Density Of Carbon Dioxide Research Articles

TiO2/P(AM-co-AMPS) monolith prepared by CO2-in-water HIPEs and its potential application in wastewater treatment

Removing dyes and antibiotics from wastewater remains the current requirement for a global health problem. The ionic macroporous adsorbent is an efficient solution to this problem. Herein, a novel sulfonated TiO2/poly(acrylamide-co-2-acrylamido-2-methylpropanesulfonic acid) [TiO2/P(AM-co-AMPS)] macroporous composite monolith was first prepared by copolymerization of AM and AMPS in mTiO2-costabilized CO2-in-water Pickering high internal phase emulsions (HIPEs). The composite monoliths were characterized using XRD, SEM, confocal laser scanning microscopy, EDS mapping, FTIR, TGA, and mercury injection methods. The mechanical properties of the TiO2/P(AM-co-AMPS) HIPE were also evaluated. The void diameter could be adjusted by changing the density of carbon dioxide and the amount of mTiO2. The equilibrium swelling ratios of TiO2/P(AM-co-AMPS) with different contents of crosslinking agent of 2, 5, and 10 wt% (AM+AMPS) were 93, 37, and 19 g/g, respectively. TiO2/P(AM-co-AMPS) was used to remove methylene blue (MB) and tetracycline (TC) for evaluating the adsorptive properties of the composite monoliths. Results indicated that the main adsorption driving force was the electrostatic attraction between −SO3− and MB/TC. Adsorption experiments were conducted using a batch technique. The adsorption capacities of TiO2/P(AM-co-AMPS) for MB and TC were 1660 and 1128 mg/g in a wide pH range of 3–10. The equilibrium saturation point could be reached after 90 min for MB and 360 min for TC. Thereafter, the removal of MB and TC by gravity-driven separation was presented. The breakthrough curve and reuse evaluation for the removal of MB/TC were also studied in detail.

Generation laws and distribution characteristics of carbon dioxide hydrate in a reaction kettle

We analyzed the generation characteristics of hydrate in a reaction kettle and established a convection–diffusion model of temperature and carbon dioxide. The concentration of liquid carbon dioxide and carbon dioxide dissolved in water were geometrically modeled according to the density of carbon dioxide and its solubility in water under varying temperature and pressure. The distributions of temperature, carbon dioxide and hydrate were analyzed in the reactor during hydrate formation. The factors affecting carbon dioxide hydrate formation were studied. Simulations of hydrate formation were verified by laboratory tests. The results showed that the convective diffusion of gas greatly increased the rate of hydrate formation. Temperature has a greater impact than matter transfer on hydrate formation. At the initial reaction time, the hydrate mainly existed at the boundary, the two-phase interface and the position of the liquid carbon dioxide. Hydrate finally formed in the middle and was thinnest at the interface. The solid–liquid surface tension caused the liquid water to move upward and form hydrates in the carbon dioxide phase. Hydrate formation at the interface between the initial carbon dioxide and water prevented carbon dioxide from diffusing further into the aqueous phase, which hindered further hydrate formation.

Providing enhanced security in IoT based smart weather system

Weather reporting system consist multiple devices which are playing dynamic role in producing dynamic environmental parameters such as temperature, humidity, and air pollution. It was a tedious task to bring all the devices together and make them interleaving to produce relevant measurement. Recent trends have proven that the IoT has brought all the devices and peripherals in one place to make more flexible and smart measurement. In the traditional weather monitoring system measurement method is not real time, not continuous and also tedious job to take continuous measurement. But, the IoT has completely changed the measurement scenario and improved the consistency of the measurement. In the present work the environmental parameters such rainfall, temperature, humidity, and density of carbon dioxide in the air are measured with sensors. The Arduino Uno card gathers all information from the devices which are associated with its port pins. The information is sent to cloud server for record and future retrieving. At the same time the data security in cloud been assured with encryption and decryption data while retrieving the information from cloud. This enhances the security, ease of accessing the cloud data from mobile applications, provides wise predictions and minimizes the communication overhead.

