Proposal and techno-economic analysis of a novel system for waste heat recovery and water saving in coal-fired power plants: A case study

A novel system, which systematically recover waste heat and reduce water consumption in coal-fired power plants, is proposed in this paper. Critical components of the system are two fluorine plastic heat exchangers (FHEs) located downstream and upstream of WFGD scrubber, and condensate and feed water extracted from the regenerative heater (RH) act as coolants, respectively. All recovered heat is utilized directly with no heat pump required. A thermodynamic model, where the steam/water cycle is coupled with the exhaust flue gas flow, is built to assess the performance of the system, and the economic analysis is involved to further explore the feasibility. The simulation is conducted based on parameters of a 1000 MW coal-fired power unit in operation, while coal and water saving rates, payback period, and net present value (NPV) are used as criteria in the assessment. The results show that the system can significantly reduce coal and water consumption of the reference power unit. The temperature of condensate and feed water extraction determines the techno-economic performance of the low- and high-temperature FHEs (LFHE and HFHE), respectively. Lower condensate temperature and higher feed water extraction temperature are more beneficial. Compared with the case of only LFHE, integrating HFHE into the system will increase the overall coal and water saving rates obviously, although the performance of LFHE is weakened. All layouts of the system presented in this paper are techno-economically feasible, and the layout in Case 4 where HFHE is installed in parallel with RH6 is the optimal one. Coal and water saving rates, and NPV of the optimal layout are up to 4.11 g/kWh, 95 t/h, and 102,739,000 RMB, respectively, while the payback period is less than 4 y. Application of this system is beneficial to mitigating the environmental problems caused by coal-fired power generation.