Distillation | Part 2 | Question and answer on Distillation

COMPARISION OF SINGLE AND MULTIPLE EFFECT EVAPORATOR

Comparison of single and multiple effect evaporator Single-effect evaporators Single-effect evaporators are used when the throughput is low, when a cheap supply of steam is available, when expensive materials of construction must be used as is the case with corrosive feedstocks when the vapour is so contaminated so that it cannot be reused. The feed and saturated steam with temperature at T F and T S respectively enter the heat- exchange section Condensed steam leaves as condensate or drips. The solution in the evaporator is assumed to be completely mixed. Hence, the concentrated product and the solution in the evaporator have the same composition. Temperature T 1 is the boiling point of the solution. The temperature of the vapor is also T 1 , since it is in equilibrium with the boiling solution. The pressure is P 1 , which is the vapor pressure of the solution at T 1 If the solution to be evaporated is assumed to be dilute and like wat

EXAMPLES OF MASS TRANSFER

Example of mass transfer Mass transfer operations The operation carried out for separating the component of the mixture, involving the transfer of (mass) material from one homogeneous phase to another, due to the difference in vapor pressure, solubility or diffusivity and in which driving force for transfer is a concentration the difference is called mass transfer operations Example:- Distillation, Gas absorption, Liquid Extraction, Drying Example of mass transfer operations Depending upon phase contact between Gas, liquid and solid phase following are the classification of the mass transfer operations Gas-gas phase contact The fragrance of incense sticks after lightning diffuse from one room to another room. Gas-liquid contact A cup of water left in a room eventually evaporate as a result water molecules diffusing into the air. This is liquid to gas diffusion. Gas absorption:- If a mixture of ammonia and air is contacted with liquid water, a large portion of

DIFFERENCE BETWEEN UNIT OPERATION AND UNIT PROCESS

Difference between Unit operation and Unit process The chemical process is a combination of unit processes and Unit operation. Hence the Difference between Unit operation and Unit process as follows. Unit process The unit process involves a chemical change or sometimes it referred to as chemical changes along with physical change leading to the synthesis of various useful product It also provides basic information regarding the reaction temperature and pressure, the extent of chemical conversions and yield of product of the reaction, nature of reaction whether endothermic or exothermic, type of catalyst used. Example: hydrogenation, oxidation, nitration, etc Unit operations The operations carried out in the chemical process industry involving physical changes in the materials handled or in the system under consideration are called Unit operations Hence unit operations involve the physical separation of the products obtained during various unit processes. I

CHEMICAL ADDA

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