CO2 Concentration Profiles Research Articles

Drone CO2 measurements during the Tajogaite volcanic eruption

Abstract. We report in-plume carbon dioxide (CO2) concentrations and carbon isotope ratios during the 2021 eruption of Tajogaite volcano, island of La Palma, Spain. CO2 measurements inform our understanding of volcanic contributions to the global climate carbon cycle and the role of CO2 in eruptions. Traditional ground-based methods of CO2 collection are difficult and dangerous, and as a result only about 5 % of volcanoes have been directly surveyed. We demonstrate that unpiloted aerial system (UAS) surveys allow for fast and relatively safe measurements. Using CO2 concentration profiles we estimate the total flux during several measurements in November 2021 to be 1.76±0.20×103 to 2.23±0.26×104 t d−1. Carbon isotope ratios of plume CO2 indicate a deep magmatic source, consistent with the intensity of the eruption. Our work demonstrates the feasibility of UASs for CO2 surveys during active volcanic eruptions, particularly for deriving rapid emission estimates.

Carbon dioxide capture by aqueous glucosamine solutions: Pilot plant measurements and a theoretical study

AbstractA comprehensive investigation of the potential of aqueous glucosamine solutions as an eco‐friendly solvent for CO2 capture was performed. It includes an experimental study in a pilot plant setup and a theoretical analysis with a rate‐based model. The model was validated against the measured column profiles of temperature and CO2 concentration in both liquid and gas phases. Model‐based parameter sensitivity studies revealed inherent challenges for an effective absorption process. A slow reaction rate and suboptimal chemical equilibrium conditions were identified as key limitations, restricting the absorption efficiency and CO2 loading capacity of the glucosamine solution. Furthermore, an analysis of the dissociation constant of this novel absorbent was performed and its significance with respect to the (limited) performance, capability, and efficiency evaluation was highlighted.

Concentration of CO2 in the Local Working Area during the Joint Operation of a Gas Infrared Heater and an Air-Exchange System

The formation of local areas in large buildings with regulated thermal conditions is an urgent task. The use of gas infrared heaters for this purpose raises questions on the utility of an air-exchange system and the monitoring of the combustion product concentration. In this study, the modeling of heat transfer processes on premises with a gas infrared heater and an air-exchange system was conducted. The carbon dioxide concentration in the local working area when using a light-type gas infrared heater was determined. The regularities of current formation for circulating air and combustion products on the premises at various air-exchange rates were analyzed. The profiles of CO2 temperatures and concentrations in the local working areas on the left and right of the equipment model are shown. The article makes a conclusion about the influence of air velocity from the air-exchange system based on average values of carbon dioxide concentration on the premises and in the local working area. The possibility of increasing the temperature in the local working area without exceeding the permissible CO2 concentrations (less than 1000 ppm) has been identified. The formulated approach allows us to predict the available modes of the air-exchange system to create the highest possible comfort heating parameters while maintaining an acceptable degree of air pollution from combustion products.

High temperature CO2 capture in lithium orthosilicate packed fluidized bed: Gamma ray densitometry based numerical model and its experimental validation

BackgroundLithium orthosilicate (Li4SiO4) is steadily emerging as the default solid sorbent for high temperature CO2 capture in industrial settings. Li4SiO4 is also one the few materials qualified to serve as both catalyst and sorbent in sorption enhanced steam reforming process for high purity carbon neutral H2 production. Application of packed fluidization technique to enhance CO2 uptake in packed bed of pure Li4SiO4 particles has not been reported until now. MethodsGamma ray densitometry (GRD) technique is employed to non-intrusively obtain average voidage of Li4SiO4 packed fluidized bed as a function of operating time and axial bed coordinate. Based on the experimental results of GRD technique, a numerical model is developed to obtain the transient cross-sectional profiles of internal bed temperature and gas phase CO2 concentration as high temperature carbonation of Li4SiO4 progresses in packed fluidized bed. The numerical model is validated using experimentally obtained internal bed temperature and breakthrough curves. Temporal variation of bed effective thermal conductivity has been evaluated from model temperature profiles. FindingsIt was observed that the time averaged effective thermal conductivity and net solid weight gain of packed fluidized bed is around 1.7–2.3 and 1.1–1.3 times that of unary packed bed respectively at specified process parameters for high temperature CO2 capture.

