Influence Of CO2 Concentration Research Articles

CO2 diffusion in shale oil based on molecular simulation and pore network model

Field practices show that CO2 huff and puff can effectively promote the exploitation of shale resources, and CO2 diffusion is noteworthy as a crucial mechanism of enhanced oil recovery (EOR). Understanding the confinement effect on CO2 diffusion is imperative to accurately characterize the fluid transport in shale nanopores and further upscaling. We integrate molecular simulation and pore network model (PNM) to study CO2 diffusion behavior at the nanoscale and pore scale. We first explored CO2 diffusion into heptane in kerogen and calcite pores using molecular dynamics, and analyzed the impacts of pore size, molar fraction, temperature, and pore pressure on the confined Fick diffusion. Based on the molecular simulation results, a model characterizing the ratio of the confined diffusion coefficient to that of the bulk phase is constructed for further upscaling. Based on the PNM containing organic and inorganic pores, we established a model to simulate the CO2 diffusion at the pore scale by introducing the characterization model at the nanoscale into the convective diffusion equation. Considering the microscale effects and the influence of CO2 concentration on diffusion is beneficial to improve the simulation accuracy at the pore scale. The estimated CO2 diffusion coefficients are in good agreement with the experimental results. This work provides better insight into CO2 diffusion behavior in shale oil, which can afford effective support for industrial exploitation and the breakthrough of the technical bottleneck of shale oil production.

Effects of Temperature, Precipitation, and CO2 on Plant Phenology in China: A Circular Regression Approach

Leveraging circular regression, this study analyzed phenological data from China spanning the period 2003 to 2015, meticulously examining the effects of temperature, precipitation, and CO2 concentrations on the phenological patterns of woody and herbaceous plants. For woody plants, the results showed that rising temperatures and increased precipitation notably advanced early growth phases, such as budburst, leaf unfolding, and first flowering (p < 0.001). Specifically, CO2 concentrations had a pronounced impact on the leaf unfolding phase (p < 0.001). In contrast, autumnal events, particularly fruit maturity, autumn coloring, and leaf fall, were delayed by warmer temperatures and higher precipitation (p < 0.001), Of these events, only fruit maturity demonstrated sensitivity to CO2 concentration variations. In the realm of herbaceous plants, elevated temperatures and precipitation collectively hastened the budburst phase (p < 0.001), which is an effect further accentuated by high CO2 levels (p < 0.001). Moreover, rising temperatures and augmented precipitation were instrumental in advancing the flowering phase (p < 0.001). Conversely, warmer conditions slowed down the fruiting process (p < 0.001), with this delay somewhat mitigated by the effects of increased precipitation. Interestingly, while CO2 concentrations had negligible influence on the flowering and fruiting stages, they noticeably delayed seed dispersal and the initiation of senescence (p < 0.001). Overall, the prevailing trend suggests that plants, whether woody or herbaceous in nature, tend to prolong their growth season under warmer and more humid conditions. The influence of CO2 concentration, however, is contingent upon the specific phenological phase and plant type. Our findings emphasize the nuanced and stage-specific responses of plant phenology to temperature, precipitation, and CO2, highlighting the value of using circular regression in ecological studies.

Experimental study on the influence of CO2 concentration on the crystallization law of wastewater drainage pipes

Experimental study on the influence of CO2 concentration on the crystallization law of wastewater drainage pipes

Chemically modified hydrate swapping and hydrate stability during multistage CO2-N2 injection schemes

