Carbon Dioxide Capture Process Research Articles

An intermittently moving bed adsorption process for carbon dioxide capture

The goal of this study is to propose an intermittently-moving-bed adsorption (I-MBA) process as a potentially viable technology for CO2 capture from large CO2 sources. In the I-MBA process, sorbent particles are circulated between adsorption and desorption beds intermittently by the operation of on–off valves. The associated process model and the relevant operational strategy for the I-MBA process were also proposed. The intermittent migration of the adsorbent mass was described by the model as an intermittent reset and a transition of bed state variables. A heat transfer enhancement factor was devised to express the effect of the local mixing of adsorbent particles, and the relevant parameter values were identified using experimental data. To ensure numerically stable calculations, especially when the two disjoint profiles are concatenated by adsorbent moving, a method that adaptively adjusts the number and location of collocation points was also developed. The performance of the I-MBA process was thoroughly analyzed through experiments and numerical simulations for various cases of the operation sequence. The proposed process was evaluated to produce CO2 with a purity of over 95% and a recover of over 83%.

Human health risks of post- and oxy-fuel combustion carbon dioxide capture technologies: Hypothetically modeled scenarios

Carbon dioxide (CO2) capture technology has become an available technology for ensuring reduction of greenhouse gas emissions from fossil-fuel based electricity generating plants. Since public acceptance of this technology depends critically on a reliable demonstration of its safety, it is important that the risks associated with carbon capture technology be fully understood so that standards and regulatory frameworks required for its deployment can be formulated.The objective of this paper is to evaluate the predicted risk to human health associated with the Boundary Dam Power Station (BDPS) close to Estevan, Saskatchewan, Canada. This study aims to predict the potential instead of actual risks to human health because real data from the power plants’ stacks are unavailable. Instead, the study relies on data that were entirely derived from the Life Cycle Assessment (LCA) studies (Koiwanit et al., 2014a,b; Manuilova, 2011). The risk assessment was conducted based on two tools: (i) the American Meteorological Society's Environmental Protection Agency Regulatory Model (AERMOD), and (ii) Health Canada's Air Quality Benefits Assessment Tool (AQBAT). The conventional lignite-fired electricity generation station at the BDPS is used as a reference case. This work presents the predicted risks to human health due to exposure to air pollution which has been released by the post-combustion carbon dioxide capture process, and compare the risks with those posed by the oxy-fuel CO2 capture technology.Nitrogen dioxide (NO2), particulates less than 2.5μm in diameter (PM2.5), and sulfur dioxide (SO2) emissions were modeled in a circular pattern of 10 degree increments with 25 zones of 100m on each increment. This study demonstrates that the reductions in the atmospheric concentrations of NO2, PM2.5, and SO2 accounted for the largest improvements in human health impacts, particularly in terms of acute respiratory, asthma symptoms, and restricted activity health outcomes. In addition, the oxy-fuel CO2 capture system reduced emissions to the atmosphere more effectively than the post-combustion CO2 capture technology. Therefore, the former technology's contribution to reducing air pollution is more significant than that of the latter.

Model-Based Approach for the Evaluation of Materials and Processes for Post-Combustion Carbon Dioxide Capture from Flue Gas by PSA/VSA Processes

This work presents a mathematical modeling framework for the simulation and optimization of PSA/VSA processes for postcombustion CO2 capture from dry flue gas (85% N2, 15% CO2). The modeling framework is first validated against literature data, illustrating good agreement in terms of several process performance indicators. Accordingly, the model is used to evaluate three available potential adsorbents for CO2 capture, namely, zeolite 13X, activated carbon and metal organic framework (MOF), Mg-MOF-74. A two-bed configuration (six-step VSA cycle) with light product pressurization has been employed in all simulations. The results from systematic comparative simulations demonstrate that zeolite 13X has the best process performance among the three adsorbents, in terms of CO2 purity and CO2 recovery. On the other hand, Mg-MOF-74 appears to be a promising adsorbent for CO2 capture, as it has considerably higher CO2 productivity compared to the other two adsorbents. Furthermore, process optimization studies using...

