Final Sulfur Content Research Articles

РОЗРОБКА РОЗРАХУНКОВИХ МОДЕЛЕЙ ПИТОМИХ ВИТРАТ МАГНІЮ ТА ВМІСТУ СІРКИ В ЧАВУНІ ПРИ ДЛЯ УПРАВЛІННЯ ПРОЦЕСОМ ІНЖЕКЦІЙНОЇ ДЕСУЛЬФУРАЦІЇ ЧАВУНУ

Built and put into operation experimental industrial and industrial installations and cast iron desulfurization departments ensured a reduction of sulfur content in cast iron to 0.005-0.010% in industrial conditions. The purpose of the work is to reliably predict the calculation of the necessary consumption of magnesium from various conditions - the initial sulfur content, the mass of cast iron and the given final sulfur content to ensure the reduction of desulfurization costs. In addition, it is important to predict the current content of sulfur in cast iron depending on the consumption of magnesium in order to increase the reliability of the achieved content of sulfur in molten iron. The developments carried out to assess the regularities of the processes of out-of-furnace desulfurization of cast iron by monoinjection of granular magnesium made it possible to obtain calculation models for the assessment of existing and newly built capacities for desulfurization of cast iron in ladles of different sizes (40-350 t) at different initial sulfur contents in cast iron (0.02-0.07 %) and requirements for the final content of sulfur in cast iron (≤0.002-0.015%). Calculation models are presented.

Розробка номограм та розрахункових моделей питомих витрат магнію та вмісту сірки в чавуні при різних умовах інжекційної десульфурації чавуну

Built and put into operation experimental industrial and industrial installations and cast iron desulfurization departments ensured a reduction of sulfur content in cast iron to 0.005-0.010% in industrial conditions. The purpose of the work is to reliably predict the calculation of the necessary consumption of magnesium from various conditions - the initial sulfur content, the mass of cast iron and the given final sulfur content to ensure the reduction of desulfurization costs. In addition, it is important to predict the current content of sulfur in cast iron depending on the consumption of magnesium in order to increase the reliability of the achieved content of sulfur in molten iron. The developments carried out to assess the regularities of the processes of out-of-furnace desulfurization of cast iron by monoinjection of granular magnesium made it possible to obtain calculation models for the assessment of existing and newly built capacities for desulfurization of cast iron in ladles of different sizes (40-350 t) at different initial sulfur contents in cast iron (0.02-0.07 %) and requirements for the final content of sulfur in cast iron (≤0.002-0.015%). Calculation models are presented.

Application of ionic theory to calculate sulfide capacity of slags

The article considers the issues of sulfur removal in the ladle-furnace unit. The sulfur distribution coefficient depends on sulfide capacity of the slag, sulfur activity coefficient, oxidizing potential of the medium and equilibrium constant. The sulfide capacity CS of slags is one of the most important characteristics of refining capacity of the slags used in extra-furnace steel processing. One of the factors affecting the sulfide capacity is temperature. The formula was proposed showing the dependence of sulfide capacity on the optical basicity and temperature, in the temperature range of 1650 – 1400 °C and when the optical basicity Λ is not more than 0.75; the error of the presented formula does not exceed 6 %. The formula for calculating the optical basicity is proposed, which takes into account the influence of basic, acidic oxides and amphoteric oxide Al2O3. It is shown that slags, completely consisting of a homogeneous phase, have an increased optical basicity of aluminum oxide. Heterogeneous slags have a reduced optical basicity of Al2O3 in comparison with homogeneous slags. Perhaps, this fact can be explained by the fact that in homogeneous slags there is a deficiency of the basic oxide CaO and in the conditions under consideration Al2O3 compound begins to exhibit more basic properties than acidic ones, thus, in homogeneous slags, the optical basicity of aluminum oxide is increased and approaches optical basicity of CaO oxide. Calculations carried out on the basis of real heats have shown that with an increase in the content of Al2O3 oxide in the slag, its optical basicity decreases. Known value of the optical basicity makes it possible to determine sulfide capacity of the slag, sulfur distribution coefficient between metal and slag, and, accordingly, final sulfur content in the metal. The research results have shown that it is advisable to apply the ionic theory of slags for the sulfide capacity determination.

