Chemical Engineering Separation Processes Quiz

Separation Techniques

• Separating agent: Stripping vapor (MSA)
• Example: Stream stripping of naphtha, kerosene, and gas oil side cuts from crude distillation unit to remove light ends

Azeotropic Distillation

• Formation of minimum-boiling azeotropic mixtures
• Separating agent: Liquid entrainer (MSA) and heat transfer (ESA)
• Example: Separation of acetic acid from water using n-butyl acetate as entrainer to form azeotrope with water

Liquid-Liquid Extraction

• Widely used when distillation is impractical, especially for temperature-sensitive mixtures
• Separating agent: Liquid solvent (MSA)
• Example: Recovery of Aromatics

Liquid-Liquid Extraction (Two Solvents)

• Each solvent has its own specific selectivity for dissolving the components of the feed mixture
• Separating agent: Two liquid solvents (MSA1 and MSA2)
• Example: Use of propane and cresylic acid as solvents to separate paraffins from aromatics and naphthenes

Leaching

• Referred to as solid-liquid extraction
• Widely used in metallurgical, natural product, and food industries
• Separating agent: Liquid solvent
• Example: Extraction of sucrose from sugar beets with hot water

Disadvantages of MSA

• Need for additional separator to recover the MSA for recycle
• Need for MSA makeup
• Possible contamination of the product with the MSA
• More difficult design procedures

Distillation

• Most widely utilized industrial separation technique
• Involves multiple contacts between counter currently flowing liquid and vapor phases
• Separating agent: ESA and sometimes work transfer
• Example: Purification of styrene

Extractive Distillation

• Used when volatility differences between species to be separated are small
• Separating agent: Liquid solvent (MSA) and heat transfer (ESA)
• Example: Separation of acetone and methanol

Absorption

• Used when the feed is all vapor and the stripping section of the column is not needed
• Separating agent: Liquid absorbent (MSA)
• Example: Separation of carbon dioxide from combustion products by absorption with aqueous solutions of an ethanolamine

Stripping

• A liquid mixture is separated by contacting liquid feed with a stripping agent
• Also called maximum-boiling azeotropes
• Example: Water and ethanol

Single-Stage Equilibrium Contact for Vapor-Liquid System

• Two different phases are brought into intimate contact with each other and then are separated
• The components have different volatilities so that they will partition between the two phases to different extents
• The two phases can be separated by gravity or other mechanical means

Basic Distillation Setup

• Distillation is a method of separating mixtures based on differences in volatility of the components in a boiling liquid mixture
• It is a unit operation, or a physical separation process, and not a chemical reaction
• A vapor contacts a liquid, and mass is transferred both from the liquid to the vapor and from the vapor to the liquid