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Raschig Rings (raschig + ring)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Supercritical carbon dioxide separation of bergamot essential oil by a countercurrent process

FLAVOUR AND FRAGRANCE JOURNAL, Issue 5 2003
Marco Poiana
Abstract The ef,ciency of separation of bergamot essential oil, performed by a countercurrent column ,lled with Raschig rings and using supercritical carbon dioxide as partition solvent, is affected by various parameters. In the experiments explained in this work, the direct effect of CO2 density was shown and the ratio between the amount of oil loaded to on the column and the amount of CO2 used were discussed. The conditions that produced extracts with a similar volatile fraction composition of starting material and with a high yield (more than 80% of recovery) were those with a low feed:solvent ratio; the lowest bergaptene content was obtained at low CO2 density or at high feed:solvent ratio. A good result was observed at a CO2 density of 206 g/dm3 (8 MPa of pressure and a temperature gradient of 46,50,54 °C) and a feed:solvent ratio of 9.4,9.6; in this separation, a yield of 74,77% and a bergaptene content lower than 0.01% was measured. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Axial mixing in modern packings, gas, and liquid phases: II.

AICHE JOURNAL, Issue 1 2000
Two-phase flow
Axial mixing measurements of air and water under two-phase flow conditions were made in a large-scale packed column (0.43 m diameter) using tracer experiments. Part I of this article dealt with single-phase mixing in the same column, with the same internals. Four packings were studied: 25.4-mm ceramic Raschig rings, 25.4-mm metal Pall rings, Sulzer BX structured packing, and Flexipac 2 structured packing. Air and water flowed countercurrently through the column at atmospheric pressure and at gas rates varying from 0.25 kg/m2·s up to the flooding point, and liquid rates from 3.25 to 8.5 kg/m2 ·s. A diffusion-type model served to reproduce the experimental response curves obtained for both phases. The results confirmed previous observations for first-generation packings: axial mixing in the gas increases with both gas and liquid rates, whereas liquid-phase axial mixing is a decreasing function of liquid rate and is insensitive to gas rate up to the flooding point. It was also found that the BX packing produces the least mixing in both phases. The largest mixing effects in the gas phase are found for the Raschig rings, and the largest mixing effects for the liquid phase are found for Flexipac 2. Correlations were developed to reproduce the results, yielding an average ±22% difference between experimental and correlated data. [source]

Hydrodynamics and mass transfer in a pulsed packed column

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2000
Yu Jie
Abstract The hydrodynamics and mass transfer characteristics of a pulsed packed column (PPC) filled with a stainless steel super mini ring (SMR), ceramic and stainless steel Raschig rings have been studied using a 30% tributyl phosphate-kerosene (dispersed phase)/acetic acid/water (continuous phase) system. Experiments were performed in a 100 mm internal diameter column with 1.0 m height of packing. The mass transfer and axial mixing parameters were estimated simultaneously from the measured concentration profiles of two-phase based on the backflow model. It was found that pulsation has great influence on hydrodynamics and mass transfer characteristics of PPC with the SMR. Hoxp and Hox decrease significantly with pulsation, whereas flooding velocity decreases only slightly. Comparison among the three types of packing showed that the SMR has superior characteristics both in terms of capacity and mass transfer efficiency. The influence of mass transfer on characteristics of PPC was also studied. New empirical equations of characteristic velocity, Hoxand Hoxd were proposed and good agreement between calculated and experimental data was obtained. Les caractéristiques de l'hydrodynamique et du transfert de matiére dans une colonne pulsée garni (PPC) contenant des super mini-anneaux (SMR) d'acier inoxydable et des anneaux de Raschig de céramique et d'acier inoxydable (s.s.) ont été étudiées à l'aide du système 30% de phosphate de tributyl-kérosène (phase dispersée)/acide acétique/eau (phase continue). On a mené des expériences dans une colonne de 100 mm de diamètre intérieur avec une hauteur de garnissage de 1.0 m. Les paramètres de transfert de matière et de mélange axial ont été estimés simultanément à partir des profils de concentration mesurés de deux phases d'après le modèle de reflux. On a trouvé que la pulsation avait une grande influence sur les caractéristiques de l'hydrodynamique et de transfert de matière de la colonne PPC avec le SMR. Hoxp et Hox diminuent de maniére significative avec la pulsation, tandis que la vitesse d'engorgement ne diminue que Iégèrement. Une comparaison entre les trois types de garnissage montre que le SMR possède des caractéristiques supérieures à la fois en termes de capacité et d'efficacité du transfert de matière. L'influence du transfert de matière sur les caractéristiques de la colonne PPC a également été étudiée. De nouvelles équations empiriques de la vitesse caractéristique, Hox et Hoxd, sont proposées et un bon accord est obtenu entre les données calculées et les données expérhentales. [source]