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  • 2018 Volume 38 Issue 6
    Published: 15 June 2018
      
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  • Techno-Economic Analysis of the Combined Boiler Heating Surface-Thermoelectric Module Power Generation
    YOU Yun, PAN Weiguo, JIANG Weiting, WANG Jian, ZHENG Minjie, DAI Kunpeng
    2018, 38(6): 425-430.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To further improve the generating efficiency of thermal power plants, a combined method of thermoelectric module with boiler heating surfaces was proposed based on the semiconductor thermoelectric power generation technology, following which, calculation models were established for the heat transfer rate and area of boiler heating surfaces and for the combined thermoelectric module-heating surface power generation, while a power output calculation model and a techno-economic analysis model were set up for the combined system. Results show that the calculation models established are reasonable. As a new energy-saving technology, the combined power generation technology can help to improve the total power generating efficiency of a thermal power plant by about 2.9%, indicating obvious economic benefits and high investment feasibility.
  • Big Data Mining Technology Based on Parallel Algorithm and Its Application in Power Plant Boiler Performance Optimization
    LIU Binghan, FU Zhongguang, WANG Yongzhi, WANG Pengkai, GAO Xuewei
    2018, 38(6): 431-439.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To meet the ever-increasing demands of massive data mining that traditional methods are not able to deal with, a new algorithm was proposed based on rough set attribute reduction method and improved classical K-meas clustering algorithm by applying big data mining technology, so as to realize parrallel computation on MapReduce framework of Hadoop platform. Taking the massive data of a 600 MW coal-fired power unit as the mining object, the new algorithm was applied to optimize the adjustable operation parameters that may affect the boiler efficiency under typical load conditions. Results show that the new method can be used to determine the optimal target values of massive operation data, with remarkable effects in energy saving and emission reduction; the optimal target values mined by the new algorithm represent historical optimal reachable values, which may serve as a reference for operation optimization of similar boilers.
  • Modeling Research of a CFB Boiler Combustion System Based on Neural Network
    LI Guoqiang, QI Xiaobin, CHEN Bin, ZHANG Lu
    2018, 38(6): 440-446.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To accurately predict the NOx emission from boilers of thermal power plants, a 300 MW subcritical circulating fluidized bed (CFB) boiler was taken as the object of study, for which a model was established using fast learning network with parallel layer perceptron. Firstly, the validity of the proposed network was tested using classical regression data sets, and the results were subsequently compared with other neural networks, so as to examine its learning ability and stability. Then the sample data collected from the thermal power plant were taken as the input and output variables of the model proposed. Finally, the prediction results were compared with those of extreme learning machine, fast learning network, kernel extreme learning machine and incremental extreme learning machine, etc. Results show that the model established based on fast learning network with parallel layer perceptron has a good prediction accuracy and generalization ability, which may accurately and effectively predict the NOx emission from boilers of thermal power plants.
  • Dynamic Co-combustion Experiments with Low Calorific Raw Coal and High Calorific Pulverized Coal in a CFB Boiler
    PAN Xiongfeng, MA Suxia, CHEN Jun, PAN Yanlong, LI Kaiyong, LIU Zhongyuan
    2018, 38(6): 447-451.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem of slow response to load instructions of a circulating fluidized bed (CFB) boiler, dynamic co-combustion experiments were conducted with low calorific raw coal and high calorific pulverized coal in a 220 t/h CFB boiler, so as to study the effects of pulverized coal on the dynamic combustion process in the boiler. Results show that during co-combustion process, the load change rate would respectively be 6.03 MW/min (3.57% ECR/min) and 4.16 MW/min, when the pulverized coal is added through secondary air ducts and coal pipes accordingly; whereas, in the single raw coal combustion process, the load change rate would be only 2.69 MW/min in response to a step change of coal feeding, indicating that the method of co-combustion can excavate the potential of a CFB boiler in peak shaving operation. The co-combustion way with pulverized coal fed through secondary air ducts could produce higher combustion efficiency than that through coal pipes, resulting in higher rate of load change. The insufficient combustion of pulverized coal fed through coal pipes may cause reburning in the return feeder.
