## 5 Thermodynamic Evaluation
### Energy Analysis and Results  
Exergy analysis could find the prime location and quantity of irreversible losses in thermodynamic systems and propose methods to improve the whole system's performance. The exergy of fuel (\(EX_{\text{f}}\), MW) is calculated as follows [31]. \[EX_{\text{f}}=m_{\text{f}}\times q_{\text{f}}\times(1.0064+0.1519\frac{w(\text {H})}{w(\text{C})}+0.0616\frac{w(\text{O})}{w(\text{C})}+0.0429\frac{w(\text {N})}{w(\text{C})}) \tag{7}\]  
where \(m_{\text{f}}\) is the fuel consumption rate, kg/s; \(q_{\text{f}}\) is the net calorific values of fuel, kJ/kg; \(w(\text{C})\), \(w(\text{H})\)\(w(\text{O})\) and \(w(\text{N})\) are the mass contents of hydrogen, carbon, oxygen and nitrogen in fuels. The exergy of a fluid (\(EX_{\text{fd}}\), MW) is expressed as [26]:  
\[EX_{\text{fd}}=m_{\text{fd}}\times[h-h_{0}-T_{0}\times(s-s_{0})] \tag{8}\]  
where \(m_{\text{fd}}\) is the mass flow of a fluid, kg/s; \(T_{0}\) is the ambient temperature, K; \(h\) and \(h_{0}\) are the enthalpy of a fluid at the current and environmental states, kJ/kg; \(s\) and \(s_{0}\) are the entropy of a fluid at the current and environmental states, kJ/(kg\(\cdot\)K). The ambient temperature and pressure are 15 \({}^{\circ}\)C and 1 atm. \begin{table}
\begin{tabular}{c c c c c} \hline  & **Parameter** & **Initial Design** & **Proposed Design** & **Difference** \\ \hline \multirow{4}{*}{WTEU} & MSW consumption rate (kg/s) & 5.79 & 5.79 & 0 \\  & Live steam mass flow (kg/s) & 13.50 & - & - \\  & Exhaust steam mass flow (kg/s) & 9.96 & - & - \\  & Boiler efficiency (\%) & 78.55 & 78.55 & 0 \\ \hline \multirow{4}{*}{CFPU} & Coal consumption rate (kg/s) & 59.72 & 59.72 & 0 \\  & Live steam mass flow (kg/s) & 506.35 & 506.21 & \(-\)0.14 \\  & Reheat steam mass flow (kg/s) & 432.31 & 444.56 & +12.25 \\  & Exhaust steam mass flow (kg/s) & 322.17 & 330.52 & +8.35 \\  & Boiler efficiency (\%) & 93.22 & 93.22 & 0 \\ \hline \multirow{4}{*}{Total power generation (MW)} & 669.32 & 673.23 & +3.91 \\  & Total auxiliary power (MW) & 34.73 & 34.40 & \(-\)0.33 \\  & Net total power generation (MW) & 634.59 & 638.83 & +4.25 \\  & Net power generation of WTEU (MW) & 8.00 & 12.25 & +4.25 \\  & Net waste-to-energy efficiency (\%) & 19.73 & 30.21 & +10.48 \\  & Net total energy efficiency (\%) & 41.84 & 42.12 & +0.28 \\ \hline \end{tabular}
\end{table} 
Table 14: Comparison of the energy analysis results between the initial and proposed designs. Figure 5: Energy flow diagrams of the initial and proposed designs. (**a**) Initial design; (**b**) proposed design. The exergy efficiency of WTE system (\(\eta_{\text{ex,w}}\)) and the total exergy efficiency of proposed system (\(\eta_{\text{ex,tot}}\)) are defined as:  
\[\eta_{\text{ex,w}}=\frac{P_{\text{w}}}{EX_{\text{w}}} \tag{9}\]  
\[\eta_{\text{ex,tot}}=\frac{P_{\text{tot}}}{EX_{\text{w}}+EX_{\text{c}}} \tag{10}\]  
where \(EX_{\text{w}}\) is the exergy of MSW, MW; \(EX_{\text{c}}\) is the exergy of coal, MW. Contrastive analysis between the initial and suggested systems is carried out to explore the energy synergism of combined design, and Table 15 summarizes the results. The exergy loss variation of major equipment is illustrated in Figure 6, and the following points deserve attention before and after system integration. 1. The exergy loss in WTE boiler is declined by 0.52 MW, because heat transfer temperature difference of those heat exchangers in WTE boiler diminishes. The exergy loss in CFPU boiler is decreased by 0.38 MW, primarily triggered by the cold reheat steam temperature increase. As a result, the total boiler exergy loss is reduced by 0.89 MW. 2. The exergy loss in all STs is shrunk by 1.78 MW with sharing a higher efficiency and larger scale steam turbine generator set. 3. As the saturated steam from WTE boiler drum is sent to the extraction steam pipe of RH2, the exergy loss of RHs of CFPU increased by 0.38 MW.