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surface coating/finish and impact on paste dryer performance?

surface coating/finish and impact on paste dryer performance?

surface coating/finish and impact on paste dryer performance?

I am debottlenecking a continuous dryer which fouls at high production rates.  The dryer is 316 stainless steel

Adhesion (cohesion) of the sodium organic salt to the mill finished stainless steel is very high at the operating temperature 300 F.  It is highly agglomerating and forms crust if not mechanically disturbed.  

The dryer is built as a heated horizontal cylinder (16 in dia, 60" long, containing a 3" center shaft with a spiral of blades that intermesh with stationary hooks, to clean the heated blades (~ 3 mm clearance).  

Heat transfer surface cannot be added.  What coatings and/or surface finish will limit fouling allowing me to push the heat transfer higher?

If I only modify the cylinder interior, I imagine sliding but the hooks would result in surface renewal.  Is there a negative to not coating the hooks, shaft and blade?  Poor forced convective surface renewal? Poor bulk turnover? Increased stress on the hooks?

If I modify all surfaces, can I be too slick?

RE: surface coating/finish and impact on paste dryer performance?

Sputter-deposited molybdenum disulfide or tungsten disufide would work -- both are low friction coatings that generally resist chemicals -- but it would not be easy to coat the interior of your cylinder.  You might have to add a base hard coating.  Coating the blades would depend on whether or not they can be detached.

Jim Treglio

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