Liquid-gas equilibria

The most widely used and still simple theoretical approach for describing a gas-liquid equilibrium for a volatile compound A is expressed by Henry s law ... 

TABLE 4.1. Boiling Points and Gas-Liquid Equilibrium Characteristics (Henry s Law Constants) for Both Odorous and Nonodorous Compounds in Water at 25°C (Thibodeaux, 1996 Sander, 2000). 

Since members of a homologous series have incremental boiling point differences and if the amount of any homolog in the moving gas phase is related to vapor pressure at the temperature of the experiment, plots of log k vs. carbon number should also be a straight line. (The enthalpy of vaporization increases monotonically with carbon number.) This in fact is observed in gas-liquid equilibrium separation systems. It is the basis of retention index systems pioneered by Kovats for qualitative identification. 

The ratio [Sc(Cp )2Ph] / [Sc(Cp )2H] was obtained from relative heights of H nuclear magnetic resonance (NMR) peaks, and [C6H6] was calculated from the density of benzene. The determination of [H2] was more complicated because this substance is also involved in a gas-liquid equilibrium. The procedure used by the authors is as follows. 

It is also possible to create a redundancy between measurements with models linking several variables. Static and robust models like acid-base equilibrium and gas-liquid equilibrium can be used easily. However, models with strong assumptions and/or with unknown validity should be used with caution. In this last case, we also have to take into account that the model itself can be faulty and a dimension of the state-universe of the corresponding bba is the faulty state of the model. 

Gas-liquid relationships, in the geochemical sense, should be considered liquid-solid-gas interactions in the subsurface. The subsurface gas phase is composed of a mixture of gases with various properties, usually found in the free pore spaces of the solid phase. Processes involved in the gas-liquid and gas-solid interface interactions are controlled by factors such as vapor pressure-volatilization, adsorption, solubility, pressure, and temperature. The solubility of a pure gas in a closed system containing water reaches an equilibrium concentration at a constant pressure and temperature. A gas-liquid equilibrium may be described by a partition coefficient, relative volatilization and Henry s law. 

Raoult s and Dalton s equations both represent the partial pressure of a component in a gas mixture. In the case of Raoult s equation, the gas must be in equilibrium with a liquid. These equations may be combined by eliminating partial pressure. The resulting equation relates the compositions of the gas and liquid phases in equilibrium to the pressure and temperature at which the gas-liquid equilibrium exists. 

This check should be routinely made before any gas-liquid equilibrium calculation. 

Compare your answers with the laboratory measured specific volume of reservoir liquid at bubble point, 0.0353 cu ft/Ib. 13-18, The gas-liquid equilibrium calculations for a two-stage separation of a retrograde gas have been completed. Results are given below. 

The gas-liquid equilibrium calculations for a three-stage separation of a retrograde gas have been completed. Results are given below. 

A convergence pressure of 10,000 psia should have been used for this mixture. See Figure 14-4. Obtain K-factors at pk = 10,000 and repeat the gas-liquid equilibrium calculation. 

Gas-liquid equilibrium for a volatile oil has been calculated for a pressure of 1500 psia and a temperature of 150°F. Results are given below. A convergence pressure of 5000 psia was used to obtain K-factors. What convergence pressure should have been used ... 

The following equation is not as accurate as the K-factor graphs of Appendix A24. However, certain solution techniques for gas-liquid equilibrium calculations with equations-of-state require initial trial values of K-factors. Equation B-61 is useful for this purpose. 

An additional problem arises when the stability of the critical phase involving the gas-liquid equilibrium in a binary system is studied. The conditions of stability of a homogenous system at constant pressure are d2A/dV2)T x> 0 and d25/dx )T P > 0 from Equations (5.136) and (5.141), respectively. The question arises of which of the two conditions becomes zero first as the boundary between stable and unstable phases is approached. 

However, for mixtures of TPP and toluene, a third (liquid) phase forms in the presence of the gas and the solid, at pressures well below the critical pressure of toluene. At higher pressures, gas-liquid and solid-liquid equilibria were observed, rather than gas-solid equilibrium. Thus, phase compositions for gas-liquid equilibrium were measured for this binary mixture to give TPP solubilities in each of the fluid phases. Pressures and temperatures for three-phase, solid-liquid-gas equilibrium were also measured for both binary mixtures. 

The following experimental techniques were used to measure the pressures and temperatures for solid-liquid-gas equilibrium, phase compositions (bubble and dew points) for gas-liquid equilibrium, and solid solubilities in supercritical pentane. Experimental procedures and the apparatus are described in detail elsewhere (13). 

Bubble points for gas-liquid equilibrium were measured at constant temperature by observing the pressure at which the equilibrium gas phase disappeared upon injection of small amounts of solvent into the view cell. The equilibrium composition of the liquid phase was obtained from the known composition in the cell. Other pressures and corresponding compositions at this temperature were obtained by repeating the procedure for different porphyrin loadings. 

The organic liquid solvent initially contains 0.001 mole fraction DMSO. The required solvent flow rate is to be 1.5 times the minimum. The gas-liquid equilibrium relationship is given by ... 

Had the column operated at equilibrium, then the maximum amount of solute would have been removed and we would have used the minimum amount of liquid. Given the gas-liquid equilibrium relationship ... 

Several investigations of these petrochemical processes address the question of co-current versus countercurrent operation [1, 9, 10]. Whereas reactive distillation is a countercurrent operation by definition, in HDS, HC and HDN countercurrent operation is favorable because the gas-liquid equilibrium (GLE) of H2S and ammonia lies to high extent on the gas side. However, this cannot be generalized. As shown in Fig. 8.3, an internal loop can occur if the gas flow, which stripped the... 

A - gas reactant A a - adsorbing tracer app - apparent value e - at gas-liquid equilibrium gl - gas-liquid... 

The regenerated extraction gas leaves the second regeneration column at its head and is cooled down in (WT3) to a temperature of approximately 20°C. Depending on the type of extraction solvent the buffer vessel (KP) contains liquid phase in equilibrium state with gas or merely gas of high density. In the last case a pressure controlled pneumatic pump feeds fresh solvent into the circular process. If a gas/liquid equilibrium is achieved in the buffer vessel the gas pressure remains constant until a minimal amount of liquid remains there. For this purpose two optical sensors are introduced into the buffer vessel registrating the minimum and maximum extraction liquid level If the level falls below minimum, fresh liquid extraction solvent is refilled. 

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