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    Boiler Technology
  • Boiler Technology
    Experimental Study on Slagging Mechanism in an Opposite Firing Boiler and the Countermeasures
    DANG Lingui, CHEN Guoxi, WANG Chunyu, LI Min, CUI Erguang, XU Mingfeng
    2015, 35(10): 781-785.
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    Cold tests and numerical simulation were conducted to study the causes leading to slagging in an opposite firing boiler with swirl burners, which was found to be formed mainly in the area surrounding the burners through site and macro-morphology inspection, and was subsequently found to be caused by outlet airflow divergence through cold tests. Simulation results proved the outlet airflow divergence to be resulted from large cone expansion angle, which could be solved by adding a new cone to reduce the angle. By taking appropriate countermeasures, the boiler slagging is obviously alleviated and the safety of unit operation is remarkably improved.
  • Boiler Technology
    Design of Control Programs for Air/Gas Circulation and Combustion Subsystem of an Oxy-fuel Combustion Boiler
    HUANG Yongli, LIU Jie, LIU Zhaohui, ZHENG Chuguang
    2015, 35(10): 786-791.
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    Based on technical feasibility, operational safety, equipment usability and system reliability of the oxy-fuel combustion technology, several design criteria were discussed and set up for control programs of the air/gas circulation and combustion subsystem in an oxy-fuel boiler. Results show that the main difference between oxy-fuel and traditional air combustion system lies in the control of boiler side air/gas circulation subsystem and burning subsystem, including following major processes: mode switching, oxygen supply and air distribution, combustion control, air/gas circulation as well as gas discharge and compression, etc. The control principles and strategies proposed can satisfy the control requirements of every process in relevant systems.
  • Boiler Technology
    Effects of Pyrolysis Temperature on Pyrolysis Products of Two Kinds of Coal in a Fluidized-bed Reactor
    XIA Zhixiang, CEN Jianmeng, TANG Wei, LI Chao, FANG Mengxiang, WANG Qinhui, LUO Zhongyang
    2015, 35(10): 792-797.
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    A comparative analysis was conducted on the pyrolysis process of Xiaolongtan lignite and Lizuizi bituminous coal under different pyrolysis temperatures using a small-scale fluidized bed pyrolysis reactor, thus obtaining the change rule of pyrolysis product yield and components. Results show that compared with Lizuizi bituminous coal, the low rank Xiaolongtan lignite has a higher pyrolysis gas yield containing high concentrations of H2 and CO2, and low concentration of CH4, and has a lower tar yield containing high concentration of hydrocarbons. When the pyrolysis temperature is raised from 500 ℃ to 700 ℃, the gas yield of both Xiaolongtan lignite and Lizuizi bituminous coal increases significantly, while the semi-coke yield decreases. The tar and pyrolysis water yield rises first and then decreases with the increase of temperature, which reaches the maximum at 550-600 ℃. With the rise of pyrolysis temperature, the concentration of H2 in coal gas increases obviously, and that of CO2 decreases to some extent; whereas the mass fraction of hydrocarbons in tar decreases and that of naphthalene aromatics increases simultaneously.
  • Boiler Technology
    Passive Location of Multi-source Leakage in Power Plant Boilers Based on Multiple TDOA Recognition
    AN Liansuo, FENG Qiang, SHEN Guoqing, JIANG Genshan, ZHANG Shiping, WANG Peng
    2015, 35(10): 798-804.
    Abstract ( )   Knowledge map   Save
    To solve the problem of multi-source leakage in power plant boilers, key technologies of passive location about multiple time delay of arrival (TDOA) recognition and location were studied. The specific way is to measure the multiple TDOA using GCC-PHAT, study the accuracy of GCC-PHAT through Gaussian white noise within boiler background noise, choose SI algorithm for location, exclude false leakage source by three-array maximum heterogeneous density cluster algorithm, and simulate the leakage condition under single-, dual- and triple-source environments. Results show that the GCC-PHAT algorithm can effectively identify the multiple TDOA under multi-source environments, and the range of error is 0.01 ms under the signal-to-noise ratio(SNR) of -6 db. With the rise of array elements, the accuracy of SI algorithm increases, and that of three-array maximum heterogeneous density cluster algorithm is kept within 1.3%. The number and position of leakage source can be effectively identified through multiple TDOA recognition and triple-array maximum heterogeneous density cluster algorithm.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    A Method to Diagnose the Performance Degradation of a Gas Turbine Based on Transient Process
    ZHANG Meng, ZHOU Dengji, ZHANG Huisheng, SU Ming
    2015, 35(10): 805-809.
