Showing papers on "Calcium oxide published in 2010"
TL;DR: It was found that calcium oxide was well distributed in the sorbents with metal oxide nanoparticles on the surface acting as physical barriers, and the CO2 capture capacity of the sorBents was largely maintained over multiple cycles of utilization.
Abstract: Sorbents for high temperature CO2 capture are under intensive development owing to their potential applications in advanced zero emission power, sorption-enhanced steam methane reforming for hydrogen production and energy storage systems in chemical heat pumps. One of the challenges in the development is the prevention of sintering of the sorbent (normally a calcium oxide derivative) which causes the CO2 capture capacity of the material to deteriorate rapidly after a few cycles of utilization. Here we show that a simple wet mixing method can produce sintering-resistant sorbents from calcium and magnesium salts of d-gluconic acid. It was found that calcium oxide was well distributed in the sorbents with metal oxide nanoparticles on the surface acting as physical barriers, and the CO2 capture capacity of the sorbents was largely maintained over multiple cycles of utilization. This method was also applied to other organometallic salts of calcium and magnesium/aluminum and the produced sorbents showed similar...
218 citations
TL;DR: The sorbent CG- CaO showed a much lower decomposition temperature and higher predicted residual conversion after prolonged cycles, compared with CC-CaO.
Abstract: A screening of potential calcium precursors for the production of CaO sorbents for CO2 capture at high temperature was conducted in this work. The precursors studied include microsized calcium carbonate (CC-CaO), calcium hydroxide (CH-CaO), nanosized (<70 nm) calcium carbonate (CC70 nm-CaO), nanosized (<160 nm) calcium oxide (CaO160 nm-CaO), calcium acetate hydrate (CA-CaO), calcium l-lactate hydrate (CL-CaO), calcium formate (CF-CaO), calcium citrate tetrahydrate (CCi-CaO), and calcium d-gluconate monohydrate (CG-CaO). The capture capability of these sorbents was investigated using a thermogravimetric analyzer (TGA) for multiple capture cycles. CG-CaO exhibited the best capacity for capturing CO2 with a 1-min conversion of 65.9% and a 30-min conversion of 83.8% at the ninth cycle. Subsequently, a further parametric study was conducted to examine the effect of reaction conditions such as reaction temperature (550−750 °C) and CO2 gas concentration (1−15%) on the capture capacity of CG-CaO. The sorbent CG-C...
211 citations
TL;DR: The results show that the slag is a crystalline heterogeneous material whose main components are iron oxides, calcium (magnesium) compounds (hydroxide, oxide, silicates, and carbonate), elemental iron, and quartz.
Abstract: The chemical and mineralogical composition of steel slag produced in two ArcelorMittal steel plants located in the North of Spain, as well as the study of the influence of simulated environmental conditions on the properties of the slag stored in disposal areas, was carried out by elemental chemical analysis, XRF, X-ray diffraction, thermal analysis, and scanning electron microscopy with EDS analyzer. Spectroscopic characterization of the slag was also performed by using FTIR spectroscopy. Due to the potential uses of the slag as low cost adsorbent for water treatment and pollutants removal, its detailed textural characterization was carried out by nitrogen adsorption−desorption at 77 K and mercury intrusion porosimetry. The results show that the slag is a crystalline heterogeneous material whose main components are iron oxides, calcium (magnesium) compounds (hydroxide, oxide, silicates, and carbonate), elemental iron, and quartz. The slags are porous materials with specific surface area of 11 m2g−1, cont...
142 citations
TL;DR: In this paper, a post-combustion carbonate looping process is based on the capture of carbon dioxide from the flue gases of an existing power plant in a circulating fluidized bed reactor (CFB) of calcium oxide (the carbonator) particles.
141 citations
TL;DR: In this article, a mesoporous network of zinc oxalate has been used as a solid catalyst for transesterification processes, which can reveal the corresponding pore size distributions, thus avoiding lixiviation of the active phase in the reaction medium.
140 citations
TL;DR: In this article, a modified CaO-based mesoporous CO2 sorbent with high sorption capacity (about 10mol/kg sorbent) and long-term durability was developed.
119 citations
TL;DR: Reaction rates of both fresh and regeneration sorbents with CO(2) were controlled by a combination of the surface chemical reaction and diffusion of product layer, and the operating parameters on reaction between solid sorbent and CO( 2) gas at high temperature were investigated.
109 citations
TL;DR: In this paper, a new class of CaO-based absorbents with much improved high-temperature durability was developed by wet physical mixing of calcium acetate with nano MgAl2O4 spinel particles followed by hightemperature calcination.
