Taking into consideration that the

Taking into consideration that the target value of 100 ppm CO in the product gas of themethanation reactor has to be achieved, this corresponds to 98% CO conversion and 1.85% H2conversion. The further rise in temperature and H2 consumption is caused by the unwanted CO2methanation. The excess of H2 conversion is here characterized by the factor EH2 = XH2/0.0185,which is the ratio of the actual H2 conversion to the minimum conversion of 1.85%, if only COmethanation takes place and the residual CO content of 100 ppm needed for PtRu-anodes is justreached. Table 4 indicates that an inlet temperature of 130 ◦C is an appropriate value to avoid very highoutlet temperatures (>240 ◦C). In this case, 2.6 kg of catalyst (52 g Ru) would be needed. The outlettemperature is then 221 ◦C, which is a reasonable value to limit the RWGS and CO2 methanation. EH2would then be 1.2, i.e., 20% more hydrogen (H2 conversion of 2.22% compared to 1.85%) is consumedcompared to the ideal case without CO2 conversion instead of here 0.7%. In order to be on the safe side,a certain surplus of the reactor size is advisable. Therefore, Table 4 also shows the reactor parameters,if the reactor length and mass of catalyst would be by a factor 1.5 or 2 larger compared to 100 ppmresidual CO content. For a factor of 1.5 (mcat = 3.9 kg) and Tin = 130 ◦C, the resulting values are XCO= 99.95% (residual CO content of 3 ppm), XCO2= 1.6%, and EH2= 1.45. The feed gas of the fuel cellwould then consist of 77.2% H2, 9.8% CO2, 10.8% H2O, and 2.1% CH4. The reactor size is then 7.8 L,e.g., a cylinder with a length of 44 cm and diameter of 15 cm. An option is also an increase of the Rucontent (here 2 wt-%), which would decrease the size and mass of the reactor further.