Effects of Naphthalene on the Performance of Ni/YSZ Anode-Supported SOFCs

Abstract

The operation of SOFCs on biomass-derived fuels demands an intrinsic tolerance of the cells towards biogenic contaminants like tars. In order to develop more robust cells, the behaviour of state-of-the-art Ni/YSZ anode supported cells at 700 °C in presence of naphthalene as model tar was extensively studied. As reported in literature naphthalene blocks the active sites of nickel catalysts and therefore hinders the utilisation of methane and carbon monoxide in the fuel gas. This study shows that the loss in performance is greater than only the contribution of this inertisation of CH4 and CO and that the behaviour of the cell voltage is similar to the poisoning with H2S. We also found that the operation temperature is a major parameter when tolerance limits for naphthalene have to be defined. The analysis of electrical impedance data helped to understand the underlying poisoning processes.

Experimental Investigation of Naphthalene Induced Degradation of Reversible Solid Oxide Cells Operated on Bio-Syngas

“…The tar concentration is chosen to induce a degradation effect that is sufficiently larger than the uncertainties. Compared with reference data, 13 the standard operation of the Ni-YSZ cell reproduced similar results for the voltage and the EIS, validating the setup and method.…”

“…This is in line with the observations of prior experiments. 13 In the DRT, all four processes are affected, with a focus on the first two. The process at the highest frequency has a high risk of being an artifact due to the limited measured frequencies up to 10 kHz.…”

“…Fuel electrode supported single cells (FESCs) operated under internal reforming conditions between 700 °C and 750 °C show a fast voltage degradation during the exposure to naphthalene concentrations between 0.05 g Nm −3 and 0.4 g Nm −3 . 13,17,18 The operation under a H 2 /N 2 mixture increases the robustness towards the tar, a stable operation at 0.3 g Nm −3 naphthalene is possible. 17 For a 2-cell stack operated under internal reforming conditions at 705 °C, a voltage degradation similar to the single cells is observed immediately at the start of the exposure to 2 g Nm −3 naphthalene.…”

“…14 In these investigations, Ni-YSZ electrodes and Ni-YSZ substrate layers are utilized and no carbon depositions are reported. 13,14,17,18 In all investigated electrolyte supported cells (ESCs), Ni-GDC electrodes are used. For operations under internal reforming conditions between 830 °C and 900 °C, a voltage degradation under load is reported for naphthalene concentrations between 0.3 and 3.1 g Nm −3 .…”

“…The utilization of model tars tends to overestimate the influence of real tars 8 and is, therefore, a conservative approach commonly used. The most prominent utilized model tars are naphthalene, [9][10][11][12][13][14][15][16][17][18] toluene, 8,10-12,15,17-32 phenol 14,33 and benzene. 4,10,11,26,27,34,35 In comparative studies, naphthalene shows the lowest tendency to coke formation 11 and the highest impact on the catalytic methane reforming 12 as well as on the electrochemical performance.…”