scholarly journals Recovery of Cenospheres and Fine Fraction from Coal Fly Ash by a Novel Dry Separation Method

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3576
Author(s):  
Jan Wrona ◽  
Witold Żukowski ◽  
Dariusz Bradło ◽  
Piotr Czupryński
Keyword(s):  
Fly Ash ◽  
Coal Fly Ash ◽  
Fine Fraction ◽  
Free Fall ◽  
Raw Material ◽  
Fluidised Bed ◽  
Air Chamber ◽  
Pneumatic Separation ◽  
Bed Separation ◽  
Separation Product

Aluminosilicate microspheres are a valuable fraction of coal fly ash with diverse applications due to their low density. Currently, there is no efficient and ecologically rational method of cenosphere recovery from fly ash. A combination of dry methods for the recovery of both fine ash particles and aluminosilicate microspheres from coal fly ash is presented. It is comprised of fluidised bed separation followed by screening and pneumatic separation in a free-fall air chamber. Fluidised bed separation was assisted by a mechanical activator to prevent agglomeration. This step reduced the portion of material that required further treatment by 52–55 wt.%, with the recovery of microspheres exceeding 97%. Then, the concentrates were individually subjected to pneumatic separation. The final separation product for the fly ash containing 0.64 wt.% cenospheres was a cenosphere concentrate that constituted about 17 wt.% of the initial fly ash. The recovery of cenospheres was around 81%. Usage of a combination of dry methods allowed for maintaining almost 83 wt.% of the raw material in its dry form. Furthermore, the produced fly ash grain fractions could be used for different industrial purposes.

Thermal Behavior of Celsian Ceramics Synthesized from Coal Fly Ash

2012 ◽  
Vol 1373 ◽  
Author(s):  
Jorge López-Cuevas ◽  
David Long-González ◽  
Carlos A. Gutiérrez-Chavarría
Keyword(s):  
Fly Ash ◽  
Thermal Behavior ◽  
Coal Fly Ash ◽  
Thermal Analyses ◽  
Linear Thermal Expansion ◽  
Raw Material ◽  
Synthesis Conditions ◽  
Calcination Step ◽  
Heating Microscopy ◽  
The Mean

ABSTRACTCelsian with a chemical composition of Ba0.75Sr0.25Al2Si2O8, is synthesized by using coal fly ash (byproduct of a Mexican coal-burning power plant, composed mainly by SiO2 and Al2O3) as main raw material. The thermal behavior of the synthesized material is evaluated by differential (DTA) and gravimetric (TGA) thermal analyses as well as by heating microscopy; its coefficient of linear thermal expansion (CTE) is also determined. Heating microscopy shows that cylinders of compacted powdered Celsian start sintering at ∼1140 ºC, which is associated with a considerable contraction occurring up to 1500 ºC. The mean CTE value of the material in the temperature range of 30-1100ºC is slightly affected by the synthesis conditions employed. Synthesis at 1400 or 1300 ºC during 10 h, with a pre-calcination step at 900 ºC/5h in both cases, produce mean CTE values of 5.15 x 10-6 and 5.43 x 10-6 ºC-1, respectively. On the other hand, Celsian synthesized at 1400 ºC/10 h, without the pre-calcination step, has a mean CTE value of 5.25 x 10-6 ºC-1. Lastly, the DTA/TGA analysis of the synthesized material shows that a slight weight gain takes place from room temperature to 1100ºC, which is followed by a slight weight loss up to 1300ºC. This is attributed to oxidation and evaporation of some of the impurities present in the material.

scholarly journals Acetone-Sensitive Thin Films Comprising Coal Fly Ash Na-X Zeolites and Sol–Gel Nb2O5 Matrix

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2399
Author(s):  
Katerina Lazarova ◽  
Silviya Boycheva ◽  
Marina Vasileva ◽  
Denitza Zgureva-Filipova ◽  
Biliana Georgieva ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Fly Ash ◽  
Coal Fly Ash ◽  
Sol Gel ◽  
Optical Quality ◽  
Film Deposition ◽  
Reflectance Spectra ◽  
Raw Material ◽  
X Zeolites