Development of a calculation method for evaluating technological parameters of the desulphurization process in a ladle

To fulfil the requirements for pipe steels of strength group D in terms of sulfur content, the metal is subjected to ladle desulfurization. In the course of desulfurization, in order to reduce its duration, steel is mixed in the ladle by blowing with argon. To optimize the desulfurization process, a methodology has been developed for evaluating its technological parameters, which allows determining under production conditions the intensity of steel blowing in the ladle. As initial data for comparative calculations of the technological parameters of the process of desulfurization of pipe steel in a ladle according to the developed method, the indicators of industrial melts were used, including the chemical composition of steel and the main technological data characterizing the production parameters of desulfurization of pipe steels of strength group D. The algorithm for using the proposed technique provides for the calculation of sulfur activity and the coefficient of sulfur activity in a steel melt of a given composition; determination of the oxidizing potential of the slag-metal system and the sulfide capacity of the slag; calculation of the equilibrium sulfur distribution coefficient between steel and slag, as well as the volumetric mass transfer coefficient under equilibrium and production conditions. To determine the thermodynamic characteristics of the interaction of sulfur dissolved in a metal with slag, the sorption ability of the slags of the analyzed melts with respect to sulfur was calculated. Data are presented on the effect of sulfur activity in experimental melts on the final sulfur content in steel. The rational limits of the value of the integral indicator of the composition of refining slags and volumetric mass transfer coefficient, which provide the best indicators of the process of desulfurization of steel, were determined. The dependences of the influence of the volumetric mass transfer coefficient on the duration of the process and the final sulfur content in the metal were established. The proposed methodology for assessing the technological parameters of steel desulfurization can optimize the duration of its individual stages and, thereby, reduce the cost of the process as a whole.

Three-phase trickle-bed reactor model for industrial hydrotreating processes: CFD and experimental verification

Catalytic hydrotreating (HDT) is a process used to remove impurities from refinery streams, reacting a given feed with hydrogen at high temperature and pressure in a trickle-bed reactor. In order to optimize the operation of such reactors, one needs information about the detailed performance of the reactor. However, mathematical models of such reactors have not received due attention in last decades. Therefore, this work aimed at revisiting a plug flow HDT model to predict the performance of industrial diesel hydrotreating reactor, which considers most of the HDT reactions, gas-liquid and liquid-solid mass transfer, as well as the influence of catalyst deactivation and quenches injection on model predictions. A fourteen pseudo-component reactional network was proposed and successfully used. Computational fluid dynamics (CFD) predictions verified the plug flow behavior of the industrial HDT reactor. Both the CFD and plug flow models were verified using real process plant data, inspecting residual sulfur content and temperature profiles, with maximum relative error of 14%. Pressure and species concentration profiles as well as the effect of inlet pressure and temperature on final sulfur content were predicted and discussed. Catalyst deactivation is an important factor for accurate prediction of industrial HDT over time of campaign.

Operational Costs of Hot Metal Desulphurization Processes

The main components of the operational costs structure of the Kanbara Reactor, Magnesium Mono-Injection and Co-Injection desulphurization processes for hot metal are discussed here. The pros and cons of lime, magnesium and calcium carbide as desulphurization agents are discussed, too. The aim of this work is to compare the updated operational costs reported in the literature in the last decade among the above processes using the accumulated annual inflation rates of US dollar, euro and Indian rupees. Besides, the operational costs of the process are discussed in terms of the initial and final sulphur content and the degree of desulphurization. The KR process presents the lowest reagents costs, whereas the co-injection process presents the highest reagents costs. The KR process presents the highest iron and temperature losses given the great amount of slag generated and the intense agitation of the rotary impeller. The co-injection process presents an exponential growth of the desulphurization costs as higher desulphurization degree is required.

