Direct Utilization of Methane in Microtubular-SOFC

Abstract

This paper analyzes the possibilities for application of micro-tubular SOFC (mSOFC) with partial oxidation catalyst (CPOX) located at the cell inlet for direct utilization of hydrocarbons. Applied system reduced coke deposition without integration into the cell structure and allowed application of traditional Ni:zirconia cermet for direct hydrocarbons utilization. The key problem in the proposed Microtubular Solid Oxide Fuel Cell (mSOFC) system is where the part of the cell is outside of the hot zone. This is caused by the temperature distribution (TD). Despite the good resistance to thermal shock, the long-term operation with unequal TD can cause cell damage. The TD was measured along and across the cell (internally and externally) under different operating conditions. H 2 and CH 4 were used as fuels in the first instance. Different mixtures of fuel and air and different forms of the catalyst were tested for the CPOX of hydrocarbons. Different forms/geometries of the catalyst were tested to optimize the system design. The paper mainly focuses on solving problems with temperature distribution along and across the mSOFC cell.

Catalytic Reforming System Suitable for Transportation Applications

“…Application of such catalyst makes sense for small‐scale portable units where a small amount of a catalyst is needed. The gas hourly space velocity (GHSV) was 30 L h −1 g cat −1 and was lower than for indirect internal reforming tested in previous work . According to literature , , methane conversion is expected to be around 85–95%, at a temperature of 700–750 °C, 1 bar, proportion CH 4 :air in gas 1:2.4 and GHSV 30 L h −1 g cat −1 .…”

“…The temperature of the catalyst bed was not monitored. However, early results confirmed the formation of a hotspot around 5 mm from the reactor inlet with a temperature 50–70 °C above the external reactor temperature.…”

Application of silver in microtubular solid oxide fuel cells

“…All tests were conducted under ambient air-condition on the cathode side. Details about the cell test system were described in previous papers [28,29].…”

“…The cell with the CPOX catalyst was fed with the mixture of CH 4 and air in the molar ratio 1:2.4. Approximately, 70% of the fuel was converted on the catalyst before it reached the anode [28]. The power of the cell was around 0.14 W cm −2 at 0.7 V. Low operation temperature (650 °C) decreased the rate of oxygen reduction and conductivity of the YSZ electrolyte.…”

“…The process of cell passivation/activation resulted in the difference in temperature distribution along and across the cell and could result in some microcrack formation in the electrolyte. Also, the risk of coke deposition on the anode during OCV was significant because no steam was formed from fuel electrooxidation and only 60-70% of fuel was converted on the CPOX catalyst [28]. Formed coke and temperature gradient may also result in microcracks formation in the electrolyte structure.…”