Hoppers percolation

The extraction principles employed by most percolation extractors are the same, but the method by which each achieves countercurrent flow of solvent to flakes is different. The shallow-bed, chain extractor (Fig. 11.12), which resenibles a full-loop conveyor, is one of today s widely used extractors. Crown Iron Works (Minneapolis, MN) manufactures this type of extractor. In early versions that still exist in the industry, flakes are fed into an inlet hopper and are conveyed down the first leg of the loop where they are washed with moderately dilute miscella to extract surface oil and penetrate the cells. As the flake bed moves into the bottom horizontal section, full miscella is recycled through the bed for filtering, and then to a liquid cyclone for final... 

If effective, this technique would provide a very neat solution to the problem of mixing powders for many processes and would be particularly attractive if very large volumes of material were to be mixed. It presupposes that all the material is in motion and that there is no hold-up of material within the cycle. Segregation is likely to be a problem both on the free surface of the hopper and within the bulk of the material due, in both cases, to percolating segregation. 

Early extractor designs based on solvent percolation were basket-type extractors in which flaked seeds were placed in baskets with perforated bottoms. These systems looked like an enclosed bucket elevator. The baskets were supported by endless chains in a sealed housing and continuously raised and lowered at a slow rate (1 revolution/h). Each basket was filled with flaked seeds by an automatic feed hopper at the top. As the basket started descending solvent is sprayed over the baskets. The spent flakes in baskets ascended to the top of the housing on the opposite side of the feed hopper. At the top baskets were automatically inverted and spent seeds were discharged into a hopper, from which they were transferred to a meal desolventizer on a conveyor belt. Basket type extractors were bulky and hard to maintain. The newer extractor designs are horizontal and rotary type. The design principle for horizontal extractors is similar to the basket-type extractors but the baskets rotate in a... 

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