| 摘要 |
A continuous, counter-current freeze concentration system and method for concentrating aqueous solutions such as fruit juices, coffee and cold water soluble tea extracts, milk, beer, wine, vinegar, and the like in which the aqueous liquid is passed through one or more concentrating stages, each of which include a crystallizer associated with a gradient column, to crystallize ice in each of the stages and increase the concentration of the liquid, and the ice formed in each stage is passed in reverse direction through the stages. Ice crystals are separated and removed from the system in a wash column associated with the first stage, and concentrated liquid is removed as product from the last stage. The environment viscosity of ice crystals formed in each stage is reduced by forming the ice crystal fraction of the slurry produced in the crystallizer of each stage into a porous rising bed of agglomerated ice crystals in the gradient column associated with the crystallizer, and contacting the ice bed with a counter current flow of more dilute liquor whereby liquor occluded on the ice crystals is displaced with more dilute liquor as the ice bed rises in the column. The degree of compaction and thus the porosity of the ice bed formed in each gradient column is controlled. Ice removed from the porous ice bed is transferred to the more dilute liquor and is supplied to the crystallizer of a preceding concentrating stage or to a wash column. Liquor separated from the slurry and displaced from ice crystals in the gradient column is introduced into the gradient column of the succeeding stage and recirculated to the crystallizer of that stage. This reduction in the environment viscosity of ice crystals facilitates the removal of liquor occluded on the ice and promotes the growth of ice crystals in the system. |
