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    Boiler Technology
  • Boiler Technology
    Modeling and Prediction of H2S Concentration in a Coal-fired Boiler Based on BP Neural Network
    XIANG Minghui, LIANG Zhanwei, SUN Yichao, WANG Xingang
    2020, 40(6): 433-439. https://doi.org/10.19805/j.cnki.jcspe.2020.06.001
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    Prediction models for the H2S concentration in a coal-fired boiler were established respectively based on BP neural network algorithm and GA-BP algorithm, which were evaluated with the samples obtained from combustion adjustment experiments. Results show that overfitting happens when the model built on the basis of BP algorithm is used to predict the H2S concentration, while the model based on GA-BP algorithm has better approximation and generalization capability, which can be used to effectively predict the H2S concentration in a boiler, and therefore may serve as a reference for further control of H2S concentration in the boiler and for operation optimization of the unit.
  • Boiler Technology
    Numerical Simulation on Co-firing Characteristics of Coal and Biomass Gas in a 300 MW Boiler
    LI Jiahu, WANG Xiaotao, GAO Shuo, ZHANG Meng
    2020, 40(6): 440-446. https://doi.org/10.19805/j.cnki.jcspe.2020.06.002
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    To study the co-firing characteristics of coal and biomass gas for coal-fired boilers, a co-combustion model was built for a 300 MW subcritical boiler to simulate the combustion process of pure pulverized coal and mixed fuel using Fluent software, and to find out the variation law of in-furnace velocity field, temperature field, gas component and NOx distribution at different arrangements of biomass gas nozzles, during which, the quantity of biomass gas was calculated according to 20% of total heat input of the boiler under co-firing conditions. Results show that, compared with the condition of pure pulverized coal combustion, all the parameters, such as the maximum in-furnace temperature, the outlet gas temperature and the outlet NO concentration, are lower than that under co-firing conditions. The position of biomass gas nozzles has a great influence on the temperature distribution and NO emission when the overall structure of the furnace is not changed.
  • Boiler Technology
    Experimental Study on SO3 Generation and Emission of a 300 MW Energy Saving CFB Boiler
    LI Dongxiong, XU Hong'en, NIU Yongjun, ZHENG Lixing, HAN Haojie, CHENG Fangqin
    2020, 40(6): 447-453. https://doi.org/10.19805/j.cnki.jcspe.2020.06.003
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    To study the variation law of SO2 and SO3 concentration in the flue gas at outlet of a 300 MW circulating fluidized bed (CFB) boiler and its bag filter, where in-furnace limestone desulfurization and external semi-dry desulfurization combined with dust removal were adopted at different loads, experimental tests were conducted. Results show that with the increase of boiler load, the SO2 concentration in raw outlet gas of boiler decreases, while the SO3 concentration increases. In the presence of excess oxygen in the boiler and under the grading supply of secondary air, both the furnace temperature and fluidizing velocity are the main factors influencing the in-furnace SO3 concentration, leading to the obvious increase in SO3 concentration at the load above 75%, which gets up to 18.5 mg/m3 at 100% load. For the external flue gas sulfur/ash removal system, the combined action of slaked lime, desulfurization ash recycling as well as process water helps to reduce the SO3 concentration to be below 1.4 mg/m3, indicating high sulfur/ash removal ability and good load adaptability of the integral semi-dry CFB system.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Experimental Study on Performance Optimization of an Ultra-supercritical Steam Turbine over the Whole Load Range
    XU Maoying, LIU Wei, SHEN Mingke
    2020, 40(6): 454-459. https://doi.org/10.19805/j.cnki.jcspe.2020.06.004
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    To obtain the sliding pressure curve with small change in unit economy over the whole load range, performance optimization tests were carried out on a 1 000 MW ultra-supercritical steam turbine unit, including the overall performance test, the wide-load steam distribution test, the variable back pressure performance test and the circulating pump optimization test, etc. The sliding pressure curve over the whole load range was optimized according to the actual back pressure characteristic curve and the results of the circulating pump optimization test, thus to achieve high efficiency of the unit with required rate of load respone. Results show that when the unit runs at the same load under different openings of the high-pressure control valve, the full-open operation mode would result in the highest cylinder efficiency, the lowest heat consumption, the highest unit economy, but relatively slow load response simultaneously.The requirement on load response could be satisfied at 38% opening of the high-pressure control valve.
