Synergetic effects of cement bonded copper ore and red mud as oxygen carrier during in-situ gasification chemical looping combustion of coal char

Oxygen carrier (OC), which should be both highly-reactive and thermal-resistant, plays an important role in chemical looping combustion (CLC). In this work, fine copper ore bonded with red mud by cement is used as OC for in-situ gasification chemical looping combustion (iG-CLC) of coal char in a batch fluidized bed reactor. 8.7 wt% of copper ore is designed to mix with 71.3 wt% of red mud and the weight percent of cement added into the OC is 20 wt% (denoted as Cu10.9Red89.1@C). The results indicate that this OC exhibits better combustion performance than those of single material OCs, due to its excellent reactivity towards char gasification products. Subsequently, synergetic effect between red mud and copper ore is observed and then extensively evaluated. It is found that the designed OC shows a higher synergetic level in comparison to Cu20Fe80@C (16 wt% of copper ore bonded with 64 wt% of iron ore by 20 wt% of cement) during the iG-CLC reaction with both anthracite and lignite chars. Due to the synergetic effect, the average instantaneous carbon conversion rate of both chars is increased by ca. 6%. Both alkali metal salts and copper ore (capable of oxygen uncoupling) contribute to the promotion of char gasification and oxygen transfer rate. Furthermore, the Cu10.9Red89.1@C OC maintains good and stable combustion performance during 16 redox cycles with anthracite char as fuel, regardless of the gradual loss of sodium contents. Overall, the synergetic effect of Cu10.9Red89.1@C on char conversion is attained and quantified by comparative analysis, and the proposed Cu10.9Red89.1@C appears as a competitive OC for industrial implementation of iG-CLC process.