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Reconciling Change in Oi-Horizon 14C With Mass Loss for an Oak Forest

Description: First-year litter decomposition was estimated for an upland-oak forest ecosystem using enrichment or dilution of the {sup 14}C-signature of the Oi-horizon. These isotopically-based mass-loss estimates were contrasted with measured mass-loss rates from past litterbag studies. Mass-loss derived from changes in the {sup 14}C-signature of the Oi-horizon suggested mean mass loss over 9 months of 45% which was higher than the corresponding 9-month rate extrapolated from litterbag studies ({approx}35%). Greater mass loss was expected from the isotopic approach because litterbags are known to limit mass loss processes driven by soil macrofauna (e.g., fragmentation and comminution). Although the {sup 14}C-isotope approach offers the advantage of being a non-invasive method, it exhibited high variability that undermined its utility as an alternative to routine litterbag mass loss methods. However, the {sup 14}C approach measures the residence time of C in the leaf litter, rather than the time it takes for leaves to disappear; hence radiocarbon measures are subject to C immobilization and recycling in the microbial pool, and do not necessarily reflect results from litterbag mass loss. The commonly applied two-compartment isotopic mixing model was appropriate for estimating decomposition from isotopic enrichment of near-background soils, but it produced divergent results for isotopic dilution of a multi-layered system with litter cohorts having independent {sup 14}C-signatures. This discrepancy suggests that cohort-based models are needed to adequately capture the complex processes involved in carbon transport associated with litter mass-loss. Such models will be crucial for predicting intra- and interannual differences in organic horizon decomposition driven by scenarios of climatic change.
Date: June 27, 2005
Creator: Hanson, P J; Swanston, C W; Garten, Jr., C T; Todd, D E & Trumbore, S E
Partner: UNT Libraries Government Documents Department

Mine-to-Mill Optimization of Aggregate Production

Description: Mine-to-Mill optimization is a total systems approach to the reduction of energy and cost in mining and processing. Developed at the Julius Krutschnitt Mineral Research Center in Queensland, Australia, the Mine-to-Mill approach attempts to minimize energy consumption through optimization of all steps in the size reduction process. The approach involves sampling and modeling of blasting and processing, followed by computer simulation to optimize the operation and develop alternatives. The most promising alternatives are implemented, and sampling is conducted to quantify benefits. In the current project, the primary objective was to adapt Mine-to-Mill technology to the aggregates industry. The first phase of this work was carried out at the Bealeton Quarry near Fredericksburg, Virginia. The second phase was carried out at the Pittsboro Quarry south of Chapel Hill, North Carolina. Both quarries are operated by Luck Stone Corporation of Richmond, Virginia. As a result of the work, several conclusions can be drawn from the project which should assist DOE in assessing the applicability of the Mine-to-Mill approach to the aggregates industry. 1. Implementation of MTM guidelines at Pittsboro has resulted in tangible improvements in productivity. It is clear that MTM guidelines represent an energy savings of around 5% (primary and secondary) and an overall energy savings of 1%. This 1-5% energy savings is also consistent with simulated results for Bealeton had side-by-side shots used to evaluate the technology been carried out in the same rockmass. 2. Luck Stone clearly runs their operations at a high standard. Hence the percentage improvement realized in this project may represent the lower end of what might be expected overall in the aggregates industry. 3. Variability in ore types across both Bealeton and Pittsboro suggests a 2:1 difference in hardness which contradicts the misconception that quarry rock is homogenous. Therefore, the idea of comparing side-by-side blasts ...
Date: September 30, 2006
Creator: Adel, Greg; Kojovic, Toni & Thornton, Darren
Partner: UNT Libraries Government Documents Department

