Sulfur Content In Iron Research Articles

Analysis of the use of magnesium-containing additives in the charge of iron flux in order to reduce CO2 emissions

The growing requirements for the quality of finished steel products oblige to obtain steel with a low content of harmful impurities, especially sulfur. The main charge for steel production in the conditions of JSC EVRAZ NTMK is vanadium iron, the external desulfurization of which leads to large losses of valuable vanadium. Therefore, the smelting of iron with a low sulfur content is an urgent task. The main way to reduce sulfur in iron is to increase the basicity of the slag (B2), but MgO is the best desulfurizer. The paper evaluates the effectiveness of the use of various magnesium-containing materials in the conditions of the blast-furnace stage of JSC EVRAZ NTMK, taking into account CO2 emissions. The possibility of replacing limestone in the iron flux charge with dolomite, as well as with steel converter slag, is considered. Both materials will increase the proportion of MgO in blast-furnace slag, however, the use of dolomite is accompanied by a two-fold increase in CO2 emissions compared to limestone. Converter steel slag (CSS) does not contain carbonates, thus eliminating the formation of CO2 during the limestone decomposition. An additional advantage of CSS is its high content of valuable vanadium and manganese. The effect of an increase in MgO in slag on its melting point is considered. It has been established that an increase in the proportion of MgO to 14% will not cause difficulties in the processing of blast-furnace smelting products and will reduce the sulfur content in iron and the formation of titanium carbides and carbonitrides.

Acidithiobacillus ferrooxidans and mixed Acidophilic microbiota oxidation to remove sulphur impurity from iron concentrate

This study reports the bacterial properties of mixed Acidophilic microbiota with sulfur as electron donor and Acidithiobacillus ferrooxidans (A. ferrooxidans) with FeS2 as electron donor and conducted microbial desulfurization experiments. The results showed that mixed Acidophilic microbiota and A.ferrooxidans could effectively reduce the sulfur content in iron concentrate, with the desulfurization efficiency of 79.8 % and 45.7 % in 30 days. And the recovery rates were above 90 % and 88 % respectively. The results of the Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS) showed that both bacteria oxidized the iron concentrate and removed the sulfur-containing impurity from the surface of the ore sample. According to the enrichment of elemental phosphorus on the sulfur of the ore sample, it can be deduced that the bacteria were oxidized. After the leaching of A.ferrooxidans, it was found that jarosite was generated, which was consistent with the conclusion of Stereomicroscope morphological observation. Based on X-ray photoelectron spectroscopy analysis, it was concluded that mixed Acidophilic microbiota could reduce the deposition on the surface of iron concentrate after the leaching of sulfate and improve the bioleaching efficiency. The conversion route of sulfur was identified to be from S2-/S22- to Sn2-/S0, and finally SO42-. In conclusion, a model for the oxidation of iron concentrate by A.ferrooxidans and Mixed Acidophilic Microbiota during bioleaching has been proposed.

Characterization of the Putative 2×[4Fe-4S]-binding NQO9 Subunit of the Proton-translocating NADH-Quinone Oxidoreductase (NDH-1) of Paracoccus denitrificans: EXPRESSION, RECONSTITUTION, AND EPR CHARACTERIZATION

Molecular properties of the NQO9 subunit of Paracoccus denitrificans NDH-1, which is predicted to contain 2x[4Fe-4S] clusters, were investigated using recombinant expression techniques and EPR spectroscopy. The full-length form of NQO9 subunit co-expressed with thioredoxin in Escherichia coli at ambient temperature was found dominantly in the cytoplasmic membrane with low amplification. Genetic deletion of relatively hydrophobic and less conserved N-terminal stretches (30 or 40 amino acid residues long) of the NQO9 subunit resulted in the overexpression of the truncated soluble form of the subunit in a high yield in the cytoplasm. The purified soluble form of the NQO9 subunit contained only a small quantity of Fe and S(2-) (2.0-2.2 mol each per mol of subunit). However, the iron-sulfur content was considerably increased by in vitro reconstitution. The reconstituted NQO9 subunit contained 7.6-7.7 mol each of Fe and S(2-) per molecule and exhibited optical absorption spectra similar to those of 2x[4Fe-4S] ferredoxins. Two sets of relatively broad axial-type EPR signals with different temperature dependence and power saturation profile were detected in the dithionite-reduced preparations at a low temperature range (8-18 K). Due to a negative shift (<600 mV) of the apparent redox midpoint potential of the iron-sulfur clusters in the soluble form of the truncated NQO9 subunit, the following two possible cases could not be discriminated: (i) two sets of EPR signals arise from two distinct species of tetranuclear iron-sulfur clusters with two intrinsically different spectral parameters g(, perpendicular) = 2.05, approximately 1.93, and g(parallel, perpendicular) = 2.08, approximately 1.90, and respective slow (P((1)/(2)) = 8 milliwatts) and fast (P((1)/(2)) = 342 milliwatts) spin relaxation; (ii) two clusters exhibit similar intrinsic EPR spectra (g(parallel, perpendicular) = 2.05, approximately 1.93) with slow spin relaxation. When both clusters in the same subunit are concomitantly paramagnetic, their spin-spin interactions cause a shift of spectra to g(parallel, perpendicular) = 2.08, approximately 1.90, with enhanced spin relaxation. In either case, our EPR data provide the first experimental evidence for the presence of two [4Fe-4S] iron-sulfur clusters in the NQO9 subunit.

