Method for the separation of toner particles based on particle density differences

A baseline life-cycle inventory (LCI) performed on toner used in the xerographic process reveals that the system is mainly a classical "cradle to grave" model, although recycle streams within the system improve the overall environmental performance. The majority of the solid process waste produced (95%) is associated with post-toner production processes, and the majority of the air emissions in the system result from energy use. Post-production processes combine for just over 85% of the total energy used in the system, with customer use accounting for 58% of the total. The LCI results also show a 29% reduction in virgin material use and a 24% reduction of solid waste production over the life-cycle when waste toner is recycled.; Full color xerographic copiers and printers produce a mixed waste stream of the four colored toners. To maintain the gains realized through the recycling of toner, a separation process must be developed. In this thesis, the use of centrifugal split-flow thin-celled (SPLITT) fractionation as a method for separating toner particles was examined. The system was designed and operated in the equilibrium mode of SPLITT fractionation, where the separation was based on particle density differences. Numerical modeling showed a significant presence of secondary flows for all channel configurations. The dependence of secondary flow on the Ekman number was quantified and three flow regimes were discovered. For NEk>0.05, secondary flows are isolated near the end walls and are relatively small in magnitude. The vortices transition to a rectangular flow pattern for 0.05>N Ek>0.009. Below NEk=0.009, secondary flows become less structured, and multiple vortices develop near the end walls. The impact of secondary flows on the separation show a degradation in the performance as the Ekman number of the system is decreased.; An experimental SPLITT fractionation device was tested as a binary separation process. With the system run in an antiparallel orientation, the recovery of the more dense fraction was very high (90-99.7%), while the recovery of the less dense fraction was much lower (60-75%). This result was predicted by the numerical model due to the orientation of the vortices in antiparallel systems. An asymmetric outlet splitter was shown to enhance the purity of the more dense fraction without overly degrading the purity of the less dense fraction. With this modification, a purity of greater than 90% was achieved for both outlet streams.