The long-term vibration of ZGM133G-I type medium speed coal pulverizers in a power plant causes weld fatigue fracture of the powder delivery pipeline, which results in coal powder leakage, polluting the environment and seriously affecting the operation of the unit. Based on the mechanical vibration analysis and field test of medium-speed coal pulverizers, this paper studies the influence of operating parameters such as loading force, speed of separator and output of coal pulverizers on the vibration of coal pulverizers. The results show that, the vibration of medium-speed coal pulverizers is mainly caused by the mechanical equipment itself and the setting of operating parameters. The size and separator type of coal pulverizers are not the inevitable factors that cause the vibration of coal pulverizers, but the wear and damage of mechanical structure will cause the vibration of coal pulverizers. In order to reduce the vibration of medium-speed coal pulverizers, it is necessary to comprehensively consider the output of coal pulverizers and the fineness of coal powder according to the test results, and reasonably control the loading force, separator speed and output.

Creep rupture is one of the most common failure modes of pipelines used in thermal power plants. Residual life prediction is an effective guarantee to ensure the safety, utilization and benefit maximization of equipment. Based on the creep rupture test data of 2.25Cr-lMo heat-resistant steel in actual service for over 200 000 hours, the selection principle of TTP parameters and its influence on the accuracy of life prediction are analyzed by comprehensively considering the working stress and TTP parameters. The relationship curve family of Z-parameter method is used to characterize the vertical dispersion of pipeline durability data in different power plants. The stress-TTP-reliability curve for evaluating the reliability of life prediction is established, and the relationship between the predicted life of different power plant pipelines and the working state of the unit is obtained. The creep residual life of different power plant samples at 540 ℃/45.26 MPa is 1.725 6×10⁵ h and 3.378 8×10⁵ h respectively, and the predicted reliability reaches 99%, which provide maintenance suggestions for the operation reliability of power plant equipment.

The fault early warning of the coal mill is of great significance to the safe operation of thermal power unit, but the operation of the coal mill has many interference noises and a high degree of coupling, which makes the fault early warning more difficult. Based on this, this paper proposes a fault warning method based on wavelet packet transform (WPT) and Transformer. Firstly, the signal is denoised by the wavelet packet analysis method with adaptive threshold value. Then, the characteristic parameters related to the fault measurement point are selected as input to establish a Transformer coal pulverized prediction model based on the self-attention mechanism. Finally, the kernel density estimation method is used to analyze the prediction deviation and determine the warning threshold. Taking a 660 MW medium-speed coal mill as the research object and using actual data for verification, the experimental results show that the prediction accuracy of the proposed method is higher than that of CNN, LSTM, and CNN+LSTM models, and it can provide early warning of coal mill failures.

It is necessary to break the technical barrier and make breakthroughs in information system, control system, device and other aspects when reforming large thermal power excitation system domestically. The article first systematically concludes and summarizes the key technologies of modern excitation technology, including control and command subsystems, communication subsystems, rectifier subsystems, and excitation subsystems. It analyzes and summarizes the research status, existing problems, and difficulties involved in each technology at home and abroad. Secondly, the localization and replacement process of the HN-i6200 excitation system for large-scale supercritical 670 MW thermal power units was described. Targeted design was carried out to meet the special requirements of the excitation system operation for thermal power units, and highly reliable domestic DC breakers were developed. Through experimental research, the operation strategy of the excitation system for thermal power units was overcome, and a nationally produced HN-i6200 excitation system was successfully developed. The on-site testing and system modeling have verified the working performance of the nationwide production excitation system, providing technical and practical references for the localization of excitation technology in the power industry.

During the operation of SCR flue gas denitrification system in coal-fired units, ammonium bisulfate (ABS) in flue gas causes ash scale slabbing at the cold end of the air preheater and increases the difficulty of purging and cleaning ash. To this end, ABS premixed ash samples were prepared and pressed and heated at different temperatures, and a new test method was designed to compare the changes in compressive strength of the samples and explore the influence law of ABS on the mechanical strength of ash scale. The experimental results showed that: 1) ABS premixed ash samples underwent physical agglomeration and chemical reaction during the heating of slabbing at 147-220 ℃, and the compressive strength was increased by about 95.50% at maximum, among which physical agglomeration played a dominant role with about 88%-89% influence and the influence of chemical reaction accounted for about 10%-12%; 2) ABS slabbed ash samples under heating at 220-300 ℃, ABS vaporization precipitation rate reached up to 96.43%, the ash sample from the slab state to loose, compressive strength from 195.50% of the blank sample to 110.17%. It is proved that the means of high temperature heating is feasible to reduce the ABS content in the blockage and create conditions for improving blowing and cleaning from the perspective of ash scale.

