Municipal Solid Waste Incineration Ash Research Articles

Metal behavior during vitrification of incinerator ash in a coke bed furnace

In this study, municipal waste incinerator ash was vitrified in a coke bed furnace system and the behavior of metals was investigated. Coke and lime were added to provide heat which facilitated vitrification. Ash contributed more than 90% of metal (except for Ca) input-mass. Metal species with low boiling points accounted for the major fraction of their input-mass adsorbed by air pollution control devices (APCDs) fly ash. Among the remaining metals, those species with light specific weights in this furnace tended to be encapsulated in slag, while heavier species were mainly discharged by ingot. Meanwhile, the leachability of hazardous metals in slag was significantly reduced. The distribution index (DI) was defined and used as an index for distribution of heavy metals in the system. A high DI assures safe slag reuse and implies feasibility of recovering hazardous heavy metals such as Cr, Cu, Fe, Pb and Zn. The vitrification in a coke bed furnace proved to be a useful technology for the final disposal of MSW incinerator ash. The heavy metals are separated into the slag, ingot and fly ash, allowing safe reuse of the slag and possible recovery of the metals contained in the ingot and ash fractions.

Investigation of accelerated carbonation for the stabilisation of MSW incinerator ashes and the sequestration of CO2

Accelerated carbonation has been used for the treatment of contaminated soils and hazardous wastes, giving reaction products that can cause rapid hardening and the production of granulated or monolithic materials. This technology provides a route to sustainable waste management and it generates a viable remedy to the problems of a decreasing number of landfill sites in the UK, global warming (due to greenhouse gas emissions) and the depletion of natural aggregate resources, such as sand and gravel. The application of accelerated carbonation (termed Accelerated Carbonation Technology or ACT) to sequester CO2 in fresh ashes from municipal solid waste (MSW) incinerator/combined heat and power plants is presented. The purpose of this paper is to evaluate the influence of fundamental parameters affecting the diffusivity and reactivity of CO2 (i.e. particle size, the reaction time and the water content) on the extent and quality of carbonation. In addition, the major physical and chemical changes in air pollution control (APC) residues and bottom ashes (BA) after carbonation are evaluated, as are the optimum reaction conditions, and the physical and chemical changes induced by accelerated carbonation are presented and discussed.

Simulation of Municipal Solid Waste Incinerator Ash/Cement Systems by Means of Factorial Experiments

In the present paper, the behavior of municipal solid waste incinerator ash in cement-based systems was simulated by spiking experiments on portland cement making use of pure compounds, including MgCl\d2, K\d2SO\d4, Zn(NO\d3)\d2, and NaNO\d2, which were selected based on the findings from previous investigation. A 2\U4-1\N fractional factorial design was used to arrange the program of experiments. The evolution of physical and mechanical properties as well as acid neutralization capacity with curing time was studied with the aid of statistical analysis. Based on the results from the present work, a model was developed for prediction of unconfined compressive strength and buffering capacity of incinerator ash—portland cement mixtures. The good agreement between predicted and measured values indicated that the behavior of incinerator ash in cementitious systems is largely to be ascribed to the four selected compounds.

Replacement of raw mix in cement production by municipal solid waste incineration ash

The feasibility of municipal solid waste incineration (MSWI) ash utilized as the replacement of raw mix in cement production is investigated. Result shows that sieving, self-grinding, and magnet separation processes are necessary to remove the debris, salt, and metallic contents that existed in the MSWI ash. By using the pretreated MSWI ashes, the produced cement specimens were in compliance with the unconfined compression strength (UCS) standard in Taiwan at small replacement percentage (<5%). When ash replacement percentage is large (more than 10%), the strength development of specimens would be hindered due to the deficient formation of the calcium silicate. Calculation on lime saturation factor (LSF) also shows a descending trend in consequence of the increase in replacement percentage. Thus, compositional effect should be taken into consideration for promoting the calcium silicate formation at the case of large ash replacement. In this research, adjustment of chemical composition was achieved by adding 183 g calcium oxide per kilogram of cement raw mixture with 15% ash replacement. After adjustment, the produced cement could develop seven- and fivefold increase on UCS compared with those without calcium oxide supplement at 3 and 7 days of curing, respectively. Results concluded that the MSWI ash was suitable in reuse for cement production under a well-conditioned situation.

