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  • Research & Analysis
    Cause Analysis on Local Thinning of Water Wall Tube in a Subcritical Boiler
    Li Xianshuang, Gao Chenglong, Wang Shuo
    2021, 35(4): 227-230. https://doi.org/10.19806/j.cnki.fdsb.2021.04.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The reasons of local corrosion and thinning of water wall tube in a subcritical boiler were analyzed by means of macroscopic inspection, chemical composition analysis, hardness test, metallographic analysis, scanning electron microscopy and energy dispersive spectroscopy, etc. The results show that alkali metals react with sulfides in flue gas to form a coking adhesion which is rich in sulfate on outer surface of the water wall tube during operation of the boiler. Free sulfur atoms decomposed by the adhension and coal powder react with the outer protective film of the pipe wall and the matrix. This results in serious high temperature sulfur corrosion of the pipe wall, which causes the outer wall of the water-cooled pipe to thin continously.
  • Research & Analysis
    Study on Hydrodynamic Characteristics of a 300 MW Subcritical Boiler at Low-load
    Meng Qiang, Wang Chengliang, Li Hongtao, Gao Peng, Wang Yujing, Lü Weizhi
    2021, 35(4): 231-235. https://doi.org/10.19806/j.cnki.fdsb.2021.04.002
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A 300 MW natural circulation boiler was taken as the research object to build the flow network system, which composed of flow loop, pressure node and connecting pipe. Based on the conservation equations of mass, momentum and energy, the mathematical model of water wall flow rate and wall temperature was established to study the hydrodynamic characteristics under low load. The results shown that, under 20% and 30% load conditions, the circulation ratio is larger than the limit circulation ratio. The mass flux distribution and circulation flow rate in the boiler water wall are distributed with higher in the middle and lower in the ends. The larger the heat load is, the larger the corresponding mass flow rate is, and the stagnation phenomenon will not occur under normal low load operation conditions, which can ensure the hydrodynamic safety of the unit.
  • Research & Analysis
    Research on Thermal Performance of a Straight-through All-glass Vacuum Collector
    Li Guoshuai, Luo Xianfeng, Zhao Dandan, Gong Jinghu, Li Liangguang
    2021, 35(4): 236-241,247. https://doi.org/10.19806/j.cnki.fdsb.2021.04.003
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The thermal performance of a single straight-through all-glass vacuum heat collecting tube was analyzed and evaluated, based on which, a one-dimensional mathematical model of heat transfer was established, and the iterative temperature solution method was used to analyze the factors affecting the performance of the straight-through all-glass vacuum collector with MATLAB software. Results show that the thermal performance of the collector is significantly influenced by the ambient temperature, wind speed and solar radiation intensity; therefore, the thermal performance can be effectively improved by taking full advantages of the meteorological parameters. The higher the inlet temperature of working fluid is, the lower the instantaneous thermal efficiency would be, with basically constant temperature difference between the inlet and outlet. With an increase in flow rate of the working fluid, the temperature difference between the inlet and outlet declines at first, and then gets stable. Therefore, appropriate operating parameters should be selected in actual applications to optimize the thermal performance of the collector. The accuracy of the model has been verified by experiments, and the thermal performance of the straight-through all-glass vacuum heat collecting tube has been proved to be better than that of the traditional type through comparative experiments.
  • Research & Analysis
    Numerical Simulation of Steam Condensation in Wet Saturated Flue Gas
    Zhang Zhouyan, Zhu Xiaoliang
    2021, 35(4): 242-247. https://doi.org/10.19806/j.cnki.fdsb.2021.04.004
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    Condensation heat transfer process of wet saturated flue gas in a horizontal tube was simulated. Simulation results conformed to theoretical calculation results within ±10% relative error. The flue gas velocity and volume fraction of various components under turbulent conditions were analyzed. Effect of the non-condensable gases on steam condensation was fully considered to improve the reliability of the numerical calculation results. A faster and more effective numerical prediction method of the steam condensation heat transfer process in wet saturated flue gas was realized, which would provide a reference for flue gas condensation convection heat transfer study.
