Hematite reduction

A few processes with reactive solids are listed in Table 8.1. Oxidation of zinc ore, that is, zinc sulfide, is a process in which the size of the reactive solid particle remains approximately the same zinc sulfide is oxidated to zinc oxide. Similar reactions occur, for example, in the oxidation process of pyrite to hematite. Reduction processes of metallic oxides with hydrogen in the production of pure metals are also processes in which the size of the solid phase remains unchanged. Another example of a reduction process is the reduction of magnetite to metallic iron. 

Table 111. The Thermodynamics Equilibrium Constant K and 0(CO) of Hematite Reduction...

Hematite is the main component of iron oxidized pellets, and the reduction reaction process of hematite follows the principle of gradual transformation. The reducing agent is the simulation of coal gas, of which the main component is hydrogen and carbon monoxide. When temperature is higher than 570 C, oxide transformation process during the hematite reduction is as follows ... 

Assuming that the initial iron oxide is hematite, Fe202, and this ore is completely converted to FeO, ie, no metallic iron is formed, the reduction would be 33.33%. Thus the relationship between metallization and reduction is... 

The reduction of iron ore is accompHshed by a series of reactions that are the same as those occurring in the blast furnace stack. These include reduction by CO, H2, and, in some cases soHd carbon, through successive oxidation states to metallic iron, ie, hematite [1309-37-17, Fe202, is reduced to magnetite [1309-38-2], Fe O, which is in turn reduced to wustite [17125-56-3], FeO, and then to metallic iron, Fe. The typical reactions foUow. 

Some results of the reduction of hematite by graphite at 907 to 1,007°C in the presence of lithium oxide catalyst were correlated by the equation 1 — (1 — xY = kt. The reaction of solids ilmenite and carbon has the mechanism... 

Iron, a large component of steel, is obtained by reducing iron(III) oxide (present in hematite ore) with hydrogen in a blast furnace. Steam is a byproduct of the reaction. Calculate AS° at 230°C for the reduction of one mole of Fe203. 

The most important metallurgical process involving carbon is the reduction of hematite ore, which consists largely of iron(III) oxide, Fe203, mixed with silicon dioxide, Si02. Reduction occurs in a blast furnace (Figure 20.4a) typically 30 m high and 10 m in diameter. The... 

Iron has been the dominant structural material of modem times, and despite the growth in importance of aluminum and plastics, iron still ranks first in total use. Worldwide production of steel (iron strengthened by additives) is on the order of 700 million tons per year. The most important iron ores are two oxides, hematite (Fc2 O3) and magnetite (Fc3 O4). The production of iron from its ores involves several chemical processes that take place in a blast furnace. As shown in Figure 20-22. this is an enormous chemical reactor where heating, reduction, and purification all occur together. 

The liquid-phase reduction method was applied to the preparation of the supported catalyst [27]. Virtually, Muramatsu et al. reported the controlled formation of ultrafine Ni particles on hematite particles with different shapes. The Ni particles were selectively deposited on these hematite particles by the liquid-phase reduction with NaBFl4. For the concrete manner, see the following process. Nickel acetylacetonate (Ni(AA)2) and zinc acetylacetonate (Zn(AA)2) were codissolved in 40 ml of 2-propanol with a Zn/Ni ratio of 0-1.0, where the concentration of Ni was 5.0 X lO mol/dm. 0.125 g of Ti02... 

This discrepancy might be explained if after about an hour the reaction approached equilibrium and slowed due to a diminishing thermodynamic drive. If the Fe+++ produced did not precipitate on the hematite surface, and did not form either hematite or goethite (FeOOH), it would accumulate in solution and weaken the drive for uranyl reduction. As the saturation index for hematite reached about 1.7, or about 1.25 for goethite, reaction would cease. 

Figure 6.6 In situ XRD of an alumina-supported iron catalyst during reduction in H2 at 675 K reveals the transition of a-Fe202 (hematite) via Fe(04 (magnetite) to metallic iron as a function of time. The graph shows the degree of reduction of supported and unsupported oc-Fe203 as determined from the XRD measurements (from Jung and Thomson f 14]).

The Rate of reductive Dissolution of Hematite by H2S as observed between pH 4 and 7 is given in Fig. 9.6 (dos Santos Afonso and Stumm, in preparation). The HS" is oxidized to SO. The experiments were carried out at different pH values (pH-stat) and using constant PH2s- 1.8 - 2.0 H+ ions are consumed per Fe(II) released into solution, as long as the solubility product of FeS is not exceeded, the product of the reaction is Fe2+. The reaction proceeds through the formation of inner-sphere =Fe-S. The dissolution rate, R, is given by... 

Photocatalytic Reductive Dissolution of Hematite in the Presence of Oxalate... 

In the absence of oxygen the photocatalytic reductive dissolution of hematite in the presence of oxalate occurs according to the following overall stoichiometry (Siffert and Sulzberger, 1991) ... 

In aerated suspensions no measurable (in the time-frame of typical experiments) reductive dissolution takes place and hematite acts as a photocatalyst for the oxidation of oxalate by 02 ... 

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