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Unit 2: An Overview of
Chemical Process Technology
Introduction to the Chemical Industry for Technical Assistance Providers
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Unit 2: An Overview of Process Technology
Outline of this Unit
An introduction to process technology
organizing concepts
unit operations view of process technology
introduction to main process operations Environmental considerations of unit ops
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Unit 2: An Overview of Process Technology
Learning Objectives
Gain an understanding of the unit ops view
of process technology
Gain familiarity with key pieces of process
equipment
Understand environmental implications of
process equipment
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Unit 2: An Overview of Process Technology
Making Sense of Process Technology
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Unit 2: An Overview of Process Technology
Behind the Complex Appearance,Chemical Manufacturing is Simple
Raw materials are mixed and/or reactedto
create useful products
These products are separatedin one or more
steps
Between each step, process streams may be
heatedor cooledto optimum temperatures
In some cases, products may be
mechanicallyprocessedto convenient form for
transport and use
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Introduction to Chemical Reactors
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Trade-offs in Reactor Design
Want to maximize
product throughput
conversion efficiency
selectivity
flexibility process safety
controllability
Want to minimize
byproduct formation
energy use
downstream
separations physical complexity
capital cost
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Some Common Reactor Types
Batch
Semi-batch
Continuous
Stirred tank Packed bed
Fluidized bed
Electrolytic cells
Bioreactors
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Batch Reactor
Reactants added to vessel and products emptiedafter completion of reaction
some reactants may be added continuously(semi-batch)
often referred to asstirred tank reactor
Agitator mechanism
Insulating jacket
Pipes & valves tocontrol conditions
Primarily small-scale
(e.g. specialty chem)and experimentalprocesses
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Batch process characteristics
Not enough product demand to make continuously
More practical and feasible for multi-step synthesis
Can reduce overall process complexity
Allows chemists to maximize yield of desiredcompound, which can reduce waste
Easier to operate, maintain and repair
Can be adapted to multiple usesimportant for
facilities producing many different products (e.g.specialty)
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Reactors in Series:A Battery of Stirred Tanks
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Continuous Reactor
Reactants added and products
removed at constant rate
constant volume in reactor
Continuous stirred tank
CSTR equipmentsimilar to batch reactor
Pipe (tubular) reactor
tubing arranged in coil,
jacketed in heat transferfluid
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Continuous Reactor Characteristics
Good for high productionused primarily for
large-scale operations (>20 million pounds/yr
product)
Usually dedicated to single product
Requires significant automation and capital
expenditures
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Other Continuous Reactor Types
Packed bed
Tubular reactor packed with solid catalyst
particles
Catalyst increases reaction rate and
conversion
Fluidized bed
Combination of continuous stirred-tank
and packed-bed
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Reactorspotential wastes
Byproducts
Spent catalysts, salts, filter aids,etc
Waste (gas, liquid, solid) from reactivation of
catalyst in fluidized bed
Discharge of fluidizing gas
Off-spec product
Cleaning waste
Vent gases from reactor charging Contaminated cooling water
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Shell and tube heat exchanger
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Heat ExchangePotential Wastes
Thermal degradation in process streams
Contaminated exchange fluid by process streams
Liquid waste from blowdown
Vapor and mist from cooling towers Cleaning chemicals from maintenance
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Separations
Most chemical reactions are not complete
(some unreacted inputs remain)
Side reactions may result in one or more
unwanted (or desired) byproducts
Separations needed to obtain purified
product to be used by
customers or
downstream
manufacturers
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Distillation
Separates liquids having differing boiling
points
Can separate solutions where all components
are appreciably volatile (fractionation)
Mixture heated to boiling of most volatile
component (i.e. lowest boiling point),
compound becomes gaseous, then
condensed again in attached vessel.
Additional compounds can be isolated frommixture by increasing temperature to
appropriate boiling point(s)
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Distillation Column
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Unit 2: An Overview of Process Technology
Example of extraction process-50/50 acetone/water mixture
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Unit 2: An Overview of Process Technology
Liquid-Liquid Extraction Unit
Courtesy Pressure Chemical Co.
Pressure Chemical Co.
3419 Smallman Street
Pittsburgh, PA 15201-1997
412 682-5882
www.pressurechemical.com
http://www.pressurechemical.com/http://www.pressurechemical.com/ -
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Unit 2: An Overview of Process Technology
Filtration
Separates solids from liquids or gases
feedstock preparation
product or catalyst recovery
Slurry or mixture of liquid and suspended
particles passed through porous barrier
Alternative form is centrifugation
Slurry placed in porous basket, spun rapidly
and outward force pushes liquid through filter Fluid reclaimed on outside of basket
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Unit 2: An Overview of Process Technology
Other Separations Processes
Gas-Liquid Distillation(single stage=flash)
Evaporation
Gas Absorption
Liquid-Liquid
Liquid extraction
Product washing
Solid-fluid
Filtration
Adsorption and ion exchange
Crystallization
Drying
Leaching
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Unit 2: An Overview of Process Technology
Separations - potential wastes
Distillation:
Overhead vapor contamination of contact or non-
contact cooling water, steam jet condensate, etc
in distillation operations
Still bottoms
non-condensable gases
Filtration:
Filtrate, filter cake and filter presses from filtration
processes
Extraction: Vapor loss from headspace over extraction
Liquid or solid non-product phase
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Unit 2: An Overview of Process Technology
Materials Handling Equipment
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Unit 2: An Overview of Process Technology
Ancillary Equipment and Processes
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Unit Summary
Despite diversity of processes, underlyingequipment and phenomenology is relatively
simple
Unit Ops paradigm helps provide unifying
framework for understanding processtechnology
Each process unit has characteristic waste
and emission sources/causes
Emissions stem from both intrinsic andextrinsic causes
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