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• Addition of OBDCR showed insignificant impacts on heavy metal emission and leaching. • Ba showed the highest cumulative leaching amount among other heavy metals. • Full stage leaching of Mn, Zn, Ni, and Pb were controlled by diffusion. • Life-time leaching prediction revealed that the leaching of Ni and Mn should be focused. Oil-based drill cutting residues (OBDCR) are hazardous waste generated by the thermal desorption of oil-based drill cuttings. Recently, the utilization of OBDCR as building materials has attracted extensive attention, but the environmental risks during preparation and long-term usage remained unclear. In this study, OBDCR with a 40 % (wt./wt.) mixing ratio was used to prepare sintered bricks, and the emission and leaching behaviors of Ba, Mn, Zn, Ni, Cr, and Pb were investigated. The results indicated that the addition of OBDCR in bricks showed insignificant increase in the emission of Ba, Mn, Zn, Ni, and Cr, whereas the emission of Pb slight decreased from 10.5 to 8.6 μg/m3. The volatilization rates of these heavy metals were considerably low, with Ni showed the highest volatilization rate of only 1.45 % in OBDCR bricks. Moreover, the leaching behavior of Ba, Mn, Zn, Ni, Cr, and Pb in bricks were studied. The results indicated that surface wash-off was the main controlling leaching mechanism of Ba and Cr, whereas the leaching of Mn, Zn, Ni, and Pb was controlled by diffusion. The Elovich and second-order kinetic equation were identified as the leaching models for Mn, Zn, Pb, and Ni. The life-time leaching predictions of OBDCR bricks indicated that the leaching of Ni and Mn after 10 and 20 years of leaching were 0.1529, 0.257, 0.1530, and 0.274 mg/L, respectively, exceeding the relevant standards. Therefore, the leaching risks of Ni and Mn should be emphasized when using OBDCR bricks with a 40 % OBDCR mixing ratio. [ABSTRACT FROM AUTHOR]

The advancement of co-processing solid wastes in coal-fired boilers is significant for waste recycling and contributes to the sustainable development of the coal-fired power industry. However, concerns over the emission of dioxins during co-processing have prompted a comprehensive investigation into the dioxin emission properties. In this study, the PCDD/F emission concentrations of seven coal-fired boilers, including three pulverized coal boilers and four circulating fluidized bed boilers were examined. The results indicate that co-processing solid wastes in coal-fired boilers did not lead to an increase in the mass concentration of dioxins in either the flue gas or solid samples, and the international toxic equivalents (I-TEQ) of dioxins in the flue gas complied with prevailing emission standards (0.1 ng I-TEQ/Nm3) in China, proving that coal-fired boilers co-processing would not raise the emission risk of dioxins. The types of waste during co-processing had minimal effect on the I-TEQ of dioxins. A significant proportion of PCDD/Fs was observed in the ash samples, while only 13.0–25.7% and 0.7–6.8% of dioxins were distributed in the boiler slag and the flue gas, respectively. The emission factor of dioxins under the blank conditions ranged from 0.009 to 0.327 ng I-TEQ/kg-coal, while it ranged from 0.015 to 0.129 ng I-TEQ/kg-(coal+waste) under the co-processing conditions. The reduction of emission factor under co-processing condition could be attributed to the significant decrease of dioxins I-TEQ. [Display omitted] • Co-processing wastes in boilers did not lead to an increase in the I-TEQ of dioxins. • The type of waste during co-processing had minimal effect on the I-TEQ of dioxins. • A significant proportion of PCDD/Fs was observed in the ash samples. • The emission factor of dioxins ranged from 0.015 to 0.129 ng I-TEQ/kg-(coal + waste). [ABSTRACT FROM AUTHOR]