A core-flooding setup under high-pressure and low-temperature conditions was utilized to create artificial sedimentary CH4 hydrates, that were subjected to multistage injections of fresh CO2-N2 gas mixtures to study CH4 recovery yield, CO2 storage, and hydrate stability in response to various chemical treatments. The effect of chemical type (methyl alcohol, sodium dodecyl sulfate, and L-methionine), number of fresh injections, injection pressures, and influence of CO2 concentration were examined to support the sustainability and efficacy of the process. Electrical resistivity was also measured to investigate hydrate stability under different injection schemes and chemicals. Higher recovery and storage were observed in the presence of additives (compared to pure water) was observed, suggesting that enhanced but delayed formation kinetics at the gas/liquid interface and unstable mixed hydrate reformation were the major contributing factors. During gas injection, the gas/liquid boundary moved within the pore space, and nucleation initiated at this interface. Therefore, chemical additives were used to enhance, but delay, formation kinetics at the injected-gas/residual-water boundary. This caused release of additional in-situ heat, that dissociated CH4 hydrates, increased the total contact time, and improved gas diffusion. A porous morphology in the presence of chemicals may also provide additional pathways through hydrate films for improved gas migration. The number of fresh CO2-N2 injections increased CH4 recovery, and the efficiency of the injection scheme was dependent on initial hydrate saturation. No significant reduction in hydrate stability was observed after the first injection of dilute CO2 gas mixture. Multiple injections of fresh CO2-N2 gas may further enhance the hydrate stability.

Influence of CO2 concentration on the performance of MgO cement mixes

This paper investigated the influence of different CO2 concentrations on the microstructural and mechanical development of reactive MgO cement (RMC) concrete. Combination of various analyses revealed the enhancement of hydrated magnesium carbonate (HMC) phases with relatively superior micro-mechanical properties as the CO2 concentration increased from ambient (~0.04%) to accelerated (5–20%) levels. The higher CO2 diffusion within samples cured under 5–20% CO2 increased the compressive strength by ~5 times. While samples cured under 20% CO2 revealed high early strengths, the formation of a dense HMC layer on the sample exterior led to limitations on further CO2 diffusion. Use of 5% CO2 produced comparable strengths as 20% CO2 at 28 days, highlighting the potential of using lower concentrations. Samples cured under 10% CO2 revealed the best performance at 28 days, thereby defining this environment as the most favorable condition for the development of microstructural and mechanical properties of RMC concrete.

Optimization upstream CO2 deliverable with downstream algae deliverable in quantity and quality and its impact on energy consumption

Algae CO2 biofixation provides a promising opportunity due to earn carbon credits and valuable end uses. For balancing technology, energy and economy issues in practical utilization, this approach quantitively interprets the contradictions from upstream CO2 source with a wide range of initial concentration to downstream CO2 biofixation product including edible algae and algal biomass. The influence of upstream CO2 deliverable on algal quantity and quality have been assessed, and the influence of CO2 concentration on CO2 transport mode choice has been also assessed coupling the transportation distance. In downstream algal fixation, quantitively relationship of algal growth have been established. The assessment discovered that direct energy consumptions complied with logarithmic relationship with specific productivities while both direct energy and indirect energy consumption complied with linear relationship with protein content. According to sensitive uncertainty analysis, initial CO2 concentration is a critical parameter to influence significantly energy consumption in upstream CO2 deliverables and algal quality while the contents of protein and specific productivity are the critical sensitive parameters in downstream algae deliverables. Potential modification systems are achieved for significantly reducing energy consumption by improving specific productivity and carbon abundance with low protein content in algae.

Keeping Doors Closed as One Reason for Fatigue in Teenagers—A Case Study

(1) Background: Healthy teenagers are often sleepy. This can be explained by their physiology and behavioral changes; however, the influence of CO2 concentration above 1000 ppm should not be neglected with respect to sleep dissatisfaction. (2) Methods: CO2 concentrations were measured in two similar bedrooms occupied by girls aged 9 and 13 years old. The scheme of measurements included random opening and closing of the bedroom doors for the night. Additionally, the girls evaluated their sleep satisfaction in a post-sleep questionnaire. (3) Results: During the night, the CO2 concentration varied from 402 to 3320 ppm in the teenager’s bedroom and from 458 to 2176 ppm in the child’s bedroom. When the bedroom doors were open, inadequate indoor air quality (IEQIII and IEQIV categories) was observed in both the teenager’s and child’s bedroom during 11% and 25% of the night, respectively; however, closing the doors increased the contribution of moderate (IEQIII) and low (IEQIV) categories of air to 79% and 86%, respectively. The girls were dissatisfied only when the bedroom door was closed. The satisfied category of sleep was selected only by the younger girl. (4) Conclusions: Opening the bedroom door during the night can decrease the CO2 concentration 55–64% without reducing thermal comfort.

