Thermodynamic Properties Of CO2 Research Articles

Fracture Morphology Influencing Supersonic CO2 Transport: Application in Geologic CO2 Sequestration

AbstractGeologic carbon sequestration requires CO2 injection into the storage formation at high‐injecting pressure. Such high pressure could induce choked flow accompanying huge variations in thermodynamic properties of CO2 at a converging‐diverging (CD) fractures in the storage formation. In this study, high‐velocity CO2 transport through CD fractures was investigated to quantify the effect of fracture morphology on occurrence of both choked flow and shockwave that constrain the mass flow rate of fluid. In addition, variations in thermodynamic CO2 properties including Mach Number (Ma), defined by the ratio of fluid velocity to sound speed, and shock properties were investigated. The morphological characteristics of CD fractures were determined by nine properties, such as throat diameter, throat length, inlet diameter, outlet diameter, throat diameters of two‐connected CD fractures, fracture wall curvature, roughness amplitude, and frequency. As a result, the throat diameter crucially affected choked flow occurrence and maximum Ma. When the inlet and outlet diameters varied, the profiles for Ma variation were consistent in the converging and diverging segments, respectively. In addition, regardless of change in the throat length, the position of maximum Ma was nearly constant with showing the position length ratio of 0.13–0.14. However, roughness of fracture wall significantly influenced the Ma variation and occurrence of shock. In particular, backflows segregated from the main CO2 flow were observed near the wall roughness.

Exergetic and energetic evaluation of a modified tc-CO2 refrigeration system assisted with an absorption chiller using natural refrigerants

Transcritical CO2 (tc-CO2) refrigeration system is a pertinent option for refrigeration at low temperature, but it has high energy consumption with low coefficient of performance (COP) and exergetic efficiency. Thermodynamic properties of CO2 are favorable to be used as refrigerant with zero ozone depletion potential (ODP) and very low global warming potential (GWP). The tc-CO2 system rejects a huge amount of energy at higher temperature in the gas cooler which can be utilized to run the absorption chiller and produce desired cooling effect, in various combinations. The current research focuses on the energy and exergy analysis of a tc-CO2 refrigeration system that aspires to accomplish low-temperature refrigeration. A single-effect absorption chiller is used to give subcooling to the tc-CO2 refrigeration system, which is powered by the heat available at high temperatures and pressures at the exit of the compression process of the former system, rather than any other external heat source. A work recovery turbine is also used as the expansion device to reduce throttling losses and electricity consumption to power the integrated system. The parametric study reveals that there is a significant improvement in the refrigerating capacity, COP and exergetic efficiency of the system.

Molecular dynamics investigation on Widom line of binary mixtures of supercritical carbon dioxide containing noble gases

This work focuses on the effects of the addition of noble gases (Xe and Kr) at different concentrations on the thermodynamic properties and Widom line (WL) of supercritical carbon dioxide (S-CO2), as well as the microstructures of the binary mixture at different thermodynamic state points. Three thermodynamic properties (volume expansivity αp, isothermal compressibility κT, and isobaric heat capacity Cp) of CO2 + Xe and CO2 + Kr binary mixtures are investigated in the near-critical region (280–370 K, 8–14 MPa), and both of them significantly reduce the peaks of the three thermodynamic properties compared to pure CO2, and this effect enhances as the concentration of noble gases increases. The WL constructed by the maxima of the three thermodynamic properties of the CO2 + Xe binary mixture rotates clockwise around the critical point on the P-T plane as the concentration of Xe increases, while the same WL of the CO2 + Kr binary mixture shifts in the direction of temperature decrease on the P-T plane as the concentration of Xe increases. The Radial distribution function (RDF) of Xe and Kr in CO2 binary mixtures both exhibit significant first and blurry second peaks of RDF in the near-critical region consistent with pure CO2, which suggests the miscibility and homogeneity between CO2 and the two noble gases combined with visualization of the simulated mixture system.

