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    Boiler Technology
  • Boiler Technology
    Mass Transfer Simulation of Multi-component Particles in a Fluidized Bed
    SONG Xiaojiao, WANG Qi, YANG Xuesong, YIN Weijie
    2021, 41(1): 1-7. https://doi.org/10.19805/j.cnkij.cspe.2021.01.001
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    To reveal the mass transfer characteristics of active particles, the Euler-Euler multi-fluid model was used to simulate the adsorption process of steam in a multi-component fluidized bed with the presence of inert particles by means of CFD approaches, simultaneously using the bubble-based drag model and multi-component mass transfer model, so as to obtain the volumetric distribution of solid particles and mass concentration of steam in the fluidized bed, verify the rationality of the bubble-based drag model, and to analyze the effects of inlet gas velocity, steam mass concentration and bed pressure on the process of steam adsorption. Results show that the bubble-based drag model can reproduce the process of steam adsorption well; both the decrease of inlet gas velocity and the increase of inlet steam mass concentration are beneficial to the improvement of mass transfer characteristics and steam adsorption rate.
  • Boiler Technology
    Effect of Primary Air Blade Inclination Angle on Combustion and NOx Emission of a Cyclone Boiler with Slag-tap Furnace
    WANG Weishu, HUANG Zhihao, FANG Fan, LIAO Yihan
    2021, 41(1): 8-13. https://doi.org/10.19805/j.cnkij.cspe.2021.01.002
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    For the cyclone boiler with slag-tap furnace purely burning high-alkali coal, the aerodynamic field, temperature field and component distribution characteristics were numerically studied under different inclination angles of primary air blade, while the influence of the blade angle on the combustion and NOx emission characteristics in the furnace was analyzed. Results show that, the aerodynamic field in the cyclone boiler with slag-tap furnace is good; the flue gas fills the furnace in high degree, and the cyclone burners arranged in staggered and reverse direction can enhance the combustion. Within the range of the conditions studied, as the angle of primary air blade decreases, the flue gas temperature decreases, and the NOx concentration at furnace outlet decreases first and then increases. The overall temperature in the furnace and the combustion efficiency of pulverized coal are higher, and the NOx concentration at furnace outlet is the lowest, when the angle of primary air blade is 30°.
  • Boiler Technology
    Analysis and Calculation on Carbon Emission Characteristics of CFB Boiler Units
    GAO Jianqiang, SONG Tongtong, ZHANG Xue
    2021, 41(1): 14-21. https://doi.org/10.19805/j.cnkij.cspe.2021.01.003
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    Based on the features of circulating fluidized bed (CFB) boiler, the carbon emission characteristics were analyzed from the following three aspects:coal burning process, desulfurization process and auxiliary system energy consumption, etc. According to the CO2 generation mechanism, calculation methods were proposed for the CO2 generation coefficient K per unit standard coal consumption in the coal burning process, in-furnace dry desulfurization process and off-furnace calcium desulfurization process, respectively, while a calculation model was given for the carbon intensity of CFB boiler unit. Taking the 300 MW CFB boiler unit as an example, a study was conducted using the calculation model established to investigate the influence of coal quality change on the CO2 generation coefficient per unit standard coal consumption and the variation law of carbon emission intensity with the load of the CFB boiler unit. Results show that the coal quality, desulfurization efficiency, Ca/S ratio, unit load and the auxiliary power consumption are the main factors influencing the intensity of carbon emission of the CFB boiler. The CO2 generation coefficient per unit standard coal consumption corresponding to low calorific value and high sulfur coal is higher than that corresponding to high calorific value and low sulfur coal. Under the condition of a certain coal quality, the carbon emission intensity of CFB boiler is positively correlated with the Ca/S ratio in the furnace, and negatively correlated with the load of the unit; for every 1% decrease in load, the carbon emission intensity increases by 2.41 g/(kW·h), which increases by a greater extent with the decrease in unit load under low load conditions.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    NOx Emission Prediction and Optimization for Gas Turbines Based on Data and Neural Network
    ZHAO Gang, ZHU Huaxin, LI Suhui, ZHU Min, WEI Xiaofeng
    2021, 41(1): 22-27. https://doi.org/10.19805/j.cnkij.cspe.2021.01.004
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    Based on a large sum of operation data from power plants, the artificial neural network was used to model the parameters concerning the NOx emission and combustion stability of a gas turbine, while a sensitivity analysis was conducted on the parameters influencing the combustion performance to find out the correlation between the inputs and outputs. Subsequently, the parameters at actual operation point were adjusted, and the results of model prediction were compared with that of qualitative analysis based on physical mechanism. It has been found that the results of model calculation are basically consistent with the qualitative analysis, that is, the NOx emission grows with the increase of fuel flow rate and decreases with the increase of IGV opening; the combustion stability index (CSI) reduces with the increase of fuel flow rate and rises with the increase of IGV opening.
