Freeze crystallization for the removal of water from a solution of

Abstract

A freeze crystallization concentration system is disclosed for separating a liquid feed stream into a more purified liquid and a concentrate in which only a single pass through a freeze-crystallizer and ice separator is required. The crystallizer, which converts the initial feed stream into a slurry of ice and concentrate, includes a scraped surface heat exchanger that produces, pumps and removes an ice slurry and uses a secondary cooling system to ensure that the crystallizer will operate in any required position and is not sensitive to motion. The separator includes a rotating drum which separates the ice crystals from the surrounding concentrate by the use of centrifugal force and without the use of screens or filters. An auger, rotating at a different speed than the drum, may be located at the center of the drum for removing the ice crystals. A second drum, attached to the first drum, removes the concentrate with a stationary pivot tube under pressure created by the centrifugal force, without the concentrate being exposed to air. The ice crystals can then be conducted to the wash column to be separated from the remaining concentrate, grown and melted into pure water. The concentrate exiting the separator can be either removed from the system or a small amount can be diverted back to the crystallizer to be mixed with the feed stream from the wash column if a higher concentration is required.