5.1 Ideal Batch Reactors
5.2 Steady-state Mixed Flow Reactors
5.3 Steady-state Plug Flow Reactors
Basic assumption 1: Homogeneous & Isothermal reactions rate equation = f(composition)
Continuous flow reactors
Basic assumption 2: steady-state operation of continuous flow reactors
rate equation = f(composition) = 0
5.1 Ideal Batch Reactor
For reactant A,
Material balance :
For constant-volume reaction
For volume-changing reaction
General equation showing the time required to achieve a conversion XA for either
isothermal or nonisothermal operation
New terminology
Space-time:
Space-velocity:
A space-velocity of 5 hr-l means that
five reactor volumes of feed are being fed into the reactor per hour.
A space-time of 2 min means that
every 2 min one reactor volume of feed is being treated by the reactor.
5.2 Steady-state Mixed Flow Reactors
5.2 Steady-state Mixed Flow Reactors
For reactant A,
Material Balance:
(V : volume of reactor)
For constant-volume reaction
For constant density systems
Example) How to add rate equation into reactor equation
1) 1st-order reaction
2) 2nd-order reaction
3) 1st-order reaction For volume-changing systems
Example 5.1 Reaction Rate in a Mixed Flow Reactor
(Constant density system)Example 5.2 Kinetics from a Mixed Flow Reactor
From the stoichiometry (2A R), expansion factor :
(Volume-changing system)
When the mechanism of reaction is not known,
we often attempt to fit the data with an nth-order rate equation of the form
Example 5.3 Mixed Flow Reactor Performance
Liquid phase reaction (Constant density system)
Since limiting component is B
XB = 0.75
For constant volume reaction
Volumentric flow rate into and out of the reactor
5.3 Steady-state Plug Flow Reactors
For reactant A, Material balance:
In a plug flow reactor, the composition of the fluid varies from point to point along a flow path;
the material balance for a reaction component must be made for a differential element of volume dV.
For constant-volume reaction
Example) How to add rate equation into reactor equation
1) Zero-order reaction
2) 1st-order irreversible reaction (A products)
3) 1st-order reversible reaction ( ) For volume-changing systems
4) 2nd-order irreversible reaction (A+B products)
Example 5.4 Plug Flow Reactor Performance
From the stoichiometry (A 3R) & 50% inerts expansion factor :
(Volume-changing system)
The integral can be evaluated in any one of three ways: graphically, numerically, or analytically.
1) Graphical Integration
Counting squares or estimating by eye
The integral can be evaluated in any one of three ways: graphically, numerically, or analytically.
2) Numerical Integration Using Simpson's rule
3) Analytical Integration
Example 5.5 Plug Flow Reactor Volume
From the stoichiometry (4A R + 6S), expansion factor :
(Volume-changing system)
From the stoichiometry (4A R + 6S), expansion factor :
New terminology
Space-time:
Holding-time:
For constant density systems (all liquids and constant density gases) For changing density systems
General expression for Batch reactor