In this study, thin composite films of a sol–gel Nb2O5 matrix doped with coal fly ash Na-X zeolites were deposited by the spin-coating method. Fly ash of lignite coal collected from the electrostatic precipitators of one of the biggest TPPs in Bulgaria was used as a raw material for obtaining zeolites. Zeolite Na-X was synthesized by ultrasonic-assisted double stage fusion-hydrothermal alkaline conversion of coal fly ash. In order to improve the optical quality and sensing properties of the deposited thin films, synthesized zeolites were wet-milled for 60, 120, and 540 s prior to film deposition. The surface morphology of zeolite powders was studied both by scanning electron microscopy and transmission electron microscopy, while their porosity was investigated by N2-physisorption. Refractive index, extinction coefficient, and thickness of the films were determined through fitting of their reflectance spectra. The sensing ability of thin films towards acetone vapors was tested by measuring the reflectance spectra prior to and during exposure to the analyte, and the change in the reflection coefficient ∆R of the films was calculated. The influence of milling time of zeolites on the sensing and optical properties of the films was assumed and confirmed.

scholarly journals Studies on the CO2 Capture by Coal Fly Ash Zeolites: Process Design and Simulation

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8279
Author(s):  
Silviya Boycheva ◽  
Ivan Marinov ◽  
Denitza Zgureva-Filipova
Keyword(s):  
Fly Ash ◽  
Co2 Capture ◽  
Carbon Capture ◽  
Low Cost ◽  
Coal Fly Ash ◽  
Cost Effective ◽  
Thermal Recovery ◽  
Raw Material ◽  
Dynamic Adsorption ◽  
Co2 Capture Capacity

At present, mitigating carbon emissions from energy production and industrial processes is more relevant than ever to limit climate change. The widespread implementation of carbon capture technologies requires the development of cost-effective and selective adsorbents with high CO2 capture capacity and low thermal recovery. Coal fly ash has been extensively studied as a raw material for the synthesis of low-cost zeolite-like adsorbents for CO2 capture. Laboratory tests for CO2 adsorption onto coal fly ash zeolites (CFAZ) reveal promising results, but detailed computational studies are required to clarify the applicability of these materials as CO2 adsorbents on a pilot and industrial scale. The present study provides results for the validation of a simulation model for the design of adsorption columns for CO2 capture on CFAZ based on the experimental equilibrium and dynamic adsorption on a laboratory scale. The simulations were performed using ProSim DAC dynamic adsorption software to study mass transfer and energy balance in the thermal swing adsorption mode and in the most widely operated adsorption unit configuration.

Effect of Mechanical Activation on the Synthesis of Ba-Celsian and Sr-Celsian using Precursor Mixtures Containing Coal Fly Ash

2016 ◽  
Vol 1812 ◽  
pp. 89-94
Author(s):  
Claudia M. Lopez-Badillo ◽  
Jorge López-Cuevas ◽  
Carlos A. Gutiérrez-Chavarría ◽  
José L. Rodríguez-Galicia ◽  
Elia M. Múzquiz-Ramos
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Solid State ◽  
Mechanical Activation ◽  
Solid State Reaction ◽  
Milling Time ◽  
Coal Fly Ash ◽  
Raw Material ◽  
Attrition Mill ◽  
Sintered Materials

ABSTRACTBaAl2Si2O8 and SrAl2Si2O8 were synthesized by solid-state reaction of stoichiometric mixtures of either BaCO3 or SrCO3 with coal fly ash and Al2O3. The mixtures were mechanically activated in an attrition mill for up to 12 h and then reaction-sintered at 900-1300 °C, aiming to promote the formation of BaAl2Si2O8 and SrAl2Si2O8 as well as the conversion from their hexagonal (Hexacelsian) into their monoclinic (Celsian) forms, which is associated with improved mechanical properties in the sintered materials. Especially in the case of SrAl2Si2O8, the formation of Celsian was favored at relatively low sintering temperatures by increasing milling time. Although only the SrAl2Si2O8 composition was fully converted into Celsian, the Hexacelsian to Celsian conversions obtained for the mechanically-activated BaAl2Si2O8 composition were significantly higher than those previously reported in the literature for this compound. This could be attributed to the use of coal fly ash as raw material, which contains mineralizers that promote the mentioned conversion.

scholarly journals Magnetite concentrate from coal fly ash of Kashirskaya GRES- the raw material for the production of metal products by reduction smelting

