Abstract:Combinations of discrete equipment units were often used in suspension crystallization freeze concentration process in the past, and as a result, the system was large and complicated to run. In this study, a multi-stage intelligently controlled freeze concentrator prototype was tested and validated. This prototype adopted a trinity structure, which combined a scraped surface heat exchanger (SSHE), a crystallizer and a washing column and equipped with an intelligent control unit. Based on the equipment, this study used the concentrated apple juice as an example to test the performance parameters of the freeze concentrator. The concentration ratios of the first, second and third stages of freeze concentration were 1.84, 1.40 and 1.32, respectively. The crystallization rates were 0.44, 0.36 and 0.22, respectively. The partition coefficients of solid solutes in ice crystals and mother liquor were 0.03, 0.04 and 0.11, respectively. The recovery of solid solutes were 0.99, 0.99 and 0.98, respectively. The heat transfer coefficients of SSHE at the cooling stage were 0.23±0.00 kJ·m-2·℃-1, 0.11±0.02 kJ·m-2·℃-1 and 0.22±0.02 kJ·m-2·℃-1, respectively. The heat transfer coefficients of SSHE at the freezing stage were 0.54±0.03 kJ·m-2·℃-1, 0.44±0.02 kJ·m-2·℃-1 and 0.29±0.01 kJ·m-2·℃-1, respectively. The rates of ice production were 0.90±0.05 kg/h, 0.90±0.05 kg/h and 0.30±0.06 kg/h, respectively. The results showed that the system is simple and efficient, and the operational control of complex freeze concentration can be completed by the machine.
