No description available.

[pt] O alto forno é um reator metalúrgico cujo objetivo consiste na produção de ferro-gusa. O consumo de combustível/redutor no processo de redução de minério de ferro em altos fornos, representa mais de 50 por cento do custo do gusa. No sentido de aumentar a produtividade e reduzir o consumo de combustível/redutor são empregadas técnicas de injeção de combustíveis auxiliares pelas ventaneiras dos altos fornos. A combustão de gás natural (GN) injetado nas ventaneiras produz grande quantidade de hidrogênio, esse gás é melhor redutor se comparado ao monóxido de carbono, pois ele possui velocidade de reação maior com os óxidos de ferro e, além disso, a geração de CO2 no processo de redução é diminuída quando comparado ao uso do carvão pulverizado (PCI), que é atualmente o material de injeção mais usado no Brasil. Este trabalho propõe a simulação da combustão de GN injetado pelas ventaneiras de um alto forno, utilizando o software CHEMKIN. As simulações provenientes deste software são amplamente utilizadas para otimização da combustão, sendo possível explorar rapidamente o impacto das variáveis de projeto sobre o desempenho do processo. Os resultados provenientes dessa simulação computacional em condições típicas de alto forno permitiram a previsão da temperatura de chama adiabática e a quantificação dos gases redutores de óxidos de ferro: H2 e CO. A partir da variação dos parâmetros de processo foi possível obter resultados úteis para a tomada de decisão, visando controlar e otimizar o processo. / [en] The blast furnace is a metallurgical reactor whose goal is to produce pig iron. The fuel / reductant in the reduction of iron ore in the blast furnace process, represents more than 50 percent of the cost of the iron. In order to increase the productivity of the blast furnace and reduce fuel consumption / reducer injection techniques are employed by tuyeres of materials that act as fuel / reducer. The combustion of natural gas injected into the tuyeres produces large amounts of hydrogen, which replaces part of the carbon monoxide as reducing gas in the tank. The hydrogen gas is better compared to the reductant carbon monoxide, because it has reaction rate with the iron oxides and, moreover, the CO2 generation in the process of reduction is decreased when compared to the use of pulverized coal (PCI), which is currently the material most commonly used injection by tuyeres in Brazil. This paper proposes the simulation of combustion of natural gas injected into the tuyeres of a blast furnace, using the CHEMKIN software package. Simulations from this software are widely used for optimization of combustion, which can quickly explore the impact of design variables on the performance of the process, using accurate models of chemical kinetics. The computer simulation results from the combustion of natural gas at typical conditions of blast furnaces allowed the prediction of the adiabatic flame temperature and the reaching of the reducing gases of iron oxides: H2 and CO. From the variation of process parameters was possible to obtain useful results in order to control and optimize the process.

No description available.

No description available.

In an effort to free up valuable storage space, an obsolete dual tube furnace facility was repurposed to process legacy and newly generated reaction by-products for reuse and/or evaluation. These materials consist of magnesium oxide and unreacted chemicals including small amounts of uranium. They will be converted to their safest form. The repurposing of the facility was not a simple undertaking as all of the utilities with the exception of electricity were disconnected from the facility and the furnaces were more than 50 years old. A 2-part project consisting of a construction phase and transition to operations phase was initiated to accomplish the task. Because funding was done in a piecemeal fashion, the dynamics of restarting the facility was accomplished using creative project management. Lessons learned will provide invaluable information for future sustainability endeavors that require the renovation of an out-service facility to meet current and future needs.

