Session: 06-04: CSP Receivers and Reactors III

Paper Number: 169873

169873 - Modeling of a Fluidized Catalyst Bed Receiver-Reactor for Solar Methane Reforming 

Abstract: 

Endothermic methane or biogas reforming driven by concentrating solar energy can provide a means for capturing solar energy into fuel streams and thereby provide long-term storage and transport of solar energy in the form of fuels or chemicals derived from the reforming syngas product.  Receiver-reactor designs based on catalyst particles fluidized with reactant gases provides very high receiver-wall heat transfer coefficients [1] that can maintain receiver walls at reasonable temperatures above the required reforming reaction temperatures of 700 to 800 ºC. The highly endothermic reforming and the use of mild fluidization with high solid volume fractions provides effective heat and mass transport within the receiver reactor to enable effective conversion of the concentrated solar wall fluxes into stored chemical energy in the product syngas.  Partially porous particles impregnated with nickel catalysts can support reaction rates that match pressurized fluidized reactant flows to convert solar fluxes as high as 300 kW m^-2 on receiver walls of a volumetric receiver-reactor concept that enhances the particle-wall heat transfer and enables higher solar flux to be converted to useful products. Predicting the performance of such receiver-reactor requires modeling at the receiver-reactor scale using a reduced-order model that solves 1-D vertically discretized continuity, species, momentum, and energy balances, as well modeling the porous particle gas transport and catalytic surface chemistry. This study explores the effects of receiver-reactor operating conditions and particle microstructures on fluidized bed receiver-reactor performance for CH₄reforming with CO₂ and H₂O to product syngas.

To ensure high CH₄ reforming fractions, reactor bed temperatures must maintain well above 750 ºC to avoid reverse water gas shift and methanation reactions, that consume product H₂ and CO.  The receiver-reactor must maintain acceptable wall temperatures T_w at reasonable solar wall fluxes, the fluidized bed reactor must maintain bed-wall heat transfer coefficient h_T,w above 1500 W m^-2 K^-1, which are attainable with internal finned surfaces at relevant mild fluidization conditions.  To explore this receiver-reactor concept, a 2-m high SiC-tubular receiver-reactor is simulated withNi-impregnated Al₂O₃ particles with d_p = 250 mm and inlet gas temperature T_g,in = 700 ºC and pressure P_g,in = 5 bar for a range of mean incident solar fluxes up to 400 kW m^-2.  To achieve significant methane conversion X_CH4 and desirable syngas product ratios n_H2/n_CO = 1.0 for downstream synthetic fuel production, inlet compositions  set to n_CO2/n_CH4 = 2.0 and n_H2O/n_CH4 = 1.25 can operate at a solar efficiency h_sol > 80% and X_CH4 > 70%. For an industrial scale reactor at extended size, X_CH4 can reach 80% with higher reactor temperatures and higher wall heat transfer coefficients facilitated by internal fin surfaces.  

References:

[1] Brewster KJ, Martinek J, Municchi F, Arthur-Arhin WJ, Fosheim JR, Ma Z, et al. Reduced order modeling of a fluidized bed particle receiver for concentrating solar power with thermal energy storage. Solar Energy. 2025;289:113322.

Presenting Author: Akbar Laksana Colorado School of Mines

Presenting Author Biography: Akbar Laksana is a Ph.D. graduate research assistant in the Advanced Energy System program at the Colorado School of Mines. Mr. Laksana has a B.S. in Mechanical Engineering from the Institute of Technology Bandung n Indonesia and an M.S. degree in Mechanical Engineering from Georgia Tech University where he studied combustion. Akbar is currently doing research on solar receivers and reactors for concentrating solar applications working with Prof. Greg Jackson at Mines and Dr. Alon Lidor at NREL.