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Open Storage Piles and Dust Control

In discussing the open storage dust problem and possible solutions, one obvious question arises – what are the economics of placing large bulk storage under cover? Several known, practical, workable solutions to the open storage dust problem are described. These include the following which will be dealt with in some detail:

A. Open pile surface crusting agents
B. Open pile surface moistening systems
C. Dust control at the transfer points – (dust suppression and collection)

As might be expected, this artificial surface crust traps the loose, small particles by means of a chemical bonding agent on the face of the pile. By spraying such a bonding agent over the pile surface, a thin solid crust is formed (about 3/8″), which will normally last from several months to a year depending on conditions. As an example of the crust durability. These crusting agents are normally applied by a conventional tank-truck sprayer system which is loaded with the liquid crusting agent, which travels around the perimeter of the piles, applying the crusting agent to the surface.

One of the organic polymer type systems offered is the Johnson-March SP-301 system. The vendor states that it can maintain a crust up to one year’s time. The generalized application recommendation is

Nitric Acid Processing Copper Concentrates

The process parameters for effective utilization of nitric acid as an oxidant for copper-iron sulfides have been developed. Leaching variables found to be important were acid concentration, temperature, time, atmosphere, pressure, mineral type, particle size, and percent solids. Particular attention was devoted to analysis and control of fumes evolved during the oxidation.

Numerous references have cited the effectiveness of HNO3 in oxidizing copper sulfides. The gaseous reaction products reported were NO and NO2).

3CuS + 2HNO3 + 3H2SO4 → 3CuSO4 + 3S° + 2NO↑ + 4H2O

CuS + 2HNO3 + H2SO4 → CuSO4 + S° + 2NO2↑ + 2H2O

Experimental Technique

Most of the leaching experiments were performed in a one-liter glass reaction kettle equipped with condenser, cooling coil, agitator, pH probe, heating mantle, thermometer, acid burette, and sampling tube. The sulfide, Concentrate “A”, used for the experiments assayed 28 percent Cu, 25 percent Fe, 31 percent S, 0.29 percent Mo, 3.5 oz Ag/ton, and 0.4 oz Au/ton. The major mineral constituents were chalcopyrite (60 percent), bornite (10 percent), gangue (14 percent), and pyrite (10 percent). When pure mineral sulfides were employed, they were natural specimens ground and sized to meet experimental requirements.

Elemental sulfur was extracted from leach residues

Molybdenum Flotation

The development drilling program of the Copper Cities mine indicated that the molybdenum content of the ore would be about 0.011% MoS2. The molybdenum content of the Miami mine at the same time was about 0.025% M0S2.

The bench scale testing was followed by pilot plant testing. Sixteen 20 in. Fagergren cells and eight No. 7 Denver cells were purchased to provide roughing and cleaning circuits and small Hydroseal pumps, Clarkson reagent feeders and other ancillary equipment was provided.

The pilot plant was shut down and a six hearth, 8′-6″ O. D. Pacific multiple hearth furnace was purchased and installed to take the place of the unsuccessful screw conveyor dryer. This furnace was located just outside of the mill building and adjacent to the truck-trailer loading dock. A cross conveyor beneath the concentrate conveyor diverted a portion of concentrate to the furnace. The rate of diversion was controlled by a moveable vane in the discharging concentrate stream.

After several such incidents, the plant was again shut down and the furnace was converted from up draft to down draft operation by making one of the bottom hearth inspection doors into a stack breeching and attaching the stack to it. This change effectively stopped the

Mine Drainage Pollution Control by Reverse Osmosis

The most common method of treating nine drainage to prevent water pollution consists of neutralization and aeration. This process removes the acidity, iron, aluminum, and some other heavy metals, but does not render a water suitable for domestic or industrial use because of the high dissolved solids, hardness, and sulfate in the treated water. The Environmental Protection Agency (EPA), has been sponsoring and conducting research since 1966 on the use of reverse osmosis (R.O.) for the treatment of mine drainage.

Reverse Osmosis

Flow from a dilute solution through a semi-permeable membrane to a core concentrated solution, is the age old phenomenon of osmosis. If a pressure greater than the osmotic pressure is applied to the concentrated solution, the process can be reversed and the flow will be from the concentrated to the dilute solution, thus the name reverse osmosis. The semi-permeable membrane can be selected so that only pure water will pass through, leaving all or at least the major portion of other ions in the concentrated solution. By this means water can be demineralized.

Three major membrane configurations ore currently available, i.e., spiral wound, tubular, and hollow fine fiber. Each configuration has major advantages and disadvantages.

Tubular systems have extremely low

Mea Cyclic Magnetic Separator

At the 1971 Annual Meeting we presented a paper on the results obtained by wet magnetic separation on very fine, slightly magnetic material. Considerable interest was shown in a corollary subject, namely, on the type of magnetic construction of the Magnetic Engineering Associates (MEA) high-intensity magnetic separator (HIMS).

It is well-known that passage of a direct electric current through a wire shaped in the form of a loop results in a magnetic field being created in the volume enclosed within the loop. The magnetic field is proportional to the amperes of electric current passing through the wire. If the wire is in the form of a solenoid consisting of n turns, the magnetic field is n times larger. Hence the expression ampere-turns commonly associated with magnetic separators.

In a wet magnetic separator such as the HIMS magnetic separator, there is another force exerting traction on the particle, and that is the force of the fluid (liquid) on the particle. It is, therefore, essential to examine the relationship of the fluid to the magnetic field.

