Luckman Muhmood | KJ Somaiya college of engineering (original) (raw)

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Papers by Luckman Muhmood

Industrial & Engineering Chemistry Research, 2013

ABSTRACT In many pyrometallurgical applications, subprocesses such as emulsification, droplet, bu... more ABSTRACT In many pyrometallurgical applications, subprocesses such as emulsification, droplet, bubble or jet formation, coalescence, and surfactant adsorption occur at small time scales (typically milliseconds to fractions of seconds), both at slag/metal and slag/gas interfaces. These phenomena are surface tension driven and - due to the high-temperature environment - very difficult to investigate in a quantitative manner. Under these dynamic conditions, the instantaneous surface tension of slags may vary in time as well as along its surface and may change dramatically the rate of the involved processes. This paper presents a new high-temperature experimental setup to study and measure the dynamic surface tension of slags, the mechanisms of slag jet and droplet formation, and the capillary breakup of molten slag jets. It features a three zone furnace with optical access, and a droplet generation device incorporating a back-pressure system in combination with a stopper for precise slag flow control. The first successful results of controlled formation of calcia/alumina droplets and coherent jets in an argon environment are discussed. Various time-dependent phenomena such as droplet formation and elongation, necking, breakup, oscillation, satellite formation, and jet disintegration were investigated and quantified using a high-speed camera system. A dynamic pendant drop method was applied to determine the surface tension. The obtained values are in excellent agreement with literature data.

AIChE Journal, 2014

ABSTRACT This paper presents experiments on the capillary breakup of slag jets at high temperatur... more ABSTRACT This paper presents experiments on the capillary breakup of slag jets at high temperatures. The impact of external excitations on the disintegration process was investigated in a furnace with optical access filmed at frame rates up to 10000 fps. A synthetic calcia-alumina slag was used to form jets at different temperatures (1570 to 1660°C) and jet velocities (0.6 to 1.4 ms-1). The impact of external vibration on the breakup was evident: For low jet velocities, the jet length decreased, the droplet size increased, satellite droplet formation was hindered, and a distinct 'pumping mechanism' was observed. For jets with higher velocity, the jet length decreased by 30%, the droplet generation frequency increased from 20 to 250 droplets per second, the drop sizes were uniform, and satellite formation was also suppressed. In this case, the ideal case in which the volume of one wave instability forms one droplet was achieved. © 2014 American Institute of Chemical Engineers AIChE J, 2014

International Journal of Materials Research, 2012

The dynamics of oxygen transport along the slag -metal interface of pure iron and alumina-saturat... more The dynamics of oxygen transport along the slag -metal interface of pure iron and alumina-saturated CaO -Al 2 O 3 -SiO 2 slag was studied using high-temperature X-ray image analysis. The oscillations of the metal drop occurring due to the interfacial movement of oxygen atoms driven by Marangoni forces were studied in detail. The change in interfacial area during the oscillations was measured using a digitizing software and MATLAB. It was observed that the interfacial velocity as a function of oxygen exhibits insignificant variation with temperature. Further, the values obtained for the interfacial velocity using oxygen concentration difference at the interface were slightly lower in comparison to those using sulfur. The possible reason for this lower velocity could be that, although oxygen is a smaller atom compared to that of sulfur, the energy barrier at the free iron surface is higher for oxygen, thus hindering its motion along the interface.

High Temperature Materials and Processes, 2012

The following paper revolves around the research work conducted in collaboration during his brief... more The following paper revolves around the research work conducted in collaboration during his brief visits to the Materials Process Science Division at Royal Institute of Technology, Stockholm. The paper focuses on the thermodynamic aspects of CaO-FeO-SiO 2 and CaO-FeO-SiO 2 -MnO slag oxidation in air and sulfur transport through CaO-Al 2 O 3 -SiO 2 slag. The thermodynamics of slag oxidation in air opens potential new areas in terms of focus on effective recovery of iron oxide from the slag. The slag transport studies are of fundamental nature and focuses on a novel technique to calculate the diffusion of species through slag by analyzing its corresponding concentration in the metal phase. p. 4) PM (CS6) WDG (210×280mm) DGMetaScience J-2634 HTMP 31:4-5 pp. 5-8 2634_31_0067 (p. 5) PMU:(idp)07/

