Showing papers on "Calcium oxide published in 1978"

Composite dental material

Abstract: An improved composite dental material includes an inorganic component of glass particles separated into two interconnected vitreous phases which have been etched to produce a porous surface layer. The inorganic glass particles are combined with an organic resin to provide the composite dental material. Preferable glass compositions include a mixture of silicon dioxide, boron oxide, aluminum oxide and strontium oxide, with one or more from the group of calcium oxide, zinc oxide, stannic oxide, and zirconium oxide as optional modifying ingredients.

Method of reducing the sulfur oxide content of combustion gases resulting from combustion of sulfur-containing fossil fuels

Abstract: Sulfur-containing fossil fuels are combusted in the presence of calcium carbonate or calcium magnesium carbonate, whereby the sulfur oxides formed by combustion react with the calcium oxide or calcium magnesium formed from the carbonate during the combustion, thereby to form calcium sulfate or calcium magnesium sulfate. The sulfur oxide content of the combustion gas is thereby reduced. The calcium oxide or calcium magnesium oxide is removed from the combustion, and is slaked with water to form the corresponding hydroxide. This hydroxide is recycled to the combustion zone or to the combustion gases emanating from the combustion zone, whereby the quantities of the carbonate used in the combustion can be reduced.

Activation of calcium oxide as a sorbent

Abstract: The sorbent capacity of calcium oxide with respect to sulfur dioxide is increased by calcining limestone or dolomite in an atmosphere where the partial pressure of carbon dioxide is greater than 40 percent of the equilibrium partial pressure of carbon dioxide over calcium carbonate at the reaction temperature. Where dolomite is the starting material, it may be calcined in a two-step heating process in which the atmosphere during the first heating stage contains carbon dioxide and the temperature is maintained in the dissociation range of magnesium carbonate (Mg CO3); the atmosphere of the second heating stage also contains carbon dioxide, but the temperature is maintained in the calcium carbonate (CaCO3) dissociation range. Calcium oxide so produced in such an atmosphere of carbon dioxide sufficient to delay calcination is found to have relatively large mouthed pores capable of sorbing increased amounts of sulfur.

Process for converting coal ash slag into portland cement

Abstract: Disclosed is a manufacturing process for converting coal ash slag from a slagging coal gasifier into a marketable cement product having the characteristics and qualities of portland cement. This process comprises the steps of transferring molten slag from a slagging coal gasifier to a melt chamber and reacting it with a mineral containing lime, for example: calcium oxide, calcium hydroxide or calcium carbonate, to form a homogeneous cement product. This cement product is then transferred to a quench chamber where it is allowed to cool and solidify in the form of clinkers, which are later reduced to powder form. This process also provides an efficient means to conserve energy when producing a portland cement and provides an effective and economical way to dispose of a waste product while increasing the cost efficiency of a slagging coal gasifier.

Process for the selective ortho-alkylation of phenolic compounds

Abstract: This invention relates to a process for the selective ortho-alkylation of a phenolic compound having at least one ortho-positioned a hydrogen atom by catalytically reacting the phenolic compound with an alcohol in the vapor phase. In this process, the reaction of the phenolic compound with the alcohol is carried out at a temperature of from 300° to 550° C. in the presence of a mixed oxide catalyst of manganese, silicon, and one or more additives selected from the group consisting of magnesium oxide, calcium oxide, strontium oxide, and barium oxide. The catalyst used in this invention exhibits not only excellent catalytic activity in the selective ortho-alkylation of phenols but also continuous stability of the activity, good shapability, and good mechanical strength.

Solid closed ended tubular oxygen sensor

Abstract: A solid closed ended tubular oxygen sensor element, particularly useful for sensing the oxygen content of exhaust gases from internal combustion engines. The closed end of the tubular element which is adapted to be exposed to the hot exhaust gases is made of zirconium oxide stabilized with yttrium oxide and/or ytterbium dioxide. The remaining main portion of the tubular element is made of zirconium dioxide stabilized with calcium oxide. The invention also provides methods of manufacturing these tubular elements.

Deformation of lime modified clay after freeze-thaw

Abstract: The addition of small quantities of lime to a subgrade soil greatly improves its resistance to deformation which has been found to be extremely useful during construction under wet conditions. Soil suction, dynamic strength, and resilient characteristics of a glacial till commonly used for highway subgrade construction were studied experimentally. Changes in material properties resulting from variations in water content, lime content, confining pressure, and deviator stress intensity before and after subjecting the material to freezing and thawing were the variables considered. The results of the study indicated that the resilient characteristics of the till were so greatly improved due to the addition of lime that under certain conditions, a lime stabilized layer within a pavement structure would likely fail in tension and that the material could eventually behave essentially as a granular material.

