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An individual-based simulation model, EFIMOD, was used to simulate the response of forest ecosystems to additional nitrogen deposition. The general scheme of the model includes forest growth depending on nitrogen uptake by plants and mineralization of soil organic matter. The mineralization rate is dependent on nitrogen content in litter and forest floor horizons. Three large forest areas in Central European Russia with a total area of about 17 000 km2 in distinct environmental conditions were chosen. Simulations were carried out with two climatic scenarios (stable climate and climate change) and different levels of nitrogen deposition. The simulations showed that increased nitrogen deposition leads to increased productivity of trees, increased organic matter content in organic soil horizons, and an increased portion of deciduous tree species. For the climate change scenario, the same effects on productivity and shifts in species composition were predicted but there was a negative effect on the accumulation of organic matter in soil. [ABSTRACT FROM AUTHOR]

Soil carbon storage simulated by the Coupled Model Intercomparison Project (CMIP5) models varies 6-fold for the present day. We show that this range already exists at the beginning of the historical simulations and demonstrate that it is mostly an artifact of the representation of microbial decomposition and its response during the spin-up procedure used by the models. The 6-fold range in soil carbon, once established, is maintained through the present and to 2100 almost unchanged even under a strong business-as-usual emissions scenario. By highlighting the role of the response of decomposition to spin-up in explaining why current CMIP5 soil carbon stores vary widely, we identify the need to better constrain the outcome of this procedure as a means to reduce uncertainty in transient simulations. [ABSTRACT FROM AUTHOR]

The aim of our study was to use the coupled climate-carbon cycle model HadCM3C to quantify climate impact of ecosystem changes over recent decades and under future scenarios, due to changes in both atmospheric CO2 and surface albedo. We use two future scenarios - the IPCC SRES A1B scenario, and a climate stabilisation scenario (2C20), allowing us to assess the impact of climate mitigation on results. We performed a pair of simulations under each scenario - one in which vegetation was fixed at the initial state and one in which vegetation changes dynamically in response to climate change, as determined by the interactive vegetation model within HadCM3C. In our simulations with interactive vegetation, relatively small changes in global vegetation coverage were found, mainly dominated by increases in scrub and needleleaf trees at high latitudes and losses of broadleaf trees and grasses across the Amazon. Globally this led to a loss of terrestrial carbon, mainly from the soil. Global changes in carbon storage were related to the regional losses from the Amazon and gains at high latitude. Regional differences in carbon storage between the two scenarios were largely driven by the balance between warming-enhanced decomposition and altered vegetation growth. Globally, interactive vegetation reduced albedo acting to enhance albedo changes due to climate change. This was mainly related to the darker land surface over high latitudes (due to vegetation expansion, particularly during winter and spring); small increases in albedo occurred over the Amazon. As a result, there was a relatively small impact of vegetation change on most global annual mean climate variables, which was generally greater under A1B than 2C20, with markedly stronger local-to-regional and seasonal impacts. Globally, vegetation change amplified future annual temperature increases by 0.24 and 0.15 K (under A1B and 2C20, respectively) and increased global precipitation, with reductions in precipitation over the Amazon and increases over high latitudes. In general, changes were stronger over land - for example, global temperature changes due to interactive vegetation of 0.43 and 0.28 K under A1B and 2C20, respectively. Regionally, the warming influence of future vegetation change in our simulations was driven by the balance between driving factors. For instance, reduced tree cover over the Amazon reduced evaporation (particularly during summer), outweighing the cooling influence of any small albedo changes. In contrast, at high latitudes the warming impact of reduced albedo (particularly during winter and spring) due to increased vegetation cover appears to have offset any cooling due to small evaporation increases. Climate mitigation generally reduced the impact of vegetation change on future global and regional climate in our simulations. Our study therefore suggests that there is a need to consider both biogeochemical and biophysical effects in climate adaptation and mitigation decision making. [ABSTRACT FROM AUTHOR]

Substantial amounts of mercury (Hg) in the terrestrial environment reside in soils and are associated with soil organic carbon (C) pools, where they accumulated due to increased atmospheric deposition due to anthropogenic activities. The purpose of this study was to examine potential sensitivity of surface soil Hg pools to global change variables, particularly affected by predicted changes in soil C pools, in the contiguous US. To investigate, we included a soil Hg component in the Community Land Model based on empirical statistical relationships between soil Hg /C ratios and precipitation, latitude and clay; and subsequently explored the sensitivity of soil C and soil Hg densities (i.e. areal-mass) to climate scenarios in which we altered annual precipitation, carbon dioxide (CO2) concentrations, and temperature. Our model simulations showed that current sequestration of Hg in the contiguous US accounted for 15 230metric tons of Hg in the top 0-40 cm of soils. In the simulations, these soil Hg pools were most sensitive to changes in precipitation because of strong effects on soil C pools plus a direct effect of precipitation on soil Hg /C ratios. Soil Hg pools were predicted to increase beyond present-day values following an increase in precipitation amounts and decrease following a reduction in precipitation. We found pronounced regional differences in sensitivity of soil Hg to precipitation, which were particularly high along high-precipitation areas along the West and East Coasts. Modeled increases in CO2 concentrations to 700 ppm stimulated soil C and Hg densities, while increased air temperatures had small negative effects on soil C and Hg. The combined effects of increased CO2, increased temperature, and increased or decreased precipitation were strongly governed by precipitation and CO2 showing pronounced regional patterns. Based on these results, we conclude that the combination of precipitation and CO2 should be emphasized when assessing how climate-induced changes in soil C may affect sequestration of Hg in soils. [ABSTRACT FROM AUTHOR]

Carbon dioxide emissions from wild and anthropogenic fires return the carbon absorbed by plants to the atmosphere, and decrease the sequestration of carbon by land ecosystems. Future climate warming will likely increase the frequency of fire-triggering 5 drought; so that the future terrestrial carbon uptake will depend on how fires respond to altered climate variation. In this study, we modelled the role of fires in the global terrestrial carbon balance for 1901-2012, using the global vegetation model ORCHIDEE equipped with the SPITFIRE model. We conducted two simulations with and without the fire module being activated, with a static land cover. The simulated global fire car10 bon emissions for 1997-2009 are 2.1PgCyr-1, which is close to the 2.0 PgCyr-1 as given by the GFED3.1 data. The simulated land carbon uptake after accounting for emissions for 2003-2012 is 3.1 PgCyr-1, within the uncertainty of the residual carbon sink estimation (2.8±0.8 PgCyr-1). Fires are found to reduce the terrestrial carbon uptake by 0.32 PgCyr-1 over 1901-2012, that is 20% of the total carbon sink in a world 15 without fire. The fire-induced land sink reduction (SRfire) is significantly correlated with climate variability, with larger sink reduction occurring in warm and dry years, in particular during El Niño events. Our results suggest a symmetrical "respiration equivalence" by fires. During the ten lowest SRfire years (SRfire = 0.17 PgCyr-1), fires mainly compensate the heterotrophic respiration that would happen if no fires had occurred. By 20 contrast, during the ten highest SRfire fire years (SRfire = 0.49 PgCyr-1), fire emissions exceed their "respiration equivalence" and create a substantial reduction in terrestrial carbon uptake. Our finding has important implication for the future role of fires in the terrestrial carbon balance, because the capacity of terrestrial ecosystems to sequester carbon will be diminished by future climate change characterized by increased drought 25 and more severe El Niño events. [ABSTRACT FROM AUTHOR]

