Assessment and application of equilibrium slag–metal phosphorous partition for basic oxygen steelmaking (original) (raw)
Related papers
Thermodynamics of Phosphorus and Sulphur Removal during Basic Oxygen Steelmaking
2010
Removal of impurity elements from hot metal is essential in basic oxygen steelmaking. Oxidation of phosphorus from hot metal has been studied by several authors since the early days of steelmaking. Influence of different parameters on the distribution of phosphorus, seen during the recent work of the authors, differs somewhat from that reported earlier. On the other hand, removal of sulphur during steelmaking has drawn much less attention. This may be due to the magnitude of desulphurisation in oxygen steelmaking being relatively low and desulphurisation during hot metal pre-treatment or in the ladle furnace offering better commercial viability. Further, it is normally accepted that sulphur is removed to steelmaking slag in the form of sulphide only. However, recent investigations have indicated that a significant amount of sulphur removed during basic oxygen steelmaking can exist in the form of sulphate in the slag under oxidising conditions. The distribution of sulphur during steelmaking becomes more important in the event of carry-over of sulphur-rich blast-furnace slag, which increases sulphur load in the BOF. The chemical nature of sulphur in this slag undergoes a gradual transition from sulphide to sulphate as the oxidative refining progresses.
Insights Thermodynamic in Basic Oxygen Steel Making Process
ISIJ International
In this study, a thermodynamics model was developed for the basic oxygen steelmaking (BOS) process (combined top & bottom blown), which was used to calculate the transient carbon, silicon, manganese, and phosphorus contents, as well as their slag composition, for different input hot metal-carbon contents. The model considered three different zones, and the volume of different phases was calculated using the Equip module of the FactSage macro processing code. The results of the model showed that manganese, phosphorus, and iron oxidation rates were high for input hot metal with low carbon content (3%). Additionally, the model predicted transient metal composition, and metal bath temperature, which were similar to plant observations for input carbon percentages ranging from 4 to 4.5.
Development of a new phosphorus partition relation for Australian steelmakers
2016
Phosphorus is generally undesirable in steel. Decreasing availability of low phosphorus iron ores and the desire to recycle waste materials like basic oxygen steelmaking (BOS) slags is driving renewed interest in phosphorus removal. A number of phosphorus partition (LP) equations have been proposed in the literature for specific slag compositions and temperature ranges at equilibrium. These LP equations have been evaluated against the historic data on the phosphorus removal from an industrial top blown bottom stirred basic oxygen convertor. Further, the performance of these partition equations has been used to inform the development of a new LP model more suitable to the prevailing conditions in the Australian steelmaking industry. The new model has been used to isolate the key factors controlling dephosphorisation, namely lower temperature, higher basicity and higher oxygen potential. This LP model has allowed secondary factors influencing dephosphorisation to be assessed, includin...
Thermodynamic Modelling of Phosphorus in Steelmaking Slags
High Temperature Materials and Processes, 2013
The published phase diagrams of some key P2O5-containing systems which are relevant to the steelmaking slag and the available experimental data on phosphorus partitioning between liquid iron and slags consisting of SiO2-Al2O3-Fe2O3-FeO-MnO-MgO-CaO-Na2O have been reviewed and assessed. A set of data under carefully controlled experimental conditions, which was considered to be more reliable based on the assessment, was selected for optimising the generalised central atom (GCA) model parameters of phosphorus-containing slag systems. The developed model database is proved to be able to represent the liquidus temperature of some key P2O5-containing systems and the phosphorus distribution ratio between the steelmaking slags and liquid iron reasonably well. With the developed GCA model database, the dephosphorization reaction in the steelmaking process was modelled under various operating conditions such as slag chemistry and temperature. The results show that the phosphorus distribution ...
Phosphorus Partition between Liquid Steel and CaO-SiO 2 -P 2 O 5 -MgO Slag Containing Low FeO
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2007
CaO-SiO2-FeOx -P2O5-MgO bearing slags are typical in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influences of FeO concentration and basicity on the equilibrium phosphorus partition ratios were experimentally determined at temperatures of 1873 and 1923 K, for conditions of MgO saturation. The partition ratio initially increased with basicity but attained a constant value beyond basicity of 2.5. An increase in FeO concentration up to approximately 13 to 14 mass pct was beneficial for phosphorus partition.
New trends in basic oxygen furnace dephosphorization
Journal of Mining and Metallurgy, Section B: Metallurgy
Except for special grades of steel where it is used as an alloying element, phosphorus is regarded as an impurity that must be removed. Considering the conventional integrated iron and steelmaking, there are primarily two processes for phosphorus removal. The first is a hot metal dephosphorization (DeP) process that is applied to a blast furnace for hot metal before the steelmaking process. The second is the basic oxygen furnace steelmaking (BOS), a unique method primarily used for steelmaking, with the exception of stainless steels. Hot metal phosphorus content has a direct impact on BOS. An increase of phosphorus in hot metal is mainly related to the use of high P2O5 containing iron ores. In the current literature review, new trends of phosphorus removal in converter steelmaking are outlined. The double-slag practice was reported to be successful when hot metal P content was larger than 0.100%. It was indicated that the tapping temperature was critical for the production of low-ph...
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2007
CaO-SiO2-FeOx -P2O5-MgO bearing slags are typically used in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influence of factors such as FeO content and basicity on the phosphorus partition ratio was investigated at two different temperatures. The partition ratio initially increased with basicity but remained constant beyond a basicity of 2.5 to 2.6. An increase in the FeO content up to 18 to 20 mass pct was beneficial for the phosphorus partition at a basicity level of 2 to 3, but a higher concentration of FeO resulted in a decrease in the phosphorus partition ratio; the FeO concentration corresponding to this transition varied with basicity and temperature. At even lower basicities, however, the equilibrium phosphorus partition showed either no change, or a marginally decreasing trend, with an increase in the FeO content.
Dephosphorisation in Bof Steelmaking
2009
Phosphorus content in hot metal has been increasing in the last years at Huachipato Steel plant, as low phosphorus iron ore availability has been decreasing, with a clear tendency to continue the same trend. This has led to study the phosphorus slag-metal partition ratio at the BOS furnaces both in high carbon and low carbon steelmaking. Steel and slag samples were taken both for high carbon and low carbon steels. Some samples were also taken during the blow to evaluate slag composition evolution. Blowing practices at CSH consider obtaining high carbon steels via catch-carbon practices. Blowing patterns are designed to obtain partition coefficients around 80 for high carbon steels. Low carbon steels, with harder blowing practices, attain values close to 100. Vanadium behaves very much like phosphorus, and its average partition coefficients measured are around 200 for high carbon steels, and 400 for low carbon steels. Both phosphorus and vanadium presence in the BOF high carbon steel...