Torben Laursen - Academia.edu (original) (raw)

Papers by Torben Laursen

J Chem Eng Data, 2003

In total, 14 isotherms for systems composed of the components nitrogen, carbon dioxide, dimethyl ... more In total, 14 isotherms for systems composed of the components nitrogen, carbon dioxide, dimethyl ether (DME), water, ethanol, and 1-propanol were measured. Experimental data for all the phases present, vapor-liquid equilibria (VLE), or vapor-liquid-liquid equilibria (VLLE), in the temperature range (25 to 45)°C and in the pressure range (5 to 102) bar, are presented. The data were not correlated.

Industrial Engineering Chemistry Research, Nov 24, 2009

ABSTRACT

Fluid Phase Equilibria, Feb 1, 2005

In this paper, we report on a new method for computing stability limits (i.e., spinodal curves) a... more In this paper, we report on a new method for computing stability limits (i.e., spinodal curves) and critical points in mixtures containing polydisperse polymers. At points on the spinodal curve, the determinant of a matrix is zero. When the model is an equation of state in temperature, volume and the mole numbers of C components, the matrix is of dimension C by C. Polymer characterization may entail use of very many pseudo-components, thereby complicating evaluation of the necessary determinant. The new analysis in this paper shows that the same result can be obtained by zeroing a determinant with only two dimensions required for a polymer of a given type, regardless of the number of pseudo-components used to characterize the polymer. The analysis does not rely on algebraic operations seeking closed-form evaluation of the determinant. It applies to mixtures with any number of non-polymer species and with more than one type of polymer; features not possible with earlier methods. Critical points are on the stability limit and satisfy a second condition. In this paper, the second criticality criterion is evaluated through an easily obtained third-order numerical derivative of the Helmholtz free energy.

From Natural Gas to Heavy and Waxy Oils, the friction theory (FT) has been extensively applied to... more From Natural Gas to Heavy and Waxy Oils, the friction theory (FT) has been extensively applied to the accurate description of the rheological behavior of a wide range of reservoir fluids. The method works in a self-consistent manner; by taking advantage of fundamental thermodynamic models widely used in the oil industry (such as cubic or even SAFT-type equations of state) delivers an integrated approach extended to rheological properties. The main application of the FT is within the area of flow assurance, which is essential for all aspects of the petroleum industry. The flexibility and accuracy that the FT models deliver can, therefore, provide essential evaluation tools for flow assurance as well as many other potential applications where viscosity is a key parameter. The FT models can be applicable to the full range of temperature and pressure conditions typically found in the oil industry (i.e. from low- to high-temperature and pressures up to around 100 MPa). In this work, seve...

The rheological behavior under simple shear for a wide number of Newtonian fluids has been accura... more The rheological behavior under simple shear for a wide number of Newtonian fluids has been accurately described by the friction theory, from pure compounds to complex mixtures such as petroleum fluids. Recently, this approach has been further extended to the modeling of the non-Newtonian behavior found in waxy-heavy oils. Thus, the f-theory is now capable of reproducing the viscosity reduction with the shear-rate and additionally, the presence of the two Newtonian regions, located at low and high values of the strain-rate. This has been achieved for reservoir fluids using cubic equations of state, widely used in the oil industry, with the friction theory. The extension to polymeric systems requires the use of a more advanced fundamental model intended for chain molecules, such as the PC-SAFT equation of state. A shear-thinning viscosity is typically observed in concentrated polymer solutions. Initial results using the PC-SAFT friction theory successfully described the rheological be...

