SO3 Content Research Articles

The whole process test and analysis of flue gas SO3 in coal-fired power plant under variable load conditions

Under the current situation of ultra-low emission, it is of great significance to study the formation and removal of SO3 in various equipments of coal-fired power plants. At present, most researches on SO3 in coal-fired power plant focus on the influence of single equipment on flue gas SO3 under a certain load condition. In this research, a 300MW generating unit is tested under variable load conditions to explore the variation law of SO3 in various equipments under variable load conditions. The results show that SO3 is mainly generated in the boiler furnace and SCR denitrification device, and the total removal rate of SO3 is 84.6%. However, the removal efficiency of SO3 in electrostatic precipitators and the wet desulfurization systems shows great differences. Under full load condition, the removal rate of SO3 is 46.8% - 69.8%. When the load changes, the SO3 removal rate changes with the change of load, and the ESP is affected by the load most. The SO3 content in the ash increases from 11.267mg/g under 50% load to 14.763mg/g under 100% load, and such changes are mainly determined by flue gas temperature and flue gas flow.

Composition-structure-property effects of antimony in soda-lime-silica glasses

Float glass-type SiO2-Na2O-CaO glasses with 0 – 10 mol% Sb2O3 were melted and their compositional, structural, thermal and optical properties characterised. All glasses were X-ray amorphous and increasing Sb2O3 content progressively decreased glass transition temperature (Tg) and dilatometric softening point (Td), despite increases in Al2O3 content from greater crucible corrosion. 121Sb Mössbauer spectroscopy confirmed that Sb was predominantly incorporated as Sb3+ (Sb3+/ΣSb ~ 0.9) and Raman spectroscopy showed that Sb substantially decreased average (Si, Al)-O Qn speciation. Both techniques confirmed that Sb3+ ions were incorporated in trigonal pyramidal [:SbO3] polyhedra. XRF and Raman spectroscopies confirmed that SO3 content decreased with increasing Sb2O3 content. TGA analysis showed, as a linear function of Sb2O3 content, mass gain commencing at 700°C, reaching a maximum at 1175°C, then mass loss above 1175°C, consistent with oxidation (Sb3+ → Sb5+) then reduction (Sb5+ → Sb3+). The TGA samples were shown to have attained or approached Sb redox equilibrium during measurement. Optical absorption spectroscopy (UV-Vis-nIR) showed red-shifts of the UV absorption edge with increasing Sb2O3 content, consistent with increasing intensity of far-UV absorption bands from Sb3+ and Sb5+ s→p transitions. UV-Vis-nIR fluorescence spectroscopy evidenced a broad luminescence band centred at ~25,000 cm−1, attributed to the 3P1→1S0 transition of Sb3+, which is Stokes shifted by ~15,000 cm−1 from the 1S0→3P1 absorption at ~40,000 cm−1. The most intense emission occurred at 0.5 mol% Sb2O3, with concentration quenching reducing luminescence intensities at higher Sb2O3 contents. Additions of Sb2O3 to float-type soda-lime-silica glasses could thus enable lower melting energies and/or new solar energy applications.

Properties and durability of concrete containing fluidized bed combustion (FBC) fly ash

As the supply of conventional pozzolans fall further behind concrete industry’s demand, interest in non-traditional pozzolanic materials continues to grow. One such material is fluidized bed combustion (FBC) fly ash. In this study, two compositionally different FBC fly ashes from North America were used at 20% mass replacement of Portland cement in a pavement-grade concrete mixture. The effects of these fly ashes on the fresh, hardened, and durability properties of concrete and equivalent mortars were evaluated. It was observed that desirable slump, air content, air-voids structure, and strength development can be achieved in concrete with FBC fly ash. Further, FBC fly ashes improved concrete’s resistivity, formation factor, and resistance to chloride penetration. Drying shrinkage performance was also acceptable. While the high SO3 content of one fly ash did not cause a deleterious expansion by itself, the concrete containing the high SO3 fly ash was more prone to sulfate attack.

