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  • Research & Analysis
    Discussion on Heating Capacity Expansion Retrofit for a 600 MW Supercritical Unit
    Li Feng, Yang Yu, Luo Shunxu
    2024, 38(5): 269-273. https://doi.org/10.19806/j.cnki.fdsb.2024.05.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To meet the requirement of improving the industrial steam supply capacity under low load condition in a 600 MW supercritical unit with flexible peak regulation, under the premise of ensuring the safety of steam turbine, following two feasible technical schemes were compared and selected from the aspects of safety, flexibility, and economy, namely the schemes of the cold reheated steam replaced by the reheater desuperheating water and by partial No.2 high-pressure heater extraction steam. Results show that, although the scheme of the cold reheated steam replaced by the reheater desuperheating water has a better economy, it highly depends on the reliability of the operation monitoring system, which has a certain risk during operation. The scheme of the cold reheated steam replaced by partial No.2 high-pressure heater extraction steam is finally selected, although the scheme has a poor economy, it provides a more safe and reliable operation for the unit.
  • Research & Analysis
    Assessment of the Impact of Ambient Temperature and Humidity on Oxygen Production in Air Separation System
    Mu Yanfei, Yu Yang, Song Shilei, Zhang Bo, Li Xiaoyu
    2024, 38(5): 274-277. https://doi.org/10.19806/j.cnki.fdsb.2024.05.002
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The seasonal fluctuation of ambient temperature and humidity has a significant impact on the efficiency and oxygen production of air separation system. To quantitatively evaluate the influence of ambient temperature and humidity on the oxygen production power consumption of an air separation system in an integrated gasification combined cycle (IGCC) power plant in Tianjin, a computational model for the oxygen production per unit power of the air separation system was established by binary regression method, based on the actual operating data of the air separation system throughout the year. Results show that, the established regression model accurately reflects the effect of temperature and humidity on system power consumption, with a high correlation coefficient (R2) of 0.901 between the model-predicted results and the actual operation data. In winter, when the temperature and humidity are lower, the oxygen production per unit power of the air separation system is approximately 18.78% higher than that in summer, indicating that the power consumption of oxygen production in summer is significantly higher than that in winter. This is mainly due to the relatively higher air mass flow rate at the air compressor inlet in winter. Consequently, it is recommended to arrange the system operation and maintenance during summer, and maintain the stable operation during winter.
  • Research & Analysis
    Magnetization Test of Generator Stator Core Based on Variable Frequency Current Excitation
    Gu Haocheng
    2024, 38(5): 278-282. https://doi.org/10.19806/j.cnki.fdsb.2024.05.003
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to explore the temperature rise trend of the stator core surface and fault points and the variation of the short-circuit current of the fault point under the excitation of variable frequency current, the short-circuit fault points with different coil turns were selected on the stator core, while the magnetization test of the stator core under the power frequency (50 Hz) and high frequency (250 Hz) was carried out to record the temperature rise of the core under different frequencies. The magnetization test of the core was carried out under the same working condition by applying different frequencies (50, 100, 150, 200, 250, 300 Hz) of sine wave to record the fault current of the simulated fault point of the core under different exciting current frequencies. Test results show that, the temperature rise trends have a good similarity between the stator core surface and the fault points with high frequency current excitation, and there is no significant change in the short-circuit currents of fault points under different frequency conditions. It is verified that the magnetization test of generator stator core based on variable frequency current excitation is feasible.
  • Research & Analysis
    Comprehensive Comparison and Analysis on Cold Air Heating System Schemes in Boiler
    Xie Xingyun, Wang Daoyuan, Cui Tilei, You Tongtong, Yu Shuai, Liu Qi, Lin Mingquan
    2024, 38(5): 283-287. https://doi.org/10.19806/j.cnki.fdsb.2024.05.004
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to explore a better system for preventing the corrosion of air preheater, taking a 660 MW ultra-supercritical coal-fired unit in Jiangsu Province as an application object, comparisons were conducted on following present commonly used three systems in actual operation, namely the system of hot air recirculation combined with low temperature economizer, the system of steam-medium air heater combined with low temperature economizer, and the system of water-medium air heater combined with low temperature economizer. After which, the most suitable system for the unit was selected from the aspects of structure, performance and economy. Results show that, under winter condition, the system of water-medium air heater combined with low temperature economizer has a best comprehensive performance with a better reliability, a better adjustability, a maximum coal saving, and a shortest investment payback period.