Dynamic Real-Time Measurements and a Comparison of Gas and Wood Furnaces in a Dual-Fuel Heating System in Order to Evaluate the Occupants’ Safety and Indoor Air Quality

Due to rising energy costs, there is a trend to return to conventional heating systems powered by solid fuel. A rise in the combination of new and old energy sources is creating unintended dual-fuel heating systems. These systems combine an old solid-fuel furnace and a new gas furnace. Usually, the old furnace was meant to be replaced by the new one and their cooperation was never intended when installing the new heating system. The occupants decided to leave the old system in fear of a rise in prices of gas or electricity or temporary problems with their supply. The study focuses on such a system and its influence on indoor air quality and thermal comfort. A series of dynamic measurements with an IoT remote sensor array in a chosen household was conducted to evaluate the behaviour of the system as well as effects on the indoor environment. Sensors measured the CO2 concentration and thermal profile in a household when using a dual-fuel heating system consisting of an old wood furnace from the 1980s and a recently installed new gas furnace. The results showed that none of the heat sources posed a threat to the occupants. Contaminants were safely removed by the exhaust systems of the furnaces. The thermal comfort, however, was influenced more by the wood furnace where fluctuations in the temperature were noticed, especially during the night. The gas furnace maintained a stable temperature that was more suitable for the occupants.

CO2 diffusion in dry and hydrous leucititic melt

Abstract. Using the diffusion couple technique, diffusion of CO2 in a leucititic melt from the Colli Albani Volcanic District in Italy was investigated at temperatures between 1200 and 1350 ∘C in an internally heated pressure vessel at 300 MPa. To examine the effect of dissolved H2O in the melt, experiments were performed for a nominally dry melt (0.18 ± 0.03 wt % H2O) and for a hydrous melt containing 3.36 ± 0.28 wt % H2O. Diffusion experiments were run for 40 to 120 min and terminated by rapid quench. CO2 concentration profiles were subsequently measured via attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and fitted with error functions to obtain individual diffusion coefficients. For the anhydrous and hydrous sample series, seven diffusion coefficients were determined each. Diffusivity was found to increase exponentially with temperature for both melts following an Arrhenius behaviour. The Arrhenius equation for the nominally dry leucititic melt is described by log⁡DCO2=-1.44(±0.24)⋅10000T-1.95(±1.59), where DCO2 is the diffusion coefficient in m2 s−1 and T is the temperature in K. In the experimental temperature range, H2O has an accelerating effect on CO2 diffusion. At 1200 ∘C, diffusivity increases from 1.94 × 10−12 m2 s−1 in the dry melt to 1.54 × 10−11 m2 s−1 in the hydrous melt. The Arrhenius equation for the leucititic melt containing 3.36±0.28 wt % H2O is given by log⁡DCO2=-1.09(±0.30)⋅10000T-3.41(±1.99). The activation energies for CO2 were determined to be 275 ± 47 kJ mol−1 for the anhydrous melt and 209 ± 58 kJ mol−1 for the hydrous melt. The high CO2 activation energy in the leucititic melt indicates that the diffusion might be partly attributed to the carbonate species. At high magmatic temperatures above 1200 ∘C, CO2 diffusivity in the leucititic melt is only slightly lower than CO2 diffusion in rhyolitic and basaltic melts, suggesting that CO2 diffusion in natural melts is relatively independent from the bulk melt composition at such temperatures. CO2 diffuses slower than other volatile components such as halogens and H2O in depolymerized silicate melts. Thus, a fractionation of volatiles can occur during magma ascent and degassing. The experimental data on CO2 diffusion can be used for modelling the degassing mechanisms of ultrapotassic mafic melts.

The Impact of Long-Term Clinoptilolite Administration on the Concentration Profile of Metals in Rodent Organisms.

