The present study was carried out to investigate theformation and chemical development of non-metallic inclusionsduring ladle treatment of steel. To begin with, an investigation of the deoxidation processand the impact of aluminium addition was carried out. For thispurpose, a new experimental setup was constructed. The setupallowed the examination of the deoxidation process as afunction of time by using a quenching technique. Preliminaryexperiments showed that homogeneous nucleation of alumina tookplace in the areas supersaturated with aluminium. Theseexperiments also showed that agglomeration of alumina particleswas a very rapid process, even when the convection in the meltwas negligible. In order to examine whether aluminium supersaturation occursduring industrial practice, the deoxidation of liquid steelwith aluminium wire injection in a gas-stirred ladle wassimulated by mathematical modeling using a Computational FluidDynamics (CFD) approach. The results showed that theconcentration of aluminium in the vicinity of the aluminiumwire injection was high enough to generate homogeneousnucleation of alumina. Aiming at an understanding of the inclusion chemistry duringthe ladle process, an industrial study was performed atUddeholm Tooling AB. The impact of slag-lining reactions andladle glaze as a source of inclusions in the melt was alsostudied. The experimental results were analysed from athermodynamic viewpoint to gain an insight into the origins ofthe inclusions and their changes along the process of the ladletreatment. Six types of inclusions were found in the steel. Thetypes of inclusions present varied along the history of theladle treatment. Three types of inclusions were found in theliquid steel before deoxidation, namely type A (a liquidinclusion with high SiO2 concentration), type B (spinel) andtype C (a combination of type A and type B). Thermodynamicanalysis indicated that these types of inclusions could begenerated by the reaction between the Electric Arc Furnace(EAF) slag and the ladle glaze, during the filling of theladle. The addition of aluminium resulted in the formation ofalumina inclusions (type E), which agglomerated and separatedfrom the steel very fast. The spinel inclusions of type B werefound to be unstable at low oxygen potentials. The inclusionsof this type would react with the liquid metal forming theinclusions of type F (spinel in the centre surrounded by anoxide solution containing Al2O3, CaO and MgO). Further,reaction between the liquid metal and inclusions of type Fwould result in the inclusions of type G, an oxide solutionmostly consisting of Al2O3 and CaO with small amounts of MgOand SiO2. The inclusions of type G were the only inclusionsfound in the steel before casting.

<p>The present study was carried out to investigate theformation and chemical development of non-metallic inclusionsduring ladle treatment of steel.</p><p>To begin with, an investigation of the deoxidation processand the impact of aluminium addition was carried out. For thispurpose, a new experimental setup was constructed. The setupallowed the examination of the deoxidation process as afunction of time by using a quenching technique. Preliminaryexperiments showed that homogeneous nucleation of alumina tookplace in the areas supersaturated with aluminium. Theseexperiments also showed that agglomeration of alumina particleswas a very rapid process, even when the convection in the meltwas negligible.</p><p>In order to examine whether aluminium supersaturation occursduring industrial practice, the deoxidation of liquid steelwith aluminium wire injection in a gas-stirred ladle wassimulated by mathematical modeling using a Computational FluidDynamics (CFD) approach. The results showed that theconcentration of aluminium in the vicinity of the aluminiumwire injection was high enough to generate homogeneousnucleation of alumina.</p><p>Aiming at an understanding of the inclusion chemistry duringthe ladle process, an industrial study was performed atUddeholm Tooling AB. The impact of slag-lining reactions andladle glaze as a source of inclusions in the melt was alsostudied. The experimental results were analysed from athermodynamic viewpoint to gain an insight into the origins ofthe inclusions and their changes along the process of the ladletreatment. Six types of inclusions were found in the steel. Thetypes of inclusions present varied along the history of theladle treatment. Three types of inclusions were found in theliquid steel before deoxidation, namely type A (a liquidinclusion with high SiO2 concentration), type B (spinel) andtype C (a combination of type A and type B). Thermodynamicanalysis indicated that these types of inclusions could begenerated by the reaction between the Electric Arc Furnace(EAF) slag and the ladle glaze, during the filling of theladle. The addition of aluminium resulted in the formation ofalumina inclusions (type E), which agglomerated and separatedfrom the steel very fast. The spinel inclusions of type B werefound to be unstable at low oxygen potentials. The inclusionsof this type would react with the liquid metal forming theinclusions of type F (spinel in the centre surrounded by anoxide solution containing Al2O3, CaO and MgO). Further,reaction between the liquid metal and inclusions of type Fwould result in the inclusions of type G, an oxide solutionmostly consisting of Al2O3 and CaO with small amounts of MgOand SiO2. The inclusions of type G were the only inclusionsfound in the steel before casting.</p>

