Power Equipment

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  • 2020 Volume 34 Issue 1
    Published: 15 January 2020
      
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  • Modeling on Transforming Behavior and Process of K-containing Species into Particles in Flue Gas from Biomass Combustion
    Yue Aolei, Sheng Changdong
    2020, 34(1): 1-8. https://doi.org/10.19806/j.cnki.fdsb.2020.01.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A mathematic model of plug flow reactor was applied to describe the transforming process and behavior of K-containing species into submicron particles in the flue gas from biomass combustion, while a research was conducted on the following aspects, such as the transforming behavior of pure KCl gas into submicron particles, and the influence of the presence of K2SO4 particles and the sulfation of KCl on the transformation of KCl from gas state into solid particles, etc. Research results show that the starting temperature of the homogeneous nucleation of pure KCl gas is approximately 700℃, and with the rise of cooling rate and the decrease of initial volume fraction of KCl gas, the number concentration of KCl particles increases and the average particle size decreases. The homogeneous nucleation of KCl gas may be suppressed by the presence of K2SO4 particles at a certain number concentration. In the flue gas containing KCl, SO2, O2 and H2O, the KCl would convert into K2SO4 through sulfation, and the particles formed by nucleation would suppress the nucleation but drive the condensation of KCl gas into submicron particles.
  • Effects of Flue Gas Recycle on the Steam Temperature of a 1 000 MW Double-reheat Boiler
    Han Lei
    2020, 34(1): 9-13. https://doi.org/10.19806/j.cnki.fdsb.2020.01.002
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    Based on thermodynamic calculations of a 1 000 MW double-reheat boiler, the effects of flue gas recycling rate on the following parameters were researched, such as the furnace temperature, the distribution of radiation and convention heat transfer and the steam parameters, etc. Results show that with the increase of flue gas recycling rate, the theoretical combustion temperature in the furnace decreases obviously, and the temperature at panel bottom changes slightly; the heat absorption of radiation heating surface drops significantly, while that of convection heating surface rises remarkably; the closer the convection heating surface is to the rear of flue duct, the more sensitive the steam parameters would be to the recycling rate. When the recycling rate is increased by 1%, the main steam temperature would be decreased by 3.20 K, while the temperature of primary reheat steam increased by 2.44 K, and that of secondary reheat steam increased by 2.72 K. The reheat steam temperature could be effectively controlled by adjusting the recycling rate of flue gas.
  • Flow Field Optimization of a Primary Air Duct for the Medium-speed Coal Mill of Thermal Power Plant
    Wang Yu, Wei Hongqi, Shen Mengmeng
    2020, 34(1): 14-19. https://doi.org/10.19806/j.cnki.fdsb.2020.01.003
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    To solve the problems of large deviation of pulverized coal concentration at the outlet of a ZGM medium-speed pulverizer and the inaccurate measurement of inlet volume of primary air in a power plant, the flow field in the cold and hot primary air pipeline and in the pulverizer was simulated using FLUENT software, based on which, the primary air duct and the air measurement device were optimized and adjusted. Results show that the deflection of inlet air flow in the branch of coal mill primary air duct has been reduced, while the uniformity of inlet flow field of primary air improved, the velocity deflection at outlet section of wind ring reduced, and the system resistance lowered, after optimization of the primary air flow field. The number of measuring points in the new measurement device is significantly larger than that in the original one, which helps to improve the measurement accuracy remarkably.
  • Research on Water-jet Cooling Effect Optimization for a Condenser Extraction System
    Wang Jun, Zhu Lingyu, Wu Zhengyong, Lu Chengbin, Yao Yongling, Huang Enhe
    2020, 34(1): 20-23. https://doi.org/10.19806/j.cnki.fdsb.2020.01.004
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    To optimize the water-jet cooling effectiveness in an extraction system for the composite vacuum pump of a 600 MW unit condenser, a mathematical model was established for the extraction system, while an analysis was conducted on the effects of water-jet flow on the power consumption of the pump set. When the water-jet cooler is applied, the temperature of mixed gas should be cooled down as much as possible to prevent the steam from condensation, thus reducing the power consumption of the pump set.
  • Main Equipment Selection and Economic Analysis of Building-type Distributed Energy Systems
    Zhang Jun, Sun Yifan, Chen Wei, Chen Juncheng, Lu Qiliang
    2020, 34(1): 24-26,31. https://doi.org/10.19806/j.cnki.fdsb.2020.01.005
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    A comparison was conducted on the economy of two different building-type distributed energy systems, together with an introduction to the basic situations, and an analysis on the application and economy of two installation options. Results show that different forms of users require the building-type distributed energy systems with complicated boundary conditions, for which, the main equipment could be selected in different ways. It is suggested that the scheme with optimal economy should be selected based on comparative calculations for a variety of installation options.