Unified method for the determination of chemical composition in different types of materials using Wavelength Dispersive X-ray Fluorescence Spectrometry

Abstract The aim of the article is to show that determination of the main chemical composition with Wavelength Dispersive X-ray Fluorescence Spectrometry method does not require the use of separate analytical applications and procedures for the tests of materials of different origin. This is however conditioned upon calcination of the tested initial sample at the temperature of 815 °C to remove organic matter and its preparation for X-ray measurements by fusing into a borate bead. Within the framework of the conducted research a special analytical application measuring 10 oxides: SiO2, Al2O3, Fe2O3, CaO, MgO, Na2O, K2O, SO3, TiO2 and P2O5 was developed. Standards and certified reference materials (CRMs) were applied for calibration. Synthetic standards with the use of oxides and salts of purity of 99.99% were also prepared to complete the measuring points on the calibration curves The curves determined based on the measuring points have high correlation coefficients and accuracy. The α empirical correction coefficients were applied to correct matrix effects. The range of the method was confirmed based on the measurements of 13 synthetic standards. The average values of the standard deviations in the lower range of the calibration curves were between 0.0008% for K2O and 0.0056% for Na2O and 0.0054% for MgO. The average values of the relative standard deviation were in the range between 1.81% for K2O and 13.92% for MgO and 11.21% for Na2O, respectively. In the upper range of the calibration curves, the average values of standard deviation were between 0.079% for TiO2 and 0.962% for P2O5, and the relative standard deviation was between 0.05% for SiO2 and 2.39% for P2O5. The accuracy of the developed WDXRF method was assessed based on the measurement of 10 certified reference materials representing all the tested materials (cement, coal ash, slag, fire clay, sediment and soil). Out of 98 conducted measurements (two CRMs did not contain the declared content of P2O5 and SO3 respectively), in 68 measurements, relative errors were below 5%, and, in next 27 measurements, they were between 5% and 10%. The errors were comparable for all the tested materials which confirms that in WDXRF analyses of borax beads the type, kind and origin of a sample do not affect accuracy of the obtained measurements.

The Effects of Fineness and TEA-Based Chemical Admixture on Early Strength Development of Concrete in Construction Site Applications.

This study examines effects of cement fineness and chemical admixtures of early strength agents on the early strength development of concrete. Three cement types were selected, namely ASTM type-I ordinary Portland cement (OPC), fineness ordinary Portland cement (FOPC), and ASTM type-III early Portland cement (EPC), and the mixing proportions of concrete were set by adding a triethanolamine-based chemical admixture to FOPC. The evaluation items considered in this study included raw material analysis, compressive strength, and maturity (D∙h). The time required for the development of concrete strength of 5 MPa in the three cement types was estimated and compared. The results revealed that using FOPC enhances the strength development of concrete owing to its higher fineness and SO3 content compared to OPC. In addition, it has been observed that using both FOPC and TCA yields a similar performance to that observed using EPC, in light of the improved early strength development at low temperatures.

Study on hydration characteristics of circulating fluidized bed combustion fly ash (CFBCA)

Circulating fluidized bed combustion fly ash (CFBCA) is a by-product of the coal-fired process in power plants. In this paper, the hydration characteristics of CFBCA are studied. The pozzolanic activity of CFBCA and pulverized coal combustion fly ash (PCA) at different ages was tested, the hydration products, microstructure of CFBCA-cement paste and PCA-cement paste and the elements distribution of Si, Al and Ca on the surface of fly ash particles were studied. Then the effects of pH value and SO3 content on the dissolution of active SiO2 and active Al2O3 from CFBCA and PCA were further discussed. The experimental results show that the pozzolanic activity of CFBCA is higher than that of PCA, and the surface of CFBCA is more easily corroded and the active SiO2 and active Al2O3 are easy to dissolve in the hydration process. CaO and anhydrite (CaSO4•II) contained in CFBCA play an important role in promoting the dissolution of active SiO2 and active Al2O3. In addition, the loose structure of CFBCA and the low degree of polymerization of [SiO4] and [AlO6] are also one of the reasons for its higher hydration activity than PCA. Relevant research revealed the hydration mechanism of CFBCA, and provided a theoretical basis for its application in cement and concrete.