Laser-matter Interaction with Submerged Samples

Description: With the long-term goal in mind of investigating if one could possibly design a 'universal solid-sample comminution technique' for debris and rubble, we have studied pulsed-laser ablation of solid samples that were contained within a surrounding fluid. Using pulses with fluences between 2 J and 0.3 J, wavelengths of 351 and 527 nm, and samples of rock, concrete, and red brick, each submerged in water, we have observed conditions in which {micro}m-scale particles can be preferentially generated in a controlled manner, during the laser ablation process. Others have studied laser peening of metals, where their attention has been to the substrate. Our study uses non-metallic substrates and analyzes the particles that are ablated from the process. The immediate impact of our investigation is that laser-comminution portion of a new systems concept for chemical analysis has been verified as feasible.
Date: March 25, 2010
Creator: Mariella, R; Rubenchik, A; Norton, M; Donohue, G & Roberts, K
Partner: UNT Libraries Government Documents Department

Pulverization Induced Charge: In-Line Dry Coal Cleaning

Description: The technical feasibility of separating mineral matter and pyrite from coal as it is transported from pulverizers to burners in pulverized coal combustion units will be examined. The charge imparted on coal during pulverization and transport to pulverized coal (PC) burners in a utility boiler will be quantified. In addition to field charge measurements, an existing computational model will be extended to numerically simulate charged particle motion in a turbulent gas through an electric field. Results from the field tests and numerical modeling will be employed in design and construction of a laboratory scale pulverizer/classifier. This laboratory unit will be used to quantify the magnitude and differential charge imparted on bituminous and subbituminous coals during pulverization and classification at temperatures and with gaseous constituents typical to utility PC units. An electrostatic separator, designed for in-line operation between pulverizers and PC boilers, will be used to clean prepulverized coals. Theoretical and experimental data are to be used in preparing a preliminary design for a full-scale, (15 ton/hr) in-line, electrostatic coal cleaning device. Finally, the economic potential for application to PC units will be assessed.
Date: January 21, 1998
Creator: Stencel, John M.
Partner: UNT Libraries Government Documents Department

Pulverization Induced Charge: In-Line Dry Coal Cleaning

Description: The technical feasibility of separating mineral matter and pyrite from coal as it is transported from pulverizers to burners in pulverized coal combustion units will be examined. The charge imparted on coal during pulverization and transport to pulverized coal (PC) burners in a utility boiler will be quantified. In addition to field charge measurements, an existing computational model will be extended to numerically simulate charged particle motion in a turbulent gas through an electric field. Results from the field tests and numerical modeling will be employed in design and construction of a laboratory scale pulverizer/classifier. This laboratory unit will be used to quantify the magnitude and differential charge imparted on bituminous and subbituminous coals during pulverization and classification at temperatures and with gaseous constituents typical to utility PC units. An electrostatic separator, designed for in-line operation between pulverizers and PC boilers, will be used to clean prepulverized coals. Theoretical and experimental data are to be used in preparing a preliminary design for a full-scale, (15 ton/hr) in-line, electrostatic coal cleaning device. Finally, the economic potential for application to PC units will be assessed.
Date: May 26, 1998
Creator: Stencel, John M.
Partner: UNT Libraries Government Documents Department

[Coal comminution] progress reports. Semi-annual report, October 1, 1997--March 1, 1998

Description: This report presents the objectives, approach, and progress on six projects being undertaken at the University of Utah. The six projects, all related to the comminution of coal, are: Administration and Comminution Reference Center; Optimal energy utilization strategies for comminution; Ball mill scale-up; Ball media motion computer code; Fracture of brittle particles in constrained beds measured on the ultrafast load cell; and Development of a prototype oscillating ball mill.
Date: August 1, 1998
Partner: UNT Libraries Government Documents Department

Cosmic bombardment V: Threat object-dispersing approaches to active planetary defense

