UTN FRRo

Rosario del Tala, Argentina
Rosario del Tala, Argentina
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Manassaldi J.I.,UTN FRRo | Mussati S.F.,UTN FRRo | Mussati S.F.,CONICET | Scenna N.J.,UTN FRRo | Scenna N.J.,CONICET
Energy | Year: 2011

Thermal efficiency of Combined Cycle Power Plants (CCPPs) depends strongly on the Heat Recovery Steam Generation (HRSG) design which links the gas cycle with the steam cycle. Therefore, the HRSG must be carefully designed in order to maximize the heat exchanged and to improve the overall performance of the plant. In this paper, a mixed integer non-linear programming (MINLP) model to simultaneously optimize the equipment arrangement, geometric design and operating conditions of CCPPs is proposed. General Algebraic Modelling System (GAMS) is used to implement and to solve the mathematical model. The HRSG model involves discrete decisions connected with the geometric design and the selection of tube diameters as well as the length and width of each solid fin. Continuous variables are used to model the operating conditions of the HRSG and steam turbines (ST). The solution strategy for the resulting model comprises two phases: the first one focuses the process optimization but considering only global energy and mass balances and this phase provides initial-bounds values for the second phase where the complete and rigorous model involving discrete decisions is solved. Different case studies with increasing complexity have been successfully solved. Model validation and results obtained from the MINLP model by considering different objective functions are discussed. © 2010 Elsevier Ltd.


Mores P.,UTN FRRo | Scenna N.,UTN FRRo | Scenna N.,CONICET | Mussati S.,UTN FRRo | Mussati S.,CONICET
International Journal of Greenhouse Gas Control | Year: 2012

A comprehensive and simplified rate based mathematical model of a packed column for CO 2 capture using aqueous monoethanolamine (MEA) solution is developed. The absorption unit model takes into account the effect of kinetic reactions on the mass transfer, the thermodynamic non-idealities, the hydraulics of the random packing and the absorber dimensions (diameter and height). It is implemented into the optimization environment GAMS (General Algebraic Modeling System).The proposed NLP model was validated by comparison of obtained results with published experimental data. Good accuracy of results has been obtained for experimental pilot plant scales. Once validated, the model was used to investigate the influence of main process parameters and the effect of different correlations to compute the effective interfacial area for mass transfer (a/a t) on the absorption efficiency. Obtained results indicate that model solutions depend strongly on the correlations used to compute the (a/a t). In addition, results assuming thermal equilibrium and thermal non-equilibrium in liquid and vapor phases were also compared. For both conditions and specific cases, similar concentration and temperature profiles in the liquid phase in the absorber were obtained.Finally, results obtained by solving different optimization problems are discussed. More precisely, the optimization consisted in determining the operating conditions to maximize the absorption efficiency defined as the ratio between the CO 2 recovery in rich solution and the packing volume of the column. The effect of the main process parameters on the optimized results was also investigated. © 2011 Elsevier Ltd.


Mores P.,UTN FRRo | Scenna N.,UTN FRRo | Mussati S.,UTN FRRo | Mussati S.,CONICET
Energy | Year: 2012

This paper deals with the simultaneously optimization of operating conditions (pressures, temperatures and flow-rates) and dimensions (diameter and height) of the amine regeneration unit in the post-combustion CO 2 capture process. The proposed model takes into account the effect of kinetic reactions on the mass transfer, the hydraulics of the random packing and the pressure drop along the column. In addition, profiles of temperature, composition and flow-rate along the height of the regenerator are also predicted.The resulting mathematical model is implemented into the optimization environment General Algebraic Modeling System (GAMS) which is a high-level modeling system for mathematical programming and optimization. The benefits of the mathematical programming techniques (equation-oriented modeling tools) are exploited for the simultaneous optimization not only of the operating conditions but also the dimensions of the all piece of equipments (heat exchangers, regeneration unit, condenser and reboiler).The mathematical model was successfully verified by comparison of the obtained results with published experimental data and simulated solutions obtained by a process simulator (HYSYS). Once validated, the model was used for optimization purpose.Finally, in order to study the effect of the main process parameters on the optimized results a sensitivity analysis is also investigated and discussed in detail. © 2012 Elsevier Ltd.


Mores P.,UTN FRRo. | Scenna N.,UTN FRRo. | Mussati S.,UTN FRRo. | Mussati S.,CONICET
Chemical Engineering Research and Design | Year: 2011

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. © 2010 The Institution of Chemical Engineers.

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