Distinctive geochemical features of biotite types from the subeconomic Sonajil porphyry-type Cu deposit, northwestern Iran: Implications for analysis of porphyry copper deposit mineralization potential

The geochemical characteristics of four biotite types comprising least-altered magmatic biotite (LA-Mbt), least-altered equilibrated magmatic biotite (LA-Eq Mbt), equilibrated magmatic biotite (Eq-Mbt), and secondary hydrothermal biotite (S-Hbt) types from a subeconomic low-grade porphyry Cu system named Sonajil are compared with the economic high-grade Sungun porphyry Cu-Mo deposit situated in the Western Alborz-Azerbaijan structural zone of Iran; the proximity of the two porphyry copper deposits helps to evaluate mineralization potential of the intrusive bodies. The classification scheme for biotite types is based on petrographic data, back-scattered electron images, and compositional attributes. Whereas both of the S-Hbt types at Sonajil and Sungun are related to the overlapping alteration zones of high potassic / low phyllic, the S-Hbt types at Sungun are Mg-rich and fall within the compositional field confined by two endmembers of eastonite and phlogopite. The S-Hbt types at Sonajil are Fe-rich plotting in the compositional field enclosed by two endmembers of eastonite and siderophyllite. The mean of MgO, MnO, TiO2, Na2O, SiO2, and F (wt%) contents of the biotites help in characterizing the geochemical features of the mineralized magmatic rocks contrasted with subeconomic intrusions. Biotite types of the Sungun Porphyry stock display much higher SO3 contents (0.06 wt% on average) compared to those of biotite types of the Sonajil Porphyry stock (<0.01 wt% on average). Fluorine contents (0.9 wt% F on average) in the Sungun Porphyry biotites are the highest ones, whereas the biotite types of the Sonajil Porphyry stock have 0.8 wt% F (on average). Biotite types of the Sonajil and Sungun Porphyry stocks exhibit approximately equal Cl contents (0.15 wt% on average). Magmatic biotites of the productive Sungun Porphyry stock were characterized by higher temperatures (760 °C on average) compared to those of unproductive Sonajil Porphyry stock (747 °C on average). The LA-Mbt types of the Sonajil Porphyry point to oxygen fugacities (ƒO2) with values ranging from 10−16.27 to 10−14.40 bars, while LA-Mbt types at Sungun deposit were formed under oxygen fugacities between 10−15.4 to 10−13.8 bars. There is a positive correlation between the amount of Cu (wt%) in the Porphyry stocks and the wt% SO3 in the biotites of Porphyry stocks. The hydrothermal fluids related to alteration zones in the subeconomic Sonajil have approximately the same range of log(ƒH2O)/(ƒHCl) and log(ƒHF)/(ƒHCl) values to those of fluids associated with other economic deposits, such as Los Pelambres and Casino. Therefore, it can be recommended that evaluating of log(ƒH2O)/(ƒHCl) and log(ƒHF)/(ƒHCl) ratios of fluids in equilibrium with biotites alone cannot be a discriminating parameter. Confirmation by SO3 (wt%) content of the biotite types, by linkage between SO3 content of biotites and Cu grade, by halogen (wt% F and Cl) chemistry of biotite types, by halogen intercept values of F, Cl, and F/Cl, and by hydrothermal fluid halogen fugacity ratios, all illustrate the capacity of SO3 content (wt%) of biotites to be a reliably exploration index and highlight the critical role of fluorine compared to chlorine in discrimination of unproductive and productive porphyry Cu systems.

