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    Boiler Technolog
  • Boiler Technolog
    Experimental Study on Water Wall Heat Load Distribution of Supercritical Pressure W-flame Boilers
    YANG Yong, YU Guying, CHEN Duanyu, ZHOU Wentai,YANG Yao, WANG Pu, LI Jianping
    2015, 35(6): 429-436.
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    By measuring the water wall temperature and calculating the heat load in furnace of 2×600 MW supercritical pressure W-flame once-through boilers, the heat load distribution was analyzed under different working conditions. Results show that the heat load distribution at lower water wall is highly affected by the mode of coal mill operation; during start-up process, the heat load distribution is not uniform at lower water wall, but most of the heat load is kept within 400 kW/m2; under full load conditions, the heat load is high and unevenly distributed; the combustion of front wall is stronger than that of rear wall.
  • Boiler Technolog
    Fuzzy Comprehensive Evaluation on Combustion Stability and Economy of a Power Plant Boiler Based on Furnace Parameters Measurement
    WANG Dongfeng, LIU Qian, ZHAO Wenjie, HAN Pu
    2015, 35(6): 437-444.
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    The effects of furnace parameters on combustion stability and economy of a boiler were analyzed. A new comprehensive method for evaluating the boiler combustion stability and economy was presented from three aspects, i.e. furnace temperature, O2 volume fraction and CO mass concentration. Taking a 680 MW coal-fired boiler as an example, fuzzy comprehensive evaluation of the boiler combustion stability and economy was carried out based on furnace parameters measurement. Results show that the evaluation of boiler combustion stability and economy can be effectively completed by the method proposed under different working conditions.
  • Boiler Technolog
    Relationship Between Combustion Characteristic Temperature and Metamorphic Grade of Coal
    ZHU Chuan, LUO Yunfei, ZHANG Yuhong, GAO Yan
    2015, 35(6): 445-450.
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    Effects of ignition temperature, peak temperature and burnout temperature of coal on the volatile matter w(Vdaf) and carbon content w(Cdaf) reflecting metamorphic grade of the coal were investigated by thermogravimetric experiments and vitrinite reflectivity analysis, so as to study the relationship between the position of combustion rate peak and the metamorphic grade. Results show that under temperature-programmed conditions, the ignition temperature increases with the rise of metamorphic grade; the peak temperature and burnout temperature show a good linear relationship with the ignition temperature, with correlation coefficients of R2=0.961 4 and R2=0.956 6 respectively. The relative position of combustion rate peak well reflects the degree of metamorphic grade, i.e. the relative position of combustion curve and combustion rate peak for the coal with high metamorphic grade lies in the high temperature region, whereas the relative position of combustion curve and combustion rate peak for the coal with low metamorphic grade lies in the low temperature region.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Influence of Journal Temperature Difference on Vibration of the Sliding Bearing
    HE Wenqiang, TIAN Yongwei, YANG Jiangang
    2015, 35(6): 451-456.
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    Based on the journal temperature calculation model set up by considering oil thermal phenomenon of the sliding bearing, both the factors influencing the temperature difference and the effects of temperature difference on the bearing vibration were analyzed, which were subsequently studied on a test rig and a turbo-generator, while the journal temperature difference was measured at different rotational speeds, so as to verify the calculated results. Study results show that the journal temperature difference would get up to a certain value with the increase of operation time, and there is a close relationship between the unsteady vibration and the journal temperature difference; the journal temperature difference affects the vibration of sliding bearing. For overhung rotors, the journal temperature difference may easily result in unsteady vibration, which can be mitigated by raising the oil temperature.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Simulation of Flow Process of Two Droplets with Large Density Ratio Impacting on Liquid Film by Two-phase Lattice Boltzmann Method
    LI Long, JIA Xiaodong, LIU Yongwen, SU Ming
    2015, 35(6): 457-462.
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    Based on the latest developed two-phase lattice Boltzmann model, the flow process of two droplets impacting on liquid film was simulated, which have certain level interval with large density ratio,while the dynamic process of droplets impacting on liquid film was studied with different original distance between two droplets and different Reynolds number,so as to analyze the effects of original distance, Reynolds number and other parameters on the impacting and splashing behavior. Meanwhile, the variation of the height of splashed water in the middle area with time was investigated, and the mechanism of impacting and splashing was also analyzed. Results show that,within certain range,the larger the original distance and the Reynolds number ar,the faster the rise of the splashed height will be in the middle area;larger Reynolds number would lead to stronger impacting, when some droplets would separate from the top of the splash.
