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The kinetics of ’salting-out’ of neutral sodium sulfate from sulfuric acid solution

University of British Columbia

The equilibrium phase diagram for the system sodium sulfate-methanol/water-sulfuric acid at 35° was determined. The nucleation, and growth characteristics of sodium sulfate have been studied in a laboratory scale crystallizer (Mixed Suspension Mixed Product Removal 'MSMPR') under carefully controlled conditions of supersaturation, temperature, agitation rate and residence time. From a statistical analysis of the data it was found that supersaturation, temperature, the interactions of supersaturation with temperature and agitation rate with temperature had positive effects on growth and nucleation rates, while agitation rate, residence time, the interactions of agitation rate with supersaturation, residence time with supersaturation had negative effects on growth and nucleation rates. The 'order' of the nucleation process, b, defined by B = K[sub= N]S[sup= B] was about 5. The growth rate, defined by G = K[sub= G]S[sup= c] Was first order (C = 1). For both processes the activation energy varied from 12 to 15 kcal/mol. The growth process was considered to be surface integration controlled for the various conditions tested. The nucleation rate was considered essentially to be homogeneous nucleation. A non-linear mathematical relationship was developed for both growth rate and nucleation rate in terms of the three factors, temperature, supersaturation and residence time. In both the growth and nucleation rate models the measured data fit poorly. This indicates that the model (a reaction rate type) poorly represents the data for crystallization found in this study.

Text

2010-03-22

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http://hdl.handle.net/2429/22258

Chemical and Biological Engineering

University of British Columbia

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