Thesis (M.S.)--University of Wisconsin--Madison, 1982. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 211-214).

A study involving in-plant measurements, laboratory analysis and mathematical modelling was conducted to elucidate the kinetics of the zinc slag fuming process. The traditional assumption has been that the process operates at thermodynamic equilibrium. The results of industrial measurements at five different companies has demonstrated that this approach is not correct. Chemical assays of the slag show carbon levels in the range of 0.1 - 1.0% and char particles have been extracted from slag samples. Tuyere back-pressure measurements revealed that the predominant mode of gas injection behavior is bubbling. This evidence indicates that a portion of the coal injected into the furnace is entrained in the slag. A model of the direct coal particle-slag reaction was developed and incorporated into an overall model of the slag bath. This model included the behavior of the water-jacketed wall, a treatment of coal combustion in the tuyere gas stream, and a model of the entrained coal residence time. Fitting of the data to eleven industrial fuming cycles showed that the fraction of coal entering the bath was consistently about 35%. About 50% of the coal is combusted in the tuyere gas stream and 10% passes through the bath unconsumed. Calculated oxygen utilization ranged from 70-95%, dependent on slag depth. The slag fuming process is therefore kinetically controlled. There are essentially two critical parameters: the fraction of coal entrained in the slag, and the rate of ferrous iron oxidation. The rate of ferric reduction balances ferric inputs to the bath by displacing previously reduced zinc from the entrained coal-slag reaction bubbles. Process efficiency can be increased therefore by increasing entrainment of coal in the bath, perhaps by the use of high pressure injection, and by reducing ferrous iron oxidation. The latter objective may be achieved by more complete combustion of tuyere coal or pre-combustion. A significant control advantage might be gained by separating these two functions to different sets of tuyeres. In continuous fuming operations the model would suggest that improved efficiencies could be obtained by using a more coarsely ground coal, higher fixed carbon coals, and operating at intermediate temperatures. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

A rotating disk technique was used to determine the dissolution rate and diffusivity of CaO and MgO in slags. The dissolution rate was deduced from the measured changes in concentration of oxides in slag with respect to reaction time. The experimental set- up was initially tested with dissolution of magnesia in the CaO ??? 55 wt% Al2O3 slag at 1430 ??C and a measured rate of 2.7 ??10 -5 g/cm2.s was obtained. The dissolution rate was increased by slag chemistry and ranged from 6.5??10-5 to 2.1??10-4 g/cm2.s. The dissolution rate of CaO was measured in CaO ??? 42 wt% Al2O3 ??? 8% SiO2 based slag. The measured dissolution rates were found to be strongly dependent on the slag chemistry and temperature and ranged from 5.03??10 -5 to 3.3??10 -4 g/cm2.s. The dissolution rates were strongly dependent on the rotation speed and results indicate mass transfer in the slag phase to be rate- limiting step. The diffusivity of MgO / CaO was calculated from the dissolution rate and solubility data, using known mass transfer correlations. The diffusivity of MgO in the calcium aluminate slag at 1430 ??C was found to be about 1.1??10-5 cm2/s. Additions of 5 and 10 wt% Fe2O3 increased the diffusivity by a factor ~ 1.5 to 3, respectively. However, with introduction of (CaF2 5 wt% + Fe2O3 5 wt%) and (CaF2 5 wt% + Fe2O3 10 wt%) in the slag, the diffusivity increased considerably by a factor of about 29 and 11, respectively. The diffusivity of CaO in calcium aluminosilicate was measured to be in the order of 10-6 to 10-5 over a temperature range of 1430 ??? 1600 ??C. CaF2 increased the diffusivity by a factor of 3 to 5 while MnOx and FeOx, ilmenite and TiO 2 increased the diffusivity substantially and SiO2 had an opposite effect. The measured diffusivities are in accord with published data on comparable systems and are discussed with reference to Eyring theory. It was concluded that MnOx, FeOx and ilmenite in the slag increase the dissolution rate and diffusivity of lime, showing comparable results with respect to CaF2.

