Archive

  • Select all
    |
    Boiler Technology
  • Boiler Technology
    Calculation of Heat Storage Coefficient for Ultra Supercritical Once-through Boilers
    GU Junjie, ZHANG Yongtao, CAO Xiguo, DONG Ze
    2015, 35(3): 173-177.
    Abstract ( )   Knowledge map   Save
    A calculation method has been proposed for heat storage coefficient of ultra supercritical once-through boilers: First, the length of each phase state in the water wall is calculated by program based on thermodynamic properties of the water and steam. Second, the mass, volume, and energy balance equations are used to obtain the heat storage coefficient of both the water wall and superheater. Taking a 660 MW ultra supercritical power plant as an example, heat storage coefficients of the water wall and superheater were respectively calculated at four different loads using design data of the boiler. Calculation results show that the boiler's heat storage coefficient is about 60 s, in which the water wall accounts for 15%-30%, and the superheater accounts for 70%-85%.
  • Boiler Technology
    Combustion and NOx Emission Characteristics of Coal-Textile Dyeing Sludge Mixture in a Tangentially-fired Boiler
    YIN Libao, XU Qisheng, HU Zhifeng, MA Xiaoqian, CHEN Yumeng, YU Zhaosheng
    2015, 35(3): 178-184.
    Abstract ( )   Knowledge map   Save
    Using Fluent software, numerical simulation was conducted to combustion and pollutant emission characteristics of a tangentially-fired boiler burning coal blended with different ratios and moistures of textile dyeing sludge. Results show that with the rise of blending ratio of textile dyeing sludge, the overal temperature in furnace drops a little, and the NOx emission rises rapidly first and steady later on, and the turning point is at the blending ratio of 10% textile dyeing sludge; with the rise of sludge moisture, the overall temperature in furnace reduces slightly, and the average outlet temperature of furance with 40% moisture is only 8.11 K lower than the case with 10% moisture; the NOx emission rises with the growth of sludge moisture; considering the furnace combustion and NOx emission characteristics, it is thought to be reasonable to blend 10% textile dyeing sludge with 40% moisture into the coal, and the optimum secondary air distribution from top to bottom is 3∶1∶2∶4.
  • Boiler Technology
    Effects of Low-NOx Retrofit on NOx Formation in a Tangentially-fired Boiler
    FU Zhongguang, SHI Li, DUAN Xuenong, ZHU Guangming, Lü Dangzhen
    2015, 35(3): 185-190.
    Abstract ( )   Knowledge map   Save
    Numerical simulation was conducted to NOx formation characteristics in a 300 MW tangentially-fired boiler before and after low-NOx retrofit, so as to analyze the effects of low-NOx retrofit on the NOx formation characteristics. Results show that the design of stabilized combustion cavity in the original dual-channel self-stabling burner obviously increases its thermal NOx emission. The combustion of both dense and dilute pulverized coal-air mixture flow in the new horizontal bias burner is under the condition deviating from the chemical equivalent ratio, which lowers the flue gas temperature around burners and compresses the emission of thermal NOx. Rare oxygen combustion also reduces the combustion efficiency, and increases the production of fuel NOx in cold ash hopper and in upper furnace area above tertiary air flow.
    • Automatic Control and Detecting Diagnosis
  • Automatic Control and Detecting Diagnosis
    PID Parameter Tuning Based on Improved DE Algorithm and the Application
    WANG Peng, LIU Lin, CHEN Zhe, ZHAI Yongjie, ZHOU Jielian
    2015, 35(3): 191-196.
    Abstract ( )   Knowledge map   Save
    By introducing PID regulation-based formulas and adaptive operators into differential evolution (DE) algorithm, an improved differential evolution (IDE) algorithm was proposed, in which PID regulation-based formulas were used to guide the production of initial population in DE algorithm, so as to reduce random optimization and improve convergence rate of DE algorithm, and subsequently to obtain PID parameters adaptively without depending on experience of tuning engineers. Simulation studies were conducted to steam temperature control system of circulating fluidized bed (CFB) boilers with substantial parameter uncertainties, frequent disturbance and large time delay, and the IDE algorithm was applied to the main steam temperature control system of a 300 MW CFB boiler. Results show that the IDE algorithm is fast in searching, simple in calculation and effective in optimization of tuning parameters. Compared with GA method, the proposed method can obtain better control quality and system robustness in PID parameter tuning, with which the steam control effect can be significantly improved.
  • Automatic Control and Detecting Diagnosis
    Experimental Study on Sound Transmission Across Tube Arrays Based on Phononic Crystal Theory
    JIANG Genshan, LIU Yuechao, CHEN Duoduo, WU Yapan, XU Weilong
    2015, 35(3): 197-204.
