California Mining Journal (PH 16-14)(April 1943) (36 pages)

California Mining Journal, April, 1943 Nine enormous capacity of a single small unit is its outstanding feature. Advances in Pyrometallurgy In California’s early base-metal production days, the coarse sulphide ores, encountered in depth, were piled in heaps on level ground and, with the aid of cordwood, set on fire and allowed to “burn” slowly for several months, at which time they became sufficiently low in sulphur so as to be amenable to blast furnace or reverbratory furnace reduction. Since this early day, roasting has progressed through the various stages of hand-rabbling in long stationary furnaces, of mechanically rabbled vertical shaft furnaces, to the present-day large capacity “flash” roasters. The “several months” once required for roasting can now be accomplished in a few hours, the cost Jikewise being reduced to a mere fraction of that of the early days, and with a total elimination of the noxious fumes attending the early-day roasting where all waste gases were, perforce, discharged into the atmosphere. The low cost of installation of flash roasters, their low operational cost and high tonnage capacity has led to even the dry grinding of lump ores so that they, too, may partake of the low costs of operation as contrasted with the older roasters utilizing only lump ores. Pyrometallurgical Separation and Concentration There are, in nature, certain types of mineralogical occurrences of the metals of copper, lead, zinc and iron which have not proven amenable to the numerous and various methods of concentration or separation prior to smelting and, further, their association creates deleterious combinations no matter what manner of smelting is followed. The metal zinc is the worst offender of the lot, and its presence may be considered a just reason for the assessment of a penalty in smelting either lead or copper, while at the same time the particular ore may not be acceptable to a zinc plant because of high values in iron, lead or copper. This state of affairs was in a great measure remedied by the advent of flotation, especially where the individual constituent minerals were separable by fine grinding; but California’s desert ores are amenable neither to flotation nor to dirct smelting. These ores are the oxidized surface and near-surface minerals of lead and zine; principally the silicate and carbonate of zinc with minor Purr J. RAGOOLAND 754-58 Natoma St. zinc sulphide; the sulphate and sulphide of lead and containing small amounts of the oxide-copper minerals, a few dollars in gold value and several ounces of silver. The fine grained massive sulphide ores of the Foothills Copper Belt and the Shasta Region also provide some ores not amenable to flotation or smelting and hence it is to the pyrometallurgical separation of these mutually interfering metals that we must turn. The Waelz Process In 1927, in treating the zinc silicate dumps ef the Jead and zinc mines of Upper Silesia (Poland), research work on the volatilization temperatures of lead and zinc brought on experimentation culminating in what is now known as the “Waelz process.” This precess. now in active operation at several places in the United States, is particularly applicable to our desert ores, and is in part applicable to other California ores. The cost of the process, as to initial investment as well as day-to-day operation, is not at all excessive, In fact, the sale of the recovered zine product should return more than the cost of the operation, thus saving the amount of the formerly assessed penalty and its attendant non-payment for zinc. The added return in the form of higher prices per ton for the high-grade lead oxide concentrates also adds to the total eventual return per ton of mined ore. The effect of a locally situated plant of this type with low freight rates and high return per ton will enable California’s mine operators to enjoy a greater profit on ore now mined, or conversely, it will increase their reserves of available marketable ore. In either case the potential metal production of California will be greatly enhanced. Pyrometallurgical Recovery of Zinc from Slag In the case of a high copper ore or concentrate containing relatively small amounts of zinc, it is the practice to force all the zinc into the slag. In the past, this slag has been discarded, but in recent years a method of zinc recovery has been worked out so that today zinc recovery from current as well as old slags is quite profitable. One California copper property has available, at today’s high zinc price, more gross value in their old slag dumps than was originally derived from the copper ore treated in the furnace. Other Methods There has been some interest in the inRagooland-Rroy L Puong HEmlock 1143 stallation of electrothermic plants to utilize new hydroelectric power and zinc retort plants that require a maximum of fuel, both gag and oil for heating and coal for chemical reactions, but the cost of the former and the high labor consumption of the latter would hold against either method for the duration. Dust, Fume and Smoke Abatement In the early years of smelting in California, the