Abstract
One of the main challenges for commercialising calcium looping (CaL) as a CO2 capture technology is maintaining a high level of sorbent reactivity during long-term cycling. In order to mitigate the decay in carrying capacity, research has moved towards producing enhanced sorbents. However, this creates potential problems related to ease of scaling up production techniques and production costs, and raises the question as to whether such approaches can be used at large scale. On the other hand, a key advantage of CaL over other carbon capture technologies is synergy with the cement industry, i.e., use of spent sorbent as a feedstock for clinker production. In this work two enhanced materials: (i) limestone doped with HBr through a particle surface impregnation technique; and (ii) pellets prepared from limestone and calcium aluminate cement, were tested in a 25 kWth dual fluidised bed pilot-scale reactor in order to investigate their capture performance and mechanical stability under realistic CaL conditions. Moreover, the spent sorbent was then used as a raw material to make cement, which was characterised for phase and chemical composition as well as compressive strength. The HBr-doped limestone showed better performance in terms of both mechanical strength and stability of the CO2 uptake when compared to that of pellets. Furthermore, it was shown that the cement produced has similar characteristics and performance as those of commercial CEM 1 cement. This indicates the advantages of using the spent sorbent as feedstock for cement manufacture and shows the benefits of synthetic sorbents in CaL and suitability of end-use of spent sorbents for the cement industry, validating their synergy at pilot scale. Finally, this study demonstrates the possibility of using several practical techniques to improve the performance of CaL at the pilot scale, and more importantly demonstrates that commercial-grade cement can be made from the lime product from this technology.
Highlights
CO2 emissions from the power generation and industrial sectors have increased rapidly in recent decades, and represent the greatest contributors to the greenhouse gas effect [1]
The results presented in this work are in accordance with those obtained by Symonds et al [13] with regard to the use of calcium aluminate pellets; their performance appears worse than the performance of natural limestone
The use of enhanced materials for Calcium looping (CaL) was studied at pilot scale in this work
Summary
CO2 emissions from the power generation and industrial sectors have increased rapidly in recent decades, and represent the greatest contributors to the greenhouse gas effect [1]. A portfolio of low-carbon technologies needs to be deployed in order to mitigate the effects of these emissions in many natural systems. Carbon capture and storage (CCS) is part of this portfolio and has been proposed as a route for the decarbonisation of power generation and carbon-intensive industrial sectors [2,3]. Calcium looping (CaL) is a second-generation technology for CO2 capture, which has attracted a fair amount of research activity [4,5,6,7,8]. A CaL system (Fig. 1) consists of two interconnected fluidisedbed reactors and is based on the reversible carbonation of lime.
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