    Abstract ( )   Knowledge map   Save
    Based on analysis of phononic crystal theory, experimental studies were conducted to sound transmission across tube arrays with different tube rows and pitch sizes at different environmental temperatures, so as to analyze the relationship between sound pressure level (SPL) insertion loss and the structural parameters of tube array. Above results were compared with those obtained by plane wave expansion method and Comsol software simulation. Results show that the band gaps of sound transmission obtained in the experiment agree well with those by theorectic calculations, and sometimes, “transparent gaps” may be observed in the “stop gaps”.
  • Automatic Control and Detecting Diagnosis
    Fault Diagnosis of Wind Turbine Gearbox Based on EITD-WPT Method
    XIANG Ling, YAN Xiaoan
    2015, 35(3): 205-212.
    Abstract ( )   Knowledge map   Save
    An ensemble intrinsic time-scale decomposition (EITD) method was proposed based on the cubic spline interpolation and linear transformation of intrinsic time-scale decomposition (ITD), combining which with wavelet packet transform (WPT), fault diagnosis of wind turbine gearbox can be realized. First, cubic spline interpolation is used to fit the baseline control points and decompose the vibration signal into several proper rotation components (PRCs). Then, wavelet packet transform is applied to decompose the PR component of the biggest correlation coefficient and to compute the energy distribution of wavelet packet coefficients, and those wavelet packet coefficients with relatively bigger energy are selected to reconstruct the PR component. Finally, correlation dimensions of the reconstructed PR component are calculated and fault diagnosis of the vibration signals are achieved. The method was applied to the analysis of vibration signals in a wind turbine gearbox. Results show that the correlation dimension of the vibration signals processed with EITD-WPT can be used to identify the working states and fault types of wind turbine gearbox more effectively, compared with that with EMD and EMD-WPT.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Numerical Simulation on Fluid Flow and Heat Transfer in a Corrugated Plate Air Preheater
    QIN Yun, GUAN Xin, DUN Zhe, LIU Haojun
    2015, 35(3): 213-218.
    Abstract ( )   Knowledge map   Save
    Numerical simulation was conducted to fluid flow and heat transfer in a corrugated plate air preheater, so as to analyze the effects of following factors on performance of the air preheater, such as structure features of the corrugated plate, inclination angle, height and pitch of the corrugation, as well as the plate spacing, etc. Results show that with the rise of inclination angle and corrugation height, the heat transfer performance improves, but the pressure drop increases also, and under the condition of β=45° and H=10 mm, the heat transfer performance reaches the optimum; the heat transfer performance is slightly influenced by corrugation pitch, but greatly affected by plate spacing. Considering the compactness of air preheater, the structure with small plate spacing is preferred so as to obtain better heat transfer performance of the air preheater.
  • Auxiliary Equipment Technology
    Numerical Analysis on Heat Transfer of Quad-section Rotary Air Heaters
    CHEN Changxian, SUN Fengzhong, TIAN Silai, LI Fei, WU Yanyan
    2015, 35(3): 219-223.
    Abstract ( )   Knowledge map   Save
    To solve the problem of low-temperature corrosion existing in actual operation of quad-section rotary air heaters, a 3D heat transfer model was set up based on CFD software Fluent for the air heater by defining the rotor heat surface temperature as user-defined scalar (UDS) and by solving the scalar equation. Taking the quad-section rotary air heater in a 300 MW circulating fluidized bed boiler as an example, the 3D temperature distribution of both working fluid and heater surface was simulated, while causes leading to the difference of heat transfer performance between hot- and cold-section of the rotor were analyzed. Results show that the difference of heat transfer performance and capacity is mainly caused by different shapes and materials of the hot- and cold-section. Low-temperature corrosion is easy to happen in the heat surface at hot-section inlet of right secondary air side, where the metal temperature should be kept above acid dew point so as to retard the low-temperature corrosion.
  • Auxiliary Equipment Technology
    Effects of Radiator Heat Load Distribution on Operation Performance of the Indirect Air-cooling System
    TIAN Songfeng, LIU Huiyang, CHAI Yanqin
    2015, 35(3): 224-229.
    Abstract ( )   Knowledge map   Save
    Taking the SCAL indirect air-cooled tower as an object of study, a detail model was established according to the actual size of cooling tubes and the arrangement way of triangular support and tower proper, with which three-dimensional numerical simulation was conducted to its inner and outer flow field based on RNG k-ε turbulence model and porous medium model, so as to study the effects of wind speed and radiator heat load on operation performance of the air-cooled tower. Simultaneously, an optimized scheme was proposed for improving the heat load distribution of various cooling sectors against the condition of partial load operation of radiator. Results show that both the ventilation rate and the exit velocity of air-cooled tower reduce with the drop of radiator heat load, and the reduction tendency decreases with the rise of wind speed. The inner flow field significantly improves after optimization of the heat load distribution, in which case, both the ventilation rate and the exit velocity of air-cooled tower increase.
