Research On In-situ Raman Spectroscopy And Process Optimization Of Methane-fueled Solid Oxide Fuel Cells

The solid oxide fuel cell using partial internal steam reforming of methane as fuels has the potential for avoiding carbon deposition and large local thermal stress,and it can also improve the system efficiency by internal coupling of heat,which has a promising future.Using high temperature in-situ Raman spectroscopy to investigate the mechanism of carbon deposition and removal,and using numerical methods to analyze optimization strategies for operating conditions are of great value.A test system with both high temperature in-situ Raman spectroscopy and electrochemical test was designed and built.The carbon deposition and removal mechanisms for methane-fueled SOFC anode process were investigated using this test system.Optimization strategies for partial internal steam reforming of methane were studied by numerical methods.A high temperature in-situ Raman spectroscopy test system suitable for electrode surface/interface reaction mechanism research was designed and built.The system can provide a temperature environment from room temperature to 850? for SOFC double chamber operations,it can obtain high temperature in-situ optical mapping and Raman spectroscopy by introducing quartz glass as the optical window.The spatial resolution of Raman spectroscopy is 5 micron.The material properties of Ni-YSZ anode and mechanism of carbon deposition and removal of methane on anode surface were studied using the in-situ test system.The Ni-YSZ anode is chemically stable and reversible in redox cycles.The types of carbon deposited on anode surface by introducing methane were highly related to methane concentrations.Only highly ordered graphite(carbon G)was formed in the case of low methane concentrations(Argon as carrier gas),and both graphite and disordered carbon(carbon D)were formed in the case of high methane concentrations.The Raman spectroscopy dynamic experiment revealed that the anode surface preferentially formed ordered carbon G when introducing methane,with the deepening of carbon deposition process,it changed to the formation and growth of carbon D.By introducing steam,the deposited carbon could be removed directly,and the removal rate was positively correlated to the methane concentrations.A unit cell model with real planar cell structure from the Shanghai Institute of Silicate of Chinese Academy of Sciences(SICCAS)was developed by coupling heterogeneous chemical/electrochemical reactions,charge transfer,mass and energy transfer processes.The model was validated and then used to study the optimized strategy of SOFC running on partial internal steam reforming of methane.Proper methane steam reforming reaction can optimize the electrochemical active components(hydrogen and carbon monoxide)inside the cell and the heat production rate distribution,when compared to the condition of complete external steam reforming of methane.The methane internal steam reforming ratio affected the cell performance,the maximum temperature difference within the unit cell,and the local temperature gradient.There was an optimal ratio of reforming under certain conditions.