Phase equilibrium behavior of the carbon dioxide and argon system has been investigated at the te... more Phase equilibrium behavior of the carbon dioxide and argon system has been investigated at the temperatures 213, 223, 243, 263, 273, 283, and 299 K. The full vapor-liquid equilibria phase envelope has been measured at all temperatures using an analytical technique where the compositions of both the liquid and vapor phase have been measured. In addition, the fluid compositions at the three-phase line and phase equilibria involving solids at 213 K have been measured. The three-phase line was determined at 213 K with an estimated uncertainty of 2 kPa. Otherwise, the estimated uncertainty is better than 13 mK for the temperature measurements, 3.2 kPa for the pressure measurements, and 0.12 % in total combined uncertainty in terms of mole fraction for all the 107 measured data points. The new data have been compared with existing models, and estimates for the critical points of the 7 isotherms have been made. Together with recently established experimental results for homogeneous density, speed of sound, and dew-point pressure, the vapor-liquid-equilibrium data were used to develop an improved Helmholtz-energy-explicit mixture model. This new model enables the calculation of highly-accurate data for all types of thermodynamic properties. Its development is part of the ongoing work on setting up an extended multi-fluid mixture model for the description of carbon-dioxide-rich mixtures with various impurities as relevant for CCS applications.
A new setup for the measurement of vapor-liquid phase equilibria of CO 2-rich mixtures relevant f... more A new setup for the measurement of vapor-liquid phase equilibria of CO 2-rich mixtures relevant for carbon capture and storage (CCS) transport conditions is presented. An isothermal analytical method with a variable volume cell is used. The apparatus is capable of highly accurate measurements in terms of pressure, temperature and composition, also in the critical region. Vapor-liquid equilibrium (VLE) measurements for the binary system CO 2 +N 2 are reported at 223, 270, 298 and 303 K, with estimated standard uncertainties of maximum 0.006 K in the temperature, maximum 0.003 MPa in the pressure, and maximum 0.0004 in the mole fractions of the phases. These measurements are verified against existing data. Although some data exists, there is little trustworthy data around critical conditions, and our data indicate a need to revise the parameters of existing models. A fit made against our data of the vapor-liquid equilibrium prediction of GERG-2008/EOS-CG for CO 2 +N 2 is presented. At 223 and 298 K, the critical region of the isotherm are fitted using a scaling law, and high accuracy estimates for the critical composition and pressure are found.
Vapor-liquid equilibrium measurements for the binary system CO 2 +CO are reported at 253, 273, 28... more Vapor-liquid equilibrium measurements for the binary system CO 2 +CO are reported at 253, 273, 283 and 298 K, with estimated standard uncertainties of maximum 9 mK in temperature, maximum 3 kPa in pressure, and maximum 0.001 in the mole fractions of the phases in the mixture critical regions, and 0.0003 in the mole fractions outside the critical regions. These measurements are compared with existing data. Although some data exist, there are little trustworthy literature data around critical conditions, and the measurements in the present work indicate a need to revise the parameters of existing models. The data in the present work have significantly less scatter than most of the literature data, and range from the vapor pressure of pure CO 2 to close to the mixture critical point pressure at all four temperatures. With the measurements in the present work, the data situation for the CO 2 +CO system is improved, enabling development of better equations of state for the system. A scaling law model is fitted to the critical region data of each isotherm, and high accuracy estimates for the critical composition and pressure are found. The Peng-Robinson EOS with the alpha correction by Mathias and Copeman, the mixing rules by Wong and Sandler, and the NRTL excess Gibbs energy model is fitted to the data in the present work.