Description: Earth-impacting comets and asteroids with diameters {approx}0.03 - 10 km pose the greatest threats to the terrestrial biosphere in terms of impact frequency-weighted impact consequences, and thus are of most concern to designers of active planetary defenses. Specific gravitational binding energies of such objects range from 10{sup -7} to 10{sup -2} J/gm, and are small compared with the specific energies of 1x10{sup 3} to 3x10{sup 3} J/gm required to vaporize objects of typical composition or the specific energies required to pulverize them, which are 10{sup -1} to 10 J/gm. All of these are small compared to the specific kinetic energy of these objects in the Earth- centered frame, which is 2x10{sup 5} to 2x10{sup 6} J/gm. The prospect naturally arises of negating all such threats by deflecting, pulverizing or vaporizing the objects. Pulverization-with-dispersal is an attractive option of reasonable defensive robustness. Examples of such equipments - which employ no explosives of any type - are given. Vaporization is the maximally robust defensive option, and may be invoked to negate threat objects not observed until little time is left until Earth-strike, and pulverization-with-dispersal has proven inadequate. Physically larger threats may be vaporized with nuclear explosives. No contemporary technical means of any kind appear capable of directly dispersing the -100 km diameter scale Charon- class cometary objects recently observed in the outer solar system, although such objects may be deflected to defensively useful extents. Means of implementing defenses of each of these types are proposed for specificity, and areas for optimization noted. Biospheric impacts of threat object debris are briefly considered, for bounding purposes. Experiments are suggested on cometary and asteroidal objects.
Date: May 24, 1995
Creator: Teller, E.; Wood, L.; Ishikawa, M. & Hyde, R.
Partner: UNT Libraries Government Documents Department

Pulverization induced charge: In-line dry coal cleaning. Technical progress report No. 7, January 1, 1996--March 31, 1996

Description: Task 1 on charge determinations has been completed with additional measurements taken at the TVA Widows Creek plant. The probe which was designed and constructed for the field charge measurements proved to be effective in determining the average charge of pulverized coal particles. The charge measurements conducted at EKP`s Spurlock Station power plant and TVA`s Widows Creek plant have both yielded results which are in the same order of magnitude as those determined in controlled laboratory experiments. Under Task 3, coal separation determinations, separation tests performed on-site, combined with the charge measurements, showed that the charge generated by coal pulverization was sufficient for electrostatic separation of coal from mineral matter. These tests were conducted using a separation probe with different electric field strengths, i.e., different voltages were used across the two copper plates to generate the electric field. The results under four conditions were consistent and similar in terms of separation.
Date: August 1, 1996
Partner: UNT Libraries Government Documents Department

COMPREHENSIVE INVESTIGATION OF THE LIBERATION CHARACTERISTICS OF PYRITE AND OTHER ASH-FORMING MINERALS FROM COAL

Description: The objective of this project is the development of methods for the measurement, prediction and modeling of the liberation characteristics of mineral matter and pyrite from coal, and to implement these findings in viable computer-simulation systems for coal cleaning plants. The central thrust of the project will be based on using the Andrews-Mika diagram as a convenient and experimentally verifiable model for the liberation characteristics of the constituents of coal during comminution. In order to establish the Andrews-Mika diagram, it is necessary to develop efficient techniques for density fractionation and for the measurement of the liberation spectrum in products obtained from the comminution of narrow composition fractions of coal. Dense-liquid techniques are used to produce fractionated samples, and image-analysis techniques, using linear-intercept analysis, are used to measure the liberation spectrum. The prediction of the liberation of mineral matter and pyrite from coal after comminution is based on a linear stochastic model for the description of the mineralogical texture and the random fracture pattern associated with the comminution process. Stereological correction of the distribution of linear grades is required for both the measurement and prediction of the true distribution of volumetric grades in the particle population.
Date: March 22, 1999
Partner: UNT Libraries Government Documents Department

