Centrifugation

Objectives, principle & applications of Centrifugation,
principles, construction, working, uses, merits and demerits of –
Perforated basket centrifuge,
Non-perforated basket centrifuge,
Semi continuous centrifuge &
Super centrifuge.

1. CENTRIFUGATION By Yogeshwary Bhongade Assistant Professor Gondia college of Pharmacy, Gondia

2. CONTENT Objectives, principle & applications of Centrifugation, principles, construction, working, uses, merits and demerits of – Perforated basket centrifuge, Non-perforated basket centrifuge , S emi continuous centrifuge & Super centrifuge.

3. Introduction It is the process in which centrifugal force is used as driving force for the phase separation. Centrifugation is a technique used for the separation of particles from a solution according to their size, shape, density, viscosity of the medium and rotor speed. The particles are suspended in a liquid medium and placed in a centrifuge tube. The tube is then placed in a rotor and spun at a define speed.

4. Applications Widely used in bulk drug industry to separate crystaline material for separation Production of biological product Evaluation of suspention and emultion Determination of molecular weight of colloids

5. Equipment for centrifugation 1. Filtration centrifuge - Perforated Basket Centrifuge - Semicontinuous Centrifuge 2. Sedimentation Centrifuge - Non-Perforated Basket Centrifuge - Supper centrifuge

6. Perforated Basket Centrifuge Principle A basket is rotated at high speed. Feed is incarporated at the centre and suspention is carried out by perforated wall. Construction It consist of verical perforated drum. The drum is fitted with filter cloth. This assembly is fitted with casing

7. Working The slurry is fed at centre Liquid force out throufg the filter cloth is collected in gap between the drum and casing and drained out. The particle are collected on the filter cloth and can be simply wiped out.

8. Semicontinuous Centrifuge Principle Based on filtration centrifuge Separation is through perforated wallbse on difference in densities of solid and liquid phase. Construction Vertical perforate basket is mounted on horizontal shaft Fees and wash pipe are introduced through the open side of the perforated basket. Wash pipe is connected theough the diphragm valve throufg air supply. Hydraulic cylinder attachment is made in such a matte that discharge chute enters from the side of basket.

9. Working Perforated basket rotate while the slurry is introduced from the side pipe The slurry passes through the perforated wall during centrifugation. The solid are retain in the basket while the iltrate is allowed to leave in the basket. Further cake is washed with water and the wash is allowed to leave the basket throufh the filtrate outlet. once the desired thickness is achived the feeler cuts of the air supply to diphragm valve that automatically shuts off the entry of slurry. The hydraulic cylinder is attached which lift the knifealong with the discharge chute. The crystals are scraped off and collected from the solid outlet.

10. Advantages Solid can direclty drain out from bowl. Fast process

11. Disadvantages Complex construction

12. Non-Perforated Basket Centrifuge Construction Consist of plane vertical drum which rotate at desired speed. Skimmers or weirs are provided to remove the liquid.

13. Working Solid get deposited on the wall, followed by heavier liquid and the lighter liquid. The liquid is removed by weirs and solids are removed bu the end by scrapper.

14. Super centrifuge Principle based on sedimentation sentrifuge Separation is based on difference in densities of two immiscible liquids without a porous barrier. Construction It consist of hallow cylinder bowl of small diameter. The bowl is suspended from a flexible spindle at the top and guided at the bottom by loose fit bushing. It is rotated on its longitudinal axis. Provision is made at bottom for the feed inlet using pressure system

15. Two liquid outlet are provided at different height at top of the bowlfor simultaeous recovery of separated liquids

16. Working Bowl is allowed to ratate at high speed upto 2000RPM Feed is introduced from the bottom During Centrifugation two liquid gets separated based on difference in densities. The heavier liquids are thrown against the wall of bowel and lighter remains in the middle. Both liquid rise to top due to the conical shape of the bowl and exert pressure. The liquids are separated simultaneously and are collected from different outlet.

17. Advantages Contineuous process Separate two immisible liquids Rapid process Disa dvantages Hifg energy consuption Expensive High cost of maintainace

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