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.

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 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.

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.

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.

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.

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.

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.

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.

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.