As the feed contained seventy percent by mole water, the bottoms flow was specified to be seventy percent of the feed. Once the bottoms to feed ratio and the reflux ratio were specified sensitivity runs could be performed to determine the best location for the feed and side streams. It was determined that the column would have more difficulties with flooding if the feed stream entered near the bottom of the column. From these results the feed was located at stage forty-three. The desired location of the pure stream was known to be very high in the column.
Ethylene oxide is more volatile than acetaldehyde and water but less volatile than formaldehyde.
Most of the formaldehyde goes out the top in the distillate stream, creating a relatively pure stream with minor amounts of formaldehyde. The results of the sensitivity run for the location of the high-purity stream indicate that the purity of this stream increases with increasing height in the column. Knowing the relative volatilities of the components, this side stream would be most effective at acetaldehyde removal at a lower stage. The purity of the product streams steadily increased until it reached a maximum at stage forty. At this point the purity decreased as the side stream location neared the feed location at which point a marked decline occurred.