OPTIMIZATION OF COMMINUTION CIRCUIT THROUGHPUT AND PRODUCT SIZE DISTRIBUTION BY SIMULATION AND CONTROL

Description: 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 he product size distribution, so that the amount of excessively fine material produced can be minimized. This will save energy by reducing the amount of material that is ground below the target size, and will also reduce the quantity of materials wasted as ''slimes'' that are too fine to be useful. This will be accomplished by: (1) modeling alternative circuit arrangements to determine methods for minimizing overgrinding, and (2) determining whether new technologies, such as high-pressure roll crushing, can be used to alter particle breakage behavior to minimize fines production. In previous quarters, it was determined that the primary grinding mills were operating at less than full capacity, suggesting that a shift of grinding load to the primary mills could liberate more material before it reached the secondary mills, allowing more complete liberation with a coarser grind. In the eighth quarter, further analysis was carried out to determine the full extent of the benefit that could be obtained by this shift in grinding load. A key part of this analysis was the development of a correlation of the circuit capacity with (a) ore work index, (b) the quantity of primary mill ''pebbles'' that were crushed by a cone crusher in the circuit, and (c) the fraction of the crushed pebbles that were also processed by a high-pressure roll mill.
Date: January 1, 2003
Creator: Kawatra, S.K. & T.C. Eisele, H.J. Walqui
Partner: UNT Libraries Government Documents Department

OPTIMIZATION OF COMMINUTION CIRCUIT THROUGHPUT AND PRODUCT SIZE DISTRIBUTION BY SIMULATION AND CONTROL

Description: 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 he product size distribution, so that the amount of excessively fine material produced can be minimized. This will save energy by reducing the amount of material that is ground below the target size, and will also reduce the quantity of materials wasted as ''slimes'' that are too fine to be useful. This will be accomplished by: (1) modeling alternative circuit arrangements to determine methods for minimizing overgrinding, and (2) determining whether new technologies, such as high-pressure roll crushing, can be used to alter particle breakage behavior to minimize fines production. In the seventh quarter of this project, analysis of the plant operation identified sources of overgrinding in the circuit. Overgrinding was primarily caused by two effects: (1) The hydrocyclones used to close the circuit and remove fully-ground particles from the circuit were preferentially returning high-density ore particles to the secondary mills for regrinding even after they were already ground to pass the desired product size, and (2) The primary grinding mills were operating at less than full capacity, suggesting that a shift of grinding load to the primary mills could liberate more material before it reached the secondary mills, allowing more complete liberation with a coarser grind. Circuit modeling is underway to determine how best to modify the circuit to reduce these effects.
Date: October 1, 2002
Creator: Kawatra, S.K.; Eisele, T.C. & Walqui, H.J.
Partner: UNT Libraries Government Documents Department

A PURPOSE ORIENTED MAGNETIC SEPARATOR: SKIMMER

Description: A magnetic separator was designed to selectively separate fine-liberated magnetite. The conceptual design was simulated using CFD techniques. A separator tank was fabricated and a magnetic drum was used to capture magnetic particles. The initial tank design was modified to eliminate application oriented problems. The new separator was able to produce a fine product as a concentrate at relatively high feed rates. A plant simulation showed that such a device could lower circulating loads around ball mills by 16%, thereby creating room for a 5-8% increase in throughput at the same energy level. However, it was concluded that further improvements in terms of both size and mineral selectivity are needed to have a marketable product.
Date: August 9, 2005
Creator: Ersayin, Salih
Partner: UNT Libraries Government Documents Department

Sediment transport time measured with U-Series isotopes: Resultsfrom ODP North Atlantic Drill Site 984