In order to develop a system to estimate a country-scale soil organic carbon stock change (SCSC) in agricultural lands in Japan that enables to take account effect of land-use changes, climate, different agricultural activity and nature of soils, a spatially- explicit model simulation system using Rothamsted Carbon Model (RothC) integrated with spatial and temporal inventories was developed. Future scenarios on agricultural activity and land-use change were prepared, in addition to future climate projections by global climate models, with purposely selecting rather exaggerated and contrasting set of scenarios to assess system's sensitivity as well as to better factor out direct human influence in the SCSC accounting. Simulation was run from year 1970 to 2008, and to year 2020, with historical inventories and future scenarios involving target set in agricultural policy, respectively, and subsequently until year 2100 with no temporal changes in land-use and agricultural activity but with varying climate to investigate course of SCSC. Results of the country-scale SCSC simulation have indicated that conversion of paddy fields to croplands occurred during past decades, as well as a large conversion of agricultural fields to settlements or other lands that have occurred in historical period and would continue in future, could act as main factors causing greater loss of soil organic carbon (SOC) at country-scale, with reduction organic carbon input to soils and enhancement of SOC decomposition by transition of soil environment to aerobic conditions, respectively. Scenario analysis indicated that an option to increase organic carbon input to soils with intensified rotation with suppressing conversion of agricultural lands to other land-use types could achieve reduction of CO2 emission due to SCSC in the same level as that of another option to let agricultural fields be abandoned. These results emphasize that land-use changes, especially conversion of the agricultural lands to other land-use types by abandoning or urbanization accompanied by substantial changes in the rate of organic carbon input to soils, could cause a greater or comparable influence on country-scale SCSC compared with changes in management of agricultural lands. A net-net based accounting on SCSC showed potential influence of variations in future climate on SCSC, that highlighted importance of application of process-based model for estimation of this quantity. Whereas a baseline-based accounting on SCSC was shown to have robustness over variations in future climate and effectiveness to factor out direct human-induced influence on SCSC. Validation of the system's function to estimate SCSC in agricultural lands, by comparing simulation output with data from nation-wide stationary monitoring conducted during year 1979-1998, suggested that the system has an acceptable levels of validity, though only for limited range of conditions at current stage. In addition to uncertainties in estimation of the rate of organic carbon input to soils in different land-use types at large-scale, time course of SOC sequestration, supposition on land-use change pattern in future, as well as feasibility of agricultural policy planning are considered as important factors that need to be taken account in estimation on a potential of country-scale SCSC. [ABSTRACT FROM AUTHOR]

The effect of an EU emission trading scheme (EU ETS) on CO2 abatement technology development is limited, according to many empirical studies. This is the result of an existing low carbon price and the future uncertainty of the development of the carbon market. Carbon price stabilisation mechanisms, especially the carbon price floor, may serve to supplement the ETS and cope with this problem. We are concerned with how the carbon price floor affects the investment in carbon abatement technology, the resulting CO2 abatement, and how to best design such a carbon floor price. In this paper, we focus on carbon capture and storage (CCS) technology by building a CCS investment and operation decision model based on real options theory. We consider investment timing and CCS operation flexibility and we also design a model for carbon price evolution with a carbon price floor using the Monte Carlo simulation method. We determine the floor prices above which immediate CCS investment is occuring, and those at which CO2 emissions can be eliminated. According to the simulation results, the carbon price floor has a significant effect on promoting CCS investment. The marginal effect of an increasing carbon price floor first rises and then falls; when the floor price reaches a threshold value, its marginal effect becomes minimal. Based on the simulation results, the carbon floor price for EU ETS could be set at about 20 EUR/t CO2 to stimulate the CCS investment, while it should be increased to 30 EUR/t CO2 to sufficiently promote CO2 abatement. [ABSTRACT FROM AUTHOR]

Capturing carbon dioxide (CO2) from large point sources and depositing it in a geological formation is an efficient way of decreasing CO2 concentration in the atmosphere. A comprehensive study is required to perform a safe and efficient CO2 capture and storage (CCS) project. The study includes different steps, such as selecting proper underground storage and keeping track of CO2 behavior in the storage environment. Numerical reservoir simulators are the conventional tools used to implement such an analysis. The intricacy of simulating multiphase flow, having a large number of time steps required to study injection and post-injection periods of CO2 sequestration, a highly heterogeneous reservoir, a large number of wells, etc., will lead to a complicated reservoir model. A single realization for such a reservoir takes hours to run. Additionally, a thorough understanding of the CO2 sequestration process requires multiple realizations of the reservoir model. Consequently, using a conventional numerical simulator makes the computational cost of the analysis too high to be practical. In this paper, we examine the application of a relatively new technology, the Surrogate Reservoir Model (SRM), as an alternative tool to solve the aforementioned problems. SRM is a replica of full-field reservoir simulation models. It can generate outputs in a very short time with reasonable accuracy. These characteristics make SRM a unique tool in CO2 sequestration modeling. This paper proposes developing an SRM for a CO2 sequestration project ongoing in the SACROC unit to model pressure behavior and phase saturation distributions during different time steps of the CO2 storage process. [ABSTRACT FROM AUTHOR]

Although the world understands the possible threat of the future of climate changes, there remain serious barriers to be resolved in terms of policy decisions. The scientific and the societal uncertainties in the climate change policies must be the large part of this barrier. Following the Paris Agreement, the world comes to the next stage to decide the next actions. Without a view of risk management, any decision will be “based on neglecting alternatives” behavior. The Ministry of the Environment, Japan has established an inter-disciplinary research project, called Integrated Climate Assessment—Risks, Uncertainties, and Society (ICA-RUS) conducted by Dr. Seita Emori, National Institute for Environmental Studies. ICA-RUS consists of five research themes, i.e., (1) synthesis of global climate risks, (2) optimization of land, water, and ecosystem for climate risks, (3) analysis of critical climate risks, (4) evaluation of climate risk management options, and (5) interactions between scientific and social rationalities. We participated in the fourth theme to provide the quantitative assessment of technology options and policy measures by integrating assessment model simulations. We employ the multi-model approach to deal with the complex relationships among various fields such as technology, economics, and land use changes. Four different types of integrated assessment models, i.e., MARIA-14 (Mori), EMEDA (Washida), GRAPE (Kurosawa), and AIM (Masui), participate in the fourth research theme. These models contribute to the ICA-RUS by providing two information categories. First, these models provide common simulation results based on shared socioeconomic pathway scenarios and the shared climate policy cases given by the first theme of ICA-RUS to see the ranges of the evaluation. Second, each model also provides model-specific outcomes to answer special topics, e.g., geoengineering, sectoral trade, adaptation, and decision making under uncertainties. The purpose of this paper is to describe the outline and the main outcomes of the multi-model inter-comparison among the four models with a focus upon the first and to present the main outcomes. Furthermore, in this study, we introduce a statistical meta-analysis of the multi-model simulation results to see whether the differently structured models provide the inter-consistent findings. The major findings of our activities are as follows: First, in the stringent climate target, the regional economic losses among models tend to diverge, whereas global total economic loss does not. Second, both carbon capture and storage (CCS) as well as BECCS are essential for providing the feasibility of stringent climate targets even if the deployment potential varies among models. Third, the models show small changes in the crop production in world total, whereas large differences appear between regions. Fourth, the statistical meta-analysis of the multi-model simulation results suggests that the models would have an implicit but common relationship between gross domestic product losses and mitigation options even if their structures and simulation results are different. Since this study is no more than a preliminary exercise of the statistical meta-analysis, it is expected that more sophisticated methods such as data mining or machine learning could be applicable to the simulation database to extract the implicit information behind the models. [ABSTRACT FROM AUTHOR]

