Incinerator Slag Research Articles

Feasibility analysis of 3D printed concrete with sludge incineration slag: Mechanical properties and environmental impacts

This study substituted sludge incineration slag for natural sand in the application of 3D printed concrete technology (3DCP). It analyzed the influence of the sludge incineration slag incorporation on the workability, printability, mechanical properties, and the solidifying effect of heavy metals in 3DCP. Furthermore, the environmental and economic benefits were also examined. The results indicated that the incorporation of sludge incineration slag accelerated the loss of workability factors such as flowability and consistency in 3DCP. However, it significantly enhanced the early strength of 3DCP and improved its buildability. Additionally, the addition of sludge incineration slag diminished the mechanical properties of 3DCP. When the substitution rate reached 50 % of natural sand with sludge incineration slag, the strength of the 3D printed specimens decreased by 22.1 %. Experimental investigations at a micro-scale indicated that the porosity of interlayer interfaces was a crucial factor causing strength reduction and could be ameliorated by appropriately increasing the extrusion amount to address excessive pore sizes. Toxicity leaching tests for heavy metals demonstrated that the maximum heavy metal leaching concentration in 3DCP specimens with sludge incineration slag incorporation was 0.14 mg/L, meeting the specified requirements. The 3DCP with sludge incineration slag incorporation not only addressed the difficulty in handling incineration bottom slag but also conserved natural sand resources, presenting outstanding environmental and economic benefits. For instance, by substituting 100 % natural sand with sludge incineration slag, there were 5 % reduction in carbon emissions and 30 % increase in economic benefits.

Fault monitoring method of domestic waste incineration slag sorting device based on back propagation neural network

The main monitoring points of traditional sorting equipment fault monitoring methods are usually limited to the inlet and outlet, making it difficult to monitor the internal equipment, which may affect the accuracy of fault monitoring. Therefore, a new fault monitoring method based on back propagation neural network has been studied and designed, which is mainly applied to the sorting device of domestic waste incineration slag. The fault monitoring modeling variables of the domestic waste incineration slag sorting device are selected to determine the operation status of the sorting device. Based on back propagation neural network, a fault monitoring model for the sorting device of municipal solid waste incinerator slag is constructed, and the fault data of the sorting device is trained in the model, so that the fault data of the sorting device can be optimized faster, thus improving the accuracy of fault monitoring. Through comparative experiments with traditional methods, it has been confirmed that this fault monitoring method based on back propagation neural network has significant advantages in detection performance, demonstrating its potential in practical applications.

Durability of geopolymer stabilized domestic waste incineration slag blending macadam in pavement base

In order to achieve the high quality and large-scale utilization of domestic waste incineration slag (WIS) in pavement base, a geopolymer prepared using fly ash from domestic waste incineration was used to replace the cement to stabilized WIS blending macadam used in the pavement base. The durability of the geopolymer stabilized WIS blending macadam (called as GeoWIS) was investigated, including the water stability, freeze-thaw resistance and dry shrinkage. The strength formation was identified using SEM analyses. Furthermore, the durability of GeoWIS was investigated and compared with those of cement stabilized macadam (CSM). Results show that the 7 days compressive strength of GeoWIS meets the strength criterion of the asphalt pavement base (≥2 MPa), except for the combination of 8% geopolymer and 100% WIS. The water stability coefficient and residual compressive strength ratio of GeoWIS increase as the geopolymer increases and WIS decreases. The cumulative dry shrinkage and dry shrinkage coefficient decrease as the WIS increases, while the cumulative water loss rate of GeoWIS increases. SEM analysis shows that the geopolymer reaction generates C-S-H gels, N-A-S-H gels, and Aft, which is the source of the GeoWIS strengths. GeoWIS has better water stability than CSM, and its freeze-thaw resistance and average dry shrinkage coefficient are lower than the average values for CSM.

