Mineral Processing Engineering

Heap Leaching Practices

The Alligator Ridge Mine is located 70 miles northwest of Sly in White Pine County, Nevada. Development of the mine began in the late 1970’s as a joint venture between Amselco Minerals, Inc. and Occidental Minerals Corporation, with Amselco as the operating partner. Early in 1983 Nerco Minerals Company acquired Occidental’s share of the property. The mine and ore processing facility have operated at capacity since 1981 producing 680,000 tonnes of ore and 1,900 kg of gold per year.

The gold ore deposits at Alligator Ridge consist of disseminated micron-size gold particles in a silicified siltstone matrix. The deposit comprises three separate but adjacent areas of mineralization that are designated as Vantage 1, Vantage 2, and Vantage 3 after the name of the basin in which the deposits lie.

Heap Leaching – Background

Given a material of suitable porosity to allow diffusion of the lixiviant into and out of ore particles, successful heap leaching depends on obtaining maximum exposure of ore particles to solution flowing through the heap. Two criteria must be satisfied to assure maximum exposure of ore to lixiviant: (1) heaps must be uniformly permeable to solution flow and (2) solution must be uniformly distributed over the surface of

By |2018-10-16T17:05:43+00:00October 14th, 2018|Categories: Leaching|Tags: |Comments Off on Heap Leaching Practices

Grinding Mill Cost

A comminution circuit is an important integral part of a mineral processing plant. Nearly 40% of the capital cost and 30 to 40% of the operating cost are taken up by the crushing and grinding circuit. Therefore, considerable care should be given to the design and selection of this circuit.

Autogenous, semi-autogenous, and conventional grinding circuits have all been used for processing copper ores. The emphasis lately has been towards the use of autogenous or semi-autogenous grinding systems. The reason is obvious. For a given tonnage, the initial investment required for an autogeneous and semi-autogenous system is generally lower. However, the operating cost may not be lower. Autogenous grinding has a definite advantage over the others in that no media are used in grinding. Semi-autogenous grinding does use media; consequently, the operating cost may not be lower. The operating cost of a given grinding circuit is basically a function of the ore type.

Energy is no longer a cheap commodity. While some British Colombia operations are fortunate to obtain energy at a very low cost (1.5¢ to 2¢/kWh), some of the Southwestern U.S. operations are already paying approximately 4¢/kWh. In some developing countries, cost of power exceeds 8¢/kWh. According to a General

By |2018-10-15T18:55:50+00:00October 14th, 2018|Categories: Grinding|Tags: |Comments Off on Grinding Mill Cost

Grate Kiln System

The economics of pellet plant operation, in terms of fuel and power consumption, flexibility in the selection of the cheapest fuel source, system availability, maintenance costs, and the simplicity of process design, contribute to the determination of building and profitably operating a pellet plant. Design innovations, supported by actual field data, have been initiated into the GRATE-KILN System design to positively address these factors.

Process Design Improvements

The GRATE-KILN System has changed significantly in design concept since the first systems were commissioned for Cleveland Cliffs Iron Company in the early 1960’s through the most recent startup of the LKAB KP-79 plant in Kiruna, Sweden in 1981.

Initial GRATE-KILN plants were designed with no heat recuperation systems and typically consisted of a two pass, downdraft drying and downdraft preheat grate cycle. A preheat bypass system was installed to complement the preheat off-gas supply so that these two streams delivered the required downdraft drying heat supply.

The first GRATE-KILN System with heat recuperation was supplied to Sydvaranger AB in Kirkenes, Norway. This facility was commissioned in 1972. The heat recuperation design consisted of a duct from the annular cooler which was introduced into each preheat fan via the outlet chamber of the preheat cyclone

By |2018-10-15T18:54:55+00:00October 14th, 2018|Categories: Pyrometallurgy|Tags: |Comments Off on Grate Kiln System

Ways to Recover Gold from Cyanide Heap Leach Solutions

Cyanidation of gold and silver ores by conventional mining and milling techniques has been practiced for over a century. During the past decade, heap leaching has emerged as a viable process for treating certain gold and silver ores. The rapid development of heap leaching for gold and silver ores is largely a result of lower capital and operating costs and faster start-up time than that offered by conventional mining and milling. In general, these features make heap leaching an ideal approach for exploiting either small or large low-grade disseminated deposits of gold and silver considered to be uneconomic by conventional methods.

cyanide heap leach solutions flowsheet


cyanide heap leach solutions composition

Technology Status

Gold recovery from alkaline cyanide solution is typically accomplished by carbon adsorption or zinc cementation (Merrill Crowe). These and other emerging technologies, particularly resin ion exchange, solvent extraction, and direct electrowinning, are discussed, emphasizing the unique features of each process alternative.

