Dioxin Emissions Research Articles

Pollution Characteristics and Emission Factors of PCDD/Fs from Iron and Steel Industry

The pollution level, emission characteristics, and emission factors of PCDD/Fs from a number of steel plants were investigated in a particular province of China. The results showed that the concentration of PCDD/Fs was at a low level and decreased by 1-2 orders of magnitude compared with that in 2005-2019. In detail, the concentrations of PCDD/Fs ranged from 0.003-0.557 ng·m-3(I-TEQ), and the mean value was 0.165 ng·m-3 for the sintering process. Moreover, the concentrations of PCDD/Fs ranged from 0.006 to 0.057 ng·m-3, and the mean value was 0.025 ng·m-3 for the electric furnace process. In addition, the concentration of PCDD/Fs in the iron and steel industry from 2005 to 2020 increased first and then decreased, especially after the implementation of the new emission standard and the ultra-low emission control of conventional pollutants such as smoke, showing a significant decline. The results of fingerprint analysis showed that 2,3,7,8-TCDF was the largest congener contributing to the mass concentration, and lower chlorinated PCDFs were increased. This result differed from those of previous studies in which highly chlorinated PCDFs and PCDDs dominated, indicating that the generation source of PCDD/Fs had changed. The congener and isomer profiles of PCDD/Fs in flue gas from the sintering process were similar to those in the flue gas from the electric furnace process. Additionally, showing the characteristics of the typical high-temperature thermal process, the de novo synthesis may be the dominant mechanism of formation of PCDD/Fs in the sintering process and electric furnace process. The emission factor was 0.003-0.5 μg·t-1 (I-TEQ), and the average emission factor was (0.18±0.22) μg·t-1 for the sintering process. The emission factor was 0.04-0.5 μg·t-1, and the average emission factor was (0.27±0.23) μg·t-1 for the electric furnace process. These values were far lower than those of the standard toolkit for identification and quantification of dioxin and furan emissions released by UNEP in 2013 and the emission factors in the dioxin emission inventory of China in 2004. It is suggested that the emission factors of PCDD/Fs in the iron and steel industry of China should be studied and updated.

Prediction of dioxin emission from municipal solid waste incineration based on expansion, interpolation, and selection for small samples

Dioxin (DXN), which is named a “century poison”, is emitted from municipal solid waste incineration (MSWI). The first step to effectively control and reduce DXN emissions is the application of soft sensors by utilizing easy-to-detect process data. However, DXN samples for data-driven modeling are extremely lacking because of the high cost and long period of measurement. To address the above issue, this work proposes a DXN emission prediction method based on expansion, interpolation, and selection for small-sample modeling, i.e., EIS-SSM, involving three main steps: domain expansion, hybrid interpolation, and virtual sample selection. First, the domain of samples is determined by domain extension, a great number of virtual samples in this domain are generated through hybrid interpolation, and the optimal virtual samples are chosen for virtual sample selection. Afterward, a prediction model for DXN emission is constructed using the optimal samples and raw small samples. Two cases, that is, a benchmark dataset and a DXN dataset from an actual MSWI plant, are applied to implement the proposed method. Results showed that compared with the non-expansion and existing expansion methods, the proposed method exhibits an improved performance by 48.22% and 13.68%, respectively, in the benchmark experiment and by 72.44% and 34.67%, respectively, in the DXN emission prediction experiment. Therefore, the proposed method can substantially improve the prediction of DXN emission from MSWI.

Does the pollution halo hypothesis exist in this "better" world? The evidence from STIRPAT model.