  • Influence of Inlet and Outlet Parameters of Low Pressure Cylinder on the Flow Field and Blade Temperature under Small Flow Conditions
    Xu Jiamin, Liu Wangkou, Lin Runda
    2020, 34(1): 27-31. https://doi.org/10.19806/j.cnki.fdsb.2020.01.006
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    A five-stage single-channel model was established for the low-pressure cylinder of the steam turbine in a power plant, based on which, multi-case calculations and analyses were conducted using numerical simulation to obtain the flow field distribution and the last-stage blade temperature at five different inlet and outlet parameters, and to analyze the effects of following factors on the flow field distribution and the last-stage blade temperature, such as the inlet steam flow, the inlet steam specific volume, the inlet steam temperature and the outlet steam pressure of the low-pressure cylinder, etc. Results show that under the condition of small flow, reflux first appears in the outlet area near the root of last-stage blade, and the highest temperature of last-stage blade appears near the exit edge in the top area of stator blade; the smaller the inlet flow is, the more serious the reflux will be, resulting in more obvious blast effect and higher surface temperature of the blade. Increasing the inlet specific volume has little effect on the reduction of flow separation, while reducing the inlet steam temperature and outlet steam pressure of low-pressure cylinder would be beneficial to the reduction of the surface temperature of last-stage blade and the improvement of the blast effect.
  • Study on Design Schemes for the Cylinder of Supercritical Carbon Dioxide Turbines
    Ni Jian, Qian Yong, Zhou Yong, Qin Xiaowen, Liu Haijie, Liao Xiang
    2020, 34(1): 32-36. https://doi.org/10.19806/j.cnki.fdsb.2020.01.007
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    To optimize the design of high-parameter supercritical carbon dioxide turbine cylinders, 3 design schemes were proposed by improving the structure, replacing the material and adjusting the sealing form for the cylinder. The safety of above design schemes was analyzed by means of finite element method in high-parameter supercritical carbon dioxide environments. Combined with cost analysis, the two schemes respectively with comb-tooth seal and upper and lower half-cylinder were not recommended, while the safety and low-cost scheme with dry gas seal in cylindrical form was chosen.
  • Structure Design and Optimization for the Pedestal of a 350 MW Turbo-Generator Set
    Li Chun, Ma Xiaobing, Mu Zhewen
    2020, 34(1): 37-40,44. https://doi.org/10.19806/j.cnki.fdsb.2020.01.008
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    To optimize the pedestal structure of a turbo-generator set, a model was established for the pedestal using MFSAP software, while an analysis was conducted on the dynamic characteristics of the pedestal with 5 groups of data concerning the cross section of the column. Results show that at the points on the pedestal with disturbing force, the vibration linear displacement in z-line is higher than that in x-line and y-line, and with the decrease of the column cross section, the linear displacement tends to grow generally. The turbine would not resonate with the pedestal during operation. The cross section of the column is recommended to be 2 200 mm×1 800 mm on the generator side and 1 800 mm×1 600 mm on the turbine side.
  • Design and Selection Optimization of an Online Backwashing System for the Y-type Filter of Thermal Power Units
    Chen Bingbing
    2020, 34(1): 41-44. https://doi.org/10.19806/j.cnki.fdsb.2020.01.009
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    To solve the clogging problem existing in the filter of a pump set with full capacity and single-column configuration during the operation of an ultra-supercritical thermal power unit, an online controllable backwashing system was proposed for the Y-type filter. The working principle and implementation method of the system were elaborated based on theoretical research and engineering application, while following items were summarized, such as the control logic of the filter, and the empirical formulas for the effective flow area and the nozzle diameter, etc., which may serve as a theoretical reference for design and selection optimization of the online backwashing system for Y-type filters in 1 000 MW units, indicating broad application prospects.
  • Analysis on Runback Control Technology of 350 MW Supercritical CFB Units
    Duan Bao, Fan Long, Li Jihong
    2020, 34(1): 45-50. https://doi.org/10.19806/j.cnki.fdsb.2020.01.010
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    Based on therich experience in runback (RB) performance tests of 350 MW supercritical CFB units, an in-depth analysis was conducted on the control strategy and technical difficulties, after which, following solutions were proposed, such as appropriately setting the trigger conditions, target load and target pressure values, etc. Meanwhile, more specific instructions were mentioned for the combustion control from the aspect of fuel quantity control, air-gas system interlock, as well as bed temperature and bed pressure control. It is suggested that the features of combustion hysteresis and large heat storage of supercritical CFB units should be considered in the feed water control, so as to achieve sound coupling between the coal and water during RB control, and ensure stable adjustment of the main parameters.
