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Mixing of suspensions with pitched six blade turbines

Ceres D., Moravec J., Jirout T., Rieger F.

Inżynieria i Aparatura Chemiczna

2010

Nr 1

25-26

Two pitched six-blade turbines of different diameters were used in measurements of just suspension impeller speed in fine and standard suspensions. Dependences of the modified Froude number on particle size and their concentration were determined from the measurements in standard suspensions and the impeller speed for fine clay suspensions were calculated. The obta-ined values were compared with experimental results taken from measurements in fine suspensions.

Dwa mieszadła turbinowe z pochylonymi łopatkami zastosowano w pomiarach szybkości mieszania niezbędnej dla wytworzenia zawiesin drobnoziarnistych i standardowych. Zależności zmodyfikowanej liczby Fronda od wielkości cząstek i ich stężenia określono na podstawie badań przeprowadzonych w zawiesinach standardowych. Z zależności tej wyznaczono prędkość obrotów niezbędną dla wytworzenia zawiesiny drobnoziarnistej. Wartości obliczone porównano z wynikami doświadczalnymi otrzymanymi dla zawiesin drobnoziarnistych.

Mixing of fine suspensions - effect of particle concentration

Moravec J., Ceres D., Rieger F.

Inżynieria i Aparatura Chemiczna

2010

Nr 3

77-78

The effect of particle concentration on impeller speed necessary for fine suspension mixing is presented in the paper. A single down pumping pitched six-blade impeller with the vessel to impeller diameter ratio Did = 3 was used for mixing of chalk suspension. Measurements were carried out in cylindrical baffled vessels with diameters of 200 and 300 mm. The mean volumetric diameter of particles was 4.6 μm and the mean volumetric concentration changed in the range from 2.5% to 40%.

W pracy przedstawiono wpływ stężenia cząstek na częstość obrotów mieszadła niezbędną dla wytworzenia drobnoziarnistej zawiesiny całkowitej. Pompujące ku dołowi pojedyncze mieszadło z sześcioma pochylonymi łopatkami o stosunku średnicy zbiornika do średnicy mieszadła Did = 3 użyto do mieszania zawiesiny kredy. Pomiary przeprowadzono w zbiorniku cylindrycznym (średnica 200 i 300 mm) z przegrodami. Średnia średnica objętościowa cząstek wynosiła 4,6 μm, a ich stężenie zmieniano w granicach od 2,5 do40%obj.

Mixing system for highly concentrated fine-grained suspensions

Moravec J., Jirout T., Rieger F., Krátký L.

Polish Journal of Chemical Technology

2009

Vol. 11, nr 4

52-56

The mixing equipment for highly concentrated fine-grained suspensions must be designed differently from the equipment in which a suspension with a low concentration of the solid phase or bigger particles is mixed. It is due to the different rheological properties of the suspensions. In this work we are trying to find a suitable mixing system for a highly concentrated fine-grained suspension. The aim was to determine an effect of particular geometrical parameters of the tested mixing systems on a suspension process, especially from the energetic viewpoint. The energetic costs of all the used mixing systems were compared on the basis of the power consumption which was necessary for reaching the state of sufficient suspension movement in the whole mixed bulk. As a result, it was confirmed that multistage impellers can be used even in standard vessels (with a liquid level height equal to a vessel diameter) with a profit. During experiments, the state of sufficient movement was determined by a visual observation of the suspension at the vessel bottom, at the wall and also at the suspension level.