Carbon Dioxide Flow Research Articles

Generation of atmospheric pressure plasma in molecular gas flows

We have investigated an atmospheric pressure discharge, similar to a plasma jet, in the N2 and CO2 gas flows. We have also carried out an experimental modeling with the argon Ar flow. It has been shown that the use of a tantalum cathode and a copper anode provides a stable discharge in the nitrogen and carbon dioxide flows. We have studied the dependence of the discharge voltage on the discharge current (VAC). Optical emission spectra of discharge glow was investigated also. Using a single probe and a thermocouple, we have studied the axial distribution of the floating potential in the plasma jet and the gas temperature at the anode nozzle exit of the plasma generator. In applying to polymer surface modification, we have determined the optimal operation conditions: gas flow rate up to 5 l·min−1; continuous or pulsed working regime; discharge current about 80 mA; pulse duration up to 10 µs; pulse repetition rate 50 kHz.

Effects of capillary pressures on two-phase flow of immiscible carbon dioxide enhanced oil recovery in fractured media

CO2-EOR in a geological formation not only increases oil production but also ensures geological sequestration of CO2. The capillary pressure is an essential factor during the process of immiscible CO2-EOR in fractured media. Two classical capillary pressure models are adopted to investigate the effects systematically based on a unified pipe-network method. The identical capillary pressures in fractures and the rock matrixes have little effect on the fluid flow and saturation distribution of CO2. This implies that the capillary pressure can be neglected in this condition. The effect cannot be ignored when different capillary pressures are assigned for fractures and rock matrixes. The saturation of CO2 reaches its highest value at the fracture outlet tip if the capillary pressure in a fracture is smaller than that in the rock matrix. The phenomenon of saturation concentration of CO2 at the fracture tip is caused by the capillary pressure difference. For non-connected fractures, the saturation concentration causes CO2 to enter the adjacent fractures more easily. Thus, the capillary pressure difference enlarges the effect of fractures on the CO2 flow, and shorten the breakthrough time of CO2. Hence, both the storage amount of CO2 and the production of oil in geological media are reduced.

Modeling heat transfer in a supercritical carbon dioxide flow with greatly variable thermophysical properties

A mathematical model of carbon dioxide isobaric flow under supercritical pressure in the condition of a constant heat flux on the surface of a cooled pipe is discussed. Criterion dependencies for heat transfer are analyzed. The effect of greatly variable heat capacity is shown. A method has been developed for taking this factor into account in numerical calculations. Areas are found with the so-called degraded heat transfer.

EFFECTIVENESS OF CORRECTION OF DISCUSSION OF CARBOHYDRATE METABOLISM IN RATS WITH CRANIOCEREBRAL INJURY

The development and introduction into practice of emergency neurology of new drugs capable of influencing secondary neuronal damage in patients with traumatic brain injury (TBI) has made a significant impact on the recovery of such patients. Aim of the work was to evaluate the magnitude of cerebroprotective action of amantadine sulfate in terms of impaired carbohydrate metabolism of the brain against the background of experimental TBI. Materials and methods. The experimental model of severe TBI was caused by the action of a carbon dioxide flow under pressure, which was created using a gas balloon of pneumatic gun. The therapeutic effect of amantadine sulfate on TBI model was evaluated with a 5 mg/kg dose. The pseudo-operated animals and control group received 0.9 % NaCl solution at a dose of 2 ml/kg with IV administration. Results. The obtained results confirm the formation of a hypo-energetic state in the brain cells of rats on the background of TBI, which is probably a consequence of the suppression of the processes of oxidative phosphorylation and its conjugation with tissue respiration. TBI is accompanied by activation of anaerobic glycolysis and inhibition of aerobic glucose oxidation, proving that there is an imbalance between the levels of lactate and pyruvate intermediates. 8-day infusion of rats with traumatic brain injury of amantadine sulfate, inhibited anaerobic glycolysis hyperactivation, stimulated tissue respiration processes, reduced signs of lactic acidosis and development of secondary alteration of brain cells by non-oxidized products. Conclusions. In the course of the experiment, it was found that the treatment of rats, with TBI model, with 0.9 % NaCl solution did not significantly contribute to the restoration of impaired energy metabolism (p<0.05) and did not reduce the manifestation of metabolic acidosis in the damaged brain (p<0.05). The use of amantadine sulphate in TBI rats significantly corrects carbohydrate metabolism disorders than 0.9 % NaCl solution and contributes to the reduction of metabolic acidosis in the damaged brain (p<0.05).

