Power Equipment

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  • 2020 Volume 34 Issue 3
    Published: 15 May 2020
      
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  • Effect of Cracks on Temperature Distribution in Concrete-based Solar Thermal Storage Modules
    Liu Guangpeng, Zhu Huijun
    2020, 34(3): 149-153. https://doi.org/10.19806/j.cnki.fdsb.2020.03.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Numerical simulations were conducted on the heat release properties of concrete modules with different kinds of cracks, with focus on the effects of crack direction, location, length and width on the heat release process, following which, the instantaneous temperature distribution at the end of heat release was given. Results show that circumferential and axial cracks seriously increase the thermal resistance, when corresponding concrete modules should be replaced in time. Whereas radial cracks grow inside the concrete module, which have little effect on the heat transfer, but when they extend to the surface of the module, both the heat transfer area and the turbulence intensity would be increased, resulting in elevated temperature difference, larger thermal stress and higher risk of crack propagation in the concrete modules.
  • Optimization and Retrofit of a SCR Denitrification System with Variable Cross Sections
    Zhou Shuai, Wei Hongqi, Wu Hao, Zhao Chuanhui
    2020, 34(3): 154-160. https://doi.org/10.19806/j.cnki.fdsb.2020.03.002
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problems of low denitrification efficiency in the selective catalytic reduction (SCR) denitrification system and severe abrasion in the air preheater of a 600 MW power unit, the problems were analyzed by numerical simulation, following which, the SCR denitrification system was optimized and retrofitted. Results show that the design of multi-disc guide plates arranged at small angles in the variable cross-section duct at economizer outlet could help to eliminate the vortex caused by the difference of gas velocities between front and rear wall, improve the gas velocity distribution in the upstream of ammonia injection area and reduce the flow resistance in the area. By comparing the vortex static mixing ammonia injection, the linear ammonia injection and the partition ammonia injection, the way of partition ammonia injection is found to be able to effectively improve the distribution of the mole ratio of NH3 to NOx in the first-layer catalyst, resulting in an increase in denitrification efficiency and a decrease in ammonia slip. Moreover, the gas velocity distribution at the inlet of air preheater could be improved, while the abrasion in the air preheater could be relieved, by arranging guide plates in the duct between the outlet of SCR denitrification reactor and the inlet of air preheater.
  • Analysis on Factors Influencing the Receiver Thermal Efficiency in a Tower-type Solar Thermal Power System
    Sun Chengjin, Ge Tingting, Qian Jun, Fan Lingping, Xu Lihua
    2020, 34(3): 161-165. https://doi.org/10.19806/j.cnki.fdsb.2020.03.003
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The heat flux distribution on the surface of a receiver in the tower-type solar thermal power system was analyzed, while a formula to calculate the thermal efficiency of the receiver was obtained based on the heat balance equation, so as to study the effects of following factors on the receiver thermal efficiency, such as the emissivity, absorption rate, wind speed and ambient temperature, etc. In addition, the comprehensive thermoelectric efficiency was evaluated for the system at different concentrating ratios and receiver temperatures. Results show that the ambient temperature has slight influence on the thermal efficiency of the receiver, but the influence of wind speed could not be neglected. When the wind speed is more than 12 m/s, the convective heat loss would be larger than the radiative heat loss. A layer of appropriate coating may help to improve the thermal efficiency of the receiver; for the tower-type solar thermal power system with a high concentrating ratio, the thermal efficiency could be increased by about 5.0 percentage points. The comprehensive thermoelectric efficiency has a peak point for a given concentrating ratio. The research results may serve as a reference for the design of the receiver and the optimization of relevan tower-type solar thermal power systems.
  • Research on Profile Design of Front- and Rear-loaded Turbine Blades
    Sun Qi, Deng Guoliang, Zhong Zhuhai
    2020, 34(3): 166-169. https://doi.org/10.19806/j.cnki.fdsb.2020.03.004
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The profile of front- and rear-loaded turbine blade was proposed based on the design of twisted and bowed blade. That is to apply rear-loaded profile for the root and tip region, where the secondary flow loss is high, and to apply front-loaded profile for the area at middle height, where the secondary flow loss is low. Results show that the pressure distribution on the meridian surface of a front- and rear-loaded turbine blade presents the C pattern, which is capable of controlling the secondary flow loss in radial direction. The secondary flow loss in stator and rotor blade could be further reduced by setting a reasonable installation angle for the blade.