Assessing the effects of municipal solid waste incinerator bottom ash on the decomposition of biodegradable waste using a completely mixed anaerobic reactor.

Experimental lab scale anaerobic reactors were used to assess the effect of municipal solid waste incinerator (MSWI) bottom ash on the process of biodegradation of organic materials typical of those found in municipal solid waste (MSW). Three reactors were used in the trial and each of these received the same daily organic load of simulated MSW but varying loads of MSWI bottom ash. The reactors were monitored over a period of 200 days for pH, alkalinity, volatile acids, total organic carbon (TOC), biogas production, gas composition and heavy metals. The addition of ash appeared to have beneficial effects on the degradation process as there was an increase in gas production, alkalinity, and pH, coupled with a decrease in the TOC concentration of leachate when compared with a control reactor without MSWI ash addition. After 200 days operation, the alkalinity and gas production in the anaerobic reactor receiving 6g ash per day was twice that of the reactor receiving 3g of ash per day and four times that of the control reactor. A number of tests were carried out on the ash sample to investigate the possible reasons for enhancement of the biodegradative process. These included a shake flask batch leaching test using distilled water, determination of the acid neutralising capacity by titration curve, and the quantification of six heavy metals and four light metals. In the reactors receiving ash the concentrations of Ca, Na, K, Mg ions were found to be significantly higher and these may provide a higher alkalinity which could promote the digestion process. Soluble concentrations of Cd, Cr, Cu, Ni, Pb, and Zn were in the range of 0.02-0.2, 0.01-2.5, 0.01-0.3, 0.01-1, 0.01-1.2, and 0.01-1 mgl(-1) respectively and at these concentrations it is unlikely that they would prove inhibitory to the digestion process.

Electrodialytic removal of heavy metals from different fly ashes: Influence of heavy metal speciation in the ashes

Electrodialytic remediation, an electrochemically assisted extraction method, has recently been suggested as a potential method for removal of heavy metals from fly ashes. In this work, electrodialytic remediation of three different fly ashes, i.e. two municipal solid waste incinerator (MSWI) fly ashes and one wood combustion fly ash was studied in lab scale, and the results were discussed in relation to the expected heavy metal speciation in the ashes. The pH-dependent desorption characteristics for Cr differed between the two MSWI ashes but were similar for Cd, Pb, Zn and Cu. Thus, it was expected that the speciation of Cd, Pb, Zn and Cu was similar in the two ashes. However, in succeeding electrodialytic remediation experiments significant differences in removal efficiencies were observed, especially for Pb and Zn. In analogous electrodialytic remediation experiments, 8% Pb and 73% Zn was removed from one of the MSWI ashes, but only 2.5% Pb and 24% Zn from the other. These differences are probably due to variations in pH and heavy metal speciation between the different ashes. Cd, the sole heavy metal of environmental concern in the wood ash, was found more tightly bonded in this ash than in the two MSWI ashes. Approximately 70% Cd was removed from both types of ashes during 3 weeks of electrodialytic remediation, although the total concentration was a factor of 10 lower in the wood ash. It was suggested that complex Cd-silicates are likely phases in the wood ash whereas more soluble, condensed phases are dominating in the MSWI ashes.

Characterization of Slags and Ingots from the Vitrification of Municipal Solid Waste Incineration Ashes

