lecture7Semibatch Reactors化学反应器分析
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The only difference here is that the temperature at the reactor inlet depends on the outlet temperature and the recycle.
Semibatch reactors
For uniform injection rate
Semibatch reactors
Energy balance equation Expansion work is negligible, and assuming isobaric operation,
Dimensionless
Example
Solution
Select the total feed into the reactor as the reference stream
Solution
Solution
Solution
Solution
Solution
Exercise
Exercise
Plug-flow Reactor With Distributed Feed
Plug-flow reactor with distributed feed
Maintain one reactant at a high concentration and another reactant at low concentration in order to improve the yield of a desirable product.
Distillation Reactor
Distillation reactor
A distillation reactor is a liquid-phase ideal batch reactor where volatile products are generated and continuously removed from the reactor, a species balance equation for species j that is not removed from the reactor:
Semibatch Reactors
Review
❖Design equations of ideal Batch reactors
❖Design equations of ideal CSTR
❖Design equations of ideal PFR
Semibatch reactors
(a) liquid phase (variable volume) (b) gas phase (constant volume).
For liquid-phase reactions, assuming constant density and constant specific heat capacity When there is no change in phase
Semibatch reactors
For gas-phase reactions，the rate enthalpy added by the injection stream
R=0, Plug flow reactor, R=,CSTR
RECYCLE REACTOR
For nonisothermal recycle reactors, The energy balance equation is the same as that of a plug-flow reactor,
Plug-flow reactor with distributed feed
For nonisothermal operations,
Plug-flow reactor with distributed feed
For nonisothermal operations, Dimensionless
RECYCLE REACTOR
Dimensionless
RECYCLE REACTOR
For liquid-phase reactions
R=0, Plug flow reactor, R=,CSTR
RECYCLE REACTOR
For gas-phase reactions For isobaric operations,
Distillation reactor
Overall material balance
Dimensionless
Distillation reactor
Distiion reactor
Example The dehydration of two heavy organic species, reactants A and B, is carried out in a distillation reactor where the water, product C, is being removed continuously. The reactor is initially charged with a 60-L organic solution that contains 200 mol of reactant A and 300 mol of reactant B. The reactor is operated isothermally at 200℃, and the following reactions take place in the reactor: Reaction 1: A (liquid) →C (g) + D (liquid) Reaction 2: B (liquid)→ 2 C (g)+ E (liquid) The rates of the chemical reactions are r1 =k1CA and r2 =k2CA. a. Derive the design equations and plot the reaction operating curves.
Plug-flow reactor with distributed feed
The local molar flow rate of species j at volume V from the inlet is
Where λ(x) is the local volumetric injection rate per unit reactor volume
For liquid-phase reactions, When the injection flow rate is uniform,
Plug-flow reactor with distributed feed
For gas-phase reactions,
For uniform injection along the reactor, and assuming negligible pressure drop,
For uniform injection rate,
Plug-flow reactor with distributed feed
For nonisothermal operations, For most liquid-phase reactions,
For gas-phase reactions,
Semibatch reactors
the specific molar-based heat capacity of the reference state
low concentration of reactant A and a low temperature is preferable
for isothermal operation
One or more reactants are added continuously during the operation and no material is withdrawn It is desirable to maintain a low concentration of one reactant
The design equation of a semibatch reactor
Semibatch reactors
Semibatch reactors
the design equation of semibatch reactors with a uniform injection rate is
Distillation reactor
Distillation reactor
For isothermal operation,
Recycle Reactor
RECYCLE REACTOR
It is identical to the design equation of a plug-flow reactor. The main difference between the recycle reactor and a plug-flow reactor is in the way the volumetric flow rate and the concentrations of the species vary along the reactor.
Differentiating
Semibatch reactors
Energy balance For reactors with negligible shaft work
Dimensionless For liquid-phase semibatch reactors
Semibatch reactors
Plug-flow reactor with distributed feed
Design Eqs. Dimensionless Reference stream
the dimensionless design equation, written for the mth-independent reaction.
It is identical to the design equation of an ideal batch reactor. The difference between the two cases is in the variation of the reactor volume and species concentrations during the operation.
Plug-flow reactor with distributed feed
Design Eqs. Species j, that is not injected along the reactor over reactor element dV.
It is identical to the design equation of a plug-flow reactor. The only difference between the two is the way the volumetric flow rate and the species concentrations vary along the reactor.
Semibatch reactors
❖ Species j, that is not fed continuously into the reactor.
Semibatch reactors
For the mth-independent reaction: The only differences between batch and semibatch operations are the way the reactor volume and the species concentrations vary during the operation. liquid-phase reactions.
