ch01 overview of separation process.pptx
DESCRIPTION
Separation C1TRANSCRIPT
+BKF3463
UNIT OPERATION 1
Dr. Syed Mohd Saufi
2012/2013-II
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Chapter 1Overview of Separation ProcessChapter 1 in Henley, Seader & Roper’s Book
+ Topic Outcomes (TO) Describe and explain the phenomena of
separation processes Classify separation processes depending on
its needs and physical properties of fluids Determining the suitable methods for
separation processes
+ Introduction Separation process in early civilization
Extract metals from ores, perfumes from flowers, dyes from plants, and potash from the ashes of burnt plants
Evaporate sea water to obtain salt Refine rock asphalt Distill liquors.
Kidney – organ containing membranes that separates water and waste products of metabolism from blood
Chemist – use chromatography to separate complex mixtures quantitatively (lab scale) and preparative separation techniques to recover chemicals
Chemical engineers – concerned with the manufacture of chemicals using large scale separation methods
Industrial chemical processes include equipment for separating chemicals in the process feed(s) and/or species produced in reactors within the process.
+ Industrial Chemical Process Chemical plant is a physical facility in which the raw materials
undergo chemical and physical changes in order to make the desired products
In general, chemical plant contains some or all of the following Feed preparation facilities – bring raw materials to correct
composition or physical properties Reactors – provide conditions to allow desired chemical reactions to
take place under control Separator – separate desired products from raw materials, byproducts
and wastes Environmental control facilities – handle waste for safe reuse or
disposal Product formulation facilities – mix, formulate, package and store the
final products Material transfer equipment – move solids, liquids and gases Energy transfer equipment – supply refrigeration, heat and work
Except for the reactor, majority of chemical plant involve with unit operation (nowadays modern nomenclature use the term “separation process” rather than unit operation.
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Introduction to chemical process – principles, analysis, synthesis by Murphy
+ Industrial Chemical Process
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Introduction to chemical process – principles, analysis, synthesis by Murphy
+ Basic Separation Techniques The creation of a mixture of chemical species from the
separate species is a spontaneous process that requires no energy input.
The into pure components, is not a spontaneous process and thus requires energy.
A general separation schematic is shown in Figure below as a box wherein species and phase separation occur, with arrows to designate feed and product movement. The feed and products may be vapor, liquid, or solid; one or more separation operations may be taking place; and the products differ in composition and may differ in phase
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+Common Separation Techniques1) Separation by phase creation Creates a second phase, immiscible with the feed phase, by
energy (heat and/or shaft-work) transfer or by pressure reduction.
Common operations of this type are distillation, which involves the transfer of species between vapor and liquid phases, exploiting differences in volatility (e.g., vapor pressure or boiling point) among the species; and crystallization, which exploits differences in melting point
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+Common Separation Techniques2) Separation by phase addition Adds another fluid phase, which selectively absorbs, extracts,
or strips certain species from the feed. The most common operations of this type are liquid–liquid
extraction, where the feed is liquid and a second, immiscible liquid phase is added; and
absorption, where the feed is vapor, and a liquid of low volatility is added.
In both cases, species solubilities are significantly different in the added phase.
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+Common Separation Techniques3) Separation by barrier The use of a barrier,
usually a polymer membrane, which involves a gas or liquid feed and exploits differences in species permeabilities through the barrier.
4) Separation by solid agent Contacting a vapor or
liquid feed with a solid agent
Most commonly, the agent consists of particles that are porous to achieve a high surface area, and differences in species adsorbability are exploited
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+Common Separation Techniques5) Separation by force field or gradient External fields (centrifugal, thermal, electrical, flow, etc.) are
applied in specialized cases to liquid or gas feeds Example is electrophoresis for separating proteins by
exploiting differences in electric charge and diffusivity.
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+Common Separation Techniques The size of the equipment is determined by rates of mass transfer
of each species from one phase or location to another, relative to mass transfer of all species.
The driving force and direction of mass transfer is governed by the departure from thermodynamic equilibrium, which involves volatilities, solubilities, etc.
Fluid mechanics and heat transfer play important roles in separation operations
The extent of separation possible depends on the exploitation of differences in molecular, thermodynamic, and transport properties of the species.
Properties of importance are:
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+Separation by Phase Addition or Creation If the feed is a single-phase solution, a second separable
phase must be developed before separation of the species can be achieved.
The second phase is created by an energy separating agent (ESA) and/or added as a mass-separating agent (MSA).
An ESA involves heat transfer or transfer of shaft work to or from the mixture. An example of shaft work is the creation of vapor from a liquid phase by reducing the pressure.
An MSA may be partially immiscible with one or more mixture components and frequently is the constituent of highest concentration in the added phase.
Disadvantages of using an MSA are 1) need for an additional separator to recover the MSA for recycle,2) need for MSA makeup,3) possible MSA product contamination, and4) more difficult design procedures.
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+Separation by Phase Addition or Creation Alternatively, the MSA may be miscible with a liquid
feed mixture, but may selectively alter partitioning of species between liquid and vapor phases.
When immiscible fluid phases are contacted, intimate mixing is used to enhance mass-transfer rates so that the maximum degree-of-partitioning of species can be approached rapidly.
After phase contact, the phases are separated by employing gravity and/or an enhanced technique such as centrifugal force
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+Separation by Phase Addition or Creation
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+Separation by Phase Addition or Creation
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+Separation by Phase Addition or Creation
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+ Separation by Barriers Use of microporous and nonporous membranes as
semipermeable barriers for selective separations Membranes are fabricated mainly from natural fibers
and synthetic polymers, but also from ceramics and metals.
Membranes are fabricated into flat sheets, tubes, hollow fibers, or spiral-wound sheets, and incorporated into commercial modules or cartridges.
For microporous membranes, separation is effected by rate of species diffusion through the pores; for nonporous membranes, separation is controlled by differences in solubility in the membrane and rate of species diffusion.
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+ Separation by Barriers
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+ Separation by Solids Agents The solid, in the form of a granular material or packing, is
the adsorbent itself, or it acts as an inert support for a thin layer of adsorbent by selective adsorption or chemical reaction with species in the feed.
Adsorption is confined to the surface of the solid adsorbent, unlike absorption, which occurs throughout the absorbent.
The active separating agent eventually becomes saturated with solute and must be regenerated or replaced.
Such separations are often conducted batchwise or semicontinuously. However, equipment is available to simulate continuous operation.
Three main process Adsorption Chromatography Ion exchange
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+ Separation by Solids Agents
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+ Separation by External Field or Gradient External fields can take advantage of differing degrees of response of
molecules and ions to force fields. The common techniques and combinations are:
1. Centrifugation - establishes a pressure field that separates fluid mixtures according to molecular weight.
2. Thermal diffusion - if a temperature gradient is applied to a homogeneous solution, concentration gradients are established, and thermal diffusion is induced.
3. Electrolysis 4. Electrodialysis - cation- and anion-permeable membranes carry a
fixed charge, thus preventing migration of species of like charge. 5. Electrophoresis - which exploits the different migration velocities of
charged colloidal or suspended species in an electric field, a versatile method for separating biochemicals.
6. Field-flow fractionation - an electrical or magnetic field or thermal gradient is established perpendicular to a laminar-flow field. Components of the mixture travel in the flow direction at different velocities, so a separation is achieved.
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+ Separation by External Field or Gradient
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+ Selection of Feasible Separations
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+ Selection of Feasible Separations
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+ Selection of Feasible Separations
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+ Thank You
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