Evaluation of multi-functional iron-based carrier from bauxite residual for H2-rich syngas production via chemical-looping gasification

Abstract

Solid-fueled chemical-looping gasification (SF-CLG) is a chemical looping technology integrated with gasification for poly-generation, i.e. syngas and power production. This flexible platform could avoid costly air separation unit, providing low cost H 2-rich syngas for the production of fuel chemicals, ammonia, methanol, etc. One key to successful SF-CLG is the development of a multi-functional cyclic solid material that can be treated in large quantities. The solid circulating between the two reactors is the means for oxygen, heat, and catalyst transport. This study demonstrates a cost-effective oxygen carrier (OC) developed from Bauxite residual of alumina industry, containing sufficient active content, multi-supporting materials, and promoter. It is proposed to be a cyclic material to transport oxygen and heat from the air reactor to gasifier to promote gasification, and in its reduced form to catalyze internal syngas reforming. The catalytic functions of this OC for char gasification and syngas reforming were validated. Syngas composition and yield, gasification rate, and OC behavior were investigated at different fuel/OC ratio, and by successive redox cycle in a fluidized bed reactor. The compatibility of new composite materials with the proposed auto-thermal SF-CLG was confirmed based on thermodynamics and the material's physical and chemical properties. Keywords: H 2 rich syngas production; chemical looping gasification; solid fuel; iron-based oxygen carrier With gaseous fuel feed stock, the integration of chemical looping with syngas production yields several types of technologies, such as steam reforming chemical-looping combustion (SR-CLC), auto-thermal chemical looping reforming (a-CLR), and partial oxidation for syngas production [3-7]. These technologies using Nibased oxygen carrier (OC), have been investigated and successfully demonstrated in continuous facilities with thermal inputs ranging from 500 W to 140 kW [4, 8-9]. Here the Ni-based OCs functions as lattice oxygen transport materials and catalysts for fuel combustion, decomposition and steam reforming.

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

“…Figure displays SEM images of OC #3 before and after reaction testing. The fresh OC (Figure 5A,B) was porous on the surface and covered with small angular particles; this morphology is similar to that observed in OCs produced from other red mud sources . However, the particle sizes of OC #3 were smaller than those in synthetic Fe 2 O 3 ‐based OC with Al 2 O 3 .…”

“…These changes are in agreement with what would be expected by the morphology changes observed in the SEM images after reaction testing, Figure , in which particle sintering and agglomeration was observed. In comparison with other, previously tested red mud OCs, the BET surface areas and the pore volumes in Table were considerably higher, by as much at approximately 6 to 8 times greater. The declines of BET surface area and porosity, along with the increased average pore size, indicate that the collapse of micropores during the redox cyclic process and the surface area and pore volume are ascribed to macropores.…”

“…One main concern is the feasibility of using RM with low Fe 2 O 3 content as an effective OC. Another concern is figuring out the stability of Na in such a high Na content condition, which is not included in the existing investigations . Moreover, this study on the utilization of RM wastes in CLC may help huge amounts of indigenous Chinese RM find a way out and play a positive role in environmental protection.…”

“…Elsewhere, Chen et al developed RM from the United States as an OC for coal‐fueled CLC and primarily investigated the regeneration and reduction behavior of RM OCs in a simulated CLC process. They also proposed an RM OC to serve as a multi‐functional OC, which transported oxygen and heat for solid fuel gasification, while its reduced form was used as a catalyst for syngas reforming for auto‐thermal solid‐fueled chemical looping gasification (SF‐CLG) technologies . Bao et al evaluated the functions of inert supports (Al 2 O 3 , SiO 2 , TiO 2 , and CaO) as well as the sodium content in RM and proved that inert supports have a positive effect on the reactivity by developing a porous structure in the OC particle.…”

“…They also proposed an RM OC to serve as a multi-functional OC, which transported oxygen and heat for solid fuel gasification, while its reduced form was used as a catalyst for syngas reforming for auto-thermal solid-fueled chemical looping gasification (SF-CLG) technologies. 32 Bao et al 33 evaluated the functions of inert supports (Al 2 O 3 , SiO 2 , TiO 2 , and CaO) as well as the sodium content in RM and proved that inert supports have a positive effect on the reactivity by developing a porous structure in the OC particle. Ortiz et al 34 analyzed the performance of an RM OC with respect to gas combustion using a simulated PSA off-gas, methane, and syngas and found that RM OC had high oxygen transport capacity (2.4 wt.%) and reactivity for H 2 , CO, and O 2 but a noticeably lower reactivity for CH 4 at 950 C. Mendiara [35][36][37] and Abad 38 et al compared five potential OCs (ie, ilmenite, bauxite waste, hematite, copper ferrite, and synthetic material) for the iG-CLC with coal and found that bauxite waste and hematite minerals presented the best performance for iG-CLC based on the results obtained.…”