Measurement of bubble size distribution in fermentors
SummaryThe “photoelectric probe method” for measuring bubble size distributions was adapted for application in turbid liquids. It can now be used for investigations of the influence of hydrodynamics and liquid phase properties on bubble formation, dispersion, and coalescence in submersed fermentation systems. With cultures of Candida utilis, cell concentrations showed little effect on bubble size and gas-liquid interface.
Blasengrößenverteilung in technischen Begasungsapparaten
Zur Berechnung der Austauschprozesse in Gas/Flussigkeits-Gemischen ist die Kenntnis der Phasengrenzflache erforderlich, die sich uber die Blasengrosenverteilung bestimmen last. Es wurde daher ein Mesverfahren zur Bestimmung der Blasengrosenverteilung eines beliebig erzeugten Gas/Flussigkeits-Gemisches entwickelt. Die Blasen werden uber einen Trichter in eine Kapillare geleitet und dort mit Hilfe einer photoelektrischen Sonde ausgemessen. Die Verteilungskurven wurden fur verschiedene technische Begasungsapparate ermittelt und uber diese Kurven auch der Einflus mehrerer Versuchsgrosen wie Gaszerteiler, Apparatetyp usw., wobei zur Beurteilung Mittelwert und Breite der Verteilung herangezogen wurden.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.