Nitrous Sulfuric Acid Pressure Leaching of Platinum Group Metals Sulfide PGM
Simplistically, nitrogen species oxidize the sulfide and solubilize some of the metal values. In essence, the silver, copper and less noble metals are dissolved in the leach. The slurry is screened, thickened and filtered. Two different solids are produced. First, sulfur pellets are recovered. Then, the insoluble fine leach residue, consisting primarily of lead sulfate, […]
Acid Rain and Smelter Agreement
In July 1985, as the U.S. copper industry contracted and the Mexican industry expanded, a transborder pollution agreement was signed which included smelter air pollution control in the “Gray Triangle”: Cananea, Nacozari and Douglas. Since then the Douglas smelter has been closed, a year earlier than initially required; though its new smelter is operating, SO2 […]
Vacuum Induction Melting
The effect of fluoride inclusions on the properties of titanium produced from the Bureau of Mines developed induction slag melting process is of concern to the titanium industry. The objective of the research was to determine the effect of removing the nonconductive molten calcium fluoride (CaF2) slag used as an insulator between the titanium and […]
Aluminium Recycling Furnace Refractories
We studied the problem of corundum formation on refractory linings in aluminum recycling furnaces. A laboratory test was developed for evaluating refractories in contact with molten recycled aluminum and identifying the mechanism of corundum formation. A test apparatus was designed and constructed to evaluate the performance of refractory samples. Corundum mechanism formation studies indicated that […]
Effect of Fluoride on Slag
The effect of fluoride inclusions on the properties of titanium produced from the Bureau of Mines developed induction slag melting process is of concern to members of the titanium industry. The objective of the research was to determine the effect of CaF2 inclusions on the properties of titanium and its survival rate during melting. The […]
Hydrochloric Acid Leaching of Merrill Crowe Precipitate
Significant copper levels were anticipated in the precipitate due to cyanide soluble species in the ore. Original design called for a hydrochloric acid leach of precipitates to remove excess zinc and copper prior to fusion. It was thought that the use of hydrochloric acid would result in low silver losses because of the low solubility […]
Natural Flake Graphite & Carbon Fiber VS Dolomite-Carbon Refractories
We investigated the role of imported natural flake graphites in dolomite-carbon refractories used in steelmaking processes and evaluated carbon fibers as a potential substitute. Varying quantities (1.5-30 pct) of natural flake graphite and carbon fibers were added to test samples. The effect of the additions on modulus of rupture (75°-2,750° F), deformation under load (2,750° […]
Effect of Impurities on Gold Adsorption on Activated Carbon
We performed batch equilibrium contact experiments to examine the ability of activated coconut-shell carbon to adsorb various metal cyanide complexes. Tests were also conducted to determine the effect these cyanide complex impurities might have on the adsorption of gold by the activated carbon. Metal cyanide species included in the investigation were antimony, arsenic, cadmium, calcium, […]
Silver Refining
Precipitates mixed with diatomaceous earth from the precipitation filter unit are dried in a filter press and mixed with borax and soda ash. This mixture is then melted in a diesel-fired furnace and cast in a silver dore cone. This cone is then melted in another furnace into an anode 7 inches by 9 inches […]
Electric Arc Furnace
The U.S. Bureau of Mines is conducting an ongoing research project to better understand the phenomena involved within electric arcs utilized in electric furnace steelmaking. With a better understanding of the physical and electrical characteristics involved, dynamic or predictive control of electric arc furnaces may be possible. A mathematical model is presented, but not solved, […]