Pinch Point Analysis of Heat Exchangers for Supercritical Carbon Dioxide with Gaseous Admixtures in CCS Systems

Carbon dioxide (CO2) captured in carbon dioxide capture and storage (CCS) processes is transported and stored in a supercritical state. Heat exchangers, especially recuperators, with CO2 on both the hot and the cold side are often impacted by the occurrence of a pinch point, that is, area of closest approach between hot and cold temperature curves. CO2 in CCS systems is not pure, and even small amount of admixtures can have a significant effect on the location and impact of the pinch point, on heat transfer properties and exchanger sizing. This work investigates the effects of several admixtures on these parameters. It is found that these admixtures may have a slightly positive effect on recuperative heat exchangers. However, these admixtures also result in a significant size increase of CO2 coolers.

관내 이산화탄소 압력강하에 아르곤 불순물이 미치는 영향에 관한 실험적 연구

During the carbon-dioxide capture and storage(CCS) process, is captured from large point source, and then injected and stored in stable geological structure for thousands and more years. Inside the captured flow, various impurities, such as , , argon, etc, are included inevitably. These impurities affect on the CCS process on various aspects. In this study, we designed and built experimental facility to evaluate the various impurity effect on the pipeline flow, and analyzed the effect of argon ratio and pressure variation on the pressure drop of flow. By comparing experimental data with 4 kinds of pressure drop model, we figured out and recommended the Cicchitti's model since it showed most accurate result among compared models in this study.

Toward the Development and Deployment of Large-Scale Carbon Dioxide Capture and Conversion Processes

In light of the depletion of fossil fuels and the increased daily requirements for liquid fuels and chemicals, CO2 should indeed be regarded as a valuable C1 additional feedstock for sustainable manufacturing of liquid fuels and chemicals. Development and deployment of CO2 capture and chemical conversion processes are among the grand challenges faced by today’s scientists and engineers. Very few of the reported CO2 capture and conversion technologies have been employed for industrial installations on a large scale, where high-efficiency, cost/energy-effectiveness, and environmental friendliness are three keys factors. The CO2 capture technologies from stationary sources and ambient air based on solvents, solid sorbents, and membranes are discussed first. Transforming CO2 to liquid fuels and chemicals, which are presently produced from petroleum, through thermochemical, electrochemical, photochemical, and biochemical routes are discussed next. The relevant state-of-the-art computational methods and tools a...

Systematic study of aqueous monoethanolamine‐based CO2 capture process: model development and process improvement

AbstractIn this paper, we present improvements to postcombustion capture (PCC) processes based on aqueous monoethanolamine (MEA). First, a rigorous, rate‐based model of the carbon dioxide (CO2) capture process from flue gas by aqueous MEA was developed using Aspen Plus, and validated against results from the PCC pilot plant trials located at the coal‐fired Tarong power station in Queensland, Australia. The model satisfactorily predicted the comprehensive experimental results from CO2 absorption and CO2 stripping process. The model was then employed to guide the systematic study of the MEA‐based CO2 capture process for the reduction in regeneration energy penalty through parameter optimization and process modification. Important process parameters such as MEA concentration, lean CO2 loading, lean temperature, and stripper pressure were optimized. The process modifications were investigated, which included the absorber intercooling, rich‐split, and stripper interheating processes. The minimum regeneration energy obtained from the combined parameter optimization and process modification was 3.1 MJ/kg CO2. This study suggests that the combination of a validated rate‐based model and process simulation can be used as an effective tool to guide sophisticated process plant, equipment design and process improvement.

Carbon Dioxide Capture and Utilization by Alkanolamines in Deep Eutectic Solvent Medium

The major drawback of the aqueous alkanolamine-based carbon dioxide capture process is the high energy penalty for the regeneration of the absorbent. To overcome this weakness, we studied the absorption of CO2 in alkanolamines dissolved in greener and nontoxic deep eutectic solvents. Among the alkanolamines in various deep eutectic solvent media, 2-amino-2-methyl-1-propanol in choline chloride: urea (1:2) medium was found to exhibit the highest absorption capacity for CO2 gas. In addition to that, the value-added product, 2-amino-2-methyl-1-propanol carbamate, was obtained from all deep eutectic solvent medium, which was analyzed by Fourier transform infrared and 1H and 13C nuclear magnetic resonance spectroscopic techniques. Under optimized conditions, the maximum yield of 82%, 2-amino-2-methyl-1-propanol carbamate was obtained. The deep eutectic solvent used for the process has been recovered and reused for 4 cycles. Thus, the 2-amino-2-methyl-1-propanol in deep eutectic solvent medium emerges to be a n...