  • Research & Analysis
    Thermal Economy Analysis for Low Pressure Heater Drain Pump Based on Regional Equivalent Enthalpy Drop Method
    Jiang Xiaolong
    2021, 35(4): 248-252,284. https://doi.org/10.19806/j.cnki.fdsb.2021.04.005
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    Based on the regional equivalent enthalpy drop method, a method of thermal economy analysis was proposed for low pressure heater drain pump. The influence of following factors in each region on the steam turbine net power generation was researched, such as the drain water flow rate, exchanged heat and pump power. The accuracy of the proposed method was verified in a 1 000 MW double reheat unit. Results show that with considering the drain water enthalpy and pump power, the method is more fit to be applied to the thermal economy analysis of low pressure heater drain pump for a new unit, and to optimize the layout of drain pump. Influenced by the drain water flow rate and extraction steam efficiency, an optimized position for setting one drain pump can be obtained. Compared with setting one drain pump, the energy saving effect reduces significantly with setting a second drain pump.
    • Material Technology
  • Material Technology
    Fracture Analysis for the Last Stage Blade in Low-pressure Rotor of Steam Turbine
    Liu Zhimin, Shi Yongfeng
    2021, 35(4): 253-257. https://doi.org/10.19806/j.cnki.fdsb.2021.04.006
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem that the last stage blade of a low-pressure rotor cracked during operation in a gas-steam combined cycle unit, the reason of the fracture was obtained through macroscopic inspection, chemical composition analysis, mechanical performance test, fracture analysis and metallographic structure analysis. Results show that the water erosion of the last stage blade is exacerbated by the backflow at the blade back, which is resulted from the small-flow operation of the last stage blade. The fatigue cracks are produced during long-term operation in the stress concentration positions, which are caused by the discontinuous structure at the junction of Stellite alloy and the base material. The last blade cracks with the combined action of above two aspects.
  • Material Technology
    Failure Analysis of the Platen Reheater in a 600 MW Subcritical Boiler
    Zhang Jianwei
    2021, 35(4): 258-262. https://doi.org/10.19806/j.cnki.fdsb.2021.04.007
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem of the tube explosion of the platen reheater in a 600 MW subcritical boiler, analyses were conducted on the tube explosion through experiments and comparisons for the tube samples, combined with the estimation of wall temperature and the strength check for the tube. Results show that the mechanical property of the 12Cr1MoVG steel tube is decreased due to the long-term over-temperature operation, and the high-temperature strength of the tube cannot meet the requirement due to the short-term over-temperature during operation. Meanwhile, the effective bearing thickness is reduced. The tube explosion of the platen reheater is resulted from the combined effect of above aspects.
    • New Energy
  • New Energy
    Economy Analysis on Single Reheat Scheme in an Agroforestry Biomass Power Generation Unit
    Wang Xiao, Zhou Gaoqiang
    2021, 35(4): 263-266. https://doi.org/10.19806/j.cnki.fdsb.2021.04.008
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Taking a typical 30 MW agroforestry biomass power generation unit as the research object, comparisons were conducted on initial investment, power generation income and fuel cost of conventional scheme and reheat scheme, and the economy of reheat scheme in the biomass power generation unit was analyzed. Results show that compared with conventional scheme, the initial investment with reheat scheme increases 19.56 million yuan. From the point of power generation income and fuel cost, respectively, the static pay off periods of initial investment variations with reheat scheme are both about 5 years, which presents a good economy. This may serves as a reference for installation and heat-engine type selection in agroforestry biomass power generation units.
    • Automatic Control
  • Automatic Control
    Electrical Control System of Natural Gas Distributed Energy Station Based on DCS
    Wang Haijun, Wang Zhenwu, Yang Xin, Li Rui
    2021, 35(4): 267-271. https://doi.org/10.19806/j.cnki.fdsb.2021.04.009
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    According to the technologic characteristics of nature gas distributed energy systems, the function and characteristic of a typical electrical control system in a nature gas distributed energy station was illustrated. Practice results show that the proposed system has a good effect for application. This may serve as a reference for the design and construction of the electrical control system in nature gas distributed energy stations.
    • Operation & Retrofit
  • Operation & Retrofit
    Optimization and Modification on a 220 t/h CFB Biomass-fired Boiler
    Li Dingqing, Li Debo
    2021, 35(4): 272-277. https://doi.org/10.19806/j.cnki.fdsb.2021.04.010
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    For a 220 t/h high temperature and high pressure circulating fluidized bed (CFB) biomass-fired boiler, the fuel properties existed differences with the designed fuel, the combustion of gas phases in the furnace was unstable, and the emission of NOx presented on a high-level. In order to reduce NOx emissions and improve the boiler efficiency, optimized and modified measures had been done such as optimization of biomass fuel pretreatment and feeding system, modification of staged combustion, reducing of the cyclone separator resistance. The results show that optimization and modification has achieved as significant results, the release of NOx concentration can be controlled under 100 mg/m3, the CO concentration can be controlled under 2×10-3, and the boiler efficiency increases by 5.1%.
