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Dicalcium ferrite: A chemical heat pump in integrated carbon capture and chemical looping combustion for the steel industry

Accepted version
Peer-reviewed

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Authors

Sukma, MS 
Zheng, Y 
Scott, SA 

Abstract

An integrated calcium and chemical looping combustion using dicalcium ferrite (Ca2Fe2O5, C2F), a mixed phase from iron and calcium oxides, is proposed here to remove carbon (CO + CO2) contained in the blast furnace gas from the steel industry. C2F is particularly attractive in chemical looping hydrogen production due to its lower P_(O_2 ), therefore C2F can split steam into H2. Here, the low P_(O_2 ) property allows C2F to have endothermic combustions in CO and H2 combustion (Stage 1 in the carbonator). The heat of combustion is chemically stored as reduced-carbonated C2F to be utilised for sorbent regeneration (Stage 2 in the calciner), essentially pumping the heat from the carbonator to the calciner. Combustion that occurred at P_CO⁄P_(CO_2 ) of the typical BFG in which the C2F should have not been able to combust CO, suggesting an enhanced combustion phenomenon. Experiments demonstrated in a fluidised bed and a thermogravimetric analyser led to indications that rather than following reaction pathways in an order of (i) C2F is reduced into CaO and metallic Fe and (ii) the CaO is absorbed CO2 in Stage 1, C2F might directly form Fe + CaCO3 under a mixture of CO and CO2, allowing the C2F to react with BFG. Reincorporation of the reduced-carbonated oxides into C2F drives lower decarbonation temperatures compared to CaO alone, suggesting a promising route to improve energy efficiency in capturing carbon in the hard-to-decarbonise steel industry.

Description

Keywords

4004 Chemical Engineering, 40 Engineering, 4016 Materials Engineering, 4011 Environmental Engineering, 13 Climate Action

Journal Title

Chemical Engineering Journal

Conference Name

Journal ISSN

1385-8947
1873-3212

Volume Title

Publisher

Elsevier BV
Sponsorship
Engineering and Physical Sciences Research Council (EP/S030387/1)