Concentration pressure

Nonporous Dense Membranes. Nonporous, dense membranes consist of a dense film through which permeants are transported by diffusion under the driving force of a pressure, concentration, or electrical potential gradient. The separation of various components of a solution is related directiy to their relative transport rate within the membrane, which is determined by their diffusivity and solubiUty ia the membrane material. An important property of nonporous, dense membranes is that even permeants of similar size may be separated when their concentration ia the membrane material (ie, their solubiUty) differs significantly. Most gas separation, pervaporation, and reverse osmosis membranes use dense membranes to perform the separation. However, these membranes usually have an asymmetric stmcture to improve the flux. 

Fig. 20. Pressure concentration curves of MmNi (—) and LaNi (— ) at 45°C where open circles denote absorption and closed circles desorption of hydrogen. H/M represents the ratio in the hydride of the mole fraction of hydrogen to the mole fraction of the metal.

FIG. 11-100 Temperahire -pressure-concentration diagram of saturated LiBr-water solutions (Vl- K Stoecke7 and J. Jones Refrigeration and. Conditioning)... 

Capture efficiency is the fraction of generated contaminant that is directly captured by the hood. Measurement of capture efficiency involves measuring concentration of process-generated contaminant or a tracer material. Using process-generated contaminant requires use of instruments suited to each specific contaminant and its conditions (temperature, pressure, concentration, form, etc.). In order to facilitate these measurements, a tracer is often substituted for the process-generated contaminant. The tracer is usually a gas (sulfur hexafluoride, nitrous oxide, helium, or similar), but an aerosol (particles) can also be used (potassium iodide, polystyrene particles, microbiological particles, etc.). The chosen tracer should be as similar to the real contaminant as possible, but at the same time should... 

To select a process, determine flow rate, temperature, pressure, concentration of the acid gases in the inlet gas, and allowed concentration of acid gases in the outlet stream. With this information, calculate the partial pressure of the acid gas components. 

Tlie negative sign indicates Uiat diffusion occurs in Uie direction of decreasing concentration. Diflfusivity is a fiuiction of temperature, pressure, concentration, pliase, and Uie nature of the other components. 

Systems of two or more hydrocarbon, chemical and water components may be non-ideal for a variety of reasons. In order to accurately predict the distillation performance of these systems, accurate, experimental data are necessary. Second best is the use of specific empirical relationships that predict tvith varying degrees of accuracy the vapor pressure-concentration relationships at specific temperatures and pressures. 

The similarity between the plots of c/r vs. c shown in Figs. 47 and 48 and those for tc/c vs. c shown in Figs. 38 and 39 is apparent. Deviations from ideality (i.e., the changes in iz/c and in c/r with c) have the same origin for both types of measurements. As with the osmotic pressure-concentration ratio, the change of c/r with c may be reduced by choosing a poor solvent. A further advantage of a poor solvent enters because of the smaller size assumed by the polymer molecule in a poor solvent environment, which reduces the dissymmetry correction. 

They showed further that the limiting slope (RTA2) of the plot of the osmotic pressure-concentration ratio tz/c against the polymer concentration in a binary solvent mixture should be proportional to the value of the quantity on the left side of Eq. (17),f with V2 representing the volume fraction of solvent in the nonsolvent-solvent mixture which is in osmotic equilibrium with the solution. The composition of the liquid medium outside the polymer molecules in a dilute solution must likewise be given by V2. The composition of the solvent mixture within the domains of the polymer molecules may differ slightly from that outside owing to selective absorption of solvent in preference to the nonsolvent. This internal composition is not directly of concern here. If the solution is made sufficiently dilute, the external nonsolvent-solvent composition v2 = l—Vi) will be practically equal to the over-all solvent composition for the solution as a whole. Hence... 

Fig. 145.—Osmotic pressure-concentration ratios ( in g./cm and c in g./lOO ml.) for poly-(4-vinylpyridine) in alcohol, O, coordinates left and below poly-(N-butyl-4-vinylpyridinium bromide) in alcohol, coordinates right and above and the same polymer in alcoholic 0.61 N lithium bromide, 3 coordinates left and below. °> ...