Multinational corporation has changed their host countries. The new wave of FDI inflow attracted the interest of policymakers. FDI has significant effects on both productivity and carbon dioxide emissions. The host countries should carefully consider the advantages and disadvantages of FDI to their nation. The previous literature has not illustrated the global context’s theoretical halo or haven pollution hypothesis. Using panel data of 96 countries between 2004 and 2014, our empirical results confirm the haven pollution hypothesis in both developing and developed countries. We employ the different general methods of moments (GMMs) to engage FDI in traditional STIRPAT theoretical frameworks. The empirical results contribute to the evidence of the EKC theory. The country’s income level has been used to modify our models. The affluence of the economy, urbanization, FDI, and industrial sector would cause harmful effects on carbon dioxin emissions globally. The paper implies the two models which can be used for both developed and developing countries. The policymaker can use both short-run and long-run elasticities from those models to implicate their country’s FDI inflow strategy.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-022-21654-4.

Levels, time trends, and distribution of dioxins and polychlorinated biphenyls in fishes from the Baltic Sea

Fish absorb dioxins from the environment through water and contact with sediments but the main source is food. These contaminants also enter the human body with food, including through the consumption of fish. This study presents the dioxin and polychlorinated biphenyl (PCB) concentrations in 145 samples of four fish species (herring, sprat, sea trout, salmon) caught in the southern Baltic Sea. The study results permit assessing whether the efforts made in recent years to reduce dioxin and PCB emissions into the environment have translated into decreases in concentrations of these pollutants in Baltic Sea fishes and whether these raw fish materials meet food law requirements. The safest fish species with regard to dioxins were designated, as were those of which consumption should be limited. The influence of fish age (length) and weight on dioxin and dioxin-like polychlorinated biphenyl (dl-PCB) concentrations was investigated. The correlation between fat content and dioxin concentration was determined. The Baltic Sea region and fishing ports from which the least contaminated fish come were also determined. The studies indicated that dioxin and PCB concentrationsin fishes from Polish fishing areas are currently lower than they were twenty years ago.

Effect of Water Molecule on the Complete Series Reactions of Chlorothiobenzenes with H/·OH: A Theoretical Study

The chlorothiobenzenes (CTBs) are the principal precursors for the formation of polychlorinated thianthrene/dibenzothiophenes (PCTA/DTs), which have high toxicity and wide distribution in the environment. Under the pyrolysis or combustion conditions, CTBs can react with H/·OH radicals to form the chlorothiobenzyl radicals (CTBRs) through abstraction of the chlorothiobenzyl-hydrogen. The water molecule can play an important role in this process. The coupling of CTBRs is the essential first step in forming PCTA/DTs. In this paper, quantum chemical calculations were carried out to investigate the formation of CTBRs from the complete series reactions of 19 chlorothiobenzene (CTB) congeners with H/·OH radicals in the presence of the water molecule. Using the MPWB1K/6-311 + G(3df,2p)//MPWB1K/6-31 + G(d,p) energy level, schematic energy profiles were constructed with the water molecule and then compared with the non-hydrated case. The present study shows that structural parameters and thermal data, as well as CTBRs formation potential from CTBs, are strongly dominated by the chlorine substitution at the ortho-position of CTBs. Meanwhile, the water molecule can promote the CTBR formation from CTBs abstracted by H/·OH, which has a stronger catalysis effect on the H abstraction from CTBs by OH than from CTBs by H. This study may provide reference parameters for future experimental research, which would enhance measures to reduce dioxin emission and establish dioxin control strategies.

Sustainable Energy Transition in Thailand: Drivers, Barriers and Challenges of Waste-to-Energy at Krabi Province

