Model for ferric sulfate leaching of copper ores containing a variety of sulfide minerals: Part II. Process modeling of in situ operations

The Lin-Sohn Leach simulation (DLS) computer model was used to simulate copper extraction from run-of-mine fragment size distributions expected for underground modifiedin situ solution mining. Ventilation was found to be a key variable in obtaining good copper recoveries, and the rate of ventilation was found to vary with ore type and through time. Improving recoveries and recovery rates with improved fragmentation was found to be more difficult than expected. Limitations on surface kinetics and bacterial ferric ion generation often erode benefits expected from reduction in diffusion limitation. Control of fines formation is difficult with the current state of the art in blasting. Fines may also improve the initial leaching rate at the expense of increased ventilation cost and more limited ultimate recovery. Ore grade was found to be less important to solution mining than to conventional copper recovery. Mineralogy was found to be crucial to solution mining economics. Mineralogy affects the grade of the ore and the importance of that grade. Pyrite was found to be helpful in increasing the ultimate copper recovery from ore but, at the same time, was found to reduce the rate of that recovery. Recovery rates were found to be very sensitive to mineral grain size, and calibration of DLS to a given ore may be especially important in this variable. Tortuosity and porosity of ore fragments appear relatively unimportant over the ranges typical of sulfide copper porphyry ore. Modifiedin situ solution mining appears to be a competitive option when a favorable ore type is available. The DLS computer code may be a valuable aid in screening options and selecting the most favorable orebodies.     

Integral measurements in a simulated fast breeder reactor blanket

Much of the breeding of fissile material and a significant fraction of the energy production in proposed fast breeder reactors will occur in a blanket of fertile material surrounding the reactor core. Current uncertainties in neutron cross sections and calculational methods have much greater significance for blanket design than for core design. The Purdue University Fast Breeder Blanket Facility (FBBF), designed to simulate the neutron behavior in fast breeder reactor blankets, has recently been completed. The facility is now being used to perform integral neutron reaction rate measurements. Such measurements provide tests of nuclear cross sections and calculational methods used in the design of fast breeder reactor blankets.     

Process mineralogy of suspended particles from a simulated commercial flash smelter

Polished sections of pyrometallurgical intermediate products from a simulated commercial flash furnace were examined by reflected light microscopy, scanning electron microscopy-energy dispersive spectrometry and electron backscatter analysis, and microprobe analysis for phase and textural relationships. The smelter feed is a copper concentrate from a porphyry copper deposit. The concentrate consists primarily of chalcopyrite, bornite, and pyrite with smaller amounts of covellite, chalcocite, molybdenite, magnetite, galena, and sphalerite. The flash furnace reactions for pyrite and chalcopyrite can be observed by reflected light microscopy. Reacted angular particles of pyrite exhibit successive rims of fibrous pyrrhotite and hematite or magnetite. Reacted angular chalcopyrite particles show successive rims of bornite, digenite, and chalcocite. Spherical particles, formed by the complete melting of former pyrite and chalcopyrite particles, consist of variable amounts of granular pyrrhotite with magnetite rims and minor hematite. Spherical particles, formed by the complete melting of former chalcopyrite particles, exhibit exsolution intergrowths with varying proportions of intermediate solid solution, bornite, digenite, and chalcocite, and have rims of hematite, magnetite, and copper-iron spinel. Electron microprobe analyses show that the iron oxides contain significant copper and minor zinc in their structures. Sphalerite and molybdenite do not show evident mineralogical reactions.     

Resonance properties of dielectric waveguide gratings: theory andexperiments at 4-18 GHz

The guided-mode resonance characteristics of dielectric waveguide gratings are presented. The sharp resonance features predicted theoretically are experimentally observed in the microwave region (4-18 GHz) and are shown to be in agreement with theory     

Okadaic acid inhibits alkaline phosphatase activity in MC3T3-E1 cells

Alkaline phosphatase activity is regulated by various hormones and growth factors at least in part through the phosphorylation of target proteins during the bone cell differentiation. To investigate the role of protein phosphorylation in alkaline phosphatase activity in MC3T3-E1 osteoblast, we used okadaic acid which is a potent specific inhibitor of serine/threonine protein phosphatases to type 1 and 2A. Alkaline phosphatase activity in cellular layer was measured by spectrophotometer using p-nitrophenyl phosphate as substrate and data were expressed as p-nitrophenyl of nmol/min/mg of protein. Okadaic acid (1-50 ng/ml) caused the inhibition of alkaline phosphatase activity in MC3TC-E1 cells. At 50 ng/ml of okadaic acid showed the maximal inhibitory effect on alkaline phosphatase activity. Okadaic acid (50 ng/ml) also inhibited alkaline phosphatase activity in all differentiation stages. These results indicate that okadaic acid inhibits alkaline phosphatase activity in MC3T3-E1 cells.     

