Extraction processes Karr column

The above process is repeated ten times, the broths obtained are combined, the pH is adjusted to 6, the combined broths are filtered, and the resulting filtrate is extracted countercurrently at the rate of 128 gallons per hour with about the same rate of butanol, in a 12" diameter by 11 ft. high Karr extraction column. A water backwash of 0.2 times the butanol rate is employed at the top of the extraction column to minimize the carry-over of water soluble components. The butanol extract is concentrated to approximately a 5% solution which comprises the feed to the center of a 3" diameter by 20 ft. high Karr fractional liquid extraction column. This column is operated at a water to butanol ratio of about 10 to 1, and the butanol extract contains the product. The butanol extract is concentrated by evaporation to a solution or paste containing about 5 to about 20% ent solids then about 25 to about 50 volumes of n-hexane are added, and the resulting slurry filtered. The precipitated product is then vacuum-dried to give a solid compound. 

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