Increasing CO2 Pressure Research Articles

Interfacial tension and contact angle in CO2‐water/nanofluid‐quartz system

AbstractNanoparticles can modify the interface properties that are critical for fluid flow in porous media. The interfacial tension (IFT) between CO2 and water and the contact angle (CA) of a water droplet on a mineral surface under high CO2 pressure are critical parameters for CO2‐related applications such as CO2 geological sequestration and CO2‐enhanced resource recovery. This study investigated the IFT and CA in a water‐CO2‐quartz system and a nanofluid (water including either Al2O3 or TiO2 nanoparticles)‐CO2‐quartz system. The values of the IFT and CA were obtained by axisymmetric drop shape analysis (ADSA) for a droplet on a quartz surface in a chamber pressurized with CO2. The effect of nanoparticles on the IFT and CA was explored by comparing the values for the pure water‐CO2‐quartz system. In addition, the effect of CO2 adsorption onto the substrate on the wettability was investigated. The results show that the values of the IFT decrease with increasing CO2 pressure, and the addition of nanoparticles to pure water lowers the IFT further (∼up to a 40% reduction in the liquid CO2 pressure range). The de‐wetting phenomenon was observed for both gaseous and liquid CO2 conditions. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.

A Comprehensive Overview of CO2 Flow Behaviour in Deep Coal Seams

Although enhanced coal bed methane recovery (ECBM) and CO2 sequestration are effective approaches for achieving lower and safer CO2 levels in the atmosphere, the effectiveness of CO2 storage is greatly influenced by the flow ability of the injected CO2 through the coal seam. A precious understanding of CO2 flow behaviour is necessary due to various complexities generated in coal seams upon CO2 injection. This paper aims to provide a comprehensive overview on the CO2 flow behaviour in deep coal seams, specifically addressing the permeability alterations associated with different in situ conditions. The low permeability nature of natural coal seams has a significant impact on the CO2 sequestration process. One of the major causative factors for this low permeability nature is the high effective stresses applying on them, which reduces the pore space available for fluid movement with giving negative impact on the flow capability. Further, deep coal seams are often water saturated where, the moisture behave as barriers for fluid movement and thus reduce the seam permeability. Although the high temperatures existing at deep seams cause thermal expansion in the coal matrix, reducing their permeability, extremely high temperatures may create thermal cracks, resulting permeability enhancements. Deep coal seams preferable for CO2 sequestration generally are high-rank coal, as they have been subjected to greater pressure and temperature variations over a long period of time, which confirm the low permeability nature of such seams. The resulting extremely low CO2 permeability nature creates serious issues in large-scale CO2 sequestration/ECBM projects, as critically high injection pressures are required to achieve sufficient CO2 injection into the coal seam. The situation becomes worse when CO2 is injected into such coal seams, because CO2 movement in the coal seam creates a significant influence on the natural permeability of the seams through CO2 adsorption-induced swelling and hydrocarbon mobilisation. With regard to the temperature, the combined effects of the generation of thermal cracks, thermal expansion, adsorption behaviour alterations and the associated phase transition must be considered before coming to a final conclusion. A reduction in coal’s CO2 permeability with increasing CO2 pressure may occur due to swelling and slip-flow effects, both of which are influenced by the phase transition in CO2 from sub- to super-critical in deep seams. To date, many models have been proposed to simulate CO2 movement in coal considering various factors, including porosity, effective stress, and swelling/shrinkage. These models have been extremely useful to predict CO2 injectability into coal seams prior to field projects and have therefore assisted in implementing number of successful CO2 sequestration/ECBM projects.

Molecular Dynamics Study of Combustion Reactions in Supercritical Environment. Part 3: Boxed MD Study of CH3 + HO2 → CH3O + OH Reaction Kinetics.

The kinetics of reaction CH3 + HO2 → CH3O + OH in supercritical carbon dioxide media at pressures from 0.3 to 1000 atm in the temperature range (600-1600) K was studied using boxed molecular dynamics simulations at QM/MM theory level with periodical boundary conditions. The mechanism of this process includes two consecutive steps: formation and decomposition of CH3OOH intermediate. We calculated the activation free energies and rate constants of each step, then used Bodenstein's quasistationary concentrations approximation to estimate the rate constants of the reaction. On the basis of the temperature dependence of the rate constants, parameters in the extended Arrhenius equation were determined. We found that reaction rate of each step, as well as overall reaction, increases with increasing CO2 pressure in the system. The most effective zone for the process is T = 1000-1200 K, and the CO2 pressure is about 100 atm.