Abstract: With efficient energy recovery, calcium-oxide-based absorbents that operate at elevated temperatures have an advantage over absorbents that operate at lower temperatures for CO2 capture from coal power plants. The major limitation of these absorbents is that the carbonation and decarbonation reactions of CaO and CaCO3 are far from complete or reversible. Rapid loss of CO2 capacity over many carbonation/decarbonation cycles is always observed because of severe absorbent sintering. We have found that this sintering effect can be effectively mitigated by properly mixing calcium oxide precursors with small rod-like MgAl2O4 spinel nanoparticles. A new class of CaO-based absorbents with much improved high-temperature durability was developed by wet physical mixing of calcium acetate with nano MgAl2O4 spinel particles followed by high-temperature calcination. CaO−MgAl2O4 (32 wt % spinel content) material provides 34 wt % CO2 capacity after 65 carbonation−decarbonation cycles (650 and 850 °C, respectively), corre...
98 citations
01 Feb 2010-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the anodic testing of calcium ruthenate for electrowinning in calcium chloride-calcium oxide melts was performed and the results showed that it exhibited a low rate of corrosion in melts containing a small amount of calcium oxide, capable of producing oxygen on its surface and did not contaminate the melt.
Abstract: Studies were performed investigating the anodic testing of calcium ruthenate for electrowinning in calcium chloride–calcium oxide melts. The results showed that calcium ruthenate may be suitable as an inert anode in calcium chloride containing melts as it exhibited a low rate of corrosion in melts containing a small amount of calcium oxide, capable of producing oxygen on its surface, and did not contaminate the melt. To reduce the amount of ruthenium in the anode, solid solutions of calcium ruthenate in calcium titanate were investigated. At low concentrations, the solid solution is a semiconductor with a relatively low conductivity at room temperature, but at the temperature of operation, 1173 K, the material is an excellent electronic conductor. The other way of reducing the amount of ruthenium is to coat the solid solution onto a substrate. In this way, the substrate would give the mechanical strength while the coating would give the electrical conductivity and corrosion protection. Calcium ruthenate-based anodes can endure long-term use in the laboratory under an applied electrical field with oxygen being liberated on the anode indicating that these materials are candidates for the electrowining in calcium chloride–calcium oxide melts.
93 citations
TL;DR: In this article, the influence of different admixtures (water repellents, water retainers, polypropylene fibre and a viscosity modifier) on the pore size distribution of hardened specimens was assessed and related to the water absorption capacity.
92 citations
TL;DR: In this article, a microprobe and ICP-mass spectrometry on 61 elements were used to identify the starting mixtures of wood ash glass. But the majority of the wood ash glasses contain europium anomalies within the group of rare-earth elements (REE).
Abstract: Medieval wood ash glass classified as 6 early medieval wood ash glasses, 17 wood ash glasses, 5 early wood ash lime glasses, 7 wood ash lime glasses and 9 mixed alkali glasses has been analyzed by microprobe and ICP-mass spectrometry on 61 elements. Their calcium oxide to potassium oxide ratio (CaO/K2O) increases from early to late medieval glasses according to an increase of the proportion of twigs in the bulk amount of wood (logs plus twigs). Twigs because of their relatively large proportion of bark contain more calcium than wood logs. The ratio CaO/K2O of the glasses from not yet evaluated excavations can be used for dating. The observation that the 25 minor elements Be, Sc, V, Cr, Ge, Y, Nb, REE (La to Lu), Ta, W and Bi occur in almost equal concentrations in the five subtypes of wood ash glass makes it highly probable that these elements were introduced into the starting mixtures of the glasses by means of quartz from quartz-rich sand with heavy minerals. The majorities of the wood ash glasses contain so-called europium anomalies within the group of rare-earth elements (REE). Their Eu concentrations normalized to those of the Continental Earth's Crust are lower than the normalized samarium and gadolinium concentrations. These Eu anomalies are apparently inherited from the granitic source of quartz in the upper Continental Earth's Crust. Soda ash and soda lime glass as the other major types in the history of glass contain no Eu anomaly. Therefore a different source of quartz has caused this important element constellation for these glass types. The elements K, Cu, Rb and S are physiologically separated from Ca, P, Mn, Sr and B during the growth of the wood and bark, respectively, in the trees. Different sources of the metals Cu and Co were used for colouring the glasses of our report.
TL;DR: In this paper, solid base catalysis of calcium oxide for transesterification of soybean oil with refluxing methanol was investigated, and the collected catalyst consisted of calcium glyceroxide, Ca[O(OH) 2 C 3 H 5 ] 2.
