Search Documents

By G. L. Hundley

An anhydrous chlorination process has been developed by the Bureau of Mines for the production of copper, ferric oxide, and sulfur from chalcopyrite. The first part of the process is a chlorination step in which elemental sulfur and a mixture of iron-copper chlorides are produced. This paper describes the second step of the process in which the copper and iron chlorides are reacted with oxygen to selectively convert the iron chloride to ferric oxide and chlorine leaving the copper in the chloride form. The chlorides are pulverized and dropped countercurrent to a flow of oxygen in a vertical 20-cm-diam. reactor at 800° C. By leaching with brine, the copper chloride may be separated from the insoluble iron oxide and reduced to copper powder by electrowinning. It has been demonstrated that 70 to 80 pct of the iron can be converted to oxide in a single-stage operation with a chlorine content in the offgas of 80 pct. After removal of the oxygen, this chlorine could be recycled to the chlorination step. A two-stage operation will convert 98 to 99 pct of the iron in the mixture to insoluble oxides. The offgas from the second stage contains 70 pct chlorine.

Jan 1, 1974

By Lewis V. Wade

This report provides background information concerning a mine roof simulator currently being considered by the Bureau of Mines. The simulator is a mechanical device with the ability to simulate the forces and displacements associated with mine roof over an area 20 by 20 feet. The topics covered in the report include a conceptual description of the system, definition of system capabilities, discussion of how such capabilities were decided upon, description of available control modes, and a comparison between the mine roof simulator facility and similar facilities existing elsewhere.

Jan 1, 1974

By H. J. Lechtenberg

This Bureau of Mines report investigates solvent injection as a means of increasing oil production from low-gravity oilfields; thus, wells in two California oilfields that produce from reservoirs having low-gravity oil were injected with highly aromatic solvents to increase their oil recovery. The wells were either allowed to soak or the solvent was circulated for a period of time. In some of the wells, the solvent was followed by a slug of water. The post-stimulation production rate was considerably higher than the prestimulation rate of the wells. Wells in which the solvent was not followed by water showed an immediate increase in oil production, and essentially all of the solvent was recovered. The wells in which solvent was followed by water essentially showed a delay in the increase in oil production, thus indicating a temporary water block. The results show that the production rate is usually increased by the injection of solvent, and the method may prevent early abandonment of marginal producers. Cumulative post-stimulation oil production indicates that cyclic solvent injection treatment can be an economic success.

Jan 1, 1974

By C. Edward Chamberlain

A Bureau of Mines procedure was developed for the analysis of volatile matter in airborne coal dust-rock dust mixtures prior to, and resulting from, coal mine fires and explosions. Dust in the 10-to 20-mg weight range can be analyzed. Volatile matter is determined by a greatly scaled-down version of the empirical macro-scale method used by the Bureau. The alkaline earth carbonates in the rock dust are dissolved in acid prior to the volatile matter determination of the residue, and the rock dust content is calculated from the analysis of calcium and magnesium by atomic absorption.

Jan 1, 1974

By Henry E. Blake

The Bureau of Mines has been engaged in a continuing research effort to develop processes for increasing the recovery and utilization of fluorine from low-grade resources. This current research has shown that over 98 percent of the fluorine in phosphate rock is extracted when the ore is treated with excess phosphoric acid in the presence of water vapor at 150° to 180° C. More than 80 percent of the fluorine can be recovered as fluosilicic acid, which can then be converted to commercially useful hydrogen fluoride or fluorspar by previously developed Bureau processes. Extraction of P205 from the ore was about 98 percent in batch tests and 90 percent in semicyclic tests.

Jan 1, 1974

By Albert W. Deurbrouck

Dense-medium cyclone tests in 4-and 8-inch-diameter units have shown the ability of cyclones to make sharp separations down to 100 mesh when washing coals of a finer top size than normally fed to dense-medium cyclones. The reduced top size of the feed apparently allows the finer size particles to report to the proper product by reducing the effect of very coarse particles in the congested separation zone of the dense-medium cyclone.

