Chlorine-induced Gas-Solid coupled corrosion behaviors of tube materials in high steam parameter MSW incinerator.

The fast development of the waste incineration industry requires deeper insights into heating surface corrosion behavior at higher operating parameters with complex corrosion sources. This research investigates the corrosion behaviors of three types of plates, namely SA210-C, TP310, and 12CrMoV, when subjected to simulated flue gas and fly ash deposition simultaneously at temperatures ranging from 500℃ to 620℃. The results indicate that the weight loss due to coupling corrosion was 2.5 to 84.5 times higher than that of gas-phase corrosion under the same operating conditions. Among the three stainless-steels, TP310 demonstrates superior corrosion resistance. It is worth noting that, under the gas-solid coupling corrosion conditions, we observed a distinct two-layer structure of corrosion products. Despite the fly ash simulants detaching over time, the two-layer structure remained unchanged. Based on the theory of eutectic molten salt formation, we propose that alkali metal chlorides only initiate the formation of the molten layer in the initial stage of corrosion. Furthermore, we offer additional suggestions for the mechanism of sustaining the molten layer in the absence of alkali metal chlorides.

LCA of recycling aluminium incineration bottom ash, dross and shavings in a rotary furnace and environmental benefits of salt-slag valorisation.

Recycling aluminium in a rotary furnace with salt-fluxes allows recovering valuable alloys from hard-to-recycle waste/side-streams such as packaging, dross and incinerator bottom ash. However, this recycling route generates large amounts of salt-slag/salt-cake hazardous wastes which can pose critical environmental risks if landfilled. To tackle this issue, the metallurgical industry has developed processes to valorise the salt-slag residues into recyclable salts and aluminium concentrates, while producing by-products such as ammonium sulphate and non-metallic compounds (NMCs), with applications in the construction or chemical industries. This study aims to assess through LCA the environmental impacts of recycling aluminium in rotary furnaces for both salt-slag management routes: valorisation or landfill. It was found that this recycling process brings forth considerable net environmental profits, which increase for all the considered impact categories if the salt-slag is valorised. The main benefits arise from the production of secondary cast aluminium alloys, which is not unexpected due to the high energy intensity of aluminium primary production. However, the LCA results also identify other hotspots which play a significant role, and which should be considered for the optimisation of the process based on its environmental performance, such as the production of by-products, the consumption of energy/fuels and the avoidance of landfilling waste. Additionally, the assessment shows that the indicators for mineral resource scarcity, human carcinogenic toxicity and terrestrial ecotoxicity are particularly benefited by the salt-slag valorisation. Finally, a sensitivity analysis illustrates the criticality of the metal yield assumptions when calculating the global warming potential of aluminium recycling routes.

Mechanism of soot and particulate matter formation during high temperature pyrolysis and gasification of waste derived from MSW.

This research investigates the formation mechanism of soot and particulate matter during the pyrolysis and gasification of waste derived from Municipal Solid Waste (MSW) in a laboratory scale drop tube furnace. Compared with CO2 gasification atmosphere, more ultrafine particles (PM0.2, aerodynamic diameter less than 0.2 µm) were generated in N2 atmosphere at 1200℃, which were mainly composed of polycyclic aromatic hydrocarbons (PAHs), graphitic carbonaceous soot and volatile alkali salts. High reaction temperatures promote the formation of hydrocarbon gaseous products and their conversion to PAHs, which ultimately leads to the formation of soot particles. The soot particles generated by waste derived from MSW pyrolysis and gasification both have high specific surface area and well-developed pore structure. Compared with pyrolysis, the soot generated by gasification of waste derived from MSW had smaller size and higher proportion of inorganic components. The higher pyrolysis temperature led to the collapse of the mesoporous structure of submicron particles, resulting in a decrease in total pore volume and an increase in specific surface area. Innovatively, this research provides an explanation for the effect of reaction temperature/ CO2 on the formation pathways and physicochemical properties of soot and fine particulate matter.

Desulfurization and upgrade of pyrolytic oil and gas during waste tires pyrolysis: The role of metal oxides.

