Power Equipment

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  • 2018 Volume 32 Issue 3
    Published: 15 May 2018
      
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  • Numerical Simulation on Steady Flow in Last Stage of a Steam Turbine under Low Volume Flow Conditions
    Wang Zhi, Liu Yimiao, Jiao Qingya
    2018, 32(3): 153-157.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The steady flow in last stage of a steam turbine under different volume flow conditions was studied with the help of three-dimensional viscous numerical software-CFX by the way of changing the back pressure, with focus on the analysis of the ability to do work and the characteristics of flow field considering the meridional streamline and the axial section streamline under low volume flow conditions. Results show that, the relative volume flow decreases with the rise of back pressure, indicating worsened flow conditions; under low volume flow conditions, the streamline at the root of last stage rotor blade moves upward, where separation flow occurs; when the volume flow reduces to a certain value, the last stage rotor blade turns to the blast condition, and vortex flow appears on the top clearance, which further expands to the flow passage of stator blade.
  • Performance Evaluation of a Power Plant System Integrated with Chemical Looping Air Separation
    Zhao Yaxian, Xie Wenxia, Zhang Jun, Xie Jihong, Du Yong, Yan Haixian
    2018, 32(3): 158-162.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A model of power plant system integrated with chemical looping air separation (CLAS O2/CO2) was established based on Aspen Plus software, while a model of O2/CO2 cyclic combustion was set up with the higher temperature separation unit for O2 and CO2 in chemical looping combustion to replace the lower temperature air separation unit in conventional oxy-fuel combustion power plant (ASU O2/CO2) system, so as to study the effects of following factors on the performance of the system, such as the extracting temperature of flue gas, the excessive air ratio and the type of oxygen carrier, etc., after which, optimal parameters of the CLAS O2/CO2 system were obtained. Results show that the net efficiency of the CLAS O2/CO2 system is 38.8%, which is 13.5% higher than the ASU O2/CO2 system and 1.8% higher than the system of integrated gasification combined cycle with CO2 capture and storage (IGCC CCS), when zero emission of CO2 can be achieved simultaneously.
  • Forecasting of Flame Center Position in the Furnace Based on Water Wall Temperature of the Boiler
    Chen Youfu, Xu Songmei, Guan Shipian, Ding Jianliang, Yao Xudong, Zhao Lingling
    2018, 32(3): 163-167.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    According to the principle of radiation heat transmission in the furnace, a method was proposed for the prediction of flame center position based on water wall temperature of the boiler. Taking a 600 MW supercritical tangentially fired boiler as an example, the position of flame center was predicted under 75% BMCR condition, and the prediction data were subsequently compared with actual measurements. Results show that a correlation model can be built between the outlet temperature of lower water wall and the offset of flame center position. According to the change rule of water wall temperature, the position of flame centre can be predicted. Featured by low investment, high prediction accuracy and simple prediction process, the method proposed has wide application prospects in engineering projects, since it only requires the measuring points already existing in the boiler.
  • Effects of Cu-based Catalyst on Tar and Aromatic Hydrocarbons from Wheat Straw Pyrolysis under Different Atmospheres
    Sun Tingting, Xiao Jun, Song Min
    2018, 32(3): 168-174.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The experiments of wheat straw pyrolysis were carried out at different temperatures (600 ℃, 700 ℃ and 800 ℃) and under different atmospheres (nitrogen or nitrogen with steam) in a horizontal tube furnace, with the Cu-based (Cu/Al) catalysts prepared by impregnation method, so as to further study the influences of Cu/Al catalysts on the pyrolysis product distribution and tar composition. Results show that Cu/Al catalysts can increase the gas yield whereas decrease the solid and liquid production rates in both atmospheres, and the changing trends of pyrolysis gas products and tar compositions with temperatures are consistent with those using Al2O3; besides, Cu/Al catalysts are beneficial to promoting secondary cracking of volatiles and inhibiting polymerization of polycyclic aromatic hydrocarbons (PAHs), which would result in reduced PAHs and their derivatives.
  • Cracking Failure Analysis of a Secondary Superheater Elbow
    Chen Xun
    2018, 32(3): 175-178.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To find the causes leading to the initiation and propagation of the crack on a two-stage superheater elbow in a power plant, a number of tests were conducted, such as visual and microscopic examination, chemical analysis, and mechanical property tests, etc. Results show that the crack origins in the inner wall of the elbow, where the temperature is relatively low, which is of the creep fatigue type, formed by thermal stress. Phase change occurs in the cracking area under over-temperature conditions, and the high temperature promotes the growth of the crack.
