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A membrane contactor process for pre-combustion CO 2 capture from shifted synthesis gas originated from IGCC power plant is assessed from the technical and economical point of views. The process is designed as pressure swing absorption and desorption in a closed loop. The design basis for process simulation were synthesis gas containing CO 2 and H 2 only, and the CO 2 capture efficiency was fixed to 90%. The CO 2 gas was absorbed in ionic liquid [bmim][TCM] inside a hydrophobic, porous hollow fibre membrane contactor. One-dimensional mathematical model of membrane contactor developed in MATLAB was integrated to the process simulation software (HYSYS) through Cape-Open simulation compiler. The energy evaluation of this process revealed that compressors are the most energy demanding process equipment. The specific energy requirement for this process is estimated 0.75 MJ/kg CO 2 . A parametric study was also performed to analyse the effect of CO 2 concentration in feed gas and liquid to gas ratio. The capital cost investment and total operating costs of CO 2 capture unit were also evaluated. The capital investment required for capturing 0.14 M ton CO 2 /year including CO 2 compression is 47.4 M $, and the operating cost per year is 9.04 M $. The membrane absorber contributed about 39% to total investment cost. The specific cost of this capture unit is calculated to be 87 $/ton CO 2 . [ABSTRACT FROM AUTHOR]

Aerosols are systems of droplets or wet particles suspended in gases. In post combustion CO 2 absorption systems aerosols can be formed by spontaneous phase transitions in supersaturated gas phases or by droplets or particles entering the absorber with the gas to be treated. Micron and sub-micron mist droplets and fog formed in these processes cannot be removed by conventional demisting devices and because amine may be absorbed in the droplets this may increase dramatically the amine emissions from absorption columns as reported previously ( Khakharia et al., 2015; Schaber et al., 2002 ). Thus, it is important to understand the mechanisms governing droplet growth and amine uptake through absorber as well as the effect large numbers of aerosol droplets can have on the bulk gas phase composition. A model developed and implemented in Matlab, predicts how the gas phase composition and temperature change along the absorber taking into account mass and heat transfer to and from both the bulk liquid and the droplet phase. The objective of this work, compared to earlier work, Majeed et al. (2017) , is to study the possible effect of gas phase component depletion on the droplet growth and droplet internal variable profiles and how this varies with initial droplet size and composition, droplet number concentration and amine volatility. For MEA, as a relatively volatile solvent it is seen that gas phase depletion already takes place at number concentrations above 10 5 droplets/cm 3 with an initial droplet radius of 1.5 μ and 5 M MEA initial concentration. For initial droplet radius 0.15 μ and 0.0001 M MEA initial concentration, which may be a more realistic case, hardly any depletion effect is seen up to 10 7 droplets/cm 3 . With change in amine volatility it is seen that the gas phase depletion effect is significantly stronger in the case of low volatility than for MEA at high droplet number concentrations. It is found that gas phase amine depletion has a strong effect on droplet growth. [ABSTRACT FROM AUTHOR]

Dynamic modeling of post-combustion CO 2 capture has gained increasing attention the recent years. One of the main motivations behind this drive is the current limited knowledge of the operational flexibility of carbon capture units integrated with power stations. The present work presents an evaluation of various flexible operating modes through dynamic simulations of the Brindisi CO 2 capture pilot plant using the K-Spice ® general simulation tool. The evaluated modes are; load following, exhaust gas venting, varying solvent regeneration and solvent storage. Solvent storage gives a large potential for flexible operation with the possibility of maintaining 90% instantaneous CO 2 capture rate over the whole 24 h simulated period. Two large solvent storage tanks are however required as part of the process configuration in order to realize flexible operation by solvent storage. Exhaust gas venting and varying solvent regeneration does not require any additional process installations or modification, but their potential is limited by the maximum CO 2 capture capacity during off-peak electricity price periods in order to reach a time average CO 2 capture rate of 90%. Exhaust gas venting seems to be the favorable option of the latter two. [ABSTRACT FROM AUTHOR]

