Optimization of Comminution Circuit Throughput and Product Size Distribution by Simulation and Control

The goal of this project is to improve energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process are being used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced can be minimized. The goal is to save energy by reducing the amount of material that is ground below the target size, while simultaneously reducing the quantity of materials wasted as ''slimes'' that are too fine to be useful. This is being accomplished by mathematical modeling of the grinding circuits to determine how to correct this problem. The approaches taken included (1) Modeling of the circuit to determine process bottlenecks that restrict flow rates in one area while forcing other parts of the circuit to overgrind the material; (2) Modeling of hydrocyclones to determine the mechanisms responsible for retaining fine, high-density particles in the circuit until they are overground, and improving existing models to accurately account for this behavior; and (3) Evaluation of advanced technologies to improve comminution efficiency and produce sharper product size distributions with less overgrinding

Fracture Initiation in the Directionally Solidified NiO‐CaO Eutectic

Initiation of fracture in the directionally solidified, lamellar NiO‐CaO eutectic was examined using the indentation fracture technique. Fracture could not be induced along the interphase boundary on transverse sections of the directionally solidified eutectic. Instead, radial cracks evolved at angles of approximately 35° and 55° with respect to the lamellar interface and were consistent with median/radial crack formation on (TlO) and (001) planes, respectively. Indentation of single‐crystal NiO resulted in fracture only along {110} planes. Crack initiation on {110} planes in both materials was attributed to a dislocation coalescence model proposed by Keh et al. while crack formation on (001) planes in the eutectic was believed to be initiated by a Stroh‐type mechanism involving dislocation pile‐ups. Variations in the interlamellar spacing resulted in a Hall‐Petch‐type behavior for the hardness but had little effect on the fracture toughness of the eutectic. Copyright © 1987, Wiley Blackwell. All rights reserve