Process of melting down and purifying silicon

Abstract: A process of melting down and purifying silicon, which comprises melting silicon in at least half of the amount up to double of the amount of a silicate melt heated by resistance heating up to a temperature of at least 1,420° C., said melt consisting of 2-30% by weight of calcium oxide, 5-35% by weight of magnesium oxide, wherein the sum of calcium oxide and magnesium oxide will be 15-38% by weight, 0.5-28% by weight of aluminum oxide and 45-70% by weight of silicon dioxide, and wherein, to the melt are added at least 0.29% by weight of elementary and/or chemically bound copper, preferably 0.50-3% by weight, calculated on the silicon amount.

Gas-solid reactions II: Reduction of cobalt sulfide in the presence of calcium oxide

Abstract: The results of an experimental program to test the applicability of the grain-cell model to complex gas-solid reactions are presented. The hydrogen reduction of solid cobalt sulfide (CO9/8S) in the presence of calcium oxide was chosen for study. Powders of both solids were mixed in a molar ratio of 3.0 (CaO:Co9/8S), compressed into pellet form, then reduced by hydrogen in the temperature range 600-800°C. The experimental results at different operating conditions were compared with the grain-cell model, using the Thiele type modulus (H) as an adjustable parameter. In the presence of excess calcium oxide, the structural-kinetic parameter (γ) was essentially zero, and (H) was found to be the effective parameter, controlling reduction rates. Good agreement between experimental results and model was obtained.

Lateritic soil as a raw material for building blocks

Abstract: High strength building blocks can be produced from mixtures of slaked lime and lateritic soil compacted at high pressure and moist-cured at temperatures between 80 degrees and 100 degrees C Other technical properties such as elasticity, shrinkage, water adsorption and resistance to efflorescence appear to be satisfactory A hydraulic binder mineral, C3AH6 (tricalcium aluminate hexahydrate) is formed directly by reaction between slaked lime and kaolinite in lateitic soils when the compacted mixtures are cured between 80 degrees and 100 degrees C

Process for producing synthetic magnesite - dolomite sinter

Abstract: A method of increasing the magnesia content in dolomite sinter produced from dolomite. Crushed dolomite is calcined to form a physical mixture of particulate magnesium oxide (MgO) and calcium oxide (CaO) and the mixture is hydrated to develop a size differential between the calcium hydroxide and the magnesium hydroxide. The hydroxides are dried without dehydration and separated into two component portions on the basis of size. One portion of the mixture is rich in Ca(OH) 2 and the other is rich in Mg(OH) 2 . The portion of the mixture primarily comprised of Mg(OH) 2 is then calcined to form the synthetic sinter.

Comparison of various carbonates as absorbents of sulfur dioxide from combustion gases

Abstract: Sulfur dioxide combines best with magnesium oxide obtained by calcination of magnesite at 750/sup 0/C. Sulfonation of magnesite at 750/sup 0/C yields a mixture of oxide and sulfate of magnesium with some carbonate and calcium oxide and sulfate. FeO . Fe/sub 2/O/sub 3/ is also present. In the first stages CaO is more active than MgO, but with the increasing conversion the difference in their reaction rates is reduced. Soda shows a much higher activity toward SO/sub 2/ than Mg and Ca carbonates. The reactivity is one to two orders higher than for the most active CaO. Soda remains active even at conditions of high conversion of the carbonate.

Flux for use in centrifugal casting of bimetallic pipes

Abstract: Disclosed is a flux intended for use in centrifugal casting of bimetallic pipes and comprising calcium oxide, silicon oxide, boron oxide, sodium oxide and sodium fluoride, said components being contained therein in the following amounts: Percent by weight CaO, the base SiO 2 : . . 7 to 10 B 2 O 3 . . . 10 to 12 Na 2 O . . . 18 to 24 NaF . . . 20 to 25

Thermistor for high temp. use - employing mixts. of terbium oxide and ytterbium oxide

Abstract: Thermistor for use at high temps. contains a sintered mixt. of terbium oxide and ytterbium oxide. The pref. thermistor contains 10-90 atomic % terbium, and may also contain up to 2 wt.% calcium oxide. Used for temp. measurement and control above 200 degrees C, esp. for exhaust gas purificn. of motor vehicles; glass melting furnaces; domestic ovens; or in the metallurgical and chemical industries.

Method and apparatus for producing metallic calcium

Abstract: PURPOSE:To efficeintly recover high grade metallic calcium by mixing calcium oxide powder with carbon powder; granulating the mixt. with a binder; contacting the granules with a plasma flame; and rapidlyy cooling the granules with an inert gas.

Process for pelletizing and neutralizing solid mixtures of metal chlorides

Abstract: A process is provided wherein solid mixtures of metal chlorides of, for example, ferric chloride, ferrous chloride, vanadium chloride and chromium chloride are (1) mixed with an alkaline material such as, for example, calcium oxide, calcium hydroxide and calcium carbonate, followed (2) by adding water to the resulting mixture to granulate said mixture whereby the metal chlorides are rendered substantially insoluble in water.