  • Research & Analysis
    Research on a New Type of High-pressure Trip and Overspeed Limit Device for Steam Turbine
    Li Qing
    2024, 38(5): 288-291,305. https://doi.org/10.19806/j.cnki.fdsb.2024.05.005
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The structure and working principle of a high-frequency electromagnetic cut-off directional valve applied to a new type of high-pressure trip and overspeed limit device for steam turbine were introduced. A digital twin simulation model of the device was established through virtual simulation platform, and the relevant actions required by the device under various working conditions of the steam turbine was simulated. Results show that, the new type of high-pressure trip and overspeed limit device for steam turbine has good reliability and dynamic characteristics.
  • Research & Analysis
    Multi-factor Linear Regression Prediction for Heat Value Loss of Coal Yard Based on LSTM
    Rao Hua, Wu Linxing, Chen Shaolong, Wu Aijun, Du Wei, Xu Huifang, Yan Xiaozhong, Zhan Yi
    2024, 38(5): 292-299. https://doi.org/10.19806/j.cnki.fdsb.2024.05.006
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem of the heat value losses in the coal yards of thermal power plants, a comprehensive multi-factor linear regression model for heat value loss prediction based on long short-term memory (LSTM) neural network was proposed. The environmental factors in the location of the coal yard were predicted by LSTM neural network, and a regression equation between the change of coal pile heat value and the total value of various factors within the cumulative time was established, so as to calculate the heat value losses in future through considering the influencing values of predictive factors. With the on-spot collected data of the coal yard and after the ash content equivalence processing on the high heat value, analyses were conducted on the multi-factor regression for the dependent variable heat value by the recorded environmental factor data, while a mathematical model for heat value loss was established. Based on the construction of LSTM neural network to predict the multi-factor change, the change of heat value was predicted through importing prediction data into the the regression model. Simulation results show that the prediction accuracy for environmental factors of multi-factor LSTM neural network is higher than those of single factor and traditional autoregressive integrated moving average (ARIMA) models, and the multi-factor LSTM neural network has a strong stability.
    • Environmental Technology
  • Environmental Technology
    Application of Full Load Denitrification Technology for 330 MW Subcritical Units
    Li Kewen, Zhou Yong, Ma Jianyu, Jian Yuxiang
    2024, 38(5): 300-305. https://doi.org/10.19806/j.cnki.fdsb.2024.05.007
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In view of the circumstance that it is difficult to meet the requirement of ultra-low emissions of nitrogen oxides (NOx) under deep peak regulation conditions in coal-fired units, detailed researches were conducted on the application of the full load denitration technology for 330 MW subcritical units. Combined with technical route principles, for a controlled circulation boiler in a 300 MW subcritical coal-fired unit, the denitrification effects before and after retrofit were compared and analyzed. Results show that, the denitrification system can put into operation before gird connection through the deep coupling of following four technologies, namely the implement of hot water recirculation retrofit in economizer, the change of steam turbine start-up mode from high pressure cylinder start-up to high and medium pressure cylinders combined start-up, the start operation of No.6 high-pressure feedwater heater during unit start-up process, and the selection of selective catalytic reduction (SCR) denitrification catalyst with a wide temperature range. Meanwhile, the hourly average mass concentration of NOx emission is consistently below 35 mg/m3, which meets the requirement of ultra-low emission value (50 mg/m3).
    • Fault Diagnosis
  • Fault Diagnosis
    Research on Fault Warning of Steam Turbine of Feed Water Pump Based on Multivariate State Estimation Technique
    Wei Wei, Fu Longxia, Hu Yiqun, Luo Yun
    2024, 38(5): 306-312. https://doi.org/10.19806/j.cnki.fdsb.2024.05.008
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to realize the fault early warning of steam turbine of feed water pump, based on parameter estimation of multivariate state estimation technique (MSET) and residual warning, a fault early warning method was proposed. The steam turbine of feed water pump of a 350 MW ultra-supercritical unit was selected as the research object, the key parameters characterizing its operation characteristics were selected, and the operation history data from distributed control system (DCS) were collected. The abnormal data were cleaned by truncation method and boxplot method, and the normal operating condition sample database of operating parameters was constructed by equidistant sampling method. The parameter estimates were obtained based on MSET, and the residual warning threshold was determined by sliding window method, and the fault early warning model of steam turbine of feed water pump was established. Finally, the actual operating data was used for verification. Results show that, under normal working conditions, the average relative error of the estimated value of the model is less than 3%, which can effectively identify the abnormal state in the operation of the steam turbine of feed water pump. The model is applied to the big data platform of the power plant to realize the intelligent monitoring and fault early warning of the steam turbine of feed water pump, which has great engineering practical value.
