Assessment of Possibilities for Operation of Ni-Catalyst Partial Oxidation Reformers in SOFC Systems after Soot Formation

Solid oxide fuel cells (SOFCs) allow us to directly convert the chemical energy of fuel into electricity. With their emissions consisting mainly of Н₂О and СО₂, SOFC-based power generation systems are highly efficient (with efficiency up to 70%) and environmental friendly, which makes them increasingly attractive for the use in stationary power generation systems. The mixture of CO and H₂(synthesis gas) supplied to the SOFC anode can be produced from the natural gas using the dry or steam reforming or partial oxidation methods. The partial oxidation of methane, that is typically done with Ni catalysts, seems the best option for start-up systems of power plants with the anode gas recirculation or other applications where no water supply can be possibly organized. In this case, carbon deposition on the parts of reformer can be a problem, particularly, where the air-gas mixture supply system works abnormally.

The simple method of calculation of thermodynamically equilibrium composition of partial fuel oxidation products was used to calculate the degree of air consumption  in a reformer which permits to avoid soot formation. The value  ensuring auto thermal process in CPOX reformer was determined.  Air flow rate used in reaction with synthesis gas and for cooling the reformer, was calculated also.

An experiment is carried out to simulate the abnormal operation of the CPOX reformer with further soot formation on the Ni-catalyst and its walls. The results show that even in the event of the abnormal operation and carbon deposition in it, the CPOX reformer can continue working. Specifically, the carbon gasification takes place. The CO-content of the synthesis gas in this case is twice as much, on the average; however, this is not of critical character for SOFC systems.