Ash Formation Research Articles

A STATE OF ART AND PROSPECTS OF FLY ASH MANAGEMENT

The basic data on the volume of formation and composition of fly ash, which is a product of coal combustion at thermal power stations, are given. The analysis of the current state of ways of managing fly ash makes it possible to distinguish the following main directions: physical-mechanical, physical-chemical, biological and combined methods of handling it, which are used in agriculture (use as fertilizers and pesticides; chemical land reclamation: regulation of the structure and pH of the soil); during earthworks (reinforcement of weak and expansive soils, use as tamponage compositions, arrangement of embankments and dams); road construction (strengthening of the soil for the lower layers of the road surface; production of asphalt, cement-concrete mixtures for arranging the foundations of road clothing, as well as crushed stone-sand and gravel-sand mixtures reinforced with cement); building materials industry (cement, concrete, building solutions, geopolymers, bricks, building blocks, glass, glass ceramics, building ceramics, porous ceramics, rolled waterproofing materials); in protective coatings (paints, enamels, enamel glass, shotcrete, heat-protective and heat-insulating coatings); as sorbents and catalysts and their carriers; in mechanical engineering (abrasive, frictional, filtering and lubricating materials, materials for soldering, foundry sand forms or rods); as other materials (pigments, polymer composites, elements of chemical sources of electric current, accumulators of certain substances, carbon nanoparticles (fullerenes, nanotubes), cosmetics and hygiene products); in pyrometallurgical and hydrometallurgical methods of recovery of chemical elements; in alloys and metal matrix composites; for extracting rare earth elements. Currently, the most appropriate methods of disposal of fly ash are either its direct use with a minimal change in its properties, or its use with minimal processing and minimization of the formation of new waste, in particular in the building materials industry and road construction. Bibl. 164, Fig. 3.

Silver-Palm Kernel Expeller Ash Formation by Combustion Technique and its Congo-red Removal Activity

Silver-Palm Kernel Expeller Ash Formation by Combustion Technique and its Congo-red Removal Activity

Comparative experimental study of ash formation behaviors during the fixed-bed gasification of coal water slurry and dry pulverized coal prepared from Shenmu coal

The mechanism of ash formation during coal gasification is very important for the safety and stability of gasifier operation. This study comparatively investigated the ash formation behaviors during the gasification of coal water slurry and dry pulverized coal. Shenmu coal was gasified in a CO2 atmosphere at 900 °C using a fixed-bed reactor to prepare chars and ashes. Computer-controlled scanning electron microscopy was employed to characterize the compositions and particle sizes of minerals in the raw coal, coal water slurry gasification ash, and dry pulverized coal gasification ash. Morphological characteristics reveal that, during gasification, coal water slurry gasification char exhibits obvious agglomeration compared to the dry pulverized coal gasification char. The changes of mineral compositions indicate that, during both coal water slurry and dry pulverized coal gasification, minerals follow nearly identical transformation pathways, but the degrees of transformation are different. The influence of char agglomeration on heat transfer may be the reason for the less transformation of K Al-silicate and kaolinite during the coal water slurry gasification. Furthermore, in comparison to dry pulverized coal gasification, more Ca in calcite and S in pyrite transfer into gypsum during the coal water slurry gasification. The results from thermodynamic equilibrium calculations indirectly suggest that this may be attributed to the limited internal diffusion of CO2 within coal water slurry gasification char resulting from char agglomeration during gasification. Overall particle size distributions of minerals in raw coal, coal water slurry gasification ash, and dry pulverized coal gasification ash demonstrate that the degrees of mineral fragmentation are almost consistent during both coal water slurry and dry pulverized coal gasification. However, differences in the degrees of mineral transformation led to different particle size distributions of various minerals between coal water slurry gasification ash and dry pulverized coal gasification ash. This study mainly focuses on the influence of water in coal water slurry on ash formation, and it has not considered the influence of other factors, such as ash content, hydrophilicity, caking property, and gasification reactivity of coal, which need further research to explore.

