Showing papers on "Calcium oxide published in 2000"

Preparation of Active Absorbent for Dry-Type Flue Gas Desulfurization from Calcium Oxide, Coal Fly Ash, and Gypsum

Abstract: As compared to a commercial absorbent prepared from Ca(OH)2, gypsum (CaSO4) and coal fly ash, an absorbent prepared by use of CaO in place of Ca(OH)2, exhibited a higher activity for dry-type flue gas desulfurization . The order of the addition of the raw materials in the slaking procedure has much effect on the activity of the resulting absorbent. The activity of the absorbent increased further upon hydrothermal treatment following the kneading procedure. The period of hydrothermal treatment was reduced to 3 h to attain the activity which exceeds 20% of the activity of the commercial absorbent which requires an optimum hydrothermal treatment period of 10 h. The activity enhancement by use of CaO is considered to result from exothermic heat of slaking CaO. At a high temperature, the reaction of CaO with a SiO2 component included in the coal fly ash facilitates the formation of calcium silicate. The formation of calcium silicate was suppressed by the existence of CaSO4 in the slaking procedure.

Compositional Variations in the Calcium Phosphate Layer Growth on Gel Glasses Soaked in a Simulated Body Fluid

Abstract: The growth of calcium phosphate layers on the surface of SiO2−CaO−(P2O5) bioactive glasses immersed in a simulated body fluid (SBF) under static and dynamic conditions has been studied by XRD, SEM,...

The hydration of α-tricalcium phosphate

Abstract: It can be said that this article took the lead in studying a bioceramic group called calcium phosphate cement or apatite cement. The active promotion of calcium phosphate cementing materials has been made since the Monma-Kanazawa paper appeared. Many researchers have long believed that tricalcium phosphate is stable in water. However, the authors of this paper reported that α-tricalcium phosphate (α-TCP) converts to hydroxyapatite in hot water (80-100°C) and produces hardened porous products. The main results were as follows: bulk densities of 0.9-1.2 g/cm 3 , compressive strengths of 15-16 MPa and diametral strengths of 2-3 MPa. The resulting products were composed of calcium-deficient hydroxyapatites. This phenomenon was very peculiar since some other calcium phosphate did not show such a hardening property even if a similar phase change occurred. Generally, cement-type materials possess many advantages different from densely sintered ceramics. If calcium phosphate cementing materials were created, they would be a significantly new type of calcium phosphate material and also to be bioactive. Therefore, this paper concerning the hydration-hardening of α-TCP has attracted the attention of material researchers. At nearly the same time, the possibilities of various cementing calcium phosphate compositions were proposed by Brown and Chow based on thermodynamic considerations. The following two basic patents have been issued; H. Monma et al., Production of porous apatite, Jpn. Pat. 1103653 (Jul. 16, 1982), Appl. 53-124025 (Oct. 7, 1978) and W. E. Brown et al., Dental restorative cement pastes, U. S. Pat. 45185430 (May 21, 1985), Appl. No. 539740 (Oct. 6, 1983). Subsequently, many studies on cementing calcium phosphate materials have increasingly appeared in technical and medical journals. Details of the hydration reaction of α-TCP were clarified. The hydration-hardening of α-TCP was made even at room temperature using various additives, and its possibility as a practical cementing material was significantly improved. A mixture of α-TCP and calcium hydrogenphosphate dihydrate was found to have good hydration-hardening properties (H. Monma et al., J. Ceram. Soc. Japan, 96, 878 (1988)). This combination gave the following results; about a 10-min setting time, 50-60% porosity and 15-20 MPa wet compressive strength. Presently, the compressive strength has been improved to 50-90 MPa. After this author's paper, the following studies were made. The mixture of tetracalcium phosphate and calcium hydrogenphosphate dihydrate first proposed by Brown and Chow has been continuously investigated by many researchers, and its hardening properties were improved by using dilute phosphoric acid and adding synthetic hydroxyapatite powder. About 470 kinds of combinations using various calcium phosphates, calcium carbonate, calcium oxide, sodium fluoride, calcium sulfate hemihydrate, etc., were evaluated, and some available combinations for use as cementing materials were developed as follows: Lemaitre et al. in 1987, Mirtchi et al. in 1990, Bermudez et al. in 1993, and Driessens et al. in 1994. The glassy powder in the system of CaO-SiO 2 -P 2 O 5 was developed as a bioactive cementing material (Kokubo et al., 1991). Hardened porous materials prepared from these calcium phosphate cements also became important also as supports for drug delivery systems.