TL;DR: In this article, the solid base catalysis of calcium glyceroxide was investigated by IR spectroscopy using methanol as the molecular probe, and the measured spectra indicated that calcium oxide was combined with methanols at the temperature of 333 K and the chemical composition of the produced calcium compound was estimated at CH 3 O-Ca-O(OH) 2 C 3 H 5.
Abstract: When calcium oxide is employed for transesterification of vegetable oil at reflux of methanol, calcium oxide is turned into calcium glyceroxide by combining with glycerol of the by-product. As well as calcium oxide, calcium glyceroxide seemed to catalyze the vegetable oil transesterification. In the present paper, the solid base catalysis of calcium glyceroxide was investigated by IR spectroscopy using methanol as the molecular probe. The measured spectra indicated that calcium glyceroxide was combined with methanol at the temperature of 333 K. Chemical composition of the produced calcium compound was estimated at CH 3 O-Ca-O(OH) 2 C 3 H 5 . The IR spectrum of the calcium alkoxide indicated that hydrogen bond was formed among the glyceroxyl OH groups and methanol. Data from the soybean oil transesterification, which was carried out at 298 K, elucidated that the calcium alkoxide functioned as the solid base catalyst. At the same reaction temperature, calcium glyceroxide did not interact chemically with methanol, and sent out only the homogeneous catalysis.
TL;DR: In this article, the role of Ca, the efficiency of lime charge and the mechanism of the transformation process are discussed, especially within the context of high temperature and high silica bauxite processing.
TL;DR: Acid neutralization trials indicate that even CKD samples with low free lime contents could be effective at neutralizing acidic wastewaters.
TL;DR: In this article, the formation mechanism of high-calcium fly ashes, the mineralogical, physical, and chemical properties of several high calcium fly ashes and their different density fractions (2.89 g/cm3) from a coal-fired power plant were characterized by X-ray diffractometry (XRD), field scanning electron microscopy equipped with energy dispersive x-ray analysis (FSEM-EDX), and Xray fluorescence spectroscopy (XRF), and the occurrence of calcium in coal was determined using sequential extraction tests.
Abstract: To understand the formation mechanism of high-calcium fly ashes, the mineralogical, physical, and chemical properties of several high calcium fly ashes and their different density fractions ( 2.89 g/cm3) from a coal-fired power plant were characterized by X-ray diffractometry (XRD), field scanning electron microscopy equipped with energy dispersive X-ray analysis (FSEM-EDX), and X-ray fluorescence spectroscopy (XRF). The occurrence of calcium in coal was determined using sequential extraction tests. The results show that the carbonate-bonded calcium is the dominant species in Xiaolongtan coal, and the ion-exchangeable calcium only occupies 19.2% of total calcium. The major calcium-bearing minerals in low temperature ash (LTA) of the feed coal, lignite from the Yunnan province, include calcite, bassanite, and dolomite. The fly ashes examined contained aluminosilicates with a high concentration of calcium oxide. The major minerals include mullite, quartz, lime, anhydrite, and ge...
TL;DR: In this article, the reaction conditions, such as the concentration of the Ca2+ ion, ageing time and power of the ultrasonic device show important roles in the size, morphology and growth process of the final products.
Abstract: Calcium hydroxide nanostructures have been synthesised by the reaction of calcium acetate with sodium hydroxide or tetramethylammonium hydroxide by a sonochemical method. Reaction conditions, such as the concentration of the Ca2+ ion, ageing time and power of the ultrasonic device show important roles in the size, morphology and growth process of the final products. The calcium oxide nanoparticles have been obtained by heating of calcium hydroxide nanostructures at 600°C. The calcium hydroxide and calcium oxide nanostructures were characterised by transmission electron microscopy, scanning electron microscopy and X-ray powder diffraction.
Patent•
21 Jan 2010TL;DR: A geopolymer composite binder is provided in this article, which includes at least one fly ash material having less than or equal to 15 wt% of calcium oxide, and a gelation enhancer.
Abstract: A geopolymer composite binder is provided herein, the composite binder including (i) at least one fly ash material having less than or equal to 15 wt% of calcium oxide; (ii) at least one gelation enhancer; and (iii) at least one hardening enhancer having a different composition from a composition of the at least one fly ash material.
TL;DR: In this article, a modified wet chemical precipitation route was used to synthesize calcium phosphates with different and reproducible phase compositions after thermal processing (hydroxyapatite [HAp], β-tricalcium phosphate [β-TCP] and HAp/βTCP) by modified wet-chemical precipitation route.
