Facing the frequency security problem caused by large-scale integrations of fluctuating new energy, the participation of thermal power units coupled with flywheel energy storage in frequency regulation can effectively improve the active power support capability of the power grid from the generation side, which is an effective guarantee for the frequency security of the power grid. According to the output control strategy and capacity configuration of flywheel energy storage systems, this paper proposed a combined method of flywheel control strategy and capacity configuration for primary frequency regulation to optimize the thermal power unit operations. Firstly, a coordinated frequency regulation control strategy of flywheel energy storage considering the real-time power output of thermal power units is designed. An economic evaluation model considering the primary frequency regulation benefit of power plants is proposed, and a refined particle swarm optimization algorithm is utilized to tackle the problem. Finally, the actual data of a 315 MW unit in a power plant from the northern part of China are simulated and verified. The result shows that the proposed integrated configuration strategy can effectively improve the frequency modulation effect of the power grid while taking the cost of energy storage investments into account. The research results are of great significance for promoting engineering applications of flywheel energy storage participating in frequency regulation services.

To provide guidance for the flexible operation of 350 MW supercritical CFB boiler, experimental investigations were conducted on the flow and heat transfer characteristics of water with low mass flux in vertical upward smooth tube under subcritical pressure. Flow and heat transfer experiments were performed under the conditions of 12~15 MPa pressure, 350~440 kg/(m²·s) mass flux, 135~220 kW/m² inner wall heat flux. Furthermore, the dynamic characteristics of the tube were experimentally studied by decreasing pressure and increasing inner wall heat flux, based on the 26 MPa heat transfer experiments. The results of the heat transfer experiments indicate that changing pressure affects the heat transfer performance and enthalpy range of the saturated boiling region. The influence of mass flux on heat transfer performance is only reflected in the sub cooled zone, and the heat transfer performance is enhanced with the increase of mass flux. Increasing heat flux decreases the heat transfer performance in the saturated boiling region. Meanwhile, the correlations of the heat transfer coefficient and friction resistance of water in the tube were fitted based on the experimental data. The dynamic experimental results show that the greater the pressure step, the greater the mass flux increment, and the greater the change in the outlet enthalpy and outlet wall temperature. The step of heat flux only affects the outlet enthalpy and outlet wall temperature. The greater the step of heat flux, the greater the change in the outlet enthalpy and outlet wall temperature. This work can provide guidance for supercritical CFB boiler in low load and flexible variable load operation.

In order to explore the low-carbon and environmentally friendly thermal power generation technology and improve the utilization efficiency of clean energy, a power generation system consisting of Allam cycle and clean heat sources is proposed. The thermodynamic models of the main equipment in the system are established, the advantages and principles of the coupled system are explained by comparing with the reference system, and the influence of the design parameters on the system performance is studied through parametric analysis. The calculation results show that the low-grade clean heat source can effectively solve the heat imbalance problem of the Allam regenerator, thereby heating the recycling stream to a higher temperature. Under typical design parameters, the exergy efficiency of the coupled system can reach 54.07%, which is 4.01% higher than that of the reference system. The output power and exergy efficiency of the coupling system first increase and then decrease with the increment of the turbine inlet temperature. With the increase of the temperature and the mass flow rate of the clean heat source, the output power of the coupled system increases, while the exergy efficiency first increases and then decreases. The research results of this paper can provide data support and theoretical support for low-carbon power generation technology.

In order to improve the flexibility of coal-fired units, a flexible peaking operation method is proposed by combining the heat storage by extracting the reheated steam and secondary air heating by extracting the main steam. Taking the ultra-supercritical 660 MW indirect air-cooled unit as the object of study, the performance of the unit under different peaking schemes at 30% BMCR operating conditions, the energy reuse rates under different heat release conditions and the performance of the combined load reducing operation mode are analyzed. The results show that the energy reuse rates of extracting main steam heat storage, extracting main steam heating secondary air and extracting hot reheat steam heat storage are 55.13%, 84.74% and 46.24%, respectively, at a peak-load shaving capacity of 20 MW with 75% THA heat release condition. Under the premise of ensuring the safety of boiler combustion and heating surface, the combined load reducing operation mode can achieve a peak peak-load shaving capacity of 46 MW, and the energy reuse rate can reach 74% when the heat release condition is 75% THA. This study can provide a reference for flexible peak-load regulation of coal-fired units.

