Behavior Of Ash Research Articles

Study of Mechanical and Tribological Behavior of Fly ash with E-Glass fibre Reinforced AL MMC’s

AMC’s specimen made by liquid stir casting technique, by addition of fixed 3% E-glass fibers and fly ash particles in different proportions (4, 6 and 8 wt.%) prepared the matrix phase. A uniform distribution of reinforcement is obtained with good bonding with matrix. Dry sliding wear behavior of the aluminum alloy and the composites has been studied and tested using a pin-on-disc wear and friction monitor. The testing carried out on sliding velocity of 1.5, 2.5 and 3.5 m/s and load ranges from 1, 2 and 3kgf. The composite shows better mechanical properties than the base alloy. Abrasive wear resistance improves by addition of fly ash reinforcement

Effect of Deashing Treatment on Ash Fusion Characteristics of Biochar from Bamboo Shoot Shells.

To investigate the influence of deashing on fusion characteristics, a combined method of water and acid washing with different sequences (water washing followed by acid washing, and acid washing followed by water washing) was used to treat the biochar of bamboo shoot shells (BBSSs). The results show that deashing decreased the K content of the biochar from 50.3% to 1.08% but increased the Si content from 33.48% to 89.15%. The formation of silicates and aluminosilicates from alkali metal oxides with silicon was an inevitable result of ash phase transformation at the high temperatures used to improve the fusion temperature (>1450 °C). The thermochemical behavior of ash mainly occurs at 1000 °C. The deashing treatment significantly reduced the reaction intensity during the high-temperature process. This significantly increased the thermal stability of the ash. The adjustment of the washing sequence had a slight impact on the chemical compositions, but the differences in ash micromorphology were obvious. Deashing treatments with different washing sequences can significantly improve ash fusion properties effectively and reduce the risk of scaling, slagging, and corrosion. This study provides a new and reasonable strategy for the deashing of biochar to commercially utilize bamboo shoot shell resources.

Interfacial Behavior of Slag, Fly Ash, and Red Mud-Based Geopolymer Mortar with Concrete Substrate: Mechanical Properties and Microstructure

Geopolymer, as a new type of solid waste-based inorganic cementitious material, exhibits outstanding behavior in terms of physical and chemical performance, macromechanical properties, long-lasting stability, and features potential application development tendency in the field of repair and reinforcement of existing concrete structures. This paper investigated the interfacial behavior of geopolymer mortar with OPC concrete substrate under different slag, fly ash and red mud mixing proportions, while cement mortar was used as a control group for the research. The interfacial bonding properties of the geopolymer mortar to the OPC concrete substrate were elaborated by carrying out split tensile test, double-sided shear test, and three-point bending test. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to further analyze the microstructural characteristics and physical phase components of the interfacial transition zone between the geopolymer mortar and the OPC concrete substrate. The results indicated that the compressive strength of slag-fly ash-red mud-based geopolymer mortar under different mixing ratio conditions was consistently superior to that of cement mortar, where the optimum mixing ratio for the geopolymer mortar was S33F33R33. Overall, the interfacial bonding properties of the geopolymer mortar to the OPC concrete substrate gradually increased with the increment of the slag content, however, an evolutionary trend of minor enhancement followed by a gradual reduction was observed with the growth of the fly ash and red mud content.

Numerical simulation of solidification of boiler molten ash impinging on vertical wall based on Smoothed Particle Hydrodynamics method

In order to study the whole process of the high temperature liquid slag fly ash produced after the combustion of high alkali coal as power coal in the boiler furnace, which moves in the furnace and impinges on the water wall, the heat exchange occurs and then the cooling phase transformation deposits and slags, and the possible factors of slagging particles are studied by changing the environmental variables. In this paper, based on Smoothed Particle Hydrodynamics (SPH), the dynamic behavior of boiler molten ash impacting vertical wall is studied, and the flow spreading and solidification model of molten slag impacting vertical wall is established. Thus, the process of phase change deposition of slag particles against wall is simulated. By observing the phase distribution of slag and the change in spreading process, the complete process of the slag particles hitting the wall, spreading, shrinking and solidifying is analyzed. Based on the cohesive and repulsive surface force method, a temperature-dependent surface tension model is established to simulate the effect of surface tension on flow characteristics when molten ash impinges on low-temperature vertical walls. The influences of slag impact velocity, initial temperature and water wall temperature on deformation and solidification heat transfer are discussed. The results show that the initial velocity and initial temperature of slag particles affect the phase change deposition velocity and the final spreading factor of slag, while the temperature of the water wall has little effect on the deposition deformation and solidification process of slag.