Interfacial kinetics of hydrogen with liquid slag containing iron oxide

Abstract: Interfacial kinetics on the hydrogen reduction of liquid Fe t O in Fe t O-M x O y slag (M x O y = CaO, SiO2, Al2O3, and TiO2) has been studied at 1673 K. Because the rate of hydrogen reduction was very fast, the rate was controlled by gas-phase mass transfer under most of the experimental conditions. The effect of CaO or SiO2 addition on the interfacial chemical reaction rate of hydrogen reduction was empirically evaluated as a function of the ferrous-ferric ratio in the slag. The observed interfacial chemical reaction rates in Fe t O-CaO and Fe t O-SiO2 slags showed reasonable agreement with the estimated values. Most of the available literature data on the reduction rate of liquid iron oxide by solid carbon, hot metal, and reducing gases were also reviewed and compared with the results of the present work. It was found that the rate of hydrogen reduction of liquid iron oxide slag is much faster than that with other reducing agents such as solid carbon, carbon dissolved in the liquid iron, and CO gas.

Kinetics of high-pressure removal of hydrogen sulfide using calcium oxide powder

Abstract: Sulfidation reaction of CaO at high pressure (up to 2 MPa) and high temperature (up to 900°C) to remove H2S in a coal-fired gasifier was studied in a high-pressure and temperature differential-bed flow-through reactor. Experimental conditions selected are typical for pressurized gasifiers. Effects of total pressure, H2S partial pressure, reaction temperature, fuel gas composition, and CaO surface area on the extent of sulfur capture and sorbent conversions were determined. The gasifier pressure affected the in-situ calcination of calcium carbonate particles through reduction in available surface area and pore volume of CaO formed, thus limiting the sulfidation conversion. Time-resolved conversion data of CaO sulfidation were analyzed using a modified grain model. The model incorporates external and internal diffusion, surface reaction, product layer diffusion, and the structural changes of the sulfiding CaO particle. The activation energy for the reaction was 37 kcal/mol. The estimated product layer diffusivity was 8×10−15 m2/s at 800°C with an associated activation energy of 38.4 kcal/mol—typical of solid state diffusion of ionic species through the product layer. The extent of conversion increased with increasing initial surface area and porosity of CaO particles. The high-pressure sulfidation reaction data for CaO will be useful in understanding and optimizing the in-gasifier H2S capture using calcium-based sorbents.

Incorporating subgrade lime stabilization into pavement design

Abstract: The benefits of subgrade lime stabilization are incorporated, for the first time, into the design of a major interstate highway pavement in Pennsylvania. The project comprises widening and complete reconstruction of 21 km of the Pennsylvania Turnpike in Somerset County. Field explorations indicated that the subgrade is fairly homogeneous and consists primarily of medium to stiff clayey soils. To safeguard against potential softening due to rain, lime modification has been traditionally utilized as a construction expedience for highway projects with clayey subgrade. Such an approach, however, does not take advantage of the added strength of the lime-stabilized subgrade in pavement design. Lime improves the strength of clay by three mechanisms: hydration, flocculation, and cementation. The first and second mechanisms occur almost immediately upon introducing the lime, and they have been investigated in the study; the third is a prolonged effect. Laboratory tests were performed to accurately capture the immediate benefits of lime stabilization for design. Both treated and natural clayey samples were subjected to resilient modulus and California bearing ratio testing. To prevent cementation, the lime-treated specimens were not allowed to cure. Nevertheless, they showed significant increases in strength, which, when incorporated into design, reduced the pavement thickness and resulted in substantial savings.