  • Auxiliary Equipment Technology
    Study of Liquid Film Flowing on the Packing with Sine Wave Form and Related Thermal Economic Analysis
    CHENG Youliang, YANG Xinghui, HAN Fuqiang
    2015, 35(3): 230-236.
    Abstract ( )   Knowledge map   Save
    To study the flow and heat transfer characteristics of liquid film flowing on the packing with sine wave form and to analyze the influence of its cooling effect on thermal economy of the power plant, numerical simulations were conducted to the liquid film with different amplitudes, wavelengths and at different inclined angles using Fluent software based on reasonable physical models. According to the outlet water temperature obtained by numerical simulation, the effects of the packing structure on thermal economy of the power plant were analyzed. Results show that for fixed inclined angle and amplitude, the film thickness reduces and the outlet water temperature increases with rising wavelength; for fixed wavelength and amplitude, the film thickness increases and the outlet water temperature drops with rising inclined angle; for fixed inclined angle and wavelength, the film thickness increases while the outlet water temperature drops with rising amplitude.
    • Environmental Science
  • Environmental Science
    Flow Field Optimization for CFB Boiler Rear Duct with Ammonia-sprayed AFGD System
    FANG Lijun, YIN Rongrong, GAO Jianqiang, CHENG Shaowei
    2015, 35(3): 237-244.
    Abstract ( )   Knowledge map   Save
    Site tests were conducted to an advanced ammonia-sprayed flue gas desulfurization (AFGD) system designed for rear duct of a circulating fluidized bed (CFB) boiler, during which the CaO content in ash and the SO2 mass concentration in flue gas were measured after ammonia injection, while the flow field inside the rear duct was simulated, so as to analyze the running track and mass concentration of ammonia droplets in the duct and the pressure drop of outlet flue gas at different positions and angles of the nozzle, and to determine optimum nozzle position and angle, when better mixing effects of gas-liquid two-phase flow can be obtained. Results show that highest ammonia fullness and best mixing effect can be achieved in the duct, if the mass flow of ammonia is 0.056 kg/s, the upper nozzle is horizontally placed at y=2.4 m, and the lower nozzle is placed at y=1.6 m with a downward angle of 45° to the horizontal plane, in which case, the desulfurization efficiency can reach 60.13%, with a flue gas pressure drop of 42.3 Pa. The flue gas pressure drop obtained by numerical simulation agrees well with that of the experimental measurement.
  • Environmental Science
    Experimental Study on CO2/CH4 Separation Respectively by Membrane, Chemical and the Combined Method
    LING Fan, ZHANG Zhongxiao, FAN Junjie, AN Haiquan
    2015, 35(3): 245-250.
    Abstract ( )   Knowledge map   Save
    Separation efficiencies of CO2/CH4 by membrane separation and chemical absorption were studied respectively in a hollow fiber membrane contactor test rig and a packed tower test rig, and subsequently a new CO2 removal technology was proposed. CO2/CH4 separation experiments were carried out in the new test rig combining the hollow fiber membrane with the packed tower, so as to analyze the influence of various factors on the CO2 removal effect, and to compare the CO2 removal efficiency among the three separation methods. Results show that the membrane separation has low CO2 removal efficiency and low CH4 recovery ratio, which suits to deal with the gas of small flow rate with undemanding separation efficiency; the chemical absorption has high separation efficiency and high CH4 recovery ratio, which suits to process the gas with demanding separation efficiency; the combined method has low separation efficiency and high CH4 recovery ratio, which suits to deal with the gas of high flow rate with undemanding separation efficiency.
    • Energy System Engineering
  • Energy System Engineering
    Open Circulating Water System Optimization Based on LSSVM and Firefly Algorithm
    WANG Xi, ZHANG Xuedong, SI Fengqi, XU Zhigao
    2015, 35(3): 251-255.
    Abstract ( )   Knowledge map   Save
    To optimize the pump operation in open circulating water system, a soft sensing model was established for the static head using least square support vector machine (LSSVM) regression according to the characteristics that the water flow rate changes with the variation of static head. An objective function of equal efficiency curve was set up for the circulating water pump based on the prediction model of condenser vacuum to solve the equal efficiency operating points by firefly algorithm (FA). Results show that the maximum relative error of static head between predicted data of soft sensing model and actual measurements is 4%; the maximum relative error of condenser vacuum between predicted data of condenser vacuum prediction model and actual measurements is 3% by analyzing 100 samples. Referring to enumeration method, the firefly algorithm is relatively accurate in optimization of equal efficiency operating points, which therefore provides a new approach for solution of discrete optimization problems.