Selectivity in Froth Flotation

分离不同的材料在矿物加工、回收和许多其他加工应用中是重要的。泡沫浮选是一种分离过程，在此过程中，异质物料被磨成小颗粒，使每个颗粒主要由一种成分组成。然后将颗粒悬浮在液体浴中，通过浆液上升的气泡选择性地携带（或漂浮）由所需材料组成的颗粒到顶部。加入各种化学物质，以保证只有所需的颗粒粘在上升的气泡上。虽然这个过程的一些单独的步骤被很好地理解，但它们复杂的相互作用使得很难预测分离的选择性和有效性。该项目将使用基于各种工艺步骤的数学模型的数值模拟来再现泡沫浮选的动力学。建模允许单独修改流程的每个步骤，或者打开或关闭流程，准确地评估各种流程如何相互作用，并为不同的操作条件设置选择性。过去二十年来，多相流直接数值模拟的重大进展使该项目成为可能，但到目前为止，这种模拟主要集中在相对简单的物理系统上。该项目将制定先进的多尺度战略，以正确地考虑几个同时发生的物理过程，并量化各种控制变量的影响。本项目的主要智力优势是开发了计算策略来模拟复杂的多相、多物理场和多尺度过程，并使用它们来确定泡沫浮选的选择性如何取决于特定的配置和操作条件。该技术基于有限体积/前置跟踪的混合数值方法，其中控制方程在固定的结构化网格上求解，但不同流体和相之间的界面使用连接的标记粒子进行跟踪，形成非结构化的移动网格。除了精确跟踪移动的流体界面和相边界外，移动界面网格允许以相对直接的方式包含润湿性，并且极大地促进了小尺度界面过程的多尺度模型的包含，例如传质和薄膜的排水。该项目的更广泛影响包括适用于大范围耦合多尺度过程的建模策略的发展，以及在复杂过程的数值模型的开发和应用方面对人们的教育。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.