Calcium oxide

About: Calcium oxide is a research topic. Over the lifetime, 7600 publications have been published within this topic receiving 66104 citations. The topic is also known as: caustic lime & quicklime.

Phase Diagram Approach to the Fluxing Effect of Additions of CaCO3 on Australian Coal Ashes

Abstract: This paper presents a phase diagram approach to predict the melting temperatures of coal ash/flux mixtures and the viscosity versus temperature characteristics of the molten slags. This is illustrated by calcium oxide fluxing studies of three Australian bituminous coal ashes covering a range of silica to alumina ratios. Reasonable agreement was obtained between the observed melting temperatures of the calcium oxide/coal ash mixtures and predictions based on equilibrium phase diagrams for the ternary system silica, alumina, and calcium oxide or for the quaternary system silica, alumina, calcium oxide, and ferrous oxide. The approach is supported by energy dispersive scanning electron microscopy (SEM), SEM microprobe, and X-ray diffraction (XRD) studies of the slags. Slag viscosity measurements were made with a rotational viscometer over the range 1200−1600 °C. The measured viscosities were compared with predicted values using a model based on experimental results for the ternary system silica, alumina, and...

Eggshell waste to produce building lime: calcium oxide reactivity, industrial, environmental and economic implications

Abstract: Eggshells wastes are produced in huge amounts worldwide. The recycling or valorization of this waste, which otherwise is usually disposed in landfills, represents an opportunity within a circular economy perspective. In the present work, the potential of chicken eggshell waste to produce calcitic lime was explored. After collection from an industry supplier, the waste was thoroughly characterized for its mineralogical, chemical, and thermal properties. The material was calcined at 1000 °C, and the obtained calcium oxide was evaluated for its reactivity in wet slaking tests. Comparison was made with commercial limestone used as reference. It was found that the calcium oxide from eggshell waste belonged to the most reactive class (R5—60 °C within 10 min), the same of the calcium oxide from limestone. However, different times were obtained to reach 60 °C (25 s and 4:37 min:s) and for 80% of the reaction (28 s and 5 min) for calcium oxide from limestone and eggshell waste, respectively. The lower reactivity of calcium oxide from eggshell waste was related to its larger size particles with smoother surfaces and lower specific surface area in comparison to limestone calcium oxide. Industrial, environmental and economic implications concerning the use of this waste to produce lime were also evaluated. The eggshell waste could be all consumed at an industrial scale in Portugal allowing for approximately 2.6% partial substitution of limestone in a lime factory.

Thin tin-oxide film alcohol-gas sensor

Abstract: Alcohol-gas sensors have been fabricated from thin-film tin oxide. The thickness of the tin-oxide film is 500A˚. The sensor electrode has been formed by evaporating 500A˚of titanium and 1000A˚of platinum on to the tin-oxide film by using an electron-beam evaporator. Calcium oxide and aluminium have been used as dopants for improving the sensor characteristics. It is found that by doping the sensor with 2% calcium oxide, the operating temperature can be reduced from 500°C to 200 or 300°C, and the sensitivity and selectivity of the sensor are enhanced. The sensor has a linear response to alcohol concentration from 1 to 10% by volume. The sensor has been also employed in testing the alcohol concentration in commercial wines. The results obtained from the gas sensor correlate with the value labelled on the wine bottles.

An evaluation of lime and cement stabilization

Abstract: Stabilization of clay materials is of interest to any engineer who must deal with this type of soil. Stabilization techniques can be mechanical or chemical, or both, but the addition of a stabilizing agent is generally the favored approach. Lime in one form or another has been the most widely used stabilization agent for clay. However, portland cement to stabilize clay has been promoted and used in some applications. It was the purpose of this research to define the effectiveness of hydrated lime and portland cement on three Texas clays. Variables evaluated included two levels of treatment, two levels of pulverization, two compaction efforts, two moisture conditions, and a range of curing times. On the basis of the results and conditions of this test program, lime treatment of expansive, high-plasticity soils was more favorable for compressive strength attainment than was cement treatment of these soils. In general, lime treatment produced higher dry-conditioned strengths, but the major advantage was in the wet-conditioned strengths. Lime treatment provided significantly better resistance to moisture damage when these soils were compacted by the modified compactive effort. Cement treatment of low-plasticity sandy clay produced significantly higher compressive strengths than did lime treatment of this soil.