Pyrolysis can effectively convert waste tires into high-value products. However, the sulfur-containing compounds in pyrolysis oil and gas would significantly reduce the environmental and economic feasibility of this technology. Here, the desulfurization and upgrade of waste tire pyrolysis oil and gas were performed by adding different metal oxides (Fe2O3, CuO, and CaO). Results showed that Fe2O3 exhibited the highest removal efficiency of 87.7 % for the sulfur-containing gas at 600 °C with an outstanding removal efficiency of 99.5 % for H2S. CuO and CaO were slightly inferior to Fe2O3, with desulfurization efficiencies of 75.9 % and 45.2 % in the gas when added at 5 %. Fe2O3 also demonstrated a notable efficacy in eliminating benzothiophene, the most abundant sulfur compound in pyrolysis oil, with a removal efficiency of 78.1 %. Molecular dynamics simulations and experiments showed that the desulfurization mechanism of Fe2O3 involved the bonding of Fe-S, the breakage of C-S, dehydrogenation and oxygen migration process, which promoted the conversion of Fe2O3 to FeO, FeS and Fe2(SO4)3. Meanwhile, Fe2O3 enhanced the cyclization and dehydrogenation reaction, facilitating the upgrade of oil and gas (monocyclic aromatics to 57.4 % and H2 to 22.3 %). This study may be helpful for the clean and high-value conversion of waste tires.

Fuel properties and incineration behavior of poultry litter blended with sweet sorghum bagasse and pyrolysis oil.

The incineration of poultry litter (PL) effectively reduces the volume of waste in line with the United Nations Sustainable Development Goal of "affordable and clean energy". However, mono-incineration is associated with considerable challenges due to the varying moisture, structural and chemical composition and low energy yield. The aim of the present work was to investigate the influence of sweet sorghum bagasse (SS) and pyrolysis oil (PO) on improving the fuel properties of PL and mitigating ash related burdens during incineration. The different biomass feedstocks were produced by combining PL with SS at 0.0% (T0), 25% (T1), 50% (T2), 75% (T3) and compared with 100% SS (T4). In order to achieve high energy potential and low ash deposition, the parallel samples were additionally mixed with 10% PO to improve the energy value. The experimental results show that increasing the proportion of SS and adding PO to the mixtures increases the volatile matter and decreases the moisture and ash content. The addition of PO also increases the carbon and hydrogen content. The use of SS and PO thus increased the values of the ignitability index and apparently also the flammability by 30.0%-49.4% compared to pure PL. SS and PO shifted the HHV of the starting material from 16.90 to 18.78 MJ kg-1. In addition, SS + PO improved the flame volume and red color intensity of the PL blends based on the image analysis method. However, the presence of SS and PO did not sufficiently improve the ash-related index values, which requires further investigation.

Highly efficient carbonation and dechlorination using flue gas micro-nano bubble for municipal solid waste incineration fly ash pretreatment and its applicability to sulfoaluminate cementitious materials.

Cement production is a primary source of global carbon emissions. As a hazardous waste, municipal solid waste incineration fly ash (MSWI-FA) can be pretreated as a cementitious and effective carbon capture material. This study proposes an efficient carbonation dechlorination pretreatment and resource recovery strategy using flue gas micro-nano bubble (MNB) to wash MSWI-FA. The results showed that the flue gas MNB water washing reaction solution inhibited CaCO3 boundary layer blocking and adsorption on NaCl and KCl leaching. Under low water-to-solid ratio and CO2 concentration conditions, two-step washing reduced the MSWI-FA chlorine content to <1%, improving the dechlorination effect by 19.72% compared to conventional carbonation. The flue gas MNB water accelerated the precipitation of Ca2+ and Ca(ClO)2 in the form of calcite. The higher the CO2 concentration in the flue gas MNB, the better the fragmentation and purification of the MSWI-FA shell, leading to improved dechlorination and CO2 fixation. Under optimized conditions, the mean particle size of MSWI-FA decreased by 47.82%, and the CO2 fixation rate reached 73.80%, with a 58.35% increase in the washing carbonation rate. MSWI-FA pretreated by flue gas MNB washing was used as both the raw material and supplementary cementitious material for sulfoaluminate cementitious (SAC) material, exhibiting excellent compressive strength and heavy metal stabilization. The maximum compressive strength of the MSWI-FA-based SAC material cured for 28 d reached 130 MPa. Cr leaching was inhibited with increased hydration time, and the leaching concentration was far below the standard limit.

Low-temperature catalytic oxidation of PCDD/Fs over MnCeCoOx/PPS catalytic filter.

