Separating different materials is important in mineral processing, recycling and many other processing applications. Froth flotation is a separation process in which heterogeneous material is ground up into small grains, so that each grain consists mostly of one constituent. The grains are then suspended in a liquid bath, and gas bubbles rising through the slurry selectively carry (or float) the particles consisting of the desired material to the top. Various chemicals are added to guarantee that only the desired particles stick to the rising bubbles. While some of the individual steps of this process are well understood, their complex interactions make it very difficult to predict the selectivity and effectiveness of the separation. This project will use numerical simulations based on mathematical models of the various process steps to reproduce the dynamics of froth floatation. The modeling allows each step of the process to be modified separately or turned on and off, assessing exactly how the various processes interact and collectively to set the selectivity for different operating conditions. This project is made possible by major advances in direct numerical simulations of multiphase flows over the last two decades, but up to now such simulations have focused on systems with relatively simple physics. The project will develop advanced multiscale strategies to correctly account for several simultaneous physical processes and to quantify the influence of the various control variables.
The primary intellectual merit of this project is the development of computational strategies to model complex multiphase, multiphysics and multiscale processes and their use to determine how selectivity in froth flotation depends on the specific configuration and operating conditions. The development is built on a hybrid finite-volume/front-tracking numerical approach, where the governing equations are solved on a fixed structured grid, but the interface between the different fluids and phases is tracked using connected marker particles that form an unstructured moving grid. In addition to accurately track moving fluid interfaces and phase boundaries, the moving interface grid allows wettability to be included in a relatively straightforward way and greatly facilitates the inclusion of multiscale models for small scale interfacial processes, such as mass transfer and draining of thin films. The broader impact of the project include developments of modeling strategies applicable to a wide range of coupled multiscale processes and the education of people in the development and applications of numerical models for complex processes.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