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    Applying the definition of accumulative deviation and based on transient process, a comparison was made to operating parameters of a gas turbine before and after performance degradation, during which the direct relationship between partial degradation of performance and deviation of operating parameters was obtained, and the accumulative deviation based on transient process caused by performance degradation was compared with that calculated using steady-state model. Results show that the diagnosis based on transient process is more sensitive than steady-state calculation, and some operating parameters based on transient process can be used to characterize and diagnose the performance degradation.
  • Steam Turbine and Gas Turbine
    Study on Simulation Accuracy of Combustion Models for Stabilized Non-premixed Bluff-body Flames
    YANG Zhao, LI Xiangsheng
    2015, 35(10): 810-815.
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    To investigate the characteristics of different combustion models in predicting the non-premixed bluff-body flame, numerical simulations were conducted on Sandia HM1 flames using eddy dissipation concept (EDC) model, laminar flamelet model and chemical equilibrium model coupled with two different reduced mechanisms, of which the results were compared with experimental measurements. Results show that all the combustion models could predict the temperature field and component distribution under experimental conditions. Among the three combustion models, the laminar flamelet model behaves the best because of its high prediction accuracy and high calculation speed. The EDC model succeeds in predicting the trend but over-predicts the temperature in the near-axis region. The chemical equilibrium model has advantages in predicting fully mixed region in the rear of combustion chamber. Due to its high accuracy and high speed, the laminar flamelet model may serve as a reference for further simulation of non-premixed bluff-body flames.
    • Automatic Control and Measurement Technology
  • Automatic Control and Measurement Technology
    Wet Steam Measurement for Steam Turbines Based on RGB Three Wavelength Bands Light Extinction and Single Frame Single Exposure Imaging Method
    LIU Hao, ZHOU Wu, CAI Xiaoshu, LIANG Zhihong, AI Dongming,NIE Danwen, WEI Mingye
    2015, 35(10): 816-823.
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    To reveal the mechanism of wet steam two-phase flow in steam turbines, a measurement probe was developed based on RGB three wavelength bands light extinction and single frame single exposure imaging method (SFSEI), of which the measurement accuracy was verified by experiments with 2 100 nm and 960 nm standard polystyrene particles and standard round calibration board with the diameter ranging from 50 μm to 400 μm. The probe was then applied to measure the wet steam behind the last stage of a 330 MW steam turbine in fixed pressure operation at 227 MW. Results show that along blade height direction, the size of fine droplets varies from 0.7 μm to 0.9 μm, with wetness ranging from 6% to 9%; the maximum velocity and diameter of coarse droplets may get up to 225.7 m/s and 200 μm, respectively; the velocity, size and flow angle of coarse droplets are different along the blade height. The probe system helps to effectively measure the parameters of wet steam in steam turbines, which therefore may serve as a reference for further research of wet steam.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Numerical Simulation on Separation Performance of Single-and Double-cone Separators
    SHEN Xianfeng, LIU Hanzhou, WEI Wei
    2015, 35(10): 824-829.
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    Numerical simulation was conducted to the gas-solid two-phase flow in single- and double-cone separators using CFD Fluent software. Results show that under same entry conditions, the double-cone separator, compared with single-cone one, is easier to throw particles to wall surface and bring them to the discharged port, due to its greater near-wall tangential velocity and greater axial velocity in the downstream area; the radial velocity of double-cone separator, though greater than that of single-cone one as well, hardly affects the separation performance. To the solid flow field, particles injected from different positions differ greatly in trajectory, which are easier to be separated if being injected from outside in comparison with from inside, or being injected from bottom in comparison with from top. Under same entry conditions, the separation efficiency increases with the rise of particle size, and the separation efficiency of double-cone separator is higher than that of single-cone separator.
    • Environmental Science
  • Environmental Science
    Simulation and Experimental Study on Atomizing Desulfurization Technology Adopted in Flue Duct of Desulfurization Tower
    LIU Dingping, FANG Lei, XIAO Shang
    2015, 35(10): 830-834.
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    A new technology was proposed for flue gas desulfurization at inlet flue duct of desulfurization tower, in which high-efficient atomizing nozzles are arranged at both sides of the duct, so as to premix the flue gas with atomized limestone slurry before entering the desulfurization tower, and to elongate the contact time of the slurry with flue gas. To verify the feasibility of this technology, Fluent software was used to simulate the flow field of the mixture. Results show that the technology helps to improve the uniformity of the flue gas mixture. The desulfurization efficiency may be raised from 96.75% to 97.85% when the atomizing desulfurization technology is adopted, in the case of the SO2 concentration being 1 500 mg/m3, and the A, B, C and D four spraying layers are all put into operation.
  • Environmental Science
    Correction on Catalyst Activity of SCR Denitrification System in Large Power Plant Boilers
    LI Debo, LIAO Yongjin, XU Qisheng, ZENG Tinghua
    2015, 35(10): 835-839.
