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  • Research & Analysis
    Modeling of Thermophoresis Deposition and Analysis of the Influencing Factors
    Sun Hengqing, Sheng Changdong
    2020, 34(2): 75-80. https://doi.org/10.19806/j.cnki.fdsb.2020.02.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A model was established for the thermophoretic deposition based on thermophoresis mechanism of the initial deposition layer on the heating surface of a boiler, which was validated with the experimental and model results in relevant literature, while the prediction accuracy of the model was improved by considering the dynamic changes of surface temperature with the growth of the deposition layer. Results show that high flue gas temperature and high alkali metal concentration both promote the thermophoresis deposition, which is slightly influenced by flue gas flow. Meanwhile, high tube wall temperature inhibits the thermophoresis deposition. Under same conditions, the thermophoresis deposition process of K2SO4 has a high degree of similarity with that of Na2SO4, which is independent of the composition of aerosol particles. When the size of aerosol particles is less than 1 μm, the thickness of initial deposition layer would be independent of the particle size distribution.
  • Research & Analysis
    Influence of Potassium Salts on Water Gas Shift Reaction in Supercritical Water
    Ding Qizhong, Zhang Jun, Zhao Liang, Lu Qi'an
    2020, 34(2): 81-86. https://doi.org/10.19806/j.cnki.fdsb.2020.02.002
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    The influence of potassium salts in biomass on the process of water gas shift reaction (WGSR) was discussed, so as to study the effects of single or mixed potassium salt on the WGSR in supercritical water under different technological conditions. Results show that the gaseous products of WGSR are H2, CO and CO2. All the potassium salts can promote the H2 yield significantly, and KHCO3 has the strongest influence on H2 yield than other salts involved. An increase in temperature and reaction time can both result in higher H2 yields, while the effects of pressure and K+ concentration are complicated. The accelerated effect of potassium salts could be explained by the formation of intermediate products oxalate and formate.
  • Research & Analysis
    Mechanism of FAC in Once-through Boiler Units and the Corresponding Inhibition Methods
    Yu Yang, Kang Yanchang, Zhou Yang
    2020, 34(2): 87-91. https://doi.org/10.19806/j.cnki.fdsb.2020.02.003
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    To solve the problem that flow accelerated corrosion (FAC) is easy to occur in once-through boiler units, which may result in a higher rate of scaling and salt accumulation in the equipment of related water-steam systems, an introduction was presented on the FAC mechanism, the migration process of iron corrosion products and the FAC inhibition methods, based on case analysis. Results show that the FAC in once-through boiler units could be effectively inhibited by feed water oxygenation treatment (OT).
  • Research & Analysis
    Research on Ellipse Formula Improvement Based on Turbines with a Finite Number of Stages
    Chen Xiaoxin, Xu Jianqun, Mao Baoxue
    2020, 34(2): 92-95. https://doi.org/10.19806/j.cnki.fdsb.2020.02.004
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    To solve the problem existing in application of ellipse formula to turbines with a finite number of stages, the optimal index of elliptic operator was calculated by changing the isentropic index, and with the establishment of mass flow pressure ratio model and sonic pressure ratio model, the formula derivation and modeling were conducted for the turbine with a finite number of stages under two critical conditions respectively. Results show that the result calculated based on the improved ellipse formula is more close to the Pengtemen coefficient than that based on traditional ellipse approximation formula. When energy loss exists in actual flows, to maximize the stage flow, the mass flow pressure ratio model is to be adopted, whereas, to make the stage outlet achieve the sonic speed, the sonic pressure ratio model would be preferred. Both the models can meet the precision requirements in engineering applications.
  • Research & Analysis
    Research on Prediction of Pollutants Emission from Thermal Power Units Based on XGBoost
    Zhou Hong, Chen Bin, Li Zhongqin, Gao Fei
    2020, 34(2): 96-99. https://doi.org/10.19806/j.cnki.fdsb.2020.02.005
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    To effectively utilize the operation data and external data of thermal power units for the prediction of pollutants emission, the features of the data were extracted, while the NOx emission rate was predicted based on the XGBoost algorithm. Results show that for the prediction of NOx emission rate, the root mean squared error is 2.43 and the mean relative error is 15.9%, which may guide the production personnel in planning and scheduling activities.