A disposal method for fly ash from a municipal solid waste incinerator (MSWI-FA) that involved a water washing pretreatment and co-processing in a cement kiln was tested. The mass flows of toxic heavy metals (HMs), including volatile HM (Hg), semi-volatile HMs (Pb, Cd, Tl, and As), and low-volatility HMs, and polychlorinated dibenzo-p-dioxin/polychlorinated dibenzofuran (PCDD/Fs) in the input, intermediate, and output materials were characterized. The flue gas Hg concentrations from tests 0, 1, and 2, fed with 0, 3.1, and 1.7 t/h of dried-washed FA (DWFA), were 28.60, 61.95, and 35.40 μg N m −3 , respectively. Co-processing of DWFA did not significantly affect the metal concentration in clinker as most of the major input metals, with the exception of Cd, Pb, and Sb (which came from DWFA), were from raw materials and coal. Co-processing of DWFA did not influence on the release of PCDD/Fs; baseline and co-processing values ranged from 0.022 to 0.039 ng-TEQ/N m 3 , and from 0.01 to 0.031 ng-TEQ/N m 3 , respectively. The total destruction efficiency for PCDD/Fs in MSWI fly was 82.6%. This technology seems to be an environmentally sound option for the disposal of MSWI-FA. [ABSTRACT FROM AUTHOR]

The consumption of milk in China is increasing as living standards rapidly improve, and huge amounts of aseptic composite milk packaging waste are being generated. Aseptic composite packaging is composed of paper, polyethylene, and aluminum. It is difficult to separate the polyethylene and aluminum, so most of the waste is currently sent to landfill or incinerated with other municipal solid waste, meaning that enormous amounts of resources are wasted. A wet process technique for separating the aluminum and polyethylene from the composite materials after the paper had been removed from the original packaging waste was studied. The separation efficiency achieved using different separation reagents was compared, different separation mechanisms were explored, and the impacts of a range of parameters, such as the reagent concentration, temperature, and liquid–solid ratio, on the separation time and aluminum loss ratio were studied. Methanoic acid was found to be the optimal separation reagent, and the suitable conditions were a reagent concentration of 2–4 mol/L, a temperature of 60–80 °C, and a liquid–solid ratio of 30 L/kg. These conditions allowed aluminum and polyethylene to be separated in less than 30 min, with an aluminum loss ratio of less than 3%. A mass balance was produced for the aluminum–polyethylene separation system, and control technique was developed to keep the ion concentrations in the reaction system stable. This allowed a continuous industrial-scale process for separating aluminum and polyethylene to be developed, and a demonstration facility with a capacity of 50 t/d was built. The demonstration facility gave polyethylene and aluminum recovery rates of more than 98% and more than 72%, respectively. Separating 1 t of aluminum–polyethylene composite packaging material gave a profit of 1769 Yuan, meaning that an effective method for recycling aseptic composite packaging waste was achieved. [ABSTRACT FROM AUTHOR]

• Firing bricks with 15% remediated soil immobilizes 90.6–99.9% of most heavy metals. • Selenium shows only 64.3% retention and is mainly lost through volatilization. • As and Pb in outer layers are 2.2–4.3 times higher than in inner layers. • Spinel formation reduces Ni, Mn, Cu, and Zn leaching, especially in inner layers. • Both layers meet heavy-metal leaching standards, ensuring low environmental risk. Rapid industrialization has led to the widespread accumulation of heavy metal-contaminated soils, posing significant environmental and health risks. Utilizing remediated soil for the production of sintered bricks offers a sustainable and effective solution. However, the migration and immobilization mechanisms of heavy metals during the sintering process, both within the tunnel kiln and the brick matrix, require detailed investigation. This study examined the distribution of heavy metals in the tunnel kiln and analyzed the differences in heavy metal content and leaching behavior between the inner and outer layers of the bricks. Bricks containing 15% remediated soil were prepared, and it was observed that the majority of heavy metals were effectively immobilized, with retention rates ranging from 90.6% to 99.9%. Selenium (Se), however, exhibited significant volatility, with a retention rate of only 64.3%. The outer layer of the brick body contained higher concentrations of As and Pb compared to the inner layer. Conversely, leaching tests showed lower leaching rates of Mn, Ni, Cu, and Zn in the inner layers, while As and Pb exhibited higher leaching rates in the inner layers. These findings underscore the varying migration and transformation behaviors of different heavy metals during sintering, both within the kiln and the brick layers. The study highlights the potential of doped sintered bricks as sustainable building materials, ensuring effective heavy metal stabilization with minimal environmental risk, and providing a promising pathway for the safe reuse of contaminated soils. [ABSTRACT FROM AUTHOR]

