The “double high” characteristics of new power system make its frequency stability face a huge challenge. Energy storage assisted thermal power unit frequency regulation technology has become a key core technology to ensure the stable operation of the new power system. The mainstream form of energy storage used in this technology, lithium battery storage, suffers from short lifespan and poor safety in use. The features of supercapacitor energy storage like high power, long cycle life, and high security, are highly compatible with the energy-storage requirements of frequency regulation of the energy storage assisted thermal power unit, but the supercapacitor’s response to the continuous unidirectional command is poor. Therefore, it is necessary to explore the technical route of hybrid energy storage to achieve complementary advantages of the two types of energy storage. The hybrid energy storage capacity configuration of supercapacitor and lithium battery was studied, the energy storage capacity configuration method based on the actual AGC frequency regulation command was designed, considering the characteristics of power-type energy storage devices and energy-type energy storage devices. Moreover, the frequency regulation performance and economy of three typical capacity configuration schemes were compared, and the optimal scheme was determined. Finally, engineering verification was carried out. The actual operation data show that, the supercapacitor hybrid energy storage system can improve the frequency regulation performance of the thermal power unit by 59.77%, extend the service life of the lithium battery to 3.6 times, and improve the system economy.

Butterfly valves are widely used in industrial field, and under certain working conditions, strong unstable flow will occur in the butterfly valve and cause vibration in pipeline system. By taking the connecting pipe of the medium and low pressure cylinder of a 600 MW heating unit as the research object, the mechanism of unstable flow in the butterfly valve and the vibration of the connecting pipe was revealed through the combination of field measurement and steady numerical simulation. Then, based on the flow pattern optimization, a new type of butterfly valve with valve plate and diversion structure was designed, and the unsteady numerical simulation of the maximum vibration condition of the original butterfly valve and the optimized butterfly valve was carried out. The results show that, after adding the flow-guiding structure to the valve plate, most of the main steam flow moves along the middle of the steam inlet pipe of the low-pressure cylinder. This can effectively weaken the exciting force generated by unstable flow and suppress the vibration of the connecting pipe. The new butterfly valve proposed can be applied to suppress the vibration of the pipeline system with small opening of the butterfly valve.

With the proposal of “double carbon target”, the pace of low-carbon transformation of power system has been further accelerated. The flue gas waste heat utilization systems have been widely applied in thermal power units. As the core equipment of the flue gas waste heat utilization system, the flue gas cooler has a high failure rate in actual operation due to factors such as limited space in the flue gas layout, high flue dust concentration, and ammonium bisulfate deposition. This not only reduces the recovery of flue gas waste heat, but also increases system resistance, resulting in an increase in fan power consumption and even affecting the unit’s load capacity and environmental emission. On the basis of extensive researches on the operation of more than 250 sets of flue gas coolers in the thermal power industry, typical faults commonly found in flue gas coolers, such as leakage, boiler ash deposition, bottom flue ash deposition, and low-temperature flue gas corrosion, are summarized. The causes of the above typical faults and their coupling relationships are analyzed in depth. Moreover, the targeted preventive measures are proposed to provide guidance for transformation and operation/ maintenance of flue gas coolers.