Effects of ash formation during co-firing refuse-derived fuel with coal on initial superheater material degradation

ABSTRACT Refuse-derived fuel (RDF) has significant potential as a co-firing fuel in power plants. However, its different characteristics from coal, particularly the high chlorine (Cl) concentration in the ash deposits, can degrade metal elements during combustion. This study aims to investigate the effect of adding RDF to coal on the initial degradation of materials caused by ash deposits during combustion. This research is conducted on a laboratory scale using a drop tube furnace to simulate pulverized coal boiler conditions, analyzying ash deposits, mineral transformations, and evaluating the microstructure of the probe material. The results show that the chlorine content in the R-10 at 0.035 wt% substantially affects the initial degradation of 18Cr-Ni during combustion. The oxide layer begins to degrade in the second hour due to ash deposits, reaching 2.38 μm. The presence of Ca (1.11%), K (1.66%), Na (4.46%), and Cl (0.42%) increases to 1.12% on the metal surface, gradually attacking the substrate area and forming cavities. Degradation increases linearly up to probe-8, resulting in a thickness loss of 3.81 μm and a significant reduction in chromium content, which decreases by 12.54%. These findings highlight the importance of understanding the impact of chlorine levels in RDF, which can aggressively attack and corrode metals.

Extraction and characterization of Bougainvillea glabra fibers: A study on chemical, physical, mechanical and morphological properties

Bougainvillea glabra fibers (BGFs) present a promising avenue for sustainable material development owing to their abundance and favorable properties. This study entails a thorough investigation into the composition, physical characteristics, mechanical behavior, structural properties, thermal stability, and hydrothermal absorption behavior of BGFs. Chemical analysis reveals the predominant presence of cellulose (68.92 %), accompanied by notable proportions of hemicellulose (12.64 %), lignin (9.56 %), wax (3.72 %), moisture (11.78 %), and ash (1.75 %). Physical measurements ascertain a mean fiber diameter of approximately 232.63 ± 8.59 μm, while tensile testing demonstrates exceptional strength, with stress values ranging from 120 ± 18.26 MPa to a maximum of 770 ± 23.19 MPa at varying strains. X-ray diffraction (XRD) elucidates a crystalline index (CI) of 68.17 % and a crystallite size (CS) of 9.42 nm, indicative of a well-defined crystalline structure within the fibers. Fourier-transform infrared spectroscopy (FTIR) confirms the presence of characteristic functional groups associated with cellulose, hemicellulose, wax, and water content. Thermogravimetric analysis (TGA) delineates distinct thermal degradation stages, with onset temperatures ranging from 102.76 °C for water loss to 567.55 °C for ash formation. Furthermore, hydrothermal absorption behavior exhibits temperature and time-dependent trends, with absorption percentages ranging from 15.26 % to 32.19 % at temperatures between 30 °C and 108 °C and varying exposure durations. These comprehensive findings provide essential insights into the properties and potential applications of BGFs in diverse fields such as bio-composites, textiles, and environmentally friendly packaging solutions.

Ash Formation during Combustion of Rice Husks in Entrained Flow Conversion Conditions

Ash Formation during Combustion of Rice Husks in Entrained Flow Conversion Conditions

Use of waste fermented black carrot powder dried by different methods as a substitute in noodle production

This study delved into various aspects of noodle production, emphasizing the impact of waste fermented black carrot powder (WFBCP) concentration and drying techniques. Higher concentrations of WFBCP increased cooking times, particularly in freeze-dried (FD) samples, resulting in varying water absorption and notable cooking losses. Color variations, influenced by both WFBCP concentration and drying methods, led to generally darker hues in the FD samples. Significant differences in the water content were observed across treatments. Ash content increased significantly with higher WFBCP concentrations, particularly at 40%, indicating the impact of WFBCP on ash formation. Noodle samples exhibited a significant rise in oil content with increasing WFBCP concentration, reaching a peak at 20%. Total Phenolic Content notably increased at higher WFBCP concentrations, peaking at 40%, suggesting potential nutritional benefits. Similarly, antioxidant activity increased significantly with higher WFBCP concentrations, indicating enhanced protection against food oxidation. Total monomeric anthocyanin content surged with increased WFBCP concentration, establishing WFBCP as a noteworthy source of anthocyanins. HPLC analysis revealed elevated levels of phenolic compounds when WFBCP was added to noodles, with FD-WFBCP showing the highest content. Freeze-drying effectively preserved the phenolic compounds, while the protein content remained stable. Sensory analysis, conducted using a 0–10 scale, emphasized the impact of processing methods and WFBCP concentrations on attributes such as color, stickiness, chewing, flavor, and overall rating. This study underscores the importance of precise control over WFBCP concentrations and processing for enhancing noodle attributes. Principal component analysis, explaining 90.8% of the total variation, highlights distinct differences between control and treated samples.