The Journal of Supercritical Fluids, 2001

In this thermodynamic description of phase behavior between CO2, N2 and wood resin, the resin fro... more In this thermodynamic description of phase behavior between CO2, N2 and wood resin, the resin from spruce wood has been represented by a model system composed of three main components from the resin (oleic acid, α-pinene and abietic acid). A new simple experimental equipment for the determination of gas solubility in substances with high stickiness and viscosity at sub- and

Journal of Chemical & Engineering Data, 2003

In total, 14 isotherms for systems composed of the components nitrogen, carbon dioxide, dimethyl ... more In total, 14 isotherms for systems composed of the components nitrogen, carbon dioxide, dimethyl ether (DME), water, ethanol, and 1-propanol were measured. Experimental data for all the phases present, vapor-liquid equilibria (VLE), or vapor-liquid-liquid equilibria (VLLE), in the temperature range (25 to 45)°C and in the pressure range (5 to 102) bar, are presented. The data were not correlated.

Journal of Chemical & Engineering Data, 2002

Industrial & Engineering Chemistry Research, 2009

ABSTRACT

Fluid Phase Equilibria, 2006

It is shown that the equilibrium ratio between mole fractions of a polymer pseudo-component in an... more It is shown that the equilibrium ratio between mole fractions of a polymer pseudo-component in any two phases is related to the molar mass of the pseudo-component in a simple way. The relationship permits evaluating all the equilibrium ratios for the polymer components in terms of any two. This property holds true for all the equations of state commonly used for polymer-solvent phase equilibria. The consequence is that only two equilibrium equations have to be solved for any polydisperse polymer, regardless of the number of pseudocomponents. Equilibrium for the other pseudo-components is guaranteed when the dependence between the equilibrium ratios is accounted for. The paper presents a Newton-Raphson formulation of cloud-point calculations equivalent to that proposed by Koak and Heidemann but with a reduced number of equations to be solved regardless of the number of components used to characterize the polymer. It is shown that computations of many different kinds can be performed within the same general problem formulation.

Fluid Phase Equilibria, 2006

It is shown that the equilibrium ratio between mole fractions of a polymer pseudo-component in an... more It is shown that the equilibrium ratio between mole fractions of a polymer pseudo-component in any two phases is related to the molar mass of the pseudo-component in a simple way. The relationship permits evaluating all the equilibrium ratios for the polymer components in terms of any two. This property holds true for all the equations of state commonly used for polymer-solvent phase equilibria.

J Chem Eng Data, 2003

In total, 14 isotherms for systems composed of the components nitrogen, carbon dioxide, dimethyl ... more In total, 14 isotherms for systems composed of the components nitrogen, carbon dioxide, dimethyl ether (DME), water, ethanol, and 1-propanol were measured. Experimental data for all the phases present, vapor-liquid equilibria (VLE), or vapor-liquid-liquid equilibria (VLLE), in the temperature range (25 to 45)°C and in the pressure range (5 to 102) bar, are presented. The data were not correlated.

Industrial Engineering Chemistry Research, Nov 24, 2009

ABSTRACT

Fluid Phase Equilibria, Feb 1, 2005

In this paper, we report on a new method for computing stability limits (i.e., spinodal curves) a... more In this paper, we report on a new method for computing stability limits (i.e., spinodal curves) and critical points in mixtures containing polydisperse polymers. At points on the spinodal curve, the determinant of a matrix is zero. When the model is an equation of state in temperature, volume and the mole numbers of C components, the matrix is of dimension C by C. Polymer characterization may entail use of very many pseudo-components, thereby complicating evaluation of the necessary determinant. The new analysis in this paper shows that the same result can be obtained by zeroing a determinant with only two dimensions required for a polymer of a given type, regardless of the number of pseudo-components used to characterize the polymer. The analysis does not rely on algebraic operations seeking closed-form evaluation of the determinant. It applies to mixtures with any number of non-polymer species and with more than one type of polymer; features not possible with earlier methods. Critical points are on the stability limit and satisfy a second condition. In this paper, the second criticality criterion is evaluated through an easily obtained third-order numerical derivative of the Helmholtz free energy.

