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Impact: particle concussion by single rigid force (hammer) Compression: particles break down by two rigid forces (nut crackers) Shear: produced when the particles are compressed between the edges of two hard surfaces moving tangentially. Attrition: arising from particles scraping against one another or against rigid surface.
Size reduction equipment
✓ Cutter mill Mechanism: fracture of the particles between knives……….. Compression roller mill The gap is adusted for the control of size reduction Mechanism: compression Impact hammer mill✓ Mechanism : impaction
Atrrition roller mill
Mechanism: attrition ….. three rolls rorate with different speed.
Mechanism : impaction by large balls and attrition by small balls ✓ Get-O-mizer /micronizer /ultra fine grinders Particles are produced in particle size range (1- 20pm). Role of the elliptical chamber "classification zone": o Small particles are separated towards inner wall to discharge and then to cyclone. o Large particles are separated toward outer wall for another particle grinding. Mechanism of size reduction: o Impaction of particles to wall. o Inter particular attrition friction between particles. The disadvantages of hammer impact mill is : Heating build up during milling may result in product degradation. The advantages of attrition roller mill: effective for the size reduction and dispersing solids in suspension , pastes and ointments. The advantages of size reduction: Uniform mixing and drying. - Improve rate of absorption. - Improve dissolution rate. - Uniform flow.
Mixing equipment
material ) due to gentle blending Use less power than ribbon mixer.
Drying
It is an important operation in pharmaceutical practice. It is usually the last stage in manufacturing before packaging. It is important that the residual moisture is low enough in the final product to Prevent product deterioration. Ensure free- flowing properties. ✓ Tray dryer Heat is supplied with Electric or steam Temp. (30 – 120 C o ) Surface area and number of trays must be specified ✓ Fluidized bed dryer Fluidization is the operation by which fine solids are transformed into a fluid like state through contact with a gas (air). feed Rotating shaft discharge Conical vessel Helical conveyer
Advantages of fluidized bed dryer : Provides good contact between air and particles to obtain efficient drying.(efficient than tray dryer) A batch of tablet granules can be dried in 20-30 mins, whereas compartment drier can be dried in several hours. Suitable for: o Drying of pharmaceutical components. o Spray granulation. o Film coating. o Use with binders dissolved in highly inflammable organic solvents.
Granulation
It is Making the particles close to adhere to form large particles called granules. Objectives of granulation: To improve mixture flow. To improve compaction characteristics of the mixture. To prevent segregation of the constituents of the powder mixture. To reduce dust and moisture absorption. Granulation may be wet or dry Examples of equipment used for granulation:
- Oscillating granulator. (wet granulation)
- Fluidized bed granulator. (wet granulation)
- Mixer granulator. (wet granulation)
- Roller compaction machine. (dry granulation)
- Chilsonator. (dry granulation)
Centrifugation equipment
Clarification is a process which involves the removal or separation of a solid from fluid or fluid from fluid. Clarification can be achieved using Filtration and Centrifugation. Filtration is the separation of a solid from a liquid or gas by means of porous medium. Reasons for filtration: Improve appearance of solutions. Remove potential irritants. Liquid sterilization. Detection of micro-organisms present in liquids. Examples of centrifugation equipment
- Perforated basket centrifuge.
- Disc bowl centrifuge
- Tubular centrifuge.
Perforated basket centrifuge✓
Advantages : Occupy small floor space. Used for slurry of high solid content even for paste consistency. Disadvantage: High labor cost.
Tubular centrifuge
Disadvantage: Small size leads to limited capacity. Uses : Can separate liquid from small size solids or liquid from liquid. & Cleaning of fats and waxes. & For antibiotic manufacturing.
Disc bowl centrifuge✓
Advantages Has a large capacity. Uses: o Separation of solids from liquid. o Separation of mixture of water and dirt from relatively low density oil.
Heat Transfer
It is the transfer of heat from region of high temperature to a region of low temperature. The driving force is the temperature difference. Mechanisms of heat transfer: Conduction Convection Radiation Conduction: It is the transfer of energy from one molecule to the other adjacent to it without displacement of particles. It is the main mechanism in case of solids. Eg. Conduction of heat along a metal rod when one end is heated. Convection: It is the transfer of energy from region to another by fluid motion. Eg. Convection of heat when water is heated in a glass beaker. Heat is transferred from lower → middle → upper layers. It is confined to liquids and gases not solids. It may me: o Natural: Caused by difference is density arising from temperature gradient. o Forced: By mixing. Radiation: All bodies with temperature > absolute zero radiate heat in the form of electromagnetic waves which travel in straight line at the speed of light. When this radiation falls on a 2nd surface, it may be: transmitted, reflected or absorbed. The absorbed fraction is transformed into heat.
outer vessel and water drips down into the bottom o Allow the dry steam to changes its direction rapidly and passes up and out through the pipe.
Steam Traps
We cannot use a tap to separate water from the bottom of the steam dryers.. WHY? This would permit the escape of steam also steam traps are used to prevent outlet of live steam. Types: Mechanical Depends on: the physical difference between condensate and steam. Thermostatic Depends on: the temperature difference between condensate and steam. "The condensate have lower temperature than steam".
Float type steam trap (mechanical)
When the condensate level rises, the float rises and the outlet is opened till the condensate is discharged, Then the float falls and the outlet is closed and so on.
balanced pressure steam trap (thermostatic)
It consists of a closed capsule:
- has corrugated surface.
- made of cu alloy and fixed at the top.
- Contains a liquid having a b. p < water. When the capsule is surrounded by steam, the liquid inside it will boil and the capsule expand& outlet is closed. In presence of condensate, the capsule become cold and contracts and opens outlet & discharges condensate.
Heat exchanger equipment
Tubular heat exchanger
single pass tubular heater(1-1)
It is a bundle of parallel tubes surrounded by a cylinder shell and provided with two distribution chambers. The steam is introduced into the space surrounding the tubes. The condensed steam is drained from the drips. The feed (fluid to be heated) is pumped into one distributing head then flow through the tubes to other distributing head and finally discharged from the outlet. It is called 1-1 heat exchanger.. WHY? It has 1 shell side pass (i.e. steam flow in 1 direction only) has 1 tube side pass (i.e. feed flow in 1 direction only). The vent: Is an opening that separates air from steam.. Allow the escape of a mix of air and steam at the beginning of the operation. Closes only when the steam is present alone. The Drip: Is an opening that separates water from steam ... Allows the escape of the condensed steam and retain steam.
Fixed-head heat (1-4) exchanger
It is called 1-4 heat exchanger.. WHY? It has 1 shell side pass It has 4 tube side pass At each end, the tubes have a fixed plate to shell. The heated fluid makes 4 passes in the exchanger. Baffles increase the velocity of flow outside the tube hence giving better heat transfer, Disadvantages: 1- Tube bundle cannot be removed for cleaning. 2- Tubes have no chance for expansion.
floating head heat exchanger(1-2)
Shell outlet (^) Baffles Shell inlet Shell outlet Shell inlet