An intelligent modeling approach for prediction of thermal conductivity of CO2

In the design of a carbon dioxide capture and storage (CCS) process, the thermal conductivity of carbon dioxide is of special concern. Hence, it is quite important to search for a quick and accurate determination of thermal conductivity of CO2 for precise modeling and evaluation of such a process. To achieve this aim, a robust computing methodology, entitled least square support vector machine (LSSVM) modeling, which is coupled with an optimization approach, was used to model this transport property. The model was constructed and evaluated employing a comprehensive data bank (more than 550 data series) covering wide ranges of pressures and temperatures. Before constructing the model, outlier detection was performed on the whole data bank to diagnose and delete erroneous measurements and doubtful data from the experimental dataset. It was found that the proposed LSSVM model had a very accurate prediction of thermal conductivity of CO2 with an average absolute relative error of 0.79% and a coefficient of determination of 0.999. In addition, more than 90% of the experimental data points were estimated with an absolute relative error smaller than 2% by the developed model.

Characterization of ilmenite used as oxygen carrier in a 100 kW chemical-looping combustor for solid fuels

Chemical-looping combustion (CLC) is considered to be the most promising and economically viable process for carbon dioxide capture. The oxygen carrier has a central role in the chemical-looping combustion process. Ilmenite, a natural mineral composed of FeTiO3, has been extensively used as oxygen carrier in CLC systems due to its availability, relatively low cost and demonstrated reactivity. During the looping process ilmenite undergoes a series of chemical and mechanical transformations that eventually lead to the break-down of particles into smaller fragments, which are unfit for use in circulated fluidized bed (CFB) applications.In the present study a 100kW chemical-looping system was operated with ilmenite particles as oxygen carrier and with biomass char as fuel. Ilmenite particles were collected at the end of the run. The collected particles were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDS). Thermodynamic predictions of the expected compounds at the given conditions were also used to compare with the experimentally obtained results.The aim of the study was to understand the change in morphology and chemical compositions of the collected ilmenite particles and to relate them to the exposure conditions in the CLC reactor.It was found that the aging of the ilmenite particles could be distinguished based on the particle morphology. Furthermore, a possible mechanism for the transformation of the ilmenite particles during the cyclic chemical-looping process was proposed.

CO2 Capture in Wet and Dry Superbase Ionic Liquids

The solubility of carbon dioxide in five tetraalkylphosphonium superbase ionic liquids, namely the trihexyltetradecylphoshonium phenoxide, trihexyltetradecylphoshonium benzotriazolide, trihexyltetradecylphoshonium benzimidazolide, trihexyltetradecylphoshonium 1,2,3-triazolide, and trihexyltetradecylphoshonium 1,2,4-triazolide was studied experimentally under dry and wet conditions at 22 °C and at atmospheric pressure, using a gravimetric saturation technique. The effects of anion structure and of the presence or absence of water in the solution on the carbon dioxide solubility were then deduced from the data. 1H and 13C-NMR spectroscopy and ab initio calculations were also conducted to probe the interactions in these solutions, as carbon dioxide and water can compete in the ionic liquid structure during the absorption process. Additionally, the viscosity of selected superbase ionic liquids was measured under dry and wet conditions, in the presence or absence of CO2, to evaluate their practical application in carbon dioxide capture processes. Finally, the recyclability of the trihexyltetradecylphoshonium 1,2,4-triazolide under dry and wet conditions was determined to probe the ability of selected solvents to solubilize chemically a high concentration of carbon dioxide and then release it in a low energy demand process.

Corrosion of Carbon Steel in MDEA-Based CO2Capture Plants Under Regenerator Conditions: Effects of O2and Heat-Stable Salts

The corrosion behavior of carbon steel UNS K02600 in 50 wt% methyldiethanolamine solutions was investigated in the back-ground of the carbon dioxide (CO2) capture process in fossil fuel-fired power plants for the purpose of carbon capture and storage. A series of experiments was conducted under regenerator conditions (120°C) with different combinations of CO2 loading (0.3 mol/mol and 0.05 mol/mol), O2, and heat-stable salts (including sulfate, formate, and N,N-bis[2-hydroxyethyl] glycine). The corrosion behavior of carbon steel was investigated using electrochemical techniques (open circuit potential, linear polarization resistance, and potentiodynamic polarization), surface analytical techniques (scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction), and weight-loss methods. The results showed that the corrosion rate of carbon steel initially decreased and then stabilized with time in CO2-loaded methyldiethanolamine solution due to the formation of an iron carbonate (...