The thesis work consists of two parts. First, the development of two-dimensional numerical models of a Bridgman unidirectional solidification furnace, and second, the construction work of the furnace at KTH. The aim is to build a Bridgman furnace which is capable of close control over temperature gradient and growth rate such that the solidification structures of a duplex stainless steel (SAF2507) could be replicated at a laboratory scale for different cooling rates.Two numerical models of Bridgman furnace are created using COMSOL Multiphysics. The models are used as predictive tools to simulate the locations of solidification front and the temperature gradients at the solidification fronts, which are parameters difficult to access during experiments. Different hot zone temperatures of the furnace (1500~1550 °C) and different sample pulling rates (0.5~10 mm/s) are studied in simulations. The major finding from modeled results is that the temperature gradient of the sample at the solidification fronts range from 5 ~ 17 K/mm, which are lower than the furnace temperature gradient of ~50 K/mm. The corresponding steady-state cooling rates range between 5 ~ 85 K/s. The next step is to validate the models with experimental temperature profiles of the furnace, and decide whether the furnace design should be modified to achieve the cooling rates of interests. / Examensarbetet består av två delar. Först utvecklingen av tvådimensionella numeriska modeller av en Bridgman enkelriktad stelningsugn, och för det andra konstruktionsarbetet för ugnen vid KTH. Syftet är att bygga en Bridgman-ugn som har förmåga att kontrollera temperaturgradienten och tillväxthastigheten så att stelningsstrukturerna i ett duplex-rostfritt stål (SAF2507) skulle kunna replikeras i laboratorieskala för olika kylningshastigheter. Två numeriska modeller av Bridgman-ugnen skapas med COMSOL Multiphysics. Modellerna används som prediktiva verktyg för att simulera placeringen av stelningsfronten och temperaturgradienterna vid stelningsfronterna, vilket är parametrar som är svåra att komma åt under experiment. Olika varmzonstemperaturer i ugnen (1500~1550 °C) och olika provdragningshastigheter (0.5~10 mm/s) studeras i simuleringar. Det viktigaste fyndet från modellerade resultat är att provets temperaturgradient vid stelningsfronterna sträcker sig från 5 ~17 K/mm, vilket är lägre än ugns temperaturgradient på ~ 50 K/mm. Motsvarande stabilitetskylningshastigheter varierar mellan 5 ~ 85 K/s. Nästa steg är att validera modellerna med experimentella temperaturprofiler för ugnen och bestämma om ugnsutformningen ska modifieras för att uppnå intressens kylningshastigheter.

The carbon footprint from the iron, steel and other metal sectors has become a problem both environmentally and economically. The purpose of this report is to propose a concept of an electrified reheat furnace for the steel industry in the making of sheet metal. The aim is to reduce the environmental impact from the steel industry. The approach in this report has been to analyse relevant facts to propose a fully electrified concept. The concept is divided into two sections. The first section of the concept consists of a preheating furnace with the purpose to heat the slabs to 850 °C before it enters the second section. The preheating furnace contains 1447 – 2412 MoSi2 heating elements due to considering different efficiencies. The second section consists of 13 induction heating modules heating the slabs to a homogenous temperature of 1250 °C. By applying electrical heating in a walking beam furnace approximately 100 000 tonne carbon dioxide can be reduced annually. In conclusion, the proposed concept could be a feasible solution in order to avoid carbon emission and obtain the same production rate as the existing reheating furnaces. However, it is suggested that further investigations and analysis are performed regarding this concept to verify the total efficiency of the reheating furnace and to theoretically determine the required power input / Koldioxidutsläppen från järn, stål och andra metallindustrier har blivit ett problem både urmiljö och ekonomisk synpunkt. Syftet med denna rapport är att föreslå ett koncept av en heltelektrifierad uppvärmningsugn för stålindustrin i processen för att skapa plåt. Målet meddenna studie är att reducera stålindustrins påverkan på växthuseffekten. Metoden i denna rapport har varit att analysera relevant fakta för att sedan kunna föreslå ettkoncept av en helt elektrifierad ugn. Det föreslagna konceptet är uppdelad i två delar. Denförsta delen består av en förvärmningsugn med målet att värma stålet till 850 °C innan ståletgår in i den andra delen. Förvärmningsugnen består av 1447 – 2412 stycken MoSi2värmeelement med hänsyn till ugnens verkningsgrad. Den andra delen består utav 13 styckeninduktionsvärmemoduler som värmen stålet till en homogentemperatur på 1250 °C. Genomatt använda elektricitet för att värma ugnen minskar koldioxidutsläppen med 66 kg per tontillverkas stål. Sammanfattningsvis, det föreslagna konceptet kan vara en möjlig lösning för att minskakoldioxidutsläpp och samtidigt bibehålla samma produktionshastighet som existerandeuppvärmningsugnar. Däremot är det förslaget att vidare studier och analyser görs påkonceptet för att verifiera den totala verkningsgraden av ugnen och för att bestämma denexakta energiförbrukningen.