  • Steam Turbine and Gas Turbine
    Effect of Hole Blockage on the Film Cooling Effectiveness of a Blade on the Suction Side
    GUO Yunxiu, LI Guangchao, ZENG Rui, ZHANG Wei, ZHU Jianyong
    2021, 41(1): 28-35. https://doi.org/10.19805/j.cnkij.cspe.2021.01.005
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    To study the influence mechanism of hole blockage on the film cooling effectiveness caused in the spraying process of thermal barrier coatings, the change rule of film cooling effectiveness was numerically investigated at the blockage ratio of 0.2, 0.5 and 0.8 on the suction surface, and at the blowing ratio of 0.5, 1.0, 1.5 and 2.0. Results show that the larger the blockage ratio is, the more obvious the decrease will be in film cooling effectiveness, with smaller film coverage in the downstream of the hole. Compared with no blockage case, the average spanwise film cooling effectiveness reduces by 51%-98% when the blockage ratio is 0.8, which drops by 24%-86% when the blockage ratio is 0.5; for the blockage ratio of 0.2, the degradation of average spanwise film cooling effectiveness is less than 5%. The change of film cooling effectiveness at small and medium blockage ratio is obviously affected by the blowing ratio, while that at large blockage ratio is less affected. With the increase of blockage ratio, the momentum flux in the throat area of film cooling hole rises, resulting in smaller coverage of film due to the lifted coolant jet.
    • Automatic Control
  • Automatic Control
    Optimized Compensation for Set Values of Superheated Steam Temperature in Supercritical Unit Based on Neural Network
    MA Liangyu, CHEN Tingting, LIU Wenjie, LI Qianqian
    2021, 41(1): 36-42. https://doi.org/10.19805/j.cnkij.cspe.2021.01.006
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    Neural network models were developed for the characteristics of a superheated steam temperature (SST) system based on historical data. On the premise of not changing the original SST control logic and PID parameters, a real-time optimization strategy was proposed for the set values on the top level of control loop to improve the SST control effect, which combines feedback compensation with feedforward compensation based on ANN prediction model. Simulation experiments were carried out with the help of a full-scope simulator for a 600 MW supercritical power unit. Results show that the SST control quality can be obviously improved by using the optimized compensation scheme for set values, which is proved to be effective.
    • Monitoring and Measurement
  • Monitoring and Measurement
    Research on Diagnosis Method of Wind Turbine Yaw Gearbox Based on SCADA Data Feature Extraction
    DENG Zihao, LI Luping, LIU Rui, YANG Bo, CHEN Xi, LI Zhonggui
    2021, 41(1): 43-50. https://doi.org/10.19805/j.cnkij.cspe.2021.01.007
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    To solve the serious problem in a wind turbine yaw system that is difficult to deal with, a neural network diagnosis model was proposed for the yaw gearbox of a wind turbine based on SACDA monitoring data. Seven SCADA characteristic parameters reflecting operation conditions of the yaw gearbox were extracted by ReliefF and kernel density-mean algorithm, while six fault characteristic indexes were extracted and taken as the input of the diagnosis model to identify the normal state, wear state and broken tooth state of the yaw gearbox. Results show that the training accuracy of the neural network model meets the requirements of diagnosis, which can be applied in the fault diagnosis of yaw gearboxes.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Numerical Simulation and Analysis on Viscous Bottom Layer of Turbulent Transcritical Water Flows
    WANG Chao, CHEN Can, LI Hongyuan, XU Hong
    2021, 41(1): 51-56. https://doi.org/10.19805/j.cnkij.cspe.2021.01.008
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    To investigate the variation of the viscous bottom layer of turbulent transcritical water flows in power stations, the SST k-ω turbulence model was used to numerically simulate the changes of the viscous bottom layer with the following control parameters, such as the inlet temperature, heat flux and mass flow rate, etc. Results show that the changes of the viscous bottom layer of water flows across the critical area are not monotonous, and the subcritical inflection point SubIT, pseudo-critical point PCT and supercritical inflection point SupIT are the key points influencing the changes of the thickness and velocity gradient of the viscous bottom layer. Inlet temperature only changes the position of the peak and valley of the thickness and velocity gradient of the viscous bottom layer, but does not change their values. The increase of the mass flow rate helps to reduce the peak and valley values of the thickness while increase the peak and valley values of the velocity gradient. The rise of the heat flux will increase the peak value of the thickness, which has almost no effect on the peak and valley values of the velocity gradient.
