Mineral Processing Engineering

In-Situ Leaching Simulation – Uranium Ores

A laboratory method for the simulation of in-situ leaching of uranium was developed under contract to the Interior Department’s Bureau of Mines. Simulation tests using sulfuric acid, ammonium bicarbonate and sodium carbonate as reagents, and hydrogen peroxide as oxidant were carried out with representative ores from Texas and Wyoming. The tests not only yielded recovery rates of uranium and permeability changes, but also qualitative inferences on the chemical and physical phenomena which occur underground. Leaching with basic solutions was found to be kinetic constrained and with acid solutions, equilibrium constrained. The rapid permeability changes observed when leach solutions were introduced, were probably caused by gas blockages in the packing. Precipitation of calcite or gypsum and the reaction of clay to leach solutions had slow and gradual effect on the packing permeabilities.

The In-Situ Simulation System

The following features were considered in arriving at an acceptable design:

  • Ore sample container of representative geometry (cylindrical, rectangular slab, etc.) capable of operating at temperature and pressure constraints occurring in in-situ leaching, o Adequate sampling ports for obtaining solution and ore samples for analysis and characterization.
  • Sufficient Instrumentation to monitor all operating parameters (flow, pressure, temperature, etc.) and to allow identification of the state
By |2019-01-14T15:34:47+00:00January 14th, 2019|Categories: Leaching|Tags: |Comments Off on In-Situ Leaching Simulation – Uranium Ores

In-Situ Leaching & Borehole Mining

Terms such as in situ mining, in situ leaching, solution mining, borehole mining, and slurry mining have been used in different ways to describe a wide range of mining operations where a commodity is usually extracted remotely by activities that are conducted from the surface. As used in this publication, in situ mining is a general term that includes both leaching and borehole (or slurry) mining methods. In situ leaching does not include dump or heap leaching where the ore is blasted and/or dug and placed in areas specially prepared for leaching, but is reserved for the process where chemical solutions are circulated through the ore body. Although the ore may be blasted to increase permeability for in situ leaching, it is not transported. The term borehole mining is used for the process where a hydraulic jet is used to slurrify a mineral commodity which is then pumped to the surface through a pipe.

In situ mining has been characterized as an extraction method having significant potential for increasing productivity and extending reserves. Leaching and borehole mining can lower the cutoff grade of ores having appropriate characteristics. Other advantages attributed to in situ mining include low capital costs, quick return on

By |2019-01-14T15:34:21+00:00January 14th, 2019|Categories: Leaching|Tags: |Comments Off on In-Situ Leaching & Borehole Mining

In Situ Leaching of Copper Economic Feasibility

An economic simulation model was developed to predict the amount of copper recovered from copper oxide deposits and the cost of producing it as a function of the deposit parameters. The economic simulation model includes models of fragmentation design and cost, copper extraction, solution distribution and recovery, effluent solution cutoff grade, and financial analysis.

Economic Simulation Model

The economic system simulation model is composed of a number of models which calculate the amount of ore reserve of the property being investigated, calculate the fragmentation cost of an in situ leaching operation, simulate the copper recovery process, calculate the optimum cutoff grade and amount of copper produced, and calculate the rate of return on Investment based on the analysis of the cash flow resulting from the in situ leaching operation.

This model was developed to calculate the blast design parameters and fragmentation cost for in situ leaching operations as a function of the deposit parameters. The model is based on blasting an ore zone or an ore zone plus overburden by either a coyote blast or a vertical blasthole system. The model calculates the blast design parameters and the fragmentation cost based either on a user input powder factor value or on

By |2019-01-14T15:32:24+00:00January 11th, 2019|Categories: Leaching|Tags: |Comments Off on In Situ Leaching of Copper Economic Feasibility

Copper Lead Separation with Activated Carbon

In many multiple-sulphide ore flotation processes, it is desirable to concentrate each of the various valuable minerals into separate products. Although there are a variety of techniques and chemicals which can be employed to produce efficient separation, two basic types of flotation circuits are used: The Differential Flotation Circuit and the Bulk/Selective Flotation Circuit.