  • Research & Analysis
    Experimental Study on Combustion Characteristics of Double-layer Plasma Burners in an Ultra Supercritical Boiler
    Ma Wuming, Chen Lu, Li Ming
    2020, 34(2): 100-105,110. https://doi.org/10.19806/j.cnki.fdsb.2020.02.006
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    An introduction was presented to the combustion characteristics of plasma burners respectively in layer A and layer D of a 1 000 MW ultra supercritical boiler, while an analytical study was conducted on the cold-state aerodynamic test results, the heating rate and boosting rate of the main steam during startup, the mass concentration variation of the NOx entering the SCR denitrification reactor, the gas temperature variation and the water wall temperature variation at furnace outlet, etc. This may serve as a reference for the economy, safety and environmental protection of the unit with double-layer plasma burners.
    • Material Technology
  • Material Technology
    A New Ferritic Heat-resistant Steel
    Fu Rui, Zhao Shuangqun, Wang Yanfeng
    2020, 34(2): 106-110. https://doi.org/10.19806/j.cnki.fdsb.2020.02.007
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Literature researches and analyses were conducted on a new kind of w(Cr)=15% (15% Cr) ferritic heat-resistant steel with the purpose of finding out the design ideas, strengthening mechanism, microstructure and properties, and the research status. Results show that the 15% Cr ferritic heat-resistant steel has better microstructure stability, with creep rupture strength and steam oxidation resistance higher than traditional w(Cr)=9%-12% ferritic steels, which may be taken as a potential steel for high-temperature components of 650℃ ultra-supercritical thermal power plants.
  • Material Technology
    Study on Properties of Nano-composite Electrolyte Material NSDC
    Tian Wentao, Yang Fan, Zhang Chonghui, Zhang Xixin, Dong Ting
    2020, 34(2): 111-114. https://doi.org/10.19806/j.cnki.fdsb.2020.02.008
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To improve the power output and to elongate the stable running time of nano-composite electrolyte materials, SDC (Ce0.8Sm0.2O1.9) and 1.2 times excess sodium carbonate NSDC (SDC-Na2CO3) composite were prepared by carbonate co-precipitation method, for which, comparative analysis was conducted. Results show that the open circuit voltage of a pure NSDC electrolyte battery may reach 0.87 V, with a maximum instantaneous power density up to 450 mW/cm2, and a higher performance than that of a pure SDC battery at same temperatures. After being mixed with a certain proportion of LCNC (Li1.2Co0.2Ni1.5Cu0.1O3), the stable working time of NSDC electrolyte battery can reach 9 h, which is able to quickly enter a stable working state, when the voltage is not improved significantly.
  • Material Technology
    Experimental Study on Cr3C2-NiCr Wear-resistant Coating Prepared by HVOF Spraying
    Xu Yuan, Ren Xiao, Wang Ziqi, Jia Junyang
    2020, 34(2): 115-119. https://doi.org/10.19806/j.cnki.fdsb.2020.02.009
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    To obtain the process parameters in preparation of Cr3C2-NiCr wear-resistant coating on the surface of St T16/25Mo alloy, the coating was successfully prepared by high-velocity oxygen-fuel (HVOF) spraying. Results show that the structure of Cr3C2-NiCr coating is compact, with low porosity, high micro hardness and bonding strength. The coating is expected to have excellent high-temperature resistance, corrosion/wear resistance and oxidation resistance, with thickness meeting relevant standard, proving the HVOF spraying process parameters to be reasonable. Therefore the Cr3C2-NiCr coating may be applied in the production of following key components, such as valve stems, valve heads and guide bushings.
    • Nuclear Technology
  • Nuclear Technology
    Optimization on Maximum Performance of a Shaking Table for Nuclear Equipment Qualification
    Ge Lei, Li Zhiyong, Lu Xing
    2020, 34(2): 120-123. https://doi.org/10.19806/j.cnki.fdsb.2020.02.010
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    In view of the problem that the designed maximum performance cannot be achieved in the debugging process of a newly built shaking table, the rigidity of the actuator system for the shaking table was analyzed and studied, following which, the rigidity of both the actuator joint and the transition plate was found to be too low. According to the research results, the actuator joint and transition plate were optimized, resulting in an increased resonance frequency of the actuator, a reduced resonance amplification coefficient of corresponding systems, and finally making the shaking table achieve its maximum design performance.