Measurement and Modeling of the Solubility of Dodecylcyclohexane in Supercritical Carbon Dioxide

In developing the application of using supercritical carbon dioxide (sc-CO2) to extract fresh base oil from waste lubricant oil, the equilibrium solubility data is very valuable. In this study, the equilibrium solubilities for one of the single lubricant oil component, dodecylcyclohexane, were determined in the temperature T = 313.2 K, 328.2 K, 343.2 K, 358.2 K, 373 K and at pressures up to 17.76 MPa. Phase equilibrium solubility measurements were made in a high-pressure visual cell with variable volume, based on the static-analytic method. Oil solubility is strongly dependent on the density of carbon dioxide (CO2), which increased with pressure at constant temperature while decreased with temperature at same pressure. The solubility data were correlated using three density-based models: Mendez-Santiago and Teja (MST) equation, del Valle and Aguilera equation, Adachi and Lu equation, the results showed that all of these models can represent the experimental data well. Since the Adachi and Lu model provided the best regression analysis (R2) and the lowest average absolute relative deviation (AARD) than the other two models in the examined experimental range, indicating the nonlinear equation of Adachi and Lu model best agreement with the experimental data.

Physical properties of switchable-hydrophilicity solvent systems: Triethylamine, water and carbon dioxide

Physical properties like density, viscosity, refractive index and conductivity of switchable hydrophilicity solvent (SHS)systems (triethylamine (TEA), water, and carbon dioxide) as a function of concentration at different temperatures ranging from 283.15 K to 308.15 K have been determined. These data have been used to calculate apparent molar volume, limiting apparent molar expansibility of solute and the relative viscosity of the studied solutions. The viscosity coefficients B have been determined from the Jones-Dole equation. The limiting apparent molar volumes and experimental slopes (Av) derived from the Masson equations have been interpreted in terms of solute-solute and solute-solvent interactions. From the volumetric and viscometric data, the structural effect of TEAH-bicarbonate salt in aqueous solvent has been discussed.

The retention factors and partial molar volumes of ibuprofen at infinite dilution in supercritical carbon dioxide at T= (308.15, 313.15, 323.15, 333.15, 343.15 and 353.15) K

Here is presented the first experimental data for the infinite dilution partial molar volumes of ibuprofen in supercritical carbon dioxide. The measurements were carried out by supercritical fluid chromatography using chemically bonded polyethylene glycol and carbon dioxide as stationary and mobile phases, respectively. The chromatographic retentions of ibuprofen at infinite dilution in supercritical carbon dioxide were measured at six supercritical isotherms of 308.15, 313.15, 323.15, 333.15, 343.15 and 353.15 K and at a pressure range of 8.50–40.00 MPa. The partial molar volumes were determined from the partial derivatives of the retention factors with respect to the densities and were in the range of −2.364 × 10−3 to 1.680 × 10−4 m3/mol. A reverse behaviour was observed, where the partial molar volumes decreased monotonically with decreasing pressure from positive to negative values in all temperature regions investigated. It was also found that the infinite dilution partial molar volumes showed a sharp decrease near the critical point of carbon dioxide. The experimental partial molar volumes were correlated with isothermal compressibilities and densities of carbon dioxide. The correlation proposed in this study could predict the experimental data with an average absolute relative deviation of 4.6% for 80 data points, which is better than that previously reported in the literature.

Mono- and poly-unsaturated triacylglycerol fractionation from Chlorella sp. using supercritical carbon dioxide