Influence of sulfur trioxide in clinker on the hydration heat and physical properties of Portland cement

The cement industry has achieved stable usage of waste gypsum board in clinker production. However, few studies have focused on the heat of hydration and physical properties of cements with high-SO3 clinker with different C3A and gypsum contents. Clinker with different amounts of SO3 and coexisting C3A was prepared in an electric furnace. Cement samples were then prepared by adding gypsum. Increasing the clinker SO3 content accelerated the alite reaction and caused aluminate hydrate reaction to occur later. Compressive strength at 3 days increased with SO3 content whereas that after 28 days decreased. The drying shrinkage strain of mortar decreased with increasing SO3 content of the clinker and gypsum at each C3A content. The decrease of drying shrinkage attributed to SO3 in the clinker was smaller than that caused by gypsum SO3. As the clinker SO3 content increases, cement physical properties can be maintained by adjusting the gypsum content.

Non-ammonia enrichment of rare earth elements from rare earth leaching liquor in a magnesium salt system I: Precipitation by calcium oxide

Combining the environmental advantage of magnesium salt compound leaching agent, calcium oxide was used as a precipitant to enrich rare earth elements from rare earth leaching liquor in a magnesium salt system. The use of magnesium salt compound leaching agent and calcium oxide precipitant can achieve the effective circulation of Ca and Mg, and finally solve the ammonia-nitrogen pollution problem in the whole extraction process of the weathered crust elution-deposited rare earth ore. The study suggested that alkaline rare earth sulfates and rare earth hydroxides could generate in the precipitation process, which was proved by the Hazen model calculation and the calcium oxide addition experiments. What's more, it was showed that, under the optimum precipitation conditions, the precipitation efficiency of rare earth was 99.72% and the purity of rare earth concentrate is 82.21%, and the SO3 content in the rare earth concentrate was as high as 13.44% because of the formation of alkaline rare earth sulfates during the precipitation process. In order to reduce the SO3 content, the stirring washing of the precipitation enrichment with an sulfate removal agent was proposed in this paper. The anion of the sulfate removal agent could compete with sulfate ions in the stirring washing process. As a result, sodium hydroxide could be the first choice for further detailed study. When the precipitation enrichment was washed with sodium hydroxide, the purity of the rare earth concentrate was 88.03% and the SO3 content was 7.51% respectively. Hence, a feasible operation would be provided for the non-ammonia enrichment of rare earth from leaching liquor in a magnesium salt system. The research in this paper could have great significance for environmentally-friendly extraction of the weathered crust elution-deposited rare earth ore and the improvement of resource utilization.

Deterioration Process of Concrete Exposed to Internal Sulfate Attack.

Damage to concrete structures with gypsum-contaminated aggregate occurs frequently. Aggregates in much of the southern part of China are contaminated with gypsum. Therefore, in this study, the effects of using different quantities of gypsum-contaminated aggregate on the expansion and compressive strength of concrete were investigated over a period of one year. Two groups of concrete were designed with the gypsum-contaminated aggregate containing different parts of fine and coarse aggregate, respectively. The SO3 contents were 0%, 0.5%, 1%, 1.5%, 3%, 5%, and 7% by weight of aggregate. X-ray diffraction (XRD), thermogravimetry (TG), and differential scanning calorimetry (DSC) were used to analyze the change in mineral composition over time. The microstructure was also studied by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results showed that significant expansion and great loss in compressive strength did not occur in concrete if the content of SO3 lay below 1.5% and 3% in fine and coarse aggregates, respectively. The concentration of sulfate ions in concrete was not enough to form new a phase of gypsum. During the process of internal sulfate attack, the content of gypsum decreased and the content of ettringite increased. Ettringite was the main reason for the expansion damage of concrete. Additionally, the fracture mode of internal sulfate attack on concrete was the crack extension from gypsum to paste; finally, the aggregate separated from the paste.