Jan 1, 1974

By J. R. Allsup

In cooperation with the Division of Advanced Automotive Power Systems Development, Environmental Protection Agency, the Bureau of Mines studied a conventional spark-ignition engine as a prime mover for use in a hybrid system. The study involved both steady-state and transient engine operation with ignition timing, air-fuel ratio, exhaust gas recirculation, oxidizing type catalytic converters, engine speed, and power output as variables. Data were obtained from two 1971 model 350-cubic-inch-displacement engines mounted on engine dynamometer stands. When the hybrid engine was operated with an oxidizing catalyst at power output levels required for a 4,000-lb curb weight hybrid vehicle, carbon monoxide and hydrocarbon emissions could be reduced to approximately 2.0 grams and 0.3 gram per brake horsepower-hour, respectively. With exhaust gas recirculation, oxides of nitrogen emission levels could be reduced to approximately 1.2 grams per brake horsepower-hour.

Jan 1, 1974

By George S. Koch

A mathematical simulation model has been devised to guide the layout of underground mine workings, drill stations, and drill holes that are established in order to search for tabular ore bodies. Developed and tested for elliptical ore shoots in fissure veins in the Galena mine, Coeur d'Alene district, Idaho, the model can also be applied to ore bodies contained within sedimentary beds (for instance, many types of uranium, copper, and gold ore bodies) or other tabular structures. Programed for a time-shared digital computer, the model contains both stochastic and deterministic variables. Stochastic or natural variables include the number of ore shoots and their sizes, orientations, locations, and values. Deterministic or controllable variables include (1) locations and costs of workings; (2) drill-station locations and costs; and (3) drill hole azimuths, inclinations, lengths, and deflections, if any. For various assumptions about the stochastic variables, the model is run while the controllable variables are changed deliberately. Thus, layouts are devised to determine the percentages of the total number of assumed ore shoots found at different costs. In order to choose among the various layouts, cost-effectiveness measures are calculated.

Jan 1, 1974

By R. L. Schmidt

Research conducted over the past 20 years in France, Great Britain, and the United States on the use of the large-hole burn cut has established cer¬tain advantages for this system. Advantages include longer pull and more complete fragmentation from blast rounds. However, research is needed to establish a set of parameters for optimum performance. As part of the Bureau of Mines Advancing Mining Technology for Marginal Resources program, the Twin Cities Mining Research Center, Twin Cities, Minn., acquired a horizontal rotary drill capable of boring holes up to 24 in. in diameter. This was used for a series of underground experiments at White Pine mine, White Pine, Mich., during 1973. Exceptional results were obtained with a 12-1/4-in void hole that yielded up to 18 ft of pull in a 10- by 20-ft drift, Fragmentation was excellent, and the compactness of the muck pile facilitated loading.

Jan 1, 1975

By M. B. Shirts

Numerous alternative processes have been proposed as being potentially more economical or less polluting than the traditional smelting of copper sulfide concentrates. One such process as recently developed in the laboratory by the Bureau of Mines is composed of a two-stage fluid-bed, oxidation-reduction roasting followed by ammoniacal leaching, solvent extraction, and electrowinning. A copper-leaching recovery of 97.4 percent was obtained, and electrolysis of the acid strip solution deposited metal assaying 99.99 percent copper. The roaster gases contain over 95 percent of the sulfur at a concentration of 12 percent which is better suited for acid making or elemental sulfur production than conventional smelter gas. When considering byproduct recovery, a preliminary estimate indicates copper production costs are com-parable to the conventional smelters.

Jan 1, 1975

By J. B. Janus

This report continues a series of analyses of coal samples made by the Bureau of Mines in connection with the yearly purchase of several million tons of coal for various Government agencies. Listed are the analytical data on the composition and quality of tipple and de livered samples of coal collected during fiscal year 1974.

