Smelting – Melting – Refining

Copper Stabilization

“Stabilization” of copper differs from sin in at least one respect – no one seems to be against it. Every time a tycoon in the producing industry pontificates on the economic history of copper, or prophesies its future, he is likely to praise the virtues of “stabilization”. Consumers of copper constantly bemoan fluctuations in the supply and price of the metal. Governments in some producing countries, to a greater or lesser degree dependent upon exports of copper for foreign exchange and upon taxation of copper profits for substantial parts of their budgets, are perhaps more eager than any other group for “stabilization”.

Compared with earlier periods, that represents a very considerable degree of stabilization. It came about basically because of two things:

First, the existence of sufficient world productive capacity to take care of world demand, notwithstanding the occasional serious strikes representing important losses of production. Without the excess capacity, they could only have meant a runaway price.

Second, the voluntary reductions in production rates made by many of the major producers at an early enough time to prevent excessive accumulation of stocks, with a resultant serious erosion of price.

If the situation prevailing over the last three years is what is meant by

Smelting of Military Electronic Scrap

Gold, silver, and platinum group metals are widely used in electronic and electrical components to provide long-term reliability, Construction of military equipment consumes the largest proportion of the precious metals used in the electronic and electrical industry. Due to obsolescence and damage, military electronics are presently being scrapped at the rate of about 15,000 tons per year. This scrap averages approximately 100 troy ounces of silver, 5 troy ounces of gold, 1 troy ounce of palladium, and lesser amounts of other precious metals per ton.

The high level of development and use of military electronic hardware that soon becomes obsolete assures an expanding supply of scrap electronic components from military sources.

Because of its highly variable and complex nature, military electronic scrap is practically impossible to sample and analyze for metal content. This fact coupled with the inflexibility of presently used scrap-processing methods, limits disposal to a relatively small part of the scrap that is now generated and has been accumulated by military reclamation operations. The Bureau of Mines is currently investigating alternative methods for efficient, low-cost recovery of the precious and base metals in diverse mixtures of military electronic scrap.

Leaching techniques were tried initially for processing the electronic scrap. Nitric acid

Smelting & Refining Terms and Conditions – Typical Example

One of the most frequently asked questions is: “Where is copper (price and usage) going?” I will not attempt to forecast either the future price of copper or the future growth of the copper industry; rather I would like to discuss the current trends experienced in the smelting and refining terms and conditions for sales and/or purchases of copper concentrates.

A brief review of contract language and terms, together with a review of the common jargon, I believe, would be helpful. To accomplish this review, I will first list what I consider the four basic parts or sections of a basic ore contract and then illustrate basic terms with calculations.

Most ore contracts contain or refer to items in the following basic outline:

A) 1. Contracting Parties
2. Product
3. Quality
4. Quantity
5. Duration

B) 1. Delivery Basis (F.O.B., C.&F., C.I.F., etc.)
2. Shipping Schedule
3. Constructive Delivery

C) 1. Metal Payments and/or Return of Metal
2. Treatment and Refining and Delivery Deductions
3. Penalty Items

D) 1. Weighing, Sampling and Assaying
2. Settlement
3. Force Majeure
4. Diversion
5. Arbitration
6. Definitions
7. Specific Issues: Environmental Situations, Economic Stabilization, Duties, etc.

Many of the above items are self-explanatory and need no further discussion; others I will comment upon and advise what ideas or attitudes reflect recent trends.


How Minor Element Affects Copper Matte Smelting

Minor-element interactions in equilibrated samples of copper matte and silica-saturated iron silicate (fayalite) slag have been studied by the Bureau of Mines to gain basic and fundamental scientific information that will support the mineral industry’s effort to improve productivity, increase energy efficiency, and reduce undesirable environmental impacts. This work was carried out as an adjunct to a previous Bureau investigation on the behavior of minor elements in copper matte smelting operations The previous study focused on the combined disposition of five minor elements (As, Sb, Bi, Se, and Te) present simultaneously in the matte-slag system, whereas the present study reports the individual behavior of the same five minor elements present singly in the same matte-slag system. Any difference in the distribution or behavior between the multiple-element and the single-element study indicates the existence of a minor-element interaction.

Minor-element behavior has been studied extensively in the slag-matte-metal systems of various copper extraction processes. Mackey presents an exhaustive review of the existing literature in this area. Included are theoretical predictions of minor-element behavior made on the basis of thermodynamic data. However, in many cases, the necessary data are not available, and therefore, laboratory studies of the equilibria have been performed.

While minor-element behavior in

Improve Strength of Steel Alloys

Improve the strength and other properties of steel alloys.


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 steel tensile and yield strengthsNitrogen 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

Large Melting Furnace – City Waste

The most widely applied method for the disposal of waste materials, including sludges, dusts, scales, leachable slags from smelting or melting operations, and residues from the combustion of organic materials including municipal wastes, is to inter the materials in an appropriate landfill. Small quantities of some wastes are encapsulated within Portland cement or sulfur, and then consigned to a landfill. However, landfill disposal of wastes is at best a short-term solution, because landfills are nearing capacity and new landfills are difficult to establish. A promising and technically viable permanent solution to the problem is to melt the waste materials to produce inherently non- polluting amorphous or crystalline mixtures of inorganic oxide products, similar to slags produced by various metal industries. These products may be useful as aggregate for bituminous or Portland cement concrete, for grit blasting, as road building and construction ballast, and in the manufacture of mineral wool instead of landfill disposal.

