Slag refining

Sla.g ReHning. Unwanted constituents can be removed by transfer into a slag phase. Slag refining is also used for operations in which the Hquid metal is maintained in contact with a slag or a molten salt. This second immiscible Hquid is usually more oxidizing than the metallic phase and selective oxidation of the impurities renders them soluble in the slag or molten salt. Impurities that are less easily oxidized remain in the Hquid metal. 

Steelmaking. Steelmaking is the most economically important slag refining process (see Steel). Pig iron contains up to 4% carbon, 1% manganese, 1%... 

Harmonic light generation, 14 678-680 Harmonic spectroscopy, 23 139 Harringtonine, 2 90 Harrison Narcotic Act, 13 683 Harris slag refining process, 16 150 Harris softening process, 14 750, 754 Hartree-Fock SCF techniques, 16 736 Harvest aids, economic aspects of,... 

RCP [Recycled Clean Products] A high-temperature process for recycling sold wastes. It combines pyrolysis, smelting, and slag refining with postcombustion in a circulating, fluidized bed. Developed by Von Roll, Switzerland, and operated commercially in Germany since 1997. 

Refining by slag treatment is dependent on several parameters, such as reaction kinetics, diffusion of impurities, partition ratios, etc. Meanwhile, these parameters are dependent on the type of slag and its thermophysical and thermochemical properties. For example, viscosity, density, and interfacial properties affect the separation of slag from the metal and the duration of slag refining. 

Phosphorus - Phosphorus slag is a by-product of the elemental phosphorus slag refining process... 

Open-Arc Furnaces. Most of the open-arc furnaces are used in melting and refining operations for steel and iron (Fig. 1). Although most furnaces have three electrodes and operate utilizing three-phase a-c power to be compatible with power transmission systems, d-c furnaces are becoming more common. Open-arc furnaces are also used in melting operations for nonferrous metals (particularly copper), slag, refractories, and other less volatile materials. 

Production. Indium is recovered from fumes, dusts, slags, residues, and alloys from zinc or lead—zinc smelting. The source material itself, a reduction bullion, flue dust, or electrolytic slime intermediate, is leached with sulfuric or hydrochloric acid, the solutions are concentrated, if necessary, and cmde indium is recovered as 99+% metal. This impure indium is then refined to 99.99%, 99.999%, 99.9999%, or higher grades by a variety of classical chemical and electrochemical processes. 

HBI is an effective trim coolant for molten steel in ladle metallurgy faciUties, ladle refiners, ladle furnaces, and vacuum degassers. It provides cold iron units in an ideal size and density for penetrating the ladle slag and cooling the metal. 

In 1986 Britannia Refined Metals (Northfleet, U.K.) introduced technology for the treatment of Parkes cmst, a triple alloy of Ag, Zn, Pb, which by 1992 had been adopted by seven lead refineries (22). The technology consists of a three-stage process in which the silver-rich cmst is first Hquated to reduce its lead content, then placed in a sealed furnace where the 2inc is removed by vacuum distillation and, finally, the silver—lead metal is treated in a bottom blown oxygen cupel (BBOC) to produce a Htharge slag and dorn metal. 

Dead-burned magnesia, characterized by large crystaUite size and very low chemical reactivity, is resistant to the basic slags employed in the metals refining industry. It reacts very slowly with strong acids, and does not readily hydrate or react with carbon dioxide unless finely pulverized. 

A thorough review of the principles of siUcon and ferrosiUcon refining has been pubUshed (5,6). The equiUbrium ternary diagram between the Si02—CaO—AI2O2 slag and the Si—Al—Ca alloy at 1550°C is shown in Figure 1 (6). 

Ferrosihcon production is a nearly slag-free process. Most of the impurities introduced into the furnace via the raw materials and any other sources are transferred to the product. In order to produce high purity grades of ferrosihcon, the tapped ahoy is refined by treating with gas mixtures and slag additions. The principle of ferrosihcon refining is quite similar to that of sihcon. Details on the thermochemistry of ferrosihcon refining and practical examples are available (24). 

Refining. The cmde tin obtained from slags and by smelting ore concentrates is refined by further heat treatment or sometimes electrolytic processes. 

---