Chapter 2 Example

Reactors in Series: CSTR-PFR-CSTR

Using either the data in Table E2-W.1, calculate the reactor volumes V1, V2, and V3 for the CSTR/PFR/CSTR reactors in series sequence shown in Figure E2-W.1 along with the corresponding conversion.

                

                                     Figure E2-W.1 CSTR/PFR reactor in series.

 

Table E2-W.1 Processed Data

X

0

0.2

0.4

0.6

0.8

0.010

0.0091

0.008

0.005

0.002

100

110

125

200

500

200

220

250

400

1000

 

Solution

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Solution

We again use the plot of

               

                   Figure E2-W.2 Levenspiel plot for CSTR/PFR/CSTR sequence.

(a)  The CSTR design equation for Reactor 1 is

                                                                                                                  (E2-W.1)

            at X = X1 = 0.4 the (FA0/-rA1) = 300 dm3

            V1 = (300 dm3) (0.4) = 120 dm3

      The volume of the first CSTR is 120 dm3.

(b)Reactor 2: PFR The differential form of the PFR design is

                                                                                                                     (E2-W.2)

      Rearranging and integrating with limits

            when V = 0       X = X1 = 0.4

            when V = V2     X = X2 = 0.7

                                                                         (E2-W.3)

      Choose three point quadrature formula with

                                                                (E2-W.4)

      Interpreting for (FA0/-rA) at X = 0.55 we obtain

                        

      The volume of the PFR is          

(c)  Reactor 3: CSTR

            Balance

                                                                                                (E2-W.5)

            Rearranging

                                                                                                             (E2-W.6)

                                                                                                         (E2-W.7)

                                                                                                         (E2-W.8)

                                                                                                     (E2-W.9)

                                           

            The volume of the last CSTR is 180 dm3.

                                     

 

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