Extraction of unsaturated triacylglycerols from microalgae is important towards the viability of a sustainable biorefinery. Supercritical carbon dioxide was used to extract and enrich the mono- and poly-unsaturated triacylglycerols using a step-wise extraction scheme where the supercritical carbon dioxide density was increased from 450 to 550 to 750 mg/ml over a total of 170 min. At the lowest density of 450 mg/ml, saturated fatty acid triacylglycerols comprised 88% (mol) of the extract while mono- and poly-unsaturated triacylglycerols were over 60% and 80% (mol) at 550 and 750 mg/ml supercritical carbon dioxide respectively. This extraction scheme was informed by solubility and intermolecular interactions of mixed triacylglycerols. Chrastil's solubility parameters suggested that saturated fatty acid triacylglycerols were susceptible to intermolecular interactions while mono- and poly-unsaturated triacylglycerols are less susceptible to these interactions. Combined with the low solubility of mono- and poly-unsaturated triacylglycerols and high solubility of saturated fatty acid triacylglycerols at low densities, these phenomena were combined to demonstrate how supercritical carbon dioxide can be tuned to fractionate mono- and poly-unsaturated triacylglycerols from saturated fatty acids from microalgae. This is significant as supercritical carbon dioxide extraction technology is scalable and suitable as a first unit process for separations in a biorefinery setting.

Molecular scale modeling approach to evaluate stability and dissociation of methane and carbon dioxide hydrates

A comprehensive knowledge and precise estimation of the dynamic, structural, and thermodynamic characteristics of hydrates are needed to assess the stability of gas hydrates. Thermodynamic model and experimental studies can be utilized to compute the physical and dynamic properties of hydrate structures. The use of molecular dynamic (MD) simulation is a well-established approach in gas hydrate studies at the atomic level where the properties of interest are obtained from the numerical solution of Newtonian equations. The present work uses MD simulations by employing the constant temperature-constant pressure (NPT), constant temperature-constant volume (NVT) conditions, and the consistent valence force field (CVFF) to monitor the stability and decomposition of methane and carbon dioxide gas hydrates with different compositions. The effects of temperature and composition on the hydrate stability are investigated. In this study, we also compute the radial distribution function, mean square displacement, diffusion coefficient, lattice parameter, potential energy, dissociation enthalpy as well as the density of methane and carbon dioxide under various thermodynamic and process conditions. The formation of methane and carbon dioxide bubbles is studied to investigate bubble evolution during hydrate dissociation. The sizes of methane and carbon dioxide bubbles are not the same due to different solubility conditions of methane and carbon dioxide in liquid water. In addition, the influences of pressure and temperature on the lattice parameter and density of clathrate hydrates are discussed. The obtained results are consistent with previous theoretical and experimental findings, implying that the methodology followed in this work is reliable. The most stable arrangement of methane and carbon dioxide molecules in the gas hydrate is found. The insights/findings of this study might be useful to further understand detailed transport phenomena (e.g., molecular interactions, gas production rate, carbon dioxide replacement, and carbon dioxide capture) involved in the process of carbon dioxide injection into gas hydrate reservoirs.

A novel statistical approach for prediction of thermal conductivity of CO[formula omitted] by Response Surface Methodology

In the present article, a novel statistical approach was developed to accurately predict the thermal conductivity of CO2 using response surface methodology (RSM). The Artificial Neural Network (ANN) was also used for the modeling of the thermal conductivity of CO2. To develop the proposed models, 1910 experimental data were used including pressure, temperature and density of carbon dioxide as the input variables in the models. The performance of the models was fortified using statistical analysis and the values of 0.57, 1.25, 0.99993 and 0.99931 were obtained for AARD% and R2 of ANN and RSM models, respectively. The obtained results were compared with four conventional models to investigate the ANN and RSM accuracy. The results showed that the developed models were useful to predict CO2 thermal conductivity at wide ranges of temperature and pressure. It was found that the developed ANN model gives the best fit and satisfactory agreement with the experimental data. Also the proposed correlation presents higher accuracy compared with all previous correlations for prediction of CO2 thermal conductivity at different condition.

