The Problem

At a Dow Chemical facility, flaked material during part of the manufacturing process was produced with excess surface moisture within the product. For further processing, most of this water would have to be removed. Dow's engineers decided to investigate whether a new surge hopper could be designed to dry the product by forcing hot, dry gas countercurrent to the flowing material, which would be much less costly than using commercially available dryers.

Process requirements dictated that the bin dry the products uniformly to less than 1000 ppm water, thus removing approximately 10% water by weight. The drying also had to be done in less than 60 minutes, to assure product stability.

Jenike & Johanson's Solution

For the dryer to be effective, two major design considerations had to be met. First, the velocity profile of the product in the dryer had to be uniform to control drying time. The way to accomplish this was to ensure a mass flow pattern well within the mass flow limits and to maintain a level of material in the cylinder section. The second major consideration was to keep the superficial gas velocity low enough to prevent the product from becoming locally fluidized.

Jenike & Johanson determined the basic dimensions of the dryer from these requirements and the material's flow properties.

The Result

According to Karl Jacob of Dow's Solids Processing Lab, "the pilot design worked as predicted, confirming uniform material flow without any product carryover while meeting moisture specifications. We saw no signs of product quality degradation. The pilot design basically confirmed Jenike & Johanson's design and again highlighted their expertise. This has assured us that a full scale production unit will be highly successful, thereby saving substantial amounts of money and time over commercially available equipment. Jenike & Johanson continues to show us they are a leader in the area of solids handling."

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