Characterization Of Coal Fly Ash Research Articles

Comparative study on the characteristics of coal fly ash and biomass ash geopolymers

Comparative study on the characteristics of coal fly ash and biomass ash geopolymers

Waste to concrete material: Potential Study of Chemical Characterization of Coal Fly Ash and Bottom Ash

This research focuses on the chemical properties of coal fly ash (CFA) and coal bottom ash (CBA) obtained from Sultan Azlan Shah Power Plant and compares them with the characteristics of ordinary Portland cement (OPC). Coal has been recognised as a significant fuel source in Malaysia, where it is extensively employed in the creation of steel, cement, and power. When coal is burned to create power, several different types of coal ash are created, including fly ash, bottom ash, boiler slag, and clinker. Fly and bottom ash, however, are the main coal ash waste products that have been created. In an effort to create sustainable concrete from waste, a number of studies have been carried out to ascertain the chemical characteristics of fly and bottom ash. These tests include Energy Disperse X-Ray (EDX), Mineralogy (XRD), and X-Ray Fluorescence (XRF). From the SEM result, fly ash has smaller particles and a spherical, uniform shape than bottom ash and cement. Fly and bottom ash from the Sultan Azlan Shah power plant contain a number of elements, including Silicon (Si), Aluminium (Al), Oxygen (O), Calcium (Ca), Titanium (Ti), Iron (Fe), Magnesium (Mg), Potassium (K), Carbon (C), and Sodium, according to Energy Dispersive X-Ray (EDX) test. The fly ash is primarily an amorphous material, with the presence of quartz crystalline phase (SiO2) at 24.3% and bottom ash at 31.1%, according to X-ray Diffraction (XRD) data. For the mullite phase (3AlO3.2SiO2), fly and bottom ash show results of 24.9% and 14.5%, respectively. According to an X-ray fluorescence (XRF) investigation, the main constituents of fly and bottom ash are silica, iron, and alumina. Fly ash is classified as Class F because it has a high concentration of SiO2, Al2O3, and Fe2O3 while OPC has a high CaO value. With the right composition and material preparation, CFA and CBA from the Sultan Azlan Shah Power Plant can be used as a cement replacement in concrete.

Synthesis and characterization of coal fly ash based multipurpose ultrafiltration membrane

In this work, coal fly ash was used as a major precursor to synthesize a multipurpose ceramic membrane by uniaxial compaction method. SEM, XRD and FTIR analysis were performed to identify the morphology, crystallinity and functional groups of the membrane. SEM image confirmed the porous structure and defect free membrane surface. XRD analysis revealed the existence of mullite, quartz and hematite crystalline phases. The minimum membrane sintering temperature was identified as 800 °C by Thermogravimetric analysis (TGA). The membrane porosity and average hydraulic pore radius were estimated as 39.8% and 41 nm, respectively. The membrane pure water flux increased from 2.09 to 11.31 m3/m2 sec while increasing the applied pressure from 69 to 483 kPa. A fixed concentration of Rhodamine B, Bovine Serum Albumin and Vanillin (50 mg/L) were tested with synthesized membrane to examine the separation performance at 207 kPa applied pressure. The separation efficiency of the ceramic membrane was in the order: Rhodamine B (95.2%) > Bovine Serum Albumin (92.8%) > Vanillin (39.4%). The results obtained in this study demonstrate that coal fly ash generated in thermal power plants could be effectively utilized to fabricate a multipurpose ultrafiltration membrane for different separation and purification applications in industries.

