Tame a Troublesome Thermowell

Readers suggest solutions for a fluid-bed corrosion issue.

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1) a ceramic coating;
2) and, by traditional tempering, called precipitation hardening. Common ceramic coatings include titanium nitride, tungsten carbide and diamond-like carbon.)
Kevin Burke, marketing manager
Parker Hannifin Corp., Huntsville, Ala.

Our plant relies on an old batch fluid bed dryer (See Figure 1.) We can’t afford buying a new dryer, let alone its floor space. The dryer is difficult to operate because of loss of fluidization during the early part of the drying process. The baghouse employs a timer-controlled shaker that’s mechanically unreliable. When the shaker operates, the discharge valve to the blower momentarily closes. This is all that’s needed for solid to accumulate in the bowl above the screen.

Operators often beat the bowl to keep the solid fluid. They have another trick: To fluidize the solid early in the batch, they open the door of the bowl — when the discharge valve opens air is drawn into the bowl, creating a vacuum to lift the wet solid: the door closes. When it was installed, the dryer ran without so much operator attention. Since then two steam heaters have corroded and have been abandoned in-place (the air flows through them). Can you suggest some ways to avoid dryer problems and make the dryer easier to operate?

Send us your comments, suggestions or solutions for this question by September 11, 2009. We’ll include as many of them as possible in the October 2009 issue and all on ChemicalProcessing.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.

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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