Liquid load moderate

They can handle liquids with moderate solids loading. 

If the design of Figure 4-41 is used for liquid-vapor separation at moderately high liquid loads, the liquid sliding down the walls in sheets and ripples has somewhat of a tendency to be torn off from the rotating liquid and become re-entrained in the upward gas mov ement. 

In the spray regime, and at low liquid loads in the froth regime, increasing the fractional hole area reduces entertainment (201, 204, 205, 382). This reduction is particularly large when fractional hole area is less than 0.08, but it becomes small when fractional hole area exceeds 0.10. Entrainment is essentially unaffected by fractional hole area at moderate and high liquid loads (> 3 gpm/in) in the froth regime (176, 201, 205). 

Envelope types of downcomers (Fig. 6.14c and d) are sometimes used in low-liquid-load applications. They are often used to satisfy the minimum downcomer width criterion or to minimize liquid leakage. In moderate- and high-liquid-load applications, minimum downcomer width and liquid leakage are rarely mqjor factors, and this type of downcomer is seldom used. 

The upper vapor capacity boundary of the operating region is controlled by both spray and tray flood. Spray is dominant under low liquid loadings, while tray flood becomes dominant at moderate and large liquid loadings. 

Up to the first limit line AA, the so-called loading line, the pressure drop curves Ap/H of irrigated packings at small and/or moderate liquid loads up,i and up,2 run parallel... 

This equation is applicable to vacuum rectification and absorption, operated under low and/or moderate liquid loads up. 

For practical reasons, key importance has been attached to the turbulent flow range, ReL > 2, as this is the range mostly used for operating packed columns containing large packing elements in rectification processes under normal pressure and vacuum conditions and/or in pressure rectification and in absorption processes at moderate liquid loads. 

The first German edition concentrates on the description of the fluid dynamics of columns with random and structured packings in the vacuum and normal pressure range of up to approx. 2 bar and for specific liquid loads of up to 100 m m h for gas-liquid systems. This range covers a majority of the applications and tasks relevant in the absorption and desorption of highly and/or moderately soluble gases as well as in rectification under vacuum and normal pressure. 

The process which was developed hy DOW involves cyclodimerization of hutadiene over a proprietary copper-loaded zeolite catalyst at moderate temperature and pressure (100°C and 250 psig). To increase the yield, the cyclodimerization step takes place in a liquid phase process over the catalyst. Selectivity for vinylcyclohexene (VCH) was over 99%. In the second step VCH is oxidized with oxygen over a proprietary oxide catalyst in presence of steam. Conversion over 90% and selectivity to styrene of 92% could he achieved. ... 

Carbowax 4000, gas-liquid phase adsorption contributes only Moderately to the retention of all solutes, decreasing rapidly with increasing liquid phase loading. At low phase loadings adsorption at the gas-liquid interface nay contribute between 3 and 42% to the retention of the solutes investigated... 

Since the liquid is saturated with hydrogen, only the liquid-to-particle mass transfer coefficient and the intrinsic rate constant will be significant. In the case that the reaction is fast, the reaction rate will depend only on the liquid-sold mass transfer resistance. Since the particle are very small (10 micrometers), and the loading is moderate (0.8% mass), the Sherwood number will be that of lonely spheres, so Sh = 2. For this case we can take Sh = =4 [50], rather safely. 

B. Sealed Tube Preparations. Sealed tube reactions and purifications afford good exclusion of the atmosphere and permit operations at moderate pressures. The latter capability makes it possible to work with highly volatile solvents, such as liquid ammonia, at room temperature. Since the sealed tube is often loaded on a high-vacuum line, the details on these techniques are given in Chapter 9. 

If an inert material is initially adsorbed on the fixed bed comprising an appropriate adsorbent and a catalyst, the heat of adsorption—having the same order of magnitude as the latent heat of evaporation—will be released (Figure 15). Since no reaction takes place in this phase, moderate temperature excursions are acceptable, and recycle flows over external heat exchangers or injection of liquid adsorptives may serve as heat sinks. In the subsequent reaction phase, the heat liberated by an exothermic reaction on the catalyst is taken up by the desorption of the inert from the previously loaded neighboring adsorbent particles. As long as this desorption occurs, the heat of reaction will not lead to major temperature increases. Sooner or later, of course, the adsorbent will be depleted and the temperatures will drift upward, at which point the adsorption phase must be repeated. 

In this reaction system, CO2 absorption takes place at moderate liquid-phase loads mainly via (R18). This can be explained as follows in spite of the fact that reaction (R17) is faster than (R18), the MEA concentration is much higher than that of OH--ions. 

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