Low gas-liquid interactions

This equation is reproduced in Figure 5 for different values of Lj-. The experimental system considered in this figure consists of water flowing through a bed of 3 mm diam. spheres with a porosity equal to 0.35. The pressure drop is assumed to be negligible (6. pjE). Comparison of Eq.16 with the correlation proposed by Specchia et al. (18), for the low gas-liquid interaction regime,... 

The following developments will be restricted to laminar liquid flow with very low gas-liquid interactions that is the flow regime prevailing with the operating conditions adopted in the experimental work. Application of Eq.8, with some simplifications, will be presented for the modelling of the different processes controlling the apparent reaction rate at the bed scale. 

In the case of low gas-liquid interactions - i.e. the trickling flow regime - fluid flow is no more governed by these fluid-fluid interactions but rather by fluid-solid interactions. 

These few examples of percolation problems evidence the influence that percolation structures may have cxi fluid flow hydrodynamics when fluid-solid interaction is the factor determining fluid flow through packed beds (i.e. at low gas-liquid interactions). 

Mass transfer (the C term), which involves collisions and interactions between molecules, applies differently to both packed and capillary columns. Packed columns are mostly filled with stationary phase so liquid phase diffusion dominates. The mass transfer is minimized by using a small mass of low-viscosity liquid phase. Capillary columns are mostly filled with mobile phase, so mass transfer is important in both the gas and liquid phases. A small mass of low-viscosity liquid phase combined with a low-molecular weight carrier gas will minimize this term. 

The last term accounts for the resistance to mass transfer in the gas phase. Low-loaded liquid coatings cause the Cg term to be significant. Equation 2.82 was further extended to account for velocity distributions due to retarded gas flow in the layers (C ) and the interaction of the two types of gas resistance (C2) ... 

E. Wasserman (The DuPont Company, U.S.A.). When you talk about the possible phases of something like C60 (is it a gas, a liquid or a low density liquid of high compressibility), we really have to compare it with another phase which may be accessible under the same temperature and pressure conditions. In many such cases, some of the features of C60 are due to intermolecular interactions, in some of the more condensed phases, rather than to individual molecular properties that you were concentrating on. For example, the very strong tenacity of one C60 molecule to bond to another, as well as to incorporate solvent molecules in the interstitial spaces, depends critically on how well they seem to fit together, as well as to the intrinsic forces that may be found in smaller molecules. We find that if you have small degrees of substitution of C6, for example, alkyl groups, the volatility increases dramatically. 

Abstract—Gas-liquid interfacial areas a and volumetric liquid-side mass-transfer coefficients kLa are experimentally determined in a high pressure trickle-bed reactor up to 3.2 MPa. Fast and slow absorption of carbon dioxide in aqueous and organic diethanolamine solutions are employed as model reactions for the evaluation of a and kLa at high pressure, and various liquid viscosities and packing characteristics. A simple model to estimate a and kLa for the low interaction regime in high pressure trickle-bed reactors is proposed. 

The same result is obtained for countercurrent flow. The increase of gas flow rate from 0.02 to 0.19 kg/m2s has no influence on the liquid hold-up. At low gas flow rates, interaction between the two fluids is negligible and the texture of the liquid is identical to that of the liquid flow alone. This result has already been observed by Van Swaaij el al. [5] in a column packed with Raschig rings and operating with a countercurrent flow. 

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