  • Study on Welding Procedure and Anti-deformation Measures for Generation Ⅲ Nuclear Core Barrel Shells
    Wang Lili, Li Shuangyan, Zhang Maolong
    2018, 32(3): 179-183.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Parameters of submerged arc welding without back gouging were obtained by a series of welding procedure tests for generation Ⅲ nuclear core barrel shells, while the welding contraction data were acquired by girth welding shrinkage tests with proper type of groove and support tooling. By simulating the manufacture of the upper part of core barrel shell, the procedure and anti-deformation measures were determined for the submerged arc welding without back gouging, which can meet the requirement on product properties and welding deformation. Above study results are conductive to improve the welding efficiency, reduce the welding deformation and cut down the production cost for generation Ⅲ nuclear core barrel shells.
  • Full Load Operation Practice of a Denitration Unit with Zero Retrofit on the Equipment
    Sun Weipeng, Chen Shaohua, Jiang Yong, Feng Tingyou, You Liang, Zhu Chenliang
    2018, 32(3): 184-187.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem that the denitration unit can’t be put into use during start-up period of a 1 036 MW coal-fired power unit, a series of countermeasures were put forward and taken, such as raising the flue gas temperature to satisfy the requirement of related catalyst, optimizing the start-stop control strategy, improving the initial temperature of both the turbine proper and the reheater system with the use of conventional high-temperature catalyst before equipment retrofit, keeping the flue gas baffle on the reheater side, indirectly improving the feed water temperature under the premise securing the normal operation of the boiler water circulation system, etc., and finally full load operation of the denitration unit was successfully realized, which may serve as a reference for same type of power plants.
  • Analytical Study on Economic Boundary of a Thermal Power Unit during Co-firing Process
    Jin Shengxiang
    2018, 32(3): 188-193.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To study the economical boundary of a thermal power unit during co-firing process, the effects of following factors on the co-firing economy were studied, such as the coal price, the calorific value and the production cost, etc. Based on comprehensive analysis of the fuel cost and production cost, and by turning the relation expression between production cost and complicated factors into the one taking low calorific values as the variables, a model was set up for determination of both the co-firing economy boundary and the maximum co-firing benefit. This may serve as a reference for coal and power enterprises in working out co-firing plans.
  • Effects of Air Volume Ratio on High Temperature Corrosion of the Water Wall in a W-flame Boiler
    Yang Taiyong, Zhang Qingfu, Liu Ruidong, Lin Weikang, Zhou Wentai
    2018, 32(3): 194-197,211.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The effects of air volume ratio on high temperature corrosion of the water wall in a W-flame boiler were studied by measuring the near-wall flue gas composition under different load conditions. Results show that the central part of the front wall is characterized by low oxygen content under the condition of different loads and different total air volumes. The CO content is closely related to the oxygen content; the formation of H2S is closely related to the excess air coefficient, and the H2S content increases with rising oxygen content. The phenomenon of high temperature corrosion is controllable under experimental conditions, and it can be further mitigated by appropriately optimizing the air distribution in the front wall, rear wall and along furnace width direction.
  • Selection of an Induced Draft Fan after Ultra-low Emission Retrofit of a 600 MW Unit
    Tang Zhongshun, Wang Haixiu, Zhang Yanqiang, Zhou Qiule
    2018, 32(3): 198-202.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem that the induced draft fan could not operate safely and stably in BMCR working condition after ultra-low emission retrofit of a 600 MW power unit, a matched capacity-increasing technical retrofit was conducted for the induced draft fan, while a study was carried out on the selection process, and an analysis was made on the operation performance after retrofit. Results show that the retrofitted induced draft fan can operate safely and stably, which may serves as a reference for retrofit of similar units.
  • Application of Energy-saving Technology in Air and Flue Gas System of Thermal Power Units
    Liu Haixia
    2018, 32(3): 203-207.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem existing in air and flue gas system of thermal power units, an analysis was conducted on the energy-saving technology in collaborative optimization of the air and flue gas system, while an evaluation was performed on application benefits of various energy-saving technologies, such as optimized selection of relevant equipment based on wide load safety and economic operation, single and double configuration, variable seed regulation and different drive modes, etc. Results show that above technologies can help to achieve the energy-saving purposes, which may serve as a reference for application of various energy-saving technologies in air and flue gas systems of domestic power plants.
