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  • 2014 Volume 34 Issue 1
    Published: 15 January 2014
      
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  • Online Monitoring of Steamside Oxide Scale in Hightemperature Heatsurface Tubes of Boiler
    BIAN Shaoshuai，PAN Longxing，HUO Yong
    2014, 34(1): 1.
    Abstract ( )   Knowledge map   Save
    A number of models were built up respectively for online monitoring of tube wall temperatures at hightemperature heating surfaces, oxide scale growth, online calculation of scale stress and for exfoliation evaluation of the oxide scales. Based on these models, a management system for steamside oxide scale on hightemperature heating surfaces of boiler was developed and applied to a 600 MW supercritical power boiler. Results show that with the oxide scale management system, thermal deviation can be reduced along flue duct width direction, which will result in reduced infurnace tube wall temperature of deviated panels, and lowered growth rate of oxide scales; deposition and exfoliation of oxide scales can also be prevented by online monitoring of corresponding temperatures and scale stress.
  • Impacts of Bed Inventory and Air Distributor Resistance on Bed Overturn in Circulating Fluidized Bed with Pantlegs
    2014, 34(1): 7.
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    Based on twophase flow granular dynamics, a twodimensional CFD numerical model was developed to investigate the impacts of bed inventory and air distributor resistance on the bed inventory overturn process in circulating fluidized bed with pantlegs. Results show that with the rise of bed inventory, the lateral solid flow rate rises, resulting in increased possibility of bed inventory overturn; whereas with the rise of air distributor resistance coefficient, the lateral solid flow rate drops, resulting in reduced possibility of bed inventory overturn. These phenomena can be explained by the mechanism of positive and negative feedback. The pressure drop ratio of air distributor and bed inventory may serve as an important parameter to evaluate the selfbalance ability of furnace with pantlegs.
  • Waveletbased Detection on Local Singularities of Pressure Fluctuation Signals from Wind Cap in Bubbling Fluidized Bed
    2014, 34(1): 13.
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    Modulus maxima lines of pressure fluctuation signals measured from the wind cap in a cold bubbling fluidized bed setup were calculated using wavelet modulus maxima method under conditions of different fluidization numbers, static bed heights and bed material particle sizes, so as to analyze the influence of above factors on the singularities of corresponding pressure fluctuation signals. Experimental results show that the local singularities of pressure fluctuation signals increase with decreasing fluidization number, rising static bed height and increasing bed material particle size, indicating that the wavelet modulus maxima lines can be used to describe the local singularities of pressure fluctuation signals, and to reflect the gassolid fluidization conditions in bubbling fluidized beds at different fluidization numbers, static bed heights and bed material particle sizes.
  • Influence of Heat Treatment on Residual Stress in LP Welded Rotor of Nuclear Steam Turbines
    2014, 34(1): 19.
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    An axisymmetric finite element model for LP welded rotor of large nuclear steam turbine was established using commercial package ABAQUS, while a welding heat source model set up with DFLUX subroutine in ABAQUS, based on which numerical simulations were performed to the welding process, and subsequently relevant calculation and analysis were carried out to the residual stress distribution in the weld zone, so as to analyze the influence of heat treatment on the residual stress distribution. Results show that the welding residual stress lies only in the weld and heat affected zone, distributing symmetrically about the weld, without influencing the stress distribution in other areas of rotor; after heat treatment, no biaxial tensile stress is found on the weld surface, and high residual stress distributes along the center line of the weld; heat treatment has a significant effect on peak value and gradient of the residual stress.
  • Numerical Simulation on Thermal Shock Process in AP1000 DBA Testing
    2014, 34(1): 25.
