化工学报 ›› 2022, Vol. 73 ›› Issue (2): 923-932.doi: 10.11949/0438-1157.20210887

• 能源和环境工程 • 上一篇    下一篇

超低排放燃煤机组硒的迁移转化及飞灰对其富集特性

刘轩1(),苏银皎1,滕阳1,张锴1(),王鹏程2,李丽锋2,李圳2   

  1. 1.华北电力大学热电生产过程污染物监测与控制北京市重点实验室,北京 102206
    2.山西河坡发电有限责任公司,山西 阳泉 045011
  • 收稿日期:2021-06-30 修回日期:2021-10-19 出版日期:2022-02-05 发布日期:2022-02-18
  • 通讯作者: 张锴 E-mail:15210289575@163.com;kzhang@ncepu.edu.cn
  • 作者简介:刘轩(1994—),男,博士研究生,15210289575@163.com
  • 基金资助:
    国家自然科学基金联合基金重点项目(U1910215)

Selenium transformation in ultra-low-emission coal-fired power units and its enrichment characteristics in fly ash

Xuan LIU1(),Yinjiao SU1,Yang TENG1,Kai ZHANG1(),Pengcheng WANG2,Lifeng LI2,Zhen LI2   

  1. 1.Beijing Key Laboratory of Emission Surveillance and Control for Thermal Power Generation, North China Electric Power University, Beijing 102206, China
    2.Shanxi Hepo Power Generation Company Limited, Yangquan 045011, Shanxi, China
  • Received:2021-06-30 Revised:2021-10-19 Published:2022-02-05 Online:2022-02-18
  • Contact: Kai ZHANG E-mail:15210289575@163.com;kzhang@ncepu.edu.cn

摘要:

采用微波消解法和氢化物发生-原子荧光光谱法考察了9台超低排放在役机组硒迁移转化规律,探究了循环流化床(CFB)和煤粉炉(PC)机组飞灰特性差异对硒吸附能力的影响。燃烧后煤中硒几乎全部呈现挥发态,底渣中残留量极低。与浓度归一化和质量分布法相比较,相对富集系数法可以客观地评价燃煤副产物中硒的富集能力,两类机组中硒均主要富集于飞灰中。CFB较低炉膛温度和添加CaO可以降低入炉煤中硒释放比例并增强飞灰对硒的吸附能力,故其底渣和飞灰中硒的富集程度均高于PC,导致脱硫石膏中硒富集程度低于PC。飞灰对硒的吸附量随比表面积或孔容积增大而增大,但随粒径或孔径增大而减小。CFB飞灰中未燃尽碳含量高、形状不规则、表面粗糙且存在较多蜂窝状孔隙,导致其对硒的富集程度高于PC飞灰。

关键词: 煤燃烧, 污染, 硒迁移转化, 微波消解, 吸附

Abstract:

Microwave digestion and hydride generation-atomic fluorescence spectrometry were used to investigate the migration and transformation of selenium (Se) in nine ultra-low emission units in service. The characteristics of fly ash from circulating fluidized bed (CFB) and pulverized coal (PC) units are compared for understanding the Se adsorption ability in fly ash. After combustion, Se in coal is essentially volatilized in gas but only a small amount is remained in bottom slag. Compared to concentration normalization method and mass distribution method, relative enrichment factor method is more suitable to evaluate the Se enrichment ability for feed coal and combustion by-products, which indicates that Se is enriched in fly ash from both CFB and PC units. Low combustion temperature and CaO additive in CFB boiler can not only reduce Se release ratio from coal but also enhance the Se adsorption ability in fly ash. As a result, Se enrichment in bottom slag and fly ash from CFB is more than that from PC, while Se in gypsum from CFB unit is less than that of PC. Moreover, Se adsorption content is heavily depended on the physical properties of fly ash. The amount of selenium adsorbed by fly ash increases with the increase of specific surface area or pore volume, but decreases with the increase of particle size or pore size. The fly ash from CFB unit has high unburned carbon content, irregular shape, rough surface and more honeycomb pores, which makes Se enriched in fly ash from CFB more than that of PC.

Key words: coal combustion, pollution, selenium migration and transformation, microwave digestion, adsorption

中图分类号: 

  • TQ 53

表1

所选燃煤机组容量、类型及取样类型"

机组编号机组容量烟气尾端污染物控制设备取样点
CFB1135 MWSNCR+FF+WFGD入炉煤+底渣+飞灰
CFB2200 MWSCR+FF+WFGD入炉煤+底渣+飞灰+脱硫石膏
CFB3300 MWSNCR/SCR+FF+WFGD入炉煤+底渣+飞灰+脱硫石膏
CFB4300 MWSNCR+FF+WFGD入炉煤+底渣+飞灰+脱硫石膏
PC1300 MWSCR+ESP+WFGD入炉煤+底渣+飞灰+脱硫石膏
PC2330 MWSCR+ESP+WFGD+WESP入炉煤+底渣+飞灰+脱硫石膏
PC3350 MWSCR+ESP+WFGD+WESP入炉煤+底渣+飞灰+脱硫石膏
PC4600 MWSCR+ESP+WFGD+WESP入炉煤+底渣+飞灰+脱硫石膏
PC5600 MWSNCR/SCR+FF/ESP+WFGD+WESP入炉煤+底渣+飞灰+脱硫石膏

图1

燃煤电厂入炉煤及副产物中硒平均含量"

表2

燃煤机组入炉煤工业分析"

燃煤机组入炉煤工业分析/%(质量,空气干燥基)
水分灰分挥发分固定碳
CFB12.2341.5029.7226.55
CFB21.2461.2018.6218.94
CFB32.3633.9624.9438.74
CFB42.3839.7624.7433.12
PC10.9041.6712.2645.17
PC21.2529.3210.6758.76
PC32.6715.0529.9552.33
PC43.9816.4225.5754.03
PC52.8329.6727.3240.18

图2

飞灰和底渣与入炉煤中硒含量的比值"

图3

飞灰和底渣中硒质量分布"

图4

飞灰和底渣中硒相对富集系数"

图5

不同粒径飞灰中硒含量"

图6

不同粒径飞灰中未燃尽碳含量"

图7

CFB4和PC1机组不同粒径飞灰吸附和脱附等温曲线"

图8

CFB4机组和PC1机组飞灰SEM图"

图9

不同粒径飞灰中硒吸附含量与其比表面积关系"

图10

不同粒径飞灰中硒吸附含量与其孔容积关系"

图11

CFB4机组和PC1机组不同粒径飞灰中硒吸附含量与其孔径关系"

图12

CFB4机组和PC1机组不同粒径飞灰孔容积分布图"

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