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    25 March 2020, Volume 42 Issue 3
    Research on water pollution prevention and control technology of fossil-fired power plants with once-through cooling system #br#
    HU Dalong,RAN Qiong,WANG Zhengjiang,XIONG Weijun,XU Zhen,
    2020, 42(3):  1-7. 
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    In order to meet the increasingly strict environmental requirements,fossil-fired power plants are carrying out
    large-scale wastewater treatments. According to the statistics including water intake quantity for unit power generation,
    water discharge per unit power generation,total wastewater discharge and water discharge rate of four power plants which
    are once-through cooling units in coastal and riverside areas,the water usage and discharge conditions of chemical
    demineralised water systems,desulfurization systems,ash-slag disposal systems in power plants are analyzed. The common
    problems existing in the main systems need water supply of once-through cooling power plants in coastal and riverside areas
    were summarized,and a water pollution control technology was put forward combined with the actual situation of the power
    plants. Firstly,the water flow should be optimized by adjusting the water-demand systems. Secondly,water-saving
    technology is taken to reduce the amount of wastewater production. Thirdly,wastewater is reused after treatment to reduce
    the terminal amount. Finally,the terminal wastewater is concentrated or solidification. After the optimization on the fossilfired power plant with once-through cooling system,the water intake quantity for unit power generation could be reduced to
    0.160-0.240 m3(/ MW·h)
    Status and progress of numerical simulation in flue gas evaporation technology for desulfurization wastewater #br#
    ZHANG Fufeng1,LIU Daokuan2,QU Baozhong2,YU Ziyan1,WU Kai2,MA Shuangchen2
    2020, 42(3):  8-18. 
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    With the increasingly strict regulations and standards of power industry in China,implementation zero discharge
    on desulfurized wastewater from thermal power plants is imminent.Since flue gas evaporation technology is simple,and of
    low investment and operating costs,it has become the primary method for zero emission. With the rapid development of
    computer technology,CFD is widely used in gas flow and droplets numerical simulation of flue gas evaporation technology.
    The droplet evaporation mechanism,gas-liquid two-phase flow and its numerical research are concluded,and the CFD
    numerical methods and the results of flue gas evaporation technology are summarized. It provides theoretical basis and
    technical support for the following engineering practices of flue gas evaporation technology,and proposes a development
    direction for it.
    Design of the desulfurization wastewater bypass flue evaporation system in a 300 MW coal-fired power plant #br#
    WANG Qunkui1,JIN Yinjia2*,SONG Da1,ZHENG Changle3
    2020, 42(3):  19-24. 
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    The bypass flue evaporation treatment process for desulfurization wastewater from coal-fired power plants is of
    low cost in investment and operation,and easy to operation. Its performance is affected by many factors such as unit load,
    flue gas temperature,and flue gas field. An optimization design is made on the bypass flue evaporation system in a 300
    MW coal-fired power plant based on the gas indexes,variations of wastewater quality and quantity. According to the
    operational parameters of the bypass flue evaporation system,it runs stably and meets the designing requirements. With 4.5
    m3/h water evaporation quantity,the mass fraction of chloride ions in pulverized fuel ash after desulfurization wastewater
    evaporation process is within 0.25%,which will not affect the comprehensive utilization of pulverized fuel ash,but will
    decrease the boiler efficiency by approximately 0.43 percentage points. In order to minimize the impact on the boiler
    efficiency,the desulfurization wastewater should be concentrated and reduced.
    Techno-economic analysis on membrane distillation in desulfurization wastewater ZLD process of coal-fired power plants #br#
    GAO Yonggang,SHI Zhiwei
    2020, 42(3):  25-30. 
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    Membrane distillation(MD),an emerging cut-edge technology,has advantages of anti-corrosion,anti-oxidation,low
    operation cost and so on.It can be applied in desulfurization waste water zero liquid discharge(ZLD)process of coal-fired power
    plants.Furthermore the plate-type multiple-effect MD process has been applied in waste acid recycling,ZLD of desulfurization
    waste water containing chromium and high dissolved salt,and other industrial areas.Reasonable technical routes of three types of
    membrane distillation applied in desulfurization waste water ZLD treatment were proposed after analyzing. Taking the 8 t/h
    desulfurization waste water treatment process for a coal-fired power plant as an example,techno-economic analysis was made on
    seven desulfurization wastewater treatment processes. The analysis results indicate that MD technology is suitable for
    desulfurization waste water ZLD process,and can save investment and operation cost in equipment for coal-fired power plants.
