Reactive absorption with an aqueous solution of amines in an absorber/stripper loop is the most mature technology for postcombustion CO 2 capture (PCC). However, most of the commercial-scale CO 2 capture plant designs that have been reported in the open literature are based on values of CO 2 loadings and/or solvent circulation rates without an openly available techno-economic consideration. As a consequence, most of the reported designs may be suboptimal, and some of them appear to be unrealistic from practical and operational viewpoints. In this paper, four monoethanolamine (MEA) based CO 2 capture plants have been optimally designed for both gas-fired and coal-fired power plants based on process and economic analyses. We have found that the optimum lean CO 2 loading for MEA-based CO 2 capture plants that can service commercialscale power plants, whether natural-gas-fired or coal-fired, is about 0.2 mol/mol for absorber and stripper columns packed with Sulzer Mellapak 250Y structured packing. Also, the optimum liquid/gas ratio for a natural gas combined cycle (NGCC) power plant with a flue gas composition of approximately 4 mol % CO 2 is about 0.96, while the optimum liquid/gas ratio for a pulverized-coal-fired (PC) power plant can range from 2.68 to 2.93 for a flue gas having a CO 2 composition that ranges from 12.38 to 13.50 mol %.

Post-combustion CO 2 capture systems are gaining more importance as a means of reducing escalating greenhouse gas emissions. Moreover, for natural gas-fired power generation systems, exhaust gas recirculation is a method of enhancing the CO 2 concentration in the lean flue gas. The present study reports the design and scale-up of four different cases of an amine-based CO 2 capture system at 90 % capture rate with 30 wt. % aqueous solution of MEA. The design results are reported for a natural gas-fired combined cycle system with a gross power output of 650 MW e without EGR and with EGR at 20, 35 and 50 % EGR percentage. A combined process and economic analysis is implemented to identify the optimum designs for the different amine-based CO 2 capture plants. For an amine-based CO 2 capture plant with a natural gas-fired combined cycle without EGR, an optimum liquid to gas ratio of 0.96 is estimated. Incorporating EGR at 20, 35 and 50 %, results in optimum liquid to gas ratios of 1.22, 1.46 and 1.90, respectively. These results suggest that a natural gas-fired power plant with exhaust gas recirculation will result in lower penalties in terms of the energy consumption and costs incurred on the amine-based CO 2 capture plant.

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A semiempirical model for estimating the heat capacity of aqueous solutions of alkanolamines, both before and after CO 2 absorption, has been developed, and the model parameters for several systems have been obtained using regression techniques. Furthermore, the heat capacity data for pure monoethanolamine (MEA), diethanolamine (DEA), Nmethyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), and piperazine (PZ), as well as the heat capacity data for aqueous solutions of the alkanolamines that have been reported in the open literature, have been analyzed. Given that the data reported by the several different authors for the same system were not weighted during the regression, key statistics of the model predictions against the experimental data set used in the model fitting have been used in the assessment of the relative accuracy of the experimental data reported by different authors for the same system. Overall, the model predictions are in excellent agreement with most of the experimental data that have been reported.

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