Waste-to-Energy (WtE) has been considered as an option to eliminate Krabi’s problems of municipal solid waste (MSW) management. A survey on WtE potential as well as key drivers, barriers, and challenges to overcome the barriers was conducted in this study. The study found high WtE potential due to huge amount of many years accumulated MSW in couple with the increasing trend of new daily waste generation. Meanwhile, Krabi is an island having land limitation for landfill. The urgent need to eliminate the huge amount of MSW has become a key driver for WtE implementation. One more key driver of WtE is Krabi Goes Green roadmap with target to generate electricity from 100% renewable energy by the year 2026. Another key driver is disruptive effects of MSW management roadmap under Section 44 of Thailand's Constitution 2017. By the way, implementation of WtE is facing with public opposing due to concerning of dioxin and air pollutant emissions from solid waste combustion. How to ensure zero emission of dioxin and air pollutants is very challenging to achieve public trust and acceptance. High temperature combustion as well as installation of high efficiency end-of-pipe treatment together with real-time monitoring system was recommended by some interviewees of the present study. In addition, due to MSW management and WtE power plant investment must involve with many organizations; therefore, stakeholders' open mind consultation and policy integration among relevant governmental agencies are highly recommended.

Formation and control of dioxins during thermal desorption remediation of chlorine and non-chlorine organic contaminated soil

Formation and emission of dioxins is a great concern during thermal desorption remediation of organic contaminated soil. The differential formation of dioxins from chlorine organic contaminated soil (COCS) and non-chlorine organic contaminated soil (NCOCS) is still unclear and the control technique for the dioxins generated is an urgent need. In this study, the formation and distribution characteristics of dioxins were investigated in the thermal desorption unit combined with flue gas purification system during COCS and NCOCS treatments. Although organic contaminates were well desorbed, de-novo formation of dioxins was observed for both COCS and NCOCS, as well as synthesis from precursors for NCOCS. The gas-phase dioxin in the flue gas purification system continuously decreased during NCOCS thermal desorption, while the dioxin concentration in the quench tower sharply increased from 0.46 to 2.13 ng/Nm3 through de-novo synthesis during COCS treatment. Furthermore, the emission of dioxins only slightly reduced (for COCS) or even increased (for NCOCS) at 70% operating load. The catalytic adsorption tower within modified activated carbon and V5-Mo5-Ti catalyst after bag filter can reduce the emission of dioxins up to 91.4% at the condition of secondary combustion chamber closure, demonstrating that the catalytic adsorption tower can replace the secondary combustion chamber for controlling dioxin emission. More importantly, the highly toxic low-chlorinated polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDD/PCDFs) were selectively removed from flue gas by the catalytic adsorption tower. These results reveal the differential formation characteristics of dioxins during COCS and NCOCS thermal treatments and highlight V5-Mo5-Ti/ modified activated carbon as a promising catalytic adsorption material to control the emission of dioxins from the thermal desorption of organic contaminated soil.

Curbing dioxin emissions from municipal solid waste incineration: China's action and global share

China generates the world's second-largest amount of municipal solid waste (MSW) and incinerates the largest quantity of MSW. However, data on the latest dioxin emissions from MSW incineration (MSWI) and the related global share were lacking. In the context of MSW classification, distinguishing the long-term MSW generation and incineration quantity, and dioxin emissions was necessary for macro-control and policy-making by the Chinese Government. By considering population size and GDP per capita, China's MSW generation toward 2050 was projected based on Monte Carlo simulation. Moreover, dioxin emission factors were also assumed based on the diffusion rate of four grades of air pollution control devices (APCDs). Finally, we show that the quantity of China's MSW generation in 2050 will be 363.50 million tonnes (Mt) with 341.06–382.45 Mt of 75% certainty. China's dioxin emissions from MSWI were approximately 15.46 g I-TEQ in 2019, which accounted for 26.1% of total emissions from global MSWI. We discuss dioxin emission reduction scenarios depending on MSW diversion and APCD upgrades. China's dioxin emissions will be 70.38 g I-TEQ for the business-as-usual scenario, and the dioxin emissions will be 9.29 g I-TEQ (within the range of 8.88–9.64 g I-TEQ) for the optimal scenario in 2050. Moreover, in 2050, the APCD diffusion rate will account for 98.8% of the sensitivity of dioxin emissions from China's MSWI. According to the assumed scenarios, there is a dioxin emission reduction potential of 18.6% and 86.8% in 2050 by MSW diversion alone and maximum APCD upgrades combined with food waste diversion, respectively.