2021 ◽  
Vol 1942 (1) ◽  
pp. 012048
Author(s):  
D V Zinoveev ◽  
L M Delicyn ◽  
Y V Ryabov ◽  
R V Kulumbegov ◽  
A S Zakunov ◽  
...  
Keyword(s):  
Fly Ash ◽  
Coal Fly Ash ◽  
Raw Material ◽  
Magnetite Concentrate ◽  
Reduction Smelting ◽  
Metal Products

Synthesis and Characterization of Cordierite, Mullite and Cordierite-Mullite Ceramic Materials using Coal Fly Ash as Raw Material

MRS Advances ◽  
2017 ◽  
Vol 2 (62) ◽  
pp. 3865-3872
Author(s):  
J. López-Cuevas ◽  
E. Interial-Orejón ◽  
C.A. Gutiérrez-Chavarría ◽  
J.C. Rendón-Ángeles
Keyword(s):  
Fly Ash ◽  
Flexural Strength ◽  
Vickers Microhardness ◽  
Coal Fly Ash ◽  
Ceramic Materials ◽  
Raw Material ◽  
X Ray Diffraction ◽  
Mullite Ceramic ◽  
Two Temperatures

AbstractCordierite (Mg2Al4Si5O18), Mullite (Al4+2xSi2-2xO10-x) and Cordierite-Mullite ceramic materials were obtained from a stoichiometric mixture of coal fly ash (CFA) as a source of SiO2 and Al2O3, plus high-purity MgO and Al2O3. The starting stoichiometric mixtures were homogenized, and then uniaxially pressed, cold isostatically pressed, and sintered at 1200-1600 °C for 2-5 h. The sintered materials were characterized by X-ray diffraction, scanning electron microscopy, Vickers microhardness, density and four-point flexural strength. In general, the desired phases tended to form in the composites at temperatures of 1350 or 1400 °C, with a considerable amount of glassy phase developing from 3 h onwards at one of those two temperatures, depending on the composite composition. The microstructure of the composites consisted of a matrix of Cordierite and interwoven needles of Mullite. The bulk density decreased, while the flexural strength and the Vickers microhardness increased with increasing nominal content of Mullite in the composites. A synergistic effect taking place between Cordierite and Mullite enhances the mechanical properties of the composites.

Parameters Affecting the Synthesis of X and A Zeolites from Coal Fly Ash

2021 ◽  
Vol 2 (1) ◽  
pp. 53-59
Author(s):  
A. Korpa ◽  
V. Teneqja ◽  
S. Gjyli ◽  
A. Andoni
Keyword(s):  
Fly Ash ◽  
Industrial Waste ◽  
Acid Treatment ◽  
Coal Fly Ash ◽  
Exchange Capacity ◽  
Raw Material ◽  
Crystallization Time ◽  
Zeolite Synthesis ◽  
Different Types ◽  
Type Zeolite

This paper summarizes the investigation results on the main parameters affecting the synthesis of type X and A zeolites using coal silicious fly ash (FA) as raw material. The synthesis was performed by dissolution of alkali-fused alumino-silicates, followed by hydrothermal treatment. The experimental data confirm that fly ash SiO2/Al2O3 ratio, NaOH/FA ratio, acid treatment of pre-fused fly ash, salinity of solution have a significant effect on type and properties of newly formed zeolites. In summary, the results show that A and X-type zeolite form with FA SiO2/Al2O3 ratio < 1.12 and > 1.86, respectively. Moreover, FA characterized by SiO2/Al2O3 mole ratio of 3.15 is suitable for X-type zeolite synthesis while A-type zeolite does not form without NaAlO2 addition. The crystallization occurs faster at higher temperatures although above 90°C X-type zeolite evolves into more stable phases whereas increasing the crystallization time from 1 to 72 hours, the yield of the synthetic products enhances from 60 to 75%. The use of seawater is responsible for the synthesis of X-type showing both lower purity and specific surface area. However, the synthetic products are characterized by high exchange capacity (> 320 meq/100 g), thus suggesting their successful application as adsorbents and catalysts in different types of wastewater and industrial waste treatments.

