PHARMACEUTICAL ENGINEERING, SIZE SEPARATION, BPHARM THIRD SEM

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1. SIZE SEPERATION PRESENTED BY : M.NAVEEN KUMAR B.PHARM SECOND YEAR (THIRD SEMESTER) AADHIBHAGAWAN COLLEGE OF PHARMACY RANTHAM GUIDED BY : Mr.L.GOPI M.PHARM ASST PROF OF DEPARTMENT OF PHARMACEUTICS AADHIBHAGAWAN COLLEGE OF PHARMACY RANTHAM

2. PHARMACETICAL ENGINEERING

3. CONTENTS : INTRODUCTION OBJECTIVES MECHANISM OF SIZE SEPERATION OFFICIAL STANDARD OF POWDERS SIEVES TYPES OF SIEVES EQUIPMENTS FOR SIZE SEPERATION

4. INTRODUCTION 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 . This technique is based on physical differences b/w the particles such as size , shape and density . Size separation (or classification) is a process in which particles of desired size are separated from other fractions

5. OBJECTIVES During tablet granulation the granules should be within narrow size range, otherwise, weight variation will take place during tablet punching. 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.,

6. MECHANISM OF SIZE SEPERATION The working of mechanical sieving devices are based on any of the following methods.  AGITATION  BRUSHING  CENTRIFUGAL

7. AGITATION Sieves may be agitated in a number of different ways, such as: Oscillation : This sieve is mounted in a frame that oscillates back and forth. It is a simple method but the material may roll on the surface of the sieve. Vibration : The sieve is vibrated at high speed by means of an electric device. The rapid vibration is imparted to the particles on the sieve which helps to pass the powdered material through it.

8. Gyration : In this method, a system is made so that sieve is on rubber mounting and connected to an eccentric fly wheel. This gives a rotary movement of small amplitude to sieve which turn gives spinning motion to the particles that helps to pass them through a sieve. Agitation methods are not continuous methods' but can be made so by inclination of the sieve and the provision of separate outlets for undersize and oversize particles.

9. BRUSHING In this case, a brush is used to move the particles on the surface of the sieve and to keep the meshes clear. The brush is rotated in the middle in the case of a circular sieve but spiral brush is rotated on the longitudinal axis in case Of a horizontal cylindrical sieve.

10. CENTRIFUGATION In this method, a high speed rotor is fixed inside the vertical cylindrical sieve, so that on rotation of rotor the particles are thrown outwards by centrifugal force. The current of air which is produced due to high speed of rotor helps in sieving the powder.

11. OFFICIAL STANDARD OF POWDERS Grade of powder SIEVE THROUGHWHICH ALL PARTICLES MUST PASS Sieve through which not more than 40 percent of particle pass Coarse 10 44 Moderately coarse 22 60 Moderately fine 44 85 fine 85 Not specified Very fine 120 Not specified

12. SIEVES Sieves are constructed from wire cloth with square meshes, woven from wires of brass, bronze, stainless steel or any other suitable material. The wires should be of uniform circular cross-section and should not be coated or plated. There should not be any reaction between the material of the sieve and the substance which is being sifted from it.

13. TYPES OF SIEVES WIRE SIEVE PERFORATED SIEVE HORIZONTAL SIEVE WOVEN WIRE SIEVE BAR SCREEN BOLTING CLOTH SIEVE PUNCHED PLATES ( PERFORATED SCREEN )

14. EQUIPMENT FOR SIZE SEPERATION Some of the equipment discussed below are : Sieve shaker Cyclone separator Air separator Bag filter Elutriation tank

15. SHIEVE SHAKER PRINCIPLE : In this method, the fine powder is separated from the coarse powder by using sieves of desired number. The degree of fineness of a powder is known with the help of sieve through which the powdered material is passed. Sieves are numbered in order to distinguish from each other. It is used to shake a stack of test sieves which are placed in order (largest aperture on the top and smallest on the bottom), so that materials get sifted through according to particle sizes. Sieve shakers can replace manual hand sieving to conduct sample size reduction, material separation and assist particle analysis.

16. CONSTRUCTION : Select the sieves with mesh sizes that are to be used and stack them together beginning with a pan at the bottom. Then the finest sieve followed by increasing coarser sieves with the coarsest on top. Place stack of sieves in the shaker with the bottom pan resting on the cradle platform. Cover the top sieve so that the stack can be easily secured in the shaker. Secure the stack with the sieve hold down bar on the top of the stack and screw the nuts on the vertical support rods firmly against the holder. Adjust and tighten the nuts at the top of the vertical support rods according to the weight of the material in the sieves.

