Scale-up rules for flocculation

• Published in: International journal of mineral processing Vol. 167; pp. 79 - 85
• Main Authors: Šulc, Radek, Ditl, Pavel
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10.10.2017
• Subjects: Flocculation; Flocculation kinetics; Mixing; Rushton turbine; Scale up; Scale up; Mixing; Rushton turbine; Flocculation; Flocculation kinetics
• ISSN: 0301-7516; 1879-3525
• DOI: 10.1016/j.minpro.2017.08.003

We present here a study of three baffled tanks, 0.15m, 0.20m and 0.30m in inner diameter, agitated by Rushton turbine, with reference to scaling up the flocculation kinetics. A clay slurry was used as a model wastewater. The experiments were carried out at mixing intensity 40W/m3 and clay concentration 0.58g/L. The model wastewater was flocculated with the Sokoflok 16A organic flocculent (solution 0.1wt%) in the range of dimensionless flocculent dosage DF⁎ from 0.448 to 5.241mg/g. The flocs that formed were separated by means of sedimentation. The operational conditions were designed according to following proposed scale-up rules: i) P/V=const., ii) tF⁎=N·tF=const., iii) DF⁎=const. and iv) used=const. Applying the proposed scale-up rules, the flocculation efficiency was found to be practically the same irrespective of vessel size and flocculation dosage. For the given flocculated system and process conditions, the maximum degree of turbidity removal Ze⁎max=96.1±0.6% was found for dimensionless flocculation time 1916±5% and dimensionless flocculent dosage DF⁎=3.128mg/g±8%, regardless of vessel size. The approach to scale-up proposed by Camp (1955) is discussed and criticized in the light of present-day mixing theory, and an explanation is offered of the shortcomings of this approach, and why it gives incorrect scale-up results. •Scale up of flocculation was investigated in three vessels of different size.•Scale up of complex process such as flocculation requires multidimensional approach•Camp number cannot be used for design of flocculators.