Geochemical, mineralogical and toxicological characteristics of coal fly ash and its environmental impacts

Coal and coal-based products (by-products), along with other fossil fuels should be used with caution because of their impact on human health and the global climate. In the light of the environmental impact these fossil fuels cause, it's essential to understand the elemental configuration of coal-derived samples and their impact on the ecosystem. Some reports in past have described, geochemical and mineralogical physiognomies of fly-ash and their impact on the environment. However, a comprehensive investigation of various aspects of fly ash like geochemistry, mineralogy, morphology, and toxicological effects has been very sparse and the present study reports the above aspects. The ICP-OES studies confirm the presence of various elements (Al, Ca, Fe, Mg, Na, P, S, Si, and Ti) in the samples. The XRD analysis exposed the presence of minerals like Quartz, H-Hematite, Anatase, Muscovite, and Rutile, in addition to the various phases such as amorphous and crystalline in the fly-ash. Specific samples also possessed Ilmenite which is uncommon in many other samples. Chromium and lead, the well-known heavy metals to cause soil and water pollution in the neighbourhood were found to be existing in higher concentrations in the fly-ash samples, whereas cadmium was found to be the least among the toxic elements found in the samples. The samples were subjected to FE-SEM analysis, which reveals the presence of irregularly shaped minerals and unburnt carbon known to reduce the burning efficiency of coal, especially in power plants. Toxicology studies reported in the work suggested that fly-ash is toxic to the environment at higher concentrations than at lower concentrations.

Mineralization characteristics of coal fly ash in the transition from non-supercritical CO2 to supercritical CO2

The accelerated mineralization of fly ash is a potential way to achieve CO2 emissions reduction. However, the slow reaction at the diffusion control stage is the bottleneck. Due to the strong diffusion of supercritical CO2, it has been to strengthen mineralization, but the degree of improvement in mineralization efficiency and the changes that take place in the transition from non-supercritical to supercritical CO2 are not clear. In the mineralization process, CaO in the ash reacts with CO2 to form CaCO3. In order to exclude the influence of other alkaline oxides, powdered and block CaO were used to research the mechanism, and experiments were then carried out on samples of fly ash with different CaO content. Firstly, powdered CaO was used to conduct dry and wet mineralization experiments. In dry mineralization, the mineralization efficiency of the process changes in two stages as the pressure increases, first undergoing a gentle-increase and then a rapid one. Diffusion depth experiments on block CaO show that the supercritical diffusion depth is higher than the non-supercritical diffusion depth by a factor of 1.22, indicating that supercritical CO2 can improve the degree of mineralization in diffusion stage. The presence of water could promote mineralization. In wet mineralization, the efficiency of the process changes in three stages as the pressure increases, with first a gentle increase then a more rapid one and finally an attenuated rate of increase. The supercritical mineralization efficiency at 8 MPa was 55.27%, a factor of 2.09 larger than for non-supercritical mineralization at 3 MPa (26.39%). This is because that supercritical CO2 has increased the diffusion and greatly improved solubility in water. The results of DFT calculations show that H2O can promote the adsorption of CO2 by CaO, which is one of the reasons why water promotes mineralization. Finally, wet mineralization experiments on fly ash show that at 8 MPa, the mineralization efficiencies of HB, SD, SX and YN fly ashes are 1.94, 1.30, 2.03 and 1.62 times their values at 3 MPa. Although the difference in efficiency is affected by the CaO content, supercritical CO2 can effectively improve the mineralization efficiency.

Preparation and characterization of coal fly ash reinforced polymer composites: An overview

Preparation and characterization of coal fly ash reinforced polymer composites: An overview

Characterization of Coal Fly Ash, Bottom Ash and their Possibilities as Catalysts for Biodiesel Production

Coal fly ash (CFA) and bottom ash (BA) obtained from coal fired power plants in Thailand and local supplier were characterized using XRF, XRD and N2 adsorption-desorption techniques. Their possibilities for conversion of palm oil into biodiesel were investigated. Selected CFA was also modified with lanthanum (La) at different La loading and the influence of La loading on biodiesel conversion was evaluated. The resulted showed that the Class C CFA as contained large amount of CaO (free lime) could catalyze the transesterification to achieve the highest FAME content of 89% under the operation conditions; the reaction temperature of 200 °C, the reaction pressure of 39 bars, the catalyst loading of 5 wt% of oil, the molar of oil to methanol of 1:30 and the stirring speed of 600 rpm for 5 h. The addition of La on the Class C CFA had a negative effect on conversion of palm oil. The FAME content decreased gradually from 89 to 62% with increasing La loading from 0 to 1 wt%.

