Fluid phase system

Sampling of a two-fluid phase system containing powdered catalyst can be problematic and should be considered in the reactor design. In the case of complex reacting systems with multiple reaction paths, it is important that isothermal data are obtained. Also, different activation energies for the various reaction paths will make it difficult to evaluate the rate constants from non-isothermal data. 

Lenhard, R. J. and Parker, J. C., 1988, Experimental Validation of the Theory of Extending Two-Phase Saturation-Pressure Relationships to Three-Fluid Phase System for Monotonic Drainage Paths Water Resources Research, Vol. 24, pp. 373-380. 

During the historical chromatographic period, separations were developed mostly on a trial-and-error experimental basis due to lack of understanding of the underlying principles and the inability to address the complex interactions in fluid-phase systems by a computing approach. 

Figure 16.2. Diffusional transfer in a two-fluid phase system.

The analysis carried out and the result (8.1.412) achieved do not indicate any influence due to the overaU cocurrent or countercurrent flow pattern there is no apparent influence of the concentrate chamber concentration. Actually there is see equation (3.4.115a). But the value of (Qim/<5m) is so small that there is hardly any transfer of cations from the concentrate chamber to the diluate chamber tbrougb tbe CEM, and similarly for anions through the AEM. This is an example where an external force trumps the generally assumed influence of flow patterns in two fluid-phase systems. 

This is currently the most important area of large-scale use of membrane contactors. Three general classes of two fluid phase systems are relevant gas-liquid (also vapor—liquid), liquid-liquid, and supercritical fluid-liquid. We will describe/touch upon the following aspects of each of such two-phase systems basis of contacting, membranes used for contacting, mass transfer issues, and applications. 

In fact, it is often possible with stirred-tank reactors to come close to the idealized well-stirred model in practice, providing the fluid phase is not too viscous. Such reactors should be avoided for some types of parallel reaction systems (see Fig. 2.2) and for all systems in which byproduct formation is via series reactions. 

We discuss classical non-ideal liquids before treating solids. The strongly interacting fluid systems of interest are hard spheres characterized by their harsh repulsions, atoms and molecules with dispersion interactions responsible for the liquid-vapour transitions of the rare gases, ionic systems including strong and weak electrolytes, simple and not quite so simple polar fluids like water. The solid phase systems discussed are ferroniagnets and alloys. 

As illustrated ia Figure 6, a porous adsorbent ia contact with a fluid phase offers at least two and often three distinct resistances to mass transfer external film resistance and iatraparticle diffusional resistance. When the pore size distribution has a well-defined bimodal form, the latter may be divided iato macropore and micropore diffusional resistances. Depending on the particular system and the conditions, any one of these resistances maybe dominant or the overall rate of mass transfer may be determined by the combiaed effects of more than one resistance. 

Tetralin. Tetralin is a trade name of Du Pont for 1,2,3,4-tetrahydronapththalene [119-64-2] C qH 2- Tetralin, a derivative of naphthalene, is made by hydrogenating one ring completely and leaving the other unchanged. Tetralin is produced by several manufacturers and is one of the oldest heat-transfer fluids. Tetralin can be used both in Hquid- and vapor-phase systems. The normal boiling point is 207°C. 

Dowtherm G is a mixture of di- and triaryl compounds and has good flow characteristics at low temperatures. Dowtherm G is highly stable, and the products of decomposition consist of high molecular weight materials which remain in solution in the Hquid. Dowtherm G is intended for use in Hquid-phase systems. The fluid has a striking odor even at extremely low concentrations. 

Marlotherm Heat-Transfer Fluids. Two heat-transfer fluids are manufactured by HbIs America Madotherm S is a mixture of isomeric diben2ylben2enes intended for Hquid-phase systems, and Marlotherm L is a mixture of ben2yl toluenes that are suitable for both Hquid- and vapor-phase appHcations. Marlotherm L can be pumped readily at temperatures as low as —50° C and can be used in vapor-phase systems at temperatures from 290—350°C. The low temperature characteristics of Marlotherm enable it to be used in processes involving both heating and cooling. 

Therm alane Heat- Transfer Fluids. Coastal Chemical Co. manufactures three heat-transfer fluids intended for Hquid-phase systems. 

Syltherm XLT is a polydimethylsiloxane intended for Hquid-phase systems which operate at low temperatures. Syltherm 800 is a modified dimethylsiloxane polymer intended for Hquid-phase systems. The recommended maximum fluid temperature is greater than the autoignition temperature. 

The fugacity coefficient of thesolid solute dissolved in the fluid phase (0 ) has been obtained using cubic equations of state (52) and statistical mechanical perturbation theory (53). The enhancement factor, E, shown as the quantity ia brackets ia equation 2, is defined as the real solubiUty divided by the solubihty ia an ideal gas. The solubiUty ia an ideal gas is simply the vapor pressure of the sohd over the pressure. Enhancement factors of 10 are common for supercritical systems. Notable exceptions such as the squalane—carbon dioxide system may have enhancement factors greater than 10. Solubihty data can be reduced to a simple form by plotting the logarithm of the enhancement factor vs density, resulting ia a fairly linear relationship (52). 

The performance of adsorption processes results in general from the combined effects of thermodynamic and rate factors. It is convenient to consider first thermodynamic factors. These determine the process performance in a limit where the system behaves ideally i.e. without mass transfer and Idnetic limitations and with the fluid phase in perfect... 

An initially clean activated carbon Led at 320 K is fed a vapor of benzene in nitrogen at a total pressure of 1 MPa. The concentration of benzene in the feed is 6 mol/m. After the Led is uniformly saturated with feed, it is regenerated using benzene-free nitrogen at 400 K and 1 MPa. Solve for Loth steps. For sim-phcity, neglect fluid-phase acciimiilation terms and assume constant mean heat capacities for stationary and fluid phases and a constant velocity. The system is described by... 

FIG. 17-2 Schematic phase diagram in the region of upward gas flow. W = mass flow solids, lh/(h fr) E = fraction voids Pp = particle density, Ih/ft Py= fluid density, Ih/ft Cd = drag coefficient Re = modified Reynolds uum-her. (Zenz and Othmei Fluidization and Fluid Particle Systems, Reinhold, New York, 1960. )... 

A eoaleseer aehieves separation of an oily phase from water on the basis of density differences between the two fluids. These systems obviously work best with non-emulsified oils. Applications historically have been in the oil and gas industry, and hence the most famous oil/water separator is the API separator (API being the abbreviation for the American Petroleum Institute). 

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