Siderite precipitation using by-product red gypsum for CO2 sequestration

In this research, the feasibility of CO2 mineral carbonation by the use of by-product red gypsum (RG obtained from Huntsman Tioxide, Terengganu, Malaysia) to form iron carbonate (FeCO3) was evaluated. Toward this aim, the wide-range conditions of key procedure variables such as reaction temperature, reaction time, and CO2 pressure on the rate of mineral carbonation were studied. In addition, preliminary analyses on red gypsum were carried out to determine its physical and chemical characteristics. The feasibility of direct carbonation of RG to form FeCO3 was assessed at different CO2 pressures of 1 to 70 bar and different reaction temperatures of 25 to 200 °C to discover the effects of the key functions on overall direct carbonation. In general, increasing CO2 pressure to 10 bar was found to increase the overall FeCO3 purity and carbonation efficiency to 97% and 98%, respectively. Moreover, the reaction temperature affected the conversion rate at two different functions. First, FeCO3 purity and its carbonation efficiency increased to the maximum values when the reaction temperature increased to 150 °C, and then they were slightly decreased to 91% and 92%, respectively, with increase of temperature to 200 °C. The results also showed that the maximum product purity is achieved at optimum reaction time of 150 min.

Dispersion properties of CO2 and polar organic solvents with the same alkyl chain length mixtures using in situ FTIR spectroscopy

To investigate the microscale dispersion properties of CO2 in polar organic solvents with equivalent alkyl chain lengths, the volume expansion coefficients and solubilities of CO2 in 2-hexanone, hexanal, and 1-hexanol were measured at 318 K under different pressures. A modified Fourier-transform infrared spectroscopy technique was applied in situ to study the microcosmic mechanisms of volume expansion in the three mixtures, from ambient pressure to the supercritical state of CO2 at 318 K. The results show that CO2 and 2-hexanone/hexanal form 2-hexanone-CO2 and hexanal-CO2 aggregations, respectively, with increasing CO2 pressure; the dispersion state of CO2 molecules in the solvent is the primary factor causing the volume increase of the mixture and CO2 solubility. During this process, the original microstructure of the liquid 2-hexanone and hexanal can be broken, and it becomes easier for CO2 molecules to dissolve in the 2-hexanone and hexanal solvents.

Thermal radiation of magma ocean planets using a 1‐D radiative‐convective model of H2O‐CO2 atmospheres

AbstractThis paper presents an updated version of the simple 1‐D radiative‐convective H2O‐CO2 atmospheric model from Marcq (2012) and used by Lebrun et al. (2013) in their coupled interior‐atmosphere model. This updated version includes a correction of a major miscalculation of the outgoing longwave radiation (OLR) and extends the validity of the model (P coordinate system, possible inclusion of N2, and improved numerical stability). It confirms the qualitative findings of Marcq (2012), namely, (1) the existence of a blanketing effect in any H2O‐dominated atmosphere: the outgoing longwave radiation (OLR) reaches an asymptotic value, also known as Nakajima's limit and first evidenced by Nakajima et al. (1992), around 280 W/m2 neglecting clouds, significantly higher than our former estimate from Marcq (2012). (2) The blanketing effect breaks down for a given threshold temperature Tϵ, with a fast increase of OLR with increasing surface temperature beyond this threshold, making extrasolar planets in such an early stage of their evolution easily detectable near 4 μm provided they orbit a red dwarf. Tϵ increases strongly with H2O surface pressure, but increasing CO2 pressure leads to a slight decrease of Tϵ. (3) Clouds act both by lowering Nakajima's limit by up to 40% and by extending the blanketing effect, raising the threshold temperature Tϵ by about 10%.

The Influence of Supercritical Carbon Dioxide (SC‐CO2) on Electrolytes and Hydrogenation of Soybean Oil

AbstractThe electrochemical hydrogenation of soybean oil with supercritical carbon dioxide (SC‐CO2) has been studied to seek ways for substantial reduction of the trans fatty acids (TFA). The solubility of CO2 in electrolytes and the conductivity of electrolytes were investigated using a self‐made electrochemical hydrogenation reactor. The optimum hydrogenation parameters were assessed. Both the solubility of CO2 in electrolytes and the conductivity of electrolytes increased with increasing CO2 pressure. When the pressure reached a critical point of CO2, the solubility of CO2 expressed as a mole fraction was 0.42 in cathode electrolyte and 0.1 in anode electrolyte. At 8 MPa, the conductivity of electrolytes was 1.5 times higher than that at 2 MPa. When the pressure was higher than the critical point of CO2, the solubility of CO2 in electrolytes and the conductivity of electrolytes reached a stable value. The optimum condition for electrochemical hydrogenation of soybean oil in SC‐CO2 were reaction pressure (8 MPa), reaction temperature (48 °C), current (125 mA), agitation speed (300 rpm), and reaction time (8 h). Fatty acid profile, iodine value, and TFA content were evaluated at the optimum parameters. This investigation showed that the electrochemical hydrogenation of soybean oil in SC‐CO2 was improved. The reaction time was shortened by 4 h, and TFA content was reduced by 35.8% compared to traditional hydrogenation process.

