External liquid saturation

As the catalyst particles are porous, the total liquid saturation P is the sum of internal or intraparticle liquid saturation and interparticle or external liquid saturation. The external liquid saturation is further divided into residual or static liquid saturation (jSs), and free draining or dynamic saturation The... 

Bext is the external liquid saturation (outside the particles) and can be represented as o. o... 

Fig. 7 - Influence of the gas superficial velocity on the external liquid saturation...

The external liquid saturation Sext be represented, for an upflow system, as ... 

The bed void volume available for flow and for gas and liquid holdup is determined by the particle size distribution and shape, the particle porosity, and the packing effectiveness. The total voidage and the total liquid holdup can be divided into external and internal terms corresponding to interparticle (bed) and intraparticle (porosity) voidage. The external liquid holdup is further subdivided into static holdup eLs (holdup remaining after bed draining due to surface tension forces) and dynamic holdup eLrf. Additional expressions for the liquid holdup are the pore fillup Ft and the liquid saturation SL ... 

Fig. 20. Schematic representation of a composite membrane (Figs. 1 and 7) at liquid saturation showing a single gelled particle enmeshed in PTFE microfibers as described in the text. The bold straight lines represent the PTFE fibers. The entangled network of curved lines represent the crosslinked polymer that supports the liquid saturated gel. Each empty circle (o), superimposed on the curvy lines, represents a set of molecules (

If the feed is a saturated vapor at 7 and Fy, then ATI = 0 and q = 0. The vapor rate leaving the feed tray is simply the sum of vapor from the bottom column section and the feed, 1/ = 1/ -i- F. Since no external liquid is involved, the liquid rate entering the tray from the upper section equals the liquid rate leaving it L,. = L,. ... 

When a column system involving gel particles carrying a small number of fixed negative charges, which are distributed uniformly throughout the gel interior, is saturated with an aqueous solution of a 2 1 salt, K A , the relation between the distribution coefficient of anion A", K, and the salt concentration in the external liquid phase, C, can be derived from Donnan equation [ref. 49]... 

For deep desulfurization, trickle-bed reactor technology may also be improved by using a two-phase reactor. Thereby, the oil is externally pre-saturated with H2 and only the liquid phase is passed over the catalytic fixed bed. To discuss the... 

Hence, for deep desulfurization, a two-phase reactor (oil externally pre-saturated with H2 and solid catalyst) could be an alternative to the trickle bed. The H2-recycle is then redundant, and scale-up problems do not occur. In addition, the two-phase technology utilizes the maximum intrinsic chemical reaction rate as pore diffusion does not play a role in the slow desulfurization of refractory compounds left in predesulfurized feedstocks. For a trickle bed this rate is an upper limit, which caimot, or only hardly, be reached with regard to improper gas-liquid distribution and/or wetting of the catalyst. A laboratory-scale tricHe-bed and two-phase reactor with pre-saturation are compared in Figure 6.8.10 for a model oil. 

The gas flow rate is taken into account because it affects the external total liquid saturation 3t ... 

A suspension of 40 g 3-acetylaminomethyl-5-amino-2,4,6-triodobenzoic acid in 180 ml acetic anhydride were mixed with 0.4 ml concentrated sulfuric acid. An exothermic reaction was thereby initiated. Acetylation was completed by heating to 80°C for three hours. The reaction mixture was then evaporated to dryness in a vacuum at a temperature not exceeding 50°C. The residue was treated with a mixture of 30 ml concentrated aqueous ammonium hydroxide and 40 ml water, whereby the solid material dissolved with spontaneous heating. Within a few minutes, the ammonium salt of the acetylated product started precipitating. The precipitate and residual liquid were cooled externally with ice after about 15 minutes. The salt was separated from the liquid by filtration with suction, and was washed with ice cold saturated ammonium chloride solution. 

Physical examples of the three types are afforded by a gas contained in a cylinder under an external pressure equal to the gas pressure, by a superheated liquid, and by a mixture of water and saturated steam, under the same conditions respectively. 

A liquid solution may be separated into its constituents by crystallising out either pure solvent or pure solute, the latter process occurring only with saturated solutions. (At one special temperature, called the cryohydric temperature, both solvent and solute crystallise out side by side in unchanging proportions.) We now consider what happens when a small quantity of solute is separated from or taken up by the saturated solution by reversible processes. Let the saturated solution, with excess of solute, be placed in a cylinder closed below by a semipermeable septum, and the w7hole immersed in pure solvent. The system is in equilibrium if a pressure P, equal to the osmotic pressure of the saturated solution when the free surface of the pure solvent is under atmospheric pressure, is applied to the solution. Dissolution or precipitation of solute can now be brought about by an infinitesimal decrease or increase of the external pressure, and the processes are therefore reversible. If the infinitesimal pressure difference is maintained, and the process conducted so slowly that all changes are isothermal, the heat absorbed when a mol of solute passes into a solution kept always infinitely... 

