Simulation investigation on performance of a power-water cogeneration system coupled with a two-stage thermal vapor compressor

The shortage of freshwater resources is becoming increasingly serious. A thermal power plant coupled with a low-temperature multi-effect distillation seawater desalination (single-stage thermal vapor compressor (TVC)) has been widely used. To reduce the water production cost effectively, a two-stage TVC is proposed in this study. The simulation work for the system performance under single- and two-stage TVC is analyzed. Results show that the performance of the system coupled with the two-stage TVC is superior under most conditions, and an optimal intermediate pressure (16 kPa) of the two-stage TVC is found for minimum coal consumption. When the power plant load is higher than 70% THA, the cogeneration system performs well, and the motive steam of the two-stage TVC comes from extraction point No. 5. Otherwise, the motive steam that comes from extraction point No. 4 is a suitable choice. The maximum coal consumption reduction value is 1.48 t/h. To deal with the low operation load of power plants in China, 60% THA load of power plant is a suitable choice for two-stage TVC of power-water cogeneration system.