The Thermodynamic Properties of CO2 up to 200 MPa Including the Critical Region, Calculated by a New Combined Equation of State with Few Parameters

Heat capacities Cv, Cp, and sound velocity W of carbon dioxide are calculated on the basis of a new thermal combined equation of state (EoS) with a low number of regulated constants. This equation includes a new regular EoS with 11 coefficients, a scaling EoS with six coefficients, and a regular transition function containing two adjustable parameters. Calculating results for thermodynamic properties of CO2 in the regular behavior range of up to 200 MPa correspond to the accuracy level of modern practical equations of state with large numbers of determined constants. This makes it possible to calculate the properties of CO2 in the critical region, taking into account the achievements of scaling theory. To determine the constants of the calculated equations, only p,ρ,T-data for CO2 were used. The experimental and tabular data on Cv, Cp, S, H, and W were not involved except isochoric heat capacity Cv in the ideal gas state. These data were used to compare the calculated results with the experimental and tabulated values. The universal critical exponents were taken in accordance with the three-dimensional Ising model. The average errors in describing the thermal properties of CO2 do not exceed errors: rms error is 0.93 % in pressure and max deviation in Cv is 10 %. Divergences in the critical region relate to application of the scaling equation of state, in contrast to the regular equations. The comparison was made with calculated Cv, Cp using the current crossover EoSs for CO2.

A comprehensive thermal assessment of dry cooled supercritical CO2 power cycles

In arid areas, dry cooling technology is a preferable alternate of wet cooling mainly owing to the scarcity of abundant water supply. However, the supercritical CO2 power cycle still offers considerable thermal performance even at higher ambient temperature using dry cooling. The novelty of this work is the exhaustive designing of dry cooler for supercritical CO2 cycles (recompression and partial cooling) in concentrating solar power application. Prior to the design of tower, a preliminary analysis is conducted in achieving the optimum main compressor inlet temperature (33 °C-recompression and 40 °C-partial cooling) at which the cycle delivers the maximal efficiency. The comparison is performed at same higher and lower pressure and for the partial cooling, the intermediate pressure is optimized. At relatively higher compressor inlet temperatures (above 50 °C), the partial cooling achieves higher efficiency while at lower temperatures (30–49 °C), the recompression shows superior performance. An iterative nodal method is used for the air-cooled finned tube heat exchanger units that takes account of the dramatic variation in thermodynamic properties of CO2 with the bulk temperature. Kroger’s detailed methodology of designing dry cooler is adapted with the implementation of nodal approach for CO2 property variation. A dry cooling tower with 52.45 m height is essential for the recompression cycle, whereas the partial cooling requires two towers of the height of 35.4 m and 38.7 m. A thermal assessment is carried out on the dry cooler under various cycle fluid inlet temperatures and ambient temperatures. During hot and humid ambient conditions, lower compressor inlet temperatures (up to 53.1 °C) are obtained with the recompression cycle compared to partial cooling (up to 64.5 °C). In extreme climate condition of 50 °C air temperature, the recompression cycle provides superior thermal efficiency (46.5% against 45.5%). For future commercialization of dry cooled sCO2 power plant, the recompression cycle is preferred due to its superior performance and lower capital cost for cooling tower design and solar field. The work demonstrates the impact of dry cooling tower design strategy in the context of cycle thermal assessment under various working condition.

Thermodynamic properties of CO2 + SO2 + CH4 mixtures over wide ranges of temperature and pressure. Evaluation of CO2/SO2 co-capture in presence of CH4 for CCS

In this work, density, vapor-liquid equilibrium and speed of sound measurements of the mixtures [CO2 + 4.72 mol% SO2 + 1.85 mol% CH4] and [CO2 + 0.09 mol% SO2 + 1.54 mol% CH4] were performed over the temperature range 263–373 K and at pressures of up to 30 MPa for density and up to 190 MPa for speed of sound. For the speed of sound measurements, the mixtures were doped with ≅0.8 mol% CH3OH. We compared our results to the values calculated using an extended version of the equation of state for combustion gases (EOS-CG) that includes binary models for the CO2 + SO2 and CO2 + CH4 subsystems, and a perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state, validating both equations in this way. From our experimental results, we evaluated the impact of the simultaneous presence of SO2 and CH4 as impurities in anthropogenic CO2 on selected parameters for carbon capture and storage technology. With the understanding that chemical effects have not been considered, we concluded that the presence of 4.72 mol% SO2 compensates for the negative effect of 1.85 mol% CH4 on most of the studied parameters, resulting in a favorable fluid for carbon, capture and storage, contrary to the mixture with 0.09 mol% SO2 and 1.54 mol% CH4.