Ductile‐to‐brittle transition behavior of low molecular weight polycarbonate under carbon dioxide

We investigated the stress–strain behavior of low molecular weight polycarbonate for optical disc grade (OD‐PC) under carbon dioxide (CO2) at various pressures, and compared the results with that under ambient pressure at various temperatures. Elongation at break decreased sharply with increased CO2 pressure at around 2 MPa, while the elastic modulus decreased gradually up to 6 MPa. These results indicate that the tensile property changed from ductile to brittle with increased CO2 pressure, although the molecular motion is accelerated due to the plasticization effect of CO2. Such ductile‐to‐brittle transition is similar to that observed under elevated temperatures caused by chain disentanglement due to accelerated molecular motion. Although the changes of tensile properties were similar, the craze structure obtained by the brittle behavior was different, i.e., a filamented‐craze structure was obtained under high‐pressure CO2, while a lace‐like one was obtained under elevated temperatures. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

Experimental Investigation of CO<sub>2</sub>-Water-Rock Interactions during CO<sub>2</sub> Flooding in Carbonate Reservoir

Injecting CO2 into underground reservoir to displace oil is a viable means of reducing greenhouse gas emission to the atmosphere and enhancing oil recovery. To evaluate the effect of CO2-water-rock interactions on the characteristics of carbonate reservoir at high pressure, the mineralogy of calcite, the ion concentration in the reacted solution, the surface texture of calcite, the permeability of calcite after reacted with injected CO2 and deionized water was investigated by X-ray diffraction (XRD), inductive coupled plasma-atomic emission spectrometry (ICP-AES), scanning electronic microscope (SEM), and sand-packed model at pressure of 5.0 MPa. The results show that the mineral dissolution of calcite would occur when interacting with injected CO2 and water. The mineral dissolution of calcite caused the change of surface texture of calcite and increase in Ca2+, HCO-3 ion concentration in the solution. With the increase of CO2 pressure, the surface dissolution of calcite appeared more obvious. With the increase of reaction temperature, the surface dissolution of calcite also appeared more obvious and Ca2+, HCO-3 ion concentration in the solution increased first, then decreased. The mineral dissolution of calcite caused the improvement in water permeability of calcite/quartzsand-packed model.

Rheological properties of HDPE and LDPE at the low-frequency range under supercritical CO2

The effects of temperature, pressure (using helium as the pressurizing medium) and dissolved CO2 concentration on the rheological properties of linear high-density polyethylene (HDPE) and branched-chain low-density polyethylene (LDPE) were carefully investigated using a high-pressure rheometer. The results showed that at low pressure, the rheology of the PEs was sensitive to pressure increase. As the pressure increased to higher values, the rheology leveled off for HDPE and increased for LDPE. Under supercritical CO2, the plasticization of the dissolved gas contributed primarily to the thickening effect of pressure. Furthermore, the loss factors decreased with increasing pressure and increased with increasing CO2 pressure. Lastly, the effect of gas concentration was described by the Fujita-Kishimoto model on the assumption that the coupled effect of pressure and CO2 concentration could be separated.

Process simulation of mineral carbonation of phosphogypsum with ammonia under increased CO2 pressure

The mineral carbonation of phosphogypsum offers many advantages in sequestering CO2, solving the pollution problem of phosphogypsum stacking, and manufacturing high value-added chemical products with low energy consumption and cost. Using the Aspen Plus process simulation software, this work simulates a novel process for the mineral carbonation of phosphogypsum with ammonia under increased CO2 pressure. This process is divided into five sections, namely, pre-carbonation, enhanced carbonation, flash separation, gas phase absorption, and (NH4)2SO4 fertilizer production. With its large-scale application, this new process allows the sensitivity analysis of many operation conditions, identifies the optimal conditions for reducing the ammonia and energy consumption of (NH4)2SO4 fertilizer production, and achieves a high carbonation conversion with a fast reaction rate. The optimal conditions (6bar enhanced carbonation pressure, 1bar flash pressure, 38°C ammonia absorption solution temperature, 1.05 ammonia excess ratio, 1.024 CO2 excess ratio, and 0.94 mass ratio of water to gypsum) yield the highest carbonation conversion, ammonia utilization ratio, and enhanced carbonation temperature of 99.9%, 95.2%, and 138.5°C, respectively, all of which can help achieve a fast carbonation reaction rate.