• Chemical industrial kilns can be used for co-processing of hazardous waste. • Co − processing of hazardous waste in CWSG has little effect on the operating stability of the gasifier. • Low environmental risks of PAHs in CWSG during co − processing process. • LMW PAHs mainly distributed in exhaust gas, MMW and HMW PAHs mainly distributed in solid waste. Chemical industrial kilns were found to be used for waste treatment, however it is still in the research stage. In our study, field tests were conducted to find the emission and distribution characteristics of polycyclic aromatic hydrocarbons (PAHs) during co-processing of hazardous waste in an industrial scale coal-water slurry gasifier (CWSG), which is applied to ammonia production. Changes of temperature, pressure and gas production of CWSG were recorded under both blank condition (i.e., regular production) and test condition (i.e., feedstock mixed with hazardous waste). Concentration of PAHs in all the solid waste, waste water, and exhaust gas under two conditions were analyzed. Results showed that co-processing of hazardous waste has little impact on the operation stability of CWSG, the temperature were ranged at 1330–1350 ℃ in CWSG, the pressure and gas production were stabled at 1.0–1.3 MPa and 12,000–14,000 Nm3/h respectively. Low environmental risks of PAHs in regular production and weren't increased by the addition of hazardous waste. Distribution trends of PAHs with different molecular weights in solid-liquid-gas three phases were basically the same under both two conditions. 92.96 %−93.68 % low molecular weights (LMW, 2–3rings) PAHs distributed in exhaust gas, 50.84 %−71.66 % middle molecular weights (MMW, 4 rings) PAHs distributed in solid waste, and 85.3 %−86.77 % high molecular weight (HMW, 5–6 rings) PAHs distributed in solid waste, while the content of PAHs in waste water was generally low. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low-temperature thermal treatment is highly efficient and low energy consumption. • The degradation and ash discharge phases of dioxins are comprehensively considered. • Temperature is the main factor for the degradation and ash discharge stages. • The increase in oxygen content promotes the desorption of dioxins to the gas phase. • Below 200℃, the oxygen content has little effect on the ash discharge stage. Dioxins in municipal solid waste incineration fly ash (MSWIFA) can cause significant risks to the environment and human health. In this study, the low-temperature thermal treatment of MSWIFA under industrial conditions was simulated in the laboratory to investigate the process parameters for dioxin degradation and ash discharge stages. Correlation analysis and dioxin fingerprint characterization were used to analyze the degradation and ash discharge processes. The degradation efficiency of low-temperature thermal treatment was influenced by multiple factors. At 400℃ for 90 min and 1% O 2 , the dioxin removal rate was 95.80%, the detoxification rate was 91.73%, and the residual dioxin toxicity in MSWIFA was 22.7 ± 17.8 ng I-TEQ/kg, which was in line with the limit value of 50 ng I-TEQ/kg in the "Technical specification for pollution control of fly-ash from municipal solid waste incineration" (HJ1134-2020). The increase in dioxins during ash discharge did not follow a linear relationship with the process parameters. This was assumed to be related to the MSWIFA composition, as some components containing P, Si, and Al at 150 °C may inhibit dioxin formation. The dioxin increased only by 0.79 ± 2.65 ng/kg, an increase in toxicity of 0.42 ± 0.10 ng I-TEQ/kg, when treated at 150 °C for 30 min and 10% O 2. [ABSTRACT FROM AUTHOR]