A new equation of state to predict S-CO2 flow with real gas effects

The accuracy of the thermodynamic properties prediction from the different Equation of state (EOS) varies upon the range of temperature and pressure. Despite the variety of EOS available, there is no de facto for selecting an EOS for particular computational modeling. The EOS model recently developed by Kumar and Kim (K-K EOS) determines more accurately the thermodynamic properties of CO2 than earlier models. In this present study, K-K EOS is successfully implemented in the computational analysis of compressible supercritical CO2 flow (S-CO2) in the thermodynamic region near and away from the vapour-liquid critical point. Computational results of SCO2 flow with the real gas properties predicted with the K-K EOS is compared with Span and Wagner (SW EOS) and ideal EOS.

A fracture-propagation-control model for pipelines transporting [formula omitted]-rich mixtures including a new method for material-model calibration

This work considers a predictive numerical modelling approach for fracture-propagation control in CO2-transport pipelines, an area where current engineering tools do not work. Fluid–structure interaction model simulations are compared with three published medium-scale crack-arrest experiments with CO2-rich mixtures. The fluid flow is calculated by a one-dimensional homogeneous equilibrium model, and the thermodynamic properties of CO2 are modelled using the Span–Wagner and the Peng–Robinson equation of state. The pipe material is represented by a finite-element model taking into account large deformations and fracture propagation. Material data commonly found in the literature for steel pipes in crack-arrest experiments is not sufficient to directly calibrate the material model used here. A novel three-step calibration procedure is proposed to fill the information gap in the material data. The resulting material model is based on J2 plasticity and a phenomenological ductile fracture criterion. It is shown that the numerical model provides good predictions of the pressure along the pipe, the ductile fracture speed and a conservative estimate of the final crack length. An approximately plane-strain stress state ahead of crack tip implies that a fracture criterion accounting for a wide range of stress states is not necessary.

Solvation Dynamics of CO₂(g) by Monoethanolamine at the Gas-Liquid Interface: A Molecular Mechanics Approach.

A classical force field approach was used to characterize the solvation dynamics of high-density CO2(g) by monoethanolamine (MEA) at the air–liquid interface. Intra- and intermolecular CO2 and MEA potentials were parameterized according to the energetics calculated at the MP2 and BLYP-D2 levels of theory. The thermodynamic properties of CO2 and MEA, such as heat capacity and melting point, were consistently predicted using this classical potential. An approximate interfacial simulation for CO2(g)/MEA(l) was performed to monitor the depletion of the CO2(g) phase, which was influenced by amino and hydroxyl groups of MEA. There are more intramolecular hydrogen bond interactions notably identified in the interfacial simulation than the case of bulk MEA(l) simulation. The hydroxyl group of MEA was found to more actively approach CO2 and overpower the amino group to interact with CO2 at the air–liquid interface. With artificially reducing the dipole moment of the hydroxyl group, CO2–amino group interaction was enhanced and suppressed CO2(g) depletion. The hydroxyl group of MEA was concluded to play dual but contradictory roles for CO2 capture.

Thermodynamic properties of a CO2 – rich mixture (CO2 + CH3OH) in conditions of interest for carbon dioxide capture and storage technology and other applications