Analysis of Mechanical Properties and Pore Structure of Mortar Prepared from Municipal Solid Waste Incineration Slag

Abstract The disposal of a large amount of bottom ash generated from the incineration of municipal solid waste has become the focus of research in solid waste and environmentalism. Using municipal solid waste incineration bottom ash (MSWI BA) to prepare mortar can not only solve the problem of insufficient natural river sand resources, but also play a role in treating a large amount of MSWI BA to alleviate urban pressures. In this study, macroscopic properties of mortar were systematically investigated by rheological, mechanical, and drying shrinkage tests, and the influence of MSWI BA on the internal pore structure and interfacial transition zone of mortar has been analyzed by mercury intrusion porosimetry (MIP), scanning electron microscope (SEM) and back scattered electron imaging (BSE). The results show that the rheological model of fresh mortar mixed with MSWI BA as fine aggregate is more consistent with the modified Bingham model, and its plastic viscosity decreases and then increases with the increase of MSWI BA, while the yield stress shows an increasing trend. The compressive strength and splitting tensile strength of mortar decrease with the increase of MSWI BA; the smaller the water-cement ratio and aggregate-binder ratio, the greater the strength loss. The incorporation of MSWI BA improves the flexural strength and compression-flexure ratio of M5/M10 mortar, and the splitting tensile strength of M5 mortar at 28 days is increased by 30 % with 20 % MSWI BA. Additionally, the incorporation of MSWI BA reduces the drying shrinkage properties of mortar and improves the volume stability. At the same time, it increases the number of pores above 50 nm inside the mortar and the content of ettringite at the interface.

Analysis of direct shear test of incineration slag reinforced with waste tire strips by discrete element method

The mechanical properties of incineration slag and waste tire reinforced incineration slag (RIS) were investigated by a series of large direct shear tests. The results show that the addition of waste tire strips can improve the shear mechanical properties of incineration slag. The mechanical behavior and evolution law of RIS were mainly studied by macroscopic laboratory tests, discrete element method (DEM) simulation and microscopic theory analysis. At the same time, the microscopic mechanical properties are analyzed from the microscopic perspectives of contact force chain, porosity, velocity field, stress deflection, fabric analysis and coordination number. At the microscopic level, the contact force chain, the principal stress field and the contact fabric all show similar evolution laws. It reflects the consistency of the microscopic response of particles under the effect of macroscopic external force. The porosity and coordination number reflect the macroscopic dilatancy of the sample from the microscopic change, and explain the reinforcement mechanism from the microscopic point of view.

Mechanical and environmental properties of geopolymer-stabilized domestic waste incineration slag in an asphalt pavement base

Domestic waste incineration slag (WIS) includes fly ash and slag. Fly ash is classified as hazardous waste because it contains heavy metals. Most of slag are directly stacked or landfilled due to problems such as large output and low utilization rate. Harmless treatment is imminent. If WIS is used effectively in the road engineering, which can realize the high-quality and high-efficiency recycling of WIS, and it is of great significance to save resources and protect the environment. This study applies a geopolymer prepared from WIS fly ash as a stabilizing agent in WIS blending macadam for use as a pavement base mixture, and reports the mechanical properties (unconfined compressive strength, splitting strength, and resilience modulus) of the geopolymer-stabilized WIS blending macadam (GeoWIS). The leaching concentrations of harmful heavy metals of GeoWIS soaked in water were also investigated. Finally, the strength formation and heavy metal stability mechanisms were explored. The unconfined compressive strength, splitting strength, and compressive resilient modulus of GeoWIS all increased with increasing geopolymer content and decreasing WIS content. The strength of GeoWIS was derived from its geopolymerization and hydration products (C-S-H gel, N-A-S-H gel, and AFt). When the geopolymer content reached 12%–14%, the GeoWIS without natural macadam met the strength criterion of the asphalt pavement base. Through physical adsorption and chemical bonding, the geopolymer significantly reduced the leaching of harmful heavy metals. In GeoWIS with 50% WIS and stabilized with 10% geopolymer, the Cr, Ni, Cd, and Pb concentrations met the grade Ⅲ groundwater standard. Concentrations of heavy metals leached from GeoWIS are low and exert little impact on environment.