Abstract: The recent years have seen growing attention towards the study of dynamic behavior in post-combustion CO2 capture plants using amines, albeit, apparently contesting yet without comparison or critique. This paper reviews what has been reported in literature concerning issues pertinent to transient behavior of CO2 capture including interaction with power plants. Details of models used, their validation and modeling tools as well as an attempt to piece-out convergent points from the various conclusions are given. Knowledge gaps and areas that still need more attention are emphasized. [Copyright &y& Elsevier]

Abstract: The effect of heat distribution or inter-heating on the total energy requirement for CO2 stripping is investigated. Here we look at retrofit design of an existing column. It means the height and diameter of the stripper is given. The results show that inter-heating can have both negative and positive effects on the total energy requirement. If only one heat source at constant temperature exist, the inter-heating will increase the total energy requirement. If there are other heat sources at different temperatures, inter-heating can be beneficial. It depends on the energy price of the different heat sources and the temperature profile of the column. If there are some hot streams available to utilize the heat in the inter-heater, the total energy requirement will decrease. As a case study utilizing heat from lean amine in the inter-heater is investigated. The simulation results show a saving up to 6.4 and 11.3 percent by one and two inter–heater respectively [Copyright &y& Elsevier]

Abstract: The dynamic behavior of three process configurations proposed for CO2 capture from flue gas is investigated. In the previous paper () the different configurations were investigated with respect to energy requirement and capital costs and the best configurations were defined based on CO2 avoided cost and total capture cost. In addition to the economy, the dynamic behavior is important when operation of the plant is considered. In this study the transient behavior of the vapor recompression and the split-stream configurations are investigated when different disturbances happen, and the results are compared with the conventional configuration as a benchmark. All process configurations are operationally feasible with the proposed control configuration. The results show that the conventional configuration is the most inherently resilient to disturbances, and that the vapor recompression configuration can handle disturbances better than split-stream configuration. The same relative reduction in reboiler duty has more negative effect (more reduction in capture ratio) for split-stream configuration than two other configurations. The control structure generated is able to control the plant for all configurations except the situation where the reboiler duty is an active constraint. In this situation the energy loss will increase and it is better to find another control variable to pair with reboiler duty. This will be done in future studies. [Copyright &y& Elsevier]

Abstract: The aqueous absorption technology is one of the most feasible options for post combustion CO2 capture. High energy requirement is the main problem for this technology. Intercooling is possibly one of the strategies that can reduce the energy consumption in some cases. It is used in other industries like oil refineries and has a promising effect on energy use reduction. However, the effect may depend on the absorbent system used and the configuration of the process. In this study, the effect of intercooling is investigated for monoethanolamine (MEA) and diethanolamine (DEA). The results show that the best location for intercooling, based on minimizing energy requirement per kg of CO2 captured is about 1/4th to 1/5th of the height of the column from the bottom. The effect of different parameters like lean loading, amine concentration, cooling temperature, etc is investigated in this study. The results for MEA and DEA are compared to see the effect of solvent on intercooling performance. [Copyright &y& Elsevier]

Abstract: Considerable effort on research in CO2 capture technologies has been directed towards steady state systems while less seems to have been done for the same systems in transient state. This work presents a dynamic model for CO2 absorption using aqueous mono-ethanolamine (MEA). Validation against experimental results both obtained at steady state and dynamic conditions is included. A parametric sensitivity study of the underlying model equations is carried out based alternative parameter correlations for the reaction rate constant. It is concluded that validated results for one specific pilot plant don’t necessarily apply to other plants of different sizes under other operational conditions. Furthermore, a parametric sensitivity study for the other parameters as well as for the rest of the CO2 capture process is also warranted. [Copyright &y& Elsevier]

