## 3 Results
### Plant Model Results
An effective operational handle to trade-off H\({}_{2}\) production for additional electricity would be to operate the PSA with a higher off-gas desorption pressure (such that the size of the associated compression unit is reduced), but this is limited to the extent that H\({}_{2}\) production in water splitting step of the GSPOX is sufficient to reach COT GT values in the extra firing chamber (unless the H\({}_{2}\) product is also employed for extra firing, which would imply additional penalties and process variations). Heat rejected comparatively increases relative to the SMR H\({}_{2}\) production plant without CO\({}_{2}\) capture due to the inherent thermodynamic inefficiencies related to a larger fuel degradation for power generation, reaching a degree of overall losses comparable to the SMR MDEA capture process. The effective use of low-grade heat across the plant in the H\({}_{2}\)-power configurations for additional electricity production prevents the need to export any LP steam. Interestingly, both GSPOX H\({}_{2}\)-power plants deliver a similar electricity output, underlying the higher efficiency of the Advanced GT power production scheme, which accomplishes the same amount of electricity production with a lower fraction of the heating value (given the fact that the H\({}_{2}\) production is somewhat higher due to the increased recovery in the PSA). Scale is another important consideration in such combined power and hydrogen plants. The plant with Advanced GT technology will need to be very large (around 20\(\times\) the heat input of the plants presented in this work), given the size of the heavy-duty gas turbines required to maximize firing temperature and efficiency. Such plants can only be considered for the longer-term future when a large hydrogen market has been established. Efficiencies representative of the Current GT technology can be achieved by much smaller industrial gas turbines [55], only requiring an increase in plant size of ~3\(\times\). Such a plant could supply an industrial cluster with power and hydrogen, avoiding any dependency on a broader integrated hydrogen market. For the GSR and GSPOX H\({}_{2}\) plants, a small export of LP steam is needed in both cases. Furthermore, electricity imports of approximately 5% of the natural gas heat input are required. However, the heat rejected is reduced to around 16% of the heat input, in effect around 4%-points and 11%-points below the unabated SMR plant and SMR plant with MDEA CO\({}_{2}\) capture, respectively. In terms of emissions, MDEA absorption integration achieves a CO\({}_{2}\) avoidance of approximately 85% (Figure 12), similar to earlier published works. CO\({}_{2}\) emissions are not curtailed entirely due to a small remaining fraction of CO, CH\({}_{4}\) and CO\({}_{2}\) present in the PSA off-gas used as fuel in the reformer. The CO\({}_{2}\) avoidance for the GSR and GSPOX is approximately 5%-points above the MDEA benchmark, due to the large capture rate (>95%) achieved with inherent CO\({}_{2}\) capture in the GS concepts. However, CO\({}_{2}\) avoidance is considerably less than the CO\({}_{2}\) capture rate due to the associated emissions resulting from the imported electricity generation. On the other hand, for the H\({}_{2}\)-power co-generating concepts, since electricity is produced with inherent CO\({}_{2}\) capture, the CO\({}_{2}\) avoidance is largely above the capture ratio, reaching values above 140%. In terms of equivalent specific emissions, reflected in Figure 15, the value decreases for the SMR plant without capture due to a small export of steam (and associated CO\({}_{2}\) avoidance of a boiler), whereas for the plant with MDEA capture it increases, due to the associated emissions of electricity imports. A similar trend is seen for the GSR and GSPOX H\({}_{2}\) production plants. For the concepts that produce additional electricity with CO\({}_{2}\) capture, the equivalent specific emissions become negative. Finally, regarding the  
Figure 14: Power-energy breakdown for the different plants.