Intro Lecture Flashcards
What is a chemical/biological plant?
A reactor surrounded by separators.
What percentage do separation account for when it comes to capital and operating costs?
Represent 40-70% of capital and operating costs in a facility.
What type of feed is used in mechanical operations?
Feed is heterogeneous (i.e.
consists of more than one phase)
What type of feed is used in diffusional operations?
Feed is homogeneous (i.e. singlephase multicomponent mixture)
What is the purpose of mechanical operations?
Purpose: separate the phases
What is the purpose of diffusional operations?
Separate one or more
components via selective transfer
into a second phase
What examples of mechanical operations?
e.g. filtration, clarification,
decantation, centrifugation
What are examples of diffusional operations?
e.g. distillation, absorption,
extraction,
What is interphase operation?
Mass transfer between two
immiscible phases in direct contact
What is intraphase operation?
Mass transfer between two miscible
phases that are separated by a
permeable barrier called a
membrane
Examples of Interphase Operation
e.g. gas permeation, dialysis and
reverse osmosis
What do the molecules do during phase equilibria?
Molecules continually vaporize and
condensing
Which parameters don’t change in equilibrium?
- Temperature
- Pressure
- Mole fractions of each phase
Describe thermal equilibrium
vapor temperature = liquid temperature
Describe mechanical equilibrium?
vapor pressure = liquid pressure
What happens during phase equilibrium?
Rate at which A is vaporizing is equal
to rate at which A is condensing
What is the gibbs phase rule for non-reacting systems?
F=C-P+2
What is an azeotrope?
Composition in liquid and vapour
phase is identical. Cannot separate by
distillation.
What is a stage?
Device or a combination of devices in which two essentially
immiscible phases are brought into intimate contact to allow mass
transfer between them, and then are mechanically separated.
What is an equilibrium stage?
Phases are
assumed to be in equilibrium with
each other at separation.
Describe the relationship between a substance’s volatility and its boiling point?
The lower the boiling point, the more volatile the substance is.
When the does the mole fraction of A in vapour phase = mole fraction of A in liquid phase?
When the system is an azeotrope
If xa = ya, can A and B be separated using vaporization?
No, because the composition of the liquid and vapour are the same
What is the rate of separation limited by?
The rate of mass transfer
Is there mass transfer for a system at equilibrium?
No
What is the goal of separation processes?
Enhance the rate of mass transfer of certain species relative to others to effect a concentration or enrichment of components.