Method of accelerating the hardening and increasing the strength of Portland cement

Abstract: Method for accelerating the hardening and increasing the strength of Portd cement by mixing Portland cement with water and with a mixture containing dialuminum pentahydroxychloride, calcium sulfate and calcium oxide in weight ratios of 1:3.5 to 4.3:1.3 to 1.8, respectively, and up to 2 parts by weight of an alkali metal nitrite at temperatures up to 90° C. and thereafter hardening the mixture at temperatures up to 100° C. The mixing can be carried out either by wet mixing or dry grinding the ingredients.

Method for regenerating calcium sulfoxy compounds produced in the combustion of carbonaceous fuels in fluidized beds

Abstract: In methods for combusting carbonaceous sulfur-containing fuels in a fluidized bed wherein the fluidized bed contains at least one calcium compound selected from the group consisting of calcium oxide, calcium hydroxide, calcium carbonate and calcium bicarbonate to absorb sulfur oxides formed during the combustion of the carbonaceous fuel thereby producing calcium sulfoxy compounds having the formula CaSO x wherein x is 3 or 4, an improvement comprising (a) withdrawing a stream of fluidized bed solids containing said calcium sulfoxy compounds and mixing the fluidized bed solids and said calcium sulfoxy compounds with water to produce a slurry; (b) reacting the CaSO x compounds with NH 3 , H 2 O and CO 2 to produce water-soluble ammonium sulfoxy compounds such as NH 4 (HSO x ) where x is 3 or 4 and CaCO 3 ; and (c) separating the ammonium sulfoxy compounds from the fluidized bed solids and CaCO 3 .

Admixture for obtaining rapid hardening portland cement and a method by which it is to be performed

Abstract: Composition for obtaining rapidly hardening portland cement containing caum sulfate and calcium oxide wherein active di-aluminium trioxide is included in the form of di-aluminium pentahydroxychloride having the weight ratio of Al 2 O 3 :CASO 4 :CaO equal to 1:3.5 to 4.3:1.3 to 1.8. A method by which the composition is to be utilized, wherein 4 to 8 parts by weight of the composition are mixed with water, and initially introducing the dialuminium pentahydroxychloride. After its dissolution there are added, in succession, the calcium sulfate and the calcium oxide which are stirred and mixed with 100 parts by weight of pure clinker portland cement having a strength not less than 350. With the mixture thus obtained there are mixed cement pastes, cementsand mortars and concretes.

Reactivity of Lime and Related Materials with Sulphur Dioxide

Abstract: Dynamic TG studies were made on the uptake of sulphur dioxide by lime and related materials used as absorbents for the desulphurisation of industrial flue gases. Samples of quicklime, hydrated lime, limestone, magnesite and dolomite of widely different surface areas and particle sizes were calcined on a mass-flow balance in atmospheres containing various amounts of sulphur dioxide. Their relative effectiveness in reacting with sulphur dioxide could be seen rapidly by comparing the reaction rates with temperature and gas composition for each solid reactant. This indicated that only calcium oxide or calcium hydroxide could be reasonably considered as industrial desulphurising agents for use below 500°C. The greater reactivity of the hydrated lime samples at temperatures lower than those required for the other absorbents was related to the simultaneous formation of activated quicklime, especially at temperatures above 400°C.

Purification of recovered lactam

Abstract: PURPOSE:To obtain high quality lactam, by dispersing magnesium oxide or calcium oxide in the aqueous solution of crude lactam before the purification of the recovered lactam, adding an alkali metal hydroxide to the dispersion, and separating the produced floc. CONSTITUTION:The recovered lactam especially obtained by the depolymerization of polycapramide with a phosphoric acid catalyst is purified by the following procedures. Magnesium oxide or calcium oxide is dispersed in the aqueous solution of the recovered crude lactam, an alkali metal hydroxide is added to the dispersion, and the produced floc (agglomerate) is separated. After the removal of the floc, the product is if necessary subjected to the activated carbon treatment, ion exchange treatment, etc., concentrated, and distilled under reduced pressure to obtain purified lactam. The concentration of the aqueous solution of the crude lactam is 20-50wt%, the particle diameter of magnesium oxide or calcium oxide is <=150mu, and the amount of the magnesium oxide, etc. is 0.05- 10wt% of the lactam.

Treating method for exhaust gas

Abstract: PURPOSE:To make harmful components of exhaust gas harmless efficiently by use of a catalyst consisting principally of aluminum oxide, and contg. calcium oxide and one or more kinds of platinum gr. elements.

Chemical detoxification of exhaust gases - by reaction of calcium oxide and aluminium powder with water

Abstract: Toxic exhaust gases of internal combustion engines and stationary heating installations are detoxified by the use of calcium oxide and/or of earth alkaloid oxides in conjunction with water or steam, when the oxides react to hydroxides. Pref. the earth alkaloid is Al powder. The reaction of oxides to hydroxides in the presence of water produces a large increase in their surface area so the detoxification capacity of the molecules is greatly improved.