ІНФОРМАЦІЙНО-МАТЕМАТИЧНЕ ЗАБЕЗПЕЧЕННЯ ТЕХНОЛОГІЇ ДЕСУЛЬФУРАЦІЇ ЧАВУНУ

The concept of the expert decision-making system for technological process management, created earlier at the Iron and Steel Institute of the National Academy of Sciences of Ukraine, provides for the choice of a rational technology for out-of-furnace desulfurization of cast iron. The purpose of this work is the further development of information and mathematical support of the expert system module for out-of-furnace processing of cast iron by co-injection of magnesium and lime in the framework of the target project to create end-to-end technology for high quality metal products. An integrated database of cast iron desulfurization process of a number of metallurgical enterprises of the People's Republic of China and the domestic DMK plant is presented. Based on the analysis of technological data, empirical equations were obtained to determine the final sulfur content in the cast iron melt, as well as the expression for estimating the specific consumption of metallic magnesium in the reagent. The developed models for calculating the specific consumption of reagents are the basis of the algorithm for calculating the indicators of the process of desulfurization of cast iron with co-injection of magnesium and lime. The input parameters are: temperature of cast iron, mass of cast iron, chemical composition of cast iron and slag, sulfur content initial and final, the proportion of magnesium in the reagent. Replenishment of the database with information on the technology of desulfurization of cast iron with a mixture of magnesium and lime allowed to clarify the existing and obtain descriptive models for these reagents. The developed information and mathematical support of the subsystem of out-of-furnace processing of pig-iron takes into account material and energy costs for redistribution, providing resource savings and the required quality of metal products.

Effect of Vanadium and Titanium on Desulfurization of CaO Slag in Liquid Iron

The possibility of vanadium and titanium participating in the CaO desulfurization reaction has been evaluated. The desulfurization products of CaO which were added to liquid iron containing vanadium–titanium in lab conditions were observed. At the early stage of adding CaO, titanium and sulfur ware agglomerated on the surface of CaO particles. The particles were composed of CaO, TiO2, and CaS. However, vanadium oxide was not detected. It was proposed that the titanium rather than the vanadium could react with CaO and sulfur. The desulfurization kinetics experiment showed that the high titanium content in liquid iron reduced desulfurization velocity, while vanadium had little effect on the desulfurization. The reason for this was that the TiO2 which surrounded the CaO particle impeded the mass transfer of sulfur. The vanadium and titanium had a little influence on the final sulfur content of CaO desulfurization. The theoretical discussion of these phenomena was carried out. The controlling reaction of final sulfur content was (CaO) + [S] + [C] = (CaS) + CO(g).

An impact of the ladle lining on the refining of reinforced steel when blowing with powders

When refining steel by blowing powders, the ladle lining material plays a serious role. The dependency graphs of the degree of desulfurization on the consumption of silicocalcium powder during blowing in ladles lined with various materials have been presented. It has been noted that the amount of FeO in the slag seriously affects the average degree of desulfurization. With a large amount of FeO in the slag, the degree of resulfurization is greatly increased. The placement plan of the unit for refining the liquid steel in the ladle has been illustrated. Simultaneously, for powder blowing, a device diagram of the ladle furnace fitted with equipment for blowing liquid steel with powders has been presented. In this equipment, powder lining can be used and steel blowing with silicocalcium based powders can be carried out. The degree of desulfurization is also seriously affected by the initial amount of sulfur in the metal charge for steelmaking The presence of a roof in the pouring ladles improves the conditions for metal blowing, oxidation and metal loss are reduced. It has been observed that the process of refining liquid steel in a ladle is complex and depends on many factors. The amount of sulfur in the primary metal charge, the lining of the ladle, the composition of the powder of the blown material and the technological parameters of the blowing are important. The complete desulfurization of steel by blowing with powders primarily depends on the initial amount of sulfur in the metal. It has been found that there is a linear dependence of the final sulfur content on its initial content in steel when metal is blown in a ladle with a mixture of 70 % MgO, 20 % CaO, and 10 % CaF 2 . The desulfurization of steel by blowing with powders, especially by blowing magnesium and calcium alloys, can be significantly affected by ladle lining