Metallurgical and Materials Transactions B, 2012

In the present work, the interfacial movement resulting from sulfur mass transfer at the slag/ me... more In the present work, the interfacial movement resulting from sulfur mass transfer at the slag/ metal interface was monitored by X-ray sessile drop method in dynamic mode at temperature 1873 K (1600°C) under nonequilibrium conditions. The experiments were carried out with pure iron and CaO-SiO 2 -Al 2 O 3 -FeO slag (alumina saturated at the experimental temperature) contained in alumina crucibles with well-controlled partial pressures of oxygen and sulfur. The impact of oxygen potential on the droplet oscillation as sulfur from the gas phase reaches the metal drop through the intermediate slag phase was monitored. The interfacial velocity was investigated. It was found that the increases of interfacial velocity and the maximum oscillation time were mainly attributed to the partial pressure of oxygen increases. The experiment results were explained by previous ab initio calculations. The thermo-physical and thermo-chemical properties of slag were also found to influence interfacial velocity.

Cement and Concrete Research, Jan 1, 2009

The cementitious and pozzolanic behavior of electric arc furnace steel slag, both as received and... more The cementitious and pozzolanic behavior of electric arc furnace steel slag, both as received and treated has been studied in detail. The as received slag was completely crystalline and multi-phasic with Fe-substituted monticellite as the predominant phase. Treatment of this slag, remelting and water quenching, results in reduction of Fe-oxide content coupled with an increase in basicity index which makes it more hydraulic compared to the as received slag. The remelted slag has several phases with merwinite as the dominant phase. Thermal analysis of the hydrated slag shows that treating the as received slag increases the water absorption capacity, a property essential for cementitious behavior. Compression strength of the slag blended cements was studied and it was found that substitution of 20% ground granulated blast furnace slag with electric arc furnace steel slag does not decrease the strength beyond 28 days. The control cement has a strength of 58.6 MPa compared to 58 MPa for the cement comprising of 20% untreated slag. The substitution of this untreated slag with treated slag exhibits the highest strength, 61 MPa and a potential for further strength increase after 28 days. In the case of cement mix with no blast furnace slag, substitution of 15% clinker with steel slag does not decrease the strength significantly, 64.4 MPa compared to 66.5 MPa for the control cement. Substituting 30% clinker in the cement mix with electric arc furnace slag however results in significant decrease in strength, 53.4 MPa. The pozzolanic strength of the slag was found to increase significantly due to remelting from 2.0 MPa for the as received slag to 8.0 MPa for the treated slag.

Metallurgical and Materials Transactions …, Jan 1, 2010

Density measurements of a low-silica CaO-SiO 2 -Al 2 O 3 system were carried out using the Archim... more Density measurements of a low-silica CaO-SiO 2 -Al 2 O 3 system were carried out using the Archimedes principle. A Pt 30 pct Rh bob and wire arrangement was used for this purpose. The results obtained were in good agreement with those obtained from the model developed in the current group as well as with other results reported earlier. The density for the CaO-SiO 2 and the CaO-Al 2 O 3 binary slag systems also was estimated from the ternary values. The extrapolation of density values for high-silica systems also showed good agreement with previous works. An estimation for the density value of CaO was made from the current experimental data. The density decrease at high temperatures was interpreted based on the silicate structure. As the mole percent of SiO 2 was below the 33 pct required for the orthosilicate composition, discrete SiO 4À 4 tetrahedral units in the silicate melt would exist along with O 2ions. The change in melt expansivity may be attributed to the ionic expansions in the order of