Lime Requirement for Stabilization

Abstract: Lime is used in construction as a rapid and economic method of improving the strength and stiffness characteristics of clay soils. For economical design, an engineer must know how much lime is required to initiate the required improvements. If lime stabilization is to be compared with alternative solutions in the early stages of a project, it must be possible to make this assessment rapidly and with the minimum expenditure on additional specialist testing. The ASTM Standard Test Method for Determining Stabilization Ability of Lime (MDSAL) aims to determine the quantity of lime required for stabilization using simple methodology to generate results quickly. Additional, much lengthier testing is recommended to verify the lime requirement if lime is considered feasible following MDSAL testing. Problems have been found in the execution of the test and interpretation of results, concluding in inconsistency in the lime quantities calculated. This inconsistency could lead to substantial differences in the estimated cost of the overall scheme and possibly to the unwarranted rejection of lime stabilization as a potential solution. The methodology of the MDSAL test through practical experimentation is reviewed and recommendations for its future use are made. The sensitivity of the test to changes in lime quality, volume of water added, and temperature of the soil-water-lime mixture is examined. It is shown that, although extremely sensitive to changes in these parameters, a revised interpretation of test data means that a reliable and consistent result can be achieved. The scientific basis for this revised interpretation is also demonstrated.

Method of chemically loading fibers in a fiber suspension

Abstract: A method of continuously loading fibers in a fiber suspension with calcium carbonate The fibers include a fiber wall surrounding a lumen A reactant solid in the form of calcium oxide and/or calcium hydroxide is mixed into the fiber suspension with a resultant initial process pH of between 11 and 12 The fiber suspension is transported at a consistency of between approximately 15 and 30% into an inner chamber of a closed reactor A reactant gas is injected into the reactor, whereby the reactor is pressurized to a pressure between 5 and 150 psi A temperature of the fiber suspension within the reactor is controlled at a range between −10° C and 80° C The fibers within the fiber suspension are loaded with calcium carbonate as a result of a chemical reaction between the reactant solid and the reactant gas in the reactor over a predetermined reaction time A specific type of calcium carbonate crystals are grown on the fiber walls of the fibers, depending upon the initial process pH, temperature, pressure and reaction time

Chemical transformation of some biologically relevant calcium phosphates in aqueous media during a steam sterilization

Abstract: The purpose of this study was to investigate the effect of steam sterilization on some biologically relevant calcium phosphates: CaHPO4· 2H2O (DCPD), calcium deficient apatite (CDA) and biphasic calcium phosphate (BCP). Suspensions of 0.2 g of each calcium phosphate compound with 5.0 ml of deionized water were prepared and steam sterilized in an autoclave (20 min at 121 °C). After sterilization the suspensions were filtered and the dried solids characterized with scanning electron microscopy, IR-spectroscopy and X-ray diffraction. The pH and calcium concentrations of the filtrates were determined with ion selective electrodes. Similar measurements were made with the same samples which were not sterilized. The sterilization procedure was found to result in the dehydration of DCPD and hydration of calcium oxide incorporated into the BCP. Solution pH was observed to change from 7.3 to 5.5 for the solutions in equilibrium with DCPD and from 8.5 to 10.6 for those in equilibrium with BCP. Minor changes both with the solid and liquid phases were found to occur during the steam sterilization of CDA. These results indicate that steam sterilization may have different effects on different calcium phosphate suspensions: it can result in dehydration of DCPD, fast hydration for CaO in BCP, but no significant effect on CDA.

Method of producing titanium or zirconium metal

Abstract: Titanium metal is produced using titanium dioxide as the starting material. A molten metal collection pool is first prepared in a reaction vessel from zinc and calcium. A molten salt mixture is then added to the vessel comprised of a mixture of calcium chloride and calcium fluoride. The titanium oxide starting material is then added along with additional calcium and the contents are mechanically stirred while maintaining at a temperature of about 800 DEG C. The titanium reacts spontaneously with the calcium, producing titanium powder and calcium oxide. The titanium becomes embedded in the molten zinc pool and settles to the bottom of the vessel, where it is removed and the titanium separated from the zinc by vacuum distillation or a suitable electrochemical process. The same process applies for producing zirconium from zirconium dioxide.

Soil remediation by permanganate oxidation

Abstract: The permanganate ion and an alkaline earth metal base of calcium and/or magnesium are distributed into the soil by a means of mechanical mixing to destroy contaminants in the soil and groundwater by chemical oxidation. The disclosed method produces a stable, post-treatment, manganese dioxide precipitate that does not adversely effect the ground water with high dissolved manganese concentrations. The permanganate salts may include potassium, magnesium or sodium permanganate, and the preferred alkaline earth metal bases may include calcium oxide, calcium hydroxide, magnesium oxide and magnesium hydroxide. Dolomite quick lime may be used to supply an inexpensive source of the desired calcium and/or magnesium base. The calcium and/or magnesium base may be added before, during or after the addition of the permanganate salt.

