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  • 2018 Volume 38 Issue 3
    Published: 15 March 2018
      
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  • Operation Control Mode of a CFB Boiler Co-firing High Ratio of Coal Slime and the Application
    HONG Feng, GAO Mingming, LIU Jizhen, MOU Ben, BO Yunhe
    2018, 38(3): 169-175.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Taking the most widely used coal slime pump system as an object of study, the characteristics of CFB boilers co-firing high ratio of coal slime were analyzed from operation and control two aspects, while the energy conversion way was discussed for actual operation processes. A reasonable control strategy was then proposed for CFB boilers co-firing high ratio of coal slime, which uses boiler heat storage to stabilize the fluctuation and to optimize the process of energy conversion. The control strategy was finally applied to actual operation of a 300 MW CFB boiler. Results show that after being put into operation, the optimized system has helped to upgrade the control level, increase the coal slime blending ratio and improve the operation stability of the unit, resulting in obvious economic benefits.
  • Effects of Flue Gas Quenching on Ash Fouling Characteristics of Zhundong Coal
    RAN Shenming, ZHANG Xiuchang, SHI Huijuan, YUE Pengfei, WANG Jinsheng, ZHOU Qi, NIE Li, HU Xiukui
    2018, 38(3): 176-181.
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    The effects of flue gas quenching on ash fouling characteristics of Zhundong coal were studied in a 3 MW pulverized coal-fired (PC) and a circulating fluidized bed (CFB) boiler test system, during which the fouling ash was examined by XRD and XRF, respectively. Results show that gas quenching can reduce the fouling in both the PC and the CFB boiler. The initial fouling of Zhundong coal is mainly caused by Na2SO4 that may capture CaSO4 before coagulation, thus worsening the ash fouling. Flue gas quenching makes Na2SO4 condensed and solidified before touching the test tube, which plays a role in reducing ash fouling.
  • Synergetic Effects of Gas Co-firing and Air Staging on Heat Distribution of a Boiler
    LIANG Zhanwei, CHEN Hongwei, ZHAO Zhenghui, ZHANG Meiyou
    2018, 38(3): 182-187.
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    Taking a pulverized coal boiler co-firing blast furnace gas and coke oven gas as an object of study, the effects of gas blending ratio and air staging mode on heat absorption of the main and reheat steam were studied. Results show that only co-firing blast furnace gas or coke oven gas would have contrary effects on the distribution of radiation heat transfer and convection heat transfer; when blast furnace gas and coke oven gas are simultaneously co-fired, the heat absorption of main steam and reheat steam is mainly in the convective way, and the total heat absorption of both the steam increases; with the rise of secondary air damper opening of blast furnace gas, the heat absorption of reheat steam increases, but for main steam, the increase of convection heat transfer can not offset the reduction of radiation heat transfer; the convection heat transfer of both the main and reheat steam reduces with rising secondary air damper opening of pulverized coal, but increases with rising SOFA damper opening.
  • Research on Design, Manufacture and Maintenance of HP Shrink-ring Barrel-casing of a Steam Turbine
    SHI Jinyuan, WANG Yong, LIU Dongqi, DENG Zhicheng, WEI Qi, YANG Yu, LIN Runda
    2018, 38(3): 188-192.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    An introduction was presented to key technologies for design, manufacture and maintenance of the shrink-ring barrel-casing in a steam turbine, including conventional design method, FEA-based design method, manufacturing process assurance method and interference force monitoring method for maintenance of the shrink-ring barrel-casing. In addition, a strength design method was proposed for the shrink-ring barrel-casing respectively in steady-state rated load condition, start-up and shut-down transient process, while a creep design method put forward for the casing in steady-state rated load condition, as well as a tightness design method for the split of casing in start-up and shut-down transient process. As an application example, the design data of a shrink-ring and the thickness of the gasket used in maintenance of a cracked shrink-ring barrel-casing in a 600 MW supercritical steam turbine were given, and the reason of cracking was subsequently analyzed. Results show that by reasonably increasing the thickness of the gasket between shrink-ring and barrel-casing, the actual interference in the first assembly can be made to meet the design requirements, when the tightness between the shrink-ring and the barrel-casing would be under control.
