ChE 414 - Separation Processes_Preliminary Examination

Separation processes

Defined as those operations which transform a mixture of substances into two or more products which differ from each other in composition.

Distillation

Separates various chemical component according to volatility.

Alkylation

To react small hydrocarbon molecules to create larger ones.

Catalytic reforming

To modify the structure of medium-sized hydrocarbons

Fluid catalytic cracking

To break apart very large hydrocarbon molecules. Uses Carbon rejection and is endothermic.

Hydrocracking

To break apart very large hydrocarbon molecules. uses hydrogenation and is exothermic.

Phase creation

Involves the creation of a second phase that is immiscible with the feed phase.

Phase addition

Introduce the second phase into the system in the form of a solvent that selectively dissolves some of the species in the feed.

By barrier

Uses barriers which restricts or enhances the movement of a certain chemical species with respect to other species.

By solid agent

Addition of solid particles which act directly or as inert carriers for other substances as to cause separation.

By force field or gradient

External fields of various types are applied for specialized separations.

Rate of separation

Separation variable that is governed by mass transfer.

Extend of separation

Separation variable limited by thermodynamic equilibrium

Partial condensation or vaporization

Its separating agent is heat transfer; it is when feed mixture includes species that widely differ in their tendency to condense or vaporize.

Flash vaporization

Separating agent is pressure reduction; it is caused by reducing the pressure of the feed with a valve.

Distillation

Its separating agent is ESA; it is when the volatility among species are not sufficiently large. Involves multiple contacts flowing in liquid and vapor phases.

Extractive distillation

Its separating agent is liquid solvent or MSA; it is when volatility differences between species to be separated are too small.

Absorption

Its separation agent is MSA, Liquid absorbent; it is when the feed is all vapor and the stripping section of the column is not needed to achieve the desired operation.

Stripping

Its separating agent is MSA; it is when a liquid mixture is separated, generally at elevated temperature and ambient pressure, by contacting liquid feed with a stripping agent.

Azeotropic distillation

Its separating agent is MSA and ESA; it is for the formation of minimum-boiling azeotropic mixture.

Liquid-liquid extraction

Its separating agent is MSA; it is widely used when distillation is impractical, especially when mixture to be separated is temperature-sensitive.

Leaching

Its separating agent is a liquid solvent; it is to promote diffusion of the solute out of the solid and into the liquid solvent.

Microporous membranes

Separation is affected by differing rates of diffusion through the pores.

Nonporous membranes

Separation occurs because of differences in both solubility and the rate of diffusion through the membrane.

Osmosis

Involves transfer by a concentration gradient of a solvent through a membrane into a mixture of solute and solvent.

Reverse osmosis

Transport of solvent in the opposite direction and is affected by imposing a pressure higher than osmotic pressure on the feed side.

Dialysis

Transport by concentration agent of a small solute molecules sometimes called crystalloids through a porous membrane.

Microfiltration

Retention of molecules typically in the size range from 0.02 to 10 micrometers

Ultrafiltration

Retention of molecules typically in the size range from 1 to 20 nanometer.

Pervaporation

The species being absorbed by and transported through nonporous membrane are evaporated.

Adsorption

Used to remove components present in low concentrations in non-adsorbing solvents or gases and to separate the components in gas or liquid mixture.

Chromatography

A method for separating the components of a feed gas or liquid mixture by passing the feed through a bed of packing,

Ion exchange

Resembles adsorption in that solid particles are used and regeneration is necessary, however involves chemical reaction.

Centrifugation

Established a pressure field that separates fluid mixtures according to molecular weight.

Electrolysis

When water is decomposed into hydrogen at the cathode and oxygen at the anode. Uses electrical force field.

Electrodialysis

Cation and anion-permeable membranes carry a fixed charge, preventing the migration of species of like charge.

Saturated condition

A condition wherein the maximum possible composition is reached given the set of conditions.

Triple point

The point which three states coexist.

Critical point

The point which the substance is indistinguishable between liquid and gaseous state.

Fusion curve

The curve which represents the transition between liquid and solid states.

Vaporization curve

The curve which represents the transition between gaseous and liquid states.

Sublimation curve

The curve which represents the transition between gaseous and solid states.

Dew point

The temperature at which the saturated vapor starts to condense.

Bubble point

The temperature at which the liquid starts to boil.

Positive azeotrope

These are azeotropic mixtures with a lower boiling point than its constituents.

Negative azeotrope

These are azeotropic mixtures that has a boiling point higher than its constituents.

Partial condensation or vaporization

Best separation process for the following: Recovery of H2 and N2 from ammonia by partial condensation and high-pressure phase separation.

Flash vaporization

Best separation process for the following: Recovery of water from seawater.

Distillation

Best separation process for the following: Purification of styrene.

Absorption

Best separation process for the following: Separation of carbon dioxide from combustion products by absorption with aqueous solutions of an ethanolamine.

Extractive distillation

Best separation process for the following: Separation of acetone and methanol.

Stripping

Best separation process for the following: Stream treating of naphtha, kerosene, and gas oil side cuts from crude distillation unit to remove light ends.

Azeotropic distillation

Best separation process for the following: Separation of acetic acid from water using n-butyl acetate.

Liquid-liquid extraction

Best separation process for the following: Recovery of aromatics

Leaching

Best separation process for the following: Extraction of sucrose from sugar beets and hot water.

Reverse osmosis

Best separation process for the following: Desalination of sea water

Dialysis

Best separation process for the following: Recovery of caustic from hemicellulose.

Microfiltration

Best separation process for the following: Removal of bacteria from drinking water.

Ultrafiltration

Best separation process for the following: Separation of whey from cheese.

Pervaporation

Best separation process for the following: Separation of azeotropic mixtures

Gas permeation

Best separation process for the following: Hydrogen enrichment

Gas permeation

Separation of gas mixture through membranes.

Adsorption

Best separation process for the following: Purification of p-xylene

Chromatography

Best separation process for the following: Separation of xylene isomers and ethylbenzene.

Ion exchange

Best separation process for the following: Demineralization of water.

Centrifugation

Best separation process for the following: Separation of uranium isotopes.

Electrolysis

Best separation process for the following: Concentration of heavy water.

Electrodialysis

Best separation process for the following: Uses cation and anion, it is the desalination of sea water.

Homogeneous azeotrope

An azeotrope that contains one liquid phase in contact with the vapor.

Heterogeneous azeotrope

An azeotrope that usually form two liquid phases with widely differing composition.