CO2 Mass Fraction Research Articles

CFD analysis of a rotary kiln using for plaster production and discussion of the effects of flue gas recirculation application

In this study, the CFD analysis of the rotary kiln is carried out for examining effects of various parameters on energy consumption and efficiency of the rotary kiln. The flue gas recirculation using in many applications is a useful method for combusting of fuel unburned in the flue gas. Also, effects of flue gas recirculation on the combusting of fuel, operating temperature and efficiency of the rotary kiln are discussed in this study. The rotary kiln, which is considered in this study, is used in plaster plant. Two different CFD models were created and these models are compared according to many parameters such as temperature distribution, mixture fraction, the mass fraction of O2, CO, CO and CH4 in the combustion chamber. It is found that the plaster plant has a great potential for an increase in energy efficiency. Results obtained for producers of rotary kiln and burner will be useful for determining better design parameters.

Effect of intake oxygen concentration on diesel–n-butanol blending combustion: An experimental and numerical study at low engine load

The blends of n-butanol and diesel are easy to achieve the premixed low-temperature combustion (PLTC) without larger exhaust gas recirculation (EGR) rate to maintain combustion stability and reduce emissions. Engine experiment and numerical modeling coupled with a new reduced mechanism were used to investigate both combustion and emission characteristics of D100 (pure diesel) and B30 (30% n-butanol and 70% diesel) under different intake oxygen concentrations (IOCs: 21%, 19%, 17%, and 15%). With the decrease in IOC, the maximum heat release rate (HRR) of D100 increased, while the maximum HRR of B30 first increased and then decreased. NOx emissions of two fuels differed slightly and both significantly decreased. Soot emission of D100 increased, while that of B30 first increased and then decreased. Moreover, under the same IOC, soot emission of B30 was less than that of D100. The chemical kinetic analysis shows that the addition of n-butanol consumed a certain amount of OH, slowed down the oxidation of n-heptane and toluene, and finally prolonged the ignition delay period. Additionally, decreasing in IOC suppressed the low-temperature O2-addition reactions of n-heptane and n-butanol to retard the reaction processes, prolonging the ignition delay. The numerical results show that as the decrease in IOC, the combustion rate decreased, the timings taken for the complete consumption of reactants and the formation of important intermediate products (CH2O, CO, H2O2, and OH) as well as soot precursors (C2H2, A1, and A4) were significantly delayed. Besides, the maximum mass fractions of CH2O, CO, and H2O2 increased, while the maximum OH mass fraction decreased. The formation of soot precursors exhibited similar trends, and reached the maximum mass fraction at an IOC of 17%. Specifically, the increase in soot emission of B30 was caused by the decrease in oxidation, while the decrease was mainly induced by the decrease in formation.

Pressurized CO 2 releases in the framework of carbon sequestration and enhanced oil recovery safety analysis: Experiments and model

Abstract Hazard studies related to Carbon Sequestration (CCS) and Enhanced Oil Recovery (EOR) lack of appropriate descriptive models of pressurized CO2 releases. The complex inherent phenomena linked to a rapid depressurization in addition to the generalized lack of approachable and targeted experimental data, makes current QRA procedure inadequate. In light of this, the proposed work aims at achieving two correlated targets. Firstly, the results of an experimental campaign performed on CO2 pressurized releases are proposed. Secondly, a source model for multiphase CO2 pressurized releases is illustrated in terms of filling existing gaps. The reported experimental campaign focuses on the estimation of useful parameters to be used in the modeling procedure namely the experimental discharge coefficient and the thermodynamic nature of the expansion transformation. Bulk and discharge orifice pressure and temperature profiles are illustrated, focusing on how a multiphase CO2 release alters main discharge parameters. The proposed modeling approach allows for the collection of details on the expansion degree of reversibility and heat transfer effects are inferred showing that ideal isentropic and isenthalpic paths are never matched. Its application well matches collected data and gives good prediction of the total discharge time. In addition, direct unobservable dynamics inside the closed tank are assessed, notably the instantaneous dense CO2 mass fraction and peculiar evolutions during phase change mechanisms in the liquid-vapor and solid-vapor domains.