Heavy metals are dangerous systemic toxicants that can induce multiple organ damage, primarily by inducing oxidative stress and mitochondrial damage. Clinoptilolite is a highly porous natural mineral with a magnificent capacity to eliminate metals from living organisms, mainly by ion-exchange and adsorption, thus providing detoxifying, antioxidant and anti-inflammatory medicinal effects. The in vivo efficiency and safety of the oral administration of clinoptilolite in its activated forms, tribomechanically activated zeolite (TMAZ) and Panaceo-Micro-Activated (PMA) zeolite, as well as the impact on the metallic biodistribution, was examined in healthy female rats. Concentration profiles of Al, As, Cd, Co, Pb, Ni and Sr were measured in rat blood, serum, femur, liver, kidney, small and large intestine, and brain using inductively coupled plasma mass spectrometry (ICP-MS) after a 12-week administration period. Our results point to a beneficial effect of clinoptilolite materials on the concentration profile of metals in female rats supplemented with the corresponding natural clinoptilolite materials, TMAZ and PMA zeolite. The observed decrease of measured toxicants in the kidney, femur, and small and large intestine after three months of oral intake occurred concomitantly with their most likely transient release into the bloodstream (serum) indicative of a detoxification process.

The synergy of light/fluid flow and membrane modification of a novel membrane microalgal photobioreactor for direct air carbon capture

In this paper, a novel microalgal attached membrane photobioreactor based on the modified polyvinylidene difluoride (PVDF) / polyvinyl pyrrolidone (PVP) composite membrane for microalgae direct air carbon capture is developed and optimized. The Computational Fluid Dynamics (CFD) simulation, molecular dynamic study (MDS) and experimental study are adopted to investigate the synergy between light transmission and fluid flow, CO2 transmission mechanism inside the membrane and microalgae cells. The modified composite membrane is proposed and processed to improve the carbon sequestration rate of the microalgal attached membrane photobioreactor (AM-PBR). First, the synergy angle between the light transmission direction and fluid flow direction of the flat-plate photobioreactor (FP-PBR) is analyzed. To improve the synergy of light and fluid flow, the AM-PBR is proposed. Secondly, for the MDS part, the models of PVDF membrane and polytetrafluoroethylene (PTFE) membrane are developed. A three-layer simulation model is proposed to reveal the transmission mechanism of CO2 from the gas-liquid layer to the microalgae cell membrane layer. Several parameters including CO2 diffusion coefficient, CO2 concentration profile and velocity profile of CO2 are analyzed to compare the performance of different membranes and working conditions. Then, for verification of the simulation work, AM-PBR experiments are designed. To further enhance the CO2 transmission and microalgae attached performance, different PVDF/PVP composite membranes are assessed. The carbon sequestration rate of the modified membrane is improved according to the experiments. Finally, the novel microalgae membrane photobioreactor with the modified PVDF/PVP membrane is developed and the carbon sequestration rate of the PBR system is improved. The results showed that the best ratio for PVDF and PVP is 2:1 with 20 wt% solution, and with this modified membrane the carbon sequestration rate of the PVDF/PVP-based AM-PBR is 18.61% higher than the original PVDF-based AM-PBRs. The proposed novel AM-PBR is especially useful for low-concentration CO2 direct air carbon capture.

Modeling of Carbon Dioxide Separation by Aqueous Ammonia Solution in a Hollow‐Fiber Membrane Contactor

AbstractCO2 separation from gaseous mixtures in a hollow‐fiber membrane contactor (HFMC) with conventional solvents has a high energy cost. Aqueous ammonia is an industrial solvent candidate that provides better features. A mass transfer model was developed to investigate the effect of operating parameters on the separation performance of an HFMC using aqueous ammonia for CO2 removal. The governing equations were solved numerically. The influence of the liquid flow rate, liquid concentration, and gas flow rate on CO2 removal was studied at different CO2 inlet concentrations. The liquid flow rate had a slight effect on the CO2 concentration at the shell exit, while the CO2 removal significantly changed with variation of the gas flow rate. Moreover, the proposed model can predict CO2 removal as well as axial and radial CO2 concentration profiles in the HFMC as a function of the main operating parameters.

