http://digital.csic.es/bitstream/10261/78793/1/Progress%20in%20chemical-looping%20combustion%20and%20ref....2012.pdf

Progress in chemical-looping combustion and reforming technologies

Chemical-looping combustion (CLC) for inherent CO2 separations—a review

Three-reactors chemical looping process for hydrogen production

The world-wide consumption of natural gas (NG) and other fossil fuels (e.g., coal and crude oil) is ever increasing. However, most CO2 resulting from either NG combustion or other processes is released into the atmosphere without capture. Chemical looping combustion (CLC) is a two-step combustion technology for power and heat generation with inherent CO2 capture, using either gaseous fuels or solid and liquid fuels. A previous review focused on CLC of solid fuels or CLC of all types of fuels but did not give an in-depth and specific discussion of gaseous fuel CLC systems. China is one of the largest consumers of NG, coal, and crude oil in the world, and it is essential to develop an alternative technology to take the place of gaseous fuel (e.g., NG) combustion. This Review summarizes recent research and development work on CLC using gaseous fuels, including a technological and economic assessment, types of oxygen carriers (OCs), reactor types, coke formation and OCs poisoning, efficiency and exergy analys...

CO2 Capture with Chemical Looping Combustion of Gaseous Fuels: An Overview

An overview of technologies for fossil fuel-fired power plants with drastically reduced CO2 emissions is given. Post-combustion capture, pre-combustion capture, and oxyfuel technology are introduced and compared. Current research results indicate that post-combustion capture may lead to slightly higher losses in power plant efficiency than the two other technologies. However, retrofitting of existing plants with oxyfuel technology is complex and costly, and retrofitting of pre-combustion capture is not possible. On the other hand, post-combustion capture can be retrofitted to existing power plants with only minimal effort. Based on the mature technology of reactive absorption, it can be implemented on a large scale in the near future. Therefore, post-combustion capture using reactive absorption is discussed here in some detail.

CO2 Capture for Fossil Fuel‐Fired Power Plants

Chemical-Looping Combustion (CLC) is a process where fuel oxidation is carried out through an intermediate agent — a metal oxide — circulated across two fluidized bed reactors: a reduction reactor, where an endothermic reaction reduces the metal oxide and oxidizes the fuel, and an oxidation reactor, where an exothermic reaction oxidizes the metal oxide in air. Overall, the system carries out the same job of a conventional combustor, with the fundamental advantage of segregating the oxidation products (CO2 and H2 O) into an output flow free of nitrogen and excess oxygen. The flow exiting the reduction reactor consists of water and CO2 , the latter readily available for liquefaction, transport and long-term storage. The hot, vitiated air from the oxidation reactor is the means to produce power through a thermodynamic cycle. This paper reports of a study supported by the ENI group to assess the potential of the integration between CLC and combined gas-steam power cycles. More specifically, we focus on four issues: (i) optimization of plant configuration; (ii) prediction of overall efficiency; (iii) use of commercial gas turbines; (iv) preliminary economic estimates. The CLC system is based on iron oxides which, to maintain their physical characteristics, must operate below 900–1000°C. Given the crucial importance of the temperature of the vitiated air generated by CLC on the performance of the combined cycle, we consider two options: (i) “unfired” systems, where natural gas is fed only to the CLC system, (ii) “fired” systems, where the vitiated air is supplementary fired to reach gas turbine inlet temperatures ranging 1000–1200°C. Results show that unfired configurations with maximum process temperature 850–1050°C and zero emissions reach net LHV plant efficiencies ranging 43–48%. Fired cycles where temperature is raised from 850 to 1200°C by supplementary firing can achieve 52% net LHV efficiency with CO2 emission about one half of those of a state-of-the-art combined cycles. Fired configurations allow significant capital cost and fuel cost savings compared to unfired configurations; however, a carbon tax high enough to make them attractive (close to 50 €/ton) would undermine these advantages.Copyright © 2004 by ASME

Giampaolo Pelliccia

Papers

Chemical Looping Combustion for Combined Cycles with CO2 Capture

Chemical-Looping Combustion for Combined Cycles With CO