17. WORKING : Size separation of powder is done by passing the powdered material through a set of sieves. Sieves are arranged in descending order i.e. sieve of larger size is at the top and the smallest one at the bottom. The bottom sieve is attached to the receiving pan. The material is placed in the uppermost sieve. The sieves are shaken with the help of mechanical sieve shaker or electromagnetic devices. It helps the particles to pass through the sieves.

18. ADVANTAGES :  Test sieve shakers are capable of conducting sample size reduction utilizing maximum number of 10 test sieves in one experiment.  Sieving analysis with a shaker has the advantage of accuracy.  Using a sieve shaker is a more efficient method compared with manual hand sieving.  Once the timer is set up the experiment will run automatically without needing users to be present.  Shakers provide more flexibility than manual hand sieving, especially when the sieving analysis requires assistance with liquid or glass beads. With some models of shaker, the user can adjust sieving power and speed according to the size, weight and density of the samples.

19. DISADVANTAGES :  Chance of clogging of sieve if powder is not properly dry.  During shaking, attrition may occur.  Not suitable for particle smaller than 50µm.  For material finer than 100 mesh , dry sieving can be significantly less accurate. USES :  Sieving methods is used in dosage form development of tablet and capsule.  Sieve shaker is used for particle size analysis of variety of materials.  It is suitable for coarse material down to 150µm.

20. CYCLONE SEPERATOR PRINCIPLE : In cyclone separator centrifugal force is used to separate solid from fluids. The separation process depends on particle size and particle density. It is also possible to allow fine particles to be carried with the fluid.

21. CONSTRUCTION : It consists of a short vertical, cylindrical vessel with a conical base. The upper part of the vessel is fitted with a tangential inlet. The solid outlet is at the base. Fluid outlet is provided at the center of the top portion, which extends inwardly into the separator. Such an arrangement prevents the air short-circuiting directly from the inlet to the outlet of the fluid.

22. WORKING : The solids to be separated are suspended in a stream of fluid (usually air or water). Such feed is introduced tangentially at a very high velocity, so that rotary movement takes place within the vessel. The centrifugal force throws the particles to the wall of the vessel. As the speed of the fluid (air) diminishes, the particles fall to the base and collected at the solid outlet. The fluid (air) can escape from the central outlet at the top.

23. TYPES :  Wet cyclone  Dorrclone  Vertical cyclone separator  Single - cyclone separator  Multi - cyclone separator ADVANTAGES :  It involves low capital cost.  It is high efficiency for 5 - 200µm particles.  It produces high volume flow rate.  It can operate at high temperature.  Its maintenance requirement are less.  It requires a small space for installation.  It can be operated at a wide range of temperature and pressure.

24. DISADVANTAGES :  Its operating cost is high due to pressure drop.  It cannot be used for sticky materials.  Show on low efficiency for small materials.  It shows reduced efficiency when overloaded than it capacity.  It cannot handle viscous flow. USES :  Cyclone separators are used to separate solid particles from gases.  It is also used for size separation of solids in liquids.  It is used to separate the heavy and coarse fraction from fine dust.  In tablet compression cyclone is used to extract waste powder before it reaches the central extraction system.  It is used in production of API through drying system such as a spray or fluid bed drying.  It can be used in air-handling system to produce particle free clean air.

25. AIR SEPERATOR PRINCIPLE : The cyclone separator alone cannot carry out size separation on fine materials. For such separations a current of air combined with centrifugal force is used. The finer particles are carried away by air and the coarser particles are thrown by centrifugal force, which fall at the bottom.

26. CONSTRUCTION : It consists of a cylindrical vessel with a conical base. A rotating plate is fitted on a shaft placed at the center of the vessel. A set of fan blades are also fitted with the same shaft. At the base of the vessel two outlets are provided: one for the finer particles and the other for coarse particles. WORKING : The disc and the fan are rotated by means of a motor. The feed (powder) enters at the center of the vessel and falls of the rotating plate. The rotating fan blades produce a draft (flow) of air in the direction as shown in the diagram. The fine particles are picked up by the draft of air and carried into space of settling chamber, where the air velocity is sufficiently reduced so that the fine particles are dropped and removed through the fine particle outlet. Particles too heavy to be picked up by the air stream are removed at the coarse particle outlet.

27. ADVANTAGES :  It is used for separation large to medium sized particles >15µm  It does not have any moving parts.  It is a simple instrument and easy to operate.  It can be used in low and high temperature . DISADVANTAGES :  Its is separate yield is low.  It cannot separate to smaller particles.  If particles are too fine ˂5µm its efficiency decreases.  Not suitable for wet and sticky materials.

