Microwave-assisted grinding
The use of rapid microwave heating to stress-fracture ore samples is discussed. Iron ores containing hematite, magnetite, and goethite were subjected to microwave energy in batch operations at 3 kW and heated to average maximum temperatures between 840 degrees C and 940 degrees C. Scanning electron microscope (SEM) photomicrographs verified fracturing along grain boundaries and throughout the gangue matrix. Standard Bond grindability tests showed that microwave heating reduced the work index of iron ores by 10 to 24%. Using a continuous-feed belt in a microwave applicator, samples heated more uniformly and quickly than in batch operations. In a microwave chamber designed to simulate a continuous-throughput operation at 3 kW, the grindability of a taconite ore was improved by 13% at a bulk temperature of 197 degrees C. Because stress cracking occurred at a lower temperature, less energy was consumed, thereby improving cost effectiveness. To further improve the economics, preliminary tests were conducted to increase heating rates by using higher microwave powers. The beneficial effects in the grinding circuit and in the extractive operation are discussed.<<ETX>>
The Effects of Power Level on the Microwave Heating of Selected Chemicals and Minerals
The effect of power level on the microwave heating characteristics of a variety of reagent-grade chemicals and minerals has been determined in a Bureau of Mines study. Heating rates of the powdered samples are presented for incident power ranging from 500 to 2,000 W at 2.45 GHz. The apparatus consisted of a WR 975 waveguide-applicator mounted to WR 284 waveguide sections and connected to a 3-kW power source. Tests were conducted in an alumina crucible enclosed in a fused-quartz beaker that was fitted with a Teflon lid to allow for a controlled inert atmosphere and thermocouple insertion. In general, heating rates increased as input power increased. Exceptions to this were some very high-lossy (microwave receptive) and very low-lossy materials that showed negligible changes with increased power. Microwave data collected should provide insight as to possible chemical and mineral processing applications as well as to assist in predictions of processing parameters.
Complex Systems Architecture Framework: Extension to Multi-objective Optimization
This paper shows the utility to follow an architecture framework in order to design complex systems with a holistic approach. Multi-objective Optimization techniques extend and complete the architecture framework to support trade-off analysis and decision making in the Systems Engineering design process. The merging and combination of these two approaches, decision making and systems engineering, contribute to the efficient design of systems by helping to meet needs and constraints stemming mainly from the system analysis.