Naslov
Effect of impeller off-bottom clearence on crystal growth kinetics of borax in dual-impeller batch cooling crystallizer

Autori
Kaćunić, Antonija ; Ćosić, Marija ; Rušić, Davor ; Kuzmanić, Nenad

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
CD-Rom of Abstracts / - , 2017, 1-1

Skup
13th International Conference on Chemical and Process Engineering

Mjesto i datum
Milano, Italija, 28.05.2017. - 31.05.2017

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
crystallization ; PBT dual impeller ; crystal growth kinetics

Sažetak
The aim of this work was to experimentally investigate the influence of impeller off-bottom clearance on crystal growth kinetics of disodium tetraborate decahydrate (borax) in a dual-impeller batch cooling crystallizer. Examinations were carried out in a crystallizer of 15 dm3 with liquid height to crystallizer diameter ratio (H/dT) of 1.3. In this research, two pitched blade turbines (PBT) with diameter D/dT=0.33, were mounted on the same shaft with a constant spacing between impellers (s/D=1.0). Mixing was performed at the impeller speed which ensured the state of complete suspension in the system (N=NJS). The impeller off-bottom clearance (C/D) was varied from 0.2 to 1.3. Crystallization was carried out by a controlled cooling of the solution saturated at 30°C. Concentration of the solution was measured in line by potentiometric method, while the changes of crystal size over time were determined by optical microscope and image analysis software. Experimental results indicate that impeller off-bottom clearance influences the change of crystal size over process time. But, regardless of the impeller off-bottom clearance, crystal growth is integration limited. The value of an order of crystal growth rate changes insignificantly with C/D ratio, while the crystal growth rate constant is affected by the change in hydrodynamics. Obtained results are a consequence of the hydrodynamic conditions in the dual- impeller crystallizer. In order to analyze the overall fluid flow pattern, in which an interaction of the flows generated by each of the impellers occurred, photographs of the flows were taken and simulations by VisiMix 2000 Turbulent were made. Taking into account the values of kinetic parameters of crystal growth, characteristic of obtained crystals, power consumption and the overall fluid flow pattern, it is possible to define the impact of impeller off- bottom clearance on borax crystal growth kinetics.

Izvorni jezik
Engleski

Znanstvena područja
Kemijsko inženjerstvo

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