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    A model was set up to simulate the thermal shock process in first second of design basis accident (DBA) testing for AP1000 nuclear power plant safetyrelated equipment, in which superheated steam was injected into the test chamber from a steam accumulator. Using Fluent software, numerical simulation was carried out to the transient thermal shock, so as to obtain transient evolution and space distribution of various factors in the system, such as the temperature, pressure, velocity and species concentration etc. Results show that after entering into test chamber, the supersonic steam jet is to be blocked by a baffle plate, which then mixes with and compresses the air inside the chamber, and finally makes the temperature and pressure of the medium rapidly get up to required values; the pressure distribution transiently gets uniform in the chamber, but the temperature distribution depends on the steam flow, which, with the continuous filling of steam, tends to get uniform after one second; by injecting hightemperature highpressure superheated steam into test chamber from accumulator, the process can satisfy the requirements of DBA thermal shock testing within one second.
  • Edge Detection of Flame Images Based on Complex Contourlet and Improved Mathematical Morphology
    WU Yiquan,ZHU Li,ZHOU Huaichun
    2014, 34(1): 32.
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    To further improve the performance of edge detection for flame images, a method of edge detection based on complex Contourlet transform and improved mathematical morphology was proposed. Firstly, the flame image was decomposed into lowfrequency and highfrequency components through complex Contourlet transform. Then the lowfrequency subband coefficients with less edges and minutiae were processed using improved mathematical morphology so as to detect the weak edges and ensure accurate location, while the highfrequency subband coefficients with more edges and minutiae detected using the method of complex Contourlet modulus maxima, with which noise can be suppressed effectively. Finally, the complete edge of flame image was obtained by fusion. Results show that the proposed method has significant advantages in terms of subjective visual effect and objective quantitative assessment indexes such as peak signal to noise ratio (PSNR) and so on, clearer and more complete edge contour and very strong antinoise performance, in comparison with Cannny method, wavelet modulus maximum approach, Contourlet modulus maxima and Contourlet morphology method.
  • Study on Calibration Method for Online Measurement of Mercury Vapor
    SHI Juan,CAI Xiaoshu,CHEN Jun
    2014, 34(1): 39.
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    To solve the environmental pollution problems caused by waste mercury vapor emitted during the calibration of online measurement system for mercury vapor in exhaust gas, a spectrometric method based on saturated vapor principle was proposed for the calibration purpose, and subsequently corresponding calibration tests were performed in the temperature range of 258.65273.55 K. Results show that the calibration can only be performed by changing the mass concentration of mercury vapor in a small temperature range, which, however can be expanded by modifying the temperature coefficient. The linear correlation coefficient obtained by experiment is R2=0.998 5, and the maximum deviation between measured and calibrated mass concentration is only 5.2%. The calibration setup is featured by simple structure, low cost and no environmental pollution.
  • Combination Optimization of Coal Mills for Peak Load Regulation of Ultrasupercritical Units
    FANG Yanjun,TANG Mian,QIN Xiaojie
    2014, 34(1): 45.
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    To satisfy the energysaving requirements of coal mills in a 660 MW power unit, an energy consumption model was built up, of which the constraints were set based on actual operation conditions. After initialization improvement, inertia weight improvement and mutation operator introduction, the classical PSO algorithm was applied to combination optimization of the mills, during which Matlab simulation was carried out after all the parameters were determined by tests. Results show that the optimized coal mill combination obtained by improved PSO algorithm will contribute much to energy saving of related coal mills.
  • Numerical Simulation on Optimization of SCR Denitrification System for Coalfired Boilers
    LING Zhongqian1,ZENG Xianyang,HU Shantao,ZHOU Hao,CEN Kefa
    2014, 34(1): 50.
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    Taking the selective catalytic reduction (SCR) reaction system of a 300 MW coalfired boiler as an example, numerical simulation was made to the denitration characteristics of the SCR reactor with different structures by fluid mechanics calculation software, so as to analyze the effects of guide plate layout on distribution of both the flow field and the ammonianitrogen ratio in the SCR reactor. Results show that both the flow field and NH3 volume fraction within the SCR reactor are severely uneven, the denitration efficiency of SCR reactor is relatively low and the ammonia escape rate is relatively high, when there is no guide plate installed in the flue; by adopting the initial solution, the flow filed in the SCR reactor is improved greatly, but the deviation of ammonianitrogen ratio distribution at inlet of the first catalyst layer is more than 5%; whereas, in the final solution, the deviation of velocity distribution at inlet of the first catalyst layer is  3.84%, where the deviation of ammonianitrogen ratio distribution is  3.79%, the denitration efficiency of SCR reactor reaches 83%, and the NH3 escape rate is lower than 5×10-6
  • Experimental Study on Drag Reduction Performance of DRA for Flue Gas Desulfurization Systems
    2014, 34(1): 57.
