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Coal-sand attrition system and its importance in fine coal cleaning

Description: The primary objective of this project is geared toward the substitution of steel media by fracturing silica sand as a grinding media for ultrafine coal grinding. The experimental silica is as follows: (1) design and fabrication of attrition cell; (2) sample procurement, preparation, and characterization; (3) batch grinding tests; (4) continuous grinding test; and (5) fracture mechanics.
Date: December 2, 1991
Creator: Mehta, R.K.
Partner: UNT Libraries Government Documents Department

Coal-sand attrition system and its importance in fine coal cleaning. First quarterly report, September 1, 1991--November 30, 1991

Description: The primary objective of this project is geared toward the substitution of steel media by fracturing silica sand as a grinding media for ultrafine coal grinding. The experimental silica is as follows: (1) design and fabrication of attrition cell; (2) sample procurement, preparation, and characterization; (3) batch grinding tests; (4) continuous grinding test; and (5) fracture mechanics.
Date: December 2, 1991
Creator: Mehta, R. K.
Partner: UNT Libraries Government Documents Department

Coal-sand attrition system and its' importance in fine coal cleaning

Description: The primary objective of this project is geared toward the substitution of steel media by fracturing silica sand as a grinding media for ultraline coal grinding. The project has been divided into four subgroups for bookkeeping purposes and possible ease of execution. Some of the tasks would be executed simultaneously as overlapping is inevitable. The grouping is as follows: (1) sample procurement, preparation, and characterization; (2) batch grinding tests; (3) continuous grinding tests; and, (4) fracture mechanics. The hardgrove indices for the four coals employed in this work have finally been determined by the personnel at the R and D Center of Drummond Coal Company using 14 [times] 28 mesh feed size materials. The values obtained for the respective coals are given in Table 1.
Date: January 1, 1992
Creator: Mehta, R.K. & Schultz, C.W.
Partner: UNT Libraries Government Documents Department

Coal-sand attrition system and its` importance in fine coal cleaning. Eighth quarterly report, June 1, 1992--August 31, 1993

Description: The research efforts on the importance of a coal-sand attrition continued with work in four categories: Continuous grinding tests using steel media; fracture tests on coal samples compacted at different pressure; SEM-Image analysis of feed and ground product coal samples; zeta potential measurements of coal samples ground by different media, and flotation test of coal samples ground by different media. Results are described.
Date: August 26, 1993
Creator: Mehta, R. K. & Schultz, C. W.
Partner: UNT Libraries Government Documents Department

Coal-sand attrition system and its` importance in fine coal cleaning. Quarterly report, May 31, 1991--August 31, 1992

Description: The primary objective of this project is geared toward the substitution of steel media by fracturing silica sand as a grinding media for ultraline coal grinding. The project has been divided into four subgroups for bookkeeping purposes and possible ease of execution. Some of the tasks would be executed simultaneously as overlapping is inevitable. The grouping is as follows: (1) sample procurement, preparation, and characterization; (2) batch grinding tests; (3) continuous grinding tests; and, (4) fracture mechanics. The hardgrove indices for the four coals employed in this work have finally been determined by the personnel at the R and D Center of Drummond Coal Company using 14 {times} 28 mesh feed size materials. The values obtained for the respective coals are given in Table 1.
Date: December 1, 1992
Creator: Mehta, R. K. & Schultz, C. W.
Partner: UNT Libraries Government Documents Department

Cost optimization of stirred ball mill grinding

Description: On going research at the University of Alabama has shown that stirred ball mill grinding is the highest cost unit operation in the beneficiation of Eastern Oil Shales. Minimization of that cost is critical if oils derived by beneficiation and hydroretorting of Eastern shales are to become an economic alternative to conventional crude oils. Cost optimization of stirred ball milling is a substantially different problem than optimizing a conventional (tumbling) mill operation. For conventional mills minimum cost is virtually synonymous with minimum energy consumption. Because the technology is mature and well understood, the operator can predictably optimize within a very narrow range of operating conditions. In contrast, stirred ball milling offers the operator several more ``degrees of freedom`` in selecting operating conditions. An example is the selection of rotor speed. In general, lower speeds result in lower energy consumption per ton of material ground but at the cost of reduced mill capacity per unit volume. Because stirred ball mills have a high capital cost per unit volume the trade off between energy consumption and capacity becomes critical. This paper presents a generalized total cost mode for stirred ball milling and examines data generated in the grinding of oil shales in terms of the model. The paper also discuss the role of the cost model in guiding future research in grinding circuit optimization.
Date: December 31, 1991
Creator: Schultz, C. W. & Mehta, R. K.
Partner: UNT Libraries Government Documents Department

