Process Puzzler: Fix a Fluid Flow Flaw

Readers suggest solutions for dryer difficulties.

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Is the dehumidifier still performing to specs? The chilled water lines could be partially plugged and not providing the humidity removal. Is it possible to obtain a humidity probe that could be inserted into the process air stream to monitor the dewpoint or relative humidity percentage? If it works better in the winter than in the summer, this may be a clue.

The filter shaker mechanism undergoes violent forces by design. By nature, it can be a maintenance headache. Is a rebuild in order?

Is the air stream flow monitored? Are there differential pressure (dP) transmitters measuring across the HEPA filter, the product bowl and the exhaust filter? Are any of these dPs showing unusual behavior that would indicate a loss of air flow during normal (non-filter-shake) conditions? If there is an air flow transmitter, is it acting erratically? Installation of an ammeter on the blower is a cheap and consistent way of monitoring air flow across the dryer since most blower curves are almost linear for motor load versus airflow.

Opening the dryer bowl gate to fluidize the bed makes me wonder if the pressure drop of the abandoned steam coils is compromising the available blower static pressure. Is there a payback to increasing production by eliminating the pressure drop of the abandoned coils? Can this dP be measured?
Steve Duckro, associate director process engineering
Eurand, Inc., Vandalia, Ohio

One of our welders got hurt cutting into a carbon steel header for a chilled brine line to install another chiller in the closed-loop system. He purged the piping but not the room. An invisible gas ignited from his torch. Our plant environment contains chlorine and other corrosives. What was source of the gas? How can we prevent future accidents and what do we need to change in the system to avoid such safety problems?

Send us your comments, suggestions or solutions for this question by November 6, 2009. We’ll include as many of them as possible in the December 2009 issue and all on Send visuals — a sketch is fine. E-mail us at 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.

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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