A Numerical Simulation Study into the Effect of Longitudinal and Transverse Pitch on Deposition of Zhundong Coal Ash on Tube Bundles

In this paper, the dynamic deposition behavior of Na-enriching Zhundong coal ash on tube bundles with varying longitudinal and transverse pitches was numerically studied. By using a modified critical viscosity model, an improved CFD deposition model has been established and key parameters, including deposit mass and morphology, particle trajectories and impaction and sticking probabilities, as well as the heat flux distribution, have been analyzed. The results show that the ash deposited on tubes in the first row is, respectively, 1.74 and 3.80 times higher than that on the second and third rows, proving that ash deposition in the downstream is lessened. As the longitudinal pitch increased from 1.50 D to 2.50 D, deposit mass in the downstream increased two times, suggesting that an increase in longitudinal pitch would aggravate ash deposition. The effect of transverse pitch, however, with the least deposit propensity at St/D = 1.75, is non-linear due to the joint effect of adjacent tubes and walls in affecting particle trajectory. In addition, due to the non-uniform distribution of the deposit, heat flux across the tube is the smallest at the stagnation point but becomes six times higher at two sides and the leeward, which makes the thermal damage of these sides to be warranted as a practical concern.

Heavy metals behavior of co-combustion ash from sewage sludge and coal slime: Temperature and mixing ratio dependence, interactions and speciation

Co-combustion of municipal sludge (SS) and coal slime (CS) is an effective route to achieve the co-disposal of solid wastes. This work addresses the problem of heavy metal pollution in co-combustion ash, aiming to reveal the effect of interactions in SS-CS co-combustion on the behavior of heavy metals and the control mechanism of minerals using the inductively coupled plasma mass spectrometry (ICP-MS) technique and the Community Bureau of Reference (BCR) method. The residual rate of heavy metals in CS ash monotonically decreased with increasing combustion temperature, while the residual rate of heavy metals in SS tended to increase when it was burned at high temperatures. Increased temperature enhanced the effect of SS-CS interaction on heavy metals. The interaction significantly inhibited the volatilization of As, and the As residue of the blend containing 50% CS (5SS5CS) at 1000 °C was 14.9% higher than the theoretical value. Typical minerals in SS had significant effects on heavy metal migration in CS, and the effects of CaO and Fe2O3 on heavy metals were mainly due to chemical interactions, in which CaO fixed As in the form of Ca3(AsO4). Density functional theory calculations show that the optimal adsorption sites for both As and As2O3 on the CaO(001) surface were O-top sites, and the presence of O defect on the surface led to enhanced interaction of As2O3 with the surface. Co-combustion led to an increase in the residual fractions of heavy metals, but the exchangeable and acid soluble fraction of As in 5SS5CS was still as high as 19.3%, so the ecological impact of As should be considered in further utilization of the co-combustion ash.

Assessment of the Long-Term Leaching Behavior of Incineration Bottom Ash: A Study of Two Waste Incinerators in Germany

The long-term leaching behavior of incineration bottom ash (IBA) was studied with large-scale samples from two German waste incinerators with grate technology. The observation period was up to 281 days. The aging processes proceeded faster in the outdoor storage of the samples. The dominant factor in the leaching behavior is the pH, which starts at values above 12 and decreases to values below 10 (outdoors, <11 indoors). Most heavy metals exhibit minimum solubility in this pH range. The solubility of Sb depends on the prevailing Ca concentration, due to the formation of low-soluble Ca antimonate. The very low sulfate concentrations observed in the leaching tests with fresh IBA could be explained by the presence of ettringite. In the course of the aging reaction, ettringite is transformed into gypsum. The results from batch tests were compared with those from column tests, showing reasonable agreement. Leaching dynamics can be better followed with column tests. All results confirm that the use of IBA is possible under German law.

