Role of solvents in CO2 capture processes : the review of selection and design methods

Solvent selection and design are imperative in the CO2 capture process. The efficiency and the overall cost of the process are directly affected by the solvent as a consequence of the effect of solvent on factors such as CO2 absorption capacity, size of equipment, and solvent regeneration energy. This review paper aims to review the most important solvents and mixtures of solvents, absorbing CO2 via chemisorption, physisorption and chemi-physisoprtion. Characteristic and structure of different solvents are presented with the advantages and disadvantages of each being highlighted. Mixtures of solvents include chemical or physical solvents only, and combinations of physical and chemical solvents are categorised. In addition to common solvents, phase change solvents are also described. Once a comprehensive list of solvents is presented, different methods of solvent selection and design are illustrated, namely methods involving experiments, process and equilibrium models, predictive models, and computer-aided molecular design (CAMD). The importance of integrated solvent and process selection and design is also discussed. The most recent and selected progress studies in each section are reviewed in detail

CO₂ capture using ionic liquids: thermodynamic modeling and molecular dynamics simulation

Global climate change is happening now, and the average temperature of Earth is rising. Several evidences show that one of the main reasons for global warming is the increased concentration of greenhouse gases (GHGs) in the atmosphere, particularly carbon dioxide (CO₂). CO₂ is mostly producing from burning fossil fuels. One of the effective strategies to reduce CO₂ emissions is implementing carbon capture in fossil fuel power plants. Current post-combustion carbon capture techniques typically employ amine-based solvents, such as monoethanolamine (MEA), for the absorption of CO₂. Although alkanol amines have an acceptable absorption capacity, their high vapor pressure, solvent loss during desorption, and high corrosion rate make amines absorption plants energy-intensive. In recent years, Ionic Liquids (ILs) have been emerged as promising alternative solvents for physisorption and chemisorption of acid gases due to their unique physiochemical properties, including negligible vapor pressure, high thermal stability, tunability, and being environmentally safe. ILs require to be screened based on technical, economical, and environmental aspects. The main challenges of using ILs are increasing CO₂ capture capacity of ILs, and detailed understanding of the diffusivity of CO₂ in ILs, the effect of additives in solubility, selectivity features of ILs, phase behavior of gas-IL systems, and absorption mechanism. These challenges can be addressed using either experiment, thermodynamic modeling, and/or molecular simulations. In this study, the potential of the screened imidazolium-based ILs is investigated using thermodynamic modeling. The extended Peng–Robinson (PR) and Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) EOSs are implemented to evaluate the solubility and selectivity of CO₂ in pure ILs and their mixture with water and toluene. The effects of water and toluene on solubility and viscosity of ILs are investigated. Low concentrations of water (< 1 wt%) do not affect solubility; however, with increasing water concentration, the solubility of CO2 is decreased. On the other hand, with increasing water content, the IL viscosity significantly decreases, which is in the favor of using viscous ILs for CO₂ separation. In this thesis, Molecular Dynamics (MD) simulation is performed to determine the properties of ILs ([Bmim][BF₄] and [Bmim][Ac]), their structures, and molecular dynamics. A great agreement is noticed between the density and viscosity of the studied ILs from MD simulations and experimental data, indicating the accuracy of our simulation runs. This study also includes the effect of temperature and anion type on the structuring of ions and their self-diffusivities. Bulk systems of ILs and CO₂ are studied to evaluate the influence of temperature and types of ions on the diffusivity of CO₂ in the solvent as well as structural characteristics. A comprehensive analysis of the characteristics of the interface of IL/CO₂ is performed to explore species distribution, gas behavior at the interface, and molecule orientation. At the interface, CO₂ creates a dense layer which interrupts the association of cations and anions, leading to a decrease in the surface tension. In addition, a comprehensive study on hydrophilic IL, 1-Butyl-3-methylimidazolium acetate or [Bmim][Ac], is conducted to evaluate the thermophysical properties, excess energy, structure, and dynamic characteristics of IL/Water and IL/Water/CO2 systems, using MD simulation approach. The effect of water on radial distribution functions, coordination numbers, water clusters, hydrogen bonding, and diffusivity coefficients of the ions is assessed. The presence of water in IL mixture, even at high concentrations of water (>0.8 mole fraction), increases the diffusivity of cation, anion, water, and CO2 molecules in the mixture due to hydrophilicity of [Bmim][Ac] IL. MD simulations generate reliable and accurate results while dealing with systems including water, CO₂, and IL for carbon capture. In this thesis, novel and robust computational approaches are also introduced to estimate the solubility of CO₂ in a large number of ILs within a wide range of temperatures and pressures. Four connectionist tools- Least Square Support Vector Machine (LSSVM), Decision Tree (DT), Random Forest (RF), and Multilinear Regression (MLR)- are employed to obtain CO₂ solubility in a variety of ILs based on thermodynamic properties and Quantitative Structure-Activity Relationship (QSPR) model. Among different types of descriptors, the most important input variables (e.g., Chi_G/D 3D and Homo/Lumo fraction (anion); SpMax_RG and Disps (cation)) are selected using Genetic Algorithm (GA)-MLR method. A great agreement between the predicted values and experimental measurements is attained while using RF and DT techniques developed based on descriptors and thermodynamics properties. The structural descriptors-based models are more accurate and robust than those built on critical properties