Synthesis and characterization of coal fly ash and palm oil fuel ash modified artisanal and small-scale gold mine (ASGM) tailings based geopolymer using sugar mill lime sludge as Ca-based activator

The continuous accumulation of artisanal and small-scale gold mining (ASGM) tailings in the Philippines without adequate storage and disposal facility could lead to human health and environmental disasters in the long run. In this study, ASGM tailings was simultaneously stabilized and repurposed as construction material via geopolymerization using coal fly ash, palm oil fuel ash and a powder-based alkali activator. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) identified iron sulfides in the tailings containing arsenic (As), cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn), which could be released via weathering. The average unconfined compressive strengths (UCS) of tailings-based geopolymers at 14 days curing were 7.58 MPa and 7.7 MPa with fly ash and palm oil fuel ash, respectively. The tailings-based geopolymers with palm oil fuel ash had higher UCS most likely due to CASH reaction product formation that improved strength formation. The toxicity characteristic leaching procedure (TCLP) results showed very low leachabilities of As, Pb and Fe in the geopolymer materials suggesting ASGM tailings was effectively encapsulated within the geopolymer matrix. Overall, the geopolymerization of ASGM tailings is a viable and promising solution to simultaneously stabilize mining and industrial wastes and repurpose them into construction materials.

Synthesis and characterization of coal fly ash supported zinc oxide catalyst for biodiesel production using used cooking oil as feed

Coal fly ash-zinc oxide composite (CFA/ZnO) was developed, characterized and applied as a catalyst in the transesterification of used cooking oil (UCO) with methanol to obtain biodiesel. The prepared supported catalyst was characterized by TGA/DTA, gas sorption, TEM-EDX, FTIR and XRD techniques. Taguchi design approach was used for the optimization of biodiesel synthesis from UCO. Amongst the studied process variables, reaction temperature, reaction time and methanol/oil molar ratio most significantly affected the biodiesel yield and fatty acid methyl ester (FAME) content. At the optimum temperature of 140 °C, the time of 3 h, methanol/oil molar ratio of 12:1 and catalyst loading of 0.5 wt%, the biodiesel yield was 83.17%. The FAME content of the biodiesel produced was found to be 98.14 wt%. Moreover, the catalyst regeneration and reusability were studied to verify its stability, and it was established that the CFA-ZnO could be reused for up to four successive cycles with negligible loss in performance.

Development and characterization of coal fly ash through low-energy ball milling

A paradigm shift from monolithic materials to composite materials has been observed in recent times to achieve the ever changing demands of the manufacturing sector. The composites are being explored in terms of industrial and thermal power plant wastes used as reinforcements. Being a prominent thermal power plant waste, fly ash disposal and utilization is gravitating environmentalists and researchers to propose innovative ideas and feasible implementations. To trace and adjoin an effort to add value to aforementioned cause, an investigation was conducted on fly ash which was milled in tumbler ball mill with predefined input parameters viz. spindle speed, ball-to-powder ratio, and milling time. Low-energy mill has an extensive application in preparation of new materials, their activation and process of synthesis for potential merits like cost-effectiveness, reliability, low maintenance and ease of operation over its contemporary high-energy mill. The modifications in chemical and morphological properties of milled fly ash sample were characterized through X-ray diffraction (XRD) technique, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results inferred that the ball-milling process aimed at reducing crystallite domain size of milled fly ash, and also affected the microstructure, functional groups and led to decline in degree of crystallinity. The milling time was observed as a significant factor to impact extent of these changes. The particles of the raw spherical-shaped fly ash (regularly 5 μm size) were broken down into smaller particles of average crystallite domain size ∼ 30 nm, this change indicated an increase in amorphousness which helped in achieving better compatibility and significantly higher reactivity. The pattern and peaks of XRD for original crystallinites significantly diminished and resulted in broadened peaks. This can be interpreted by the smaller particle size and low degree of crystallinity. The research defined the achievement of nanostructured fly ash with low energy mill technique.