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    Drag reduction experiments were carried out in a desulfurization circulation system with high polymers PEO and PAM, so as to analyze the drag reduction performance and mechanism of above polymers in desulfurization slurry, and to discuss related influencing factors. Moreover, an evaluation was made to the drag reduction performance of PEO and PAM according to different drag reduction rates. Results show that the optimal concentration of PEO and PAM are 600 mg/L and 200 mg/L respectively, with corresponding maximum drag reduction rates of 48.13% and 38.35%, indicating high drag reduction effectiveness of PAM and PEO.
  • Thermodynamic Analysis of CO2 Capture from Coalfired Flue Gas Using Cabased Sorbent
    ZHANG Xuelei,GAO Pei
    2014, 34(1): 63.
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    To reduce the CO2 emission from coalfired power plants, a 1 000 MW supercritical power unit was taken as an example, for which a CCCR (cyclic calcination/carbonation reaction) flow chart was built up to capture CO2 from the flue gas with Cabased sorbents, so as to obtain the relationship among the CO2 capture efficiency, the CO2 purge percentage, the Ca/C molar ratio and the gassolid separation efficiency. Effects of above key parameters on thermodynamic performance of the system were analyzed simultaneously by the help of Aspen Plus software. Results show that the thermal efficiency for power generation will drop by 8.73 percentage points, compared with the design value, under the capture efficiency of 90% CO2 and 100% SO2; all the circulation solids flow, calcination energy consumption and thermal efficiency for power generation reduce with rising purge percentage and decreasing gassolid separation efficiency; with the rise of CO2 capture efficiency, both the circulation solids flow and the calcination energy consumption increase, but the thermal efficiency for power generation decreases.
  • Experimental Study and Quantum Chemistry Calculation on Coal Ash Fusion Behavior and Related Mineral Evolution Mechanism
    DAI Baiqian,WU Xiaojiang,CHEN Yushuang,ZHANG Zhongxiao
    2014, 34(1): 70.
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    Two typical kinds of coal respectively with high and low ash fusion point were taken as the object of study, corresponding ash fusion behavior and related mineral evolution mechanism under hightemperature gasification conditions were analyzed using XRD and SEMEDX method, and calculated with quantum chemistry method. Results show that the high ash fusion temperature (AFT) of ash A is resulted from the formation of large amount of mullite at high temperatures; whereas the low AFT of ash B is caused by fluxing minerals such as anhydrite and soda feldspar etc. existing in ash B, and also by the chemical reaction of CaO with mullite to form anorthite and gehlenite during ash melting process. Since mullite is likely to combine with electron acceptors rather than with electron donors, it easily reacts with metal cations such as Ca2+, Mg2+, Fe2+, Na+ and K+ etc., to generate some other minerals, therefore, the ash fusion behavior can be controlled through adding different kinds of metal cations to change the AFT of coal ash.
  • Influence of Piping Thermal Efficiency on Thermal Economy of a 1 000 MW Double Reheat Power Unit
    2014, 34(1): 77.
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    Taking a 1 000 MW ultra supercritical double reheat power unit as the object of study, the influence of following factors on the unit thermal economy was quantitatively analyzed, such as the pipeline heat loss, the auxiliary system loss and the working medium leakage loss. Results show that in consideration of all above factors, the piping thermal efficiency is 97.394%, and the standard coal consumption per unit production of power supply is 271.935 g/(kW·h), and compared with the condition that no piping loss is produced, the piping thermal efficiency is reduced by 2.606%, while the standard coal consumption per unit production of power supply increased by 4.584 g/(kW·h), indicating that it is necessary to consider the piping thermal efficiency when evaluating the thermal economy of a double reheat power unit.