CO2 CAPTURE PROJECT - AN INTEGRATED, COLLABORATIVE TECHNOLOGY DEVELOPMENT PROJECT FOR NEXT GENERATION CO2 SEPARATION, CAPTURE AND GEOLOGIC SEQUESTRATION

The CO{sub 2} Capture Project (CCP) is a joint industry project, funded by eight energy companies (BP, ChevronTexaco, EnCana, Eni, Norsk Hydro, Shell, Statoil, and Suncor) and three government agencies (1) European Union (DG Res & DG Tren), (2) Norway (Klimatek) and (3) the U.S.A. (Department of Energy). The project objective is to develop new technologies, which could reduce the cost of CO{sub 2} capture and geologic storage by 50% for retrofit to existing plants and 75% for new-build plants. Technologies are to be developed to ''proof of concept'' stage by the end of 2003. The project budget is approximately $24 million over 3 years and the work program is divided into eight major activity areas: (1) Baseline Design and Cost Estimation--defined the uncontrolled emissions from each facility and estimate the cost of abatement in$/tonne CO{sub 2}. (2) Capture Technology, Post Combustion: technologies, which can remove CO{sub 2} from exhaust gases after combustion. (3) Capture Technology, Oxyfuel: where oxygen is separated from the air and then burned with hydrocarbons to produce an exhaust with high CO{sub 2} for storage. (4) Capture Technology, Pre -Combustion: in which, natural gas and petroleum coke are converted to hydrogen and CO{sub 2} in a reformer/gasifier. (5) Common Economic Model/Technology Screening: analysis and evaluation of each technology applied to the scenarios to provide meaningful and consistent comparison. (6) New Technology Cost Estimation: on a consistent basis with the baseline above, to demonstrate cost reductions. (7) Geologic Storage, Monitoring and Verification (SMV): providing assurance that CO{sub 2} can be safely stored in geologic formations over the long term. (8) Non-Technical: project management, communication of results and a review of current policies and incentives governing CO{sub 2} capture and storage. Technology development work dominated the past six months of the project. Numerous studies are making substantial progress towards their goals. Some technologies are emerging as preferred over others. Pre-combustion Decarbonization (hydrogen fuel) technologies are showing good progress and may be able to meet the CCP's aggressive cost reduction targets for new-build plants. Chemical looping to produce oxygen for oxyfuel combustion shows real promise. As expected, post-combustion technologies are emerging as higher cost options that may have niche roles. Storage, measurement, and verification studies are moving rapidly forward. Hyper-spectral geo-botanical measurements may be an inexpensive and non-intrusive method for long-term monitoring. Modeling studies suggest that primary leakage routes from CO{sub 2} storage sites may be along wellbores in areas disturbed by earlier oil and gas operations. This is good news because old wells are usually mapped and can be repaired during the site preparation process. Many studies are nearing completion or have been completed. Their preliminary results are summarized in the attached report and presented in detail in the attached appendices

2009 Annual Progress Report: DOE Hydrogen Program

This report summarizes the hydrogen and fuel cell R&D activities and accomplishments of the DOE Hydrogen Program for FY2009. It covers the program areas of hydrogen production and delivery; fuel cells; manufacturing; technology validation; safety, codes and standards; education; and systems analysis

Energy: A continuing bibliography with indexes, issue 38

This bibliography lists 1367 reports, articles and other documents introduced into the NASA scientific and technical information system from April 1, 1983 through June 30, 1983