A multi-perspective study on the influence of physical and chemical properties of 5 types of fly ash on the performance of high-volume blended fly ash cementitious slurry

The study has investigated the influence of the physical and chemical properties of five types of fly ash on the performance of high volume blended fly ash cementitious (HFC) materials. The study found that the vitreous element composition of fly ash exhibits a superior correlation with compressive strength as compared to the overall element composition. Moreover, the cumulative heat displays a stronger correlation with compressive strength than the heat flow. Besides, the packing density has a significant effect on the compressive strength of HFC materials. Whereas, the slurry flowability largely depends on the water film thickness. In practical engineering, the slurry compressive strength can be predicted by testing the fly ash vitreous content, cumulative heat data and the packing density of mixed particles in concert. The findings are significant as in practical projects, the performance of cementitious materials is often unstable due to different sources and batches of fly ash. The study provides insights into the factors affecting the rheological properties of the slurry and the hydration behaviour of different fly ash blended slurries.

Reactivity of MSWI-fly ash in Mg-K-phosphate cement

In this study, the behaviour and reactivity of Municipal Solid Waste Incineration Fly Ash (MSWI-FA), introduced in the formulation of magnesium potassium phosphate cement (MKPC), was investigated by considering the waste either as fully inert or reactive. MSWI-FA induced structural and compositional modifications in MKPC as a consequence of dissolution/precipitation processes which involved many MSWI-FA elements (e.g., Ca, Mg, Al, Si, Zn) and led to the formation of mostly amorphous phosphate secondary products. The reaction path has been described in terms of the early fast dissolution of MSWI-FA, with precipitation of very low solubility phases, and subsequent late precipitation due to pH changes and water subtraction during MKPC gelification. The increase in amorphous content peaked to 50 wt.% and it has been related to the improved behaviour with respect to the leaching of heavy metals (reduced by 70-99%), pointing to this cement as an excellent matrix for their chemical stabilization. The obtained MKPC microstructure exhibited better mechanical performance, with an improvement of up to 60% in compressive strength. All in all, the results indicated that the incorporation in MKPC is a viable recycling opportunity for MSWI-FA, although, for an effective cement formulation, its reactivity must be taken into account.

Leaching kinetics and reactivity evaluation of fly ash based on the synergistic effect of alkali and sulfate

This work evaluates the reactivity of various minerals of fly ash based on the backscattered electron images analysis (BSE-IA) method and discusses the influencing factors and kinetics of Si and Al selective leaching of fly ash in alkali solution and alkali-sulfate composite solution, respectively. The relationships among the physicochemical properties, dissolution behavior, and reactivity of fly ash have been revealed. There are three typical phases in fly ash, namely the Si–Al phase, Ca–Si–Al phase, and Fe phase. The Ca–Si–Al phase is more soluble and preferentially participates in the reaction process than the other two phases. The dissolution process is greatly affected by temperature. Alkali and sulfate have a compound synergistic effect and SO42− further promotes the dissolution of Si and Al mainly by changing the gel property wrapped on the surface of fly ash particles. The leaching kinetics results indicate that the internal diffusion controls the reaction process. The research method and system in this work can be applied to other solid waste, providing reference significance for quickly exploring its reaction activity. Moreover, the synergistic effect of alkali and sulfate can be used to establish an alkali-sulfate composite cementitious system, guiding the application of fly ash as a supplementary cementitious material.

