DESIGN AND PERFORMANCE EVALUATION OF AN INDUSTRIAL COMBINED HEAT AND POWER PLANT INTEGRATED WITH MOLTEN SALT HEAT STORAGE SYSTEM

For facilitating the penetration of renewable energy, combined heat and power (CHP) plants should provide peak shaving services for the power grid, which will inevitably influence the heat supply. The integration of a thermal heat storage system is an effective way to enhance the operational flexibility of the industrial CHP unit that supply industrial steam to process steam users. In this study, off-design models of a reference 350 MW CHP unit are developed and validated. Then, the molten salt heat storage system is integrated within the reference CHP unit, and different heat sources of molten salt heat storage systems are analyzed. The heat sources to heat molten salt are outlet of turbine stage group 5 and hot-reheat steam pipe in case 1 and case 2. The exergy efficiencies are 71.25% and 65.12% for case 1 and case 2, respectively. The influences of parameters, including molten salt temperature and the CHP power load, on exergy efficiency are also analyzed, and the operation flexibility enhancement of CHP unit is evaluated. Results show that when the maximum mass flow rate of steam supplied by molten salt heat storage system is 30 kg s^-1, the decrements of minimum power load for case 1 and case 2 are 239.69 MW and 48.89 MW, respectively, and the increment of maximum power load for case 1 and case 2 are 21.61 MW and 30.65 MW, respectively. The study may provide guidance for enhancing flexibility of thermal power plant by molten salt heat storage system.