Abstract
The designs of cryoconcentrators of block type BV-2 and BL-20 have been developed. The influence of design and operating parameters on the kinetics of freezing of pomegranate juice was investigated. A decrease in the operating temperature of the refrigeration unit contributes to a more intensive growth of the ice block. When the temperature of the coolant decreases by 1.2 times, the productivity of the BV-2 unit increases by 27 %, and of the BL-20 unit by 12 %. For BL-20, an increase in the initial concentration by 3 times leads to a decrease in productivity by 2.5...1.5 times. The influence of the temperature of the coolant and the initial concentration of the juice on the rate of concentration change has been determined. At low initial concentrations of solutions (10...15 %), a sharp increase in concentration is observed at the final stage of freezing. The dry matter content of the juice is increased by 16 % at high concentrations, only 4 %. The kinetics of the ice block separation process has been studied. At the first stage (duration 10...15 minutes), the concentration of effluents is 2...3 % higher than the concentration of the solution. On the second, increases by 6...10 %. In the third stage, there is a monotonous decrease in effluent concentration (2.5 % / hour). The results of experimental modeling are generalized. The obtained equation in similarity numbers allows calculating the mass transfer coefficients with an error of no more than 20 %. The developed designs of the BL-20 and BV-2 cryoconcentrators are semi-industrial units. With block cryoconcentration, a concentration of pomegranate juice of 47° Brix was achieved, which is higher than in traditional devices. The results obtained can be applied for further development and creation of industrial plants with optimal improved product parameters.
Highlights
Concentrating fruit juices is one of the oldest methods that can significantly extend the shelf life of fresh produce.In principle, there are 3 ways to solve the problem of removing water from a solution
When the temperature of the coolant decreases by 1.2 times, the productivity of the BV-2 unit increases by 27 %, and of the BL-20 unit by 12 %
For BL-20, an increase in the initial concentration by 3 times leads to a decrease in productivity by 2.5...1.5 times
Summary
Concentrating fruit juices is one of the oldest methods that can significantly extend the shelf life of fresh produce. The advantages of reverse osmosis include: low energy costs; improving the quality of the concentrate due to the low process temperature; good sanitary conditions of production. All this is explained by the fact that membrane technology does not require energy consumption for phase transformations of water. The essence of the invention is that cooled rod crystallizers are immersed in a container with a pre-cooled product, on the surface of which blocks of ice are frozen They are removed from the container and kept in air at a positive temperature. The very holding of the block is carried out until a predetermined value of dry substances is reached in the flowing solution, which is determined by the permissible losses of dry substances in the molten block
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