Taking the gas fuel control valve of gas turbine as the research object, based on the computational fluid dynamics method, the flow field distribution and flow change rule of the gas fuel control valve under the actual operating conditions are studied, and the flow characteristic curve of the valve is fitted. The results show that the mass flow of the control valve at the same opening has nothing to do with the change of the pressure behind the valve, and is in a blocked flow state when the pressure in front of the valve is 2.650 MPa and the pressure ratio behind the valve to that in front of the valve is 0.49~0.78; Under the same pressure ratio, the discharge coefficient is approximately linear with the opening, which is consistent with the actual requirements of the project; There is a linear correlation between the flow coefficient and throat area. By optimizing the valve core profile, the linear curve of throat area with opening is improved, and the linearity of the flow characteristic curve is improved.

In order to accelerate the achievement of the goals of "carbon peaking" and "carbon neutrality", a series of laws, regulations, and institutional documents on greenhouse gas control have been introduced by the country, local governments, and industries. Nitrous oxide (N₂O), as a gas with strong greenhouse effects, has attracted increasing attention from researchers. This article summarizes the current research status of N₂O at home and abroad, compares the N₂O emissions of typical coal-fired boilers, analyzes the generation mechanism, influencing factors, suppression methods, and removal methods of N₂O during the combustion process, explores N₂O emission reduction strategies for coal-fired boilers, and provides suggestions. It is necessary to strengthen the formulation of N₂O related standards, research and development of new technologies, and demonstration applications for coal-fired boilers. Further research is needed on the influencing factors of N₂O, such as pressurized oxygen enrichment conditions and coal moisture content, to further improve the suppression and removal methods.

In order to ensure that the supercritical CFB boiler has good wide-load operation characteristics and the ability of deep peak regulation, the transient heat transfer characteristics between the working fluid and the water wall under the change of transcritical pressure are experimentally studied. Experiment adopted Φ25.0 mm×3.5 mm vertical upward tube, the near-critical steady heat transfer experiment and the transcritical pressure step transient heat transfer experiment were carried out under the experimental conditions of 20~23 MPa of pressure and 400~800 kg/(m²·s) of mass flow rate. The results showed that under the near-critical pressure, increasing the flow rate, reducing the heat flux on the inner wall, and reducing the pressure can reduce the dryness when the DNB heat transfer deterioration occurs, and increase the corresponding fluid enthalpy value, and delay the occurrence of the heat transfer deterioration. When the transcritical pressure step changes, the heat transfer deterioration may occur in the heating pipe, resulting in the wall temperature rising rapidly, but the temperature will fall back to the normal value with the increase of the flow rate. The heat transfer between the wall temperature rising point and the inner wall surface goes through the heat transfer deterioration stage, the subcooled boiling heat transfer enhancement stage and the single liquid phase heat transfer stage. The influence of each parameter on the heat transfer deterioration in the transcritical pressure step change experiment is the same as that in the near-critical steady state experiment. The decrease of flow rate and the increase of heat flux on the inner wall will advance the location of the heat transfer deterioration, and the wall temperature rise will be greater.

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.

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 dynamic model of resistive type molten salt heater was established by Dymola software, and the transient characteristics and internal temperature field of resistive type molten salt heater under electrical load and molten salt flow disturbance and different arrangement modes were studied on the basis of verifying the effectiveness of the model. The results show that the influence of large disturbance of electric load and molten salt flow on the dynamic characteristics of resistance type molten salt heater tends to be the same, and reaches its limit condition at 110 s and 105 s respectively. However, the occurrence of the limit condition can be greatly delayed when the two disturbances are coordinated. Multiple electric heaters arranged in series or in parallel can slow down the change of molten salt temperature, but increase the system cost. The research conclusion can provide reference for the design, control and debugging of resistance molten salt heater.

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.

An effective disposal method of municipal sewage sludge is burning sewage sludge together with coals in coal-fired circulating fluidized bed (CFB) boilers. At an appropriate weight ratio of sewage sludge in fuel blend, the co-combustion of sewage sludge and coals will not cause significant adverse effects on power plant production, and make use of the calorific value of sewage sludge. This study summarizes the progress of research and application in CFB boilers co-firing coal and sewage sludge, involving the emissions and controls of pollutants during the co-combustion of sewage sludge and coals, the weight ratio of sewage sludge in fuel blend under the reliable boiler operation, and sludge drying. The operational problems associated with the co-combustion of wet sludge and coals are analyzed. The applications of coal-water slurry suspension combustion technology and oxygen-enriched combustion technology in the disposal and utilization of sewage sludge are presented. The study points out that the drying and incineration of sewage sludge combined with advanced flue gas purification technology is one of the mature processes for the application of coal-fired CFB boilers in sewage sludge incineration, which can avoid the environmental impact of odours generated during the storage, drying and transportation of sewage sludge, and provide effective controls of a variety of pollutants. The conclusions of investigation and analysis can provide a reference and basis for the design and safe operation of CFB boilers co-firing coal and sewage sludge.

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.

This paper explains the overall impact of the dual carbon strategy on coal power and the development problems it faces. The status quo and key technologies of clean emissions, energy conservation and carbon reduction, heat supply and efficiency improvement, and flexible operation of coal-fired power units are sorted out and analyzed, and the development prospects of coal power are prospected, and the conclusion is drawn that the development of coal power is positively viewed based on China's resource endowment and energy strategic security, and attention should be paid to the research and development and application of clean, efficient and flexible coal power technology, and the advantages of various new energy sources are complemented and dynamically coordinated to promote the steady development of new power systems.