Coal-sand attrition system and its importance in fine coal cleaning. Final report

Description: It is known that ultra-fine coals are prerequisite for the deep cleaning of most US coal seams if environmental pollution arising from the use of such coals is to be minimized. Therefore, the production of finely liberated coal particles in conjunction with reduced heavy metal contaminants at low costs is desirable, if not mandatory. The liberation of intimately disseminated impurities from the coal matrix therefore, demands that the material be ground to a high degree of fineness. Similarily, some technologies for coal utilization require superfine particles (i.e., sizes less than ten microns). This implies additional costs for coal preparation plants due to the high energy and media costs associated with fine grinding operations. Besides, there are problems such as severe product contaminations due to media wear and impairment of the quality of coal. Hence, proper choice of grinding media type is important from the viewpoints of cost reduction and product quality. The use of natural quartz sand as grinding media in the comminution of industrial minerals in stirred ball mills has been indicated. The advantages of natural sand compared to steel media include low specific energy inputs, elimination of heavy metal contaminants and low media costs. In this work, the effect of rotor speed, solids concentration and feed-size are studied on four coals in conjunction with silica sand and steel shot. The results obtained are used to evaluate the suitability of silica sands as an alternative grinding media. for coal. Coal-sand and coal-steel systems are compared in terms of specific energy consumption, product fineness, media/wear contaminationanalysis and calorific values, liberation spectrum and particle shape characteristics. In general cleaner flotation concentrate was obtained from coals when they were ground with sand media. The zeta potential of coals was found to be different and lower when they ground with sand.
Date: August 1, 1993
Creator: Mehta, R. K. & Zhu, Qinsheng
Partner: UNT Libraries Government Documents Department

M-shell x-ray production cross sections in thin targets of ₇₉Au, ₈₂Pb, ₈₃Bi, and ₉₂U by 0.3 - 2.6-MeV ₁¹H+ and ₂⁴He+ ions

Description: Article discussing M-shell x-ray-production cross sections in thin targets of ₇₉Au, ₈₂Pb, ₈₃Bi, and ₉₂U by 0.3 - 2.6-MeV ₁⁴H+ and ₂⁴He+ ions.
Date: October 1982
Creator: Mehta, R.; Duggan, Jerome L.; Price, J. L.; McDaniel, Floyd Del. (Floyd Delbert), 1942- & Lapicki, Gregory
Partner: UNT College of Arts and Sciences

M-shell x-ray production cross sections for 0.5-2.5-MeV Be+ ions incident upon selected elements from praseodymium to bismuth

Description: This article discusses M-shell x-ray production cross sections for 0.5-2.5-MeV Be+ ions incident upon selected elements from praseodymium to bismuth.
Date: January 15, 1988
Creator: Price, J. L.; Duggan, Jerome L.; McDaniel, Floyd Del. (Floyd Delbert), 1942-; Lapicki, Gregory & Mehta, R.
Partner: UNT College of Arts and Sciences

Removal of heavy metal ions from oil shale beneficiation process water by ferrite process

Description: The ferrite process is an established technique for removing heavy metals from waste water. Because the process water resulting from oil shale beneficiation falls into the category of industrial waste water, it is anticipated that this process may turn out to be a potential viable treatment for oil shale beneficiation process water containing many heave metal ions. The process is chemoremedial because not only effluent water comply with quality standards, but harmful heavy metals are converted into a valuable, chemically stable by-product known as ferrite. These spinel ferrites have magnetic properties, and therefore can be use in applications such as magnetic marker, ferrofluid, microwave absorbing and scavenging material. Experimental results from this process are presented along with results of treatment technique such as sulfide precipitation.
Date: December 31, 1991
Creator: Mehta, R. K.; Zhang, L.; Lamont, W. E. & Schultz, C. W.
Partner: UNT Libraries Government Documents Department

Coal-sand attrition system and its` importance in fine coal cleaning. Seventh quarterly report, March 1, 1993--May 31, 1993

