The large-scale integration of new energy into the grid has caused increased frequency fluctuations in the grid, making the frequency modulation task of thermal power units heavy and frequent, exacerbating the aging of the unit, flywheel energy storage assisted thermal power unit frequency modulation can improve the frequency modulation performance of the unit. The principle of primary frequency modulation of flywheel energy storage auxiliary unit is discussed, and the flywheel energy storage’s frequency modulation characteristics are analyzed. Combining with the world’s largest capacity flywheel energy storage, the full power control strategy for primary frequency modulation of flywheel energy storage auxiliary units is proposed, and applied to the shakedown test of China’s first set of flywheel energy storage auxiliary thermal power unit’s primary frequency modulation to verify the effectiveness of the control strategy. The field test results show that, the primary frequency modulation performance of the flywheel energy storage auxiliary thermal power unit is good. After the proposed primary frequency modulation strategy is adopted, the qualification rate of the primary frequency modulation action of the unit increases by 21.26%, and the integral electricity contribution index of the primary frequency modulation increases by 3.45 times. The primary frequency modulation mode of flywheel energy storage auxiliary thermal power unit has certain guiding significance to solve such problems.

To address the challenges posed by the reverse peak shaving characteristics of new energy generation units to the smooth operation of the power grid, coal-fired units urgently need to improve their flexible operation and deep peak shaving capabilities. This article proposes three schemes of molten salt heat storage and heat release for a 670 MW reheating unit, including using a steam ejector to allocate the steam inlet flow rate of the reheater. By using Ebsilon to establish the thermal model, this article analyzes the performance of the coupled system. The results show that all schemes can effectively expand the peak shaving range of the unit. Under energy-storage conditions, the thermal economy of steam-extraction is better than using electrical heating at the same peak shaving depth. The heat-storage scheme of integrating steam ejector to allocate extraction steam to compensate for reheat inlet flow can effectively solve the problem of reheater over temperature caused by a large amount of extracted main steam. Under heat-release conditions, using molten salt to heat high pressure feed water can acquire better thermal and economic benefits. In the combination scheme of heat storage and release, C1-S2 exhibits the best economic performance, with an upward peak shaving depth of 76.89 MW, and a cyclic thermal efficiency and thermal efficiency of 42.48% and 41.31%, respectively.

By the end of 2021, over 95% of coal-fired thermal power units in China have achieved ultra-low emission of nitrogen oxides, with the remaining being W-flame boilers that burn anthracite. Due to the high mass concentration of nitrogen oxides generated, which often reaches 750~1 200 mg/m³, achieving ultra-low emissions is difficult, making it the “last mile” for China to achieve ultra-low emission policies. At present, selective catalyst reduction (SCR) denitration flow field technology mainly includes “SCR partition hybrid dynamic leveling technology”, “full flue section mixing flow field technology”, and “conventional accurate ammonia injection technology”, etc. Taking a W-flame boiler of which the design denitration efficiency needs to be up to 95% as an example, this paper compares the performance indicators of various technologies through CFD simulation, and the indicators of the “SCR partition hybrid dynamic leveling technology” are significantly superior to other technologies. After the project transformation, when the mass concentration of nitrogen oxides at the denitration system inlet is 1 000 mg/m³ and that at the system outlet is lower than 50 mg/m³, the ammonia escape can be kept less than 3 μL/L, far exceeding the maximum design efficiency of the conventional SCR denitration system. The research provides a new technical route for ultra-low NO_x emission of W-flame boilers.

In industrial production processes, time delays can have adverse effects on the performance of control systems, and may even lead to system instability. This article investigates the stability issues of time-delay in the load/speed control loop of a heavy-duty gas turbine from the perspective of switching systems. The model of GE MS109FA 275 MW heavy-duty gas turbine under 100% load is taken as the research object. The load/speed control loop with time-varying delay is transformed into a class of switching system by augmenting the state variable and selecting the change of time delay as the switching signal. By using the norm correlation lemma, a necessary and sufficient condition to ensure the stability of the load/speed control loop with time-varying delay is derived and the stability verification algorithm is given. The hardware-in-the-loop simulation is carried out based on the domestic heavy-duty gas turbine NuCON control system. The results of this study can provide theoretical references for the design and parameter adjustment of heavy-duty gas turbine control system.