The flue gas recirculation device in the conventional circulating fluidized bed (CFB) oxy-fuel combustion system has been taken out and replaced with pure oxygen combustion, which is expected to reduce the overall energy consumption and CO₂ capture cost of the unit. Pure oxygen combustion will bring about problems such as uneven distribution of heat load and fluidization difficulty under minimal smoke gas flow, so a new boiler design should be carried out according to the flow pattern and heating surface layout in the furnace. This paper adopts the arrangement of immersed tube heating surface in the dense phase area to solve the local over-temperature problem. At the same time, a unique furnace structure design of "wide at the bottom and narrow at the top", reducing the size of the bed material, increasing the primary air ratio and other methods are used to deal with the difficulties of material fluidization. Based on the CFB flow and heat transfer theory, a heat transfer calculation method of pure oxygen combustion CFB boiler is established, and a conceptual design of 130 t/h ultra-high pressure pure oxygen combustion CFB boiler is completed. The basic structure and overall layout scheme of boiler furnace, immersed evaporating heating tube, immersed superheater, cyclone, loop seal and economizer are given. Preliminary analysis shows that the new pure oxygen combustion CFB boiler can solve the problems of uneven distribution of heat load caused by high oxygen concentration combustion and the difficulty of material fluidization under minimal smoke gas flow. The designed boiler thermal efficiency can reach 94.83%, and the volume fraction of CO₂ and H₂O in the outlet flue gas is 57.1% and 38.4%, respectively. This paper lays a foundation for the future development of pure oxygen combustion CFB boiler technology and engineering practice for CCUS-EOR.

The coupling of thermal units with flywheel energy storage system can effectively improve the frequency regulation performance of AGC, solve the problems of long response time, slow climbing rate and low regulation accuracy of thermal units when tracking AGC commands, and obtain the auxiliary revenue of frequency regulation. This paper proposes a flywheel energy storage system control strategy for engineering practice, taking into account the requirements of the "two rules" of the Northwest Power Grid on AGC climbing performance, to improve the performance index of the combined system participating in AGC frequency regulation while preserving flywheel power. The results show that the proposed strategy improves the performance of the combined thermal power units and storage systems in AGC, and the economic efficiency of the power plant is significantly improved.

The natural draft tower of air cooled condenser system require neither mechanical ventilation fan, nor circulating water pump of the indirect dry cooling system, which significantly reduces the noise, house service consumption and net coal consumption of power plant, according with the requirements of the "low-carbon" development era. However, this system has never been applied to large-fossil fired power units, it is necessary to understand the influence of environmental wind direction on heat dissipation of the natural draft tower of air cooled condenser. Using the FLUENT software, numerical simulations of the natural draft tower of air cooled condenser under different wind directions for 2×660 MW unit were conducted to obtain the distribution characteristics of ventilation and heat dissipation of each cooling triangle under different wind directions, the overall heat dissipation performance of the cooling tower and the impact of environmental wind direction on the general layout of the cooling tower and main plant. The results indicate that the central line of the natural draft tower of air cooled condenser of the 2 units should be parallel to the dominant wind direction preferentially.

In view of the heat compensation equipment widely used in combined heat and power (CHP)plant, the feasible operation region model and coal-saving rate model of the CHP plant equipped with a solid heat storage electric boiler are constructed. The effects of the solid heat storage electric boiler, the electrode electric boiler and the water storage heat accumulator on the heat-supply capacity, regulation ability and operation cost of the CHP plant are compared and analyzed. Based on the current status of a CHP plant, a general model for combined dispatching of the CHP plant with flexibility to configure heat compensation equipment is established. Combining with the actual operation data of the CHP plant, the above models are verified and the differences in operation flexibility, scene adaptability, coal-saving effect and operation cost among different heat compensation equipment are quantitatively analyzed. The results show that under the same heating capacity, the solid heat storage electric boiler has the strongest flexibility and the lowest coal saving rate. The heat accumulator has the best coal-saving effect, but the scene adaptability is lower than other heat compensation schemes. The model and research results can provide theoretical tools and reference for the optimal operation of CHP plants.

Three-dimensional computational fluid dynamics simulations are performed for a 650 ℃ grade 1 000 MW ultra-supercritical swirl-opposed firing boiler with low NO_x combustion in the furnace. The flow and combustion characteristics in the furnace and the NO_x concentration in the flue gas are investigated under various conditions of overfire air. It is shown that setting a staggered overfire air and injecting the lower OFA with the angle 15°downward into the furnace is helpful to reduce NO_x concentration and improve the burnout rate. A lower overfire air ratio results in a higher temperature in the region of the combustor and a shorter distance between the high-temperature region and the heating surface. As the overfire air ratio increases, the NO_x concentration of the flue gas at the exit of the furnace first decreases and then increases, and the optimal overfire air ratio is around 33.9%.

Aiming at the problem of low probability of occurrence events such as coal mill failures that are difficult to extract and used for machine learning classification, resulting in low fault diagnosis accuracy, a PCA-FINCH high-precision fault diagnosis method for small samples is proposed. Firstly, based on principal component analysis PCA, fault detection is carried out on the historical data that characterizes the operating state of the equipment, and the occurrence of faults is detected and the fault samples are identified through the T² control limit and the Q control limit, and the fault samples are extracted to form a small sample fault set; Secondly, based on the FINCH classifier, the obtained small sample fault set is accurately classified to realize the fault diagnosis of the equipment. Finally, the method is verified using a historical data set containing coal mill faults. The results show that the PCA-FINCH fault diagnosis method proposed can achieve high-precision classification of small-sample faults, and its accuracy is 2.61 percentage points, 1.74 percentage points and 1.85 percentage points higher than that of decision tree CART, random forest RF and support vector machine SVM, respectively, and its convergence speed is excellent.