Reacting gas-surface interaction and heat transfer characteristics for high-enthalpy and hypersonic dissociated carbon dioxide flow

Hypersonic carbon dioxide reacting gas-surface interaction occurs on the heat shield of high-speed Mars entry capsules, which has great influences on the heat transfer characteristics. Based on hypersonic reacting flow solver with complex surface thermochemistry, the hypersonic chemical non-equilibrium flow with oxygen/carbon gas mixture was numerically simulated, and the interaction between non-equilibrium flow and surface reactions was numerically analyzed to reveal the mechanism of aerodynamic heating from surface thermochemistry. Numerical results of catalytic effects show that the near-wall thermochemical behaviors are essentially dominated by the near-wall diffusion and chemical reactions. Various surface reactions alter the flow structure in the boundary layer, and generate different aerodynamic heating patterns. Results from ablating simulations indicate that the ablating surface can induce additional near-wall diffusion and injection energy though their influence on the thermal boundary layer structure is neglectably small. The modeling of reacting gas-surface interaction can be of benefit to promoting the fidelity and precision of aerodynamic heating with complex surface thermochemistry.

Emission of Carbon Dioxide from the Dark Chestnut Soil in West Kazakhstan

The necessity of studying and assessing emissions of carbon dioxide from the agricultural soils is related to the important role played by the soil in their formation. Active release of carbon dioxide shows changes in the content of the organic matter in the soil and its biological activity. Carbon dioxide emissions can be influenced both by biotic and anthropogenic factors. Due to the negative effect of grazing and arable plots on the soil respiration, unequal emission of carbon dioxide is noted. The research was aimed at assessing the dynamics of carbon dioxide emissions from the dark-chestnut soil, depending on the nature of the soil use in agriculture. The studies for determining the carbon dioxide flow rate were performed according to the standard variant of the closed dynamic chamber method. The results of studying the content and emission of carbon dioxide from the dark-chestnut soil of the agricultural lands in Western Kazakhstan are shown. The content and reserves of humus in the 100 cm layer of the studied soils are low, and the soil is characterized by low humus content. The total annual flow of carbon dioxide from the virgin lands is higher than that from the arable lands but is less than that from the pastures.

Antioxidant Activity and Total Polyphenols Content of Camellia Oil Extracted by Optimized Supercritical Carbon Dioxide

AbstractIn this study, Camellia oil is co‐extracted from Camellia oleifera seeds and green tea scraps by supercritical carbon dioxide (SC‐CO2), which is optimized on the extraction yield, ABTS‐scavenging activity, and total polyphenols content (TPC) of oil by single‐factor experiments combined with response surface methodology (RSM). The extraction temperature, pressure, dynamic time, carbon dioxide (CO2) flow rate, and seed mass ratio were investigated with single‐factor experiments. The results indicated the optimum CO2 flow rate and dynamic extraction time were 15 L hour−1 and 60 min (i.e., 2.382 kg CO2/100 g sample). Furthermore, the complicated effects of extraction temperature (40–50 °C), pressure (20–30 MPa), and seed mass ratio (0.25–0.75) were optimized by RSM based on the Box–Behnken design (BBD). The models with high R‐squared values were obtained and used to predict the optimum operating conditions of the process. Under the optimum operating conditions (i.e., temperature of 46 °C, pressure of 30 MPa, and seed mass ratio of 0.35), the extraction yield, ABTS‐scavenging activity, and TPC of oil were 14.43 ± 0.17 g/100 g sample, 73.70 ± 0.34%, and 2.18 ± 0.05 mg GAE/g oil, which were in good agreement with the predicted values. In addition, the experiments indicated that the Camellia oil obtained was rich in polyphenols, resulting in better oxidation stability and antioxidant activity than the original oil.

