Ahmed Hannachi - Academia.edu (original) (raw)
Papers by Ahmed Hannachi
Ore Geology Reviews, 2010
The Wadi Abu Khushayba area in southwestern Jordan hosts an auriferous, quartz-veined shear zone ... more The Wadi Abu Khushayba area in southwestern Jordan hosts an auriferous, quartz-veined shear zone with features of an epithermal low-sulfidation gold system. The quartz-lode and quartz-carbonate mineralization is characterized by open-space textures, typically with sharp-walled veins and multi-stage brecciation of the late Neoproterozoic (~560Ma) rhyolitic and granophyric host rocks. Silicic alteration by cryptocrystalline quartz is abundant; potassic alteration is expressed
Separation and Purification Technology, 2007
In the present work, the purification of the wet process phosphoric acid (WPA) with mixtures of m... more In the present work, the purification of the wet process phosphoric acid (WPA) with mixtures of methyl isobutyl ketone (MIBK) and tri-butyl phosphate (TBP) was investigated. Based on a three step purification process, the optimal solvent mixture composition that yielded the highest purified acid with the greatest possible P 2 O 5 recovery was obtained for an MIBK percentage of 55%. Acid recovery increased for higher solvent MIBK contents whereas the impurities' contents were lower for near equal TBP and MIBK percentages in the binary solvent mixture. The phase diagram of the ternary system H 3 PO 4 -water-optimal solvent mixture was determined. The partition ratios for H 3 PO 4 as well as three trace metallic impurities were also obtained. Relative purification was better for Mg. The lowest selectivity was that of Fe which, unlike for the other trace elements does not improve when the solvent rate increases. The best purifications are obtained for the higher solvent mixture rates. While TBP has the highest selectivity, compared with MIBK, the solvent mixture is more selective for extracting H 3 PO 4 .
Reconsidering water scaling tendency assessment
Aiche Journal, 2006
Evaluation methods of the CaCO3 scaling risk are still far from being well understood and in many... more Evaluation methods of the CaCO3 scaling risk are still far from being well understood and in many cases lack accuracy. Most of the saturation indices and models used so far for predicting scaling are based on the thermodynamic data of calcite, which is considered to be the most stable form of the different calcium carbonate varieties. However, surpassing the solubility product of anhydrous calcium carbonate forms (calcite, aragonite, and vaterite) is not sufficient to induce spontaneous precipitation. The solubility product of the CaCO3·H2O constitutes a lower limit for spontaneous germination. Based on the thermodynamic data of the monohydrate form, a novel scaling index is established and referred to as the Monohydrated form of the Langelier Scaling Index (MLSI). The ability of the MLSI to correctly predict the scaling phenomenon was verified and compared to that of the well-known Langelier Scaling Index (LSI) for several experimental results gathered from the available literature in the scaling field. Unlike the LSI, the MLSI was able to predict the instantaneous CaCO3 precipitation in scaling water. For water in the temperature range between 25 and 60°C, a classification of scaling/equilibrium state according to MLSI values is presented. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Technical evaluation of a small-scale reverse osmosis desalination unit for domestic water
Desalination, 2007
Journal of Plastic Film & Sheeting, 1989
Coextruded multilayer plastic sheets used in the packaging industry are usually calendered betwee... more Coextruded multilayer plastic sheets used in the packaging industry are usually calendered between two rolls to reduce the original sheet thickness coming from the die. To meet certain thickness criteria for each layer as well as for the calendered sheet, the operating parameters, such as roll speeds, size, temperatures and minimum gap width, have to be specified. Due to the intractability of the problem by analytical methods, numerical methods have to be used. The Lubrication Approximation Theory (LAT) is employed and the solution is achieved by using a Newton-Raphson iterative scheme which determines both the unknown a priori flow domain and the interface locations for a combination of layers. The analysis provides the pressure distribution, separating force, torque, power consumption and temperature rise. Several cases of 2-, 3-and 9-layer calendering are presented and a design criterion of equal interfacial viscosities is put forward to determine the operating temperatures in the process
Advances in Polymer Technology, 1993
Coextrusion flows of polymer solutions and melts to produce polymeric sheets are studied employin... more Coextrusion flows of polymer solutions and melts to produce polymeric sheets are studied employing (a) the Lubrication Approximation Theory for a quick determination of interface development and pressure drops for each material; and (b) the Finite Element Method, which uses a u-v-p-T-h formulation for the velocities, pressures, temperatures, and interface location and solves in the flow domain the full conservation and constitutive equations. The determination of the interface is part of the solution process. Simulations have been carried out for several cases of two-layer coextrusion of polymer solutions (Oppanols, i.e., polyisobutylenes) and compared with experimental data available in the literature. A three-layer coextrusion case is also studied with a barrier ethylene vinyl alcohol and an adhesive layer tying a polystyrene layer, and the results are compared with experimental data. For low flow rates, the interface location agrees closely with experiments. For high flow rates, a tendency for encapsulation occurs, which cannot be captured by the present purely viscous two-dimensional simulations. © 1993 John Wiley & Sons, Inc.
