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  • 1.
    Gustavsson, Joel
    KTH, Tidigare Institutioner, Materialvetenskap.
    Reactions in the Lower Part of the Blast Furnace with Focus on Silicon2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The thermodynamic conditions for the behaviour of silicon in the lower part of the blast furnace have been the focus of the thesis. More specifically, the influences of temperature, carbon activity, total gas pressure and Fe reoxidation on silicon have been studied.

    Calculations show that an increased temperature gives higher equilibrium ratio between silicon in hot metal and slag. Furthermore, laboratory reduction studies shows that the carbon activity in the cohesive zone increase with an increased reduction time. Increased carbon activity will increase the equilibrium silicon content in liquid metal.

    Equilibrium calculations based on tapped hot metal and slag shows that the equilibrium silicon content of the liquid metal phase is higher than measured at tapping. Around the raceway area the equilibrium silicon content is very high. The high equilibrium silicon content makes it important to differ between the conditions under operation and the conditions of samples taken out of the blast furnace before studied. The equilibrium silicon content is strongly correlated to the CO gas partial pressure. Often this partial pressure is changed during sampling and cooling of samples. At tapping the equilibrium partial pressure of CO has been calculated to higher values than the total gas pressure inside the blast furnace.

    Metal droplets found in tapped slags are probably formed by reduction of FeO. In the periphery part of the lower part of the blast furnace, it is believed that mainly FeO oxidises silicon in hot metal. It is not expected that the metal droplets in the slag is formed if FeO oxidises dissolved silicon. Instead, the iron droplets may form at reactions with gas, coke carbon or coal powder carbon. Around some droplets increased magnesium content has been found. This may be due to reactions with gaseous magnesium that, according to thermodynamic conditions, is easy to form. It has been reported that much FeO may be formed in the raceway area. The metal droplets may indicate how much FeO that reacts with other components than liquid iron. The iron found in metal droplets in the slag corresponds to between 0.02 and 0.2 wt-% FeO in the slag.

  • 2.
    Gustavsson, Joel
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Andersson, Margareta A.T.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    A thermodynamic study of silicon containing gas around a blast furnace raceway2005Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 45, nr 5, s. 662-668Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The equilibrium conditions for silicon transfer from ash to the liquid metal phase via SiO gas have been discussed by several authors. However, no published calculations have been found using the most modern thermodynamic models available. Since there are major differences in the results of calculations using different thermodynamic models and the models are continuously being improved, new equilibrium calculations on SiO and SiS gas formation have been performed using the recently developed models. Different ingoing compositions of coke ash, coal powder ash and blast air were used in the calculations. The compositions chosen represent blast furnace no. 3 at SSAB in Lulea, Sweden. Temperature was found to be the major factor influencing the equilibrium silicon level in the gas phase. At low temperatures (below 1 600 degrees C the total gas pressure was also seen to influence the silicon content in the gas phase. The main reason for this is that below 1 600 degrees C, the amount of liquid slag at equilibrium increases with the total gas pressure. Liquid slag contains large amounts of silica that then can not be found in the gas phase. Higher carbon activity is usually expected to result in higher SiO gas levels in the blast furnace. The equilibrium calculations show that increased carbon activity increases the amount of silicon in the gas phase at temperatures up to about 1 600 degrees C, but that at higher temperatures SiC is formed that decreases the equilibrium silicon level in the gas phase.

  • 3.
    Gustavsson, Joel
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Andersson, Margareta A.T.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Comparison of calculated equilibrium and operation data for blast furnace with focus on silicon2009Inngår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 36, nr 5, s. 341-353Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An investigation of reactions involving blast furnace hot metal, slag and gas at equilibrium was carried out. Performed calculations were based on estimated total gas pressures, measured temperatures and hot metal and slag compositions. Calculated element contents of liquid phases were found to be very similar to their corresponding values determined through measurement when formation of the gas phase was suppressed. This resulted in higher equilibrium CO partial pressures compared to the measured total gas pressure in the bustle ring. When only equilibrium conditions were considered, the predicted amount of silicon was much higher than the measured. A comparison of activity coefficients of elements in the hot metal using different calculation models was also carried out. Two different models based on dilute solutions were compared with the TCFe3 database developed for the software Thermo-Calc, which can handle higher alloying concentrations. Considerably different calculation results were found among the different models studied.

  • 4.
    Gustavsson, Joel
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Shoyeb, M.
    Sarma, D. S.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Characteristics of metal droplets in slag tapped from the blast furnace2006Inngår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 77, nr 1, s. 5-13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Slag samples, hot-metal samples and hot-metal temperatures were obtained during tapping of two blast furnaces. Sampling was carried out at different time points during tapping of three separate heats. The size distribution and composition of metal droplets found in the slag were determined using scanning electron microscopy. Only metal droplets above 0.75 mu m could be counted and analysed. All droplets were below 8 mu m in diameter and the great majority of these droplets were found to be between 0.75 and 2 Pm. The size distribution did not differ significantly for different slag samples. Iron was the main droplet component. Electron probe microanalysis showed that the droplets contained small amounts of carbon. The percentage of the area in a studied cross-section that was covered with metal droplets varied between 0.01 and 0.07%. Calculations based on Stoke's law showed that the distance droplets travel in the slag is in the micron range. Slag samples taken in the beginning of slag tapping contained more droplets than those taken in the middle of slag tapping, an indication that most droplets can be found in the area near the furnace wall. Some droplets were determined to have magnesium enrichment at the external surface.

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