## 3 System Description
### Reference Coal-Fired Power Unit  
The CFPU locates in northern China, which adopts one supercritical parameter and variable pressure operation boiler. The sketch map of the selected 660 MW CFPU is described in Figure 2. The steam turbine generator set comprises one high-pressure steam turbine (HPST), one intermediate-pressure steam turbine (IPST), two low-pressure steam turbines (LPSTs) and one electricity generator (EG). The regenerative steam extraction system employs eight RHs to heat feedwater (RH1-8), and the extraction steam and feedwater parameters are depicted in Table 4. The main operating parameters of CFPU are given in Tables 5 and 6, respectively. Due to the relatively higher parameters of steam from SH outlet and reheater (RHR) outlet and the comparatively complete steam-water cycle, the net power efficiency of CFPU could reach 42.44%, which is far higher than that of WTE plants. The reductant provided for the SCR denitration reactor of CFPU boiler is the ammonia produced by urea hydrolysis, and ammonia is a suitable reactant widely used in power plants to remove NOx in the flue gas. The inlet flue gas volume of the SCR denitration device is 2,200,000 Nm\({}^{3}\)/h in this power unit, and the inlet NOx concentration is approximately 900 mg/(Nm\({}^{3}\)). The NOx removal rate of SCR reactor exceeds 90%, and its outlet NOx concentration is calculated as 40 mg/(Nm\({}^{3}\)). The mass flow of the consumed urea is calculated according to the following formulas [38]. The mass concentration of urea solution entering the hydrolysis device is 50%. The saturated steam at 180 \({}^{\circ}\)C is used for urea hydrolyzing in UHU, and the operating temperature of UHU is controlled at 150 \({}^{\circ}\)C. Moreover, catalysts can be added to accelerate reaction velocity based on the conventional urea hydrolysis process and improve the operational flexibility of device. [PERSON] et al. [32] estimated the necessary heat of the urea hydrolysis process. According to the theoretical \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{2}{c}{**Parameter**} & **Unit** & **Value** \\ \hline \multicolumn{2}{c}{Fuel consumption rate (coal)} & kg/s & 59.72 \\ \hline \multirow{4}{*}{ECO} & Inlet fluid & - & Feedwater \\  & Inlet pressure & MPa & 29.30 \\  & Inlet temperature & \({}^{\circ}\)C & 275.2 \\  & Mass flow & kg/s & 506.35 \\ \hline \multirow{4}{*}{SH} & Outlet fluid & - & Superheated steam \\  & Outlet pressure & MPa & 24.20 \\  & Outlet temperature & \({}^{\circ}\)C & 566.0 \\  & Mass flow & kg/s & 506.35 \\ \hline \multirow{4}{*}{RHR} & Inlet/outlet pressure & MPa & 4.24/3.82 \\  & Inlet/outlet temperature & \({}^{\circ}\)C & 308.4/566.0 \\  & Mass flow & kg/s & 432.31 \\ \hline \multirow{4}{*}{Exhaust gas temperature} & \({}^{\circ}\)C & 122.0 \\  & Total power generation & MW & 659.57 \\ \cline{1-1}  & Net power generation & MW & 626.59 \\ \cline{1-1}  & Boiler efficiency & \% & 93.22 \\ \cline{1-1}  & Net power efficiency & \% & 42.44 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Major parameters of the CFPU. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Parameter**} & **Unit** & **RH1** & **RH2** & **RH3** & **RH4** & **RH5** & **RH6** & **RH7** & **RH8** \\ \hline \multirow{3}{*}{Extracted steam} & Pressure & MPa & 5.81 & 4.11 & 2.02 & 1.01 & 0.39 & 0.13 & 0.06 & 0.02 \\  & Temperature & \({}^{\circ}\)C & 352.5 & 316.2 & 473.3 & 359.4 & 253.1 & 136.8 & 86.7 & 61.0 \\  & Mass flow & kg/s & 28.53 & 40.49 & 19.74 & 26.43 & 24.04 & 12.76 & 16.09 & 15.20 \\ \hline \multirow{3}{*}{Feedwater} & Inlet/outlet temperature & \({}^{\circ}\)C & 252.0/ & 213.0/ & 185.9/ & 140.0/ & 103.7/ & 83.9/ & 58.2/ & 33.3/ \\  & Outlet mass flow & kg/s & 506.35 & 506.35 & 506.35 & 506.35 & 391.16 & 391.16 & 391.16 \\ \hline \multirow{3}{*}{Drain water} & Temperature & \({}^{\circ}\)C & 257.5 & 218.6 & 191.4 & - & 109.2 & 89.4 & 63.8 & 38.9 \\  & Mass flow & kg/s & 28.53 & 69.02 & 88.76 & - & 24.04 & 37.38 & 53.47 & 68.67 \\ \hline \hline \end{tabular}
\end{table}