Abstract Carbon emissions pose a serious threat to the continued survival of this planet. All sectors of society must, therefore, lower their emissions, this includes the steel industry. The production of steel is based on iron ore reduction by carbon. In an attempt to relieve the steel industry from its inherent fossil dependence an initiative called HYBRIT has been started. It aims to supplant carbon reduction with hydrogen reduction. Currently, there is no economically viable industrial production of steel that uses fossil-free hydrogen as reduction agent. In order to create economic viability for such a process work has to be conducted to innovate and optimize. This study aims to be a part of that optimization process by creating a tool for optimizing the slag system with regards to phosphorus removal. 26843 slag compositions were evaluated using modules written in “Matlab” combined with “Thermo-Calc”. 1583 possible slag compositions were found to be suitable for phosphorus removal. These compositions were then optimized after slag weight in order to minimize slag associated cost. The compositions were tested against two theoretical raw materials with varying initial phosphorus content 250 ppm and 125 ppm. It was found that the initial phosphorus concentration of the raw material has a substantial impact not only on the slag costs but also the slag praxis that should be used.

yes / Test results of thirty six ground granulated blast-furnace slag (GGBS)-based mortars and eighteen fly ash (FA)-based mortars activated by sodium silicate and/or sodium hydroxide powders are presented. The main variables investigated were the mixing ratio of sodium oxide (Na2O) of the activators to source materials, water-to-binder ratio, and fine aggregate-to-binder ratio. Test results showed that GGBS based alkali-activated (AA) mortars exhibited much higher compressive strength but slightly less flow than FA based AA mortars for the same mixing condition. Feed-forward neural networks and simplified equations developed from nonlinear multiple regression analysis were proposed to evaluate the initial flow and 28-day compressive strength of AA mortars. The training and testing of neural networks, and calibration of the simplified equations were achieved using a comprehensive database of 82 test results of mortars activated by sodium silicate and sodium hydroxide powders. Compressive strength development of GGBS-based alkali-activated mortars was also estimated using the formula specified in ACI 209 calibrated against the collected database. Predictions obtained from the trained neural network or developed simplified equations were in good agreement with test results, though early strength of GGBS-based alkali-activated mortars was slightly overestimated by the proposed simplified equations.

<p>Current industrial practice in the steel Industry involves the use of natural gas with high methane content as a primary energy source. Natural combustion produces greenhouse gases, and with the continued focus on managing and reducing harmful emissions from industrial processes, there is a need for research into alternative sources of energy. Among several alternatives that have been studied is hydrogen: a non-carbon-based fuel. This work uses a coupled computational fluid dynamics (CFD)-finite element analysis (FEA) combustion model to investigate hydrogen utilization as a fuel in a reheat furnace and how it impacts the quality of the steel produced by understanding the three dimensional (3D) flow behavior, furnace temperature profile, thermal stress distribution, heat flux, formation of iron oxides, emission gases and mode of heat transfer onto the steel slabs. The modeling process integrates the five different zones of a pusher type reheating furnace (top and bottom) and modeled using Ansys Fluent 2020R1 and Ansys Workbench 2022R1. Changes in these parameters are determined by comparison to a baseline case that uses methane as fuel and maintaining the same heat input in terms of chemical energy into the furnace. Global mechanism was used for hydrogen and two step mechanism was used for methane combustion. Results revealed a 2.6% increase in average temperature to 1478K across the furnace for hydrogen which resulted in 6.45% increase in maximum heat flux into the slabs. Similar flue gas flow patterns were seen for both cases and heat transfer mode from the combustion gases to the slabs was primarily by radiation (~97%) for both methane and hydrogen. 11.5% increase in iron oxide formation on the slab was recorded for the hydrogen case, however, the bulk of the iron oxide formed was more of wüstites which are the easiest form of iron oxide to descale. However, elevated nitrogen oxide (NOx) levels were recorded for hydrogen combustion which led to further study into NOx mitigation techniques. Application of the staged combustion method using hydrogen fuel showed potentials for NOx reduction. The use of regenerative burners further conserved exergy losses in hydrogen fuel application. Insignificant deviation from base case thermal stress distribution and zero carbon emission from the hydrogen case indicates the usability of hydrogen as an alternative fuel in reheating furnace operations. </p>