Investigation of desulfurization of Inconel 718 superalloys by ESR type slags with different TiO2 content

In the present study, effect of CaF2–CaO–Al2O3–MgO–TiO2 slag with various TiO2 contents on the desulfurization of Inconel 718 alloy was investigated at 1773K to provide the fundamental information for the establishment of desulfurization procedure during electroslag remelting (ESR) process. The melt-quenching method did not accurately determine the change in content of sulfur and oxygen in the nickel-based alloy with time for the present study, which uses a novel experimental apparatus. The results indicated that the final sulfur content in the nickel-based alloy increased from 7 to 9ppm when the TiO2 content in slag of CaF2–CaO–Al2O3–MgO–TiO2 system increased from 2.17 to 10% without addition of deoxidizer. In order to further expound the desulfurization mechanism, meanwhile, the relationship between the oxygen activity at slag–metal interface and reaction time under conditions of various TiO2 in the slag was studied by coupling with the developed mass transfer model. The calculated oxygen content in bulk metal has a good corresponding relationship with the measured oxygen content in the nickel-based alloy. The oxygen activity at slag–metal interface increased up to 9.6ppm when TiO2 content was 10% in the slag, giving rise to the decrease in desulfurization ratio in high TiO2 content. The optimal condition for simultaneously ensuring low sulfur content and maintaining oxidative elements, such as Al and Ti, uniformly from bottom to top of the ESR ingot is also discussed.

Intensified approach for desulfurization of simulated fuel containing thiophene based on ultrasonic flow cell and oxidizing agents

Intensified desulfurization of simulated crude fuel containing thiophene has been investigated using ultrasonic flow cell in combination with oxidizing agents such as peracetic acid, hydrogen peroxide (H2O2) and Fenton reagent at ambient conditions. The effect of thiophene loading, recirculation flow rate and the oxidant loading on the extent of desulfurization has been studied at 1 L capacity. Combination of ultrasound and hydrogen peroxide at optimized loading of 8% resulted in higher extent of desulfurization (38%) as compared to only ultrasound (17%). Higher degree of enhancement in extent of desulfurization (57% as the actual value) was observed for combination of ultrasound and peracetic acid at loading of 10%. Significant increase in extent of desulfurization was obtained for the combination of ultrasound and Fenton reagent (2 g/L FeSO4 + 10% H2O2) with actual extent being 87%. The conventional approaches of only hydrogen peroxide and only Fenton without ultrasound resulted in much lower extent of desulfurization as 22 and 40% respectively confirming the synergism for the combined process involving ultrasound. Maximum desulfurization extent as 96% was obtained for the approach of ultrasound combined with Fenton reagent at 2 g/L of FeSO4 and 15% H2O2 addition in three stages and 80 min of treatment time. The analysis of treated samples using HPLC spectra revealed that no other by-products or unwanted chemical species were formed during the treatment. The process intensification benefits have been clearly established in terms of much higher extent of desulfurization for combined approaches with the final sulfur content below minimum limit (5 ppm) whereas most of the conventional desulfurization approaches (without ultrasound) resulted in sulfur retention up to 10 ppm in final treated fuel.

Optimization of Co-Injection Desulfurization of Vanadium Bearing Hot Metal

The desulphurization process parameters of vanadium bearing hot metal were optimized. It is found that it has the best desulfurization effect in 100t hot metal ladle, when the lance position is 280mm, the ratio of lime to Mg is 3:1, and the Mg injection rate is 9kg/min. The Si and Ti content of hot metal can increase the activity of S. With the increase of Si and Ti content of hot metal, the final sulfur content has a reduction trend. When the content of Si and Ti is lower than 0.35%, the final sulfur content of hot metal increases, and the hit rate decreases. The effect of hot metal temperature on desulfurization end point hit rate is obvious. When the hot metal temperature is between 1300~1320°C, the hit rate of desulfurization end point is higher. When the temperature is below 1300°C or above 1320°C, the sulfur content increases. After optimization of process parameters, the Mg and lime consumption per ton of hot iron are reduced by 0.11kg and 0.54kg, respectively, with the average hit rate of desulfurization end point increased by 22.6% and 10.7%, respectively.