A hybrid data-driven and mechanistic model soft sensor for estimating CO2 concentrations for a carbon capture pilot plant

Integrating post-combustion carbon capture and storage (CCS) facilities into fossil fuel power plants is considered an important step for reaching global carbon emission reduction targets. When the number of gas analyzers in such CCS units is limited, variations in the load of the power plant pose a challenge to determine the gaseous CO2 concentration profile in the absorber. A dynamic hybrid model for estimating the carbon capture absorber’s gaseous CO2 concentration profile has been proposed in this study. The model is built using actual process data collected from a carbon capture pilot plant and it combines data-driven and reaction kinetic (mechanistic) modeling approaches to act as a soft sensor along the absorber column. A subset of the process data is used for training the data-driven models and for estimating the parameters of the mechanistic model respectively. Dimensionality reduction techniques are applied to the data-driven model to reduce the input size and hence the size of the dynamic model elements. The outputs of the two models are fused by comparing the computed covariance matrices. A particular challenge for this work is that the collected process data has missing spatial labels and temporal values for the CO2 concentration measurements. The presented models are obtained using an encoding and interpolation approach for the missing information. For comparison, an alternative approach based on semi-supervised learning has been implemented. The performance of the resulting soft sensors is verified by using process data from previously unseen operating conditions. The soft sensor based on the proposed hybrid model outperforms the soft sensor trained by semi-supervised autoencoder. Overall the results indicate that the proposed approach can estimate the CO2 concentration percentage with an average root mean squared error of 0.123.

Effects of CO2 and N2 dilution on the characteristics and NOX emission of H2/CH4/CO/air partially premixed flame

For the combustion of the mixture of blast furnace gas, natural gas, and coke oven gas in industrial burners, how to improve combustion efficiency and reduce pollutant emission are of significance. To accomplish this, an industrial partially premixed burner with a combustion diagnostic system is used to experimentally reveal the characteristics and NOX emission of H2/CH4/CO/air flame under CO2, N2, and CO2/N2 (replacing half of N2 with CO2) dilution. NOX emission and flame length, temperature profile, along with CO, CH4, and CO2 concentration profiles are analyzed with the three diluents in the fuel stream under different dilution rates (0–32% by volume). Experimental results show that for lean H2/CH4/CO combustion, greater proportions of CO2 in the diluent affect flame characteristics in various ways. These effects include longer flame length, lower highest flame temperature, the highest flame temperature being located farther away from the nozzle, and the highest CO2 concentration being located nearer the nozzle. Furthermore, results of CO, CH4, and CO2 concentrations indicate that chemical reactions in the flame are significantly affected by CO2 owing to the series reaction CH4⇌CH3→CO⇌CO2. Finally, increasing diluents or the ratio of CO2 in diluents has the benefit of reducing NOX emission.

A differential CO2 profile probe approach for field measurements of soil gas transport and soil respiration#

AbstractBackgroundGas exchange between soil and atmosphere is of great importance for greenhouse gas cycles. As gas transport in soil is generally dominated by diffusion, the soil gas diffusion coefficient (DS) is crucial to understand fluxes between soil and atmosphere. Estimating DS is still a great source of uncertainty when calculating soil gas fluxes such as soil respiration from soil gas profiles. In situ measurement of the effective exchange coefficient (Deff) not only reduces this uncertainty, but also allows to quantify non‐diffusive transport processes in addition to the purely diffusive exchange (DS), which cannot be investigated by laboratory measurements or the application of soil gas diffusivity models. Even though several methods for in situ Deff measurement exist, they often lack in the temporal resolution to identify short‐term effects on Deff or require laborious set‐ups, which makes them unsuitable for a fast and mobile application.AimsOur objective was to test an improved profile probe for model‐based soil gas flux analyses that allows in situ monitoring of (1) soil CO2 profiles with high temporal resolution, (2) soil gas transport coefficients, including non‐diffusive transport processes, (3) soil–atmosphere CO2 flux, and (4) soil respiration profiles.MethodsWe developed a CO2 profile probe with build‐in sensors that can easily be installed in soil to gain continuous CO2 concentration profiles. The probe includes the option to inject CO2 as a tracer gas to estimate Deff. To account for changes in natural CO2 concentrations in the soil, we tested two approaches: firstly, a differential approach using two probes, an injection probe and a reference probe, and secondly, a stand‐alone approach in which changes in natural CO2 concentrations are estimated by a statistical model using its main environmental drivers. The resulting tracer gas profiles were used to fit a finite element gas diffusion model to derive Deff. Using the derived Deff values and the CO2 profiles allowed calculating CO2 fluxes. The approach was tested with controlled laboratory experiments using different mineral substrates to compare the diffusivity estimates of the in situ method with laboratory measurements on soil cores. Additional laboratory experiments included artificial CO2 sources to simulate soil respiration in order to evaluate the gradient‐based estimation of soil respiration profiles. In a second step, both approaches were tested under natural conditions in the field.ResultsThe derived Deff values agreed well with laboratory measurements of DS and DS‐transfer functions. The artificial CO2 sources could accurately be estimated with the gradient method. In the field under calm conditions, both approaches for the estimation of the changing natural CO2 profile gave comparable results. Under windy conditions, the stand‐alone approach gave unrealistically high values, whereas the differential approach using a reference profile still gave reliable results. We observed a clear relationship between Deff and wind‐induced pressure pumping in the topsoil. The estimated surface CO2 efflux agreed well with chamber measurements.ConclusionsThis new set‐up enables monitoring of diffusive and non‐diffusive soil gas exchange and soil respiration in situ with high resolution and relatively low effort.