Description: For the four coals employed in this work, it was not possible to effectively grind the minus 50 mesh feed even at the lowest solids concentration range tried. The reason for this is the low feed rate which makes it impossible to obtain a uniform flow as the coarse particles in the feed tend to settle down and form sediment in either the tubing system or the grinding chamber. Besides, only moderate levels of solids concentration could be employed as high solids concentration are also fraught with sedimentation problem. Attempts to increase the flow rate resulted in the grinding media being taken out of the mill together with the slurry. As a result of these limitations posed by the instrument, further tests were restricted to using minus 100 mesh feed size and moderate levels of feed rate and Pulp density. Some of the results obtained are given in Tables I - 4 for the different coals used. It can be seen from the tables that the softest coal (Pocahontas No. 3 in this case) requires about 2 or 3 passes in order to obtain very fine product while the harder coals would require 4 or more passes. The number of passes required for the harder coals can be reduced either by increasing the residence time of the slurry in the mill by decreasing the feed rate or preferably by increasing the stirring speed. Both of these actions will inevitably lead to a slight increase in the media wear. The media wear observed in grinding Pocahontas No. 3 in three cycles was 1.3% while the corresponding values for grinding both Illinois No. 6 and Black Creek coals in four cycles were 0.5% and 1.5% respectively.
Date: June 29, 1993
Creator: Mehta, R. K. & Schultz, C. W.
Partner: UNT Libraries Government Documents Department

L-shell ionization in high-z targets by carbon and silicon ions

Description: L-shell ionization in Ho, Er, Tm, Ta, W, Tl, Pb and Bi by 20 MeV carbon ions and 37.5 MeV silicon ions has been investigated. The observed L/sub ..cap alpha../L/sub ..gamma../ x-ray intensity ratios are compared with the estimates based on PWBA and BEA calculations. The energy shifts in the L/sub ..cap alpha../, L/sub ..gamma../sub 1// and L/sub ..gamma../sub 4// x rays are attributed to the presence of M shell spectator vacancies.
Date: January 1, 1980
Creator: Rao, P. V.; Albridge, R. G.; Ramayya, A. V.; Andrews, M. C.; Mehta, R.; McDaniel, F. D. et al.
Partner: UNT Libraries Government Documents Department

₁¹H+ - and ₂⁴He+ - induced M-shell x-ray-production cross sections for selected elements in the rare-earth region

Description: Article on ₁¹H+ and ₂⁴He+ -induced M-shell x-ray-production cross sections for selected elements in the rare-earth region.
Date: December 1983
Creator: Mehta, R.; Duggan, Jerome L.; Price, J. L.; Kocur, P. M.; McDaniel, Floyd Del. (Floyd Delbert), 1942- & Lapicki, Gregory
Partner: UNT College of Arts and Sciences

Cost optimization of stirred ball mill grinding

Description: On going research at the University of Alabama has shown that stirred ball mill grinding is the highest cost unit operation in the beneficiation of Eastern Oil Shales. Minimization of that cost is critical if oils derived by beneficiation and hydroretorting of Eastern shales are to become an economic alternative to conventional crude oils. Cost optimization of stirred ball milling is a substantially different problem than optimizing a conventional (tumbling) mill operation. For conventional mills minimum cost is virtually synonymous with minimum energy consumption. Because the technology is mature and well understood, the operator can predictably optimize within a very narrow range of operating conditions. In contrast, stirred ball milling offers the operator several more degrees of freedom'' in selecting operating conditions. An example is the selection of rotor speed. In general, lower speeds result in lower energy consumption per ton of material ground but at the cost of reduced mill capacity per unit volume. Because stirred ball mills have a high capital cost per unit volume the trade off between energy consumption and capacity becomes critical. This paper presents a generalized total cost mode for stirred ball milling and examines data generated in the grinding of oil shales in terms of the model. The paper also discuss the role of the cost model in guiding future research in grinding circuit optimization.
Date: January 1, 1991
Creator: Schultz, C.W. & Mehta, R.K. (Alabama Univ., University, AL (United States). Mineral Resources Inst.)
Partner: UNT Libraries Government Documents Department

M-shell electron capture and direct ionization of gold by 25-MeV carbon and 32-MeV oxygen ions

Description: M-shell x-ray production cross sections have been measured for thin solid targets of Au for 25 MeV /sup 12/C/sup q+/ (q = 4, 5, 6) and for 32 MeV /sup 16/O/sup q+/ (q = 5, 7, 8). The microscopic cross sections were determined from measurements made with targets ranging in thickness from 0.5 to 100 ..mu..g/cm/sup 2/. For projectiles with one or two K-shell vacancies, the M-shell x-ray production cross sections are found to be enhanced over those by projectiles without a K-shell vacancy. The sum of direct ionization to the continuum (DI) and electron capture (EC) to the L, M, N ... shells and EC to the K-shell of the projectile have been extracted from the data. The results are compared to the predictions of first Born theories i.e. PWBA for DI and OBK of Nikolaev for EC and the ECPSSR approach that accounts for energy loss, Coulomb deflection and relativistic effects in the perturbed stationary state theory. 25 references, 3 figures, 1 table.
Date: January 1, 1984
Creator: Andrews, M.C.; McDaniel, F.D.; Duggan, J.L.; Miller, P.D.; Pepmiller, P.L.; Krause, H. et al.
Partner: UNT Libraries Government Documents Department

