Fugitive VOC Emissions from Equipment and Pipeline Systems in Coal-Chemical Enterprises: Leak Characteristics, Emission Evaluations, and Reduction Effectiveness Identifications

Volatile organic compounds (VOCs) from coal-chemical enterprises pose a significant challenge to the environment and sustainability. Nevertheless, the fugitive VOC emissions from equipment and pipeline systems, and the application research of leak detection and repair (LDAR) technology within coal-chemical enterprises have received limited attention, impeding sustainable development goals. This study selected three representative coal-chemical enterprises to conduct large-scale LDAR surveys in 2022 and 2023. Based on field measurements exceeding 260,000 affected components per year, leak characteristics, emissions, and LDAR effectiveness were analyzed and evaluated from three aspects: enterprise-wide, process-specific, and component-level. The one-way analysis of variance revealed no statistically significant differences in overall leak concentrations between enterprises, whereas significant differences between component types. Non-flanged connectors had a higher leak level, followed by open-ended lines, pumps, valves, and flanges. The process-specific leak ratios (0.29~1.71%) and emission contributions (9.33~35.31%) were highest in downstream units, whereas leak ratios (0.05~0.08%) and emission contributions (0.75~10.57%) were lowest in midstream and upstream units, respectively. The component-level ratios were pronounced for open-ended lines (1.84%) and valves (0.79%), while emissions were primarily concentrated on flanges, non-flanged connectors, and valves (96.1~99.1%). The repair ratios (87.42%, 90.88%), emission reduction rates (58.56%, 60.45%) under restorations, and decreases in leak ratios (44.59%) and emissions (33.22%) over consecutive years comprehensively identified the LDAR effectiveness. Finally, the precise control and policy implications were discussed accordingly. These findings aimed to provide basic references for coal-chemical enterprises in precise control and sustainability policies.