Triaxial test analysis and discrete element simulation of CFBC

In order to explore the mechanical behavior and crack propagation of cement fly ash stabilized brick-concrete gravel (CFBC) base mixture under three-dimensional compression, firstly, the triaxial loading tests of three different proportions of mixtures were carried out through laboratory tests. The axial load is controlled by a load control loading system, the sampling frequency is 5 Hz, and the triaxial specimen is loaded at a rate of 0.1 MPa /s.The stress–strain curves of the mixture under four different confining pressures were obtained, and the failure characteristics and strength characteristics were analyzed. Secondly, the SEM analysis of the specimens under different confining pressures was carried out, and the microstructure parameters of the mixture under four different confining pressures of 0 MPa, 0.5 MPa, 1.0 MPa and 1.5 MPa were studied based on the PCAS analysis software. On this basis, a three-dimensional discrete element model was established to numerically reproduce the triaxial test of the specimen. The results show that the failure mode of the specimen is mainly related to the confining pressure, and the crack shape has the characteristics of top-down in the direction of principal stress.Through the stress–strain curve, it can be seen that with the increase of confining pressure, the peak stress of the specimen is also increasing. In the BCA1 ratio, the peak stress of the 1.5 MPa confining pressure is increased by 23 % compared with the non-confining pressure. In addition, the cement fly ash stabilized brick-concrete gravel mixture specimen has a larger bearing capacity than other concrete brittle materials.PCAS pore analysis showed that the main controlling factors affecting the porosity of the mixture were brick content and confining pressure, which in turn affected the shear strength and peak stress of the mixture, and the porosity of BCA1 < BCA3 < BCA5; the numerical simulation results show that the failure mode and stress–strain curve of the specimens with the shear strength error of less than 3 % and the friction angle error of less than 6 % are in good agreement. The maximum displacement particle clusters appear on the upper and lower edges of the specimen, and the sliding zone angle of the specimen is about 45° under all stress paths except the horizontal sliding zone under the uniaxial stress state, which reflects that the numerical model is consistent with the mechanical response at the macro scale. The use of three-dimensional discrete element models in the field of construction engineering can simulate and optimize the use of the above materials in construction sites to minimize waste and maximize efficiency.

Towards a comprehensive understanding of PM1 formation in pressurized oxy-fuel combustion: A study comparing model predictions with experimental data

Oxy-fuel combustion is pivotal for fossil fuel power plants to attain net zero carbon emissions. While atmospheric pressure oxy-fuel combustion has garnered significant attention, its economic feasibility is questionable. This has led to the proposition of pressurized oxy-fuel combustion as a more economically viable alternative. A critical aspect, the formation of submicron ash aerosols (PM1), has implications for ash deposition in boilers and presents environmental concerns. Despite its significance, limited research exists on PM1 formation in this context. This study introduces a robust model, partitioned into combustion, vaporization, nucleation and condensation, and coagulation sub-models, to predict PM1 formation in pressurized oxy-fuel combustion. Key findings include: 1) Pressure escalation from 0.1 MPa to 1.5 MPa inhibits the CO formation and further reduces mineral vaporization ratio from 2.30 % to 0.12 %. 2) Elevated pressures decrease the critical nucleation diameter to about 5 nm, 4 nm, and 3 nm for pressures of 0.1 MPa, 0.8 MPa, and 1.5 MPa, respectively. 3) Coagulation primarily occurs within the diffusion layer around fuel particles, with its thickness diminishing as pressure increases. The model's predictions align closely with existing experimental data, underscoring its utility in understanding ash behavior in pressurized oxy-fuel combustion. Furthermore, this study not only bridges the knowledge gap in the field but also offers industry stakeholders a valuable tool to optimize combustion processes, mitigate environmental risks, and drive the transition towards more sustainable fossil fuel utilization.