  • Overall Design of a 50 MW Steam Turbine for CSP System
    Qian Yong, Ni Jian, Zhou Yong
    2020, 34(3): 170-173. https://doi.org/10.19806/j.cnki.fdsb.2020.03.005
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To meet the special requirements of concentrated solar power (CSP) systems, an introduction was presented to the overall design of a 50 MW steam turbine for CSP system, with following technical measures taken, such as split cylinder double speed design, placement of unit in lower platform, axial exhaust turbine, modular delivery, and so on. The scheme adopted has been proved to be reasonable and effective in actual manufacture and installation, which may serve as a reference for the design and manufacture of similar CSP steam turbines.
  • Layout Schemes and Cost Analyses of Combined Cycle Units with F-class Gas Turbines
    Yan Weichun
    2020, 34(3): 174-178. https://doi.org/10.19806/j.cnki.fdsb.2020.03.006
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    For combined cycle units with F-class gas turbines, an introduction was presented to typical layout schemes of the combined cycle unit, including four arrangement forms of the power train island. For all the schemes, the layout features were discussed, while their initial investment was compared. This may serve as a reference for layout of combined cycle units with F-class gas turbines.
  • Modeling and Simulation of Multi-effect Evaporation Concentration Process for Desulfurization Wastewater of Coal-fired Power Plants
    Liu Min, Liu Pingyuan, Zhao Liang
    2020, 34(3): 179-183. https://doi.org/10.19806/j.cnki.fdsb.2020.03.007
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A calculation model was established for the multi-effect evaporation concentration process of desulfurization wastewater with Aspen Plus software to calculate the fresh steam mass flow, condensate mass flow and concentrated water mass flow at rated concentration ratio and different feed rates of wastewater, for 2×660 MW units with a treatment capacity of 22.5 t/h. By comparing the simulation results with actual operation data of the unit, their maximum relative error is found to be -4.19%, proving the model established to be accurate and reliable, which may serve as a reference for the design of multi-effect evaporation concentration facilities for desulfurization wastewater.
  • Experimental Study on Multi-point NOx Sampling for the Flue Gas Denitrification System in a 600 MW Unit
    Bai Guangyuan, Zhang Weiwei, Wu Bin
    2020, 34(3): 184-187,195. https://doi.org/10.19806/j.cnki.fdsb.2020.03.008
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem that single-point sampling can not reflect the actual NOx emission and to improve the automatic regulation quality of the ammonia injection control valve, a multi-point method was proposed for sampling the NOx concentration in the flue gas, based on the basic principle of SCR denitrification, for which, an application analysis was conducted according to the field conditions. Results show that the multi-point sampling method can improve the measurement accuracy and speed for the outlet NOx emission of the SCR denitrification system, solve the problem that the measured final NOx emission (the outlet value of the desulfurization system) is higher than the outlet value of the SCR denitrification system, and optimize the tracing and control effectiveness for the SCR denitrification system during the process of boiler load variation.
  • Experimental Study on Flue Gas Dust Removal by Condensation Process for a Coal-fired Power Plant
    Jiang Haitao, Lin Ke, Li Gang, Zhang Xing, Ji Yuanliang, Zhang Yubin
    2020, 34(3): 188-190. https://doi.org/10.19806/j.cnki.fdsb.2020.03.009
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    A flue gas bypass line was set up at the tower outlet of a wet flue gas desulfurization (WFGD) system in a 300 MW coal-fired unit to measure the heat-transfer coefficient, gas side resistance and dust removal performance of the plastic heat-transfer tube bundles with condensation process. Results show that the heat-transfer coefficient is above 350 W/(m2·K); the gas side resistance significantly increases with rising velocity of flue gas; the dust removal efficiency gets up to 56.8%, and the outlet mass concentration of dust particles is about 4.5 mg/m3. Via the technology, not only dust removal can be realized, but also the heat and water can be recycled from the flue gas.
  • Study on the Design of a Digital Rod Control System for Nuclear Power Plant
    Bu Jiangtao
    2020, 34(3): 191-195. https://doi.org/10.19806/j.cnki.fdsb.2020.03.010
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    An introduction is presented to the main functions of the rod control system in a nuclear power plant and corresponding design points for the third generation passive nuclear power plant. In view of the difficulties existing in the design of current domestic rod control systems, a design concept was proposed for the digital rod control system based on DCS and FPGA+DSP controllers, with focus on the analysis and research of the two major functional devices: logic cabinet and power cabinet. The advantages of the design scheme for the digital rod control system were finally summarized.