    Research on low-temperature waste heat flash evaporation technology applied in desulfurization wastewater zero discharge of 300 MW units #br#
    HOU Zhifu1,WEI Xiaoyi2,XING Shutao2,ZHAO Zhouming1,ZHANG Zhihua1
    2020, 42(3):  31-36. 
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    Zero liquid discharge(ZLD)of flue gas desulfurization(FGD)wastewater from coal-fired power plants has
    attracted lots of public attentions. A low-temperature flue gas waste heat flash evaporation technology for FGD wastewater
    advanced treatment was proposed ,and has been applied in a pilot project who can process the wastewater at 15 m3/h. The
    results show that the process system is of simple structure,stable and reliable operation,high recovery rate of
    condensation water ,and zero desulfurization wastewater discharge.The system achieves the goal of ZLD. The process needs
    no dosing pretreatment,and takes gypsum as crystal seed to realize divalent salt crystal separation during the wastewater
    concentration. The direct desulfurization treatment cost of the system is low which is about 19.42 yuan per cubic meter.
    Comparing the water quality indexes of raw water and condensation water,except for the ammonia nitrogen removal rate,
    the removal rates of SS,COD,Ca2+,Mg2+,SO42-,Cl- are higher than 96%. They have basically reached the water quality
    standard for boiler makeup water according to The reuse of urban recycling water—Water quality standard for urban
    miscellaneous water consumption(GB/T 19923—2005)
    Process schemes and fuzzy evaluation of moisture and waste heat recovery systems in coal-fired power plants #br#
    MA Shuangchen,WU Kai,SUN Yao,LIU Chang,XING Haoru
    2020, 42(3):  37-44. 
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    Recovering the moisture and waste heat in the flue gas of coal-fired power plants is of significance energy-saving
    potential. Both environmental and economical performances should be considered while selecting the moisture and waste
    heat recovery process scheme.Based on the description and characteristics of the primary scheme,the advanced scheme
    and the optimization scheme of a administration power plant,a fuzzy analytic hierarchy process evaluation model was
    established to construct an evaluation index system within four types of indexes which were technical performance,
    economic performance,environmental performance and system adaptability indexes. By indexes equalization,judging the
    matrix construction and calculating the weight,a ranking for the three schemes was obtained which was expected to provide
    a reference for the technological scheme evaluation on key techniques such as white plume elimination,flue gas waste heat
    recovery,and wastewater zero discharge in coal-fired power plants. The analysis results of the model show that the
    membrane-based flue gas moisture recovery + thermal membrane coupled wastewater treatment is superior to the primary
    and advanced schemes in terms of economy,environmental protection,technology,and system adaptability.
    Characteristics of water quality and quantity of flue gas recovery water from coal-fired#br# power plants and analysis of utilization methods of recycled water #br#
    MA Shuangchen1,GONG Chunqin1,GU Tao2,SUN Yao1,HE Chuan2,
    2020, 42(3):  45-51. 
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    The source of moisture in wet flue gas discharged by coal-fired power plants was studied,and the impact of
    saturated water vapor after wet desulfurization on environment were explored. The water quality characteristics of the
    recovery water from different flue gas water recovery processes were inductively analyzed. Taking the operation data of a
    330 MW unit as an example,the moisture content in the flue gas at the outlet of its wet desulfurization system(WFGD)is
    calculated. If 60% moisture in the flue gas can be recycled,the power plant will realize zero consumption of desulfurization
    water. Following the requirements on the water quality of thermal power plant water systems,the routes of the flue gas
    recovery water recycled as flue gas desulfurization makeup water,circulating cooling water,boiler makeup water and other
    unit water are briefly described. Finally,the techno-economic comparison of the flue gas water recovery processes is
    carried out. Comprehensive consideration should be made on a power plant characteristics while selecting a suitable
    process for it. Since condensed flue gas recovery water contains minerals and fine particles,condensed flue gas recovery
    process is considered to have certain removal effect on pollutants in the flue gas.A deepen understanding of water vapor
    impacts on environment is one of the keys to the Battle for Blue Sky.
    Technical characteristics and application of a new ammonia desulfurization ultra-low emission technology #br#
    SHEN Yaguang,GUO Huanhuan,WEI Pingbo,SHEN Hanjie
    2020, 42(3):  52-58. 
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    In order to solve the excessive discharges of soluble salts,aerosols and other dusts that are common in the
    ammonia desulfurization process,a new ammonia desulfurization ultra-low emission technology was developed. Adopting
    the concept of crystallization in the tower and oxidation outside the tower,the technology takes specific designs on the
    concentration area,absorption area,water scrubbing area and dust/mist removal area of the absorption tower respectively.
