Chemical Engineering Department Government Engineering College Bhuj Prepared By: ( to ) B.E. Sem-III(Chemical) Guided By: Prof. D. R. Gandhi Prof.S.R.Banker “Problems and Theory for Material Balance of Unsteady state Operations”

Absorption and stripper Distillation column Extraction Drying humidification

Introduction Flow sheet

 Absorbers and strippers are often used in conjunction with each other. Absorbers are often employed to remove trace components from gas streams. Strippers are often applied to remove the trace components from the liquid in a more concentrated form. Absorption and stripping operations are carried out in vertical, cylindrical columns or towers containing plates or packing elements. The plates and packing provide a surface area for the liquid and gas to come into contact facilitating mass transfer between the two streams. The gas and liquid streams for both operations are commonly counter-current fore more effective mass transfer. The columns are simpler than those for distillation are because they commonly do not include a condenser or a re boiler.

 There are two types of absorption. The two types are chemical and physical. In chemical absorption, the liquid solvent reacts with the gas stream and remains in solution. In physical absorption, the solute in the gas is more soluble in the liquid solvent and, therefore, the solute is transferred to the liquid. Chemical is usually preferred over physical because the equilibrium for chemical absorption is much more favorable for the separation. However, physical absorption is important since it can be applied when chemical absorption is not possible.

A diagram of an absorber-stripper system is shown in figure 0. The gas containing the solute to be removed enters at the bottom of the absorber column. In the column, the gas is placed in contact with the solvent that removes the solute and the purified gas exits the top of the column. Recycled solvent enters the top of the absorber column and exits the bottom where it is boiled and sent to the top of the stripping column. The solute in the solvent is removed in the stripping column by a stripping gas that enters

Outline  Where we are, where we want to be.  How to get there.  What we used and what we got.  The trouble.  The model.

 12 tray bubble-cap distillation column  Isoproply alcohol water separation

 Same distillation column  Ethanol water separation

 Operate column at total reflux  Determine stage efficiency  Model the column in Aspen  Compare Aspen model to real IPA separation results  Apply the Aspen model to an Ethanol separation

Equilibrium curveStripping operating line Rectifying operating lineMurphree-vapor efficiency

 Liquid-liquid extraction is a useful method to separate components (compounds) of a mixture

 By shaking the layers (phases) well, you increase the contact area between the two phases.The sugar will move to the phase in which it is most soluble: the water layer

 Now the water phase tastes sweet, because the sugar is moved to the water phase upon shaking.** You extracted sugar from the oil with water.**In this example, water was the extraction solvent ;the original oil-sugar mixture was the solution to be extracted; and sugar was the compound extracted from one phase to another. Separating the two layers accomplishes the separation of the sugar from the vegetable oil

 Liquid-liquid extraction is based on the transfer of a solute substance from one liquid phase into another liquid phase according to the solubility. Extraction becomes a very useful tool if you choose a suitable extraction solvent. You can use extraction to separate a substance selectively from a mixture, or to remove unwanted impurities from a solution.In the practical use, usually one phase is a water or water-based (aqueous) solution and the other an organic solvent which is immiscible with water.  The success of this method depends upon the difference in solubility of a compound in various solvents. For a given compound, solubility differences between solvents is quantified as the " distribution coefficient "

 Here is the universal rule: At a certain temperature, the ratio of concentrations of a solute in each solvent is always constant. And this ratio is called the distribution coefficient, K.

 Chemically active (acid-base) extraction  Most organic compounds are more soluble in organic solvents than in water, usually by the distribution coefficient K > 4  However, specific classes of organic compounds can be reversibly altered chemically to become more water- soluble.

 Introduction to Drying in the Pharmaceutical Industry.  Introduction to the Drying process.  Dyers selection for a Pharmaceutical process.  Case Study: Trouble shouting the drying step and its impact on formulation.

 Drying can be described by three processes operating simultaneously: 1. Energy transfer from an external source to the water or organic solvent  Direct or Indirect Heat Transfer 2. Phase transformation of water/solvent from a liquid-like state to a vapour state  Mass Transfer (solid characteristics) 3. Transfer vapour generated away from the API and out of the drying equipment

Basic Concepts  Functions of the of the upper airway: assure that inspired gas is:  Warmed (convection).  Humidified via evaporation from the mucosa  Filtered  During exhalation:  Expired gas transfers heat back to the mucosa (convection)  Condensation occurs on the mucosal surfaces and water is reabsorbed by mucus (rehydration)

 Dry – bulb temperature  Wet bulb temperature  Dew point : DP=<DB  Adiabatic saturation temperature(AST): It is the temperature that the vapour – gas mixture would rich if it were saturated through an adiabatic process. H= kg vapour kg dry(non-condensable)gas

 Humidity is essentially the water vapor in a gas.  This water vapor can be described in several ways, as: 1. Absolute humidity - The actual content of water vapor in a gas measured in milligrams per liter. 2. Potential humidity - The maximum amount of water vapor that a gas can hold at a given temperature. 3. Relative humidity - The amount of water vapor in a gas as compared to the maximum amount possible, expressed as a percentage 4. Body humidity - The absolute humidity in a volume of gas saturated at body temperature of 37 C; equivalent to 43.8 mg/L

 It is needed to maintain normal bronchial hygiene  It promotes functions of the normal mucociliary escalator  It maintains the body's vital homeostasis  Without humidity:  The nearly 100 ml of mucus secreted daily would become quite thick and tenacious.  Actual lung parenchyma would dry up, causing a loss of normal compliance which would restrict lung movement and reduce ventilation.

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