CO 2 carriers are considered as a solution for CO 2 transport as a part of Carbon Capture and Storage. CO 2 carriers' design is similar to that of commercial liquefied gas carriers and core technology of liquefied gas carriers is to handle boil-off gas during voyages. This paper introduced newly developed CO 2 boil-off gas re-liquefaction processes making use of cold LNG fuel and investigated economic feasibility of newly developed processes by comparison with a conventional boil-off gas re-liquefaction process. New processes enabled considerable main equipment costs saving and additional fuel cost saving for re-liquefying boil-off gas. Simulation study results showed total amount of boil-off gas in a LNG fueled CO 2 carrier could be re-liquefied by LNG fuel consumed during the voyage and comparative cost assessment results demonstrated those newly developed processes could be applied into a LNG fueled CO 2 carrier with insignificant additional cost. The finding of this paper confirms those newly introduced processes are technically and commercially feasible at present and will contribute to growing the potential market of LNG as a marine fuel as well as commercializing CCS technology by providing more cost-effective solution for CO 2 shipping. [ABSTRACT FROM AUTHOR]

This paper studies the performance of a coal-fired power plant integrated with Ca-looping CO 2 capture system with recarbonation process. The Ca-looping CO 2 capture system with/without the recarbonation process are simulated using the ASPEN PLUS™ software and integrated in a coal-fired power plant with the net system efficiency of 41.57%. Simulation results of the two systems are compared, and a sensitivity analysis of the key parameters is taken. The results show that, when the CO 2 capture rate is 85%, the net system efficiency of the coal-fired power plant integrated with the traditional Ca-looping CO 2 capture system without recarbonation process is 30.66%. The efficiency penalty is 10.91% compared with that of the benchmark coal-fired power plant without CO 2 capture. While the net efficiency of the coal-fired power plant integrated with the Ca-looping CO 2 capture system with recarbonation process is 34.3% and the efficiency penalty is only 7.27%. The analysis results show that reducing the amounts of both calcium sorbents and the fresh sorbent supplement in cycles can further improve the efficiency of the overall system. The achievements from this paper will provide the valuable reference for the CO 2 capture from the coal-fired power plant with lower energy consumption. [ABSTRACT FROM AUTHOR]

Integrated energy systems (IESs) can improve energy efficiency and reduce carbon emissions, essential for achieving peak carbon emissions and carbon neutrality. This study investigated the characteristics of the CHP model considering P2G and carbon capture systems, and a two-stage robust optimization model of the electricity-heat-gas-cold integrated energy system was developed. First, a CHP model considering the P2G and carbon capture system was established, and the electric-thermal coupling characteristics and P2G capacity constraints of the model were derived, which proved that the model could weaken the electric-thermal coupling characteristics, increase the electric power regulation range, and reduce carbon emissions. Subsequently, a two-stage robust optimal scheduling model of an IES was constructed, in which the objective function in the day-ahead scheduling stage was to minimize the start-up and shutdown costs. The objective function in the real-time scheduling stage was to minimize the equipment operating costs, carbon emission costs, wind curtailment, and solar curtailment costs, considering multiple uncertainties. Finally, after the objective function is linearized with a ψ-piecewise method, the model is solved based on the C&CG algorithm. Simulation results show that the proposed model can effectively absorb renewable energy and reduce the total cost of the system. [ABSTRACT FROM AUTHOR]

Oxy-fuel combustion is a next-generation combustion technology that shows promise to address the need of low-cost carbon capture from fossil fueled power plants. Oxy-fuel combustion requires expensive preprocessing in an air separation unit to separate pure oxygen from air for the combustion process, which reduces the overall efficiency of the process. This paper employs ASPEN Plus process simulation software to model a simple oxy-fuel combustor and investigates the effect of various parameters on the energy output. The composition of the flue gas is carefully examined. The results of this study provide a starting point for optimized oxy-fuel combustion operation for maximum energy output, which will be crucial for future deployment of oxy-fuel combustion technology. [ABSTRACT FROM AUTHOR]

The combined removal of SO2 and CO2 using aqueous ammonia has many advantages over the conventional processes, such as the ability to capture multiple pollutants, the low cost of absorbent, high CO2 loading capacity, and the capacity to regenerate solvent at low temperature. In this paper, a closed-loop CO2 absorption-desorption process integrated with packed column flue gas desulfurization system was investigated. The CO2 absorption was modeled using the rigorous rate-based RateFrac model in Aspen Plus, whereas the SO2 column and CO2 stripper were modeled based on the RadFrac equilibrium model. The thermodynamic properties of the components were estimated with the Electrolyte NRTL model. The model was coupled with chemical equilibrium and kinetic reactions of the NH3-CO2-H2O and NH3-SO2-H2O system. The predicted results of temperature profile, variation in CO2 concentration along the column, SO2 removal efficiency, and CO2 separation rates agreed with published experimental results. To optimize the operating conditions, the impacts of performance parameters are investigated including flue gas temperature, concentration of CO2 and SO2 in flue gases, and the temperatures of the lean solution and ammoniated water. Furthermore, the performance efficiency of the stripper column is analyzed in terms of reboiler heat duty and CO2 regeneration rate, for the stripper operating pressure range of 2-20 bar and the stripper inlet temperature range of 60-105 °C. The results show that the suggested model is an adequate approach for the combined removal of CO2 and SO2 from the stack gases. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the potential use of renewable energy sources (various sorts of biomass) and solid wastes (municipal wastes, sewage sludge, meat and bone meal etc.) in a co-gasification process with coal to co-generate hydrogen and electricity with carbon capture and storage (CCS). The paper underlines one of the main advantages of gasification technology, namely the possibility to process lower grade fuels (lower grade coals, renewable energy sources, solid wastes etc.), which are more widely available than the high grade coals normally used in normal power plants, this fact contributing to the improvement of energy security supply. Based on a proposed plant concept that generates 400–500 MW net electricity with a flexible output of 0–200 MWth hydrogen and a carbon capture rate of at least 90%, the paper develops fuel selection criteria for coal blending with various alternative fuels for optimizing plant performance e.g. oxygen consumption, cold gas efficiency, hydrogen production and overall energy efficiency. The key plant performance indicators were calculated for a number of case studies through process flow simulations (ChemCAD). [Copyright &y& Elsevier]

Abstract: The storage of CO2 in deep saline aquifers is due to the large available capacities and the common occurrence of these formations one of the major options for carbon dioxide sequestration. Besides the multiphase flow aspects geochemical, thermal and mechanical processes may alter the conditions within the reservoir as well as in the cap rock. Whereas single aspects of these processes can be investigated with experiments a multi-process simulator allows evaluating their combined consequences for the storage system over short and long time scales. In this paper the newly coupled software ECLIPSE-OpenGeoSys is presented that allows a combined simulation of multiphase flow, transport and geochemical reactions. ECLIPSE provides a fast and efficient solution for the multiphase flow whereas the open-source scientific software OpenGeoSys is used for calculating transport and geochemical reactions. This paper presents the code structure of the interface. Furthermore the coupled software is successfully applied to benchmarks [Copyright &y& Elsevier]