Modeling the flow of carbon dioxide during the drilling of oil, gas, and geothermal energy

Using carbon dioxide as a resource for enhancing the exploitation of fossil energy and geothermal energy, while realizing the geological storage of carbon dioxide, is an important direction in carbon dioxide capture, utilization, and storage studies. A carbon dioxide wellbore flow model is developed by considering the wellbore heat transmission, fluid dynamics, potential energy, and viscous friction heat. The flow characteristics of carbon dioxide and the controllable influence factors of the bottom hole pressure under different geothermal gradients are analyzed. The results indicate that the liquid carbon dioxide pumped into the drill-string enters the supercritical state at a depth of 454.8 m, and returns to the liquid state at a depth of 439.8 m in the annulus under the conditions stated here. The geothermal gradient has a significant influence on the density, pressure, and state of carbon dioxide in both the drill-string and the annulus. A larger choke pressure at the wellhead and a higher flow rate are required to obtain the same target bottom hole pressure under a high geothermal gradient. The injecting temperature has little influence on the pressure profile in the annulus. We herein establish a solid theoretical foundation for drilling technology with carbon dioxide.

On the prediction of solubility of alkane in carbon dioxide using the LSSVM algorithm

The increasing global energy demand and declination of oil reservoir in recent years cause the researchers attention focus on the enhancement of oil recovery approaches. One of the extensive applicable methods for enhancement of oil recovery, which has great efficiency and environmental benefits, is carbon dioxide injection. The CO2 injection has various effects on the reservoir fluid, which causes enhancement of recovery. One of these effects is extraction of lighter components of crude oil, which straightly depends on solubility of hydrocarbons in carbon dioxide. In order to better understand of this parameter, in this study, Least squares support vector machine (LSSVM) algorithm was developed as a novel predictive tool to estimate solubility of alkane in CO2 as function of carbon number of alkane, carbon dioxide density, pressure, and temperature. The predicting model outputs were compared with the extracted experimental solubility from literature statistically and graphically. The comparison showed the great ability and high accuracy of developed model in prediction of solubility.

Investigation on hydrodynamic and formation of nano particle by RESS process: The numerical study

The particle formation by supercritical technology is an active research field. Rapid expansion of supercritical fluid (RESS) is a promising new technology for particle formation using supercritical fluids. In this study, numerical modeling of particle formation of TBTPP (5, 10, 15, 20-tetrakis (3, 5-bis (trifluoromethyl) phenyl) porphyrin) through RESS process is investigated. The RESS process contains two pre-expansion (nozzle part) and expansion vessel (supersonic free jet) parts. In the first section, mass, momentum and energy balances in addition to extended generalized Bender equation of state (egB-EoS) as accurate equation of state is used to calculate temperature, pressure, density and velocity of supercritical carbon dioxide (SC-CO2) based on mathematical modeling and computational fluid dynamics (CFD) simulation methods. Both models include friction in the nozzle and heat exchange in the expansion vessel and in the nozzle region. Using calculated pressure and temperature, the solubility of TBTPP in the supercritical CO2 is predicted by Peng-Robinson EoS with Kwak-Mansoori mixing rule and the results are compared with experimental data and a semi-empirical correlation. Supersaturation, homogenous nucleation and critical radius of TBTPP based on classical nucleation theory are calculated. The effect of pre-expansion temperature on supersaturation, nucleation and critical radius parameters is also studied. The results of hydrodynamic and particle formation modeling present the same trend as reported in the literature.

On the prediction of solubility of alkane in carbon dioxide using a novel ANFIS-GA method

ABSTRACTRecently attention to the enhancement of oil recovery processes increases because of increasing energy demand and problems of declination of reservoirs. One of the effective and applicable approaches in the enhancement of oil recovery is carbon dioxide injection which also has a positive effect on the environment. The carbon dioxide injection can enhance oil recovery by various approaches. The extraction of lighter components of crude oil is known as one of the effects of carbon dioxide injection. The solubility of hydrocarbons in carbon dioxide is known as one of the dominant factors which can influence the hydrocarbon extraction from crude oil. Due to the importance of this parameter, in the present paper, Adaptive neuro-fuzzy inference system (ANFIS) joint with Genetic algorithm (GA) was developed to forecast the solubility of hydrocarbon in carbon dioxide based on carbon number of alkane, carbon dioxide density, pressure, and temperature. The ANFIS-GA solubility values were compared with the real solubility values. The determined coefficients of determination for training and testing phases are 0.96741 and 0.91648, respectively. So it is obvious the model has great capacity in the prediction of solubility.

