Reduction furnace

The high lead slag from the smelting furnace is tapped continuously and transferred down a heated launder directly into the reduction furnace through a port in the side of the vessel. Lump coal for reduction is fed continuously to the furnace by conveyor and dropped direcdy into the bath. Heating for the endothermic reduction reactions is provided by oil injected down the lance. The combustion air stoichiometry is set at 95% of that required for complete oil combustion. Air is injected into the top of the furnace to afterbum the volatile materials from the coal and provide additional heat to the top of the furnace. Reduction temperatures range from 1170 to 1200°C to maintain slag duidity. 

The cmde lead and discard slag from the reduction furnace are tapped continuously through a single taphole into molds. The discard slags have a 1 to 2% lead oxide content and 1 to 2% of lead metal prills (pellets). 

The off-gas from each furnace is cooled in an evaporative gas cooler and cleaned in a reverse pulse baghouse before being either vented to atmosphere or used in manufacturing sulfuric acid. The baghouse dust from both the smelting and reduction furnaces is combined and recycled through the smelting furnace. 

Refractories for Electric Reduction Furnaces. Carbon hearth linings are used in submerged-arc, electric-reduction furnaces producing phosphoms, calcium carbide, all grades of ferrosilicon, high carbon ferrochromium, ferrovanadium, and ferromolybdenum. Carbon is also used in the production of beryllium oxide and beryllium copper where temperatures up to 2273 K ate requited. 

Subsequently, the dried ore is reduced in an electric furnace to ferronickel. Drying of the ore ensures smooth operation in the reduction furnace. As another example, reference may be drawn to the processing of kaolinite, Al2(Si05)(0H)4, for the recovery of alumina. The mineral is leached with dilute sulfuric acid. In the hydrated form, the mineral is insoluble in dilute mineral acids, and on drying at 400 to 800 °C, kaolinite is converted to the amorphous form, metakaolin, A1203 2 Si02 ... 

The industrial practice for the production of tantalum consists of two steps. In the first, the carbide is made by charging a graphite crucible with an intimate, pelletized mixture of lamp black and tantalum pentoxide and heating it in a high-frequency furnace under a dynamic vacuum (10 torr). In the next step, the ground carbide and the requisite amount of tantalum pentoxide are mixed, palletized, and fed to a reduction furnace where the reduction to the metal occurs. The formation of tantalum carbide as well as the reduction to the metal occur at about 2000 °C. The product leaving the reduction furnace is in the form of pellets or roundels (small cylinders) of porous metal, usually sintered together. 

Figure 3. Key factors to achieve efficient post-combustion in an iron-bath smelting reduction furnace. (From Takahashi et al., 1992.)...

Shinotake, A., and Takamoto, Y., Combustion and Heat Transfer Mechanism in Iron Bath Smelting Reduction Furnace, La Revue de Metallurgie - CIT, p. 965 (1993)... 

Takahashi, K., Muroya, M., Kondo, K., Hasegawa, T., Kikuchi, I., and Kawakami, M., Post Combustion Behavior in In-Bath Type Smelting Reduction Furnace, AS /./ Ini., 32 102 (1992)... 

Carbonyl sulfide is an intermediate in this reaction. A mixture of sulfur dioxide and oxygen was blown into the bottom of coke-fired reduction furnace and sulfur vapor condensed from the off-gases. Trail is the location of a large mine and smelter in British Columbia. The process was originally used in the 1930s for abating air pollution from the smelter, but when the demand for sulfuric acid for fertilizer production increased in 1943 it became obsolete. See also Boliden (1), RESOX. 

Tobias et al. [665] have described a method in which the GC effluent is passed into a combustion furnace to convert the organic hydrogen content into water, which is then selectively reduced to hydrogen in a reduction furnace containing Ni metal. The final stream is transmitted to the IRMS via a heated Pd filter, which passes only hydrogen isotopes to the ion source. For a benzene sample a precision of < 5 %o was obtained for <52HSMOw> which approaches the performance of off-line techniques and the requirements for studies of natural variability. This already meets requirements for analysis of D-labeled compounds used in tracer studies [666,667]. 

The electric furnace process (Fig. 11) for the conversion of phosphate rock into phosphorus was described by Horton et al. [15] in a paper that also presented the results of a pilot plant study of treating the wastes produced. The process, as well as the handling of the various waste streams for pollution control, are discussed in Section 9.5.2. In processing the phosphate, the major source of wastewater is the condenser water bleedoff from the reduction furnace, the flow of which varies from 10 to 100 gpm (2.3-22.7 m /hour) and its quality characteristics are presented in Table 7. 

It is interesting to note a recent announcement of the installation in the Portsmouth City Museum, United Kingdom of a large reduction furnace to stabilize ion antiquities, cannon in particular (41). It is indicated that experiments will be conducted to determine the feasibility of treating archaeological iron using the furnace, but not destroying the metaFs microstructural characteristics. ... 

Manufacture Calcium carbide is manufactured by reacting highly purified calcium oxide with coke in an electrical arc reduction furnace at 2000 to 2200°C ... 

Electrocorundum is obtained by reduction melting of the purest possible bauxite or alumina at ca. 2000°C with coke and anthracite in an arc reduction furnace, the impurity oxides in the raw material (iron, titanium, silicon) being thereby reduced and to a large extent removed. 

FIGURE 5.27. Rotary reduction furnace. By courtesy of Wolfram Bergbau- und Hiittenges. m.b.H., Austria. 

Equipment for converting from fossil fuels to hydrogen Hydrogen driven metal reduction furnaces Safety devices Hydrogen detectors for Industry Homes Vehicles Aircraft... 

Figure 7.12 Zirconium-reduction furnace, KroU process.

Research and Bench-Scale Feasibility Studies. The reaction between carbon and sulfur dioxide at elevated temperatures is well known and has been used for numerous processes. For example, sulfur was produced at Trail, British Columbia from 1935 to 1943 by blowing sulfur dioxide and oxygen into the bottom of a coke-fired reduction furnace. Coke was charged at the top and ash was removed on a rotary grate at the bottom of the furnace. The hot zone of the furnace was kept at 1300°C to maintain rapid reaction rates and smooth operation. Sufficient sulfur dioxide was added to the gas to react with the carbon monoxide and carbon oxysulfide contained in the reduction furnace off-gas. Coal was con-... 

Iron oxide also can be reduced in a direct reduction furnace, which operates at much lower temperatures (1300-2000°F) than a blast furnace and produces a solid "sponge iron" rather than molten Iron. Because of the milder reaction conditions, the direct reduction furnace requires a higher grade of iron ore (with fewer impurities) than that used in a blast furnace. The iron from the direct reduction furnace is called DRI (directly reduced iron) and contains —95% iron, with the balance mainly silica and alumina. 

Direct reduction furnace a furnace In which Iron oxide Is reduced to Iron metal using milder reaction conditions than In a blast furnace. (21.8)... 

Furnaces of various types— MnOa reduction furnaces, CS2 manufacture furnace. 

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