Long-term sulfate attack on recycled aggregate concrete immersed in sodium sulfate solution for 10 years

The effect of recycled concrete aggregate (RCA) on concrete performance against external sulfate attack (ESA) is not yet fully known. In this paper, recycled aggregate concretes (RAC) with 0, 50, 75 and 100% of RCA contents were evaluated after 10 years of exposure immersed in 50g/l sodium sulfate solution. Sulfate ingress profiles were obtained by wet chemical analyses and FRX. Also, the mineralogy of the ingress profile was evaluated by thermogravimetric analyses. Finally, microcracking development in samples was evaluated by optical fluorescent microscopy image analysis. Although RAC showed a slight increase in sulfate ingress, due to its higher porosity (about 30% higher SO3 content near the surface for 50% or higher replacement ratio than control concrete), a dense new matrix still allows a good performance of RAC to external sulfate attack with even 100% RCA content.

Analysis and Control Technology of blue Smoke in Coal-fired Power Plants

The control of blue Smoke in coal-fired power plants is of great significance to the atmospheric environment. The emission of SO3 from coal-fired power plants is an important factor of blue Smoke production, which mainly comes from boiler combustion and selective catalytic reduction (SCR) denitration. When the content of SO3 in the flue gas is too high, it will cause problems such as dust accumulation, low-temperature acid corrosion, increased air preheater resistance, and degraded performance of the electric precipitator, which will affect the economical efficiency and safety of the unit. In this paper, the causes of blue Smoke in coal-fired power plants are analyzed, the conversion rate of SO3 is calculated and verified, and technical measures to control colored plumes are proposed.

Study on the essential properties of recycled powders from construction and demolition waste

Recycled fine aggregates and waste powders can be ground into ultrafine powders, defined as recycled powders (RPs), for effective utilization of construction and demolition (C&D) waste. However, the performance of RPs relies on their original sources, the complex components of which hinder their applications. In this study, six common types of RPs were prepared from different sources of C&D waste with their properties comparatively examined in detail, including the chemical composition, micro morphology, fineness and hydration heat. Subsequently, the water requirements of standard consistence and setting time of pastes incorporating different RPs, together with the flowability and mechanical properties of the corresponding mortars were investigated. The results showed that the irregular and rough shapes of RPs required higher water consumption to achieve a standard consistency of paste. The higher alkali-content and lower content of SO3 of RPs contributed to the higher heat evolution rates of pastes with RPs in the first 30 min, but the pastes with RPs exhibited lower cumulative hydration heats than cement after 1d. The additional use of RPs decreased the flowability, density and strength of mortar. The mixed brick powder and clay brick powder had the relative positive impact on the mechanical properties of mortar at later ages, illustrating their great potential for use in cement matrix. The maximum reduction of strength was about 20% when the replacement ratio was limited to 30%.

Assessing the effect of fly ash with a high SO3 content in hybrid alkaline fly ash pastes (HAFAPs)

Hybrid alkaline fly ash pastes (HAFAPs) are a new generation of alkaline-activated binders that use low amounts of Portland cement and high amounts of fly ash (FA). New sulfur emissions requirements in power plants are generating quantities of FAs with high SO3 (>5%) content, which are discarded into landfills. This paper investigates the effects of high-SO3 FA on the mechanical properties, durability, and characterizing chemical behavior of HAFAPs. The main results indicate that depending on the exposure condition, high SO3 content leads to the generation of efflorescence, affecting the mechanical performance and durability of HAFAPs.

Influences of Chemical Composition and Fineness on the Development of Concrete Strength by Curing Conditions

In this study, the influences of chemical composition and fineness on the development of concrete strength by curing conditions were investigated through performance evaluation of high SO3 Portland cement (HSPC) and ordinary Portland cement (OPC). At the same fineness (3800 cm2/g), the initial and final setting times of HSPC were 92 and 98 min less than OPC. Early mortar compressive strength was approximately 176% higher after 24 h. After curing for 15 h, 18 h, and 24 h, the maturity of HSPC concrete (107.4%, 109.6%, and 111.7%) and early compressive strength (146.4%, 170.7%, and 154.5%) were higher than measured for OPC concrete. HSPC fineness was 111.8% higher than OPC, leading to early activation of the hydration reaction. By X-ray fluorescence analysis, the SO3 content of HSPC was 107.9% that of OPC. The applicable time for HSPC concrete form removal was shorter than that for OPC concrete. The relationships y = −10.57 ln(x) + 47.30 and y = −9.84 ln(x) + 44.05 were estimated for predicting the early-age strength OPC and HSPC concrete. Therefore, applying HSPC concrete to an actual construction site is expected to shorten the construction period and reduce the heating curing cost in winter compared to OPC concrete.