  • Sectional Crossover Retrofit of Heating Tubes for Reduction of Boiler Thermal Deviation
    CHONG Peian, XU Hongtao, DING Shifa
    2018, 38(6): 452-457.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To reduce the thermal deviation existing in high-temperature heating tubes in the same panel or in different panels of a boiler, an analysis was conducted on the operation status, while relevant calculations were carried out, after which the causes leading to the thermal deviation were found, and subsequently a retrofit scheme was put forward by sectional crossover and other structural modification. Results show that the retrofit requires little engineering work, which may be used to reduce the thermal deviation of high-temperature heating surfaces, thus effectively controlling the wall temperature and securing the safety operation of the boiler.
  • Numerical Investigation and POD Analysis on Unsteady Flow Field in Tip Region of a Transonic Compressor Rotor
    LIU Zhenxiong, ZHU Xiaocheng, DU Zhaohui
    2018, 38(6): 458-466.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Time-accurate simulations were performed to investigate the unsteady flow field in tip region of a transonic axial compressor NASA rotor35. Taking the transient results of unsteady flow field in the tip region as snapshots, the flow behavior was further analyzed under near stall conditions by applying proper orthogonal composition (POD) method to extract POD modes. Results show that no oscillation occurs in the blade tip flow field under high mass flow conditions, which can be regarded as steady flow field; whereas under low mass flow near stall conditions, periodic oscillation occurs in the tip region, which is resulted from the secondary vortex formed by the breakdown of tip leakage vortex after shock wave, the tip leakage flow without rolling up into tip leakage vortex and the incoming flow.
  • Influence of Elevation Adjustment on Shaft Seal Clearance of a Multi-support Turbo-Generator Unit
    GU Jiahui, FENG Kun, YANG Jiangang, ZHU Yiming
    2018, 38(6): 467-471.
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    By means of transferring matrix and differential method, an analytical model was established for the influence of elevation adjustment of multi-support shafting bearings on the clearance of adjacent shaft seals, considering the effects of bearing elevation adjustment on the bearing load, the effects of bearing load on both the eccentricity and deflection angle as well as the elastic influence of the shaft, which was subsequently applied to the calculation and analysis of a large scale steam turbine. Results show that the change of seal clearance is mostly less than the adjustment of bearing elevation due to the influence of oil film and elastic deformation of the shaft. Compared with the intermediate bearing, the gap of the shaft seal near free end is not sensitive to the change of bearing elevation. The lower the bearing load, the smaller the influence of elevation adjustment on the clearance change. To deal with an oil-film instability fault, the scope of elevation adjustment could be enlarged. The change of seal clearance is sensitive to that of elevation adjustment at low speeds due to poor damping effect of thin oil film.
  • Experimental Study on Flow Field Optimization and Ash Hopper Pre-precipitation of an Economizer
    ZHAO Chao, CHEN Hongwei, DENG Huaiming, WANG Guangtao, ZHANG Qian
    2018, 38(6): 472-478.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The fly ash collection performance of a low-temperature economizer hopper was studied in a 1:20 cold model test rig established using similarity criterion. Results show that the amount of fly ash collected by the economizer hopper can be increased by adding airfoil angle guide plate and parallel rectifier plate at the outlet of economizer, and the flue gas impact upon the upper wall of horizontal flue duct can be reduced after 90 degree turning of the flue gas passing through the hopper. Specially, the capture rate of original ash particles can reach 19.26%, being 10.71% higher than that without airfoil angle guide plate and parallel rectifier plate. The capture rate of fly ash particles larger than 88 μm, which may seriously wear the SCR denitration catalyst, is 54.09%, being 33.65% higher than that before retrofit, and simultaneously with less energy loss. The retrofit can effectively alleviate the wear and blockage degree in SCR catalyst layers, and can reduce the load of electrostatic precipitator in fly ash collection.
  • Study on Mercury Migration and Emission Characteristics in a CFB Boiler Based on Multi-stream Tests
    CAI Weizhong, CUI Jian, DENG Yusheng, HUANG Haipeng, LIANG Shuxiong, DUAN Lunbo
    2018, 38(6): 479-483.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Mercury migration and emission characteristics were studied for a 410 t/h circulating fluidized bed (CFB) boiler. The flue gas was sampled simultaneously in the upstream and downstream of the electrostatic precipitator (ESP) and at the outlet of wet flue gas desulfurization (WFGD) unit based on Ontario hydro method. At the same time, following streams were also sampled, such as the fuel, bottom ash, fly ash, gypsum, desulphurization wastewater, limestone slurry and flush water flow, etc., so as to find the mass balance ratio of Hg. Results show that the mass balance ratio of Hg is within 101.10%-117.58%, proving the test results to be reliable. The majority of Hg moves to the fly ash, accounting for 70.95% of the total, and about 27.37% Hg emits to the atmosphere, mainly in the phase of gaseous element. The removal efficiency of Hg by ESP unit and WFGD system is 58.1% and 36.2%, respectively. The ESP+WFGD installed in CFB power plants can well control the amount of Hg emitted to the atmosphere.