Experimental vapor-liquid equilibrium data for the CO2/CH4 mixture have been measured at 293.13 K... more Experimental vapor-liquid equilibrium data for the CO2/CH4 mixture have been measured at 293.13 K, 298.14 K and 303.15 K, with emphasis on the mixture critical area. The maximum estimated standard uncertainties are 3 mK in temperature, 2 kPa in pressure and 0.0008 in mole fraction. The scaling law of statistical thermodynamics has been fitted to the critical region data of each isotherm and very good estimation of the critical point is achieved with a maximum uncertainty of 10 kPa in critical pressure and 0.0009 in critical molar composition. The measurements have been validated against experimental data taken from the literature, where available, and against the prediction of the GERG-2008 model. The Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR) Equations of State using the classic van der Waals one fluid mixing rules, the perturbed chain statistical association fluid theory (PC-SAFT) and the Universal Mixing Rule-Peng Robinson (UMR-PRU) model have been fitted to the data of each isotherm with very satisfactory results. UMR-PRU yields the lowest deviation, especially concerning the critical point area, with an overall absolute average deviation (AAD) of 0.18% in bubble point pressure and 0.43% in CO2 mole fraction of the vapor phase. In the critical points, UMR-PRU results in an average % AAD equal to 1.55 in critical pressure and 0.99 in the critical point composition.
Vapor-liquid equilibria (VLE) data of the ternary mixture of CO 2 þ N 2 þ CH 4 were measured at t... more Vapor-liquid equilibria (VLE) data of the ternary mixture of CO 2 þ N 2 þ CH 4 were measured at the isotherms 223 K, 253 K, 273 K, 283 K, and 298 K and for pressures in the range of 0.8 MPae9.3 MPa. The 62 experimental dew or bubble point data points have been measured using an analytical technique. For each temperature, the ratio between N 2 and CH 4 mole fraction in the total composition has been close to constant, enabling the data to be visualized as quasi phase envelopes. Estimated standard measurement uncertainties (k ¼ 1) better than 14 mK in temperature, 1.5 kPa in pressure, and 0.06 mol% in composition are reported, yielding a total uncertainty in terms of composition better than 0.07 mol%. The experimental data were compared to the EOS-CG-2019 model, which is a state-of-the-art Helmholtz energybased equation of state for the mixture of CO 2 þ N 2 þ CH 4. All deviations between model and experimental data points are below 0.5 mol% for liquid compositions and 1.0 mol% for vapor compositions. The deviations between model and experimental points in the ternary mixture of CO 2 þ N 2 þ CH 4 follow the same trends seen in earlier reports between model and experimental data for the binary mixtures of CO 2 þ N 2 and CO 2 þ CH 4. In addition, the model was analysed with respect to other thermophysical properties available in the literature. To a large extent, the results presented in this work validate the assumption that the thermodynamic properties of the multicomponent system CO 2 þ N 2 þ CH 4 can be described purely based on the pure component and binary mixture contributions.
For more efficient, robust and inexpensive CCS systems, improvements of the models describing the... more For more efficient, robust and inexpensive CCS systems, improvements of the models describing the behavior of fluids involved in CCS are required. Accurate models in turn require experimental data of high quality, which are still lacking for many important properties when impurities are present. SINTEF Energy Research and the Norwegian CCS Research Centre (NCCS) are addressing the lack of phase equilibrium data in CCS by performing accurate measurements of important systems using a purpose-built setup. So far, the binary mixtures of CO2 + N2, CO2 + O2, CO2 + CH4, CO2 + Ar, and CO2 + CO have been investigated. In the present paper, some examples from the measurements on CO2 + Ar and CO2 + CO systems are provided, illustrating that trusting models could lead to serious consequences if they are not supported by independently verified data.
A facility designed for precise measurements of phase equilibria of CO2-rich mixtures relevant fo... more A facility designed for precise measurements of phase equilibria of CO2-rich mixtures relevant for CCS conditioning and transport is demonstrated. The setup aims for high accuracy in pressure, temperature, and composition measurements for pressures between 4 and 200 bar and temperatures between-60 and 150 °C. In this paper, the test measurement of the N 2 / CO 2 system in the vicinity of the critical point for CO 2 , have shown the ability to produce measurements with the high accuracy and repeatability in temperature, pressure and composition
This paper describes the experimental rig that has been constructed for the measurements of phase... more This paper describes the experimental rig that has been constructed for the measurements of phase equilibrium of CO 2-rich mixtures under relevant conditions for CCS transport and conditioning. The rig is believed to have an accuracy better than 10 mK in temperature and 0.10 % in pressure. Measurements will be performed using the analytical technique, which means that composition of all phases will be measured. In the years to come, a comprehensive experimental plan will be executed, resulting in new and accurate phase equilibrium data relevant for CCS conditioning and transport.
