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    Boiler Technology
  • Boiler Technology
    Numerical Study of Gas-Solid Flow Field in a 600 MW CFB Boiler with Anti-wear Beams
    XIA Yun-fei, CHENG Le-ming, ZHANG Jun-chun, WANG Qin-hui, FANG Meng-xiang
    2013, 33(2): 81-87.
    Abstract ( )   Knowledge map   Save
    Numerical simulations were carried out to study the effect of anti-wear beams on the distribution of solids mass concentration and axial velocity both in the furnace and in the region close to the furnace wall in a 600 MW circulating fluidized bed (CFB) boiler with breeches legs, so as to comprehensively analyze the influence of granular flow on the wall abrasion. Results show that the anti-wear beams weaken the M-shape distribution of solids axial velocity in the furnace; with anti-wear beams installed on the water wall, the average solids mass concentration decreases slightly in the lower dilute region but increases slightly in the upper dilute region. Anti-wear beams block the falling down of dense particles close to the wall, which reduce both the thickness of the return flow region and the falling velocity of particles, and the smaller the gap between granular flow and wall surface is, the more obvious the influence will be. Within the area between two anti-wear beams, especially within the range of beam height, the increase degree of mass concentration and falling velocity of particles adhering to the wall is higher than that without anti-wear beams. For water walls protected with anti-wear beams, the total wall abrasion caused by adhering granular flow is less than that without anti-wear beams; however, the local abrasion around anti-wear beams may be worse than that without anti-wear beams.
  • Boiler Technology
    Dynamic Bed Temperature Modeling of Large-scale CFBB
    ZHANG Xuan, CHANG Tai-hua
    2013, 33(2): 88-92.
    Abstract ( )   Knowledge map   Save
    Through dynamic characteristic analysis on the structure and in-furnace temperature of a circulating fluidized bed boiler (CFBB) , balance equations were set up respectively for oxygen volume fraction, bed material flow, carbon residue and dynamic energy in the furnace, cyclone separator and external bed, following which dynamic models were established, by taking the coal feed rate, primary air flow, secondary air flow, slag discharge and fly ash flow as the input variables. Based on the field data of Sichuan Baima 300 MW CFBB, numerical simulations were carried out using Matlab software, during which dynamic response of bed temperature was obtained under step disturbance of primary air flow and coal supply. Results show that the simulation results agree well with the actual operation data and can better reflect the dynamic response of bed temperature under disturbance of input variables.
  • Boiler Technology
    Study on Heat Release and Carbon Residue of CFB Boiler with Breeches Legs
    GAO Ming-ming, LIU Ji-zhen, NIU Yu-guang, LEI Xiu-jian, TANG Jun, CHEN Feng
    2013, 33(2): 93-99.
    Abstract ( )   Knowledge map   Save
    To overcome the deficiency of delayed heat release signals from circulating fluidized bed (CFB) boiler, a method was put forward for calculation of the heat release and carbon residue by using easily measured signals of the combustion process. The specific way is to firstly divide the combusion system into dense phase area, dilute phase area and adiabatic cyclone separator area, then calculate the combustion share in adiabatic cyclone separator area based on materials mass and heat balance model, and finally build up carbon residue model by mechanism analysis and heat release model according to carbon residue and air volume. Based on experimental data of a 300 MW CFB boiler, and using extended Kalman filter technology, the in-furnace carbon residue and heat release were calculated respectively at loads of 285 MW and 200 MW, of which the results were compared with relevant literature data. Results show that the calculated results basically agree with relevant literature data, proving the model to be accurate and reasonable.
  • Boiler Technology
    Parameter Optimization for NOx Emission Model of Power Plant Boilers Based on Gravitational Search Algorithm
    NIU Pei-feng, XIAO Xing-jun, LI Guo-qiang,MA Yun-fei, CHEN Gui-lin, ZHANG Xian-chen
    2013, 33(2): 100-106.
    Abstract ( )   Knowledge map   Save
    Taking a 330 MW coal-fired boiler as an object of study, an optimized NOx emission model was established for the boiler using Least Squares Support Vector Regression (LSSVR) and Gravitational Search Algorithm (GSA), with which the boiler NOx emission was successfully predicted. Results show that compared with Genetic Algorithm, Artificial Bee Colony and Particle Swarm Optimization, the GSA algorithm has a higher capability in parameter optimization, emission prediction and data generalization, which may therefore help to reduce NOx emission of power plants.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Influence of Bolt Relaxation on Creep Strength of Turbine Casings
    MAO Jian-feng, WANG Wei-zhe, ZHANG Jun-hui, CHEN Han-ping
    2013, 33(2): 107-111.