This thesis presents a review of optimal production scheduling in the steel industry. Steel production encompasses various processes, such as the ‘’Blast Furnace’’ and ‘’Hot-Rolled Steel Sheets Mill’’. However, this thesis specifically focuses on the steel making process due to its intermediate nature and substantial influence on profits and costs. \\\\This paper presents a MILP scheduling method to tackle practical steel scheduling problems. The scheduling of steel process poses a significant challenge due to complicated constraints and machine rules, making it a time-consuming task to obtain an optimal solution. To address this problem, a strategy has been proposed to break down the huge and complex problem into smaller sub-problems. The foundational concept behind this approach was initially introduced by Harjunkoski and Grossmann (2001). However, further improvements are proposed in this thesis by introducing a more flexible model for process and grading selections, tailored to practical steel scheduling problems. The thesis presents a strategy to obtain optimal steel making process scheduling by using a MILP approach. In addition, this thesis shows an optimal steel making process scheduling under processing time uncertainty. Uncertain processing time can have great impact the schedule accuracy. To tackle with this problem, a stochastic scheduling model is represented. Moreover, this thesis illustrates an improvement to generate a practical scheduling of steel making process by making use of real processing time data. To validate the effectiveness of our proposed methods, we provide a small example for each step of the scheduling process. The results demonstrate that our approach yields reasonable scheduling solutions. / Thesis / Master of Applied Science (MASc) / In this work, we propose a decomposition strategy for solving practical complex scheduling problems in the steel-making process within a sufficiently short computation time. While there are various processes involved, such as the Cold-Rolled Steel Sheets mill and Steel Pipe mill, we focus on the steel-making process. The optimal scheduling of this process is crucial for increasing profits, reducing waste, and minimizing costs. However, scheduling optimization for the steel-making part presents significant challenges due to complex constraints and specific process rules. To address these challenges, we suggest a decomposition strategy in Chapter 3 of this thesis. This strategy primarily involves breaking down the large and complex scheduling problems into smaller subproblems. While a basic solution strategy is provided in the work of Harjunkoski and Grossmann (2001), our research introduces several improvements tailored to practical scheduling problems. For example, the original paper suggests grouping products together only if they have the same grade. In practical scheduling, however, it is often necessary to mix products of different grades within the same group to maximize productivity and operate efficiently. Additionally, the original paper considers only a single machine for each downstream process. In reality, there are often multiple machines involved in each downstream process. Therefore, our research addresses this challenge by incorporating two refining machines and two continuous casting processes into the scheduling formulations for the downstream process. As a result, the suggestions presented in this paper contribute to handling more flexible patterns of scheduling problems. In Chapter 3, the formulation is based on the aforementioned idea, and its validation is confirmed through a case study. While the obtained scheduling results may not be optimal, they are reasonable for each step when compared to the perspective of an experienced person. Furthermore, the computational time required for each step is less than 1 minute. As a result, the proposed scheduling strategy can effectively solve practical scheduling problems within a limited time frame. The strategy is specifically designed to incorporate mixed grade grouping, as well as multiple and flexible structures for downstream processes. In addition, in the steel industry, fluctuation in process time is inevitable because of the high temperature and high-speed conditions to produce products. To address these problems, in Chapter 4, we propose a strategy to incorporate processing time uncertainty into a decomposition strategy. The strategy is based on the two-stage stochastic scheduling formulation. In practical steel industries, there are many preparations before producing the products such as setting a specific condition and maintaining the facilities, and the preparations are based on the scheduling product's order. Therefore, in this formulation, the variables defining the product's order are regarded as the first decision variables to reflect a practical scheduling problem. The formulation is based on this concept, and its validation is confirmed through application to a practical case study. The results are reasonable by comparing to the knowledge of an experienced person. Furthermore, the computational time required for this strategy is also less than 1 minute. Therefore, the strategies presented in this thesis offer an efficient approach for addressing practical steel-making scheduling problems.