Influences of composition and reaction conditions on molecular structure, hygroscopicity, and swelling behavior of alkali-silica reaction gels

Alkali-silica reaction (ASR) gel, a product of the reactions between the dissolved silica from aggregate and the alkalis from cement, governs the destructiveness of ASR and concrete deterioration. The influences of chemical composition and reaction conditions of ASR gel on its structure and properties remain unclear. In this work, the correlations between the molecular structure, hygroscopicity, and swelling behavior of ASR products were uncovered by investigating six CaO–SiO2-M2O systems with varying alkali/Si and Ca/Si ratios under two reaction conditions. The results indicate that the low-alkali gels have a layered silicate structure dominated by Q1 and Q2 sites similar to calcium silicate hydrate (C–S–H), whereas the high-alkali gels showed coexistence of tobermorite-type C–S–H and alkali-silicate hydrates featured with Q3 polymerization. The 29Si nuclear magnetic resonance (NMR) results showed that the mean chain length (MCL) and degree of polymerization (DP) decrease with alkali/Si and Ca/Si ratios but increase with moisture. Under 97 % RH, decreased crystallinity and enhanced formation of ASH and Q3 sites are obtained along with increased polymerization and d-spacing. The moisture uptake and swelling of the high-alkali gels showed a reverse correlation with the Ca/Si ratio, which confirms the role of calcium in suppressing the formation of ASH and the dominant role of Q3 sites in determining the hygroscopicity of ASR products.

The impact of 2021 large forest fires on vegetation and soils, on the territory of distribution of light soil-forming rocks in Central Yakutia

The influence of catastrophic forest fires in 2021 on the vegetation cover and soils of the middle taiga on the territory of distribution of light soil-forming rocks of Central Yakutia has been studied. Obtained results showed the cardinal dynamics of species diversity and productivity of the larch and pine forests surface vegetation in their natural state and in burnt areas. The stock of grass-shrub cover aboveground phytomass on the control larch and pine forests is higher for 5 and 10 times than that in the burnt areas, respectively. The work carried out revealed the effect of forest fires on the morphological structure (formation of pyrogenic layer, manifestation of pyro- and cryoturbations), the depth of thawing, the water regime of permafrost soils under larch and pine forests on control and burnt sites in the first year after strong fires. The soils in the study area are predominantly permafrost illuvial-ferruginous podzols. The study revealed an increase in the permafrost table depth of these soils, an increase in the level of ground water, and a decrease in acidity in the upper part of the profile. Intense ash formation was found due to the burning of litter. The characteristic of the current state of vegetation and soil cover is given.

Ash Formation and Associated Interactions during Co-Combustion of Wheat Straw and Sewage Sludge

The aim of the present work was to investigate ash formation and associated interactions during the pulverized fuel co-combustion of biomass fuels. Combustion experiments were carried out with narrowly sized wheat straw (WS), sewage sludge (SS), and their blends in a drop tube furnace at 1100 °C and 1300 °C. The resulting residual ash and fine particulate matter (PM10) were characterized with various analyses. It was observed that co-combustion influences size distributions of the residual ash particles and generally generates larger residual ash particles close to those of SS combustion. The interaction of K capture by minerals enhances the melting and consequently increases the production of large and melting ash particles during co-combustion. It was found that blending SS with WS has not only the positive interaction of K capture by minerals from SS ash to significantly reduce submicron ash formation, but also the positive interaction of transforming alkali chlorides into alkali sulfates to reduce the corrosiveness of submicron ash particles. Co-combustion of SS with WS can also reduce the presence of alkali chloride at PM1–10, lowering the propensities of deposition and corrosion of the fine residual ash particles.

