Exergy Analysis and Thermal Optimization of a Double-Turbine Regeneration System in a Ultra-Supercritical Double-Reheat Unit

Improving the primary steam parameters is one of the most direct ways to improve the cycle efficiency of a powergeneration system. In the present study, the typical problem connected to the excessively high superheat degree ofextraction steam in an ultra-supercritical (USC) double-reheat unit is considered. Using a 1000 MW power plantas an example, two systems (case 1 and case 2) are proposed, both working in combination with a regenerativesteam turbine. The thermal performances of these two systems are compared with that of the original systemthrough a heat balance method and an exergy balance strategy. The results reveal that the two coupled systemscan significantly reduce the superheat degree of extraction steam, turbine heat rate, and coal consumption of theunit and improve the energy utilization efficiency. These results will provide useful theoretical guidance to futureinvestigators wishing to address the general problem relating to energy conservation and modelling of the coupledextraction steam regenerative system of USC double-reheat units.

Multi-model Predictive Control of Ultra-supercritical Coal-fired Power Unit

The control of ultra-supercritical(USC) power unit is a difficult issue for its characteristic of the nonlinearity, large dead time and coupling of the unit. In this paper, model predictive control(MPC) based on multi-model and double layered optimization is introduced for coordinated control of USC unit. The linear programming(LP) combined with quadratic programming(QP) is used in steady optimization for computation of the ideal value of dynamic optimization. Three inputs(i.e. valve opening, coal flow and feedwater flow) are employed to control three outputs(i.e. load, main steam temperature and main steam pressure). The step response models for the dynamic matrix control(DMC) are constructed using the three inputs and the three outputs. Piecewise models are built at selected operation points. Double-layered multi-model predictive controller is implemented in simulation with satisfactory performance.

Vibration of 1000-MW Ultra-Supercritical Turbine-Generator Unit with Simens Technology

The layout features of unit shafting and their effects on vibration, as well as evaluation criteria, were introduced for a 1000-MW ultra-supercritical turbine-generator unit with Simens technology. Based on vibration diagnosis and treatment for more than 10 units, some typical vibration faults were summarized, such as the vibration fluctuation of the high pressure (HP) rotor, abnormal vibration increases of the No.3 bearing pedestal and large vibration of the exciter rotor during its critical speed range. The vibration characteristics and the causes of faults and countermeasures were analyzed. Three applications for further illustration were given. The vibration fault identification method, control measures, and applications can provide a reference for vibration diagnoses and treatment of same type units.

Energy-Saving Optimization Study on 700℃ Double Reheat Advanced Ultra-Supercritical Coal-Fired Power Generation System

700°C double reheat advanced ultra-supercritical power generation technology is one of the most important development directions for the efficient and clean utilization of coal.To solve the great exergy loss problem caused by the high superheat degrees of regenerative steam extractions in 700°C double reheat advanced ultra-supercritical power generation system,two optimization systems are proposed in this paper.System 1 is integrated with the back pressure extraction steam turbine,and system 2 is simultaneously integrated with both the outside steam cooler and back pressure extraction steam turbine.The system performance models are built by the Ebsilon Professional software.The performances of optimized systems are analyzed by the unit consumption method.The off-design performances of optimization systems are analyzed.The results show that:the standard power generation coal consumption rates of optimization systems 1 and 2 are decreased by 1.88 g·(kW·h)^(–1),2.97 g·(kW·h)^(–1)compared with that of the 700°C reference system;the average superheat degrees of regenerative steam extractions of optimized systems 1 and 2 are decreased by 122.2°C,140.7°C(100%turbine heat acceptance condition),respectively.The comparison results also show that the performance of the optimized system 2 is better than those of the optimized system 1 and the 700°C reference system.The power generation standard coal consumption rate and the power generation efficiency of the optimized system 2 are about 232.08 g·(kW·h)^(–1)and 52.96%(100%turbine heat acceptance condition),respectively.