For Example 21.12, suggest realistic ways to compensate for the disturbance. An example of a nonrealistic compensation method is to reduce the air feed (process side), which is probably fixed upstream. It is also assumed that, if the feed composition is not the fault, it cannot be changed from design conditions. Usually, manipulations of the process or process variables are less desirable/possible than changes to utility flows or conditions. Again, assume that only one parameter at a time is manipulated.

Example 21.12

An absorber is designed to be 20 m tall, and it is known that H_oV is 4 m. The absorber is designed to treat 40 kmol/h of air containing acetone with a mole fraction of 0.002 and reduce the mole fraction to 0.0001. Pure water is the solvent, at a rate of 20 kmol/h. The column temperature is 26.7°C, and the pressure is 1.2 atm.

Raoult’s law may be assumed to apply, and

It is now observed that the outlet mole fraction of acetone in the air is 0.0002. List as many possible causes of this situation as you can, assuming that only one fault exists at a time. Quantify what is happening in the column for each case, that is, what parameter is off and what is the off-specification value?

Transcribed Image Text:

In P* (atm) 3598.4 T(K) +10.92 (E21.12a)