| Freezing separation technology,widely used in food,chemical,biological,pharmaceutical and other fields,is characterized by normal pressure,low temperature,low energy consumption etc.Freezing separation installation in interface-progressing process is a kind of equipment used for concentrating and separating feed liquid when the flake ice was formed on the low temperature surface.The installation is typical of simple structure,convenient treatment for ice and good adaptability for feed liquid.Aiming at the equipment,a sery of systematic analyses and experimental studies were conducted in the paper.Three technical schemes(coil type,pipe type and scraper type)were proposed in the paper,which make it possible to achieve interface-progressing freezing separation.All their working principle and basic characteristics were analyzed,and overall comparison about their cost,energy consumption,material adaptability,etc was carried out.The results display that pipe type and scraper type refrigerating separation installation have comprehensive advantages in dealing with medium-scale and large-scale feed liquid,while the coil type separation installation is more suitable for small-scale feed liquid treatment.For the characteristics of coil type refrigerating separation installation which has complex operating conditions,the paper shows the outcome of theoretical research on the performance of the installation and established physical and mathematical models.By calculated,the changes about freezing rate and thawing proportion were analyzed,which were changed by the changes of refrigerant evaporation temperature,condensing temperature,feed liquid temperature,ice thickness and other parameters.The results reveal that the suitable freezing ratio and thawing rate can be obtained by adjusting the process parameters of coil type refrigerating separation installation in freezing and thawing process.Guided by the above work,coil type refrigerating separation experimental installation was designed and built,and pre-cooling,freezing and thawing experiment was conducted respectively.The results indicate that:at the stage of pre-cooling,the liquid circulation can be used for avoiding the partial recovery of the temperature effectively during the cooling process;at the stage of freezing,average 10 min freezing rate up to 0.003 mm/s,solute removal proportion can reach 85%,When the material liquid temperature 3.3?,the water temperature of 16.7?,while with the increase of the concentration of the liquid and the decrease of the evaporating temperature,solute entrainment in the ice layer will be obtained;at the stage of thawing,the thawing ratio near coil side is much higher than ice water,and at the end of thawing,ice detached from the coil to enhance thawing process significantly. |
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