  • Technical Retrofit of a Bituminous Coal-fired Boiler for Co-firing Large Proportion of Lignite
    Zhang Shulin, Cao Hui, Li Jianning, Xiong Xianwei, Wang Pu
    2018, 32(3): 208-211.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problems existing in a bituminous coal-fired boiler when co-firing large proportion of lignite, such as insufficient output of the pulverizer and low load operation, etc., a retrofit scheme was proposed to increase the primary air temperature by adding a steam heat exchanger in the hot primary air duct before entering the coal mill, thus achieving secondary reheating of the hot primary air, so as to raise the primary air temperature by more than 30 K, in which case, the purpose of co-firing large proportion of lignite could be realized. Results show that the co-firing proportion of lignite could be increased by about 15% after adding the steam heat exchanger, when the output temperature of the coal mill is kept below 70℃, and the primary air rate returns to the design value.
  • Analysis on Miss Operation of Main Throttle Valve during Valve Switching of a HP-IP Cylinder United Start-up Unit and the Countermeasures
    He Donghui, Ye Zhenqi, Zhao Yizhou
    2018, 32(3): 212-215,219.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem of miss operation of the main throttle valve (TV) during TV-governing valve (GV) switching in the start-up period of a 670 MW supercritical power unit at the rotating speed of 2 900 r/min, a series of researches were conducted, such as analyzing the combined start-up speed and the control logic of valve switching, comparing the parameters change before and after valve switching, studying the internal structure and action mechanism of the main throttle valve, and performing force analysis while TV opening, after which the problem was found to be caused by too low main and reheat steam pressure. It is proposed to adjust the main and reheat steam pressure before valve switching, as far as possible to reduce the GV opening to lower the differential pressure before and after the valve, so as to ensure the success and shorten the time of valve switching. This may serve as a reference for valve switching of similar power units.
  • Analysis on Condenser Vacuum Drop Caused by Relief Valve and the Solutions
    Tan Jiangfeng
    2018, 32(3): 216-219.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    By analyzing the reasons leading to the fast decline of condenser vacuum in an M701F3 gas-steam combined cycle unit during start-up process, the problem was found to be caused mainly by the relief valve in the low-pressure cylinder cooling steam pipeline, and subsequently corresponding countermeasures were put forward, which may serve as a reference for trouble shooting of similar units.
  • Vibration Analysis of MGGH Flue Duct in a 600 MW Unit and Corresponding Countermeasures
    Jiang Jianwei, Zhu Wei, Liao Xiaochun
    2018, 32(3): 220-222.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem of obvious vibration and noise occurring in heating up period of a 600 MW unit’s Mitsubishi recirculated nonleak type gas-gas heater (MGGH) when the load gets up to 400 MW with an airflow rate of 1 750 km3/s or above, vibration measurements were conducted, during which the problem was found to be caused by Karman vortex formed when the flue gas passing through relevant heating surfaces. It is suggested that an anti-vibration baffle should be added to eliminate the MGGH vibration.
  • Analysis and Comparison of Boiler Efficiency Tests Specified in Standard GB/T 10184 of Edition 2015 and Edition 1988
    Wang Aiying, Chen Lianjun, Liu Mingyuan
    2018, 32(3): 223-226.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Main differences of boiler efficiency tests respectively specified in standard GB/T 10184 of edition 2015 and edition 1998 were analyzed without considering the addition of desulfurizer. The introduction of fuel efficiency in edition 2015 is referred to as the boiler efficiency, which does not take into account the degree of effectiveness of the incoming heat upon the output heat; the boundary of heat balance system is changed, i.e. the inlet of air preheater is defined as the system inlet boundary; the reference temperature is set to be 25 ℃; the heat input, heat loss and correction items are all adjusted.
  • Case Analysis for Heat Calculation of a MPS Medium-speed Roller Coal Mill Pulverizing System with Chinese/German Standards
    Yin Mingquan, Wang Chunmin, Liu Huan
    2018, 32(3): 227-230.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A theoretical analysis was conducted on the main difference of heat calculation ways respectively specified in DL/T 5145—2012 "Technical code for design and calculation of pulverized coal preparation system of fossil-fired power plant" and corresponding German standard, and subsequently a comparison was made among 4 actual engineering cases. Results show that the main difference between above two standards lies in the aspects of mechanical energy, ventilation rate and heat loss coefficient, which basically has no relationship with the start temperature of the drying agent.