A rotating disk technique was used to determine the dissolution rate and diffusivity of CaO and MgO in slags. The dissolution rate was deduced from the measured changes in concentration of oxides in slag with respect to reaction time. The experimental set- up was initially tested with dissolution of magnesia in the CaO ??? 55 wt% Al2O3 slag at 1430 ??C and a measured rate of 2.7 ??10 -5 g/cm2.s was obtained. The dissolution rate was increased by slag chemistry and ranged from 6.5??10-5 to 2.1??10-4 g/cm2.s. The dissolution rate of CaO was measured in CaO ??? 42 wt% Al2O3 ??? 8% SiO2 based slag. The measured dissolution rates were found to be strongly dependent on the slag chemistry and temperature and ranged from 5.03??10 -5 to 3.3??10 -4 g/cm2.s. The dissolution rates were strongly dependent on the rotation speed and results indicate mass transfer in the slag phase to be rate- limiting step. The diffusivity of MgO / CaO was calculated from the dissolution rate and solubility data, using known mass transfer correlations. The diffusivity of MgO in the calcium aluminate slag at 1430 ??C was found to be about 1.1??10-5 cm2/s. Additions of 5 and 10 wt% Fe2O3 increased the diffusivity by a factor ~ 1.5 to 3, respectively. However, with introduction of (CaF2 5 wt% + Fe2O3 5 wt%) and (CaF2 5 wt% + Fe2O3 10 wt%) in the slag, the diffusivity increased considerably by a factor of about 29 and 11, respectively. The diffusivity of CaO in calcium aluminosilicate was measured to be in the order of 10-6 to 10-5 over a temperature range of 1430 ??? 1600 ??C. CaF2 increased the diffusivity by a factor of 3 to 5 while MnOx and FeOx, ilmenite and TiO 2 increased the diffusivity substantially and SiO2 had an opposite effect. The measured diffusivities are in accord with published data on comparable systems and are discussed with reference to Eyring theory. It was concluded that MnOx, FeOx and ilmenite in the slag increase the dissolution rate and diffusivity of lime, showing comparable results with respect to CaF2.

A rotating disk technique was used to determine the dissolution rate and diffusivity of CaO and MgO in slags. The dissolution rate was deduced from the measured changes in concentration of oxides in slag with respect to reaction time. The experimental set- up was initially tested with dissolution of magnesia in the CaO ??? 55 wt% Al2O3 slag at 1430 ??C and a measured rate of 2.7 ??10 -5 g/cm2.s was obtained. The dissolution rate was increased by slag chemistry and ranged from 6.5??10-5 to 2.1??10-4 g/cm2.s. The dissolution rate of CaO was measured in CaO ??? 42 wt% Al2O3 ??? 8% SiO2 based slag. The measured dissolution rates were found to be strongly dependent on the slag chemistry and temperature and ranged from 5.03??10 -5 to 3.3??10 -4 g/cm2.s. The dissolution rates were strongly dependent on the rotation speed and results indicate mass transfer in the slag phase to be rate- limiting step. The diffusivity of MgO / CaO was calculated from the dissolution rate and solubility data, using known mass transfer correlations. The diffusivity of MgO in the calcium aluminate slag at 1430 ??C was found to be about 1.1??10-5 cm2/s. Additions of 5 and 10 wt% Fe2O3 increased the diffusivity by a factor ~ 1.5 to 3, respectively. However, with introduction of (CaF2 5 wt% + Fe2O3 5 wt%) and (CaF2 5 wt% + Fe2O3 10 wt%) in the slag, the diffusivity increased considerably by a factor of about 29 and 11, respectively. The diffusivity of CaO in calcium aluminosilicate was measured to be in the order of 10-6 to 10-5 over a temperature range of 1430 ??? 1600 ??C. CaF2 increased the diffusivity by a factor of 3 to 5 while MnOx and FeOx, ilmenite and TiO 2 increased the diffusivity substantially and SiO2 had an opposite effect. The measured diffusivities are in accord with published data on comparable systems and are discussed with reference to Eyring theory. It was concluded that MnOx, FeOx and ilmenite in the slag increase the dissolution rate and diffusivity of lime, showing comparable results with respect to CaF2.

A rotating disk technique was used to determine the dissolution rate and diffusivity of CaO and MgO in slags. The dissolution rate was deduced from the measured changes in concentration of oxides in slag with respect to reaction time. The experimental set- up was initially tested with dissolution of magnesia in the CaO ??? 55 wt% Al2O3 slag at 1430 ??C and a measured rate of 2.7 ??10 -5 g/cm2.s was obtained. The dissolution rate was increased by slag chemistry and ranged from 6.5??10-5 to 2.1??10-4 g/cm2.s. The dissolution rate of CaO was measured in CaO ??? 42 wt% Al2O3 ??? 8% SiO2 based slag. The measured dissolution rates were found to be strongly dependent on the slag chemistry and temperature and ranged from 5.03??10 -5 to 3.3??10 -4 g/cm2.s. The dissolution rates were strongly dependent on the rotation speed and results indicate mass transfer in the slag phase to be rate- limiting step. The diffusivity of MgO / CaO was calculated from the dissolution rate and solubility data, using known mass transfer correlations. The diffusivity of MgO in the calcium aluminate slag at 1430 ??C was found to be about 1.1??10-5 cm2/s. Additions of 5 and 10 wt% Fe2O3 increased the diffusivity by a factor ~ 1.5 to 3, respectively. However, with introduction of (CaF2 5 wt% + Fe2O3 5 wt%) and (CaF2 5 wt% + Fe2O3 10 wt%) in the slag, the diffusivity increased considerably by a factor of about 29 and 11, respectively. The diffusivity of CaO in calcium aluminosilicate was measured to be in the order of 10-6 to 10-5 over a temperature range of 1430 ??? 1600 ??C. CaF2 increased the diffusivity by a factor of 3 to 5 while MnOx and FeOx, ilmenite and TiO 2 increased the diffusivity substantially and SiO2 had an opposite effect. The measured diffusivities are in accord with published data on comparable systems and are discussed with reference to Eyring theory. It was concluded that MnOx, FeOx and ilmenite in the slag increase the dissolution rate and diffusivity of lime, showing comparable results with respect to CaF2.

