Liq-liq extraction Flashcards
stagewise contact in liq-liq extraction
- single contact (equal to equilibrium distillation)
- co-current multiple contact or simple multi-stage contact
- counter current multi-stage or multiple contact
- with reflux (equal to fractional distillation)
-w/out reflux
- continuous contact (differential contact)
relative enrichment of solute in extract phase compared in the raffinate phase after one stage
separation factor
defined for a given solute as the solute concentration in the extract phase divided by in the raffinate phase can be obtained in a single stage of contacting
Partition ration, K
it is thermodynamic potential of a solvent to extract a certain solute (can be a factor of temperature and composition)
K-value
capacity of the extract phase to carry the solute relative to the feed phase
Extraction factor, E
extraction factor, E, determines largely the
Theo
required solute to transfer from feed to extract phase
N
extraction factor, E, is analogous to
stripping factor in distillation
the maximum concentration that extract phase can hold for a solute or else the two solvent will not coexist anymore or the solute will precipitate and become the barrier of the two solvents
loading capacity
they allow operation with minimal solvent that’s why ideal for economical purpose
higher partition ration (equal or greater than 10)
what mutual solubility is ideal?
low
The solvent should have little tendency to react with the product to avoid by-products
stability
what is the preferred density difference between the solvent and feed phase to get a high liq-liq separation?
0.1 to 0.3 g/mL
_____ viscosity is preferred since higher viscosity generally increases mass- transfer resistance and liquid-liquid phase separation difficulty.
Low
Preferred ______ values for interfacial tension between the feed phase and the extraction solvent phase generally are in the range of _________.
high, 5 to 25 dyn/cm
The economical recovery of solvent from the extract and raffinate is critical to commercial success. Solvent properties should facilitate ______ options for recovery, recycle and storage
low-cost
solvent properties
- low cost
- anticipated ambient temperature
- ## low potential for fire and reactive chemistry hazards
Solvents that are liquids at all anticipated ambient temperatures are
desirable since they avoid the need for freeze protection and/or thawing of frozen
solvent prior to use.
freezing point
Solvents with low potential for fire and reactive chemistry hazards are
preferred as inherently safe solvents. In all cases, solvents must be used with
awareness of potential hazards and in a manner consistent with measures needed
avoid hazards.
Safety
Solvents with low mammalian toxicity and good warning properties are desired. Low toxicity and low dermal absorption rate reduce the potential for injury through acute exposure.
Industrial hygiene
The solvent must have physical or chemical properties that allow effective control of emissions from vents and other discharge streams.
Preferred properties include low aquatic toxicity and low potential for fugitive
emissions from leaks or spills.
Environmental requirements
It is desirable to use as the extraction solvent a material that can serve
a number of purposes in the manufacturing plant. This avoids the cost of storing and handling multiple solvents. It may be possible to use a single solvent for a number of different extraction processes practiced in the same facility, either in different equipment operated at the same time or by using the same equipment in a series of product campaigns.
Multiple uses
It is desirable for a solvent to allow the use of common, relatively inexpensive materials of construction at moderate temperatures and pressures.
Materials of construction
The solvent should be readily available at a reasonable cost. Considerations include the initial fill cost, the investment costs associated with maintaining a solvent inventory in the plant (particularly when expensive extractants are used), as well as the cost of makeup solvent.
Availability and cost