A novel perspective process for alumina extraction from coal fly ash via potassium pyrosulfate calcination activation method

Alumina extraction is considered as one of the promising trends for the value-added use of coal fly ash (CFA). In this study, a moderate potassium pyrosulfate (K2S2O7) calcination activation method was used to extract alumina from CFA. The calcined conditions including X1: K2S2O7/Al2O3 molar ratio (2–4), X2: calcining temperature (180–220 °C), X3: calcining time (2–4 h) was optimized by using response surface method based on 3-factor 3-degree Box-Behnken design. The effects of confirmed factors were fitted in a quadratic regression polynomial equation. The main and interacting influences between variables were studied by using the analysis of variance and 3D plots, respectively. The results show the alumina extraction rate was more influenced by K2S2O7/Al2O3 molar ratio. The optimized conditions were identified as K2S2O7/Al2O3 as molar ratio 3.55:1, calcining temperature up to 212 °C and calcining time of 3.1 h, in which the alumina extraction rate was recorded as 93.28%. The characteristics of CFA and leaching residues were studied by using XRD, SEM and 27Al and 29Si MAS-NMR. Results show that K2S2O7 removes the aluminum and effectively breaks the high polymerization units of Si–O–Al and Al–O. The mineral transformation during calcined reaction follows as K2S2O7 + CFA (mullite, corundum, and amorphous phase) → aluminum tri-potassium sulfate → leached residues rich in silicate + leached metal ions. The surface chemical reactions controlled the calcining process. The apparent rate constant was found to be 3.12 to 4.18 × 10−3 min−1 at the temperature range of 180–220 °C, respectively. The apparent activation energy was refereed to be 13.579 kJ/mol. These findings indicate that the potassium pyrosulfate calcination activation method gets a high level of the extracting rate, and is industrially applicable to extract alumina.

Coal Fly Ash Characterization from Cement Industry “X” as an Initial Study in Its Utilization

The discharge of fly ash from the coal combustion process has become a matter of concern over the last few decades. Most of the fly ash will be disposed of in the landfill. This disposal gives a negative impact on the environment through the heavy metal contained in fly ash. Coal fly ash characterization is needed to be done to get proper information about coal fly ash before it could be utilized. In this research, coal fly ash characterization from one of cement industry in Indonesia has been done by a qualitative and quantitative method. This research carried out some instrumentation such as Scanning Electron Microscopy (SEM), X-ray fluorescence spectrometer (XRF) and SEM – Electron Dispersive X-ray spectroscopy (SEM-EDX) to analyze the coal fly ash sample. The result showed that the main component in this coal ash sample is SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, and MgO. This information will be used as an initial study in coal fly ashes utilization research in the next research.

Study of the parameters of zeolites synthesis from coal fly ash in order to optimize their CO2 adsorption

The coal fly ash (CFA) from a coal gasification plant was used as raw materials for X zeolites synthesis by fusion and hydrothermal method and the ability of CFA-derived zeolites to adsorb CO2 was studied. After characterization of CFA, factors affecting the synthesis of different zeolites from this CFA, i.e., NaOH/CFA weight ratio, crystallization temperature and crystallization time were investigated. X-ray powder diffraction showed that only the experimental conditions corresponding to 1.2 NaOH/CFA, 7 h and 90 °C have led to a mixture composed by NaX and amorphous compounds without the formation of other crystalline structures. This product has a specific surface area of 498 ± 4 m2/g and exhibits a CO2 adsorption capacity of 2.18 molCO2/kg, corresponding to 57% of commercial 13X. Results showed that this feature is directly related to this specific crystalline product and not to other zeolitic forms or to amorphous phases. The design of experiment, named central composite full factorial, was accounted to optimize these synthesis parameters in order to maximize the CO2 adsorption capacity of the CFA-derived zeolites. Thermogravimetry experiments showed that the experimental setting corresponding to 1.4 NaOH/CFA, 80 °C and 7 h has led to a material with an adsorption capacity of 3.3 molCO2/kg, the 86% of commercial 13X. Furthermore, results highlighted that all the examined synthesis parameter are significant for the purpose of improving CO2 adsorption capacity of CFA-derived zeolites but too high values entail the production of more stable and useless (for this purpose) zeolites.