Vitrification was used to convert hazardous metal-bearing fly ash from municipal solid waste (MSW) incineration into useful products in this work. In addition to volume/mass reduction, some parameters such as basicity, metal leachability, density, porosity, water absorption, and compressive strength of the slags and ingots vitrified from fly ash and fly ash/additive (bottom ash and cullet) mixtures (at 1450°C for 1.5 h) were investigated. The more the bottom ash or cullet added to the fly ash, the lower the specimen basicity, leading to a more amorphous glassy matrix. Amorphous glassy slags were obtained when the specimen basicity was around 0.24-1.24. All slags were in compliance with the limits of TCLP (Toxicity Characteristic Leaching Procedure) in Taiwan, United States, and Japan. The vitrification process reduced the leaching amount and ratio of Cr and Pb, significantly lowered the leaching ratio of Cd, but raised the leaching ratios of Zn and Cu. The slag metal leachability (particularly for Cu) was mainly influenced by the metal content in slags, not the slag (crystal or glassy) structure or basicity. After vitrification, an over 50% specimen volume reduction was achieved and most of the specimen mass moved to the slag phase. The ingots, mainly consisting of Fe, also met Taiwan and U.S. TCLP requirements and were suitable for a higher purity metal recovery. The slags and ingots were approximately 2- and 6-fold as dense as the specimens before vitrification, respectively. The slags were found to have very small porosities, low water absorptions, and high compressive strengths (>550 kg/cm 2 ), so they may be considered as candidate materials for waterproof and construction.

Modelling heavy metal and anion effects on physical and mechanical properties of Portland cement by means of factorial experiments

The aim of the present work was to investigate the influence of a number of heavy metals (Cd, Cr(III), Cu, Pb and Zn), as well as anions (CI‐, SO2‐ 4 ) on the physical and mechanical properties of cementitious pastes, including setting time, bulk density and unconfined compressive strength. The above mentioned species and their concentrations were selected in order to simulate addition of 20% municipal solid waste incinerator ash to Portland cement. Spiking experiments were performed according to a 27–3 IV fractional factorial design by addition of pure compounds containing the contaminants of interest to Portland cement. The results from the experimental campaign, which were interpreted using statistical analysis techniques, showed that the investigated contaminants variously affected the hydration process of cement. The ranking for final setting time values was Zn(NO3)2 > K2SO4 > NaCl > mean response > Cr(NO3)3 > NaCl+Cr(NO3)3, Cd(NO3)2+Pb(NO3)2 or CuCl2+Zn(NO3)2 interaction, whereas the ranking for UCS values during hardening was Zn(NO3)2 > CuCl2 > NaCl+K2So4, CuCl2+Pb(NO3)2 or Cd(NO3)2+Zn(NO3)2 interaction > mean response. Conversely, none of the selected contaminants was found to significantly influence ultimate strength.

Plant and soil microbial community responses to solid waste leachates diffusion on grassland

This work aims to define the effect on soil-plant relationships and soil quality of adding leachates from municipal solid waste incinerator (MSWI) ashes on recipient experimental grasslands. Leachates from MSWI-bottom ashes (BA) and MSWI-solidified air pollution control residues (SAPCr) contained a large content of salts and may be a source of an important disturbance of biological functioning of soils or grassland in the neighbourhood of systems containing such residues. Leachates obtained from solid waste were spread on field experimental plots with indigenous grasses (herbaceous fallow) or with introduced vegetation (seedlings of an indigenous colonial bentgrass: Agrostis tenuis). After the spreading of leachates, some effects on vegetation (at day 180 and day 480) and on bacteria communities of soil (at day 90 and at day 480) were assessed. On soil, a significant increasing of Na+ percentage of the exchange complex (ESP) was observed. The colonial bentgrass was found to be more sensitive to BA phytotoxicity than indigenous grasses, with a decrease of root (43%) and aerial (29%) biomass 180 days following the contamination. Conversely, a positive effect on the biomass was observed following the addition of SAPCr leachate. The use of a molecular tool to assess the effects on soil eubacteria community (A-RISA) showed a significant large modification of the community structure with SAPCr leachate, when a low effect was observed with BA. Grass cover and root influence on the behaviour of the bacterial communities with respect to the leachates were shown.