Methanol can be an impurity in transported and stored anthropogenic CO2 in carbon dioxide capture and storage technology; likewise, methanol is one of the most useful CO2 modifiers for supercritical processes. Therefore reliable values of thermodynamic properties of CO2 – rich mixtures CO2+CH3OH are needed. We measured the following properties of a (CO2+CH3OH) mixture with xCO2=0.9700 in dense phase at six temperatures from 263.15K to 313.15K:•The speed of sound, c, up to 194.49MPa, using a double-path pulse-echo method at 5MHz, for which a repeatability study gave an overall standard uncertainty of c, u(c)=5.9×10−4c.•The density, ρ, at pressures ⩽20.00MPa using a vibrating-tube densimeter with a standard uncertainty, u(ρ)=0.4kg/m−3.Combining our c and ρ experimental values and the isobaric specific heat capacity, cp, from the GERG equation of state (EoS), we calculated ρ, cp, the volume-dependent solubility parameter, δV, and the Joule–Thomson coefficient, μJT, at pressures ⩽195.0MPa. We are the first to report the adaptation for compressed gases of a calculation method based on numerical integration previously used only for liquids. The experimental and calculated values were compared with those from the PC-SAFT and GERG EoSs, allowing us to validate both EoSs to represent the experimental properties of the system under most conditions studied and the calculation method up to 195.0MPa.

Thermodynamic properties of CO2 during controlled decompression of supercritical extraction vessels

Very fast decompressions of extraction vessels reduce the temperature of their walls below the −10°C limit when they become brittle. Therefore, decompression of large vessels operating at high pressure may set a lower limit to extraction time in industrial multi-vessel supercritical CO2 extraction plants (thus negatively influencing production cost), but this has rarely been studied. This work studied decompression of CO2 initially at 30MPa in a 3.96L vessel vented through a partially opened needle valve. Slow CO2 venting avoided a two-phase (liquid–gas) mixture in the vessel. Pressure drop was fast at the beginning and end of decompressions, and comparatively slower within the 10–15MPa interval, before CO2 crossed the pseudocritical line. Temperature dropped at the beginning of decompressions, remained comparatively constant in the intermediate period, and increased at the end. Decompression time was inversely proportional to valve opening, and was shorter when starting at 60 than 50°C. The initial drop in temperature was proportional to valve opening, and similar for different starting temperatures. When the vessel was packed with pretreated (either pressed or pressed and pelletized) and extracted rosehip or raspberry seeds, depressurization time was proportional to the porosity of the packed bed and independent on other properties of the substrate. Being flow through the needle valve choked, venting rate was determined by its opening and the continuously changing physical properties of CO2 in the vessel. To estimate the changes in internal energy of the CO2 in the vessel that define vessel wall's temperature, the heat provided by the service fluid (in our case water circulated through the vessel jacket), the heat yield by the walls, lid, and bottom of the high-pressure vessel, and the heat yield by the substrate charge need to be incorporated to the transient heat balance model of the depressurization process. The experimental results obtained in this work can be used to validate a model of the depressurization process that could simulate decompressions of industrial vessels as a function of their size and shape, the extraction conditions, and the packed substrate. Predicted decompression times would therefore set restrictions to the setup times required to replace exhausted by fresh substrate in industrial vessels, in studies of minimization of production cost.

Solubilities and thermodynamic properties of CO2 in choline-chloride based deep eutectic solvents

The solubilities of CO2 in three kinds of deep eutectic solvents, (choline chloride+phenol), (choline chloride+diethylene glycol) and (choline chloride+triethylene glycol), were determined at temperatures ranging from 293.15K to 323.15K under pressures up to 600.0kPa using isochoric saturation method. The mole ratios of choline chloride to phenol were selected as 1:2, 1:3 and 1:4, the others as 1:3 and 1:4. Henry’s constants and thermodynamic properties such as standard Gibbs free energy, enthalpy, and entropy changes of CO2 solvation were calculated from the correlation of solubility data. Results revealed that the solubility of CO2 increased with increasing pressure and decreased with increasing temperature. The enthalpies of solution were negative at all conditions.

PVTx Properties of a Two-phase CO2 Jet from Ruptured Pipeline

Span and Wagner equation of state (SW EOS) have been used to investigate changes in the thermodynamic properties of CO2 during a depressurization process from a pipeline into marine environment. The process is assumed to be isenthalpic, as only the thermodynamic change at the moment of depressurization is considered. The calculations show that the depth location of the pipeline influences greatly the density, temperature and volume changes, because of the difference in the surrounding pressures. In general the two-phase area is reached at depths shallower than 600 meters, which yields for the Norwegian Continental Shelf, as it is mainly shallower than 500 meters depth. There is a rapid decrease in density in the two-phase area causing a rapid expansion in the volume of CO2 from 4MPa to 1MPa. At the shallowest depth considered (100m) the volume fraction consist almost entirely of gas, and the density change give a significant increase in volume.

