Kinetics of Reduction of FeO from Slag by Graphite and Coal Chars

Abstract

The rates of reduction of FeO from iron-saturated FeO-CaO-Al 2 O 3 -SiO 2 slags by graphite, coke, bituminous coal and anthracitic coal chars at temperatures in the range 1 673-1 873 K have been measured using a sessile drop technique. The extents of reaction were determined using EPMA analysis of quenched samples, and on line gas analysis using a quadrupole mass spectrometer. The reaction rates have been shown to be dependent critically on carbon type. For the reaction geometry used in this investigation the reduction rates of graphite and coke are observed to be faster than with coal chars. This unexpected finding is shown to be associated with differences in the dominant chemical and mass transfer mechanisms occurring at the reaction interface. High reaction rates are observed to occur with the formation of liquid Fe-C alloy product and the associated gasification of carbon from the alloy. The rates of reduction by coal chars are determined principally by the chemical reaction at the carbon/gas interface and slag phase mass transfer.KEY WORDS: slag; reduction; carbon; char; kinetics.tion tube, and this stand could be moved from the base of the reaction tube into the hot zone. The hot zone length is approximately 80 mm, over which the temperature varies by Ϯ2 K.The extents of reaction in the slag samples were measured by two methods, i) electron probe X-ray microanalysis (EPMA) of quenched slag samples, and ii) on line quadrupole mass spectrometer measurements (QMS) of the resulting gas composition and mass flows. 2) EPMAThe quenched slag samples were mounted and polished cross sections were examined using scanning electron microscope (SEM) and electron probe X-ray microanalysis (EPMA) with wavelength dispersive spectrometers. The quenched silicate slags formed glass on cooling from the furnace to room temperature enabling the iron oxide concentrations within the slag phase to be accurately measured at various positions within the cross section. The mean FeO concentrations reported in this study are obtained from measurements across the whole section of the sample. Figure 1 shows the sample geometry, and a schematic of the furnace-quadrupole mass spectrometer (QMS) facility is shown in Fig. 2. A gas mass flow controller is used to introduce ultra high purity argon gas (99.999 %) at a known rate into the reaction tube. The argon inlet tube is positioned close to and above the sample to provide a continuous gas flow across the surface of the slag sample. A gas sampling capillary is positioned at the mouth of the crucible; this enables the reaction gases to be extracted from the reaction site for analysis by the mass spectrometer. The gas flow, the configurations and dimensions of the various tubes were selected so as to ensure laminar plug flow of the product gases into the sampling capillary and to provide a fast, reproducible response to changes in gas composition. This was confirmed by injecting tracer gas "spikes" in the gas lines. The resulting peaks that were detected by the mass spectrometer decayed over ...

The Influence of Ash Impurities on Interfacial Reactions between Carbonaceous Materials and EAF Slag at 1550°C

“…A number of gas bubbles were generally seen trapped within the slag droplet; these were small in size except for a few large ones. Teasdale and Hayes 22) have used a gas ferrying mechanism, wherein CO gas produced in the initial reaction between carbon and slag gets transported through the gas phase and reacts with FeO in slag to produce CO 2 and metallic iron. This CO 2 is ferried back to carbon, where gasification of CO 2 to CO takes place via the Boudauard reaction.…”

Kinetics and Mechanism of the Simultaneous Carbothermic Reduction of FeO and MnO from High-Carbon Ferromanganese Slag

“…The kinetics and mechanism of FeO reduction by the dissolved carbon in liquid iron through these subreactions has been studied already. [3,5,6,10,17] According to Pomfret and Grieveson, [3] reaction [3] takes place through subreactions [4] and [8] at the slag/gas and at the gas/metal interfaces, where a gas layer exist at the slag/metal contact area. The dissolution/ transfer rate of carbon to the metal can affect reaction [3] regarding the different carbon materials.…”

“…[16] Furthermore, a higher carbothermic FeO reduction rate from silicate slags that contain initial metal also has been observed. [17] The objective of the current study is to investigate the MnO reduction from HCFeMn slag with different carbon materials and under the conditions of the existence of a metal phase in the system. In this case, the interaction of a synthetic slag that contains MnO and FeO with different carbon materials is studied using the sessile drop wettability technique.…”

Carbon/Slag Interactions between Coke/Rubber Blends and EAF Slag at 1 550°C

“…[17][18][19] However, limited work has been done to consider the carbon type and its characteristics upon its interactions with the slag.…”

“…16) Along the years, several techniques have been developed to study the slag foaming and gas generation phenomena as a function of slag chemistry. [17][18][19] However, limited work has been done to consider the carbon type and its characteristics upon its interactions with the slag.…”