  • Nuclear Technology
    Analysis and Treatment on High Shaft Vibration of a Turbo-Generator Set in Nuclear Power Station
    Jia Kaili, Huang Qianjin, Cai Yongjun
    2020, 34(2): 124-128. https://doi.org/10.19806/j.cnki.fdsb.2020.02.011
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    To solve the problem of high vibration that approaches the trip value encountered by shaft 11 in No.2 turbo-generator set of a nuclear power plant during startup after overhaul, fault diagnosis was conducted, based on which, the most possible cause was believed to be the loosened shrunk coupling. Two abnormities were found in the subsequent examinations, such as the deflected coupling and the unevenly tightened connection bolts, and the root cause of the failure was determined to be the loosened shrunk coupling by means of further analysis and calculation on the vibration mechanism that may be resulted from the two abnormities. The problem was finally solved by replacing the exciter rotor.
    • Environmental Technology
  • Environmental Technology
    An Ammonia Spraying Optimization Method Based on Modified Dynamic Performance of the SCR Denitrification System
    Li Dou, Si Fengqi, Sun Shuanzhu, Wang Weiqun, Zhang Youwei, Wang Lin
    2020, 34(2): 129-134. https://doi.org/10.19806/j.cnki.fdsb.2020.02.012
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    Based on dynamic characteristics of the SCR denitrification system, a modified formula was deduced to optimize the theoretical volume flow of reductant, which was verified with simulation results and actual operation data. Results show that the optimized control method helps to reduce the fluctuation of NH3/NOx molar ratio during dynamic process of SCR denitrification systems and improve the control effect on NOx emission.
  • Environmental Technology
    Full-load Expansion Technology for a Wide-load SCR Denitrification System
    Ma Yun, Lu Fengshi
    2020, 34(2): 135-140. https://doi.org/10.19806/j.cnki.fdsb.2020.02.013
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To realize full-load operation of a selective catalytic reduction (SCR) denitrification system for environmental protection purposes, full-load operation tests were conducted with a wide-load SCR denitrification system in start-up process of the unit, during which, the recirculation flow rate of economizer was controlled by the flow control valve and outlet control valve of the boiler circulating pump, while the bypass flow of economizer was controlled by the water bypass valve. On the premise of ensuring the safety of the equipment and system, the heat absorption of economizer was reduced during startup, and the flue gas temperature at the inlet of SCR denitrification reactor was increased, thus making the inlet flue gas temperature of SCR denitrification reator before grid connection meet the lowest temperature requirement of denitrification catalyst, so that the SCR denitrification system could be put into operation.
    • Design & Manufacture
  • Design & Manufacture
    Design Optimization of a Three-dimensional Twisted Blade for the High Efficiency Impeller of a Circulating Water Pump
    Ma Xiqiang, Zhang Meifeng, Hong Yujia
    2020, 34(2): 141-143. https://doi.org/10.19806/j.cnki.fdsb.2020.02.014
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    Based on the three-dimensional flow theory of impeller, computational fluid dynamics (CFD) simulation was conducted on the flow path of an impeller using k-ε equation and standard SIMPLE algorithm. To optimize the design of the impeller, the pressure field and velocity field in the flow path were analyzed. Results show that the efficiency of the impeller and its adaptability to the working condition could be effectively improved by retrofitting the flow path of the impeller, thus reducing the power consumption of the pump to achieve high efficiency and energy saving purposes.
    • Operation & Retrofit
  • Operation & Retrofit
    Discussion on Key Problems in Air-cooling Units Based on Flugel Formula and Big Data
    Xu Songquan, Yang Bo, Wen Jue, Wei Jiang, Yang Wenfei, Xue Kangkang
    2020, 34(2): 144-148. https://doi.org/10.19806/j.cnki.fdsb.2020.02.015
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Operating characteristics of 34 air-cooling units were obtained through calculation and analysis. Deep research results show that the qualified rate of the air-cooling island/tower and the cold-end system is 76.47% and 17.64%, respectively. Heat-transfer deterioration mainly happens on the turbine side of the air-cooling system, due to the actual heat load being higher than the design value of the low-pressure cylinder. To ensure that the units can run normally under full load at design temperatures in summer, 80% of the units need to run their auxiliary cooling systems. Both the temperature field and the steam distribution of relevant air-cooling systems deviate from their design values in a certain degree.