The Effect of CaO Addition on Mechanical Properties of Ceramic Tiles

Stoneware clay, fired clay (as a grog), calcite waste and class C fly ash in various mixing rations were the basic raw materials for the mixture for production of dry pressed ceramic tiles. Mechanical properties (water absorption, bulk density, apparent porosity, flexural strength) as well as mineralogical composition were studied on samples with different source of calcium oxide after firing at 900, 1000, 1100 and 1200°C. It was found that samples with addition of calcite waste contain dmisteinbergit and anorthite. This minerals help to improve the strength of the body and reduce porosity fired at lower temperatures. Class C fly ash has not significantly influence on properties of the fired body as calcite waste

Role of CaO addition in the local order around Erbium in SiO2 –GeO2 –P2O5 fiber preforms

International audienceThe development of materials for optical signal processing represents a major issue in present technology. In this contribution we present a study on Er-doped fiber preforms where particular attention is devoted on how the addition of CaO in the glass modifies the local environment of the rare earth. The results from photoluminescence and Extended X-ray Absorption Fine Structure (EXAFS) are compared and a clear link between the width of the emission line at 1.5 µm and the amorphous/crystalline local structure around the Er3+ ion is evidenced

ASPEN plus modelling of air–steam gasification of biomass with sorbent enabled CO2 capture

AbstractThe work deals with the modelling and simulation of carbon dioxide capture in air–steam gasification of saw dust using ASPEN Plus process simulator. The proposed quasi-steady state model incorporates pyrolysis, tar cracking and char conversion using existing experimental data. Prediction accuracy of the developed model is validated by comparing with available experimental results. Effects of CaO addition in air–steam gasification are analysed through key operating parameters such as gasification temperature, equivalence ratio, steam to biomass ratio and gasification efficiency. Maximum H2 mole fraction of 31.17% is obtained at a temperature of 900 K, equivalence ratio of 0.25, and steam to biomass ratio and sorbent to biomass ratio of unity. The H2 and CO2 mole fractions are found to be increased and decreased by 28.10% and 42.6%, respectively, when compared with the corresponding non- sorbent case

ASPEN plus modelling of air-steam gasification of biomass with sorbent enabled CO2 capture

The work deals with the modelling and simulation of carbon dioxide capture in air-steam gasification of saw dust using ASPEN Plus process simulator. The proposed quasi-steady state model incorporates pyrolysis, tar cracking and char conversion using existing experimental data. Prediction accuracy of the developed model is validated by comparing with available experimental results. Effects of CaO addition in air-steam gasification are analysed through key operating parameters such as gasification temperature, equivalence ratio, steam to biomass ratio and gasification efficiency. Maximum H2 mole fraction of 31.17% is obtained at a temperature of 900 K, equivalence ratio of 0.25, and steam to biomass ratio and sorbent to biomass ratio of unity. The H2 and CO2 mole fractions are found to be increased and decreased by 28.10% and 42.6%, respectively, when compared with the corresponding non- sorbent case

Erbium-doped nanoparticles in silica-based optical fibres

Developing of new rare-earth (RE)-doped optical fibres for power amplifiers and lasers requires continuous improvements in the fibre spectroscopic properties (like shape and width of the gain curve, optical quantum efficiency, resistance to spectral hole burning and photodarkening...). Silica glass as a host material for fibres has proved to be very attractive. However, some potential applications of RE-doped fibres suffer from limitations in terms of spectroscopic properties resulting from clustering or inappropriate local environment when doped into silica. To this aim, we present a new route to modify some spectroscopic properties of RE ions in silica-based fibres based on the incorporation of erbium ions in amorphous dielectric nanoparticles, grown in-situ in fibre preforms. By adding alkaline earth elements, in low concentration into silica, one can obtain a glass with an immiscibility gap. Then, phase separation occurs under an appropriate heat treatment. We investigated the role of three alkaline-earth elements: magnesium, calcium and strontium. We present the achieved stabilisation of nanometric erbium-doped dielectric nanoparticles within the core of silica fibres. We present the nanoparticle dimensional characterisation in fibre samples. We also show the spectroscopic characterisation of erbium in preform and fibre samples with different compositions. This new route could have important potentials in improving RE-doped fibre amplifiers and laser sources.Comment: arXiv admin note: text overlap with arXiv:1201.111