Carbon in Column (CIC)

The essence of the carbon-in-column process alternative is the adsorption of gold from alkaline cyanide solution by activated carbon. For typical carbon-in-column operation, the cyanide leach solution is

By |2018-10-15T18:53:35+00:00October 14th, 2018|Categories: Precious Metals|Tags: |Comments Off on Ways to Recover Gold from Cyanide Heap Leach Solutions

Fluid Energy Grinding & Drying

High pressure fluid energy grinding, or jet milling, is a versatile method of continuously fracturing solids into fine particles to gain substantial increases in exposed surface area.

Applications in the minerals industries include calcium carbonate, talc, barytes, mica, diatamaceous earth, bauxite, rutile, coal, kaolin, sepiolite, diamonds, etc.

The underlying principle of all jet action fluid energy mills is to induce particles to collide with each other at high velocity causing one or both to fracture into smaller particles. Multiple collisions enhance the reduction process and, therefore, multiple jet arrangements are normally incorporated in the mill design.

The motive elastic fluid is normally air at up to 100 psig (6.9 Bars) or steam at up to 300 psig (20.7 Bars). Inert compressed gases such as nitrogen or carbon dioxide can be used under certain circumstances involving volatile materials.

Total Concept Size Reduction Systems

Although it is possible to introduce large section feed into a jet mill, it is generally undesireable to do so. Such practice can lead to high rates of abrasive wear, and be an energy intensive mode of operation.

This leads us to define jet milling techniques as being aimed at the “fine end” of the total size reduction spectrum, generally with finished

By |2018-10-15T18:51:10+00:00October 13th, 2018|Categories: Non-Metallic & Industrial|Tags: |Comments Off on Fluid Energy Grinding & Drying

Ferric Cure Dump Leaching Process

This dump leach process for treatment of mixed oxide/sulfide ore includes: strict mineralogical control of ore placed for leaching, controlled leach pad construction, solution saturation and curing of the pads with higher acid concentrations, and, finally, rinsing of the cured pads for removal of dissolved copper.

The ore treatment route has been drastically changed over the 68 years of mining history at Inspiration. Excluding copper pricing structures, the key element precipitating these changes has been the ore body itself. It is a typical porphyry copper system consisting of disseminated and stockwork mineralization emplaced in schist and intrusive rocks. The primary mineralization is not strong, with secondary mineralization having played an important role in upgrading the ore deposit. Since the deposit was formed by supergene processes and is a naturally soft, low acid consuming ore with fine fracturing and fragmentation during mining, it is ideally suited for hydrometallurgical processing.

Development of the “Ferric Cure” Process

The “Cure” concept originated in 1973 with an effort to increase the recovery of copper from the Ox-Hide orebody. Although this ore body consisted of oxide minerals only, the analytical method used by Inspiration for determining acid soluble copper showed that only 40 to 50 percent of

By |2018-10-15T18:48:47+00:00October 13th, 2018|Categories: Leaching|Tags: |Comments Off on Ferric Cure Dump Leaching Process

Remove Copper from Moly by Ferric Chloride Leaching

The Anaconda Minerals Company operates a molybdenite and copper producing mine and mill facility near Tonopah, Nevada. Included with the milling facility is a ferric chloride leach plant for removal of copper mineralization from the molybdenite concentrates. Discussed are the engineering and construction schedules associated with the leach plant. The chemistry associated with the process along with a description of the process flow, equipment, and operating parameters are contained in the paper.

Process Chemistry

The chemistry of the extraction of base metals with chloride oxidants can be viewed at several levels of complexity, much like increasing the power of a microscope to observe finer details. At the least complex level, the extraction of copper and lead from a molybdenite concentrate, as it relates to the Tonopah mineralogy, can be described by the following stoichiometric equations:


4FeCl3 + CuFeS2 → 5FeCl2 + CuCl2 + 2S……………………………………………………..(1)

2FeCl3 + PbS → PbCl2 + 2FeCl2 + S…………………………………………………………….(2)

2FeCl3 + ZnS → ZnCl2 + 2FeCl2 + S…………………………………………………………….(3)

