You are in charge of a process to manufacture a polymer in which acetone is used as a solvent. The last step is a drying oven in which residual acetone is removed from the polymer into an air stream. The air is fed to the absorber in Example 24.1. All flows, mole fractions, and physical property data in Example 24.1 are assumed to hold.

It is necessary to scale up polymer production as much as possible. Upstream, there is a spare reactor, dryer, and peripherals, because the plant has been operating below capacity for many years. However, the acetone scrubber was designed and installed recently for the current production capacity. Therefore, it is anticipated that the acetone scrubber will be the process bottleneck. What limit does the acetone scrubber place on scale-up? How would you debottleneck this situation?

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Example 24.1 Generate a list of causes for the observed change in absorber output. First, examine input changes, and then examine process operation changes. The knowledge of packed-bed absorber performance illustrated on the Colburn graph is a good starting point. Any or all of these parameters could be different from design conditions. Potential input problems include the following: 1. Increased Flowrate of Gas to Be Treated: A disturbance in A is a possible cause. Intuitively, if it is the gas rate, G, that has been disturbed, an increased gas rate would be the cause of an increased acetone concentration in the exit gas stream. This would result in a decrease in A. 2. Decreased Flowrate of Water: This would also result in a decrease in A. 3. The Water Does Not Enter Acetone Free: If the entering water contains acetone, intuitively, less acetone can be absorbed.