With the continuously increasing proportion of installed capacity from new energy sources, higher flexibility demands are imposed on coal-fired power generation units, including supercritical circulating fluidized bed (CFB) boilers. By taking a 350 MW supercritical CFB boiler as the research object, the computational particle fluid dynamics (CPFD) method was employed to simulate the furnace response characteristics under variable load conditions, focusing on parameters such as furnace temperature, near-wall particle concentration, and average heat flux density on heating surfaces. The effects of combustion and circulation interventions on the rate of load change were also explored. The results indicate that, during load ramp-up operation, the response rate of average heat flux density in low load range (30%~50% of the unit rated load) decreases by about 38% compared with that in high load range (above 50% of the rated load). Focusing only on the high load range, the heat flux density responds faster during load ramp-down, with the rate of change about 31% higher than that during ramp-up. Under varying load amplitudes, the particle suspension concentration and convective heat transfer intensity inside the furnace can respond rapidly, while temperature changes lag slightly, indicating that CFB boilers rely more on variations in the heat transfer coefficient for rapid thermal regulation. Through combustion interventions, such as substituting 40% of the original coal feedstock with fine coal particles sized several hundred microns, the change in furnace temperature can be effectively accelerated, with the response rate of average heat flux density during ramp-up in the high load range increasing by about 43%, and by nearly 16% in the low load range. Additionally, implementing circulation interventions, such as adding a certain amount of fine bed material during ramp-up, can rapidly increase the particle suspension concentration in a short time and thus effectively improve the response rate of the heat transfer coefficient on the heating surface. If hot fine material is further added (for example, through a hot circulating ash storage and return system), the response rate of the average heat flux density during ramp-up in the high load range can be improved by approximately 31%, and by about 13% in the low load range. The study elucidates the internal response mechanisms of CFB boilers under variable loading conditions, confirms the feasibility of improving load change rates through circulation and combustion interventions, and provides a reference for further tapping the flexibility potential of supercritical CFB boilers and improving their variable load capability.

The accurate prediction of SO₂ and NO_x emission mass concentrations can effectively guide the control of pollutants emissions, which is of great significance for the environmental protection operation of circulating fluidized bed (CFB) units. A 330 MW CFB unit is taken as the research object, and the Pearson coefficient is used to realize the screening of input variables, and the interquartile range (IQR) method is applied to screen the outliers and replace them with the normalization at the same time, to complete the data preprocessing. Subsequently, the features of input variables are extracted by convolutional neural network (CNN), and by entering into the gate-recurrent unit (GRU) the time-series features are processed. The multi-head self-attention (MHA) mechanism is introduced to capture the important relationships between features, and the model output is obtained after training. Finally, the results of the test set are evaluated using the mean absolute error (MAE), mean absolute percentage error (MAPE), and the coefficient of determination (R²). The results show that the model is able to predict the pollutants mass concentration in CFBs more accurately and achieve good prediction results, and the superior performance of the model is proved by the comparison of ablation experiments with the model. The proposed CNN-GRU-MHA model can realize the monitoring and optimization guidance of pollutants emissions CFB units, so that the power plant can adjust the operation parameters in time to ensure that the pollutants emissions meet the standards.

A novel power generation system integrating an organic Rankine cycle (ORC) with an air-cooled coal-fired power plant is proposed to achieve cascaded utilization of steam energy and enhance output power capability. Based on the efficient thermoelectric conversion characteristics of the ORC system at low and medium temperatures, the steam expanding to a certain level in the coal-fired unit is extracted to drive the ORC system for higher output power. This coupling scheme can achieve the multiple purposes of increasing output power, recovering exhaust steam waste heat and preventing air cooler icing in winter. Focusing on a 600 MW coal-fired power plant, thermodynamic performance evaluation has been carried out. The results show that, when the extraction flow rate is 160 kg/s, the thermal efficiency of the system at 50% THA, 75% THA and 100% THA loads increases by 3.48, 1.72 and 1.08 percentage points, respectively. The exergy efficiency increases by 3.38, 1.68 and 1.05 percentage points, and the coal consumption rate decreases by 27.72, 12.88 and 7.92 g/(kW·h), respectively. The heat recovery rate reaches 64.57%, 25.64% and 15.40%, respectively. This approach not only improves the performance of existing air-cooled coal-fired power plants, but also reduces coal consumption, and the research results can provide a way to improve the overall performance of power plants.

In order to evaluate the vibration safety of the central full partition wall of the world’s first lignite-fired 700 MW high-efficiency ultra-supercritical CFB boiler, a three-dimensional non-constant hydrodynamic model of the boiler is constructed, and the distribution of the gas-solid flow field within the furnace chamber is simulated. Furthermore, the pressure distribution and its fluctuation law of the gas-solid flow acting on the surface of the central full diaphragm wall within the furnace are solved. The vibration signals of the furnace wall of a supercritical 350 MW CFB boiler with a similar furnace structure are measured and analyzed spectrally to assess the frequency of pressure fluctuations in the furnace. The dynamic stress on the central diaphragm wall under fluctuating pressure in the furnace is calculated using the pressure fluctuations in the furnace obtained from simulation calculations and experimental tests as the excitation. The results demonstrate that the dynamic stress level of the central full diaphragm wall is below the permissible stress of the material, indicating that the central full diaphragm wall is safe.