Journal of Plastic Film & Sheeting, 1991
Roll coating is at the heart of production of films which can be composed of many layers. The flu... more Roll coating is at the heart of production of films which can be composed of many layers. The fluids may be Newtonian or shear-thinning, usually described by a power law. The fluids' rheology along with operating parameters, such as roll speeds, their size and minimum gap width, must be considered in order to achieve a desirable coating thickness. Numerical studies are undertaken based on the Lubrication Approximation Theory (LAT) for the isothermal analysis of forward roll coating of multilayer sheets, which are considered as slightly shear-thinning fluids (power-law indices > 0.6). The solution process is based on an iterative Newton-Raphson scheme. It provides the unknown a priori flow domain, interface locations for different layer combinations, layer thicknesses after splitting, pressure and stress distributions, torque and power consumption. A parametric study based on power-law index ratios and consistency index ratios for double-layer sheets is presented. A case of a 3-layer roll-coated sheet is also examined.
Journal of Plastic Film & Sheeting, 1990
Roll coating is at the heart of production of films which can be composed of many layers. The flu... more Roll coating is at the heart of production of films which can be composed of many layers. The fluids may be Newtonian or shear-thinning, usually described by a power law. The fluids' rheology along with operating parameters, such as roll speeds, their size and minimum gap width, must be considered in order to achieve a desirable coating thickness. Numerical studies are undertaken based on the Lubrication Approximation Theory (LAT) for the isothermal analysis of forward roll coating of multilayer sheets, which are considered as slightly shear-thinning fluids (power-law indices > 0.6). The solution process is based on an iterative Newton-Raphson scheme. It provides the unknown a priori flow domain, interface locations for different layer combinations, layer thicknesses after splitting, pressure and stress distributions, torque and power consumption. A parametric study based on power-law index ratios and consistency index ratios for double-layer sheets is presented. A case of a 3-layer roll-coated sheet is also examined.
Ore Geology Reviews, 2010
The Wadi Abu Khushayba area in southwestern Jordan hosts an auriferous, quartz-veined shear zone ... more The Wadi Abu Khushayba area in southwestern Jordan hosts an auriferous, quartz-veined shear zone with features of an epithermal low-sulfidation gold system. The quartz-lode and quartz-carbonate mineralization is characterized by open-space textures, typically with sharp-walled veins and multi-stage brecciation of the late Neoproterozoic (~560Ma) rhyolitic and granophyric host rocks. Silicic alteration by cryptocrystalline quartz is abundant; potassic alteration is expressed
Separation and Purification Technology, 2007
In the present work, the purification of the wet process phosphoric acid (WPA) with mixtures of m... more In the present work, the purification of the wet process phosphoric acid (WPA) with mixtures of methyl isobutyl ketone (MIBK) and tri-butyl phosphate (TBP) was investigated. Based on a three step purification process, the optimal solvent mixture composition that yielded the highest purified acid with the greatest possible P 2 O 5 recovery was obtained for an MIBK percentage of 55%. Acid recovery increased for higher solvent MIBK contents whereas the impurities' contents were lower for near equal TBP and MIBK percentages in the binary solvent mixture. The phase diagram of the ternary system H 3 PO 4 -water-optimal solvent mixture was determined. The partition ratios for H 3 PO 4 as well as three trace metallic impurities were also obtained. Relative purification was better for Mg. The lowest selectivity was that of Fe which, unlike for the other trace elements does not improve when the solvent rate increases. The best purifications are obtained for the higher solvent mixture rates. While TBP has the highest selectivity, compared with MIBK, the solvent mixture is more selective for extracting H 3 PO 4 .