O debate sobre o problema siderúrgico nacional no Brasil ganhou corpo no final da década de 1900 e estendeu-se até 1941, com a criação, pelo governo federal brasileiro, da Companhia Siderúrgica Nacional (CSN) para construir e explorar a usina siderúrgica de Volta Redonda, que foi saudada como a solução do problema, encerrando assim um debate de mais de três décadas. Por esse motivo e pela importância simbólica de que se revestiu a CSN para o Estado Novo, a historiografia foi bastante marcada por esse desfecho particular, que à luz do próprio debate não tinha nada de necessário. Tendo isso em vista, esta tese visa reconstruir e analisar os esforços, debates e conflitos em torno da questão siderúrgica ao longo da Primeira República. Buscamos identificar os principais agentes que intervieram e pesaram no direcionamento das políticas governamentais relativas ao setor siderúrgico e procuramos apresentar as principais propostas feitas e iniciativas tomadas por esses agentes, bem como mapear as implicações dessas iniciativas e propostas para o desenvolvimento do setor. Três dos principais eixos em torno dos quais giraram os debates foram os seguintes: i) a contraposição entre a \"pequena siderurgia\" e a \"grande siderurgia\" e a questão correlata da escolha entre o carvão importado, o carvão nacional e o carvão vegetal; ii) a questão do vínculo entre a exportação de minério de ferro e a siderurgia nacional e, por fim, iii) a questão da localização da usina. Procuramos compreender como se deram as interações entre essas três dimensões ao longo do debate, bem como identificar a origem das defesas de cada uma das posições a cada momento. A tese está dividida em quatro capítulos centrais. Num primeiro, descrevemos a evolução do setor siderúrgico brasileiro entre 1900 e 1940, procurando avaliar as dimensões quantitativa e qualitativa desse desenvolvimento. Num segundo capítulo, tratamos do surgimento, no final da década de 1900 e início da década seguinte, de uma série de propostas de exportação do minério de ferro da região ferrífera de Minas Gerais, que foram vinculadas e subordinadas à produção siderúrgica no país. Dessa forma, o problema siderúrgico ganhou corpo entrelaçado à questão da exportação de minério. Num terceiro capítulo, tratamos do importante contrato da Itabira Iron Ore Co. de 1920 e da reação imediata, interna e externa, que ele suscitou. Por fim, num quarto capítulo, identificamos a configuração de um modelo alternativo ao da Itabira Iron para a solução do problema siderúrgico, baseado em insumos estritamente nacionais, desvinculado da exportação de minério de ferro e capitaneado pelo governo mineiro, bem como a polarização resultante do debate sobre o problema siderúrgico. / The debate over the Brazilian national steel-making problem took shape in the end of the 1900 decade and lasted until 1941, with the creation, by the Brazilian federal government, of the Companhia Siderúrgica Nacional (CSN - National Steel Company) to build and exploit the Volta Redonda steel mill, which was hailed as the solution to the problem, thus closing a debate more than three decades long. Due to this and due to the symbolic importance to the Estado Novo with which the CSN was impregnated, the historiography was significantly marked by this particular outcome, which in light of the own debate was by no means necessary. Bearing this in mind, this dissertation aims at reconstructing and analyzing the efforts, debates and conflicts surrounding the steel-making question along the Brazilian First Republic. We attempt to identify the main agents which intervened and weighted in directing government policy relative to the steel sector and try to present the main proposals done and initiatives attempted by these agents, as well as to map the implications of these initiatives and proposals to the development of the sector. Three of the main axes around which the debates turned were the following: i) the counterpoint between \"small-scale steel-making\" and \"large-scale steel-making\" and the correlate choice between imported coal, national coal and charcoal; ii) the question of the link between iron ore export and national steel-making; and, at last, iii) the question of the location of the steel mill. We attempt to understand how these three dimensions interacted along the debate, as well as to identify the origin of the defenses of each of these positions at each moment. The dissertation is divided into four main chapters. In a first one, we describe the evolution of the Brazilian steel-making sector between 1900 and 1940, attempting to evaluate the quantitative and qualitative dimensions of this development. In a second one, we deal with the emergence, in the end of the decade of 1900 and beginning of the following one, of a series of proposals for the export of iron ore from the iron region in Minas Gerais, which were linked, or rather subordinated, to the steel production in the country. Thus the steel-making problem took shape entwined to the question of iron ore export. In a third chapter, we handle the important 1920 Itabira Iron Ore Co. contract and the more immediate reaction, internal and external, which it gave rise to. Finally, in a last chapter, we identify the configuration of a model alternative to the Itabira Iron\'s to the solution of the steel-making problem, based on strictly national inputs, detached from the iron ore export and led by the mineiro government, as well as the resulting polarization of the debate over the steel-making problem.