High capacity mobile lime slaker

Abstract: A continuous preparation of calcium hydroxide slurry can be made on a mobile apparatus that uses an eductor to initially combine metered flows of calcium oxide and water. The calcium hydroxide slurry is retained in a deaerating sump and then pumped into a serpentine centrifugal mixer so that the reaction of the calcium oxide and the water is safely complete. Because the apparatus allows the calcium hydroxide slurry to be recirculated into the deaerating sump, the slaking process can continue even when it is necessary to pause the discharge of slurry to change transport tankers.

Speciation of Combustion-Derived Particulate Phase Arsenic

Abstract: The speciation of inorganic arsenic compounds produced in pulverized coal combustion was investigated in a bench-scale study conducted under fuel-lean combustion conditions. Results suggest that at temperatures of 850–1100 K, and in the absence of particulate, arsenic initially condenses as As2O3 rather than the thermodynamically favored As2O5. Synthetic fly ash in the form of uniform 0.25 μm spherical silica particles produced by sol-gel methods, added to the experimental system to simulate the presence of combustion-derived fly ash, did not affect arsenic speciation, nor did doping of the silica particles with small amounts of calcium. As(V) was only observed at these temperatures when calcium was added to the system as calcium acetate, producing a reactive calcium oxide fume and leading to the formation of calcium arsenate. From these results, it was concluded that the formation of arsenic(V) in combustion systems requires either the oxidation of As2O3, which appears to be a kinetically limite...

Composition for restoring defects in calcified tissues

Abstract: A composition for restoring defects in calcified tissues comprises an amorphous bioactive particulate consisting essentially of calcium, silicon and oxygen. Said agent may be selected from the group consisting of : a) a reaction product of an organic silicate source and a source of calcium; b) a calcium containing hydrolysis product of tetraethylorthosilicate; c) a calcium containing silica sol-gel; d) a binary calcium oxide and silicate precipitated material; e) a synthetic analog of a naturally occurring wollastonite-like calcium silicate; and f) a precipitated reaction product of soluble calcium source and a silicate solution. A process for producing the amorphous bioactive particulate consists essentially of adding a sufficient amount of a solution of a soluble calcium source to a solution of a silicate or silicate precursor to cause a precipitation of calcium-containing silicate particulate.

Deoxidizer for edible oil and process for regenerating edible oil using this deoxidizer

Abstract: PROBLEM TO BE SOLVED: To obtain a deoxidizer which may safely realize simplified and efficient deoxidization of edible oils, and to provide a process for regenerating edible oils using this deoxidizer SOLUTION: The deoxidizer for edible oils is selected from the group consisting of magnesium oxide, calcium oxide, magnesium carbonate, calcium carbonate, calcium silicate, magnesium silicate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, synthetic magnesium phyllosilicate, silica, magnesia, silicon dioxide and activated clay and is granulated into a particle size of from 50 to 200 μm

Distribution equilibria of Pb and Cu between CaO-SiO 2 -Al 2 O 3 melts and liquid copper

Abstract: The distribution equilibria of lead and copper between CaO-SiO2-Al2O3 melts and liquid copper were measured at 1623 K under a controlled H2-CO2 atmosphere. The distribution ratios were plotted against the oxygen partial pressure, and reasonable oxide forms dissolved in the melts were estimated from the slopes of the plots. The activity coefficients of lead oxide (PbO) and cuprous oxide (CuO0.5) increased with increasing slag basicity, defined by X CaO/X SiO2. The temperature dependence of the activity coefficients of lead oxide and cuprous oxide was also measured.

Millennial Special Leading Papers on Ceramics in the 20th Century: the Best of JCerSJ The Hydration of α-Tricalcium Phosphate

