The investigations of reducing Fe1‐xO in liquid state with H2+Ar mixtures, in top blowing stream of gas reactor, by using thermobalance method have been carried out. To make the system more homogeneous pure iron crucibles were used in the experiment. The experiments were carried out in the range of gas flow rate V = (5+80) · 10−6 m3/s and in 1723 K. Reduction rate depends on hydrogen partial pressure and flow rate of gas mixture. The logarithm of apparent reduction rate constant is a linear function of logarithm of gas flow rate. In experimental conditions of this work, the initial rate of reduction satisfies the relation . Thus it has been shown that the reduction process is controlled by the mass transfer in the gaseous phase. Sherwood numbers obtained from observed values of reduction rates and empirical equation of the gas‐phase mass transfer rate are correlated by equation . The values of mass transfer coefficient in gas phase calculated from Sherwood numbers are consistent with the values of apparent reduction rate constant and with estimated rate constant of chemical reaction of liquid Fe1‐xO reduction.
Im vorliegenden Beitrag wurde der Einfluß des Erweichungsprozesses auf die Reduktionsgeschwindigkeit von Sinter untersucht. Dabei wurde die Reduktionsgeschwindigkeit von Hochofensinter in einem Temperaturbereich um den Erweichungspunkt bestimmt. Es wurde ein rapider, mit dem Erweichungseffekt wie auch mit dem Porositätsschwund verknüpfter Geschwindigkeitsrückgang festgestellt. Diese Erscheinung findet in einem Temperaturbereich statt, der den Temperaturen des Erweichungsbeginns beim untersuchten Sintermaterial im vorreduzierten Zustand entspricht. Somit ist der Erweichungsvorgang als grundlegende Ursache für die festgestellte Abnahme der Reduktionsgeschwindigkeit zu betrachten. Mikroskopische Direktbeobachtungen der Reduktion von Sinter im Erweichungszustand zeigten Erscheinungen, die zu einem Porositätsschwund führen. Messungen des Porenvolumens und der spezifischen Porenoberfläche an Sinter – vor wie nach abgeschlossener Erweichung und Reduktion – bestätigten die Porositätsabnahme. Diese erschwert den Reduktionsgaszufluß zu den Eisenoxiden und verlangsamt so die Reduktionsgeschwindigkeit.
The most objective methods of determining the usefulness of quartzite for the ferrosilicon smelting process are industrial research methods, but such studies are long-lasting and costly. In order to test the usefulness of thermo-gravimetric method to evaluate technological properties of quartzites in a laboratory, thermo-gravimetric studies of quartzites samples from various deposits were carried out. These quartzites are used or were used as a raw material in industrial ferrosilicon process. The study consisted of measuring the weight loss of powder samples in the form of mixture of quartz with graphite of molar ratio SiO2 + 3C during heating under an argon atmosphere in the temperature range up to 1500°C. The evaluation of technological properties of quartzites was done by comparing the curves of relative weight loss with industrial technological data of the ferrosilicon smelting process. It was established that the results of thermo-gravimetric studies show satisfying agreement with observations of industrial process, whereas quartzites of improved technological properties revealed a lower weight loss in thermo-gravimetric studies. Studies of this type can be useful as one of the methods of objective assessment of usefulness of quartzites for the ferrosilicon smelting process.
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