Conversion smelting

Alternating current is converted to direct current (dc) for the smelting cells by siUcon rectifiers. High conversion efficiency (over 99%) and minimum capital costs are achieved when the rectified voltage is 600—900 V dc. Because aluminum smelting cells operate at 4.5—5.0 V, 130 or more cells are coimected in series, forming what the industry calls a potline, which may operate at 50—360 kA. 

Re OPe from Flue Gases. Recovery of sulfur dioxide from flue gases has been described (25,93,227). The stack gas from smelting often contains sufficient sulfur dioxide (ca 6 wt %) for economic conversion to sulfuric acid the lower concentration ki power plant stack gases generally requkes some method for concentrating the sulfur dioxide. 

Sulfur Dioxide Emissions and Control. A substantial part of the sulfur dioxide in the atmosphere is the result of burning sulfur-containing fuel, notably coal, and smelting sulfide ores. Methods for controlling sulfur dioxide emissions have been reviewed (312—314) (see also Air POLLUTION CONTROL PffiTHODS COAL CONVERSION PROCESSES, CLEANING AND DESULFURIZATION EXHAUST CONTROL, INDUSTRIAL SULFURREMOVAL AND RECOVERY). 

The environmental problem of sulfur dioxide emission, as has been pointed out, is very much associated with sulfidic sources of metals, among which a peer example is copper production. In this context, it would be beneficial to describe the past and present approaches to copper smelting. In the past, copper metallurgy was dominated by reverberatory furnaces for smelting sulfidic copper concentrate to matte, followed by the use of Pierce-Smith converters to convert the matte into blister copper. The sulfur dioxide stream from the reverberatory furnaces is continuous but not rich in sulfur dioxide (about 1%) because it contains carbon dioxide and water vapor (products of fuel combustion), nitrogen from the air (used in the combustion of that fuel), and excess air. The gas is quite dilute and unworthy of economical conversion of its sulfur content into sulfuric acid. In the past, the course chosen was to construct stacks to disperse the gas into the atmosphere in order to minimize its adverse effects on the immediate surroundings. However, this is not an en-... 

It may be perceived that a continuous, sulfur dioxide-rich stream can be produced if the smelting and converting operations of conventional technology can be combined in one continuous operation, and this has been attempted in the Noranda process. However, in the largest present-day installation subscribing to this process, the units are used primarily as smelters, with the conversion implemented in separate, conventional converters. 

Copper conversion is accomplished by a pyrometallurgical process known as smelting. During smelting the concentrates are dried and fed into one of several different types of furnaces. There the sulfide minerals are partially oxidized and melted to yield a layer of matte, a mixed copper-iron sulfide, and slag, an upper layer of waste. 

Carbon monoxide reacts with combined metal in the ore and reduces it into uncombined molten metal. Smelting iron, for example, proceeds by the conversion of iron oxide, in the ore, to uncombined iron metal ... 

Smelt, J.H., Leistra, M., Houx, N.W.H., and Dekker, A. Conversion rates of aldicarb and its oxidation prodncts in soils. III. 

The lead-chamber process supplied the world s need for sulfuric acid for a century and a half. In the late nineteenth century, the contact process replaced the lead-chamber process. The contact process utilized sulfur dioxide, SOj, which was produced as a byproduct when sulfur-bearing ores were smelted. The contact process was named because the conversion of sulfur dioxide to sulfur trioxide, SO3, takes place on contact with a vanadium or platinum catalyst during the series of reactions ... 

Energy demand, the implementation of sulfur oxide pollution controls, and the future commercialization of coal gasification and liquefaction have increased the potential for the development of considerable supplies of sulfur and sulfuric acid as a result of abatement, desulfurization and conversion processes. Lesser potential sources include shale oil, domestic tar sands and heavy oil, and unconventional sources of natural gas. Current supply sources of saleable sulfur values include refineries, sour natural gas processing and smelting operations. To this, Frasch sulfur production must be added. 

Hie manufacturing operations succeed each other in the following ordor —1. The calcination of the ores, by which the carbonaceous and volatile matters am burned off, and the whole reduced in bulk to prepare them for the smelting furnace 2. The extraction or reduction of the metal in Hie form of cast-iron by smelting 3. The conversion of the cast-iron into malleable or wrought iron by puddling end rolling and 4. The reconversion of the comparatively puro malleable iron into that particular carbide which is known as steel. 

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