Experimental analysis and behavior of corrosion-damaged fly ash blended reinforced concrete beam under flexural loading

Experimental analysis and behavior of corrosion-damaged fly ash blended reinforced concrete beam under flexural loading

Mechano-Noncatalytic Wet Treatment Method for Extracting Ash from Biomass at Room Temperature and Its Effect on Ash Behaviors

Mechano-Noncatalytic Wet Treatment Method for Extracting Ash from Biomass at Room Temperature and Its Effect on Ash Behaviors

Physicochemical, Hydration and Steady Shear Rheological Properties of Flours Derived From Different Crop Residues From the Honduran Agro–Food Industry

This study aimed to determine the physicochemical, hydration, and rheological characteristics of flours derived from different crop residues (taro, cassava, maize, and banana) affected by climate change in Honduras and to investigate their potential application in food processes. The physicochemical (moisture content, ash, protein, crude fat, starch, amylose content, and color), hydration (water absorption capacity (WAC), water absorption index (WAI), water solubility index (WSI), swelling power (SP), true and bulk density), pasting (pasting temperature, peak, trough, breakdown, setback, and final viscosity), and rheological properties of the flours were evaluated. Taro flour had the highest values of ash content, WAI and SP and the lowest for crude fat, amylose content, bulk density and peak, breakdown, setback viscosity and consistency index. Cassava flour had the highest breakdown viscosity and flow behavior index values and the lowest for protein content, hysteresis loop area, yield stress, and consistency index. Maize flour had the highest crude fat, protein, and amylose content, bulk density, WAC, setback viscosity, hysteresis loop area, and yield stress, and the lowest values were for ash, protein content, WSI, pasting temperature, breakdown viscosity, and flow behavior index. Banana flour had the highest starch, carbohydrate, WSI, pasting temperature, peak viscosity and consistency index, and the lowest value for protein content, WAI and SP. The study's results have determined the compositional value and functionality of the flours obtained from the agro-residues studied for their potential use in different food products. Keywords: Crop residues flour; Food security; Change climatic; physicochemical characterization; steady shear

Effects of Salinity and Curing Time on Compression Behavior of Fly Ash Stabilized Marine Clay

This study involves an experimental examination of compression behaviors of fly ash stabilized marine clay cured at different times concerning the influences of pore water salinity. A set of laboratory one-dimensional compression tests was conducted on soft Lianyungang marine clay specimens with various pore water salinities and stabilized with fly ash. Test results indicated that both salinity and curing time influenced the compression characteristic of fly ash stabilized clay. The presence of fly ash obviously reduced the compressibility of the untreated marine clay sample. The semi-logarithmic compression curve of untreated pure soil was a straight line, whereas fly ash stabilized clay samples exhibited the pattern of two straight lines. All the fly ash stabilized soil specimens were well represented by two straight lines in the bilogarithmic coordinate, making it convenient to determine the compression yield stress. The compression index at the pre-yield stage was not susceptible to the variation in the salinity and curing period, whereas at the post-yield stage it exhibited a downward tendency as salinity and curing time increased. The value of yield stress for stabilized marine clay specimen exhibited a downward tendency with increasing salinity, whereas it increased significantly within 7 days and tended to level off with the elapsed curing time. The adverse effect of salinity and the positive influence of curing time on yield stress should be considered in engineering applications.

Combustion Performance of Agropellets in an Experimental Fixed Bed Reactor versus a Commercial Grate Boiler. Validation of Ash Behavior.

Agrobiomass is presented as a suitable alternative to contribute to the fossil fuel decarbonization strategy at the European level. To achieve the ambitious objectives established in this regard: (i) new biomass resources need to be used and therefore initially tested in order to confirm its potential for different applications, such as energy production, and (ii) biomass supply capacity needs to be enlarged; therefore, agroindustries converted into Integrated Biomass Logistic Center (IBLC) can play a key role. In this research, eight different agropellets (blends of wheat straw and maize stalk with forestry wood) were produced in a IBLC and tested in a commercial boiler, comparing the results with previous ones obtained in a fixed bed reactor test campaign and to a base case (woody pellets). This paper includes both individual results in terms of bottom ash, deposition, and a final comparison of ash behavior in both facilities. All biofuels tested showed an adequate performance in terms of efficiency and emissions, being slightly better for the agropellets produced with wheat straw. Regarding sintering and deposition, the tendencies found in the reactor investigation were also observed in the commercial boiler. Moreover, the assessment of the results from the boiler and reactor's tests proved that reactor experiments are representative and may be used to test new biofuels more efficiently in terms of effort and time allocated and could be used to predict sintering and deposition phenomenon occurrence.