Amine functionalized hierarchical bimodal mesoporous silicas as a promising nanocomposite for highly efficient CO2 capture

Amine loaded solid adsorbents are promising for the post-combustion CO2 capture. A current challenge is how to synthesize support with excellent pore structure by cost-effective methods as supports for amine loading. Herein, hierarchical bimodal mesoporous silica (HMS) was synthesized by using P123 as template through the partitioned cooperative self-assembly process. The prepared HMS is found to have large pore volumes and hierarchical pore networks. Subsequently, a series of tetraethylenepent amine (TEPA) functionalized adsorbents is prepared and CO2 capture measurements were implemented in a fixed-bed reactor to investigate the effects of TEPA loading and mesoporous structure. And the influence of CO2 concentration on capture performance was also studied in both In-situ DRIFTS and adsorption kinetic ways. The results show that the CO2 capture amount of HMS is up to 5.82 mmol/g at 70 wt.% TEPA loading and 75 ℃ with 15 vol% CO2. The large pore volumes significantly increase the amine loading and the interconnected hierarchical mesopores networks facilitated the dispersion of amine. The higher CO2 concentrations is conducive to the formation of carbamic acid and the decrease of CO2 adsorption activation energy, thereby facilitating the CO2 adsorption. In addition, poly (propylene glycol) bis (2-aminopropyl ether) (PEA) was also introduced in the adsorbent to further improve the adsorption performance. The results show that the introduction of PEA can offer increased CO2 capture amount, improved thermal stability and regenerability due to the participation of the ether group in the reaction of CO2 with the amine group and improved the thermal stability of the TEPA and PEA co- functionalized adsorbent.

Influence of CO2 Concentration and Inorganic Species on the Gasification of Lignocellulosic Biomass Derived Chars

The recent bio-based economy directions towards the renewable energy development result in an overwhelming compulsion to identify new environmental friendly processes for biomass conversion. Combustion, gasification, and pyrolysis have been identified as promising thermo-chemical conversion techniques for energy and biofuels production. However, many drawbacks need to be solved for developing their applications at large scale. Among the various problematics, the influence of inorganics on char gasification reactivity remains an open issue. Hence, the effect of alkaline and alkali earth metal (potassium and calcium) under different CO2 concentrations (20–100%) have been here investigated by thermal gravimetric analysis. Surprisingly, the presence of calcium did not improve the reactivity as expected, but a decrease in the gasification kinetics was observed, when compared to the gasification of the char obtained from washed biomass containing a lower amount of calcium species. On the other hand, K-species clearly act as activators, in particular at high char conversion ratios. The char gasification rate was higher at high CO2 concentration for all samples, and the effect of CO2 concentration was maximized for the K-enriched char.

Influence of CO2 concentration and N:P ratio on Chlorella vulgaris-assisted nutrient bioremediation, CO2 biofixation and biomass production in a lagoon treatment plant

Abstract Microalgae are among green trends for wastewater nutrient bioremediation, valuable biomass production, and CO2 biofixation. Currently, limited information is available regarding combined effects of nitrogen:phosphorus (N:P) ratio and CO2 concentration on growth characteristics and nutrient removal capacity of Chlorella vulgaris cultivated in lagoon systems. The current work sought to address simple effects and interaction effects of various N:P ratios and CO2 concentrations on growth kinetics of microalgae, using samples taken from effluents of a domestic settling lagoon. The findings revealed that the medium supplemented with 16% CO2 and N:P ratio of 10 was the most productive culture, generating maximum biomass concentration, specific growth rate, biomass productivity, and CO2 biofixation rate of 0.7900 g L−1, 0.4170 d−1, 0.08500 g L−1 d−1 and 0.1430 gCO2 L−1 d−1, respectively. Moreover, C. vulgaris adapted and grew well even under CO2 levels as high as 24% in the wastewater. The microalga also demonstrated to uptake both nitrogen and phosphorous in the range of 70.00–95.00%. These observations support the possibility of CO2 bioremediation along with removal of nitrogen and phosphorous to below the most European restrictive limits for effluent discharges, while the increase in COD concentration caused by microalgae should be taken into account.

