White Paper · 9 min read
Closed-Loop Hydrocarbon Extraction: Process, Safety, and Throughput Planning
A closed-loop hydrocarbon system extracts cannabinoids and terpenes by passing a liquefied solvent through biomass inside a sealed vessel, then recovering that solvent for reuse instead of venting it — the "closed loop" is what makes the process both efficient and, done correctly, safer than an open blast. Every model in Decimal's hydrocarbon line runs at 2 cycles per hour with C1D1 explosion-proof construction. This guide covers how the process works, what room classification actually requires, and verified throughput across the line so you can plan capacity before you buy.
How a Closed-Loop Hydrocarbon System Works
Liquefied hydrocarbon solvent is pushed through a material column packed with biomass, dissolving cannabinoids and terpenes as it passes through. The resulting solution moves to a collection vessel, where the solvent is evaporated off and recovered for the next run rather than released. What's left behind is the crude extract.
Because the solvent stays inside a sealed system throughout, a closed-loop design limits vapor release compared to an open blast — but it does not eliminate the need for explosion-proof equipment and room design. The solvent is still flammable at every stage of the process.
Safety Classification and Room Requirements
C1D1 is a room requirement, not just an equipment spec: Every model in the HX line ships with C1D1 explosion-proof touchscreen controls, but the room housing the system also needs to meet Class I Division 1 electrical and ventilation requirements. Confirm your local authority having jurisdiction's specific requirements before finalizing a room design.
C1D1 (Class I, Division 1) describes a location where flammable vapor is expected to be present continuously or periodically under normal operating conditions. That classification drives electrical equipment selection, ventilation rates, and often the physical separation of the extraction room from the rest of the facility.
Passive vs. Falling-Film Solvent Recovery
The 5.HX uses passive solvent recovery, while the 15.HX and 40.HX add a falling-film condenser. A falling-film condenser generally recovers solvent faster by increasing the surface area the solvent contacts as it condenses, which matters more as batch size and run frequency scale up.
Throughput by Model
| Model | Batch size | Cycles per hour | Recovery method |
|---|---|---|---|
| 5.HX | 5 lbs. per run | 2 | Passive solvent recovery |
| 15.HX | 200+ lbs. per 8-hour shift | 2 | Falling-film condenser |
| 40.HX | Up to 40 lbs. per run | 2 | Falling-film condenser |
| 75.HX | Roughly double the scale of the 40.HX | 2 | Falling-film condenser |
Planning Checklist Before You Scale Up
- Confirm your room's electrical and ventilation design meets C1D1 requirements for the batch size and run frequency you're planning.
- Size solvent recovery and storage capacity to match your target cycles per shift, not just a single run.
- Plan biomass prep and post-run cleanup time into your cycle math — 2 cycles per hour is the extraction step, not the whole shift.
- Confirm parts and consumables availability for gaskets, seals, and filters before committing to a run schedule.
Common Mistakes and Quality Risks
- Sizing a room's electrical and ventilation design around the equipment spec sheet alone, without a C1D1 review from a qualified electrical engineer.
- Assuming a closed-loop system removes the need for explosion-proof room design because the solvent is "contained."
- Planning shift throughput from the machine's rated cycles per hour without adding biomass prep, cleanup, and solvent recovery time.
- Deferring gasket and seal replacement past the manufacturer's guidance, which is a common cause of unplanned downtime — see our maintenance and parts strategy guide.
Topics covered
- hydrocarbon
- closed-loop
- C1D1
- safety
- throughput
Related Equipment
- 5.HX Hydrocarbon Extractor
- 15.HX Hydrocarbon Extractor
- 40.HX Hydrocarbon Extractor
- 75.HX Hydrocarbon Extractor
Related Parts & Supplies
Related Reading
Frequently Asked Questions
What does C1D1 mean for a hydrocarbon extraction room?
C1D1 (Class I, Division 1) is an electrical classification for locations where flammable vapor is expected to be present continuously or periodically during normal operation. It drives electrical equipment selection and ventilation design for the room, in addition to the equipment itself.
What's the difference between passive and falling-film solvent recovery?
Passive solvent recovery, used on the 5.HX, relies on standard condensation. A falling-film condenser, used on the 15.HX and 40.HX, increases the surface area the solvent contacts during condensation, which generally recovers solvent faster as batch size and run frequency scale up.
How many runs can I get per shift on a closed-loop hydrocarbon system?
Every model in the HX line is rated at 2 cycles per hour for the extraction step itself. Actual runs per shift also depend on biomass preparation, solvent recovery, and cleanup time, which vary by facility and operator experience.
Is closed-loop hydrocarbon extraction safer than an open blast?
A closed-loop design limits solvent vapor release compared to an open blast because the solvent stays inside a sealed system. It does not eliminate the need for C1D1 explosion-proof equipment, ventilation, and trained operating procedures — the solvent remains flammable throughout the process.
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