A Study on the Method of Calculating the Dioxin Emission Factor of Municipal Waste and Medical Waste Incineration Facilities

Dioxin is unintentionally generated during waste incineration and heat treatment processes. The Stockholm Convention conducts research, development, and monitoring to eradicate persistent organic pollutants (POPs), so some countries are currently calculating dioxin emissions. Emissions are also being calculated in Korea, and we would like to improve the dioxin calculation method currently in use. In this study, two different calculation methods were used and compared. Calculation method A is now in use, and data measured on the same day was used as the calculation factor. Calculation method B was developed, where the average of the annual data was used as the calculation factor. The emission factors were calculated using methods A and B for municipal waste incineration facilities with a 2 t/h or higher processing rate. The method A results were 81 ~ 204 ng I-TEQ/ton, and the method B results were 79 ~ 284 ng I-TEQ/t. Also, the emission factors were calculated using both methods for medical waste incineration facilities with a processing rate of 1 t/h or higher. The method A results were 834 ~ 2,737 ng I-TEQ/t, and the method B results were 737 ~ 2,049 ng I-TEQ/ton. The range of fluctuations was small. In the future, if the facility operation data of small incineration facilities are confirmed, it is judged that comparative analysis is also helpful.

Emission Characteristics of Polychlorinated Dibenzo-p-Dioxins/Dibenzofurans (PCDD/DFs) in Commercial Bio-SRF and SRF Incineration Plants

Incineration plants using solid refused fuel (SRF) should control their air pollution materials to minimize environmental impact. This study evaluated the emission of polychlorinated dibenzo-p-dioxin/dibenzofurans (PCDD/DFs) congener patterns in seven commercial incineration plants in Korea using SRF and biomass SRF (bio-SRF). We examined the reduction rate differences of PCDD/DFs, depending on the air pollutant control device. All seven incineration plants sufficiently managed their dioxin emissions. However, both SRF and bio-SRF incineration plants showed active chlorination reactions and resulted in a large amount of highly chlorinated dioxins. The average dioxin concentration was 0.02 ng international toxic equivalency quantity (I-TEQ)/Sm3. Ratios of 1,2,3,4,6,7,8-HpCDF and 1,2,3,7,8-PeCDF were high in the waste heat boilers of both SRF and bio-SRF incineration plants. The octachlorinated dibenzofuran (OCDF) ratio was only high in the SRF incineration plants. Octachlorodibenzo-p-dioxin (OCDD) and OCDF exhibited high dioxin ratios. SRF incineration plants had a low ratio of OCDF to 1,2,3,4,6,7,8-HpCDF. In addition, the reduction rate of PCDD/DFs was substantially high after treatment with the air pollutant control device.

Dioxin emission and distribution from cement kiln co-processing of hazardous solid waste.

Cement kiln collaborative disposal technology can not only dispose of hazardous waste but also provide energy for the cement industry. However, the addition of hazardous waste may promote the formation of dioxins in cement kilns. In this study, typical hazardous solid wastes, such as solidified fly ash, electroplating sludge, and industrial residue, were co-processed in a cement kiln with different feeding positions and different feeding amounts. The concentrations of dioxins in the flue gas, clinker, and precalciner furnace slag were investigated. The effect of adding mixed hazardous solid waste on the formation of dioxin was also studied. The results showed that the concentration of dioxin in the flue gas without added hazardous waste was 1.57ng/m3, and the concentration varied from 1.03 to 6.49ng/m3 after the addition of hazardous waste. In addition, the concentration of dioxin in the flue gas and solid samples increased substantially when the co-processing ratio doubled. The large amount of Cu in solidified fly ash promoted the formation of dioxins, while the higher S content in the electroplating sludge suppressed the formation of dioxins. Compared with the addition of single hazardous waste, the concentration of dioxin in precalciner furnace slag increases by about 300%. Furthermore, the distributions of isomers in the clinker and precalciner furnace slag were similar. 1,2,3,4,6,7,8-HpCDD and OCDD accounted for a large proportion of the mass concentration, and the contribution rate ranged from 48.7 to 82.0%. Most importantly, correlation analysis showed that the concentration of dioxin was closely related to the copper content, hazardous waste types and additive proportion, with correlation coefficients of 0.79, 0.83, and 0.89, respectively. This study provides a basis for exploring the high environmental benefits of disposing of hazardous solid waste by co-processing in cement kilns.

