recycled after expansion, and monitored in occupied rooms as an asphyxiant. It is not flammable, so the room is usually not electrically classified, but the pressure and monitoring design are stringent.
How is heat rejected from extraction chillers?
Through air-cooled condensers or water-cooled condensers on a cooling tower or dry cooler, sized with the chillers for the warmest ambient; low-temperature refrigeration rejects more heat per unit of cooling than comfort cooling, and the heat rejection is a plant utility that is often overlooked until the chillers trip on a hot day.
Can extraction cooling be shared with post-processing cooling?
A central low-temperature loop can serve extractors, cold traps, winterization and crystallization if it is sized for the combined load and the lowest temperature and balanced with isolation per user; warmer duties (formulation, storage) are usually served by a separate chilled-water loop so they do not consume low-temperature capacity.
What instrumentation do solvent tanks and recovery vessels need?
Level, pressure and temperature indication and alarms, high-level shut-offs, relief with discharge to a safe location, and, in the room, gas detection interlocked to ventilation and power; instruments inside the classified area are intrinsically safe or rated. The instrumentation is part of the equipment listing or peer review the fire marshal reviews.
How are cold lines insulated?
With closed-cell insulation (polyisocyanurate, elastomeric or cellular glass) sized for the temperature, with sealed vapor barriers at every joint and penetration so moisture cannot reach the cold surface and ice, and with jacketing in wash-down or outdoor areas. Failed vapor barriers produce ice, dripping floors and lost capacity.
What happens when a facility adds extractors without adding cooling?
Extraction temperatures drift warmer, cold traps lose efficiency and solvent loss rises, winterization takes longer, and the chiller runs continuously; operators stagger runs and lose throughput. The loop and chiller are sized with headroom and stub-outs at the start, or a second chiller is added in parallel with the loop re-balanced.
Who reviews the tank farm and chiller installation?
The fire marshal or building official under the fire code reviews the tank farm, relief, classification and the extraction equipment’s listing or peer review; the state cannabis regulator inspects the facility; and where ASME vessels and high-pressure CO2 are involved, the vessel documentation is part of the review. The reviews happen before equipment is ordered if the schedule is to hold.
Can an extraction facility be built in an existing warehouse?
Yes: the extraction room is built as a rated enclosure inside the shell, the tank farm and chillers are placed outside or in rated spaces, solvent and cold loops enter through rated penetrations, and post-processing occupies conventional space. The building’s electrical, ventilation and sprinkler systems are extended to serve the hazard, and the review is done before the lease is signed if possible.
Tank farm or chillers: what does Paul Industries install at an extraction site?
Hydrocarbon, ethanol and CO2 storage and tank farms with containment, grounding and relief; recovery vessels and receivers with relief and instrumentation; low-temperature chillers, heat transfer fluid loops, insulation and balancing; tank cooling; heat rejection; solvent and glycol piping through rated penetrations; and coordination with the electrical contractor and fire marshal.
Related: Cannabis & Botanical Extraction Facility Systems · Process & Storage Tank Installation · Process Chiller Installation & Service · Cannabis Extraction Facility Piping and Utilities · Plant Utilities: Steam, Heating, Chilled Water & Ice Builders · Sanitary Heat Exchanger Installation & Service · Request a quote · Cannabis Post-Processing Cleanrooms and Controlled Rooms