Reconsidering water scaling tendency assessment
Aiche Journal, 2006
Evaluation methods of the CaCO3 scaling risk are still far from being well understood and in many... more Evaluation methods of the CaCO3 scaling risk are still far from being well understood and in many cases lack accuracy. Most of the saturation indices and models used so far for predicting scaling are based on the thermodynamic data of calcite, which is considered to be the most stable form of the different calcium carbonate varieties. However, surpassing the solubility product of anhydrous calcium carbonate forms (calcite, aragonite, and vaterite) is not sufficient to induce spontaneous precipitation. The solubility product of the CaCO3·H2O constitutes a lower limit for spontaneous germination. Based on the thermodynamic data of the monohydrate form, a novel scaling index is established and referred to as the Monohydrated form of the Langelier Scaling Index (MLSI). The ability of the MLSI to correctly predict the scaling phenomenon was verified and compared to that of the well-known Langelier Scaling Index (LSI) for several experimental results gathered from the available literature in the scaling field. Unlike the LSI, the MLSI was able to predict the instantaneous CaCO3 precipitation in scaling water. For water in the temperature range between 25 and 60°C, a classification of scaling/equilibrium state according to MLSI values is presented. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Technical evaluation of a small-scale reverse osmosis desalination unit for domestic water
Desalination, 2007
Journal of Plastic Film & Sheeting, 1989
Coextruded multilayer plastic sheets used in the packaging industry are usually calendered betwee... more Coextruded multilayer plastic sheets used in the packaging industry are usually calendered between two rolls to reduce the original sheet thickness coming from the die. To meet certain thickness criteria for each layer as well as for the calendered sheet, the operating parameters, such as roll speeds, size, temperatures and minimum gap width, have to be specified. Due to the intractability of the problem by analytical methods, numerical methods have to be used. The Lubrication Approximation Theory (LAT) is employed and the solution is achieved by using a Newton-Raphson iterative scheme which determines both the unknown a priori flow domain and the interface locations for a combination of layers. The analysis provides the pressure distribution, separating force, torque, power consumption and temperature rise. Several cases of 2-, 3-and 9-layer calendering are presented and a design criterion of equal interfacial viscosities is put forward to determine the operating temperatures in the process
Advances in Polymer Technology, 1993
Coextrusion flows of polymer solutions and melts to produce polymeric sheets are studied employin... more Coextrusion flows of polymer solutions and melts to produce polymeric sheets are studied employing (a) the Lubrication Approximation Theory for a quick determination of interface development and pressure drops for each material; and (b) the Finite Element Method, which uses a u-v-p-T-h formulation for the velocities, pressures, temperatures, and interface location and solves in the flow domain the full conservation and constitutive equations. The determination of the interface is part of the solution process. Simulations have been carried out for several cases of two-layer coextrusion of polymer solutions (Oppanols, i.e., polyisobutylenes) and compared with experimental data available in the literature. A three-layer coextrusion case is also studied with a barrier ethylene vinyl alcohol and an adhesive layer tying a polystyrene layer, and the results are compared with experimental data. For low flow rates, the interface location agrees closely with experiments. For high flow rates, a tendency for encapsulation occurs, which cannot be captured by the present purely viscous two-dimensional simulations. © 1993 John Wiley & Sons, Inc.
Journal of Plastic Film & Sheeting, 1991
Roll coating is at the heart of production of films which can be composed of many layers. The flu... more Roll coating is at the heart of production of films which can be composed of many layers. The fluids may be Newtonian or shear-thinning, usually described by a power law. The fluids' rheology along with operating parameters, such as roll speeds, their size and minimum gap width, must be considered in order to achieve a desirable coating thickness. Numerical studies are undertaken based on the Lubrication Approximation Theory (LAT) for the isothermal analysis of forward roll coating of multilayer sheets, which are considered as slightly shear-thinning fluids (power-law indices > 0.6). The solution process is based on an iterative Newton-Raphson scheme. It provides the unknown a priori flow domain, interface locations for different layer combinations, layer thicknesses after splitting, pressure and stress distributions, torque and power consumption. A parametric study based on power-law index ratios and consistency index ratios for double-layer sheets is presented. A case of a 3-layer roll-coated sheet is also examined.
Journal of Plastic Film & Sheeting, 1990
Roll coating is at the heart of production of films which can be composed of many layers. The flu... more Roll coating is at the heart of production of films which can be composed of many layers. The fluids may be Newtonian or shear-thinning, usually described by a power law. The fluids' rheology along with operating parameters, such as roll speeds, their size and minimum gap width, must be considered in order to achieve a desirable coating thickness. Numerical studies are undertaken based on the Lubrication Approximation Theory (LAT) for the isothermal analysis of forward roll coating of multilayer sheets, which are considered as slightly shear-thinning fluids (power-law indices > 0.6). The solution process is based on an iterative Newton-Raphson scheme. It provides the unknown a priori flow domain, interface locations for different layer combinations, layer thicknesses after splitting, pressure and stress distributions, torque and power consumption. A parametric study based on power-law index ratios and consistency index ratios for double-layer sheets is presented. A case of a 3-layer roll-coated sheet is also examined.