O debate sobre o problema siderúrgico nacional no Brasil ganhou corpo no final da década de 1900 e estendeu-se até 1941, com a criação, pelo governo federal brasileiro, da Companhia Siderúrgica Nacional (CSN) para construir e explorar a usina siderúrgica de Volta Redonda, que foi saudada como a solução do problema, encerrando assim um debate de mais de três décadas. Por esse motivo e pela importância simbólica de que se revestiu a CSN para o Estado Novo, a historiografia foi bastante marcada por esse desfecho particular, que à luz do próprio debate não tinha nada de necessário. Tendo isso em vista, esta tese visa reconstruir e analisar os esforços, debates e conflitos em torno da questão siderúrgica ao longo da Primeira República. Buscamos identificar os principais agentes que intervieram e pesaram no direcionamento das políticas governamentais relativas ao setor siderúrgico e procuramos apresentar as principais propostas feitas e iniciativas tomadas por esses agentes, bem como mapear as implicações dessas iniciativas e propostas para o desenvolvimento do setor. Três dos principais eixos em torno dos quais giraram os debates foram os seguintes: i) a contraposição entre a \"pequena siderurgia\" e a \"grande siderurgia\" e a questão correlata da escolha entre o carvão importado, o carvão nacional e o carvão vegetal; ii) a questão do vínculo entre a exportação de minério de ferro e a siderurgia nacional e, por fim, iii) a questão da localização da usina. Procuramos compreender como se deram as interações entre essas três dimensões ao longo do debate, bem como identificar a origem das defesas de cada uma das posições a cada momento. A tese está dividida em quatro capítulos centrais. Num primeiro, descrevemos a evolução do setor siderúrgico brasileiro entre 1900 e 1940, procurando avaliar as dimensões quantitativa e qualitativa desse desenvolvimento. Num segundo capítulo, tratamos do surgimento, no final da década de 1900 e início da década seguinte, de uma série de propostas de exportação do minério de ferro da região ferrífera de Minas Gerais, que foram vinculadas e subordinadas à produção siderúrgica no país. Dessa forma, o problema siderúrgico ganhou corpo entrelaçado à questão da exportação de minério. Num terceiro capítulo, tratamos do importante contrato da Itabira Iron Ore Co. de 1920 e da reação imediata, interna e externa, que ele suscitou. Por fim, num quarto capítulo, identificamos a configuração de um modelo alternativo ao da Itabira Iron para a solução do problema siderúrgico, baseado em insumos estritamente nacionais, desvinculado da exportação de minério de ferro e capitaneado pelo governo mineiro, bem como a polarização resultante do debate sobre o problema siderúrgico. / The debate over the Brazilian national steel-making problem took shape in the end of the 1900 decade and lasted until 1941, with the creation, by the Brazilian federal government, of the Companhia Siderúrgica Nacional (CSN - National Steel Company) to build and exploit the Volta Redonda steel mill, which was hailed as the solution to the problem, thus closing a debate more than three decades long. Due to this and due to the symbolic importance to the Estado Novo with which the CSN was impregnated, the historiography was significantly marked by this particular outcome, which in light of the own debate was by no means necessary. Bearing this in mind, this dissertation aims at reconstructing and analyzing the efforts, debates and conflicts surrounding the steel-making question along the Brazilian First Republic. We attempt to identify the main agents which intervened and weighted in directing government policy relative to the steel sector and try to present the main proposals done and initiatives attempted by these agents, as well as to map the implications of these initiatives and proposals to the development of the sector. Three of the main axes around which the debates turned were the following: i) the counterpoint between \"small-scale steel-making\" and \"large-scale steel-making\" and the correlate choice between imported coal, national coal and charcoal; ii) the question of the link between iron ore export and national steel-making; and, at last, iii) the question of the location of the steel mill. We attempt to understand how these three dimensions interacted along the debate, as well as to identify the origin of the defenses of each of these positions at each moment. The dissertation is divided into four main chapters. In a first one, we describe the evolution of the Brazilian steel-making sector between 1900 and 1940, attempting to evaluate the quantitative and qualitative dimensions of this development. In a second one, we deal with the emergence, in the end of the decade of 1900 and beginning of the following one, of a series of proposals for the export of iron ore from the iron region in Minas Gerais, which were linked, or rather subordinated, to the steel production in the country. Thus the steel-making problem took shape entwined to the question of iron ore export. In a third chapter, we handle the important 1920 Itabira Iron Ore Co. contract and the more immediate reaction, internal and external, which it gave rise to. Finally, in a last chapter, we identify the configuration of a model alternative to the Itabira Iron\'s to the solution of the steel-making problem, based on strictly national inputs, detached from the iron ore export and led by the mineiro government, as well as the resulting polarization of the debate over the steel-making problem.