Modeling the dynamics of remobilized CO2 within the geologic subsurface

Long after CO2 is injected into a brine aquifer, most reservoir-scale fluid dynamic simulations predict large fractions of the original plume will become immobilized via capillary trapping and dispersed throughout the formation. We begin our analysis with a reservoir in this state and consider the effects caused by a depressurization of the domain (e.g. from a nearby production well or newly formed fracture between neighboring reservoirs) and predict the fraction of CO2 that will be remobilized as a result. We then model the dynamics of this remobilized CO2 in two distinct steps: (1) vertical rise within the reservoir, followed by (2) spreading of mobile CO2 into the far-field of the domain and justify this approach from a scaling analysis of the governing equations. We show that a model of relative permeability that takes account of insights from percolation theory near the minimum CO2 saturation leads to much more rapid rise and subsequent radial spreading of remobilized CO2 than a traditional empirical correlation such as the Brooks-Corey model. Furthermore, we find that over a broad range of remobilized CO2 mass fraction and Bond number, the radial extent of the mobile plume does not exceed a factor of 1.8 times the radius of the original immobilized CO2 region.

Effect of pressure, temperature, and mass fraction of CO2 on the state of the resin in crude oil

ABSTRACTThis paper focus on the main influence factors (temperature, pressure, and mass fraction of CO2) on the state of resin in the crude oil during CO2 flooding by using a visualization method. The state of resin is not affected by the variation of the temperature. Only when the pressure is increased to a certain value, the state of resin can be affected by the variation of the pressure. During the variation of the mass fraction of CO2, the state of the resin has a significant change, including the growth out of nothing, expansion from small to large, and transformation from a adsorbed solid to a flowable liquid. During the actual application process of CO2 flooding in oilfield, the influence of the temperature can be ignored, the appropriate mass fraction of CO2 is below 30% and the gas injection pressure should maintain a relatively low value. The results can provide a theoretical basis to avoid the resin aggregation during CO2 flooding.

Performance improvements evaluation of an automobile air conditioning system using CO2-propane mixture as a refrigerant

The main purpose of this work is to enhance the energy efficiency of CO2 automobile air conditioning system. Theoretical analysis demonstrated that the mixture of CO2 and propane can improve its performance, thus, experiments have been carried out to see effects of various CO2-propane mass fractions of 100/0, 90/10, 80/20, 70/30, 60/40, 50/50 on the system performance at different ambient temperatures and gas cooler frontal air velocities. Experimental results show similar trends with those from the theoretical results. It has been shown that under the same compressor speed, system COP reaches highest at 60% of CO2 mass fraction, which is 29.4% higher than pure CO2 system and even achieves equal level of the R134a system, the optimum pressure and discharge temperature are reduced up to a maximum of 40% and 47 °C during the research range. Furthermore, comparison was carried out under the same cooling capacity by adjusting compressor speed for different mass fraction of CO2, results demonstrate that the use of CO2-propane mixtures yields a maximum COP rise of 22%even when cooling capacity is kept constant. A new optimum high pressure control algorithm for the transcritical CO2-propane mixture cycle has been developed based on the experimental data within a deviation of 5%.

Numerical Study of the Combustion of CH4-C3H8/ Air: Application to a Combustion Chamber with Two Coaxial Jets

In this study, we studied numerically the non-premixed combustion provided by two coaxial methane-propane/air jets in a 3D cylindrical combustion chamber. To study this kind of phenomenon we used a special treatment of the mathematical model and we chose two models of computation PDF and LES. In order to find the aero-thermo-chemical characteristics in the burner, namely: axial velocity, temperature and mass fraction of carbon monoxide CO. Using commercial calculation software CFD Fluent The objective of this work is to research the fuel that reduces the emission of carbon monoxide CO, which is considered a gas toxic to the environment, by comparing the two fuels CH4 and C3H8. The results give methane fuel reduces carbon monoxide as a pollutant chemical species in combustion products compared to propane fuel.

Thin film membrane for CO2 separation with sweeping gas method

Different from gases separation technology using membranes and solvent, solvent-free gas separation technology is more economically and energy efficient. Due to its inherent low permeance of the membrane, the means using sweeping or vacuum are two main options to increase the mass flow rate of the fast gas (with higher selectivity) on the permeate side. This study models a typical membrane for CO2 separation and investigates the effects of different parameters on the total mass flow rate, mass fraction of CO2 and the mass flow rate of CO2 in the permeate outlet. These parameters are the permeate outlet pressure, mass flow rate of mixed feeding and sweeping gases, membrane length and the height of gases zones. The results show that the mass flow rate of CO2 in the permeate side can be enhanced dramatically by using sweeping gas method. But the mass fraction of CO2 in permeate outlet is also significantly affected by this method. The increase of membrane length enhances both the mass fraction and mass flow rate of CO2 in permeate outlet. But mass fraction of CO2 on permeate outlet reaches its peak when membrane length exceeds 150 mm. The height of gases zones, however, have very limited effects on both the mass fraction and mass flow rate of CO2 in the permeate outlet. This study provides a good guideline for designing industrial gases separation systems using membranes.