Dependence of Radiance of Burning Coal Bed on Ash Formation and Dew Condensation

Abstract In this study, coal samples with different moisture contents were prepared using a drying and humidification system. Coal samples were placed in a crucible and ignited using a heating wire, to which power was applied during coal combustion. The combustion radiance of coal samples with three moisture contents (0, 20, and 50%) was measured using a narrow-angle radiometer at three temperatures (10, 25, and 50 °C). A numerical simulation model was developed to predict the unsteady radiation characteristics of a coal layer burning on one-dimensional planar plates. The unsteady energy balance equation and radiative transfer equation were solved using the semi-implicit Runge–Kutta method and discrete ordinates method. In addition, the effect of dew condensation on the radiance was investigated. The greatest reduction in radiance was observed during the burning of the high-moisture coal. Furthermore, the effect of ash (converted from coal) on radiance was examined. The results demonstrated that certain changes in the optical properties during the burning of coal to ash can alter the absorption as well as anisotropic scattering, and thereby the radiance, as combustion proceeds.

Reuse and Valorization of Solid Digestate Ashes from Biogas Production

Digestate is produced in large quantities by the anaerobic digestion process, which is recognized to be a promising technology for producing bioenergy from biological waste. Digestate is a highly humid by-product containing organic and inorganic substances, including nutrients that make it suitable for soil applications. However, it can be considered a high-risk environmental contaminant if it is not correctly treated. For these reasons, thermochemical treatment is one of the alternatives for valorizing the digestate, leading to a high ash quantity. This review aims to investigate the formation of ash derived from thermochemical valorization treatments of digestate. Furthermore, considering the compositions of the elements present in these ashes, an additional objective is to identify possible prospects for the reuse of these ashes following a circular economy approach.

Biomass Utilization for Cement Manufacturing

India generates around 750 million tonnes of agro waste with surplus availability of 230 million tonnes, this huge quantity of biomass can act as a potential resource for energy recovery to the tune of 28 GW of power. The biomass as a raw material for energy generation is encouraged by different government policies. The biomass has to be utilized in a sustainable way for maximum resource re-circulation enhancing circular economy. Although the utilization of biomass for direct energy recovery is encouraged, it has an inherent problem of ash generation. But co-processing of this biomass in cement plant leads to an effective solution as it helps in complete thermal and material recovery without any formation of ash. Pre-processing is not needed for single type of biomass, while for mixed and heterogeneous biomass, preprocessing may be needed similar to the case of industrial wastes in coprocessing. Thus co-processing of biomass in cement plant as an alternative way of addressing the surplus agro waste was studied. A one-year study was carried out at one of the cement plants to analyse the potential of co-processing of agro waste such as rice husk, soya bean agro waste and gram husk in cement kiln. The study based on statistical data revealed operational & environmental sustainability. The economic potential was analysed based on the substitution benefit. The analysis further revealed insignificant impact on parameter like stack emission, clinker quality, leach property and cement property. The findings of study thus revealed the sustainability of co-processing agro waste in cement kilns.

Технология утилизации и использования золошлаковых отходов для обеспечения экологической безопасности региона

Introduction. By burning coal, thermal power plants receive thermal energy and generate electrical energy. The negative side of this process is the formation of ash and slag waste. The relevance and significance of this problem is due to the fact that technogenic waste from the CHP is not processed, and current ash waste accumulates and occupies huge areas, which removes them from land use. This problem is especially relevant for Almaty, where ash and slag waste from the burning of coal from the Ekibastuz deposit in Kazakhstan is concentrated. Currently, in Kazakhstan, ash and slag waste from thermal power plants is accumulated in the amount of more than 500 million rubles, the reserves of which continue every year. The storage of ash and slag waste leads not only to the seizure of significant land areas, but also causes very significant pollution of almost all environmental components in the area of their location. Therefore, at mining enterprises that have their own thermal power plants, it is very urgent to solve the issues of reducing the burden on the environment by developing technologies for the disposal of ash and slag using them in the production of road surfaces. The purpose of the research. The study of the physico-chemical properties of ash and slag waste to reduce the anthropogenic load on the environment. Research materials. For the research, samples of Ekibastuz coal ash taken from the ash dumps of the CHPP-3 in Almaty were used. Research methods. The work was carried out using a DRON-3M diffractometer to determine the phase composition of ash and slag waste. The chemical composition of fly ash was determined by the X-ray fluorescence spectrometer EDX-8000. The granulometric composition was analyzed using an Analizette 22 MicroTec Fritsch GmbH (Germany). Microphotography of fly ash was taken using a Superprobe-733 scanning electron microscope with software. To determine the physical and mechanical properties of the bases using bitumen-ash-slag binder, the crushed stonegravel-sand mixture is initially mixed with ash-slag. From the finished bitumen – mineral mixture, samples are prepared by pressing – cylinders with a size of 5x5 cm. The ultimate strength was determined for two types of samples. The first are dry, tested immediately after receiving samples by pressing, the second are samples that are tested after water saturation. Research results and discussion. Based on the study of the physic-mechanical properties of the binder with the use of ash and slag, a technology for obtaining BZSHV has been developed. Various compositions are proposed – types of bitumen, depending on the type of base of asphalt concrete mixtures. Studies have shown that the introduction of ash and ash-slag mixtures from the burning of stone and brown coals as a mineral powder for the preparation of asphalt concrete mixtures makes it possible to obtain a material with regulatory physic-chemical characteristics. Conclusion. The results of the study of the main physic-chemical characteristics of the ash of Ekibastuz coal, selected from the ash dumps of the CHP-3 of Almaty city, are presented. It is shown that the use of ash in the manufacture of asphalt pavement will reduce the area of occupied land and the load on the environment, as well as improve the operational characteristics of the pavement. Suggestions for practical application. The results of the research can be useful in solving the environmental problem of utilization of ash and slag waste of the CHP.