    Two-stage water scrubbers with different mass concentrations, are combined with high-efficiency demisters and
    precipitators,and two-stage mist eliminators. The oxidation tank outside the tower adopting three-layer distribution plate
    technology can fully oxidize the slurry,and its overall oxidation rate is over 99%. Two-stage water scrubbing tank can
    maximize the washing effect by controlling the mass concentration and taking stage-by-stage water replenishment,which
    ensures the water balance of the system. This technology is applied in the ammonia desulfurization ultra-low emission
    reconstruction in Fulaerji Thermal Power Plant of Huadian Environmental Protection Engineering & Technology Company
    Limited.It can meet the requirements of the national ultra-low emission standards and pass the operation test.
    Application of modern prediction and optimization algorithms in FGD systems
    CAO Jianzong1,LIN Chenyu2,CHEN Wentong1,LIU Qi2,ZHOU Quan2,
    2020, 42(3):  59-66. 
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    The continuous development of artificial intelligence technology has impacted quantitative analysis flue gas
    desulfurization(FGD)system in various factors,and has created favorable condition for its desulfurization efficiency and
    economic cost. By analyzing the details of the network construction and parameter selection in FGD system SO2 emission
    prediction calculated by neural network algorithm,the application characteristics of the algorithm in FGD system is
    discussed. In addition,targeted discuss is made on the optimization of booster fan,oxidation fan and syrup circulation
    pump,which aims at refining the detailed design and optimization targets of the prediction + optimization algorithm in FGD
    systems.

     

    Measurement method and regularity analysis on carbon oxidation factor of coal-fired power units in China #br#
    WU Handong1,ZHAO Chunli1,2,PENG Zun3
    2020, 42(3):  67-71. 
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    Carbon oxidation factor(COF)is one of the important parameters for measuring the carbon emissions of coalfired power units. Selecting a proper COF measurement method is of great significance to improve the accuracy of the
    carbon emission measurement for coal-fired power units. The default COF value of coal-fired power units given by the
    Intergovernmental Panel on Climate Change(IPCC)is 1,which has a deviation from the actual COF value of China. Based
    on the carbon balance analysis,a COF calculation model is proposed. By analyzing 70 COF samples taken according to
    their technical characteristics,fuel characteristics,operating characteristics,and geographical distribution in China,the
    results show that there are differences between the tested values in China and the default COF given by IPCC,whose
    variation range is approximately 0.5%-6.0%. In addition,the quality of coal is another important factor affecting COF.
    Upon taking coal of a poor quality ,parameters,such as unit capacity and unit load,will seriously affect COF value. With
    the adjustment of the unit structure and development of technical levels ,the actual COF value of coal-fired power plants in
    China will be closer to the default COF value of IPCC.
    Progress in research on the treatment and solidification of wet desulfurized sludge in coal-fired power plants #br#
    LI Lei1,QIAO Lin2,LIU Zhensheng1,QU Baozhong2,LIU Daokuan2,
    2020, 42(3):  72-77. 
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    As a by-product of desulphurization wastewater treatment in coal-fired power plants,desulphurization sludge is
    of intensive heavy metals and complex composition,which makes it difficult to dispose. To expound the characteristics and
    hazards of the desulfurized sludge,the dewatering technologies,heavy metal removal technologies and resource utilization
    applied for the desulfurized sludge are analyzed based on its component analysis. The discussion focuses on the current
    sludge solidification technology,and also involves solidification affecting factors and difficulties at this stage. The
    solidification technology is evaluated and predicted according to the actual situation,which points out the development
    direction and provides a reference for the future research on the stabilization treatment of desulfurization sludge.
    Ecological significance of white mud desulfurization discussed from the ecological properties of limestone #br#
    XU Dongsheng1,FAN Shuaijun2,LI Defeng1,XU Fang2,MA Caini2,MA Shuangchen2*
    2020, 42(3):  78-84. 
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    Limestone feedstock is widely applied for desulphurization in coal-fired power plants because of its low purchase
    cost. In order to avoid the resource depletion and ecosystem degradation,and,it is necessary to quantify the ecological cost
    of using limestone in power plant desulfurization process from a sustainable development level,which can intuitively
    display the disadvantages of white mud disposal and limestone desulfurization in the paper industry. The ecological value of
    limestone mines and the environmental problems in ore extraction are introduced,the ecological cost of limestone ore
    mining is calculated by replacement cost method .The significance of replacing the limestone by white mud is demonstrated
    from the clean production and circular economy,and it will ensure the enterprises' efficient management and provide a
    new concept for reducing the high-concentrated pollutant emission.