Study On The Performance And Polarization Of Solid Oxide Full Cell Using H₂ And CO As Fuel

Solid oxide fuel cell (SOFC) is an all solid-state energy conversion device operated athigh temperature with the advantage of high efficiency and srong fuel adaptability.Electrical performance of SOFC fueled by H₂-CO is studied using fuels such as natural gas,syngas and coal gas which are widely used in industry; the epilogue in the anode is analyzedwith GC(Gas Chromatograph), which lays a foundation for the next research work onelectrode reactions and kinetics. An electrochemistry mathematics model is established basedon the exchange current density and gas diffusion coefficients dependent on the cellmicrostructures (porosity and pore size) and operational parameters (temperature, pressureand gas composition). The calculation results are valuable references in optimization design.The main context include three aspects:(1) The performance of Ni-YSZ/YSZ/LSM electrolyte-supported SOFC using H₂ andCO as fuels under different conditions is tested. The experiment results show that:â‘ Theperformance of SOFC increases with the rise of temperature and pressure;â‘¡After N₂ whichis used as diluting gas is inflated, cell performance increases obviously compared to thecondition that fuel is just pure syngas. Furthermore, suitable concentration of N₂ selected willlead to better cell performance. Under the optimum condition, the concentration of N₂ is30％～50ï¼…and current density is 45％～55ï¼….(2) The composition of epilogue in the anode is inspected with GC and the performanceof the SOFC is tested. Mass balance is calculated considering the chemical reaction in theanode in order to research the main reasons for carbon deposition.â‘ The increase of thereaction rates of the H₂ is avail for the decrease of the amount of the carbon deposition;â‘¡Compared to the condition under high current density, there is more amount of carbondeposition under low current density so operating under high current density is avail for thedecrease of carbon deposition.(3) An mathematical model is developed to analyze the electrical performance of theplanar solid oxide fuel cells. One important feature of the present model is that the influencesof structural/operational parameters on the concentration and activation over potentials weretaken into consideration in terms of effective diffusion coefficients and exchange currentdensity, respectively. The simulated results show that: The grain size is far smaller than thepore size and 104-grade exchange current density can be obtained. Ohmic overpotential andanodic activation overpotential are the main reasons for voltage loss. The performance of SOFC is improved significantly by decreasing the thickness of Electrolytes. The Ohmicoverpotential decrease rapidly with the increasing temperature. Therefore, the performance ofthe SOFC can be greatly improved by increasing the temperature. Calculation results from themodel and the experimental data are compared and found to agree well.Compared with theexperimental data, the average error of calculated results is 4.5%, which is caused byneglecting interface contact impedance and carbon deposition.