Abstract
Integrated gasification combined cycles (IGCC) are promising power production systems from solid fuels due to their high efficiency and good environmental performance. Chemical looping combustion (CLC) is an effective route to reduce the energy penalty associated with CO2 capture. This concept comprises a metal oxygen carrier circulated between a reduction reactor, where syngas is combusted, and an oxidation reactor, where O2 is withdrawn from an air stream. Parallel to CLC, oxygen carriers that are capable of releasing free O2 in the reduction reactor, i.e., chemical looping oxygen production (CLOP), have been developed. This offers interesting integration opportunities in IGCC plants, replacing energy demanding air separation units (ASU) with CLOP. Gas switching (GS) reactor cluster technology consists of a set of reactors operating in reduction and oxidation stages alternatively, providing an averaged constant flow rate to the gas turbine and a CO2 stream readily available for purification and compression, and avoiding the transport of solids across reactors, which facilitates the scale up of this technology at pressurized conditions. In this work, exergy analyses of a gas switching combustion (GSC) IGCC plant and a GSOP–GSC IGCC plant are performed and consistently benchmarked against an unabated IGCC and a precombustion CO2 capture IGCC plant. Through the exergy analysis methodology, an accurate assessment of the irreversible loss distribution in the different power plant sections from a second-law perspective is provided, and new improvement pathways to utilize the exergy contained in the GSC reduction gases outlet are identified.
Highlights
CO2 capture and storage (CCS) is expected to be a key technology in order to meet the climate change targets of global warming increase below 1.5 ◦ C with respect to pre-industrial levels [1].In order for CCS to become a cost-effective solution for energy decarbonization, it is essential to reduce the energy penalty associated with it
A metallic oxygen carrier is transferred between interconnected fluidized reduction and oxidation reactors and exposed to syngas and air streams respectively to achieve inherent CO2 capture, obtaining two outlet streams consisting of the products of combustion, where pure CO2 is obtained after water condensation, Energies 2020, 13, 544; doi:10.3390/en13030544
It can be seen that the energy penalty associated with CO2 capture is approximately 10% points for the precombustion
Summary
CO2 capture and storage (CCS) is expected to be a key technology in order to meet the climate change targets of global warming increase below 1.5 ◦ C with respect to pre-industrial levels [1].In order for CCS to become a cost-effective solution for energy decarbonization, it is essential to reduce the energy penalty associated with it. A promising solution for reducing the efficiency loss of CO2 abatement, which increases the specific capital cost ($/kW) of the plant and the costs related to fuel production and transport, consists of integrated gasification combined cycles (IGCC) with inherent carbon capture by means of gas fuelled chemical looping combustion (CLC) [2]. A metallic oxygen carrier is transferred between interconnected fluidized reduction and oxidation reactors and exposed to syngas and air streams respectively to achieve inherent CO2 capture, obtaining two outlet streams consisting of the products of combustion, where pure CO2 is obtained after water condensation, Energies 2020, 13, 544; doi:10.3390/en13030544 www.mdpi.com/journal/energies. Slow progress in the scale up of pressurized interconnected fluidized beds has been reported [4] To overcome this challenge, a solution involving a reactor cluster operating alternatively in reduction and oxidation stages, with the metallic carrier remaining in each reactor, has been proposed [5]. Several oxygen carriers have been tested in the lab scale and a nickel oxide (NiO) with alumina (Al2 O3 ) support has proved to be mechanically stable and fluidize well at high air reactor temperatures [6], which are required to attain high thermal efficiencies [7]
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