Final Sulfur Content Research Articles

A model of reoxidation from the top slag and the effect on sulphur refining during vacuum degassing

A 2‐dimensional fluid‐flow model covering 3 phases (steel, slag and gas) has been augmented to include thermodynamic equations to study simultaneous reoxidation and desulphurization, including macro kinetic behaviour. The numerical simulations were isothermal. Predicted steel and slag component concentrations were compared with plant data from vacuum degassing and the agreement was found to be quite good. When the initial FeO content in the slag was increased, the predicted desulphurization rate decreased, the final sulphur content in the steel increased, and aluminium loss increased. When the temperature was increased, the predicted aluminium loss decreased somewhat. The effect of changes in temperature on the predicted final sulphur content was influenced by the initial FeO content in the top slag. The results show that the model can be used for future work on the dynamic modelling of slag/metal reactions if the initial FeO content is less than 3–4% (by weight).

The production of ultra clean coal by chemical demineralisation

A high-volatile UK coal, with a particle size of <500μm, an ash content of approximately 7.9% by weight and a sulphur content of 2.6% by weight, was treated with aqueous HF followed by aqueous HNO3. The reaction residence time and temperature for both treatments were 3h and 65°C, respectively. HF reduces the ash content to approximately 2.6% by weight. The remaining ash largely consists of fluoride compounds such as AlF3, NaAlF4, CaF2 and MgF2, which form during leaching, and pyrite (FeS2), which does not react with HF. HNO3 then further reduces the ash content to approximately 0.6% by weight, by dissolving fluoride compounds and the Fe present as FeS2. The remaining ash consists largely of unreacted FeS2, which is encapsulated in the coal structure. This investigation also showed that HNO3 only reacts with FeS2 above a particular HNO3 concentration, which suggests that it is consumed preferentially, and to a certain extent, with the organic coal structure. The final sulphur content following treatment with HF and HNO3 was 1.4% by weight.

Determination of sulfide capacities of CaO-SiO2 slags containing CaF2 and B2O3 by an encapsulation method

The sulfide capacities of CaO-SiO2 melts containing CaF2 and B2O3 have been measured by simultaneous equilibration of samples within quartz capsules at 1503°C. In this method, the compositions of both the condensed phases and the static gas environment adjust to es-tablish a mutual equilibrium. Although the sulfurizing potential,PS2/PO2, is neither preset nor directly measured, the sulfide capacities,Cs, of all samples within the capsule are related by the following equation:CS(j)=(pct S)j/(pct S)i · CS(i)· Hence, the sulfide capacities of all samples may be calculated from the measurement of the final sulfur content of each sample and the inclusion of a “reference” slag sample for which CS is known from previous measurements. In the present study, quartz capsules containing as many as fifty slag samples including several reference samples have been equilibrated. With considerable difficulty the encapsulation-equilibration method atl503°C has been developed into an acceptable procedure. The influences of CaF2 and B2O3 on the sulfide capacities of several CaO-SiO2 melts have been measured. The results may be summarized as follows: 1) for melts of fixed CaO/SiO2 ratio, the addition of CaF2 increases sulfide capacity and the addition of B2O3 decreases sulfide capacity, 2) the substitution of CaF2 for CaO does not alter sulfide capacity significantly, and 3) the substitution of B2O3 for SiO2 increases sulfide capacity slightly. These results have been obtained for melts with CaO/SiO2 mass ratios ranging from 1.00 to 1.28 and with flux additions up to 10 wt pct.

Influence of Sulfur on Initial Permeability of Commercial 49% Ni–Fe Alloys

Attainment of high initial permeability in commercial 49% Ni–Fe alloys is shown to be a function of the sulfur content and grain size. Low sulfur material was obtained by desulfurization during melting or by strip annealing. μ40 of the low sulfur material was significantly higher than that of normal commercial material at annealing temperatures below 1200°C. When annealed at 1200°C, μ40 for the initially low sulfur material was slightly lower because of a smaller grain size or a higher final sulfur level. Analysis of sulfur content of annealed material by the methylene-blue technique allowed a direct correlation between μ40 and sulfur content in secondary recrystallized structures. In general, μ40 values in excess of 10 000 cannot be obtained unless final sulfur content is less than 12 ppm. Highest initial permeabilities result from a coarse-grained secondary recrystallized structure and low impurity contents.

Developments in basic oxygen process steelmaking practices at great lakes

Therefore, one can see the importance in developing these practices in the BOP. The presence of hot metal slag was shown to be influential in the final steel sulfur content and the end-point carbon and temperature. Low-manganese hot metal resulted in higher hot metal charges, increased spar usage, increased lance skulls, lower manganese residual, and increased nitrogen in the steel.