Mineral Processing Engineering

Manganese in Situ Leach Mining

In Situ Leach Mining Characterization

Site specific geologic data are critical to evaluate the applicability of ISLM to a mineral deposit. Examples of data collected are regional and local stratigraphic information, geometric configuration of the ore body, geologic structure including orientations of fractures and faults, effective porosity and permeability of bedded rock units, interconnectivity of cross-cutting fractures, and regional and local hydrologic conditions.

Manganese mineral textures include massive, fracture-hosted, disseminated, interstitial, and encapsulated. Physical relationships between ore and gangue minerals include grain boundary relationships, grain sizes, effective surface areas, and the location and abundance of ore and gangue minerals with respect to the rock matrix and microfractures.

Drilling Program

The stratigraphic top of the iron-formation is a hematitic chert unit (average thickness 40 m, 131 ft). This unit consists of an upper subunit of thin-bedded chert (average thickness 7 m, 22 ft) and a lower subunit of massive, hematite- and goethite- spotted, oolitic chert (average thickness 33 m, 109 ft). Locally, this chert is replaced by massive hematite and minor goethite, especially towards the base of the subunit. Manganese content in this unit is less than 1%.

Virginia Formation: 51.5-97.8 m, 169-321 ft depth. This formation consists of a well-bedded,

By Jorge|2018-08-15T21:51:30+00:00August 12th, 2018|Categories: Hydrometallurgy|Tags: 992|Comments Off

Hydrology Geochemistry & in Situ Leach Mining of Copper Oxide Ore

The U.S. Bureau of Mines is developing technologies that will increase mining productivity, efficiency, and worker safety while decreasing environmental impact. In situ leach mining is one of these technologies. There are many advantages in using in situ leach mining over heap leaching and other types of solution mining, however, one of the most severe limitations of in situ leach mining is that the natural permeability conditions of the formation dictate fluid accessibility to the ore minerals. Even though technologies for permeability enhancement for in situ leach mining are currently under development at the Bureau, none have been demonstrated to be economical at production scales. Furthermore, in most oxide copper ores, which are the current focus of Bureau research activities, the natural permeability of the rock is relatively low, and any subsequent decrease in permeability will adversely impact the productivity of the in situ leach mining operation.

This paper is an initial attempt to assess the impact that leach solution-rock interactions have on the hydrologic performance of in situ leach mining of porphyry-hosted copper oxide deposits. The underground in situ leach mining operation at the Cyprus Casa Grande mine in south-central Arizona provides an opportunity to study these effects because of

By Jorge|2018-08-15T21:57:10+00:00August 11th, 2018|Categories: Hydrometallurgy|Tags: 992|Comments Off

Pebble Crushing Circuit Design

The design of a pebble crushing circuit as an integral part of a North American style primary autogenous or semi- autogenous grinding circuit presents certain challenges to the process design engineer. Initially, the process requirement for pebble crushing has to be determined as part of:

the design of a new plant
the relief of a bottleneck in an existing plant due to new ore characteristics in the mill feed
the necessity to expand production in cases where grinding equipment has not been correctly sized in the first place, i.e., design throughput has not been achieved

If pilot plant-scale testwork is not possible, the process design engineer will have to rely on certain indicators which, individually or in combination, can be interpreted to predict the necessity of a pebble crushing circuit for achieving production objectives. The usual definition of critical size is that size range, typically 12-50 mm, which can build up in a mill charge due to the inability of or in the absence of a sufficient complement of larger ore particles and/or steel media to crush it.

Indicators

Rock Quality Designation, or RQD, has been used since the 1960s to provide a measure of the quality of a rock

By Jorge|2018-08-15T21:49:10+00:00August 11th, 2018|Categories: Grinding|Tags: 992|Comments Off

Comminution Model Types

Many types of mathematical models are used in comminution and mineral processing. These models can generally be classified into one or more of the four categories shown above.