Saturated hydrocarbons (waxes), fatty acids, metal soaps, fatty acid amides and esters (primarily Cig-Cis) act as internal lubricants, fluoro elastomers as external lubricants. Many other polymer additives, e.g. antistatic agents, antifogs, antioxidants, UV stabilisers, etc., act as lubricants in the barrel of the extruder once they are in the liquid form. 

With an increase of E beyond a certain value specific to the liquid, the free-ion yield increases sublinearly with the field, eventually showing a saturation trend at very high fields (see Mathieu et al.,1967). Freeman and Dodelet (1973) have shown that a fixed electron-ion initial separation underestimates the free-ion yield at high fields, and that a distribution of thermalization distance must be used to explain the entire dependence of Pesc on E. Therefore, the theoretical problem of the variation of free-ion yield with external field is inextricably mixed with that of the initial distribution of electron-cation separation. 

Phase equilibrium requires that A2 = Al and hence that the integral vanish. All conditions are satisfied if the points 1 and 2 are located such that the areas A = B. This geometry defines the Maxwell construction. It shows that stable liquid and vapour states correspond to minima in free energy and that AL = Ay when the external pressure line cuts off equal areas in the loops of the Van der Waals isotherm. At this pressure that corresponds to the saturated vapour pressure, a first-order phase transition occurs. 

An atmosphere of vapour always resides above a liquid, whether the liquid is pure, part of a mixture, or has solute dissolved within it. We saw on p. 180 how the pressure of this gaseous phase is called its saturation vapour pressure, s.v.p. The s.v.p. increases with increased temperature until, at the boiling point 7)ix>ii i, it equals the external pressure above the liquid. Evaporation occurs at temperatures below 7(boii), and only above this temperature will the s.v.p. exceed The applied pressure in a rotary evaporator is less than p, so the s.v.p. of the solvent can exceed the applied pressure (and allow the liquid to boil) at pressures lower than p. ... 

Precipitation of the active component precursor starts when its concentration in the liquid phase reaches the saturation point Cs. At this point the degree of pore volume filling is Us. If the precursor is not volatile, one can determine Us as a ratio of Us=U0C0/CS. The redistribution of the precursor is minimal if Us< t/cr h. Aspiration of Us to U0 results in a predominant yield of the precursor at the external surface of a support grain. 

The term ionization may refer to different processes depending on the context. For radiation effects in the gas phase, it usually implies the removal of the least bound electron to infinity. Such a theoretical definition is not feasible in the condensed phase and it is necessary use a heuristic or operational procedure. Thus, in liquid hydrocarbons, one may use the electron scavenging reaction or a conductivity current to quantify the electrons liberated from molecules. It has only been possible to extrapolate the conductivity current at a low irradiation dose and at a relatively low external field to saturation in the cases of liquefied... 

Estimate the height of the bed to achieve the same performance of the reactor by using the appropriate simplified model, assuming that the liquid phase remains saturated with 02 throughout the reactor length, plug-flow conditions exist, and the external wetting of the catalyst particle is complete. 

Here px is the saturation pressure at the temperature used, Pl is the external pressure on the liquid, n( is the number of ions in the nucleus, e is the electrical charge per ion, and e is the dielectric constant.. The agreement between predicted critical temperatures of superheat and measured values is good within 15° or 20° F. 

For studies in aqueous solutions, the external reference electrode is often an Ag/AgCl/KCl electrode. Electrical contact with the solution is achieved using a disc-like membrane made of porous fritted glass. Because ions have a tendency to migrate across the membrane, a small potential Ej is generated by this liquid junction. This phenomenon can be minimised by inserting a saturated KC1 solution as a salt bridge. 

If the lid is removed, and the external surroundings have partial pressure Ph2o less than 23.8 Torr ( relative humidity < 100% ), then water will evaporate from the beaker into the surroundings until the beaker is empty, because only vapor is stable under these conditions. However, if the external surroundings have partial pressure Ph2o >23.8 Torr, water will condense from the surroundings to fill the beaker, because only liquid is stable under these conditions. Thus, the saturation vapor pressure ( 100% relative humidity ) corresponds to the unique concentration (partial pressure) of water vapor that can coexist at equilibrium in the atmosphere above liquid water at 25°C. Other (T, P) points on the vapor-pressure curve can be interpreted analogously. 

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