Development and testing of ilmenite granules for packed bed chemical-looping combustion

Chemical-looping combustion (CLC) is a promising technology that integrates power production and CO2 capture with a low energy penalty. CLC has been successfully demonstrated using interconnected fluidized bed reactor systems. However, high pressure operation allows the use of inherently more efficient power cycles than low pressure fluidized bed solutions. With the aim to work at elevated pressures, dynamically operated packed-bed reactors have been proposed for CLC. In a packed-bed CLC reactor bigger oxygen carrier particles are used to avoid very large pressure drops and the required mechanical properties of these particles are quite different from the properties needed in a fluidized bed CLC system. In this work different particles have been developed and tested for application in a packed-bed CLC reactor. Ilmenite was chosen as base material because of its good reactivity with syngas, the natural availability and related low cost. Different ilmenite pellets with different composition and shape were developed and their mechanical properties before and after thermal and chemical cycling were analysed and compared. The reactivity of the particles and the influence of different reaction conditions were also studied in a thermogravimetric analyser. It was found that the thermal and chemical stresses produced an important deterioration of the mechanical properties of the pellets. The type of additive used during the production process showed an important effect on the mechanical properties of the granules. Only the granules produced with Mn2O3 as additive demonstrated acceptable suitable mechanical properties after thermal and chemical cycling. (C) 2014 Elsevier B.V. All rights reserved.