Abstract: A significant number of efforts are underway to develop and assess technologies that will lead to technically and economically viable routes to reduce the CO2 emissions of fossil energy systems, particularly coal-fired power plants. Developing technologies to reduce emissions from these sources is essential for controlling atmospheric levels of CO2 because of the widespread reliance on coal as an inexpensive and abundant energy source. Two major systems-level design challenges exist. The first is how to design new plants that incorporate CCS technology. The second is how to retrofit existing plants to capture CO2. Both design challenges can benefit from an optimization approach, which considers the application of multiple potential technologies and analyzes ways in which the whole plant-wide system can be integrated to increase overall efficiency. This paper will present a modular framework for the analysis and optimization of power generation systems with CCS that helps to meet these design challenges. In order to more completely understand the economic and operational tradeoffs associated with the various potential carbon capture technologies, and how they can be applied to new and existing plants, a unified, systemic framework has been developed to provide a common basis for evaluation. Given the complexity of the design problem and the fact that new technologies are continually being developed, this framework is modular in nature and incorporates algorithms for the selection, integration and optimization of carbon capture technologies for both new and existing plants. In addition to the framework itself, this paper discusses simulation modules representing various capture technologies and power plant components. The framework provides the means to link the various modules together in order to provide a holistic, systems perspective of plant wide operations. Results of analyses and optimization scenarios performed with the framework are also presented. [Copyright &y& Elsevier]

Abstract: Many deep saline aquifers suitable for carbon dioxide (CO2) sequestration contain measurable concentrations of hydrogen sulfide (H2S). These aquifers are described here as sour saline aquifers and the other ones as ordinary saline aquifers. Sour saline aquifers occur wherever even minor amounts of anhydrite or other sulfate sources are present in the formation. In this paper, compositional modeling of CO2 injection into such aquifers is studied. When CO2 is injected into a sour saline aquifer, the H2S initially dissolved in the brine will be exsolved and released into an expanding CO2 plume. At any time after the start of CO2 injection, the region swept by the plume consists of two sub-regions. The first of these is an inner sub-region extending from the injection well, and is characterized by the absence of H2S in both aqueous and gaseous phases. The dissolved H2S in this inner sub-region is nearly completely removed from the brine via an exsolution process. The second sub-region extends from the outer edge of the inner sub-region to the leading edge of the plume. In this outer sub-region, the mole fraction of H2S in the gas plume gradually increases toward the leading edge and reaches a peak value. While the gas plume is expanding the size of the outer sub-region enlarges. Following the discussion of these phenomena, in the next part of the paper, injection of acid gases (mixtures of H2S and CO2) into sour saline aquifers and ordinary saline aquifers is explored. In contrast to sour aquifers, unsaturated water in an ordinary aquifer will strip away H2S from the CO2 stream and consequently the mole fraction of H2S toward the gas front decreases. The highly toxic nature of H2S gas suggests the need to account for dissolved H2S in sour saline aquifers when establishing risk assessment, monitoring, and management strategies at CO2 storage sites. [Copyright &y& Elsevier]

Abstract: Geological storage of CO2 is a viable option for the mitigation of greenhouse gas emissions. Two main reservoir types exist; porous formations such as saline aquifers or depleted oil or gas reservoirs and, of lesser importance in terms of storage capacity, coal or shale reservoirs. These reservoirs have distinct storage mechanisms; in the porous formations the CO2 is stored within the porosity by compression and/or dissolution in the formation fluid, whereas in coal or shale, the CO2 is primarily stored by adsorption. Geological storage scenarios exist where these two reservoir types could be present within a geological sequence and come into contact with migrating CO2. In order to simulate this situation simulators are required which represent the mechanisms operating for both reservoir types. One aspect of the work presented in this paper involves further development of the coal seam gas reservoir simulator, SIMED II, to include CO2 dissolution in formation waters and a more accurate Equation of State, the Span and Wagner model, to describe CO2 density. The modified model is first tested through a code comparison study with TOUGH2 for CO2 storage in a saline aquifer with dissolution in formation water, which finds that the two simulators are in close agreement. The second component of this paper involved investigating the potential impact that coal seams could have on CO2 storage in saline formations. A series of hypothetical cases are constructed to investigate the impact of coal seams as (1) a layer within the target aquifer above the injection point, (2) two layers separated by an aquifer above the injection point, (3) a layer in the target aquifer below the point of injection, and (4) a layer in the overburden. The results show that coal seams can have a significant impact on CO2 storage and migration behaviour by providing extra storage capacity and influencing the CO2 flow path both vertically and horizontally. The potential impact of coal seams in these scenarios is related to a range of factors but key ones are the adsorption capacity and the permeability. The results also demonstrate that coal seam permeability decrease due to CO2 adsorption induced coal swelling, although regarded as a technical obstacle to CO2 injection in the deep unminable coal seams to enhance coalbed methane recovery and for CO2 storage in coal, would further influence the CO2 flow path, helping to reduce the upward CO2 flow due to buoyancy and pressure. This could act to reduce CO2 contact with cap rocks and lower the risk of CO2 leakage. [Copyright &y& Elsevier]

Abstract: This paper investigates the potential use of lower grade coals in an IGCC-CCS plant that generates electricity and produces hydrogen simultaneously with carbon dioxide capture and storage. The paper underlines one of the main advantages of gasification technology, namely the possibility to process lower grade coals, which are more widely available than the high-grade coals normally used in European power plants. Based on a proposed plant concept that generates about 400 MW net electricity with a flexible output of 0–50 MWth hydrogen and a carbon capture rate of at least 90%, the paper develops fuel selection criteria for coal fluxing and blending of various types of coal for optimizing plant performance e.g. oxygen consumption, hydrogen production potential, specific syngas energy production per tonne of oxygen consumed, etc. These performance indicators were calculated for a number of case studies through process flow simulations. The main conclusion is that blending of coal types of higher and lower grade is more beneficial in terms of operation and cost performance than fluxing high-grade coals. [Copyright &y& Elsevier]

Abstract: Modelling CO2 storage in saline aquifers on a reservoir scale, for example, for feasibility studies and risk analyses is very demanding with respect to computational cost due to the complex geometries that need to be described and due to the diversity of interacting hydraulic, thermal, mechanical, and geochemical processes. In most cases it is not necessary to be able to describe all these processes for the whole simulation time period or for the entire model domain. Within this paper it is outlined how model coupling could help in reducing the model complexity and increasing model efficiency while the relevant processes are still taken into account. Since the work on this topic is at an early stage, this paper is restricted to a discussion of coupling concepts. [Copyright &y& Elsevier]

Abstract: Oxyfuel combustion is one of the promising technologies to enable CCS for new and existing coal-fired power plants. For retrofit applications, oxyfuel is an attractive option because it does not have major impact on the boiler-turbine steam cycle. This paper presents a case study for retrofitting oxyfuel combustion technology in large state-of-the-art power plants that are originally commissioned and operated in air-fired mode. The overall process design for the modified power plant is outlined; necessary modifications of relevant components are explained. The paper also discusses results of experiments and numerical calculations on combustion behavior in the furnace. Retrofit measures ensure that the power stations still can run under both air-fired and oxyfuel-fired conditions if required by regulations/market conditions. This provides additional operational and commercial benefits for the operator of the plant and reduces the technical risk of implementing new components and processes not yet proven in the power sector. [Copyright &y& Elsevier]