In order to realize compressor blade fouling and surge faults early warning, a typical fault warning method of gas turbine compressor combining thermodynamic model with artificial neural network was proposed. The simulation model of gas turbine thermodynamic performance was built according to the modularization idea, and the dynamic calibration of the model was completed by using the actual operation data of the gas turbine to form a high-precision gas turbine performance analysis model, and the key indicators such as exhaust flow rate, turbine front temperature and heat consumption can be calculated. Based on the thermal performance simulation model and combined with the compressor typical faults expert experience and professional knowledge, the main characteristic parameters affecting compressor faults were determined, and the compressor blade fouling and surge warning models were abstracted. The historical health data were selected to train the models using the artificial neural network algorithm to obtain the deviation curve, and the early warning of typical compressor faults can be realized by monitoring the deviation changes between the predicted value and the measured value of the early warning model, the example to verify the validity of the measured data of a GE 9F gas turbine compressor was given. The results showed that the method can accurately capture the compressor blade fouling and surge faults, and improve the warning time window compared with the traditional threshold alarm method. The research achievement can be directly deployed in the gas turbine power plant and provide real-time guidance for operation and maintenance personnel to make overhaul and maintenance decisions

In order to achieve the desired flexibility, high efficiency, and cost-effectiveness in the startup and operation of thermal power units, the utilization of the BEST small steam turbine with a small generator for the implementation of a double-turbine reheat system unit is crucial for enhancing the operational economy of the unit. According to the starting mode of the BEST system and unit, combined with the historical process and data of the starting and operation of the debugging and adjustment test, a characteristic analysis test of the BEST system in multi-mode startup and operation was conducted. The existing control logic was optimized, and an operation control strategy for the BEST small steam turbine with a small generator was proposed. The system addresses the issue of lacking control strategies in various aspects, such as the starting and control of the BEST system, converter start-stop control, BEST small steam turbine and converter non-disturbance switching, run back, load dumping conditions, and ensures uninterrupted operation control of the entire process of the BEST system. After optimization, the crucial parameters of the BEST system remain secure and stable during operation. The control method holds significant reference value for similar units equipped with the BEST system.

Labyrinth seals are widely used in various types of turbomachinery due to their simple structure, convenient maintenance, and long service life. The shunt injection devices can reduce the flow-induced vibration caused by the spiral effect and improve the stability of the sealing system by affecting the circumferential flow inside the seal cavity. The three-dimensional numerical models of shunt injection labyrinth seal were established to calculate and analyze the impact of the shunt injection nozzle on the dynamic characteristics of the seal under different structural parameters. The results show that the smaller the tilt angle of the anti-swirl nozzle, the greater the system damping and stability. When the tilt angle is 30°, the effective damping is 4 times that of the vertical angle incident; the shape of the anti-swirl nozzle has a small impact on the sealing dynamic and flow characteristics. The cross stiffness of both nozzle hole types is negative, and the difference in cross stiffness between the two is about 5 kN/m at low frequencies and 1~2 kN/m at high frequencies; the more nozzles there are, the more they can suppress the circumferential flow of the rotor, which is beneficial for system stability.

A comprehensive evaluation model for the start-up and shutdown decision-making of the milling system, taking into account the energy consumption and tracking performance of the unit load, has been proposed to address issues such as subjective decision-making based on manual experience, high labor intensity in operation, and difficulty in exploring energy-saving optimization potential. This model safely incorporates the grid load scheduling command signal as input. Furthermore, a milling system start-stop intelligent decision-making method based on deep reinforcement learning has been studied, and a closed-loop control system for the automatic start-stop of the milling system has been developed. The research results have been verified through simulation and successfully applied to a commonly used coal milling system in a certain ultra-supercritical 1 000 MW unit, achieving energy savings. The findings of this study can provide effective reference for the development of unmanned or minimally manned operation techniques for thermal power units.

A method was proposed to solve the problem of oil sludge treatment environmentally by sending the pretreated oil sludge into a 330 MW pulverized coal boiler co-firing with coal. The combustion characteristics of the oil sludge were studied by thermogravimetric analysis, and it was proved to be easy to ignite with a high calorific value close to coal, which could improve the boiler’s low-load stable combustion ability. Numerical simulation results showed that the combustion center shifted downward slightly after the oil sludge was sent into the boiler, while the NO_x content decreased. The experimental results proved that the minimum stable combustion load rate can be 20.00% by the benefit of oil sludge co-firing. The temperature at the coal-burner layer increased by 30~50 ℃ and the carbon content of the fly ash decreased from 4.79% to 3.80%. The fire detection analog signal of the coal burner was found to be more stable which validated the positive effect of the oil sludge co-firing at low load condition. The boiler efficiency increased by 0.23 percentage point which reduced the net coal consumption rate by 0.7 g/(kW·h). Moreover, about 3.7 t/h coal was saved at 120 MW load. The method was verified to have a significant energy-saving effect.

The urea hydrolysis technology for ammonia production has been widely used in the preparation of denitration reducing agents for thermal power units. However, if the quality of urea is not up to standard, the urea hydrolyzer will leak, and the drainage from the urea hydrolyzer will be reused in the condenser, which will cause great harm to the thermal system. The article analyzes the serious salt accumulation and superheater tube explosion in the water and steam system caused by the leakage of a urea hydrolyzer in a coal-fired unit, and proposes a solution to the salt accumulation problem. The problem has been successfully solved, after the unit is started, all quality criterion of water and steam meet the requirements of Quality Criterion of Water and Steam for Power Plant and Steam-generating Equipment (GB/T 12145—2016). This article provides a solution for analyzing and treating the cause of salt accumulation in the water and steam system for reference.