Showing papers on "Calcium oxide published in 2013"

Transient studies of low-temperature dry reforming of methane over Ni-CaO/ZrO2-La2O3

Abstract: The low temperature reforming of methane by carbon dioxide is studied over a calcium oxide promoted Ni catalyst supported on a tetragonal zirconia stabilized by lanthana, which presents an improved stability compared to the non-promoted catalyst. Steady-state catalytic activity measurements, diffuse reflectance infrared Fourier transform spectroscopic analysis and isotopic temporal analysis of products experiments reveal the occurrence of a bifunctional mechanism on the promoted catalyst: methane is activated on the Ni particles, carbon dioxide interacts with the calcium oxide to form carbonates which scavenge carbon from nickel at the Ni-O-Ca interphase, thus restoring Ni particles to the original state. This is assumed to hinder the formation of deactivating coke, which explains the improved catalytic stability of the promoted catalyst. The main route for the carbon deposit formation is found to be the methane cracking in spite of the low temperature reaction.

Nano-mechanical characterization of synthetic calcium–silicate–hydrate (C–S–H) with varying CaO/SiO2 mixture ratios

Abstract: Synthetic calcium silicate hydrate (C–S–H) made with calcium to silicate (C/S) mixture ratios of 0.9, 1.2 and 1.5 respectively is characterized. C–S–H was produced by extracting calcium oxide (CaO) from calcium carbonate (CaCO3) and then mixing it with micro-silica (SiO2) and deionized water to make slurry. The slurry was continuously mixed for 7 days, then the excess water was removed and thermo gravimetric analysis (TGA) was conducted. The drying method was equilibrated to 11% relative humidity (RH). The stoichiometric formula of the synthetic C–S–H were approximated as C0.7SH0.6, C1.0SH0.8 and C1.2SH2.4 for C/S mixture ratios of 0.9, 1.2 and 1.5 respectively. The dried powders were characterized using X-ray diffraction analysis (XRDA), and 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The powders were also compacted with 95 MPa pressure and nanoindentation of the compacted specimens were then undergone to mechanically characterize the synthetic C–S–H. The experiments provide insight on the nanoscale mechanical characteristics of C–S–H.

System and method for treatment of produced waters

Abstract: The systems and methods disclosed herein process produced/flowback water, such as high total dissolved solids produced water, to generate high purity, high value products with little to no waste. The generated high purity, high value products include caustic soda, hydrochloric acid, and/or sodium hypochlorite. Further, the methods and systems disclosed herein generate high quality brine for electrolysis through the systematic removal of contaminants such as but not limited to suspended solids, iron, sulfides, barium, radium, strontium, calcium, magnesium, manganese, fluoride, heavy metals, organic carbon, recoverable hydrocarbons, silica, lithium, and/or nitrogen containing compounds. Further, some products generated by the systems and methods disclosed herein may be recovered and reutilized or sold for other uses, such as carbon dioxide, calcium oxide, chlorine, magnesium oxide, calcium carbonate, and/or barium sulfate.

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...

Phosphorus Sorption and Lime Requirements of Maize Growing Acid Soils of Kenya

Abstract: In Kenya, maize (Zea mays L.) is mainly grown on acid soils in high rainfall areas. These soils are known for low available phosphorus (P), partly due to its sorption by aluminium (Al) and iron oxides. The study determined soil P sorption, lime requirements and the effects of lime on soil pH, Al levels and available P on the main maize growing acids soils in the highlands east and west of Rift Valley (RV), Kenya. Burnt lime containing 21% calcium oxide was used. The soils were strongly to extremely acid (pH 4.85-4.07), had high exchangeable Al 3+ (> 2 cmol Al kg -1 ) and Al saturation (> 20% Al), which most maize germplasm grown in Kenya are sensitive to. The base cations, cation exchange capacity and available P (< 10 mg P kg -1 bicarbonate extractable P) were low, except at one site in the highlands east of RV indicative with history of high fertilizer applications. Highlands east of RV soils had higher P sorption (343-402 mg P kg -1 ) than the west (107-258 mg P kg -1 ), probably because of their high Al 3+ ions and also the energies of bonding between the soil colloids and phosphate ions. Highlands east of RV also had higher lime requirements (11.4-21.9 tons lime ha -1 ) than the west (5.3-9.8 tons lime ha -1 ). Due to differences in soil acidity, Al levels and P sorption capacities within and between highlands east and west of RV, blanket P fertilizer and lime recommendations may not serve all soils equally well.