  • Qualification Method for Class 1E I&C Equipment of CAP Series Nuclear Power Plants
    Yuan Dongying, Shang Heng
    2020, 34(3): 196-199. https://doi.org/10.19806/j.cnki.fdsb.2020.03.011
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    By analyzing the operating environment and significant aging mechanism of instrumentation and control (I&C) equipment, as well as the qualification requirements of relevant domestic and foreign standards and codes, the qualification test items of Class 1E I&C equipment for CAP series nuclear power plants were determined. Meanwhile, common methods, standards and test parameters were suggested for the EMC test, mechanical aging test, environment test, vibration test and seismic test, with key points affecting the equipment qualification test expounded.
  • Control Strategy for Automatic Feed Pump Combining and Retreating in a 600 MW Coal-fired Power Unit
    Bai Yonggang, Zhuang Wei, Sun Hui, Ding Gang, Leng Yuzhu
    2020, 34(3): 200-205,214. https://doi.org/10.19806/j.cnki.fdsb.2020.03.012
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    The control strategy for automatic feed pump combining and retreating was configured and optimized, which has been successfully applied in a 600 MW power unit. Results show that during the implementation of the automatic control strategy, all the parameters are superior to that of manual manipulation, and it takes less than 10 min for pump combining and less than 8 min for pump retreating; the maximum fluctuation of feed water mass flow is 75 t/h, and the time of deviation is kept within 3 min, while the maximum fluctuation of drum level is 60 mm. The control strategy for automatic feed pump combining and retreating is of practical significance in reducing the labor intensity of operators and improving the automation level and reliability of relevant power units.
  • Analysis of Subcritical Boiler Final-stage Superheater Tube Burst Caused by Accumulation of Oxide Scales and the Preventative Measures
    Zhang Lei, Dong Weidong, Ding Shifa
    2020, 34(3): 206-209. https://doi.org/10.19806/j.cnki.fdsb.2020.03.013
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    To solve the problem of tube burst occurring in the final-stage superheater of a 330 MW unit, an analysis was carried out on the tube burst reasons, features and the regular pattern. Results show that the problem is found to be caused by the accumulation of large amount of oxide scales on the surface of the final-stage superheater tubes, which led to the blockage in the tube banks during hydraulic test, and finally resulted in overheating of relevant tubes. To ensure long-term safety operation of the unit, corresponding preventative measures and maintenance strategies were proposed.
  • Comparison and Analysis on Three Methods for Improving Drying Capacity of a Medium-speed Pulverizing System for Lignite-fired Boilers
    Liu wenjian, Pan Shaocheng, Li Wenji, Yi Guangzhou, Mo Chunhong
    2020, 34(3): 210-214. https://doi.org/10.19806/j.cnki.fdsb.2020.03.014
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    An introduction is presented to three methods for improving the drying capacity of a medium-speed pulverizing system for lignite-fired boilers, together with an analysis on the system features, operation conditions and existing problems, while their advantages and disadvantages were compared. Results show that the primary hot air steam-heating system is simple in layout, easy to implement, with high efficiency of boiler, low cost of system, and obvious effect in improvement of the drying capacity.
  • Discussion on Optimization of Operation Parameters for a 1 000 MW Ultra Supercritical Unit
    Zhou Zhengdao, Hua Zhigang, Bao Weiwei, Zhang Xiaohui, Li Jihong
    2020, 34(3): 215-218,222. https://doi.org/10.19806/j.cnki.fdsb.2020.03.015
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    Taking a 1 000 MW ultra supercritical unit as an object of study, the effects of following operating parameters on the unit economy under four major working conditions were calculated and analyzed, such as the back pressure in summer, the percentage of make-up water, the margin of inlet steam flow and the length of last stage blade, etc., after which, the parameters were optimized. Results show that after optimization, the heat consumption of the unit could be effectively reduced by 24 kJ/(kW·h) when it runs at partial load for a long time, resulting in improved economy of the unit.
  • Cause Analysis and Solutions for Problems Influencing the Condenser Vacuum of a Heating System
    Yao Yao, Wang Lei
    2020, 34(3): 219-222. https://doi.org/10.19806/j.cnki.fdsb.2020.03.016
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem influencing the condenser vacuum in a heating system, an analysis was conducted based on an introduction to the condensate recovery system, following which, the problem was found to be caused by the design defect lying in the layout of the connection pipe between the heating system and the condenser through static calculation, and subsequently the following 3 schemes were proposed, such as the addition of one-stage water seal, multi-stage water seal and electric isolation valve, respectively. By analyzing the advantages and disadvantages of 3 schemes, the scheme of adding a one-stage water seal is finally selected.