Jan 1, 1975

By C. R. Summers, J. N. Murphy

In response to the Coal Mine Health and Safety Act of 1969, mandatory noise standards have been developed that specify time-noise limits of mine personnel exposure. Most affected by elevated noise levels is the pneumatic roof bolter operator, both in terms of levels near or in excess of 115 dbA and in terms of length of exposure. Therefore, the principal emphasis of this Bureau of Mines report is on pneumatic drill noise control. It is not the intent of this report to suggest any drill redesign; instead, methods are suggested to reduce the noise level by complementing existing machines. An integral muffler system and a separate muffler system were tested in an attempt to lower pneurnaric drill noise levels. Pneumatic drills, when new, operate at about 115 dbA when drilling in sandstone. Using the drill muffler systems, it was possible to decrease the noise level of a 115 -dbA s rope drill to approximately 100 dbA.

Jan 1, 1974

By C. R. Summers

In response to the Coal Mine Health and Safety Act of 1969, mandatory noise standards have been developed that specify time-noise limits of mine personnel exposure. Most affected by elevated noise levels is the pneumatic roof bolter operator, both in terms of levels near or in excess of 115 dbA and in terms of length of exposure. Therefore, the principal emphasis of this Bureau of Mines report is on pneumatic drill noise control. It is not the intent of this report to suggest any drill redesign; instead, methods are suggested to reduce the noise level by complementing existing machines. An integral muffler system and a separate muffler system were tested in an attempt to lower pneumatic drill noise levels. Pneumatic drills, when new, operate at about 115 dbA when drilling in sandstone. Using the drill muffler systems, it was possible to decrease the noise level of a 115-dbA stope drill to approximately 100 dbA.

Jan 1, 1974

By Robert W. Freedman, Robert L. Craft, William G. Humphrey

As part of a continuing effort to reduce the weight and bulk of equipment that mining personnel must carry underground, the Bureau of Mines and the Mining Enforcement and Safety Administration (MESA) investigated accurate and convenient gas samplers for use by mine inspectors in sampling mine atmospheres. The samplers are septum-stoppered glass vials commonly used for routine blood sampling. These lightweight, compact samplers yield results comparable with those obtained with conventional bottle samplers of 250-ml nominal capacity.

Jan 1, 1975

By Robert W. Freedman

As part of a continuing effort to reduce the weight and bulk of equipment that mining personnel must carry underground, the Bureau of Mines and the Mining Enforcement and Safety Administration (MESA) investigated accurate and convenient gas samplers for use by mine inspectors in sampling mine atmospheres. The samplers are septum-stoppered glass vials commonly used for routine blood sampling. These lightweight, compact samplers yield results comparable with those obtained with conventional bottle samplers of 250-ml nominal capacity.

Jan 1, 1975

By M. E. Poad

Structural properties of steel-fiber-reinforced shotcrete and polymer-impregnated shotcrete, both plain and fiber-reinforced, were investigated by the Federal Bureau of Mines, Spokane Mining Research Center. The research center has found that flexural strengths can be increased by as much as 106 percent, and splitting-tensile strength by 50 percent, by introducing randomly oriented steel fibers. A slight decrease of compressive strength was found in the fiber-reinforced shotcrete. Polymer-impregnated shotcrete exhibited a threefold to fourfold increase in compressive and splitting-tensile strength. The techniques of preparing shotcrete with the dry process, using both fast-set agents and regulated-set cement, are described, along with the results of physical-property testing. Physical properties include compressive and splitting-tensile strengths, tangent and secant moduli, and stress-strain curves for plain shotcrete, fiber-reinforced shotcrete, and polymer-impregnated plain and fiber-reinforced shotcrete. Flexural strengths for plain and fiber-reinforced shotcrete are also reported. Steel-fiber shotcrete is the more promising of the new structural materials for ground support, and additional research is recommended.

