Chemical Looping Combustion-Analysis of Natural Gas Fired Power Cycles With Inherent CO2 Capture

Abstract

In this paper an alternative to so-called ‘oxy-fuel’ combustion has been evaluated. Chemical Looping Combustion (CLC) is an innovative concept of CO2 capture from combustion of fossil fuels in power plants. CLC is closely related to oxy-fuel combustion as the chemically bound oxygen reacts in a stoichiometric ratio with the fuel. In CLC, the overall combustion takes place in two steps. In a reduction reactor fuel is oxidised by the oxygen carrier i.e. the metal oxide MeO which is reduced to metal oxide with a lower oxidation number, Me. Me flows to an oxidation reactor where it is oxidised by oxygen in the air. In this way pure oxygen is supplied to fuel without using an energy intensive traditional air separation unit. This paper presents thermodynamic cycle analysis of a CLC-power plant. A steady-state model has been developed for the solid-gas reactions occurring in the reactor system. The model is applied to analyse the system under two configurations; a combined cycle and a conventional steam cycle. A turbine-cooling model has also been implemented to evaluate the turbine cooling penalty in the combined cycle configuration. Effects of exhaust recirculation for coking prevention and incomplete fuel conversion have also been investigated. Performance of the oxygen carrier has been idealised except for the degrees of reduction and oxidation. Energy needs for CO2 capture have properly been taken into account. The results show that an optimum efficiency of 49.7% can be achieved under given conditions with a CLC-combined cycle at zero emissions level. With turbine cooling, efficiency falls by 1.2% points under the same conditions. The CLC-steam cycle is capable of achieving 40.1% efficiency with zero emissions. The results show that CLC has high potential for power generation with inherent CO2 capture. This work will be useful in designing CLC systems after the reactor system has been analysed experimentally for long-term operations.

Progress in Chemical-Looping Combustion and Reforming technologies

“…Simulations showed that there is a 0.5% efficiency drop for each 1% decrease in fuel conversion [398], although the advantage of CO 2 separation would still remain [297].…”

“…However, up to the present there is no proper design of a pressurized (1-3 MPa) CLC plant using two interconnected pressurized fluidized beds. Systems composed by a combined cycle have been analyzed in depth [393,398]. Additionally, the use of an air-based gas turbine and a CO 2 -turbine with an integrated heat recovery system was analyzed [25,26,114].…”

“…The Chemical-Looping principle may be applied either in a gas turbine cycle with pressurized oxidation and reduction reactors, or in a steam turbine cycle with atmospheric pressure in the reactors. At atmospheric pressure, the use of a steam cycle could achieve about 40-42% efficiency when using gaseous or solid fuels [300,398] including energy demands for CO 2 compression before transport and sequestration. The compression of CO 2 reduces the efficiency by about 2% [115].…”

Comparative analysis of hydrogen production systems from biomass based on different absorbent regeneration processes

“…Based on the conception of chemical-looping combustion (CLC) [9,10], taking into account the need for pure oxygen in the regenerator, as well as the catalysis of NiO on the steam reforming [11,12], we select NiO as the oxygen carrier to design Fig. 3.…”

Parametric study of chemical looping combustion for tri-generation of hydrogen, heat, and electrical power with CO2 capture

“…The principles of CLC were introduced in the early 1980s (Richter and Knoche, 1983;Ishida et al, 1987). Since 1983, studies have been performed on process integration (Ishida and Jin, 1994;Anheden, 1997;Copeland et al, 2000;Wolf et al, 2001Brandvoll and Bolland, 2002;Naqvi et al, 2004), selection and preparation of oxygen carriers (Copeland et al, 2002;Ishida et al, 1998Ishida et al, , 2002Cho et al, 2002Cho et al, , 2004Ryu et al, 2002;Mattisson et al, 2001), and reactor design Johansson, 2002;Johansson et al, 2002;Kronberger et al, 2004;Ad! a anez et al, 2003).…”