    Abstract ( )   Knowledge map   Save
    The 2×105 h creep damage calculation was conducted for a turbine casing under the action of bolt relaxation using finite element method, so as to analyze and compare the laws governing the variation of corresponding maximum principal strain, Mises stress and casing creep damage with time, under conditions with and without consideration of bolt relaxation. Results show that if not considering bolt relaxation, the creep damage will be underrated, and the result will be relatively conservative. The effect of bolt relaxation is tightly related to the geometric position, the closer the distance to the bolt hole, the stronger the compensation effect will be.
  • Steam Turbine and Gas Turbine
    Rotating Stall Control for Axial Compression System with Close Coupled Valves
    LIU Zhen-xiong, DU Zhao-hui, ZHU Xiao-cheng
    2013, 33(2): 112-116.
    Abstract ( )   Knowledge map   Save
    Based on classical Moore-Greitzer model, and using backstepping method, a third-order Moore-Greitzer model with close coupled valve was proposed for rotating stall control of an axial compression system, to which numerical study was carried out. Results show that the designed control system can effectively suppress the rotating stall in axial compression systems, which enables the compressor to work stably in high-performance range, with an elevated boosting ability and enlarged working range.
    • Automatical Controlling and Detecting Diagnosis
  • Automatical Controlling and Detecting Diagnosis
    Study on Novel Robust PID Control Strategy Based on Non-linear Filtering
    LI Jun, WAN Wen-jun, ZHANG Xi
    2013, 33(2): 117-122.
    Abstract ( )   Knowledge map   Save
    Combining non-linear filter link and traditional PID control algorithm, a novel robust PID control strategy based on non-linear filtering was proposed. The mechanism of improving the robustness of process control system by employing such control strategy was analyzed from the prospective of frequency-domain characteristics. Simulation experiments were conducted on response characteristics of process control system under step and square wave disturbance, and the control strategy was adopted to optimize the regulation system for superheated steam temperature in a power plant. Results show that the novel PID control strategy can improve both the response speed and stability of the system, further enhance the robustness of traditional PID control strategy, so as to obtain better control quality.
  • Automatical Controlling and Detecting Diagnosis
    Multi-objective GA and Static H∞ Loop-shaping Design of Controllers for Steam Generator Water Level
    ZHOU Shi-liang, LIU Yu-yan, DUAN Feng
    2013, 33(2): 123-129.
    Abstract ( )   Knowledge map   Save
    A design method was proposed for robust controller with given structure based on multi-objective genetic algorithm (GA) and static H∞ loop shaping procedure. Using the method, a controller for steam generator water level at low load with structure of proportional-derivative cascaded filter was designed, with which simulation tests were carried out on response of the control system under step changes of both the water level and steam flow as well as at pressure fluctuation of the feed water. Simulation results show that the robust stability and performance of the designed control system are better than those of other three H∞ loop shaping based schemes, via the derived controller, higher control quality and stronger robustness may be obtained under given step changes of feed water and steam flow.
  • Automatical Controlling and Detecting Diagnosis
    Soft-sensing Technology of SO2 Emission for Coal-fired Power Plants
    ZHENG Hai-ming, YANG Zhi
    2013, 33(2): 130-134.
    Abstract ( )   Knowledge map   Save
    To solve the problem of high installation and maintenance cost of continuous emission monitoring system (CEMS) for flue gas pollutants from coal-fired power plants, a soft-sensing technology is proposed for prediction of the SO2 emission. The specific way is to firstly build up a model using BP neural network, then configure and optimize the link weights and threshold value of BP network using genetic algorithm, and finally establish a new soft-sensing model. Predicted results based on the new soft-sensing model were compared with actual measurements. Results show that the new model has a high prediction accuracy and stability, which may be used to predict SO2 emission from coal-fired power plants.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Numerical Simulation of Direct Air-cooling Condenser with Rotary Flow Field and Spray Humidification
    ZHOU Lan-xin, HUI Xue-song, LI Wei-hua, MA Shao-shuai, SUN Hui-liang
    2013, 33(2): 135-140.
    Abstract ( )   Knowledge map   Save
    Based on Simple algorithm and k-ε model, combined with heat and mass transfer theory for air-water two-phase flow, 3D numerical simulations were carried out for a 600 MW direct air-cooling unit by using MRF model to treat the fan model, so as to analyze the influence of spray humidification on the condenser pressure. Results show that by applying MRF model to treat the fan model, the air spirals up in the unit, and both the air flow field and temperature distribution on heat exchanger is closer to actual conditions. The maximum pressure drop of condenser 8.97 kPa appears when the nozzles are symmetrically arranged 3.5 m away to trestle center of the fan, 1.6 m above the outlet plane of fan shell, and the angle between spraying direction and positive direction of y axis is 210° in the xy plane, with a nozzle pressure of 0.8 MPa and nozzle diameter of 0.4 mm.