鉄系圧粉体の焼結時の寸法変化におよぼす硫黄の影響

The effect of sulfur on the dimensional change during sintering was examined by using two different water-atomized iron powder groups with about 0.01 and 0.3mass% sulfur. The compacts of Fe-2mass%Cu-0.8mass%C-0.75 mass% zinc sterate were sintered in endogas and those of the Fe-C system were sintered in Hz and Ar to investigate the mechanism.In endogas in the case of the high sulfur powder, the suppression of the carburization by the atmosphere occurred in the α-Fe region and that by graphite occurred in γ-Fe, and the copper growth increased leading to more expansion during sintering. The suppression of the carburization also occurred in H2 and Ar in the case of the high sulfur powder, whereas it occurred only in Ar in the case of the low sulfur powder. By sintering Fe-C compacts containing excess graphite in Ar, it was found that the carbon solubility in γ-Fe decreased with increasing sulfur content in iron powder.The addition of FeS to the low sulfur powder brought about the suppression of the carburization and an extreme expansion in comparison with MnS. The mechanism was discussed from the view of thermodynamics.

Characterization of a new type of ferredoxin from Desulfovibrio africanus

A new ferredoxin designated ferredoxin III has been isolated from Desulfovibrio africanus grown on media high in iron. Native ferredoxin III is a dimer constituted by two identical subunits of approx. 7500. It is distinguished from the two other ferredoxins (I and II) isolated from this microorganism by its amino acid composition, N-terminal sequence, spectral properties and ironsulfur content. The amino acid composition of D. africanus ferredoxin III is typical of ferredoxins with an excess of acidic over basic residues and the absence of histidine and arginine residues. The absorption spectrum of ferredoxin III exhibits two maxima, at 408 nm ( ϵ = 58.5 · 10 3 M −1 · cm −1) and 285 nm ( ϵ = 82 · 10 3 M −1 · cm −1), with a shoulder at 305 nm ( ϵ = 75 · 10 3 M −1 · cm −1). Its A 408/A 285 absorbance ratio is 0.78. Ferredoxin III contains approx. 12–13 atoms each of iron and labile sulfur. This is in agreement with the high value of the extinction coefficient at 408 nm, which is slightly higher than 3-fold that of one [4Fe-4S] cluster. However, the number of cysteine residues of the protein (six residues), which is about the half that of iron atoms, is indicative of the presence of a new type of iron-sulfur cluster in ferredoxin III. The protein is unstable in a low ionic strength environment; the addition of neutral salts stabilizes the protein conformation. The data on the biological activity of ferredoxin III as compared to the two other ferredoxins from D. africanus show that the three iron-sulfur proteins function with equal effectiveness as electron carrier in the phosphoroclastic reaction and the H 2-sulfite reductase system.

The effect of calcium carbide on the sulfur content in iron

The effect of calcium carbide on the sulfur content in iron

Changes in pig iron sulfur content in the course of tapping

Changes in pig iron sulfur content in the course of tapping

Sulfides and oxides in Fe−Mn alloys: Part I. Phase relations in Fe−Mn−S−O system

This is a critical review of available equilibrium data between phases involving Fe, Mn, S, and O. Using the Morey-Williamson theorem, and that modified by Darken, the sulfur and oxygen potential diagrams are constructed for the Fe−S−O system involving nine univariant and three invariant equilibria. The solubility of sulfur in wustite-saturated iron is evaluated; the sulfur content of iron in equilibrium with wustite and liquid oxysulfide reaches a maximum of 143 ppm at 1200°C; this is about one half of that corresponding to the solidus of the Fe−S system. An estimate is made of the phase equilibria in the Fe−Mn−S−O quaternary system involving gamma iron and Mn(Fe)O phases. There is a eutectic invariant at ∼900°C, and the liquid miscibility gap invariant is estimated to be at ∼1225°C. From the expected phase relations and equilibria, it is deduced that if sufficient oxygen and sulfur,i.e. Mn(Fe)O and Mn(Fe)S phases, are present in Fe−Mn alloys, there may be a liquid oxysulfide phase present at temperatures above 900°C, depending on the concentration of manganese in solution. The higher the manganese content in solution, the higher is the temperature above which a liquid phase is present,e.g. for 10 ppm Mn, 900°C and for ∼90 pct Mn, ∼1225°C. A mechanism is suggested for the precipitation of sulfides and oxysulfides near the surface of steel during heating in an oxidizing atmosphere. In the Appendix by Darken and Gurry, results are given of the melting temperatures of mixtures of wustite and pyrrhotite in equilibrium with iron, from an investigation carried out about thirty years ago.

Reducing the sulfur content of iron in the blast-furnace smelting process

Reducing the sulfur content of iron in the blast-furnace smelting process