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Diesel CPO for SOFC
Gepubliceerd door: Publicatie datum:
ECN Waterstof en Schoon Fossiel 23-4-2009
ECN publicatienummer: Publicatie type:
ECN-E--09-031 ECN rapport
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Within the research program Reforming of liquid fuels for fuel-cells, ECN started a project on the development of a diesel CPO reformer for SOFC in 2005. The application in mind is a small scale (5kWe) diesel fed auxiliary power unit (APU). The goal of the project is to develop the technology required to transform a liquid logistic fuel into a reformat suitable for the operation of a SOFC.
The emphasis of this work is on the development of a cold-flame assisted evaporator/mixer coupled to a catalytic CPO reformer. The application of cold-flame evaporation and mixing allows the reformat to be directly fed to the SOFC without further heating or cooling. Moreover, once cold-flames are ignited and stabilized, pre-heating of the air and fuel becomes obsolete. These aspects justify the development described in this report. In the cold-flame evaporator/mixer, the cold-flames are stabilized by means of a recirculation tube. The momentum of the fuel spray of the nozzle induces the required recirculation. The cold flame evaporator/mixer was coupled to a catalytic reformer reactor, transforming the hydrocarbon+air feed into a CO+H2 rich reformate.
The reformer was coupled to a SOFC to be able to verify the quality of the reformat obtained with this reformer. The SOFC therefore served as an analysis tool. Characteristically, the reformat was held at 800°C all the way towards the SOFC. For this, high temperature flange connections and steel-ceramic expansion connections were successfully applied.
It is demonstrated that that cold-flame evaporation of liquid fuels is a feasible means of feed preparation for a catalytic reforming reactor. The quality of the resulting reformat is adequate to be fed to the SOFC. The reformat quality, however, decreased with time-on-stream due to fouling of the reformer by carbon-depositions. These carbon-depositions were essentially located on the fuel injector, which is the coldest part of the reformer. The depositions were initiated by condensation of hydrocarbons. Although different nozzle configurations were tested, the depositions could not be suppressed sufficiently.
It was shown that the performance of the cold­flame evaporator strongly depends on the characteristics of the diesel spray feeding this evaporator. For a further development of the cold-flame evaporator, the spray characteristics in combination with the cold-flame reactions and the fluid recirculation within the evaporator should be modelled via computational fluid dynamics.

The second most important recommendation would be to test commercial diesels. In this study a fully paraffinic model diesel was used. The aromatics present in commercial diesel are known to significantly influence the cold-flame characteristics of the fuel since the aromatics are relatively unreactive at cold-flame conditions.

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