%0 Journal Article
%T Materials for Chemical-Looping with Oxygen Uncoupling
%A Tobias Mattisson
%J ISRN Chemical Engineering
%D 2013
%R 10.1155/2013/526375
%X Chemical-looping with oxygen uncoupling (CLOU) is a novel combustion technology with inherent separation of carbon dioxide. The process is a three-step process which utilizes a circulating oxygen carrier to transfer oxygen from the combustion air to the fuel. The process utilizes two interconnected fluidized bed reactors, an air reactor and a fuel reactor. In the fuel reactor, the metal oxide decomposes with the release of gas phase oxygen (step 1), which reacts directly with the fuel through normal combustion (step 2). The reduced oxygen carrier is then transported to the air reactor where it reacts with the oxygen in the air (step 3). The outlet from the fuel reactor consists of only CO2 and H2O, and pure carbon dioxide can be obtained by simple condensation of the steam. This paper gives an overview of the research conducted around the CLOU process, including (i) a thermodynamic evaluation, (ii) a complete review of tested oxygen carriers, (iii) review of kinetic data of reduction and oxidation, and (iv) evaluation of design criteria. From the tests of various fuels in continuous chemical-looping units utilizing CLOU materials, it can be established that almost full conversion of the fuel can be obtained for gaseous, liquid, and solid fuels. 1. Introduction In the last decade, chemical-looping combustion (CLC) has emerged as a viable and efficient alternative for combustion with carbon capture. The interest in CLC is mainly due to the intrinsic separation of from the rest of the flue gases during combustion, that is, nitrogen and unused oxygen, which means that no energy or equipment is needed for gas separation, which is in contrast to competing CCS technologies, that is, oxyfuel, postcombustion, and precombustion. An added advantage of CLC is the possibility to obtain 100% carbon capture, which is difficult to achieve in, for instance, post- or precombustion. Chemical-looping with oxygen uncoupling (CLOU) is very similar to CLC and has the same advantages with respect to efficiencies and degree of carbon capture, but the mechanism of fuel conversion is different, and this could result in significant advantages with respect to fuel conversion rates, which can have positive implications with respect to system performance. Below follows a description of both the CLC and CLOU technologies. This is followed by a simple thermodynamic analysis for some relevant metal oxides in Section 2. A detailed overview of the experimental research conducted on different oxygen carrier materials for CLOU is then carried out in Section 3. An overview of kinetic data
%U http://www.hindawi.com/journals/isrn.chemical.engineering/2013/526375/