Mineral Processing Engineering

Heap Leaching Modular Mill Design

Heap leaching of gold and other precious metals has revolutionized the precious metals industry, and has become a common milling technique. One heap leach milling process, the carbon loading and stripping mill, loads the metal on carbon (using activated charcoal or char), strips the metal from the char, and recovers the metal by electroplating. The system is simple and economic, particularly when applied to oxidized ores with relatively high gold content.

The Modular Station/Movable Column System

The system is modular: several loading and stripping stations (Figure 1) can be employed at various places on the property, as dictated by operational needs.

modular mill design

 

The Movable Char Column

For char control the column has two integral valves. The dump valve mounted on the bottom is used to dump the load of char. The stripping valve mounted 1.1 m (42 in) from the bottom is where the stripping solution overflows when removing the metal from the char. During stripping, a cover and insulated jacket are fitted to the column to retain heat needed for the stripping reaction.

The Loading Station

The loading station (Figure

By | 2018-05-22T16:11:38+00:00 May 17th, 2018|Categories: Precious Metals|Tags: |Comments Off on Heap Leaching Modular Mill Design

Improved Recovery of Coarse Florida Phosphate

Each year about 50 million tons of flotation tailings are discarded in Florida phosphate operations. These tailings only contain about 4 pct of the phosphate in the ore; however, over half of the phosphate in the tailings is concentrated in the plus 600-µm size fraction at grades of up to 20 pct P2O5. Many of the phosphate producers have attempted to solve this problem by floating the plus 425-µm flotation feed separately. However, phosphate recoveries in these circuits are typically only 60 pct. For seven sampled phosphate operations, the phosphate content of the plus 600-µm fatty acid tailings ranged from 15 to 25 pct P2O5. In every case the plus 600-µm fatty acid tailings was higher in grade than the overall flotation feed. Attempts to efficiently recover this coarse phosphate have apparently been unsuccessful at these seven phosphate operations. Recovery of this coarse phosphate would provide an additional 0.9 to 2.25 million metric tons of phosphate annually and add an additional year to the reserves of these important deposits.

A typical central Florida phosphate matrix is composed of three different mixtures of minerals. The plus 1-mm portion is chiefly phosphate pebbles

By | 2018-05-22T16:13:26+00:00 May 17th, 2018|Categories: Flotation|Tags: |Comments Off on Improved Recovery of Coarse Florida Phosphate

Chemical and Biological Upgrading of Stillwater Platinum-Group Metal Converter Matte

The conventional processing sequence for treating sulfide flotation concentrates containing Cu, Ni, Fe, and platinum-group metals (PGM) includes matte smelting followed by leaching of the metal values. In mid-1990, Stillwater Mining Company began operation of a production smelter in Columbus, MT, to treat the flotation concentrate produced at the Stillwater Mine in Nye, MT. The smelter operation, which consists of a submerged arc electric furnace followed by a top blown rotary converter, produces 1.5 ton-per-day of a high sulfide, Cu-Ni matte containing approximately 2 pct combined PGM and Au. The matte is shipped to Belgium for toll refining due to the excessive penalties charged by domestic refiners for high base metal and sulfide content.

The first stage of Baglin’s process sequence utilized an atmospheric pressure sulfuric acid leach to selectively remove Ni and Fe without solubilizing the Cu or PGM, according to the reaction:

MS + 2H+ → M²+ + H2S (g) M=Fe, Ni……………………………………………………(1)

The second-stage oxidizing leach was conducted to remove Cu from the first-stage residue and leave a high-grade precious metals product. Ferric chloride in a hydrochloric acid medium or ferric sulfate in a sulfuric acid medium were found to

By | 2018-05-16T17:35:31+00:00 May 16th, 2018|Categories: Pyrometallurgy|Tags: |Comments Off on Chemical and Biological Upgrading of Stillwater Platinum-Group Metal Converter Matte

Polymer Agglomeration

By eliminating the need for cement, a polymeric agglomeration program could improve material handling operations, as well as offer the following additional savings. First, the polymer application uses only lime for adjusting basicity, the polymer does not contribute any alkalinity to the heap. Because lime is more soluble than cement, detoxification of the heap becomes much faster and less costly for the mine relative to rinsing cement alkalinity. The following graph compares the detoxification rate of cement and polymer over a 33 day cycle.

