Short Path Distillation 3t4b66

A Seminar Report on “Short Path Distillation”

Prepared by : Soham M. Shah Guided by : Mrs N.H.Tahilramani

Introduction

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Short path distillation is a technique by which heat sensitive chemicals can be distilled efficiently. Short path distillation is usually performed under vacuum at a pressure less than 0.001 mbar It is a process in which distillation apparatus consist of condenser and evaporator fitted in a single unit. The distance between evaporator and condenser surface is only of few centimeters. Hence it provides lowest distillation temperature and short residence time. Thus reduces possibility of thermal degradation of product

Górak, A., and H. Schoenmakers eds., “Distillation: Operation and Application,,” 1st ed., Elsevier Inc., Oxford, U.K., pp. 368-375 (2014)

Principle

The principle of short path distillation can be understood from the figure below:

Fu, Z. J., et al., “Technology Research on Molecular Distillation Separation of Renewable Waste Lubricating Oil, ” Advanced Materials Research, 726, pp. 2979-2982 (2013).

Construction

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

Residue Discharge Heater jacket Roller wiper Space under vacuum Internal condenser Feed Geared motor Heating medium inlet Heating medium outlet Exhaust Cooling medium inlet Cooling medium outlet Distillate discharge

Working

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Feed is continuously fed at top through a rotating distributor plate. Distributor is rotated using motor. Distributor plate distributes feed uniformly on the heat transfer surface. Feed flows down on heat transfer surface by gravity and gets heated. Heat required can be provided by thermic fluid, steam or hot water. This heat causes partial vaporization of feed. Vapor travel through the distillation gap to condenser surface where heat is removed by cooling coils. Cooling medium can be cooling water, chilled water, oil or brine.

Thakore, S. B., and B. I. Bhatt, “Introduction to Process Engineering and Design, ” 7th ed., McGraw-Hill. India, pp. 493-500(2007).

Types of short path distillation units.

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There are mainly two types of short path distillation units based on force used for distribution of liquid feed: 1. Falling film short path distillation unit; which uses gravitational force to allow the liquid to be distributed as a thin film on a vertical vaporizer surface . 2. Centrifugal short path distillation unit; which uses centrifugal force generated by rotor to promote the formation of thin film. The separation principle of both type of distillation unit is same There is also a third kind of short path distillation unit based on working; –. Reactive short path distillation unit; which is a combination of reactor and a short path distillation unit –. Reactive short path distillation can be of both; falling film or centrifugal unit type.

Górak, A., and H. Schoenmakers eds., “Distillation: Operation and Application,,” 1st ed., Elsevier Inc., Oxford, U.K., pp. 368-375 (2014)

Factors affecting short path distillation

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The parameters affecting the molecular diffusion are feed and condensation temperature, feed rate, pressure and concentration of feed. With increase in temperature and decrease in pressure, the separation increases. By increasing the temperature, product purity increases but its yield decreases.

Kulkarni, S. J., “Molecular Distillation: A Review on Applications and Affecting Parameters, ” International Journal of Research (IJR), 2(1), pp. 310-313 (January 2015).

Application

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Separation of fat soluble vitamins. Grape seed oil deacidification. Separation of fatty acids from vegetable oil. Increasing citral concentration in lemongrass oil. Removing phthalates from sweet orange oil. Separation of waxes, fats and natural oils. For fish oils, petroleum residues, solvent removals. In fractionation of milk fat. For enrichment of carotene. For recovery of polyphenols, tocopherols and sterols from deodorizer distillate.

-Górak, A., and H. Schoenmakers eds., “Distillation: Operation and Application, ” 1st ed., Elsevier Inc., Oxford, U.K., pp. 368-375 (2014). -Thakore, S. B., and B. I. Bhatt, “Introduction to Process Engineering and Design, ” 7th ed., McGraw-Hill, India, pp. 493-500 (2007).

Short path distillation for recovery of Polyphenols from deodorizer distillate

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Polyphenols are identified as the natural compounds which impart antioxidant property and thus improve shelf life. During physical refining of rapeseed oil, polyphenols gets separated and concentrates in the distillate along with fatty acids, tocopherols, sterols, etc. Thus oil obtained as bottom product is lean in polyphenols and hence lags in antioxidant property. So in order to obtain natural antioxidant, deodorizer distillate is treated in short path distillation to separate them from free fatty acids which act as oxidants.

Meyer, F., et al., “Application of short path distillation for recovery of polyphenols from deodorizer distillate, ” European Journal of Lipid Science and Technology, 113 11), pp. 1363-1374 (November 2011).

Short path distillation for recovery of Polyphenols from deodorizer distillate

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The effect of various parameters was studied experimentally which is stated as follows: – At 110°C about 43% of the material was evaporated to the distillate phase whereas at 170°C the total distillate yield was approximately 86%. – A separation factor near one is equivalent to an inefficient separation. – Separation efficiency between FFA and tocopherols increases with decrease in evaporation temperature with decrease in distillate rate. – Whereas when experiment were carried out for different feed rates (100-300 mL/h) at 110°C no significant change was observed

Meyer, F., et al., “Application of short path distillation for recovery of polyphenols from deodorizer distillate, ” European Journal of Lipid Science and Technology, 113 11), pp. 1363-1374 (November 2011).

Advantages and Disadvantages •

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Advantages – Can be used for thermally sensitive substances. – Components with high boiling points can be distilled easily due to high vacuum. – There is minimum pressure drop in the system due to short distance between vaporizer and condenser unit. – It requires relatively less maintenance. – High purity of end products is obtained. Disadvantages ─ high vacuum is required for carrying out distillation. ─ High operating cost. ─ If residence time increases, than thermal decomposition of heat sensitive material may occur. ─ The starting natural form is sometimes lost during process.

-Rizvi, S. H. ed., “Separation, Extraction and Concentration Processes in the Food, Beverage and Nutraceutical industry, ” 1st ed. Woodhead Publishing Limited, Cambridge, U.K. (2010) -Thakore, S. B., and B. I. Bhatt, “Introduction to Process Engineering and Design, ” 7 th ed., McGraw-Hill, India, pp. 493-500 (2007). -http://www.avta-us.com/basics.html referred on 29/09/2015

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