smoke, dust and fume from the various smelting plants were commonly discharged freely into the atmosphere. This practice led, ultimately, to numerous legal suits aimed at abating this nuisance, the practice of which was legally curtailed in various areas about 1915. Since that date, however, many advances have been made leading to the extraction of dust, fume and acid gas from the discharge of smelter stacks, so that today this nuisance need not be perpetrated upon the adjacent countryside and, further, the materials saved by extraction from these gases may be either returned to the furnace for the extraction of their metallic content or converted into salable by-products. The removal of the acid-gas content requires either the absorption of the sulphur dioxide by basic aluminum sulphate or the making of sulphuric acid by the oxidation of the sulphur dioxide. Sulphuric Acid from Smelter Gases In making sulphuric acid from cleaned smelter gases, there are two processes: (1) the “Chamber” proces: which effects the necessary union of sulphur dioxide, oxygen and water through the agency of the oxides of nitrogen. and (2) the “Contact” process in which sulphur dioxide and oxygen are caused to unite under proper temperature ard pressure conditions, by passing the gases (meintained at optimum sulphur dioxide content) over a “contact” or catalytic agent, which is usually finely disseminated platinum held on an asbestos screen. The resulting sulphur trioxide gas is converted to sulphuric acid by merely bringing it into contact with water. The contact process is the more widely used, especially in the forming of the higher strengths of acid. The uses of sulphuric acid are very many, perhaps the greatest volume of consumption being that of forming soluble fertilizers from the natural phosphates. Otherwise, nearly every chemical process utilizes sulphuric acid somewhere in its chemical manipulations. Gro. L. Broy San Francisco, Calif. Specializing in Recovery of Strategic Metals andGold from Black Sand and Placer Concentrates PROMPT SETTLEMENT ON VALUES RECOVERED In Our Analytical Departmeut We Make Analyses for STRATEGIC METALS—Spect WE ALSO SPECIALIZE IN THE RECOVERY OF Our Quantitative Analytical Charges conform with rates published in U. S. Bureau o We Offer Accurate Spectrographic Qualitative Analyses for $6; Gold Tests, SUBMIT YOUR SAMPLES rographic, Qualitative-Quantitative. PLATINUM AND IRIDUM { Mines Paper IC6999R, which are very reasonable, $1; Platinum Detection Tests, $1.50— Field Representatives :— A. S. Hasty, Oakland J. A. Garp, Auburn G. A. Botas, Los Angeles E. L. Var, Ati :caderv.

California Mining Journal, April, 1943 Nine enormous capacity of a single small unit is its outstanding feature. Advances in Pyrometallurgy In California’s early base-metal production days, the coarse sulphide ores, encountered in depth, were piled in heaps on level ground and, with the aid of cordwood, set on fire and allowed to “burn” slowly for several months, at which time they became sufficiently low in sulphur so as to be amenable to blast furnace or reverbratory furnace reduction. Since this early day, roasting has progressed through the various stages of hand-rabbling in long stationary furnaces, of mechanically rabbled vertical shaft furnaces, to the present-day large capacity “flash” roasters. The “several months” once required for roasting can now be accomplished in a few hours, the cost Jikewise being reduced to a mere fraction of that of the early days, and with a total elimination of the noxious fumes attending the early-day roasting where all waste gases were, perforce, discharged into the atmosphere. The low cost of installation of flash roasters, their low operational cost and high tonnage capacity has led to even the dry grinding of lump ores so that they, too, may partake of the low costs of operation as contrasted with the older roasters utilizing only lump ores. Pyrometallurgical Separation and Concentration There are, in nature, certain types of mineralogical occurrences of the metals of copper, lead, zinc and iron which have not proven amenable to the numerous and various methods of concentration or separation prior to smelting and, further, their association creates deleterious combinations no matter what manner of smelting is followed. The metal zinc is the worst offender of the lot, and its presence may be considered a just reason for the assessment of a penalty in smelting either lead or copper, while at the same time the particular ore may not be acceptable to a zinc plant because of high values in iron, lead or copper. This state of affairs was in a great measure remedied by the advent of flotation, especially where the individual constituent minerals were separable by fine grinding; but California’s desert ores are amenable neither to flotation nor to dirct smelting. These ores are the oxidized surface and near-surface minerals of lead and zine; principally the silicate and carbonate of zinc with minor Purr J. RAGOOLAND 754-58 Natoma St. zinc sulphide; the sulphate and sulphide of lead and containing small amounts of the oxide-copper minerals, a few dollars in gold value and several ounces of