European plastics additives use to reach 2.7 million tonnes by 2006

Municipal solid waste incinerator (MSWI) ash has a similar chemical composition to traditional cement kiln feed components, making it a potentially viable replacement for traditional materials in the absence of deleterious components invariably present in ash. This supposition should be confirmed by lab-scale experimentation prior to full-scale implementation. This study explores lab-scale cement manufacturing using varying replacement percentages of unwashed and water-washed MSWI bottom ash. The use of unwashed MSWI ash as a kiln feed is associated with a considerable decrease in tricalcium silicate content. Each replacement percentage of washed bottom ash incorporation resulted in an approximate tricalcium silicate content of 45%, while unwashed bottom ash specimens had tricalcium silicate contents of approximately 35%. Aluminate concentrations in ash-amended clinkers were considerably higher than reference clinkers, which may require additional gypsum to ensure proper setting. The effects of mineralogical differences were reflected in cement reactivity. Unwashed MSWI ash-amended specimens should be monitored for chloride and alkali content. Results of this study highlight the simultaneous impact of washed and unwashed MSWI bottom ash addition as kiln feed on clinker formation, and the special considerations for clinker production and behavior. The addition of MSWI ash as cement kiln feed is beneficial provided it is washed and appropriately controlled below 8% to reduce deleterious phase composition.

RECOVERY OF HEAVY METALS IN ELECTROSTATIC PRECIPITATOR ASH BY CARBON DIOXIDE AS A PRE-EXTRACTION REAGENT

This study investigated the efficiency of heavy metal separation and recovery in electrostatic precipitator (ESP) ash from a municipal solid waste incinerator (MSWI) when carbon dioxide is used as the pre-extraction agent. The experiments were conducted at 120°C with pH values of 3–6 and liquid-to-solid (L/S) ratios varying from 10:1 to 40:1. The results indicate that an increase in the L/S ratio enhances the separation and recovery efficiency of heavy metals in the MSWI ash. The separation efficiency of Cd, Cr, and Zn increased significantly with the increased L/S ratio. The pH level was the prominent factor affecting the extraction of heavy metals from ESP ash: at pH 3–4, maximum amounts of Cd and Cr were extracted. However, due to the increased release of ions with increased CO3 2−, Zn was relatively soluble at high pH values. In cases with an L/S ratio of 40:1 and pH 3, the Cd, Cr, and Cu extraction amounts were 86.4%, 71.2%, and 34.9%, respectively. Pb and its compounds remained in a stable state under experimental conditions. The above results point toward the feasibility of heavy metal recovery and fly ash reutilization when carbon dioxide is used as the pre-extraction agent. Both greenhouse gas (CO2) emissions and acid extraction operating costs are reduced with this process.

Model comparison of flow through a municipal solid waste incinerator ash landfill

The drainage discharge of a municipal solid waste incinerator (MSWI) bottom ash landfill was simulated using various modelling approaches. Two functional models including a neural networks approach and a hydrological linear storage model, and two mechanistic models requiring physical/hydrodynamic properties of the waste material, HYDRUS5 and MACRO (Version 4.0) were used. The models were calibrated using an 8-month data set from 1996 and validated on a 3-month data set from winter 1994/1995. The data sets comprised hourly values of rainfall, evaporation (estimated from the Penman–Monteith relationship), drainage discharge and electrical conductivity. Predicted and measured discharges were compared. The discharge predicted by the functional models more exactly followed the discharge patterns of the measured data but, particularly the linear storage model, could not cope with the non-linearity of the system that was caused by seasonal changes in water content of the MSWI bottom ash. The fit of the neural networks model to the data improved with increasing prior information but was less smooth than the measured data. The mechanistic model that included preferential discharge, MACRO, better modelled the discharge characteristics when inversely applied, indicating that preferential flow does occur in this system. However, even the inverse application of HYDRUS5 could not describe the system discharge as well as the linear storage model. All model approaches would have benefited from a more exact knowledge of initial water content.