PREPARATION OF CALCIUM OXIDE FROM Achatina fulica AS CATALYST FOR PRODUCTION OF BIODIESEL FROM WASTE COOKING OIL

Abstract: Preparation of calcium oxide from Achatina fulica shell has been carried out systematically by decomposition for 3 h at various temperatures i.e. 600, 700, 800 and 900 ?C. Formation of calcium oxide was characterized using XR diffractometer. The calcium oxide obtained with the optimum temperature decomposition was characterized using FTIR spectroscopy to indicate the functional group in the calcium oxide. The results showed that XRD pattern of materials obtained from decomposition of Achatina fulica shell at 700 ?C is similar with XRD pattern of calcium oxide standard from Joint Committee on Powder Diffraction Standards (JCPDS). The IR spectra of calcium oxide appear at wavenumber 362 cm-1 which is characteristic of CaO vibration. Application of calcium oxide from Achatina fulica shell for synthesis of biodiesel from waste cooking oil results in biodiesel with density are in the range of ASTM standard.

Thermodynamic and Kinetic Study of CO2 Capture with Calcium Based Sorbents: Experiments and Modeling

Abstract: The steam gasification of biomass in the presence of calcium oxide offers a viable route for the dual purpose of hydrogen production and carbon dioxide (CO2) capture. Although previous studies have dealt with experimental and intrinsic rate constants of carbonation and calcination of calcium looping cycles, the data has not been compared with thermodynamic or kinetic simulation. In this study, the thermodynamic and kinetic simulation of the CO2 capture process using two calcium-based sorbents (i.e., Imasco dolomite and Cadomin limestone) have been studied using Aspen Plus software. The thermodynamic simulation was able to predict the overall trend of the CO2 adsorption on dolomite and limestone. However, a kinetic model was also applied to achieve a more accurate analysis. The results show good agreement between the modeling and the experimental data obtained using a thermogravimetric analyzer (TGA). A shift in the reaction mechanism was observed with respect to temperature. The experimental data and kine...

Effect of lime treatment on geotechnical properties of Dunkirk sediments in France

Abstract: The increasing cost associated with high-quality materials has lead to the need for sediments to be treated and then used in road construction in the context of durable development. Therefore, the modification and stabilisation of Dunkirk marine sediments by using lime is necessary to study for their potential use in road construction. Based on the physical characteristics of untreated sediments, a series of laboratory tests to investigate the geotechnical properties of untreated sediments and lime-treated sediments, such as unconfined compressive strength tests, standard oedometer tests, direct shear tests and triaxial tests, were performed. Lime was added in percentages of 3% and 6%, by weight of dry sediments. The test results show a significant improvement in unconfined compressive strength and shear strength due to the addition of lime. From the strain–stress relationship of compressive strength tests, it can be found that the failure mode of solidified sediments develops gradually from plastic failu...

CaO-based sorbents for CO2 capture prepared by ultrasonic spray pyrolysis

Abstract: We report the ultrasonic spray pyrolysis (USP) synthesis and characterization of composite calcium oxide-based sorbents for carbon dioxide capture. Inclusion of a small amount of Al2O3 into the CaO matrix (as low as Al/Ca: 0.03) yielded significant enhancement of resistance to recycling degradation. The effective homogenous dispersion of additives in the CaO matrix and the relatively high surface area materials obtained via USP explain the sorbent's high performance. All materials were characterized by XRD, STEM, TEM, SEM, and TGA (for CO2 uptake measurements). Two common phases of CaAlxOy, Ca12Al14O33 and Ca3Al2O6, were formed during multiple cycles of calcination and CO2 uptake.

Pozzolan-quicklime binder

Abstract: The Invention employs direct use of ground quicklime with pozzolan(s) according to its own principles for attaining highest compressive strengths with a determined optimum content (rate) by binding more amounts of active calcium oxide to pozzolan(s) and obtains higher strength cements compared to the known ones and by inclusion of portland products, calcium sulphates resources, activators, chemical additives and other materials enhances higher strengths and properties. With Invention's quicklime based methods, 18%-38% more active calcium oxide compared to hydrated lime practices can be bound in the reaction for developing stronger ties to reach to compressive strengths and properties that could satisfy almost all market needs expected from general purpose cements in more economically and most environmentally friendly manner.

Shear Strength Parameters of Improved Peat by Chemical Stabilizer

Abstract: The present research aimed to discuss the applicability of cationic grouts in geotechnical engineering. The effects of several cationic stabilizers such as monovalent (sodium silicate), divalent (calcium oxide and calcium chloride), and trivalent (aluminum hydroxide) were investigated on shear strength improvement of tropical peat samples. The unconfined compressive strength (UCS) tests were performed after the time frame of 7, 21, and 30 days as curing time, respectively. Apart from the physicochemical characteristics of the stabilized peat, scanning electron microscopy and energy-dispersive X-ray spectroscopy tests were also carried out to study the ongoing microstructural changes. It is to be noted that the shear strength values for peat samples rose to 8, 6, 6, and 4 % of sodium silicate, calcium oxide, calcium chloride, and aluminum hydroxide, respectively. The highest observed UCS outcome is the one taken from the calcium oxide where the UCS of treated peat after 30-day curing time increased to 76 kPa. The strength changes resulted from the various cationic stabilizers can best be explained via the consideration within the mineralogical composition as well as those physicochemical changes happening in the peat.

