Logarithmic mean partial pressure

D. Rectification in vertical wetted wall column with turbulent vapor flow, Johnstone and Pigford correlation =0.0.328(Wi) Wi P>vP 3000 < NL < 40,000, 0.5 < Ns. < 3 N=, v,.gi = gas velocity relative to R. liquid film = — in film -1 2 " [E] Use logarithmic mean driving force at two ends of column. Based on four systems with gas-side resistance only, = logarithmic mean partial pressure of nondiffusing species B in binary mixture. p = total pressure Modified form is used for structured packings (See Table 5-28-H). 

Pbm Logarithmic mean partial pressure kPa atm X Parameter used in entrainment -/- -/-... 

Pbm = logarithmic mean partial pressure of inert gas, atm P = total pressure, atm NRc = Reynolds number, gas phase Nsc = Schmidt number, gas phase... 

The logarithmic mean partial pressure driving force is ... 

The 35% increased flow rates will require that 1,342 Ib-mol/h of CO2 are absorbed. The CO2 concentration in the inlet and outlet gas streams, as well as the CO2 concentration in the inlet and outlet MEA solutions, will be the same as at the original lower rates. The logarithmic mean partial-pressure driving force also will be unchanged. 

The overall driving force for mass transfer is AT = Pg—Pi, where Pi is the concentration of oxygen in the liquid phase expressed as an equivalent partial pressure. For the experimental conditions, T/ 0 due to the fast, liquid-phase reaction. The oxygen pressure on the gas side varies due to the liquid head. Assume that the pressure at the top of the tank was 1 atm. Then Tg = 0.975 atm since the vapor pressure of water at 20°C should be subtracted. At the bottom of the tank, 1.0635 atm. The logarithmic mean is appropriate AT =1.018 atm. Thus, the transfer rate was... 

This means that representing the equilibrium adsorbate mass (or volume) adsorbed versus concentration (or partial pressure) should be a straight line if plotted on logarithmic scales. Other theoretically based correlating equations are available for the adsorption of gases and vapors9, but all equations have their limitations. 

Since part of the gas mixture (e.g. air) is absorbed as it bubbles through the liquid column, the composition of the gas mixture changes. Furthermore, the pressure in the liquid is higher at the gas inlet than in the head space above it. This difference in partial pressure is taken into account by the mean logarithmic concentration difference, Acm ... 

Fig. 9. Schematic design of a carbon dioxide partial pressure (pC02) electrode. C02 diffuses through the membrane into or out of the electrolyte where it equilibrates with HCO, thus generating or consuming protons. The respective pH change of the electrolyte is sensed with a pH electrode and is logarithmically proportional to the pC02 in the measuring solution. Since the electrolyte may become exhausted, one can replace it through in/out lines. These can also be used to re-calibrate the pH electrode. Therefore, the electrode is retractable by means of a mechanical positioner...

We will complete our discussion of chemical potential by using Equation IV. 17 to obtain the logarithmic term in concentration that is found for fij in a liquid phase. First, it should be pointed out that Equation IV. 17 has no concentration term per se for the chemical potential of species j in a gas phase. However, the partial pressure of a species in a gas phase is really analogous to the concentration of a species in a liquid e.g., PjV = rijRT for gaseous species/ (Eq. IV.15), and concentration means number/volume and equals n/V, which equals P/RT. 

The kc, fcy, k, and kg are all mass transfer coefficients that, respectively, have the units cm/sec, g mole/sec cm, g mole/sec cm and g mole/sec cm atm. The Pa s are partial pressure for component A, and Ybm is the logarithmic mole fraction of the nondiffusing component (analogous to the logarithmic mean temperature difference) ... 

The partial pressure of CO2 at the bottom of the column is 4.024 atm, while at the top of the column it is 0.00199 atm. After reduction of these values by the equilibrium partial pressure of CO2 above the MEA solutions, the logarithmic mean-pressure driving force is 0.522 atm. The logarith-... 

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