  • Response and Stress Calculation of Blades Under the Action of Shaft Torsional Vibration in Turbo-Generator Sets
    YANG Kun, ZHAO Pengcheng, GU Yujiong, NIE Shenbin, GONG Mingxiang
    2018, 38(3): 193-197.
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    A rotor-blade model was established for analysis of the coupled shaft torsional vibration and blade bending vibration, which was used to analyze the last stage long blades in a 600 MW turbo-generator set. Based on the model, the method combining Riccati transfer matrix algorithm with Newmark-β method was used to obtain the displacement response curve of blades when shaft torsional vibration happens. Through Ansys calculation, the displacement-stress curve of blade was acquired, while the dangerous section of blade was determined, together with the stress history obtained, which may serve as a reference for online fatigue life analysis and safety assessment of the rotor and blade.
  • Development and Application of the Parallel Hot Start-up Technology in a Gas-Steam Combined Cycle Unit
    WANG Zhenyu
    2018, 38(3): 198-202.
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    To shorten the hot start-up period of a gas-steam combined cycle unit, the start-up control logic of existing Siemens F class combined cycle units was investigated, and subsequently a mathematical model was built up for the combined cycle efficiency in start-up period based on actual running parameters of the unit. The parameters were then optimized under the limitation of steam turbine stress regulation, and subsequently different combinations of optimized parameters were obtained for parallel start-up of the gas turbine and steam turbine, thus a set of hot parallel start-up technologies were developed, which were then applied in the control logic of an actual unit. Results show that after applying above technologies, the unit operates safely, and the hot start-up period from steam turbine clutching to completion has been shortened by 43%, indicating improved economy and peak regulation capability of the power plant.
  • Dynamic Data Driven Modeling for Thermal Processes Based on Delay Estimation and Kalman State Tracking
    DONG Ze, YIN Erxin, HAN Pu
    2018, 38(3): 203-210.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Aiming at the difficulty in obtaining steady-state data for modeling of conventional thermal processes using historical data, a dynamic data driven modeling method was proposed based on delay estimation and Kalman state tracking, in consideration of following three aspects, such as the modeling data selection, modeling data processing and modeling method design, etc., which takes dynamic history data as the modeling data, end data input as the steady-state input component, as well as pure delay time and steady-state output component as the two dimensions of optimization variables. According to the values mentioned above, the data were processed. Meanwhile, Kalman filtering algorithm was used to obtain the initial state of a system, and combining the optimization algorithm, the system was then modeled, which was subsequently applied to an inert area object of a finishing superheater in a thermal power unit. Results show that the modeling method can directly use the dynamic history data to identify the model parameters, and the model established has high accuracy, which may serve as a reference for further study of dynamic data driven modeling.
  • Fault Diagnosis of a Medium-speed Coal Mill Based on Grey Box Model
    SUN Shuanzhu, JIANG Yefeng, DONG Shun, ZHOU Ting, DAI Jiayuan, LI Yiguo
    2018, 38(3): 211-220.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A grey box model was established for medium-speed coal mill by combining the mechanism analysis method with data identification algorithm, which has higher accuracy and stronger robustness and overcomes the deficiencies of pure mechanism modeling, such as complicated modeling process and long modeling time, etc. The grey box model is then used to calculate the residual of mill output, and by the way of wavelet transform, the residual trend is extracted. In addition, a fault detection method is proposed based on the slope threshold of residual trend signals, while the random forests algorithm is employed to create a fault classifier to identify the type of mill faults. Results show that the fault diagnosis method proposed can realize early fault detection, which has high recognition rates.
  • Effects of Tip End-plate Installation Position on the Aerodynamic Performance of an Axial Flow Fan
    JUAN Zhihui, WANG Jun, TANG Jun, XIE Bochao
    2018, 38(3): 221-225.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To analyze the effects of tip end-plate installation position on the aerodynamic performance of an axial flow fan, a numerical model was established with tip end-plate installed respectively on the pressure and suction surface, whose thickness is twice as large as that of the blade. Results indicate that the tip end-plate installed either on pressure surface or on suction surface can both reduce the leakage flows in tip clearance. The tip end-plate installed on pressure surface increases the leakage vortex and aerodynamic loss, which reduces the total pressure and fan efficiency, while that on suction surface reduces the leakage vortex and aerodynamic loss, delays the vortex shedding, makes the shedding point move away from the suction surface, thus increasing the total pressure and fan efficiency, in which case the values of total pressure efficiency have been raised by 0.6% at the designed flow rate point.
