Distillation L-1
Course Coordinator: Dr Shina Gautam
Class and Sem: Chemical Engineering, V sem
Shroff S R Rotary Institute of Chemical Technology,
Ankleshwar, Gujarat
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Distillation definition
• “Distillation is an unit operation which involves separation of a
vaporizable component from a multi-component system and
subsequent condensation of vapours.”
• “Distillation is a process of separating the component substances
from a liquid mixture by selective evaporation and condensation.”
• “Distillation is defined as the separation of the components of a liquid
mixture by a process involving vaporization and subsequent
condensation at another place.”
• It’s a physical process for separating a liquid mixture into two or more
of its components by partial vaporization and condensation.
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Simple distillation
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• The Basic Principle: The vapor formed has a different composition
from the remaining liquid.
• But, when, the vapor and liquid have the same composition
=> the liquid mixture is known as an azeotrope or azeotropic mixture
• Thus, distillation is modeled on an equilibrium basis and an approach
to equilibrium is used in determining equilibrium stages.
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Constant pressure VLE
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T-xy diagram
• The upper curve provides the temperature-vapor composition (t-y*).
• The lower curve is temperature-liquid composition (t-x).
• Horizontal lines are tie lines, it joins vapor and liquid composition at
equilibrium.
• There are an infinite number of such tie lines.
• A mixture on the lower curve is a saturated liquid, a mixture on the upper
surface is a saturated vapor.
• In between these points there is a mixture of liquid and vapor, average
composition is represented by middle of this joining lines.
• The relative amounts of the equilibrium phase are related to the segment of
tie lines
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• The lower curve is called bubble point-temperature curve.
• The term boiling point for a solution ordinarily has no meaning since
vaporization occurs over a temperature range that is from bubble
point to dew point.
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Thank You