  • Flue Gas Purification Model of a Waste Incinerator with Rotating Spray
    JIA Zhennan, LI Chunxi, YIN Shui'e, YE Xuemin
    2018, 38(6): 484-492.
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    A gas-solid-liquid mass transfer model, a chemical reaction model and a slurry droplet model were set up for the deacidification tower with rotating spray in a waste incineration plant to analyze the evaporation and mass transfer processes. The accuracy and reliability of above models were verified by comparing the experimental results with actual operating data. Based on simulation of the internal dynamics in deacidification tower of a certain waste incineration plant, the deacidification efficiency as well as the distributions of pressure, temperature, velocity and acid gas concentration were obtained. Results show that the deacidification reaction mainly occurs in the upper part of central axis in the deacidification tower; some of the droplets that have not evaporated completely are blown to the tower wall due to the influence of flue gas recirculation, leading to the possible risk of slagging and corrosion as well as the increment of thermal stress of tower wall, which is not conducive to the long-term stable operation of the deacidification tower; the slurry droplets evaporate completely in 5 seconds after entering the deacidification tower.
  • Effects of Wind Direction on Aerodynamic Performance of Building Augmented Vertical Axis Wind Turbines
    ZHU Haitian, HAO Wenxing, LI Chun, DING Qinwei, YU Wan
    2018, 38(6): 493-500.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To make full use of the locally enhanced wind around buildings, an unsteady numerical simulation was conducted on a vertical axis wind turbine in building environment. The flow field around an original three-straight-blade vertical axis wind turbine with NACA0021 airfoil was numerically studied and compared with experimental results, while the features and advantages of a building augmented vertical axis wind turbine in capturing wind energy were investigated considering the altitude supremacy of skyscrapers, the effect of enhanced wind speed by building diffusers and the local wind direction. Results show that the power coefficient of a building augmented vertical axis wind turbine may be promoted up to 2.47 times of the original one, but its load fluctuation is stronger, which places a higher requirement on the safety and reliability of the building, and it is rather sensitive to the wind direction, the arrangement of building diffusers and the building profiles, etc.
  • Threshold Denoising Method for Acoustic Emission Signals from Hydraulic Turbine Cavitation Based on EMD
    LIU Zhong, SONG Jiacheng, ZOU Shuyun, YUAN Xiang, ZHOU Yungui, CHEN Ying
    2018, 38(6): 501-507.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Aiming at the influence of random noises on the acoustic emission signals in the cavitation condition monitoring of hydraulic turbines, a threshold denoising method was proposed based on empirical mode decomposition (EMD) for acoustic emission signals from hydraulic turbine cavitation. Firstly, EMD was used to decompose the acoustic emission signals to some intrinsic mode functions (IMFs). Then the first half of IMFs were denoised according to the given threshold rules. Both the denoised IMFs and the unprocessed ones were reconstructed to get the denoised acoustic emission signals. This method was implemented on the simulated signals and those collected in a cavitation experiment, and the denoising effects were compared with those obtained by the wavelet threshold denoising method, the wavelet packet threshold denoising method and the conventional EMD denoising method. Results show that the method proposed is better than other three algorithms in the noise reduction of acoustic emission signals from hydraulic turbine cavitation, which combines the self-adaptive decomposition characteristics of EMD and the advantages of threshold denoising method with good performance.
  • Research and Application of the Key Installation Technologies for AP1000 Reactor Coolant Pumps
    HU Guofeng
    2018, 38(6): 508-512.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To make the installation of AP1000 reactor coolant pumps meet the design requirments, researches were conducted on the measurement technology, jack-up process and horizontal transportation route in the steam generator. Results show that the laser measurement can completely meet the precision requirement of pump installation. The optimum jack-up velocity lies in the range of 3.0~4.0 mm/min, and the least distance between pump and wall on the optimum horiziontal tranportation route is 18 mm. Based on the research, the installation of all the AP1000 reactor coolant pumps can completely meet the design requirmens.