  • Experimental Study on NOx Reduction by Ammonia in High-temperature Fuel Rich Zone
    YUE Pujie, ZHANG Jian, ZHANG Zhongxiao, BI Degui, JI Xinqiang, FU Zhenhua, BAI Hao
    2018, 38(3): 226-230.
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    Taking urea solution as the amino reducing agent, experimental tests were conducted in a one-dimensional tube furnace, so as to study the mechanism of NOx reduction, and to analyze the effects of amino reducing agent on the NOx reduction under different conditions of air stoichiometric ratio (ASR), nitrogen stoichiometric ratio (BNSR) and reaction temperature (T). Results show that at experimental temperatures, the NOx concentration drops with reducing values of ASR; in the case of ASR ≤ 0.95, the NOx concentration reduces with rising BNSR, but the reducing degree tends to slow down when BNSR>2; under lower ASR conditions, high temperature is beneficial to the reduction of NOx concentration; for ASR=1.2, the NOx concentration increases rapidly with the rise of BNSR at different temperatures.
  • Effects of FGD Waste Water Conditioning on Metal Corrosion and High-temperature Chlorine Valorization
    MA Shuangchen, CHAI Jin, JIA Shaoguang, TAN Yu, ZHANG Runpan, WU Kai
    2018, 38(3): 231-236.
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    Corrosion resistance of carbon steel 20 and stainless steel 304 in FGD waste water of different pH values was studied using electrochemical method, while the variation law of gaseous chlorine volatilization and the inhibiting effects of different pH value conditioning agents on the chlorine volatilization were explored during evaporation of the waste water under different pH value conditions. Results show that when the pH value of waste water lies in 9-10, both the general corrosion and crevice corrosion of the two steels would be relatively slight, with less volatilization of chlorine. Meanwhile Ca(OH)2 can inhibit chlorine volatilization effectively, this is beneficial to the solid phase transition of salts from FGD waste water.
  • Characteristic Study on Tower Shadow Effect of Large-scale Horizontal-axis Wind Turbines
    HU Danmei, PAN Yang, ZHANG Jianping
    2018, 38(3): 237-245.
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    To study the tower shadow effect on the performance of large-scale horizontal-axis wind turbines, numerical simulations were carried out on a single wind turbine using Fluent software by taking a NREL 5 MW wind turbine as the object of study. Results show that the tower shadow effect mainly occurs in the time domain from azimuth angle 140° to 210°. When the blades are rotating, the tower shadow would cause a significant fluctuation in the torque and axial thrust at different circumferential positions. With the rise of wind speed, the relative fluctuation of torque increases, while that of axial thrust reduces. For large-scale wind turbines, blade tips are working at a high linear velocity, when the rotation effect of rotor should be considered in the process of studying the tower shadow effect. For the wake formed in the downwind of rotor, the larger the rotating radius is, the more obvious the wake will be, and its length is about twice the rotor diameter.
  • Economic Analysis of a Direct Solar Trough Medium & High Temperature Steam Generation System
    WANG Shuhui, XIONG Yuanquan, XIE Yinhang
    2018, 38(3): 246-252.
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    A direct solar trough medium & high temperature steam generation system was designed, for which, a numerical model was established, following concepts were proposed, such as the levelized cost of steam energy and the amount of saved coal, etc., while the factors influencing the system thermal efficiency and the steam energy levelized cost were analyzed. Results show that when the solar radiation rises from 100 W/m2 to 1 000 W/m2, the thermal efficiency of system would increase from 47.2% to 66.3%, and the working fluid flow would increase from 0.07 kg/s to 1.05 kg/s. When the ambient temperature rises from 15℃ to 33℃, the thermal efficiency would increase slowly from 64.5% to 64.7%, while the fluid flow may remain basically unchanged. For an annual radiation time of 3 200 h, the investment cost of above direct solar trough medium & high temperature steam generation system may be as low as 631.30 $/kW, and the levelized cost of steam energy can be reduced to 26.82 $/t, making the system have a strong market competitiveness.