    • Environmental Science
  • Environmental Science
    Numerical Simulation on Single-tower Process of Ammonia Desulfurization System Based on Aspen Plus
    HONG Wen-peng, HE Hui-ying, LIU Guang-lin, WANG Hai-gang
    2013, 33(2): 141-146.
    Abstract ( )   Knowledge map   Save
    Taking the chemical process of a single-tower ammonia desulfurization system as an object of study, numerical simulation was carried out to its adsorption, neutralization and oxidization process using Aspen Plus process software, so as to obtain corresponding parameters, such as the material flow and components at each nodal, chemical reaction condition, desulfurization efficiency and product quality, etc., and analyze the influence of main process parameters on the desulfurization efficiency. Results show that the desulfurization efficiency rises with reducing inlet mass concentration of SO2 and increasing Liquid-gas ratio, which may reach 95% at an liquid-gas ratio of 7.5-10 L/m3. The efficiency increases with rising flue gas flow and liquid ammonia quantity; however, when the liquid ammonia quantity gets up to a certain value, the desulfurization efficiency starts falling instead of rising.
  • Environmental Science
    Microstructure Evolution of Procedural Products During Limestone Calcination and Carbonation
    WEI Ri-guang, CHEN Jiang-tao, CHEN Hong-wei, CHEN Long
    2013, 33(2): 147-152.
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    Microstructure evolution of procedural products during limestone calcination and carbonation was studied. Results show that the procedural products exhibit a type IV nitrogen adsorption-desorption isotherm at different stages of limestone calcination and carbonation, including a typical H1 hysteresis loop during calcination and initial carbonation process. The specific surface area and pore volume of calcined products increase linearly with the calcination time, while those of carbonated products reduce exponentially with the carbonation time. The pore volume of completely decomposed products of limestone distributes in bimodal shape, of which the peak values rise with calcination reaction and reduce with carbonation reaction. Different types of pores make a different contribution to the pore volume and area. The micro-pore only makes a certain amount of contribution to the pore area, while the meso-pore and macro-pore make a large contribution to both of them. With the rise of specific surface area and pore volume, the calcination conversion rate of limestone increases linearly and the carbonation conversion rate decays exponentially.
  • Environmental Science
    Investigation on Mechanical Properties of 30Cr2Ni4MoV LP Rotor Steel After Long-term Service
    ZHAO Shuang-qun, LIN Fu-sheng
    2013, 33(2): 153-159.
    Abstract ( )   Knowledge map   Save
    Mechanical properties of 30Cr2Ni4MoV low-pressure (LP) steam turbine rotor steel were investigated by microstructure analysis, room- and high-temperature tensile tests, room-temperature impact tests and fracture appearance transition temperature tests, so as to study the variation reasons of its strength and ductility. Results show that segregation of elements C, Cr, Ni and Mo exists in the central part of LP rotor at the generator end. The microstructure of LP rotor differs greatly at different locations and no obvious changes are observed in the quantity and size of carbides at high-temperature service locations. The room-temperature tensile properties are clearly different at different locations and no decreasing occurs in the tensile strength at high-temperature service locations. The impact ductility is almost the same for all locations close to the outer rim, which is obviously different for areas near the center hole. The difference of total impact energy is mainly from the crack propagation energy and the crack forming energy is almost the same for all locations. The fracture appearance transition temperature increases for locations enduring high service temperatures. The property non-uniformity is found to be caused by composition segregation and microstructure difference formed during manufacture of the LP rotor due to its too large size.
  • Environmental Science
    Simulation and Experimental Study on Welding Temperature and Residual Stress Field of New Heat-resistant Steel
    DAI Zhen, JIANG Yun-jian, ZHANG Jian-ye, LI Wei, XIE Hang-yun, WANG Wei-feng
    2013, 33(2): 160-165.
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    Using finite element software Abaqus and the element birth and death technique, the multi-pass welding process for P92 main steam pipeline was simulated so as to obtain the welding temperature field and residual stress field, to which experimental tests were carried out with thermal infrared imager and X-ray diffraction technique. In addition, causes leading to type IV cracking of the new ferrite heat-resistant steel were subsequently analyzed. Results show that for both the welding temperature field and residual stress field, the simulated results agree well with that of the experiment, proving the newly-built finite element model to be accurate and reliable in simulation of the welding temperature field and residual stress field. The equivalent stress (Mises stress and the largest main stress) is found to be the main cause leading to the type IV creep failure of the new ferrite heat-resistnat weld joints.