Reaction mechanism of arsenic capture by a calcium-based sorbent during the combustion of arsenic-contaminated biomass: A pilot-scale experience

Large quantities of contaminated biomass due to phytoremediation were disposed through combustion in low-income rural regions of China. This process provided a solution to reduce waste volume and disposal cost. Pilot-scale combustion trials were conducted for in site disposal at phytoremediation sites. The reaction mechanism of arsenic capture during pilot-scale combustion should be determined to control the arsenic emission in flue gas. This study investigated three Pteris vittata L. biomass with a disposal capacity of 600 kg/d and different arsenic concentrations from three sites in China. The arsenic concentration in flue gas was greater than that of the national standard in the trial with no emission control, and the arsenic concentration in biomass was 486 mg/kg. CaO addition notably reduced arsenic emission in flue gas, and absorption was efficient when CaO was mixed with biomass at 10% of the total weight. For the trial with 10% CaO addition, arsenic recovery from ash reached 76%, which is an ∼8-fold increase compared with the control. Synchrotron radiation analysis confirmed that calcium arsenate is the dominant reaction product

Incorporation of calcium in glasses: a key to understand the vitrification of sewage sludge

The quantity of sewage sludge generated daily by wastewater treatment plants represents a major environmental problem and a financial burden for plant operators. Valorization strategies focusing on reusing sewage sludge as a raw material are currently developed. Vitrification can help us reduce the volume of waste and binds the components in the structure of chemically stable glasses and glass‐ceramics. In this study, the vitrification of sewage sludge inside a basaltic rock has been simulated by producing glasses and a glass‐ceramic from basalt enriched in calcium that lie between the stability fields of pyroxene and melilite in the system CaO‐MgO‐SiO2‐Al2O3. CaO addition causes the oxidation of the melt at above the liquidus, increases the crystallization temperature, decreases the melting temperature and improves the microhardness of the glasses Glass‐ceramic processes improves the properties of the Ca‐doped basalt glass. The microhardness of the glass (8.2 GPa) and the glass‐ceramic (8.6 GPa) and leaching tests (in the ppb range) place both the glass and the glass‐ceramics at the high end of the mechanical properties and chemical resistance of ceramic tiles for the building industry

Process recovery after CaO addition due to granule formation in a CSTR Co-Digester : a tool to influence the composition of the microbial community and stabilize the process?

The composition, structure and function of granules formed during process recovery with calcium oxide in a laboratory-scale fermenter fed with sewage sludge and rapeseed oil were studied. In the course of over-acidification and successful process recovery, only minor changes were observed in the bacterial community of the digestate, while granules appeared during recovery. Fluorescence microscopic analysis of the granules showed a close spatial relationship between calcium and oil and/or long chain fatty acids. This finding further substantiated the hypothesis that calcium precipitated with carbon of organic origin and reduced the negative effects of overloading with oil. Furthermore, the enrichment of phosphate minerals in the granules was shown, and molecular biological analyses detected polyphosphate-accumulating organisms as well as methanogenic archaea in the core. Organisms related to Methanoculleus receptaculi were detected in the inner zones of a granule, whereas they were present in the digestate only after process recovery. This finding indicated more favorable microhabitats inside the granules that supported process recovery. Thus, the granule formation triggered by calcium oxide addition served as a tool to influence the composition of the microbial community and to stabilize the process after overloading with oil

Investigations of Zr(IV) in LiF-CaF2: stability with oxide ions and electroreduction pathway on inert and reactive electrodes

In this work, a detailed electrochemical study of the molten LiF-CaF2-ZrF4 system is provided in the 810-920°C temperature range, allowing the determination of the reduction potential, the diffusion coefficient and the reduction mechanism of dissolved Zr(IV) on an inert Ta electrode. Addition of CaO in the molten salt is shown to cause Zr(IV) precipitation into a mixture of solid compounds, most likely ZrO2 and ZrO1.3F1.4. Underpotential deposition of Zr on Cu and Ni electrodes is also evidenced