polymer-agglomeration-cyanide-detoxification-profiles

Before the polymer could be applied to the heap leach ore, preliminary tests were conducted which would determine the programs performance. The tests included a strength and stability evaluation of the two agglomerants, polymer and cement, and a bottle roll leachability test.

polymer agglomeration data

polymer agglomeration strength and stability test

 

polymer-agglomeration-column-leach-tests

benefits of polymer agglomeration at newmont gold company

By | 2018-05-17T18:32:01+00:00 May 16th, 2018|Categories: Precious Metals|Tags: |Comments Off on Polymer Agglomeration

In-Line Static Mixer Flotation Contact System

Conventional froth flotation is one of the most widely used mineral beneficiation processes. Unfortunately, long residence times are often required to achieve complete flotation. These slow flotation kinetics have been associated with the hydrodynamics within the flotation cell. While flotation cell manufacturers have optimized the mixing hydrodynamics, little effort has been made to improve the flotation hydrodynamics within the flotation cell.

A conventional flotation cell has both a turbulent region, where bubble-particle attachment occurs, and a quiescent region, where the ore-laden froth is removed from the cell. The flotation rate of a single particle in this environment is a function of the probabilities of bubble-particle collision, attachment, and the motion of the bubble moving into the froth. To increase the flotation rate of a flotation cell, the number of bubble-particle collisions must be increased. One way to increase the number of collisions is to increase the number of bubbles, either by decreasing the bubble size or by increasing the air flow rate to the flotation cell. Unfortunately, the bubble size is limited by the mechanical action in a conventional cell, and at high air flow rates, the mechanical cell’s agitation is

By | 2018-05-17T18:34:29+00:00 May 16th, 2018|Categories: Flotation|Tags: |Comments Off on In-Line Static Mixer Flotation Contact System

Heap Leach Pad Remedial Design

A spent ore pile is located approximately 2,000 m. southwest of the mine and approximately 1,000 m. northeast of the active pad and plant facilities. The pile was constructed on a gentle northwest slope dipping 12 to 13 degrees. The pile is bordered by a small river to the northwest and by a larger river to the northeast. Both rivers eventually flow into Bolivia.

Project Objectives

In early 1991, elevated cyanide levels in surface water samples collected from the adjacent rivers was identified. The logical source of cyanide appears to be associated with leakage from the pile or the active pads.

Laboratory Investigation

Soil Index Test

Laboratory index tests were conducted on samples recovered from the test pits. Select but representative samples were subjected to the following index tests:

  • Moisture Content (ASTM D2216)
  • Grain Size Analysis (ASTM D422)
  • Atterberg Limits (ASTM D4318)
  • Specific Gravity (ASTM D854)

Interface Shear Strength Tests

Most direct shear interface tests on goesynthetic liner materials are conducted with rigid backing material. For application were the subgrade for a liner is prepared with extreme care these types of tests are expected to produce appropriate design values.

By | 2018-05-17T18:37:37+00:00 May 16th, 2018|Categories: Leaching|Tags: |Comments Off on Heap Leach Pad Remedial Design

Hydrophobic Bacteria & Hematite Flotation

It is envisioned that the utilization of nonpathogenic microorganism and/or extracellular surfactant derived from microorganism as a flotation collector will replace some of the environmentally toxic flotation collectors and at the sometime improve flotation efficiency. The selection screening, and judicious selection of appropriate microorganism as flotation collector has been a challenge to process engineers.

Surface Chemistry of Mycobacterium Phlei

M. phlei is a gram-positive procaryotic cell. It has a rod like shape with 1-1.5 µm in diameter and 5 µm in length. However, the shape can be altered depending on the culture method and rate of growth. Figure 1a shows the Scanning Electron Microphotograph of M. phlei at pH 3.

From the foregoing it can be realized that the surface composition and surface chemistry of M. phlei, in a microscopic scale, resemble to conventional flotation collectors. In this paper, particular attention is focused to elucidate the role of M. phlei as a flotation collector of hematite and to correlate flotation results with bacterial adhesion, hydrophobicity and electrokinetics behavior.

