## 3 Results and Discussion
In ARR-3, the contribution of RYield, operating at 240 bar but at 25 \({}^{\circ}\)C, is reduced due to heat exchanged in HE02, which allows a certain heat integration to increase the temperature from 25 to 350 \({}^{\circ}\)C, and also to the greater impact in the RGibbs block, since all inputs are now at 350 \({}^{\circ}\)C (in ARR-1,2 the temperature of the stream coming from the RYield block is 800 \({}^{\circ}\)C). In ARR-4, solid biomass is converted into a series of liquid model compounds representative of that specific biomass, instead of solid C and gaseous H\({}_{2}\) and O\({}_{2}\), leading to a very small contribution of RYield. Somewhat more heat is exchanged in HE02 as a result of the state and composition of the stream that passes through. The behavior of ARR-5 is similar to that of ARR-3, and the pressure in RYield must be the same as that of RGibbs, because if it were ambient pressure, the heat exchanged in HE01 would increase significantly due to the gaseous state of part of the stream leaving the RYield block. Finally, the arrangement ARR-6 is similar to ARR-4, with a lower contribution of RYield, which is almost irrelevant, and a slightly higher electrical consumption in the pump. Heat exchange takes place in one heater (HE01). The energy required in the SCWG reactor (RYield + RGibbs) is the lowest of all arrangements after ARR-5. It is shown that, if the RYield block operates at ambient temperature, the sensitive heat can be used for energy integration, which is possible for ARR-3 to ARR-6 where the organic feed stream is definitively included in heat integration. At this point, we wonder what process arrangement is the best for applying energy integration to the SCWG of solid biomass. As we want to use as much sensitive heat as possible in the heat exchangers placed between the stream entering the process and the reactor inlet using other process streams downstream of it, we should select the arrangement that requires the lowest thermal power for the reaction (RYield + RGibbs). However, the heat load in HE01 must be realistic, i.e., somewhat higher than, but also close to, that of the case in which only water is heated, as there is 90 wt.% water in the biomass. Therefore, ARR-5 is unrealistic, as the heat load in HE01 is 54% higher than for ARR-1,2. This is because the vapor fraction of the stream leaving HE01 in ARR-5 is 21% (the liquid and solid fractions are 75% and 4%, respectively). The high vapor fraction significantly reduces the absolute mass enthalpy, leading to a larger amount of heat exchanged in HE01. Furthermore, ARR-5 does not include a pump, so its \begin{table}
\begin{tabular}{c c c c c c} \hline  & **ARR-1, 2** & **ARR-3** & **ARR-4** & **ARR-5** & **ARR-6** \\ \hline RYieldD & 2279.75 & 1816.67 & 40.49 & 1867.31 & 18.99 \\ \hline SEP-ASH & balance & balance & balance & balance & balance \\ \hline PUMP (*) & 177.40 & 177.40 & 177.40 & - & 186.65 \\ \hline HE01 & 3855.61 & 3855.61 & 3855.61 & 5950.79 & 4089.70 \\ \hline HE02 & - & 165.44 & 211.37 & - & - \\ \hline RGIBBS & 4560.36 & 4850.45 & 6580.75 & 3036.75 & 6559.52 \\ \hline RYieldD + RGIBBS & 6840.11 & 6667.12 & 6621.24 & 4904.05 & 6578.51 \\ \hline SYSTEM & 10,873.45 & 10,873.45 & 10,873.45 & 10,873.45 & 10,873.45 \\ \hline \end{tabular} (*) For the pump, the numbers are electrical power rather than head loads (kWe).  
\end{table} 
Table 2: Heat loads (kW) of the process units for different arrangements (base case). electrical power cannot be calculated. If the pressure in HE01 were 1 atm, the results would be even more unrealistic because the heat exchanged would increase to 7840 kW, since the vapor fraction would be 96%. Therefore, the most realistic arrangements are ARR-3, -4, and -6. The former involves heating a stream with a vapor fraction of 60% (a solid fraction of 40%) in HE02, while the other two arrangements (-4 and -6) handle always-liquid streams if the temperature is below the critical temperature of the water.