Abstract: In this work calcium phosphates were synthesized by modified wet chemical precipitation route. Contrary to the conventional chemical precipitation route calcium hydroxide was homogenized with planetary mill. Milling calcium oxide and water in planetary ball mill as a first step of synthesis provides a highly dispersed calcium hydroxide suspension. The aim of this work was to study the influence of main processing parameters of wet chemical precipitation synthesis product and to control the morphology, phase and functional group composition and, consequently, thermal stability and microstructure of calcium phosphate bioceramics after thermal treatment. The results showed that it is possible to obtain calcium phosphates with different and reproducible phase compositions after thermal processing (hydroxyapatite [HAp], β-tricalcium phosphate [β-TCP] and HAp/β-TCP) by modified wet-chemical precipitation route. The β-TCP phase content in sintered bioceramics samples is found to be highly dependent on the changes in technological parameters and it can be controlled with ending pH, synthesis temperature and thermal treatment. Pure, crystalline and highly thermally stable (up to 1300°C) HAp bioceramics with homogenous grainy microstructure, grain size up to 200–250 nm and high open porosity can be successfully obtained by powder synthesized at elevated synthesis temperature of 70°C and stabilizing ending pH at 9.
TL;DR: The radio-opacity of the resulting cement was three times greater than that of cortical bone because of the presence of strontium ions, a feature that complies with the requirements for vertebroplasty.
TL;DR: In this article, the authors evaluate hydrated lime-treated hot-mix asphalt (HMA) mixtures through various laboratory tests, including the dynamic modulus test and performance tests to characterize permanent deformation and fatigue damage resistance both in displacement-controlled and force-controlled modes.
TL;DR: In this paper, the authors used different techniques, including differential thermal analysis, polarizing microscope, X-ray diffraction and indentation microhardness to obtain colored glass and glass-ceramic materials.
Abstract: Cement kiln dust from Rabigh plant in Saudi Arabia was examined for use in the preparation of glass-ceramic materials. The cement kiln dust made up about 70 wt.% of the batch constituents depending on the composition. The cement kiln dust composition was sometimes modified by additions of other ingredients such as silica sand, granite and magnesite. The batches were melted and then casted into glass which was subjected to heat treatment to induce crystallization. Different techniques were used in the present study, including differential thermal analysis, polarizing microscope, X-ray diffraction and indentation microhardness. The colored glass and glass-ceramic materials obtained, possess very high hardness indicating high abrasion resistance, which make them suitable for many applications under aggressive mechanical conditions.
Patent•
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TL;DR: In this article, the authors define a glass as a mixture of silicon dioxide (65-72), aluminum oxide (11-17), sodium oxide (0.4-1.8), calcium oxide (4-12), zinc oxide ( 0-10), and fluorine (0-2), where the weight ratio of calcium oxide/magnesium oxide is 1.8.
Abstract: Glass comprises (in wt.%, based on oxide) either: silicon dioxide (65-72), aluminum oxide (11-17), sodium oxide (0.1-8), magnesium oxide (3-8), calcium oxide (4-12) and zinc oxide (0-10); silicon dioxide (65-72), aluminum oxide (11-17), sodium oxide (0-8), potassium oxide (0-2), magnesium oxide (3-8), calcium oxide (4-12) and zinc oxide (0.1-10); or silicon dioxide (65-72), aluminum oxide (11-17), sodium oxide (0.5-8), magnesium oxide (3-8), calcium oxide (4-12), zinc oxide (0-10) and fluorine (0-2), where the weight ratio of calcium oxide/magnesium oxide is 1.4-1.8.
TL;DR: In this article, the authors used X-ray photoelectron spectroscopy (XPS) analysis to compare the chemical composition of native oxide films formed spontaneously on commercial pure magnesium and AZ31, AZ80 and AZ91D alloys.
Abstract: The present work uses X-ray photoelectron spectroscopy (XPS) analysis to compare the chemical composition of native oxide films formed spontaneously on commercial pure magnesium and AZ31, AZ80 and AZ91D magnesium alloys. The study considers both the outer surface and inner regions of the films with the assistance of argon ion bombardment. Possible relationships are established between the alloy Al content and the native oxide film characteristics. The Al content is very similar in the oxide films on all three studied alloys. XPS identifies a much greater film thickness on AZ80 and AZ91D specimens than on AZ31 and pure Mg specimens, which seems to be related with the presence ofphase (Mg17Al12) on the AZ91D alloy surface and of the eutectic � -Mg/� on the AZ80 alloy surface. Considerable Ca segregation is observed (directly related with the calcium impurities content in the bulk material) towards the outer surface of the metal, where it appears in the form of calcium oxide. Direct correspondence is found between the thickness of the native oxide film formed spontaneously on the surface of magnesium and its alloys and their subsequent corrosion resistance in exposure to a 3.5 wt% NaCl solution.