3CuCl2 + CuFeS2 → 4CuCl + FeCl2 + 2S………………………………………………………(4)

2CuCl2 + PbS → PbCl2 + 2CuCl + S……………………………………………………………..(5)

2CuCl2 + ZnS → ZnCl2 + 2CuCl + S……………………………………………………………..(6)


2FeCl2 + Cl2 → 2FeCl3…………………………………………………………..(7)

CuCl + FeCl3 → CuCl2 +

By |2018-10-15T18:45:59+00:00October 13th, 2018|Categories: Leaching|Tags: |Comments Off on Remove Copper from Moly by Ferric Chloride Leaching

Oxide Nickel Ore Extraction

“Invention” in the present context means any change from “conventional” process technology that shows a reasonable chance of reducing costs, increasing revenues, or both, in the production of a commodity. This can be anything from a simple rearrangement of flowsheet steps to a completely different basis for processing. And the result may reduce costs by more efficient use of energy or labor or reagents; may increase revenues by better recovery of the primary product or by introducing the recovery of previously ignored by-products; may insure sales volume (and thereby cash flow) through higher product purity or an improved product form. “Necessity” is the perceived need to attain at least one of these classes of results. This perception of necessity, however, varies widely from management to management and from project to project.

Elements of “Necessity”

The expectation of continuing growth in nickel demand led to the conclusion that the principal requirement to be imposed on a process for extracting nickel from laterite was that it be able to meet the investment criteria of the prospective producer. The growing shift in demand from Class I (cathode, briquettes, carbonyl pellets) to Class II (ferronickel, nickel oxide sinter) products served primarily to broaden the

By |2018-10-12T19:11:16+00:00October 12th, 2018|Categories: Pyrometallurgy|Tags: |Comments Off on Oxide Nickel Ore Extraction

Amine Extraction of Gold from Cyanide Solutions

Only a modest amount of research has been reported for the solvent extraction of gold from cyanide solution. The technical literature indicates that of the amine extractants, only tertiary and quaternary amines have been studied. Not unexpectedly, it was found that gold extraction with quaternary amines was possible for all pH values, but stripping proved to be difficult. Extraction with tertiary amines was limited to acidic solutions as has been reported on numerous occasions for the extraction of anions with simple, weak base amines that undergo protonation.

Concern for organic losses to the raffinate can not be dismissed lightly and would require the use of solvent extraction equipment which would minimize such losses. For example, the use of a centrifugal contactor can produce aqueous raffinates containing less than 5 ppm dispersed organic. Alternately, a carbon-column, flotation cell, or coalescer could be used to scavenge such organic dispersions in the raffinate stream.


The equilibrium distribution of a particular metal between the organic and aqueous phases was determined after contacting 50 mls of the two phases by rapid stirring for 10 minutes. The pH was adjusted by small additions of concentrated H2SO4 or NaOH and was continually monitored by a combination pH

By |2018-10-12T19:09:30+00:00October 12th, 2018|Categories: Hydrometallurgy|Tags: |Comments Off on Amine Extraction of Gold from Cyanide Solutions

Gold Project Ore Processing Plant Engineering Design

The pouring of the first dore bar on April 21, 1983, marked the conclusion of an engineering and construction project which brought about the revival of mining in Mercur Canyon, 105 km (65 miles) southwest of Salt Lake City, Utah. Previous mining activity in the canyon had ceased at the beginning of World War II, when all gold mines were shut down. The Mercur Project was completed under budget and six weeks ahead of schedule.

Project Description

The Mercur Gold Project consists of a 2700 tonne (3000 ton) per day carbon-in-leach (CIL) gold plant. In addition to the process facilities, the project incorporated the following:

a) Upgrading and modifying of the existing 11 km (7 miles) of Tooele County road, from State Highway 73 to the project area
b) Site earthwork, including construction sediment dams, project area roads and initial mine haul roads
c) Preproduction stripping of Mercur Hill-Lulu ore body
d) Tailings disposal, including embankment, pipeline and recovery systems
e) Offices, laboratory, shops, warehouse and security facilities
f) Thirteen km (8 mile) water supply line and two 365-m (1200-ft) deep water wells.

In order to meet both objectives, initial discussions centered on the plot plan and the best location for the facilities, including consideration of the

By |2018-10-12T19:08:13+00:00October 12th, 2018|Categories: Precious Metals|Tags: |Comments Off on Gold Project Ore Processing Plant Engineering Design

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