Effect of a mixture of carbon dioxide and steam on ejector performance: An experimental parametric investigation

The results are presented for an experimental investigation characterizing the performance of a steam ejector when the secondary fluid is a mixture of steam and a non-condensable gas. In the context of post-combustion carbon capture, carbon dioxide was chosen as the non-condensable for this work. In order to study the pure steam ejector over a wide operating range, performance curves were prepared for primary pressures of 350, 450 and 550 kPa, with secondary pressures of 50, 70 and 90 kPa. Effects of the primary nozzle position, the primary pressure, the secondary pressure, and the nozzle diameter were evaluated. For a reference primary pressure of 450 kPa and secondary pressure of 70 kPa, performance curves were prepared for four levels of entrained CO2 in the secondary fluid mixture, up to 45% by mass, and for four nozzle throat diameters ranging from 4.03 to 5.09 mm. It was observed for the first time that in contrast with the pure steam ejector performance curves, increasing amounts of entrained CO2 improved the critical entrainment ratio, but the critical pressure remained unchanged. This behaviour was in sharp contrast with that of a pure steam ejector. A linear relationship was observed between the increase in the entrainment ratio of a steam ejector and the mass fraction of CO2 contained in the ejector secondary fluid.

Synthesis of an intensive blue pigment with low cobalt content

A new blue Co-based inorganic-organic hybrid pigment was fabricated through a rapid one-step synthetic route. The blue pigment was characterized by field-emision scanning electron microscopy, transmittance electron microscopy, X-ray photoelectron spectroscopy, CNH elemental analysis, mercury porosimetry, thermogravimetric analysis, inductively coupled plasma mass spectrometry, and L*a*b* system. The pigment has a foam-like microstructure and its apparent (skeletal) density is 1.4g/cm3. The mass fraction of Co in the pigment is as low as 7.5%. The pigment shows brilliant blue color and its L*, a*, and b* values are 47.5, 20.1, and −41.6, respectively. Moreover, the L*, a*, and b* values can be adjusted simply by changing the composition of the pigments.

Numerical studies of CO formation during biogas combustion

This work deals with the LES (Large Eddy Simulation) of methane (CH4) and biogas non-premixed jet flames with the goal of examining the impact of CO2 addition on the formation of carbon monoxide. To model the chemistry, Equilibrium Chemistry (EC) as the cheapest approach was considered first, followed by a global kinetic model and a reduced reaction mechanism describing the combustion of syngas (CO + H2) combined with the reaction CH4 + 0.5 O2 → CO+ 2 H2. Highly diluted laminar jet flames were studies first to decouple the chemistry from the turbulence. All three models predict a considerable increase in the mass fractions of CO in the presence of CO2 in the fuel. Turbulent jet flames were subsequently considered which could not be simulated using equilibrium chemistry owing to numerical problems. The two chemical kinetic models predict a strong increase in CO.

Effect of pressure, temperature, and mass fraction of CO2 on the stability of the asphaltene constituents in crude oil

ABSTRACTThis paper focus on the main influence factors (temperature, pressure, and mass fraction of CO2) on the state of asphaltene in the crude oil during CO2 flooding by using high temperature and high pressure microanalysis system of solid precipitation. For the simulated oil sample – CO2 system, the state of asphaltene is not affected by temperature within this range of 50°C to 100°C, the particle size of the asphaltene has an increase with the increase of the pressure from 8MPa to 40 MPa. When the mass fraction of CO2 is less than 35%, the state of the asphaltene has not changed and the asphaltene particles are in a suspension state. When the mass fraction of CO2 increases to 40%, the aggregation of the asphaltenes occurs and then form precipitation. With the further increase of the mass fraction of CO2, the particle of the asphaltene aggregates has a significant increase. For the field development project design of CO2 flooding, the influence of the temperature can be ignored, the appropriate mass fraction of CO2 is below 35% and the gas injection pressure should maintain a relatively low value. The results can provide a theoretical basis to avoid the asphaltene precipitation during CO2 flooding.

