Showing papers on "Calcium oxide published in 2004"

Effects of Calcium Oxide on the Cracking of Coal Tar in the Freeboard of a Fluidized Bed

Abstract: The effects of calcium oxide on tar cracking in the freeboard of a fluidized bed under different freeboard conditions have been investigated in order to reduce or eliminate the tar produced in coal pyrolysis and simultaneously to make coal gas of high qualities. Because no bubbles are in the freeboard, the tar would be contacted well with calcium oxide, and the tar cracking is improved. The results show that tar conversion increases apparently with the addition of calcium oxide, but the effect of calcium oxide on the tar conversion decreases gradually with freeboard temperature and is small above 700 °C, especially when the percentage of calcium oxide is increased from 6% to 12%. At lower freeboard temperature of 650 °C, the effect of calcium oxide on the tar conversion increases with residence time, apparently; however, at 750 °C the effect of calcium oxide on the tar conversion is only apparent at short residence time. The rate of tar cracking can be expressed by a simple first-order reaction, and the a...

Cementitious materials including stainless steel slag and geopolymers

Abstract: Cementitious materials including stainless steel slag and geopolymer can be added to conventional cement compositions, such as Portland cement, as a partial or total replacement for conventional cement materials The stainless steel slag may comprise silicates and/or oxides of calcium, silicon, magnesium, iron, aluminum, manganese, titanium, sulfur, chromium and/or nickel The geopolymer may comprise aluminum silicate and/or magnesium silicate In a preferred embodiment, curing of concrete materials by the action of water on the cementitious materials is enhanced with the addition of an activator component selected from calcium bromide, calcium nitrate, calcium nitrite, calcium chloride, calcium oxide, and sodium bromide

Thermal protective coating for ceramic surfaces

Abstract: A coating admixture, method of coating and substrates coated thereby, wherein the coating contains colloidal silica, colloidal alumina, or combinations thereof; a filler such as silicon dioxide, aluminum oxide, titanium dioxide, magnesium oxide, calcium oxide and boron oxide; and one or more emissivity agents such as silicon hexaboride, carbon tetraboride, silicon tetraboride, silicon carbide, molybdenum disilicide, tungsten disilicide, zirconium diboride, cupric chromite, or metallic oxides such as iron oxides, magnesium oxides, manganese oxides, chromium oxides, copper chromium oxides, cerium oxides, terbium oxides, and derivatives thereof. In a coating solution, an admixture of the coating contains water. A stabilizer such as bentonite, kaolin, magnesium alumina silicon clay, tabular alumina and stabilized zirconium oxide is also added.

Foamed fly ash cement compositions and methods of cementing

Abstract: Methods of cementing and low density foamed cement compositions therefor are disclosed. A low density foamed cement composition of the invention comprises fly ash comprising calcium oxide or calcium hydroxide, water present in an amount sufficient to form a slurry, a foaming and foam stabilizing surfactant or a mixture of surfactants present in an amount sufficient to facilitate foam and stabilize the foamed cement composition, and sufficient gas to foam the foamed cement composition.

High temperature glass fiber insulation

Abstract: Improved glass compositions for glass fibers typically useful for fire resistant blankets or containers to provide high burn-through resistance at temperatures in excess of 2,300°F and typically comprising 10.23% to 81.81% silica, 2.0% to 25.91% alumina, 0% to 12.0% sodium oxide, 0% to 6.0% potassium oxide, 3.0% to 15.0%calcium oxide, 1.80% to 10.50% magnesium oxide, 1.0% to 18.0% ferrous+ferric oxide, and 0% to 4.0% titanium dioxide; the improved glass compositions may include 0% to 9% lithium oxide, 0% to 9% boron oxide, 0% to 5.0% zirconium oxide, 0% to 6.0% manganese oxide, and 0% to 4.0% phosphorous oxide.

Performance of soil stabilization agents

Abstract: Poor subgrade soil conditions can result in inadequate pavement support and reduce pavement life. Soils may be improved through the addition of chemical or cementitious additives. Such chemical additives range from waste products to manufactured materials and include lime, Class C fly ash, portland cement and proprietary chemical stabilizers. These additives can be used with a variety of soils to help improve their native engineering properties. This report contains a summary of the performance of lime, cement, Class C fly ash, and Permazyme 11-X used with a wide range of soils. Each of the chemical additives tested is designed to combine with the soil to improve the texture, increase strength and reduce swell characteristics. These products were combined with a total of eight different soils with classifications of CH, CL, ML, SM, and SP. Durability testing procedures included freeze-thaw, wet-dry, and leach testing. Atterberg limits and strength tests were also conducted before and after selected durability tests. Changes in pH were monitored during leaching. Relative values of soil stiffness were also tracked over a 28-day curing period using the soil stiffness gauge. Lime and cement stabilized soils showed the most improvement in soil performance for multiple soils, with fly ash treated soils showing substantial improvement. The results showed that for many soils more than one stabilization option may be effective for the construction of durable subgrades. The enzymatic stabilizer did not perform as well as the other stabilization alternatives. It is recommended, based on the results of this research, that some testing of the contribution of proposed stabilization agents be conducted prior to construction. For pavement designs that expect a relatively limited strength contribution from the soil, the primary anticipated benefit of stabilization is generally the control of volume change.

