Reactors Flow Reactors Mixed Flow Reactors (MFR) Continuous Stirred Tank Reactors (CSTR) Back Mixed...

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