A percolation model of fly ash formation during the combustion of non-uniform porous char

An improved percolation model has been introduced to predict the particle size distributions (PSDs) of produced residue during pulverized coal char combustion. A three-dimensional cluster of interconnected sites representing a single char particle is constructed at a given size. These sites are classified into surrounding gas, macropores, carbon, or ash. Non-uniform porous char structures and the melting performances of the ash particle have been considered to approach the most realistic scenario. The char fragmentation and ash coalescence process is simulated by checking the connectivity and proximity of occupied sites. The effects of char particle sizes are addressed by using char PSD data as the input to the model. The numerical results were compared with the measured PSDs of fly ash and show a good agreement. The effects of porous char structure and included minerals on the sizes of produced particles during combustion are further investigated. The simulation results indicate that the mean sizes of produced particles initially decrease (N<0.7) and then increase with char consumption. The char fragmentation behavior dominates in the preliminary and middle stages of char burning, while the ash coalescence is the primary behavior in the char burnout stage. The mean sizes of produced particles increase with the lower char porosity and the higher extent of pore aggregation. The size difference between PM20 and PM20+ increases when the macropores are repositioned to be aggregated. The mean sizes are positively related to the ash content and ash coalescence parameter in the middle and late stages of char burning.

Metakaolin-based geopolymers filled with volcanic fly ashes: FT-IR, thermal characterization, and antibacterial property

Abstract In countries where volcanic activity is widespread, fly ash (FA) formation can represent both a waste to be disposed of and a resource of inorganic substances that can be utilized. Among the technologies able to incorporate FA, geopolymers (GP) or inorganic aluminosilicate amorphous materials are very suitable for this purpose. In this study, GP are realized using metakaolin (MK), sodium hydroxide solution (NaOH 8 M), sodium silicate solution (Na2SiO3), and FA as filler (20 wt% with respect to MK content). The samples were cured at 25 or 40°C for 24 h and the physicochemical, thermal, and antibacterial properties of this material through the integrity test, weight loss test, Fourier-transform infra-red spectroscopy (FT-IR), thermogravimetric analysis (TGA), and Kirby-Bauer assay were assessed. Integrity and weight loss tests indirectly revealed the stability of the macroscopic 3D networks and that the curing at 40°C led to more stable GP. The shift of the Si–O–T absorption band (from 1,090 cm−1 of the MK to 1,017–1,012 cm−1 of the specimens with and without FA) in FT-IR spectra suggested the occurrence of the geopolymerizazion reactions, while TGA study confirmed the higher stability of samples cured at 40°C (with a mass loss equal to 7–13% at 800°C under nitrogen atmosphere). Finally, the antimicrobial activity shed light on the ability of the synthesized GP with the filler and treated at 40°C to have a great effect against Escherichia coli and Pseudomonas aeruginosa.

