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Wet comminution of calcium carbonate in a stirred bead mill

100%

Garcia F. , Le Bolay N. , Frances C.

tom Z. 27

85-94

Investigations were carried out in a batch system. The particle size distribution of calcium carbonate was determined by means of a Malvern Mastersizer S laser meter, and its change during grinding was described using a statistic log-normal law. At the final stage of the process the phenomena of secondary agglomeration were observed. Additionally, changes in specific surface were investigated by the BET method and rheological properties of the suspension containing 30% d.m. were described. The latter was found to be well described by Herschel-Bulkley's law.

Badania wykonano w układzie periodycznym. Skład granulometryczny węglanu wapnia określano za pomocą miernika laserowego (Malvern Mastersizer S), a jego zmianę w czasie mielenia opisywano z wykorzystaniem statystycznej funkcji logarytmiczno-normalnej. W końcowym etapie procesu wykazano występowanie zjawiska wtórnej aglomeracjo. Ponadto zbadano zmiany powierzchni właściwej metodą BET oraz własności reologicznych zawiesiny zawierającej 30% suchej masy. Wykazano, że te ostatnie dobrze opisuje prawo Herschel'a Bulkley'a.

Study on the rheological properties of Baker's yeast suspension

75%

Solecki M. , Heim A. , Owczarz P. , Kilbey G. , Delia M. L. , Frances C.

International Journal of Applied Mechanics and Engineering

2005

tom Vol. 10, no spec

137-142

Rheological properties of a suspension of baker's yeast Saccharomyces cerevisiae at the concentration ranging from 0.002 to 0.17g d.w./cm3 were investigated. Flow curves were determined at the temperature 4oC by means of cylindrical rotary one- and double-gap rheometers and a capillary rheometer. A significant effect of an increasing concentration of microorganisms on the growth of apparent viscosity of the suspension was reported. At lower concentrations and shear rates, significant discrepancies were often observed between properties determined by rheometers of different constructions and sizes. This follows from different properties of particular devices that are revealed especially near the limiting measuring ranges. For very small shear rates yield stresses were observed. Results of mathematical modeling and a complete analysis of results show that the yeast suspension has the properties of Newtonian liquids.