LIQUID-LIQUID EXTRACTION

NAME: SUMAN KUMAR PAULROLL NO.: 16AG63R09M.TECH, FOOD PROCESS ENGINEERINGIIT KHARAGPUR

CONTENTS Introduction Principle Single stage batch extraction Continuous multistage counter current extraction Liquid-liquid extraction equipment Parameters of LLE Extraction of soybean oil by LLE Applications Advantages and limitations Conclusions

INTRODUCTION Extraction

Extraction is a separation process consisting in the separation of

a substance from a solid or liquid mixture..

Liquid-liquid extraction

It is a method to separate compounds based on their relative

solubilities in two different immiscible liquids.

In liquid-liquid extraction the extraction takes place from one

liquid medium to another.

Feed contains the desired solute. Its comes in contact with the solvent. Mass transfer takes place. The extract is the solvent rich solution contains the extracted

solute. The raffinate is the residual feed solution, may contain little

solute.

PRINCIPLE It is a mass transfer and thermodynamic process and it works based

on the partition or distribution coefficient.

Partition Coefficient

It is the ratio of concentrations of a compound in a mixture of two immiscible phases at equilibrium.

Given as,

Where,

OPERATING MODES OF EXTRACTION

Extraction

Batch

Single stage

Multistage

Continuous Counter current

Single Stage Batch Extraction

Multistage Batch Extraction

Continuous Counter Current Multistage

LIQUID-LIQUID EXTRACTION EQUIPMENT

Vessels in which mixing is done by mechanical agitation Agitated columns Mixer-settlers Centrifugal extractors

Vessels in which mixing is done by flow of the fluid

Spray extraction towers Packed extraction towers

AGITATED COLUMNS Two most important types

a) Scheibel Tower The agitators are mounted at fixed intervals on a central

vertical shaft. Wire-mesh packings are installed to improve coalescence

and separation of the phases.

b) Karr Reciprocating Plate Tower Perforated trays moves up and down. More uniform drop size distribution.

Scheible Tower Karr Column

MIXER-SETTLERS A mixer-settler device ordinarily

consisted of two parts: A mixer for contacting the

two liquid phases. A settler for their mechanical

separation. It provides efficient mass

transfer.

SPRAY EXTRACTION TOWERS The heavy liquid enters at the

top of the spray tower, fills the tower as the continuous phase.

The light liquid enters through a nozzle distributor at the bottom, which disperses or sprays the droplets upward.

The light liquid coalesces at the top and flows out.

In some cases the heavy liquid is sprayed downward into a rising, light continuous phase.

PARAMETERS OF LLE Solvent selection Operating conditions Mode of operations Extractor type Design criteria

SOLVENT SELECTION Partition coefficient High selectivity Density Interfacial tension Viscosity Stability Cost Toxicity and flammability Corrosivity

APPLICATIONS In Food Industry

Extraction of essential oil, flavourings etc. Caffeine extraction from tea and coffee.

Other applications: Removal of phenol from waste water. Recovery and purification of acetic acid from aqueous streams. Extraction of antibiotics and organic acids from fermented

broth. Recovery of rare earth elements.

DEACIDIFICATION OF SOYBEAN OIL Degummed soybean oil containing 1.05 ± 0.10% w/w free

fatty acids. Deacidification is done to remove this free fatty acids. It provides more stability and make it more acceptable for

consumers. It is done by extraction with ethanol. degummed soybean oil is used as the feed. Extract contains ethanol with FFAs. Raffinate contain the deacidified oil.

Advantages Heat sensitive products are processed at ambient or moderate

temperatures. Suitable at wide range of temperature. Very large capacities are possible with a minimum of energy

consumption Recovery of solvent is possible.

Limitations Time consuming. Required skilled labor.

CONCLUSION LLE is used when separation not feasible by distillation. It is a mass transfer and thermodynamic process. Selection of solvent is very important parameter for LLE. This method is widely used in various industries, and in the

laboratory for refining, isolating and purifying a variety of useful compounds.

Though it is widely used, it has some limitations.

REFERENCES1. Geankoplis, C.J., Transport Processes and Unit Operations, 4th edition,

Prentice Hall of India, ISBN 81-203-2614-8, 2004.2. Ghosh, R., Principles of Bioseparations Engineering, World Scientific

Publishing Co. Pte. Ltd., ISBN 981-256-892-1, 2006.3. McCabe, W.L., Smith, J.C., Harriott, P., Unit Operations of Chemical

Engineering, 5th ed., McGraw-Hill, ISBN 0-07-112738-0, 1993.4. Green, W. D., Perry, H.R. (eds.), Perry’s Chemical Engineers’ Handbook,

8th edition, McGraw-Hill, ISBN 0-07-142294-3, 2008.5. Fornasero, L. M., Marenchino, N.R., and Pagliero, L.C., Deacidification of

Soybean Oil Combining Solvent Extraction and Membrane Technology, Advances in Materials Science and Engineering ,Volume 2013 , Article ID 646343, 5 pages, 2103.