9/2/2015
B. Pharm program
The open University of Sri Lanka
M. A. Siriwardhene FMS USJP

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Introduction Unit Systems
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Stoicheometry
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Material Balance
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Energy Balance
9/2/2015 M. A. Siriwardhene FMS USJP

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Industrial chemical process is based on
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Unit Operations (physical treatment)
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Unit Process (chemical treatment)
to produce economically a desired product from specific raw materials
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The raw materials are treated through physical steps to make it suitable for chemical reaction.
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Eg. Mixing and agitation of liquid
Heat flow
9/2/2015 M. A. Siriwardhene FMS USJP

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The Unit Operations is based on fundamental laws of physics and physicochemical principles.
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Unit Operations gives idea about science related to
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Specific physical operation
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Different equipments-its design
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Material of construction and operation
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Calculation of various physical parameters (mass flow, heat flow, mass balance, power and force etc.).
9/2/2015 M. A. Siriwardhene FMS USJP

9/2/2015 M. A. Siriwardhene FMS USJP

Preparation of raw materials by physical
treatment
Chemical conversion in a reactor
Chemical conversion
Stoichiometry
Reaction kinetics, Thermodynamics
Chemical equilibrium
Energy balance and mass balance
M. A. Siriwardhene FMS USJP 9/2/2015

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Efficiency of process and equipments
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Safety with respect to the process, raw chemicals, finished products
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Long term effect on environment
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Financial viability of the products as demanded by the purchaser
9/2/2015 M. A. Siriwardhene FMS USJP

Pharmaceutical Manufacture of tablets
Formulation of chemicals, mixing, granulation
Drying of granules
Screening Pressing tablet
Packaging
9/2/2015 M. A. Siriwardhene FMS USJP

Flow sheet of a typical chemical process
9/2/2015 M. A. Siriwardhene FMS USJP

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A physical quantity is expressed with its magnitude and unit.
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The official international system of units is the SI system.
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Other systems
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Centimeter gram
−se o d cgs)
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Foot
−pou d−se o d fps
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Engineering gravitational systems
9/2/2015 M. A. Siriwardhene FMS USJP

The units are derivable from some basic equations from basic equations with the help of arbitrarily chosen standards for mass, length, time, temperature, mole and arbitrarily chosen numerical values for the proportionality constants of the following basic equations.
9/2/2015 M. A. Siriwardhene FMS USJP

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Mass balance or material balance is the expression of the conservation of mass that involves accounting of materials in a process.
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The conservation of mass can be written as:
Rate of flow of reactant into volume element
=
Rate of flow of reactant out of volume element
+
Rate of reactant removal by reaction within volume element
+
Rate of accumulation of reactant within volume element
9/2/2015 M. A. Siriwardhene FMS USJP

Step− y−step pro edure to solve effi ie t solutio of aterial ala e problems
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Draw a block diagram of the process to show significant steps by flow sheet diagram.
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List all the available data. Indicate known quantities of the parameters on the block diagram.
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List all the information.
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Decide the system boundaries.
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Write out all the chemical reactions involved for the main products and byproducts.
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Note any other constraints if any, like azeotropes, phase equilibria, tie substances.
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Check the number of conservation equations that can be written and compared with the number of unknowns.
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Decide the basis of calculation.
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The order of steps may vary according to need of the problem.
9/2/2015 M. A. Siriwardhene FMS USJP

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In most chemical reactions carried out in industry, the components are seldom fed to the reactor in exact stoichiometric proportions.
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A reagent may be supplied in excess of the amounts theoretically required for combination with the others in order to maximize the use of an expensive reagent or to ensure complete reaction of a reagent.
9/2/2015 M. A. Siriwardhene FMS USJP

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The amount of desired compound is determined by the amount of limiting reactant.
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The percentage excess of any reactant is defined as the percentage ratio of the excess to the amount theoretically required by the stoichiometric equation for combination with the limiting reactant. So the 'Excess' refers to limiting reagent.
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The percentage excess reagent is expressed by the following:
9/2/2015 M. A. Siriwardhene FMS USJP

