EQUIPMENT AND EXPERIMENTAL

TECHNIQUES USED IN NCF

EXTRACTION & INDUSTRIAL APPLICATION

Presented by- Anjum Ayoub14/PFT/013

Near Critical Fluid

A near critical fluid (NCF) is characterized by physical & thermal properties that are between those of the pure liquid and gas.

The fluid density is a strong function of the temperature and pressure.

The diffusivity of NCF is much higher than for a liquid.

NCF readily penetrates porous & fibrous solids.

Consequently, NCF can offer good catalytic activity.

Equipment

Although there is some degree of overlap, distinction will be made between equipment that has been designed for use in either fractionation & extraction processes.

A description of large scale commercial scale plant is also omitted since accurate information of plant operating in the commercial sector is often difficult to obtain & highly process specific.

Relevant design features of large scale NCF extraction equipment are available in specialist reviews, conference proceedings & directly from manufacturers.

Near Critical Fluid Extraction (NCFE)

NCFE is based on the fact that, near the critical point of the solvent, its properties change rapidly with only slight variations of pressure.

NCF can be used to extract analytes from samples.

Main advantages of using NCF for extractions is that they are inexpensive, extract the analytes faster & more environmentally friendly than organic solvents.

For these reasons NCF, CO2 is the reagent widely used as the near critical solvent.

Extraction

Pilot plants with recirculation- The CO2 is stored at its vapour pressure, in the

condenser, as an NCL and is pumped into the extraction vessel by a high- pressure liquid pump.

The state of the CO2 in the extraction/ separation stages (SCF/NCL or gas) is determined by the temperature and pressure of the vessel.

In an extraction process the material to be extracted is placed in extraction vessel, which is purged with gaseous CO2 to remove all air from the system.

CONTD. Extraction is then started by pumping the liquid CO2

through a heat exchanger into the extraction vessel.

Flow rate, which is determined by the pump, is usually set to allow sufficient residence time in the extraction vessel for equilibrium solubility to be attained.

Solution then passes to the separation vessel, where conditions are set to minimise the solubility of the extracted components.

If the extract is a liquid it can be periodically removed from the separation vessel by a drain valve, but if is a solid it is necessary to halt the extraction to remove the deposits by washing.

INSTRUMENTATION

Near critical Fluid Extractors

NCF Extraction

It is the process of separating one component from another using NCF as the extracting solvent.

Based on the fact that, near the critical point of the solvent, its properties change rapidly with only slight variations of pressure.

Near critical combines desirable properties of gases and liquids Solubility of liquids Penetration power of gases

Process flexibility density of NC and solubility of a solute in it can be changed in a continuous manner by change of pressure.

Environmental perspective innocuous substances such as water and CO2 can be used as extracting solvents instead of organics.

PROCEDURE

Main components of the NCFE instrument are a pump, an extraction chamber, a recovery chamber and a collection device.

In order to generate a NCF, CO2 is pressurized above its critical pressure in a pump.

Mixture to be separated is placed in the extraction chamber and put in contact with the near critical fluid.

One of the elements in the mixture dissolves better in the critical fluid and leaves the residue enriched in the other components.

The loaded solvent is then transferred to a recovery chamber, where earlier component is recovered by lowering the solvent's density.

This density can be achieved by raising the temperature at constant pressure but more often it is achieve by reducing the pressure at constant temperature.

After depressurizing, two methods have been adopted for collection of the extracted analyses, these are on-line or off-line NCFE. 

PROCEDURE

In on-line NCFE, the extracted analytes are directly coupled to a chromatographic separation system such as NCF, gas chromatography (GC) or high performance liquid chromatography (HPLC) with appropriate detection.

In off-line NCFE, it allows direct collection of the extracted analytes either in a solvent or passing the NCF through a column packed with Chromatography adsorbent or can be collected in a cryogenic vessel for subsequent analysis.

PROCEDURE

NCF extraction types

Liquid-NCF extractionSimilar to liquid-liquid extractionExamples

Increasing ethanol concentration in aqueous solution

Removal of alcohol from beer Solid-NCF extraction

Similar to solid-liquid extractionExamples

Removal of caffeine from coffee beansPolymer fractionationExtraction of flavours from rose petals

Industrial applications

Near critical fluid extraction NCF decomposition Dry-cleaning Chromatography Chemical reactions Impregnation and dyeing Nano and micro particle formation Generation of pharmaceutical co-crystals Near critical drying Near critical water oxidation, hydrolysis and

gasification

CONTD.

NCF in power generation Biodiesel production Enhanced oil recovery and carbon capture

and storage Enhanced geothermal system NCF deposition Antimicrobial properties

CONCLUSION

Extraction by means of near critical carbon

dioxide can be expected to improve efficiency, including shorter extraction times and simplified procedures when compared with extraction techniques that employ organic solvents

References

www.google.com en.wikipedia.org PDF files Separation Processes in the Food and

Biotechnology Industries  By A.S. Grandison