The possibilities of pharmacological correction of the disturbance of carbohydrate metabolism in brain rates with traumatic brain injury

The development and introduction into practice of emergency neurology of new drugs capable of influencing the secondary damage of neurons in patients with traumatic brain injury (TBI) has significantly affected the recovery of such patients. The aim of the study was to evaluate the magnitude of the cerebroprotective effect of amantadine sulfate on the index of impaired carbohydrate metabolism of the brain against the background of experimental TBI. The experimental TBI model of severe severity was caused by the action of a carbon dioxide flow under pressure created using a gas balloon pneumatic gun. The therapeutic effect of amantadine sulfate on model TBI was evaluated using a dose of 10 mg/kg. The pseudoperated animals and control group received 0.9% NaCl solution at a dose of 2 ml/kg i/v. The obtained results were processed by the method of variational statistics using Student's t-test, changes of indicators were considered probable at p≤0.05. In the course of the experiment, it was found that the treatment of rats with model TBI with 0.9% NaCl solution did not significantly contribute to the restoration of impaired energy metabolism (p<0.05) and did not reduce the manifestation of metabolic acidosis in the damaged brain (p<0.05). The use of amantadine sulfate in TBI rats significantly better corrects carbohydrate metabolism disorders than 0.9% NaCl solution and contributes to the reduction of metabolic acidosis in the damaged brain (p<0.05).

New insights on boiling carbon dioxide flow in mini- and micro-channels for optimal silicon detector cooling

Whilst the thermal management needs of future silicon detectors are increasing, the required mass and volume minimization of all detector ancillaries gets more demanding. This requires highly effective active cooling in very small channels. In the context of the AIDA-2020 project, a new test stand has been developed to characterize, with unprecedented level of accuracy, boiling flows of CO2 in mini- and micro-channels with hydraulic diameter ranging from 2 down to 0.1 mm. The heat transfer coefficient and pressure drop behaviour in stainless steel tubular evaporators for saturation temperatures from ＋20 to −25 °C, mass fluxes from 1200 to 100 kg m−2 s−1 and heat fluxes from 0.5 to 3.5 W/cm2 are discussed for one diameter. In addition, high speed camera observations of CO2 flow patterns recorded on micro-structured silicon cold plates are used to help with the interpretation of the heat transfer coefficient and pressure drop trends reported.

Ethanol Dehydrogenation to Acetaldehyde over Activated Carbons-Derived from Coffee Residue

This study focuses on the production of acetaldehyde from ethanol by catalytic dehydrogenation using activated carbon catalysts derived from coffee ground residues and commercial activated carbon catalyst. For the synthesis of activated carbon catalysts, coffee ground residues were chemical activated with ZnCl2 (ratio 1:3) followed by different physical activation. All prepared catalysts were characterized with various techniques such as nitrogen physisorption (BET and BJH methods), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), temperature programmed desorption (CO2-TPD and NH3-TPD), X-ray Difraction (XRD), Fourier transform infrared spectrometer (FT-IR), and thermogravimetric analysis (TGA). The dehydrogenation of vaporized ethanol was performed to test the catalytic activity and product distribution. Testing catalytic activity by operated in a fixed-bed continuous flow micro-reactor at temperatures ranged from 250 to 400 °C. It was found that the AC-D catalyst (using calcination under carbon dioxide flow at 600 °C, 4 hours for physical activation) exhibited the highest catalytic activity, while all catalysts show high selectivity to acetaldehyde (more than 90%). Ethanol conversion apparently increased with increased reaction temperature. At 400 ºC, the AC-D catalyst gave the highest ethanol conversion of 47.9% and yielded 46.8% of acetaldehyde. The highest activity obtained from AC-D catalyst can be related to both Lewis acidity and Lewis basicity because the dehydrogenation of ethanol uses both Lewis acid and Lewis basic sites for this reaction. To investigate the stability of catalyst, the AC-D catalyst showed quite constant ethanol conversion for 10 h. Therefore, the synthesized activated carbon from coffee ground residues is promising to be used in dehydrogenation of ethanol.