Elemental characterization of coal fly ash using k0-based IM-NAA and EDXRF towards its potential utilization and environmental concern

India is a major producer of fly ash due to its coal-based thermal power plants. The elemental characterization of the fly ash facilitates its better utilization and safe disposal, which was accomplished using k0-based internal mono standard neutron activation analysis and X-ray fluorescence techniques in the present study. The fly ash was mainly composed of useful elements such as Si, Al, Fe, K and Ca. The same was also found to contain the rare earth elements from minor to trace levels in the order of Ce > La > Nd > Sm > Yb > Eu > Tb > Lu and the heavy and toxic elements such as U, Th, As, Pb etc. in minor and trace level.

An interlaboratory comparison of INAA analytical method for coal fly ash elemental characterization

Quality assurance of analytical results has become the high market demand in this globalization era. Accurate and reliable for analytical data is one of the requirements for a testing laboratory to get recognition from customers and institutions that issue certificates, which may be obtained by ensuring the validity of the used analytical methods. Validation of methods applied by laboratories can be done; one of by conducting proficiency tests or inter-laboratory comparative tests. We have been conducted the Inter-laboratory comparative tests for Neutron Activation Analysis for elemental characterization of coal fly ash. Coal fly ash samples were prepared according to ISO Guide 34 and 35, and distributed to eleven NAA laboratories in Indonesia as well as in other countries. As much as 18 elements should be analyzed by participant laboratories. The results were processed statistically using Z-score where it found that three elements (Hg, Se, and Mg) cannot be evaluated due to insufficient data and also high variations of the data, while for other elements such as As, Th, Na, and Sb showed a good agreement among participant laboratories. Through this inter-laboratory comparative testing program, it is expected that NAA laboratories, especially in BATAN, can maintain and improve their performance and quality of their analytical results.

Synthesis of di-carboxylic acid functionalized zeolites from coal fly ash for Cd (II) removal from acid mine drainage using column studies approach

Di-carboxylic acid functionalized zeolites were synthesized from coal fly ash (CFA). The materials were then evaluated for adsorption of Cd (II) from spiked aqueous solutions and acid mine drainage (AMD) in column cartridges. Characterization of CFA using SEM showed a mixture of rough edged and spherical particles of an average size of 2.387 μm. The EDS spectra indicated the presence of ions such as Na+, Ca2+ and Mg2+. These elements were vital for cation exchange applications, due to their mobility which facilitated adsorption of Cd (II) onto the zeolite surface. The optimized concentration of the activating agent was 3 M NaOH aged for 24 h at a solid/ liquid ratio of 0.125 g mL−1. The effects of H2O/SiO2 ratio, crystallization time and crystallization temperature were studied where 0.53, 140 °C and 24 h were the optimum conditions. The types of interaction between the adsorbent and Cd (II) was cation exchange and electrostatic interaction for the zeolite and the carboxylate end of the functionalized zeolite, respectively. The adsorption performance of these materials was evaluated with respect to bed-height, influent concentration and flow rate, where the optimized conditions were 6.0 cm, 8.0 mg L−1 and 1.0 mL min−1, respectively. Application of the optimized parameters were then applied for the adsorption of Cd (II) in AMD. Generally, the shorter chained oxalic acid@zeolite was observed to have a better removal efficiency in comparison to longer alkyl chain coated zeolites such as succinic acid@zeolite and adipic acid@zeolite.

Sulphates removal from AMD using CFA hydrothermally treated zeolites in column studies