Dioxin emission prediction based on improved deep forest regression for municipal solid waste incineration process

Dioxin (DXN) emission concentration is an important environmental indicator in the municipal solid waste incineration (MSWI) process. The prediction model of DXN emission can be used for pollution control to realize actual requirements of operation optimization. Therefore, a DXN emission concentration prediction model based on improved deep forest regression (ImDFR) is proposed in this study. A feature reduction layer based on out-of-bagging error is first introduced into the ImDFR to eliminate redundant variables and feed all confidence information on DXN emission into the feature enhancement layer of the MSWI process. A deep ensemble stacking model is subsequently built to depict deep features and increase diversity and accuracy using random forests, completely random forests, GBDT, and XGBoost as subforests. Finally, the predicted value of the DXN prediction model is determined in the decision layer. The DXN emission prediction model is verified using actual historical data of two incinerators operated with a daily processing capacity of 800 tons. The experimental results showed that the proposed prediction model presents higher accuracy and better generalization ability than state-of-the-art models.

CARBON NEUTRALITY OF UKRAINE BY 2050

The article presents the research results on some aspects of achieving carbon neutrality in Ukraine. Carbon neutrality is a challenge for the whole world. In 2020, the concentration of greenhouse gases in the atmosphere reached a historical maximum. The work aims to study the features of achieving carbon neutrality in Ukraine. The tasks of the work are the analysis of the components of the transition to low-carbon development, analysis of the consumption of fossil fuels, and activities related to the preservation of forests, natural steppe, and meadow ecosystems. Interest in carbon neutrality issues grows yearly, with a particularly in 2021-2022. Most articles on carbon neutrality were published by scientists from China, the USA, Great Britain, Turkey, and Pakistan. They are mainly devoted to carbon dioxide emissions, economic growth, renewable energy, energy consumption, financial development, co-integration, dioxin emissions, etc. Positive trends regarding the achievement of carbon neutrality have been identified: the supply of natural gas, coal, and peat has decreased, while the supply of renewable energy sources has increased; the share of coal and peat decreased by 26.4%, and the percentage of energy produced from renewable sources increased to 6.6%; the use of coal and peat decreased by 8.5%, natural gas by 5%, and biofuels increased by 16%; the share of biofuel use increased to 5.8%. Expenditures for environmental protection increased by 88.5%, for preserving biodiversity and habitat - by 3.6 times, and costs for air protection and climate change problems - by 2.5 times. The share of expenditures on the protection of biodiversity and habitat increased to 3.2%, and costs on atmospheric air protection and climate change problems to 19.3%. Negative trends that restrain the development of a carbon-neutral economy were also revealed: a low share of renewable sources in the structure of supply and use. Thus, the percentage of biofuel in aggregate use remains low - only 5.8% in 2020. The area of forest loss is increasing, and the area of forest regeneration has decreased by 36%. The area of reforestation remained at the same level, but the area of afforestation decreased ten times during 2010-2020.

PCDD/Fs and Dioxin-like PCBs in Chicken Eggs and Soils in Dong Nai Province, Southern Vietnam: Impacts of Raising Methods and Nearby Pollution Sources.

Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and dioxin-like PCBs (DL-PCBs) were examined in chicken egg and soil samples collected from Dong Nai Province, southern Vietnam. PCDD/F and DL-PCB levels in egg samples ranged from 5.74 to 1320 (median 350) and from 120 to 51,200 (median 1470) pg/g lipid weight (lw), respectively. Toxic equivalents to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TEQ) in egg samples ranged from 0.817 to 245 (median 10.8) pg TEQ/g lw. Higher dioxin levels were found in free-range eggs than non-free-range ones. We found significant correlation between TEQ levels in paired egg and soil samples collected from the Bien Hoa Airbase and some communities adjacent to industrial areas (Spearman's ρ = 0.671; p < 0.05), suggesting the co-occurrence of legacy and current dioxin emission sources in these areas.

National and Provincial Dioxin Emissions from Municipal Solid Waste Incineration in China

National and Provincial Dioxin Emissions from Municipal Solid Waste Incineration in China

Model framework to quantify the effectiveness of garbage classification in reducing dioxin emissions

Although waste incineration is a promising disposal method, it produces unwanted combustion by-products, such as toxic dioxins, that can be unintentionally emitted. Kitchen scraps can result in incomplete combustion of waste, which accelerates the formation of dioxins, especially for the small-sized incinerators without identical operating temperature. Consequently, garbage classification before waste incineration is critical for dioxin control in the small-sized waste incineration industries. To date, the influence of garbage classification on dioxin emissions has not been quantified. In this study, a model framework integrating the grey prediction model and autoregressive prediction model was established and used to predict future dioxin emissions from small-sized waste incineration. If garbage classification is ideally strictly implemented, annual dioxin emissions could be reduced by up to 1697 g TEQ over the next 10 years. Garbage classification reduced emissions by about 30.7% compared with incineration of mixed municipal solid waste without classification (5534 g TEQ over the next 10 years). The established model framework can effectively assess the influence of garbage classification on dioxin emissions from waste incineration, which could facilitate the widespread adoption of garbage classification.

Emissions of dioxins and dioxin-like compounds and incidence of hepatocellular carcinoma in the United States

Ambient dioxin exposure from industrial sources, excluding exposures from occupations and accidental releases/contamination, may be associated with risk of developing hepatocellular carcinoma (HCC). The objective of this study was to examine the association between county-level ambient dioxin air emissions from industrial sources and HCC risk in the US. We obtained information on 90,359 incident HCC cases diagnosed between 2000 and 2016 from population-based cancer registries across the US in the Surveillance, Epidemiology, and End Results (SEER) database. Dioxin emissions from 1987 to 2007 from a nationwide spatial database of historical dioxin-emitting facilities were linked to the SEER county of residence at diagnosis using a geographic information system (GIS). Poisson regression with robust variance estimation was used to calculate incidence rate ratios (IRRs) and 95% confidence intervals (CIs) for the association between county-level dioxin emissions and HCC rates adjusting for individual-level age at diagnosis, sex, race/ethnicity, year of diagnosis, SEER registry, and county-level information on health conditions, lifestyle factors, and socioeconomic status. There was no association between dioxin emissions based on the number of dioxin-emitting facilities within a county or average annual emissions within a county and HCC risk. In analyses by facility type, there were positive associations between county-level dioxin emissions from coal-fired power plants (adjusted IRR 1.09, 95% CI 1.01–1.17), but not with the number of these facilities. Similarly, positive associations for industrial boilers and sewage sludge incinerators were evident, but not consistent across both exposure metrics. Future research should incorporate individual-level data to further explore the findings suggested by these ecologic analyses.