Estimating carbon exchange at regional scales is paramount to understanding feedbacks between climate and the carbon cycle, but also to verifying climate change mitigation such as emission reductions and strategies compensating for emissions such 5 as carbon sequestration. This paper discusses evidence for a number of important shortcomings of current generation modelling frameworks designed to provide regional scale budgets. Current top-down and bottom-up approaches targeted at deriving consistent regional scale carbon exchange estimates for biospheric and anthropogenic sources and sinks are hampered by a number of issues: We show that top-down con10 straints using point measurements made from tall towers, although sensitive to larger spatial scales, are however influenced by local areas much stronger than previously thought. On the other hand, classical bottom-up approaches using process information collected at the local scale, such as from eddy covariance data, need up-scaling and validation on larger scales. We therefore argue for a combination of both approaches, 15 implicitly providing the important local scale information for the top-down constraint, and providing the atmospheric constraint for up-scaling of flux measurements. Combining these data streams necessitates quantifying their respective representation errors, which are discussed. The impact of these findings on future network design is highlighted, and some recommendations are given. [ABSTRACT FROM AUTHOR]

Storage of carbon dioxide in deep coal seams is a profitable method to reduce the concentration of green house gases in the atmosphere while the methane as a byproduct can be extracted during carbon dioxide injection into the coal seam. In this procedure, the key element is to keep carbon dioxide in the coal seam without escaping for a long term. It is depended on many factors such as properties of coal basin, fracture state, phase equilibrium, etc., especially the porosity, permeability and saturation of the coal seam. In this paper, a variable saturation model was developed to predict the capacity of carbon dioxide sequestration and coal-bed methane recovery. This variable saturation model can be used to track the saturation variability with the partial pressures change caused by carbon dioxide injection. Saturation variability is a key factor to predict the capacity of carbon dioxide storage and methane recovery. Based on this variable saturation model, a set of related variables including capillary pressure, relative permeability, porosity, coupled adsorption model, concentration and temperature equations were solved. From results of the simulation, historical data agree with the variable saturation model as well as the adsorption model constructed by Langmuir equations. The Appalachian basin, as an example, modeled the carbon dioxide sequestration in this paper. The results of the study and the developed models can provide the projections for the CO2 sequestration and methane recovery in coal-beds within different regional specifics. [Copyright &y& Elsevier]

This paper proposes a novel CO 2 capture technology from the integration of partial oxy-combustion and the Calcium-Looping capture process based on the multicycle carbonation/calcination of limestone derived CaO. The concentration of CO 2 in the carbonator reactor is increased by means of partial oxy-combustion, which enhances the multicycle CaO conversion according to thermogravimetric analysis results carried out in our work, thus improving the CO 2 capture efficiency. On the other hand, energy consumption for partial oxy-combustion is substantially reduced as compared to total oxy-combustion. All in all, process simulations indicate that the integration of both processes has potential advantages mainly regarding power plant flexibility whereas the overall energy penalty is not increased. Thus, the resulting energy consumption per kilogram of CO 2 avoided is kept smaller than 4 MJ/kg CO 2 , which remains below the typical values reported for total oxy-combustion and amine based CO 2 capture systems whereas CO 2 capture efficiency is enhanced in comparison with the Calcium-Looping process. [ABSTRACT FROM AUTHOR]

Conventional natural gas sweetening processes are mainly focused on the H 2 S removal with the bulk removal of CO 2 . However, the placement of natural gas processes within the carbon capture and storage (CCS) framework provides an opportunity to achieve the synergies between the two technologies. The purpose of this paper is to investigate the CO 2 capture process from the natural gas processing plants. In this study, a steady-state model has been developed that can reasonably predict the CO 2 capture mechanism from the natural gas using diglycolamine (DGA) solvent. The developed model is first validated against a commercial operating plant using the required data and operating conditions. The results show that the developed model is in good agreement with the operational data. The model is then tested for all the possible key parameters that can affect the performance of the process. Since, achieving the product specification with minimum possible energy requirement is the goal of any process plant, hence, the effect of operational parameters is investigated in terms of CO 2 content in the sweet gas and reboiler duty. [ABSTRACT FROM AUTHOR]

The paper examines a solar electric driven heat pump serving an office building located in southern Italy. To satisfy space heating and cooling demand a heat pump activated by electric energy available from solar photovoltaic plant equipped with an electric storage is here considered. Dynamic simulations to evaluate the thermo-economic performance of this system, varying photovoltaic peak power (4.5-7.5 kW) and electric battery capacity (3.2-9.6 kWh), are carried out. The proposed system achieves primary energy saving and equivalent dioxide carbon emission reduction up to about 82 % in comparison to the reference conventional system based on a natural gas fired boiler and an electric chiller. The results show that the solar energy system is more competitive when there is no battery storage and government incentives will be provided. [ABSTRACT FROM AUTHOR]

For more than a century, planted shelterbelts in Saskatchewan, Canada have protected farmyards from the elements, decreased soil erosion, sequestered atmospheric carbon, as well as provided many other ecological functions. It is estimated that there are >60,000 km of planted shelterbelts throughout the province, and considerably more in all of the Canadian Prairies. This paper details the overall process of quantifying and mapping the carbon stocks in white spruce ( Picea glauca ) shelterbelts planted in Saskatchewan. Shelterbelt data collected from field sampling sites, which were identified by a unique site selection approach, were used to parameterize two models for use in shelterbelt systems; an independent data set was used to validate model predictions. Shelterbelt tree growth was modeled with the Physiological Principles in Predicting Growth (3PG) model, and carbon flux and stocks in shelterbelts were modeled with the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3). Annual total ecosystem carbon (TEC) flux in white spruce shelterbelts increased one order of magnitude, from −0.33 to 4.4 Mg C km −1 yr −1 , for age 1–25 years, and reached a peak of 5.5 Mg C km −1 yr −1 (age 39 years). An initial soil carbon loss from the shelterbelt, caused by the land-use change, was offset in full by tree growth by age 17, 18, and 21 years for trees planted at 2.0, 3.5, and 5.0 m spacing within a row, respectively. Increase in carbon stocks, after 60 years of growth, was predicted in the litter layer (21.8 Mg C km −1 ), belowground biomass (26.1 Mg C km −1 ), and aboveground biomass (117.6 Mg C km −1 ). Across all the different provincial soils, carbon additions were 106–195 Mg C km −1 in 60-yr-old white spruce shelterbelts. Cumulatively, accounting for eight decades of white spruce shelterbelt planting and tree growth, carbon additions totaled 50,440 Mg C province-wide in 991 km of white spruce shelterbelts. The C additions represented 38% of the province-wide TEC stocks, which totaled 131,750 Mg C. The cumulative carbon storage in all components of planted white spruce shelterbelts far exceeded the initial carbon levels present at the time of shelterbelt planting. [ABSTRACT FROM AUTHOR]

