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Photograph: FIGURES 1 (LEFT) AND 2. The mixer power input for a given agitation volume can have a big effect on crystal size and shape. These both are sodium perborate tetrahydrate crystals, formed in systems with relatively low mixer power (left) and high power (right)
Genek International
1. Genck, W. J., Crystallization From Solution, Sec. 2, pp 141-172, in Schweitzer, P.A., ed., ``Handbook of Separation Techniques for Chemical Engineers,'' 3rd ed., McGraw-Hill, New York, 1997.
2. Genck, W. J., Control Crystal Size Distribution from Batch Crystallizers, Chem. Processing, pp. 50-55, April 1991.
3. Mullin, J. W., ``Crystallization,'' 3rd ed., Butterworth Heinemann, 1993.
4. Oldshue, J. Y., ``Fluid Mixing Technology,'' McGraw-Hill, New York, 1983.
Wayne J. Genck, Ph.D., is President of Genck International (3677 Sauk Trail, Richton Park, IL 60471; Phone 708-748-7200), an industrial consulting firm specializing in crystallization and precipitation, including scale-up, troubleshooting and particle-size characterization. Its industrial clients include commodity- and specialty-chemical manufacturers and pharmaceutical firms. He has widely presented courses and lectures, and is the presenter of CE's seminar, Crystallization and Precipitation. He is a recipient of the Professional Achievement Citation in Engineering from Iowa State University, where he received his Ph.D. in chemical engineering, with graduate work concentrating on crystallization.
| (available online) |
| NOMENCLATURE |
| A agitation parameter |
| b exponent for nucleation |
| B subscript o nucleation rate |
| B subscript cc crystal-crystal secondary nucleation |
| B subscript ci crystal-impeller secondary nucleation |
| C solute concentration |
| C* equilibrium solute concentration |
| CSD crystal size distribution |
| D impeller diameter |
| g supersaturation power factor for growth |
| G growth rate |
| i growth rate power factor for nucleation |
| j slurry density power factor for nucleation |
| k subscript g growth rate parameter |
| k subscript 1 nucleation rate parameter |
| k subscript n nucleation rate parameter |
| l agitation rate power factor for nucleation |
| L subscript 50 median crystal size |
| M subscript T slurry density |
| N agitator rotational speed |
| N subscript P agitator power number |
| N subscript Q agitator flow number |
| N subscript Re Reynolds number |
| P agitator power |
| Q primary agitator flowrate |
| s supersaturation |
| sg specific gravity |
| V slurry volume |
| Greek Symbols |
| mu slurry viscosity |
| rho slurry density |
In all crystallizer systems, the slurry undergoes mixing, due to mixers and the system hydrodynamics. Few engineers are aware of the impact...