The Problem

Kaiser Aluminum & Chemical Corp. produces alumina trihydrate which is calcined to make alumina, or it is dried and sold as hydrate. Kaiser needed a new, dedicated handling and storage system. According to Chess Millburn, a project engineer at Kaiser, "The handling characteristics of the wet alumina trihydrate were unknown to us. Just looking at the material, you could tell it was very different than the dry product. There was a general feeling among the plant personnel that we would have major difficulties handling it."

 

Jenike & Johanson's Solution

Per flow properties testing by Jenike & Johanson’s, we found that the wet cake was cohesive enough to arch and form stable ratholes in funnel flow silos and that a third flow pattern, expanded flow, would be most suitable. Expanded flow combines mass flow and funnel flow and consists of a mass flow section at the bottom of the silo, extending up to a large enough diameter to prevent the formation of a rathole. Above this mass flow section, the silo is designed for a funnel flow pattern. A mass flow screw feeder was recommended for discharging material from the silo. This was achieved by ensuring that the capacity of the feeder was increased in the direction of flow.

Our engineers calculated pressures exerted on the silo walls by the stored bulk solid. We analyzed two different conditions: loads applied after the initial filling of the silo, prior to any material discharge, and loads after material had started to discharge (flow loads).

 

The Result

Kaiser installed the recommended silo and loadout bin and they have been reliably handling the wet alumina trihydrate since startup. According to Mr. Millburn, "We had our doubts that the wet material could be handled at all. Fortunately, the engineers at Jenike & Johanson took the guesswork out of it for us, and provided a solution that exceeded our expectations."

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