Experimental and Numerical Investigation of Laminar Burning Velocities of Artificial Biogas Under Various Pressure and CO2 Concentration

As a renewable and sustainable fuel made from digestion facility, biogas is composed predominantly of methane (CH4) and carbon dioxide (CO2). CO2 in biogas strongly affects its combustion characteristics. In order to develop efficient combustors for biogas, fundamental flame characteristics of biogas require extensive investigation. In understanding the influence of CO2 concentration and mixture pressure on biogas combustion, the effects of CO2 concentration on the laminar burning velocity of methane/air mixtures were studied at different pressures. The studies were conducted using both numerical and experimental methods. The experiment was conducted using a constant volume high pressure combustion chamber. The propagating flames were recorded with a high speed digital camera by employing Schlieren photography technique. The numerical simulation was carried by utilizing CHEMKIN-PRO with GRI-Mech 3.0 employed as the chemical kinetics model. The results show that the laminar burning velocity of methane-air mixtures decreased with an increase in CO2 concentration and mixture pressure. Therefore, the burning velocity of biogas mixtures may decrease as the amount of CO2 in the gas increases.

Fabrication of Lithium Silicates As Highly Efficient High-Temperature CO2 Sorbents from SBA-15 Precursor.

A series of lithium silicates with improved CO2 sorption capacity were successfully synthesized using SBA-15 as the silicon precursor. The influence of Li/Si ratio, calcination temperature, and calcination duration on the chemical composition and CO2 capture capacity of obtained lithium silicates was systematically investigated. The correlation between CO2 sorption performance and crystalline phase abundance was determined using X-ray diffraction and a normalized reference intensity ratio method. Under the optimized condition, Li-SBA15-4 prepared using Li/Si = 4 that contains mainly Li4SiO4 achieved an extremely high CO2 capture capacity of 36.3 wt % (corresponding to 99% of the theoretical value of 36.7 wt % for Li4SiO4), which is much higher than the Li4SiO4 synthesized from conventional SiO2 sources. It also showed very high cycling stability with only 1.0 wt % capacity loss after 15 cycles. Li-SBA15-10 (Li/Si = 10) that mainly contains Li8SiO6 displayed an extremely high CO2 uptake of 62.0 wt %, but its regeneration capacity was poor, with only 10.5 wt % of reversible CO2 capture capacity. The influence of CO2 concentration on the CO2 capture performance of Li-SBA15-4 and Li-SBA15-10 samples was also studied. With the decrease in CO2 concentration, relatively lower temperatures are needed for its maximum CO2 capture capacity. The CO2 sorption kinetics and mechanism for Li-SBA15-4 and Li-SBA15-10 samples were explored. Overall, we have shown that the lithium silicates synthesized from SBA-15 possessed much improved CO2 sorption performance than that attained from conventional SiO2.

Laboratory investigation of carbon dioxide separation from methane using a PES/Pebax 1657 composite membrane

ABSTRACTRemoval of carbon dioxide from methane is a critical issue in the gas sweetening and treatment units. The aim of this study is to investigate the capability of PES/Pebax composite membrane in order to CO2 removal from the CH4. In this regard, permeability values of both carbon dioxide and methane have been measured. The ranges of temperature and pressure used for pure gases experiments were 20–50°C and 2.5–10 bar, respectively. Moreover, influence of CO2 concentration on the CH4 permeability and its selectivity was studied. Results indicated that the pressure and temperature have significant influence on permeability and selectivity. In addition, for the gas mixtures, experiments were carried out at 5 bar and 35°C. Results also indicated that at higher CO2 concentrations the CO2 permeability increased significantly.