The design of safe and cost-efficient CO 2-transportation systems is an integral part of CO 2 cap... more The design of safe and cost-efficient CO 2-transportation systems is an integral part of CO 2 capture and storage (CCS) deployment. To achieve this, accurate transient flow models capturing the occurrence of gas, liquid and solid CO 2 are needed. These in turn rely on experimental validation. In this work, we present a new experimental facility designed to capture pressure and temperature during the depressurization of CO 2 and CO 2-rich mixtures in a tube at high spatial and temporal resolution. Experiments with pure CO 2 starting from both gaseous and dense (liquid) states are presented, and a reference experiment with N 2 is included. The experimental results for both pressure and temperature are analysed by comparison with predictions by a homogeneous equilibrium model. Emphasis is put on the decompression-wave speed, of particular relevance for running-ductile fracture in CO 2-transportation pipelines. We observe good agreement with predicted decompression-wave speeds in the single-phase region, and fair agreement for two-phase flows when the calculations are based on the assumption of equilibrium. However, the observed 'pressure plateau', a key factor in the prediction of running-ductile fracture, can be significantly lower than that calculated assuming equilibrium.
A new setup for accurate measurement of phase behavior of CO 2-rich mixtures relevant for CCS has... more A new setup for accurate measurement of phase behavior of CO 2-rich mixtures relevant for CCS has been designed, covering a range between-60 and 150 °C in temperature and 0.4 and 20 MPa in pressure. In order to design safe and efficient infrastructure for CCS, the exact properties of these mixtures are required, and currently there are large knowledge gaps that need to be closed regarding the phase behavior. This paper reports a description of the experimental setup, how uncertainties will be verified and contained, and the very first test measurements performed using the setup.
Utilisation of natural working fluids based on hydrocarbons can reduce greenhouse gas emissions c... more Utilisation of natural working fluids based on hydrocarbons can reduce greenhouse gas emissions considerably. However, components and systems need to be developed further to fully exploit their thermophysical properties. A new heat exchanger test rig is under construction at SINTEF Energy Research's thermal laboratories in Trondheim. The rig is designed to test novel heat exchanger concepts and designs for hydrocarbons and mixtures of these. Heating, cooling, evaporation, and condensation experiments can be performed at temperatures ranging from 0thermal capacities up to around 20 kW. This paper describes the design, test capabilities and accuracy of the experimental setup.
Accurate thermophysical data for the CO 2-rich mixtures relevant for carbon capture, transport an... more Accurate thermophysical data for the CO 2-rich mixtures relevant for carbon capture, transport and storage (CCS) are essential for the development of the accurate equations of state (EOS) and models needed for the design and operation of the processes within CCS. Vapor-liquid equilibrium measurements for the binary system CO 2 +O 2 are reported at 218, 233, 253, 273, 288 and 298 K, with estimated standard uncertainties of maximum 8 mK in temperature, maximum 3 kPa in pressure, and maximum 0.0031 in the mole fractions of the phases in the mixture critical regions, and 0.0005 in the mole fractions outside the critical regions. These measurements are compared with existing data. Although some data exists, there are little trustworthy literature data around critical conditions, and the measurements in the present work indicate a need to revise the parameters of existing models. The data in the present work has significantly less scatter than most of the literature data, and range from the vapor pressure of pure CO 2 to close to the mixture critical point pressure at all six temperatures. With the measurements in the present work, the data situation for the CO 2 +O 2 system is significantly improved, forming the basis to develop better equations of state for the system. A scaling law model is fitted to the critical region data of each isotherm, and high accuracy estimates for the critical composition and pressure are found. The Peng-Robinson EOS with the alpha correction by Mathias and Copeman, the mixing rules by Wong and Sandler, and the NRTL excess Gibbs energy model is fitted to the data in the present work, with a maximum absolute average deviation of 0.01 in mole fraction.