Impact of incineration slag co-disposed with municipal solid waste on methane production and methanogens ecology in landfills

Co-landfill of incineration slag and municipal solid waste (MSW) is a main method for disposal of slag, and it has the potential of promoting methane (CH4) production and accelerating landfill stabilization. Four simulated MSW landfill columns loaded with different amount of slag (A, 0%; B, 5%; C, 10%; D, 20%) were established, and the CH4 production characteristics and methanogenic mechanisms were investigated. The maximum CH4 concentration in columns A, B, C and D was 10.8%, 23.3%, 36.3% and 34.3%, respectively. Leachate pH and refuse pH were positively correlated with CH4 concentration. Methanosarcina was the dominant genus with abundance of 35.1%∼75.2% and it was positively correlated with CH4 concentration. CO2-reducing and acetoclastic methanogenesis were the main types of methanogenesis pathway, and the methanogenesis functional abundance increased with slag proportion during stable methanogenesis process. This research can help understanding the impact of slag on CH4 production characteristics and microbiological mechanisms in landfills.

Multiscale mechanical characterizations of ultrafine tailings mixed with incineration slag

Adding a type of municipal solid waste (incinerator slag) into ultrafine tailings can effectively enhance the mechanical properties of tailings. With an aim to study the macro- and micro-mechanical properties of the tailings slag mixture (TSM), the strength parameters (internal friction angle, cohesion) and micro-mechanical properties with different slag contents were analyzed by geotechnical experiments and particle flow simulations, respectively. The macroscale experimental results demonstrated that the strength parameters of TSM were much higher than that of tailings. Strength parameters also showed non-linear-rising trends with increasing slag content. For the slag content of 40%, the maximum cohesiveness of TSM was determined at 65.2 kPa, and the corresponding friction angle was 39.9°C. Furthermore, the Particle Flow Code (PFC) micro-simulation software was used to analyze the micro-mechanical characteristics of the TSM at different slag contents. The microscale simulation outcomes indicated that the particle transport, particularly in their moving directions, became increasingly chaotic with an increase in the slag content; also, the slag particles significantly impacted the shear processing zone of the TSM. These experimental and numerical results brought more scientific insights into the shear failure mechanism of TSM.

Na2O induced stable heavy metal silicates phase transformation and glass network depolymerization

The pollution of heavy metals and chlorine salts widely exists in solid/hazardous waste, while the stable heavy metal silicates limit the heavy metals removal. This work proposed mechanism of Na2O induced stable heavy metal silicates phase transformation and glass network depolymerization to promote heavy metals chlorination volatilization. Medical waste incineration slag (MWI S) containing heavy metal silicates was used as typical sample. Compared with the control, Cu and Zn volatilization efficiencies sharply increased from 77.54% to 92.22% and 18.70% to 93.82% at 3% Na2CO3, 1200 °C, 40 min. It showed that Na2O successfully induced phase transformation from stable Zn2SiO4 and CuSiO3 to ZnO and CuO easy to react with chloride by destroying the Si–O of Zn–O–Si and Cu–O–Si, respectively. Meanwhile, Na2O effectively destructed Si–O bond to depolymerize the glass network, resulting in the percentage of Q0 and Q1 increase from 25.14% to 38.29%, reducing melt viscosity and improvement of volatilization environment to form bigger bubbles. Medical waste incineration fly ash (MWI FA) was applied as Na source to further verify that the mechanism was significantly enhance Cu and Zn volatilization efficiencies. This study provided new method to reduce heavy metal residues in glass products prepared by melting treatment of solid/hazardous wastes.

Fly ash-based waste for ex-situ landfill stabilization of per- and polyfluoroalkyl substance (PFAS)-contaminated soil