  • Steam Turbine and Gas Turbine
    Correlation of Droplet Surface Tension Correction Coefficient with Steam Expansion Rate and Inlet Parameters
    PENG Shuxuan, YANG Ailing, CHEN Eryun
    2020, 40(6): 460-468. https://doi.org/10.19805/j.cnki.jcspe.2020.06.005
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    It is difficult to predict the spontaneous condensation process of steam due to the obvious non-equilibrium characteristics of the process. Based on the non-equilibrium condensation model, and using correction coefficient to modify the surface tension of droplets, numerical simulations were carried out on the steam flow with spontaneous condensation in a Laval nozzle and a planar cascade, so as to analyze the influence of surface tension correction coefficient on the simulation accuracy for steam flow with spontaneous condensation, focusing on the correlation of optimal value of correction coefficient with the steam expansion rate and inlet parameters, and analyze their variation law with inlet parameters. Results show that under same working conditions, the optimal value of surface tension correction coefficient is not sensitive to the change of steam expansion rate, which is not significantly correlated with the total inlet temperature, and is positively correlated with the total inlet pressure. By fitting the triple relation curve between the optimal value of surface tension correction coefficient and the total inlet pressure based on numerical results, the optimal range of surface tension correction coefficient could be determined in the case that the total inlet pressure lies in the range from 1.5×104 Pa to 9.8×104 Pa, which may serve as a reference for numerical simulation of low-pressure wet steam flow in steam turbines.
  • Steam Turbine and Gas Turbine
    Operation Optimization of Advanced Gas Turbine Combined Cycle Units Based on IGV Control Strategy
    GUO Rong
    2020, 40(6): 469-474. https://doi.org/10.19805/j.cnki.jcspe.2020.06.006
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    To optimize the operation performance of advanced gas turbine combined cycle units and improve their energy efficiencies, numerical simulations were carried out under varying working conditions on an advanced unit using organic Rankine cycle to recover the waste heat from the gas turbine, so as to analyze the effects of following factors on the operation performance of the combined cycle unit, such as the ambient temperature and the angle of compressor inlet guide vane (IGV), etc., and finally to propose a modified IGV control strategy. Results show that under varying load conditions and at different ambient temperatures, the operation performance of the combined cycle unit could be optimized by regulating the ratio of fuel to air, thus to improve its energy efficiency accordingly.
    • Automatic Control
  • Automatic Control
    Superheated Steam Temperature Sliding Mode Control Based on Modified Super-twisting Algorithm
    LUO Yi, WANG Wei
    2020, 40(6): 475-480. https://doi.org/10.19805/j.cnki.jcspe.2020.06.007
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    According to the characteristics of large inertia, large time delay and nonlinearity of the controlled object as boiler superheated steam temperature in thermal power plant, the sliding mode variable structure control (sliding mode control) was applied to the cascade superheated steam temperature system. To reduce the steady-state error caused by external disturbances, and to weaken the chattering problem of sliding mode, a new sliding mode control algorithm was designed by introducing the integrating element, and using the modified super-twisting algorithm to replace the switching control. On Simulink platform, simulations were conducted for the high order model of superheated steam temperature system, such as the step response simulation, model parameter mismatch simulation and robustness simulation, etc. Results show that compared with conventional cascade PID control, the algorithm proposed has better dynamic performance, such as shorter regulation time, smaller overshoot and stronger robustness, etc.
    • Environmental Protection Technology and Equipment
  • Environmental Protection Technology and Equipment
    Experimental Research on Denitrification Process by Reagent Injection in the High-temperature Reduction Zone
    LU Xu, WU Qinglong, ZHANG Xiangyu, BAI Wengang, ZHANG Bo, GAO Ning, XU Hongjie
    2020, 40(6): 481-485. https://doi.org/10.19805/j.cnki.jcspe.2020.06.008
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    A mechanism model of denitrification process by high-temperature reagent injection was established, so as to study the effects of following factors on the denitrification efficiency, such as the reaction temperature, oxygen concentration, NSR and residence time, etc., while an experiment was carried out in a one-dimensional pulverized coal furnace. Results show that the temperature window of high-temperature reagent injection is 1 200-1 600℃, with an oxygen content being less than 1%, an NSR range of 1.0-1.3, and a residence time being more than 0.4 s. The CO concentration has nearly no effect on the denitrification efficiency. When the bituminous coal is taken as the fuel, the denitrification efficiency by high-temperature reagent injection could reach 48%.