silver. The fine grained massive sulphide ores of the Foothills Copper Belt and the Shasta Region also provide some ores not amenable to flotation or smelting and hence it is to the pyrometallurgical separation of these mutually interfering metals that we must turn. The Waelz Process In 1927, in treating the zinc silicate dumps ef the Jead and zinc mines of Upper Silesia (Poland), research work on the volatilization temperatures of lead and zinc brought on experimentation culminating in what is now known as the “Waelz process.” This precess. now in active operation at several places in the United States, is particularly applicable to our desert ores, and is in part applicable to other California ores. The cost of the process, as to initial investment as well as day-to-day operation, is not at all excessive, In fact, the sale of the recovered zine product should return more than the cost of the operation, thus saving the amount of the formerly assessed penalty and its attendant non-payment for zinc. The added return in the form of higher prices per ton for the high-grade lead oxide concentrates also adds to the total eventual return per ton of mined ore. The effect of a locally situated plant of this type with low freight rates and high return per ton will enable California’s mine operators to enjoy a greater profit on ore now mined, or conversely, it will increase their reserves of available marketable ore. In either case the potential metal production of California will be greatly enhanced. Pyrometallurgical Recovery of Zinc from Slag In the case of a high copper ore or concentrate containing relatively small amounts

of zinc, it is the practice to force all the zinc into the slag. In the past, this slag has been discarded, but in recent years a method of zinc recovery has been worked out so that today zinc recovery from current as well as old slags is quite profitable. One California copper property has available, at today’s high zinc price, more gross value in their old slag dumps than was originally derived from the copper ore treated in the furnace. Other Methods There has been some interest in the inRagooland-Rroy L Puong HEmlock 1143 stallation of electrothermic plants to utilize new hydroelectric power and zinc retort plants that require a maximum of fuel, both gag and oil for heating and coal for chemical reactions, but the cost of the former and the high labor consumption of the latter would hold against either method for the duration. Dust, Fume and Smoke Abatement In the early years of smelting in California, the smoke, dust and fume from the various smelting plants were commonly discharged freely into the atmosphere. This practice led, ultimately, to numerous legal suits aimed at abating this nuisance, the practice of which was legally curtailed in various areas about 1915. Since that date, however, many advances have been made leading to the extraction of dust, fume and acid gas from the discharge of smelter stacks, so that today this nuisance need not be perpetrated upon the adjacent countryside and, further, the materials saved by extraction from these gases may be either returned to the furnace for the extraction of their metallic content or converted into salable by-products. The removal of the acid-gas content requires either the absorption of the sulphur dioxide by basic aluminum sulphate or the making of sulphuric acid by the oxidation of the sulphur dioxide. Sulphuric Acid from Smelter Gases In making sulphuric acid from cleaned smelter gases, there are two processes: (1) the “Chamber” proces: which effects the necessary union of sulphur dioxide, oxygen and water through the agency of the oxides of nitrogen. and (2) the “Contact” process in which sulphur dioxide and oxygen are caused to unite under proper temperature ard pressure conditions, by passing the gases (meintained at optimum sulphur dioxide content) over a “contact” or catalytic agent, which is usually finely disseminated platinum held on an asbestos screen. The resulting sulphur trioxide gas is converted to sulphuric acid by merely bringing it into contact with water. The contact process is the more widely used, especially in the forming of the higher strengths of acid. The uses of sulphuric acid are very many, perhaps the greatest volume of consumption being that of forming soluble fertilizers from the natural phosphates. Otherwise, nearly every chemical process utilizes sulphuric acid somewhere in its chemical manipulations. Gro. L. Broy San Francisco, Calif. Specializing in Recovery of Strategic Metals andGold from Black Sand and Placer Concentrates PROMPT SETTLEMENT ON VALUES RECOVERED In Our Analytical Departmeut We Make Analyses for STRATEGIC METALS—Spect WE ALSO SPECIALIZE IN THE RECOVERY OF Our Quantitative Analytical Charges conform with rates published in U. S. Bureau o We Offer Accurate Spectrographic Qualitative Analyses for $6; Gold Tests, SUBMIT YOUR SAMPLES rographic, Qualitative-Quantitative. PLATINUM AND IRIDUM { Mines Paper IC6999R, which are very reasonable, $1; Platinum Detection Tests, $1.50— Field Representatives :— A. S. Hasty, Oakland J. A. Garp, Auburn G. A. Botas, Los Angeles E. L. Var, Ati :caderv.