Description: High precision uranium isotope measurements of marineclastic sediments are used to measure the transport and storage time ofsediment from source to site of deposition. The approach is demonstratedon fine-grained, late Pleistocene deep-sea sediments from Ocean DrillingProgram Site 984A on the Bjorn Drift in the North Atlantic. The sedimentsare siliciclastic with up to 30 percent carbonate, and dated by sigma 18Oof benthic foraminifera. Nd and Sr isotopes indicate that provenance hasoscillated between a proximal source during the last three interglacialperiods volcanic rocks from Iceland and a distal continental sourceduring glacial periods. An unexpected finding is that the 234U/238Uratios of the silicate portion of the sediment, isolated by leaching withhydrochloric acid, are significantly less than the secular equilibriumvalue and show large and systematic variations that are correlated withglacial cycles and sediment provenance. The 234U depletions are inferredto be due to alpha-recoil loss of234Th, and are used to calculate"comminution ages" of the sediment -- the time elapsed between thegeneration of the small (<_ 50 mu-m) sediment grains in the sourceareas by comminution of bedrock, and the time of deposition on theseafloor. Transport times, the difference between comminution ages anddepositional ages, vary from less than 10 ky to about 300 to 400 ky forthe Site 984A sediments. Long transport times may reflect prior storagein soils, on continental shelves, or elsewhere on the seafloor. Transporttime may also be a measure of bottom current strength. During the mostrecent interglacial periods the detritus from distal continental sourcesis diluted with sediment from Iceland that is rapidly transported to thesite of deposition. The comminution age approach could be used to dateQuaternary non-marine sediments, soils, and atmospheric dust, and may beenhanced by concomitant measurement of 226Ra/230Th, 230Th/234U, andcosmogenic nuclides.
Date: June 5, 2006
Creator: DePaolo, Donald J.; Maher, Kate; Christensen, John N. & McManus,Jerry
Partner: UNT Libraries Government Documents Department

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

Description: 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.
Date: March 31, 2005
Creator: Kawatra, S. K.; Eisele, T. C.; Weldum, T.; Larsen, D.; Mariani, R. & Pletka, J.
Partner: UNT Libraries Government Documents Department

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

Description: The goal of this project was to improve energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process were used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced could be minimized. The goal was to save energy by reducing the amount of material that was ground below the target size, while simultaneously reducing the quantity of materials wasted as ''slimes'' that were too fine to be useful. Extensive plant sampling and mathematical modeling of the grinding circuits was carried out to determine how to correct this problem. The approaches taken included (1) Modeling of the circuit to determine process bottlenecks that restrict flowrates 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 the potential of advanced technologies to improve comminution efficiency and produce sharper product size distributions with less overgrinding. The mathematical models were used to simulate novel circuits for minimizing overgrinding and increasing throughput, and it is estimated that a single plant grinding 15 million tons of ore per year saves up to 82.5 million kWhr/year, or 8.6 x 10{sup 11} BTU/year. Implementation of this technology in the midwestern iron ore industry, which grinds an estimated 150 million tons of ore annually to produce over 50 million tons of iron ore concentrate, would save an estimated 1 x 10{sup 13} BTU/year.
Date: July 1, 2005
Creator: Kawatra, S.K.; Eisele, T.C.; Weldum, T.; Larsen, D.; Mariani, R. & Pletka, J.
Partner: UNT Libraries Government Documents Department

TUNING SILICON NANORODS FOR ANODES OF LI-ION RECHARGEABLE BATTERIES

Description: Silicon is a promising anode material for Li-ion batteries in regarding of high capacity, low cost and safety, but it suffers poor cycling stability due to the pulverization induced by severe volume expansion/shrinkage (297%) during lithium insertion/extraction. In our previous investigation on aluminum nanorods anodes, it is found the selection of substrates in which Al nanorods grown plays the role in prevention of pulverization resulting in the increase of cycling life. Adapting this knowledge, we investigated the Si based nanorods anodes by tuning its composition and element distribution. Our results show that although the Si nanorods demonstrated higher initial anodic capacity of 1500 mAh/g, it diminished after 50 cycles due to morphology change and pulverization. By codepositing Cu, the Si-Cu composite nanorods demonstrated sustainable capacity of 500 mAh/g in 100 cycles attributing to its flexible and less brittle nature.
Date: November 23, 2010
Creator: Au, M.
Partner: UNT Libraries Government Documents Department

Pressure-shear experiments on granular materials.