Numerical studies of CO2 and brine leakage into a shallow aquifer through an open wellbore

Industrial-scale geological storage of CO2 in saline aquifers may cause CO2 and brine leakage from abandoned wells into shallow fresh aquifers. This leakage problem involves the flow dynamics in both the wellbore and the storage reservoir. T2Well/ECO2N, a coupled wellbore-reservoir flow simulator, was used to analyze CO2 and brine leakage under different conditions with a hypothetical simulation model in water-CO2-brine systems. Parametric studies on CO2 and brine leakage, including the salinity, excess pore pressure (EPP) and initially dissolved CO2 mass fraction, are conducted to understand the mechanism of CO2 migration. The results show that brine leakage rates increase proportionally with EPP and inversely with the salinity when EPP varies from 0.5 to 1.5 MPa; however, there is no CO2 leakage into the shallow freshwater aquifer if EPP is less than 0.5 MPa. The dissolved CO2 mass fraction shows an important influence on the CO2 plume, as part of the dissolved CO2 becomes a free phase. Scenario simulation shows that the gas lifting effect will significantly increase the brine leakage rate into the shallow freshwater aquifer under the scenario of 3.89% dissolved CO2 mass fraction. The equivalent porous media (EPM) approach used to model the wellbore flow has been evaluated and results show that the EPM approach could either under- or over-estimate brine leakage rates under most scenarios. The discrepancies become more significant if a free CO2 phase evolves. Therefore, a model that can correctly describe the complex flow dynamics in the wellbore is necessary for investigating the leakage problems.

Effect of gaseous CO2 on superheated steam flow in wells

In this paper, a novel model is proposed for estimating pressure and temperature in wellbores when CO2 and superheated steam (SHS) are co-injected.Firstly, a model comprised of mass, energy and momentum conservation equations are developed. Then, Coupled with real gas model and heat transfer model in formation, a comprehensive model is established. The mass, momentum and energy balance equations are solved simultaneously with finite difference method on space and the iteration method. Finally, sensitivity analysis is conducted. Results show that (a). In order to obtain a higher superheat degree, a higher injection temperature and a lower mass fraction of CO2 are suggested. (b). Superheat degree decreases with increasing injection pressure or with increasing mass fraction of CO2. (c). Superheat degree increases with increasing mass flow rate. (d). Superheat degree decreases with increasing mass fraction of CO2.

Phase behavior of Carbon dioxide/Tetramethyl orthosilicate/polymer ternary systems

The phase behaviors of carbon dioxide (CO2)/tetramethyl orthosilicate (TMOS)/poly(methyl methacrylate) (PMMA) and CO2/TMOS/poly(styrene) (PS) ternary systems were measured. The measurements were performed using a synthetic method involving observations of the bubble point and cloud point. The phase boundaries were measured at temperatures ranging from 313.2 K to 393.2 K and CO2 weight fractions ranging from 0.01 to 0.40. At a constant TMOS:polymer weight ratio of 9:1, both systems showed similar CO2 mass fraction dependence of their phase behaviors. When the vapor-liquid (VL) and vapor-liquid-liquid (VLL) phase boundaries of the ternary systems were compared with those of the binary CO2/TMOS system using polymer-free bases, they were found to be nearly identical. On the other hand, the two systems showed completely opposite polymer mass fraction dependence of their phase behaviors at a constant CO2 ratio.

Numerical Simulation of Methane-Hydrogen Combustion in the Air: Influence on Combustion Parameters

Objectives: To study the behavior of these parameters following the variation of CH4-H2 fuels in air. Methods/Statistical Analysis: We simulated the behavior of the turbulent methane-hydrogen/air flame, generated by a three-dimensional non-premixed cylindrical combustion chamber. The numerical simulations are carried out using the calculation code CFD “FLUENT”. Mathematical methods were used to solve the Navier-Stokes equations governing the flow phenomenon. Findings: The numerical results are compared and validated with the experimental data. In these conditions, the same parameters considered previously are used in the study of combustion behavior. The parameters characteristics of the flow were characterized such as the axial velocity, the temperature and the mass fraction of the carbon monoxide CO. Application/Improvements: The results show that the variation of the fuel influences the considered parameters. In addition, we confirm that hydrogen is a clean fuel without emitting CO into the environment. Keywords: CFD, Hydrogen, Methane, Numerical Simulation, Premixed Combustion, Turbulence

