In this subject the basic concepts of mass transfer are covered to enable the students to understand working of various mass transfer equipments like distillation column, gas absorption columns, dryers, cooling towers and extraction columns etc which are used in industries for purification of products
1. Introduction to Mass Transfer Operations and Classification (02 hrs)
2. Diffusion (10 hrs)
Definition of diffusion and its classification viz diffusion under concentration, pressure and thermal gradient, forced diffusion and eddy diffusion.
Role of diffusion in mass transfer, fick’s law, diffusion in the gas phase equimolar counter diffusion, diffusion through stationary gas, Mass transfer coefficient, film theory and penetration theory of mass transfer, diffusion in solids, relation between film and overall mass transfer coefficient.
Simple numerical problems based on Flick’s law definition and physical meaning of mass transfer coefficient. Important correlations (no derivation), meaning of each term
3. Distillation (12 hrs)
Relative volatility, vapour liquid equilibrium, various distillation methods, flash distillation, continuous, fractionating column with details and identification of different parts, flash distillation, steam distillation, introduction to azeotropic, extractive distillation, different types of distillation columns, concept of flooding, weeping, entrainment and loading in distillation columns
(Qualitative treatment only, final expressions and the physical meaning of terms therein – derivations excluded)
4. Gas Absorption (12 hrs)
Condition of equilibrium between gas and liquid, mechanism of absorption, material balance and design equation, operating line. Concept of transfer unit (HTU and NTU) height of column based on condition-gas film, based on condition-liquid film, height of column based on overall coefficient. HETP for packed column of distillation, equipment used, types of tower packing, properties of tower packing, problems encountered like flooding, channeling, and weeping, loading, choice of solvent, Raoult’s law and Henry’s law.
5. Humidification and Dehumidification (10 hrs)
Definition of humidity, saturated gas, relative humidity, percentage humidity, humid heat, humid volume, dew point, total enthalpy, Dry bulb and wet bulb temperature, meaning and principle only
Gas liquid contact operation: names of adiabatic and non-adiabatic equipment – natural draft cooling tower, humidifier and dehumidifier, different cooling tower arrangements, spray chambers, spray ponds
6. Leaching and Extraction (8 hrs)
Importance of leaching and extraction, leaching equipment, boll man extractor, plate tower, packed tower, spray tower, mixer settler extraction system
7. Drying (10 hrs)
Definition, industrial application, moisture content, wet and dry basis, equilibrium moisture, bound, unbound, free moisture, batch drying; direct driers, tray driers, two track driers, rate of drying curve, continuous drying, turbo type drier, rotary driers
LIST OF PRACTICALS
1. To study the rate of drying in a vacuum dryer
2. To determine the pounds of volatile compounds distilled per unit pounds of steam distlled in a steam distillation operation
3. To study the rate of drying in rotary dryer
4. To determine drying rate for a wet material
5. To study packed tower in various industries
6. To study various extractors in solvent extraction plant
7. To study a spray pond in a sugar and other industries for cooling system
8. To find out the drying characteristics of given sample and draw drying rate curve by infra-red moisture meter and rapid moisture meter.
Field visit will make the students familiar with different types of column (packed/tray) and different types of packings/trays used in the column. This will also make the students aware of auxiliary equipment/models/supports used for the columns. Along with the theoretical part, emphasis should be given to problem solving and practices especially for distillation column, absorption and humidification.