… Materials Transactions B, Jan 1, 2011

steel research international

Interfacial dilatational modulus was evaluated for slag-metal systems using oxygen and sulfur as ... more Interfacial dilatational modulus was evaluated for slag-metal systems using oxygen and sulfur as tracers at 1823 K. The high values of the dilatational modulus (5-10 times that obtained for surfactant adsorption) was directly related to the higher change in apparent interfacial tension prevailing at the slag-metal interface. The variation in the dilatational modulus was attributed to the non-uniform distribution of surface active elements at the interface and also due to the varying surface pressure. Further, experiments were designed to estimate the surface shear viscosity. A relationship was established to find the surface/interfacial shear viscosity from the Newton's law of viscosity. The order of magnitude of the interfacial shear viscosity at the slag-metal interface was estimated from the values obtained earlier for the interfacial velocity. The order of magnitude obtained for slag-metal systems was roughly 10-100 times that usually occurring in colloidal systems. The same could be attributed to the high bulk viscosities of the individual phases in slag-metal systems. The order of magnitude of the interfacial velocity was verified from the equation generated earlier by dimension analysis to be similar to those obtained from experiments.

Defect and Diffusion …, Jan 1, 2011

The Diffusion coefficient of sulfur in a ternary slag with composition of 51.5% CaO-9.6% SiO 2 -3... more The Diffusion coefficient of sulfur in a ternary slag with composition of 51.5% CaO-9.6% SiO 2 -38.9% Al 2 O 3 was measured at 1723 K by chemical diffusion from the variation of concentration of sulfur in silver metal. A MATLAB program was developed to find the concentration variation of sulfur in silver metal using various critical parameters like the diffusion coefficient of sulfur in slag available in literature, sulfur partition ratio, sulfide capacity of the slag and the its density. The P S2 and P O2 pressures were calculated from the Gibbs energy of the equilibrium reaction between CaO in the slag and solid CaS and confirming the same by using ThermoCalc. The density of the slag at 1723 K was obtained from earlier experiments. Initially the order of magnitude for the diffusion coefficient was taken from the works of Saito and Kawai but later was modified so that the concentration changes of Sulfur obtained from the program agreed with the experimental results. The diffusion coefficient of sulfur in 51.5% CaO-9.6% SiO 2 -38.9% Al 2 O 3 slag at 1723 K was estimated as 4.14x10 -6 cm 2 /sec.

… Materials Transactions B, Jan 1, 2011

… Materials Transactions B, Jan 1, 2011

Industrial & Engineering Chemistry Research, 2013

ABSTRACT In many pyrometallurgical applications, subprocesses such as emulsification, droplet, bu... more ABSTRACT In many pyrometallurgical applications, subprocesses such as emulsification, droplet, bubble or jet formation, coalescence, and surfactant adsorption occur at small time scales (typically milliseconds to fractions of seconds), both at slag/metal and slag/gas interfaces. These phenomena are surface tension driven and - due to the high-temperature environment - very difficult to investigate in a quantitative manner. Under these dynamic conditions, the instantaneous surface tension of slags may vary in time as well as along its surface and may change dramatically the rate of the involved processes. This paper presents a new high-temperature experimental setup to study and measure the dynamic surface tension of slags, the mechanisms of slag jet and droplet formation, and the capillary breakup of molten slag jets. It features a three zone furnace with optical access, and a droplet generation device incorporating a back-pressure system in combination with a stopper for precise slag flow control. The first successful results of controlled formation of calcia/alumina droplets and coherent jets in an argon environment are discussed. Various time-dependent phenomena such as droplet formation and elongation, necking, breakup, oscillation, satellite formation, and jet disintegration were investigated and quantified using a high-speed camera system. A dynamic pendant drop method was applied to determine the surface tension. The obtained values are in excellent agreement with literature data.

AIChE Journal, 2014

ABSTRACT This paper presents experiments on the capillary breakup of slag jets at high temperatur... more ABSTRACT This paper presents experiments on the capillary breakup of slag jets at high temperatures. The impact of external excitations on the disintegration process was investigated in a furnace with optical access filmed at frame rates up to 10000 fps. A synthetic calcia-alumina slag was used to form jets at different temperatures (1570 to 1660°C) and jet velocities (0.6 to 1.4 ms-1). The impact of external vibration on the breakup was evident: For low jet velocities, the jet length decreased, the droplet size increased, satellite droplet formation was hindered, and a distinct 'pumping mechanism' was observed. For jets with higher velocity, the jet length decreased by 30%, the droplet generation frequency increased from 20 to 250 droplets per second, the drop sizes were uniform, and satellite formation was also suppressed. In this case, the ideal case in which the volume of one wave instability forms one droplet was achieved. © 2014 American Institute of Chemical Engineers AIChE J, 2014