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    A new correction method was proposed for catalyst activity of SCR denitrification system in large power plant boilers. The specific way is to correct the measured data of catalyst activity obtained in laboratory with field test results, which can reflect the real denitrification capability of the SCR reactor. Results show that the method proposed may serve as a new technical means in evaluation of catalyst renewal schemes, since it has a high accuracy in performance calculation of both the catalyst and the SCR reactor, and it is able to reflect the real activity of the catalyst used.
  • Environmental Science
    Effect of Carbon Dioxide in Flue Gas on Lead Adsorption over Carbonaceous Surfaces
    GAO Zhengyang, L Shaokun
    2015, 35(10): 840-845.
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    The effect of CO2 on lead adsorption over carbonaceous surfaces was investigated by the density functional theory B3PW91 of quantum chemistry. A model of carbonaceous surface was set up, with which two models for CO2 adsorption on carbonaceous surface were optimized, while different models for elemental lead adsorption on above CO2-contained carbonaceous surfaces were obtained. Different adsorption active sites and models were considered and their adsorption energies, bond lengths and bond population were calculated. Results show that compared to elemental lead, carbon dioxide molecules are more easily to be adsorbed on carbonaceous surface, simultaneously enhancing the adsorption of elemental lead on the surface, especially in the adsorption configuration E. Both competitively and cooperatively but mainly cooperatively, the adsorption of elemental lead on carbonaceous surface is deeply affected by carbon dioxide molecules.
    • Energy System Engineering
  • Energy System Engineering
    Application Simulation of SOFC-CHP Systems
    ZHONG Jie, ZHANG Li, XU Hong, LUO Qing, LI Peijun
    2015, 35(10): 846-852.
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    To find the most suitable system process for SOFC stacks with different fuel utilization rates(Uf), so as to meet the requirements of different stacks and users on the system output, three different models were set up for 1 kW SOFC combined heat and power (SOFC-CHP) systems by Aspen Plus, including the cathode/anode exhaust gas combustion system, anode off-gas recycling system, and combined anode off-gas recycling system with exhaust gas combustion. Results show that the cathode/anode exhaust gas combustion process is a preferred option for SOFC stacks with relatively high Uf. Both the anode off-gas recycling process and the combined anode off-gas recycling process with exhaust gas combustion are preferred options for SOFC stacks with relatively low Uf; however, to achieve relatively high heat efficiency on the basis of ensuring high power efficiency, the combined anode off-gas recycling process with exhaust gas combustion is the optimal option.
  • Energy System Engineering
    Numerical Simulation on Combustion Characteristics of Methane-Propane Binary Mixture in a Reverse Flow Catalytic Reactor
    ZHU Yingying, CHEN Geng, LI Xinbao, YANG Qi
    2015, 35(10): 853-858.
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    Numerical simulation was conducted to study the combustion characteristics of methane-propane binary mixture in a reverse flow catalytic reactor. Taking the total adiabatic temperature rise as benchmark parameters, the effects of both methane ratio and superficial gas velocity on the reactor behiavor and extinction limit were studied. Results show that the reaction rate of both methane and propane is fast within a narrow zone near the entrance of reactor, but the reaction rate of methane is lower than that of propane. The temperature level in the reactor increases with rising methane ratio, and the reverse catalytic reactor exhibits a contrary behavior that the bed temperature increases with the decrease of reaction rate. The catalytic combustion process of both methane and propane is controlled by the intrinsic reaction rate and the mass transfer rate. The extinction limit is almost the same when only methane or propane is combusted, which would get higher for binary mixture combustion. The extinction limit would reach the maximum when methane ratio in the mixture is about 0.5.
    • Material Science
  • Material Science
    Study on Oxidation Behaviours of HR3C in Air and Pure Steam at 750 ℃
    YANG Zhen, LU Jintao, ZHAO Xinbao, YUAN Yong, YAN Jingbo,YIN Hongfei, DANG Yingying
    2015, 35(10): 859-864.
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    The oxidation behavior of austenitic stainless steel HR3C was studied respectively in static air and pure steam for 500 h at 750 ℃ using scanning electron microscopy and X-ray diffraction, so as to investigate the oxidation mechanism of HR3C in above 2 atmospheres, based on detail characterization on the microstructure of relevant oxide scales. Results show that a continuous layer of (Cr, Mn)2O3 scale forms on the surface of HR3C in both the atmospheres; the oxidization kinetics of HRC presents a two-stage parabolic law in static air; the existance of water vapor promotes the cracking of (Cr, Mn)2O3 scale, and accelarates the oxidation of the alloy, resulting in deviated parabolic law of the HR3C growth kinetics in pure steam; the cracking of (Cr, Mn)2O3 layer is induced by the interaction of scale/alloy interfacial voids and the growth stress in the scale, which makes bare alloy directly exposed to the high-temperature air or pure steam, thus forming Fe3O4 nodules.