## 3 Results and Discussion
The three arrangements are approaches to the feed consisting of 10 wt.% solid biomass and 90 wt.% water. ARR-6 is the most compact process arrangement that leads to the minimum energy required for the reaction and, hence, the maximum sensitive heat that can be exchanged using energy and material integration. Thus, it should be the first option for designing the process in order to apply energy integration to the thermochemical process, although ARR-4 and -3 could also be used, any of them being preferred to the typical arrangements found in the literature that follow ARR-1, 2, which does not allow for the energy integration of the biomass stream, or ARR-5, which does not lead to faithful results. Although the energy saving is not too high in the selected application (SCWG) due to the huge amount of water, if this were significantly decreased, the energy saving would increase considerably. The main operating parameters include the temperature, pressure, type of feedstock, composition and concentration of components, reaction time, and type of catalyst and its load if it is used. When an operation is considered under chemical equilibrium, the temperature, pressure, type of feedstock, composition, and concentration of components are the most relevant parameters, as the reaction time and catalyst do not have an effect. As the critical pressure of SCW is very high (>221 bar), this parameter has been kept constant at a slightly higher value (240 bar) to consider pressure losses, but it would not be realistic to use higher pressures. Therefore, once the feedstock is decided, the most significant parameters are the temperature and the feed concentration. To examine the effect of the feed concentration and the temperature at the RGibbs inlet on the energy balance, and hence on the heat integration, a sensitivity analysis was performed. Three biomass concentrations (10, 20, and 30 wt.%) and three temperatures at the RGibbs inlet (350, 400, and 800 \({}^{\circ}\)C) were used based on the schemes drawn in Figures 2 and 3. To illustrate it, Figure 7 shows the results using the ARR-6 arrangement. The thermal power obtained was similar in all case studies, i.e., for every combination of organic concentration (wt.%) and temperature (\({}^{\circ}\)C). The RYield contribution increases with the organic concentration, while the contributions of RGibbs and HE01 decrease with this variable due to the lower amount of water. However, the contribution of RYield is very small in all cases and barely affects the energy balance, so this depends only on the contributions of RGibbs and HE01. The former decreases with temperature, while the latter increases, practically by the same amount. For the RYield and RGibbs blocks, the thermal level needed to provide this energy must be the same as in the SCW reactor, i.e., a temperature higher than 800 \({}^{\circ}\)C for heat transfer, which is the thermal level used for the reactor in this study. This implies that a suitable heat source, such as a furnace, is needed. Although the most significant fraction of energy must come from an energy source with a high thermal level (>800 \({}^{\circ}\)C) for the combination of RYield and RGibbs, there is also significant heat exchanged in HE01 that makes it possible to save energy by integrating the feed stream with another process stream (such as that leaving the SCW reactor) so that the use of utilities is reduced. In fact, and as a final note, although the temperature at the SCWG reactor inlet should be as close to the reaction temperature (800 \({}^{\circ}\)C in this study) as possible to save more energy, in practice, the temperature achieved in the train of heat exchangers, represented by HE01 in this study, is usually lower, approximately 350-400 \({}^{\circ}\)C, rather than 800 \({}^{\circ}\)C, especially if the product leaving the SCW reactor passes through an expander to produce electrical energy, as proposed in previous studies published by the authors and other researchers [3].