Simulation and exergy analysis of processes for CO<SUB align="right">2 capture and utilisation for methanol production

Carbon dioxide (CO2) capture and methanol production processes were simulated using Aspen RefSYS. Exergy analysis was done with EXCEL spreadsheet. Parametric study was done on the CO2 process to investigate the effects of absorber and reboiler pressure, absorber stages and amine circulation rate on CO2 absorption, CO2 recovery and process exergy efficiency. The result shows that stripper recovered almost 90% by mass of CO2 in the flue gas. The highest irreversibility in the CO2 capture plant occurred in the rich/lean heat exchanger (820516.24 MW); this is followed by the lean cooler (481343.23 MW) and the stripper (404273.57 MW). CO2 emissions reduction was 171,838.1 tonnes CO2/yr. For the methanol plant, the highest irreversibility occurred in the distillation column (25088.4 MW). The study concluded that onsite utilisation of CO2 from thermal plant would minimise CO2 leakage during transportation or storage.

Experimental study on CO2 capture by chilled ammonia process

Aqueous, ammonia-based CO2 capture is attractive because of its low cost, low heat energy requirement, high CO2 absorption capacity, low degradation rate, and ability to capture multiple pollutants simultaneously. The most serious problem of a carbon dioxide capture process that uses aqueous ammonia is a phenomenon involving ammonia vaporization known as ammonia slip. The chilled ammonia process (CAP) is an improved ammonia-based CO2 capture technology. Recent attention has been given to the process patented by Gal (2008), which involves a system operated at a low temperature to minimize the ammonia loss due to evaporation. This study focuses on the laboratory-scale experiment for analysis of the chilled ammonia process. The CO2 absorption ratio and amount of ammonia slip are measured at various operating conditions. The concentration of ammonia is fixed at 7wt.%, while the temperature of feed gas and liquid solution was varied from 2°C to 20°C. The effect of feed gas temperature and absorbent temperature on ammonia slip and CO2 absorption efficiency is examined experimentally. The results indicate that ammonia slip and CO2 absorption efficiency are changed significantly by varying the temperature of liquid solution, while feed gas temperature showed a trivial impact on the CO2 absorption ratio and ammonia slip. Moreover, when the absorber was operated at lean solution temperature and feed gas temperature of 7°C and 10°C, respectively, the CO2 absorption efficiency was above 85% and ammonia slip was minimized.

Life cycle assessment of a hypothetical Canadian pre-combustion carbon dioxide capture process system

The methodology of life cycle assessment was applied for evaluating the environmental performance of a Saskatchewan lignite integrated gasification combined cycle (IGCC)-based electricity generation plant with and without the pre-combustion CO2 capture process. A comparison between the IGCC systems (with and without CO2 capture) and the competing lignite pulverized coal electricity generating station was conducted to reveal which technology offers more positive environmental effects. The results showed significant reduction of GHG emissions where both post- and pre-combustion CO2 capture processes are applied. With the application of the CO2 removal technology, GHG emissions were reduced by 27–86%. The performances of the IGCC systems were superior to those of the pulverized coal systems. However, in terms of other environmental impacts, multiple environmental trade-offs are involved depending on the capture technology. For the post-combustion CO2 capture process system, it was observed that the environmental impact was shifted from the air compartment to the soil and water compartments. The IGCC systems showed the same tendency of shifting from air pollution to soil and water pollution, but the amount of pollution is less significant. This is likely because the IGCC system operates at higher efficiencies; hence, it requires less fuel and produces fewer emissions.

Pilot plant results for a precipitating potassium carbonate solvent absorption process promoted with glycine for enhanced CO2 capture

The absorption performance of a glycine promoted precipitating potassium carbonate (K2CO3) solvent absorption process for carbon dioxide (CO2) capture has been presented using a laboratory scale pilot plant. Glycine has been added as a rate promoter to 40–45wt.% K2CO3 solutions to examine the enhancement of the CO2 absorption process. The laboratory scale pilot plant has been designed to capture 4–10kg/hr of CO2 from an air/CO2 mixture at a feed gas rate of 30–55kg/hr. Performance data of the absorber including pressure drop, holdup and CO2 removal efficiency has been collected from the pilot plant and presented for a range of operating conditions. The addition of glycine was found to improve the CO2 recovery rate by up to 6 times whilst also slightly increasing the pressure drop and holdup measured in the packed absorption column which is likely due to a reduction in the surface tension of the solvent. Additionally, increasing the K2CO3 solvent concentration and operating with a higher CO2 feed gas concentration were found to increase the CO2 recovery results. Finally performance data from the absorber has been used to validate an Aspen Plus simulation of the system.