Carbon sequestration with enhanced gas recovery (CS-EGR) is a well-known technology for safe and economical Carbon Capture, Utilization and Storage (CCUS). However, there is lack of a robust and comprehensive approach to study the optimization of the CS-EGR process. In this paper, a multi-objective optimization code based on a genetic algorithm is combined with the multi-phase flow solver TOUGH2 for CS-EGR applications. Using this combined numerical solver/optimizer, the optimal CO 2 injection rate is accurately determined via a series of simulations for a CS-EGR process to maximize the CH 4 recovery factor. An improvement in the recovery factor by 5% along with a shorter project life cycle is achieved by optimization. Additional optimization studies with time-dependent CO 2 injection scenarios indicate that higher production rates of CH 4 can be achieved without compromising the structural integrity of the reservoir. The results of this study pave the way for future optimization studies to enhance the appeal of CS-EGR projects and to help launch this technology on an industrial scale. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) have exhibited excellent performance on CO 2 capture. However, the lack of research on transport properties has become a bottleneck of industrial application. In order to understand the bubble behavior and mass transfer performance in CO 2 capture systems with ILs, a computational fluid dynamics (CFD) method with two improvements is developed in this paper. One improvement is that a drag force equation suitable for IL systems is introduced into the hydrodynamics model, and the other one is that the influence of CO 2 concentration in liquid phase on viscosity of ILs is considered in the mass transfer model. Based on the developed CFD method, the bubble behavior and mass transfer properties are accurately described. The simulation results of bubble diameter, velocity and aspect ratio agree well with the experimental data with the overall deviation of 7.52%, 12.17% and 5.17%, respectively. The bubble coalescence phenomenon is illustrated by pressure gradient field analysis rather than conventional pressure field analysis, which can represent the drag force and lift force directly. The simulation results also show that the CO 2 mass transfer is kinetic-controlled in pure ILs and thermodynamic-controlled in aqueous ILs, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a study of modelling post-combustion CO 2 capture process using bootstrap aggregated neural networks. The neural network models predict CO 2 capture rate and CO 2 capture level using the following variables as model inputs: inlet flue gas flow rate, CO 2 concentration in inlet flue gas, pressure of flue gas, temperature of flue gas, lean solvent flow rate, MEA concentration and temperature of lean solvent. In order to enhance model accuracy and reliability, multiple feedforward neural network models are developed from bootstrap re-sampling replications of the original training data and are combined. Bootstrap aggregated model can offer more accurate predictions than a single neural network, as well as provide model prediction confidence bounds. Simulated CO 2 capture process operation data from gPROMS simulation are used to build and verify neural network models. Both neural network static and dynamic models are developed and they offer accurate predictions on unseen validation data. The developed neural network models can then be used in the optimisation of the CO 2 capture process. [ABSTRACT FROM AUTHOR]

Safe pipeline transportation of carbon dioxide is a critical issue in the developing field of carbon capture and storage technology. Inadequate fluid thermo- and regimes for on- and offshore transport through high-pressurized pipelines can induce pipe material obsolescence or even pipeline rupture. In such cases, CO 2 (Carbon dioxide) will be released and dispersed in the ambient medium. The dispersion is influenced by the total amount of released fluid, jet pressure and direction, the released concentrations, leakage hole size, ambient material properties and is also affected by the dynamical conditions of the environmental medium. The goal of this study is the hydrodynamical characterization of carbon dioxide jet expansion and dispersion in the ambient atmosphere in case of onshore pipeline accidental leaks. Numerical simulations were carried out by means of a 3D turbulent CFD (computational fluid dynamics) code which includes multi-component flow treatment. The influence of the jet release pressure and size of the leakage hole on harmful CO 2 concentration distances will be analyzed. [ABSTRACT FROM AUTHOR]

Significant potential exists for CO sequestration in coalbed methane reservoirs of the Black Warrior basin. Reservoir simulation is an appropriate approach to estimate both the storage capacity and methane recovery enhancement. However, prior to a reliable reservoir modeling and simulation, conducting an accurate and comprehensive reservoir characterization study is necessary. The purpose of the present study is twofold: (a) to provide a rigorous reservoir characterization study required for modeling Mary Lee coal group in the Blue Creek field of the Black Warrior basin; (b) to run fluid flow simulations to predict the performance of ECBM process applied to an under pressured zone of the Mary Lee coal group. According to the current well configuration of Blue Creek field, three applicable well patterns, namely a direct line drive, an inverted 5-spot and a normal 5-spot were separately (i.e., in three distinct cases) used for simulating ECBM. Simulations were run on an approximately 32 ha (80-acre) drainage area, and included coal matrix shrinkage/swelling effects. The injected gas was assumed to be pure CO. Using an inverted 5-spot pattern, simulations predicted that after 7.5 years of CO injection, approximately 32,000 tonnes of CO would be sequestered per 32 ha of this zone and that methane recovery would be enhanced by 36 %. Using a normal 5-spot pattern, CO breakthrough would occur 2.4 years earlier, and about 40,000 tonnes CO would be sequestered. However, methane production would be enhanced by 33 %. Considering methane recovery enhancement, direct line drive pattern delivered poor results in comparison with two other patterns. As expected, the results also showed that CO injection would increase water production. [ABSTRACT FROM AUTHOR]

Abstract: There has been a large increase in anthropogenic emissions of CO2 over the past century. The use of captured CO2 can become a profitable business, in addition to controlling CO2 concentration in the atmosphere. A process for producing fuel grade methanol from captured CO2 is proposed in this paper. The process is designed and simulated with Aspen Plus. The CO2 is captured by chemical absorption from the flue gases of a thermal power plant. The hydrogen is produced by water electrolysis using carbon-free electricity. The methanol plant provides 36% of the thermal energy required for CO2 capture, reducing considerably the costs of the capture. The CO2 balance of the process showed that it is possible to abate 1.6 t of CO2 per tonne of methanol produced if oxygen by-product is sold, or 1.2 t if it is not. [Copyright &y& Elsevier]

Highlights: [•] One of the first papers investigating the potential of CO2 storage in shale formations. [•] CO2 fate into various trapping mechanisms were quantified. [•] Over 95% of the injected CO2 were instantaneously adsorbed. [•] Limited EGR effects were observed due to limited communication between wells. [ABSTRACT FROM AUTHOR]

Aqueousamine is a solvent considered for carbon dioxide (CO2)recovery from the flue gas of a refinery gas turbine by chemical absorption/desorptionprocess. The performance and the economics of this process dependon the choice of the amine absorbent, the concentration of the amineabsorbent, the number of stages in the absorber and stripper columns,and the operating conditions. We used response surface methodology(RSM)a simulation–optimization technique, which useslocal searches to estimate an appropriate direction to reduce theobjective functionto optimize the amine-based CO2capture process in a previous work [Nuchitprasittichai and Cremaschi Comput. Chem. Eng.2011, 35, 1521–1531]. However, RSM does not provide any informationabout the quality of the obtained solution. In this paper, the RSMresults are compared to those obtained by optimizing a global surrogatemodel of the system over the whole decision space with a global solver.We used an artificial neural network (ANN) as the global surrogatemodel. Depending on the accuracy of the global surrogate models, thesolutions obtained using them can be shown to be global within thebounds of the data used to generate them. The comparison is used toassess the quality of the RSM results and their relative computationalcosts. Monoethanolamine (MEA), diglycolamine (DGA), diethanolamine(DEA), methyl diethanolamine (MDEA), triethanolamine (TEA), and blendedaqueous solutions of these amines are considered in our analyses.The results reveal that the RSM algorithm yielded optimum solutionsclose to those obtained by the ANN approach for all solvents. [ABSTRACT FROM AUTHOR]

