Thermoeconomic evaluation of CO2 alkali absorption system applied to semi-closed gas turbine combined cycle

A new carbon dioxide separation system based on CO2 absorption in aqueous solutions of alkaline salts (sodium and potassium carbonate) was studied with reference to semi-closed gas turbine/combined cycle (SCGT/CC), and compared to results obtained with existing technologies. Use of calcium hydroxide for the regeneration of the exhaust solution was studied in order to obtain a tail-end product, calcium carbonate in the form of precipitated calcium carbonate (PCC) with a wide spread and continuously growing market. The alkali CO2 absorption process was compared with a conventional amine absorption process (DEA+MDEA), referring to the same SCGT/CC based on the same CO2 removal efficiency. The comparison allows foregrounding of the possible goals of the CO2 alkali absorption process with respect to previous amine cycle analyses. The modeling approach focuses on a thermodynamical and economical first comparison of the proposed cycle to previous studies carried out on CO2 absorption (Energy Convers. Manage. 40 (1999) 1917; Absorption of CO2 with amines in a semi closed GT cycle: plant performance and operating costs, ASME Paper 98-GT-395, American Society of Mechanical Engineers ASME Publishing, New York, 1998; Greenhouse Gas Control Technologies Conference, Interlaken, Switzerland, Pergamon, Oxford, 1999).