Freeze concentration system and method

A method for reducing the environment viscosity of ice crystals in an aqueous liquid slurry formed in a freeze concentration process which comprises

• forming a slurry of ice crystals in a first aqueous liquid into a porous rising bed of agglomerated ice crystals in which the ice crystals are occluded with said first liquid,
• contacting the porous ice crystal bed with a counter current flow of a second aqueous liquid which is more dilute and less viscous that said first liquid,
• controlling the porosity of the ice crystal bed so that said second liquid flows throughout the ice crystal bed to displace the first liquid occluded on the ice crystals in the lower portion of the ice crystal bed,
• removing ice occluded with said second liquid from the porous ice crystal bed, and
• transferring the ice removed from the ice crystal bed to said second liquid to form a slurry which is carried away from the ice crystal bed.

A continuous freeze concentration system for concentrating an aqueous feed liquid which comprises

• at least one concentrating stage which includes
• (a) crystallizer means for treating a first aqueous liquid-containing stream to crystallize ice from said liquid and form a slurry of ice crystals in said liquid,
• (b) gradient column means operatively connected with said crystallizer means for reducing the environment viscosity of ice crystals in the slurry introduced into the gradient column means from the crystallizer means, said gradient column means including means for separating ice crystals from the first aqueous liquid in said slurry, means for forming the ice crystals into a porous, rising bed of agglomerated ice crystals having a controlled porosity, means for introducing a more dilute aqueous liquid into the gradient column counter current to the rising porous ice bed whereby the first liquid occluded on the ice is displaced with said more dilute aqueous liquid, and means for transferring ice from the ice bed to said more dilute aqueous liquid to form a slurry thereof, and
• (c) recycle means operatively connected with said gradient column means and said crystallizer means for supplying liquid separated from ice in the gradient column means to said crystallizer means, and
• wash column means operably coupled with said gradient column means for receiving the slurry of ice in said more dilute aqueous liquid from said gradient column, said wash column means including means for introducing wash water therein and being adapted to wash and separate ice from said more dilute aqueous liquid.

A continuous counter current freeze concentration method for concentrating an aqueous liquid, which comprises

• introducing a stream of an aqueous feed liquor counter current to a porous bed of agglomerated ice crystals occluded with concentrated liquor whereby the concentrated liquor occluded on the ice crystals is displaced by feed liquor and the ice crystals grow in size,
• cooling the liquor displaced from the ice crystals in said bed to crystallize ice therefrom and form a viscous slurry of ice crystals in concentrated liquor,
• circulating the viscous slurry of ice crystals in concentrated liquor to said porous bed of ice crystals,
• separating the concentrated liquor fraction of the viscous slurry from the ice fraction,
• forming the ice fraction of said viscous slurry into a porous bed of agglomerated ice crystals occluded with concentrated liquor for contact with said feed liquor,
• controlling the porosity of the ice crystal bed,
• removing the enlarged ice crystals occluded with feed concentration liquor from the ice bed and transferring said ice crystals to feed concentration liquor to form a slurry thereof, and
• introducing the slurry of enlarged ice crystals in feed liquor into a wash column in which the ice fraction of the slurry is separated from the feed liquor and feed concentration liquor occluded on the ice crystals is displaced by wash water.

A continuous multistage freeze concentration method for concentrating an aqueous liquid, which comprises

• introducing a stream of aqueous feed liquor into a first concentrating stage counter current to a porous bed of agglomerated ice crystals occluded with liquor of intermediate concentration whereby the intermediate concentration liquor occluded on the ice crystals is displaced by feed concentration liquor and the ice crystals grow in size,
• removing intermediate concentration liquor from said first concentrating stage,
• removing enlarged ice crystals occluded with feed concentration liquor from the ice bed in the first concentrating stage and transferring the ice crystals to feed concentration liquor to form a slurry thereof,
• passing the slurry of ice crystals in feed concentration liquor to a wash column for separation of the feed concentration liquor from the enlarged ice crystals,
• introducing intermediate concentration liquor removed from said first concentrating stage into a second concentrating stage counter current to a porous bed of agglomerated ice crystals occluded with concentrated liquor whereby the concentrated liquor occluded on the ice crystals is displaced by intermediate concentration liquor,
• removing ice crystals occluded with intermediate concentration liquor from the second concentration stage ice bed and transferring the ice crystals to intermediate concentration liquor to form a slurry thereof,
• cooling the slurry of ice crystals in intermediate concentration liquor to crystallize ice from said liquor and form a thickened slurry of ice crystals in intermediate concentration liquor in which the ice crystals are occluded with said intermediate concentration liquor,
• circulating the thickened slurry to the porous ice bed in the first concentrating stage,
• separating the ice crystal fraction of said thickened slurry from the intermediate concentration liquor fraction thereof with the separated intermediate concentration liquor fraction of the thickened slurry being combined with the intermediate concentration liquor displaced from the bed of ice crystals in said first concentrating state, to form a combined stream of intermediate concentration liquor which is discharged from said first concentrating stage
• forming the ice crystal fraction of said thickened slurry into a porous bed of agglomerated ice crystals occluded with intermediate concentration liquor in the first concentration stage,
• controlling the porosity of said ice crystal bed,
• cooling the concentrated liquor discharged from the second concentrating stage to crystallize ice from the liquor and form a viscous slurry of ice crystals in concentrated liquor,
• circulating the viscous slurry to the porous ice bed in the second concentration stage,
• removing a portion of the concentrated liquor from said viscous slurry prior to introducing the viscous slurry into the second concentrating stage,
• separating the ice crystal fraction of said viscous slurry from the concentrated liquor fraction thereof with the separated concentrated liquor fraction of the viscous slurry being combined with the concentrated liquor displaced from the ice bed in said second concentrating stage, to form a combined stream of concentrated liquor which is discharged from the second concentrating stages,
• forming the ice crystal fraction of said viscous slurry into a porous bed of ice crystals occluded with concentrated liquor in the second concentration stage, and
• controlling the porosity of the ice crystal bed in the second concentration stage.