  • Engineering Thermophysics
    Effects of Venturi Tube Structure on Flow Field of the Combustion Chamber
    ZHANG Yang, ZOU Jianfeng, ZHENG Yao
    2015, 35(6): 463-468.
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    To investigate the effects of venturi tube structure on flow field characteristics of the combustion chamber, three-dimensional numerical simulation was carried out to a single stage axial swirler/venturi tube. Results show that as the divergence angle increases, both the radial expansion intensity and diameter of recirculation zone increase; when the venturi tube's divergence angle and contraction ratio change, double-, triple- and quadruple-vortex will occur in the recirculation zone, and the vortexes distributed in tandem are equivalent to the main and secondary vortex, bringing benefits to the ignition and combustion of the combustion chamber; the length and back-flow velocity of central recirculation zone increase with the rise of venturi tube's contraction ratio; the structure of triple- and quadruple-vortex is more stable than that of double-vortex, which helps to extend the range of available load, and therefore improve the performance of the combustion chamber.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Analysis and Experimental Study on Heat Transfer Formula for Plate and Shell Heat Exchangers
    LIU Jiarui, ZHAO Wei, HUANG Xiaodong, ZHANG Hua, YU Xiaoming
    2015, 35(6): 469-475.
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    Experimental studies were conducted to the heat transfer formula for plate and shell heat exchanger (PSHE), based on the assumption that the plate and shell heat exchanger is a special kind of plate heat exchanger. By analyzing and comparing the applicability of different research methods, such as wall temperature determination method, equal Reynolds number method, Wilson graphical method and equal velocity method, the equal velocity method was finally selected in the experimental study, with which test and verification experiment were respectively performed. In the test experiment, both the inlet and outlet flow rate were controlled to be the same, while in the verification experiment, the flow rate in hot side was kept constant, but that in cold side was changed. The data thus obtained were used to fit the heat transfer formula and calculate the error of heat transfer coefficient. Results show that the relative error of heat transfer coefficient is less than 5%, indicating the heat transfer formula is available, and the study method for heat transfer in plate heat exchanger may serve as a reference for plate and shell heat exchanger.
    • Environmental Science
  • Environmental Science
    Effects of Boiler Control Mode on Ammonia Escape of the SCR System in a 660 MW Ultra-supercritical Unit
    YANG Jianguo, HU Jinyi, ZHAO Hong, WAN Chaohui,KANG Kewei, CHEN Lishuai, ZHOU Ailin
    2015, 35(6): 476-480.
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    The experimental tests were carried out to a 660 MW ultra-supercritical unit to study the effects of boiler control mode on the ammonia escape. Results indicate that the ammonia escape rate would increase with the rise of denitration efficiency. Especially when the denitration efficiency is higher than 65% (designed value), the increasing rate would be larger. The NOx concentration at SCR's inlet has an optimum value (about 200 mg/m3) to corresponding the lowest ammonia escape rate. The ammonia escape rate would increase obviously with higher SOFA rate (optimum value is 18%) or oxygen concentration (optimum value is 3%),which would decrease with the reduction of unit load. When the unit load drops to 500 MW or lower, the ammonia escape rate would decrease by about 60%.
  • Environmental Science
    Flow Field Optimization for SCR System of Coal-fired Power Plants
    ZHU Tianyu, LI Debo, FANG Qingyan, CHEN Gang
    2015, 35(6): 481-488.
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    A numerical study was carried out to evaluate the gas flow uniformity and fly ash deposition in the SCR reactor of a 600 MW supercritical coal-fired unit. The influence of deflector arrangement and structure on flow field and fly ash deposition in the reactor was studied through comparing the inhomogeneity of flue gas velocity distribution in the top catalyst layer after adding ash dispersed phase. Results show that when the number of deflectors installed at reactor inlet is thirteen, the flue gas velocity would be more uniformly distributed in the top catalyst layer than other three conditions; the deflector made up by an arc panel plus a vertical panel is comprehensively considered to be the most optimal structure, which helps to further guide the gas flow and reduce the refluxing effect, and therefore makes the gas velocity be more uniform in the top catalyst layer; a group of thirteen deflectors in arc-straight shape are beneficial to the reduction of ash deposition upon the reactor wall; fly ash particles affect little on the internal field of SCR reactor, where soot blowing is generally required in actual operation.