From Natural Gas to Heavy and Waxy Oils, the friction theory (FT) has been extensively applied to... more From Natural Gas to Heavy and Waxy Oils, the friction theory (FT) has been extensively applied to the accurate description of the rheological behavior of a wide range of reservoir fluids. The method works in a self-consistent manner; by taking advantage of fundamental thermodynamic models widely used in the oil industry (such as cubic or even SAFT-type equations of state) delivers an integrated approach extended to rheological properties. The main application of the FT is within the area of flow assurance, which is essential for all aspects of the petroleum industry. The flexibility and accuracy that the FT models deliver can, therefore, provide essential evaluation tools for flow assurance as well as many other potential applications where viscosity is a key parameter. The FT models can be applicable to the full range of temperature and pressure conditions typically found in the oil industry (i.e. from low- to high-temperature and pressures up to around 100 MPa). In this work, seve...

The rheological behavior under simple shear for a wide number of Newtonian fluids has been accura... more The rheological behavior under simple shear for a wide number of Newtonian fluids has been accurately described by the friction theory, from pure compounds to complex mixtures such as petroleum fluids. Recently, this approach has been further extended to the modeling of the non-Newtonian behavior found in waxy-heavy oils. Thus, the f-theory is now capable of reproducing the viscosity reduction with the shear-rate and additionally, the presence of the two Newtonian regions, located at low and high values of the strain-rate. This has been achieved for reservoir fluids using cubic equations of state, widely used in the oil industry, with the friction theory. The extension to polymeric systems requires the use of a more advanced fundamental model intended for chain molecules, such as the PC-SAFT equation of state. A shear-thinning viscosity is typically observed in concentrated polymer solutions. Initial results using the PC-SAFT friction theory successfully described the rheological be...

The Journal of Supercritical Fluids, 2001

In this thermodynamic description of phase behavior between CO2, N2 and wood resin, the resin fro... more In this thermodynamic description of phase behavior between CO2, N2 and wood resin, the resin from spruce wood has been represented by a model system composed of three main components from the resin (oleic acid, α-pinene and abietic acid). A new simple experimental equipment for the determination of gas solubility in substances with high stickiness and viscosity at sub- and

Journal of Chemical & Engineering Data, 2003

In total, 14 isotherms for systems composed of the components nitrogen, carbon dioxide, dimethyl ... more In total, 14 isotherms for systems composed of the components nitrogen, carbon dioxide, dimethyl ether (DME), water, ethanol, and 1-propanol were measured. Experimental data for all the phases present, vapor-liquid equilibria (VLE), or vapor-liquid-liquid equilibria (VLLE), in the temperature range (25 to 45)°C and in the pressure range (5 to 102) bar, are presented. The data were not correlated.

Journal of Chemical & Engineering Data, 2002

Industrial & Engineering Chemistry Research, 2009

ABSTRACT

Fluid Phase Equilibria, 2006

It is shown that the equilibrium ratio between mole fractions of a polymer pseudo-component in an... more It is shown that the equilibrium ratio between mole fractions of a polymer pseudo-component in any two phases is related to the molar mass of the pseudo-component in a simple way. The relationship permits evaluating all the equilibrium ratios for the polymer components in terms of any two. This property holds true for all the equations of state commonly used for polymer-solvent phase equilibria. The consequence is that only two equilibrium equations have to be solved for any polydisperse polymer, regardless of the number of pseudocomponents. Equilibrium for the other pseudo-components is guaranteed when the dependence between the equilibrium ratios is accounted for. The paper presents a Newton-Raphson formulation of cloud-point calculations equivalent to that proposed by Koak and Heidemann but with a reduced number of equations to be solved regardless of the number of components used to characterize the polymer. It is shown that computations of many different kinds can be performed within the same general problem formulation.

Fluid Phase Equilibria, 2006

It is shown that the equilibrium ratio between mole fractions of a polymer pseudo-component in an... more It is shown that the equilibrium ratio between mole fractions of a polymer pseudo-component in any two phases is related to the molar mass of the pseudo-component in a simple way. The relationship permits evaluating all the equilibrium ratios for the polymer components in terms of any two. This property holds true for all the equations of state commonly used for polymer-solvent phase equilibria.