First, assume the water in which magnetic and non-magnetic particles are suspended to be stagnant. In the absence of magnetic field, the only forces acting on the particles are

Magneto-Gravimetric Separation of Nonmagnetic Solids

Stable colloidal solutions of ferromagnetic or ferrimagnetic materials are called magnetic fluids. About two generations ago, suspensions of relatively large micron-sized ferromagnetic particles in oil proved useful in clutches, brakes, and dashpots. They were called magnetic clutch materials, and their viscosities were highly dependent upon the applied magnetic field. Magnetic colloids, by contrast, are especially tailored with ultra-fine, submicron-sized particles so as to retain their fluid properties under all applied fields and field gradients. While the term “ferrofluid” was used by Rosensweig and Kaiser to designate a magnetic colloid composed of a dispersed magnetic ferrous material, we will use the term “magnetic fluid” for these colloids since they may, in principle contain other magnetic materials such as cobalt, nickel, gadolinium, or dysprosium.

Among the numerous applications (2) of magnetic fluids are the development of accelerometers, altitude control devices, and energy conversion schemes, and in the fluid computer interface where one desires to introduce an electrical signal in a fluid system without movable or consumable parts. Magnetic fluids are also used as additives to missile fuels so that they can be kept by magnetic means from entraining vapor during pumping. Metallurgical applications include the acquisition of a fluid whose apparent density can

Phase Separation Test for Liquid Ion Exchange Systems

Liquid, ion exchange is becoming more and more important in hydrometallurgical processing and recovery of metals. The key to success for this process are reagents which have suitable operating characteristics. One of these important characteristics is a relatively fast phase separation rate in the extraction and stripping circuits, as this greatly affects the size of plant required.

Pour 192 ± 2 ml of aqueous copper – iron solution and 385 ± 4 ml. of reagent solution into the phase separation unit. The liquid interface should be at the 2-½ inch mark on the graduated scale if the proper amount of aqueous solution has been added. Close the inlet port using Teflon tape on the threads of the plug. Turn on the stirrer, (previously adjusted to 1600-1800 rpm) mix for 15 minutes, and allow the phases to separate completely.

Turn on the stirrer again. After exactly 15 minutes, stop the stirrer and simultaneously start four stopwatches. Record the seconds required for the interface to reach the ½, 1, 1-½, and 2 inch scale marks, respectively. Allow the phases to settle completely. Repeat twice the 15 minute stirring and subsequent measurements.

A calculation of separation time T using the Method of Averages is faster than

Computer Simulation of Fluid Flow in a Leach Dump or Heap

The leaching of heaps or sub-marginal waste ore dumps as it is practiced throughout the Southwest as well as other parts of the world, is the major method of secondary recovery of copper. In 1970, twenty percent of all domestic copper was produced by dump leaching operations.

An exhaustive study of the phenomenology of a leach dump or heap requires detailed knowledge of the simultaneous interaction of (1) the flow of leach solution, (2) the leaching process, including biochemical processes and temperature distribution, and (3) the consolidation process, which includes weathering, and precipitation of ions such as ferric and ferrous.

Important terminology,

  1. Water Saturation (Sw) – That fraction of the total void space in a unit volume of a porous medium that is occupied by water, usually expressed as a percent.
  2. Capillary Pressure (pc) – A pressure differential between two non-wetting fluids, such as air and water. Primarily, it is a function of the saturation, Sw.
  3. Saturated Capillary Pressure Head (Pb) – Refers to a specific capillary pressure sometimes called bubble pressure head where air first forms a continuous pathway through a liquid saturated soil when it first begins to drain.
  4. Irreducible Saturation (Sri) – That value of liquid saturation where all

Leach Dump Operation

Stripping for the Lavender Pit was started in 1951, with mining operations on stream in 1954 and continuing to the present. All material removed from the pit has been classified as waste, leach material, milling ore, or direct smelting ore, depending upon grade and degree of oxidation.

Leach water is pumped through an asbestos-cement, epoxy-lined main and distributed through 8″, 6″, and 4″ polypropylene pipelines. Distribution is controlled by use of pinch valves and pinch clamps on the polypropylene pipe.

Ponds are leached for two to three months and are then given a rest time of approximately one year. The length of time a pond is under leach is determined by productivity, with longer leach time applied to areas tending to produce higher grade water.

Effluent water is collected in ponds constructed at two points of natural drainage egress and is conducted to a pumping station which relays it to the precipitation plant.

Typical results obtained are as follows:

leach-dump-operation-results

Several problems have been encountered in leaching No. 7 Dump, all of which are probably typical of most dump leaching operations.

  1. Gradually declining tenor of effluent leach water, despite continuous addition of new ore to the leach heap.

Kinetic of Dissolution of Asbestos Minerals in Water

Asbestos is a broad term embracing a number of fibrous silicate minerals. These minerals look extremely fragile, yet their fibers have a tensile strength equal to that of piano wire. Chrysotile asbestos is the only mineral that can be woven into cloth, and its fibrous structure is, if anything, even more amazing than its remarkable ability to withstand heat.

Chrysotile asbestos from Quebec, Canada was obtained from Ward’s Natural Science Establishment, Inc., Rochester, N. Y. The sample was received in block form. The mineral is a hydrated magnesium ortho-silicate containing a high percentage of magnesia and water. Its chemical formula may be expressed as either Mg3Si2O5(OH)4 or 3MgO.2SiO2.2H2O. The sample was cut by scissors into lengths of less than about one-half inch. Fine particles of chrysotile were prepared with a mortar and pestle and by dry grinding with a pebble mill. The product of grinding was sized by sieving. The minus-325-mesh fraction was kept for subsequent experimentation. Fabricated fibers of chrysotile were also prepared in a motor driven commercial blendor.

A known amount of deionized distilled water was added to a known amount of chrysotile contained in a beaker. The initial pH of the distilled water was pH 5.9 to pH 6.1.

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