4A-Molecular Sieve Synthesis by Microwave Heating with Silicon and Aluminum Materials Produced from the Coal Fly Ash

2011 ◽  
Vol 675-677 ◽  
pp. 219-222 ◽  
Author(s):  
Guang Hui Bai ◽  
Peng Cheng Li ◽  
Peng Xu ◽  
Shuang Li Chen
Keyword(s):  
Fly Ash ◽  
Pore Size ◽  
Sodium Silicate ◽  
Molecular Sieve ◽  
Coal Fly Ash ◽  
Sodium Aluminate ◽  
Raw Material ◽  
Crystallization Time ◽  
Microwave Technology ◽  
Practical Applications

A new method, using sodium silicate and sodium aluminate synthesize 4A-molecular sieve, was developed by using microwave technology. The sodium silicate was a high modulus liquor by-product of nano-silica production from coal fly ash. Meanwhile, the sodium aluminate was a process by-product of alumina extraction from coal fly ash. Reaction mixture composition was defined as follow:SiO2/Al2O3 ratio in 2.0, Na2O/SiO2 ratio in 1.5, and H2O/Na2O ratio in 65. The gelation process was completed in 1 hr. Microwave crystallization power was (800w) 30%. Microwave crystallization period can last 25 mins. The 4A-molecular sieve was obtained by collecting crystals from the reaction mixture through filtration after washing with water to pH 11-12 and drying inside isotherm oven. The calcium exchange capacity and effective pore size of the product were 316mg/g and 0.4nm respectively. Over 90% of surface pore size reached in sizes of less than or equal to 8μm. Purity of 4A-molecular sieve up to 99%. This method significantly reduced the raw material costs for sodium silicate and sodium aluminate. In addition, the adoption of microwave technology also lowered the energy usage and shortened crystallization time. All these contributed final low costs of 4A-molecular sieve product, which made it possible for many practical applications.

scholarly journals Dynamic hydrothermal synthesis of xonotlite fibers by alkali silica extraction of fly ash

2019 ◽  
Vol 14 ◽  
pp. 155892501989034 ◽  
Author(s):  
Xu Peng
Keyword(s):  
Fly Ash ◽  
Hydrothermal Synthesis ◽  
Coal Fly Ash ◽  
Synthesis Method ◽  
Morphological Characteristics ◽  
Mineralogical Composition ◽  
Raw Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Silica Material

The silica leached from coal fly ash using alkali, via the hydrothermal method, can be used as the raw material for the synthesis of xonotlite fibers through the hydrothermal synthesis method. This investigation was made to examine how the fly ash desilicated liquid influences the crystal growth and microstructure of xonotlite fibers. The obtained samples were characterized by X-ray diffraction and scanning electron microscope techniques to investigate their mineralogical composition and morphological characteristics. The results indicated that the pure desilication liquid leached from coal fly ash could be used to prepare xonotlite fibers. Xonotlite fibers with single crystal characteristics and large aspect ratio of 100–400 were successfully fabricated from fly ash desilication liquid, which is used as the silica material, at 240°C for 6 h.

scholarly journals Synthesis of ZSM-5 Zeolite Using Coal Fly Ash as an Additive for the Methanol to Propylene (MTP) Reaction

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 788 ◽  
Author(s):  
Rui Feng ◽  
Kening Chen ◽  
Xinlong Yan ◽  
Xiaoyan Hu ◽  
Yixin Zhang ◽  
...  
Keyword(s):  
Fly Ash ◽  
Coal Gasification ◽  
Coal Fly Ash ◽  
Strong Acid ◽  
Acid Sites ◽  
Raw Material ◽  
X Ray Diffraction ◽  
Strong Acid Sites ◽  
Optimized Conditions ◽  
N2 Sorption

Using ZSM-5 zeolites as catalysts for the methanol to propylene (MTP) reaction is being widely investigated and has been industrially applied. In this study, pure ZSM-5 zeolite was successfully synthesized by a direct hydrothermal method using the fly ash of coal gasification as an additional raw material. Various analysis methods such as X-ray diffraction, N2 sorption, scanning electron microscopy, and infrared spectroscopy, were employed to characterize the physicochemical properties of parent and modified zeolites. Then, the prepared ZSM-5 catalysts were tested in the MTP reaction. The results showed that pure ZSM-5 could be directly synthesized in the optimized conditions using fly ash as additional silicon and aluminum sources, and those ZSM-5 catalysts turned out to be candidate catalysts for the MTP reaction. Whereas their catalytic lifetimes were not good enough due to the strong acid sites and needed improving.

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