DISTILLATION Distillation is defined as:

a process in which a liquid or vapour mixture of two or more substances is separated into its component fractions of desired purity, by the application and removal of heat.Distillation is based on the fact that the vapour of a boiling mixture will be richer in the components that have lower boiling points.When this vapour is cooled and condensed, the condensate will contain more volatile components. At the same time, the original mixture will contain more of the less volatile materialmost common separation techniqueit consumes enormous amounts of energy, both in terms of cooling and heating requirementsit can contribute to more than 50% of plant operating costs

DISTILLATION 2 methods of distillation: eg. Ethanol-water: vapour phase = higher conc. of ethanol liquid phase = higher conc. of water rectification/fractional/distillation with reflux (returned) part of the vapour is condensed & returned as liquid back to the vessel-Reflux ratio: indicate the amount of product to be recycled back to the top of the column. The recycle is strictly needed to keep constant the internal flowrate inside the column and to enhance the separation process.Eg: 80% reflux ratio: 20% product 80% recycledall of the vapour is removed or is condensed as product

Azeotropic An azeotrope is a liquid mixture which when vaporised, produces the same composition as the liquid. (E.g.: Methanol and Methyl Acetate mixture).A mixture of two or more liquid in such a way that its components cannot be altered by simple distillationThis happens because, when and azeotrope is boiled, the vapour has the same propertions of constituents as the unboiled mixture.The azeotropic point must be shifted by using vacuum distillation or by adding additional substance.Azeotropic point

DISTILLATION steam fractional extractiveTypes of distillation: simple immiscible solvent azeotropic vacuum molecular entrainer sublimationDistillation tower at an oil refinery.

EXTRACTIONRemoval of one or more components (solutes) from solids or liquids using liquid solventLIQUID-LIQUID EXTRACTION/SOLVENT EXTRACTIONSeparation of two miscible liquids using another liquid (solvent)Eg. Vitamin A and D (solute) from fish oil (inert liquid) using liquid propene (solvent)Separation of solutes from solid using liquid solventEg. Soya milk (solute) from soya bean (inert solid) using water (liquid solvent)SOLID-LIQUID EXTRACTION/LEACHING

LIQUID-LIQUID EXTRACTION Separation by distillation is ineffective or difficult Boiling points of mixtures are close takes advantage of the relative solubilities of solutes in immiscible or nearly immiscible liquids solute dissolves more readily in the solvent in which it has a higher solubility Distribution Coefficient, K, determines the ratio of the concentration of the solute in each liquid. Flexibility in operation conditions choice is desired More than two components are present The material is heat sensitive

COUNTER CURRENT EXTRACTION raffinate is the exit residual stream containing little solute extract is the exit solvent rich stream containing the desired extracted solute lighter liquid flows upward while the heavier liquid flows downward Two immiscible fluids, usually one light and one heavy fluid, flowing continuously in opposite directions are brought together and allowed to separate

SOLID-LIQUID EXTRACTION/LEACHINGSeparation of solutes from solid using liquid solventEg. Soya milk (solute) from soya bean (inert solid) using water (liquid solvent) Leaching of toxic materials into groundwater is a major health concern In the metal industry - leaching of copper salts from ground ores using sulfuric acid or ammoniacal solutions

Mechanism of evaporation thermal separation/concentration vapour removed as top product concentrated solution as bottom product desired products concentrated solution eg. Milk vapour usually water vapour crystal eg. Salt crystal removing a liquid by boiling off some of the liquid

(a) Falling-film evaporator (b) Climbing-film evaporator

ABSORPTION eg. absorbing NH3 from air using liquid water,Acetone from air using liquid water liquid phase is immiscible in the gas phase solute is removed from a liquid by contacting it with a gas mass transfer process separating a solute (A) or several solutes from a gas phase by contacting the gas with a liquid phaseSTRIPPING/DESORPTION

HUMIDIFICATION PROCESSESWater vapour is transferred from the vapour state to the liquid stateTransfer of water from the liquid phase into a gaseous mixture of air & water vapourHumidificationDehumidificationwaterAir &water vapour

HUMIDIFICATION PROCESSES latent heat of vaporisation given off cools water only small amount of water is lost evaporation of warm water when in contact with unsaturated airWater-cooling tower packed tower

Natural draft water cooler

Dehumidification tower humidity & temperature of air reduced Operating line lies below the equilibrium lineHumidification/ cooling towerDehumidification tower Water is cooled & air humidified Operating line lies above the equilibrium line

CRYSTALLIZATION PROCESSES

CRYSTALLIZATION PROCESSES

Task of heat exchanger: to transfer the heat (Q) in the systemsWhy we transfer the heat:

COOLING

HEATING

BOILING

CONDANCE

REACTORHEATINGCOOLINGFLASH DISTILLATIONReactant AT = 30 oCReactant BT = 40 oCT = 250 oCT = 80 oCHeating and Cooling (Heat Exchanger)

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