Page 107 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

for the distillation is when the solution remaining in the still contains less than 1 mol% of reactant B. This
ensures that the crystallized API, produced in Step 5, meets specification.

Step 5: The material remaining in the still is pumped to a crystallizer, CR-301, where the mixture is
cooled under vacuum and approximately 60% of the API from Step 2 crystallizes out (time taken = 2.0 h).

Step 6: The API is filtered from the crystallizer and placed in a tray dryer, TD-301, where any entrapped
solvent is removed (time taken = 4 h).

Step 7: The dried API is sealed and packaged in a packing machine, PK-301, and sent to a warehouse for
shipment to the customer (time taken = 1.0 h).

Perform a preliminary design on the required equipment items for this batch process.

Solution

The equipment items will be designed in sequence.

Step 1: Reaction Vessel—Preheat

The reaction vessel, which is used to preheat the reactants and subsequently run the reaction, is designed
first. For the batch size specified, the volume of the liquid in the tank, V, and the volume required for the
reaction vessel, V tank , are given by Equations (E3.1a) and (E3.1b), in which it is assumed that the vessel
is approximately 60% full during operation.

(E3.1a)

(E3.1b)

Because reactors of this sort come in standard sizes, a 3000-gallon (V tank ) reactor is selected.

The heat-transfer characteristics of this vessel are then checked. For a jacketed vessel, the unsteady-state
design equation is

(E3.1c)