Abstract: In spite of the rapid development and introduction of renewable and alternative resources, coal still continues to be the most significant fuel to meet the global electricity demand. Emission from existing coal based power plants is, besides others, identified as one of the major sources of anthropogenic carbon dioxide, responsible for climate change. Advanced coal based power plants with acceptable efficiency and low carbon dioxide emission are therefore in sharp focus for current development. The integrated gasification combined cycle (IGCC) power plant with pre-combustion carbon capture is a prospective technology option for this purpose. However, such plants currently have limitations regarding fuel flexibility, performance, etc. In an EU initiative (H2-IGCC project), possible improvements of such plants are being explored. These involve using premix combustion of undiluted hydrogen-rich syngas and improved fuel flexibility without adversely affecting the availability and reliability of the plant and also making minor modifications to existing gas turbines for this purpose. In this paper, detailed thermodynamic models and assumptions of the preliminary configuration of such a plant are reported, with performance analysis based on available practical data and information. The overall efficiency of the IGCC power plant with carbon capture is estimated to 36.3% (LHV). The results confirm the fact that a significant penalty on efficiency is associated with the capture of CO2. This penalty is 21.6% relative to the IGCC without CO2 capture, i.e. 10.0% points. Estimated significant performance indicators as well as comparisons with alternative schemes have been presented. Some possible future developments based on these results and the overall objective of the project are also discussed. [Copyright &y& Elsevier]

Summary: Numerical programs for simulating flow and reactive transport in porous media is essential for predicting reservoir properties related to CO2 sequestration performance, subsurface storage and risk assessment. In this paper we solve the Navier Stokes’ equation using finite difference method, on a simulated porous rock structure, to study the velocity distribution of fluid flowing through it under a constant pressure gradient. A reactive solute carried through the fluid is allowed to interact with the minerals in the rock. This chemical reaction dissolves the mineral which changes the rock structure thus affecting its flow properties. These changes of flow properties are studied with variation in reactive solute concentration and pressure field. The different mechanisms of dissolution responsible for the variation of flow properties for the different parameters is predicted. Before the onset of homogeneous dissolution, variation in porosity follows a power-law behaviour with change in permeability when the latter is scaled by the concentration of the reactive species. The simulation results are compared with available experimental data and found to give a reasonable match. [ABSTRACT FROM AUTHOR]

Abstract: Injection of carbon dioxide captured from flue gas into coal beds is regarded as one of the value-added options of CO2 sequestration as the cost of injection can be partially or fully offset by the revenue generated through release of additional methane. The Powder River Basin is one of the major coalbed methane producing areas in the world. The paper presents findings of a preliminary reservoir simulation study on the feasibility of CO2 sequestration over a nine-section area (4.8km×4.8km) of the Powder River Basin into the thick Wyodak coal seam, one of the two major coal seams in the highly productive Fort Union formation. The reservoir model was built on the basis of information available in the public domain. Gamma ray logs from 60 wells were utilized for developing a 3-D geological model of the coal seam and overlying rocks in the area by employing geostatistical techniques. Considerable variability in gas and water production was observed in the 65 wells. This variability was utilized for capturing the reservoir heterogeneity by Gaussian geostatistical simulation, which produced realizations of fracture porosity and permeability distribution throughout the reservoir. Results of fluid flow simulation indicated that it would not be feasible to place more than one injector per 1.6km×1.6km (1mile×1mile) section of the area due to geomechanical constraint. As a preliminary estimate, it may be feasible to inject 0.658 million tons of CO2 through such injector over a period of 20 years. 12% more CO2 can be injected over the same period by using a horizontal well but the loss of injectivity may be substantial due to reduction of permeability by coal matrix swelling. The loss of permeability can partially be overcome by intermittent injection for 6 months followed by a similar soak period. Placing one vertical injector each into all the nine sections would result in a scaled-up volume of 5.5 million tons of CO2 injection. However, the nature of overlying rock could play a vital role in retention of injected CO2 and up to 20% of the gas may migrate up by buoyancy. [Copyright &y& Elsevier]

Abstract: Post-combustion capture of CO2 is regarded as a possible technology in order to reduce CO2 emission to the atmosphere. This paper provides a dynamic analysis of the absorption/desorption loop of a carbon capture plant with the help of a simulation model, built using the object-oriented Modelica Library Thermal Separation. The solvent used is an amino-acid salt. The dynamic behaviour is investigated for a reduction in regeneration heat flow rate but constant flue gas flow rate. Hereby four different control strategies are compared, one keeping the lean solvent loading constant, one keeping the solvent flow rate constant, one where flue gas bypasses the capture plant and a last one where an additional solvent tank is introduced. The simulation shows i.e. that for a constant lean solvent loading the response of the absorbed CO2 flow rate is much faster than for a constant solvent flow rate. Also the effect on the dynamic behaviour is investigated, comparing the whole cycle model to a stand-alone desorber model and to a stand-alone absorber model respectively. It was found that the dynamic responses on a short time scale are very similiar, but different on a long time scale. [Copyright &y& Elsevier]

Abstract: The paper evaluates, using modeling and simulation techniques, CO2 capture process from flue gases produced by power generation sector (post-combustion capture) in aqueous solution of mono-ethanolamine (MEA). The aim of the present article is to validate the absorber model as well as to understand the dynamic behavior of CO2 absorption process. The mathematical model of carbon dioxide absorption includes differential equations, e.g. mass and heat transfer models to study the coupled effect of temperature and concentration on the absorption rate, reaction kinetics, vapor–liquid equilibrium (VLE), hydrodynamic aspects, etc. Determinant parts of the absorption model are the effective interfacial area, the mass transfer coefficient, pressure drop and liquid hold-up models. The simulation results have shown that the column operating conditions highly influence the accuracy of the absorber model and the importance of the mass transfer and hydraulic model selection for minimize the deviation of the model results from experimental data value. The present absorber model can be applied to study column operability during dynamic operation. [Copyright &y& Elsevier]

Researchers worldwide have been measuring properties of amine-based scrubbing solutions, seeking alternatives to aqueous monoethanolamine that will reduce the costs of flue gas CO2 capture (FGCC). Because the operating costs of FGCC are closely tied to the stripper reboiler duty (Q Reb), many laboratories have been screening for low heats of desorption, ΔH Des. Recently, their logic was challenged on the grounds that Q Reb has three components, one of which is greater when ΔH Des is higher, another of which is greater when ΔH Des is lower. This paper supports that argument and concludes that the complex dependence of Q Reb on ΔH Des, and on other amine properties, makes process simulation a necessary adjunct to rational amine screening. [Copyright &y& Elsevier]

Global concentration of CO2 in the atmosphere is increasing rapidly. CO2 emissions have an impact on global climate change. Effective CO2 emission abatement strategies such as Carbon Capture and Storage (CCS) are required to combat this trend. There are three major approaches for CCS: post-combustion capture, pre-combustion capture and oxyfuel process. Post-combustion capture offers some advantages as existing combustion technologies can still be used without radical changes on them. This makes post-combustion capture easier to implement as a retrofit option (to existing power plants) compared to the other two approaches. Therefore, post-combustion capture is probably the first technology that will be deployed. This paper aims to provide a state-of-the-art assessment of the research work carried out so far in post-combustion capture with chemical absorption. The technology will be introduced first, followed by required preparation of flue gas from power plants to use this technology. The important research programmes worldwide and the experimental studies based on pilot plants will be reviewed. This is followed by an overview of various studies based on modelling and simulation. Then the focus is turned to review development of different solvents and process intensification. Based on these, we try to predict challenges and potential new developments from different aspects such as new solvents, pilot plants, process heat integration (to improve efficiency), modelling and simulation, process intensification and government policy impact. [ABSTRACT FROM AUTHOR]

