Extraction with supercritical fluids in the pharmaceutical, cosmetic and food sectors

LEWA metering pumps and process diaphragm pumps have been successfully used in the following processes:

• Extraction processes with supercritical CO₂ (Supercritical Fluid Extraction SFE), such as decaffeination, degreasing, phytoextraction, as well as the extraction of oil seed, omega fish oil, flavors and spices
• Supercritical preparative liquid chromatography (Supercritical Fluid Chromatography SFC), as well as separation of optically active substances
• Supercritical Fluid Reactions SFR
• Particle formation (e. g., Particles from Gas Saturated Solutions PGSS), such as high-pressure spraying process for pulverizing greases, baked goods, etc.
• Cleaning processes, e.g., process integrated separation of substances, such as pesticide removal (wool grease, lanolin)
• Cell breakdown, inactivation (gentle sterilization)

Industrial scCO2-Applications

Principle of the PGSS process:

1. Conditioning and melting two reactants 1 and 2
2. Feed and compression with LEWA high pressure pumps P1, P2 and P3
3. Mixing both reactants with supercritical fluid in a static mixer (SM)
4. Decompression in a spray tower (SP) via a nozzle
5. Droplet formation
6. Cooling of droplets and particle formation
7. Generation of powder in the spray tower with cyclone (ZK)

Illustration: Principle of the PGSS process

Source: Department of Process Technology, Transport processes, and particle design - technology, University Bochum

A supercritical fluid is a substance whose temperature and pressure are both over their critical point simultaneously (see diagram for CO₂).

The critical temperature is the temperature over which the substance can no longer remain liquid, regardless of the pressure level.

Critical pressure is the pressure over which the substance can no longer form gas, regardless of the temperature.

Supercritical fluids have the density and good dissolving properties of fluids, as well as the viscosity, good compressibility, and diffusability of gases.

Due to their good mixing and mass transfer properties, they are classed as a fluid.

Important advantages of supercritical fluids:

• Safe, cost-effective, environmentally friendly, non-toxic
• They can replace organic solvents
• Good influence over slight changes in operating conditions
• Operating conditions under low temperature and pressure make them attractive for research and development in the pharmaceutical & biotechnology sector.

Selection criteria for the right supercritical fluid:

• Physical-chemical properties of the desired mixture
• Task of the solvent in the process in regards to solubility
• Specific application
• Safety, especially in regards to flammability, phase behavior under operating conditions
• Cost of the fluid
• Cost of the equipment

The most frequently used supercritical fluid is CO₂.

Properties of carbon dioxide:

• Low critical temperature (31.1°C)
• Moderate critical pressure (73 bar)
• Non-flammable
• Non-toxic
• Mixable with organic solvents
• Recoverable after processing
• Diffuses faster than conventional fluid solvents
• GRAS status
• Approved by the FDA for use in food and pharmaceuticals
• Environmentally friendly
• Cost-effective