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Semibatch reaction crystallization of benzoic acid
Author(s) -
Slund Bengt L. Å,
Rasmuson Å Ke C.
Publication year - 1992
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690380303
Subject(s) - supersaturation , nucleation , crystallization , micromixing , chemistry , benzoic acid , dilution , mixing (physics) , ostwald ripening , mother liquor , crystal growth , crystal (programming language) , chemical engineering , thermodynamics , crystallography , chromatography , analytical chemistry (journal) , organic chemistry , programming language , physics , quantum mechanics , computer science , engineering
An experimental study of a semibatch reaction crystallization is presented. Dilute hydrochloric acid is fed to a stirred solution of sodium benzoate to crystallize benzoic acid. The weight mean size of the product crystals increases with increasing stirring rate, reaches a maximum, and then decreases again. Larger crystals may be produced if the reactant feed point is positioned close to the outlet stream of the impeller. At equal power input the influence of stirrer type is negligible. Decreasing reactant concentrations or feed rate increases the crystal size significantly. Experimental results are explained qualitatively focusing on nucleation and growth conditions and on feed point mixing. The feed point micromixing brings reactants together to generate supersaturation and allow for nucleation. Continued mixing, however, may partially dilute supersaturation before nucleation takes place or may restrict nuclei growth, thus promoting more efficient Ostwald ripening in the bulk. This may result in high bulk supersaturations which in turn hampers the dilution effects.