Simulation of Organic Liquid Product Deoxygenation through Multistage Countercurrent Absorber/Stripping Using CO2 as Solvent with Aspen-HYSYS: Process Modeling and Simulation

In this work, the deoxygenation of organic liquid products (OLP) obtained through the thermal catalytic cracking of palm oil at 450 °C, 1.0 atmosphere, with 10% (wt.) Na₂CO₃ as a catalyst, in multistage countercurrent absorber columns using supercritical carbon dioxide (SC-CO₂) as a solvent, with an Aspen-HYSYS process simulator, was systematically investigated. In a previous study, the thermodynamic data basis and EOS modeling necessary to simulate the deoxygenation of OLP was presented. This work addresses a new flowsheet, consisting of 03 absorber columns, 10 expansions valves, 10 flash drums, 08 heat exchanges, 01 pressure pump, and 02 make-ups of CO₂, aiming to improve the deacidification of OLP. The simulation was performed at 333 K, 140 bar, and (S/F) = 17; 350 K, 140 bar, and (S/F) = 38; 333 K, 140 bar, and (S/F) = 25. The simulation shows that 81.49% of OLP could be recovered and that the concentrations of hydrocarbons in the extracts of absorber-01 and absorber-02 were 96.95 and 92.78% (wt.) on a solvent-free basis, while the bottom stream of absorber-03 was enriched in oxygenated compounds with concentrations of up to 32.66% (wt.) on a solvent-free basis, showing that the organic liquid products (OLP) were deacidified and SC-CO₂ was able to deacidify the OLP and obtain fractions with lower olefin contents. The best deacidifying condition was obtained at 333 K, 140 bar, and (S/F) = 17.     

Physical adsorption and surface plasmons

The quantum mechanical formulation of the screening of a point charge by surface plasmons is extended to describe the coupling of a fluctuating atomic dipole with a metallic surface of planar, spherical or cylindrical shape. This allows for the calculation of the nonretarded Van der Waals attraction of an atom by a solid surface in the three different geometries. Applications of the theoretical formulae are made to obtain numerical values of the dispersion energy by a spherical particle, a spherical pore, a thin film, a slot-like prore, a cylindrical fiber or a cylindrical pore.     

A new μs isomer in 136Sb produced in the projectile fission of 238U

Rapidity correlations in 800 GeV proton interactions with emulsion nuclei are investigated for different targets and multiplicity regions. To study the energy dependence, the results have been compared with proton interactions at 200 GeV and 400 GeV. A common feature of all the interactions is the existence of strong, short-range correlations. However, no dependence of cluster parameters on primary energy or target mass is found. A marginal increase of correlation strength with multiplicity is observed. Received: 30 March 2001 / Accepted: 18 September 2001     

Evidence for shape deformations of fragments in deep inelastic collisions

The number and energy spectra of neutrons evaporated by the heavy and light fragments in deep inelastic collisions have been obtained for the system 240 MeV⁴⁰Ar +¹⁹⁷Au. They indicate that at the scission point the deformation energy is a large part of the total excitation energy espe cially for the light fragment. In the last two years, neutron emission has been studied in deep inelastic reactions^1?6. All the results are similar: the incident energy which is lost during the process is transformed into excitation energy of the final fragments and is shared between the two products proportionnally to their masses. This means that the nuclear temperature was uniform in the composite system. The excitation energy equilibration time is really very short since equilibration is achieved after reaction times as small as 10^?22 s^2,6. Moreover, no preequilibrium emission (direct neutrons-) has been observed.     

Exotic nuclei produced by heavy-ions induced fission

About thirty nuclei in theA≈100 mass region have been produced as fission fragments following the fusion-evaporation reactions^28,30Si+¹⁷⁶Yb at 145 MeV bombarding energy. These nuclei have been individually identified from their γ-ray cascades detected with the Eurogam2 array. The level schemes of several stable or neutron-rich nuclei have been extended to higher spins. From cross coincidences between transitions in complementary fragments, γ-rays de-exciting high-spin states of new isotopes can be identified and some aspects of the fission mechanism can be analyzed.     

Angular distributions in quasi-fission reactions: Evidence for incomplete relaxation of the tilting mode

The integral β^?-spectra of²³⁵U and²³⁹Pu fission products have been measured with a plastic scintillator telescope at an external neutron guide tube at the high flux reactor of the ILL in Grenoble. The highly enriched targets (150 – 800 γg/cm²) were placed in a fission chamber at a distance of approximately 110 m from the reactor core. From the measured beta-spectra absolute counting rates per MeV and fission have been calculated, which are compared with the results of earlier experiments of other authors and with recent theoretical calculations.     

Quantum Control in Foundational Experiments

We describe a new class of experiments designed to probe the foundations of quantum mechanics. Using quantum controlling devices, we show how to attain a freedom in temporal ordering of the control and detection of various phenomena. We consider wave–particle duality in the context of quantum-controlled and the entanglement-assisted delayed-choice experiments. Then we discuss a quantum-controlled CHSH experiment and measurement of photon’s transversal position and momentum in a single set-up.     

Single-mode low-loss optical fibers for long-wave infrared transmission

In this Letter, we report single-mode fibers made of chalcogenide glasses with low loss in the 5-12μm range. Glasses from the Ge-As-Te-Se system were optimized to prevent nucleation and to exhibit low density of charge carriers. Single-mode fibers were obtained through the rod-in-tube method by substituting 2% Te/Se between the core and cladding glasses. The resulting single-mode fibers had a core diameter of 30μm and exhibited losses of ~6 dB/m at 10.6μm, and as low as 3-4dB/m in the 6-10μm range.     

Niobian iron oxides as heterogeneous Fenton catalysts for environmental remediation

Heterogeneous Fenton or Fenton-like reagents consist of a mixture of an iron-containing solid matrix and a liquid medium with H₂O₂. The Fenton system is based on the reaction between Fe^2?+? and H₂O₂ to produce highly reactive intermediate hydroxyl radicals (^???OH), which are able to oxidize organic contaminants, whereas the Fenton-like reaction is based on the reaction between Fe^3?+? and H₂O₂. These heterogeneous systems offer several advantages over their homogeneous counterparts, such as no sludge formation, operation at near-neutral pH and the possibility of recycling the iron promoter. Some doping transition cations in the iron oxide structure are believed to enhance the catalytic efficiency for the oxidation of organic substrates in water. In this work, goethites synthesized in presence of niobium served as precursors for the preparation of magnetites (niobian magnetites) via chemical reduction with hydrogen at 400°C. These materials were used as Fenton-like catalysts. Both groups of (Nb, Fe)-oxide samples were characterized by ⁵⁷Fe Mössbauer spectroscopy at 298 K. The results show that increasing niobium contents raise the catalytic potential for decomposition of methylene blue, which was, in this work, used as a model molecule for organic substrates in water.