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Separation Processes > Introduction > Flashcards

Introduction Flashcards

1
Q

What is a unit operation?

A

A basic step in a chemical engineering process.

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2
Q

A method that converts a mixture of chemical substances into two or more distinct product mixtures.

A

separation process

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3
Q

unit operations classification

A

fluid flow processes
heat transfer processes
mechanical processes
thermodynamic processes
mass transfer processes

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4
Q

example of fluid flow processes

A

fluid transport, solids fluidization, mixing

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5
Q

heat trans processes examples

A

heating/cooling, evaporation/condensation

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6
Q

mechanical processes example

A

crushing, sieving, solid transportation

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7
Q

thermodynamic processes examples

A

liquefaction, refrigeration

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8
Q

mass transfer processes examples

A

absorption, distillation, extraction, adsorption, drying

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9
Q

the type of separation process used depend on

A

the type of mixture and the physical and chemical properties of the compositions of the mixture

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10
Q

What does mass transfer involve?

A

The transport or migration of one constituent from a region of higher concentration to a region of lower concentration.

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11
Q

Fill in the blank: A __________ is a basic step in a chemical engineering process.

A

[unit operation]

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12
Q

based on the nature or physical mechanism of separation

A

mechanical, diffusional, membrane separation

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13
Q

What are the two classifications of mixtures in separation processes?

A
  • Heterogeneous Mixtures
  • Homogeneous Mixtures (Solutions)
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14
Q

for heterogeneous mixtures, separation may be entirely by

A

mechanical means

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15
Q

for solutions, separation operations are known as

A

mass-transfer operations

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16
Q

a group of operations for separating the components of mixture based on the transfer of material from one homogeneous phase to another

A

mass transfer operations

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17
Q

characterized by transfer of a substance through another on a molecular scale not bulk movement

A

mass transfer operations

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18
Q

True or False: Separation processes are always chemical reactions.

A

False

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19
Q

What are some examples of mechanical separation processes?

A
  • Filtration
  • Centrifugation
  • Settling
  • Flotation
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20
Q

there are further two types of mechanical separations:

A

classification, screening

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21
Q

examples of diffusional (mass transfer)

A

distillation, absorption, extraction

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22
Q

What is the driving force in mass transfer operations?

A

Concentration difference or gradient.

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23
Q

What principle is used in the Kremser Equation?

A

Inverse Lever Arm Principle.

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24
Q

Name two types of mass transfer operations.