Development of a system dynamics model for dioxin flow and its application to the energy sector

Dioxin pollution has been problematic in Taiwan. Although the government has established emission standards and emission inventory to control dioxin pollution, such efforts only apply to pollution emissions; no attempt has been made to understand the flow of dioxins in different environmental media. In this study, the STELLA software was used to model the flow pattern of dioxins in various media. This model and the RAIDAR model established by the Canadian Environmental Model Research Center were used to simulate dioxin flow in Taiwan, and their results were compared with the measured values. The accuracies of the RAIDAR and STELLA models were 63.92% and 49.78%, respectively. This shows that the simulation with the STELLA model provided results closer to the measured values and that the error was less than ten times that of the RAIDAR model, indicating that the proposed model is predictive. In addition, we used the results of a system dynamics model for dioxin flow and an air resource co-benefits (ARCoB) model to apply the obtained results to the energy sector to quantify the co-benefits of reducing dioxin, greenhouse gas, and air pollutant emissions on the basis of the policy target for the year 2030. The total co-benefits of natural gas and renewable energy (RE) scenarios were US$9.63 billion and US$12.57 billion, respectively; the benefit-cost ratios were 2.89 and 20.67, respectively. The development of an RE policy as an alternative to a coal-fired power generation policy will contribute to the best co-benefits of integrated reductions and will also contribute to human health.

Experimental Study on Co-Pyrolysis Characteristics of Household Refuse and Two Industrial Solid Wastes

The calorific value of household refuse (HR) is greatly improved after classification, which includes the implementation of sufficient pyrolysis conditions. Therefore, a better pyrolysis effect can be achieved by co-pyrolysis with industrial solid waste (ISW) with high calorific value. In this work, HR and ISW were used as raw materials for co-pyrolysis experiments. The influence on the distribution of three-phase products after co-pyrolysis, the concentration of heavy metals and dioxins in the flue gas, and the distribution of PCDD/Fs isomers were studied. The results showed that, at a temperature of 600 °C and H/C = 1.3, of the formed material, the quantity of pyrolysis gas was approximately 27 wt.%, and the quantity of pyrolysis oil was approximately 40.75 wt.%, which mainly contained alkanes, olefins, and aromatic hydrocarbons. When S/C = 0.008, pyrolysis gas accounted for 25.95 wt.% of the formed material, and pyrolysis oil for 41.95 wt.% of the formed material. The ignition loss rate of pyrolysis coke was approximately 20%, and the maximal calorific value was 14,217 KJ/kg. According to the thermogravimetric experiment, the co-pyrolysis of HR and ISW can promote the positive reaction of pyrolysis, and the weight loss reached 62% at 550 °C. The emission of gaseous heavy metals was relatively stable, and the concentration of heavy metals slightly decreased. The main heavy metals in the ash were Cu, Fe, and Zn. The emission of dioxins could be effectively reduced by the pyrolysis of HR with ISW, and the produced dioxins were mainly synthesized from de novo synthesis. After pyrolysis, the toxic equivalent of dioxins in the flue gas was reduced from 0.69 to 0.29 ng I-TEQ/Nm3, and the distribution of dioxin isomers in the flue gas had little influence. The experimental results provide a theoretical basis for the application of co-pyrolysis technology with HR and ISW.

Simultaneous removal of mercury and 1,2-dichlorobenzene from flue gas by Ru-based catalyst

To solve the pollution problem of mercury and dioxin emission, the catalytic oxidation techniques were introduced, and Ru-based catalyst manifested an excellent performance for simultaneously removing elemental mercury (Hg0) and 1,2-dichlorobenzene (o-DCB) in flue gas. Ce-Zr-Ru presented the highest removal efficiency for o-DCB, which could reach more than 90% above 325 ℃. Besides, it had a good chemical stability, and the o-DCB removal efficiency maintained above 90% after 12 h and 5 cycles. The existence of o-DCB was beneficial for Hg0 removal, and the Hg0 catalytic efficiency of Ce-Zr-Ru can reach nearly 100% at a wide temperature window of 200–400 ℃ in the presence of o-DCB. O2 play a critical role on the catalytic reaction process, which can be activated to oxidize Hg0 and o-DCB. Moreover, the generated hydrogen chloride and chlorine species by catalyzing o-DCB would react Hg0 and HgO to form HgCl2, which can be desorbed from the surface of the catalysts and entered to flue gas.