International Journal of Energy and Environmental Engineering ISSN: 2008-9163 Vol.2 / No.3 (pp.35-47) / Summer 2011 * Corresponding author: Luis M. Romeo (e-mail: luismi@unizar.es) Tel.+34-976-761863; Fax: +34-976-732078.) Exergetic comparison of different oxyfuel technologies Isabel Guedea 1 , Carlos Lupiañez 2 , Luis M. Romeo *3 1,2,3 CIRCE (Research Centre for Energy Resources and Consumption), Universidad de Zaragoza, Mariano Esquillor, 15, 50018 Zaragoza, Spain. Received Date: 26 Apr.; 2011 Accepted: 24 May.; 2011 ABSTRACT Carbon Capture and Storage (CCS) systems have relevant energy consumption associated with the CO 2 capture process. It causes an energy efficiency reduction that diminishes the economic interests and increases the technical uncertainty of these systems. With the objective of improving the system perform- ance and reducing thermodynamic inefficiencies, the exergy analysis has been traditionally applied as a guide for design process. This work presents and compares energy and exergy analysis of two CCS sys- tems based on pressurized oxyfuel combustion, a pressurized fluidized bed combustion working under oxyfiring conditions and a chemical looping combustion using coal as fuel. The aim is to calculate CCS energy and exergy penalties, detecting irreversibilities and proposing items for optimization. It is demon- strated that opposed to energy penalty, the exergy losses do extend neither in the same quantity nor in the same equipment, leading to outstanding conclusions for system improvements. As it will be demon- strated, the exergy penalty of additional equipment for CO 2 capture does not cause relevant losses and these irreversibilities are concentrated in several systems that should be redesigned or analysed in detail to reduce the losses. Keywords CO 2 capture, exergy analysis, pressurized combustion, fluidized bed, chemical looping combustion 1. Introduction One of the main obstacles for the deployment of Carbon Capture and Storage (CCS) systems is the important energy consumption associated with the CO 2 capture process. This causes an in- crement of the operational cost that, joined to the capital cost uncertainties, reduces the attractive- ness to step forward the commercial stage. In spite of these transient drawbacks, Intergovern- mental Panel on Climate Change (IPCC) and European Technology Platform for Zero Emis- sion Fossil Fuel Power Plants (ZEP) consider CCS one of the options to reduce greenhouse gas- ses emissions in medium-long term [1-2]. To increase the system performance and re- duce the inefficiencies the exergy analysis has been traditionally used as a guide. It has demon- strated good results in the synthesis of complex systems and efficiency improvements in energy applications. This work presents an exergy analy- sis of two CCS systems based on pressurized oxy- fuel combustion. The aim is to reduce CCS en- ergy penalties, detecting irreversibilities and pro- posing items for optimization. Due to the novelty of CCS, there is a lack of literature related to the exergy analysis of differ- ent capture systems. A pioneering application of this kind of analysis applied to CO 2 capture sys- tems is the use of the exergy of liquid natural gas to reduce the energy consumption of oxygen pro- duction in an oxyfuel combined cycle [3]. Also, Archive of SID www.SID.ir