TL;DR: In this paper, the microstructure evolution of lime putty upon aging was investigated by slaking quicklime (CaO) with an excess of water for 3, 12, 24, 36, 48 and 66 months.
TL;DR: In this article, the effect of the maturation process on hardened state characteristics of hydrated powder lime mortars was analyzed, showing an air lime mortar thickening behavior with the length of the test.
TL;DR: In this article, the authors verify the mechanochemical conditions of CaTiO3 formation with the use of three calcium oxide precursors (CaO, CaCO3 and Ca(OH)2).
Abstract: Because of unique dielectric, piezoelectric, thermoelectric, optical and ferroelectric properties of titanates of alkaline earth metals, they have become an object of many scientific research. This article is concerned with mechanochemical synthesis of calcium titanate as an alternative technique to hydrothermal, sol–gel, thermal methods. The aim of this study was to verify the mechanochemical conditions of CaTiO3 formation with the use of three calcium oxide precursors—CaO, CaCO3 and Ca(OH)2. The differences in processes of calcium titanate synthesis are presented.
01 Jan 2010
TL;DR: In this article, the role of raw mix composition control and homogenization process in Portland cement production has been studied by using computer simulation (Fortran 90) to make calculations to estimate quantities of the raw materials (limestone, clay, iron ore,.. ) required to prepare kiln feed.
Abstract: The raw materials for Portland cement production are the mixture (as fine powder in the 'Dry process') of minerals containing calcium oxide, silicon oxide, aluminum oxide, ferric oxide, and magnesium oxide. The raw materials are usually quarried from local rocks which are found in some places have already practically the desired composition and in other places require addition of the clay and limestone, as well as iron ore, or recycled materials such as CKD). The homogeneity of feed chemical composition has an important relationship to fuel consumption, kiln operation, clinker formation and cement performance. Cement quality is typically assessed by its compressive strength development in mortar and concrete. The basis for this property is a well-burned clinker with consistent chemical composition and free lime. The main reason for the clinker free lime to change in a situation with stable kiln operation is variation in the chemical composition of the kiln feed. This variation in chemical composition is related to raw mix control and the homogenization process. To ensure a constant quality of the product and maintain a stable and continuous operation of the kiln, the attention must be paid to storage and homogenization of raw materials and kiln feed. This article focuses to study the role of raw mix composition control and the homogenization process. The study have been done by computer simulation (Fortran 90) to make calculations to estimate quantities of the raw materials (limestone, clay, iron ore,.. ) required to prepare kiln feed. These calculations have been done based on knowing composition of raw materials, these field data obtained from Al-Mergheb cement plant. Due to variations in the kiln feed chemical compositions that affect its burnability and eventually the fuel consumption, so the simulation done to give a suitable composition of kiln feed to allow soft burning inside kiln. A simulation of the mixing raw materials process and estimate composition of kiln feed, as well as formed clinker were done successful through fitting of the results obtained with field data of one of the plants operating in Libya.
TL;DR: In this article, the reaction sintering mechanism of dolomite-zirconia mixtures was investigated using fine grounded dolombite raw material and zirconium powder, and it was observed that CaZrO 3 synthesis was definitely finished at temperature of 1500°C in the both applied ways of the synthesis (one- or two-step process) in the two-stage process.
TL;DR: In this paper, the authors measured the carbide capacity of the CaO-SiO2-MnO slag through the wide composition region at 1773 K to understand the effective slag composition on the solubility of carbon in molten slags during SiMn production processes.
Abstract: The carbide capacity of the CaO–SiO2–MnO slag, which is the main system produced during Mn alloys processes, through the wide composition region has been measured at 1773 K to understand the effective slag composition on the solubility of carbon in molten slags during SiMn production processes. The carbide capacity is strongly affected by slag composition and this tendency can be reasonably estimated by employing the activity of lime and the activity coefficient of CaC2 as a thermodynamic factors affecting carbide capacity. Considering the high concentration of MnO during SiMn smelting process, the lime to silica ratio of 0.8 (±0.1) is recommended in view of high ability of carbon dissolution. The carbide capacity of the CaO–SiO2–MnO slag can be expressed as a linear function of the activity of lime and the optical basicity. The carbide capacity of the CaO–SiO2–MnO slag increases more significantly than the sulfide capacity does as the basicity of the slag increases.