Debutanizer feed drum

One of my friends, Steve, made such an error in designing a debutanizer. He failed to account for the methane and ethane in the existing debutanizer feed stream. The sample from the 25-psig feed vessel was taken in a bottle. The lighter components weathered off prior to lab analysis. The results were, for Steve, rather catastrophic. The debutanizer overhead product could not be fully condensed. The non-condensable vapor pressured up the overhead reflux drum. The non-condensables were vented, along with 30 percent of the butane, to the flare. Steve was... 

Alkylation generates relatively low volumes of wastewater, primarily from water washing of the liquid reactor products. Wastewater is also generated from steam strippers, depropanizers, and debutanizers, and can be contaminated with oil and other impurities. Liquid process waters (hydrocarbons and acid) originate from minor undesirable side reactions and from feed contaminants, and usually exit as a bottoms stream from the acid regeneration column. The bottoms stream is an acid-water mixture that is sent to the neutralizing drum. The acid in this liquid eventually ends up as insoluble calcium fluoride. 

A debutanizer column is considered as a typical case. A mixture of 50 mol% -butane ( C4) and 50mol% -pentane ( C5) is separated in a column with 61 stages. The feed flow rate is lOOkmol/h and the feed is introduced on Stage 23 (using the Aspen notation that the condenser is Stage 1). The design specifications are 1 mol% C5 impurity in the distillate and 1 mol% nCA impurity in the bottoms. The reflux-drum pressure is set at... 

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