Research of coal‐direct chemical looping hydrogen generation with iron‐based oxygen carrier modified by NaAlO₂

Abstract

This study reports a high-performance modified oxygen carrier (OC) in a three-cycle chemical looping process in which coal is used as the raw feedstock to produce hydrogen. A series of experiments of coal-direct chemical looping hydrogen generation (CLHG) were conducted in a batch fluidized bed reactor, in the absence or presence of the NaAlO 2. The experimental results indicated that the carbon conversion and hydrogen yield reached 87.0% and 1.30 L Á g −1 , respectively, when the coal/oxygen carrier (Fe4Al6) mass ratio was 1:20. However, FeO was the main product of the reduction process with Fe4Al6, which limits the production of hydrogen during steam oxidation. Therefore, NaAlO 2 was used to improve the reaction performance of the OC. The carbon conversion and hydrogen production of NaAlO 2-loaded oxygen carriers were 10.7% and 9.6% higher than Fe4Al6, respectively. X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and temperatureprogrammed reduction (TPR) techniques were used to characterize the oxygen carriers. According to the XRD analysis results, the addition of 5 wt% NaAlO 2 can generate NaFeO 2. The unique layer structure of NaFeO 2 can loosen the structure between Fe 2 O 3 and Al 2 O 3. Thus, the surface morphology and pore structure of the oxygen carrier were improved, which are responsible for the enhancement in reactivity rather than the catalytic effects of the alkali metal. The cycle performance of the Na0.5Fe4Al6 remained stable after multi-redox cycles, and no serious sintering phenomena were observed; in addition, the carbon conversion and hydrogen yield remained above 86% and 1.40 L Á g −1 , respectively. K E Y W O R D S chemical looping, crystal structure, Fe 2 O 3 /Al 2 O 3 , H 2 production, sodium modification 1 | INTRODUCTION Currently there is growing interest in using hydrogen as a clean energy carrier since it can provide a high Jinshuai Li and Xiuli Zhang contributed equally to this work.

Discovery of Oxygen Carriers by Mining a First-Principle Database

“…Even so, experiments indicate that CaAl 4 O 7 and CaCrO 4 are also stable up to relatively high temperatures. , Unfortunately, there seems to be no information available regarding Ca 3 Al 4 O 9 . The Na-based candidate is, nevertheless, more interesting because Na 2 CrO 4 is catalytic while NaAlO 2 has been shown to enhance the performance of an Fe-based OC …”

“…Unfortunately, there seems to be no information available regarding Ca 3 Al 4 O 9 . The Na-based candidate is, nevertheless, more interesting because Na 2 CrO 4 is catalytic while NaAlO 2 has been shown to enhance the performance of an Fe-based OC 110. Remaining Transitions without Si.…”

Study on the redox performance of Cu and Ce‐doped CoFe 2 O 4 as oxygen carriers for chemical looping hydrogen generation

“…The hydrogen produced in the SR is derived from the oxidation of reduced metal and gasification of the deposited carbon (R2 and R3). 44 The hydrogen generation capacity of OC is assessed after the removal of the hydrogen production from carbon deposition. 45 C…”

Chemical looping combustion characteristics and kinetic behaviour of Sr‐doped perovskite‐type CaFeO3 oxygen carriers: Theoretical and experimental investigations

“…The design and preparation of high-performance OCs are significant research topics for CLC. [7,[10][11][12][13] With regard to CL technology, Ca Fe OCs have attracted considerable attention because of their promising selectivity and catalytic properties. The design and preparation of Ca Fe OCs, as well as their reactivity in the CL process, have been investigated.…”