Full-loop simulation of a 1 MWth pilot-scale chemical looping combustion system

A 1 MWth pilot-scale chemical looping combustion (CLC) system is numerically simulated in the Eulerian-Lagrangian framework. Multiple chemical reactions including coal pyrolysis, char gasification, volatiles combustion, and oxidation of oxygen carriers are considered in the model. The influence of solid fuel feeding rate on the performance of the CLC system is analyzed and the parcel-scale information is obtained. The numerical results are synthetically compared with the experimental measurements. A non-uniform distribution of the gas species is observed in two reactors. Meanwhile, the relatively uniform parabolic profiles of solid holdup are displayed at different radial directions while the profiles of CO2 concentration at different radial directions are quite asymmetrical and non-uniform. Due to the strong oxidation reaction, the temperature profile in the AR is higher than that in the FR. The lognormal probability plots of solid residence time present an early peak with a long tail. Increasing coal feeding rate will promote the formation of product gas yields and solid temperature but suppresses the transport of solid particles in the CLC system.

Vertical microclimate heterogeneity and dew formation in semi-closed and naturally ventilated tomato greenhouses

The extent of the vertical microclimate heterogeneity inside a greenhouse is mostly unknown, and it can strongly affect plant production and yield quality. Tomato crop was grown in a semi-closed greenhouse equipped with horizontal ventilation and sidewall curtains, which were only opened depending on microclimate conditions; and a naturally ventilated greenhouse equipped with sidewalls curtains that were kept open. Both greenhouses had a 1,000-m2 area and a net size of 50-mesh, and were located in an arid climate zone in Israel. Vertical profiles of CO2 concentration, actual vapor pressure, air, leaf and soil temperature, net CO2 assimilation rates, stomatal conductance, and total fruit yield, fresh mass, and quality were monitored in both greenhouses for 13 days, in January 2018; CO2 concentration, actual vapor pressure, and air and soil temperature were additionally monitored in the semi-closed greenhouse for seven days in December 2016, when the ventilation was inoperative, and in December 2017, with ventilation. The vertical air temperature gradient, along with the colder microclimate inside the naturally ventilated greenhouse, led to a lack of plant uniformity and yield loss. Closing the side curtains in the fanned semi-closed greenhouse had a beneficial effect on yield, however, with mixed results for quality, due to the higher air temperature and lower carbon dioxide levels at the upper canopy. Horizontal air circulation in the semi-closed greenhouse increased transpiration and assimilation, and increased dew occurrence at night, but did not reduce the vertical heterogeneity. Significant vertical gradients affect plant physiology, and closing the curtains in winter cultivation in semi-arid/arid climates has the potential to improve fruit yield and quality. However, it must be coupled with proper air circulation and, preferably, with CO2 enrichment, or careful management of natural ventilation through side curtains, in order to maximize CO2 replenishment while minimizing heat losses.