Catalytic destruction of nitrogen oxides (NOx) combined with dust removal technique has attracted much attention, yet the application in the solid waste incineration air pollution control process is still lacking due to the complex flue gas atmosphere. In this work, the Mn-Ce-Co-Ox catalyst-coated polyphenylene sulfide (PPS) filter fiber with efficient dust removal and low-temperature polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) destruction has been prepared with a redox-precipitation method. The catalyst was uniformly grown around the PPS fiber with appropriate catalyst loading. The effects of several key operating parameters (e.g., reaction temperature, catalyst loading amount, and filtration velocity) on the catalytic efficiency were comprehensively investigated. The results show that the Mn-Ce-Co-Ox/PPS has a decomposition yield of 78.0% in PCDD/Fs and 96% in nitric oxide (NO) conversion at 200 °C. The poisoned catalytic filter exhibits a removal efficiency of 88.6% for PCDD/Fs. In addition, the catalytic filter can completely reject particles smaller than 1.0 µm with a low filtration resistance. Therefore, this efficient and energy-conserving catalytic filter shows promising applications in flue gas pollution treatments.

Troubleshooting dioxins stack emissions in an industrial waste gas incinerator.

An important source of dioxins and furans at present is waste incineration, utmost formed during combustion processes and emitted to the environment without being fully captured by waste-gas treatment equipment. In this study, monitoring campaign of International Toxic Equivalents for dioxins and furans (I-TEQDF), was carried out at pharmaceutical industrial waste incinerator to find a correlation between combustion parameters and feed composition with potential emission. Principal Component Analysis (PCA) shows that high values of dioxin emission correlate with short residence time of the flue gas in the furnace as well as low oxygen concentration. These operating conditions were further investigated, using COMSOL Computational Fluid Dynamics (CFD) simulation to calculate the temperature profiles along the furnace. The results suggest that the flame temperature profile is anticipated to exhibit cold areas (cold spots), which may be used as a proxy for dioxin formation due to incomplete combustion. Additionally, the calculated congeners furan to dioxin concentration ratio, points to their formation via de novo mechanism. SEM-EDS analysis preformed on the bag filter upstream the feed following its filtration, have shown large amount of iron, which may have served as a metal catalytic source for dioxin formation. The iron origin is most likely from corrosion of the feeding pipe, drifted with the waste gas and trapped on the bag filter. The results of this study provide a better understanding of the parameters controlling dioxin formation and emission from the plant and may assist a planning of process optimization in such a plant.

Synthesis of geopolymer using municipal solid waste incineration fly ash and steel slag: Hydration properties and immobilization of heavy metals.

In this study, a novel method for the disposal of municipal solid waste incineration fly ash (MSWIFA) was proposed. By applying geopolymer technology, steel slag (SS) and MSWIFA were used together as precursors to synthesize a cementitious material with sufficient strength that is useable in construction. The effects of the dosages of SS and alkaline activator on the properties of the geopolymer were investigated. Compressive testing was used to characterize the mechanical properties of the geopolymer. X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used for microscopic analysis. Leaching tests were performed to assess the immobilization effect of the geopolymer on heavy metals. The results showed that the compressive strength of the geopolymer reached 23.03 MPa at 56 d with 20% SS and 11% Na2O admixture. Highly polymerized hydration products, such as C-(A)-S-H gels and N-A-S-H gels, contributed to the compact microstructure, which provided mechanical strength and limited the migration and leaching of heavy metals in the geopolymer matrix. In terms of the results, this work is significant for the development of MSWIFA management.

Techno-economic impact of lower emission standards for waste-to-energy acid gas emissions.

Acid gas removal is one of the main drivers of operating costs in the flue gas cleaning lines of waste-to-energy (WtE) plants. In the light of updated technical and normative references, such as the revised Best Available Technology reference document for waste incineration in the EU, plants are required to comply with increasingly lower emission limit values (ELV). In the case of existing WtE plants, this requires selecting the appropriate option among three alternatives: intensification of current operations, installation of additional equipment (retrofitting) or substitution of equipment (revamping). The identification of the most cost-effective solution to meet the new ELVs is thus paramount. In the present study, a comparative techno-economic assessment is performed with reference to the relevant options available to WtE plants equipped with a dry acid gas treatment system, explicitly taking into account the influence of several technical and economic variables by a sensitivity analysis. The results show that retrofitting based on furnace sorbent injection is a competitive option especially in the presence of high acid gas loads in the flue gas. Despite the high investment cost, revamping based on conversion to wet scrubbing can also reduce the overall cost of treatment compared to intensification, but only if no constraints are present on flue gas temperature downstream of the acid gas treatment. If flue gas reheating is needed, e.g., for the compatibility with a downstream DeNOx treatment or to avoid plume visibility at stack, the associated costs make revamping not competitive with retrofitting or intensification. Sensitivity analysis confirms that these findings are robust even in presence of relevant variations in cost entries.

