Development of Binder-Supported CaSO₄ Oxygen Carriers for Chemical Looping Combustion of Methane

Chemical-looping combustion (CLC) has been recognized as an energy-efficient method for CO₂ capture. From thermodynamics point of view, CaSO₄ has a good availability in the cycle of CLC system. The inhibition of the poor mechanical strength and reactivity is fatal to a CLC system based on calcium sulfate (CaSO₄). In this study, three important parameters (binder, acetic acid, and water) were selected as factors of the L₉ orthogonal experiment designed to investigate the performance of the binder-supported CaSO₄ oxygen carriers by intuitive analysis. Then, the suitable oxygen carriers were comprehensively studied in a fixed bed reactor. The orthogonal experiment results showed that adding binder enhanced the mechanical strength and increased the conversion of the binder-supported CaSO₄, and the optimal extrusion condition was: 30 g CaSO₄, 12 g SB powder (sticky pseudo-boehmite), 2.5 ml acetic acid, and 15 ml water. The results of reduction reactivity showed the conversion and mass-based reaction rates of the binder-supported CaSO₄ were obviously enhanced. Moreover, the favorable performance of the binder-supported CaSO₄ was explained by formation of CaAl₂O₄. This compound was excellent thermal stability and provided a stable nanosized framework between the crystal grains observed by field emission scanning electron microscope.