The scope of this project includes: 1) surveying the stationary emission and monitoring the ambient air quality of dioxins and heavy metals; 2) establishing and updating emission inventory; 3) assisting the control, reduction and emergency response of dioxins and heavy metals emission.
The purposes of emission survey are to establish the emission factors, to improve the reliability of emission estimate quantity, and to clarify the current emission status of emission sources. Dioxin and heavy metal emission surveys were performed at three stationary sources. Additionally, steam boilers burning waste rice husk as fuel, municipal waste incinerators, and electric arc furnaces were selected for dioxin emission surveys. It was found that all of the dioxin emission concentrations can meet the emission standards. Cement rotary kilns, sintering furnaces, and municipal waste incinerators were selected to conduct emission surveys for heavy metals. Municipal waste incinerators equipped with good air pollution control devices and performed good waste recovery classification showed low emission concentrations of heavy metals that meets the emission standards. In contrast, the cement industry and sintering furnace showed higher mercury emission concentration among all harmful heavy metals.
The dioxin and heavy metal air quality monitoring campaigns were executed in May and within September and October in this year. The average dioxin concentration of 22 ambient air monitoring stations was 0.016 pg I-TEQ/m³, showing a decending trend as compared with previous monitoring results. The ambient concentrations of hazardous heavy metals obtained in general air quality monitoring stations can meet the standards of Taiwan and the European Union. The concentrations of crust element-type heavy metals were higher than the other types. The mass concentrations of 24 heavy metals accounted for about 2.5% of the total PM₁₀ mass. The ambient environment of cement plants showed higher concentrations of mercury and hexavalent chromium, which are mainly related to the use of raw materials and chromium-containing refractory bricks for the cement kiln. It is recommended to rationalize the use of raw materials and change the chromium-containing refractory bricks for reduction of the ambient heavy metal concentration.
The total dioxin emission quantity is estimated 49.32 g I-TEQ/year in 2019, slightly lower than that in 2018. The main dioxin emission sources are boilers such as coal-fired power plants, steel melting industries, and fugitive emission sources (fire, straw and agricultural waste combustion, etc.), which account for 83% of the total emissions. As for the heavy metal emissions in 2019, the total emissions of lead , cadmium, mercury, and arsenic are 30.4, 0.78, 1.76, and 3.35 metric tons/year, respectively, and comparable to those surveyed in 2018. The main heavy metal emissions are also related to energy/electricity sources, with the exception of lead that comes mainly from mobile sources. In respect of uncertainty analysis and emission level classification, the emission data for stationary source based on actual emission tests and database from air pollution fee showed better reliability. In contrast, the data for fugitive sources and mobile sources poor reliability due to lack of test data.
A total of 13 plants of emission reduction counseling were executed in this project. Among them, four of the fuel-burning boilers exceeded the emission standards due to the lack of normal operation and maintenance of the air pollution control equipment, e.g., filter bag damaged and inappropriate way of spraying activated carbon into anti-control equipment that makes the carbon impossible to effectively adsorb dioxin, etc. Suggestions for improvement were provided in this project. Two of the fuel-fired boilers have been shutdown or replaced with fuel-oil or fuel-gas boilers. The reason for exceeding the dioxin emission standard of the industrial waste incinerator is that the filter bag has not been replaced for a long time or is damaged. Follow-up improvements have been completed. The medical incinerators are advised to counsel the industry to change the activated carbon injection method to reduce the proportion of unburned carbon in fly ash.
There are totally five cremation sites mainly using catalyst decomposition towers, but the catalyst bricks used have not been replaced for a long time. It is suggested that the maintenance of filter bags and the inspection of catalyst should be strengthened to check whether the catalyst is still active and at the same time assessing the need for replacement. Cremation furnaces using activated carbon injection have the problem that fly ash cannot be properly handled. The main reason for municipal waste combustors that exceed the dioxin emission standard is that the quality of disposal of industrial waste is too complicated to be controlled. The reason for the electric arc furnace is to prevent from the lack of proper maintenance of the equipment and the poor nature of the scrap iron.
By planning and reviewing the revision of emission control standards, the emission standards for incinerator, cement kiln and lead secondary production were proposed. Assistance in planning heavy metal emission control strategy for coal-fired power plants was also implemented. Among them, the lead secondary smelting emission standard has been implemented for more than 20 years, thus it is indeed necessary to amend it. At present, the domestic emission status collection and site survey have been completed, the relevant foreign emission standard work and the proposed revision standard draft have been collected, and the subsequent administrative work will assist the revision of relevant laws.
An economic impact analysis was conducted in this project, including the actual plant reduction counseling and the draft of the revised regulations of lead secondary production, municipal waste incinerator and cement kiln to estimate the possible reductions in emissions of different pollutants. The averaged unit benefit (BPT) parameters of different stationary source industries were used in this analysis. The economic benefits derived from the reduction of cement kiln and large-scale waste incinerator regulations after revision were estimated. The analytical results showed that the economic benefit of derivation is much higher than the improvement expenditure required, and the benefit of legal revision is much larger than the benefit of dioxin reduction counseling.
