CHOICE%20OF%20REACTOR

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CHOICE OF REACTOR
REACTION TEMPERATURE

• Single Irreversible or reversible Endothermic
  Reactions high temperature
• Single Reversible Exothermic Reaction
• continuously decreasing temperature
• Multiple Reactions

Increases faster than
High temperature
Increases faster than
Low temperature
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CHOICE OF REACTOR
REACTION TEMPERATURE
Temperature Control

• Adiabatic Operation simplest and cheapest
• Indirect Heat Transfer jacket or coil
• Cold or Hot Shots injection of feed at
  intermediate points.
• Heat Barrier inert material that increases the
  overall heat capacity flowrate.
• Quench rapid cooling of reactor effluent.

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CHOICE OF REACTOR
REACTION PRESSURE
Vapor-phase

• Single Irreversible Reactions
• as high as practical
• Single Reactions with decrease in the number of
  moles
• as high as practical
• Single Reactions with increase in the number of
  moles
• continuously decreasing
• Multiple Reactions
• choose P such Selectivity is maximized

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CHOICE OF REACTOR
REACTION PRESSURE
Liquid-phase

• Effect of P is less pronounced
• P is chosen to
• Prevent vaporization of products
• Allow vaporization as a means of removing heat
• Allow selective vaporization in a rev. reaction
  to increase conversion.

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CHOICE OF REACTOR
CATALYSTS

• HOMOGENEOUS reaction occurs entirely in the
  vapor or liquid phase.
• HETEROGENEOUS catalyst is in a different phase
  from the reacting species.
• Bulk material a noble metal wire mesh
• Supported active material is dispersed over the
  surface of a porous media.

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CHOICE OF REACTOR
CATALYSTS DEGRADATION

• Deterioration comes with time and produces
• Lower Reaction Rate
• Lower Conversion
• Can compensate by increasing temperature, but
• Can degrade Selectivity
• Can accelerate catalyst degradation

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CHOICE OF REACTOR
CATALYSTS DEGRADATION

• Physical Loss
• Surface Deposits impede reaction
• Sintering reduce surface area
• Poisoning the poison reacts or bonds with
  reactant(s)

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CHOICE OF REACTOR
PRACTICAL REACTORS

• Stirred-tank Reactors
• Tubular Reactors
• Fixed-bed Catalytic Reactors
• Fixed-bed Non-catalytic Reactors
• Fluidized-bed Reactors

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CHOICE OF REACTOR
Stirred-tank Reactors

• Batch, semi-batch, or continuous
• Batch
• variable production rates
• several products in same equipment
• Continuous operation
• Automatic Control is much straightforward
• Can get closer to IDEAL CSTR is fluid is no too
  viscous.

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CHOICE OF REACTOR
Stirred-tank Reactors

• Batch, semi-batch, or continuous
• Batch
• variable production rates
• several products in same equipment

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CHOICE OF REACTOR
Stirred-tank Reactors

• Continuous operation
• Automatic Control is much straightforward
• Can get closer to IDEAL CSTR is fluid is no too
  viscous.
• Not GOOD choice for high pressure.
• Not GOOD choice if reactant or products are
  hazardous or toxic.

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CHOICE OF REACTOR
Tubular Reactors

• Bundle of tubes where the movement is in one
  direction only.
• GOOD choice when control of residence time is
  critical.
• GOOD choice for high pressure operation.

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CHOICE OF REACTOR
Fixed-bed Catalytic Reactors

• Tubular Reactor packed with catalyst solid
  particles
• Temperature control could be difficult due to
  variation along the bed.
• Exothermic reactions Local hot points can
  produce sintering. Use mixed of catalyst and
  inert solid to dilute heat.

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CHOICE OF REACTOR
Fixed-bed Non-catalytic Reactors

• GOOD for gas-solid reactions.
• Non-steady state operation.
• Need to be taken off-line for regeneration
• GOOD for Gas-liquid
• The solid bed provides active area.
• Concurrent operation is preferred if short liquid
  residence time is needed.