98/02613 Recycling of boiler and incinerator ash into value added glass products : Hnat, J. G. and Bartone, L. M. Proc. Bienn. Waste Process. Conf., 1996, 17, 129–142

This paper discusses the recycling of coal-fired boiler and incinerator ashes into value added glass products via the use of a newly developed, fossil-fuel fired, high temperature melting process. The Vortec patented Cyclone Melting System (CMS{trademark}) has a number of significant advantages for recycling solid wastes including: the oxidation of organic and metal contaminants, formation of non-leachable glasses which can be sold as value added products, high melting efficiencies, multi-fuel capability, low operating and maintenance costs and low NO{sub x} emissions. This paper summarizes some of the challenges facing process industries and utilities in the recycling and reuse of industrial solid wastes. The results of laboratory and pilot scale testing with several pulverized coal-fired boiler ashes, several municipal solid waste incinerator ashes, and a sewage sludge incinerator ash are summarized. Information on ash properties, melting characteristics, system performance, toxicity characteristics leaching procedure (TCLP) testing results, flue gas emissions, recycled products, and economics are presented. The application of the CMS to the production of several value added glass and ceramic products is also discussed.

The characteristics study on sintering of municipal solid waste incinerator ashes

The study examines the sintering of incinerator ashes from municipal solid waste while considering the compact pressure, sintering temperature, and sintering time. Experimental results indicate that the compressive strength primarily influences the compact pressure used in forming the specimens. The specimens' strengths increase at a sintering temperature ranging from 1120°C to 1140°C. However, the strength decreases with an increasing ignition loss of incinerator residues. As heavy metals are fixed and/or sealed in the sintered incinerator ashes, the process generates a ceramic-like solid having a sufficiently low metal leachability. The Pb, Cd, and Cr concentrations of the leachate from the Toxicity Characteristic Leaching Procedure (TCLP) test are 0.10–0.70 mg/l, 0.05–0.30 mg/l, and 0.35–1.25 mg/l, respectively, all complying with the regulatory limits of Taiwan EPA. The above results point toward the feasibility of recycling the incinerator ashes as a construction material by sintering.

Weathering Processes in Municipal Solid Waste Incinerator Bottom Ash Deposits

Municipal solid waste incineration (MSWI) is becoming is becoming increasingly popular worldwide. One of the main environmental concerns with regard to the utilisation or the landfilling of MSWI residues is the long-term leaching and transport of heavy metals into the environment. The concentrations of potential contaminants in MSWI bottom ash such as Cu, Pb and Zn are in the range of g/kg. The mobility of these components depends both on their geochemical properties and on the composition and reactivity of the matrix components. The matrix components of municipal solid waste incinerator (MSWI) bottom ash are Si, Ca, AI and Fe. Estimated as oxides they account for approximately 80% of the dry mass of bottom ash. Other major components are Mg, CO3, Na, K, S (as SO4 and S(II)), CI in order of abundance. Organic components make up a further 1-2% of the MSWI bottom ash material. Mineralogical studies have determined that MSWI bottom ash is composed of equal amounts of fine ash material and melted components of which half have crystallised and small quantities of metallic components, ceramics and stones. The key parameter with regard to the long-term mobility of heavy metal cations is the acid neutralising capacity ANC of MSWI bottom ash. Leaching experiments in the laboratory have indicated that Ca minerals constitute the ANC equivalent to the titration end point at pH 7.5 (Johnson et al, 1995). Leachate pH initially ranges between pH 11 and 12, due to the leaching of portlandite (Ca(OH)e). In the initial stages Ca solubility appears to be controlled by portlandite and gypsum. However, the leachate of aged deposits (>10 a) is generally buffered by CaCO3. Furthermore the buffer capacity of fresh MSWI bottom ashes (approx. 1.5 meq/g) is significantly higher than that of aged samples (0.6-1.0 meq/g). Since the initially mobile Ca cannot be washed out of bottom ash deposits within a few years and because of the apparent reduction in ANC, Ca is probably incorporated into less soluble secondary minerals. Evidence of the secondary Ca-mineral formation has been obtained by field sampling from a landfill deposit in Switzerland (Landfill Lostorf). A bulk sample (3 months old) was taken of the freshly deposited MSWI ash and 60-70 further samples were taken of a whitish deposits within the landfill (see Fig. 1). These deposits ranged from a few millimeters to centimeters in diameter The latter samples were taken from a depth of 0.5 m and were approximately a year old at the time of sampling. Secondary mineral formation was also investigated in the laboratory. In order to avoid problems arising due to the heterogeneity of the MSWI ash, ground glass (synthesized from oxides at 1400~ shock-cooled in a water bath) and oxides of the same composition as MSWI bottom ash (Si:Ca:AI:Mg:Fe = 8:4:2:1:1) were aged at 25, 55 and 80~ (liquid:solid = 2:1) for up to a year. In the glass ageing experiments, half of the Ca was added as portlandite to the suspension. Xray diffraction (XRD) measurements were made of all samples. XRD measurements of bulk MSWI bottom ash samples from the landfill deposit identified the presence of calcite (CaCO3), anhydrite (CaSO4) and ettringite (3 CaO.AleO3.CaSO4.32H20). The same minerals, with the exception of anhydrite, were detected in selected secondary mineral formations from the landfill, identified as whitish encrustations. Gypsum (CaSO4.2HzO) was found in these samples. Other identifiable minerals were Mg/K aluminosulphates and a Mg A1 hydroxide hydrate and gibbsite (AI(OH)3). A Ca silicate hydrate, riversideite (5CaO.6SiOe-H20) was identified in the bulk sample. Ca silicate hydrates were observed in the aged oxide mixtures. Ca silicate hydrates such as C a O . S i O e H 2 0 a n d t o b e r m o r i t e (5CaO.6SiO2.5H20) were identified as was a Ca aluminosilicate, katoite (3CaO.AlaO3.SiOe.4H20). Ca aluminosulphate hydroxides, such as ettringite, were detected. Mg A1 hydroxide hydrate was observed in these samples as well. The same Ca silicate hydrates, ettringite, gypsum, portlandite and Mg AI hydroxide hydrate were observed in the aged glasses, though Ca silicate hydrates were only formed at elevated temperatures.