Transient studies of low-temperature dry reforming of methane over

Abstract: a b s t r a c t The low temperature reforming of methane by carbon dioxide is studied over a calcium oxide promoted Ni catalyst supported on a tetragonal zirconia stabilized by lanthana, which presents an improved stability compared to the non-promoted catalyst. Steady-state catalytic activity measurements, diffuse reflectance infrared Fourier transform spectroscopic analysis and isotopic temporal analysis of products experiments reveal the occurrence of a bifunctional mechanism on the promoted catalyst: methane is activated on the Ni particles, carbon dioxide interacts with the calcium oxide to form carbonates which scavenge carbon from nickel at the Ni-O-Ca interphase, thus restoring Ni particles to the original state. This is assumed to hinder the formation of deactivating coke, which explains the improved catalytic stability of the promoted catalyst. The main route for the carbon deposit formation is found to be the methane cracking in spite of the low temperature reaction.

Yttria stabilized zirconia membrane stability in molten fluoride fluxes for low-carbon magnesium production by the SOM process

Abstract: The Solid Oxide Membrane (SOM) process for magnesium production involves the direct electrolysis of magnesium oxide for energy efficient and low-carbon magnesium production. In the SOM process, magnesium oxide is dissolved in a molten oxy-fluoride flux. An oxygen-ion-conducting SOM tube, made from yttria stabilized zirconia (YSZ), is submerged in the flux. The operating life of the electrolytic cell can be improved by understanding degradation processes in the YSZ, and one way the YSZ degrades is by yttria diffusion out of the YSZ. By adding small amounts of YF3 to the flux, yttria diffusion can be controlled. The diffusion of yttria into the flux was quantified by determining the yttria concentration profile as a function of immersion time in the flux and distance from the flux-YSZ interface. Yttria concentrations were determined using x-ray spectroscopy. The diffusion process was modeled using a numerical approach with an analytic solution to Fick’s second law. These modeling and experimental methods allowed for the determination of the optimum YF3 concentration in the flux to minimize yttria diffusion and improve membrane stability. Furthermore, the effects of common impurities in magnesium ores, such as calcium oxide, silica, and sodium oxide/sodium peroxide, on YSZ stability are being investigated.

Production method of active calcium silicate

Abstract: The invention provides a production method of active calcium silicate. The production method of the active calcium silicate is characterized by comprising the following steps of calcining limestone, cooling the limestone, screening the limestone to collect calcium oxide particles with the particle size of over 10 mm, conducting incineration to manufacture lime milk, wherein the concentration of the lime milk is 140-190g/L, conducting centrifugal sedimentation on the manufactured lime milk, collecting refined lime milk with the particle size less than 75 mu, filtering sodium silicate feed liquid of pre-desilication, wherein the content of seston in the sodium silicate feed liquid is enabled to be less than 0.1g/L, obtaining sodium silicate fine liquid, conducting a hydrothermal reaction on the manufactured refined lime milk and the sodium silicate fine liquid, conducting slag removal and washing on a product of the hydrothermal reaction, and obtaining the active calcium silicate. The production method of the active calcium silicate can effectively solve the problem that impurity content of the active calcium silicate serving as pack is high.

Minimization of variation in clinker quality

Abstract: Cement quality is typically assessed by its compressive strength development in mortar and concrete. The basis for this property is a well-burned clinker with consistent chemical composition and free lime. The main reason for the clinker free lime to change in situation with stable kiln operation is variation in the chemical composition of the kiln feed. This variation in chemical composition is related to raw mix control and the homogenization process. To ensure a constant quality of the product and maintain a stable and continuous operation of the kiln, the attention must be paid to storage and homogenization of raw materials and kiln feed. Due to variations in the kiln feed chemical compositions that affect its burnability and the fuel consumption. The raw materials for Portland cement production are the mixture (as fine powder in the 'Dry process') of minerals containing calcium oxide, silicon oxide, aluminum oxide, ferric oxide, and magnesium oxide. The homogeneity of feed chemical composition has an important relationship to fuel consumption, kiln operation, clinker formation and cement performance. In this regard an attempt made to deals with the mixing of raw materials process and estimation of composition of raw mill feed, kiln feed, as well as formed clinker, which were done successfully through various results obtained experimentally and various steps have been taken to reduce these variations in clinker quality.