Carbon dioxide mass transfer process

While phase equilibria for the a-tocopherol/carbon dioxide system at high pressures have been studied by several authors [1-6], only a few measurements of dynamic viscosity [7], thermal conductivity [7] and mass transfer coefficients [3] were carried out. The present study of the interfacial tension in the a-tocopherol/carbon dioxide system at temperatures between 313 and 402 K and pressures from 10 to 37 MPa aims on the one hand at completing characterisation of this system and on the other at contributing to understanding interfacial phenomena in mass transfer processes. 

Wine. The earliest known wines were made in Iran about 5400—5000 BC (25). The species of grape used is unknown and may have been either the wild grape Fitis viniferus sylvestris or a cultivated precursor of the modem wine grape V. viniferus viniferus. The source of the yeast used, and the procedures used are completely unknown. In modem times, grapes (about 21—23% sugar) are pressed the liquid must is either separated and allowed to settle for 1—2 days (for white wines) before inoculation with yeast, or the whole mass is dkectly inoculated with yeast (for red wines). In either case, while the initial fermentation takes place, the carbon dioxide formed by fermentation excludes ak and prevents oxidation. White wines are transferred to a second fermentor (racked) near the end of fermentation and kept isolated from the ak while solids, including yeast, settle out, a process that requkes about six... 

Homogeneous molecular catalysts, which have far greater connol over selectivity than heterogeneous solid catalysts, are now being tested in SCFs, and early results show that high rates, improved selectivity, and elimination of mass-transfer problems can be achieved. Supercritical carbon dioxide may be an ideal replacement medium for nonpolar or weakly polar chemical processes. More than simply substitutes for nonpolar solvents, SCFs can radically change the observed chemistry (Jessop et al., 1995). 

In many of these experiments, interfacial turbulence was the obvious visible cause of the unusual features of the rate of mass transfer. There are, however, experimental results in which no interfacial activity was observed. Brian et al. [108] have drawn attention to the severe disagreement existing between the penetration theory and data for the absorption of carbon dioxide in monoethanolamine. They have performed experiments on the absorption of C02 with simultaneous desorption of propylene in a short, wetted wall column. The desorption of propylene without absorption of C02 agrees closely with the predictions of the penetration theory. If, however, both processes take place simultaneously, the rate of desorption is greatly increased. This enhancement must be linked to a hydrodynamic effect induced by the absorption of C02 and the only one which can occur appears to be the interfacial turbulence caused by the Marangoni effect. No interfacial activity was observed because of the small scale and small intensity of the induced turbulence. 

Chlorination processes in bubble column reactors<9> are unusual in showing a significant gas-phase resistance to mass transfer. It will be seen from the low value of the Henry law constant 3 in the list of data for the example below, that the solubility of chlorine in toluene is much greater than the solubility of either the carbon dioxide or oxygen considered in the previous examples. This means that when the gas-phase mass transfer resistance is taken in combination with the liquid-phase resistance according to equation 4.19 which is derived in Volume 2, Chapter 12, then the gas side contribution to the resistance is much greater if 3 is small. 

The CNG process removes sulfurous compounds, trace contaminants, and carbon dioxide from medium to high pressure gas streams containing substantial amounts of carbon dioxide. Process features include 1) absorption of sulfurous compounds and trace contaminants with pure liquid carbon dioxide, 2) regeneration of pure carbon dioxide with simultaneous concentration of hydrogen sulfide and trace contaminants by triple-point crystallization, and 3) absorption of carbon dioxide with a slurry of organic liquid containing solid carbon dioxide. These process features utilize unique properties of carbon dioxide, and enable small driving forces for heat and mass transfer, small absorbent flows, and relatively small process equipment. 

It is a mass transfer between a mobile, solid, or liquid phase, and the adsorption bed packed in a reactor. To carry out adsorption, a reactor, where a dynamic adsorption process will occur, is packed with an adsorbent [2], The adsorbents normally used for these applications are active carbons, zeolites and related materials, silica, mesoporous molecular sieves, alumina, titanium dioxide, magnesium oxide, clays, and pillared clays. 

When a typical nonactive material is employed, the anode only acts as an electron sink. In this particular case, the scheme representing the oxidation processes can be explained as shown in Fig. 4.2. The first process that needs to be considered is the mass transfer of the compounds from the bulk zone to the anodic one. The organic compounds can undergo direct oxidation on the electrode surface. This process can either be one-stage or multistage, and proceeds until the final oxidation product is generated (usually, carbon dioxide). At the same time, the decomposition of water... 

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