Interaction of Swine Manure Ash-Oxygen Carrier Particles under Chemical Looping Conditions

Artikel i vetenskaplig tidskrift, 2025

The interaction between biofuel ashes and the oxygen carrier in chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU) processes will be a key factor for the future implementation of these processes on an industrial scale. This is important if the biofuel used is a waste product with a high ash content, as much as 30 wt %, as is dry swine manure. The main components of swine manure ash are Ca (17 wt %) and P (13 wt %). The present work studies the interactions between three different oxygen carriers, two synthetic magnetic Cu-based CLOU oxygen carriers (Cu30MnFekao7.5 and Cu30MnFe_Mag) and ilmenite, and swine manure ash. CLOU and CLC cycles were performed in a batch fluidized-bed reactor under harsh conditions using up to 33.3 wt % ash. For both CLOU oxygen carriers, the concentration of O2 released depended on rates of carrier conversion, although no agglomeration problems were found after 20 h of CLOU and CLC redox cycles with 25 wt % ash, and their CLOU reactivities also increased. However, the ilmenite sustained hard agglomeration after 20 h of CLC cycles with 25 wt % ash. After 20 h of CLC/CLOU redox cycles at 900 °C, all of the oxygen carriers showed ash particles adhering to their surface, with a higher degree of ash cover on Cu30MnFekao7.5 and ilmenite, both with minerals in their composition. Therefore, the presence of minerals in the oxygen carrier, either as a support or in the form of impurities (mainly Si and Al as kaolinite), could be related to a greater interaction with the ashes. Interaction with some ash elements resulted in ilmenite agglomeration, and the diffusion of K inside Cu30MnFekao7.5 particles was observed by using scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX), particularly on the kaolin-rich areas inside the oxygen carrier.