International Journal of Materials Research, 2012

The dynamics of oxygen transport along the slag -metal interface of pure iron and alumina-saturat... more The dynamics of oxygen transport along the slag -metal interface of pure iron and alumina-saturated CaO -Al 2 O 3 -SiO 2 slag was studied using high-temperature X-ray image analysis. The oscillations of the metal drop occurring due to the interfacial movement of oxygen atoms driven by Marangoni forces were studied in detail. The change in interfacial area during the oscillations was measured using a digitizing software and MATLAB. It was observed that the interfacial velocity as a function of oxygen exhibits insignificant variation with temperature. Further, the values obtained for the interfacial velocity using oxygen concentration difference at the interface were slightly lower in comparison to those using sulfur. The possible reason for this lower velocity could be that, although oxygen is a smaller atom compared to that of sulfur, the energy barrier at the free iron surface is higher for oxygen, thus hindering its motion along the interface.

High Temperature Materials and Processes, 2012

The following paper revolves around the research work conducted in collaboration during his brief... more The following paper revolves around the research work conducted in collaboration during his brief visits to the Materials Process Science Division at Royal Institute of Technology, Stockholm. The paper focuses on the thermodynamic aspects of CaO-FeO-SiO 2 and CaO-FeO-SiO 2 -MnO slag oxidation in air and sulfur transport through CaO-Al 2 O 3 -SiO 2 slag. The thermodynamics of slag oxidation in air opens potential new areas in terms of focus on effective recovery of iron oxide from the slag. The slag transport studies are of fundamental nature and focuses on a novel technique to calculate the diffusion of species through slag by analyzing its corresponding concentration in the metal phase. p. 4) PM (CS6) WDG (210×280mm) DGMetaScience J-2634 HTMP 31:4-5 pp. 5-8 2634_31_0067 (p. 5) PMU:(idp)07/

Metallurgical and Materials Transactions B, 2012

In the present work, the interfacial movement resulting from sulfur mass transfer at the slag/ me... more In the present work, the interfacial movement resulting from sulfur mass transfer at the slag/ metal interface was monitored by X-ray sessile drop method in dynamic mode at temperature 1873 K (1600°C) under nonequilibrium conditions. The experiments were carried out with pure iron and CaO-SiO 2 -Al 2 O 3 -FeO slag (alumina saturated at the experimental temperature) contained in alumina crucibles with well-controlled partial pressures of oxygen and sulfur. The impact of oxygen potential on the droplet oscillation as sulfur from the gas phase reaches the metal drop through the intermediate slag phase was monitored. The interfacial velocity was investigated. It was found that the increases of interfacial velocity and the maximum oscillation time were mainly attributed to the partial pressure of oxygen increases. The experiment results were explained by previous ab initio calculations. The thermo-physical and thermo-chemical properties of slag were also found to influence interfacial velocity.

Cement and Concrete Research, Jan 1, 2009

The cementitious and pozzolanic behavior of electric arc furnace steel slag, both as received and... more The cementitious and pozzolanic behavior of electric arc furnace steel slag, both as received and treated has been studied in detail. The as received slag was completely crystalline and multi-phasic with Fe-substituted monticellite as the predominant phase. Treatment of this slag, remelting and water quenching, results in reduction of Fe-oxide content coupled with an increase in basicity index which makes it more hydraulic compared to the as received slag. The remelted slag has several phases with merwinite as the dominant phase. Thermal analysis of the hydrated slag shows that treating the as received slag increases the water absorption capacity, a property essential for cementitious behavior. Compression strength of the slag blended cements was studied and it was found that substitution of 20% ground granulated blast furnace slag with electric arc furnace steel slag does not decrease the strength beyond 28 days. The control cement has a strength of 58.6 MPa compared to 58 MPa for the cement comprising of 20% untreated slag. The substitution of this untreated slag with treated slag exhibits the highest strength, 61 MPa and a potential for further strength increase after 28 days. In the case of cement mix with no blast furnace slag, substitution of 15% clinker with steel slag does not decrease the strength significantly, 64.4 MPa compared to 66.5 MPa for the control cement. Substituting 30% clinker in the cement mix with electric arc furnace slag however results in significant decrease in strength, 53.4 MPa. The pozzolanic strength of the slag was found to increase significantly due to remelting from 2.0 MPa for the as received slag to 8.0 MPa for the treated slag.