Kinetics of the reaction between hydrogen sulfide and lime particles

The reaction between hydrogen sulfide and lime is important, among others, as a component reaction of the hydrogen reduction of metal sulfides in the presence of lime, and in the desulfurization of fossil fuels. The results of experiments on the kinetics of this reaction are presented in this paper. The experiments were carried out in the temperature range 873 to 1073 K, using a thermogravimetric analysis technique. A “pore blocking” model was found to fit the reaction rate, which was initially rapid and leveled off at less than the complete conversion. An activation energy of 76.1 kJ/mol (18.2 kcal/g-mole) was obtained. The reaction was first order with respect to hydrogen sulfide concentration in a gaseous mixture with hydrogen. A higher initial moisture content in the calcium oxide particles resulted in a considerably higher reaction rate. Formerly Graduate Student in the Department of Metallurgy and Metallurgical Engineering, University of Utah     

Simultaneous fluid-solid reactions in porous solids: Reactions between one solid and two fluid reactants

A general model describing simultaneous independent reactions between one solid reactant and two fluid reactants is presented. Such reaction systems ar attention in the areas of oil shale retorting, direct reduction of metal oxides with reformed natural gas, coal gasification, etc.The model has been formulated in general terms so as to allow the incorporation of specific details of an actual system. The law of additive reaction t previously proposed for single fluid-solid reactions has been applied to the reaction system under consideration, and it has yielded useful approximate solutions for various aspects of the simultaneous reactions, which otherwise must be obtained by numerical methods.     

The selective oxidation of mixed metal sulfides with lime in the presence of steam without emitting sulfur-containing pollutants

The selective oxidation of mixed metal sulfides with lime in the presence of steam was studied as a function of the mixing ratio of the constituents, temperature, and steam concentration. Two combinations of samples were used in this study: ZnS/PbS/CaO and ZnS/FeS/CaO. The steam oxidizes one or both of the metal sulfides, and the hydrogen sulfide produced reacts with lime to form calcium sulfide and regenerate steam. There is no net consumption or generation of gaseous species; therefore, this process can be carried out in a closed system. The free energy of the reaction is negative only for certain metal sulfides, and thus selective oxidation for mixed sulfides can be achieved. An overall rate equation developed in this work satisfactorily predicted the experimental data obtained in the temperature range 823 to 1113 K. The potential implications of the results of this work in the treatment of complex sulfide ores are discussed. This paper is based on a presentation made in the T.B. King Memorial Symposium on “Physical Chemistry in Metals Processing” presented at the Annual Meeting of The Metallurgical Society, Denver, CO, February, 1987, under the auspices of the Physical Chemistry Committee and the PTD/ISS.     

Successive gas-solid reaction model for the hydrogen reduction of cuprous sulfide in the presence of lime

As an alternative to conventional smelting processes for producing metals from sulfide ores, which suffer from SO₂ emission problems, direct reduction in the presence of lime has in recent years attracted much attention. In this work, a mathematical model of successive gas-solid reactions in a porous pellet has been applied to the hydrogen reduction of cuprous sulfide (Cu₂S) in the presence of lime. The model has been formulated by incorporating the intrinsic kinetics of the individual reactions obtained from separate experiments, and compared with the experimental results on the hydrogen reduction of chalcocite mixed with lime particles. The model predictions were in good agreement with experimental measurements of the overall rate of reaction and the degree of sulfur fixation over a wide range of experimental conditions. The mathematical model not only can predict the performance of a given system but also enables one to design the optimum pellet properties and reaction conditions in terms of the reaction rate and sulfur fixation. Formerly Graduate Student in the Department of Metallurgy and Metallurgical Engineering, University of Utah.