In 1984, the ASME Research Committee on Industrial and Municipal Waste asked the U.S. Bureau of Mines about the feasibility of melting (vitrifying) ash residues produced by the combustion of municipal wastes. A demonstration melting test of dry combined bottom ash and fly ash from a waste-to-energy (WTE)

Precious Metal Refining

Precious Metal Refining: Dore is a mixture of gold and silver typically containing less than 5% base metal impurities. The exact composition varies widely depending on its source and processing history. Dore producers, in deciding whether or not to refine their dore, can custom design a facility around a single feedstock. Refiners, in contrast, must handle a variety of feedstocks. The ratio of gold to silver and the type and relative amounts of impurities determine the most effective refining sequence.

The typical strategy adopted by large refiners is base metal removal followed by the separation of gold and silver (known as parting), culminating with fine gold production. Platinum group metals are recovered and separated after gold. Figure 2 shows how three types of dore bullion can be integrated into this general scheme. Since it is all encompassing, the processing path for low-silver high-copper dore is described below.


After melting incoming dore for homogenization and sampling (discussed in a later section), most base metals are removed prior to parting gold and silver. This step is generally done pyrometallurgically, sometimes in the same equipment used for initial melting. In some cases, this step may be performed at the mine rather than at the

Partially Fluxed Pellets with Low Silica for Blast Furnace

Pot Grate tests were carried out in the pilot plant at Samarco producing pellets containing SiO2 between 2.0% and 2.2% in a wide range of basicity to be used in blast furnace.

Due to the fact that the tests depend on the various steps carried out sequence which can influence the results of the tests,, some criteria were adopted to restrict the number of variables in the process in order to facilitate the results of the analysis. The pellets were composed of concentrate, bentonit hydrated calcific lime and metallurgical coal, all regularly used in the pellet plant.

A large variety of blast furnace pellets we produced at pilot plant with binary basicity varying between 0,80 and 0,95. These pellets, after chemical analysis, were separated into 05 groups of different binary basicity (0,80; 0,84; 0,87; 0,90; 0,95).

The analysis of the results of the tests oi a pilot scale in conjunction with the customer led to the realization of a test on an industrial scale of production of pellets to comply with an experimental shipment of 50,000 DMT.

Based on the tests carried out in the pilot plant, binary basicity range of low SiO2 pellets (2,0%) produced in the industrial test should be between 0,90

Effect of Hydrogen Chloride / Cyanide Concentrations in Burning Chlorine & Nitrogen Fire

Within the mine health and safety program, the U.S. Bureau of Mines (USBM) continues its studies of belt materials’ properties during combustion to prevent mine fires and fire fatalities. The atmosphere produced by a fire is a dynamic, rapidly changing combination of toxic gases, particulates, reduced oxygen (O2), and high temperatures. In this atmosphere, visibility is generally low. Each component of this combination is capable of producing conditions that are incompatible with human life. As statistics have shown, the majority of fire fatalities results from smoke inhalation, prolonged by the inability to escape because of poor or nonexistent visibility, and not from burns. Therefore, the identification of the hazardous combustion products, evolved from materials under different fire conditions and times, is important.

During a fire, irritant [hydrogen chloride (HCl)] and asphyxiant [hydrogen cyanide (HCN) and carbon monoxide (CO)] gases may be present. Irritant gases produce sensory irritation of the eyes and of the upper respiratory tract, and pulmonary irritation. Most irritants produce signs and symptoms characteristic of both sensory and pulmonary irritation.

Hydrogen chloride gas concentrations of 100 ppm are immediately dangerous to life and health (IDLH). At this concentration, a breathing apparatus must be used; in case of apparatus failure, a

Electric Arc Furnace Steelmaking using Scrap

This investigation is part of the Bureau of Mines program to develop technology that emphasizes the reuse of recycled, economically important materials, including iron and steel scrap. In addition, the research helps meet the basic objective of substituting abundant domestic materials for imported strategic commodities such as fluorspar.

Scrap Preheating

Of the 84.6 million st of raw steel produced in the United States in 1983, 31 pct or 26.2 million st was produced in the electric arc furnace. Nearly all of this steel was derived from cold ferrous scrap materials using a series of backcharges whereby the furnace roof is opened periodically to admit additional scrap. It has been reported that 489 kW·h of energy is lost from a 40-st furnace each time the roof is opened to permit backcharging. The overall average energy consumption for steel produced by this process is approximately 535 kW·h/st. This represents 140 billion kW·h used to produce domestic steel by the electric arc furnace process in 1983, the last year for which figures are available. Increasing electric power costs, coupled with the need to improve efficiency and productivity of electric furnace steelmaking operations to compete with cheaper imported steel, provide an incentive to decrease

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