Flexible thermal power plants integrated with CO 2 capture systems can balance the intermittent power generation of renewable energy sources with low-carbon electricity. Among these power systems, natural gas combined cycles will play a fundamental role because of their faster operation and higher efficiency. Optimisation-based control strategies can enhance the flexible power dispatch of these systems and improve their performance during transient operation. This work proposes a model predictive control (MPC) strategy to stabilise these power plants with post-combustion CO 2 capture based on temperature swing chemical absorption and provide offset-free reference tracking. A delta-input formulation with disturbance modelling is proposed, as it provides more efficient computation with offset-free control. Data-based models were developed to replicate the performance of the actual power and capture plants. Prediction of nonlinear behaviour was accomplished by creating a network of local linear models, which allowed the formulation of the dynamic optimisation program in the MPC strategy as a convex quadratic programming problem. A case study demonstrated the effectiveness of the proposed MPC to balance drastic changes on power demand and keep specified capture ratios. Furthermore, the reduced deviations achieved in the reboiler temperature suggest that the nominal value of this parameter could be increased to improve the desorption process without risks of reaching temperatures where the solvent would degradate. [ABSTRACT FROM AUTHOR]

Mass transfer and mathematical modelling of CO 2 absorption in a tubular membrane contactor using 1-Butyl-3-methylimidazolium Tricyanomethanide ([Bmim][TCM]) for pre-combustion CO 2 capture has been studied in this work. A 1D-model was developed based on resistance in series model and CO 2 material balance. The developed model was validated with the experimental data, and good agreement was observed between the simulated and experimental results. A new mass transfer resistance term is added to reflect the non-flat concentration profile in the liquid phase. Simulation results indicate that the liquid phase resistance contributes 67% and 44% to the total mass transfer resistance for non-wetted and wetted modes of membrane respectively. The resistance that occurred due to considering transport in liquid phase contributes 31 and 20% for non-wetted and wetted modes of membrane contactor respectively. CO 2 flux along the axial length of membrane contactor was modeled, giving the maxima at the gas outlet. The influences of operational constraints including liquid/gas flow rates, operation pressure/temperature, length of membrane contactor, and CO 2 concentration in feed gas were also inspected. [ABSTRACT FROM AUTHOR]

A dynamic model of the post-combustion CO 2 capture process based on chemical absorption is used to investigate the transient behavior and dynamic responses of the process and to detect stabilization time when various disturbances are introduced. Plant dimensions and parameter settings are based on the SINTEF CO 2 capture pilot plant at Tiller in Norway, and the overall process model is validated using two sets of steady state pilot plant data. A deviation between model and pilot plant results of −0.8% and −4.5% in absorbed CO 2 and 2.6% and 1.2% in desorbed CO 2 is seen for the two cases used in validation, respectively, which is within the observed pilot plant CO 2 mass balance error of ±6%. The simulated absorber and desorber temperature profiles show also adequate agreement to the pilot plant measurements. The process model is further used to simulate set-point changes in flue gas flow rate, reboiler duty and solvent flow rate in order to investigate typical stabilization times at various locations in the process. As expected, mixing models such as the absorber sump and reboiler will introduce time constants that affect the dynamic response profiles, while plug flow models such as the cross heat exchanger and lean cooler causes pure transport delays and no additional settling time. Mass transfer and chemical reaction rates causes some process inertia, but it is relatively small compared to the inertia of larger mixing vessels such as the absorber sump, reboiler and buffer tank and transport delay caused by plug flow. Changes to the solvent flow rate are also seen as a larger disturbance to the process compared to changes in flue gas flow rate and reboiler duty, reflected by longer process stabilization time to reach new steady state conditions. The estimated 90% settling times for the response in CO 2 capture rate in the Tiller pilot plant are less than 1 h, 3.5–6 h and 3.5–4 h for step changes in flue gas flow rate, solvent flow rate and reboiler duty, respectively. [ABSTRACT FROM AUTHOR]