Geco Concentrator Metallurgy

The testwork was aimed at improving selectivity in samples of a copper/lead ore from the GECO mine located at Manitouwadge, Ontario. The basic components of the flotation circuit involve the combination of a differential circuit for copper/zinc separation and a bulk/selective circuit for copper/lead separation. The use of a bulk/selective circuit for removing galena from chalcopyrite is an obvious choice upon examining the relative quantities of the two minerals in the bulk concentrate.

activated-carbon-metallurgical-results

 

Adsorption of Amyl Xanthate on Activated Carbon

The adsorption tests, using 100 milligram samples of activated carbon were carried out in 50 ml centrifuge tubes completely filled with freshly prepared xanthate solution to minimize the presence of air bubbles. Agitation was provided by rotating the sample in a 12 inch diameter drum at 40 rpm.

The adsorption isotherm demonstrates the high affinity of

By |2019-01-12T18:54:31+00:00January 11th, 2019|Categories: Flotation|Tags: |Comments Off on Copper Lead Separation with Activated Carbon

Room and Pillar Hard Rock Mining Lighting

St. Joe Minerals Corporation, recognizing the need for improving the illumination of the working places in their mines, entered into a cooperative research agreement with the Bureau of Mines to utilize the Bureau’s expertise in this field. Some similarity in the environment in which coal and hard rock miners work has allowed the application of developed coal mine illumination technology and equipment to be utilized in hard rock, room and pillar mines.

It was commonly agreed that improving the illumination system of the Joy, two-boom drill jumbos would be the first priority under the cooperative research effort. Each drill jumbo is operated for about 5½ to 6 hours each drill shift by a crew of two miners. Each drill crew is responsible for keeping their drill heading safe from potentially dangerous “loose” rock sometimes found on the ribs, face and back. To do the job of drilling the face and to maintain the safety of the heading, quality illumination is certainly needed.

Mercury vapor, high intensity discharge lamps, were not utilized because of poor voltage regulation caused by long trailing power cables, often exceeding 400 feet (122 meters), utilized to energize the drill jumbos. This, along with frequent power fluctuations, would require

By |2019-01-12T18:55:06+00:00January 11th, 2019|Categories: Mining|Tags: |Comments Off on Room and Pillar Hard Rock Mining Lighting

Dump Leaching Hydrology

Dump leaching and in-situ solution mining have received considerable attention during the past few years due to their apparent economic viability and minimal environmental impact. Solution mining actually dates back to the 17th century when leaching of copper ore was first reported. However, modern day leaching didn’t begin on a wide scale until the mid-1900’s. In-situ mining for copper, nickel, salts, and oil shale is currently looking more attractive as the technology advances.

Hydrology of Dump Leaching

To assist in understanding the various factors which affect the hydrology of dump leaching, a basic understanding of a typical leaching system should be reached. In general, a dump leaching system used for extraction of copper consists of a mineralized waste dump usually containing rock too low in grade to extract; a leach solution application system suitable to the rock/ore type and dump construction; and a recovery system capable of capturing the maximum solution flow.

The several factors which are known to affect the hydrology of dump leaching can be divided into three main categories as follows:

dump-leaching-stratification

Five main solution application techniques are used through the copper and evaporite industry today. They are:

  1. Pond – irrigation
  2. Trickle
By |2019-01-14T15:31:32+00:00January 10th, 2019|Categories: Leaching|Tags: |Comments Off on Dump Leaching Hydrology

High Gradient Magnetic Separator

High-intensity wet magnetic separators have been successfully introduced into, the mineral processing field over the past ten to fifteen years, due largely to rapid advancements in magnet design. Wet magnetic separation, until recent years, was applied solely to the concentration of minerals of high magnetic susceptibility, such as magnetite, at relatively coarse sizes. Now, however, high-intensity separators are capable of treating weakly paramagnetic minerals and have extended the range of treatable particle size down to about one micrometre.

Basic Principles of Magnetic Capture

For the purpose of initially analysing the forces involved in particle capture, an idealized situation describing the separation process can be applied. A spherical paramagnetic particle in a fluid moving at constant velocity, approaches a ferromagnetic wire of circular cross section. A uniform magnetic field applied perpendicular to the wire axis magnetizes the wire and a magnetic force acting on the particle is developed. If the magnetic force is large enough to overcome the competing hydrodynamic force then the particle will adhere to the wire.

