Semibatch Reactors
Semibatch Reactors

## Semibatch Reactors

The reactant that starts in the reactor is always the limiting reactant.

### Three Forms of the Mole Balance Applied to Semibatch Reactors:

 1. Molar Basis 2. Concentration Basis 3. Conversion

 For constant molar feed: For constant density:

Use the algorithm to solve the remainder of the problem.

### Example: Elementary Irreversible Reaction

Consider the following irreversible reaction:

The combined mole balance, rate law, and stoichiometry may be written in terms of conversion and/or concentration:

 Conversion Concentration Number of Moles

Polymath Equations:

Conversion Concentration Moles
d(X)/d(t) = -ra*V/Nao d(Ca)/d(t) = ra - (Ca*vo)/V d(Na)/d(t) = ra*V
ra = -k*Ca*Cb d(Cb)/d(t) = rb + ((Cbo-Cb)*vo)/V d(Nb)/d(t) = rb*V + Fbo
Ca = Nao*(1 - X)/V ra = -k*Ca*Cb ra = -k*Ca*Cb
Cb = (Nbi + Fbo*t - Nao*X)/V rb = ra rb = ra
V = Vo + vo*t V = Vo + vo*t V = Vo + vo*t
Vo = 100 Vo = 100 Vo = 100
vo = 2 vo = 2 vo = 2
Nao = 100 Fbo = 5 Fbo = 5
Fbo = 5 Nao = 100 Ca = Na/V
Nbi = 0 Cbo = Fbo/vo Cb = Nb/V
k = 0.1 k = 0.01 k = 0.01
Na = Ca*V
X = (Nao-Na)/Nao
 Polymath Screenshots: Conversion Concentration Polymath Equations Polymath Equations Summary Table Summary Table Conversion vs. Time Conversion vs. Time Concentration vs. Time Concentration vs. Time Volume vs. Time Volume vs. Time

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