This project's main tasks include: (1) atmospheric environment dioxin and heavy metal environmental monitoring, (2) dioxin emission characteristics of stationary sources investigating, (3) emission inventories of dioxin and heavy metal updating, (4) emission reduction consulting for stationary sources and administrative support regarding emergency response to pollution incidents.
In the two atmospheric monitoring sessions conducted in the 2023, sampling for dioxins and heavy metals took place during May to July and Septemebr to October. The average dioxin concentrations at 22 air quality monitoring stations across the country were 0.018 and 0.009 pg I-TEQ/m³ (0.017 and 0.009 pg WHO-TEQ/m³) for the respective periods, while the concentrations of polychlorinated biphenyls (PCBs) were 0.0018 and 0.0013 pg WHO-TEQ/m³. The annual average values were both lower than historical averages in the corresponding calendar months. Heavy metals, primarily crustal elements, accounted for an average proportion of approximately 1.53~6.39% of PM₁₀. However, some northern stations were influenced by overseas pollution transmission in May, resulting in higher mercury concentrations. High mercury concentrations also happened in Kao-Ping area in May, but the concentrations decreased in the October.
In the emission inventory update section, the estimated dioxin emissions in Taiwan for the 2022 were approximately 41.12g I-TEQ/year, lower than the emissions in the 2021. The primary reason for the reduction was the decreased activity in the metal manufacturing industry. The electric arc furnaces had lower average emission factors and activity levels in 2022, contributing to the reduction. The main stationary sources included boilers in power generation, the iron and steel smelting industry (sintering furnaces, electric arc furnaces), and waste incinerators, accounting for 55.9% of the total emissions.
For heavy metals, the estimated emissions in the 2022 for lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As) are approximately 26.73, 0.698, 1.442 and 2.221 tons/year respectively. In terms of uncertainty analysis, the emission coefficient uncertainty is lower due to regular stack test conducted in high emission potential industries. However, there is higher uncertainty in mobile and fugitive sources.
Mercury distribution investigation was carried out for 2 cement kilns in Yilan County and Hualien County. Both kilns exhibited mercury circulation, with Yilan County's cement kiln showing more significant circulation. Mercury in the kiln's waste gas was adsorbed and re-entered the kiln, potentially leading to increasing emission concentrations over time. The main mercury input sources included washed fly ash, iron slag, clay, and limestone. The mercury main output was stack emission. The iron slag was a major mercury source in both cement kilns. The source of high mercury content in iron slag should be conducted, possibly related to coal combustion fly ash, and exploring the feasibility of using alternative materials to lower the mercury content.
This project conducted emission reduction consulting for 8 emission sources, including non-ferrous secondary smelting furnace, boilers, large-scale municipal waste incinerators, and electric arc furnaces. One of the emission source was the supplier of iron slag to cement kilns. According to this project and past research done by the local government, iron slag is a major mercury source in cement kilns. Experts recommend investigating the reasons for high mercury content in iron slag, possibly related to coal combustion fly ash, and exploring the feasibility of using alternative materials with lower mercury concentrations. In one of the two participated non-ferrous secondary smelting facilities, the high dioxin stack emission concentrations were mainly due to particle accumulation in pipelines. Experts suggest pipeline cleaning frequency enhance and improvements in particle control devices. The other participant, with dioxin emissions close to the emission standard, may be influenced by an increased chlorine content in the incoming materials. This year, two using circulating fluidized bed boilers were included for emission reduction consulting. One burned solid recovered fuel (SRF) and other used wood chips. Both facilities had high dioxin emission concentrations in the past stack test results. Despite national fuel component standards, the significant variation in SRF chlorine content poses operational challenges. Guidance given by the experts for these participants included examining gas residence times in high-temperature zones, controlling appropriate sulfur content, reviewing activated carbon injection rates, and evaluating the effectiveness of particulate collection equipment. For the electric arc furnace, the accumulation of ash in the pipe before baghouse region could potentially fall in dioxin de novo temperature window. Experts recommended temperature control for process exhaust gases and investigating the region which has high potential falling in the dioxin re-synthesis temperature range to avoid de nove. In this year, a large-scale municipal waste incinerator exceeded the dioxin emission standards. Based on the dioxin congener, experts recommended investigating the distribution of filter cake on the filter bags to clarify concerns about the emission of fine particles.
Through the remote air quality monitoring results in the petrochemical industrial zone, it was discovered that the main concern of Hailake, Rende, and Linyuan industrial zones was chlorine compounds hazardous air pollutants (HAPs). Further investigations focused on conducting on-site monitoring within these industrial zones to confirm emission sources related to chlorine-containing processes. The results indicated that high concentrations of Vinyl Chloride Monomer (VCM) was related to components leaked in Dayang and the Formosa Plastics Renwu Plant, but the influence on fixed stations concentration was limited. Following improvements in Ethylene Dichloride (EDC) storage tanks by Taiwan VCM corporation, emissions of EDC and Chloroform (CF) from the wastewater treatment plant gradually became significant at fixed stations. Subsequently, measures were requested from the industry to plan for reducing chlorine content in original wastewater and ensuring the effective sealing of wastewater treatment units. This project aims to continually monitor and assess the effectiveness of industry improvements through these results.
Regarding the planning and review of revisions to emission control standards and related administrative procedures, this project has proposed draft amendments to emission standards for the iron and steel industry, cement kilns, and incinerators. Communication meetings were held in 2022 with industry representatives to understand the emission reduction challenges and the time required for improvements. The draft amendments to emission standards for the iron and steel industry include lowering the general air pollutant emission standards for sintering furnaces and coke ovens to encourage stable operations by the industry. For cement kilns, emission standards for mercury and fluoride were proposed to manage high potential mercury emission due to alternative material usage in cement industry. The draft amendments to incinerator emission standards were proposed lowering the general air pollutant and mercury emission standards for municipal waste incinerators. Additionally, a experience-sharing meeting was organized this year discussing insights on cremation furnace emission control.