Alkali-free aluminoborosilicate glasses and uses thereof

Abstract: An alkali-free aluminoborosilicate glass having a coefficient of thermal expansion α20/300 of between 28×10−6/K and 38×10−6/K, which has the following composition (in % by weight, based on oxide): silicon dioxide (SiO2)>58-65, boric oxide (B2O3)>6-115, magnesium oxide (MgO) 4-8, barium oxide (BaO) 0- 14-25, calcium oxide (CaO) 0-8, strontium oxide (SrO) 26- 3, or aluminum oxide (Al2O3)>14-25, calcium oxide (CaO) 0- 05- 21-25, calcium oxide (CaO) 0-8, strontium oxide (SrO)>26- 3, and which is highly suitable for use as a substrate glass both in display technology and in thin-film photovoltaics

Zinc recovery from spent ZnO catalyst by carbon in the presence of calcium carbonate

Abstract: Zinc recovery from the spent zinc oxide catalyst by carbon in the presence of calcium carbonate was studied using an X-ray diffractometer (XRD), an atomic absorption spectrometer (AAS), and a scanning electron microscope (SEM). The spent zinc oxide catalyst was determined to be composed of 87.5 wt pct zinc oxide and 3.1 wt pct zinc sulfide. The results of X-ray diffractometry revealed that calcium carbonate decomposed to calcium oxide and carbon dioxide; zinc oxide and zinc sulfide were reduced to zinc vapor and carbon monoxide evolving from solid sample; and sulfur content was scavenged as calcium sulfide remained in the solid. Steps involved in this reaction system were summarized to explain the overall reaction. The experimental results of atomic absorption spectrometry showed that the initial rate of zinc recovery and final zinc recovery can be increased by increasing either the sample height, the reaction temperature or the initial bulk density. Furthermore, they were found to increase with decrease in either the argon flow rate, the molar ratio of Zntotal/C, the molar ratio of Zntotal/CaCO3, the grain size of the spent catalyst, the agglomerate size of carbon, or the agglomerate size of calcium carbonate. Empirical expressions of the initial rate of zinc recovery and final zinc recovery have been determined.

Characterization of Ca-Bi-Mo oxide catalyst for selective propane ammoxidation, using XRD, XPS, TPRX/TPRO, and IR/Raman

Abstract: The physicochemical properties of highly active and selective Ca-Bi-Mo oxide for ammoxidation of propane to acrylonitrile were investigated by XRD (powder), IR/Raman, XPS, and TPRX/TPRO (temperature programmed reaction/temperature programmed reoxidation) techniques. It was found that the phases in the Ca-Bi-Mo oxide varied with the composition of the oxide. The modified γ-bismuth molybdate (γ-Bi 2 -MoO 6 ) and defective Ca-Bi-Mo phases produced by addition of Bi oxide played an important role in propane ammoxidation to acrylonitrile. XPS results revealed that the mole ratio of elements on the surface was different from that in the bulk. The concentration of bismuth decreased from the surface to the inner layer of Ca x Bi 1 2 - x Mo 1 2 oxide, while the concentration of calcium increased from the surface to the inner layer. The Ca-Bi-Mo oxide showed good catalytic performance when an appropriate amount of calcium oxide was present on the surface along with Bi and Mo oxides. The addition of Ca oxide into Bi-Mo oxide decreased the number of active sites for complete oxidation and increased the ability of reoxidation (O 2 consumption) of reduced catalysts.

A novel process and appratus for the manufacture of precipitated silica from rice husk ash

Abstract: A novel process for the manufacture of precipitated silica from rice husk ash, having a surface area ranging from 50-400m2/g and tap density of 80-600kg/m3 having multiple applications in the field of rubbers and plastics, paints, toothpastes, catalyst, carrier agent, insulation, stabilizing and desiccants. The process method for silica precipitation is novel, wherein the chemicals used are regenerated making it a closed loop operation. The extraction process is carried out by digesting silica present in rice husk by the addition of sodium hydroxide to manufacture sodium silicate and precipitating silica from sodium silicate by reaction with carbon dioxide. The regeneration of the sodium hydroxide is carried out by reacting the sodium carbonate from the previous step with calcium oxide or calcium hydroxide.