[Display omitted] In order to dispose solid waste reasonably and provide reference data for solid waste co-treatment in industrial kilns, coal chemical products were co-treated in a pulverized coal furnace and refuse-derived fuel was co-treated in a gasifier-coupled pulverized coal furnace system. The distribution and environmental risks of Cr and Zn in different kilns were compared and analyzed. The Cr and Zn distributions in the solid products from the pulverized coal furnace tests were similar. Fly ash contained > 80% of the Cr and Zn. In the gasifier, cyclone dust and gasification gas contained only ∼ 60% of the Cr and Zn, and gasification slag contained > 40% of the Cr and Zn. The gasification gas contained ∼ 33% of the Cr and Zn volatilized. The pulverized coal furnace temperature was > 1,500 °C. Most of the Cr and Zn volatilized and then condensed, so became enriched in the fly ash. The gasifier temperature was ∼ 750 °C, so less volatilization occurred and Cr and Zn became enriched in the gasification slag. The Cr and Zn concentrations in leachates of the solid products were lower than the limits of "GB 5085.3–2007". However, the Cr and Zn concentrations in the gasification slag and cyclone dust leachates were close to the limits and tens to hundreds of times higher than the concentrations in the pulverized coal furnace fly ash and slag leachates. The low temperatures and low-oxygen environments of gasifiers are not conducive to heavy metals being stable in the solid products, and the environmental risks posed by heavy metals in the solid products are high. The risks to the environment are less serious for co-treating solid waste in pulverized coal furnaces than gasifiers. [ABSTRACT FROM AUTHOR]

• The behaviour of Cd and Pb are closely related to the presence of Cl−1. • The concentrations of Cd and Pb increased sharply after recycling of kiln dust. • Thermodynamic software can effectively simulate the fixation of heavy metals. • Using model can optimize kiln control strategy and ash recirculation ratio. Fly ash produced from incineration of municipal solid wastes (MSW) contains heavy metals, such as Cd and Pb, that make this material difficult to manage and dispose of safely. Because the composition of fly ash is similar to cement raw meal, partial replacement of raw meal with fly ash may be a feasible way to reduce the health and environmental hazards of the ash, provided that the heavy metals can be effectively stabilized in the solid phase. This research employs proprietary thermochemical software to simulate the thermodynamic behavior and single-step fixation of Cd and Pb in industrial cement kilns. The effect of Cd, Pb and Cl loadings on the fixation and/or evaporation of Cd and Pb during the sintering process is analyzed using data from industrial cement kilns. A simplified model is created based on elemental mass balance to evaluate multi-step fixation of Cd and Pb with cement kiln dust recycle.The results indicate that Cd forms Cd(OH) 2 (g) in a highly alkaline environment, while nearly 90% Pb is volatilized as PbCl 2 (g). In the clinker, increased Cl−1 decreased the proportion of Pb and Cd, moreover, Pb and Cd increased in kiln dust with Cl−1 increased; Calculations using a kiln dust recycle model showed that, the concentrations of Pb and Cd in both kiln dust and clinker increased sharply after recycling of kiln dust in steady state. Under unstable conditions, the concentrations of Pb and Cd in kiln dust increased, as well as the heavy metals re-entering the cement kiln. [ABSTRACT FROM AUTHOR]

[Display omitted] • Contaminated soil could be used to replace 9.68% of the raw material. • Co-processing contaminated soil did not affect kiln operation or clinker quality. • The DDT destruction removal efficiency were > 99.9999% • PCDD/Fs and PCBs concentrated in cement kiln dust. Persistent organic pollutants in soil are not readily degraded in the short term. The utilization of co-processing solid waste in cement kilns has received increasing attention in recent years. Co-processing may be a good way of disposing of dichlorodiphenyltrichloroethane-contaminated soil (CS). The feasibility of co-processing CS pretreated to desorb dichlorodiphenyltrichloroethane, was assessed by performing an industrial-scale trial, focusing on the risks posed by emissions to the environment. Samples of the input and output in cement kiln were collected for determining clinker quality, production operation, pollutant emissions, cement kiln system destruction efficiency, and distribution profiles of persistent organic pollutants unintentionally produced from kiln. The destruction efficiency and destruction removal efficiency both were > 99.99% in cement kiln system at the appropriate CS feeding rate. Emissions of stack gases produced by cement kilns co-processing CS were within the reasonable range set in China. Dibenzo- p -dioxins and dibenzofurans (PCDD/Fs), and polychlorinated biphenyls (PCBs) concentrations and distribution profiles in flue gases and particulate samples from two tests showed PCBs mainly formed at the same sites as PCDD/Fs, indicating they are may formed in a similar way in cement kiln. A comparison with the processing parameters in the clinker, cement kiln dust, and flue gas under baseline and co-processing conditions, manifested that co-processing had no effect on the operation or cement quality of the cement kiln. Thus co-processing CS at a rate of 20 t/h with pretreatment process, is an environmentally sound and highly efficient treatment for CS. [ABSTRACT FROM AUTHOR]

