(296c) Solar-Driven Methane Reforming: Design and Analysis of Fluidized Bed Receiver-Reactor Concept

Current industrial-scale hydrogen production relies heavily on methane steam reforming, emitting 7 kgCO2 per kgH2 produced to meet the high-temperature requirement of the endothermic reaction [1]. The successful integration of concentrated solar thermal energy into the reforming process can significantly reduce CO2 emissions by removing CH4 combustion as the heat source for producing hydrogen at scale. The solar driven reforming converts the sun's energy into chemical bonds in syngas that can be converted to liquid chemicals for long-term storage. This work aims to design and demonstrate a fluidized catalyst bed receiver-reactor concept to efficiently utilize concentrated solar energy in driving methane steam and dry reforming. Mild fluidization of catalytic particles can provide bed-wall heat transfer coefficients hT,w up to 1500 W-m-2-K-1 [2]. Such high hT,w can enable mean wall input solar fluxes of more than 300 suns to drive the endothermic chemical reaction at desired catalyst temperatures (700-850 oC) while maintaining the receiver wall temperatures below material limits.

To validate our receiver-reactor concept, we simulated the solar reactor model using a 2-m high tubular-SiC receiver-reactor with Ni-impregnated alumina-silica particles for ranges of mean incident solar fluxes (dp = 320 mm; 700 ºC; 5 bar). The model solves vertically discretized continuity, species, momentum and energy balances, as well as radially discretized dusty gas transport [3], and catalytic surface chemistry [4]. Such a model allows identifying optimal temperatures and feed compositions to avoid side reactions that deactivate the catalysts and lead to lower hydrogen yields (e.g., exothermic coking and endothermic reverse-water gas shift); inlet composition of steam-to-methane (nH2O/nCH4) and carbon dioxide-to-methane ratio (nCO2/nCH4) dictates the methane conversion (XCH4) and syngas product ratio (nH2/nCO). Downstream synthetic fuel production usually requires nH2/nCO ≈ 2.0, while XCH4 needs to be as high as possible to minimize separation costs. With this requirement, our model results show that at inlet compositions of nCO2/nCH4 ≈ 1.0 or nH2O/nCH4 ≈ 1.5, the reactor can operate at a solar efficiency higher than 80% at XCH4 ~70%. The developed model will be further validated at a lab-scale solar reactor with infrared lamp using Ni-based catalysts. The result from this study indicates that fluidized porous particles receiver-reactor design can accommodate solar-driven methane reforming as a near-term viable solution for solar fuel or chemical production at significant scales.

References

[1] S. Sharma and S. K. Ghoshal, vol. 43, 1151-1158, doi: 10.1016/j.rser.2014.11.09.

[2] K. J. Brewster et al., Solar Energy, vol. 289, p. 113322, Mar. 2025, doi: 10.1016/j.solener.2025.113322

[3] J. Solsvik and H. A. Jakobsen, Chemical Engineering Science, vol. 66, no. 9, pp. 1986–2000, May 2011, doi: 10.1016/j.ces.2011.01.060.

[4] K. Delgado, L. Maier, S. Tischer, A. Zellner, H. Stotz, and O. Deutschmann, Catalysts, vol. 5, no. 2, pp. 871–904, May 2015, doi: 10.3390/catal5020871.