Ab Initio Thermodynamic Study of the CO2 Capture Properties of Potassium Carbonate Sesquihydrate, K2CO3·1.5H2O

By combining density functional theory and lattice phonon dynamics, the thermodynamic properties of CO2 absorption/desorption reactions with dehydrated potassium carbonates through K2CO3·1.5H2O + CO2 = 2KHCO3 + 0.5H2O(g) are analyzed. The energy change and the chemical potential of this reaction have been calculated and used to evaluate its thermodynamic properties and phase transitions. The results indicate that the K2CO3·1.5H2O can only be applied for postcombustion CO2 capture technology at temperatures lower than its phase transition temperature, which depends on the CO2 pressure and the steam pressure with the best range being PH2O ≤ 1.0 bar. Above the phase transition temperature, the sorbent will be regenerated into anhydrous K2CO3. If the steam pressure PH2O is much greater than 1.0 bar, it is possible to use the K2CO3·1.5H2O sorbent for precombustion CO2 capture technology. Compared to anhydrous K2CO3, K2CO3·1.5H2O requires less energy for regeneration.

Effect of contaminants on the thermodynamic properties of CO2 -rich fluids and ramifications in the design of surface and injection facilities for geologic CO2 sequestration

Abstract Geologic storage may involve injection of impure carbon dioxide (CO 2 ) streams in order to lower capture costs. The contaminants in the purified CO 2 stream depend on the type of power plant and the capture scheme. For on oxy-fuel based combustion cycle, we have previously evaluated the effect of presence of oxygen, nitrogen and argon on the CO 2 phase diagram and the critical properties of mixtures in these systems. For a 320 km pipeline, we established a base case for pure CO 2 , and evaluated the difference in compressor power requirements as each contaminant was added in fixed proportions. The key finding was that if the mixture encountered a two-phase region along the pipeline, the pressure drop becomes punitive. We proposed a minimal adjustment of operating conditions (or the temperature and pressure profile along the pipeline) to avoid the two-phase region and concomitant prohibitive pressure losses. In this paper, we consider the influence of hydrogen sulfide and water on the phase behavior of the CO 2 -rich captured stream. Specifically, we examine the phase equilibria and the PVT properties, and compare the GERG–2008 equation of state (EoS) computations with experimental data. In general, CO 2 -rich effluent mixtures from oxy-fuel plants may undergo phase separation at higher pressures than that for pure CO 2 for the temperature range likely to be encountered in surface and injection facilities designed for CO 2 sequestration. In addition, density, compressibility, and reactive properties of these mixtures may be significantly different from pure CO 2 . Consequently, operation of large geologic CO 2 storage sites must anticipate how these differences in the thermodynamic properties of the injected fluids may affect compressor power requirements, pipeline transport, well design, and wellbore and reservoir integrity.

Thermodynamic properties of carbon dioxide derived from the speed of sound

Thermodynamic properties of CO2 are derived from speed of sound in the temperature range 300 to 360 K (from 0 to 6 MPa), and 300 to 220 K (from 0 to 90% of the saturation pressure). The density, the specific heat capacity at constant pressure, and the specific heat capacity at constant volume are obtained by numerical integration of differential equations connecting the speed of sound with other thermodynamic properties. The set of differential equations is solved as the initial value problem, with the initial values specified along the isotherm at 300 K in terms of several accurate values of the density and the specific heat capacity at constant pressure. The density, the specific heat capacity at constant pressure and the specific heat capacity at constant volume are derived with the absolute average deviations of 0.018%, 0.19%, and 0.18%, respectively. The results of numerical integration are extrapolated to the saturation line for ρ, cp, and cv with the absolute average deviations of 0.056%, 2.31%, and 1.32%, respectively.