A numerical analysis as a good tool for a prediction of final sulphur steel ladle content

This work presents the industrial results of sulfur level prediction at the end of vacuum degassing (VD) of low carbon Al-Si killed steels. The effect of plant conditions, such as slag chemistry, temperature, oxygen levels of the molten steel, and slag weight on desulphurization was investigated based on the measured results and thermodynamic calculations. The variables which influence steel desulfurization such as the sulfur capacity, the initial sulfur content, and the amount of ladle slag at the end of the VD process are also defined. The desulfurization procedure was numerically analyzed using the results of 31 heats under real plant conditions in which the measured final sulfur content had been reduced to less than of 10 ppm. A method for prediction of the slag amount based on the material balance of sulfur and aluminum is also presented. The values of the sulfur capacity were determined according to the well-known KTH and optical basicity based models. The obtained results of the regression equation show a predictive final sulfur level ability of R=0.911. This was proved as satisfactory.

Chemical Degradation of Indigo Potassium Tetrasulfonate Dye by Advanced Oxidation Processes

The experimental degradation of a water soluble dye, potassium indigo tetrasulfonate salt, has been studied using stand-alone ozonation and photocatalytic oxidation process. Progress of the dye oxidation was followed by UV-VIS spectrophotometric measurements at controlled operating conditions. The organic content of reaction samples was measured to verify the process efficiency in dye mineralization. According to current results, almost complete color removal was obtained for ozonation within about 1 h reaction time. The reduction of the organic load was almost 80% from its original while initial sulphur content decreased to 32.5%. Dye conversion of 100% was obtained by means of a photocatalytic process using TiO2 as catalyst at 294 nm irradiated UV light. This complete color removal for the catalytic process was observed within 7 min of reaction time. The calculated initial rate of reaction of photocatalysis treatment was 8 times faster than that of ozonolysis. However, the remaining organic load of photocatalysis was almost 88% from its original while the final sulphur content was 27.3%. This contrasting behavior of the performance of the type of oxidation process stressed importance of physicochemical phenomena and intermediates molecules present during dye degradation. An insightful and mechanistic aspect of the dye oxidation was developed by performing quantumchemical calculations.

A mathematical model for the dynamic desulfurization process of ultra-low-sulfur steel in the LF refining process

In order to obtain the dynamic variation rule of the sulfur content of liquid steel in the LF refining process, a complete mathematical model including a desulfurization kinetic model and temperature model in the deep desulfurization process is presented, based on the practical production and reaction mechanism of ultra-low-sulfur steel in a LF. The results show that the calculated values of the sulfur content in liquid steel using the model fit the experimental values well, and the relative error is less than 8%. The effects of refining slag on the desulfurization process are analyzed in this paper, which shows that slag basicity is most important at the early and middle stages of the process, while slag weight is most important at the middle and late stages. The effect of the above factors on the final sulfur content of liquid steel is further analyzed quantitatively. The simulated results provide a theoretical basis to segment control the refining process in order to achieve the maximum effect, improving efficiency, saving energy and reducing consumption.

Effect of Additives on Desulfurization Capability of CAS-OB Refining Ladle Slag

To avoid slag sticking onto the ladle snorkel during the CAS-OB refining and alloying process, CaO-B2O3 and CaO-CaF2 were respectively employed as modifiers added into the ladle slag. The desulfurization capability of modified slag was investigated. The results of experiments on sulphur partition equilibrium between metal and slag indicate that the sulphur content of metal can be further decreased by the modified slag. When CaO-B2O3 is used as additive and the mass ratio of CaO to B2O3 is 1:1, the desulfurization ratio of slag to liquid steel is 50%, the final sulphur content can be controlled at 0.002%. The efficiency of desulfurization is fine. When CaO- CaF2 is employed as additive and the mass ratio of CaF2 to CaO is 2:8, the final sulphur content of metal can be controlled lower than 0.004%, the efficiency of desulfurization is also acceptable.

