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.

Limestone Acidification Using Citric Acid Coupled with Two-Step Calcination for Improving the CO2 Sorbent Activity

Abstract: This work investigates the acidification of a natural limestone source using citric acid in order to produce porous calcium oxide (CaO) CO2 sorbent, with good stability in high-temperature operatio...

Low temperature pyrolysis of coal or oil shale in the presence of calcium compounds

Abstract: A coal pyrolysis technique or process is described in which particulate coal is pyrolyzed in the presence of about 5 to 21 wt. % of a calcium compound selected from calcium oxide, calcined (hydrate) dolomite, or calcined calcium hydrate to produce a high quality hydrocarbon liquid and a combustible product gas which are characterized by low sulfur content. The pyrolysis is achieved by heating the coal-calcium compound mixture at a relatively slow rate at a temperature of about 450° to 700° C. over a duration of about 10 to 60 minutes in a fixed or moving bed reactor. The gas exhibits an increased yield in hydrogen and C 1 -C 8 hydrocarbons and a reduction in H 2 S over gas obtainable by pyrolyzing cola without the calcium compound. The liquid product obtained is of a sufficient quality to permit its use directly as a fuel and has a reduced sulfur and oxygen content which inhibits polymerization during storage.

Synthesis, Application, and Carbonation Behavior of Ca2Fe2O5 for Chemical Looping H2 Production

Abstract: Chemical looping hydrogen production uses the oxidation and reduction of metal oxides, typically iron, to produce hydrogen. This work focuses on the modification of iron oxide with calcium oxide to form an oxygen carrier containing dicalcium ferrite (Ca2Fe2O5), which presents favorable thermodynamics for achieving higher conversions of steam to hydrogen, compared to chemically unmodified iron oxide. Different methods of synthesis, viz. mechanochemical synthesis and coprecipitation, were used to produce Ca2Fe2O5, and their resulting performances were compared. Consistent with thermodynamic predictions, it was found that CO2, or steam, was sufficient to fully regenerate the reduced carriers to Ca2Fe2O5. The cyclic stability of the oxygen carriers were studied in fluidized bed reactors and by thermogravimetric analysis (TGA). Good stability of the materials was observed for up to 50 cycles, with no evidence of agglomeration, even up to 950 °C. The rate of deactivation was found to correlate with the purity o...

Stabilization of Soft Clay Subgrades in Virginia: Phase I Laboratory Study

Abstract: Many pavement subgrades in Virginia consist of wet, highly plastic clay or other troublesome soils. Such soils can be treated with traditional lime and cement stabilization methods. Alternatives, including lignosulfonates and polymers, are available, but their performance record is mixed and solid engineering data are lacking, which prevents reliable design. The goal of this research was to screen a suite of traditional and non-traditional stabilizers against three Virginia soils that have caused problems during construction or resulted in poor performance in service. The selected stabilizers were: quicklime, hydrated lime, pelletized lime, cement, lignosulfonate, synthetic polymer, magnesium chloride, and a proprietary cementitious stabilizer. A laboratory procedure was developed and applied to three Virginia soils obtained from Northern Virginia, Staunton, and Lynchburg. Key findings from the research include: (1) traditional lime and cement stabilizers were far more effective than liquid stabilizers (lignosulfonate, synthetic polymer, and magnesium chloride) in increasing strength; (2) the liquid stabilizers were ineffective on soils with a high moisture content; (3) the proprietary cementitious stabilizer was more effective in increasing strength than lime for all cases tested but was not as effective as the cement stabilizer; (4) quicklime and hydrated lime increased the workability of the soils although they did not produce strengths comparable to cement; (5) the strength of soils stabilized with cement and the proprietary cementitious stabilizer can be estimated based on the water-amendment ratio of the mixture; and (6) the strength of soils stabilized with lime can be estimated based on a combination of the plasticity index and the water-amendment ratio of the mixture. The benefits of subgrade stabilization are that it improves the strength, stiffness, and durability of soft subgrade soils. Such improvement allows a reduction in the required thickness of overlying pavement courses and/or an increase in pavement life. Quantifying the life cycle cost benefits requires performing pavement design studies based on anticipated traffic levels, desired serviceability, etc. The preferred design method would be a mechanistic design, which requires resilient modulus values for the stabilized subgrade and other pavement layers. Neither resilient modulus testing nor pavement design studies were included in the scope of the work for this project, but they should be included in subsequent phases.