Abstract: It can be said that this article took the lead in studying a bioceramic group called “calcium phosphate cement” or “apatite cement.” The active promotion of calcium phosphate cementing materials has been made since the Monma-Kanazawa paper appeared.Many researchers have long believed that tricalcium phosphate is stable in water. However, the authors of this paper reported that α-tricalcium phosphate (α-TCP) converts to hydroxyapatite in hot water (80-100°C) and produces hardened porous products. The main results were as follows: bulk densities of 0.9-1.2g/cm3, compressive strengths of 15-16MPa and diametral strengths of 2-3MPa. The resulting products were composed of calcium-deficient hydroxyapatites. This phenomenon was very peculiar since some other calcium phosphate did not show such a hardening property even if a similar phase change occurred.Generally, cement-type materials possess many advantages different from densely sintered ceramics. If calcium phosphate cementing materials were created, they would be a significantly new type of calcium phosphate material and also to be bioactive. Therefore, this paper concerning the hydration-hardening of α-TCP has attracted the attention of material researchers. At nearly the same time, the possibilities of various cementing calcium phosphate compositions were proposed by Brown and Chow based on thermodynamic considerations. The following two basic patents have been issued; H. Monma et al., “Production of porous apatite, ” Jpn. Pat. 1103653 (Jul. 16, 1982), Appl. 53-124025 (Oct. 7, 1978) and W. E. Brown et al., “Dental restorative cement pastes, ” U.S. Pat. 45185430 (May 21, 1985), Appl. No. 539740 (Oct. 6, 1983).Subsequently, many studies on cementing calcium phosphate materials have increasingly appeared in technical and medical journals. Details of the hydration reaction of α-TCP were clarified. The hydration-hardening of α-TCP was made even at room temperature using various additives, and its possibility as a practical cementing material was significantly improved. A mixture of α-TCP and calcium hydrogenphosphate dihydrate was found to have good hydration-hardening properties (H. Monma et al., J. Ceram. Soc. Japan, 96, 878 (1988)). This combination gave the following results; about a 10-min setting time, 50-60% porosity and 15-20MPa wet compressive strength. Presently, the compressive strength has been improved to 50-90MPa.After this author's paper, the following studies were made. The mixture of tetracalcium phosphate and calcium hydrogenphosphate dihydrate first proposed by Brown and Chow has been continuously investigated by many researchers, and its hardening properties were improved by using dilute phosphoric acid and adding synthetic hydroxyapatite powder. About 470 kinds of combinations using various calcium phosphates, calcium carbonate, calcium oxide, sodium fluoride, calcium sulfate hemihydrate, etc., were evaluated, and some available combinations for use as cementing materials were developed as follows: Lemaitre et al. in 1987, Mirtchi et al. in 1990, Bermudez et al. in 1993, and Driessens et al. in 1994. The glassy powder in the system of CaO-SiO2-P2O5 was developed as a bioactive cementing material (Kokubo et al., 1991). Hardened porous materials prepared from these calcium phosphate cements also became important also as supports for drug delivery systems. At present, α-TCP-based cementing materials are being used a a dental pulp lining (Sankin Co. Ltd., 1986), root canal filling (Sankin Co., Ltd., 1987) and osteoporosis filling (Mitsubishi Materials Co., Ltd., 2000).

Production of fertilizer consisting of incineration ash as raw material

Abstract: PROBLEM TO BE SOLVED: To make it possible to recycle incineration ash of phosphorus- containing sludge and industrial waste as a phosphoric fertilizer by adding additives including magnesium, calcium, or the like, at need to the incineration ash and melting the mixture, then forming slag by rapid cooling and pulverizing the slag. SOLUTION: The incineration ash preferably containing 10 to 40 wt.% phosphoric acid is used as the raw material and is subjected to component regulation by adding ≤50% P, ≤60% Mg, ≤80% Ca, or the like, at need thereto and after the mixture is melted, the mixture is formed as the slag by rapid cooling and the slag is pulverized. The addition quantities of these additives, such as phosphoric acid, magnesium oxide and calcium oxide, are respectively specified to 20 to 25% P (in terms of P2O5), 2.5 to 4.5 molar ratio (by P2O5) Mg (in terms of MgO) and 2.5 to 4.5 molar ratio (by P2O5) Ca (in terms of CaO). As a result, the natural resources included in the incineration ash are effectively utilized and the disposal amount thereof may be decreased. COPYRIGHT: (C)2001,JPO

