Key Takeaways & Executive Findings
- •• • Ultra-low emission transformation reduced PCDD/Fs emission concentrations by 86.5% (sintering), 95.1% (converter), and 66.9% (electric arc furnace), with emission factors falling to 0.11, 0.009, and 0.014 μg I-TEQ·t−1 product, respectively—demonstrating process-specific co-benefits that enable compliance with Stockholm Convention obligations. • • National PCDD/Fs emissions from iron and steel in 2022 under transformation were 104 ± 26 g I-TEQ versus 2049 ± 763 g I-TEQ without, a 94.9% reduction—quantifying the substantial environmental gain and informing inventory updates. • • Post-transformation congener profiles shifted from high-chlorinated to low-chlorinated dominance, yet 2,3,4,7,8-PeCDF remained the primary toxicity contributor (35%–56%), indicating that toxicity-oriented control must target this specific congener despite overall reductions. • • Field data from representative processes and air pollution control devices underpin the emission factors, but the lack of post-transformation studies elsewhere limits extrapolation; further on-site measurements are essential to refine national estimates.
Abstract
China's iron and steel industry has undergone comprehensive ultra-low emission transformation, meeting stringent limits for conventional pollutants, yet the fate of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) remains unclear. This study combined field sampling and literature review to analyze PCDD/Fs emission characteristics from sintering, converter, and electric arc furnace processes before and after transformation, and calculated national emissions for 2022. Results demonstrate that ultra-low emission transformation effectively reduces PCDD/Fs emissions. Specifically, emission concentrations decreased by 86.5%, 95.1%, and 66.9% for sintering, converter, and electric arc furnace, respectively, with corresponding emission factors dropping to 0.11, 0.009, and 0.014 μg I-TEQ·t−1 product. Under the transformation scenario, total national emissions were 104 g I-TEQ (uncertainty ±26 g), a 94.9% reduction from the unreformed scenario (2049 ± 763 g I-TEQ). Congener profiles shifted from high-chlorinated dominance to low-chlorinated dominance, while toxicity equivalent distribution remained dominated by 2,3,4,7,8-PeCDF (35%–56%). This study quantifies the co-benefit of PCDD/Fs reduction, providing critical data for updating China's emission inventory and formulating toxicity-oriented control policies.
1. Introduction
China's iron and steel sector, a cornerstone of industrial output, has historically been a major source of unintentional persistent organic pollutant releases, particularly polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Prior to ultra-low emission mandates, conventional air pollution control devices (APCDs) achieved only partial removal, leaving PCDD/Fs emissions poorly characterized and often exceeding regulatory thresholds. The 2004 national inventory attributed 33.2% of total PCDD/Fs emissions to iron and steel processes, with sintering alone contributing the largest share. However, the transition to ultra-low emission standards—requiring stringent limits on particulate matter, sulfur dioxide, and nitrogen oxides—has inadvertently altered the formation and abatement pathways for PCDD/Fs, yet systematic quantification of these changes remained absent.
This study addresses that gap by providing the first comprehensive assessment of PCDD/Fs emission dynamics across sintering, converter, and electric arc furnace operations before and after ultra-low emission transformation. Through field sampling and literature synthesis, we establish process-specific emission factors and a national emission inventory for 2022, revealing a 94.9% reduction in total emissions. Critically, we identify a shift in congener profiles from high- to low-chlorinated species, while the toxic equivalent remains dominated by 2,3,4,7,8-PeCDF. These findings not only quantify the co-benefit of ultra-low emission controls but also highlight the need for toxicity-directed monitoring and policy, offering a data-driven foundation for updating China's PCDD/Fs inventory and advancing Stockholm Convention commitments.
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XU Jiaying, SONG Xiwen, CHEN Xiu, CHEN Yuanzheng, JIANG Yilun, DONG Wei, LI Qing (2026). Emission Changes of PCDD/Fs in the Iron and Steel Industry under Ultra-Low Emission Transformation. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025050601
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Frequently Asked Questions
What are the specific removal efficiencies of ultra-low emission transformation for PCDD/Fs across different steelmaking processes, and how do these compare to conventional APCDs?
The transformation achieved removal efficiencies of 86.5% for sintering, 95.1% for converter, and 66.9% for electric arc furnace, based on emission concentration reductions. These figures are substantially higher than typical conventional APCDs, which historically achieved partial removal (e.g., 30-70% depending on technology). The enhanced performance is attributed to the integration of advanced APCDs such as activated carbon injection and bag filters, which are part of ultra-low emission configurations.
How reliable are the national emission estimates given the limited post-transformation field data?
The national estimate of 104 ± 26 g I-TEQ for 2022 under transformation carries an uncertainty of ±25%, derived from variability in emission factors and activity data. While the study's field sampling covered representative processes and APCDs, the lack of comprehensive post-transformation data across all plants introduces potential bias. The authors acknowledge this limitation and recommend further on-site measurements to refine the inventory.
Why does the toxicity equivalent distribution remain dominated by 2,3,4,7,8-PeCDF even after congener profiles shift to low-chlorinated species?
2,3,4,7,8-PeCDF has a high toxic equivalency factor (TEF) of 0.5, so even at lower concentrations it contributes disproportionately to total I-TEQ. The shift to low-chlorinated congeners reduces overall mass but does not proportionally reduce the most toxic congeners. This underscores the need for toxicity-based emission limits rather than total mass-based limits.
What are the implications of the emission factor reductions for policy and regulatory compliance?
The emission factors for sintering, converter, and EAF dropped to 0.11, 0.009, and 0.014 μg I-TEQ·t−1 product, respectively. These values are below typical regulatory thresholds in many jurisdictions, indicating that ultra-low emission transformation can enable compliance with Stockholm Convention requirements. The 94.9% reduction in national emissions supports China's commitment to POPs reduction, but ongoing monitoring is essential to ensure sustained performance.
How do the PCDD/Fs emission reductions from ultra-low emission transformation compare to the costs and operational impacts on steel production?
The study does not provide a cost-benefit analysis, but the substantial emission reductions (86.5-95.1%) suggest significant environmental gains. However, ultra-low emission transformation involves high capital and operational costs, including advanced APCDs and energy consumption. Future research should evaluate the economic trade-offs to inform policy decisions, balancing environmental benefits with industrial competitiveness.
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