Experimental Materials and Procedure

Hematite samples were hand ground to minus 10 mesh followed by ceramic ball mill grinding to achieve required size

By | 2018-05-17T18:44:13+00:00 May 16th, 2018|Categories: Flotation|Tags: |Comments Off on Hydrophobic Bacteria & Hematite Flotation

Industrial Box Furnaces

Our heavy-duty box furnaces are designed for an intensive and continuous use. Equipped with a ramp to set point digital indicating controller, our high temperature furnaces allow you to reach and accurately maintain the desired temperature. In order to minimize the heat up and cool down times, our furnaces are insulated with the best refractory bricks. The temperature control accuracy and the quality of the insulation of our furnaces enable you to achieve maximum performance and efficiency.

  • Heavy-Duty 2300°F Furnaces/1260°C
  • General Heat Treating
  • Annealing
  • HardeningThis is our high temperature industrial batch furnace. It looks like our tabletop furnaces for their interior design but offer higher continuous temperatures.

Let’s talk about one of our heavy-duty industrial box furnaces.  These furnaces are ruggedly constructed, heavy-duty, designed with high power ratings for production heat treating, processing heavy loads. A common Model is 54 inches high, 24 inches wide, 36 inches in length. We construct our models with angle iron frame, lined with a 10 and 12-gauge sheet metal. The front face plates are nice and thick. These are heavy-duty models.

The inside of the furnace is designed with heating elements on the

By | 2018-05-15T11:53:47+00:00 May 15th, 2018|Categories: Assaying|Comments Off on Industrial Box Furnaces

Assay Furnace

As a dealer of a top Brand of manufacturers of ovens and furnaces, well known in the mining industry for the design and production of custom-built equipment. Knowledge of this industry has enabled us to design an improved assay furnace. Technologically advanced, this furnace has several unique features which facilitate its use and assure results of the highest quality.

Our BEST SELLING assay furnaces:

  • 1-year-warranty
  • 24 crucibles (30 gram crucibles)
  • Overall dimensions
    40” W x 40” D x 76” H
  • Working space
    14½” W x 22” D x 7½” H

ASSAY FURNACE FEATURES

Made of heavy gauge sheet metal, is specially formed to provide superior structural strength. The control panel is slightly recessed, providing protection for the electronic controls. All electric and electronic controls are grouped at the base of the furnace. These easy-to-read controls include:

  • PB-6 electronic analogue temperature control, calibrated at our plant;
  • PB-6 electronic over-temperature safety control, calibrated at our plant;
  • one ammeter (1 phase) or three ammeters (3 phase);
  • pilot lights and switches;
  • security compactors.

HIGH QUALITY REFRACTORY BRICKS

  • Refractory brick ensure excellent insulating properties, resulting in reduced heat-up time, increased temperature uniformity and lower production
By | 2018-05-15T11:45:24+00:00 May 15th, 2018|Categories: Assaying|Comments Off on Assay Furnace

Erosion Protection Closure of Leach Heaps & Dumps

In the foreseeable future, closure and final abandonment of precious metals heap and dump leach operations is going to become more difficult and more expensive as each year passes. Aside from the removal or destruction of the heap’s or dump’s contained cyanide which is an entirely different subject, the other major problems facing the owner of the operation to be closed are;

  1. Both U.S.government and State government agencies duplicate each others efforts in regulating mining and metallurgical facilities.
  2. Federal and State regulations for closure are poorly defined and very often are ambiguous.
  3. There is continuing pressure on the government agencies by environmental groups to change, increase and enforce existing regulations with onerous penalties.

Ultimate heights for heaps will vary because of many factors but those in relatively flat areas can be of the order of 36.5 to 42.5 meters(120 to 140 feet) and there are valley fill heaps operating at heights of 61 meters (200 feet). Dump leaches are also operating at about the same 61 meter height. Because the impervious pad on which the ore rests and which collects the pregnant solution is capital intensive the higher the heap that

By | 2018-05-18T18:25:06+00:00 May 15th, 2018|Categories: Leaching|Tags: |Comments Off on Erosion Protection Closure of Leach Heaps & Dumps

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