For vessel-based transport of liquid CO2 in carbon capture and storage chains, transport at 8 bar... more For vessel-based transport of liquid CO2 in carbon capture and storage chains, transport at 8 bar(a) enable significant cost reductions compared to transport at higher pressures for most transport distances and volumes. Transport at even lower pressures could further reduce the costs. There are, however, concerns related to dry ice formation and potential clogging in parts of the chain that could lead to operational issues when operating close to the triple point pressure of CO2. In this paper, results from an experimental campaign to de-risk and gain operational experience from the low-pressure CO2 liquefaction process are described. Six experiments using pure CO2 or CO2/N2 mixtures are presented. In four of the experiments, the liquid product pressure was continuously lowered until dry ice was detected and eventually clogged the system. In the final two experiments, the liquefaction process was run in steady-state at low liquefaction pressures for five hours to ensure that there i...
The membrane-assisted CO2-liquefaction carbon capture process has been investigated by process si... more The membrane-assisted CO2-liquefaction carbon capture process has been investigated by process simulations and laboratory experiments to validate its performance. To increase the TRL level to 7-8, a pilot facility with real flue gas from a cement plant in an operational environment is required.<br> The membrane-assisted CO2-liquefaction process is a hybrid between two carbon capture technologies, each of which are unfit for post-combustion carbon capture by itself. By combining the two technologies, they can both operate in their respective favourable regime of operation. The process consists of a single membrane stage for bulk separation of the flue gas from a CO2 concentration in the range 17–20 mol%, delivering crude CO2 with a purity up to 60–70 mol%. This bulk separation is followed by CO2 liquefaction and two stages of phase-separation for purification up to above 99 mol% purity. The final liquid CO2 stream can be pumped to the transport pressure and reheated in the case...
A first model for a hydrogen liquefaction prototype laboratory unit has been developed. The proce... more A first model for a hydrogen liquefaction prototype laboratory unit has been developed. The process is based on using a mixed component refrigerant (MCR) process for pre-cooling. The process also includes an implementation of ortho para conversion. By simulations it has been shown that this process have potential to improve the exergy efficiency for the liquefaction process and thereby also the energy requirements for hydrogen liquefaction. One of the key points in the design work has been to find a refrigerant that is sufficiently wide-boiling and at the same time not freezing at the low temperature end. The goal has been to reach sub-cooling to below 75 K without freezing out any component of the MCR.
Phase equilibrium behavior of the carbon dioxide and argon system has been investigated at the te... more Phase equilibrium behavior of the carbon dioxide and argon system has been investigated at the temperatures 213, 223, 243, 263, 273, 283, and 299 K. The full vapor-liquid equilibria phase envelope has been measured at all temperatures using an analytical technique where the compositions of both the liquid and vapor phase have been measured. In addition, the fluid compositions at the three-phase line and phase equilibria involving solids at 213 K have been measured. The three-phase line was determined at 213 K with an estimated uncertainty of 2 kPa. Otherwise, the estimated uncertainty is better than 13 mK for the temperature measurements, 3.2 kPa for the pressure measurements, and 0.12 % in total combined uncertainty in terms of mole fraction for all the 107 measured data points. The new data have been compared with existing models, and estimates for the critical points of the 7 isotherms have been made. Together with recently established experimental results for homogeneous density, speed of sound, and dew-point pressure, the vapor-liquid-equilibrium data were used to develop an improved Helmholtz-energy-explicit mixture model. This new model enables the calculation of highly-accurate data for all types of thermodynamic properties. Its development is part of the ongoing work on setting up an extended multi-fluid mixture model for the description of carbon-dioxide-rich mixtures with various impurities as relevant for CCS applications.
A new setup for the measurement of vapor-liquid phase equilibria of CO 2-rich mixtures relevant f... more A new setup for the measurement of vapor-liquid phase equilibria of CO 2-rich mixtures relevant for carbon capture and storage (CCS) transport conditions is presented. An isothermal analytical method with a variable volume cell is used. The apparatus is capable of highly accurate measurements in terms of pressure, temperature and composition, also in the critical region. Vapor-liquid equilibrium (VLE) measurements for the binary system CO 2 +N 2 are reported at 223, 270, 298 and 303 K, with estimated standard uncertainties of maximum 0.006 K in the temperature, maximum 0.003 MPa in the pressure, and maximum 0.0004 in the mole fractions of the phases. These measurements are verified against existing data. Although some data exists, there is little trustworthy data around critical conditions, and our data indicate a need to revise the parameters of existing models. A fit made against our data of the vapor-liquid equilibrium prediction of GERG-2008/EOS-CG for CO 2 +N 2 is presented. At 223 and 298 K, the critical region of the isotherm are fitted using a scaling law, and high accuracy estimates for the critical composition and pressure are found.
