In this work, we present a new approach for the multi-period design of an integrated coal-fired power-plant and an alkanolamine-based CO2 capture process. A validated[2] rate-based model of an absorber/stripper system for the chemisorption of acid gas in aqueous solvent solutions is used to represent the CO2 capture process. To account for the non-idealities that are typical of amines and water, the statistical associating fluid theory for potentials of variable range (SAFT-VR)[3],[4] is used. This is a molecular approach, specifically suited to associating fluids. The SAFT formalism is used to represent some of the equilibrium reactions characterising the system, thereby simplifying the description of the chemical reactions[5]. The dynamic operation of the power-plant is described using data obtained from a real power station describing the variation in fuel burn rates in response to changing power demand. As we lack a thermodynamically consistent method in describing the degradation effects of SOx on the solvents, we consider a model flue gas comprising N2, CO2 and H2O. All models are implemented in the gPROMS[6] software package.
Cost-optimal process design and operation are identified via a constrained, multi-parametric optimisation approach. The objective function is the minimisation of total process cost (both CAPEX and OPEX) per unit of CO2 captured. The design variables are the flowrate and state of the lean solvent stream as well as column geometry. Key performance indicators such as CO2 emissions, solvent losses to the environment as well as the minimisation of energy required for solvent regeneration and also minimisation of CO2 emissions to the atmosphere are included in the optimality criteria.
[1] Mac Dowell, N. et al, Energy. Environ. Sci., 3, 2010, 1645-1669
[2] Mac Dowell, N., Galindo, A., Jackson, G and Adjiman, C. S., Comp. Aided Chem. Eng., 28, 2010, 1231-1236
[3] Chapman, W.G., Gubbins, K.E., Jackson, G. & Radosz, M., Ind. Eng. Chem. Res. 29, 1709-1721., 1990
[4] Gil-Villegas, A., Galindo, A., Whitehead, P. J., Mills, S. J. & Jackson, G., J. Chem. Phys. 106 (10), 1997
[5] Mac Dowell, N., Llovell, F., Adjiman, C. S., Jackson, G and Galindo, A., Ind. Eng. Chem. Res., 49(4), 1883-1899, 2010
[6] Process Systems Enterprise (PSE) Ltd. http://www.psenterprise.com/index.html
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