In response to world-wide soil and groundwater contamination per- and polyfluoroalkyl substances (PFAS), stakeholders require immediate mitigation. Soil deposition in landfill is a common mitigation scheme, but PFAS losses occur via landfill leachate. These leaching losses can be reduced by strategically utilizing other deposited waste materials for ex-situ contaminant stabilization. This screening study tested activated carbon (AC) and eight types of wastes (compost, rubber granulate, bentonite clay, industrial sludge, incineration slag, incineration bottom ash (n=4), incineration fly ash-based air pollution control residue (FA-APC) (n=16)) in amending (adding 4%, 5%, 10% or 25% sorbent) field-contaminated (n=19) and PFAS-fortified (n=11) soils. A subset of FA-based residue types, all originating from grate-fire incineration (G-F-I) plants, achieved extraordinarily high removal of PFAS. The removal was up to 98% (25% addition) of the sum of six dominant PFAS for field-contaminated soil and >99% of the sum of 11 PFAS for fortified soil (10/25% addition) (>99.9% for PFOS). Calculated partitioning coefficient revealed significant trends between sorption strength and perfluorocarbon chain length (0.21-0.47 log units per CF2-moiety), indicating high importance of hydrophobic sorption (R2>0.98). However, with incremental G-F-I FA-APC addition this relationship disappeared, indicating an alternative sorption mechanism. The exceptional PFAS sorption by G-F-I FA-APC was not explained by G-F-I surface area, surface charge, soil mineral- and metal composition, or solution DOC, metal, or ion composition (H+, Ca2+, Mg2+, Al3+ and Ba2+). Although the mechanism remains unknown, this study showed that landfill sites can utilize G-F-I FA-APC for ex-situ stabilization at negative cost, thus preventing PFAS-containing leachate.

Beneficial Reuse of Municipal Solid Waste Incineration Bottom Slag in Civil Engineering

Rapid economic development has caused many disturbing problems in many countries. Waste disposal is a prominent one of those problems. Waste incineration has gradually become the most popular treatment method. Waste incineration has many advantages, such as processing capacity, short period, recycling and utilization of resources, etc., but it also produces a lot of incineration bottom slag. Landfilling is one of the methods for waste incineration bottom slag treatment. However, many domestic waste landfill sites no longer accept incineration bottom slag. Therefore, finding sufficient ways to deal with the incineration bottom slag has become an urgent problem. With the increase of environmental pressure and the development of technology, the beneficial use of incineration bottom slag has been gradually considered. Municipal solid waste incineration bottom slag is an atypical particulate material, similar to some construction materials of civil engineering. For a construction material, basic physical properties and engineering properties are important factors in its performance. However, there is limited research about the engineering performance of incineration bottom slag. The purpose of this paper is to investigate the basic physical and mechanical properties of the incineration bottom slag from one incineration plant in Wuhan and provide a theoretical basis for its application in civil engineering. Through laboratory tests, we found that the incineration slag completely meets the engineering requirements and is harmless to the environment. The incineration bottom slag can be used for road embankment filling, sludge dewatering treatment improvement, landfill site covering, it can substitute aggregates in concrete, etc.

Long-Term Behavior of Cement Mortars Based on Municipal Solid Waste Slag and Natural Zeolite-A Comprehensive Physico-Mechanical, Structural and Chemical Assessment.

Limitations in natural aggregate resources and the continuous increase in the demand for concrete as a building material, as well as the increase in the production of waste and the problem with its storage were the reasons for attempts to replace the sand fraction in cement matrices with a corresponding slag fraction. Municipal solid waste incineration (MSWI) slag, which is a product of waste incineration, can be used as an aggregate. This extends its service life and reduces landfill waste. Therefore, three types of cement mortars with different aggregate composition were prepared. In addition, to increase the durability of the cement matrix and the degree of immobilization of harmful heavy metals and salts present in the slag, a natural zeolite with pozzolanic properties was used. A set of tests was carried out on fresh mortar and hardened mortar, including strength tests after 7, 28 and 360 days. What is more, chemical tests were undertaken, including the content of chlorides and sulfates, leaching using the TCLP method and oxide composition. The conducted tests revealed that all mortars had similar strength properties and demonstrated the effectiveness of immobilizing harmful substances contained in the municipal solid waste incineration (MSWI) slag by cementing.

Powder Explosion Inhibitor Prepared from Waste Incinerator Slag: Applied to Explosion Suppression of Oil Shale Dust Explosion

In this paper, a method for waste incineration slag is proposed. An incineration acidification alkalization modification was carried out based on the characteristics of the oxides (SiO2, CaO, Al2O3, Fe2O3, and MgO) of waste incineration slag. With modified slag as the carrier and NaHCO3 as the supporter, a slag-based composite powder explosion inhibitor was prepared with the solvent-crystallization wet coating (WCSC), ball milling dry coating (DCBM), and air impact dry coating (DCAI) methods. The advantages and disadvantages of the three methods were compared and analyzed. Explosion suppression experiments on oil shale dust were carried out, and the explosion suppression mechanism was described. The explosion suppression process of the modified slag–NaHCO3 composite powder explosion inhibitor for oil shale dust was found to involve a synergy of physical and chemical inhibition. This explosion suppression mechanism indicates three requirements for the preparation and application of industrial solid waste-based composite powder explosion inhibitors. The feasibility of preparing composite powder explosion inhibitors from waste incinerator slag was discussed from the experimental point of view and its explosion suppression performance on oil shale dust was studied with the intention of providing a new form of resource utilization for waste incinerator slag.