The ignition, burnout, and slagging performance of Baoqing lignite raw coal and its dried lignite with different moisture contents was experimentally investigated using an ignition furnace and one-dimensional furnace test platform. The results show that, the ignition temperature of Baoqing raw coal is 415 ℃, which is highly prone to ignition. Compared to the influence of moisture on ignition temperature, the effect of fineness on ignition temperature is more significant. At low loads, the water and steam react with the water gas of coke in the early stages of combustion, which has a significant impact on the consumption rate of coke. Due to its high moisture content, raw coal undergoes intense reactions during the initial combustion stage, resulting in a rapid decrease in mass fraction of combustible materials in fly ash and a stronger tendency towards slagging. However, excessive moisture is not conducive to the complete combustion of coal powder in the later stage of combustion. As the fineness of coal powder R₉₀ increases, the burnout rate of coal powder decreases. But overall, the burnout rate of both Baoqing raw coal and dry coal is above 99%, indicating the Baoqing coal is highly flammable, and the effect of oxygen on burnout rate is not significant.

Improving the heat transfer efficiency between liquid lead-bismuth eutectic (LBE) and supercritical carbon dioxide (S-CO₂) is of great significance for advancing the development of advanced nuclear energy systems. The heat transfer performance of printed circuit heat exchangers (PCHE) with different channel structures (straight shaped, wing-shaped, S-shaped and Z-shaped) is investigated through numerical simulation. The results show that the thermal resistance on cold side of the heat exchanger is significantly higher than that on the hot side, with the average heat transfer coefficient of the hot side in straight-channel PCHE being 26.2 times that of the cold side. Under the condition of a fixed hot-side channel structure, the effects of different cold-side channel structures on PCHE heat transfer performance are explored. The results indicate that, compared with straight channels, the heat transfer of Z-shaped, S-shaped and wing-shaped channels increases by 23.3%, 22.2%, and 10.6%, respectively, while the specific pumping power improves by 1.48 times, 1.68 times, and 1.44 times, respectively. In addition, the dynamic performance of different PCHE designs when the cold-side flow rate increases by 20% is compared, revealing that the straight-channel PCHE has the shortest rebalancing time. The pressure drop loss is more significant than the improvement in heat transfer. These findings provide theoretical guidance for optimizing the design of LBE/S-CO₂ heat exchangers and contribute to enhancing the thermal efficiency of next-generation nuclear energy systems.

Nowadays, circulating fluidized bed (CFB) coal-fired boilers face challenges in the process of deep peak regulation, such as high CO emission concentrations and the lack of theoretical guidance for collaborative emission reduction of multiple pollutants including NO_x and SO₂. Taking a 150 t/h CFB coal-fired boiler as the research object, a model for quickly predicting mass concentrations of CO, NO_x and SO₂ emitted from the furnace is established based on the long short-term memory (LSTM) neural network, the Attention mechanism and the XGBoost algorithm. Moreover, an online emission reduction strategy is proposed by coupling with the particle swarm optimization (PSO) algorithm. 36 298 operational data points from the coal-fired boiler throughout 2023 are selected as training samples. A correlation analysis is conducted between the boiler inspection data and pollutant emission mass concentrations to determine the input parameters for the prediction model. The fitness function and boundary function are determined with the prediction model coupled with the PSO algorithm. Through the calculation of emission reduction optimization model, an online emission reduction optimization strategy for CO, NO_x and SO₂ mass concentrations of CFB boilers in different load ranges is proposed, and the feasibility of the algorithm in practical boiler tuning applications is evaluated.