Jan 1, 1975

By A. Landsberg

Chlorination of sulfide minerals and several prepared metal sulfides was studied. The resulting data were analyzed with respect to kinetics of the reactions and application to nonpolluting methods of winning metals from sulfide ores. Sulfides of iron, copper-iron, nickel, lead, zinc, silver, bismuth, arsenic, rhenium, molybdenum, and tungsten were investigated at temperatures up to 600° C. Copper-iron, lead, and zinc sulfides showed at least some product-controlled (parabolic) kinetics at the lower temperatures within the temperature ranges studied, but only nickel and silver sulfides had chlorination rates controlled by parabolic reaction kinetics in the commercially important temperature range of 450° to 600° C.

Jan 1, 1975

By J. E. Tress

The Bureau of Mines has developed a process to utilize waste heat from electric arc steelmaking furnace gases to preheat the ferrous material charged to the furnace. Four heat exchangers were designed, tested, and operated successfully on 1-ton electric arc furnaces. Briquets and pellets were charged continuously, both countercurrent to the hot furnace offgasses and at ambient temperatures. A comparison of the electrical energy consumed in each situation showed that preheating can lower energy requirements as much as 15.6 percent.

Jan 1, 1975

By F. P. Haver

Because State and Federal agencies have limited the amount of sulfur oxides that can be discharged to the atmosphere, most copper smelters plan to convert the S02 in offgases to sulfuric acid. In some cases, however, it might be preferable to use a nonsmelting method to fix the sulfur in the form of a discardable product. Research by the Federal Bureau of Mines has shown that sulfur in copper concentrate can be converted into insoluble anhydrite (CaS04) by roasting the concentrate with lime (CaO). After leaching the calcine to recover metal values, the residue may be discarded without harm to the environment. The process can use a rougher flotation product, thus reducing separation costs and saving valuable minerals (for example, molybdenite) that are now lost in making cleaner concentrate. In tests, rougher concentrate was pelletized with the theoretical amount of lime and roasted for 1 hour in a 6-1/2-inch-ID by 11-foot-long rotary kiln at 700° C. Sulfur retention was about 97 percent. Leaching the calcine with 20 percent RCI extracted approximately 99 percent of the copper, 73 percent of the iron, and 91 percent of the molybdenum. After the molybdenum was removed from the leach solution by adsorption on activated carbon, copper with a purity in excess of 99 percent was obtained by cementation on sponge iron. The strip solution then could be spray-roasted at 500° C to recover the RCI for recycle and obtain F2O3 as a byproduct.

Jan 1, 1975

By F. P. Haver

A method to recover copper and elemental sulfur from chalcopyrite concen¬trate, using a ferric chloride leach, CuFeS2 + 3FeCl3 ? CuCl + 4FeCl2 + 2S, was reported by the Federal Bureau of Mines in 1971 (Report of Investigations 7474). Since that time, additional work has been done to improve certain steps in the procedure; that is, the recovery of sulfur from the leach residue, the recovery of copper and iron from the leach solution, and the regeneration of the leach solution. It was determined that over 99 pct of the elemental sulfur in the leach residue could be extracted at ambient temperature with an ammonium sulfide solution. Heating the pregnant solution precipitated crystals of rhombic sulfur (99.5 pct purity) and liberated ammonia and hydrogen sulfide for recycle. Copper with a purity in excess of 99 pct was obtained from the leach solution by electrolysis, using a diaphragm cell, with an energy requirement of less than 0.7 kW-hr/lb. Metal was deposited as a weakly adherent powder that could be easily dislodged from the cathode and withdrawn continuously from the cell in the form of a slurry. During electrolysis, part of the Fe(II) was oxidized to Fe (III) at the anode so there was no chlorine evolution. The leach solution was regenerated by direct oxidation of the spent electrolyte with air or oxygen in a turboaerator at 80° C. This precipitated the iron dissolved during leaching in an easily filterable form, Fe203.xH20, and converted the remaining Fe(II) to Fe(III).

Jan 1, 1975