There is a limited body of research on the recovery of soluble salts from municipal solid waste incineration fly ash (MSWI-FA), with challenges stemming from the effective management of residual heavy metals and dioxins. In this investigation, we propose using water-washing treatment for fly ash dechlorination and using CO 2 aeration carbonation combined with ceramic membrane filtration to recover soluble salt resources from fly ash. This study investigated the impact of combined processes on fly ash soluble salt recovery, carbon dioxide capture and sequestration, heavy metal removal, and dioxin diffusion reduction. The findings revealed that the combined process can significantly enhance the rate of carbonation and the removal of heavy metals. Specifically, the removal rates of Pb and Zn reach 100%. The resulting CaCO 3 precipitation particle size is smaller, averaging only approximately 4 μm, with greater surface porosity, higher heavy metal and dioxin content, and dioxin toxic equivalents as high as 8.11 ng TEQ/kg. Moreover, the dioxin content in the recovered mixed salt decreased, and its dioxin toxic equivalent was only 3.228.11 ng TEQ/kg. Consequently, the combined process of CO 2 aeration combined with ceramic membrane filtration was used in conjunction to significantly reduce pollutants (heavy metals and dioxins) in the MSWI-FA recovered salt. This approach enhances the recyclable resource utilization of MSWI-FA and reduces the risk of pollution dispersal during MSWI-FA disposal and resource utilization. [Display omitted] • Removal of heavy metals from MSWI-FA water washing solution by CO 2 carbonation. • Ceramic membrane interception to control the diffusion of dioxin pollution. • The combined process improves the efficiency of pollutant removal. • Recovering low pollutant soluble salts from MSWI-FA. • Sustainable development through the technology of treating waste with waste. [ABSTRACT FROM AUTHOR]

Abstract During a three-day industrial trial, municipal solid waste incineration fly ash (FA) was co-processed in a cement kiln after water-washing pretreatment for waste-to-resource conversion. All inputs and outputs were sampled to obtain the dioxin fingerprints. During washing, the relative contents of polychlorinated dibenzo-p-dioxins and dibenzofurans in FA, washed FA and sludge were basically the same and only a simple physical migration resulted. During drying, only physical processes resulted, which included volatilization and migration. Minimal dioxins residue remained in the clinker, cement kiln dust and flue gas, and the dioxins degraded completely. Through co-processing, the dioxins degraded obviously. The main compounds synthesized include 1,2,3,4,7,8-hepta-chlorodibenzo-p-dioxin, 2,3,7,8-tetra- chlorodibenzofuran and octa-chlorodibenzofuran. A comparison of dioxins fingerprints in the clinker, cement kiln dust and flue gas under baseline and co-processing conditions showed that co-processing had no effect on the cement kiln production. The baseline sample also contained a certain amount of dioxins, possibly because of the ‘memory effect’ and heterogeneous formations. The dioxins concentrations in the clinker and FA were far lower than the national standards. Thus, no environmental risk results during co-processing. Highlights • Dioxin fingerprints studied in washing and cement kiln co-processing MSWI fly ash. • Stack emissions of PCDD/Fs were below the national limits for cement kilns. • 1,2,3,4,7,8-Hepta-CDD, 2,3,7,8-tetra-CDF and octa-CDF are major forms in the kiln. • Only simple physical migration resulted during washing pretreatment and drying. • No environmental risk of PCDD/Fs release during pretreatment and co-processing. [ABSTRACT FROM AUTHOR]

