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    Boiler Technology
  • Boiler Technology
    Study on Water Wall Temperature and Heat Load Distribution in 1 000 MW Tower-type Once-through Boilers
    CHEN Duanyu, FAN Chenghao, YANG Yong, ZHANG Fuxiang, ZHU Caiguang
    2013, 33(5): 329-334.
    Abstract ( )   Knowledge map   Save
    By measuring the water wall temperature and calculating the heat load in furnace of 2×1 000 MW ultra-supercritical pressure tower-type once-through boilers, the tube wall temperature and heat load distribution were analyzed under different working conditions at different modes of coal mill operation, including the heat load distribution of vertical water wall on upper part of the furnace. Results show that the heat load distribution in 1 000 MW tower-type once-through boiler is basically the same as that of other tangential-firing boilers. The heat load distribution along tube length direction at 54 m elevation changes greatly due to enhanced flue gas disturbance by over-fire air (OFA) above the top layer burners. The heat load on water wall along OFA nozzle centerline reduces considerably due to the entrance of OFA into boiler furnace. To avoid heat-transfer deterioration in large specific heat region, it is suggested that the water wall neighboring pseudo-critical point be arranged in low heat load areas.
  • Boiler Technology
    Equipment Retrofit for Co-combustion of Lignite in a 600 MW Unit
    FU Xiliang, WANG Yangang, WANG Rong, FAN Guoqiang, DONG Weibo
    2013, 33(5): 335-339.
    Abstract ( )   Knowledge map   Save
    Aiming at the problem that the co-combustion of a large amount of lignite in thermal power plants will cause inadequate drying capacity of coal mill and subsequently affect the safe operation of coal pulverizing system, a retrofit was implemented by changing the rotating direction of air preheater, increasing the angle of primary air chamber, mounting flexible seal to the air heater, and making capacity expansion to the mill nozzle, etc. Results show that after retrofit, the temperature of inlet hot primary air is further increased, the drying and milling capacity of coal mill are significantly raised, and the fan resistance is reduced; on the basis of meeting the requirement of co-firing a large-proportion of lignite, the fan power consumption is reduced, the stalling risk of primary air fan is lowered, which will bring enormous economic benefits to the enterprise.
  • Boiler Technology
    Operational Characteristic Analysis on CFB Coal-fired Boiler with Co-combustion of Paper Sludge
    SHENG Hongchan, HE Guobin, JIN Xiaoxiang, LOU Jun,LIU Daoyin, MA Jiliang, TANG Zhi, CHEN Xiaoping
    2013, 33(5): 340-345.
    Abstract ( )   Knowledge map   Save
    To study the influence of blending ratio of paper sludge on operating characteristics of a 130 t/h CFB coal-fired boiler, thermodynamic equilibrium calculation and flue gas/air resistance calculation were carried out. Results show that with the rise of blending ratio of paper sludge, the furnace exit gas temperature drops, the exhaust gas temperature increases, the boiler efficiency reduces, the inlet dry sludge rises significantly, the inlet coal quantity reduces slightly, the flue gas flow, fly ash mass and the attempering water flow increase remarkably, the primary/secondary air resistance and the flue gas resistance increase in rising gradient. Above results may serve as a reference for the retrofit of CFB coal-fired boilers to co-fire sludge.
  • Boiler Technology
    Distribution Law of Volatile Heating Values of Power Coal Throughout the World
    WANG Shichang, ZHANG Mingfu
    2013, 33(5): 346-350.
