Showing papers in "Mineral Processing and Extractive Metallurgy Review in 1985"

Magnesia—An important Industrial Mineral: A Review of Processing Options and Uses

Abstract: Magnesia is widely used as an important component in basic refractories, as an animal feed supplement, fertilizer, insulation material, cement, and in several environmental control procedures. The major sources of magnesia are magnesite, seawater and brines. Less important sources are dolomite, bitterns and salt deposits. This review outlines the more significant physical and chemical processes for the production of the various grades of magnesia and discusses some of the more important uses of magnesia. Consumption of magnesia in basic refractories is slowly declining and future market growth will be largely restricted to chemically reactive magnesia (caustic calcined magnesia).

Grinding Mill Power Consumption

Abstract: Equations and associated procedures for estimating power draw are inconsistent. The various methods are discussed critically. Topics discussed are: diameter exponent; loading; speed correction factors; buoyancy effects; liner wear, and effect of load dilation. Balance between effective load weight and torque-arm length determines direction of power change at critical operating points (e.g. incipient overloading). Consistent procedures for calculating the effect of charge weight on power draw in different mill types are given. Error analysis shows that the accuracy of power estimation and data correlation may depend as much on the accuracy of measurement of mill dimensions and operating variables as on the particular equation used. An equation based on the torque-arm model, and providing a compromise between existing equations, is proposed. It is simple and suitable for correlating data and estimating power draw. A data-base of power related parameters documenting mill scale-up during the past few decades ...

Shifting Patterns of Supply and Demand in the World Copper Industry

Abstract: Copper industry analysts are predicting the continued decline of traditional copper producing centers in the developed world, particularly the United States, in contrast to the continued robust growth of the industry in underdeveloped countries and consuming centers outside the U.S. These predictions are based on current trends and the theory suggested by Malenbaum of demand maturation, according to which declines in the intensity of metals' use may be an inevitable function of rising per capita income and industrial aging. On supply side, falling grades of ore, rising costs and constraints on environmental damage would aggravate the rate of such declines. This paper examines the economic, geo-technical and engineering bases for making such predictions of significant shifts in the pattern of copper supplies and demands within the framework of a multi-market equilibrium model under free trade. It finds little under competitive conditions to demonstrate that either rapid world growth of copper demands or dr...

Studies on the Flotation of Chrysocolla

Abstract: This paper summarizes the results of numerous investigations on the structure, surface properties and flotation behaviour of chrysocolla. Until the late sixties, chrysocolla was considered to be a hydrated copper silicate without fixed mineral composition. Recent articles, however, have revealed that chrysocolla is a definite mineral having an orthorhombic unit cell and a characteristic fibrous structure. The results reported by various researchers seem to indicate that mobile superficial copper ions, as well as the silica skeleton, are responsible for the similarities observed in the surface properties of all chrysocolla samples which prevail in spite of the well known differences in composition of chrysocolla specimens. The equilibrium diagram for the system copper oxide-silica-water has been introduced as a valuable tool for predicting the surface properties of chrysocolla. However, the conditioning pH is the most critical parameter which determines the surface characteristics and the flotation behavio...

Grinding Mill Operation and Scale-up: Theory and Equations

Abstract: Current scale-up equations are discussed critically. The ratio: rotational mass flow of media to axial mass flow of ore—a concept recently introduced—has been refined and extended. It can account for similar breakage in scaled mills by the trade-off between ore/media encounter frequency and average impact energy with specific energy constant. Further consequences are that in scaled mills the average number of revolutions during the residence of an element of ore in the mill, and ore flow path tortuosity, both decrease strongly while axial flow increases very strongly as mill diameter increases. These factors can result in capacity limitations when mill diameters reach a critical range, especially for coarser feed sizes of certain ores. Autogenous mills can operate satisfactorily at relatively large diameters because their large active volumes are occupied either completely or mostly by ore, resulting in higher values of nominal residence time and flow path tortuosity.

The Phosphatic Clay Waste Problem—Flocculation as a Possible Solution

Abstract: The problem of disposing of the minus 150-mesh phosphate clay waste generated during mining of phosphate rock is described. Flocculation techniques such as the Bureau of Mines polyethylene oxide-screen dewatering system are discussed. Results from field test dewatering experiments with the Bureau technique, at three different phosphate mines, showed that material initially containing about 2 to 4% solids was dewatered to a solids content of 19 to 24%. The dewatered material, when placed in a pit, continued to dewater. Results for several experiments are discussed.

Status of Underground Coal Gasification

Abstract: Underground coal gasification appears to be one of the most attractive routes for synfuels from coal because the process can produce methanol and substitute natural gas at prices competitive with existing energy sources. The technical feasibility of underground coal gasification has been well established by small scale field tests. Cost estimates based on the resultant data are favorable. The environmental effects associated with the technology appear to be acceptable. Successful commercialization of the process would probably triple the proven reserves of U.S. coal, which would be sufficient to last for hundreds of years. At this stage of development, underground coal gasification is a high risk technology and will remain so until large scale field tests are successfully carried out. These tests are recommended by the Gas Research Institute and by the American Institute of Chemical Engineers. A seven year program costing about $200 million would permit initial commercial production in ten years.

Separational Characteristics of Mineral Processing

Abstract: This paper covers: (1) Introductory definitions, (2) fractional composition analysis of ore and mineral products, (3) separation phenomenae and performance functions of typical flowsheets and prediction of grade and recovery, (4) performance (separation) functions of typical flow sheets; prediction of grade and recovery and (5) design of optimal multiproperty-multiconcentrate technologies and of minimal equipment plants.

Beneficiation with Magnetic Fluids—Magnetic Separation of the Second Kind

Abstract: Colloidal solutions of magnetite placed in a magnetic field have been used to segregate nonmagnetic materials such as nonferrous scrap metals and to concentrate precious minerals Conventional magnetic separation relies on the inherent magnetic susceptibility of the material to be separated and may be designated as magnetic separation of the first kind When the medium of separation rather than the separated particles are made magnetizable, a new system of gravity separation results In this new magnetic separation of the second kind, a magnetic fluid rather than air or water acts as the separation medium The same force that attracts magnetic objects in separations of the first kind also attracts the entire separation medium in separations of the second kind, thereby creating a reactionary force of equal magnitude in the opposite direction This force, sometimes called the levitation force, can be made to segregate nonmagnetic particles in a flowing stream according to their specific gravity The techniq