Bollman extractors

Vertical-plate extractor. Exemplified by the Bonotto extractor (Fig. 18-79), this consists of a column divided into cylindrical compartments by equispaced horizontal plates. Each plate has a radial opening staggered 180° from the openings of the plates immediately above and below it, and each is wiped by a rotating radial blade. Alternatively, the plates may be mounted on a coaxial shaft and rotated past stationary blades. The solids, fed to the top plate, thus are caused to fall to each lower plate in succession. The solids fall as a curtain into solvent which flows upward through the tower. They are discharged by a screw conveyor and compactor. Like the Bollman extractor, the Bonotto has been virtually displaced by horizontal belt or tray percolators for the extraction of oil seeds. 

Bollman extractors have largely been superseded by extractors in which the baskets are conveyed aronnd a relatively flat horizontal loop or sequence of loops. These horizontal basket conveyor extractors are usually operated as countercurrent crossflow extractors, but in soma cases mixed crossflow eountencunenl and epflow-downflow sequences are used. 

In the Bollman extractor (Fig. 10.3-10), baskets with perforated bottoms are driven around a high vertical loop a chain drive. LUpiid percolates through the solids in the baskets and drips onto the solids in the basket below. Spent solids are dumped out of the baskets by temporarily inverting them at the top of the extractor. The baskets ate then reinvetted and filled with fresh solids at the top of the leg in wliich the bask descend. Soiid-iiquid flow is concurrent in this leg and countercunent in the leg where the solids ascend. The extract (half-miscella) that collects in a sump at the bottom of the ascendiiig leg is sprayed onto the contents of the freshly filled baskets at die top the descending 1. The attract product (full-miscella) is collected at the bottom of the descending 1. ... 

In Fig. 12.8-2a an enclosed moving-bed bucket elevator device is shown. This is called the Bollman extractor. Dry flakes or solids are added at the upper right side to a perforated basket or bucket. As the buckets on the right side descend, they are leached by a dilute solution of oil in solvent called half miscella. This liquid percolates downward through the moving buckets and is collected at the bottom as the strong solution or full miscella. The buckets moving upward on the left are leached countercurrently by fresh solvent sprayed on the top bucket. The wet flakes are dumped as shown and removed continuously. 

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