Modeling particle-size distribution dynamics in a flocculation system

✍ Scribed by Jian-jun Zhang; Xiao-yan Li

• Publisher: American Institute of Chemical Engineers
• Year: 2003
• Tongue: English
• Weight: 353 KB
• Volume: 49
• Category: Article
• ISSN: 0001-1541
• DOI: 10.1002/aic.690490723

✦ Synopsis

Abstract

Flocculation dynamics accounting for both particle coagulation and aggregate breakage was simulated mathematically by using modified sectional modeling techniques. The methodological improvement included the use of a continuous‐size density function, instead of a characteristic size for each size section, the applications of a comprehensive curvilinear model for the coagulation kinetics, and the fractal scaling relationship for particle aggregates. Simulation results demonstrated that a flocculation system could arrive at a dynamic steady state after a period of flocculation when coagulation and breakage counterbalanced each other, resulting in a stationary size distribution with a unique peak mass concentration. Three distinct breakage distribution functions—binary, ternary, and normal distribution—did not differ considerably based on the simulation results of the steady‐state size distributions. A lower shear rate, breakage rate constant, a higher collision efficiency, and initial particle concentration would result in larger aggregates in a flocculation system. The numerical simulations compared well with the results of the jar‐test flocculation experiments using latex microspheres, suggesting the applicability of the curvilinear–fractal–breakage modeling system for the process simulation of the flocculation units used in water and wastewater treatment.