Browsing by Subject "Specific gravity"
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Item Falcon Centrifugal Concentrator for Gravity Upgrading of Taconite Concentrate(University of Minnesota Duluth, 1999-10-08) Wu, ChuyingThe Falcon Centrifugal Concentrator, or Gravitational Concentrator, separates materials based on differentiation of specific gravity in the centrifugal field. The Falcon Concentrator has been successfully applied in recovering ultra-fine gold from tailings. Recent work on recovery of fine hematite in Quebec has shown limited success. This project was funded by the Permanent University Fund, Minnesota Technology Institute (MTI), and USX. The project was funded in two phases, first to study its feasibility; second to investigate its application in place of flotation process that could do away with flotation reagent. The first part of this report contains the initial operation data and analysis, and the second part was to report the tests on pre-classified material, which was parallel to the project of preclassification of flotation feed, also funded by MTI. As presented in Figure 1, Falcon Concentrator contains a rotor assembly which rotate up to 1800 rpm to create 300 G of force. The slurry fed through the tube to the bottom of the rotator where centrifugal force immediately separates solids and water. The solids are pinned to the cone wall forming a compact blanket. Because of the expanding configuration of the cone, the solids move progressively towards the large diameter and ultimately to discharge. During this upward and outward progression, the blanket of solids diminishes in thickness. Light particles are drawn into the pulp stream by the overlying layer of fastmoving water and pass out with the tailings. The heavy particles migrate underneath the layer will discharged by a pinch valve assembly at control interval. These setup allowed continues operation at through put of 30 L TPH with a C 1 0 model.Item Statistical Methods for Materials Testing(Minnesota Department of Transportation, 2009-12) Gupta, Diwakar; Peterson, AmyMn/DOT provides incentives to contractors who achieve high relative density via a pay factor applied to each unit of work. To determine the pay factor, Mn/DOT divides each day of a contractor’s work into a small number of lots. Then, core samples are taken from two locations within each lot and the relative densities of the cores are calculated by performing standardized tests in materials testing laboratories. The average of these two values is used as an estimate of the lot's relative density, which determines the pay factor. This research develops two Bayesian procedures (encapsulated in computer programs) for determining the required number of samples that should be tested based on user-specified reliability metrices. The first procedure works in an offline environment where the number of tests must be known before any samples are obtained. The second procedure works in the field where the decision to continue testing is made after knowing the result of each test. The report also provides guidelines for estimating key parameters needed to implement our protocol. A comparison of the current and proposed sampling procedures showed that the recommended procedure resulted in more accurate pay factor calculations. Specifically, in an example based on historical data, the accuracy increased from 47.0% to 70.6%, where accuracy is measured by the proportion of times that the correct pay factor is identified. In monetary terms, this amounted to a change from average over and under payment of $109.60 and $287.33 per lot, to $44.50 and $90.74 per lot, respectively.