Analysis of Direct Shear Test of Incineration Slag Reinforced with Waste Tire Strips by Discrete Element Method

Analysis of Direct Shear Test of Incineration Slag Reinforced with Waste Tire Strips by Discrete Element Method

Effects of medical waste incineration fly ash on the promotion of heavy metal chlorination volatilization from incineration residues

High contents of heavy metals and Cl are major challenges for incineration residue disposal. Classification by the Chinese government and the coronavirus disease 2019 pandemic have changed the characteristics of incineration residues, thereby increasing the difficulty of disposal. In this study, medical waste incineration fly ash (MWI FA) was proposed as an additive to promote chlorination volatilization of heavy metals from municipal solid waste incineration fly ash (MSWI FA) and medical waste incineration slag (MWI S). When the mixing ratio of MWI FA to MSWI FA was 1:3, the chlorination volatilization efficiencies of Cu, Zn, Pb, and Cd at 1000 °C for 60 min were 50.2%, 99.4%, 99.7%, and 97.9%, respectively. When MWI FA was mixed with MWI S at a ratio of 1:1, the chlorination volatilization efficiencies of Cu, Zn, Pb, and Cd at 1200 °C for 40 min were 88.9%, 99.7%, 97.3%, and 100%, respectively. Adding MWI FA can replenish Cl in MSWI FA and MWI S while increasing the surface area and forming pore structures by sublimation of NaCl and decomposition of CaSO4, or can reduce the melting point and viscosity by Na2O destroying the glass matrix. Therefore, MWI FA can be co-disposed with MSWI FA and MWI S respectively to enhance the chlorination volatilization of heavy metals.

Water quenched slag from incinerator ash used as artificial stone

In this research, the incineration slag is treated with high temperature by the plasma melting treatment technology to effectively solve the resource recovery and reuse of the incineration slag. After the thermal plasma melting, the molten slag is vitrified into microcrystalline materials by cooling with water. It is called water quenched slag (WQS). Based on the characteristics of molten slag, the feasibility of reusing artificial stone resources is an importance issue. The objective of this study is to investigate mechanical properties of artificial stone made by WQS from the incinerator ash. The WQS is utilized for replacing stone powder and make artificial stone in this study. The research scope is to assess the proper ratio of coarse and fine WQS particles to produce the artificial stone. The experimental testing program includes hardness, specific gravity, water absorption, compressive strength, tensile strength, heat resistance, and toxic dissolution tests. The testing results show when the ratio of coarse and fine particles of WQS is 1:1 blended, the physical properties of the specimens are closer to those of general artificial stone; the tensile strength decrease but the compressive strength increase when more the amount of resin or WQS are mixed; in the heat resistance test, its softening point and failure point are similar to those of artificial stone. In summary, the comprehensive test results show that WQS demonstrate great potential to largely replace the stone powder component of artificial stone as an ecological and environmentally friendly material.

Recycling municipal solid waste incineration slag and fly ash as precursors in low-range alkaline cements

Application of municipal solid waste incineration (MSWI) products - fly ash (MSW-FA) and bottom ash (MSW-BA), is increasingly popular, mostly due to the need to reintroduce it in the industrial chain, but also because its technical performance is constantly enhanced by a growing research effort. This paper deals with the less popular application of these wastes without the addition of a more competent precursor. Several pastes based on MSW-FA, MSW-BA or MSW-FA+MSW-BA were prepared, using sodium silicate or sodium hydroxide. Their overall performance was then assessed through mechanical (uniaxial compressive strength - UCS and seismic wave velocity), environmental (leaching) and durability tests (freeze-thaw and wetting-drying). Cement stabilised MSW-BA pastes were also tested, for reference. Results showed that a preliminary mechanical activation, achieved by milling, is fundamental; the activation with silicate is more effective than with hydroxide, especially in the case of the MSW-BA pastes, when the UCS values are more than triplicated (3–10 MPa); the MSW-BA is a more competent precursor than the MSW-FA and the durability and leachability of the alkali activated pastes is similar to that obtained with cement. The most performing paste, in terms of UCS, was obtained with BA activated exclusively with sodium silicate, with an activator/precursor weight ratio of 0.5. In general, the low-cost solidification/stabilisation proposed in this study showed competitive with the alternative use of up to 30% cement and should be regarded as a valid alternative for simple storage or low-range applications, in substitution of Portland cement.