Numerical simulation on the deposition characteristics of MSWI fly ash particles in a cyclone furnace

In melting municipal solid waste incineration (MSWI) fly ash by cyclone furnace, the deposition characteristics of particles affect the slag flow and the secondary MSWI fly ash formation. In this study, the composition mechanism based on critical viscosity is selected as the particle deposition model to predict the deposition and rebound of particles on the furnace wall. The Riboud model with an accurate viscosity prediction performance is selected, then the particle deposition model is integrated into a commercial computational fluid dynamics (CFD) solver through the user-defined function (UDF) to realize the coupling of particle motion and deposition process. The results show that under the same case, the deposition rate decreases obviously with the increase of MSWI fly ash particle size. And the escape rate reaches a maximum at particle size 120 μm. Controlling the particle size of fly ash particles within 60 μm can effectively reduce the generation of secondary MSWI fly ash. During the forward movement of the fly ash inlet position, the escape of MSWI fly ash particles with large particle sizes has been significantly weakened. This measure not only lowers the post-treatment cost but also dramatically reduces the pretreatment step of MSWI fly ash before the melting and solidification process. In addition, the deposition rate and quality will reach the maximum values, respectively, along with gradually increasing MSWI fly ash input flow. Overall, this study has the guiding significance for reducing the pretreatment steps and post-treatment costs of MSWI fly ash by melting in the cyclone furnace.

Accumulating and communicating research: Development of a Massive Open Online Course on ash

Based on 30 years of research on ash and deposit formation, corrosion and trace element transformations in utility boilers fired with solid fuels covering the entire range from coal via biomass to waste fuels, a Massive Open Online Course (MOOC) on this was launched ultimo July 2020.The basic idea behind the Ash MOOC, is to present recent data on fuel characterization, ash formations, slagging, fouling, and corrosion, in a course that can be readily provided for students and industry people.The Ash MOOC consists of a number of modules covering: 1) course introduction, 2) fuel and ash chemistry and characterization, 3) release of critical ash-forming elements, 4) formation of fly ash and aerosols, 5) transport and adhesion of ash particles, 6) deposit build-up, consolidation and shedding, 7) high-temperature Cl-corrosion, 8) use of additives to minimize deposit formation and high-temperature corrosion, and, last but certainly not least, 9) Danish case-studies on ash and deposit formation.This paper provide a brief introduction to how the idea of an Ash MOOC was born, what it takes to make such a MOOC, how to direct such knowledge toward a very wide range of receiving audience, and, some sorts about future development of this.

Effect of regeneration method and ash deposition on diesel particulate filter performance: a review.

As countries around the world pay more attention to environmental protection, the corresponding emission regulations have become more stringent. Exhaust pollutants cause great harm to the environment and people, and diesel engines are one of the most important sources of pollution. Diesel particulate filter (DPF) technology has proven to be the most effective way to control and treat soot. In this paper, we review the latest research progress on DPF regeneration and ash. Passive regeneration, active regeneration, non-thermal plasma-assisted DPF regeneration and regeneration mechanism, DPF regeneration control assisted by engine management, and uncontrolled DPF regeneration and its control strategy are mainly introduced. In addition, the source, composition, and deposition of ash are described in detail, as well as the effect of ash on the DPF pressure drop and catalytic performance. Finally, the issues that need to be further addressed in DPF regeneration research are presented, along with challenges and future work in ash research. Over all, composite regeneration is still the mainstream regeneration method. The formation of ash is complex and there are still many unanswered questions that require further in-depth research.

Ash melting behavior and mechanism of high-calcium bituminous coal in the process of blast furnace pulverized coal injection

Abstract High-calcium bituminous coal has the advantages on combustibility, but its ash melting point is low, and it is easy to slag in blast furnace injection process. In order to explore the ash melting slag formation mechanism of high-calcium bituminous coal, the mineral evolution of ash in the combustion process of high-calcium bituminous coal and the influence of ash components on the liquid formation in the melting process were studied. The results showed that the melting behavior of ash gradually occurs with the change in the morphology, and the main mineral transformation is carried out around different deposition forms of Ca and Si. The liquid phase formation of ash at high temperature is the essential reason of its melting behavior. The higher the content of CaO, the higher the starting temperature of the liquid phase formation. The higher the content of SiO2, the lower the starting temperature of the liquid phase formation, and the more the liquid phases generated at a given temperature. Increasing the content of Al2O3 can expand the temperature range of reducing the formation of ash liquid phase to 1,473–1,673 K. When the temperature is above 1,573 K, Fe2O3 can promote ash liquid phase formation.