## 3 Results
### Plant Model Results
In this sensitivity study, it was assumed, in order not to distort the efficiency trends, that all turbomachinery components (air and PSA off-gas compressors) operate in a single adiabatic stage. Mild benefits are reached with the GSPOX configuration: The S/C clearly declines for higher pressures, as it is not required to convert as much CO in the shift units due to the higher recovery of H\({}_{2}\) in the PSA, leading to better heat recuperation of the streams fed to the cluster and increased H\({}_{2}\) efficiency. More low-grade heat is converted to steam, resulting in a consistent improvement of the equivalent efficiency, as shown in Figure 13. For the GSR, higher pressures increase the required S/C to reach the desired methane conversion in the cluster, and consequently, the H\({}_{2}\) efficiency is curta  
Figure 13: Effect of reactor operating pressure for GSR and GSPOX H\({}_{2}\) plants. that if the turbomachinery can reach the specified pressures cost-effectively (or alternatively adding intercooled stages), the GSPOX carrier will only result in small benefits relative to the GSR. However, this advantage can be expected to continue increasing for even higher pressures, although practical challenges will constrain the maximum achievable system pressure. If, for instance, higher pressure ratios are attained by means of intercooled compression, the lower air temperature entering the oxidation step will result in lower H\({}_{2}\) efficiencies relative to the single adiabatic compression mode of operation because more fuel is combusted to reach the desired reactor temperature. Simultaneously, higher pressures will reduce the number of H\({}_{2}\) and CO\({}_{2}\) compression stages required to reach delivery pressures, reducing the capital costs of these items. Thus, this parameter is closely interlinked with the remaining plant elements. However, it should also be noted that higher operating pressures in the reactor increase undesired mixing of the outlet streams from the different steps of the reactor cycle, reducing the CO\({}_{2}\) avoidance. In the range of pressures studied here, the CO\({}_{2}\) avoidance was reduced by 1.0 and 1.5%-points for GSR and GSPOX plants when increasing the pressure from 25 to 40 bar. As the advantages of GSPOX over GSR for H\({}_{2}\) production are relatively small, the present assessment is extended by integrating a combined power cycle with the GSPOX to simultaneously produce H\({}_{2}\) and power. The key operational feature from the GSPOX that allows this with reduced energy penalty is the possibility of producing a relatively pure H\({}_{2}\) stream which can be used for extra firing if the air is introduced in the cluster with an excess of O\({}_{2}\). As expected, the Advanced GT combined cycle configuration yields the most attractive results, approximately 3.4%-points of additional equivalent efficiency points compared to the model employing Current GT technology. Still, the equivalent efficiency is around 1.0%-points below the unabated SMR benchmark. Given the pressure ratio of each GT, the H\({}_{2}\) recovery and consequently the H\({}_{2}\) efficiency vary slightly. Indeed, the H\({}_{2}\) recovery drops in the PSA unit at lower inlet pressure, falling from 85.6% to 82.0%, when shifting from Advanced to Current GT technology. For the GSPOX power generating plants, given the fixed natural gas input of 129 MW (LHV basis), the net electricity production resulted in around 25 MW as shown in Figure 14 (\(\sim\)20% of the heat input) whereas the H\({}_{2}\) output (LHV basis) decreased by approximately 30% relative to the unabated SMR process.