Exercise 2 solution Lecturer: Miss Anis Atikah Ahmad Email: anisatikah@unimap.edu.my

Questions X 0.2 0.4 0.45 0.5 0.6 0.8 0.9 -rA (mol/dm3.min 1.0 1.67 5.0 The exothermic reaction A--->B + C was carried out adiabatically and the following data recorded: The entering molar flow rate of A was 300 mol/min. (a) What are the PFR and CSTR volumes necessary to achieve 40 % conversion? (b) Over what range of conversions would the CSTR and PFR reactor volumes be identical? (c) What is the maximum conversion that can be achieved in a 105 dm3 CSTR? (d) What conversion can be achieved if a 72 dm3 PFR is followed in series by a 24 dm3 CSTR? (e) What conversion can be achieved if a 24 dm3 CSTR is followed in a series by a 72 dm3 PFR? X 0.2 0.4 0.45 0.5 0.6 0.8 0.9 -rA (mol/dm3.min 1.0 1.67 5.0 1.25 0.91

Part (A) What are the PFR and CSTR volumes necessary to achieve 40 % conversion? PFR Volume: Using Simpson One-Third Rule; Recall Simpson One-Third Rule Formula:

Part (A) X 0.2 0.4 0.45 0.5 0.6 0.8 0.9 -rA (mol/dm3.min) 1.0 1.67 5.0 0.2 0.4 0.45 0.5 0.6 0.8 0.9 -rA (mol/dm3.min) 1.0 1.67 5.0 1.25 0.91 FA0/-rA (dm3) 300 180 60 240 330 Levelspiel Plot VPFR

Part (a) CSTR Volume: Substituting the value of FA0/–rA at X=0.4; VCSTR Levelspiel Plot

The volume of both reactors are identical at X=0.4-0.6, Part (B) Over what range of conversions would the CSTR and PFR reactor volumes be identical? From Levelspiel Plot; The volume of both reactors are identical at X=0.4-0.6,

Using Simpson One-Third Rule Part (B) Over what range of conversions would the CSTR and PFR reactor volumes be identical? Proving by calculation; Volume of PFR Using Simpson One-Third Rule Volume of CSTR

Part (c) What is the maximum conversion that can be achieved in a 105 dm3 CSTR? By trial and error, calculate what is X that gives a CSTR volume of 105 dm3 Trial 1: X=0.6, Trial 2: X=0.8, Trial 3: X=0.7, X=0.7 The max conversion can be achieved in 105 dm3 of CSTR is 0.7

Now, we know that the conversion must be between 0.6-0.7. Part (d) What conversion can be achieved if a 72 dm3 PFR is followed in series by a 24 dm3 CSTR? FA0=300 mol/dm3 X1=0.4 From part (a) VPFR=72 dm3 VCSTR=24 dm3 By trial and error, calculate what is X2 that gives a CSTR volume of 24 dm3 Trial 1: X2=0.6, Trial 2: X2=0.7, X2=? Now, we know that the conversion must be between 0.6-0.7.

Part (d) What conversion can be achieved if a 72 dm3 PFR is followed in series by a 24 dm3 CSTR? FA0=300 mol/dm3 X1=0.4 VPFR=72 dm3 VCSTR=24 dm3 Trial 3: X2=0.64, X2=? X=0.64 X=0.64 can be achieved if a 72 dm3 PFR is followed in series by a 24 dm3 CSTR.

Part (e) What conversion can be achieved if a 24 dm3 CSTR is followed in a series by a 72 dm3 PFR? FA0=300 mol/dm3 From part (a) VCSTR=24 dm3 X1=0.4 VPFR=72 dm3 X2=? By trial and error, calculate what is X2 that gives a PFR volume of 72 dm3 Trial 1: X2=0.8,

Part (e) What conversion can be achieved if a 24 dm3 CSTR is followed in a series by a 72 dm3 PFR? FA0=300 mol/dm3 VCSTR=24 dm3 X1=0.4 VPFR=72 dm3 X2=? By trial and error, calculate what is X2 that gives a PFR volume of 72 dm3 Trial 2: X2=0.9,

Part (e) What conversion can be achieved if a 24 dm3 CSTR is followed in a series by a 72 dm3 PFR? Trial 3: X2=0.91, X=0.91 can be achieved if a 24 dm3 CSTR is followed in a series by a 72 dm3 PFR

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