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Date of Publication:2020-01-01

Journal:Membrane Science and Technology

Volume:40

Issue:4

Page Number:80-86

ISSN No.:1007-8924

Key Words:"cooling crystallization; membrane crystallizer; heterogeneous nucleation; cry stalseeds"

CN No.:62-1049/TB

Abstract:Cooling crystallization is a widely used separation technology,which has the advantages of low energy consumption and environmental friendliness.At present,the spontaneous nucleation of the solution gradually cooling is difficult to control with high precision;artificial seed addition can improve the quality of the cooling crystallization product;however,it cannot be automated.This paper used the high heat exchange area and excellent heat transfer capacity of hollow fiber membrane modules to achieve rapid cooling at the membrane interface to promote nucleation,thereby completing the automatic nucleation and seed addition functions of cooling crystallization.Thiourea aqueous solution was used as the research system to study the cooling crystallization process of PTFE hollow fiber membranes.The results showed that the time to induce nucleation with membrane was 195 s,and the induction time to cooling crystallization of spontaneous nucleation without membrane participation was 280 s.In addition,at the same temperature,raw material concentration,and stirring speed,the use of the membrane to promote the nucleation of the cooling crystallization can effectively regulate the number and rate of seed production and achieve automatic transportation.Therefore,the quality of the prepared crystal product is excellent,the crystal morphology is complete,the purity is high(>99.5%),the average crystal particle size is large (>1.35 mm),and the particle size distribution is narrower.This novel cooling crystallization method provides a new approach for the optimization and design of the cooling crystallization process.

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