Mill Power Draw Models

The purpose of a mill power draw model is to predict what the mill power and/or torque draw will be for a mill of a certain geometry containing a specified charge being tumbled at a specified rotation rate. These models are used be designers to select mill and motor combinations for new plant designs, and are used by operators to “benchmark” the operation of an existing mill. An operating mill that draws power equal to or exceeding the model is generally a healthy mill.

Examples used in industry (and example software I am aware of):

Morrell C-model (JK SimMet & SAGMILLING.COM) and E-model
Austin SAG model (SAGMILLING.COM)
Hogg & Fuerstenau (MolyCop Tools)
Nordberg model (SAGDesign and SAGMILLING.COM)

Specific Energy Models

The purpose of specific energy models is to predict how much grinding energy is required to break a particular rock down to a specified size. A single size category, typically 80% passing, is used in order to simplify the equations. These models are also used

By David|2018-08-10T16:19:46+00:00August 10th, 2018|Categories: Grinding|Comments Off

Microwave Digestion Systems

Microwave Digestion Systems (MWD) were popularized by the US Bureau of Mines (USBM) back in the early 1980’s. The USBM published a series of papers on the topic and discussed the advantages of the system. Basically MWD is used to replace the traditional hotplate or digestion block digestion systems employed for sample digestions. This system results in a significant savings in time and expense over traditional methods of sample dissolution and is ideal for preparing solutions for analysis by atomic absorption, inductive coupled plasma or other analytical methods.

Trace metal analysis by AAS or ICP requires that the sample be in liquid state before introducing into the system. Obviously, some samples come in liquid form such as mine water or leach solutions which require little or no sample treatment prior to analysis. However, samples can also be complex matrices such as oils, ores, concentrates, tailings, soils, coal, etc. such samples are extracted using acid digestions for removal of metals prior to analysis. The objective is to have complete decomposition of the solid matrix while preventing loss or contamination of the analytes within a safe to use system.

Wet chemical digestions utilize various mineral acids such as HNO3, HCl, HF, H2SO4, HClO4 or

By David|2018-08-01T17:38:31+00:00August 1st, 2018|Categories: Uncategorized|Comments Off

Microwave Digestion

We conducted research related to Microwave Digestion in hope it would lead to the improvement of analytical procedures used to characterise metal and mineral samples. In particular, this research is directed to the reduction in time, complexity, and expense of sample dissolution for chemical and instrumental analysis.

The rapid development of automated instrumentation has enabled the analytical chemist to perform an ever-increasing number of analyses. Unfortunately, sample preparation has not kept pace with the development of analytical instrumentation.

The Bureau previous investigated a method for the rapid, low-cost dissolution of samples in plastic pressure vessels. The method consisted of acid digestion in sealed plastic bottles that were heated in a boiling water bath. After digestion the samples were water cooled. Boric acid solution was then added to each bottle, and the solutions were reheated in the boiling water bath to dissolve any precipitated fluorides.

Because dissolution was carried out in closed plastic vessels, contamination was avoided and volatile gases such as SiF4 were retained. Samples could be prepared for analysis in less than an hour, and many elements could be analyzed from this single dissolution. In an effort to speed up dissolution time even further, the Bureau has introduced a significant improvement by

By David|2018-07-22T14:37:43+00:00July 22nd, 2018|Categories: Assaying|Comments Off

Improve Strength of Steel Alloys

Improve the strength and other properties of steel alloys.

Approach

Research by the U.S. Bureau of Mines indicates that steels melted and solidified under high nitrogen pressure acquire yield and tensile strengths that are up to four times the strengths of comparable stainless steel alloys without nitrogen. Fatigue strength, creep strength, and other mechanical properties are also improved. Strengthening occurs by two mechanisms: (1) increasing dissolved nitrogen in the lattice and (2) formation of dispersed metal nitride phases.

Nitrogen Alloying

Nitrogen alloying of a steel is generally done by introducing metal nitrides during melting of the steel. The concentration of nitrogen is limited to its equilibrium solubility at 1 atmosphere. For face-centered-cubic (fee) iron, that solubility is approximately 0.4 weight percent (wt%). For body-centered-cubic (bcc) iron, solubility is 0.05 wt%. This solubility limitation can be overcome by melting the metal in a pressurized vessel.

