Continuous production of CO from CO2 by RWGS chemical looping in fixed and fluidized bed reactors

Abstract

A fixed bed and a fluidized bed reactor design for the reverse water-gas shift chemical looping (RWGS-CL) process with 80 wt% Fe 2 O 3 − Ce 0.5 Zr 0.5 O 2 as oxygen storage material (OSM) are analyzed and compared by process simulation. The influence of gas inlet flow velocity on the the reaction regime is investigated and feasible regions of operation for continuous CO production are identified. Two performance indicators are defined for the process: 1) the average CO concentration and 2) the OSM utilization. Optimization problems are solved to maximize the performance indicators and analyze their mutual dependency. The results are discussed in a Pareto plot. It is shown that a fixed bed reactor design is advantageous for the RWGS-CL process because of more degrees of freedom for operation compared to the fluidized bed reactor design. A quasi-continuous production of CO is demonstrated for both reactor designs. A steady CO production with an average CO mole fraction of x CO = 0.64 and an OSM utilization of 83.9% can be realized with two fixed bed reactors. The fluidized bed reactor configuration can potentially minimize problems associated with material sintering but the average CO concentration and OSM utilization are significantly lower compared to the fixed bed due to the limited operational freedom. The results indicate the importance of dynamic simulations for understanding and exploiting the kinetic and thermodynamic aspects of inherently dynamic processes like RGWS-CL to maximize process performance.

Chemical looping beyond combustion – a perspective

“…It is noted here that CL-SMR would become the CL-WGS process if CO instead of CH 4 were used to reduce the oxygen carrier. 42,96,170,171 Both CL-SMR and CL-WGS are also referred to as CL-water-splitting processes. 47,172 Recently the CL-DRM cycle, in which CO 2 is used to regenerate the oxygen carrier (via (R6)), has been proposed to maximize the conversion of CO 2 , captured from various emission sources, to CO. 96,162,167,[173][174][175] The modified CL-methane POx coupled with H 2 O-CO 2 splitting 176 for the oxygen carrier regeneration allows the production of syngas with identical compositions in both the reduction and regeneration steps.…”

“…42,96,170,171 Both CL-SMR and CL-WGS are also referred to as CL-water-splitting processes. 47,172 Recently the CL-DRM cycle, in which CO 2 is used to regenerate the oxygen carrier (via (R6)), has been proposed to maximize the conversion of CO 2 , captured from various emission sources, to CO. 96,162,167,[173][174][175] The modified CL-methane POx coupled with H 2 O-CO 2 splitting 176 for the oxygen carrier regeneration allows the production of syngas with identical compositions in both the reduction and regeneration steps. 121,177,178 The oxygen carriers used in the above-mentioned chemical looping processes are often called redox catalysts because they simultaneously act as an oxygen donor (i.e.…”

Efficient CO2 to CO conversion at moderate temperatures enabled by the cobalt and copper co-doped ferrite oxygen carrier

“…Therefore, the development of alternative methods, such as CO 2 splitting technology [10] , is driven by energy demand and environmental issues. Among the various options, chemical looping has attracted significant attention due to its ability to convert CO 2 to CO at much lower temperatures (60 0 −90 0 °C) [11] .…”

Recent Advances in Supported Metal Catalysts and Oxide Catalysts for the Reverse Water-Gas Shift Reaction

“…The CeO 2 lattice distortion caused by the incorporation of heterocations such as Zn increases the oxygen vacancy defects and thus accelerates the mobility of the oxygen ions, leading to a higher OSC, thus markedly enhancing its catalytic activity in the RWGSR (Lin et al, 2015 ; Wenzel et al, 2017 ). In addition, either Ce 0.75 Zr 0.25 O 2 or Ce 0.75 Zr 0.5 O 2 solid solution can be formed by the addition of Zr to the CeO 2 lattice, increasing its ability to generate oxygen vacancies and, more importantly, promoting its thermal stability, which is a very promising aspect of catalytic systems employed in reactions in which the RWGSR is one of the steps in the processes that generate hydrocarbons from CO 2 (Zonetti et al, 2014 ; Wenzel et al, 2018 ).…”