Blast furnace, alternative

Other Le d Smeltings Processes. Stricter regulations concerning lead emissions and ambient lead in ak levels (see Airpollution), and the necessity to reduce capital and operating costs have encouraged the development of alternative lead smelting processes to replace the sinter plant—blast furnace combination. 

Methods exist to make impure iron direcdy from ore, ie, to make DRI without first reducing the ore in the blast furnace to make pig iron which has to be purified in a second step. These processes, generally referred to as direct-reduction processes, are employed where natural gas is readily available for the reduction (see also Ironbydirectreduction). Carbonization of iron ore to make iron carbide as an alternative source of iron units is in its infancy as of the mid-1990s but may grow. 

The heat-exchanging surface in each stove is just under 11,500 m" (124,000 ft"). In operation, each stove is carried through a two-step 4-h cycle. In a 3-h on-gas step, the checkerbricks in a stove are heated by the combustion of blast-furnace gas. In the alternating on-wind... 

Carbon (coke) consumption, as a fuel and as a producer of the gaseous reductant, carbon monoxide, takes place in the blast furnace. An alternative source of such carbon, along with... 

One of the more important alternatives to the blast furnace for the production of iron is direct reduction of pelletised ore in a shaft reactor. The reducing gas mixture is usually obtained by steam reforming of natural gas and flows upward,countercurrent to the downward flow of solids. Sponge iron obtained by direct reduction may be used directly in arc furnaces for steel production. 

When reduced iron is heated with certain nitrogenous organic substances and metallic sodium, a cyanide is formed, the iron apparently acting as catalyser, being alternately oxidised and reduced.9 The presence of potassium cyanide m blast furnaces is thus readily accounted for. 

There have been sporadic attempts to produce aluminum by carbothermic reduction [3, 4]. In this approach, akin to the way iron oxides are reduced to iron in the iron blast furnace, the consumption of electrical energy is avoided or at least reduced. There have also been investigations of the production of aluminum by electrolysis of aluminum compounds other than the oxide (e.g. [5]). Some of these alternative electrolytic technologies have even reached a commercial scale [6] but the only method for aluminum production in industrial use today appears to be electrolysis in Hall-Heroult cells. Consequently, the present paper is confined to these cells. The literature on these cells is large. A recent search of the web of science with the subject Hall cell and similar subjects revealed 79 titles aluminum electrolysis yielded 109 publications. This number excludes papers published in the annual Light Metals volume of the Minerals Metals and Materials Society (TMS). Light Metals contains approximately forty papers each year on Hall cells. Consequently, the authors have made no attempt at a comprehensive examination of the literature on these topics. Rather we have included... 

Preparation.—In working the ores, rednetion is first effected in a blast-furnace, into which alternate layers of ore, coal and limestone are fed from the top, while air is forced in from below. In the lower part of the furnace COj is produced, at the expense of the coal higher up it is reduced by the incandescent fuel to CO, which, at a still higher point, reduces the ore. The fused metal, so liberated, collects at the lowest point, under a layer of slag and is drawn off to be castas f r iron. This product is then purified, by burning out impurities, in the process known as puddling. 

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