The partitioning and fate of heavy metals from municipal solid waste incineration plants in Taiwan

This study investigates the fate and partitioning of heavy metals in the municipal solid waste (MSW) incinerator ash collected from a typical mass burning incineration plant in Taiwan. The results indicate that large amounts of heavy metals are contributed by noncombustible composition in the MSW. Regarding the partitioning results, Cd and its high vapor pressure compounds were relatively volatile compared to the other trace metals. On average, more than 70% of the Cd was captured in the fly ash, compared to an average of less than 10% of the Cu and Cr. Pb and Zn partitioning was distributed equally between the bottom ash and the fly ash.

Characteristics of MSW Incinerator Ash for Use in Concrete

ABSTRACT The incinerator ash, the fine residue resulting from the burning of municipal solid waste (MSW), has been characterized with a view to utilizing the material to replace part of the Portlan...

97/03282 Immobilization of heavy metals from MSW incinerator ash via use of sorel cement

97/03282 Immobilization of heavy metals from MSW incinerator ash via use of sorel cement

Loss of metallic elements associated with ash disposal and social impacts

Abstract Economic, environmental and health-related impacts are discussed concerning the loss of metallic elements associated with the disposal of ash. Municipal solid waste incineration ash (MSWA), thermal power station coal ash (PSA), and sludge incineration ash from wastewater treatment facilities (WTSA) were selected as representatives of ash, due to the large amounts of them commonly generated. In the process of treatment and disposal of waste material, recycling (recycling and recovery) has been recommended and a consensus on their performances has also recently evolved. However, waste treatment in Japan is not presently elaborate enough when the total social impact is considered because metallic element recovery from waste such as ash is not taken into account. The total amounts of metallic elements in the ash were estimated. It was found that recovery of metallic elements from ash by final stage recycling could have reached approximately 30%, 22% and 45% of the aluminium, lead and zinc, respectively, that were recycled by front stage recycling. The importance of the recognition of metallic element recovery from ash is pointed out in order to pursue a better recycling system, which would further reduce the impact on the environment and human beings.

Properties of the Soil Imoroved by the Special Cement Made from Municipal Solid Waste Incineration Ashes

Properties of the Soil Imoroved by the Special Cement Made from Municipal Solid Waste Incineration Ashes