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.

Engineering Properties and Moisture Susceptibility of Silty Clay Stabilized with Lime, Class C Fly Ash, and Cement Kiln Dust

Abstract: A laboratory study was undertaken to evaluate the effectiveness of different percentages of hydrated lime, class C fly ash (CFA), and cement kiln dust (CKD) as soil stabilizers Cylindrical specimens were compacted and cured for 28 days in a humidity room having a constant temperature and controlled humidity At the end of the curing period, specimens were tested for resilient modulus ( Mr ) , modulus of elasticity ( ME ) , and moisture susceptibility using tube suction test The study revealed that the values of Mr , ME , and unconfined compressive strength (UCS) for the stabilized specimens increased with the increase in the amount of the stabilizing agent It was also found that the increase in Mr , ME , and UCS values varies with the type of stabilizing agents The CKD-stabilized specimens exhibited a higher increase in Mr , ME , and UCS values than the corresponding values of lime- and CFA-stabilized specimens Additionally, CKD-stabilized specimens exhibited the least moisture susceptibility in term

Reactivity of lime and related oxides. II. Sorption of water vapour on calcium oxide

Abstract: Calcium oxide samples differing widely in surface activity (specific surface 1 to 100 m.2g.−1) have been hydrated by exposure to water vapour at room temperature. Although the rates of hydration differ considerably, each sample takes up in chemical combination a stoicheiometric quantity of water but, in further uptake of water by the newly formed calcium hydroxide by physical adsorption, the isotherm gives no ‘stepwise’ evidence of formation of the alleged hemi-hydrate, Ca(OH)2,0.5H2O. Changes in surface area and lattice structure during hydration indicate that the most active limes become aged (agglomerated) rapidly in the presence of water vapour, and must be hydrated at very low relative pressures to maintain the same number of crystallites; limes of moderate activity can be hydrated without ageing; the least active limes undergo hydration only when the number of crystallites increases, the necessary fission of the original crystallites being accompanied by slow rates of hydration. Progressive changes in surface area during hydration are related to the volumes of the oxide and hydroxide on the basis that the reaction proceeds inwards from the outside of each particle by an advancing interface mechanism.

Production of epoxy compounds from olefinic compounds

Abstract: Chlorine and tertiary alkanol dissolved in an inert organic solvent are reacted with calcium oxide in aqueous calcium chloride to produce tertiary alkyl hypochlorite which is recovered in the organic solvent and reacted with water and olefinically unsaturated compound to produce chlorohydrin and tertiary alkanol. Chlorohydrin and tertiary alkanol recovered in the organic solvent are contacted with calcium oxide in aqueous calcium chloride to produce the epoxy compound, and tertiary alkanol recovered in the organic solvent is recycled to hypochlorite production. Calcium chloride produced as by-product in the hypochlorite production and saponification is recovered as an aqueous solution having a calcium chloride concentration of at least 25 wt. % to provide calcium chloride in a usable form.

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.