A indústria siderúrgica busca continuamente melhorias no desempenho dos refratários, como forma de melhorar sua competitividade, em um mercado caracterizado pela competição global. Um dos principais fatores de desgaste dos refratários é a corrosão, que no ambiente siderúrgico, está diretamente relacionada com a qualidade das escórias, na maioria dos equipamentos. Nesse contexto, o presente trabalho apresenta um estudo dos principais fatores que desgastam quimicamente o revestimento dolomítico, com o objetivo de entender os fenômenos que estavam impactando no desempenho dos refratários utilizados na panela de aço da Siderúrgica Riograndense. Para o estudo em questão, o comportamento químico dessas escórias foi monitorado de setembro de 2008 a outubro de 2009. Para análise didática os dados foram estratificados em três períodos, onde o período 01 corresponde aos meses de setembro, outubro e novembro de 2008, período 02 englobam os meses de fevereiro a junho de 2009 e o período 03 revela os resultados de julho a outubro de 2009. Os resultados de monitoração da qualidade da escória foram apresentados por equipamento forno elétrico a arco (FEA) e forno panela (FP). Os principais parâmetros de processo avaliados, foram a basicidade binária, teor de MgO e oxidação da escória. Os resultados foram relacionados com o desempenho do revestimento refratário aplicado na panela de aço. Para a análise dos dados foi utilizado o Minitab um software que oferece um conjunto de ferramentas estatísticas. Pode-se inferir, a partir da análise dos resultados apresentados nesse trabalho, que as ações de redução da oxidação da escória do forno elétrico através de ajustes no sistema de injeção de oxigênio das injetoras, propiciaram uma redução do óxido de ferro nas escórias do forno panela, permitindo correções da basicidade binária nesse mesmo equipamento. Estas ações em conjunto com a elevação na concentração do óxido de magnésio, através da introdução de cal dolomítica no processo, promoveram melhor formação do coating no revestimento refratário. As alterações no processo de produção do aço promoveram um significativo aumento na vida média das panelas de aço desta aciaria. / The steel industry is continually seeking improvements in the performance of refractories, as a way to improve their competitiveness in a global market. A major factor in refractories wear is chemical corrosion. In the steel industry this is directly related to the quality of the slag used in most of the equipment. In this context, this work presents a study of the main factors that causes chemical wear in dolomite refractory. The main objective was the understanding of the phenomena that were impacting on the performance of refractories used in steel ladle of Siderúrgica Riograndense. For this study, the chemical behavior of slags was monitored from September 2008 to October 2009. For better understanding the analysis, the data were stratified into three periods: period 01, from September to November 2008; period 02, from February to June 2009; and the period 03, from July to October 2009 . The results of slag quality monitoring were presented separated from the electric arc furnace (EAF) and the ladle furnace (LF). The main process parameters evaluated were the binary basicity, content of MgO and oxidation of the slag. The results were correlated with the performance of refractories used in steel ladle. For the analysis of data, it was used Minitab software which offers a set of statistical tools. It can be inferred, through out the analysis of the results presented here, that the actions to decrease oxidation of the EAF slag, by adjusting the feeding system of oxygen injectors, propitiated a reduction of iron oxide in the slag of ladle furnece, which allowed corrections in binary basicity in the same equipment. These actions together with the increase in the concentration of magnesium oxide in the FP slag, through the introduction of dolomitic lime in the process, promoted the creation of a better coating on the refractory lining. The changes in the process of steel production promoted a significant increase in average life of ladle refractory in this steel making plant.

The LD-process, called after the cities Linz and Donawitz, is used to convert pig iron into crude steel by blowing oxygen on top of the pig iron. A LD-LBE converter, Lance Bubbling Equilibrium, also stirs the melt trough a bottom stirring system. The bottom stirring in a LD-LBE converter is believed to have a positive effect alone on the phosphorous removal. Previous studies have shown that the temperature and slag composition are the main factors affecting phosphorus removal. Phosphorus binds to the slag easier at low temperature and to slag with certain levels of dissolved calcium (a process additive). Different praxes were tested and a better dephosphorisation was reached. The bottom stirrings effect on the dissolution of calcium additives is a possible explanation to the results and mechanisms presented