Dissolution rate of burnt dolomite in molten FetO-CaO-SiO2 slags.

Abstract

SynopsisCylinders of burnt dolomite with the apparent porosities of 20 to 35 were immersed into molten FetO-CaO--Si02 slaps at temperatures of 1 950 to 1 425 °C and rotated at 100 to 400 rpm. The dissolution rates were determined by measuring the decrease in radius of cylinder.The dissolution rate increased with increases in temperature and revolutional speed of cylinder, but was not affected by the difference in apparent porosity of burnt dolomite. From the analysis of experimental results, it was concluded that the dissolution rate was controlled by the mass transport of CaO in burnt dolomite for low FetO slag (slag A) and that of MgO for other slaps in the boundary layer of molten slag. Mass transport coefficients calculated were in the range of 4.7 X 10-4 to 1.7 X 10 3 cm Js at 1400 °C.It was found that the burnt dolomite after the experiment was widely covered with (Fe, Mg) 0 solid solution in the case of high FecO slag.

Influence of Magnesium Oxide Content on Kinetics of Lime Dissolution in Steelmaking Slags

“…The results obtained are consistent with the conclusions made by Umakoshi. et al 15) about limitation of lime dissolution process by magnesium oxide in slag systems with FeO content above 20%.…”

“…The increase in the concentration of MgO in lime slows down the dissolution rate of the samples. In the work 4,15) authors measured the rate of calcined dolomite samples СаСО 3 ·MgCO 3 dissolution in the slag with the composition FexO-CaO-SiO 2 , containing FeO from 20 to 65%. Authors suggested a limitation of the MgO diffusion in the slag containing FeO more than 20% through the surface layer at the interface.…”

“…4) The observed drop in the equilibrium concentration of CaO in the slag samples with the increasing content of MgO in lime can be explained by an increase in (Mg, Fe and Ca) silicates and magnesiowustite concentration in the volume of lime, which as a consequence, further complicates the process of lime dissolution. 4,8,15,17) Figure 8 shows microscopic raster images (SEM Tesla XRAY Oxford) of lime containing 4.3, 7.6 and 80% MgO, after 5 minutes of immersion in the melt at 1 500°C, and the phase composition of samples carried out with a powder diffractometer "Bruker D2 Phaser". Sample containing 80% of magnesium oxide was prepared by Voestalpine Stahl Linz consisting of periclase (MgO) and portlandite (Ca(OH) 2 ) phases.…”

A New Experimental Design to Study the Kinetics of Solid Dissolution into Liquids at Elevated Temperature

“…A so-called J-factor was introduced to express mass transfer in the liquid. Umakoshi et al [7] also used this method to investigate the dissolution rate of burnt dolomite in converter slag. They reported that the dissolution rate was not affected by the porosity of the sample.…”

“…THE rotating disk/cylinder (rod) method has been widely applied to study the dissolution of solids in liquids for decades, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] in particular for high-temperature systems such as dissolution of solid metals into liquid metals, and dissolution of ceramic solids into liquid oxides (slags). While valuable information have been gained by these studies, some misconceptions in using this method need to be addressed and analyzed.…”