Service life evaluation of RC T-girder under carbonation considering cold joint and loading effects

Carbon dioxide concentration is steadily increasing in large cities. Consequently, durability evaluation of RC (Reinforced Concrete) structures considering carbonation is becoming a serious issue. Construction joints are used for the effective construction of concrete structures. However, cold joints which are caused by delayed placing and poor surface treatment are vulnerable to shear force and the inflow of carbon dioxide. In this study, an accelerated carbonation test was performed for normal-strength concrete using NPC (Normal Portland Cement) and slag after applying tensile and compressive stresses. The carbonation characteristics were quantified considering the effects of cold joint and the induced stress, and structural analysis was performed using the section laminae approach for a 2-span continuous reinforced concrete T-beam bridge. The service life of top and bottom concretes was evaluated considering the calculated stress, existing carbonation velocity equation, and carbonation function according to the stress. The service life showed a similar trend to that of the applied moment. Changes of 103.6%–64.7% (NPC) and 78.0%–108.8% (slag) were observed on the top surface, whereas changes of 103.8%–65.9% (NPC) and 112.9%–79.6% (slag) were observed on the bottom surface. The service life significantly decreased owing to the increasing carbonation depth for the cold joint in the tension part. This suggests that special care should be taken for cold joints during maintenance.

Prediction of critical mass rate of flashing carbon dioxide flow in convergent-divergent nozzle

The prediction of a critical mass flow rate of flashing flow is of crucial importance for many applications in chemical and processing apparatus. One of the most prosperous application is the two-phase ejector as a device with flashing liquid phase as a motive fluid and vapour phase as a secondary fluid. In that case the prediction of critical flashing flow mass flow rate is necessary. A new generalised procedure of the transonic trajectory determination that uses enhanced Possible-Impossible Flow algorithm is proposed. The procedure is much faster than the commonly used Newton Critical Point (NCP) approach. The approach was applied in modelling of carbon dioxide transonic two-phase flow through the convergent-divergent nozzle by means of Homogeneous Equilibrium Model (HEM) and Delayed Equilibrium Model (DEM). These models were used to simulate flows that were experimentally and theoretically investigated in literature. The application of DEM model for determination of the supersonic trajectory part for CO2 flow is a novel contribution provided in the paper. The comparison with literature experimental data revealed that the original closure equations developed for water are improper for CO2 transonic flows, thus the adjusting attempts were demonstrated. It was revealed that the applied Darcy friction factor determination approach significantly influences on the results. Moreover, an effective DEM adjustment is impossible until Lockhart–Martinelli approach is utilised. It was shown that for CO2 case Darcy friction factor calculated by means of Friedel approach is more appropriate than the one calculated by means of the commonly used Lockhart–Martinelli approach. Nevertheless, it was demonstrated that using a frictionless approach would still give better results while adjusting DEM to better approximate the experimental pressure distributions.

Optimization of Technical Parameters of CO2 Inerting Goaf in 7271 Working Face of Yaoqiao Mine

Aiming at the problem of fire prevention and extinguishment in the 7271 working face of Yaoqiao Mine, the carbon dioxide inerting method was used to establish the influencing factors system, which combining injecting pipeline parameters, mining technical parameters and inerting gas physical parameters. Numerical simulation method was used to study the influence of different gas injection depth and different gas injection volume on the distribution of carbon dioxide flow field in the goaf. The range of gas injection parameters is determined by hierarchical simulation experiment; Taking comparative experiment between parameters obtain the optimal carbon dioxide fire prevention and inerting parameters for the 7271 working face to study injection depth and injection volume. Experiments show that the width of the oxidation zone reduced by 56m after inerting the goaf, and the width of the asphyxiation zone increased by 29m.

Evaluation of neuroprotective properties of Ademol with experimental traumatic brain injury conditions

The choice of drugs in traumatic injuries of the head is one of the most complex problems in the complex treatment of such patients. The aim was to estimate the cerebroprotective action of Ademol on the indicator of lethality of rats against the background of an experimental traumatic brain injury (TBI). The experimental model of the TBI of severe severity was caused by the action of the flow of carbon dioxide under pressure that was created using a gas cylinder pneumatic gun. The therapeutic effect of Ademol on the model TBI was evaluated at doses of 1, 2 and 4 mg/kg intravenously. Pseudo-operative animals and control group received a 0.9% NaCl solution at a dose of 2 ml/kg. The results were processed using the statistical program StatPlus 2009. Used Fisher angular transformation when accounting for results in an alternative form. In the course of the experiment, it was found that in the control group at the end of the experiment, 8 days after the TBI model, death of 90% of the rats was recorded p<0.05. Ademol showed the highest protective effect on the brain at a dose of 2 mg/kg where the death of rats was 30% on the 8th day of the experiment. The obtained data indicate that among the studied doses 1; 2 and 4 mg/kg is conventionally effective at just 2 mg/kg, in which Ademol exhibited the highest neuroprotective activity (p<0.05).

