School of Life Sciences, Anhui University, Hefei, 230601, China.
School of Resources and Environmental Engineering, Anhui University, Hefei, 230601, China.
Chemosphere. 2022 Sep;302:134859. doi: 10.1016/j.chemosphere.2022.134859. Epub 2022 May 6.
Due to its low vapor pressure, chromium (Cr) mostly emitted as fly ash particles (especially PM) into environment in coal-fired power plants (CFPPs). The ultra-low emission (ULE) control technologies used in current CFPPs may be beneficial to reducing both the regular pollutants and hazardous trace elements (e.g., Cr), but the insight into the removal efficiency of Cr by different upgrading air pollution cleaning devices (APCDs) and the environmental stability of the Cr-bearing wastes produced from those APCDs in the ULE CFPPs has rarely reported. This study investigated and compared the distribution and emission characteristics of Cr in a Chinese CFPP before and after ULE, and the leaching behavior of Cr after ULE retrofitting in combustion byproducts was also revealed. The results showed that Cr was primarily captured in bottom and fly ashes (80.85%), followed by gypsum (0.02%) and sludge from wet electrostatic precipitator (WESP) (4.52 × 10%), with only 3.02 × 10% emitted into the atmosphere. Additional WESP had a large removal efficiency of Cr with the value of 92.04%, and the overall Cr removal efficiency of selective catalytic reduction (SCR) equipment, electrostatic precipitator (ESP), wet flue gas desulphurization (WFGD) system, and WESP equipped after ULE retrofitting was 99.99%. Notably, although the mass percentage of Cr in WESP sludge was negligible, the concentration of Cr in WESP sludge was 324.04 mg/kg. The leaching concentrations of Cr in combustion byproducts were in the descending order: fly ash > WESP sludge > bottom ash > gypsum. The atmospheric emission factor of Cr in the studied power plant was 1.08 mg/t coal, which was significantly lower than those of the CFPPs before ULE retrofitting. Therefore, the ULE retrofitting for CFPP was beneficial to reduce Cr emissions. More attention should be paid to the subsequent processing problem of solid combustion byproducts, especially the WESP sludge.
由于铬（Cr）的蒸气压较低，因此主要以飞灰颗粒（尤其是 PM）的形式排放到燃煤电厂（CFPP）的环境中。目前 CFPP 中使用的超低排放（ULE）控制技术可能有利于减少常规污染物和有害痕量元素（例如 Cr）的排放，但对不同升级空气污染清洁设备（APCD）对 Cr 的去除效率以及这些 APCD 在 ULE CFPP 中产生的含 Cr 废物的环境稳定性的了解却很少。本研究调查并比较了 ULE 前后中国 CFPP 中 Cr 的分布和排放特征，还揭示了 ULE 改造后燃烧副产物中 Cr 的浸出行为。结果表明，Cr 主要被捕获在底灰和飞灰中（80.85%），其次是石膏（0.02%）和湿式静电除尘器（WESP）污泥（4.52×10%），仅有 3.02×10%排放到大气中。额外的 WESP 对 Cr 具有很高的去除效率，其值为 92.04%，选择性催化还原（SCR）设备、静电除尘器（ESP）、湿式烟气脱硫（WFGD）系统和 ULE 改造后配备的 WESP 的整体 Cr 去除效率为 99.99%。值得注意的是，尽管 WESP 污泥中 Cr 的质量百分比可以忽略不计，但 WESP 污泥中 Cr 的浓度为 324.04mg/kg。燃烧副产物中 Cr 的浸出浓度顺序为：飞灰>WESP 污泥>底灰>石膏。研究电厂 Cr 的大气排放因子为 1.08mg/t 煤，明显低于 ULE 改造前的 CFPP。因此，对 CFPP 进行 ULE 改造有利于减少 Cr 的排放。应更加关注固体燃烧副产物的后续处理问题，特别是 WESP 污泥。