Method of reducing sulfur dioxide emissions of a circulating fluidized bed boiler

Abstract: A method of reducing sulfur dioxide emissions of a circulating fluidized bed boiler. Sulfur-containing carbonaceous fuel is fed to a furnace of the boiler, and calcium carbonate is fed to the furnace at a rate relative to the first stream such that the molar ratio of calcium in the second stream to sulfur in the first stream is at most about 1.0. The fuel is combined so that the sulfur is oxidized to form sulfur dioxide. The calcium carbonate is calcined to form calcium oxide and the calcium oxide is used to sulfate the sulfur dioxide to form calcium sulfate. Flue gas particles are separated using a hot loop separator, and the separated particles are returned to the furnace. A sulfur-reduction stage downstream of the furnace further reduces the sulfur content of the flue gases.

Effect of hydrated lime on ageing behaviour of bituminous mastics

Abstract: Influence of the presence of hydrated lime in filler on short- and long-term ageing behaviour of mastics has been investigated using the RCAT device (Rotating Cylinder Ageing Test). Two fillers (limestone and an active one with 25% of hydrated lime) and four bitumen (several pen-grade and origin) have been examined. Short-term ageing 'RCAT163' and long-term ageing 'RCAT90' were linked up on the same sample. Measured characteristics were penetration, R&B, infrared spectra and some selected rheological properties. Hydrated lime improves the sensitivity to short-term ageing by all35% for Venezuelan bitumen 70/100 and by all15% for Venezuelan bitumen 50/70 and for bitumen 35/50 from the Middle East. Lime almost does not modify it for bitumen 35/50 from Venezuela. For long-term ageing, hydrated lime improves the ageing sensitivity by about 33% in case of higher pen grade bitumen (50/70 or 70/100). There is almost no effect or a slight increase in long-term ageing susceptibility for the harder bitumen (35/50). Some other improvements by lime addition are also stated. For the covering abstract see ITRD E121480.

Reactive separation of CO2 using pressure pelletised limestone

Abstract: Calcium oxide powder derived by the calcination of mesoporous calcium carbonate provides a higher conversion towards carbonation compared to calcium oxide derived from naturally occurring limestone and hydrated lime. Compaction of this high reactivity sorbent was investigated for its use in CO2 separation from flue gas. It was observed that compaction preserved the porosity of the powder. The pellets were able to attain 50–80% conversion towards carbonation over three cycles. The rate and extent of carbonation reaction reduces with increasing pellet thickness. The effect of compaction load and CO2 concentration did not show any appreciable difference in the rate of carbonation. Whereas the mesoporous calcium carbonate pellet showed appreciable drop in carbonation conversion, the pellets made from other precursors, such as natural limestone and hydrated lime, maintained a higher degree of reactivity over three cycles.

Method for producing calcium fluoride, reusing method and recycling method thereof

Abstract: To recycle fluoride by recovering calcium fluoride having a particle size and purity suitable for production of hydrogen fluoride, from a fluoride-containing effluent or a hydrofluoric acid-containing effluent. This method comprises reacting the fluoride-containing effluent or the hydrofluoric acid-containing effluent with an aqueous calcium chloride solution, under an acidic condition with hydrochloric acid where calcium fluoride has a comparatively high solubility. Calcium fluoride having a high purity and a large particle size can be deposited. The hydrochloric acid residues from the reaction or formed through the reaction is reacted with an inexpensive calcium compound such as calcium hydroxide, calcium oxide and calcium carbonate to produce an aqueous calcium chloride solution, and the aqueous calcium chloride solution is reused for the treatment of the hydrofluoric acid-containing effluent. The calcium fluoride obtained can be used as a raw material as it is for producing hydrogen fluoride, and the surplus aqueous calcium chloride solution can be supplied for other industrial uses.

Dirty sludge construction garbage light sinter free brick

Abstract: A non-burning brick is prepared from the mud from sewage treating plant, building garbage, calcium oxide, calcium sulfate, cement, ferrous sulfate, magnesium sulfate, calcium chloride, early strengthening agent MNC-AI, antifreezing agent MNC-C and water through proportionally mixing, die pressing under 25-30 MPa, and natural curing. Its advantages are light weight, high strength, no pollution and low cost.