Heat-releasing grease

Abstract: PROBLEM TO BE SOLVED: To provide a heat-releasing grease low in infiltrativeness into objects coated therewith and excellent in thermal stability and heat releasing tendency. SOLUTION: This heat-releasing grease comprises (A) a silicone oil shown by the general formula (R1 is at least one hydrocarbon group selected from methyl, ethyl, propyl, butyl, vinyl, allyl and phenyl; R2 is a 6-20C alkyl or aralkyl; and m is an integer of 3-100), (B) at least one inorganic compound selected from zinc oxide, magnesium oxide, aluminum oxide, beryllium oxide, calcium oxide, aluminum nitride, boron nitride and silicon carbide, (C) n- octadecyl-3-(3,5-di-tert-butyl-4-hydroxypheny)propionate and (D) pentaerythrityl tetrakis(3-laurylthiopropionate). COPYRIGHT: (C)2002,JPO

Glass composition, and information recording medium substrate, information recording medium, and information recording device each comprising the composition

Abstract: A glass composition is disclosed which has a high modulus of elasticity and a low density, i.e., has a high specific modulus. Also disclosed is an inexpensive glass composition which is suitable for use as an information recording medium substrate, for example, because it can be formed easily, is less apt to suffer devitrification, is suitable for mass production, and can be easily made to have high surface smoothness by polishing. The glass compositions comprise, in terms of mol %, 35 to 45% silicon dioxide (SiO2), 15 to 20% aluminum oxide (Al2O3), 3 to 10% lithium oxide (Li2O), 0.1 to 5% sodium oxide (Na2O), 15 to 30% magnesium oxide (MgO), 0 to 10% calcium oxide (CaO), 0 to 4% strontium oxide (SrO), 25 to 35% RO (MgO+CaO+SrO), 2 to 10% titanium dioxide (TiO2), 0.5 to 4% zirconium oxide (ZrO2), 4 to 12% TiO2+ZrO2, and 0 to 4% yttrium oxide (Y2O3).

Hydrated calcium aluminate based expansive admixture

Abstract: An additive, a mixture incorporating the additive and a method of formulating a mortar incorporating the additive The additive is based on calcium sulfoaluminate composed of C3AH6 and CAH10 where C=calcium oxide, A=aluminum oxide and H=water The admixture includes gypsum and calcium hydroxide The calcium aluminum hydrates are obtained by hydration of high alumina cement particles to eliminate any lack of hydration in the core of the particle The method involves the preparation of such particles and the mix incorporates the particles to produce a homogeneously hydrated cement additive

Method for producing metallic titanium

Abstract: PROBLEM TO BE SOLVED: To produce metallic titanium from titanium oxide by a continuous and circulating type process. SOLUTION: A first stage in which titanium oxide powder is mixed with a (Ca+ CaCl2) mixed phase reducing agent, this mixture is forged at 900 to 1,000 deg.C to produce titanium particles, and simultaneously, a mixed by-product of calcium chloride and calcium oxide is obtained, a secondary stage in which the reduced by-product recovered in the first stage is charged into water in which gaseous chlorine has been blown, and stirring is performed to separate the titanium particles in the aqueous solution, a third stage in which the powdery titanium recovered in the second stage is cleaned and dried and is thereafter compacted and sintered into an electrode bar, and, after that, by arc melting, a titanium ingot is obtained, a fourth stage in which the aqueous solution freed of the titanium particles in the second stage is evaporated and dried to harden and the obtained product is thereafter heated to >=800 deg.C to obtain molten calcium chloride and a fifth stage in which the molten calcium chloride recovered in the fourth stage is electrolyzed at 850 to 950 deg.C and is separated into a molten (Ca+CaCl2) mixed phase and gaseous chlorine, and the former is used as a reducing agent in the first stage, and, on the other hand, the latter as gaseous chlorine in the second stage respectively in a circulating way, are combined.

Phase equilibria of the bismuth oxide–calcium oxide–copper oxide system at 1 atm of pure oxygen

Abstract: Liquidus phase relations of bismuth oxide–calcium oxide–copper oxide are described in pure oxygen at 1 atm. CaO is the primary phase over most of the system and CuO crystallizes first along much of the copper oxide–bismuth oxide join. Two calcium–copper oxides have primary phase fields separating those of CaO and CuO; these have limited variation in Ca:Cu but extend to high Bi 2 O 3 contents. Primary phase fields of Bi–Ca oxides are limited to a region with

Phase Analysis of High-calcium Lime by TG

Abstract: A thermogravimetric method has been developed and is suggested for both the qualitative and quantitative phase analyses of high-calcium lime and calcium speciation as well. Two complementary TG measurements are proved to be satisfactory for the determination of moisture, calcium oxide, calcium hydroxide and calcium carbonate contents as well as total mineral impurities in high-calcium limes: quicklime, hydrated lime and limestone.

