Chemical Processing - November 2007 - (Page 41)

PROCESS PUZZLER < > JANUARY’S PUZZLER A hydrolysis catalyst bed is designed for removing COS, H2S and HCN at 430°F from 40,000 lb./hr. of H2 gas at 400 psig. The diameter of the packed bed is 5 ft. The maximum allowable heat-up rate for the alumina catalyst is 90°F/hour. At the extreme minimum ambient temperature, 20°F, it will take almost five hours to heat the bed safely. One idea proposed for heating the bed is to recirculate gas through a mineral oil heater and the bed until the catalyst can safely reach reaction temperature. An estimate of the heat-up time for the catalyst was made using Schumann’s curve and the method described on pp. 668–670 of Kern’s “Process Heat Transfer.” Unfortunately, an estimate of the rise in the bed by recirculating the gas indicates that it will take only 53 minutes, which is a gradient of 464°F/hour. Besides this problem, the largest practical blower that could circulate low-pressure gas would need over 1,000 hp. and could only operate up to 15,000 lb./hr. at 3 psig. Further work with the Schumann curve showed that it could take over 16 hours to achieve temperature with such a blower. After discussion, another start-up problem emerged: condensation of water on the catalyst. What can you recommend to ameliorate the condensation problem? Because a blower is not practical, what other ideas can you suggest? Send us your comments, suggestions or solutions for this question by December 10, 2007. We’ll include as many of them as possible in the January 2008 issue and all on CP.com. Send visuals — a sketch is fine. E-mail us at ProcessPuzzler@putman.net or mail to ProcessPuzzler, Chemical Processing, 555 W. Pierce Rd., Suite 301, Itasca, IL 60143. Fax: (630) 467-1120. Please include your name, title, location and company affiliation in the response. And, of course, if you have a process problem you’d like to pose to our readers, send it along and we’ll be pleased to consider it for publication. 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Table of Contents Feed for the Digital Edition of Chemical Processing - November 2007

Chemical Processing - November 2007 Contents From the Editor ChemicalProcessing.com Field Notes In Process Energy Saver Compliance Advisor PAT isn't Standing Pat Pursue the Perfect Plant Eliminate Exchanger Tubing Troubles Portable Conveyor Speeds Paint Production Process Puzzler Plant InSites Equipment & Services Product Spotlight/Classifieds Ad Index End Point

Chemical Processing - November 2007

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