Geochemical characteristics and oxidation states of the Xietongmen ore‐bearing porphyries: Implication for the genetic types of the Xietongmen No. I and No. II deposits, southern Tibet

The Xietongmen large deposit is the only known subduction‐related porphyry Cu deposit in the Gangdese Belt, Tibet, which is composed of the No. I and No. II deposits. Previous work suggests that the No. I deposit is reduced while the No. II deposit is oxidized. However, it is ambiguous that both oxidized and reduced porphyry Cu deposits occur in close proximity, in the same tectonic setting, and within a short time period. Detailed examination of the ages, whole‐rock geochemistry, zircon and apatite compositions of the Xietongmen No. I and No. II ore‐bearing porphyries are conducted to investigate their magma characteristics and the genetic types of the Xietongmen No. I and No. II deposits. Zircon U–Pb dating results show that the Xietongmen No. I and No. II ore‐bearing porphyries formed at 166.3 ± 2.6 Ma and 175.5 ± 1.0 Ma, respectively. The Xietongmen No. I and No. II ore‐bearing porphyries have similar mineral assemblage (containing amphibole phenocryst), high Sr/Y ratios and negligible negative Eu anomalies, low Ti‐in‐zircon temperatures (633−749 and 633−763°C, respectively), which indicate that their magmas are water‐rich. In addition, the Xietongmen No. I and No. II ore‐bearing porphyries have: (a) high whole‐rock V/Sc ratios (10−15 and 8−16, respectively); (b) high zircon Ce4+/Ce3+ and EuN/EuN* ratios, falling into the field of the ore‐bearing intrusions in northern Chile; (c) low apatite CeN/CeN* ratios (0.97−1.02 and 0.99−1.02, respectively), which suggest that their magmas are oxidized. The estimated magmatic S contents, based on the magmatic apatite SO3 contents, yield 0.0113−0.0507 wt% and 0.0012−0.0118 wt%, respectively for the Xietongmen No. I and No. II ore‐bearing porphyries, which suggest their magma are sulfur‐rich. Hydrous, oxidized and sulfur‐rich magmas are the parent magma of oxidized porphyry Cu deposits, together with the oxidized minerals of hematite and magnetite, therefore, both Xietongmen No. I and No. II deposit are oxidized porphyry Cu deposits, rather than that the Xietongmen No. I deposit is a reduced porphyry Cu deposit.

Rheological properties of mortar containing recycled powders from construction and demolition wastes

Various types of recycled powders (RPs) can replace cement or fly ash in preparing concrete due to the acceptable impact on the mechanical properties. However, the workability of concrete containing RPs may decrease significantly that render their practical application. This paper investigated the rheological properties of mortar containing different RPs processed from the construction and demolition wastes, which were clay brick powder (CBP), mixed brick powder (MBP) and dust powder (DP). Firstly, the basic properties of RPs were studied for a better understanding the effect on the properties of mortar. Then, the rheological properties of mortar were examined with different RPs to determine the influence of different RPs and superplasticizer dosage, respectively. The experimental results showed that RPs had higher content of Al2O3 and alkali and lower content of SO3, and accordingly, the hydration heat of pastes with RPs were found higher than that of cement paste in the first 30 min. The yield stress, plastic viscosity and thixotropy increased significantly with the use of different RPs, among which mortar with DP were the maximum. Mortar with MBP showed better rheological behavior. Whereas, CBP presented the worst compatibility with SP.

