Evaluation of Different Red Muds as Oxygen Carriers in a Fluidized Bed Thermogravimetric Analyzer

The developed fluidized bed thermogravimetric analyzer (FB-TGA) brings meaningful scientific contribution to the materials engineering on the basis of full achievement of the fluidized bed advantages in a micro scale. Red mud (RM), as a byproduct of the alumina industry, contains active Fe2O3, a high content of Na, as well as some inert Al2O3 and SiO2. In this work, three kinds of different red mud (LSRM, XFRM, and LBRM) were used as oxygen carriers, and the chemical looping combustion (CLC) characteristics were evaluated in an FB-TGA using H-2 as the reactant, with the objective of exploring the interaction behavior of these constant elements and further detecting the influence on the reactivity and stability of the red muds. The multiple redox cycle performance of different red muds, based on the attrition rate, oxygen carrier conversion, reaction rate, and oxygen transfer capacity in each cycle, was investigated. Various red muds demonstrate different reaction behaviors during multiple redox cycles. The LBRM sample possesses the best attrition resistance in comparison to the other red muds and experiences an activation process with its rate index increasing with the cycles and stabilizing at 1.6800%/s after 80 cycles. During the CLC process, for the Ca-rich red mud, the Ca element tends to act as a support in the form of Ca2Al2SiO7, while the Na element exists in the form of NaAlSiO4 for all the red mud samples. Ca2Al2SiO7 and NaAlSiO4 are stable materials with a high melting point and act as inert supports to sustain the chemical reactivity of the red-mud-based oxygen carriers.

Automated summary

The developed FB-TGA has made a meaningful contribution to materials engineering by fully utilizing the advantages of fluidized bed on a micro scale. Different types of red mud were used as oxygen carriers in a CLC process, showing varying reaction behaviors. Among them, the LBRM sample exhibited the best attrition resistance and underwent an activation process.