A mathematical model of the photosynthetic carbon metabolism has multiple steady states under the same parameter conditions

This paper analyzes a mathematical model of the photosynthetic carbon metabolism, which incorporates not only the Calvin-Benson cycle, but also another two important metabolic pathways: starch synthesis and photorespiratory pathway. Theoretically, the paper shows the existence of steady states, stability and instability of the steady states, the effects of CO2 concentration on steady states. Especially, a critical point is found, the system has only one steady state with CO2 concentration in the left neighborhood of the critical point, but has two with CO2 concentration in the right neighborhood. In addition, the paper also explores the influence of CO2 concentration on the efficiency of photosynthesis. These theoretical results not only provide insight to the kinetic behaviors of the photosynthetic carbon metabolism, but also can be used to help improving the efficiency of photosynthesis in plants.

Numerical simulations of bubble behavior and mass transfer in CO2 capture system with ionic liquids

Ionic liquids (ILs) have exhibited excellent performance on CO2 capture. However, the lack of research on transport properties has become a bottleneck of industrial application. In order to understand the bubble behavior and mass transfer performance in CO2 capture systems with ILs, a computational fluid dynamics (CFD) method with two improvements is developed in this paper. One improvement is that a drag force equation suitable for IL systems is introduced into the hydrodynamics model, and the other one is that the influence of CO2 concentration in liquid phase on viscosity of ILs is considered in the mass transfer model. Based on the developed CFD method, the bubble behavior and mass transfer properties are accurately described. The simulation results of bubble diameter, velocity and aspect ratio agree well with the experimental data with the overall deviation of 7.52%, 12.17% and 5.17%, respectively. The bubble coalescence phenomenon is illustrated by pressure gradient field analysis rather than conventional pressure field analysis, which can represent the drag force and lift force directly. The simulation results also show that the CO2 mass transfer is kinetic-controlled in pure ILs and thermodynamic-controlled in aqueous ILs, respectively.

Growth of micro- and nanocrystalline dual layer composite diamond films by microwave plasma CVD: Influence of CO2 concentration on growth of nano-layer

The high quality and smooth micro-and nanocrystalline dual layer composite diamond films were successfully prepared using H2/CH4/Ar/CO2 plasma with a synthesis process of nucleation/MCD growth/nucleation/NCD growth. The carbon dioxide content is demonstrated to be important in controlling the NCD layer grain size and growth rate. The influences of carbon dioxide concentration on the morphology, microstructure and growth rate of the deposited NCD layer are investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. It is found that the additional carbonaceous sources supplied by CO2 are favourable to increase the growth rate, and meanwhile, the oxygen related species generated would enhance the etching effect not only to eliminate the non-diamond phase of NCD but also to decrease the growth rate. The appropriate addition of CO2 can increase the high quality and growth rate, decrease the surface roughness. It is demonstrated that adding CO2 strongly affects the contents of various reaction species in plasma, which would determine the growth features of NCD layers. The deposited highly smooth and quality micro-/nano-crystal layered diamond film is also expected to be applicable in surface aroustic wave (SAW) devices and micro-electromechanical systems (MEMS).

Enhance Vitamin B12 Production by Online CO2 Concentration Control Optimization in 120 m3 Fermentation

Great amounts of carbon dioxide generated by Pseudomonas denitrificans during high aerobic vitamin B12 fermentation, while the influence of CO2 concentration on vitamin B12 production remains unclear. In this paper, we present parallel experiments to investigate various levels of inlet CO2 fractions on the physiological metabolism of P. denitrificans in laboratory scale fermentation. The results demonstrated that the oxygen transfer rate, cell growth and glucose consumption were inhibited with CO2 fraction elevated from 0.03% to 8.86 ± 0.24%, while the most exciting results showed that the specific vitamin B12 production rate and the yield to glucose were greatly stimulated when dissolved CO2 increased to 8.86 ± 0.24%. Therefore, the optimal exhausted CO2 fraction control strategy in 120 m3 fermenter was established. With the exhaust CO2 concentration was well controlled at 7.5 ± 0.25% on-line, vitamin B12 production greatly improved to 223.7 ± 3.7 mg/L, which was 11.2% higher than that of control. This strategy was proved to be significant necessary and effective for successfully scale up optimization in industrial vitamin B12 fermentation.

