Hydrocarbon + water systems

CH4 + Hydrocarbon Systems.—Liquid hydrocarbons of approximately the same size are in general completely miscible in all proportions. For mixtures of hydrocarbons differing considerably in size, however, immiscibility phenomena have been found with the exhibition of LCST s, e.g. for methane with C, to C hydrocarbons, for ethane with C30 to C38 hydrocarbons, and for hydrocarbon solvents such as heptane, cyclohexane, or benzene with polymers e.g. polyisobutene).  

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When considering pressure drop models based only on water, hydrocarbons system capacity can be significantly overstated. For Nutter random ring packings the pressure drop/capacity models fit the data within +10% over the range of commercial interest, i.e., 0.1 to 1.0 in. water/ft of packing. Pressure drop alues for design operation should... 

The experimental data for water hydrocarbon systems are relatively limited. Consequently, a generalized correlation was developed to estimate the equation for the temperature dependent kij term for those compounds for which no data are available. This generalized correlation was developed only for the SRK equation of state. The variation in the slopes of the kij... 

Experimental solubility data are available for some higher alkane - water systems (see, for example, Skripka et al., (38)). However, these data either cover only a very limited temperature range or contain results for one phase only. No attempt has been made to determine the interaction parameters for water - hydrocarbon systems where the hydrocarbon is larger than n-octane. 

Despite the importance of mixtures containing steam as a component there is a shortage of thermodynamic data for such systems. At low densities the solubility of water in compressed gases has been used (J, 2 to obtain cross term second virial coefficients Bj2- At high densities the phase boundaries of several water + hydrocarbon systems have been determined (3,4). Data which would be of greatest value, pVT measurements, do not exist. Adsorption on the walls of a pVT apparatus causes such large errors that it has been a difficult task to determine the equation of state of pure steam, particularly at low densities. Flow calorimetric measurements, which are free from adsorption errors, offer an alternative route to thermodynamic information. Flow calorimetric measurements of the isothermal enthalpy-pressure coefficient pressure yield the quantity 4>c = B - TdB/dT where B is the second virial coefficient. From values of obtain values of B without recourse to pVT measurements. 

The definition of interfacial tension given in Chapter 8 also applies to water-hydrocarbon systems. 

Figure 183. Drums with coalescers for assisting in the separation of small amounts of entrained liquid, (a) A liquid-liquid separating drum equipped with a coalescer for the removal of small amounts of dispersed phase. In water-hydrocarbon systems, the pot may be designed for 0.5 ft/sec (Facet Enterprises, Industrial Division), (b) An oil-water separator with corrugated plate coalescers (General Electric Co.).

Hydrate phase diagrams for water-hydrocarbon systems provide a convenient overview of the calculation types. These diagrams differ substantially from the normal hydrocarbon phase diagrams primarily due to hydrates and the hydrogen bonds inherent in aqueous systems. The phase diagrams of Section 4.1 provide an overview for the calculation methods in this chapter and the next. 

Hydrate Phase Diagrams for Water + Hydrocarbon Systems... 

Within a simple ternary DDAB-water-hydrocarbon system, it is reasonable to expect that the effective surfactant parameter remains approximately constant throughout the triangular phase diagram, just as it does along the upper water limit. (Note however, that the head-group area can change at low water fractions due to the effects of hydration on the polar head.)... 

Water—hydrocarbon systems, shown in Figure 3, comprise another class of systems which, rather surprisingly, can be handled accurately enough for many purposes. This work with the RKJZ method parallels similar studies by Heidemann (25) with the Soave method and by Peng and Robinson with their equation (10). As in their work, only fugacities in the hydrocarbon-rich liquid phases are fit by the model directly if liquid water is present, it is assumed to be pure, since the Cy fitting the... 

Water-Hydrocarbon Systems. The application of the PR equation to two and three-phase equilibrium calculations for systems containing water has recently been Illustrated by Peng and Robinson ( ). As in the case of other hydrocarbon-non-hydrocarbon mixtures, one fitted binary interaction parameter for water with each of the hydrocarbons is required. These parameters were obtained from experimental data available in the literature on each of the water-hydrocarbon binaries. 

A. Bahadori, H.B. Vuthaluru, M.O. Tade, S. Mokhatab 2008. Predicting water-hydrocarbon systems mutual solubility. Chemical Engineering and Technology 31, 1743—1747. 

FIGURE 11.10 Solubility of water in pure liquid hydrocarbons. The horizontal scale is (1/T), plotted from right to left, with the corresponding values of T in °F shown. This plot is a summary of all the available experimental data as of 1968. (From Daubert, T. E., and R. P. Danner. Phase equilibria in water-hydrocarbon systems. In Technical Data Book, Petroleum Refining, YoL 2, Chapter 9, Figure 9A 1.1. Washington, DC American Petroleum Institute (1978). Reproduced by permission of the American Petroleum Institute.)... 

Daubert, T. E., and R.P Danner. Phase equilibria in water-hydrocarbon systems. In Technical Data Book, Petroleum Refining, Vol. 2. New York American Petroleum Institute, Chapter 9 (1978). 

Azarnoosh and McKetta (1958) gave data for propane in water for pressures from 1 atm to 500 psia and temperatures from 60 to 280°F. They refer to previous work and mention an extensive bibliography on water-hydrocarbon systems by McKetta and Wehe (1959). For a total pressure of 14.7 psia (1 atm), the mole fraction X10 of propane was given as 5.89, i.e., Nc h = 0.0000589 at 60°F. The vs pressure plots were curved. The same authors (1959) reported data for propylene in water and cited Hiraoka (1954) on acetylene in water for pressures up to 500 psi and temperatures to 86 F, Bradbury et al. (1952) on ethylene in water at pressures up to 8000 psi and temperatures up to 212 F, and Brooks and McKetta (1955) and Brooks, Haughn, and McKetta (1955) on 1-butene and water. The propylene data were given as mole fraction x 1 O for pressures up to 500 psia and temperatures up to 220 F. was given as 1.66, which is... 

The SRK and PR EoS have been also applied to water-hydrocarbon systems by adjusting the value of a - in the attractive term to reproduce water s vapor pressure. 

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