    Abstract ( )   Knowledge map   Save
    To obtain the ignition and burnout characteristics of pulverized coal, the as-received basis net calorific value was calculated for 224 typical kinds of coal all over the world according to the law of energy conservation, while ignition index CIW and burnout index FRW proposed for pulverized coal based on coal index CI and fuel ratio FR. Results show that when the mass fraction of volatile matter (dry ash-free basis) w(Vdaf)<55%, CIW improves with increasing w(Vdaf), resulting in easy ignition of coal; whereas when w(Vdaf)≥55%, CIW reduces with increasing w(Vdaf), resulting in hard ignition of coal. When w(Vdaf)<10%, FRW increases from 46 to 600 with reducing w(Vdaf), indicating a low burnout rate of coal. For different kinds of power coal, the theoretical heating value QV0net is not a constant, and when w(Vdaf) increases from 5% to 75%, QV0net reduces from 43.5 MJ/kg to 13.4 MJ/kg. The heating value ratio of fixed carbon to volatile in 1.0 kg coal increases with reducing CIW and rising FRW.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Experimental Study on Flow Regime and Stability of High-pressure Dense-phase Pneumatic Conveying
    LU Peng, HAN Dong, PU Wenhao, CHEN Xiaoping, ZHAO Changsui
    2013, 33(5): 351-357.
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    Experimental study on flow regime of pulverized coal (300 μm) and quartz sand was visually conducted on a high-pressure dense-phase pneumatic conveying test rig at a pressure up to 4 MPa and solid-gas ratio up to 700 kg/m3, so as to obtain the flow regime of both the pulverized coal and the quartz sand under different superficial gas velocities, and analyze the influence of supplementary air volume on delivery stability of the 300 μm pulverized coal. Results show that with the reduction of superficial gas velocity, the flow regime of pulverized coal is in turn of the suspension, stratified and slug flow kind; whereas for quartz sand, the flow regime is in turn of the stratified, slug and plug flow type, with a more distinguishable difference among various patterns; the flow regime becomes unstable with reducing superficial gas velocity, which indicates in the oscillation of pipeline and the fluctuation of pressure; when 300 μm pulverized coal is conveyed, the supplementary air with excessively low flow rate will lead to pipe blocking failure; both the slug and plug flow are of the interrupted kind, and the latter one is a low-speed flow, which is even more unstable and complicated than the former one.
  • Engineering Thermophysics
    Numerical Simulation on Heat-transfer Characteristics of Radiator in 1 000 MW Direct Air-cooling Units
    HAN Zhonghe, MA Wu, WANG Zhi
    2013, 33(5): 358-363.
    Abstract ( )   Knowledge map   Save
    Taking the 1 000 MW direct air-cooling unit as an example, numerical simulation was carried out on external flow field of its radiator, so as to analyze the influence of following factors on external heat-transfer and flow characteristics of the radiator, such as the head-on wind velocity, ambient temperature, fin spacing and fin thickness, etc. Results show that with the rise of head-on wind velocity, both the external heat-transfer coefficient and flow resistance increase significantly; ambient temperature affects little on both the external heat-transfer coefficient and flow characteristics, but influences much on the total heat release. By enlarging the fin spacing, the external heat-transfer coefficient may be raised and the flow resistance may be reduced, however, this will lead to reduction of heat-transfer area per unit length of tube, resulting in decreased total heat release. For a fixed head-on wind velocity, there exists a reasonable fin spacing and fin thickness, which respectively increases and reduces with rising head-on wind velocity.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Influence of Inlet Structure on Separation Efficiency of Cyclone Separators
    SUN Sheng, ZHOU Hao, QIU Kunzan, DONG Kang, CEN Kefa
    2013, 33(5): 364-369.
    Abstract ( )   Knowledge map   Save
    Taking the 135 MW circulating fluidized bed boiler as an object of study, a cyclone separator cold-state test setup was built in the scale of 1:10, with which the influence of inlet duct structure (angular-transition and smooth-transition) and entrance inclination angle (15°, 30°, 45°) on the separation efficiency of the cyclone separator was studied. Results show that the separation efficiency of cyclone separator with angular-transition inlet duct is higher than that with smooth transition inlet duct under same working conditions; the separation efficiency firstly increases and then decreases with the rise of entrance inclination angle; the variation law of classification efficiency with inlet duct structure and entrance inclination angle agrees well with that of the total separation efficiency.