A
  • Unidirectional Mass Transfer
  • Equimolar Mass Transfer
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25
involves diffusion of the component to be separated through a stationary phase
unidirectional mass transfer
26
classifications of mass transfer operations
1. direct contact of two immiscible phases 2. direct contact of miscible phases 3. phases separated by a membrane 4. use of surface phenomena
26
rates of mass transfer of the more and less volatile components between phases are equal in magnitude but opposite in direction
equimolar mass transfer
27
Use of microporous and nonporous membranes as semipermeable barriers for selective separations.
membrane separation processes
28
What does the Phase Rule describe?
The number of degrees of freedom in a system at equilibrium.
29
What is the purpose of distillation in separation processes?
To separate components based on differences in boiling points.
30
What does the term 'equilibrium stage model' refer to?
A model used to analyze mass transfer operations based on equilibrium conditions.
31
What is the main characteristic of diffusional mass transfer?
It exploits differences in vapor pressure, solubility, or diffusivity.
32
What is the main goal of separation processes in chemical engineering?
To change the compositions of mixtures into useful products.
33
What is the role of adsorption in mass transfer operations?
To separate components based on their affinities to a solid surface.
34
What is the significance of the term 'phase equilibria' in separation processes?
It describes the equilibrium between different phases in a mixture.
35
What does the term 'solvent extraction' refer to?
A separation process where a solvent is used to selectively dissolve a component from a mixture.
36
What is the difference between heterogeneous and homogeneous mixtures?
* Heterogeneous: Composition varies throughout * Homogeneous: Uniform composition throughout
37
What is the significance of the equilibrium stage in mass transfer operations?
It represents the point at which the transfer of mass is balanced between phases.
38
Fill in the blank: __________ is a technique for separating components based on differences in solubility.
[Extraction]
39
What is the purpose of leaching in separation processes?
To extract soluble constituents from a solid by dissolving them in a liquid.
40
What type of separation process uses differences in physical state?
Distillation
41
What is the main characteristic of membrane separation processes?
They use membranes to selectively allow certain substances to pass through while blocking others.
42
What are mass-transfer operations primarily involved in?
Separation processes ## Footnote Includes operations that may lead to a pure substance or an equilibrium phase containing only one constituent.
43
What is a characteristic of a separation process?
Separations are never complete but can be brought to near completion.
44
List the types of phase contacts in mass-transfer operations.
* Gas * Liquid * Solid
45
What are examples of gas-liquid mass-transfer operations?
* Distillation * Gas absorption * Gas desorption or stripping * Humidification * Dehumidification
46
What operations fall under liquid-solid mass-transfer?
* Crystallization * Leaching * Adsorption
47
What distinguishes direct contact of miscible phases in mass-transfer operations?
Not generally considered practical industrially (e.g., thermal diffusion, sweep diffusion, centrifugation).
48
What is the role of membranes in mass-transfer operations?
Prevent intermingling of two miscible phases and allow movement through them by diffusion.
49
What is gas-liquid permeation?
A liquid component dissolves through a non-porous membrane and vaporizes at the other side.
50
What is dialysis in the context of mass-transfer operations?
Separation of a crystalline substance from a colloid using a membrane permeable only to the solvent and dissolved substance.
51
Differentiate between direct and indirect mass-transfer operations.
* Direct Operations: Produce two phases from a single-phase solution by addition or removal of heat. * Indirect Operations: Involve addition of a foreign substance.
52
What is an example of a direct mass-transfer operation?
Fractional distillation.
53
What is an example of an indirect mass-transfer operation?
Gas absorption.
54
What are the two main types of mass-transfer operations based on method of conducting?
* Unsteady-state operation * Steady-state operation
55
What is the equilibrium stage model in mass-transfer operations?
A device where two streams are brought together, allowed to reach equilibrium, then separated and withdrawn.
56
What defines the rate of transfer model in mass-transfer operations?
Evaluates the number and rate of migration of carriers of a property.
57
What is a cascade in mass-transfer operations?
A series of stages arranged for phases to flow through from one to the other.
58
What is the difference between stagewise operation and differential operation?
* Stagewise Operation: Allows establishment of equilibrium between phases. * Differential Operation: Maintains departure from equilibrium.
59
What types of operations are typically performed in stagewise operation?
* Distillation * Leaching * Liquid extraction
60
What types of operations are typically performed in differential operation?
* Gas absorption * Continuous contact operations
61
What is the significance of stage efficiency in mass-transfer operations?
It reflects the approach to equilibrium realized in any stage.
62
What are the types of separation processes?
* Absorption * Adsorption * Azeotropic distillation * Centrifugation * Chromatography * Crystallization * Distillation * Filtration * Liquid-liquid extraction * Membrane separation * Sublimation * Thermal diffusion * Ultrafiltration
63
subclassifications of direct contact two immiscible phases
direct, indirect
64
produce the two phases from a single phase solution by addition or removal of heat
direct operations
65
involve addition of foreign substance
indirect operations
66
method of conducting mass transfer operations
1. solute recovery and fractionation 2. unsteady-state operation 3. steady-state operation 4. stagewise operation 5. continuous-contact operation
67
physical models of mass-transfer operations
1. equilibrium stage model 2. rate of transfer model
68
a device in which two streams, or phases, are brought together, allowed to reach equilibrium, then separated and withdrawn
equilibrium stage model
69
the carriers of the property are visualized, their number and rate of migration are evaluated, and an expression of the rate of transfer between two streams is arrived
rate of transfer model

Separation Processes (6 decks)

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