  • Operation & Retrofit
    Analysis and Improvement of Over Temperature Tube Explosion of Boiler Platen in a 1 000 MW Boiler
    Xu Liang, Li Rongchun, Chen Chaosong
    2021, 35(4): 278-284. https://doi.org/10.19806/j.cnki.fdsb.2021.04.011
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on analysis of design and operation data of a 1 000 MW boiler after operated for a year, the main reason of over temperature of the platen was analyzed by theory of thermal deviation. The corresponding improvement scheme of throttling tube which reduces thermal deviation, and increases monitoring point of wall temperature was put forward and implemented. The problem of overheating tube explosion of the platen during normal operation of the boiler is solved, and the value of superheating steam temperature is also reached to design level. Safe operation performance of the boiler and economic benefit of the unit have been improved.
  • Operation & Retrofit
    Application of Flue Gas Temperature Rising Method in Ash Blocking Treatment of Rotary Air Preheater
    Liu Hongwei, Wu Hongbo, Li Yingchun, Li Fengquan
    2021, 35(4): 285-288. https://doi.org/10.19806/j.cnki.fdsb.2021.04.012
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    After the ultra-low emission transformation of coal-fired power plants, the sedimentation of ammonium hydrogen sulfate resulted in the increase of the pressure difference between inlet and outlet in rotary air preheater, the fluctuation of furnace negative pressure, the increase of the power consumption, and even the vibration of induced draft fan, which threatened the safe and economic operation of the unit. The flue gas temperature rising method was used to remove the ash blockage of air preheater, and it took effect. Moreover, the operation process and precautions of on-line flue gas temperature rise method were proposed.
  • Operation & Retrofit
    Analysis on Efficiency Modification Effect of Rotating and Stationary Ring in a ZGM Medium-speed Coal Mill
    Su Yang, Cong Xingliang, Chen Jian, Yu Yongsheng, Xie Hong, Xu Pengcheng, Li Wu
    2021, 35(4): 289-291,300. https://doi.org/10.19806/j.cnki.fdsb.2021.04.013
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The efficiency modification of rotating and stationary ring in a ZGM medium-speed coal mill set in a power plant had been implemented by optimizing the nozzle ring’s profile and structure besides the flow field in the coal mill. Based on the performance test data before and after the transformation, that was the unit power consumption is reduced from 10.28 kW·h/t to 7.81 kW·h/t, comprehensive correction method of unit power consumption based on coal fineness(R90) and Hardgrove grindability index (HGI) was proposed. The corrected unit power consumption had been reduced by 18.8% (from 11.96 kW·h/t to 9.72 kW·h/t). The maximum output of the coal mill was increased by 13.4% (from 52.9 t/h to 60.0 t/h), while the emission of pulverizer rejects was zero.
  • Operation & Retrofit
    Optimization and Retrofit for Flow Field of a ZGM113 Medium-speed Coal Mill
    Wang Shiqiang, Tian Hang, He Lanqing
    2021, 35(4): 292-296. https://doi.org/10.19806/j.cnki.fdsb.2021.04.014
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To mitigate the effects of the decreased output of a ZGM113 medium-speed coal mill on the unit operation in a coal-fired power plant, the flow field of the mill was optimized through simulation and analysis, and the inner structure of the mill was retrofitted. Results show that after retrofitting, the inner flow field of the mill can be optimized in general, while the performance of the mill can be improved.
  • Operation & Retrofit
    Optimization on Water Distribution System of a Super Large Cooling Tower in a Thermal Power Plant
    Wang Dong, Cheng Kai, Wang Zhihan
    2021, 35(4): 297-300. https://doi.org/10.19806/j.cnki.fdsb.2021.04.015
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on the characteristics of water distribution system of a super large cooling tower in a thermal power plant, an integrated model of hydraulic calculation was established for following parts by PIPENET software, such as nozzle, water distribution pipeline, central shaft, distribution header, etc. Analyses were conducted on hydraulic calculation of water distribution system under different operation conditions, the internal and external nozzles were optimized and selected. Results show that by using the 28 mm inner nozzle and the 30 mm outer nozzle, the water flow of water distribution system is more uniform, which can meet the requirements of practical engineering