Vapor-liquid equilibrium measurements for the binary system CO 2 +CO are reported at 253, 273, 28... more Vapor-liquid equilibrium measurements for the binary system CO 2 +CO are reported at 253, 273, 283 and 298 K, with estimated standard uncertainties of maximum 9 mK in temperature, maximum 3 kPa in pressure, and maximum 0.001 in the mole fractions of the phases in the mixture critical regions, and 0.0003 in the mole fractions outside the critical regions. These measurements are compared with existing data. Although some data exist, there are little trustworthy literature data around critical conditions, and the measurements in the present work indicate a need to revise the parameters of existing models. The data in the present work have significantly less scatter than most of the literature data, and range from the vapor pressure of pure CO 2 to close to the mixture critical point pressure at all four temperatures. With the measurements in the present work, the data situation for the CO 2 +CO system is improved, enabling development of better equations of state for the system. A scaling law model is fitted to the critical region data of each isotherm, and high accuracy estimates for the critical composition and pressure are found. The Peng-Robinson EOS with the alpha correction by Mathias and Copeman, the mixing rules by Wong and Sandler, and the NRTL excess Gibbs energy model is fitted to the data in the present work.
Experimental vapor-liquid equilibrium data for the CO2/CH4 mixture have been measured at 293.13 K... more Experimental vapor-liquid equilibrium data for the CO2/CH4 mixture have been measured at 293.13 K, 298.14 K and 303.15 K, with emphasis on the mixture critical area. The maximum estimated standard uncertainties are 3 mK in temperature, 2 kPa in pressure and 0.0008 in mole fraction. The scaling law of statistical thermodynamics has been fitted to the critical region data of each isotherm and very good estimation of the critical point is achieved with a maximum uncertainty of 10 kPa in critical pressure and 0.0009 in critical molar composition. The measurements have been validated against experimental data taken from the literature, where available, and against the prediction of the GERG-2008 model. The Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR) Equations of State using the classic van der Waals one fluid mixing rules, the perturbed chain statistical association fluid theory (PC-SAFT) and the Universal Mixing Rule-Peng Robinson (UMR-PRU) model have been fitted to the data of each isotherm with very satisfactory results. UMR-PRU yields the lowest deviation, especially concerning the critical point area, with an overall absolute average deviation (AAD) of 0.18% in bubble point pressure and 0.43% in CO2 mole fraction of the vapor phase. In the critical points, UMR-PRU results in an average % AAD equal to 1.55 in critical pressure and 0.99 in the critical point composition.
Vapor-liquid equilibria (VLE) data of the ternary mixture of CO 2 þ N 2 þ CH 4 were measured at t... more Vapor-liquid equilibria (VLE) data of the ternary mixture of CO 2 þ N 2 þ CH 4 were measured at the isotherms 223 K, 253 K, 273 K, 283 K, and 298 K and for pressures in the range of 0.8 MPae9.3 MPa. The 62 experimental dew or bubble point data points have been measured using an analytical technique. For each temperature, the ratio between N 2 and CH 4 mole fraction in the total composition has been close to constant, enabling the data to be visualized as quasi phase envelopes. Estimated standard measurement uncertainties (k ¼ 1) better than 14 mK in temperature, 1.5 kPa in pressure, and 0.06 mol% in composition are reported, yielding a total uncertainty in terms of composition better than 0.07 mol%. The experimental data were compared to the EOS-CG-2019 model, which is a state-of-the-art Helmholtz energybased equation of state for the mixture of CO 2 þ N 2 þ CH 4. All deviations between model and experimental data points are below 0.5 mol% for liquid compositions and 1.0 mol% for vapor compositions. The deviations between model and experimental points in the ternary mixture of CO 2 þ N 2 þ CH 4 follow the same trends seen in earlier reports between model and experimental data for the binary mixtures of CO 2 þ N 2 and CO 2 þ CH 4. In addition, the model was analysed with respect to other thermophysical properties available in the literature. To a large extent, the results presented in this work validate the assumption that the thermodynamic properties of the multicomponent system CO 2 þ N 2 þ CH 4 can be described purely based on the pure component and binary mixture contributions.
