Carbon dioxide fugacity

Carbon dioxide fugacity fcOi- CO2 fugacity (/coa) of ore fluids is estimated based on CO2 concentration of fluid inclusions analyzed. By using equilibrium constant of the reaction, C02(g) + H2O = H2CO3, and assuming uh20 to be unity, /CO2 can be estimated. 

Carbon dioxide fugacity (fc02h The /CO2 values can be estimated from (1) gangue mineral assemblages including carbonates and (2) fluid inclusion analyses. 

Fig. 2.26. Range of carbon dioxide fugacity (fco ) and temperature for the propylitic alteration (epidote zone) in the Seigoshi area and same active geothermal systems. Seigoshi = propylitic alteration of the Seigoshi district. The curves A-B and A -B are equilibria for epidote (Xpis = 0.30) - K-mica (oK-mica = 0-9) -K-feldspar (aK-feidspar = 0.95) - calcite assemblages at saturated water vapor pressure condition (Shikazono, 1985a).

Neill et al. [22] have described a headspace gas chromatographic method for the determination of carbon dioxide (fugacity) in seawater. This method requires a small water sample (60 ml), and provides for rapid analysis (2 min). 

Hutcheon I., Shevalier M., and Abercrombie H. J. (1993) pH buffering by metastable mineral-fluid equilibria and evolution of carbon dioxide fugacity during burial diagenesis. Geochim. Cosmochim. Acta 57, 543-562. 

H. Li, B. D. Freeman, S. Kalakkunnat, D. S. Kalika, Effect of copolymer composition, temperature, and carbon dioxide fugacity on pure- and mixed-gas permeability in poly(ethylene glycol)-based materials Free volume interpretation, J. Membr. ScL, 291, 131-139 (2007). 

The stability of acetic acid in basin brines at temperatures above which bacteria are active depends on the rates of the various reactions in which the acid participates. Under geologically relevant hydrothermal conditions, carboxylic acids are likely to undergo either decarboxylation or oxidation. Thermodynamic calculations of the decarboxylation reaction in Eq. (4) at 100°C (Shock 1988, 1989) indicate that, given methane and carbon dioxide fugacities achievable in natural waters, virtually no acetic acid/acetate should persist at equilibrium. It will be shown here that the persistence of acetic acid in basin brines for geologically meaningful time periods is in keeping with experimentally observed rates for the decarboxylation process. 

The fugacity coefficient of thesolid solute dissolved in the fluid phase (0 ) has been obtained using cubic equations of state (52) and statistical mechanical perturbation theory (53). The enhancement factor, E, shown as the quantity ia brackets ia equation 2, is defined as the real solubiUty divided by the solubihty ia an ideal gas. The solubiUty ia an ideal gas is simply the vapor pressure of the sohd over the pressure. Enhancement factors of 10 are common for supercritical systems. Notable exceptions such as the squalane—carbon dioxide system may have enhancement factors greater than 10. Solubihty data can be reduced to a simple form by plotting the logarithm of the enhancement factor vs density, resulting ia a fairly linear relationship (52). 

To illustrate this thermodynamic consistency test, Figs. 15, 16, and 17 show plots of the appropriate functions needed to calculate Areas I, II, and III, respectively, for the nitrogen-carbon dioxide system at 0°C the data are taken from Muirbrook (M5). Fugacity coffiecients were calculated with the modified Redlich-Kwong equation (R4). 

Carbon dioxide will pass out of the system into the buffer to maintain the buffered fugacity. 

FIGURE 32.4 (See color insert following page 302.) The localized minima as obtained after the GCMS simulation with carbon dioxide adsorption over single-wall CNT with a fixed fugacity of 100 kPa. 

Of the problems presented, correlation of the NH3-CO2-H2S-H2O system is most important. Data that might be used for direct empirical correlation of partial pressures or fugacities with total concentrations of ammonia, carbon dioxide, and hydrogen sulfide in the liquid are available for relatively limited ranges... 

Figures 1 to 3 present calculated equilibrium molar ratios of products to reactants as a function of temperature and total pressure of 1 and 100 atm. for the gas-carbon reactions (4), (7), and (5), (6), (4), (7), respectively. Up to 100 atm. over the temperature range involved, the fugacity coefficients of the gases are close to 1 therefore, pressures can be calculated directly from the equilibrium constant. From Fig. 1, it is seen that at temperatures above 1200°K. and at atmospheric pressure, the conversion of carbon dioxide to carbon monoxide by the reaction C - - COj 2CO essentially is unrestricted by equilibrium considerations. At elevated pressures, the possible conversion markedly decreases hence, high pressure has little utility for this reaction, since increased reaction rate can easily be obtained by increasing reaction temperature. On the other hand, for the reaction C -t- 2H2 CH4, the production of methane is seriously limited at one atmosphere pressure and practical operating temperatures, as seen in Fig. 2. Obviously, this reaction must be conducted at elevated pressures to realize a satisfactory yield of methane. For the carbon-steam reaction.

Fig. 3.23. Gas fugacity coefficients for methane and carbon dioxide at 0°C as a function of pressure using the Duan et al. (1992b) model. Reprinted from Marion et al. (2006) with permission...

Fugacity is relevant to imperfect water substance, but not to perfect carbon dioxide at practical temperatures. At 160 US dollars the tables are a good investment. 

Two example tables are given from the set for the dissociation of water substance. These are in contrast to the single table for carbon dioxide which, being a perfect gas at relevant temperatures, contains data independent of pressure, not requiring fugacity in its analysis. 

The fugacity ratio of carbon dioxide, Yco, increases tens or hundreds or times as pressure increases (Fig. 68). Correspondingly / exceeds P, and the increase in pressure with a rise in temperature leads to a nonlinear increase in fugacity. 

Use the Lewis-Randall rule and Fig. 18 to calculate the fugacities of carbon monoxide, oxygen and carbon dioxide in a mixture containing 23, 34 and 43 mole %, respectively, of these gases at 400 C and a total pressure of 250 atm. 

In the above model, the driving force is given by if - /eq). which is the difference between the fugacity of the dissolved gas and its three-phase equilibrium value. In Eq. (4a), is the intrinsic rate constant for the hydrate particle growth reaction and is the mass transfer coefficient around the particle. If the experiments are carried out under conditions such that heat and mass transfer resistances around the particle are eliminated, then k and K k. The intrinsic rate constants K, for methane, ethane, and carbon dioxide are reported in Table 3. 

If a reacting species is involved in the reaction as a pure liquid or as a solid its fugacity can be taken to be unity and the corresponding term does not appear in the product. For example, in the reduction of carbon dioxide over solid carbon 2 CO — C — COa = 0, the equilibrium relationship would be... 

The solubility increases with increase in pressure at a hxed temperature, owing to enhanced solvation due to greater attractive forces between the solute and carbon dioxide. A fundamental relationship for phase equilibrium (Prausnitz et al. 1999) can be used to relate fugacities of the solute in the solid and fluid phases as follows ... 

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