On a Highly Reactive Fe₂O₃/Al₂O₃ Oxygen Carrier for in Situ Gasification Chemical Looping Combustion

Abstract

Interest in the direct use of solid fuel in chemical looping combustion (CLC) technology makes the in situ gasification chemical looping combustion (iG-CLC) an attractive approach for the low-cost capture of CO 2 . Highly reactive material is required in iG-CLC in order to achieve a fast reaction between the fuel and oxygen carrier. In this work, a material, Fe 2 O 3 /Al 2 O 3 synthesized by sol−gel, was evaluated in a fluidized-bed reactor by reaction with lignite. This is the first time sol− gel-derived Fe 2 O 3 /Al 2 O 3 material has been used in an iG-CLC process. Operation conditions, including steam content in the fluidization gas, temperature, and potential oxygen ratio, were investigated to explore their influence on combustion and char conversion. The results show that a higher steam concentration can greatly enhance the rate of char gasification and hence the reaction between the lignite and the oxygen carrier, whereas a negligible effect of the steam content was noticed on volatile combustion. In addition, the use of the highly reactive Fe-based material prepared by the sol−gel method significantly increased the char gasification rate as compared to other previously evaluated materials. Moreover, the combustion efficiencies of volatiles and char from the lignite, respectively, were studied. Using the Fe 2 O 3 /Al 2 O 3 material enabled a low oxygen carrier inventory of 600 kg/MW th to be reached in order to achieve 99% char combustion, which is much lower than that reported in other works. These findings suggest that Fe 2 O 3 /Al 2 O 3 prepared by sol−gel is a highly reactive oxygen carrier for iG-CLC.

Advanced Chemical Looping Materials for CO2 Utilization: A Review

“…Regarding Fe-based oxygen carriers, promoter materials such as Al 2 O 3 [78,79,80,81,82], MgO [83,130], TiO 2 [84,85,86], SiO 2 [87], MgAl 2 O 4 [88,89,90,91,103], CaO [92,93], ZrO 2 [94,95,96] and CeO 2 [22,97,98,99,100] have received extensive scientific attention in the past decades. However, these promoters can easily lead to solid-solid transformation with iron oxides during a continuous cycling process [127].…”

Characterization of a sol–gel derived CuO/CuAl2O4 oxygen carrier for chemical looping combustion (CLC) of gaseous fuels: Relevance of gas–solid and oxygen uncoupling reactions

“…The CuO/CuAl 2 O 4 oxygen carrier material was prepared through the sol-gel technique which was usually used for preparing catalyst [35] and sometimes for the preparation of oxygen carrier particles being used for CLC technologies [28,[36][37][38][39][40] [28] where a similar material containing 60 wt.% CuO and 40 wt.% CuAl 2 O 4 was prepared. After crushing and sieving, the particles being sized to 125-180 μm were selected as oxygen carrier to be used in this work.…”

Chemical looping combustion of coal in a 5 kWth interconnected fluidized bed reactor using hematite as oxygen carrier

“…Initial work in CLC were mostly limited to laboratory scale work on oxygen carriers particles using thermo gravimetric analyser (TGA), and small fixed/fluidized beds to characterize over 1000 different materials based on Ni, Cu, Fe, Mn, and Co [8][9][10][11][12][13][14][15][16]. Later studies had progressed to low cost and environmentally friendly oxygen carrier, such as iron ore [17][18][19], manganese ore [20], copper ore [21], and the mixed iron and copper ore [22], including their use in entire CLC process systems at different scales [23].…”