Ultra fast-curing injection material and injection process using the same

Abstract: PROBLEM TO BE SOLVED: To obtain an ultra fast-curing injection material which may control the gelling time of the injection material to be within 10 min, exerts an excellent durability and permeability and allows crack repair of embankments and water- stopping without any water pollution caused by a diverge flow of the injection material. SOLUTION: This ultra fast-curing injection material contains a fine-powdery hydraulic material slurry wherein a dispersing agent and water are mixed with a hydraulic material fine powder essentially comprising a blast furnace slag fine powder having either a maximum particle size of 12 μm or a blaine specific surface area of from 10,000 to 20,000 cm2/g, and an ultra fast-curing admixture slurry prepared by kneading water and an ultra fast-curing admixture prepared by mixing one or more of gypsum, calcium hydroxide or calcium oxide with a material essentially comprising a calcium aluminate composition having a maximum particle size of ≤45 μm and a 85% particle size of ≤25 μm. These slurries are mixed at the initiation of injection. COPYRIGHT: (C)2001,JPO

Hot defluorination of reducing gases with lime pellets

Abstract: In IGCC and MCFC power generation systems the coal gas has to be purified from dust and deleterious gaseous species. Hot gas cleaning processes have advantages compared to conventional wet cleaning technologies. Losses of energy occurring during cooling and reheating of the gas can be avoided, and there is no formation of a wet slurry. In the present study the defluorination of reducing gases with dry absorbers such as calcium carbonate (CaCO{sub 3}) and calcium oxide (CaO) has been investigated in the temperature range 300--700 C. Two types of experiments were carried out to clarify the reaction kinetics: thermogravimetric experiments on single (or a few) pellets in which the weight change of the absorber due to its conversion to calcium fluoride was determined, and gas cleaning experiments using a laboratory scale fixed bed reactor in which the off-gas was analyzed. The results indicate that H{sub 2}-H{sub 2}O-HF and CO-H{sub 2}-CO{sub 2}-H{sub 2}O-HF gas mixtures can be defluorinated both with CaO and with CaCO{sub 3}. The calcium fluoride (CaF{sub 2}) forms as a shell around the unreacted core of calcium carbonate of the pellet, and the reaction rate is mainly controlled by gaseous pore diffusion. This is so also with respectmore » to calcium oxide at high temperatures (500 C). But at low temperatures (300 C) the reaction occurs within the bulk of the pellet.« less

Investigations on the Surface Properties of Pure and Alkali or Alkaline Earth Metal Doped Ceria

Abstract: The effect of parameters, such as initial cerium concentration and alkali or alkaline earth concentration in the reactant solution on the properties of precipitated ceria, have been investigated by nitrogen adsorption isotherm analysis, FTIR spectroscopy and X- ray powder diffraction. Increasing cerium concentration in the reactant solution has a negative effect on the surface properties of ceria, especially on calcined samples. Addition of alkali ions leads to the gradual lessening of the specific surface area; the effect is strongly depended on the ionic potential of the guest alkali ion. Co-precipitation of magnesium and cerium leads to the formation of separate magnesia solid phases within the ceria mesopores resulting in an anomalous behaviour of the surface properties of ceria. Co-precipitation of calcium and cerium results in the formation of homogeneous Ca-Ce mixed oxides with surface properties depended on the calcium content of the mixed oxide. In contrast to co-precipitation, using the incipient wetness method leads to the formation of separate calcium oxide phase within the ceria mesopores.

Heating medium and use of the same

Abstract: 35 g of a heating medium comprising 70 to 85% of powdered aluminum and 15 to 30% of powdered calcium oxide on the basis of the total weight of the heating medium is contacted with 80 ml of water to react the powdered calcium with water at a first reaction step to generate heat of reaction and calcium hydroxide, and then the calcium hydroxide is reacted at a second reaction step with powdered aluminum to generate heat of reaction to make use of approximately 3886 cal/g as the sum of the heat of reaction generated at the first reaction step and second reaction step, which can arrive at temperatures of approximately 100 ° C. for a short time which can be maintained for at least 20 minutes. The heating medium of this invention is built in a heating apparatus of a heating cooking container without increasing the weight and bulk of the container.