For more efficient, robust and inexpensive CCS systems, improvements of the models describing the... more For more efficient, robust and inexpensive CCS systems, improvements of the models describing the behavior of fluids involved in CCS are required. Accurate models in turn require experimental data of high quality, which are still lacking for many important properties when impurities are present. SINTEF Energy Research and the Norwegian CCS Research Centre (NCCS) are addressing the lack of phase equilibrium data in CCS by performing accurate measurements of important systems using a purpose-built setup. So far, the binary mixtures of CO2 + N2, CO2 + O2, CO2 + CH4, CO2 + Ar, and CO2 + CO have been investigated. In the present paper, some examples from the measurements on CO2 + Ar and CO2 + CO systems are provided, illustrating that trusting models could lead to serious consequences if they are not supported by independently verified data.
A facility designed for precise measurements of phase equilibria of CO2-rich mixtures relevant fo... more A facility designed for precise measurements of phase equilibria of CO2-rich mixtures relevant for CCS conditioning and transport is demonstrated. The setup aims for high accuracy in pressure, temperature, and composition measurements for pressures between 4 and 200 bar and temperatures between-60 and 150 °C. In this paper, the test measurement of the N 2 / CO 2 system in the vicinity of the critical point for CO 2 , have shown the ability to produce measurements with the high accuracy and repeatability in temperature, pressure and composition
This paper describes the experimental rig that has been constructed for the measurements of phase... more This paper describes the experimental rig that has been constructed for the measurements of phase equilibrium of CO 2-rich mixtures under relevant conditions for CCS transport and conditioning. The rig is believed to have an accuracy better than 10 mK in temperature and 0.10 % in pressure. Measurements will be performed using the analytical technique, which means that composition of all phases will be measured. In the years to come, a comprehensive experimental plan will be executed, resulting in new and accurate phase equilibrium data relevant for CCS conditioning and transport.
The design of safe and cost-efficient CO 2-transportation systems is an integral part of CO 2 cap... more The design of safe and cost-efficient CO 2-transportation systems is an integral part of CO 2 capture and storage (CCS) deployment. To achieve this, accurate transient flow models capturing the occurrence of gas, liquid and solid CO 2 are needed. These in turn rely on experimental validation. In this work, we present a new experimental facility designed to capture pressure and temperature during the depressurization of CO 2 and CO 2-rich mixtures in a tube at high spatial and temporal resolution. Experiments with pure CO 2 starting from both gaseous and dense (liquid) states are presented, and a reference experiment with N 2 is included. The experimental results for both pressure and temperature are analysed by comparison with predictions by a homogeneous equilibrium model. Emphasis is put on the decompression-wave speed, of particular relevance for running-ductile fracture in CO 2-transportation pipelines. We observe good agreement with predicted decompression-wave speeds in the single-phase region, and fair agreement for two-phase flows when the calculations are based on the assumption of equilibrium. However, the observed 'pressure plateau', a key factor in the prediction of running-ductile fracture, can be significantly lower than that calculated assuming equilibrium.
A new setup for accurate measurement of phase behavior of CO 2-rich mixtures relevant for CCS has... more A new setup for accurate measurement of phase behavior of CO 2-rich mixtures relevant for CCS has been designed, covering a range between-60 and 150 °C in temperature and 0.4 and 20 MPa in pressure. In order to design safe and efficient infrastructure for CCS, the exact properties of these mixtures are required, and currently there are large knowledge gaps that need to be closed regarding the phase behavior. This paper reports a description of the experimental setup, how uncertainties will be verified and contained, and the very first test measurements performed using the setup.
Utilisation of natural working fluids based on hydrocarbons can reduce greenhouse gas emissions c... more Utilisation of natural working fluids based on hydrocarbons can reduce greenhouse gas emissions considerably. However, components and systems need to be developed further to fully exploit their thermophysical properties. A new heat exchanger test rig is under construction at SINTEF Energy Research's thermal laboratories in Trondheim. The rig is designed to test novel heat exchanger concepts and designs for hydrocarbons and mixtures of these. Heating, cooling, evaporation, and condensation experiments can be performed at temperatures ranging from 0thermal capacities up to around 20 kW. This paper describes the design, test capabilities and accuracy of the experimental setup.