Kinetics of hematite to magnetite transformation by gaseous reduction at low concentration of carbon monoxide

Hematite-containing material is accumulated during exploitation and beneficiation of magnetite ore, thus forming tailings and other industrial wastes. Hence, processing the low-grade hematite ore becomes extremely important for the metallurgical industry. The transformation of weakly magnetic hematite into magnetite can enhance the efficiency of magnetic separation. In this work, chemical reduction of hematite to magnetite in an atmosphere with different gas composition was investigated. Gasification of charcoal in the flow of both air and carbon dioxide led to the formation of carbon monoxide. The output gas containing carbon monoxide was found to be an effective reductant for the transformation of hematite into magnetite. Even 5% of CO was sufficient to convert hematite into magnetite, which resulted in an increase in magnetization up to 85Am2/kg. The kinetic analysis indicated that the reduction of hematite to magnetite is a single-step process, which can be described using the first-order reaction model.

Production of Microsphere Polystyrene Using Solution Enhanced Dispersion by CO<sub>2</sub> Supercritical Fluids (SEDS)

Supercritical fluids (SCFs) process can be considered as an emerging ”clean“ technology for the production of small-size particles (e.g. micron-size). Microsphere is a material in micron scale which has been widely used as adsorbent, catalyst support, and drug delivery system. For advanced application, those materials are formulated in the form of porous microspheres. There are several methods that can be used using SCFs. One of them is Solution Enhanced Dispersion by Supercritical Fluids (SEDS). This method is considered to be suitable in obtaining the porous microsphere polystyrene. In this study, polystyrene was first dissolved into toluene (polystyrene solution) at different concentrations (i.e. 3, 5, 7, 9, 11, 13, 15 wt%) and then blown/sprayed together with supercritical carbon dioxide (CO2) through co-axial nozzle with two differents annulus diameter (i.e. 3.6 mm and 4.6 mm). Co-axial nozzle consists of two concentric pipes, inner pipe and annulus. Inner pipe for polystyrene solution flow and annulus for supercritical carbon dioxide flow. The expansion of these two of fluid was done both in atmospheric condition and in pressurized precipitator (40 bar). The resulted microsphere was analyzed by using SEM (Scanning Electron Microscope) to determine morphology and average diameter of the microsphere. The SEM analysis results showe that the smaller the initial concentration of solution used, the resulted microspheres tend to be smaller and less fibrils formed. Additionally, in the pressurized precipitator, the formed microspheres size was smaller and size distribution more narrow than that of atmospheric condition. Moreover, the use of smaller annulus diameter in co-axial nozzle produced smaller microsphere size and the size distribution was more uniform.

Assessment of carbon dioxide capture by precipitating potassium taurate solvent

One of the most mature technologies for removal of carbon dioxide from gaseous streams is chemical absorption. Among these, aqueous solutions of amino acids have been considered because of the advantages associated with their being precipitating solvents. This paper presents detailed analyses of the performance of the potassium taurate absorption system by means of a rigorous simulation in a commercial process software (ASPEN Plus®). The profiles of temperature, heat transfer, compositions, and molar flows of carbon dioxide and water have been examined. The operating line and the equilibrium curve for different lean loadings of the solvent are reported and show that the minimium reboiler duty occurs at a lean loading of 0.27. Examination of the influence of the solid-liquid separator on the reboiler duty shows that a recycle split fraction of 0.2 results in the lowest reboiler duty. Different minimum temperature approaches in the lean-rich cross heat exchanger have also been investigated.