In the present paper, the results of an activity performed in the ongoing EU project, CESAR (CO2 Enhanced Separation and Recovery) are presented. In the CESAR project five different baseline power-plants are considered. These consist of two lignite- and two bituminous-coal fired plants while the fifth is fuelled by natural gas. Part of the design work relates to identifying the benefits attainable through appropriate integration of flue-gas cooling to these baseline power-plants. It is shown that the approximate reductions in capture-cost for the studied (optimal) cases are of the order of 20% for the lignite-coal cases, 10% for the bituminous coal cases and 13% for the natural gas case using MEA as solvent. The reductions are basically due to the inclusion of pre-cooling. However, a positive effect of inter-cooling was also found for all the coal cases, while a negative cost effect was found for the natural gas case. For piperazine as solvent the positive effect of cooling was much more pronounced than for MEA and especially the effect of inter-cooling. [ABSTRACT FROM AUTHOR]

This paper deals with the modeling and optimization of the chemical absorption process to CO2 removal using monoethanolamine (MEA) aqueous solution. Precisely, an optimization mathematical model is proposed to determine the best operating conditions of the CO2 post-combustion process in order to maximize the CO2 removal efficiency. Certainly, the following two objective functions are considered for maximization: (a) ratio between the total absorbed CO2 and the total heating and cooling utilities and (b) ratio between total absorbed CO2 and the total amine flow-rate. Temperature, composition and flow-rate profiles of the aqueous solution and gas streams along the absorber and regenerator as well as the reboiler and condenser duties are considered as optimization variables. The number of trays or height equivalent to a theoretical plate (HETP) on the absorber and regenerator columns as well as the CO2 composition in flue gas are treated as model parameters. Correlations used to compute physical-chemical properties of the aqueous amine solution are taken from different specialized literature and are valid for a wide range of operating conditions. For the modeling, both columns (absorber and regenerator) are divided into a number of segments assuming that liquid and gas phases are well mixed. GAMS (General Algebraic Modeling System) and CONOPT are used, respectively, to implement and to solve the resulting mathematical model. The robustness and computational performance of the proposed model and a detailed discussion of the optimization results will be presented through different case studies. Finally, the proposed model cannot only be used as optimizer but also as a simulator by fixing the degree of freedom of the equation system. [ABSTRACT FROM AUTHOR]

Abstract: Artificial Neural Networks (ANN) are multifaceted tools that can be used to model and predict various complex and highly non-linear processes. This paper presents the development and validation of an ANN model of a CO2 capture plant. An evaluation of the concept is made of the usefulness of the ANN model as well as a discussion of its feasibility for further integration into a conventional heat and mass balance programme. It is shown that the trained ANN model can reproduce the results of a rigorous process simulator in fraction of the simulation time. A multilayer feed-forward form of Artificial Neural Network was used to capture and model the non-linear relationship between inputs and outputs of the CO2 capture process. The data used for training and validation of the ANN were obtained using the process simulator CO2SIM. The ANN model was trained by performing fully automatic batch simulations using CO2SIM over the entire range of actual operation for an amine based absorption plant. The trained model was then used for finding the optimum operation for the example plant with respect to lowest possible specific steam duty and maximum CO2 capture rate. Two different algorithms have been used and compared for the training of the ANN and a sensitivity analysis was carried out to find the minimum number of input parameters needed while maintaining sufficient accuracy of the model. The reproducibility shows error less than 0.2% for the closed loop absorber/desorber plant. The results of this study show that trained ANN models are very useful for fast simulation of complex steady state process with high reproducibility of the rigorous model. [Copyright &y& Elsevier]

Abstract: The most promising process for Post Combustion Carbon Capture (PCC) is reactive absorption. For the design and scale-up of this process, reliable process models are needed. To achieve this, the models need to not only reliably describe the physical and chemical equilibria in the reacting systems but also to account for both mass transfer and reaction kinetics. Consequently, the models are complex and contain a large number of input parameters for describing fluid dynamics and physico-chemical properties. In order to assess the required quality of the input, the sensitivity of the simulation results to the parameters has to be known. This paper presents results from such a sensitivity study for a typical operating point of a PCC pilot plant with 0.3 g/g monoethanolamine (MEA) in water as the solvent. A rate-based model and its input parameters are introduced and describe the pilot plant results well. The most relevant input parameters of the model are systematically varied and the influence of that variation on the simulation results is monitored. Absorber and desorber are considered separately. The results are sensitive to most of the studied parameters. High sensitivities are found for the interfacial area, the Henry’s law constant and the enthalpy of absorption as well as for the parameters describing the equilibrium and kinetics of the carbamate formation and the amine protonation equilibrium. [Copyright &y& Elsevier]

Abstract: It is believed that a RSAT™ (Regenerable Solvent Absorption Technology) process is the most viable nearterm technology for post-combustion CO2 capture from power plant flue gas. The Babcock & Wilcox Power Generation Group, Inc. (B&W) has deployed a suite of research tools to evaluate and develop the CO2 scrubbing technology, including laboratory, pilot-scale, and simulation modeling capabilities. Since the construction and operation of test facilities require significant resources, it is essential to effectively utilize these research tools by choosing a scale-up approach which provides robust design data for a commercial process while minimizing the amount of experimentation required. The scale-up protocol used for RSAT CO2 scrubbing processes was rigorously developed using rate-based modeling concurrent with acquiring fundamental laboratory and pilot plant data for process validation. These development activities were not conducted in series but rather overlapped to yield an optimized commercial CO2 scrubbing process in a reasonable time frame with a high degree of design confidence . This paper presents the scale-up protocol used in evaluating the RSAT process which encompasses both laboratory and pilot-scale testing as well as rate-based modeling to achieve a commercial-scale RSAT process design. This document demonstrates the qualification of test data from a packed tower scale-up point of view. Solvent screening research activities recently conducted within B&W successfully demonstrate the scale-up protocol used for RSAT process development. The time and cost of process development can be significantly reduced through rigorous rate-based modeling in conjunction with laboratory experiments and pilot plant validation. [Copyright &y& Elsevier]

Abstract: The oxy-fuel process is one of three carbon capture technologies which supply CO2 ready for sequestration – the others being post-combustion capture and IGCC with carbon capture. As yet no technology has emerged as a clear winner in the race to commercial deployment. The oxy-fuel process relies on recycled flue gas as the main heat carrier through the boiler and results in significantly different flue gas compositions. Sulphur has been shown in the study to have impacts in the furnace, during ash collection, CO2 compression and transport as well as storage, with many options for its removal or impact control. In particular, the effect of sulphur containing species can pose a risk for corrosion throughout the plant and transport pipelines. This paper presents a technical review of all laboratory and pilot work to identify impacts of sulphur impurities from throughout the oxy-fuel process, from combustion, gas cleaning, compression to sequestration with removal and remedial options. An economic assessment of the optimum removal is not considered. Recent oxy-fuel pilot trials performed in support of the Callide Oxy-fuel Project and other pilot scale data are interpreted and combined with thermodynamic simulations to develop a greater fundamental understanding of the changes incurred by recycling the flue gas. The simulations include a sensitivity analysis of process variables and comparisons between air fired and oxy-fuel fired conditions - such as combustion products, SO3 conversion and limestone addition. [Copyright &y& Elsevier]