Theoretical performance analysis of heat pump water heaters using carbon dioxide as refrigerant

The aim of this paper is to simulate the performance of an air source heat pump water heater using carbon dioxide (CO2) as a working fluid. The heat pump water heating system consists of a compressor, a gas cooler, an expansion device and an evaporator. The computer simulation model has been developed by using the heat transfer data and the thermodynamic properties of CO2. The effects on the heat pump performance by the operating parameters such as the compressor rotational speed, the inlet water temperature at the gas cooler, the inlet air temperature at the evaporator and the mass flow rate ratio of water to refrigerant were presented. For rated capacities of a 4 kW compressor with a 10 kW gas cooler and a 6 kW evaporator, the coefficient of performance is found to be between 2.0 and 3.0. The mass flow rate ratio of water and CO2 between 1.2 and 2.2 is the most suitable value for generating hot water temperature above 60°C at 15–25°C ambient air temperature. Copyright © 2007 John Wiley & Sons, Ltd.

A CASE STUDY OF A CARBON DIOXIDE WELL TEST

This paper reports on the planning, procedure, results and analysis of a carbon dioxide (CO2) well test performed on Buttress–1, a well located in the Otway Basin, Victoria, Australia. A large-scale pilot study of CO2 sequestration is planned by the Australian Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) in this area, which will involve, inter alia, taking CO2 from the Buttress reservoir and injecting it into a nearby depleted gas field. Understanding the production characteristics of this well is important to the success of this pilot, which forms part of a more extensive study to establish viable means to mitigate CO2 emissions to the atmosphere. This general backdrop forms the motivation for this study.Testing comprised of a standard suite of draw-downs and build-ups to determine reservoir/well characteristics, such as the well deliverability, the non-Darcy skin coefficient and the average reservoir permeability and volume.Compared to the wealth of experience developed over many years in testing oil and gas wells, the collective experience in CO2 well testing is extremely limited. The distinguishing features between this test and those of a typical natural gas well test need to be emphasised. Although, in general, flow testing a CO2 well should be similar to testing a natural gas well, differences in the thermodynamic properties of CO2 affect the analysis of the well test considerably. In particular, the non-Darcy skin effect is more pronounced and the wellbore and surface flow can involve dramatic phase changes, such as the formation of ice. Also, since CO2 is more compressible than a typical natural gas, the accurate measurement of the flow rate becomes more challenging. It is also apparent that the use of pseudo pressure, as opposed to simpler methods of dealing with the pressure dependency of key properties, is essential to the successful analysis of the pressure response to the CO2 production.

Studies on Carbon Dioxide Cycles for Power Generation : 2nd Report, Discussion on Several Proposed Cycles

This paper presents the performance characteristics of gas turbine cycles with supercritical back-pressure and several condensation cycles, using carbon dioxide as a working fluid. They are computed from the data on the thermodynamic properties of CO2. As a result, it is shown that thermal efficiency in CO2 cycles increases at the rate of ( 3 4 ) % in proportion to a turbine inlet temperature rise of 100 °C and is little affected by turbine inlet temperature rise of 100°C and is little affected by turbine inlet pressure higher than 200 ata. Also, thermal efficiency of CO2 gas turbine cycle with supercritical back-pressure is lower by ( 6 9 ) % than that of CO2 condensation cycles. Some CO2 condensation cycles exhibit a better performance than the conventional steam power-plant cycles at a turbine inlet pressure of about 250 ata and turbine inlet temperatures higher than 600 °C.

Computation of Thermodynamic Properties of Carbon Dioxide in the Range 0–750 Deg C

The computation of power cycles employing carbon dioxide as working fluid and extending down to the critical region requires the knowledge of the thermodynamic properties of CO2 within a wide range of pressures and temperatures. Available data are recognized to be insufficient or insufficiently accurate chiefly in the vicinity of the critical dome. Newly published density and specific heat measurements are employed to compute thermodynamic functions at temperatures between 0 and 50 deg C, where the need of better data is more urgent. Methods for the computation of thermal properties from density measurement in the low and in the high temperature range are presented and discussed. Results are reported of the computation of entropy and enthalpy of CO2 in the range 150–750 deg C and 40–600 atm. The probable precision of the tables is inferred from an error analysis based on the generation, by means of a computer program of a set of pseudoexperimental points which, treated as actual measurements, yield useful information about the accuracy of the calculation procedure.