Description: Pressure-shear experiments were performed on granular tungsten carbide and sand using a newly-refurbished slotted barrel gun. The sample is a thin layer of the granular material sandwiched between driver and anvil plates that remain elastic. Because of the obliquity, impact generates both a longitudinal wave, which compresses the sample, and a shear wave that probes the strength of the sample. Laser velocity interferometry is employed to measure the velocity history of the free surface of the anvil. Since the driver and anvil remain elastic, analysis of the results is, in principal, straightforward. Experiments were performed at pressures up to nearly 2 GPa using titanium plates and at higher pressure using zirconium plates. Those done with the titanium plates produced values of shear stress of 0.1-0.2 GPa, with the value increasing with pressure. On the other hand, those experiments conducted with zirconia anvils display results that may be related to slipping at an interface and shear stresses mostly at 0.1 GPa or less. Recovered samples display much greater particle fracture than is observed in planar loading, suggesting that shearing is a very effective mechanism for comminution of the grains.
Date: October 1, 2011
Creator: Reinhart, William Dodd (Sandia National Laboratories, Albuquerque, NM); Thornhill, Tom Finley, III (, Sandia National Laboratories, Albuquerque, NM); Vogler, Tracy John & Alexander, C. Scott (Sandia National Laboratories, Albuquerque, NM)
Partner: UNT Libraries Government Documents Department

Microbial recovery of metals from spent coal liquefaction catalysts. Quarterly report, April--June, 1992

Description: During April and May the authors began the rather laborious task of crushing each of the solvent-extracted catalyst samples for the determination of the effect of crushing on leaching rate and percent metal recovered. The crushing of these catalyst samples employed a ball mill and it took approximately 1 week to crush each sample. All catalyst samples, after crushing, were sieved to a particle size of >100 mesh. Samples of 10, and 40 mesh were also collected, but only the >100 mesh was subjected to bacterial leaching. These samples were tested using denitrifying bacteria for their ability to release Ni and Mo from these samples. The data are shown in the attached figures as well as comparisons for rates of Ni and Mo released in relation to catalyst solvent pretreatment. These data were obtained with citrate as a carbon and energy source for the microorganisms. It is quite clear that crushing the catalyst allows for a more rapid release of these metals from the catalyst samples, regardless of the organic solvent used to pretreat the catalyst. However, the effects of the different solvents are still evident, although not as striking, after the catalysts are crushed (see previous reports). There also still appears to be a greater ease in removing Mo over Ni, a case particularly prevalent if ethyl acetate, methanol or xylene is used as the pretreatment solvent. In any case, it appears that a variety of solvents will be useful and that an optimized system could yield >90% release and recovery of both Ni and Mo in as little as 10 days of treatment. Experimental data are enclosed.
Date: December 31, 1992
Creator: Sperl, P.L. & Sperl, G.T.
Partner: UNT Libraries Government Documents Department

PULVERIZATION INDUCED CHARGE: IN-LINE DRY COAL CLEANING

Description: The technical feasibility of separating mineral matter and pyrite from coal as it is transported from pulverizers to burners in pulverized coal combustion units will be examined. The charge imparted on coal during pulverization and transport to pulverized coal (PC) burners in a utility boiler will be quantified. In addition to field charge measurements, an existing computational model will be extended to numerically simulate charged particle motion in a turbulent gas through an electric field. Results from the field tests and numerical modeling will be employed in design and construction of a laboratory scale pulverizer/classifier. This laboratory unit will be used to quantify the magnitude and differential charge imparted on bituminous and subbituminous coals during pulverization and classification at temperatures and with gaseous constituents typical to utility PC units. An electrostatic separator, designed for in-line operation between pulverizers and PC boilers, will be used to clean prepulverized coals. Theoretical and experimental data are to be used in preparing a preliminary design for a full-scale, (15 ton/hr) in-line, electrostatic coal cleaning device. Finally, the economic potential for application to PC units will be assessed.
Date: July 1, 1998
Creator: STENCEL, JOHN M.
Partner: UNT Libraries Government Documents Department

