## 4 Modeling
### Integrated System Modeling  
The simulation and calculation achieve the data of proposed integrated design in EBSILON professional. Due to the removal of several devices of WTEU, the parameters of working fluid entering and leaving the WTE system have changed a lot compared to the stand-alone WTEU. The AE is arranged in the ECO space of the WTE boiler. The cold side inlet fluid extracts from the feedwater of WTEU, absorbs the flue gas heat and turns into saturated steam at specific pressure and temperature. The ammonia produced by urea hydrolysis is used to remove the NOx in coal-fired boiler. Now, the heat source (the third stage extraction steam of the STs of CFPU) for UHU is replaced by the saturated steam generated from the AE of WTE boiler. The outlet steam of AE gets into UHU to transfer heat to the urea solution, and the condensate flows into the RH6 with the drain water of RH5. The steam source used in the urea hydrolyzed is changed from the original high-temperature steam to the saturated steam produced by AE. The steam pressure reduced from the original 2.13 MPa to 1.01 MPa and its temperature decreased from 473.9 \({}^{\circ}\)C to 180.5 \({}^{\circ}\)C. At the same time, the saturated steam no longer needs to be sprayed demineralized water to reduce its temperature and pressure, which can significantly improve the safety of hydrolyzer. In addition, regardless of the type of coal entering the boiler, according to the changes in NOx concentration during the operation, the mass flow of steam required by the urea hydrolysis device can be directly adjusted for the ammonia production, which improves the operation flexibility of hydrolyzer. The critical parameters of AE are displayed in Table 10, and the comparison of UHU in initial and integrated designs is exhibited in Table 11. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Parameter** & **Unit** & **Value** \\ \hline \multirow{4}{*}{Cold side} & Inlet/outlet fluid & - & Feedwater/saturated steam \\  & Inlet/outlet pressure & MPa & 1.09/1.01 \\  & Inlet/outlet temperature & \({}^{\circ}\)C & 180.3/180.5 \\  & Mass flow & kg/s & 0.72 \\ \hline \multirow{4}{*}{Hot side} & Inlet/outlet fluid & - & Flue gas/flue gas \\  & Inlet/outlet temperature & \({}^{\circ}\)C & 271.3/235.5 \\  & Mass flow & kg/s & 35.61 \\ \hline \multirow{4}{*}{Hot side} & LMTD & \({}^{\circ}\)C & 71.6 \\  & Heat load & MW & 1.45 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Parameters of the AE in the integrated design. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Parameter** & **Unit** & **Initial Design** & **Integrated Design** \\ \hline \multirow{4}{*}{Cold side} & Inlet/outlet fluid & - & Urea solution/ & Urea solution/ \\  & Inlet/outlet temperature & \({}^{\circ}\)C & Hydrolytic gas & Hydrolytic gas \\  & Mass flow & kg/s & 0.67 & 0.67 \\ \hline \multirow{4}{*}{Hot side} & Steam pressure & MPa & 2.13 & 1.01 \\  & Steam temperature & \({}^{\circ}\)C & 473.9 & 180.5 \\ \cline{1-1}  & Steam flow & kg/s & 0.58 & 0.72 \\ \cline{1-1}  & Attempering water pressure & MPa & 1.10 & - \\ \cline{1-1}  & Attempering water temperature & \({}^{\circ}\)C & 25.0 & - \\ \cline{1-1}  & Attempering water flow & kg/s & 0.14 & - \\ \hline \multirow{4}{*}{LMTD} & \({}^{\circ}\)C & 76.9 & 77.5 \\ \cline{1-1}  & Heat load & MW & 1.41 & 1.41 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Comparison of the UHU in the initial and integrated designs. The SH and ECO of WTE boiler are separately applied to heat partial cold reheat steam from CFPU and the feedwater of WTEU in the hybrid design. The parameters of SH and ECO are shown in Table 12. The boiler efficiency is invariant when the MSW consumption rate and exhaust flue gas temperature behind ECO keep fixed. The 30.76 kg/s cold reheat steam is heated in the SH of WTE boiler, causing an increase from 308.4 \({}^{\circ}\)C to 400.0 \({}^{\circ}\)C in steam temperature, and then absorbing heat in the RHR of CFPU.