Methane Direct Internal Reforming Solid Oxide Fuel Cell Model Study

Energy is the basic foundation for human survival and the lifeblood of economic development.The clean and efficient use of energy is particularly significant in the current"double carbon"context.The SOFC is an integral part of the future clean and efficient conversion of energy.Methane fuelled SOFCs have great potential due to its large reserves,low price,ease of storage and transportation and high hydrogen to carbon ratio.Compared to external methane reforming SOFC,direct internal reforming of methane has the advantages of lower cost,higher heat utilisation and higher theoretical efficiency,making it a hot topic in SOFC research.However,the coupling of chemical and electrochemical reactions with charge,mass and heat transfer during the direct reforming of methane at the anode results in complex material and energy exchange in the cell,making it difficult to sustain smooth and efficient operation.In order to gain an in-depth understanding of the characteristics of the discharge process of methane direct internal reforming SOFC,and to obtain the influence of kinetics,operating parameters and structural parameters on the macroscopic discharge process and performance of the cell,this paper develops a macroscopic kinetic model of the anode considering anode diffusion,chemical reactions and electrode reactions,and a macroscopic kinetic model of the anode describing the influence of chemical reactions,electrode reactions coupled with momentum,heat,mass and charge transfer in a single SOFC cell,respectively.SOFC process model,and by solving and analysing the model,the following conclusions were obtained:（1）Along the SOFC anode thickness direction from the left feed to the right border,the left feed area is mainly affected by the chemical reaction kinetics,while the right side is affected by the electrochemical reaction kinetics under the change of electrochemical reaction component distribution;as the electrode reaction kinetics changes exponentially as a function of increasing overpotential,the electrochemical reaction at higher overpotential is controlled by component mass transfer,so it is necessary to consider optimising the operating conditions,anode structure The electrochemical reaction rate is matched with the component mass transfer to improve the efficiency of the anode electrochemical reaction.（2）Anode and SOFC process model calculations show that increasing the temperature can increase the reaction and electrochemical reaction rate,which in turn increases the cell current and power density;the effect of increasing the temperature on the reaction rate of MSR and WGS is greater than that on the electrochemical reaction.（3）When the effect of carbon accumulation is not considered,increasing S/C will not help to improve the electrochemical reaction rate of the anode;increasing S/C and decreasing methane content will,on the contrary,reduce the battery current density and power density;considering that increasing water vapour content is conducive to suppressing carbon accumulation,a moderate S/C value is sufficient（4）The molar fraction distribution characteristics of the anode reaction components along the anode thickness direction and the cell length direction are similar,firstly,CH₄and H₂O are consumed by rapid reaction,accompanied by a rapid increase in the molar fraction of CO,CO₂ and H₂.For H₂,due to the competition between chemical reaction generation and electrochemical reaction,there exists a maximum molar fraction,which starts to decline thereafter;for the cathode gas,along the cell length for the cathode gas,the molar fraction of oxygen decreases along the length of the cell,and the inlet flow rate will limit the performance of the cell when it is too low,while increasing the flow rate after exceeding the critical value will have little effect.（5）Increasing the porosity and specific surface area within a certain range is beneficial to the improvement of electrode performance,but needs to be considered in conjunction with kinetic and transfer factors.In conclusion,based on the established anode macro-kinetic model and SOFC single-cell process model,this study solved and analysed to obtain a quantitative understanding of the reactions,electrochemical processes and macroscopic performance in the cell,which can provide the necessary theoretical guidance for subsequent SOFC experiments,electrode optimisation and operation.