European steelmakers currently have metal-processing systems that can melt and pour tons of steel under nitrogen pressures exceeding 4 megapascals (MPa) (40 atmospheres). They have achieved nitrogen concentrations as high as 1.0 wt% in these (stainless) steels. The tensile strength is approximately twice

By David|2018-07-19T18:57:22+00:00July 18th, 2018|Categories: Smelting - Melting - Refining|Tags: 992|Comments Off

Recovering Platinum-Group Metals in Catalytic Converters

Develop new technology to encourage domestic processing of automobile catalytic converters for recovering platinum-group metals.

Background

Automobile catalytic converters are used to convert pollutants in automobile exhaust into water vapor, carbon dioxide, and nitrogen. About 1 million troy ounces of platinum-group metals arc used each year in the United States to manufacture catalytic converter. It has been estimated that about 60 pct of the used catalytic converters are being collected. Most of these used catalytic converters were not processed in the United States but were exported to Japan or Europe for processing. In 1991, about 250,000 troy ounces of platinum- group metals were recovered from scrap catalytic converters collected in the United States. Each short ton of decanned catalyst may contain 30 troy ounces of platinum-group metals valued at over $ 15,000. Development of an economic process for the recovery of platinum-group metals that can be operated on a small or large scale may increase the percentage of catalytic converters collected and encourage domestic processing to recover a platinum-group metal concentrate. This would significantly decrease the dependence of the United States on imports for these critical and strategic metals.

By David|2018-07-19T18:59:40+00:00July 18th, 2018|Categories: Recycling|Tags: 992|Comments Off

Foam Concrete Seals for Abandoned Mine Shafts and Adits

Investigate and demonstrate the possible use of low-density (45-lb/ft³) foam concrete for sealing abandoned mine openings. Although foam concrete has been used in the construction and geotechnical industries tor some decades, it has not previously been used in abandoned mine shaft reclamation.

Approach

A structurally engineered permanent mine seal for an abandoned coal mine shaft, using low-density foam concrete and other appropriate structural materials, was designed by the Bureau and installed at a field site, the No. 22 Shall in Logan County, West Virginia. The field work was conducted by a private contractor under the supervision of the West Virginia AML Section (WV AMI).

The No. 22 Shaft is situated immediately adjacent to a frequently traveled county road, A few feet away from the shaft is a branch of Pine Creek. On the other side of the road is a railroad line that serves an active mining operation located several miles away. The shaft measures 9.5 by 9 feet in cross section and is about 300 feet deep. It was used at one time as a dewatering shaft and still contains two large-diameter dewatering pipes with steel drive shafts inside them. Before

By David|2018-07-19T19:01:45+00:00July 18th, 2018|Categories: Uncategorized|Tags: 992|Comments Off

Gold Prospecting in Quebec

Gold Prospecting in Quebec

The prosperity of any nation depends, to a large extent, on its natural resources such as oil, coal, metal, timber, water-power, and fertile soil. Each one of these resources forms the basis of a huge industry. The mining and smelting industry ranks among the first since it paves the way for a number of other industries. The mines and smelters provide a market for electric power, coal, timber, and agricultural products: other industries in turn provide a market for metals and non-metals.

The real pioneering, however, is done by the prospector who goes into the wilderness to search for the ores from which the metals are to be extracted for the use of men. Prospecting is an interesting and fascinating occupation. There are many difficulties and hardships in the way but the lure of gold and the vision of finding an outcrop that may develop into a large bank account, within a reasonably short time, will urge the prospector forward.

Thus, on the outskirts of this northern hemisphere hundreds of prospectors are searching and toiling and of whom nothing is known or heard until they reach civilization and

By Jorge|2018-07-14T13:31:05+00:00July 10th, 2018|Categories: Uncategorized|Comments Off