Hydrothermally treated zeolites were synthesized from a coal combustion waste by-product, coal fly ash. Synthesis of this material involved dissolution of the coal fly ash matrix followed by crystallization of the slurry. Characterization of coal fly ash using BET indicated that the coal fly ash had a surface area of 3.141 m2 g−1. The XRD patterns on coal fly ash showed dominance of the mullite and quartz peaks and was observed to be amorphous. The optimized parameters for dissolution of the coal fly ash matrix was a concentration of 3 M NaOH aged for 24 h at a solid/ liquid ratio of 15 g/120 mL. The second stage was focused on optimization of crystallization conditions of the CFA/NaOH slurries for synthesis of zeolite. The effect of variation of water content, crystallization time and crystallization temperature were studied where the optimized conditions obtained were a H2O/SiO2 ratio of 0.53, crystallized at 140 °C for a duration of 24 h. Powder x-ray diffraction studies indicated successful conversion of coal fly ash into zeolites as the dominant coal fly ash minerals such as mullite and quartz diminished while the zeolitic hydroxysodalite phase was formed. Fourier transform infra-red studies showed formation of zeolitic bands at 948 cm−1 due to Al–O and Si–O asymmetric stretching, indicating conversion of the CFA aluminosilicate phase. Thereafter, the adsorption performance of hydrothermally treated zeolites for SO42 was evaluated. The parameters evaluated included, zeolite bed height, flow rate and concentration where the optimized conditions were 4.0 cm, 0.45 mL min−1 and 5.0 mg L−1 respectively. Application studies on AMD derived water from Fleurhof dam indicated an anion selectivity with an increasing order of Cl− < NO3– < Br− < NO2– < SO42−.

Characterization of Coal Fly Ash Based Adsorbent for CO2 Removal

The study of CO2 removal from air-CO2 mixture using coal fly ash (CFA) based adsorbent has been conducted. The sieved CFA was calcined at various temperature (200, 300 and 400 °C) for 4 hours. The calcined adsorbent pellets were characterized before utilizing in CO2 removal. Result suggested that calcination temperature slightly affected the yield of adsorbents. Increasing calcination temperature decreased the density and bulk density; but increased the percentage of adsorbed moisture of the adsorbents. SEM micrograph revealed various shape and size of the adsorbent and matched the result of XRD pattern and EDS analysis. The characterized adsorbents then were utilized to remove CO2 in an adsorption column. The inlet mixture contained 35%-vol of CO2 with flow rate of mixed gas of 200 ml/min. The highest removal was accomplished by using CFA based adsorbent pellet with particle size of 140 mesh, calcination temperature 300 °C for 4 hours. The CO2 removal efficiency was 71.43% with adsorbent capacity of 8.027 mg CO2/g adsorbent.

Coupling of bromide and on-line mechanical modified fly ash for mercury removal at a 1000 MW coal-fired power plant

Modified fly ash is a potential competitive sorbent for flue gas mercury remove in coal-fired power plant. The adsorption characteristics of coal fly ash under different temperature and modification methods were studied. On-line modified fly ash as a sorbent for mercury removal at a coal-fired power plant was carried out. The results of laboratory show that the adsorption performance of a coupled bromide and mechanical modified fly ash was better than that of inherent fly ash and mechanical modified fly ash. Furthermore, it was found that high temperatures are more favorable for mercury adsorption. In a demonstration at a full-scale 1000 MW coal-fired power plant unit, injection of the bromide and mechanical modified fly ash resulted in a decrease of the total concentration of mercury emissions at the stack. Additionally, a decrease in Hg2+ from the SCR to the ESP was found. When injected modified fly ash, the final emission concentration of mercury at the unit outlet reached 1.15 μg/m3, with a mercury emission reduction efficiency of 56.1%.

Characterization of Coal Fly Ash for Use in Synthesis of Zeolites

Due to the large quantity of fly ash produced during the combustion of coal, it has become necessary to give greater applicability to this residue of low commercial value. The residue contains inorganic oxides which can act on the crystalline structure of zeolites, namely silicon and aluminum oxide. The coal ash was submitted to physical and chemical treatments with the aim of potentiating the silicon and aluminum extraction from the residue. The pure ash and the treated ashes were characterized by: X-ray fluorescence (XRF), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transformation infrared spectroscopy (FTIR). By means of the carried out characterizations it was observed that the treatments were effective for the extraction of aluminosilicates from the matrix. The treatments did not affect the morphology, the crystalline phases and neither the chemical composition of the ashes. Seeing this, the coal ash and its treatments showed to be a precursor for the synthesis of zeolites.