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"Incineration"
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Creep characterisation and microstructural analysis of municipal solid waste incineration fly ash geopolymer backfill
In this work, an alkali-activated municipal solid waste incineration (MSWI) fly ash-based filling material was prepared with MSWI fly ash as the raw material and slag as the auxiliary material. The filling body experiences long-term creep, which may have a direct effect on the stability of the overlying strata of the mine goaf. The long-term mechanical properties of the fly ash-based filling materials were tested with a triaxial rheological apparatus. First, uniaxial creep testing was carried out at five levels of axial stress: 50%, 60%, 70%, 80% and 90% of the uniaxial compressive strength (UCS). Then, triaxial creep testing was carried out by considering the geological environment of the goaf. The creep characteristics of fly ash-based filling materials under a three-dimensional stress state were explored. The results indicate that (1) under different stress levels, the creep curves of fly ash-based filling materials can be divided into three types: decelerated creep‒stable creep, decelerated creep‒constant creep, and decelerated creep‒constant creep‒accelerated creep. (2) The total creep deformation of the fly ash-based filling material is 0.46 ~ 0.78%, which is similar to the creep deformation of soft rock. The instantaneous deformation during loading contributes most of the total deformation. (3) The polymerization products generated in the fly ash-based filling material system can effectively cement the raw material particles, and the presence of gel can effectively delay the accelerating creep process of the material. (4) A nonlinear fractional-order model composed of an Abel dashpot can fully describe the complete process of decelerating creep-constant creep-accelerating creep.
Journal Article
Characteristics of incineration ash for sustainable treatment and reutilization
Municipal solid waste incineration (MSWI) generates bottom ash, fly ash (FA), and air pollution control (APC) residues as by-products. FA and APC residues are considered hazardous due to the presence of soluble salts and a high concentration of heavy metals, and they should be appropriately treated before disposal. Physicochemical characterization using inductively coupled plasma mass spectroscopy (ICP-MS), X-ray diffraction (XRD), and X-ray fluorescence (XRF) have shown that FA and APC have potential for reuse after treatment as these contain CaO, SiO
2
, and Al
2
O
3
. Studies conducted on treatment of FA and APC are categorized into three groups: (i) separation processes, (ii) solidification/stabilization (S/S) processes, and (iii) thermal processes. Separation processes such as washing, leaching, and electrochemical treatment improve the quality and homogeneity of the ash. S/S processes such as chemical stabilization, accelerate carbonation, and cement solidification modify hazardous species into less toxic constituents. Thermal processes such as sintering, vitrification, and melting are effective at reducing volume and producing a more stable product. In this review paper, the treatment processes are analyzed in relation to ash characteristics. Issues concerning mixing FA and APC residues before treatment, true treatment costs, and challenges are also discussed to provide further insights on the implications and possibilities of utilizing FA and APC as secondary materials.
Journal Article
Comparative life cycle assessment of landfill sludge treatment technologies in China
Reasonable treatment of large amounts of sludge excavated from landfills has gained increasing attention due to the diminishing availability of landfill space in China. In this study, five landfill sludge (LS) treatment technologies using life cycle assessment (LCA) and life cycle cost (LCC) were investigated, i.e., co-incineration in coal-fired power plants (CFPP) and waste incineration power plant (WIPP), co-processing in cement kiln, bricks production, and sintering ceramsite. The LCA results demonstrate that sintering ceramsite outperforms other technologies and LCC results indicate sintering ceramsite also provides the highest economic benefit ($869.94). To further enhance environmental and economic performances of the LS treatment, the substitution of coal with natural gas and biomass can reduce Energy Conservation and Emission Reduction (ECER) index by 74% and 98%, respectively. This substitution can increase economic returns by 24% and 26%, respectively. Furthermore, national-level economic benefit and carbon emission reduction potential of different LS treatment technology alternative scenarios were assessed. Results display that a combination of 50% CFPP, 25% bricks, and 25% ceramsite (biomass) offers the highest economic gain, which is 3.02 times that of 50% CFPP and 50% cement (original case). Conversely, the replacement of 25% brick with 25% cement in the above combination result in the lowest carbon reduction, which is 9.35 times that of the original case.
Journal Article
The Resource Utilization and Environmental Assessment of MSWI Fly Ash with Solidification and Stabilization: A Review
Municipal solid waste incineration fly ash, containing heavy metals and dioxins with strong toxicity and carcinogenicity, would pose severe harm to human health and the environment. This review details the chemical composition of MSWI fly ash, summarizes the sources and pollution characteristics of heavy metals and dioxins. In this paper, various solidification/stabilization (S/S) methods and the resource utilization of MSWI fly ash with S/S, such as cement solidification, geopolymer solidification, chemical stabilization and hydrothermal treatment are comprehensively discussed. Besides, the principle of heavy metals stabilization and the mechanism of dioxins degradation are analyzed in detail. Moreover, an overall comparison of these approaches for the harmless treatment of MSWI fly ash, including pollutants solidification/decomposition, advantages, disadvantages and resource utilization approach, is carried out. The risk assessment methods of solidified and stabilized products for heavy metals were discussed. Finally, studying on degradation of dioxin and enrichment of heavy metals in MSWI fly ash by multi-synergistic treatment, inhibiting the leaching of pollutants into aqueous solution during solidification are proposed. This paper is expected to provide some reasonable development directions for the environmentally safer treatment and resource utilization of MSWI fly ash.