Semibatch reactors
For uniform injection rate
Semibatch reactors
Energy balance equation Expansion work is negligible, and assuming isobaric operation,
Dimensionless
Example
Solution
Select the total feed into the reactor as the reference stream
Solution
Solution
Solution
Solution
Solution
Exercise
Exercise
Plug-flow Reactor With Distributed Feed
Plug-flow reactor with distributed feed
Maintain one reactant at a high concentration and another reactant at low concentration in order to improve the yield of a desirable product.
Distillation Reactor
Distillation reactor
A distillation reactor is a liquid-phase ideal batch reactor where volatile products are generated and continuously removed from the reactor, a species balance equation for species j that is not removed from the reactor:
Semibatch Reactors
Review
❖Design equations of ideal Batch reactors
❖Design equations of ideal CSTR
❖Design equations of ideal PFR
Semibatch reactors
(a) liquid phase (variable volume) (b) gas phase (constant volume).
For liquid-phase reactions, assuming constant density and constant specific heat capacity When there is no change in phase
Semibatch reactors
For gas-phase reactions，the rate enthalpy added by the injection stream
R=0, Plug flow reactor, R=,CSTR
RECYCLE REACTOR
For nonisothermal recycle reactors, The energy balance equation is the same as that of a plug-flow reactor,
Plug-flow reactor with distributed feed
For nonisothermal operations,
Plug-flow reactor with distributed feed
For nonisothermal operations, Dimensionless
RECYCLE REACTOR
Dimensionless
RECYCLE REACTOR
For liquid-phase reactions
R=0, Plug flow reactor, R=,CSTR
RECYCLE REACTOR
For gas-phase reactions For isobaric operations,
Distillation reactor
Overall material balance
Dimensionless
Distillation reactor
Distiion reactor
Example The dehydration of two heavy organic species, reactants A and B, is carried out in a distillation reactor where the water, product C, is being removed continuously. The reactor is initially charged with a 60-L organic solution that contains 200 mol of reactant A and 300 mol of reactant B. The reactor is operated isothermally at 200℃, and the following reactions take place in the reactor: Reaction 1: A (liquid) →C (g) + D (liquid) Reaction 2: B (liquid)→ 2 C (g)+ E (liquid) The rates of the chemical reactions are r1 =k1CA and r2 =k2CA. a. Derive the design equations and plot the reaction operating curves.
Plug-flow reactor with distributed feed
The local molar flow rate of species j at volume V from the inlet is
Where λ(x) is the local volumetric injection rate per unit reactor volume
For liquid-phase reactions, When the injection flow rate is uniform,
Plug-flow reactor with distributed feed
For gas-phase reactions,
For uniform injection along the reactor, and assuming negligible pressure drop,
For uniform injection rate,
Plug-flow reactor with distributed feed
For nonisothermal operations, For most liquid-phase reactions,
For gas-phase reactions,
Semibatch reactors
the specific molar-based heat capacity of the reference state
low concentration of reactant A and a low temperature is preferable
for isothermal operation
One or more reactants are added continuously during the operation and no material is withdrawn It is desirable to maintain a low concentration of one reactant
The design equation of a semibatch reactor
Semibatch reactors
Semibatch reactors
the design equation of semibatch reactors with a uniform injection rate is
Distillation reactor
Distillation reactor
For isothermal operation,
Recycle Reactor
RECYCLE REACTOR
It is identical to the design equation of a plug-flow reactor. The main difference between the recycle reactor and a plug-flow reactor is in the way the volumetric flow rate and the concentrations of the species vary along the reactor.
Differentiating
Semibatch reactors
Energy balance For reactors with negligible shaft work
Dimensionless For liquid-phase semibatch reactors
Semibatch reactors
Plug-flow reactor with distributed feed
Design Eqs. Dimensionless Reference stream
the dimensionless design equation, written for the mth-independent reaction.
It is identical to the design equation of an ideal batch reactor. The difference between the two cases is in the variation of the reactor volume and species concentrations during the operation.
Plug-flow reactor with distributed feed
Design Eqs. Species j, that is not injected along the reactor over reactor element dV.
It is identical to the design equation of a plug-flow reactor. The only difference between the two is the way the volumetric flow rate and the species concentrations vary along the reactor.
Semibatch reactors
❖ Species j, that is not fed continuously into the reactor.
Semibatch reactors
For the mth-independent reaction: The only differences between batch and semibatch operations are the way the reactor volume and the species concentrations vary during the operation. liquid-phase reactions.