In situ major and trace element compositions of apatites from Luanchuan orecluster: Implications for porphyry Mo mineralization

The effects of volatile concentrations and oxidation state of magma on the Mo mineralization potential have been explored through petrographic studies and in situ electron probe micro-analyzer (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of apatites from coeval economically Mo- mineralized granite porphyry and quartz diorite, and sub-economically mineralized granite porphyry at Luanchuan orecluster. The occurrence of abundant K-feldspar xenocrysts, possibly entrained from granitic magma, in quartz diorite implying a magma mingling process. Studied apatites are fluorapatites or fluor-hydroxyapatites with decreasing OH concentrations from economically mineralized quartz diorite (0.30–0.49 apfu) through mineralized granite porphyry (0.14–0.41 apfu) to sub-economically mineralized granite porphyry (0.01–0.11 apfu). Chondrite-normalized REE patterns of all the apatites are characterized by LREE enrichment relative to MREE and HREE, and negative Eu anomaly, similar to their host magmas, indicating a melt composition control. Strontium concentration of studied apatites are probably controlled by the crystallization of plagioclase or alkali feldspar. Mineralized quartz diorite formed at a relatively reduced environment compared to other rocks, but mineralized granite porphyry and sub-economically mineralized granite porphyry formed at a similar oxidation state, based on the SO3, Eu, Ce, and Mn content variation of apatites. The OH-contents of apatites, combined with published log (H2O/HF) ratios of melt in equilibrated with biotites, reflect that economically mineralized intrusions have higher water contents than the sub-economically mineralized intrusions. In a porphyry Mo system, a high magma water content is probably a key parameter controlling Mo mineralization. Mafic magma may supply water (and heat) to ore-forming granitic magmas, enhancing their Mo mineralization potential.

Separation of Cenospheres from Lignite Fly Ash Using Acetone–Water Mixture

This work reports on the separation of cenospheres from lignite fly ash through a wet separation process-the sink-float method. A better quality of cenospheres could be achieved through a physical–chemical approach using an acetone–water mixture as a medium. This work aimed to elucidate the correlation between the structure, morphology, and composition and medium fraction variables, with data for the freshly prepared and the reused mixtures presented for comparison. The work covers a study of the macrocomponent composition of an Fe2O3–SiO2–Al2O3 system, highlighting the pair dependences of SiO2–Al2O3, Al2O3–Fe2O3, and SiO2/Al2O3–Al2O3 and revealing an interesting result in terms of geochemical characteristics categorizing the collected cenosphere fractions separated from high-calcium class C fly ash produced from a lignite coal power plant in Thailand (as magnetic cenospheres). The CaO and SO3 contents increased monotonically with increased water content, particularly for the CaO composition profile, which was found to be similar to the increased carbonate concentration measured from the mixtures after use. The physicochemical properties in terms of the self-association ability of the acetone–water mixing phase is believed to have played an important role in determining the intermolecular interactions and reactivity of ions in the liquid phase, consequently affecting the separation efficiency, recovery yield, and quality of cenospheres.

Degradation of kaolinite clay added with Al2O3–Ta2O5 in H2SO4

This study focuses on the degradation of kaolinite clay added with Al2O3 and Ta2O5, also known as tantite, to increase its resistance to an acid solution (H2SO4) at 300°C. The samples tested for degradation were previously crushed, sieved, mixed, formed under cold isostatic pressing and sintered at 1150°C. X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques were used to determine the composition and reveal the phases present in the samples. Degradation by static immersion (98wt% H2SO4) was evaluated by the ASTM C267 mass loss technique. Predominant oxides of SiO2, Al2O3 and Fe2O3 were found within the kaolinite clay, as well as other oxides in proportions lower than 2.39wt%. The immersion of natural clay in sulfuric acid (at 300°C) caused an increase in SO3 content as well as in the mass of all samples. The X-ray diffractograms revealed the presence of quartz, cristobalite, curundum and tantite, as well as a significant reduction in their peak intensities after the interaction with H2SO4. The results showed that adding 20wt% (sample M3C) and 40wt% (sample M4C) of Ta2O5 to the kaolinite clay (sample M1C), produces a more stable structure and greater resistance to attack by H2SO4.