Non-linear stability analysis of supercritical carbon dioxide flow in inclined heated channel

In this paper, the nonlinear stability analysis of supercritical carbon dioxide (SC−CO2) has been carried out using a reduced order nodalized model for a single inclined heated channel. The primary objective of the present study is to portray the generic view of linear as well as nonlinear stability characteristics of SC−CO2 channel along with the prospect of different types of bifurcation phenomena. The linear stability analysis is carried out with the help of eigenvalues of the Jacobian at steady state conditions, and stability boundary is shown in the parameter plane of pseudo-sub-cooling (Nspc) and pseudo-phase-change numbers (Ntpc). The non-linear analysis includes the detailed study of dynamic and static instabilities. Different types of bifurcation phenomena namely; sub-critical, super-critical and Generalized Hopf are observed; indicating various features of the dynamic instabilities. The first Lyapunov coefficient has been calculated to distinguish between sub-critical and super-critical Hopf bifurcations. Whereas in static instability; Ledinegg excursive phenomena, which is characterized as a saddle-node bifurcation is observed. Additionally, on saddle-node bifurcation curve, Bogdanov-Takens bifurcation points (as interaction with Hopf bifurcation) appear. These bifurcations lead to complex dynamics in the system therefore, several numerical simulations have been carried out around the stability threshold. This type of non-linear analysis is rarely reported for SC−CO2 in the existing literature. To extend this analysis, the dependence of various system design parameters on the bifurcation curve has been investigated along with the shifting of Generalized Hopf (GH) bifurcation point. Furthermore, the effect of the inclination angle of the channel on the stability threshold in parametric space is investigated.

Sub- and super-critical carbon dioxide flow variations in large high-rank coal specimen: An experimental study

Many experimental studies to date have investigated CO2 sequestration in coal using small-scale samples (usually less than 100 mm in length), and the results may not be applicable to large-scale samples which better represent in-situ conditions for the estimation of CO2 flow behaviours in coal. This study was therefore initiated to determine the sub- and super-critical CO2 flow characteristics in a large reconstituted bituminous coal sample (203 mm in diameter and 1 m in length) by performing three sets of N2 and CO2 injections with injection pressures from 6 MPa to 10 MPa under 11 MPa axial stress and at 37 °C. It was observed that, unlike N2 permeability which increases with injection pressure, CO2 permeability exhibits reductions with injection pressure due to greater swelling effects at elevated CO2 pressures. The second N2 injections into the coal sample previously flooded with CO2 showed reductions in permeability compared to the first N2 injection into the original coal sample, because the coal structure had been altered considerably by the CO2 flows. The pressure build-up at downstream for CO2 injection is always lower than that for the first N2 injection due to reduced CO2 flows as a result of decreased permeability, which also contributes to the lower pressure development at downstream for the second N2 injections. The pressure profiles along the sample are similar for the first N2 and CO2 injections with relatively greater pressure decays for CO2, while considerable pressure reductions were observed for the second N2 injections, especially in the regions near the injection point where greater CO2 pressures previously existed, causing greater structural rearrangement in those regions. The second N2 injection causes less volumetric strain of the sample than the first due to the altered coal structure induced by the prior CO2 flows which impede gas flow in the sample.

Modified Supercritical Carbon Dioxide Extraction of Biologically Active Compounds from Feijoa Sellowiana Leaves

Abstract For the first time, the modified supercritical carbon dioxide extraction (MSCE) of biologically active compounds from Feijoa sellowiana leaves was investigated. Total yield (TY) and bioactivity of biocompounds in terms of DPPH• (%DPPHsc) and HO• (%HOsc) radicals scavenging were maximized via multivariate optimization. The optimized conditions were the pressure of 272.34 bar, supercritical carbon dioxide flow rate of 1.58 mL min−1, temperature of 52.48 °C, and dynamic extraction time of 110.62 min. The predicted values of the TY, %DPPHsc, and %HOsc were 81.12 mg g−1, 85.16 %, and 75.66 %, respectively. The chromatographic analysis demonstrated gallic acid as the main biophenolic (136.20 ± 0.16 mg g−1). The scanning electron microscopy images showed dramatic disruption of cells treated with MSCE. A comprehensive comparison was made between current findings and other techniques (conventional and ultrasonic waves assisted extraction). More TY was achieved using conventional method but the bioactivity of MSCE products was considerably better.