Influence of CO2 pressure on the emission spectra and plasma parameters in underwater laser-induced breakdown spectroscopy.

Optical emission spectroscopic studies have been carried out to investigate the pressure effect of CO2 on laser-produced underwater plasma. The plasma was generated by focusing 1064 nm, 6 ns pulses from a Nd:YAG laser in a CO2-bearing solution. The temporal evolution of the continuum emission, Sr and Ba lines, and plasma electron density and temperature was characterized under CO2 pressure ranging from 10 to 300 bars. The electron density measurements were made using the Stark broadening of the 455.40 nm Ba II line, while the temperature measurements have been performed by the Saha-Boltzmann method using the Sr I-II lines at 460.73 and 407.77 nm, respectively. It was found that CO2 pressure has little effect on the emission line intensity and signal-to-background ratio. The electron density and the temperature are found to be independent of the CO2 pressure at early times. When time becomes longer, the electron density exhibits an appreciable rise as the CO2 pressure increases, while the temperature is found to be unchanged.

Determination of closed porosity in rocks by small-angle neutron scattering

Small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) have been used to study a carbonate rock from a deep saline aquifer that is a potential candidate as a storage reservoir for CO2 sequestration. A new methodology is developed for estimating the fraction of accessible and inaccessible pore volume using SANS/USANS measurements. This method does not require the achievement of zero average contrast for the calculation of accessible and inaccessible pore volume fraction. The scattering intensity at high Q increases with increasing CO2 pressure, in contrast with the low-Q behaviour where the intensity decreases with increasing pressure. Data treatment for high-Q scattering at different pressures of CO2 is also introduced to explain this anomalous behaviour. The analysis shows that a significant proportion of the pore system consists of micropores (<20 Å) and that the majority (80%) of these micropores remain inaccessible to CO2 at reservoir pressures.

A macro-scale view of the influence of effective stress on carbon dioxide flow behaviour in coal: an experimental study

Existing studies highlight the uncertainty in the process of CO2 sequestration in deep coal seams, mainly due to the associated CO2 adsorption-induced coal matrix rearrangements. This complexity is further increased by the highly heterogeneous nature of the coal mass which causes issues in reproducing field conditions under laboratory conditions. The main objective of this study is therefore to determine the permeability behaviour in coal for CO2 flow using macro-scale reconstituted coal specimens (203 mm in diameter and 1000 mm in length), particularly under various effective stress conditions. A series of core flooding experiments was conducted on Australian brown coal, using an advanced core flooding apparatus, for a range of CO2 injection pressures and axial stresses. According to the findings, CO2 permeability decreases with increasing CO2 injection pressure, and the reduction is greater for super-critical CO2 at greater depths. The critical zone of influence for CO2 injection into a selected coal seam is greater at lower injection pressures and at shallow depths, and it reduces with increasing CO2 pressure and seam depth. CO2 storage capacity in a selected coal seam is greater at lower depths and higher CO2 injection pressures. However, the reduction of CO2 storage capacity with depth was not very significant, which is important for field CO2 sequestration projects, which normally use deep seams to store CO2.

Rheology and Phase Behavior of Carbon Dioxide and Crude Oil Mixtures

The rheology of Zuata heavy crude oil, saturated with carbon dioxide, was studied at a temperature of 50 °C and pressures up to 220 bar. Observations of phase behavior were also reported and used to interpret the rheological data. The crude oil is very viscous and non-Newtonian at ambient pressure, but when brought into equilibrium with CO2, the non-Newtonian behavior was weakened and eventually disappeared at high CO2 pressures. When diluted with 10 and 30 wt % toluene, the diluted crude oils and their mixtures with CO2 behaved as Newtonian fluids. The CO2-saturated mixture of the crude oil samples showed an exponential decrease in viscosity with increasing CO2 pressure but an increase in viscosity at higher pressures. During observation through a view cell, the CO2 dissolution caused a swelling effect on the original crude oil. When saturated with CO2, the swelling effect also occurred on the 10 wt % diluted crude oil but the volume of the oil-rich phase was decreased at higher pressures. However, for t...