Spectroscopic characterization of supercritical carbon dioxide density change under isochoric heating in mesoporous glass

Density of supercritical carbon dioxide (scCO2) confined in mesoporous glass is determined at isochoric heating in the temperature range from 30 to 68 °C by measuring the Raman shift of a single vibrational band using coherent anti-Stokes Raman scattering (CARS) spectroscopy. The density in the pores appears to be significantly (∼30%) higher in the vicinity of the bulk critical temperature and asymptotically decreases at higher temperatures. Similar results have been obtained using two different glass samples with the pore radii of 2 and 3.5 nm. The spectroscopic approach applied here shows potential in precise characterization of supercritical fluid behavior under conditions of nanoconfinement.

Numerical Investigation of the Flow Behavior Inside a Supercritical CO2 Centrifugal Compressor

Centrifugal compressors are one of the best choices among compressors in supercritical Brayton cycles. A supercritical CO2 centrifugal compressor increases the pressure of the fluid which state is initially very close to the critical point. When the supercritical fluid is compressed near the critical point, wide variations of fluid properties occur. The density of carbon dioxide at its critical point is close to the liquid density which leads to reduction in the compression work. This paper explains a method to overcome the simulation instabilities and challenges near the critical point in which the thermophysical properties change sharply. The investigated compressor is a centrifugal compressor tested in the Sandia supercritical CO2 test loop. In order to get results with the high accuracy and take into account the nonlinear variation of the properties near the critical point, the computational fluid dynamics (CFD) flow solver is coupled with a look-up table of properties of fluid. Behavior of real gas close to its critical point and the effect of the accuracy of the real gas model on the compressor performance are studied in this paper, and the results are compared with the experimental data from the Sandia compression facility.

Formation ofAu–carbon nanoparticles by laser ablation under pressurizedCO2

AbstractPulsed laser ablation is known to be a promising method for synthesizing metal nanoparticles. Here, Au–carbon nanoparticles were synthesized by pulsed laser ablation under pressurized carbon dioxide. Au plate was ablated using a Nd:YAG laser with a wavelength of 532 nm and energy of 0.83 mJ in a high‐pressure chamber. The experiments were performed at temperatures and pressures of 21–25 °C and 7–15 MPa, corresponding to carbon dioxide densities of 0.75–0.89 g/cm3, respectively. The synthesized products were collected on a silicon wafer and analyzed using field emission scanning electron microscopy, transmission electron microscopy, and a scanning transmission electron microscopy system equipped with energy‐dispersive X‐ray spectroscopy. The results showed that the generated metal nanoparticles exhibited spherical and nanocluster structures. Au, C, and O were clearly found on the nanoparticle products.

Estimating density of supercritical carbon dioxide and methane using modified thermodynamic models

ABSTRACTSince the density is an important thermodynamic property of the fluid in the wide field of experimental and theoretical studies, in this work, the density of CO2 and CH4, as prominent supercritical fluids in industrial processes was investigated. To that end, five equation of state (EOS) models were used to estimate density of aforementioned. Deviation of each EOS models is validated and then they were modified to achieve lower errors in density prediction. Accordingly, their adjusted correlations reduced the average absolute errors to lower than 5.6%.

Measurement of molecular absorption spectrum with a laser locked on a high-finesse cavity

