Hydrogen metallurgical reductant

The reduction of metal oxides (M Oy) by hydrogen gas is metallurgically valuable. Water is produced in this reaction ... 

Carbonization. When coal is heated to temperatures 900 to 1200°C in the absence of air, most of the volatile matter is driven off, leaving a char, or, in the case of metallurgical bituminous coal, a coke. The atmosphere in a coke oven consists principally of hydrogen and methane. Consequently, pyrite is reduced to a mixture of iron sulfide (troilite and pyrrhotite) and iron metal [ ]. The amount of iron metal formed depends on both the temperature and the composition of the coke-oven gas. The reduction of iron sulfide to iron metal is desirable since blast furnace operation is more efficient with low sulfur coke. Calcite reacts with the liberated sulfur to form calcium sulfate, thus retaining sulfur in the coke. Calcium XANES spectra of coke produced from Pittsburgh seam coal in which all calcium is initially present as calcite indicate that approximately 70 percent of the calcite is converted to calcium sulfate during coking. 

A schematic of the plasma-metallurgical reactor based on the apphcation of a plasma fluidized bed is shown in Fig. 7-20. The reduction process is due to both carbon mixed with FeO Ti02 and hydrogen used as a gas energy carrier in the discharge. (Juasi-thermal plasma is generated in the reduction reactor by means of a spark discharge between two electrodes. 

Hydrogen reduction of chlorides in thermal plasma can be apphed not only to produce powder of individual metals but also to produce different intermetalhc compounds. The composition of the generated crystals copies the composition of the chloride mixture in the gas phase. This effect permits the production of the intermetallic compounds with the required composition. Refractory intermetallic compounds based on niobium and vanadium were synthesized from their chlorides (conversion close to 100%) in a hydrogen plasma jet generated by RF-ICP discharge (Bashkirov Medvedev, 1968). The reaction products were crystallized on a substrate sustained at a temperature of about 1000°C. The plasma-metallurgical technology is proven to be effective in the synthesis of vanadium-Hsilicon... 

Presently, hydrogen is mostly being produced from fossil fuels (natural gas, oil, and coal). Hydrogen is used in refineries to upgrade crude oil (hydro treating and hydro cracking), in the chemical industry to synthesize various chemical compounds (such as ammonia, methanol), and in metallurgical processes (as a reduction or protection gas). 

Here, two conclusions are important from this mechanism derived from metallurgical samples of magnetite/wiistite synthetic mixtures. First, the elemental iron is essential to reduce magnetite with hydrogen gas at low temperature. This elemental iron is produced from thermal decomposition of the wiistite mixture in the precursor. Stability and bulk distribution of the wiistite determine the abundance of reaction interfaces in the polycrystalline solid. The grain structure and porosity of the final catalyst is mainly predetermined by the disposition of these reaction centers representing the nuclei of the iron metal crystallines. Second, the reaction involves movement of all iron ions and allows a complete bulk restructuring of the solid at low temperature. The topochemistry of the reduction process will determine... 

The most important use of hydrogen is for hydroprocessing in the petrochemical industry, but hydrogen is also used for hydrogenation in the chemical and food industries and for reduction in the metallurgical industry. 

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