Bauxite waste with low Fe ₂ O ₃ and high Na concentration as a promising oxygen carrier in chemical looping combustion

Abstract

Summary Development of a cost‐effective oxygen carrier (OC) for chemical looping combustion (CLC) technology remains an important task to be accomplished. Bauxite waste red mud from the United States has shown promise as an OC, but bauxite waste from China has not been evaluated extensively although huge quantities of it exists. In comparison, the Chinese bauxite waste usually contains low Fe2O3 and high Na concentration. Hence, the purpose of this study was to evaluate a typical red mud (from Zibo, China) with low Fe2O3/Na mass ratio for its potential as a cost‐effective OC during CLC processing. Parametric reactor testing was accomplished with a focus on OC reactivity during CLC, and evaluations were accomplished of morphologies, elemental concentrations, and mechanical strengths before and after reaction testing; special attention was paid to the stability of Na. These results showed that Zibo red mud (a) used as an OC during CLC had satisfactory reactivity particularly after pre‐calcination at 1250°C, (b) had high contents of Na that were stable and uniformly distributed during reaction testing and formed NaAlSiO4 during sample calcination and reaction testing, and (c) showed high mechanical strengths that were similar to those of other oxygen carriers. Considering that huge amounts of this inexpensive Zibo red mud are located within areas near aluminum processing plants, it may become a promising material as an OC for CLC processing.

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

“…During the calcination process, the chemical phases of calcite, boehmite, katoite, cancrinite, sodalite, and gibbsite are decomposed following the reactions (–), with the solid products of Al 2 O 3 , NaAlSiO 4 , Ca 2 Al 2 SiO 7 , and CaO. Na 2 O and CaO could react with Al 2 O 3 to produce Ca 2 Al 2 SiO 7 (), − and they also can react with SiO 2 to produce NaAlSiO 4 (). , Ca 2 Al 2 SiO 7 and NaAlSiO 4 from the decompostion reactions (–) and solid–solid reactions ( and ) are stable materials with a high melting point. − Sodium after calcination in red mud is in the stable form of NaAlSiO 4 . …”

“…Under high temperature operation, the interaction between Na and inert Si based substances is inevitable, with a subsequent particle agglomeration being one of the biggest concerns in terms of a stable operating CLC process. Liu et al 26 found that Na in red mud exists in the form of NaAlSiO 4 due to the interactions among the substances of Na, Al, and Si in red mud under high calcination temperatures. Further, Bao et al 25 found that Na in red mud could catalyze solid fuel gasification.…”

Dechlorination Performance of Chemical Looping Conversion Using Red Mud as an Oxygen Carrier

“…The compositional analysis of RM is similar to that of the synthetic OCs, with large amounts of Fe 2 O 3 and inert compounds, such as Al 2 O 3 , SiO 2 , and TiO 2 , and AAEM-containing compounds, such as CaO and Na 2 O. Hence, many studies have been conducted on the use of RM as an OC. − More than 90% of the RM is produced by the Bayer process, , and its composition is mainly related to the type of bauxite used and the impurities therein. Generally speaking, bauxite can be divided into types containing gibbsite, boehmite, diaspore, and mixtures thereof.…”

Alkali metal modified iron‐nickel oxygen carrier to produce hydrogen‐rich synthesis gas by chemical looping gasification with pine sawdust

“…At present, the traditional gasification methods have the disadvantages of low energy efficiency, high gas production cost, and complex systems. 5,6 In order to improve gas quality and reduce production costs, biomass chemical looping gasification technology is proposed. 7 Biomass chemical looping is an emerging gasification technology.…”