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.

Solid-phase synthesis of calcium carbide in a plasma reactor

Abstract: A laboratory-scale spout-fluid bed reactor with a dc plasma torch was used to study the solid-phase synthesis of calcium carbide Calcium oxide powder with a mean particle size of 170 μm was reacted with graphite powder (130 μm) Argon was used to initiate the plasma and hydrogen gas was then added to increase power and raise the plasma jet enthalpy Experimental results showed that the reaction took place in the vicinity of the plasma jet and that conversion to calcium carbide increased linearly with reaction time The rate of conversion increased exponentially with plasma jet temperature, indicating that chemical reaction was the controlling mechanism Microscopic analysis of the solid product showed that calcium carbide was formed around both reactants, and that the reaction followed a shrinking core model Although melting and agglomeration of partially reacted particles occurred at high temperature, resulting in instability of the bed and impeding the reaction progress, high conversions are expected in a continuous process with optimized reactor design

Calcium Absorption from Corn Tortilla Is Relatively High and Is Dependent upon Calcium Content and Liming in Mexican Women

Abstract: Corn tortillas are the staple food of Mexico. During their preparation, calcium is added to the tortillas; therefore, tortillas are the main source of calcium for a large proportion of the population. The bioavailability of calcium from lime-treated tortillas in humans is not known. The objectives of the present study were to determine calcium absorption from corn tortilla, to determine the effect of lime treatment on calcium absorption from corn tortilla, and to compare calcium absorption from tortilla prepared with a commercial corn flour and tortillas prepared with the traditional lime treatment at home. Nonpregnant, nonlactating women (n = 9) were administered 3 different treatments: 1) 180 g of corn tortilla prepared from corn flour with no lime treatment (CF), 2) 180 g of corn tortilla prepared from lime-treated commercial corn flour (LTCCF), or 3) 180 g of corn tortillas prepared from lime-treated home-prepared corn flour (LTHCF). Calcium absorption was measured using an established dual-tracer stable isotope technique. Calcium absorption of CF, LTCCF, and LTHCF was (mean +/- SD): 44 +/- 3.2, 32 +/- 4.4, and 30 +/- 2.4%, respectively; the fractional calcium absorption from CF differed from that of either LTCCF or LTHCF (P < 0.01). The total amount of calcium absorbed per treatment was higher in LTHCF (98.10 mg +/- 21.7) than in LTCCF (59.9 mg +/- 23.7, P < 0.001) and CF (3.78 mg +/- 0.9, P < 0.0.001). In conclusion, calcium absorption from corn tortillas is high and dependent on calcium concentration. The addition of calcium during lime treatment increases calcium concentration and total calcium absorption.

Equilibria in the silicothermic reduction of calcined dolomite

Abstract: When a mixture of calcium oxide and silicon is heated to above 1000°C a liquid Ca-Si alloy is formed. When magnesium metal is produced by reacting calcined dolomite with silicon, the alloy still forms and is the effective reducing agent for magnesium oxide. In this investigation the thermodynamic data on the Ca-Si alloys have been related to the magnesiumproducing reaction, the calcium pressures over mixtures CaO + Si were measured using a Knudsen cell, and the magnesiumand calcium pressures over the mixtures CaO + MgO + Si were measured using the transportation method. The magnesium content of the equilibrium alloy was determined isopiestically and the identity of the silicate was established. The results constitute a complete and consistent definition of the equilibria in the magnesium production reaction, and have also yielded an improved value of thefree energy of formation of calcium orthosilicate.

Pelletizing and Coating of Synthetic Zirconia Stabilized Calcium-Based Sorbents for Application in Calcium Looping CO2 Capture

Abstract: Calcium oxide (CaO) has been investigated as a high-temperature performance sorption material for carbon capture due to its high carbon dioxide (CO2) capacity, low cost, and environmental benignity. Unfortunately, commercialized application of CaO materials has been hindered by severe capacity loss during cycling operations. In an attempt to overcome these problems, this study investigated the effects of adding zirconia-based ceramic dopants and coating sorbents with highly crystalline zirconium dioxide (ZrO2) layers derived from the hydrolysis of zirconium butoxide to control the growth of ZrO2 crystals. Uncoated natural Cadomin delivered a high CO2 capture capacity of more than 13 mol CO2/kg, while the zirconia-coated sorbents showed excellent cycling stability corresponding to a maximum capacity of retention of 79% after 21 cycles at high temperatures. More importantly, the highly crystalline ZrO2-coated sorbents doped by zirconia-based sorbents exhibited a significantly lower decay capacity compared t...