in this study. The study also aimed to investigate the use of nitrogen as stirring gas instead of argon. Nitrogen is removed from the steel during the formation of carbon oxide gases. Nitrogen was used in varying amounts as stirring gas during the first half of the oxygen blow. It proved to be safe to use as long as there was a high content of carbon in the melt. However using nitrogen beyond half of the blow showed to be risky for nitrogen sensible steels; even in small amounts since there is not enough carbon left to degas the steel from nitrogen. Slopping happens when formed gas from the LD-process is trapped in the slag. The slag level rises and sometimes it floods the converter resulting in yield losses. The influence of the bottom stirring on slopping was studied, which resulted in the conclusion that slopping cannot be avoided by simply improving the bottom stirring. Although some verification studies remains to be done, if the suggestions based on the results of this thesis were employed, savings in the oxygen and stirring gas economies could be made. Not least improvements on the iron yield. / En järnmalmsbaserad stålproduktion börjar med att järnmalm matas i en masugn tillsammans med koks, kalk och tillsatsämnen. Ut kommer råjärn med höga kol och svavelhalter. Råjärnet transporteras till stålverket i så kallade torpedvagnar. I vissa stålverk, t.ex. SSAB Special Steels i Oxelösund, renas råjärnet från svavel i torpedvagnen. I andra stålverk svavelrenar man i separata skänkar. Svavelreningen sker med bland annat kalciumkarbid som binder till svavlet. Det svavelfattiga råjärnet måste sedan renas från kol för att bli stål. Det görs i en LD-konvertern (Linz Donawitz). LD-konvertern laddas med flytande råjärn som har en kolhalt på 4,5 procent och som är runt 1350 grader varmt. Råjärnet kyls genom att cirka 20 procent skrot tillsätts. En syrgaslans sänks sedan in i konvertern ovanför smältan och reningen startar.  Syrgaslansen blåser syrgas i ultraljudsfart vilket oxiderar en del av järnet, så väl som kol, kisel, mangan, fosfor and andra föroreningsämnen i råjärnet. Kol försvinner ur konvertern i form av kolmonoxidgas. Andra oxiderade föroreningar och järnoxid bildar tillsammans en så kallad slagg som flyter ovanpå smältan. Det tillsätts även så kallade slaggbildare som förbättrar upptaget av föroreningar i slaggen. Processen varar i cirka 17 minuter och är mycket beroende av slaggen som bildas. Kol försvinner ur konvertern i form av kolmonoxidgas. Under processens gång rör man om smältan med hjälp av gaser som spolas genom botten av konvertern. Omröringen jämnar ut smältans sammansättning och temperatur. När man inte länge behöver avlägsna kol stoppas processen. Stålets temperatur är då cirka 1700 grader och kolhalten ligger nära 0,05 procent. Stålet överförs sedan till en skänk för att skilja det ur slaggen. Stålet förädlas vidare i olika processer där sammansättningen justeras så att det möter kundens krav. Sedan gjuts stålet i strängar för transport till valsverk eller kunder. Denna studie behandlar bottenomrörningen under LD-processen i SSAB Special Steels's stålverk i Oxelösund. Omrörningen sker genom åtta porösa stenar i botten av konvertern som blåser med argon eller kväve. Gasflödet genom stenarna justeras genom ett ventilsystem. Under blåsningen rör man om med hjälp av förinställda program. Omrörningens primära funktion är att avlasta syrgaslansen. I fallen där ingen bottenomrörning finns måste syrgaslansen blåsa ”hårdare” på stålet för att avlägsna kol. Avlastningen som bottenomrörningen bidrar med gör att processen även kallas för LD-LBE, där LBE står för Lans Bubbling Equilibrium. Bottenomrörningen tros ha en positiv effekt på stålets rening från fosfor. Sedan tidigare vet man att temperatur och slaggsammansättning är de största faktorerna som påverkar fosforreningen. Fosfor tas lättare upp i slaggen vid låga temperaturen samt i slagg med högre kalkhalter. Olika omrörningsprogram testades och en bättre fosforrening nåddes. Bottenomrörningen visade sig ha positiva effekter som är teoretisk kopplade till kalksmältning. Två möjliga förklaringsmekanismer hittades. Studien undersökte även användningen av kväve som omrörningsgas istället för argon, då kväve är ekonomisk fördelaktig gentemot argon. Kväve finns inlöst i råjärnet som sätts in i konvertern. Kvävgasen försvinner ur stålet under och med hjälp av kolreningen. Det visade sig vara säkert att använda kväve från start fram till halva syrgasblåset på kvävekänsliga stålsorter, var efter man sedan byte till argon. Kväve som används sent under blåset visade ge högre kvävehalter. Urkok är en kraftig volymökning av slaggen som sker när bildad gas från reningen av smältan fångas i slaggen och får slaggen att ”koka över”. Urkok resulterar i ekonomiska förluster då slaggen som lämnar konvertern vid urkok är rik på järn. Bottenomrörningens eventuella påverkan på urkok studerades. Det visade sig att urkok inte kan undvikas genom att enbart optimera bottenomrörningen.