Metallurgical and Materials Transactions …, Jan 1, 2010

Density measurements of a low-silica CaO-SiO 2 -Al 2 O 3 system were carried out using the Archim... more Density measurements of a low-silica CaO-SiO 2 -Al 2 O 3 system were carried out using the Archimedes principle. A Pt 30 pct Rh bob and wire arrangement was used for this purpose. The results obtained were in good agreement with those obtained from the model developed in the current group as well as with other results reported earlier. The density for the CaO-SiO 2 and the CaO-Al 2 O 3 binary slag systems also was estimated from the ternary values. The extrapolation of density values for high-silica systems also showed good agreement with previous works. An estimation for the density value of CaO was made from the current experimental data. The density decrease at high temperatures was interpreted based on the silicate structure. As the mole percent of SiO 2 was below the 33 pct required for the orthosilicate composition, discrete SiO 4À 4 tetrahedral units in the silicate melt would exist along with O 2ions. The change in melt expansivity may be attributed to the ionic expansions in the order of

… Materials Transactions B, Jan 1, 2011

steel research international

Interfacial dilatational modulus was evaluated for slag-metal systems using oxygen and sulfur as ... more Interfacial dilatational modulus was evaluated for slag-metal systems using oxygen and sulfur as tracers at 1823 K. The high values of the dilatational modulus (5-10 times that obtained for surfactant adsorption) was directly related to the higher change in apparent interfacial tension prevailing at the slag-metal interface. The variation in the dilatational modulus was attributed to the non-uniform distribution of surface active elements at the interface and also due to the varying surface pressure. Further, experiments were designed to estimate the surface shear viscosity. A relationship was established to find the surface/interfacial shear viscosity from the Newton's law of viscosity. The order of magnitude of the interfacial shear viscosity at the slag-metal interface was estimated from the values obtained earlier for the interfacial velocity. The order of magnitude obtained for slag-metal systems was roughly 10-100 times that usually occurring in colloidal systems. The same could be attributed to the high bulk viscosities of the individual phases in slag-metal systems. The order of magnitude of the interfacial velocity was verified from the equation generated earlier by dimension analysis to be similar to those obtained from experiments.

Defect and Diffusion …, Jan 1, 2011

The Diffusion coefficient of sulfur in a ternary slag with composition of 51.5% CaO-9.6% SiO 2 -3... more The Diffusion coefficient of sulfur in a ternary slag with composition of 51.5% CaO-9.6% SiO 2 -38.9% Al 2 O 3 was measured at 1723 K by chemical diffusion from the variation of concentration of sulfur in silver metal. A MATLAB program was developed to find the concentration variation of sulfur in silver metal using various critical parameters like the diffusion coefficient of sulfur in slag available in literature, sulfur partition ratio, sulfide capacity of the slag and the its density. The P S2 and P O2 pressures were calculated from the Gibbs energy of the equilibrium reaction between CaO in the slag and solid CaS and confirming the same by using ThermoCalc. The density of the slag at 1723 K was obtained from earlier experiments. Initially the order of magnitude for the diffusion coefficient was taken from the works of Saito and Kawai but later was modified so that the concentration changes of Sulfur obtained from the program agreed with the experimental results. The diffusion coefficient of sulfur in 51.5% CaO-9.6% SiO 2 -38.9% Al 2 O 3 slag at 1723 K was estimated as 4.14x10 -6 cm 2 /sec.

… Materials Transactions B, Jan 1, 2011

… Materials Transactions B, Jan 1, 2011