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.

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.

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.

In the domestic large circulating fluidized bed boilers designed with side wall and back wall coal feeding system, there are generally prominent problems of coal feeding delay and uneven coal feeding in the actual operation process. By analyzing the coal feeding delay problem of large CFB boiler units and the operation characteristics of the existing coal feeding system, the quantitative calculation method of coal feeding delay problem of large CFB boiler coal feeding line is put forward. Based on the case of a supercritical 600 MW CFB boiler coal feed line, the coal feed delay characteristics of the coal feed line under the condition of wide load and rapid peak regulation are obtained. The calculation results show that the coal feed delay problem is common in the variable load operation process of large CFB boiler units, which will lead to a certain degree of uneven coal feed. The variable load range, variable load rate and the number of coal feed ports on the single feed line are positively correlated with the severity of the delay problem. The calculation method and analysis results can provide design basis and technical reference for large CFB boiler coal feed line to adapt to wide load and fast peaking operation.

In order to provide methodological guidance for the load optimal distribution of thermal power units under the condition of deep peak regulation, the objective functions of optimal load distribution under medium-high load and low load are established respectively, and the load optimal distribution under different conditions is studied. The k-means clustering algorithm is used to process the data and the coal consumption characteristic curves of two units under medium-high load and low load are fitted. The objective function of load distribution is established to compare the coal consumption before and after optimization under static load distribution, incremental load distribution and continuous variable load conditions. After setting the total load instructions of the two units under the condition of deep peak shaving, the coal consumption of the two schemes of load average distribution and optimal distribution is compared. The results show that the clustering-based objective function models of optimal distribution under medium-high load and low load established by the coal consumption characteristic curve are reliable, whose optimization effect is remarkable under the condition of deep peak regulation. The k-means clustering algorithm can be used to optimize the load distribution of thermal power units and provide reference for the study of load optimal distribution under the condition of deep peak regulation of thermal power units.

Flue gas recirculation (FGR) is an important technical mean to improve the safety of circulating fluidized bed (CFB) boiler and reduce the generation of NO_x under low-load operation. In the present work, the relationships between temperature distribution of the boiler, NO_x, CO mass concentration and O₂ volume fraction of the flue gas at furnace outlet, the combustible matter content of fly ash and bottom slag and the flow rate of FGR under the load of 20%, 30% and 40% BMCR (boiler maximum continuous rating) were studied using one-dimensional chamber CFB combustion quasi-static model at a supercritical 350 MW CFB boiler. The results show that both the bed temperature and furnace exit flue gas temperature decrease with the increase of FGR flow rate, which the former decreases less than the latter. The temperature difference between the upper and lower furnace gradually decreases with the increase of FGR flow rate, which is more significantly affected by FGR flow rate at lower loads. The NO_x mass concentration of flue gas at the furnace exit shows a trend of decreasing first and then increasing with the increase of FGR flow rate, and the existence of the optimal FGR flow rate can make the unit operation economically and environmentally friendly. In addition, with the increase of the FGR flow rate, the CO mass concentration at the furnace outlet, combustible matter content of fly ash and bottom slag shows an increasing trend. The FGR significantly reduces the primary air oxygen volume fraction while ensuring that the fluidized air flow rate in the dense phase area is always higher than the protection value, which ensures the operation safety of the boiler under low load furtherly.

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.

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.

With the increasing penetration of new energy in new power system, the influence of the uncertainty of wind power output and the correlation with load on the system operation is increasingly prominent. Thus, the conventional transformer risk assessment can no longer meet the demand. Based on Copula model and Susa model, a joint probability assessment method of transformer operation risk considering wind power and load correlation is proposed. Monte Carlo method is used to calculate each risk index value and evaluate transformer operation risk. The research results show that, the conventional transformer evaluation system that does not consider the wind-load correlation will lead to a low overall risk assessment result, with the maximum error of the index up to 55.02%. Also, with the increase of wind-load correlation, the risk of thermal defects of the transformer is increasing. The research conclusions can assist to improve the accuracy of the operation risk level assessment of new power system transformers, and provide a reference for the later transformer condition assessment and maintenance plan formulation.

In order to solve the problems of user account management and security protection in current group information system, this paper proposes a three-in-one AAA system of account, authentication and audit based on zero-trust architecture. Firstly, it describes the function of user management, authentication authorization, user audit and other modules of the AAA system. Secondly, in view of the conventional network boundary protection problem, the authentication authorization method based on zero trust architecture is applied to identify the business scenario, thus to ensure the reliability of the business system environment. Lastly, it illustrates the logic of the AAA subsystem and group-level system development platform configuration. The proposed AAA system can effectively improve the business security of group-level enterprise information system, compensate for the security issues of user login account under zero-trust environment, and further improve the security protection ability of network equipment, application equipment, system and application management in group-level enterprise.

During the operation of a trough solar power station, the stability of the outlet temperature of the thermal conductor is an important control objective for the safe and reliable operation of the power station. Due to the structural characteristics of the collector tube, the outlet temperature characteristics of the trough collector have large inertia and large delay, so the outlet temperature control problem is complicated. In order to solve this problem effectively, a dynamic mathematical model of MW trough solar power collector circuit is constructed in this paper, and a temperature control system is constructed at the collector outlet. A step prediction controller for the outlet temperature of trough solar power collector circuit is proposed. Simulation experiments were carried out based on MATLAB/Simulink platform. The simulation results show that, for the groove heat collecting loop, under the disturbance of irradiation, heat conduction oil inlet temperature and ambient temperature, the stepped predictive control system has shorter adjustment time, smaller overshoot, better robustness, and significantly improved control effect compared with the traditional PID control system. The proposed predictive controller can well cope with the situation of heat conduction oil overtemperature and heat conduction oil flow fluctuation at the outlet of heat collecting field, which is conducive to the safe and stable operation of the trough heat collecting field.

The pH values of boiler feed water, steam, boiler water and other measuring points in a chemical power plant were abnormally low, and the problem could not be effectively solved by adjusting the boiler water dosing process. In order to solve this problem and ensure the safe operation of the unit, this paper discusses and analyzes the influence of water sample temperature on pH electrode, Nernst temperature coefficient slope and solution temperature coefficient (ionic activity), and verifies through experiments that the abnormally low pH measurement value is caused by the large deviation of water sample temperature from 25 ℃, and the pH measurement method cannot provide correct temperature compensation. Strict control of water sample temperature, adoption of computational pH meter or selection of high-precision pH meter with precise non-linear temperature compensation function can effectively solve the problem of abnormally low pH measurement in the water and steam system.

Taking a 660 MW wall-tangentially fired boiler as the research object, the effects of air distribution ratio on the characteristics of in-furnace coal combustion and heat transfer processes and NO_x transformation were numerically investigated. Results show that under the fixed SOFA ratio, the increase of primary air ratio makes the overall boiler performance changes in V type that deteriorates evidently at first and then gets improved somewhat. The increased in primary air ratio leads to the generation of more fuel-NO_x at the initial combustion stage, which thus increases the final NO_x emission at the furnace exit. SOFA ratio does not change the variation trend of combustion performance along with the primary air ratio, but its increase leads to the decrease of the critical primary air ratio at which coal combustion performance deteriorates significantly. The variation of primary and secondary airflow momentums caused by the air distribution ratio is the main factor affecting the overall boiler performance, and coal combustion performance deteriorates significantly when their momentums are too close. Based on this, the large increase in the primary air ratio should be avoided during the practical boiler operation process. If it is inevitable, the SOFA ratio should be decreased to alleviate the deterioration of boiler performance caused by the increased primary air ratio.