Dear Norman – I enjoyed working with you last month. A follow-up question. How come our crude tower floods with such a tiny increase in delta P?
--Sam , Washington
Sam – Fe(HS)2 deposits accumulate on the upper few trays of the crude tower, between the jet draw and the second to top tray. If fouling causes flooding starting at the top few trays, jet will entrain overhead. However, flooding progresses up a tower and not down. Thus, in your 40 tray tower, only the few trays flood, but delta P remains low. I recall explaining all this to you before, but I guess you were distracted by a text message from your girlfriend. Incidentally, iron sulfide deposits are insoluble in water and hence cannot be water off on-stream.
--Norm
P.S. You’re running your tower top temperature 20°F too cold.
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