Corrosion Behavior of X70 Mild Steel during Transportation of Gaseous- and Supercritical-CO2 Fluids

The corrosion behavior of X70 mild steel was investigated in the case of water deposited in CO2 pipeline by means of weight loss method and scanning electron microscopy (SEM). Results showed that general corrosion rate of X70 steel decreased with the increase of CO2 pressure from 4 to 12 MPa at 35 ℃. FeCO3 film and severe general corrosion was observed at 4 MPa, while thin and discontinuous corrosion product and serious pitting corrosion attack were found under other CO2 pressure conditions. It is of great corrosion risk to transport CO2 in gaseous or supercritical sta- tus for X70 mild steel if free water is formed in the pipeline.

Effect of pressure on the corrosion and carburization behavior of chromia-forming heat-resistant alloys in high-temperature carbon dioxide environments

Chromia-forming heat-resistant alloys were corroded in atmospheric CO2 (0.1MPa) and supercritical-CO2 (S-CO2, 10 and 20MPa) at 550–650°C for 1000h. The weight gain and the extent of an amorphous C layer at the oxide/matrix interface increased with increasing CO2 pressure from 0.1MPa to 20MPa, but the increase was mostly less than a factor of 2. Despite the huge difference in the test pressure, the depth of the carburized region with Cr-rich carbides was rarely affected for Alloy 800HT, resulting in similar tensile properties after corrosion in CO2 and S-CO2.

Mechanism of CO2 adsorption on Mg/DOBDC with elevated CO2 loading

Understanding the nature of CO2 adsorption in porous materials is important to developing the next generation high performance adsorbents for CO2 capture. The mechanism of CO2 adsorption in a typical metal organic framework (MOF) material, named Mg/DOBDC (DOBDC=1,4-dioxido-2,5-benzenedicarboxylate), was investigated by experiments and theoretical calculations. Needle-shaped Mg/DOBDC crystals were synthesized and characterized. CO2 adsorption isotherm at ambient conditions on Mg/DOBDC was converted to obtain open metal site coverage by CO2 with pressure. Binding energies of CO2 on open metal site and organic linker site were calculated separately using density functional theory (DFT). Furthermore, step-by-step DFT calculations were performed by adding CO2 molecules into Mg/DOBDC pores one after another to mimic the CO2 adsorption process. The results show that CO2 adsorption energy is as high as −55.5kJ/mol on the open metal site (primary site) and about −27.1kJ/mol on the organic linkers (secondary site). As CO2 pressure increases, CO2 molecules occupy the open metal sites first, then organic linker site due to the difference in adsorption energy between these two sites. Correspondingly, charges transfer from adsorbed CO2 molecules to the framework continuously with increasing CO2 loading, which results in the variation of electrostatic environment. When six CO2 molecules are loaded in one single pore, each CO2 molecule interacts with the framework with same distance and angle.

A thermodynamic study of CO2 sorption and thermal transition of PolyActive™ under elevated pressure

The sorption of CO2 in two commercial grades of multiblock copolymers (PolyActive™) is investigated using a magnetic suspension balance in the temperature range 30–70 °C. The isotherms follow Henry's law when the poly(ethylene glycol) (PEG) blocks of PolyActive™ are in a molten state. A significant deviation is observed when the PEG blocks are still in a semicrystalline state. Differential scanning calorimetry (DSC) is used to study the thermal transitions of the polymers. The melting and crystallization of the PEG blocks is studied using high pressure differential scanning calorimetry in both CO2 and N2 gas environment. A substantial decrease of melting and crystallization temperatures occurs with increasing CO2 pressure. But no change occurs under N2 pressure. The observed experimental results are discussed on the basis of established thermodynamic equations reported in the literature which provide an adequate guideline to correlate the sorption isotherms with the thermal transition of the PEG blocks.

Swelling of shale in supercritical carbon dioxide

Shale gas is an unconventional but promising natural resource. One means of producing this gas is by injecting CO2 into shale formations, and this technique has received widespread attention of late. This method not only allows the possibility of storing CO2 in shale formations but also enhances the gas recovery process. The swelling of the shale matrix caused by CO2 adsorption has important consequence with regard to the production of shale gas and the sequestration of CO2 in shale formations. In this study, an apparatus was designed and used to measure CO2-induced swelling in shale samples at temperatures between 308 and 348 K and pressures up to 15 MPa. The results show that CO2-induced swelling occurs in shale samples. With increasing CO2 pressure, the swelling of shale samples initially increases and then lessens. With increasing CO2 temperature, the maximum swelling of the shale gradually decreases. The strain induced in the shale during this process in response to a constant CO2 pressure can be divided into three regions: transient shrinkage, slow swelling and stable strain. The results of calculations employing a simplified local-density model were in agreement with the experimental data obtained from CO2-induced swelling in shale. All experimental samples exhibited anisotropic strains in response to CO2 injection, with the strains always being less in the direction parallel to the bedding plane.