Conversion
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Conversion refers to the reactants and yield refers to the products formed.
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Conversion is a measure of the fraction of the reagent that converts due to reaction.
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Conversion is expressed by the following:
9/2/2015 M. A. Siriwardhene FMS USJP

Yield
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Yield is a measure of the performance of a reactor or plant. Yield should be defined on clearly stated basis.
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'Plant yield' is a measure of the overall performance of the plant and includes all chemical and physical losses.
9/2/2015 M. A. Siriwardhene FMS USJP

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Energy balance is a mathematical or numerical expression of
'Conservation of energy' (also called first law of thermodynamics).
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Energy balance and mass balance are encountered often in the problems related to process design and operation.
9/2/2015 M. A. Siriwardhene FMS USJP

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Energy balance is carried out to know the energy needed in in a process.
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'Energy balance' exhibits a pattern of usage and suggests areas for conservation and savings.
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Energy can exist in many forms making 'energy balance' more complex than mass balance, such as
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Potential energy
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Kinetic energy
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Flow energy
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Heating energy
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Mechanical energy
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Electrical energy etc.
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Total energy is conserved as per the law of conservation of energy.
9/2/2015 M. A. Siriwardhene FMS USJP

Potential Energy
Kinetic Energy
M. A. Siriwardhene FMS USJP 9/2/2015

Energy balance in a steady state process
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Practical and theoretical yield and percent recovery
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Validation of processes and equipment's
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Material balance estimations
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Mole
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Molality
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Molarity
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Normality
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Equivalent weight
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Mole fraction
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Mole percent
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Mole volume

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Evaporation-capacity of evaporators
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Distillation-material balance in equilibrium or flash distillation process

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The Imperial System (Old system)
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The Metric System (Modern system which is simple and convenient)
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Imperial System
Weights used:
There are 2 systems of weights used in imperial system, they are:
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Apothecaries system
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Avoirduposis system

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Apothecaries system of weights
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1 pound = 12 ounces or 5,760 grains
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1 ounce = 8 drachms or 480 grains
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1 drachm
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1 scruple
= 3 scruples or 60 grains
= 20 grains
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Avoirduposis system of weights
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1 pound = 16 ounces or 7,000 grains
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1 ounce = 437.5 grains

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1 gallon
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1 quart
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1 pint
= 8 pints or 4 quarts or 160 fluid ounces
= 2 pints or 40 fluid ounces
= 20 fluid ounces
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1 fluid ounces = 8 fluid drachms or 480 minims
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1 fluid drachm = 60 minims
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1 fluid ounce = 1 ounce

Weights
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1 kilogram
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1 gram
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1 milligram
= 1000 grams
= 1000 milligrams
= 1000 micrograms
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1 microgram = 1/1000 milligrams
Measures
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1 litre
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1000 litres
= 1000 mllilitres
= 1 kilolitres

Dr Jasmina Khanam
Reader of Pharmaceutical Engineering Division
Department of Pharmaceutical Technology
Jadavpur University
Kolkatta-700032
9/2/2015 M. A. Siriwardhene FMS USJP

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Walter L. Badger, Julius T.Banchero, Introduction to Chemical Engineering.
McGraw Hill Series in Chemical Engineering.
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Olat A. Hougen, Kenneth M. Watson, Roland A. Ragatz. Chemical process principles, Part 1, Asian Students edition, Asia Publishing House.
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J M Coulson and J F Richardson,Coulson
& Ri hardso ’s Che i al E gi eeri g,
Volume 6, 2 th ed; Pergamon Press, Oxford.
• J.H. Perry, Che i al E gi eer’s Ha d ook, 4 th ed, McGraw Hill Book Company.
9/2/2015 M. A. Siriwardhene FMS USJP