    • Environmental Protection Technology and Equipment
  • Environmental Protection Technology and Equipment
    Characteristic Analysis of Desulfurization Wastewater Evaporation Based on Quadratic Regression Orthogonal Methodology
    LI Hengfan, JIAO Shiquan, HAN Zhonghe
    2021, 41(1): 57-65. https://doi.org/10.19805/j.cnkij.cspe.2021.01.009
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    To study the evaporation law of desulfurization wastewater in the tail flue of a boiler, a mathematical model was established for the evaporation and diffusion of atomized droplets in the flue gas. Based on the quadratic regression orthogonal test method, and with the simulated calculation of evaporation distance and time of desulfurization wastewater droplets under different temperatures and speeds of the flue gas and water spray volume, a significant no-lack-of-fit regression equation was obtained, while the influence of various factors on the distance and time of evaporation was analyzed. Results show that the flue gas temperature and speed as well as the water spray volume have a significant non-linear relation to the evaporation distance and time of desulfurization wastewater droplets. Higher flue gas temperature and smaller spray volume would result in shortened evaporation time and reduced evaporation distance; with the increase of flue gas flow, the evaporation time would reduce, but the evaporation distance would first decrease and then increase. According to the regression equation established, the value ranges of flue gas temperature, flue gas velocity and water spray volume have been determined within a certain safe evaporation distance, which may serve as a reference for optimal field operation of desulfurization wastewater evaporation in the tail flue of boilers.
  • Environmental Protection Technology and Equipment
    Experimental Study on Leaching Properties of Heavy Metals in Cement-based Products by FGD Wastewater Solidification
    MA Shuangchen, QU Baozhong, WAN Zhongcheng, LIU Daokuan, LIU Ya, QIAO Lin, ZHANG Jingrui
    2021, 41(1): 66-70. https://doi.org/10.19805/j.cnkij.cspe.2021.01.010
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    A new technical route was proposed for the flue gas concentrating and cement-based solidification/stabilization of desulfurization wastewater, in which, the ability of the solidifying object to fix arsenic ions and selenium ions was taken as the basis for predictive analysis of the cement-based heavy metal solidification/stabilization effects, so as to study the leaching properties of the heavy metals. The specific way is to mix the desulfurization wastewater with cement, fly ash and fluvial sand to obtain a solidifying object. After curing to a certain time for the solidifying object, the leaching rates of the arsenic ions and selenium ions were tested. Finally, the effects of the following factors on the solidifying ability to the arsenic ions and selenium ions were analyzed, such as the water-cement ratio, cement-coal fly ash (CFA) ratio and the sand amount, etc. Results show that the leaching rates of arsenic ions and selenium ions increase significantly with the rise of the amount of cementitious materials; the effects of water-cement ratio on the solidification/stabilization of arsenic ions are more significant. When the mass ratio of cement to CFA is 3.2:1, the hydration reaction of cement and CFA in the solidifying object reaches the optimal state.
  • Environmental Protection Technology and Equipment
    Co-slurryability of DMF Distillation Residue with Coal
    CHEN Zhi, LIU Jianzhong, CHEN Jian, LI Dedi, WANG Jianbin, WANG Mingxia
    2021, 41(1): 71-78. https://doi.org/10.19805/j.cnkij.cspe.2021.01.011
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    The distillation residue coal water slurry (DRCWS) was prepared by mixing the dimethylformamide (DMF) distillation residue with Shenhua coal, based on which, the slurryability, rheology and stability of the slurry fuel were experimentally tested to study the effects of additive category and residue amount on the property of the slurry. Results show that the concentration of DRCWS is lower than that of common coal water slurry (CWS); with the increase of the blending ratio of DMF distillation residue, the DRCWS concentration reduces, which drops to 61.20%, when the blending ratio is 11%. The mixing of DMF distillation residue would enhance the pseudoplasticity of the slurry; the higher the blending ratio is, the more obvious the pseudoplasticity would be. Compared with CWS, the stability of DRCWS is higher. When the blending ratio reaches 11% of the dry coal weight, the DRCWS can be stably stored for more than 7 days. By comparing the dispersion and stabilization effects of different additives, the dispersing agent NNO is found to have the best effects.
    • System Engineering
  • System Engineering
    Optimization of a Combined Power and Ejector-refrigeration System Based on 3D Construction Method of Thermodynamic Cycle
    TU Daixin, ZHANG Xiaolin, ZHANG Qiang, XU Weicong, XIA Hongwei
    2021, 41(1): 79-84. https://doi.org/10.19805/j.cnkij.cspe.2021.01.012
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    Using the three-dimensional (3D) construction method of thermodynamic cycle as an optimization strategy for a combined power and ejector-refrigeration system, the effects of the composition of non-azeotropic working fluid on the performance of the combined system were analyzed, while a comparison was conducted between the performance of a 3D thermal cycle system that takes into account the changes in the composition of the working fluid and that of a traditional 2D thermal cycle system. Results show that the 3D construction method of thermodynamic cycle can significantly improve the performance of the combined power and ejector-refrigeration system. When the evaporation temperature is 413.15 K, the thermal efficiency of the system would increase from 33.2% to 35.25%, after a separator is added to regulate the components.