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很重要。泡沫浮选是一种分离过程，其中异质材料被研磨成小颗粒，使得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，并且通过浆料上升的气泡选择性地将由所需材料组成的颗粒携带（或漂浮）到顶部。添加各种化学物质以确保只有所需的颗粒粘附在上升的气泡上。虽然该过程的一些单独步骤已被很好地理解，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个工艺步骤的数学模型的数值模拟来再现泡沫浮选的动态。 建模允许单独修改或打开和关闭过程的每个步骤，准确评估各种过程如何相互作用，并共同设置不同操作条件的选择性。这个项目是可能的多相流的直接数值模拟在过去的二十年中取得的重大进展，但到目前为止，这种模拟集中在相对简单的物理系统。该项目将开发先进的多尺度策略，以正确地解释几个同时发生的物理过程，并量化各种控制变量的影响。 该项目的主要智力价值是开发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。该开发建立在混合有限体积/前沿跟踪数值方法的基础上，其中控制方程在固定的结构化网格上求解，但是使用形成非结构化移动网格的连接标记颗粒来跟踪不同流体和相之间的界面。除了精确地跟踪移动的流体界面和相边界，移动界面网格允许润湿性以相对简单的方式被包括在内，并且极大地促进了小尺度界面过程的多尺度模型的包括，例如薄膜的传质和排水。该项目的更广泛的影响包括适用于广泛的耦合多尺度过程的建模策略的发展和复杂过程的数值模型的开发和应用的人员的教育。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.