  • Environmental Science
    Impact of Beam Structure on Catalyst Abrasion in the Denitrification System
    SHENG Bo, WEI Hongqi, ZHU Yadi
    2015, 35(6): 489-494.
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    Cold test and numerical simulation were combined to analyze the gas-solid two-phase flow over the catalyst in the SCR denitrification device. Results indicate that the abrasion of catalyst is largely caused by the beam structure. After hitting the beam, the air flow forms high-speed dusty air flow in different directions on the surface of the catalyst, strongly eroding the catalyst, which cause serious abrasion with different characteristics on catalysts under both sides of the beam. Air flow velocity is the main cause of catalyst abrasion and fly ash concentration is the secondary cause. By modifying the beam structure in an appropriate way, the air flow distribution is improved and the catalyst abrasion is reduced, resulting in guaranteed efficiency and safety operation of the denitrification device.
    • New Energy
  • New Energy
    Study on Characteristics of Woody Biomass Isothermal Carbonization
    LI Shuai, ZHANG Jubing, PIAO Guilin, XIE Hao, XIA Guangbi, JIANG Xiaoxiang
    2015, 35(6): 495-500.
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    Experimental studies on isothermal pyrolysis characteristics of pine particles were carried out in a self-developed thermogravimetric test setup, so as to analyze the carbonization law of woody biomass particles at different reaction temperatures, and to obtain the kinetic parameters. Additionally, the influence of carbonization temperature on the charcoal properties was explored based on analysis of the carbonization products. Results show that the fuel property of pine carbon approaches bituminous coal when the carbonization temperature exceeds 250 ℃, which is similar to anthracite at further elevated carbonization temperature; a certain degree of gasification reaction occurs during the carbonization process when the temperature reaches 650 ℃. The kinetic parameters vary with the reaction degree during isothermal carbonization, manifesting as gradual increase in reaction order and gradual decrease in apparent activation energy and corresponding frequency factor.
  • New Energy
    Velocity and Layout Optimization of Parabolic Trough Solar Systems
    YU Gang, LUO Na, HOU Hongjuan, YANG Yongping
    2015, 35(6): 501-508.
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    Based on study of parabolic trough solar collector structure and its photo-thermal energy conversion process, a lumped parameter dynamic model with features of multiple heat capacities and changeable physical properties was developed and subsequently verified with experimental data of LS-2 parabolic trough solar collectors. Combining with models of the pump, valve and other modules in the simulation platform, a model of parabolic trough solar system was set up and verified with actual operation data of SEGS-VI plants. On above basis, the variation trends of collecting efficiency and pump power consumption with diverse irradiation and oil velocities were analyzed, after which the optimal equivalent efficiency, oil velocity and length per loop were determined under different operating conditions. Results show that at the same inlet and outlet oil temperature, the greater the solar irradiation is, the higher the equivalent efficiency of the solar system will be. When the solar irradiation rises from 500 W/m2 to 1 000 W/m2, the optimal velocity of hot oil varies from 2 m/s to 3 m/s. Besides, under constant solar irradiation conditions, the optimal equivalent efficiency decreases with the increase of oil working temperature.
    • Material Science
  • Material Science
    Study on Steam Oxidation of 4 Boiler Tube Materials at 650 ℃/26 MPa
    MA Yunhai, ZHENG Kaiyun
    2015, 35(6): 509-516.
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    The oxidation behavior of S30432 steel, TP347H steel, TP310HCbN steel and T91 steel in water vapor atmosphere at 650 ℃/26 MPa was investigated. After oxidation for 1 500 hours, the oxidized samples were investigated gravimetrically and the oxides formed were studied by X-ray diffraction (XRD). Cross-sections through the scale were analyzed by SEM/EDS to show the thickness, morphology and microstructure and to measure the chemical composition of the oxide scales. Results show that the oxidation behavior of above materials is quite different, and their steam oxidation resistance greatly depends on the Cr content in the material. Double-layered oxides form in the S30432, TP347H, TP310HCbN and T91 steel, which include an inner Cr-rich spinel oxide layer and an outer Fe-rich oxide layer (Fe3O4 or Fe3O4+Fe2O3). The voids and cavities formed in the scale will turn into channels for outward diffusion of metallic ions and inward diffusion of oxygen and water molecules, to some extent contributed to the increase of oxidation rate. Buckling model applies to the oxide exfoliation mechanism of S30432 steel, TP347H steel and TP310HCbN steel, while wedging model applies to that of the T91 steel.