Question

Experiment data taken in a batch reactor predicted the CSTR conversion should be 50%. However, the concentration measured in the actual CSTR was 57%. Suggest a reason for the discrepancy between the predicted and measured conversion.

Answer 1

Solution.

Because,

1) Batch reactor is unsteady state reactor i.e process variable in batch reactor like concentration and conversion changes with time.

2 )On other hand, CSTR is steady state reactor, in which conversion and concentration is fixed at any time at Outlet.This difference might be responsible for conversion changes.

3) The batch reactor requires concentration uniform and same at any time , throughout the reactor , this condition may not be reach in real Batch reactor.

While in real CSTR the continuous stirring ensures that uniformity in concentration throughout and hence this may be reason behind the increased conversion of reactant in CSTR as compared to Batch reactor.

4) Batch reactor design equation is same as that of PFR design equation , assuming Batch reactor as PFR , then low conversion in PFR and high conversion in CSTR suggests that reaction may be of order less than 1 .

Reaction with order less than one gives higher conversion in CSTR as compared to PFR/BATCH reactor for same reaction.this may be another reason behind the discrepancy between measured and predicted values of conversion.

5) We also need to include , the errors (if any) in predicted conversation and nonideality in CSTR in the above discrepancy.

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