    • Operation & Retrofit
  • Operation & Retrofit
    Analysis and Treatment of Condensate Pipe Vibration Caused by Fluid Pulsation Under Deep Peak Regulation in a Thermal Power Generating Unit
    Cao Zhongxun, Zha Bingfeng, Wang Fei, Dong Xuefeng, Xiong Chenghui
    2024, 38(5): 313-317. https://doi.org/10.19806/j.cnki.fdsb.2024.05.009
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    For the problem of severe vibration of the condensate pipe in a power plant, the vibration fault analysis of the condensate pipe was conducted through on-site condensate pipe vibration tests, the support and hanger system inspection and valve defects troubleshooting. Results show that, the condensate pipe support and hanger system has three anomalies and the condensate bypass valve of the low pressure feedwater heater has internal leakage. The anomalies reduce the natural frequency of the condensate pipe, while the internal leakage of the bypass valve leads to fluid pulsation that resonates with the pipe, resulting in severe vibration of the condensate pipe. After treating the valve leakage, the maximum vibration speed of the condensate pipe decreases from 160 mm/s to 3 mm/s, effectively resolving the vibration problem of the condensate pipe. The natural frequency of condensate pipe system is increased by addressing the defects of the condensate pipe support and hanger system during the unit overhaul, avoiding the fluid pulsation frequency, and resolving the vibration problem of the condensate pipe. The method of eliminating excitation force and improving pipe system stiffness can effectively deal with the vibration of pipe system in thermal power generating unit, which is significant to ensure the long-term safe and stable operation of unit.
  • Operation & Retrofit
    Analysis and Treatment on Fault of Regenerative Feed-water Heating System in a 1 000 MW Thermal Power Unit
    Hu Zhengrong, Luo Shuyan, Wang Richeng, Yu Xinggang
    2024, 38(5): 318-322. https://doi.org/10.19806/j.cnki.fdsb.2024.05.010
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    For a newly built 1 000 MW ultra-supercritical thermal power unit, to solve following three problems in regenerative feed-water heating system during commissioning, namely the final feed-water with abnormally low temperature, the outlet feed-water of steam cooler with excessive temperature, and the liquid level of low pressure heater with fluctuation, analyses were carried out from the aspects of measurement factors, operation control parameters and system structure layouts. The reasons of faults were accurately found through analysis, while corresponding measures and suggestions were proposed for different faults. A good effect is obtained after treatment, which can eliminate the risk of equipment damage in time and improve the economy of the thermal system. This may provide a reference for the fault handling and operation optimization of the regenerative feed-water heating system in similar units.
  • Operation & Retrofit
    Analysis and Treatment of Oil Leakage from Bearing Housing Oil Baffle in a 660 MW Ultra Supercritical Pressure Steam Turbine
    Xue Qinghong
    2024, 38(5): 323-327. https://doi.org/10.19806/j.cnki.fdsb.2024.05.011
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    An analysis was conducted on an oil leakage accident in the No. 3 bearing housing oil baffle of a 660 MW ultra supercritical pressure steam turbine. Results show that, the main causes of the oil leakage are three aspects, including low inlet pressure of lubricating oil exhaust fan, insufficient steam supply of shaft seal, improper heat insulation of medium pressure steam exhaust chamber. By adjusting the operation of the turbine lubricating oil and shaft seal system, and repairing the heat insulation of the turbine, the oil leakage point can be eliminated. This case study can provide reference for operation and maintenance personnel of power plant.
  • Operation & Retrofit
    Feasibility Analysis and Application of Transforming Tubular Air Preheater into Rotary Air Preheater in a CFB Boiler
    Liu Chuan
    2024, 38(5): 328-334. https://doi.org/10.19806/j.cnki.fdsb.2024.05.012
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    By comparing the performance of tubular air preheater and rotary air preheater, a performance and efficiency improvement scheme was proposed to transform tubular air preheater into rotary air preheater for small and medium-sized circulating fluidized bed (CFB) boiler. For a 300 MW CFB boiler, the feasibility and technical scheme of air preheater transformation were evaluated, and the performance parameters and economic benefits before and after transformation were analyzed. Results show that, transforming the tubular air preheater into the rotary air preheater can effectively reduce the exhaust gas temperature of boiler, and ensure the stability of air leakage rate and flue gas resistance. This meets the needs of energy saving and consumption reduction, while improving the economy and reliability of unit operation.