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

Abstract

Solid oxide fuel cells (SOFCs) allow us to directly convert the chemical energy of fuel into electricity. With their emissions consisting mainly of 2 and С 2 , SOFC-based power generation systems are highly efficient (with efficiency up to 70%) and friendly to the environment, which make them increasingly attractive for use in stationary power generation systems. The mixture of CO and H 2 (synthesis gas) supplied to the SOFC anode can be produced from the natural gas using dry or steam reforming or the partial oxidation methods. The partial oxidation of methane, which 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 arranged. In this case, carbon deposition on the parts of reformer can be a problem, particularly, where the air-gas mixture supply system works abnormally.

Solid oxide fuel cells power unit reformer/burner/heat-exchanger module experimental study

“…As the temperature gradient is present in the reformer catalyst bed, the flow temperature near the reformer outer wall is obviously lower than the average flow temperature in the same reformer cross-section which causes the soot formation by the reaction: 2СО = С + СО 2 . The same carbon deposition zone encounter is described in the article [15,16]. In addition, the calculated methane concentration is almost twice as high as the actual one for all tests which is accounted for the fact that the reformer inlet temperature is at the level of 680-700 °C, therefore a greater amount of methane reacted.…”

Performance Evaluation Method of SOFC Power Unit with Anode Off-Gas Recirculation

“…4 depicts the dependence of carbon deposition boundary α c,rec on synthesis-gas oxygen consumption ratio at the SOFC at temperature in the range of 600-900°С. As it was mentioned above, implementing anode off-gas recirculation makes significant difference in terms of amount of air supplied to the reformer and lowers the carbon deposition boundary α c,rec ; for instance, the carbon deposition boundary in the partial oxidation scheme without anode off-gas recirculation at the temperature of 973 K, α 0.3 = c,rec (17). In case the fuel utilization ratio α 0.6 = f,out and 60% of the anode offgas is returned back to the reformer, the carbon deposition boundary is 2.5 times less than in the previous case (α c,rec = 0.12 vs 0.3 in the CPOX scheme).…”

“…In case there is no nitrogen in the fuel, the variable The nonlinear equations set [17]−[23] for methane as fuel and recirculated anode offgases as an oxidant was solved using MathCAD software (15). Solving this equations set can provide data on equilibrium chemical composition products at the recirculation start boundary 0 α f,out for various z min , reformer temperatures and α f,out .…”

“…For calculation of the carbon deposition boundary α c,rec the equations set [17]−[23] must be slightly modified, namely, the material balance equations [19] and [20] for oxygen and nitrogen, respectively, must be written as: where o air M -molar quantity of oxygen in the extra supplied oxidant (air). Using the new equations set [17], [18], [21] − [25] the amount of aerial oxygen required to prevent carbon deposition and maintain reactions [1] - [3] in the reformer for given synthesis-gas oxygen consumption ratio at the SOFC and recirculation ratio can be calculated. Fig.…”

SOFC power plant with circulating fluidized bed gasifier

“…Solid oxide fuel cells (SOFC) are high-temperature cells that operate at a temperature of 700-900°C. For SOFC as electrolyte can be used a ceramic material based on zirconia stabilized by yttrium (YSZ, for example, ZrO2 + 8 mol.% Y2O3) [21]. Advantages of SOFC allow using them in cogeneration cycles, which will have been significantly increasing the efficiency and environmental safety of the latter.…”