Hydration, Microstructure, and Properties of Fly Ash–Based Geopolymer: A Review

Abstract Geopolymers have gained attention as a potential eco-friendly alternative to Portland cement, primarily due to their reduced carbon dioxide emissions and the opportunity to repurpose industrial waste materials. Fly ash (FA), a byproduct of coal combustion, has been favored as a raw material for geopolymer concrete owing to its widespread availability and high concentrations of alumina and silica. The development and application of fly ash–based geopolymer concrete can contribute significantly to production of sustainable construction materials. An in-depth analysis of fly ash–based geopolymer concrete has been conducted to explore its potential as a substitute for traditional concrete. This review encompasses the underlying reaction mechanism, strength, long-term durability, and microstructural characteristics of geopolymer concrete. The present review paper shows that adding the optimal quantity of fly ash improves the performance of fly ash–based geopolymer when exposed to extreme durability conditions, as well as improving strength properties. The microstructural analysis shows that when fly ash is added, the microstructure of the concrete matrix would be dense and packed. However, challenges remain in adopting fly ash–based geopolymer concrete for large-scale construction projects, as the existing literature presents inconsistencies in the reported strength, durability, and test results. Further research is necessary to consolidate knowledge on the behavior and mechanism of fly ash–based geopolymer concrete and to ultimately provide comprehensive data to support its widespread implementation in the construction industry.

Strength behavior of metakaolin and fly ash treated dredged clay at high water content

This study investigated the strength behaviors of dredged clays treated with metakaolin (MK) and fly ash (FA). A series of laboratory tests including direct shear and unconfined compressive strength tests were performed on MK and FA-treated dredged clay at various MK contents and different curing times. The direct shear test results showed that the shear stress and displacement curves for all specimens tested are strain-softening types and influenced by MK content and curing time. The variation curve at a higher MK content or higher curing time is always higher than that at a lower one. The shear strength from the direct shear test at a given vertical stress consistently increases linearly with the increase of MK content while increasing parabolically with curing time. This indicates both curing time and MK content contribute to the development of the shear strength. Both strength parameters c and φ grow with increasing MK content and curing time. Unconfined compressive strength test results show the strain-softening behavior for all tested specimens. Compared with adding FA alone or MK alone, adding both fly ash and MK exhibited a better treatment effect in the unconfined compressive strength, which increases with increasing MK content and curing time.

Flexural behaviour of fly ash incorporated ferrochrome slag aggregate reinforced concrete beam

The structural behaviour of fly ash integrated ferrochrome slag aggregate concrete (FCSAC) is not widely understood owing to lack of research, although some studies have focused on its mechanical and environmental performance. The real-world use of FCSAC relies on its large-scale structural tests. This research investigates the flexural response of reinforced concrete beams fabricated with fly ash and ferrochrome slag (FCS) aggregate. A total of sixteen full-scale beams were built and tested. The beams were cast using four different concrete compositions: natural aggregate concrete (NAC) without any fly ash and FCS as the reference; FCSAC comprising 100% FCS as coarse aggregate and fly ash as partial substitution of cement at different percentages: 0%, 20% and 30%. The beams were fabricated with two different longitudinal reinforcement ratios of 0.69% and 1.86%. An eco-efficient mix proportioning method based on Particle packing optimization technique (PPOT) was adopted aiming to develop sustainable concrete. The effect of alternate resources (FCS and fly ash) and reinforcement ratios on the flexural response, cracking, ultimate load, failure pattern, ductility and toughness were examined. The experimental outcomes were compared to the predictions derived from the existing code provisions. Results revealed that the flexural performance of the FCSAC with fly ash beams was superior to that of NAC beam, despite having a lower flexural capacity than the FCSAC without fly ash beams. Moreover, the comparative study demonstrated that the fly ash-based FCSAC beams may be designed in accordance with the same guidelines as conventional concrete.