A comparative analysis between simulation and test with roughness is carried out for a supercritical carbon dioxide (S-CO₂) axial turbine with different operating conditions, focusing on the roughness impact of the turbine performance. The results show that the numerical calculation method of wall roughness is able to assess the performance of the turbine at different load conditions accurately. Compared with test result, the maximum efficiency error is 1.82 percentage point. Wall roughness degrades the overall performance of the turbine, with a maximum efficiency drop of 2.8 percentage point at Ra1.6 roughness level during the five working condition, and the turbine stage roughness has a more obvious effect on the turbine performance. In addition, the more severe of wall roughness, the greater reduction of turbine efficiency. In non-design operating conditions, the efficiency drops by 11.6 percentage point at Ra6.3 roughness level. The wall roughness exacerbates flow separation of pressure surface, causing greater friction losses and serious affecting of turbine performance. The research can provide technical support for the design and performance simulation of S-CO₂ axial turbines.

To solve the problems of uneven distribution of NO_x concentration at the outlet and excessive ammonia escape in the actual SCR operation of power plants, the SCR DeNO_x reactor was simulated numerically and a new ammonia injection optimization method for dual control of ammonia slip and nitrogen oxides emission was proposed. Taking the SCR DeNO_x system of a 660 MW unit as an example, a numerical model of visual flow field and DeNO_x reaction was established, and the change of the partitioned outlet NO_x concentration, ammonia slip and partitioned DeNO_x efficiency under different total ammonia nitrogen ratios were analyzed and compared. The results show that the relationship between partitioned DeNO_x efficiency, outlet NO_x and ammonia concentration, with the partitioned ammonia-nitrogen ratio is a two-parts linear relation separated by an inflection point, and the inflection point occurs when partitioned ammonia-nitrogen ratio is about 1.15. On this basis, the present study proposes a new optimization method for ammonia/nitrogen dual control optimization based on the combination of piecewise fitting function and optimization matrix equation. It is predicted that the 660 MW unit by using 5 zones and 42 nozzles for ammonia injection regulation, and the optimized total ammonia injection volume will decrease by 7.2% at the best compared with the uniform ammonia injection working condition. Relative standard deviation of outlet NO_x concentration and ammonia slip volume will decrease to 9.4% and 4.2% respectively, and the outlet uniformity will be significantly improved, and there is no locally over DeNO_x phenomenon.

Numerical and experimental studies are conducted on convective heat transfer performance of carbon dioxide (S-CO₂) flowing in a heated vertical helically coiled tube under supercritical pressure. The influence of flow characteristics and structural characteristics such as heat flux q, mass flow rate G, pitch P, tube inner diameter d, and spiral radius R on heat transfer are discussed, and the sensitivity of each structural parameter is studied quantitatively. A closed-loop S-CO₂ test platform was built to conduct experimental research on the convective heat transfer performance of S-CO₂ in the helically coiled tube, and the accuracy of the numerical simulation is verified based on the experimental data. Finally, the heat transfer correlation of S-CO₂ is fitted. The research has laid foundation for the thermal design method of S-CO₂ spiral-wound heat exchanger, and has certain engineering application value for the application and promotion of the spiral-wound S-CO₂ heat exchangers in nuclear power and solar thermal power generations.

This paper proposes a multi-parameter collaborative monitoring system and method for degassed hydrogen conductivity based on the combination of double water membrane degassed method and electric regeneration ion exchange technology, which can quickly measure a number of key water quality indicators such as conductivity, hydrogen conductivity, degassed hydrogen conductivity and pH. It can make comprehensive evaluation of water quality, guide thermal equipment shutdown and startup. And it can adjust normal operating water conditions. It has a great significance for ensuring water vapor quality and thermal equipment corrosion, salt accumulation and scale formation. Double water membrane degassing technology is used to measure degassed hydrogen conductivity, which can effectively remove CO₂ from water. On this basis, a method of calibration degassed hydrogen conductivity measured by standard solution is proposed, so that the accuracy of the measured value can be effectively evaluated. This method has been applied to typical gas combined cycle units and heating units for on-site supervision. It proves that the method has high measurement accuracy, can quickly and comprehensively evaluate water vapor quality, and it can assist in solving various technical problems on site. Therefore, it has strong popularization and application value.

The function of query and statistics of data is always the basis of production management and decision-making businesses. According to the results of information construction and applications for many years, the mode, function and performance of data query and statistics still do not satisfy the actual needs. A component for data query and statistics based on supervisory graph software is proposed and developed. Through the design of data path architecture, the optimization of query and statistics mechanism, the developed component has achieved personalized management, lightweight analysis and flexible query of real-time data. The query and statistic component and data link mode developed in this study have been tested and applied in practice. The results show that the function of data query and statistics achieves loose coupling with database. The component can support both the operation modes of C/S and B/S, and provide unified query and statistics of data through supervisory graph from multi-data sources and multi-level organizations. The efficiency of data query and trend query reaches or approaches the level of database native management tools, and is better than that of conventional supervisory information system (SIS) websites. The integration mechanism of data components based on graph with SIS data query and report system is proposed, which helps to reduce the repetitive cost of data use.