  • Auxiliary Equipment Technology
    Thermo-economic Analysis for Water Make-up System of Power Plant Condensers
    HU Yong, LIU Jizhen, ZENG Deliang, MENG Qingwei, LI Yazhe
    2013, 33(5): 370-374.
    Abstract ( )   Knowledge map   Save
    Dynamic characteristics of power plant condenser were studied using small disturbance theory and thermo-economic state equations, during which the influence of water atomization make-up mode on both the condenser vacuum and unit efficiency was analyzed, while the variation law of unit efficiency with water make-up mode and make-up water temperature studied with actual examples. Results show that when chemical water of a certain temperature is atomized by nozzle and fed into the system through condenser throat, the cold end loss of system may be reduced, the back pressure of unit may be lowered and the thermal economy of system may be raised; with the rise of make-up water temperature, ΔP reduces gradually while ΔN rises slowly.
  • Auxiliary Equipment Technology
    Experimental Study on Noise Characteristics of Centrifugal Pump Based on Near-field Acoustic Pressure Method
    YE Xuemin, PEI Jianjun, LI Chunxi, LIU Zi
    2013, 33(5): 375-380.
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    Experimental studies on noise characteristics of a IS65-50-160A centrifugal pump were carried out using near-field acoustic pressure method on an open test bench, during which the variation and frequency characteristics of pump noise versus net positive suction head were investigated at variable and constant flow rates, while an analysis performed to the influence of flow rate, net positive suction head and air volume at pump suction inlet on the A-weighted sound pressure level and the sound pressure level at different frequencies. Results show that the A-weighted sound pressure level increases with the flow rate and reaches the maximum in the high efficiency range under non-cavitation conditions. A-weighted sound pressure level decreases significantly in the beginning of cavitation occurrence, but rises greatly when cavitation is fully developed. The sound pressure level respectively with high frequency of 1 000 Hz and 2 000 Hz has significant contribution to the overall A-weighted sound pressure level. The sound pressure level at most flow rates has peak values at 250 Hz and 1 000 Hz, which is related with the blade passing frequency. During the cavitation process, which is induced by regulating the inlet pump valves to keep the flow rate constant, the A-weighted sound pressure level drops obviously due to air entrained from the pump inlet; the characteristic frequency of pump for cavitation test is 250 Hz, in which case the difference of peak pressure level between cavitation and non-cavitation situation is within 5.9-16.4 dB.
    • Energy System Engineering
  • Energy System Engineering
    Feasibility Study on Test Schemes for Coupling Air Turbine System of Salaqi 300 MW CFB Boiler Unit
    WANG Yuzhao, LI Jianfeng
    2013, 33(5): 381-386.
    Abstract ( )   Knowledge map   Save
    To reduce the service power rate of thermal power unit via coupling air turbine system, 3 test schemes were proposed for Salaqi 300 MW circulating fluidized bed(CFB) boiler unit, among which schemes 1 and 3 don’t need to retrofit the air heater, but scheme 2 does. Based on the survey to performance parameters and price of relevant test facilities, the calculation of heat flux distribution in each scheme was carried out and a comparison was made among the schemes. Results show that by comprehensively considering the energy-saving effect, test cost and impact on normal operation of the unit, scheme 3 is regarded as the best option among all the 3 schemes, of which the energy-saving effect is better than scheme 1 due to its lower exhaust gas temperature, and its test risk is lower than scheme 2 since it is not necessary to retrofit the air heater.
  • Energy System Engineering
    Multi-objective Optimization of Low-temperature Waste-heat ORC Power Generation Systems
    WANG Man, WANG Jiangfeng, YAN Zhequan, MA Shaolin, DAI Yiping
    2013, 33(5): 387-392.
