Reactors
Flow Reactors Batch Reactors
Mixed Flow Reactors(MFR)
Plug Flow Reactors(PFR)
Continuous Stirred Tank Reactors(CSTR)
Back Mixed Reactors(BM)
Batch Reactors
Characteristics• Reactor is charged via two holes in the top of the
tank;
• While reaction is carried out, nothing else is put in or taken out until the reaction is done;
• Tank easily heated or cooled by jacket .
• This type are used for a variety of process operations.
• A typical batch reactor consists of a tank with an agitator and integral heating/cooling system.
• These vessels may vary in size from less than 1 liter to more than 15,000 liters .
• They are usually fabricated in steel, stainless steel, glass lined steel, glass or exotic alloy .
Kinds of Phases Present• Gas phase• Liquid phase• Liquid-Solid
CEB MKII Batch Reactor
Usage• Small scale production• Intermediate or one shot production• Pharmaceutical• Fermentation• Solids dissolution• Product mixing• Chemical reactions• Batch distillation• Crystallization• Liquid/liquid extraction• Polymerization
Advantages• High conversion per unit volume for one
pass• Flexibility of operation - same reactor can
produce one product at a time and different product the next
• Easy to clean
Disadvantages• High operating cost• Product quality more variable than with
continuous operation
Sequential Batch Reactors (SBR)
Carbon Steel or Stainless
Steel Reactors
Stainless steel reactors for
chemical plant
"Glass Lined Reactors "
Reaction Vessel (Reactor)
Continuous Stirred Tank
Reactors (CSTR)
Characteristics• Run at steady state with
continuous flow of reactants and products;
• The feed assumes a uniform composition throughout the reactor;
• Exit stream has the same composition as in the tank.
Kinds of Phases Present• Liquid phase• Gas-liquid reactions• Solid-liquid reactions
Usage• When agitation is required• Series configurations for different
concentration stream.
CEM MK II CSTR
Advantages• Continuous operation• Good temperature control• Easily adapts to two phase runs• Good control• Simplicity of construction• Low operating (labor) cost• Easy to clean
Disadvantages• Lowest conversion per unit volume• By-passing and channeling possible with poor
agitation
Batch reactor Semi-Batch reactor
Stirred contained solids reactors
Plug Flow Reactors
(PFR)
CharacteristicsArranged as one long reactor or
many short reactors in a tube bank ;
No radial variation in reaction rate (concentration);
Concentration changes with length down the reactor.
Kinds of Phases PresentPrimarily Gas Phase
Usage• Large Scale• Fast Reactions• Homogeneous Reactions• Heterogeneous Reactions• Continuous Production• High Temperature
Advantages• High conversion per unit volume• Low operating (labor) cost• Continuous operation• Good heat transfer
Disadvantages• Undesired thermal gradients may exist• Poor temperature control• Shutdown and cleaning may be
expensive
Tubular reactor
Plug-flow reactors for Biomass Conversion
Industrial scale Reactor
Homogeneous Continuous Reactions (Plug Flow)
Reactive Distillation - Homogeneous
.
Reactive Distillation - Heterogeneous
creating plug-flow conditions in reactors
Fixed bed reactors
Fischer-Tropsch reaction convert synthesis gas into a mixture of alkanes and alkenes over Fe catalyst.
Fluidized bed reactor
Four major chemical reactorsin petroleum refining
THE HUMAN REACTOR
Process Design
Matters for Design Consideration
(1)Type of processing Batch Continuous Semibatch or semicontinuous
(2)Type and nature of reacting system Simple Complex (desirable,, undesirable products) Stoichiometry Phases, number of phases Catalytic (choice of catalyst) or noncatalytic Endothermic or exothermic Possibility of equilibrium limitation
Cont.
(3)Type and size of reactor Batch Continuous (stirred tank , tubular,
tower/column, bed )
(4)Mode of operation Configurational (single-stage or multistage ,
axial or radial flow, arrangement of heat transfer surface, flow pattern, contacting pattern)
Thermal (adiabatic, isothermal , nonisothermal, nonadiabatic)
Use of recycle
Cont..(5)Process conditions
T profile P profile Feed (composition, rate) Product (composition, rate)
(6)Optimality of process conditions of size of product distribution of conversion of cost (local, global context)
Cont…(7)Control and stability of operation
Instrumentation Control variables Sensitivity analysis Catalyst life, deactivation, poisons
(8)Socioeconomic Cost Environmental Safety
(9)Materials of constructional corrosion
(10)Startup and shutdown procedures
Data Required
(1)Specifications Reactants Products Throughput or capacity
(2)general data Rate data/parameters relating to
reaction (rate law/s, heat transfer, mass transfer, pressure drop, equilibrium data, other physical property data, cost data)
Tools Available The rational design of a chemical reactor is
perhaps the most difficult equipment-design task of a chemical engineer.
(1)Rate processes and rate laws Reaction kinetics Diffusion and mass transfer Heat transfer Fluid mechanics (flow patterns , mixing,
pressure drop)(2)Conservation and balance equations
Mass balances (including stoichiometry) Continuity equation Energy balance (including energetics of
reaction) Thermochemistry
Cont.(3)Equilibrium
Reaction equilibrium Phase equilibrium
(4)Mathematics Development of a reactor model Analytical or numerical methods
for solution of equations Simulation statistical analysis
of rate data
Cont..(5)Computers and computer software
Use of a PC, workstations, etc., coupled with software packages to solve sets of algebraic and/or differential equations, and to perform statistical analyses necessary for implementation of a reactor model for design or for assessment of reactor performance
Software (spreadsheet packages, simulation software, numerical equation solvers, computer algebra system)
(6)Process economics
Mechanical Design • Impeller or agitator design (as in a
stirred tank) • Power requirement (for above) • Reactor-as-pressure-vessel design• Wall thickness • Over-pressure relief • Fabrication • Support-structure design • Maintenance features