High-resolution and high-sensitivity molecular spectroscopy is widely used in fundamental molecular physics, atmospheric studies, remote sensing, industrial process monitoring, and medical diagnostics. Accurate determination of the parameters of molecule absorption lines, such as line positions, line strengths, line widths and profiles, is essential to support these studies and applications. For example, in order to retrieve the column density of carbon dioxide with a precision of one part per million (ppm), we need laboratory data of line positions with a uncertainty lower than 0.3 MHz and line intensities with a relative accuracy better than 0.5%. Here we present precision spectroscopy of molecules using a laser locked with a high-finesse cavity. The cavity made of invar is thermo-stabilized to reduce the drifts of its length and the cavity mode frequencies. The frequency of the probe laser is locked on a longitudinal mode of the cavity by using the Pound-Drever-Hall method. Another beam from the probe laser, which is frequency shifted and on resonance with a nearby longitudinal mode of the cavity, is used for cavity ring-down spectrum (CRDS) measurement. The CRDS absorption spectrum is recorded by stepping the modulation frequency of a fiber electro-optic modulator in increment of the mode spacing of the cavity. Note that the cavity mode frequencies are shifted due to the dispersion introduced by the absorption lines. Prior to the CRDS measurements, the transmittance spectra of the cavity modes are recorded by scanning the probe laser frequencies over the resonance, which allows the determination of the cavity mode frequencies with an accuracy at a Hz level. Therefore, a dispersion spectrum is also obtained using the same setup by measuring the frequency shifts of cavity modes of the samples with and without absorption. The absolute frequency of the probe laser is determined by an optical frequency comb referring to a GPS-disciplined rubidium clock. The long term drift of beat frequency between the optical frequency comb and the probe laser is measured to be about 1.8 MHz per hour, which is consistent with the thermal expansion of the cavity under a temperature drift of 50 mK. The performance of the spectrometer is demonstrated by measuring the Doppler-broadened spectra of CO2 around 6470.42 cm-1. Precise spectroscopic parameters are derived from both the absorption and dispersion spectra recorded by the same spectrometer. The line position is determined with an accuracy of 0.18 MHz, which is over one order of magnitude better than those given in previous studies and spectral databases.

Density of carbon dioxide with impurities by Coriolis flow meter, oscillation-type densitometer and equations of state

Transporting CO2 from the capture plant to the storage site may encounter challenges in the flow metering due to the unusual physical properties of CO2 – especially when containing impurities. Building on the authors’ previous work on the effect of impurities in CO2 mixtures on the performance of Coriolis flow meters, in this work, the accuracy of the density measurements of CO2 mixtures was investigated using a Coriolis meter and a high-pressure Anton Paar densitometer. The measured density data were then compared to the Peng-Robinson cubic equation of state with CO2 volume correction (PR-CO2) as well as to the multi-parameter GERG-2008 equation of state. The Average Absolute Relative Deviations (AARD) of the density predictions with PR-CO2 and GERG EOSs from the measured densities with the Anton Paar densitometer are 1.2% and 1.0%, respectively. While the Coriolis meter density values were consistently lower than the actual value in the gas phase. A correlation was obtained to correct the measured densities in the gas phase by fitting the measured densities to the prediction values using PR-CO2 and GERG EoSs at elevated pressures and temperatures. The AARD was reduced from 26.1% to 2.3% using PR-CO2 and from 25.4% to 3.6% using GERG EoSs.

Density, viscosity, refractive index and conductivity of switchable hydrophilicity solvent systems: N,N-Dimethylbenzylamine, water and carbon dioxide

Density, viscosity, refractive index and conductivity of switchable hydrophilicity solvent (SHS) systems (N,N-dimethylbenzylamine (BDMA), water, and carbon dioxide) were measured as a function of molality of BDMAH-bicarbonate salt for the SHS system at temperatures from (283.15–308.15) K. Three empirical equations were successfully applied to correlate the density, viscosity, refractive index, and electrical conductivity of the SHS systems with temperature and BDMAH-bicarbonate salt concentration. From these experimental results, apparent molar volume, limiting partial molar volume, the relative viscosity and viscosity B-coefficients were calculated. The limiting apparent molar volumes (Vϕ0) and experimental slopes (Av) derived from the Redlich-Mayer type equation have been interpreted in terms of solute-solute and solute-solvent interactions. In terms of Jones-Dole equation, the viscosity B-coefficients with large positive value and dB/dT < 0 were obtained and these facts implied that the BDMAH-bicarbonate salt is water-structure-making.