A rotating disk technique was used to determine the dissolution rate and diffusivity of CaO and MgO in slags. The dissolution rate was deduced from the measured changes in concentration of oxides in slag with respect to reaction time. The experimental set- up was initially tested with dissolution of magnesia in the CaO ??? 55 wt% Al2O3 slag at 1430 ??C and a measured rate of 2.7 ??10 -5 g/cm2.s was obtained. The dissolution rate was increased by slag chemistry and ranged from 6.5??10-5 to 2.1??10-4 g/cm2.s. The dissolution rate of CaO was measured in CaO ??? 42 wt% Al2O3 ??? 8% SiO2 based slag. The measured dissolution rates were found to be strongly dependent on the slag chemistry and temperature and ranged from 5.03??10 -5 to 3.3??10 -4 g/cm2.s. The dissolution rates were strongly dependent on the rotation speed and results indicate mass transfer in the slag phase to be rate- limiting step. The diffusivity of MgO / CaO was calculated from the dissolution rate and solubility data, using known mass transfer correlations. The diffusivity of MgO in the calcium aluminate slag at 1430 ??C was found to be about 1.1??10-5 cm2/s. Additions of 5 and 10 wt% Fe2O3 increased the diffusivity by a factor ~ 1.5 to 3, respectively. However, with introduction of (CaF2 5 wt% + Fe2O3 5 wt%) and (CaF2 5 wt% + Fe2O3 10 wt%) in the slag, the diffusivity increased considerably by a factor of about 29 and 11, respectively. The diffusivity of CaO in calcium aluminosilicate was measured to be in the order of 10-6 to 10-5 over a temperature range of 1430 ??? 1600 ??C. CaF2 increased the diffusivity by a factor of 3 to 5 while MnOx and FeOx, ilmenite and TiO 2 increased the diffusivity substantially and SiO2 had an opposite effect. The measured diffusivities are in accord with published data on comparable systems and are discussed with reference to Eyring theory. It was concluded that MnOx, FeOx and ilmenite in the slag increase the dissolution rate and diffusivity of lime, showing comparable results with respect to CaF2.

A rotating disk technique was used to determine the dissolution rate and diffusivity of CaO and MgO in slags. The dissolution rate was deduced from the measured changes in concentration of oxides in slag with respect to reaction time. The experimental set- up was initially tested with dissolution of magnesia in the CaO ??? 55 wt% Al2O3 slag at 1430 ??C and a measured rate of 2.7 ??10 -5 g/cm2.s was obtained. The dissolution rate was increased by slag chemistry and ranged from 6.5??10-5 to 2.1??10-4 g/cm2.s. The dissolution rate of CaO was measured in CaO ??? 42 wt% Al2O3 ??? 8% SiO2 based slag. The measured dissolution rates were found to be strongly dependent on the slag chemistry and temperature and ranged from 5.03??10 -5 to 3.3??10 -4 g/cm2.s. The dissolution rates were strongly dependent on the rotation speed and results indicate mass transfer in the slag phase to be rate- limiting step. The diffusivity of MgO / CaO was calculated from the dissolution rate and solubility data, using known mass transfer correlations. The diffusivity of MgO in the calcium aluminate slag at 1430 ??C was found to be about 1.1??10-5 cm2/s. Additions of 5 and 10 wt% Fe2O3 increased the diffusivity by a factor ~ 1.5 to 3, respectively. However, with introduction of (CaF2 5 wt% + Fe2O3 5 wt%) and (CaF2 5 wt% + Fe2O3 10 wt%) in the slag, the diffusivity increased considerably by a factor of about 29 and 11, respectively. The diffusivity of CaO in calcium aluminosilicate was measured to be in the order of 10-6 to 10-5 over a temperature range of 1430 ??? 1600 ??C. CaF2 increased the diffusivity by a factor of 3 to 5 while MnOx and FeOx, ilmenite and TiO 2 increased the diffusivity substantially and SiO2 had an opposite effect. The measured diffusivities are in accord with published data on comparable systems and are discussed with reference to Eyring theory. It was concluded that MnOx, FeOx and ilmenite in the slag increase the dissolution rate and diffusivity of lime, showing comparable results with respect to CaF2.