Buffering effect of the economizer against PCDD/Fs in flue gas from solid waste incineration plants.

The emission of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from solid waste incineration is always a crucial concern for the society. Less attention has been paid to differentiate its formation and migration in the low temperature range of economizer, leading to a fuzzy understanding on the control of PCDD/Fs before flue gas cleaning. This study first reveals the buffering effect against PCDD/Fs in the economizer, which is contrary to the well-known memory effect, and first recognizes the intrinsic mechanism by 36 sets of full-scale experimental data under three typical operating conditions. Results indicated that the buffering effect, which includes interception and releasing, could remove averagely 82.9 % of PCDD/Fs in flue gas and reconcile PCDD/Fs profiles. The interception effect is dominant and in compliance with the condensation law. The low temperature range of economizer is exactly suitable for the condensation of lowly chlorinated congeners, which condense behind highly chlorinated ones. The releasing effect was non-staple but stimulated by the sudden change of operating condition, proving that PCDD/Fs formation rarely exists in the economizer. The buffering effect is mainly controlled by the physical migration of PCDD/Fs among different phases. The condensation of PCDD/Fs leads to their migration from vapor phase to aerosol and solid phases during flue gas cooling in the economizer. There is no need for excessive anxiety about PCDD/Fs formation in the economizer because it rarely exists. Intensifying the condensation process of PCDD/Fs in the economizer can help relieve the pressure of end-of-pipe measures for PCDD/Fs control.

Life cycle assessment for the production of MSWI fly-ash based porous glass-ceramics: Scenarios based on the contribution of silica sources, methane aided, and energy recoveries.

Municipal solid waste (MSW) production in the world has increased by 60 % in recent years. Incineration of MSW reduces their volume in conjunction with energy recovery. Incineration produces two residues, namely bottom ash (BA) and fly ash (FA), with high concentration of heavy metals and organic pollutants, especially for FA, making them an environmental concern. Vitrification is a costly, highly safe high temperature treatment, ensuring encapsulation of heavy metals. FA vitrification requires a source of silica to be able to get vitrified. In this study, we have proposed valorizing treated (vitrified) FA through the production of porous glass-ceramics, subsequently to MSWI. The entire process, from incineration to glass-ceramics production, was evaluated for several scenarios by Life Cycle Assessment (LCA) using Sima Pro 9.0. Three main scenarios were analysed; each one considering a different silica source: bottom ash (BA), glass cullet (G) and silica sand (S), and for each scenario, three thermal recovery subscenarios were assumed: no thermal recovery used to heat FA prior to vitrification (N), heating FA prior to vitrification using incineration gases thermal recovery (T) and methane-combustion-aided thermal recovery, which exploits methane combustion to further increase the gases temperature (M). Results proved that vitrification was a technically feasible and environmentally-energetically sustainable technology. The result indicates that the most eco-sustainable scenario was using bottom ashes as a silica source together with methane-combustion-aided recovery: 0.467 kgCO2,eq, 5.83 × 10-8 carcinogenic-CTUh and 9.26 MJ required per kg of glass-ceramics produced.

Thermal co-treatment of aluminum dross and municipal solid waste incineration fly ash: Mineral transformation, crusting prevention, detoxification, and low-carbon cementitious material preparation.

Harmless disposal and resource utilization of hazardous industrial wastes has become an important issue with the green development of human society. However, resource utilization of hazardous solid wastes, such as the production of cementitious materials, is usually accompanied by a pretreatment process to remove adverse impurities that contaminate the final product. In this study, aluminum dross (AD) was thermally co-treated with another hazardous waste, municipal solid incineration fly ash (MSWI-FA), to synergistically solidify F and Na, control leaching of heavy metals, and remove chloride impurities. Significant crusting was observed when AD was thermally treated by itself, but not when AD and MSWI-FA were thermally co-treated. In the process of co-thermal treatment, the remaining Cl, Na, and K contents were reduced to as low as 0.3%, 1.8%, and 0.6%, respectively. CaO and SiO2 in MSWI-FA reacted with Na3AlF6 and Al2O3 in AD, and formed CaF2 and Na6(AlSiO4)6, which contributed to the prevention of crusting and limited the leaching concentrations of F and Na to below detection thresholds and 270.6 mg/L, respectively. In addition, heavy metals were well solidified, and dioxins were fully decomposed during thermal treatment. Finally, a sulfoaluminate cementitious material (SACM) with high early- and later-age strengths was successfully created via synergetic complementarity using thermally co-treated AD and MSWI-FA together with other solid wastes. Collectively, this study outlines a promising method for the efficient and sustainable utilization of AD and MSWI-FA.

