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论文类型：期刊论文

发表时间：2012-12-24

发表刊物：CHEMICAL ENGINEERING SCIENCE

收录刊物：SCIE、Scopus

卷号：84

页面范围：120-133

ISSN号：0009-2509

关键字：Crystal Layer Growth; Diffusion; Melt Crystallization; Parameter identification; Separations; Simulation

摘要：This paper was concerned with the model development and experimental validation of the detailed crystal layer growth and multi-ions impurity distribution process in the falling film melt crystallization (FFMC) model. The phosphoric acid (PA) was separated and purified by FFMC to obtain a hyperpure phosphoric acid (HPA), which was a vital electronic chemical in IT industry. To establish a valid model, which offered an easy and convenient path of the simulation, dynamic heat and mass balance, approaches were adopted to describe the variation of crystal layer growth rate along the crystallizer. An impurity balance approach was adopted to describe the change of distribution coefficient for multi-ion impurity. A criterion was proposed to determine the formation of branched-porous (B-P) structure. The model was validated by experimental results with various equipments and operational conditions and a good agreement was obtained. The effective distribution coefficient K-eff for multi-ion impurities were less than 0.2 (Na+), 0.25 (Fe3+) and 0.35 (Ca2+) with proper operation conditions. The resulting model was directly exploited to understand crystal layer growth and impurity distribution behaviors in FFMC from laboratory to industrial scale. More significantly, the model proposed a method for the separation effect evaluation and the key operational conditions (feed rate and cooling rate) determination which could readily develop optimal crystal layer growth route during industrial crystallization. In addition, the model was a vital base to describe the subsequent purification step of FFMC: sweating process. (C) 2012 Elsevier Ltd. All rights reserved.