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针对冷冻浓缩过程冰晶夹带造成该技术推广使用受限制的问题,采用国内外描述相变微观结构的相场模型,将体系视为水和溶质二元系统,建立冷冻浓缩过程冰晶生长的数学模型,耦合溶质场,从微观上模拟冰晶形貌演变,分析冰晶夹带溶质浓度分布规律.探讨模拟结晶时间、过冷度及模拟初始温度对冰晶夹带浓度分布的影响.结果表明:模拟结果与实验相符合.随着模拟结晶时间的延长,冰晶固液界面的溶质浓度增大,造成溶质夹带增加;过冷度小,溶质扩散率大,冰晶中溶质浓度小,过冷度越大,溶质向液相中扩散越不充分,冰晶中溶质浓度越大;模拟初始温度高,冰晶浓度分布小,模拟初始温度低时,其溶质浓度增大.适当控制这3种因素将减少冰晶的夹带率,降低冷冻浓缩过程的可溶性固形物损失.
In order to solve the problem that the technology of ice crystal entrainment is restricted because of the entrainment of ice crystals in the process of freezing and concentration, a phase model of phase-change microstructure at home and abroad is adopted. The system is regarded as binary system of water and solute, Coupled solute field was used to simulate the morphological evolution of ice crystals from the microscopic point of view, and the distribution of solute concentration in the ice crystals was analyzed. The effects of simulated crystallization time, subcooling degree and initial temperature on the entrainment concentration of ice crystals were investigated. With the increase of the simulated crystallization time, the concentration of solute in the ice crystal solid-liquid interface increases, resulting in the increase of solute entrainment. The degree of undercooling is small, the solute diffusion rate is large, the solute concentration in ice crystal is small, the degree of undercooling is larger, The less the diffusion, the greater the concentration of solute in the ice; the higher the initial temperature of the simulation, the smaller the distribution of the ice crystals, and the lower the initial temperature of the solute, the higher the concentration of solute.When proper control of these three factors will reduce the entrainment rate of ice crystals and reduce freezing Concentration process of soluble solids loss.