Effect of B<sub>2</sub>O<sub>3</sub> on Melting Temperature, Viscosity and Desulfurization Capacity of CaO–based Refining Flux

Fluorite is widely employed as fluxing agent in metallurgy flux, which inevitably leads to serious fluorine pollution. In this work, B2O3 is used as fluxing agent of CaO–based refining flux to substitute for CaF2 so as to decrease the melting temperature and to improve the speed of slag forming and the refining efficiency. The effects of B2O3 on the melting temperature, viscosity and desulfurization capacity of CaO–based refining flux were investigated. The results indicate that the fluxing action of B2O3 is better than that of CaF2 and Al2O3. For the high basicity CaO–based refining flux (mass ratio of CaO/SiO2 is 5.0–8.75), when CaF2 is substituted with B2O3, the melting temperature can be decreased remarkably. Especially, when the mass ratios of CaO/Al2O3 and CaO/SiO2 are in range of 1.1–4.0 and 5.25–8.0, respectively, the flux melting temperature is lower than 1300°C. At the same time, the temperature range, in which the flux viscosity is low, is expanded as well as the stability of flux viscosity varying with temperature is improved obviously. These variations of flux properties are favorable for refining process. The results of experiments on sulphur partition equilibrium between metal and flux indicate that the desulfurization capacity of flux can be improved markedly when CaF2 is substituted with equal mass of B2O3. When 4 mass% B2O3 is employed as fluxing agent and the mass ratio of CaO/Al2O3 is in the range of 1.5–7.0, the final sulfur content of metal can be controlled lower than 0.004%.

Use of Recycled Calcium Slag for Clean Steel Refining

Calcium slag (CS) is a by-product generated during smelting to extract calcium metal from the ore by aluminothermic reduction method. The melting point, melting speed, viscosities, surface tensions and the refining effects of CS and normal premelted refining slag (NPRS) were measured in the laboratory. Then the plant trials were done in a 150 tons Ladle Furnace (LF) in a steelmaking plant during the refining of clean steel. The results show that the properties of CS are similar to those of NPRS, and CS is a good refining agent not only in laboratory experiment but also in industrial production. By using CS, the average final sulfur content in X70 pipeline steel reaches 25×10-6; the total oxygen content in GCr15 bearing steel is 5×10-6~8×10-6; the titanium content in GCr15 bearing steel is less than 20×10-6 and lower than the steels refined by using NPRS.

Optimisation of hot metal desulphurisation at BOS2 Corus Strip Products IJmuiden

A project was started in 2002 to improve the hot metal desulphurisation by ladle treatment, whose underlying mechanism was analyzed by a process model based on fundamentals. This allowed a 10% reduction of reagent consumption. To reduce the treatment costs, calcium carbide was replaced by lime. Further results indicate the need to improve the absorption of reaction products into the slag. Lime post injection resulted in lower final sulfur content and improved slag removal.

Experimental Study on Soluble Oxygen in Hot Metal Pretreatment

The change law of oxygen activity was studied by using Fe2O3‐CaO‐CaF2 and Na2CO3/Na2SO4 fluxes under laboratory conditions. At the same time, the range of oxygen activity which is in favour of removing phosphorus and sulphur simultaneously was also investigated. The results showed that the oxygen activity in the iron melt during de‐phosphorization can reach up to 5.91×10−6~10.03×10−6 in about 5 min and then only varies within a narrow range. A final phosphorus content of 0.008% and a final sulphur content of 0.003% can be obtained if the oxygen activity is controlled within the range of 4.5×10−6~8.0×10−6.