A indústria siderúrgica busca continuamente melhorias no desempenho dos refratários, como forma de melhorar sua competitividade, em um mercado caracterizado pela competição global. Um dos principais fatores de desgaste dos refratários é a corrosão, que no ambiente siderúrgico, está diretamente relacionada com a qualidade das escórias, na maioria dos equipamentos. Nesse contexto, o presente trabalho apresenta um estudo dos principais fatores que desgastam quimicamente o revestimento dolomítico, com o objetivo de entender os fenômenos que estavam impactando no desempenho dos refratários utilizados na panela de aço da Siderúrgica Riograndense. Para o estudo em questão, o comportamento químico dessas escórias foi monitorado de setembro de 2008 a outubro de 2009. Para análise didática os dados foram estratificados em três períodos, onde o período 01 corresponde aos meses de setembro, outubro e novembro de 2008, período 02 englobam os meses de fevereiro a junho de 2009 e o período 03 revela os resultados de julho a outubro de 2009. Os resultados de monitoração da qualidade da escória foram apresentados por equipamento forno elétrico a arco (FEA) e forno panela (FP). Os principais parâmetros de processo avaliados, foram a basicidade binária, teor de MgO e oxidação da escória. Os resultados foram relacionados com o desempenho do revestimento refratário aplicado na panela de aço. Para a análise dos dados foi utilizado o Minitab um software que oferece um conjunto de ferramentas estatísticas. Pode-se inferir, a partir da análise dos resultados apresentados nesse trabalho, que as ações de redução da oxidação da escória do forno elétrico através de ajustes no sistema de injeção de oxigênio das injetoras, propiciaram uma redução do óxido de ferro nas escórias do forno panela, permitindo correções da basicidade binária nesse mesmo equipamento. Estas ações em conjunto com a elevação na concentração do óxido de magnésio, através da introdução de cal dolomítica no processo, promoveram melhor formação do coating no revestimento refratário. As alterações no processo de produção do aço promoveram um significativo aumento na vida média das panelas de aço desta aciaria. / The steel industry is continually seeking improvements in the performance of refractories, as a way to improve their competitiveness in a global market. A major factor in refractories wear is chemical corrosion. In the steel industry this is directly related to the quality of the slag used in most of the equipment. In this context, this work presents a study of the main factors that causes chemical wear in dolomite refractory. The main objective was the understanding of the phenomena that were impacting on the performance of refractories used in steel ladle of Siderúrgica Riograndense. For this study, the chemical behavior of slags was monitored from September 2008 to October 2009. For better understanding the analysis, the data were stratified into three periods: period 01, from September to November 2008; period 02, from February to June 2009; and the period 03, from July to October 2009 . The results of slag quality monitoring were presented separated from the electric arc furnace (EAF) and the ladle furnace (LF). The main process parameters evaluated were the binary basicity, content of MgO and oxidation of the slag. The results were correlated with the performance of refractories used in steel ladle. For the analysis of data, it was used Minitab software which offers a set of statistical tools. It can be inferred, through out the analysis of the results presented here, that the actions to decrease oxidation of the EAF slag, by adjusting the feeding system of oxygen injectors, propitiated a reduction of iron oxide in the slag of ladle furnece, which allowed corrections in binary basicity in the same equipment. These actions together with the increase in the concentration of magnesium oxide in the FP slag, through the introduction of dolomitic lime in the process, promoted the creation of a better coating on the refractory lining. The changes in the process of steel production promoted a significant increase in average life of ladle refractory in this steel making plant.

A indústria siderúrgica busca continuamente melhorias no desempenho dos refratários, como forma de melhorar sua competitividade, em um mercado caracterizado pela competição global. Um dos principais fatores de desgaste dos refratários é a corrosão, que no ambiente siderúrgico, está diretamente relacionada com a qualidade das escórias, na maioria dos equipamentos. Nesse contexto, o presente trabalho apresenta um estudo dos principais fatores que desgastam quimicamente o revestimento dolomítico, com o objetivo de entender os fenômenos que estavam impactando no desempenho dos refratários utilizados na panela de aço da Siderúrgica Riograndense. Para o estudo em questão, o comportamento químico dessas escórias foi monitorado de setembro de 2008 a outubro de 2009. Para análise didática os dados foram estratificados em três períodos, onde o período 01 corresponde aos meses de setembro, outubro e novembro de 2008, período 02 englobam os meses de fevereiro a junho de 2009 e o período 03 revela os resultados de julho a outubro de 2009. Os resultados de monitoração da qualidade da escória foram apresentados por equipamento forno elétrico a arco (FEA) e forno panela (FP). Os principais parâmetros de processo avaliados, foram a basicidade binária, teor de MgO e oxidação da escória. Os resultados foram relacionados com o desempenho do revestimento refratário aplicado na panela de aço. Para a análise dos dados foi utilizado o Minitab um software que oferece um conjunto de ferramentas estatísticas. Pode-se inferir, a partir da análise dos resultados