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Draft Tube Precipitators

Ground bauxite is mixed with recycled caustic soda solution (spent liquor" and fed into digesters. With proper agitation, the alumina goes into solution as sodium aluminate.

In the precipitation train, seed particles of alumina trihydrate are introduced to precipitate relatively pure alumina trihydrate crystals from the cooled, super-saturated solution. A low shear draft tube mixer maintains slurry homogeneity at minimum power while minimizing crystal degradation.

The Lightnin draft tube circulator has become the most common method of suspending alumina hydrate solids during agglomeration and precipitation in modern alumina plants. Uniform solid suspension maximizes the mass of alumina solids held in the tank. The hydraulically efficient draft tube and impeller minimizes power consumption. Scale formation is minimized to provide maximum on-line time between tank cleaning.

Our model C110 circulator impeller achieves design flow against draft tube head requirements with minimum power and wear. A true airfoil shape provides steeper head/flow curves. Steep head flow curves assure stable operation, even during process upsets, while minimizing horsepower. We design the draft tube to optimize results and the tank process, limiting maintenance and wear.

For draft tube mixing applications, Lightnin offers the broadest spectrum of impeller configurations available. Our extensive mixing experience assures we can specify the best impeller and mixer design for the process.