Viral aerosol transmission of SARS-CoV-2 from simulated human emission in a concert hall

The dispersion of aerosols was studied experimentally in several concert halls to evaluate their airborne route and thus the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreading. For this, a dummy was used that emits simulated human breath containing aerosols (mean diameter of 0.3 μm) and CO2, with a horizontal exhalation velocity of v = 2.4 m/s, measured 10 cm in front of the mouth. Aerosol and CO2 concentration profiles were mapped using sensors placed around the dummy. No substantial enrichment of aerosols and CO2 was found at adjacent seats, provided that (1) there were floor displacement outlets under each seat enabling a minimum local fresh air vertical flow of vv = 0.05 m/s, (2) the air exchange rate (ACH) was more than 3, and (3) the dummy wore a surgical face mask. Knowledge of dispersion of viral droplets by airborne routes in real environments will help in risk assessment when re-opening concert halls and theatres after a pandemic lockdown.

Refinement of the gradient method for the estimation of natural source zone depletion at petroleum contaminated sites

Rates of natural source zone depletion (NSZD) are increasingly being used to aid remedial decision making and light non-aqueous phase liquid (LNAPL) longevity estimates at petroleum release sites. Current NSZD estimate methods, based on analyses of carbon dioxide (CO2) and oxygen (O2) soil-gas concentration gradients (“gradient method”) assume linear concentration profiles with depth. This assumption can underestimate the concentration gradients especially above LNAPL sources that are typically characterized by curvilinear or semi-curvilinear O2 and CO2 concentration profiles. In this work, we proposed a new method that relies on calculating the O2 and CO2 concentration gradient using a first-order reaction model. The method requires an estimate of the diffusive reaction length that can be easily derived from soil-gas concentration data. A simple step-by-step guide for applying the new method is provided. Nomographs were also developed to facilitate method application. Application of the nomographs using field data from published literature showed that NSZD rates could be underestimated by nearly an order of magnitude if reactivity in the vadose zone is not accounted for. The new method helps refine NSZD rates estimation and improve risk-based decision making at certain petroleum contaminated sites.

Development of a rate-based model for CO2 capture using a non-aqueous hydrophobic solvent

Advanced water-lean solvents offer several advantages over aqueous amine solvents for post-combustion CO2 capture, particularly lower parasitic energy penalty, lower regeneration temperatures and lower corrosion. RTI and SINTEF have been working on developing eCO2SolTM, a non-aqueous solvent (NAS) that has shown stripper heat duties of 2.1 - 2.3 GJ/t-CO2 at pilot-scale testing at a 6-kW large bench-scale gas absorption system (BsGAS, RTI International, USA) and at the 60-kW Pilot testing unit (Tiller Plant, SINTEF, Norway). This technology will be demonstrated at the 12 MW scale at Technology Centre, Mongstad (TCM), Norway in early 2022. Development of novel solvent formulations is a time-consuming step, and models are needed to evaluate different process configurations and process conditions, to explore different energy integration strategies to minimize net heat duty and to size equipment and evaluate overall process economics. The non-aqueous solvent formulation includes novel components that have not been studied extensively in the literature. Most of the properties that are needed to develop rate-based kinetic-, thermodynamic and hydrodynamic models are not available and must be generated. This work provides details on the development of a detailed process model including the experimental measurement of properties required for the simulation model. The process model has been tested against quality pilot data gathered from the two pilot plants mentioned. The average absolute deviation (AAD%) between model prediction and experimental data for the specific reboiler duty (SRD) is within 6% for the 6-kW BsGAS at RTI and 7% for 60-kW pilot testing at SINTEF. Mass and heat transfer of the developed rate-based model was validated by predicting the temperature, CO2 loadings (molCO2/molamine) and CO2 concentration profiles of the testing units and compared favourably to experimental data.