  • Design and Application of Bypass Control Strategies for an Ultra-supercritical Double-reheat Unit
    Zhang Tianhai, Shu Jianjun, Wang Jun, Gao Aimin, Yu Guoqiang
    2020, 34(1): 51-55. https://doi.org/10.19806/j.cnki.fdsb.2020.01.011
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    Considering the features of a double-reheat unit that has a series bypass system with high, medium and low capacity under the condition of 40% boiler maximum continuous rating (BMCR), a whole process automatic control strategy was designed for the bypass system, while the control mode was optimized. Operation and test results show that the control strategy proposed for the bypass system helps to reduce the risk of unit tripping and improve the flexibility and economy of unit operation.
  • Influence of Particle Size Distribution of Pulverized Coal on the Performance of a Low-NOx Burner in Power Plant Boiler
    Liu Xiushi, Li Wenhua, Dong Yu, Du Cong
    2020, 34(1): 56-59. https://doi.org/10.19806/j.cnki.fdsb.2020.01.012
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    Based on analysis and calculation of the separator in a WR dense-dilute burner, a study was conducted on the movement trajectory of pulverized coal in the separator and on the factors influencing the separation efficiency. In addition, off-design tests were carried out on a 300 MW coal-fired boiler. Results show that the reasonable operation range of the WR low-NOx burner is above 75% rated load. When the boiler load is lower than 75% rated load, due to the redistribution of pulverized-coal particle sizes, the separation efficiency of the WR burner reduces, resulting in decreased dense-dilute combustion efficiency and increased NOx emission.
  • Comparative Analysis and Application of Retrofit Schemes for a Biserial Power Unit by Adding External Steam Coolers
    Zhu Xiaolei, Li Jianning, Zhang Yin
    2020, 34(1): 60-65. https://doi.org/10.19806/j.cnki.fdsb.2020.01.013
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    Taking the 1 000 MW power unit as an example, a comparative analysis was conducted on the performance of different retrofit schemes for the unit by adding external steam coolers, with focus on the retrofit steps and effectiveness. Results show that with the reduction of unit load, the energy-saving effectiveness becomes more obvious by adding external steam coolers. The scheme proposed would not increase the flow resistance in the pipeline and push out the steam extraction of the deaerator, but may increase the inlet gas temperature of the SCR denitrification system and reduce the heat consumption of the steam turbine, resulting in high safety and energy-saving effects of the unit.
  • Research on Leakage Detection for Vacuum Systems of Power Plants Based on Parametric Analysis
    Gu Liudong, Xu Jianqun, Huangfu Zeyu, Chen Xiaoxin, Zhang Haofeng, Zhang Jiandong
    2020, 34(1): 66-70. https://doi.org/10.19806/j.cnki.fdsb.2020.01.014
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    To avoid the sharp rise of steam temperature at No.6 bleed point of a steam turbine in a thermal power plant, the emergency drainage U-tube of No.3 low-pressure heater was supplemented with make-up water, following which, the steam temperature recovered for a short time. However, the same problem appeared again after a long period of operation. Based on the Flugel formula and Dalton law, normal and abnormal operation data of the steam temperature at No.6 bleed point were calculated and analyzed theoretically, and subsequently the leakage point was located on the drainage pipe of No.3 low-pressure heater with the aid of on-site glue sealing method, which was found to be the main cause leading to the great increase in the steam temperature and a decrease in the condenser vacuum. Above problems were finally solved after the crack was repaired, proving the results of theoretical analysis to be correct.
  • Application of Slurry Drying Technology in Coal Slurry Co-firing Process of Ultra Supercritical Units
    Wang Linwei, Chong Peian, Zhang Lei
    2020, 34(1): 71-74. https://doi.org/10.19806/j.cnki.fdsb.2020.01.015
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    Taking the ultra supercritical unit in a certain power plant as an object of study, a comparative analysis was conducted on 4 drying schemes for the slurry, among which the pretreatment way using steam to dry the slurry was adopted, while the effects of coal slurry co-firing on the unit performance were experimentally studied. Results show that when the mass ratio of slurry is 7.6%, the co-firing has little effects on the unit performance, proving the slurry drying technology to be applicable and economical in coal slurry co-firing process of ultra supercritical units.