  • Environmental Protection Technology and Equipment
    Modeling of the SCR Denitration Reactor in a Thermal Power Unit Based on Random Forest Algorithm
    XU Zhuang, KANG Yingwei
    2020, 40(6): 486-491. https://doi.org/10.19805/j.cnki.jcspe.2020.06.009
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    In view of the complex and variable process of the SCR denitration reactor in a thermal power unit, the NOx concentration at the reactor outlet is hard to be accurately predicted by mechanism modeling. Based on the historical operation data of thermal power plants, by combining the principal component analysis (PCA) with random forest (RF) algorithm, a dynamic model was established for the SCR denitration reactor. In the modeling process, the PCA method was used to calculate the contribution rate of each variable to filter the variables, then the random forest model was experimentally verified, and its prediction performance was compared with that of the support vector machine (SVM) and back propagation neural network (BPNN). Results show that it is feasible and effective to use the PCA variable selection method to determine the input variables of the SCR system model. Compared with SVM and BPNN, the SCR system model obtained by RF algorithm has better prediction effect.
  • Environmental Protection Technology and Equipment
    Study on Immobilization of Heavy Metals in a Waste SCR Catalyst During High-temperature Melting Treatment
    ZHOU Hao, XU Jianuo, ZHOU Mingxi, NI Yuguo
    2020, 40(6): 492-501. https://doi.org/10.19805/j.cnki.jcspe.2020.06.010
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    To investigate the immobilization behavior of heavy metals As, Pb, Se and V in a waste SCR catalyst during the process of high-temperature melting treatment, a series of melting experiments were conducted with the addition of composite additive CaO-Fe2O3-SiO2-Al2O3 and coke in a high-temperature tubular furnace, so as to analyze the effects of melting temperature and time on the leaching toxicity and volatilization property of the heavy metals using X-ray diffraction (XRD), scanning electron microscope (SEM) and heavy metal leaching tests. Results show that the heavy metals in waste SCR catalysts could be effectively stabilized by high-temperature melting treatment technology. The melting temperature significantly affects the leaching toxicity and volatilization property of heavy metals in a waste SCR catalyst; the leaching concentration of As, Pb, Se and V decreases remarkably with increasing melting temperature. The volatilization rate follows the order of Pb>Se>As>V, in which the volatilization rate of Pb and Se increases first and then decreases with rising temperature, and that of As and V is close to zero. With the rise of melting time, the leaching concentration of As, Se and V increases first and then decreases, while that of Pb decreases monotonously. The melting time exerts little influence on the volatilization of heavy metals in a waste SCR catalyst.
  • Environmental Protection Technology and Equipment
    Analysis on Factors Influencing the Control of Wet Plume
    ZHAO Lizheng, SUN Baomin
    2020, 40(6): 502-508. https://doi.org/10.19805/j.cnki.jcspe.2020.06.011
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    Based on the model of wet plume diffusion and pollutant sedimentation, the impact of wet plume on the environment was analyzed, while the effects of air and flue gas properties on the formation and control of wet plume were studied. Results show that the exhaust temperature has great influence on the maximum concentration of pollutants deposited from wet plume, while the air temperature affects more on the diffusion of wet plume. The technology of flue gas condensation and reheating has a wide range of applications. The ambient temperature and relative humidity have great influence on the elimination of wet plume. Flue gas condensation could help to lower the average outlet temperature after flue gas reheating and reduce the energy consumption accordingly.
    • New Energy
  • New Energy
    Physical Property Changes of the Working Medium in Transcritical Region and Aerodynamic Analysis of the S-CO2 Turbine
    WANG Zhi, KUANG Xuanyi, LIU Yali, LI Zhibin, YAN Ruiming
    2020, 40(6): 509-516. https://doi.org/10.19805/j.cnki.jcspe.2020.06.012
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    The supercritical carbon dioxide (S-CO2) turbine has been widely used in solar power generation systems, but local loss may cause partial working medium to flow in the subcritical region of the turbine. To explore the influence of physical property changes of carbon dioxide in the transcritical region on the performance of the turbine, nozzle experiments, thermodynamic and aerodynamic design, three-dimensional modeling and numerical simulation were conducted for a single-stage axial-flow turbine. It has been found that the physical properties of carbon dioxide change rapidly in the transcritical region, which is easy to produce flow separation, reflux and other phenomena. The transcritical region tends to appear at the trailing edge of nozzles and at the leading edge on suction surface of moving blades, where the efficiency drops to some extent. The appearance of transcritical region could be avoided by increasing the outlet pressure, elevating the temperature, and adjusting the speed or optimizing the airfoil, etc., thus to improve the efficiency of the turbine.