Packed column modelling and experimental evaluation for CO2 absorption using MDEA solution at high pressure and high CO2 concentrations

N-Methyl-diethanolamine (MDEA) is a potential solvent to capture CO2 at high-pressure and high CO2 concentration conditions due to its high CO2-loading capacity and the pressure-driven nature of CO2-MDEA reaction equilibrium. However, no studies have been reported on packed column modelling and experimental evaluation of CO2 absorption process using MDEA solvent for high pressure and high CO2 concentration conditions. Therefore, this study presents the experimental evaluation and modelling of CO2 absorption in the packed column using the MDEA solution at these extreme conditions. The effects of amine concentrations (0.83–3 M), liquid flowrates (3.61–5.42 m3/m2h) and feed CO2 concentrations (35–45%) have been studied on the CO2 removal efficiency at 40 bar total pressure and 1.8 kg/h gas flowrate. Highest CO2 removal efficiency is found to be 61.7% for 35% CO2 at 5.42 m3/m2h and 2 M MDEA solution. Further, a rate-based model is developed by accounting for sequential chemical reactions and associated mass transfer resistances occurring at low (<1 molCO2/molMDEA) and high CO2 (>1 molCO2/molMDEA) loadings. The developed model has been successfully validated with the experimental data. In a parity plot of CO2 concentration profiles along the column height, R2 is found to be 0.97. Further the model is applied to forecast CO2 absorption performance over the extended process conditions. It is found that 98.2% CO2 removal efficiency can be achieved for 40% CO2 at the conditions of 333.15 K temperature, 4 M MDEA concentration, and 5.42 m3/m2h liquid flowrates.

Atomic mobilities and interdiffusivities in Ni-rich fcc Ni-Co-Cr and Ni-Al-Co-Cr systems evaluated using composition profiles and HitDIC

In this paper, 15 single-phase solid/solid diffusion couples in Ni-rich fcc Ni-Co-Cr and Ni-Al-Co-Cr systems were fabricated, and the corresponding concentration profiles of Ni, Co, Cr, and Al at 1423–1523 K were determined by means of the electron probe microstructure analysis technique. The atomic mobility descriptions in Ni-rich fcc Ni-Al-Co-Cr system were established directly from the present 15 concentration profiles with the aid of HitDIC software. The interdiffusion coefficients in fcc Ni-Co-Cr and Ni-Al-Co-Cr alloys were then evaluated based on the established atomic mobilities in fcc Ni-Al-Co-Cr system together with the reported thermodynamic descriptions. The reasonability of D̃CoCoNi and D̃CrCrNi in fcc Ni-Co-Cr alloy was validated by comparing with the corresponding experimental values in Ni-Co and Ni-Cr binary alloys. The diffusion rate of Cr is larger than that of Co in both Ni-Co-Cr and Ni-Al-Co-Cr alloys, and Al diffuses faster than Cr in Ni-Al-Co-Cr alloys. The comparison between the diffusion rates of Co and Cr in Ni-Al-Co and those in Ni-Al-Co-Cr alloys suggests the addition of Al speeds up the diffusion of Co and Cr in Ni-Al-Co-Cr alloys, and the acceleration is more pronounced as the temperature increases.

Effect of Carbon Dioxide (CO2) concentration in the gas feed on Carbon Dioxide Absorption Performance using Aqueous Potassium Carbonate promoted with Glycine

This paper presented the effect of CO2concentration in the gas feed to the CO2absorption performance using a green solvent, potassium carbonate promoted with glycine (PCGLY). Recently, the performance of this solvent (with precipitates) was hindered by its poor mass transfer performance due to the blockage in packings and piping. Therefore, this study focused to study the CO2 absorption performance of non-precipitating potassium carbonate promoted with glycine. This green solvent contains aqueous blend of 15wt% potassium carbonate and 3 wt% glycine. The absorption performance of the solvent was obtained by demonstrated a few experimental works using a bench scale packed absorption column. The packing type was Sulzer metal gauze and the column consisted of six sampling point which located equidistance along the packing.The effect of CO2 concentration at the gas feed was assessed in term of its CO2 removal efficiency and concentration profile along the packing. The study shows the decreasing trend of CO2 removal as CO2 inlet concentration in the gas feed increases. The reason of this behavior is due to the limited reactant of liquid phase to absorb high CO2concentration in gas phase. The main outcome of this study demonstrated the efficient absorption which can absorb up to 79.24 % of CO2from natural gas using non-precipitated PCGLY.