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    Owing to the limitations of single-objective optimization on existing organic Rankine cycle (ORC) power generation system, a multi-objective optimization design was conducted for the low-temperature waste-heat ORC power generation system from the point of view of thermodynamic and economic aspects, by taking maximum exergy efficiency and minimum investment of system as the objective functions, selecting 5 key thermal parameters as the decision variables, such as turbine inlet temperature, turbine inlet pressure, pinch temperature difference, approach temperature difference and condenser temperature difference, etc., optimizing the ORC power generation system with working fluids R123, R245fa and isobutane using non-dominated sorting genetic algorithm (NSGA-II), and subsequently Pareto optimal solutions were obtained, from which the optimum design solution with optimal combinations of system thermal parameters was selected with the aid of an ideal point. Results show that under the given waste heat conditions, R245fa is the optimal working fluid in consideration of both the thermodynamic performance and the economic efficiency. The optimum solution shows an optimal exergy efficiency of 10.37% and a minimum investment of 4 558 400 Yuan.
  • Energy System Engineering
    Thermo-economic Analysis of Deaerator Exhaust Steam Recovery System with Steam Ejector Heat Pump
    CHEN Haiping, YU Xinwei, LU Guangwu, GAO Pei, ZHANG Xuelei
    2013, 33(5): 393-398.
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    To minimize the loss of heat and working medium from heat recovery system of steam turbines, energy-saving schemes were proposed for recovering exhaust steam from deaerator to low-pressure heater of a 600 MW unit using steam ejector heat pump, of which corresponding thermo-economic indexes were respectively calculated and compared using equivalent enthalpy drop method. Results show that among all the energy-saving schemes, scheme No.4 will produce the highest economic benefits when the exhaust steam is led to the No.5 low-pressure heater from deaerator by steam ejector heat pump. Compared with the original scheme, scheme No.4 may economize 990 t standard coal per year, based on the assumption that 0.3 g standard coal is saved for generation of 1 kW·h power and the unit annually operates for 5 500 h.
  • Energy System Engineering
    Analysis on Energy Balance and Reaction Heat of Sewage Sludge Pyrolysis Process
    HU Yanjun, ZHENG Xiaoyan, NING Fangyong
    2013, 33(5): 399-404.
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    Based on analysis of energy utilization, consumption and recovery in the process of sewage sludge pyrolysis according to the law of energy conservation, an energy balance model was proposed for the process of producing three-phase products from sewage sludge pyrolysis, with which the reaction heat of sewage sludge pyrolysis was calculated, while the energy balance of different pyrolysis processes evaluated by considering both the energy recovery and energy consumption rate. Results show that energy loss is unavoidable during utilization; the way to save energy is to raise the heat value of pyrolysis products and simultaneously reduce heat loss and abandoned energy; different pyrolysis conditions result in different heat loss; long retention time, low heating rate, and high pyrolysis temperature will lead to increased input energy and heat loss. Energy consumption evaluation proves the pyrolysis technology to be effective in recovering more energy and raising energy consumption rate.
    • Material Science
  • Material Science
    Influence of Strengthening Elements on Precipitation of Thermodynamic Equilibrium Phases in Inconel Alloy 740H
    FU Rui, LIN Fusheng, ZHAO Shuangqun, CHI Chengyu
    2013, 33(5): 405-412.
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    Thermodynamic calculation was carried out on the Ni-based Inconel alloy 740H for 700 ℃ advanced ultra supercritical (A-USC) superheaters and reheaters, so as to study the influence of the main strengthening elements on precipitation of the equilibrium phases. Results show that both γ′ and M23C6 in the alloy have a good stability in a wide temperature range. Elements Al, Ti and Nb affect much but element Co influences little on the precipitation of phases γ′, η and σ, in which Al promotes the precipitation and stabilization of γ′ and σ, but suppresses the precipitation of η, while Ti and Nb promote precipitation of all the phases γ′, η and σ. Elements C and Cr respectively affect much on the precipitation quantity and temperature of M23C6. The composition of Inconel alloy 740H can be optimized by reasonably control the mass fractions of elements Al, Ti, Nb, C, Cr and Co.