Size seperation

Size Separation: Objectives, applications & mechanism of size separation, official standards of powders, sieves, size separation Principles, construction, working, uses, merits and demerits of Sieve shaker, cyclone separator, Air separator, Bag filter & elutriation tank.

1. Topic cover 1 Size Separation: Objectives, applications & mechanism of size separation, official standards of powders, sieves, size separation Principles, construction, working, uses, merits and demerits of Sieve shaker, cyclone separator, Air separator, Bag filter & elutriation tank. Presented by : Jagruti Marathe assistant professor at R.C.P.I.P.E.R

2. Size seperation 2 Size separation is a unit operation that involves  the separation of a mixture of various size particles into two or more portions by means of screening surfaces .  Size separation is also known as sieving, sifting, screening.

3. Size seperation Objective/Application: 3  To determine particle size for the production of tablets and capsules.  To improve mixing of powders.  To improve the solubility and stability of particles during production.  To optimize feed rate, agitation, screening during production.  Quality control of raw materials.  Useful in production of tablets, capsules, suspension, emulsion, ophthalmic preparations, ointments, creams, etc.

4. Mechanism of size separation 4

5. Mechanism of size separation 5 Sieve arrangement: Descending order or sieve of large size is at the top and smallest is at the bottom. Materials displaced in the uppermost sieve. Mechanism of action of sieving involved: Agitation (oscillation, vibration, gyration) brushing Centrifugal Advantage of sieving method:  Rapid process with the requirement of little skill

6. Official standards of powders 6 Sr.No Grade of powder all particles must pass through Sieve No. /Nominal mesh aperture Sieve through which 40% of the particles pass/ Nominal mesh aperture 1 Coarse powder 10 /(1700 µm) 44 /(355 µm) 2 Moderately coarse powder 22 /(710 µm) 60/ (250 µm) 3 Moderately fine powder 44/(355 µm) 85/(180 µm) 4 Fine powder 85/(180 µm) Not specified 5 Very fine powder 120/(125 µm) Not specified Coarse or fineness of powder is expressed by Reference  to the nominal mesh aperture size of the sieve through which powder is able to pass. Indian pharmacopoeia- 5 grade of powder

7. Official standards of powders 7 Sr. No. Grade of powder Comparison of powder size 1 Coarse powder  1 2 Moderately coarse powder 1/6 3 Moderately fine powder 1/24 4 Fine powder 1/90 5 Very fine powder 1/2000 Comparison of Powder size by Grade of Powder Note: 1.70 mm=1700 µm

8. Official standards of powders 8 All the particles of which pass through a sieve with nominal mesh aperture of 180 µm (Sieve No. 85)  All the particles of which pass through a sieve with nominal mesh aperture of 125 µm (Sieve No. 120)

9. Method of size separation: 9

10. Sieve shaker 10 Principal : The powdered drug is separated according to its particles size a number of sieves in a nest. These are subjected to difference type of agitation, so that size separation is rapid. Contraction:

11. Sieve shaker 11 Working:

12. Sieve shaker 12 Advantage: It is inexpensive and rapid with reproducible results. Disadvantage: Lower limit of particles size is 50mm If powder is not dry, apertures get clogged with particles , leading to improper sieving. During shaking, attrition occurs causing size reduction of particles. This lead to error in estimation.

13. Cyclone separator 13 Principle: centrifugal force is used to separate solid form fluidized in air.(separation depends on particle s ize and density) Solids are suspended in air and Force air introduced tangentially at Higher velocity so that Rotary movement take place. Contraction:                Cyclone Separator

14. Cyclone separator 14                Cyclone Separator Working:

15. Cyclone separator 15                Cyclone Separator

16. Cyclone separator 16                Cyclone Separator Uses: It is used to separate the solids from gases. It is also used for size separation of solids in liquids. It is used for separating the heavy or coarse fraction from fine dust. Variants: Cyclone separators are also used for size separation of solids suspended in liquid such as water. Such separators are known as wet or liquid cyclone.one such apparatus used for this purpose is Dorrclone .

17. Air separator 17 Principle: In air separator ,centrifugal force is used to separate solids. The air environment is obtained by means of rotating disc and blades. To improve the separation, stationary blades are used. By controlling these blades and the speed of the rotation, it is possible to vary the size at which separation occurs. Contraction

18. Air separator 18 Working:

19. Bag filter 19 Principle : In a bag filter , size separation of fines from the milled powder is achieved into 2 steps. Step:1 Powder is passed through a bag filter by applying the suction on the opposite side of the feed entry. Step:2 pressure is applied in order to shake the bags so that powder adhering to the bag falls off, which is collected from the conical base. Construction:

20. Bag filter 20 Construction:

21. Bag filter 21 Working: The working of the bag filter consists of two steps.

22. Bag filter 22 Step Mechanism Movement of damper Contact between Contact between bags and atmosphere Filtering period Cam does not press the bell crank lever Opens Closes Shaking period Cam presses the bell crank lever Closes Open

23. Bag filter 23 Advantages : Bag filter is extremely useful for removing fines, which cannot be separated by other methods. These can be used even to remove dust. The ordinary household vacuum cleaner is a simple bag filter. Disadvantages: Bag filter is not size separation equipment as such.

24. Elutriation tank 24 Elutriation is a method of separation of particles in powder based on the low density of fine particles and high density of the coarse particles using fluid flow. Elutriation and sedimentation are different in one respect . In case of sedimentation , particles move in the direction on gravitational force, while in elutriation , some particles move against the gravitational force. In elutriation , fluid flows in opposite direction of the settling movement. The upward velocity of fluid is less than the settling velocity of the particles . Hence , time is an important factor. In particle, particles can be seen to rise with the fluid and then to move outwards to the tube- wall, where the velocity is lower and these start to fall.

25. Elutriation tank 25 Uses: These technique is applicable to insoluble solids such as kaolin, or chalk, which is subjected to wet grinding following by sedimentation or elutriation. Advantage: It is a continuous process. Separation of size fraction is quick as compare to other methods. The apparatus is more compact than that are used in sedimentation methods, Depending on the number of fractions required the same number of tubes of different area of cross-section can be connected. Disadvantage: The suspension s diluted which may be desirable in certain cases.

26. Elutriation tank 26

27. 27 Thank you