Accurate thermophysical data for the CO 2-rich mixtures relevant for carbon capture, transport an... more Accurate thermophysical data for the CO 2-rich mixtures relevant for carbon capture, transport and storage (CCS) are essential for the development of the accurate equations of state (EOS) and models needed for the design and operation of the processes within CCS. Vapor-liquid equilibrium measurements for the binary system CO 2 +O 2 are reported at 218, 233, 253, 273, 288 and 298 K, with estimated standard uncertainties of maximum 8 mK in temperature, maximum 3 kPa in pressure, and maximum 0.0031 in the mole fractions of the phases in the mixture critical regions, and 0.0005 in the mole fractions outside the critical regions. These measurements are compared with existing data. Although some data exists, there are little trustworthy literature data around critical conditions, and the measurements in the present work indicate a need to revise the parameters of existing models. The data in the present work has significantly less scatter than most of the literature data, and range from the vapor pressure of pure CO 2 to close to the mixture critical point pressure at all six temperatures. With the measurements in the present work, the data situation for the CO 2 +O 2 system is significantly improved, forming the basis to develop better equations of state for the system. A scaling law model is fitted to the critical region data of each isotherm, and high accuracy estimates for the critical composition and pressure are found. The Peng-Robinson EOS with the alpha correction by Mathias and Copeman, the mixing rules by Wong and Sandler, and the NRTL excess Gibbs energy model is fitted to the data in the present work, with a maximum absolute average deviation of 0.01 in mole fraction.
For vessel-based transport of liquid CO2 in carbon capture and storage chains, transport at 8 bar... more For vessel-based transport of liquid CO2 in carbon capture and storage chains, transport at 8 bar(a) enable significant cost reductions compared to transport at higher pressures for most transport distances and volumes. Transport at even lower pressures could further reduce the costs. There are, however, concerns related to dry ice formation and potential clogging in parts of the chain that could lead to operational issues when operating close to the triple point pressure of CO2. In this paper, results from an experimental campaign to de-risk and gain operational experience from the low-pressure CO2 liquefaction process are described. Six experiments using pure CO2 or CO2/N2 mixtures are presented. In four of the experiments, the liquid product pressure was continuously lowered until dry ice was detected and eventually clogged the system. In the final two experiments, the liquefaction process was run in steady-state at low liquefaction pressures for five hours to ensure that there i...
The membrane-assisted CO2-liquefaction carbon capture process has been investigated by process si... more The membrane-assisted CO2-liquefaction carbon capture process has been investigated by process simulations and laboratory experiments to validate its performance. To increase the TRL level to 7-8, a pilot facility with real flue gas from a cement plant in an operational environment is required.<br> The membrane-assisted CO2-liquefaction process is a hybrid between two carbon capture technologies, each of which are unfit for post-combustion carbon capture by itself. By combining the two technologies, they can both operate in their respective favourable regime of operation. The process consists of a single membrane stage for bulk separation of the flue gas from a CO2 concentration in the range 17–20 mol%, delivering crude CO2 with a purity up to 60–70 mol%. This bulk separation is followed by CO2 liquefaction and two stages of phase-separation for purification up to above 99 mol% purity. The final liquid CO2 stream can be pumped to the transport pressure and reheated in the case...
A first model for a hydrogen liquefaction prototype laboratory unit has been developed. The proce... more A first model for a hydrogen liquefaction prototype laboratory unit has been developed. The process is based on using a mixed component refrigerant (MCR) process for pre-cooling. The process also includes an implementation of ortho para conversion. By simulations it has been shown that this process have potential to improve the exergy efficiency for the liquefaction process and thereby also the energy requirements for hydrogen liquefaction. One of the key points in the design work has been to find a refrigerant that is sufficiently wide-boiling and at the same time not freezing at the low temperature end. The goal has been to reach sub-cooling to below 75 K without freezing out any component of the MCR.
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Papers by Jacob Stang