L-shell x-ray production cross sections in Nd, Gd, Ho, Yb, Au and Pb for 25-MeV carbon and 32-MeV oxygen ions

Description: L-shell x-ray production cross sections in /sub 60/Nd, /sub 64/Gd, /sub 67/Ho, /sub 70/Yb, /sub 79/Au and /sub 82/Pb have been measured for incident 25 MeV /sub 6//sup 12/C/sup +q/(q = 4,5,6) and 32 MeV /sub 8//sup 16/O/sup +q/(q = 5,7,8) ions. Measurements were made on targets ranging in thickness from 1 to 100 ..mu..g/cm/sup 2/. Echancement in the L-shell x-ray production cross section for projectiles with one or two K-shell vacancies over those for projectiles with no K-shell vacancies is observed. The sum of direct ionization to the continuum (DI) plus electron capture (EC) to the L,M,N ... shells and EC to the K-shell of the projectile have been extracted from the data. Calculations in the first Born approximation are approx. 10 times larger than the data. Predictions of the ECPSSR theory that accounts for the energy-loss, Coulomb deflection, perturbed-stationary state, and relativistic effects are in good agreement with the data for both ions.
Date: January 1, 1984
Creator: Andrews, M.C.; McDaniel, F.D.; Duggan, J.L.; Mehta, R.; Lapicki, G.; Miller, P.D. et al.
Partner: UNT Libraries Government Documents Department

Projectile charge state dependence of M-shell ionization of Au, Pb, Bi, and U by 1. 42-MeV/amu fluorine ions

Description: The present study was undertaken to determine the direct ionization and electron capture contributions to vacancy production in the M-shells of /sub 79/Au, /sub 82/Pb, /sub 83/Bi and /sub 92/U for incident /sup 19//sub 9/F ions. M-shell x-ray production cross sections have been measured for 1.42-MeV/amu /sup 19//sub 9/Fq/sup +/ ions for q = 4,5,6,8,9. Enhancements in the target x-ray production cross sections were observed for projectiles with one and two K-shell vacancies over those without K-shell vacancies. Direct ionization and electron capture contributions to the vacancy production were extracted from the data and compared to the plane wave Born approximation and to the Oppenheimer-Brinkman-Kramers calculations of Nikolaev, respectively.
Date: January 1, 1980
Creator: Mehta, R.; Duggan, J.L.; McDaniel, F.D.; Andrews, M.C.; Wheeler, R.M.; Chaturvedi, R.P. et al.
Partner: UNT Libraries Government Documents Department

Removal of heavy metal ions from oil shale beneficiation process water by ferrite process

Description: The ferrite process is an established technique for removing heavy metals from waste water. Because the process water resulting from oil shale beneficiation falls into the category of industrial waste water, it is anticipated that this process may turn out to be a potential viable treatment for oil shale beneficiation process water containing many heave metal ions. The process is chemoremedial because not only effluent water comply with quality standards, but harmful heavy metals are converted into a valuable, chemically stable by-product known as ferrite. These spinel ferrites have magnetic properties, and therefore can be use in applications such as magnetic marker, ferrofluid, microwave absorbing and scavenging material. Experimental results from this process are presented along with results of treatment technique such as sulfide precipitation.
Date: January 1, 1991
Creator: Mehta, R.K.; Zhang, L.; Lamont, W.E. & Schultz, C.W. (Alabama Univ., University, AL (United States). Mineral Resources Inst.)
Partner: UNT Libraries Government Documents Department

L- and M-shell x-ray production cross sections of Nd, Gd, Ho, Yb, Au, and Pb by 25-MeV carbon and 32-MeV oxygen ions

Description: Article discussing research on L- and M-shell x-ray production cross sections of Nd, Gd, Ho, Yb, Au, and Pb by 25-MeV carbon and 32-MeV oxygen ions.
Date: October 15, 1987
Creator: Andrews, M. C.; McDaniel, Floyd Del. (Floyd Delbert), 1942-; Duggan, Jerome L.; Miller, P. D.; Pepmiller, P. L.; Krause, H. F. et al.
Partner: UNT College of Arts and Sciences