Flue gas torrefaction of municipal solid waste: Fuel properties, combustion characterizations, and nitrogen /sulfur emissions.

Flue gas torrefaction (FGT) was proposed as the pretreatment of the municipal solid waste (MSW) combustion process to improve the fuel properties of MSW and achieve better combustion performance. The optimal FGT parameters were obtained at 300 ℃ and 30 min, with the energy-mass co-benefit index (EMCI) reaching the maximum of 23.38. FGT could significantly increase the heating value and energy density of MSW while reducing the H/C and O/C ratio. Then, the pyrolysis and combustion experiments were performed by tube furnace and TG-MS. The results proved the chemical compositions of MSW were altered, and the heat transfer was enhanced. With FGT, NOx and SO2 emissions could be reduced by 25.7 % and 52.4 %, respectively. This study provides an in-depth understanding of the mechanism of FGT and paves the way for the clean treatment and energy utilization of MSW.

Life cycle GHG emissions of MSW landfilling versus Incineration: Expected outcomes based on US landfill gas collection regulations.

From a GHG perspective, most LCA studies find incineration (MSWI) to be preferred over landfilling because of high energy recovery offsets. In some studies, however, landfilling results in less greenhouse gases (GHG) emissions than MSWI. We investigated using LCA, the landfill gas (LFG) collection efficiencies and waste composition that led to landfills resulting in less GHG emissions. Then, we explored what theoretical minimum lifetime gas collection efficiencies can be expected when following US LFG regulations. Only landfills with high LFG collection efficiencies (at least 81%) and recovery of methane for energy resulted in less GHG emissions compared to the management of the same waste stream in MSWI; required efficiency increased to 93% without LFG energy recovery. Expected theoretical lifetime LFG collection efficiencies were modeled in the range of 30-80%, with the lower rates associated with landfills having smaller input masses, high decay rates, and low concentrations of nonmethane organic compounds (CNMOC). Our modeling found that only under a limited combination of conditions (e.g., high CNMOC, high waste input rate, low decay rate) could a landfill expect to achieve a LFG collection efficiency as high as 80%, and that this value falls just under the 81-93% collection efficiency threshold needed for a landfill to result in less GHG emissions than MSWI. When exploring the influence of higher oxidation rates, changing decay rates, varying electricity grids, and inclusion of nonferrous metals recovery offsets the collection effciency range needed increased in nearly all cases; the electricity grid and nonferrous metals offsets had the greatest influence.

The health impacts of waste incineration: a systematic review.

INTRODUCTION: Waste incineration is increasingly used to reduce waste volume and produce electricity. Several incinerators have recently been proposed in Australia and community groups are concerned about health impacts. An overview of the evidence on health effects has been needed. METHOD: A systematic review of English language literature for waste incinerators and health using PRISMA methodology. RESULTS: A range of adverse health effects were identified, including significant associations with some neoplasia, congenital anomalies, infant deaths and miscarriage, but not for other diseases. Ingestion was the dominant exposure pathway for the public. Newer incinerator technologies may reduce exposure. DISCUSSION: Despite these findings, diverse chemicals, poor study methodologies and inconsistent reporting of incinerator technology specifications precludes firmer conclusions about safety. CONCLUSION: Older incinerator technology and infrequent maintenance schedules have been strongly linked with adverse health effects. More recent incinerators have fewer reported ill effects, perhaps because of inadequate time for adverse effects to emerge. A precautionary approach is required. Waste minimisation is essential. Implications for public health: Public health practitioners can offer clearer advice about adverse health effects from incinerators. We suggest improved research design and methods to make future studies more robust and comparable. We offer ideas for better policy and regulation.

Co-combustion of coal processing waste, oil refining waste and municipal solid waste: Mechanism, characteristics, emissions.