• Co-firing of coal liquefaction residue (CLR) with 15% mass does not affect boiler operation. • Co-firing CLR with 15% mass does not increase the risk of organic emissions. • Blending 15% CLR alternative fuel coal is suggested to reduce the coal consumption. • Over 99.99% destruction removal efficiency of organic marker m-dichlorobenzene. Coal liquefaction residue (CLR) is usually categorized as hazardous waste, which is inevitably generated during the coal-liquefaction process. Studies show that CLR has a high calorific value and can be used to decrease coal consumption during the co-firing process. In this regard, field tests were carried out to study the emission and environmental risks of organic pollutants during co-firing CLR in a circulating fluidized bed (CFB) boiler. In the present study, the effects of co-firing CLR on the operating conditions of the boiler and the concentrations of 16 polycyclic aromatic hydrocarbons (PAHs), hexachlorobenzene (HCB), dioxins, dioxin-like polychlorinated biphenyls (dl -PCBs), volatile organic compounds (VOCs), and total organic carbons (TOCs) in the flue gas, fly ash, and bottom ash were investigated. It is found that burning the fuel consisting of 85 % coal and 15 % CLR by mass decreases the coal consumption by 2–3 t/h while the combustion parameters almost remain intact. The performed analyses reveal that co-firing the CLR does not increase the emission of PAHs compared to pure coal combustion. Meanwhile, it is found that fly ash has a high concentration of PAHs while the concentration is relatively low in the bottom ash. Doped with m-dichlorobenzene as an organic marker, the destruction removal efficiency (DRE) exceeds 99.99 %. The releases of organic pollutants during the co-firing process are lower than the specified limit in relevant environmental standards. [ABSTRACT FROM AUTHOR]

The recycling of Al-PE (a laminated foil made from polyethylene and aluminum foil) composite packaging waste composed of low-density polyethylene (LDPE) and aluminum is of great environmental significance. This project, which evaluated the recycling of Al-PE composite packaging waste, was based on previously determined optimum conditions for using formic acid as separation reagent. Life Cycle Assessment (LCA) was utilized to examine and compare the environmental impacts of different disposal methods. Data for mass and energy fluxes and for environmental emissions were obtained from the literature and from site investigations. The results show that the environmental impacts from Al-PE packaging material waste treatment were highest for landfill disposal, followed by incineration and then recycling, and that the latter two treatments had overall beneficial effects on the environment. The landfill, incineration and recycling scenarios contributed most of their environmental impacts in the Carcinogen, Respiratory Inorganics and Fossil Fuel categories, respectively. If emissions reduction is the primary governmental goal, incineration would be the better choice, while Al-PE recycling would be the better choice for saving energy. [ABSTRACT FROM AUTHOR]

CaCr 2 O 4 (Cr (III)), mainly generated through the decomposition of CaCrO 4 (Cr (VI)), is a significant intermediate for toxic Cr (VI) formation during solid fuel combustion. In this study, the formation, oxidation and sulfation kinetics of CaCr 2 O 4 were analyzed to forecast the potential of CaCr 2 O 4 oxidation during co-firing of coal and solid waste in a circulating fluidized bed boiler. The results indicated that the formation and oxidation of CaCr 2 O 4 were fitted to a single step nucleation and growth model while CaCr 2 O 4 sulfation was fitted to a shrinking core model. CaCr 2 O 4 formation through CaCrO 4 decomposition was favored in oxygen-lean atmosphere and considerably suppressed in the presence of oxygen. In contrast, CaCr 2 O 4 oxidation was mainly determined by the contacts between CaCr 2 O 4 and CaSO 4 /CaO, which influenced not only oxidation rates but also the product species. Moreover, the oxidation reactivity of CaCr 2 O 4 was higher in the presence of CaO than that of CaSO 4. On the other hand, CaCr 2 O 4 sulfation can occur more easily than CaCr 2 O 4 oxidation, the reaction rate of which was deeply affected by sulfate product layer. Findings in this study suggested that spraying calcium in furnace for desulphurization may increase the risk of CaCr 2 O 4 oxidation. Measures including the adjustment of Ca/S ratio in blended fuel (with added limestone) and operating conditions (such as temperature and local atmosphere) in co-firing system could be taken to control CaCr 2 O 4 formation and oxidation. • Cr oxidation was determined by the formation, oxidation and sulfation of CaCr 2 O 4. • Nucleation and growth model was fitted to the formation and oxidation of CaCr 2 O 4. • CaCr 2 O 4 sulfation could be described by shrinking core model. • Available calcium content affected not only oxidation rate but also product species. • CaCr 2 O 4 sulfation was easier to occur than CaCr 2 O 4 oxidation. [ABSTRACT FROM AUTHOR]

