Smelting fuel

Figures 6.3 and 6.4 show preindustrial and present-day circulation of S in earth s surface environment. Sulfur supply to the atmosphere by industrial activities (e.g., burning of fossil fuels, smelting) is 113 x lO g year that is about eight times of flux by volcanism (14 x lO g year" ) (Kimura 1989). Riverine sulfur flux to ocean is 208 x lO g year. A half of this flux is considered to be of anthropogenic source (Holland 1978). Sulfur in environment (atmosphere, river water) is the element that is significantly affected by human activity, the greatest among elements. According to previous estimates most of sulfur in acid rain transfer to river water. However, acid rain containing sulfur reacts with soil and evaporite, leading to the formation of sulfate minerals and fixation of sulfur in soil. If we take into accotmt the amount of sulfur fixation as sulfates in soil, previously obtained...

Flash smelting is efficient because the fuel value of the sulfur and iron in the charge is fully used, and the productivity (8—12 t/d of charge processed per square meter of hearth) is higher than that of the reverberatory or electric furnace. 

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). 

In primary smelting, carbon (in the form of coal or fuel oil) is the reducing agent. During heat-up, carbon monoxide is formed by reaction with... 

Smelting. The fuel suppHed to the reverberatory furnace is in the range of 5—6 GJ/t (4.7-5.7 x 10 Btu/t) concentrate. Steam produced in the waste heat boiler is equal to ca 60% of the energy suppHed by the fuel. The additional heat recovered from the exit gases in the recuperator to preheat the combustion air is equal to ca 10% of the energy from the fuel. Hence, the heat recovered from the furnace is equal to ca 70% of the heat from the fuels. 

Sulfur dioxide Fuel combustion (coal, oil), smelting and casting, manufacture of paper by sulfite process Primary metals (ferrous and nonferrous) pulp and paper Sensory and respiratory irritation, vegetation damage, corrosion, possible adverse effect on health... 

In Western Mining s flash smelting proeess, reaetion air is preheated to 480°C (920°F) and enriehed until the oxygen eontent is 24%. The reaetion eharge and eombustion air are mixed, and heat for smelting eomes from the eombustion of fuel oil (some of it present in the flux) and sulfur in the eoneentrate. The proeess yields matte, a refined ore with 44% niekel eontent. 

Cokers produce no liquid residue but yield up to 30% coke. Much of the low-sulfur product is used for electrolytic electrodes for smelting of aluminum. Lower-quality coke is burned as fuel im.xcd with coal. 

These formerly involved the use of banks of externally heated, horizontal retorts, operated on a batch basis. They were replaced by continuously operated vertical retorts, in some cases electrically heated. Unfortunately none of these processes has the thermal efficiency of a blast furnace process (p. 1072) in which the combustion of the fuel for heating takes place in the same chamber as the reduction of the oxide. The inescapable problem posed by zinc is that the reduction of ZnO by carbon is not spontaneous below the boiling point of Zn (a problem not encountered in the smelting of Fe, Cu or Pb, for instance), and the subsequent cooling to condense the vapour is liable, in the presence of the combustion products, to result in the reoxidation of the metal ... 

The formation of acidic deposition is largely from the combustion of fossil fuels and the smelting of sulfide ores. Minor natural sources exist such as the formation of hydrochloric and sulfuric acid from gaseous volcanic eruptions. 

Charcoal is used in electrically heated furnaces to smelt specialty metals such as ferrosilicon. It is a preferred household fuel in developing countries with adequate forest resources. In the United States 95 percent of charcoal use is for barbecuing, while in Japan and Europe charcoal use is split evenly between cooking and industrial needs. 

Fla Emission to atmosphere from fossil fuel burning and metal smelting 50 65 65 75 113 77"... 

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