A rotating disk technique was used to determine the dissolution rate and diffusivity of CaO and MgO in slags. The dissolution rate was deduced from the measured changes in concentration of oxides in slag with respect to reaction time. The experimental set- up was initially tested with dissolution of magnesia in the CaO ??? 55 wt% Al2O3 slag at 1430 ??C and a measured rate of 2.7 ??10 -5 g/cm2.s was obtained. The dissolution rate was increased by slag chemistry and ranged from 6.5??10-5 to 2.1??10-4 g/cm2.s. The dissolution rate of CaO was measured in CaO ??? 42 wt% Al2O3 ??? 8% SiO2 based slag. The measured dissolution rates were found to be strongly dependent on the slag chemistry and temperature and ranged from 5.03??10 -5 to 3.3??10 -4 g/cm2.s. The dissolution rates were strongly dependent on the rotation speed and results indicate mass transfer in the slag phase to be rate- limiting step. The diffusivity of MgO / CaO was calculated from the dissolution rate and solubility data, using known mass transfer correlations. The diffusivity of MgO in the calcium aluminate slag at 1430 ??C was found to be about 1.1??10-5 cm2/s. Additions of 5 and 10 wt% Fe2O3 increased the diffusivity by a factor ~ 1.5 to 3, respectively. However, with introduction of (CaF2 5 wt% + Fe2O3 5 wt%) and (CaF2 5 wt% + Fe2O3 10 wt%) in the slag, the diffusivity increased considerably by a factor of about 29 and 11, respectively. The diffusivity of CaO in calcium aluminosilicate was measured to be in the order of 10-6 to 10-5 over a temperature range of 1430 ??? 1600 ??C. CaF2 increased the diffusivity by a factor of 3 to 5 while MnOx and FeOx, ilmenite and TiO 2 increased the diffusivity substantially and SiO2 had an opposite effect. The measured diffusivities are in accord with published data on comparable systems and are discussed with reference to Eyring theory. It was concluded that MnOx, FeOx and ilmenite in the slag increase the dissolution rate and diffusivity of lime, showing comparable results with respect to CaF2.

A rotating disk technique was used to determine the dissolution rate and diffusivity of CaO and MgO in slags. The dissolution rate was deduced from the measured changes in concentration of oxides in slag with respect to reaction time. The experimental set- up was initially tested with dissolution of magnesia in the CaO ??? 55 wt% Al2O3 slag at 1430 ??C and a measured rate of 2.7 ??10 -5 g/cm2.s was obtained. The dissolution rate was increased by slag chemistry and ranged from 6.5??10-5 to 2.1??10-4 g/cm2.s. The dissolution rate of CaO was measured in CaO ??? 42 wt% Al2O3 ??? 8% SiO2 based slag. The measured dissolution rates were found to be strongly dependent on the slag chemistry and temperature and ranged from 5.03??10 -5 to 3.3??10 -4 g/cm2.s. The dissolution rates were strongly dependent on the rotation speed and results indicate mass transfer in the slag phase to be rate- limiting step. The diffusivity of MgO / CaO was calculated from the dissolution rate and solubility data, using known mass transfer correlations. The diffusivity of MgO in the calcium aluminate slag at 1430 ??C was found to be about 1.1??10-5 cm2/s. Additions of 5 and 10 wt% Fe2O3 increased the diffusivity by a factor ~ 1.5 to 3, respectively. However, with introduction of (CaF2 5 wt% + Fe2O3 5 wt%) and (CaF2 5 wt% + Fe2O3 10 wt%) in the slag, the diffusivity increased considerably by a factor of about 29 and 11, respectively. The diffusivity of CaO in calcium aluminosilicate was measured to be in the order of 10-6 to 10-5 over a temperature range of 1430 ??? 1600 ??C. CaF2 increased the diffusivity by a factor of 3 to 5 while MnOx and FeOx, ilmenite and TiO 2 increased the diffusivity substantially and SiO2 had an opposite effect. The measured diffusivities are in accord with published data on comparable systems and are discussed with reference to Eyring theory. It was concluded that MnOx, FeOx and ilmenite in the slag increase the dissolution rate and diffusivity of lime, showing comparable results with respect to CaF2.