Irania F.,Central University of Venezuela |
Francis M.,Central University of Venezuela |
Katya R.,Central University of Venezuela |
Vannesa B.,Intevep SA
RILEM Bookseries | Year: 2015
The use of calcined clays as a pozzolanic material for mortar and concrete has received considerable attention in recent years. This interest has focused on the chemical composition and reactivity for use as a pozzolanic material, and its major contribution is recognized in enhanced mechanical strength, reduced permeability and chemical durability. Different studies have concluded that pozzolanic behavior depends on calcination temperature and surface area. It is also related to the original kaolinite crystallinity and the quantity and nature of the partners, such as quartz, rutile or feldspar minerals. © RILEM 2015
Rojas L.,Venezuelan Institute for Scientific Research |
Ruette F.,Venezuelan Institute for Scientific Research |
Peraza A.,Venezuelan Institute for Scientific Research |
Castellano O.,Intevep SA |
Soscun H.,University of Zulia
Chemical Physics Letters | Year: 2015
Interaction energies (Eint) were evaluated for n-alkanes dimers (C1-C10) using DFT-D, different functionals, and several basis sets. In addition, calculations were also carried out with DFTB-LD and MM3 and OPLS-AA force fields. Results show linear correlations of Eint with respect to those obtained from literature at high levels of theory (MP2 and CCSD(T)). Relationships between Eint and experimental heats of vaporization (ΔHv) and critical temperatures (Tc) were obtained with MP2, DFT-D, MM and DFTB-LD. This leads to good extrapolations for hairpin-hexadecane using MM3 and DFTB-LD for ΔHv and Tc, respectively. Dispersion in DFT is discussed. © 2015 Elsevier B.V. All rights reserved.
Intevep SA, Ciemat and ETH Zurich | Date: 2011-11-30
A concentrated solar radiation assembly (20) comprising a housing divided into segments by housing trusses (3); window blocks (7) positioned within the segments supported by the housing trusses (3); and, internal trusses (9) positioned on top of the window blocks (7) and within the segments. The assembly may be hermetically sealed, large-scale and refrigerated by water flow within the trusses.
Araque E.D.,Intevep SA |
Vivas G.A.,Intevep SA
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2013
Several studies recognized that cracks in delayed coke drums resulted from low cycle fatigue induced by cyclic thermal stress , , . According to a coke drum survey coordinated by API in 1996 , there are two different areas where cracks are produced. The first zone is located at the shell to skirt weld, and the second at the bulging areas found in the cylindrical section. In the second case, from 145 coke drums 57% reported that had shell bulging problems. Of the drums that bulged, 87 % also showed cracks. In order to estimate the level of stress, finite element analysis of a bulged cylinder was performed. The study was carried out running a sequentially-coupled thermo-mechanical analysis. In the first step, a thermal analysis is used to estimate the variation of temperature with time. These temperatures serve as input to a mechanical stress analysis that was made in a second step. The assessment shows the influence of thermal gradients obtained for a period of 26 months for several bulging patterns that were identified from the analysis of 28 laser mappings of coke drums. The results indicated that the level of stress could reach the plastic deformation considering that the material has yield strength equal to the minimum specified in ASME Section II, part D. The zones where maximum axial stresses were found are consistent with areas where cracking has been reported in many coke drums. Copyright © 2013 by ASME.
Intevep SA | Date: 2010-06-16
A catalyst useful for the simultaneous and selective hydrogenation of diolefins and nitriles present in a hydrocarbon feedstock includes (a) a support material selected from the group consisting of inorganic oxide, carbon, zeolite and mixtures thereof; and (b) a catalytically active metal phase including at least two metals selected from the group consisting of at least partially reduced Group IB metals and completely reduced Group VIII metals, the active metal phase being present in an amount of about 0.03 wt%.
Intevep SA | Date: 2010-03-24
A cement additive, comprising nanostructured or not particles of SiO_(2)-CaO-Al_(2)O_(3) and at least one additive selected from the group consisting of nano-sized particles of SiO_(2), 2CaO.SiO_(2), 3CaO.SiO_(2), Al_(2)O_(3), P-Ca and/or combinations thereof.
Intevep SA | Date: 2011-07-27
An additive for hydroconversion processes includes a solid organic material having a particle size of between about 0.1 and about 2,000 m, a bulk density of between about 500 and about 2,000 kg/m3, a skeletal density of between about 1,000 and about 2,000 kg/m3 and a humidity of between 0 and about 5 wt%. Methods for preparation and use of the additive are also provided. By the use of the additive of the present invention, the hydroconversion process can be performed at high conversion level.
Intevep SA | Date: 2011-05-25
A hydroconversion process includes feeding a heavy feedstock containing vanadium and/or nickel, a catalyst emulsion containing at least one group 8-10 metal and at least one group 6 metal, hydrogen and an organic additive to a hydroconversion zone under hydroconversion conditions to produce an upgraded hydrocarbon product and a solid carbonaceous material containing the group 8-10 metal, the group 6 metal, and the vanadium and/or nickel.
Intevep SA | Date: 2011-07-27
A metal recovery process, for heavy products from a hydroconversion process, containing unconverted residue and a solid carbonaceous material containing the group 8-10 metal, the group 6 metal, and vanadium and/or nickel, is provided by the invention. The recovery process comprises a thermal treatment step to convert the heavy products/residues into ash, a leaching of the ash to form supernatant containing vanadium and molybdenum in solution and a first solid containing carbonaceous material and undissolved metals (nickel, ...). The supernatant liquid is mixed with ammonium sulphate solution to produce a first precipitate containing the vanadium, and a further precipitation step to form a second precipitate containing the molybdenum.
Intevep SA | Date: 2010-07-07
A dewatered ethanol residue regenerable and non-regenerable sorbent for the removal of acid gas from hydrocarbon production gas streams and the process for the removal of acid gas from hydrocarbon gas is provided. The process includes the steps of obtaining residue from the distillation of ethanol; de-watering the residue; mixing the de-watered residue with an amine; and, contacting the hydrocarbon gas with the dewatered residue/amine mixture.