Page 130 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

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containing excess of a second reactant (density of mixture = 1050 kg/m ) in a jacketed reaction vessel, the
reactor is sealed, and the mixture is stirred and heated. Once the reaction mixture has reached 95°C, a
solid catalyst (negligible volume) is added, and reaction takes place while the batch of reactants
continues to be stirred. The required conversion is 94%, 17.5 kg of product is produced, and the time
taken is 7.0 h. The reactor is filled to 60% of maximum capacity to allow for expansion and to provide
appropriate vapor space above the liquid surface. Determine the volume of reaction vessel required to
produce 1 kg of product.

Solution

Similar calculations can be made for the reactor/mixer for processes B and C in Table 3.4, and these
results are given in Table 3.5 along with the cycle times for each process. It should be noted that even for
a preliminary design and cost estimate, other attributes of the equipment should also be considered. For
example, in order to specify fully the reactor and estimate its cost, the heating duty and the size of the
motor for the mixer impeller must be calculated. To simplify the current example, only the volumes of the
reactor are considered, but it should be understood that other relevant equipment properties must also be
considered before a final design can be completed. This procedure should be applied to all the equipment
in the process.

Table 3.5 Specific Reactor/Mixer Volumes for Processes A, B, and C

Let the single-product campaign times for the three products be t , t , and t , respectively. Applying
C
B
A
Equation (3.6), the following relationship is obtained:

(3.9)

The number of batches per campaign for each product is then given by t /t and
x cycle,x

(3.10)