28. USES :  Air separators are often attached to the ball mill or hammer mill to separate and return over sized particles for further size reduction.  It used for separation of dry powders in micron – sized that could not be separated by traditional sieves.  It can be used for the collection of metal working fluids , and coolant or oil mists.  It is often used as an air pollution control device to maintain or improve air quality in pharmaceutical production area.  It is used as dust collector in many process like recover valuable granular solid or powder from process stream.

29. BAG FILTER PRINCIPLE : In a bag filter, size separation of fines (or dust) from the milled powder is achieved in two steps. In the first step, the milled powder is passed through a bag (made from cloth) by applying suction on the opposite side of the feed entry. This facilitates the separation. In the next step, 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

30. CONSTRUCTION : It consists of a number of bags made of cotton or wool fabric. These are suspended in a metal container. A hopper is arranged at the bottom of the filter to receive the feed. At the top of the metal container, a provision is made for vacuum fan and exhaust through discharge manifold. At the top of the vessel a bell-crank lever arrangement is made to change the action from filtering to shaking. WORKING : (a) Filtering period : During this period the vacuum fan produce a pressure lower than the atmospheric pressure within the vessel. Gas to be filtered enters the hopper, passes through the bags, and out of the top of the apparatus. The particles are retained within the bags. (b) Shaking period: During this period the bell-crank lever first close the discharge manifold and air enters through the top so the vacuum is broken. At the same time it gives a violent jerking action to the bags so that they are freed from the dust. The fine particles are collected at the conical base.

31. ADVANTAGES :  It can be essentially used for removing fines which cannot be separated with other methods.  It can be used for removing dust.  Electricity consumption is low.  It has robust construction.  High quality filter bags has trouble free operation.  They are simple in construction and operation.  It help to maintain and protect healthy environment. DISADVANTAGES :  It is not a size separation equipment as such.  Comparatively it is large in size.  The maintenance cost is high as fabric used is costly.  It has limitation for its operation due to high gas temperature and high humidity. USES : 1. Bag filters are used along with other size separation equipment, e.g. a cyclone separator. 2. They are use on the top of fluidized bed dryer for drying to separate the dusts. 3. They are used to clean the air of a room. 4. Household vacuum cleaner is a simple version of bag filter 5. it is most commonly used in fluidized bed dryer

32. ELUTRIATION TANK PRINCIPLE : An elutriator is a straightforward device that divides particles into two or more groups. Elutriation occurs when a fluid moves in the opposite direction of particle sedimentation. Particle size, shape, and density all play a role in elutriation. The air elutriator is mostly utilized for particles with a diameter of less than 1 m. If the particle’s Reynolds number is less than 0.2, Stokes’ law can be used to compute the terminal velocity of any particle in any medium. The separation of particles i n an elutriator is based on their densities

33. CONSTRUCTION : The apparatus for the gravity system is essentially a vertical column with a suspension intake near the bottom, a coarse particle outlet near the base, and a fluid overflow near the top, as shown . One column will give a single separation into two fractions, but keep in mind that there will be a velocity gradient across the tube, resulting in the separation of particles of different sizes based on their distance from the wall. If more than one fraction is needed, a sequence of tubes with the increasing cross-sectional area can be connected.

34. WORKING : The material whose particles are to be separated is first levigated and the paste is transferred to elutriation tank. A large amount of water is added to tank so as to make independent particle settling. The contents in the tank are stirred to obtain uniform particle distribution. If left aside undisturbed coarse particles settle at the bottom where as small size particles remain suspended in liquid. These fines can be transferred to next elutriator in connection wherein similar process of separation takes place to obtain further fractions of fines. ADVANTAGES : 1. The process is continuous. 2. The separation is quicker than with sedimentation. 3. It has feasibility to add many columns based upon fractions required. 4. It needs no skilled operators. 5. It is a fast process than sedimentation.

35. DISADVANTAGES : 1. The suspension has to be dilute; which may sometimes be undesirable. 2. It separates particles based on their sedimentation property but not on specific features (for example, surface or shape). 3. It cannot separate different types of particles which have similar sedimentation properties. USES : 1. Following a size reduction process, both simple and multiple elutriators are employed for comparable reasons, with the goal of separating large particles, which may be returned for additional grinding, used for other purposes, or discarded depending on the conditions. 2. With liquids, it can be used to separate insoluble solids, such as kaolin or chalk, which are often subjected to wet grinding followed by sedimentation or elutriation with water. 3. With gases, it can be applicable to finer solids that would separate too slowly in liquids, to water-soluble substances, or where dry processing is required

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