Experimental study of wash columns used for separating ice from ice-slurry

The separation of ice from ice slurries is the final step in the process of freeze concentration, where wash column can be employed. Phenomena found in washing an ice bed, such as channeling, viscous fingering, clogging, liquid entrainment, and permeability were studied in an experimental wash column. The appropriate operating conditions that lead to a successful washing were proposed in this paper.

The movement of the wash front tends to induce viscous fingerings during washing of the ice bed. However, gravity is a stabilizing force that keeps the wash front horizontal. Freezing and thawing may both occur in washing, which change the porosity of the ice bed. Local thawing at the wash front may lead to the breakthrough of the washing water and develop into channeling. The opposite trend is freezing at the wash front when cold water comes into contact with the subzero Draining time, td (s) 10 12 16 18 Ripening time, tr (h) Flow velocity (mm/s) (a) Draining time varying with the ripening time. 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 Interstitial velocity (v) Velocity of approach (v∞ ) Ripening time, tr (h) Permeability, K (m2 ) (b) Flow velocity varying with the ripening time. 8×10-10 6×10-10 4×10-10 2×10-10 14 16 Ripening time, tr (h) (c) Permeability of the ice bed varying with the ripening time. Fig. 3. Ripening of ice slurry affects the permeability of the ice bed.