As for the bubble column design, consider a simple hillbilly solution: a brick tied to a mesh pad or bunch of plastic grating with polytetrafluoroethylene rope; anchor the hose connecting the tank nozzle to the bottom. This cheap improvement will increase bubble residence time.
The trouble with small dikes that are easy to step over is that they won't prevent flammable vapors from exiting a slit drain and becoming a fire hazard away from watchful eyes. Sniffing could easily miss fumes. They were probably focused on the welding and not the column.
Dirk Willard, senior process engineer
Middough Consultants, Holland, Ohio
One of our board operators saw a spike in the level of a feed tank for a distillation process during a winter startup (Figure 1). She killed the fired heater feeding the tank. The fired-heater pressure relief valve blew ten minutes later. An hour after that, after the heater relief was isolated, a field operator looked at the tank pressure gauge and sight gauge. The level transmitter read 70% (compared to 65% before the incident). Later in the day when the board operator tried to de-inventory the tank, the pump cavitated. The field operator then noticed the position indicator on the pump suction valve showed it was closed; the other valves don't have position indicators. Can you explain what caused this series of problems?
Send us your comments, suggestions or solutions for this question by May 13, 2011. We'll include as many of them as possible in the June 2011 issue and all on CP.com. Send visuals — a sketch is fine. E-mail us at ProcessPuzzler@putman.net or mail to Process Puzzler, Chemical Processing, 555 W. Pierce Road, Suite 301, Itasca, IL 60143. Fax: (630) 467-1120. Please include your name, title, location and company affiliation in the response.
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