This experimental research studies co-combustion of wet coal processing waste (filter cakes) with typical municipal solid waste (wood, rubber, plastic, cardboard) and used turbine oil, as combustible components of composite liquid fuel. Ignition mechanisms and characteristics of single droplets of three fuel composition groups have been investigated in a motionless heated air with using a high-speed video recording system. Analyzing video frames, a physical model of the process under study was developed. The values of the guaranteed ignition delay times have been determined for three fuel groups with different compositions at the ambient temperature 600-1,000 °C. The minimum values of ignition delay times are about 3 s, the maximum ones are about 25 s. In addition to the established difference in the ignition delay times, the various fuel compositions also differ in combustion temperatures. Maximum values reaching 1,300 °C for compositions with 10% of used oil. It has also been determined that fuels with municipal solid waste are notable for lower nitrogen and sulfur oxide concentrations in flue gases as compared to filter cakes in initial state. Adding used oil to such fuel compositions increases the anthropogenic emissions but these worsening environmental characteristics do not exceed the regulated allowable limits of pollutants for solid fossil fuel combustion by thermal power plants. The obtained results are the backbone for the development of an environmentally friendly, cost- and energy-efficient co-combustion technology for municipal solid waste recovery by burning it as part of composite fuels, e.g., in boiler furnaces instead of coal.

The bibliometric analysis and review of dioxin in waste incineration and steel sintering.

Facing the common treatment problems of dioxin whose major sources come from waste incineration and steel sintering, we handled a massive literature dataset from the Web of Science database and analyzed the research hotspot and development trend in this field in the past 40 years by bibliometric method. The result indicates that the field of dioxins generated from waste incineration and steel sintering has entered a stage of rapid development since 1990. China occupies a leading position in terms of comprehensive strength with the largest publications output as well as a greater influence in recent years. The most productive institutions and journals are Zhejiang University and Chemosphere, respectively. In addition, the most commonly used keywords in statistical analysis are "fly ash," "emission control," "risk assessment," "congener profile," "formation mechanisms," "sources," "catalysis," and "inhibition," which reflects the current main research direction in this field. The similarities and differences of dioxins generated in waste incineration and steel sintering are reviewed in this paper, which will provide guidance for the future research.

Waste incineration of Polytetrafluoroethylene (PTFE) to evaluate potential formation of per- and Poly-Fluorinated Alkyl Substances (PFAS) in flue gas.

In recent years, concerns over some per- and polyfluorinated alkyl substances (PFAS) have grown steadily. PFAS are a large group of chemical substances with widely differing properties. While one class of PFAS, fluoropolymers, have been demonstrated to meet the OECD criteria for polymers of low concern during the in use phase of their lifecycle, questions remain regarding waste handling at the end of useful life for products containing fluoropolymers. To show that polytetrafluoroethylene (PTFE) can be almost fully transformed into fluorine (F) (as hydrofluoric acid (HF)) and to study the possible generation of low molecular weight per- and polyfluorinated alkyl substances (PFAS), PTFE combustion under typical waste incineration conditions at the BRENDA (German acronym for "Brennkammer mit Dampfkessel") pilot plant at Karlsruhe Institute of Technology (KIT) was investigated. Results indicate that, within procedural quantitation limits, no statistically significant evidence was found that the PFAS studied were created during the incineration of PTFE. Therefore, municipal incineration of PTFE using best available technologies (BAT) is not a significant source of the studied PFAS and should be considered an acceptable form of waste treatment.

The effect of gas emission on the strength of composite products derived using alkali-activated municipal solid waste incineration fly ash/pyrophyllite-based systems.

We explored the effects of gas emission by mixtures undergoing alkali-activation of municipal solid waste incineration fly ash (MSWIFA) and pyrophyllite (the mixtures included dehydrated pyrophyllite, MSWIFA, 14 mol/L aqueous sodium hydroxide, and sodium silicate; curing proceed at 105 °C for 24 h). We measured the compressive strengths of the derived solid composites. The causes of gas emission, and the physical and chemical properties of products created under controlled gas emission, were investigated. Hydrogen was emitted after mixing MSWIFA and alkali. The compressive strength of products prepared when gas emission was complete was 2-3.4-fold greater than that of products prepared when gas emission was incomplete. X-ray micro-tomography and mercury intrusion porosimetry showed that products formed during complete gas emission tended to have smaller pores. X-ray diffraction and nuclear magnetic resonance (27Al and 29Si) indicated that the aluminum substitution levels in tectosilicate differed under such conditions, although the minerals were identical. Thus, complete gas emission after mixing improved ultimate products.