FM = V Mp dH/dX

The force is thus proportional to three terms: the volume of the particle, the particle magnetization, and the field gradient over the dimensions of the particle. A

By |2019-01-12T18:53:50+00:00January 10th, 2019|Categories: Magnetic|Tags: |Comments Off on High Gradient Magnetic Separator

High Capacity Thickener

Conventional practice is to add flocculant as a dilute solution to the feed slurry in a launder or feed pipe, possibly using staged addition so as to improve the floc growth. Mixing in launders is not necessarily optimum, and with deep launder pulp depths lower layers of slurry do not readily rise to the surface and become contacted with reagent. Baffles, ridges, and other static mixing devices, might be utilized in a launder to improve this mixing action, but these can create excessive shear or simply not provide uniform mixing conditions. To offset this, additional reagent must be added beyond that which would be predicted from a simple batch test.

The transition from feed launder to feedwell often presents several problems. Feedwells may be attached to the thickener rakes and if a lifting device is employed, sufficient clearance must be allowed between the bottom of the launder and the top of the feedwell in its raised position. This means that the entering slurry must not only be slowed down in its horizontal path, but lowered to the feedwell surface without increasing its velocity. This requires some sort of restriction, such as a valve, which in turn produces the shear which may

By |2019-01-12T18:53:01+00:00January 10th, 2019|Categories: Thickening|Tags: |Comments Off on High Capacity Thickener

Heap Leaching of Uranium

Union Carbide began looking seriously at heap leaching in 1971- At that time some 1.6 million tons of mineral averaging 0.040% U3O8 were stockpiled at various sites around the Gas Hills, Wyoming, uranium facility. Several alternatives for economically exploiting these reserves were considered and heap leaching seemed the most attractive. At the time, Western Nuclear Inc. was operating a heap leach project nearby in which the low-grade ore was leached with sulfuric acid, the product liquor treated in an on-site solvent extraction circuit, and the stripped product liquor re-acidified and recycled.

Pilot Test Program

Prior to the pilot heap test, samples of the various mineral piles were evaluated in bench-scale testing. The objectives of this study were to determine (1) the acid requirement, (2) permeability of the ore, (3) ultimate U3O8 recovery, (4) probable product liquor grade, and (5) an estimate of heap economics. These tests were conducted on small samples, usually 100 grams or less. The laboratory data on these samples indicated that the liquor would flow readily through the ore with an anticipated flow rate of 10-20 gallons per square foot per day (400-800 l/m²) compared to about 3-6 gallons per square foot (129-240 l/m²) of pond area

By |2019-01-12T18:52:11+00:00January 10th, 2019|Categories: Leaching|Tags: |Comments Off on Heap Leaching of Uranium

Hierarchical Computer Monitoring and Grinding Control

Monitoring and control of conventional industrial wet grinding circuits is conceptually straightforward. However, since production objectives and operating constraints can vary widely from plant to plant, there is probably no single overall grinding circuit control strategy which is “best” in all cases; invariably some compromise is necessary between performance desired under ideal conditions and performance achievable in practice. The recent advent of relatively low cost, reliable, high speed small computer systems is revolutionizing daily operations in increasing numbers of metallurgical processing plants.

Problem Areas in Grinding Circuit Operation

Stability in grinding circuit operation is the key short range objective of closed loop computer control at Pinto Valley. During normal production, major circuit upsets can be caused by:

  • Change in the particle size distribution of the new ore feed.
  • Change in the grindability of the ore.
  • Change in water addition to the cyclone feed sump.

Through a suitable grinding control strategy, a more consistent product can be sent to the flotation area. Thus, should the particle size distribution of the new ore feed become finer, an automatic increase in feed rate prevents over-grinding. Alternately, should the ore work index increase, a subsequent decrease in the ore feed rate to the mill prevents

By |2019-01-12T18:52:09+00:00January 10th, 2019|Categories: Grinding|Tags: |Comments Off on Hierarchical Computer Monitoring and Grinding Control

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