Application of Roots Liquid Ring Vacuum Units in the Flavor and Fragrance Extraction Industry

Roots liquid ring vacuum units are the primary vacuum equipment for flavor and fragrance extraction (especially essential oils and natural aromatics). They are perfectly suited for process requirements involving medium–high vacuum, high pumping speed, large volumes of condensable vapor, and explosion protection, and are widely used in core processes such as vacuum distillation, molecular distillation, vacuum drying, and solvent recovery.

I.  Core Application Processes (Full Process Coverage)

1. Vacuum Distillation (Core of Essential Oil Refining)

Process: Crude essential oils are distilled at low temperature under negative pressure of 500–1000 Pa to separate aromatic components such as terpenes, esters, and alcohols, purifying and stabilizing the aroma.

Unit function: Rapidly establishes stable vacuum, lowers boiling point (100℃ → 40–60℃), prevents decomposition of heat-sensitive components; high pumping speed quickly removes vapor to improve distillation efficiency.

Configuration: 1 Roots pump + 1 liquid ring pump.

2. Molecular Distillation / Short-Path Distillation (High-End Fragrance Refining)

Process: Separation is performed under ultra-high vacuum of 50–200 Pa based on differences in molecular mean free path, used to purify high-end essential oils such as rose, jasmine, and sandalwood, removing heavy metals and pesticide residues.

Unit function: Provides ultra-high vacuum and high pumping speed, enabling low-temperature (30–50℃) and short-time separation to preserve natural aroma to the greatest extent.

Configuration: Two-stage Roots + liquid ring unit.

3. Vacuum Drying (Concrete / Absolute Production)

Process: Solvent-extracted concretes are dried at low temperature under negative pressure of 1000–3000 Pa to remove solvents such as ethanol and hexane, obtaining high-concentration absolutes.

Unit function: Low-temperature drying (40–50℃) prevents aroma volatilization and oxidation; rapid removal of solvent vapor shortens drying time and improves yield.

Configuration: Single-stage Roots + liquid ring unit, with pumping speed matched to the dryer volume.

4. Solvent Recovery (Extraction Section)

Process: Solvents such as ethanol and petroleum ether used in extraction are recovered under vacuum, condensed, and recycled to reduce costs and meet environmental standards.

Unit function: Removes solvent vapor and achieves high recovery rate (≥95%) with condensers; explosion-proof design ensures safety.

5. Vacuum Filtration / Degassing

Process: Filters essential oils and removes dissolved oxygen and bubbles to improve clarity and stability.

Unit function: Provides 1–5 kPa vacuum to accelerate filtration and enhance degassing, preventing oxidative deterioration.

II. Key Selection Parameters

Vacuum level: Selected according to process requirements; the ultimate vacuum of the unit must be 0.5–1 order of magnitude higher than the process vacuum.

Pumping speed: Calculated based on distillation still volume and vapor generation rate, ensuring process vacuum is achieved within 15–30 minutes.

Explosion protection: Explosion-proof motors (Ex d IIB T4) must be used for solvent applications; pump body material can be 304/316 stainless steel for corrosion resistance.

Cooling: Working fluid temperature of liquid ring pump ≤ 30℃, equipped with closed circulating cooling system to save water and stabilize vacuum.

III. Operation and Maintenance Points

Vacuum control: Variable frequency speed regulation to accurately match vacuum requirements of different processes, saving energy and stabilizing production.

Corrosion protection: Components in contact with essential oils/solvents use stainless steel or fluoroplastics; pump chambers are cleaned regularly to prevent scaling and contamination.

Working fluid management: Softened or deionized water is used for liquid ring pumps and replaced regularly to avoid scaling and microbial growth.

Protection devices: Equipped with overload protection, temperature alarm, and gas ballast valve to prevent overheating of Roots pumps and cavitation of liquid ring pumps.