Engineering development of advanced physical fine coal cleaning for premium fuel applications. Task 6 -- Selective agglomeration laboratory research and engineering development for premium fuels

Description: The primary goal of this project is the engineering development of two advanced physical fine coal cleaning processes, column flotation and selective agglomeration, for premium fuel applications. The project scope included laboratory research and benchscale testing on six coals to optimize these processes, followed by the design, construction, and operation of a 2 t/hr process development unit (PDU). The project began in October, 1992, and is scheduled for completion by September 1997. This report represents the findings of Subtask 6.5 Selective Agglomeration Bench-Scale Testing and Process Scale-up. During this work, six project coals, namely Winifrede, Elkhorn No. 3, Sunnyside, Taggart, Indiana VII, and Hiawatha were processed in a 25 lb/hr continuous selective agglomeration bench-scale test unit.
Date: June 27, 1997
Creator: Moro, N. & Jha, M.C.
Partner: UNT Libraries Government Documents Department

IMPROVING ENERGY EFFICIENCY VIA OPTIMIZED CHARGE MOTION AND SLURRY FLOW IN PLANT SCALE SAG MILLS

Description: The U.S. mining industry operates approximately 80 semi-autogenesis grinding mills (SAG) throughout the United States. Depending on the mill size the SAG mills draws between 2 MW and 17 MW. The product from the SAG mill is further reduced in size using pebble crushers and ball mills. Hence, typical gold or copper ore requires between 2.0 and 7.5 kWh per ton of energy to reduce the particle size. Considering a typical mining operation processes 10,000 to 100,000 tons per day the energy expenditure in grinding is 50 percent of the cost of production of the metal. A research team from the University of Utah is working to make inroads into saving energy in these SAG mills. In 2003, Industries of the Future Program of the Department of Energy tasked the University of Utah team to build a partnership between the University and the mining industry for the specific purpose of reducing energy consumption in SAG mills. A partnership was formed with Cortez Gold Mines, Kennecott Utah Copper Corporation, Process Engineering Resources Inc. and others. In the current project, Cortez Gold Mines played a key role in facilitating the 26-ft SAG mill at Cortez as a test mill for this study. According to plant personnel, there were a number of unscheduled shut downs to repair broken liners and the mill throughput fluctuated depending on ore type. The University team had two softwares, Millsoft and FlowMod to tackle the problem. Millsoft is capable of simulating the motion of charge in the mill. FlowMod calculates the slurry flow through the grate and pulp lifters. Based on this data the two models were fine-tuned to fit the Cortez SAG will. In the summer of 2004 a new design of shell lifters were presented to Cortez and in September 2004 these lifters were installed in ...
Date: December 1, 2005
Creator: Rajamani, Raj K.; Latchireddi, Sanjeeva; Prathy, Sravan K. & Patra, Trilokyanath
Partner: UNT Libraries Government Documents Department

OPTIMIZATION OF COMMINUTION CIRCUIT THROUGHOUT AND PRODUCT SIZE DISTRIBUTION BY SIMULATION AND CONTROL

Description: 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 will be accomplished by: (1) modeling alternative circuit arrangements to determine methods for minimizing overgrinding and maximizing energy efficiency, and (2) determining whether new technologies, such as high-pressure roll crushing, can be used to alter particle breakage behavior to minimize fines production.
Date: October 1, 2003
Creator: Walqui, H.J.; Eisele, T.C. & Kawatra, S.K.
Partner: UNT Libraries Government Documents Department

OPTIMIZATION OF COMMINUTION CIRCUIT THROUGHPUT AND PRODUCT SIZE DISTRIBUTION BY SIMULATION AND CONTROL

Description: 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 flowrates 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.
Date: October 1, 2004
Creator: Eisele, T.C.; Kawatra, S.K. & Walqui, H.J.
Partner: UNT Libraries Government Documents Department