Performance of Porous CaO Obtained from the Decomposition of Calcium-Enriched Bio-Oil as Sorbent for SO2 and H2S Removal

Abstract: The performance of calcium oxide particles produced from the decomposition of calcium-enriched bio-oil (CEB), the product of the reaction of bio-oil and calcium hydroxide, as a sorbent for the in situ removal of SO2 and H2S from the flue gases of coal combustors and the coal gas produced in coal gasifiers, respectively, is investigated. Reactivity evolution experiments are carried out in a thermogravimetric analysis system using CaO samples prepared through decomposition of calcium-enriched bio-oil applied as a thin coating on a quartz pan or through calcination of two naturally occurring calcitic solids of high CaCO3 content. CEB is converted to CaO in one or two steps, that is, first conversion to CaCO3 in the presence of CO2 and then calcination. Calcination and sulfidation or calcination and sulfation are carried out both sequentially and simultaneously. Because of its high porosity, the CaO material that results from the decomposition of CEB is found to be capable of reaching much higher conversions ...

The effect of quicklime (calcium oxide) as an inhibitor of Burkholderia pseudomallei.

Abstract: Measurement of in vitro activity of quicklime against Burkholderia pseudomallei revealed that quicklime at concentrations of 10% or more was bactericidal for up to 35 d. The effect of quicklime as an inhibitor of B. pseudomallei in soil from a rice field was studied in a laboratory setting. The soil, collected from a rice field in north-eastern Thailand, was mixed with B. pseudomallei. In experiment 1, quicklime was mixed with the soil in different amounts. In experiment 2, quicklime was spread over the soil surface. In experiment 3, quicklime solution was poured onto the soil. It was found that the pH of the soil in experiment 1 was much higher than that in experiments 2 and 3. Only quicklime mixed with soil at a concentration of 40% or more (weight/weight) was effective in inhibiting the growth of B. pseudomallei for up to six weeks.

Method for charging a fiber suspension, and arrangement for carrying out said method

Abstract: Disclosed is a method for charging a fiber suspension containing cellulose fibers with calcium carbonate. Said method comprises the following steps: liquid or dry calcium hydroxide or calcium oxide is introduced into the fiber suspension; gaseous carbon dioxide is introduced into the fiber suspension; calcium carbonate is precipitated by the carbon dioxide; and the fiber suspension is ground during the charging process.

Thermal analysis and X-ray diffraction of synthesis of powellite

Abstract: Scheelite (calcium tungstate)is the product of one of the processing methods of wolframite by its roasting with calcium oxide or limestone or its fusion with calcium chloride, followed by acid processing of calcium tungstate with the formation of tungstic acid. Scheelite occurs in contact metamorphic deposits, hydrothermal veins and pegmatites.

Multiple reaction integrated process for desulfuizing from fume by dry method and its system

Abstract: A multiple reactions integrated process for desulfurizing from the fume by dry method includes such steps as spraying limestone powder in high-temp combustion box from its top to decompose calcium carbonate into calcium oxide and CO2, absorbing SO2 from fume by partial calcium oxide to generate calcium sulfate, spraying water to activate calcium oxide to transform partial calcium oxide to calcium hydroxide and absorb SO2 from fume to generate calcium sulfite, and using the residual calcium hydroxide and calcium oxide to desulfurize the fume in desulfurizing tower. Its system is composed of limestone powder sprayer, moistening flue, desulfurizing tower, external electric duster, draught blower and chimney.

Calcium aluminate clinker as a refractory aggregate with and without barium addition and use thereof

Abstract: The present invention provides for a refractory aggregate composition comprising an improved calcium aluminate clinker having the formula C n A x wherein C is calcium oxide and A is aluminum oxide, wherein n is an integer from about 1 to about 12, wherein x is an integer from about 1 to about 24, and wherein said clinker has from zero to less than about fifty weight percent C 12 A 7 . Analogs, derivatives and hydrates of the improved calcium aluminate clinker are provided. A refractory composition and a sprayable refractory composition are disclosed comprising the improved calcium aluminate clinker. A method for improving the insulating character and/or penetration resistance of a liner in contact with molten aluminum in an aluminum manufacturing process or during aluminum transport is provided.

Attrition resistant, zinc titanate-containing, reduced sulfur sorbents and methods of use thereof

Abstract: Reduced sulfur gas species (e.g., H 2 S, COS and CS 2 ) are removed from a gas stream by compositions wherein a zinc titanate ingredient is associated with a metal oxide-aluminate phase material in the same particle species. Nonlimiting examples of metal oxides comprising the compositions include magnesium oxide, zinc oxide, calcium oxide, nickel oxide, etc.