Size segregation is commonly observed in flows of particles with different physical and mechanical properties. It can be favorable or undesirable, depending on different industrial processes. In our case, the size segregation of ore particles in a chute flow is utilized to prepare a well-bedded feedstock for high sintering quality, and magnets are installed below the chute to enhance size segregation. Discrete element method (DEM) simulations are carried out to explore the optimal arrangement of the magnets. The system is reduced to two dimensions, and the irregular ore particles of continuous size distribution are represented by rough disks of four diameters, with their properties reasonably sampled from the sintering materials. The magnetic fields are calculated using Ansoft in advance, which excludes the influence of the ore layer itself because it is weakly magnetic only. The simulations show that the proper magnetic field can significantly enhance the segregation, and it seems that the component normal to the chute has the dominant effect on segregation but the tangential component is also critical. The simulation results are in good agreement with our experiences in the industrial systems designed with consultation to these results. We suggest that despite major simplifications, the DEM is still an effective tool for dynamic studies and the design of complex granular flows in mineral processing.

Biopolymer nanocomposites of carbon nanotubes (CNTs) which reinforced poly(hydroxybutyrate-co-valerate) (PHBV) were developed. Multiwalled carbon nanotubes were modified by an acid oxidation treatment (A-MWCNTs) to improve their dispersal in the polymer. The thermal properties, crystallization behavior, microstructure, and cross-sectional morphology of the composites were investigated. Their mechanical properties and surface contact angles were tested. The cytotoxicity of the composites to murine fibroblast L929 cells was also evaluated. The results show that A-MWCNTs are homogeneously dispersed in PHBV which demonstrate strong heterogeneous nucleation on the dynamics and kinetics of crystallization of PHBV. With the addition of A-MWCNTs, the crystallization temperature, heat of crystallization, and thermal stability of the composites increase. Consequently, the mechanical properties of the composites have been substantially improved. The composites become hydrophilic and have no obvious toxicity to the murine fibroblast L929 cells when the content of A-MWCNTs is below 1.5 wt %. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: E620-E629, 2012 Figure 7 Morphology of murine fibroblast L929 cells culturing for four days on (a) Blank group, (b) A-MWCNT/PHBV (1.5 wt %) composite. E628MA ET AL.

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