## 1 Introduction
[PERSON] [16] divided the flue gas above the grate into two parts with different chlorine concentrations and used the low-corrosive part to heat SH for higher steam temperature. [PERSON] et al. [17] combine the external superheating of live steam with the reheating of exhaust steam from a high-pressure turbine, upgrading the live steam parameters and the reheat steam parameters. Additionally, many experts have tried to decline the energy loss of exhaust flue gas. [PERSON] et al. [18] utilized flue gas recirculation to limit the temperature of combustion chamber, reducing pollutants in the flue gas and decreasing its mass flow. Less excess air could reduce flue gas mass flow too, but it is necessary to pay attention to maintain combustion stability [19]. Oxygen-enriched air was consumed by [PERSON] et al. [15] to diminish flue gas mass flow due to the reduction of the air entering furnace. Considering the complex chemical composition of exhaust flue gas, its temperature is usually higher than that of other power plants and it seriously affects the energy efficiency of WTE plants. Therefore, many researchers have presented strategies for waste heat recovery. It was suggested to exploit available low-temperature streams in WTE plants to preheat air or water to gain higher energy efficiency of heat recovery system [20]. [PERSON] et al. [12] proposed using the water in the grate cooling circuit to preheat air. It is a relatively simple way to directly heat feedwater with the flue gas waste heat [21]. Similarly, employing flue gas waste heat for district heating is also recognized [22]. Nonetheless, people would face low-temperature corrosion issues while utilizing the flue gas waste heat [23]. On account of this, it may be inevitable to eliminate the corrosive constituents of exhaust flue gas before recovering waste heat, but associated equipment is complicated and expensive [24]. Besides the mentioned ways, the efficiency of WTE plants would also be influenced by the mode of production. Many scholars have proved that combined heat and power (CHP) production could enhance power plants' energy efficiency [25, 26], while power generation might be the only energy output option under the unavailability of district network heating [27]. In addition, researchers augmented power efficiency by combining the WTE system with other energy systems [20]. [PERSON] et al. [22] connected CHP with the Organic Rankine Cycle (ORC) based on a WTE system and drew on flue gas to provide high-temperature heat for ORC. An absorption refrigeration system was incorporated into the CHP of a WTE plant to form a combined cooling, heat and power (CCHP) system, optimizing the WTE efficiency [28]. [PERSON] et al. [29] investigated the WTE systems coupled with gas combined cycles, and results demonstrated that the hybrid system could obtain higher net power efficiency and economic benefits than the separate system. A combination of a WTE plant and solar energy facilities was studied, using solar energy to attain external superheating and achieving a 4.5% net efficiency enhancement [30]. [PERSON] et al. [31] combined a WTEU and a CFPU, upgrading total power efficiency and getting economic profits. Due to the massive number of CFPUs in China, under this circumstance, research on the integration with coal-fired generating units are of great significance. The higher efficiency and greater stability of coal-fired units enable better use of the energy entering them, especially from lower energy efficiency power plants, such as WTE plants. Scholars have explored different coupling methods of a WTEU and a CFPU. However, few studies have incorporated the auxiliary devices of CFPUs into system integration. According to the national control standards for flue gas pollutants, the concentration of flue gas pollutants emitted directly after coal combustion exceeds the standard. Selective catalytic reduction (SCR) reactors are arranged in the tail flue of many power plant boilers to remove the nitrogen oxides (NO\({}_{\text{x}}\)) in flue gas.