Ch 3 Reaction Process Design Flashcards
Which reactor for a single reaction?
Plug flow or batch avoids operating whole reactor at low concentrations eg. a smaller volume
Which reactor for multiple reactions in parallel?
Need to maximise selectivity, use pfr if primary reaction has a higher order, higher concentration required.
Use CSTR if secondary reaction has a higher order, lower concentration required.
Which reactor for multiple reactions in series?
Need to operate at best residence time. Use pfr or batch as CSTR has residence time distribution.
Which reactor for biochemical reactions?
Depends on reaction rate, nutrients, inhibition of growth..
Which reactor for polymerisation reactions?
PFR better for condensation reactions to ensure uniformity of product.
CSTR better for addition reactions for the same reason.
Consider Reaction Equilibrium
Choose conditions (reaction phase, temperature, pressure, concentration) to increase equilibrium conversion.
Consider using inerts or excess reactant, removing products as they form or recycling by-products.
Consider Reaction rate
choose conditions and phase to enhance rate of desired product creation, thus reducing reactor volume
consider how pressure or number of moles affects rate in gas/vapour reactions
Consider multiple reactions
Maximise selectivity and reaction yield
HDA Process, hydrogen is fed in excess to:
Reduce the partial pressure of benzene in the secondary reaction, hence the overall rate of the sceondary reaction.
Gas-Liquid reaction configuration its important for
good contact between liquid and gases, also suitable mixing patterns in each phase
Tubular reactors:
Aproximates plug flow, material flows steadily in one direction, heat can be added or removed, can approach isothermaility.
Stirred tank reactor:
May approach ideal cstr behaviour.
Write down the idealised reactor models:
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