## 7 Discussion  
The integration method is what researchers need to consider when coupling different thermal systems. According to previous research on the integration of a coal-fired power plant and a waste incineration power plant [31; 33], aiming for the net power output of integrated system, the net power output results are compared under several integrated modes as follows:  
1. [label=()]
2. Mode 1: Directly apply the scheme of Reference [31];
3. Mode 2: Modify APHs based on reference WTEU and Mode 1;
4. Mode 3: Transport the outlet superheated steam of SH of WTEU to the RHR of CFPU based on Mode 1;
5. Mode 4: Directly adopt the scheme of Reference [33];
6. Mode 5: Change the outlet steam of SH of WTE boiler to RHR of CFPU based on Mode 4;
7. Mode 6: Modify APHs based on Mode 5;
8. Mode 7: Integrated scheme in this paper.  
Among the above seven modes, the method of APHs transformation is the same. The net power output results are presented in the Figure 7. As shown from Figure 7, the net power output of the integrated design in this paper (Mode 7) is the largest, that of Mode 1 is the second, and that of Mode 4 is the least. However, compared with the total net power output of 634.59 MW under the stand-alone designs, whichever integrated scheme can obtain a significant increase in power output. Therefore, integrated design is worthy of popularization and application.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Comparison** & **Unit** & **Initial WTE Design** & **Proposed WTE Design** & **Difference** \\ \hline Total investment & M\$ & 26.49 & 21.34 & \(-\)5.15 \\ MSW consumption per year & t & 145833 & 114583 & \(-\)31,250 \\ Annual waste disposal income & M\$ & 1.90 & 1.49 & \(-\)0.41 \\ Net power generation & MW & 8.00 & 12.25 & \(+\)4.25 \\ Net annual power generation (the 100% load of CFPU is 5500 h per year) & GWh & 56.00 & 67.38 & \(+\)11.38 \\ Annual electricity sales income & M\$ & 5.60 & 6.74 & \(+\)1.14 \\ Total annual income & M\$ & 7.50 & 8.23 & \(+\)0.73 \\ Yearly operation and maintenance cost & M\$ & 2.65 & 2.13 & \(-\)0.52 \\ Dynamic payback period & year & 11.39 & 5.48 & \(-\)5.91 \\ Net present value & M\$ & 9.60 & 24.02 & \(+\)14.42 \\ \hline \hline \end{tabular}
\end{table}
Table 20: Comparison of economic analysis results between the initial and proposed WTE designs.  
The previous works [31,33] have improved net power output effectively. Comparing the results of Mode 1 and Mode 2, it is not difficult to find that the net power output can be increased slightly when adopting the transformation of APHs. Therefore, the transformation of APHs is active. Comparing the results of Mode 1 and Mode 3, it is found that directly feeding the outlet steam of SH of WTE boiler to the RHR of CFPU boiler can also improve the overall net power output. Still, the effect is not as good as the Mode 1, therefore, using the SH of WTE boiler to heat the exhaust steam of HPST is better than using that to heat drum steam. Comparing the results of Mode 4 and Mode 5, it is more effective for net power output improvement to deliver the superheated steam from SH of WTE boiler to RHR of CFPU boiler in Mode 5. Based on Mode 5, the APHs are modified, and the net power generation is further increased, proving that the modification of APHs is valid. Comparing the results of Mode 1 and Mode 4, the integration design of Mode 1 is more favorable than that of Mode 4. Finally, after contrasting the results of Mode1 to Mode 6, the integration design in this article (Mode 7) is proposed and achieves the best net power output result. The flowcharts of these modes are depicted in Supplementary Materials.