Allgemeing�ltige Aussage zur Mindest-R�hrerdrehzahl beim Suspendieren

Chemie Ingenieur Technik (Impact Factor: 0.66). 01/1985; 57(8):692-693. DOI: 10.1002/cite.330570811
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    ABSTRACT: Widely accepted correlations and theoretical predictions for hydraulic conveying of solids in pipelines are compared with the literature on the suspension of particles in stirred tanks. Good agreement is found between the correlations and the theoretical predictions both within and between the two fields of study. The effect on the suspension velocity of introducing gas into the pipe and the stirred tank is remarkably similar. In both cases, the shear stress remains broadly unchanged when gas is added. Since the effect of the addition of gas on shear stress is quite well understood in both cases, this is a helpful result.Des corrélations et des prédictions théoriques largement acceptées pour le convoyage hydraulique de solides dans des conduites sont comparées à des données de la littérature scientifique sur la suspension des particules dans des réservoirs agités. Un bon accord est trouvé entre les corrélations et les prédictions théoriques dans et entre les deux champs d'étude. L'effet sur la vitesse de suspension de l'introduction de gaz dans la conduite et le réservoir agité est remarquablement similaire. Dans les deux cas, la contrainte de cisaillement reste largement inchangé lorsqu'il y a ajout de gaz. Ce résultat est utile car l'effet de l'ajout de gaz sur la contrainte de cisaillement est assez bien compris dans les deux cas.
    The Canadian Journal of Chemical Engineering 06/2008; 81(3‐4):351 - 359. DOI:10.1002/cjce.5450810303 · 1.31 Impact Factor
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    ABSTRACT: Suspension of solids in stirred tanks – Comparison of different calculations. The suspension of solids in stirred tanks has been the subject of various investigations over the last three decades. Though many equations for the calculation of the critical impeller suspension speed were derived and published during this period of time no conclusive descriptions have been achieved. As a consequence, serious problems arose concerning the scaling-up of the mixer, since the various equations led to completely different designs. Over the last few years new physical models have been developed to improve on this point. These models aimed to reach a better description by considering the fluid-dynamic process more accurately. This survey presents the actual state of investigation by systematically comparing the results of the latest models. Careful consideration of the experimental conditions gave fairly consistent results. The decisive problem of the scale-up procedure, however, remains unsolved.
    Chemie Ingenieur Technik 11/1988; 60(11):822-829. DOI:10.1002/cite.330601104 · 0.66 Impact Factor
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    ABSTRACT: By means of considerations, experimental results as well as high-speed photographs it is shown that in flotation machines the zone of high local energy dissipation, i.e. the impeller stream, is the active region for the realization of the microprocesses bubble dispersion and particle-bubble attachment. Because of the pressure differences as well as the turbulent pressure fluctuations existing there, it is not unlikely that gas precipitation influences the attachment events substantially. Outside of the impeller stream, the local energy dissipation is so far reduced below the mean dissipation ϵ = Pm that the preconditions for realizing these microprocesses, which are controlled by turbulence, are no more met. However, these phenomena call for further explanation. It seems to be very likely that the widespread and too simplistic ideas on the course of the particle-bubble attachment need substantial adjustments and/or completions. Moreover, the consequences which result from these findings for the hydrodynamic scale-up are discussed.
    International Journal of Mineral Processing 02/1998; 52(4):245-259. DOI:10.1016/S0301-7516(97)00070-7 · 1.46 Impact Factor