Graphical Abstract
Journal Article
Life cycle assessment of environmental impact on municipal solid waste incineration power generation
Municipal solid waste (MSW) incineration power generation is an important treatment technology, which has been widely concerned in recent years. It is of great significance to evaluate the environmental impact. This study conducted the environmental life cycle assessment of MSW incineration power plant in Yongcheng city, Henan province, China. After that, the comprehensive environmental impacts of MSW incineration power plant, landfill, and coal-fired power plant are compared. Furthermore, the energy conservation and emission reduction benefits brought by MSW incineration power plant in Yongcheng city are quantitatively analyzed. The results show that (1) the main environmental impact categories of MSW incineration power plant are human toxicity potential and acidification potential, which together account for 72.8% of the total comprehensive environmental impact. In addition, incineration is the main process of pollutant generation, which contributes 94.1% to the comprehensive environmental impact. (2) As an effective supplement to landfill and coal-fired power generation, MSW incineration power generation produces lower environmental impact. (3) Significant energy-saving and emission reduction benefits can be brought by MSW incineration power plant. Particularly, it could save energy 2.75×10
4
tce, reduce greenhouse gas emissions 3.43×10
5
t CO
2
-eq, and effectively reduce the emissions of various air pollutants for the local area annually.
Journal Article
EU policy on sewage sludge utilization and perspectives on new approaches of sludge management
This paper presents the current sewage sludge legislation in Europe and expected developments regarding the coming directives on the application of the “End-of-waste” criteria and on fertilizers. Discussion on sludge production and processing is also included. The Directive 86/278 has regulated the use in agriculture of residual sludge from domestic and urban wastewater. After 1986, this directive was transposed in the different member state legislation and currently the national limit values on heavy metals, some organic micropollutants and pathogens are placed in a rather wide range. This seems the inevitable consequence of different attitudes towards sludge management practices in the member states. The discussion by the European Joint Research Center (JRC) in Seville regarding application of end-of-waste criteria for compost and digestate has produced a final document (IPTS 2014) where sludge was excluded from the organic wastes admitted for producing an end-of-waste compost. Sludge processing in Europe seems addressed to different goals: sludge minimization, full stabilization and hygienization by thermal hydrolysis processes before anaerobic digestion, and on-site incineration by fluidized bed furnace. Thermophilic anaerobic digestion was applied with success on the Prague WWTP with a preliminary lysimeter centrifugation. Coming techniques, like wet oxidation and pyrolysis, are applied only on very few plants.
Journal Article
Environmental and human health risk evaluation of heavy metals in ceramsites from municipal solid waste incineration fly ash
Municipal solid waste incineration (MSWI) for power generation can reuse waste effectively, but it generates a large amount of fly ash enriched with heavy metals. If this fly ash cannot be treated properly, it can cause ecological damage and human health risk. According to the production of ceramsites from MSWI fly ash, an evaluation methodology is established, in which the influence of heavy metal stability on the environment is considered for the first time, and the health risks of heavy metals via different exposure pathways are distinguished. The results show that heavy metals in MSWI fly ash have moderate potential environmental risks to environment and have strong non-carcinogenic and carcinogenic risks both to children and adults. By contrast, heavy metals in ceramsites pose little risk to environment and human health. This paper explains some reasons of heavy metal content and leaching ratio change in ceramsite and also illustrates why stability is a concern through comparing the potential risk index method and the improved evaluation method. This evaluation system can be applied to different production processes of building materials using solid hazardous waste and provides a quantitative evaluation method for reducing environment and human health risks of heavy metals.
Journal Article
Review of fly ash inertisation treatments and recycling
Fly ash (FA) is a by-product of power, and incineration plants operated either on coal and biomass, or on municipal solid waste. FA can be divided into coal fly ash, obtained from power plant burning coal, flue gas desulphurisation FA, that is, the by-product generated by the air pollution control equipment in coal-fired power plants to reduce the release of SO
2
, biomass FA produced in the plants for thermal conversion of biomass and municipal solid waste incineration (MSWI) FA, that is, the finest residue obtained from the scrubber system in a MSWI plant. Because of the large amount produced in the world, fly ash is now considered the world’s fifth largest material resource. The composition of FA is very variable, depending on its origins; then, also pollutants can be very different. In this frame, it is fundamental to exploit the chemical or physical potentials of FA constituents, thus rendering them second-life functionality. This review paper is addressed to FA typology, composition, treatment, recycling, functional reuse and metal and organic pollutants abatement. Because of the general growing of environmental awareness and increasing energy and material demand, it is expected that increasing recycling rates will reduce the pressure on demand for primary raw materials, help to reuse valuable materials which would otherwise be wasted and reduce energy consumption and greenhouse gas emissions from extraction and processing.
Journal Article