Partitioning behaviors of zinc in eight coal-fired power plants with different fueled coals and air pollution control devices.

Emissions from coal-fired power plants (CFPPs) have a negative impact on the environment and metals are one of the categories of substances that have received considerable attention. In the present study, atmospheric zinc (Zn) emissions from eight CFPPs with different kinds of boilers and air pollution control devices (APCDs) in Guizhou Province, Southwest China, were investigated as well as the partitioning of this metal among boilers and APCDs. During the investigation of a CFPP, samples were taken of input and output materials during the same period. Our results give a Zn content of 32-165 mg kg for feed coal, 52-237 mg kg for bottom ash, 108-725 mg kg for fly ash, 1.2-6.0 mg kg for limestone, 1.6-7.3 mg kg for gypsum, and 1.39-7.06 μg Nm for stack gas. Most of the zinc content in the feed coal goes with the flue gas after combustion and amounts to 94.2-96.1% and 60.5-78.1% for pulverized coal-fired boilers (PC) and circulating fluidized bed boilers (CFB), respectively. Based on input Zn, a larger share (80.8-96.4%) ends up the captured fly ash of PC boilers than the case of CFB boilers (66.1-73.6%). In turn, a minor portion is captured into the flue gas desulfurization gypsum, while we found a maximum of 0.05‰ is emitted into the atmosphere. The atmospheric emission factors (EMFs) of Zn for the eight CFPPs are 7.55-57.22 mg ton coal, 4.17-22.75 μg (kWh), or 0.39-2.36 g TJ using different benchmarks. Overall, the calculated emission factors here are distinctively low with the upgrading of APCDs in recent years. An estimation of 1276 ± 1047 kg year (range: 498-3777 kg year) of Zn is emitted into the atmosphere from the CFPPs of Guizhou Province in 2017 by coupling the EMFs obtained from this study and the coal consumption by this category of power plants.