apresentados nesse trabalho, que as ações de redução da oxidação da escória do forno elétrico através de ajustes no sistema de injeção de oxigênio das injetoras, propiciaram uma redução do óxido de ferro nas escórias do forno panela, permitindo correções da basicidade binária nesse mesmo equipamento. Estas ações em conjunto com a elevação na concentração do óxido de magnésio, através da introdução de cal dolomítica no processo, promoveram melhor formação do coating no revestimento refratário. As alterações no processo de produção do aço promoveram um significativo aumento na vida média das panelas de aço desta aciaria. / The steel industry is continually seeking improvements in the performance of refractories, as a way to improve their competitiveness in a global market. A major factor in refractories wear is chemical corrosion. In the steel industry this is directly related to the quality of the slag used in most of the equipment. In this context, this work presents a study of the main factors that causes chemical wear in dolomite refractory. The main objective was the understanding of the phenomena that were impacting on the performance of refractories used in steel ladle of Siderúrgica Riograndense. For this study, the chemical behavior of slags was monitored from September 2008 to October 2009. For better understanding the analysis, the data were stratified into three periods: period 01, from September to November 2008; period 02, from February to June 2009; and the period 03, from July to October 2009 . The results of slag quality monitoring were presented separated from the electric arc furnace (EAF) and the ladle furnace (LF). The main process parameters evaluated were the binary basicity, content of MgO and oxidation of the slag. The results were correlated with the performance of refractories used in steel ladle. For the analysis of data, it was used Minitab software which offers a set of statistical tools. It can be inferred, through out the analysis of the results presented here, that the actions to decrease oxidation of the EAF slag, by adjusting the feeding system of oxygen injectors, propitiated a reduction of iron oxide in the slag of ladle furnece, which allowed corrections in binary basicity in the same equipment. These actions together with the increase in the concentration of magnesium oxide in the FP slag, through the introduction of dolomitic lime in the process, promoted the creation of a better coating on the refractory lining. The changes in the process of steel production promoted a significant increase in average life of ladle refractory in this steel making plant.

Furnace slag is the by-product from steel making process. Desulfurization slag (DS) was produced from the desulphurization process of molten irons in high temperature furnaces processes. DS is heterogeneous oxide materials which are compounded by some main oxides such as SiO2, FeO, CaO, SiO2, MnO, Al2O3, and MgO due to their mass percentage. Because DS has high pH characteristics (12.5), this limits its recycle and reuse. The objective of this study was to evaluate the potential of applying DS as the construction materials or amendments in the aquacultural industry to improve the aqualcultural water quality in the fish farm. The basic characteristic analyses show that the major chemical compositions of powder DS were CaO, SiO2, Fe2O3 and Al2O3. The major crystalline phase composed of SiO2, Ca(OH)2 and CaCO3. Results of DS release test show that when DS could increase pH and alkalinity value in water. Results of micro-structure analysis of powder DS surface showed there were many non-porous materials and heavy metals on DS. Results from the nutrient removal tests show that the ammonia nitrogen adsorption capacity were 0.036 mg/L and 0.069 mg/L when the initial concentration were 10 mg/L and 30 mg/L, respectively. Results form the adsorption model validation test indicate that the adsorption phenomena could fit in Langmuir model. The adsorption capacities of phosphate were 26.4 mg/L and 76.6 mg/L when the initial phosphate concentrations were 10 mg/L and 30 mg/L, respectively. The calculated values of thermodynamic parameters show that the adsorption reaction for ammonia nitrogen was endothermic non-spontaneous process, and the adsorption reaction for phosphate was exothermic spontaneous process. However, the enthalpy change (£GH) showed that adsorption reaction of DS for ammonia nitrogen was physical adsorption, and the adsorption reaction for phosphate was chemical sorption. In the algae culture experiment, results show that when 25 mg/L of DS was supplied, the growth rate of Chlorella sp. could be enhanced. Thus, the powder DS could enhance the growth of Chlorella sp. A field study using a fish farm as the study site was conducted to evaluate the impact of DS on fish farm water quality when DS was applied as the filling and construction materials of the fish farm. Results show that addition of DS had no significant effect on groundwater and pond water quality. Results from the organic matter analysis of the pond water using EEFM show that humus-like and soluble microbial product (SMP) materials were detected. The dominant algae in the pond water included Scenedesmus sp. and Chlorella sp. indicating the pond water quality was in good conditions. Addition of DS would increase of water alkalinity preventing the acidification of pond water due to the fish feed and fish excreta. Results of heavy metal analysis of soil, groundwater, and pond water complied with the relevant environmental standards. Results of this study will aid in understanding the characteristics of DS and the results will be useful in designing a DS reuse system to achieve the zero waste and resource reuse goal.