SILCC-Zoom: the dynamic and chemical evolution of molecular clouds

We present 3D "zoom-in" simulations of the formation of two molecular clouds out of the galactic interstellar medium. We model the clouds - identified from the SILCC simulations - with a resolution of up to 0.06 pc using adaptive mesh refinement in combination with a chemical network to follow heating, cooling, and the formation of H$_2$ and CO including (self-) shielding. The two clouds are assembled within a few million years with mass growth rates of up to $\sim$ 10$^{-2}$ M$_\mathrm{sun}$ yr$^{-1}$ and final masses of $\sim$ 50 000 M$_\mathrm{sun}$. A spatial resolution of $\lesssim$ 0.1 pc is required for convergence with respect to the mass, velocity dispersion, and chemical abundances of the clouds, although these properties also depend on the cloud definition such as based on density thresholds, H$_2$ or CO mass fraction. To avoid grid artefacts, the progressive increase of resolution has to occur within the free-fall time of the densest structures (1 - 1.5 Myr) and $\gtrsim$ 200 time steps should be spent on each refinement level before the resolution is progressively increased further. This avoids the formation of spurious, large-scale, rotating clumps from unresolved turbulent flows. While CO is a good tracer for the evolution of dense gas with number densities $n \geq$ 300 cm$^{-3}$, H$_2$ is also found for $n \lesssim 30$ cm$^{-3}$ due to turbulent mixing and becomes dominant at column densities around 30 - 50 M$_\mathrm{sun}$ pc$^{-2}$. The CO-to-H$_2$ ratio steadily increases within the first 2 Myr whereas $X_\mathrm{CO}\simeq$ 1 - 4 $\times$ 10$^{20}$ cm$^{-2}$ (K km s$^{-1}$)$^{-1}$ is approximately constant since the CO(1-0) line quickly becomes optically thick.

Numerical and Experimental Investigation of Equivalence Ratio (ER) and Feedstock Particle Size on Birchwood Gasification

This paper discusses the characteristics of Birchwood gasification using the simulated results of a Computational Fluid Dynamics (CFD) model. The CFD model is developed and validated with the experimental results obtained with the fixed bed downdraft gasifier available at the University of Agder (UIA), Norway. In this work, several parameters are examined and given importance, such as producer gas yield, syngas composition, lower heating value (LHV), and cold gas efficiency (CGE) of the syngas. The behavior of the parameters mentioned above is examined by varying the biomass particle size. The diameters of the two biomass particles are 11.5 mm and 9.18 mm. All the parameters investigate within the Equivalences Ratio (ER) range from 0.2 to 0.5. In the simulations, a variable air inflow rate is used to achieve different ER values. For the different biomass particle sizes, CO, CO2, CH4, and H2 mass fractions of the syngas are analyzed along with syngas yield, LHV, and CGE. At an ER value of 0.35, 9.18 mm diameter particle shows average maximum values of 60% of CGE and 2.79 Nm3/h of syngas yield, in turn showing 3.4% and 0.09 Nm3/h improvement in the respective parameters over the 11.5 mm diameter biomass particle.

Evaluation of flamelet/progress variable model for laminar pulverized coal combustion

In the present work, the flamelet/progress variable (FPV) approach based on two mixture fractions is formulated for pulverized coal combustion and then evaluated in laminar counterflow coal flames under different operating conditions through both a priori and a posteriori analyses. Two mixture fractions, Zvol and Zchar, are defined to characterize the mixing between the oxidizer and the volatile matter/char reaction products. A coordinate transformation is conducted to map the flamelet solutions from a unit triangle space (Zvol, Zchar) to a unit square space (Z, X) so that a more stable solution can be achieved. To consider the heat transfers between the coal particle phase and the gas phase, the total enthalpy is introduced as an additional manifold. As a result, the thermo-chemical quantities are parameterized as a function of the mixture fraction Z, the mixing parameter X, the normalized total enthalpy Hnorm, and the reaction progress variable YPV. The validity of the flamelet chemtable and the selected trajectory variables is first evaluated in a priori tests by comparing the tabulated quantities with the results obtained from numerical simulations with detailed chemistry. The comparisons show that the major species mass fractions can be predicted by the FPV approach in all combustion regions for all operating conditions, while the CO and H2 mass fractions are over-predicted in the premixed flame reaction zone. The a posteriori study shows that overall good agreement between the FPV results and those obtained from detailed chemistry simulations can be achieved, although the coal particle ignition is predicted to be slightly earlier. Overall, the validity of the FPV approach for laminar pulverized coal combustion is confirmed and its performance in turbulent pulverized coal combustion will be tested in future work.

Dependence of gigahertz microwave absorption on the mass fraction of Co@C nanocapsules in composite

Core@shell-structural Co@C nanocapsules synthesized by arc-discharge approach exhibit a significant combination of complex permittivity and permeability, thus resulting in an enhanced microwave absorption performance at gigahertz. In this work, we further present that the optimized microwave absorption capacities are associated with the mass fraction of the Co@C nanocapsules in composite, exhibiting >90% microwave attenuation at 4–15 GHz for 50 wt % loading. More importantly, our experimental results reveal that the microwave absorption performances, such as the reflection minimum, resonance frequency and bandwidth, are correlated to the mass fraction of absorbents in composite, and thus have potential implications in practical applications.