Chemical speciation, distribution and leaching behavior of chlorides from municipal solid waste incineration bottom ash

Municipal solid waste incineration (MSWI) bottom ash is an environmentally harmful solid waste that cannot be recycled without pre-treatment. The chloride content in bottom ash (BA) is a major obstacle that restricts its application as secondary building materials. Here, the chemical speciation of the chlorides in BA is systematically studied with multiple analytical techniques, i.e., quantitative XRD, microanalysis and XPS. In addition to halite (NaCl), several chloride-rich minerals are present in BA. These phases are hydrous metal oxides, ettringite, decomposed hydration products (C4A3) and incineration slag with a chloride content of 3.2%, 1.4%, 2.1% and 1.3%, respectively. For the first time, the real-time leaching profiles of chloride (up to 80 h) from BA were obtained with a chloride-ion specific electrode to explain the leaching mechanism. In the initial stage of leaching, highly soluble alkali salts (NaCl) and physisorbed chlorides (especially those adsorbed on hydrous metal oxides) are released, which is controlled by diffusion. Later, the leaching is controlled by the solubility/reactivity of the chloride-containing phases, such as ettringite and incineration slag. The results show that the release of chloride is not only a diffusion-controlled process, as reported in the literature, but also a reaction-controlled phenomenon, during which the chloride-rich phases decompose and release chlorides that are associated with them via sorption/incorporation.

Bioleaching of valuable and hazardous metals from dry discharged incineration slag. An approach for metal recycling and pollutant elimination

Recycling of process wastes will be in future an essential step to meet the demands for valuable metals of a growing market. Depending on their particle sizes incineration slags are already used to recover metals but particle size fractions below 4 mm are still difficult to recycle. Therefore, different particle size fractions (mesh size 2 and 4 mm, high energy grinded) of dry discharged slags were used for bioleaching with and without the pure cultures Acidithiobacillus ferrooxidans or Leptospirillum ferrooxidans or a mixture of Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans in batch cultures. Regarding Al, Cr, Cu, Ni, Mn and the rare earth elements Ce, La and Er, bioleaching was significantly more successful with iron oxidizing bacteria compared to abiotic controls. Metal mobilization for Al, Cu, Mn, Cr and Er with bacteria was between 70 and 100% and for Ce, Ni and La around 50% almost after 7 days, making an industrial application for the high concentrated metals like Al and Cu feasible. In addition to the recovery of valuable metals, a reduction in cost of landfilling was identified. After treatment of the slag with the microorganisms, concentrations of harmful substances in the residues could be reduced and thus a classification in lower safety levels regarding the LAGA or EU regulations was calculated.

Options for the implementation of new secondary raw materials in autoclaved aerated concrete

AbstractCurrently, the only material used as the primary siliceous component of autoclaved aerated concrete (AAC) in the Czech Republic is sand. Within the context of previously conducted research, this article evaluates the use of new types of secondary raw materials to achieve greater economic and ecological benefits during AAC production. The investigated secondary raw materials include fly and bottom ash, slag, and waste glass. AAC composite specimens with admixtures of secondary raw materials were cured by hydrothermal conditions in a laboratory autoclave for 7 and 12 h of isothermal durability 190°C. Of the secondary raw materials tested under laboratory conditions, the highest strength was obtained in the specimen with a 10% waste glass admixture. The other admixture that positively affected the mechanical characteristics of specimens was waste incinerator slag. It is clear from the results of this investigation that the use of secondary raw materials does not diminish strength, but improves mixture rheology and supports the formation of tobermorite.