Analysis of carbon dioxide-to-methanol direct electrochemical conversion mediated by an ionic liquid

An intensified process for carbon dioxide capture and conversion is proposed and analyzed, considering an electrochemical parallel plate reactor which processes a CO2-charged stream from an absorption unit at 40°C and atmospheric pressure and where the target product of the conversion is methanol.The task-specific ionic liquid 1-(3-aminopropyl)-3-methylimidazolium bromide was selected, synthesized and characterized. This ionic liquid has shown a good absorption capacity, high ionic conductivity, high chemical–electrochemical stability and acts as a charged intermediate (CO2*−) stabilizer, enabling the electrochemical reduction of absorbed CO2.The electrical energy in the electrochemical reactor was estimated to be 8.683kWhkg (CO2)−1 or 115.16g (CO2) kWh−1, too high to ensure the environmental sustainability of the process. A low concentration of carbon dioxide in the liquid phase, at ambient conditions, implies the need for a high electrode area for the process and is a major hindrance to improving the economy of the process.

The use of carbonic anhydrase to accelerate carbon dioxide capture processes

The chemical absorption of CO2 into a monoethanolamine solvent is currently the most widely accepted commercial approach to carbon dioxide capture. However, the subsequent desorption of CO2 from the solvents is extremely energy intensive. Alternative solvents are more energy efficient, but their slow reaction kinetics in the CO2 absorption step limits application. The use of a carbonic anhydrase (CA) enzyme as a reaction promoter can potentially overcome this obstacle. Native, engineered and artificial CA enzymes have been investigated for this application. Immobilization of the enzyme within the gas absorber or in a membrane format can increase enzyme stability and avoid thermal denaturation in the stripper. However, immobilization is only effective if the mass transfer of carbon dioxide through the liquid phase to reach the immobilization substrate does not become rate controlling. Further research should also consider the process economics of large-scale enzyme production and the long-term performance of the enzyme under real flue gas conditions. © 2014 Society of Chemical Industry

A life cycle assessment study of a hypothetical Canadian oxy-fuel combustion carbon dioxide capture process

For at least the next few decades, fossil fuels will be used to supply energy globally, and without a proper control technique, carbon dioxide (CO2) atmospheric emissions will continue to increase and pose an even more serious threat to human and environment. Therefore, the use of an effective carbon dioxide capture technology has become important in ensuring reduction of CO2 emissions. However, more raw materials and energy are required for the CO2 capture systems operation. Consequently, it is necessary to evaluate the environmental performance of the complete life cycle of the CO2 capture process in order to fully understand its environmental impacts. This study presents a life cycle assessment study on a hypothetical oxy-fuel combustion CO2 capture system in Saskatchewan, Canada. The study analyses the oxy-fuel carbon dioxide capture and compares it with the lignite coal fired electrical generating station that has no capture system. TRACI, the life cycle impact assessment (LCIA) method, is used to convert life cycle inventory data into environmental impacts. The observed results include a reduction in global warming and emissions to air impact categories due to capture of particulate matter (PM), trace elements, CO2 and acid gases. However, the emissions captured would eventually leach to soil and then to the ground water when landfilled. Thus, an increase in the impact categories associated with soil and water was also observed.

Performance of an ammonia-based CO2 capture pilot facility in iron and steel industry

In the present paper, we report experimental results from an ammonia-based carbon dioxide (CO2) capture process operation. A pilot facility of 1000Nm3/h to remove CO2 from blast furnace gas (BFG, ∼23% of CO2) has been constructed in an iron-making workplace, resulting in the CO2 production of 10t-CO2/d. Steam generated from waste heat recovery system has been successfully supplied to the CO2 removal unit for regeneration of absorbent solution and concentration of ammonia. Technical performance shows that the facility can capture CO2 at the rate of 90% with the purity of 99% in the product CO2 stream. Results of process simulations and process operation confirmed the improvement of process economics through heat integration and pressurized absorption. Thermal energy requirement for the regeneration of absorbent solution could be lowered to 2.5GJ/t-CO2. Accordingly, the ammonia slip has been reduced to the level of ∼10ppm in both columns of absorption and regeneration. From this study we found that the technology could be a competitive option for the economic reduction of CO2 emissions in large stationary point sources such as in iron and steel industry. Conclusively, we insist that the developed technology is extremely functional if there exists waste heat at low temperature.