Hazardous waste disposal is a serious environmental concern in China. Therefore, in this study, industrial trials were conducted in a low-temperature thermal degradation facility, a tunnel kiln, and a shaft kiln to effectively treat dioxins in municipal solid waste incineration (MSWI) fly ash. The results indicated that the low-temperature thermal degradation facility efficiently decomposed polychlorinated dibenzo-p-dioxins and dibenzofurans in the MSWI fly ash. Additionally, the concentrations of dioxins in the treated fly ash and exhaust gas were lower than the suggested standard limits and the degradation ratio of dioxins was ∼99%. Therefore, treated fly ash characterized by acceptable dioxin risks could be utilized for the production of non-fired building materials. The results from the tunnel kiln indicated complete decomposition of the dioxins in the firing and insulating sections. However, the addition of fly ash in the tunnel kiln increased the concentration of dioxins in the flue gas. This can be primarily attributed to the heterogeneous catalytic synthesis reaction in the low-temperature section of the tunnel kiln. The results from the shaft kiln indicated degradation of at least 22% of the dioxins in the ash. The dioxin concentration in the flue gas was lower than the national standard while that in the clinker was within a reasonable limit. Furthermore, the environmental risks were significantly reduced at fly ash addition ratios lower than 3%. • Industrial trials conducted to efficiently treat dioxins in MSWI fly ash. • PCDD/F concentrations measured to assess dioxin degradation efficiencies. • Dioxin concentrations decreased after treatment. • MSWI fly ash treatment by suggested technologies effectively degraded dioxins. [ABSTRACT FROM AUTHOR]

Slurry feed entrained-flow gasifier has been applied more and more in waste treatment. However, the data on the distribution and emission of arsenic (As) in such gasifiers are very limited. The fate of As in gasification system is closely related to the conditions of gasifier and subsequent gas treatment processes. In this paper, the partitioning of As in slurry feed entrained-flow gasifier with wet gas cooling cleaning system is determined. The influence of feedstock and process water are studied. It is shown that co-gasification waste with coal and the redox condition of process water have little effect on the overall distribution of As. 91.7–94.5% of As is distributed to flash wastewater under water-oxidizing condition and 85.5–99.7% of As partitions into the wastewater under water-reducing condition. Less than 4% of As enters the raw syngas. Under the condition of waste addition and reducing water, As has the risk of being released into the atmosphere with the exhaust gas (8.4–57.0 μg/Nm3). According to the data detected under water-oxidizing condition, the concentration of As in clarified water is 0.367–1.195 ppm, and that in clarifier solid is 34.06–159.84 ppm. Therefore, the reuse of clarified water as process water of wet gas treatment system and clarifier solid as feedstock of gasifier may lead to As recycling in the gasification system. • Waste co-gasification and water redox condition have little effect on As partition. • In ox- and red- water, 91.7–94.5% and 85.5–99.7% As enter wastewater respectively. • Less than 4% of As partitions into the raw syngas. • With waste co-gasification and reducing water, As has release risk with exhaust gas. • The reuse of clarified water and clarifier solid may lead to As recycling in system. [ABSTRACT FROM AUTHOR]