Another approach can be the displacement of the surface Hgands by a reactive gas such as CO, leading to unstable intermediates that will eventually condense into particles. This procedure can be apphed to M(dba)2 (dba = dibenzyhdene acetone M = Pd Pt) [26-28,33,34]. In this case, however, CO remains at the surface of the growing clusters and may modify their chemistry. The reaction conditions (temperature, gas pressure, concentration of precursors and stabilizers) have a strong influence on the nature of the particles formed, primarily on their size. 

Compared with the non-electrochemical interface discussed in the previous section, where a sofid was in contact with a surrounding gaseous atmosphere, the electrode/ electrolyte interface is a multicomponent system and, besides temperature and partial pressures/concentrations, it is also influenced by the electrode potential. This results in greater complexity, which requires additional considerations prior to deriving an expression for the interfacial stability. 

Driving force Reaction pressure Reaction pressure concentration Reaction pressure... 

In the analysis of engineering systems, one frequently encounters systems whose properties vary from point to point within the system. Just as it is possible to define local temperatures, pressures, concentrations, etc., it is possible to generalize equations 3.0.1 and 3.0.4 to define local reaction rates. 

Pressure-concentration isotherms for unmilled and ball-milled MgH2 at 350°C. (Reproduced with permission from Huot,)., Liang, G., Boily, S., Neste, A.V., and Schulz, R., J. Alloys Compel., 293-295,495-500,1999.)... 

Pick a process parameter flow, level, temperature, pressure, concentration, pH, viscosity, state (solid, liquid, or gas), agitation, volume, reaction, sample, component, start, stop, stability, power, inert. 

If, for the situation depicted in Figure 24.3, the partial pressure of A in the gas phase is to be reduced from p in to pa, out at a specified gas flow rate G and total pressure P, what is the minimum liquid flow rate, Lmin, in terms of G, P, and the partial pressures/concentrations of A and B Assume that there is no A in the liquid feed. 

The calculated reaction parameters with BP86//B3LYP methods at two higher temperatures (150 and 250 °C) are shown in Tables VI and VII, respectively. Further corrections for low H2 and olefin pressure/concen-tration and high alkane pressure/concentration (36,37) on BP86// B3LYP values are shown in Tables VIII and IX. 

Any system in stable chemical equilibrium, subjected to the influence of an external cause which tends to change either its temperature or its condensation (pressure, concentration, number of molecules in unit volume), either as a whole or in some of its parts, can only undergo such internal modifications as would, if produced alone, bring about a change of temperature or of condensation of opposite sign to that resulting from the external cause. 

The catalyst activity depends not only on the chemical composition but also on the diffusion properties of the catalyst material and on the size and shape of the catalyst pellets because transport limitations through the gas boundary layer around the pellets and through the porous material reduce the overall reaction rate. The influence of gas film restrictions, which depends on the pellet size and gas velocity, is usually low in sulphuric acid converters. The effective diffusivity in the catalyst depends on the porosity, the pore size distribution, and the tortuosity of the pore system. It may be improved in the design of the carrier by e.g. increasing the porosity or the pore size, but usually such improvements will also lead to a reduction of mechanical strength. The effect of transport restrictions is normally expressed as an effectiveness factor q defined as the ratio between observed reaction rate for a catalyst pellet and the intrinsic reaction rate, i.e. the hypothetical reaction rate if bulk or surface conditions (temperature, pressure, concentrations) prevailed throughout the pellet [11], For particles with the same intrinsic reaction rate and the same pore system, the surface effectiveness factor only depends on an equivalent particle diameter given by... 

The observable (macroscopic) properties of a system at equilibrium are constant. At equilibrium, there is no overall change in the properties that depend on the total quantity of matter in the system. Examples of these properties include colour, pressure, concentration, and pH. 

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