Sensitivity of amine-based CO2 capture cost: The influences of CO2 concentration in flue gas and utility cost fluctuations

The amine-based absorption process is the preferred technique to capture CO2 from flue gas. However, the cost of CO2 capture using an amine-based absorption process is considered high due to the solvent regeneration step. Therefore, in order to make this process a viable option for CO2 capture, its cost, especially its operating cost, must be reduced. This paper presents the results of a systematic sensitivity analysis, which covers the effects of CO2 concentration in flue gas and utility cost fluctuations on the optimum amine-based CO2 capture cost. The paper aims to determine whether the operating conditions of an existing CO2 capture plant can be changed to offset the effects of CO2 concentration in flue gas and utility cost fluctuations in order to yield the same or lower CO2 capture cost as the original plant design. It also provides an understanding of how the optimum CO2 capture cost changes with these fluctuations. The considered utility costs are the prices of amine solvent(s), electricity, process water, cooling water, and low pressure saturated steam. The response surface technique, coupled with the steepest descent method, is utilized to search for the direction of lower CO2 capture cost. The final result obtained from this methodology consists of the optimum operating conditions of the process with the minimum CO2 capture cost. The studied solvents are monoethanolamine (MEA) and diglycolamine (DGA), and diethanolamine–triethanolamine mixture (DEA–TEA). The results show that changes in the CO2 concentration in flue gas have the highest impact on the optimum CO2 capture cost of an existing plant when compared with the remaining parameters. For all solvents, the optimum CO2 capture cost shows an inversely proportional relationship to the CO2 concentration in flue gas. The optimum cost decreases by around 29–33% as the CO2 concentration increases by 50%, and the cost increases by around 86–104% as the CO2 concentration decreases by 50% when compared to the base case. The fluctuations in the utility costs do not exhibit a significant impact on the minimum CO2 capture cost.

Factors Affecting NO Reduction during O2/CO2 Combustion

O2/CO2 combustion is a promising technology to facilitate carbon capture in pulverized coal-fired power plants. The reduction of recycled NO, influence of CO2 concentration on the conversion ratio ...

Effects of CO2 concentrations on the freshwater microalgae, Chlamydomonas reinhardtii, Chlorella pyrenoidosa and Scenedesmus obliquus (Chlorophyta)

In order to investigate the possible impacts of increased atmospheric CO2 levels on algal growth and photosynthesis, the influence of CO2 concentration was tested on three planktonic algae (Chlamydomonas reinhardtii, Chlorella pyrenoidosa, and Scenedesmus obliquus). Increased CO2 concentration enhanced significantly the growth rate of all three species. Specific growth rates reached maximal values at 30, 100, and 60 μM CO2 in C. reinhardtii, C. pyrenoidosa, and S. obliquus, respectively. Such significant enhancement of growth rate with enriched CO2 was also confirmed at different levels of inorganic N and P, being more profound at limiting levels of N inC. pyrenoidosa and P in S. obliquus. The maximal rates of net photosynthesis, photosynthetic efficiency and light-saturating point increased significantly (p < 0.05) in high-CO2-grown cells. Elevation of the CO2 levels in cultures enhanced the photoinhibition of C. reinhardtii, but reduced that of C. pyrenoidosa and S. obliquus when exposed to high photon flux density. The photoinhibited cells recovered to some extent (from 71% to 99%) when placed under dim light or in darkness, with better recovery in high-CO2-grownC. pyrenoidosa and S. obliquus. Although pH and pCO2 effects cannot be distinguished from this study, it can be concluded that increased CO2 concentrations with decreased pH could affect the growth rate and photosynthetic physiology of C. reinhardtii, C. pyrenoidosa, and S. obliquus.