Carbon dioxide, absorption vapor pressure

The scrubbing liquid must be chosen with specific reference to the gas being removed. The gas solubility in the liquid solvent should be high so that reasonable quantities of solvent are required. The solvent should have a low vapor pressure to reduce losses, be noncorrosive, inexpensive, nontoxic, nonflammable, chemically stable, and have a low freezing point. It is no wonder that water is the most popular solvent used in absorption devices. The water may be treated with an acid or a base to enhance removal of a specific gas. If carbon dioxide is present in the gaseous effluent and water is used as the scrubbing liquid, a solution of carbonic acid will gradually replace the water in the system. 

Both factors depend on the respective partial vapor pressures of water and carbon dioxide and upon the distance to the radiation source. The partial vapor pressure of carbon dioxide in the atmosphere is fairly constant (30 Pa), but the partial vapor pressure of water varies with atmospheric relative humidity. Duiser (1989) published graphs plotting absorption factors (a) against the product of partial vapor pressure and distance to flame (Px) for flame temperatures ranging from 800 to 1800 K. 

Distillation of Ammonium Bicarbonate Solutions. Vapor-liquid equilibrium data for ammonium bicarbonate solutions at the boil are apparently not available in the literature. The data in the literature, however, do indicate that when the temperature of such a solution is increased, or the pressure on it decreased, the gas that is evolved is predominantly carbon dioxide. Thus, it appears that such a distillation would be two consecutive processes first, a steam stripping of the carbon dioxide in the solution, followed by a distillation of ammonia from an ammonia-water mixture containing perhaps some carbon dioxide. Possibly the ammonia, carbon dioxide, and water in the distillate product would recombine completely in the condenser to form an ammonium bicarbonate solution. Perhaps an absorption tower would be necessary to effect the recombination. 

Localized remote sensing for chemical compositions in operating PEMFC can be performed by tunable diode laser absorption spectroscopy (TDLAS). Measurement of water vapor and carbon dioxide has been reported by using TDLAS.31-36 In TDLAS measurement, the absorption of the laser beam passing through the gas sample is expressed with the partial pressure of the absorbing species, Pa (atm), by Beer s law,... 

Figure 5-21 shows computed values of the spectral emissivity eg = 8 x(T,pL,X) as a function of wavelength for an equimolar mixture of carbon dioxide and water vapor for a gas temperature of 1500 K, partial pressure of 0.18 atm, and a path length L = 2 m. Three principal absorption-emission bands for C02 are seen to be centered on 2.7, 4.3, and 15 pm. Two weaker bands at 2 and 9.7 pm are also evident. Three principal absorption-emission bands for water vapor are also identified near 2.7, 6.6, and 20 pm with lesser bands at 1.17, 1.36, and 1.87 pm. The total emissivity eg and absorptivity a 1 are calculated by integration with respect to wavelength of the spectral emissivities, using Eqs. (5-138) in a manner similar to the development of total surface properties. 

For the absorption of a gas (like carbon dioxide) into a liquid (like water) Henry s law stales that partial pressure of the gas is proportional to the mole fraction of the gas in the liquid-gas solution with the constant of proportionality being Henry s constant. A bottle of soda pop (CO2-H2O) at room temperature has a Henry s constant of l7,l(X)kPa. If the pressure in this bottle is 120 kPa and the partial pressure of the water vapor in the gas volume at the top of the bottle is neglected, the concentration of the CO2 in the liquid HjO is (a) 0.003 mol-COj/mol (6) 0.007 mol-COj/mol... 

The effluent gas of a fermentation process contains carbon dioxide and ethanol. It is required to recover 97.5% of the ethanol by absorption with water in a countercurrent absorber. Using the Kremser equation, determine the smallest number of stages required to meet the specification. Use trial calculations with number of stages ranging from 6 to 9. The A -valuc of ethanol at average column temperature and pressure may be assumed constant at 0.57. The stripping factor can be estimated based on the inlet vapor and liquid flows. 

Reversible Reaction. This type of absorption is characterized by the occurrence of a chemical reaction between the gaseous component being absorbed and a component in the liquid phase to form a compound that exerts a significant vapor pressure of the absorbed component. An example is the absorption of carbon dioxide into a monoethanolamine solution. This type of system is quite difficult to analyze because the vapor-liquid equilibrium curve is not linear and the rate of absorption may be affected by chemical reaction rates. 

When operated in conjunction with an absorber, the product becomes the vapor leaving the condenser, while the bottom stream is recycled to the absorber. A typical absorber ripper combination for the separation of carbon dioxide and hydrogen is shown in Fig. 12.3. Monoethanola-mine (MEA) is used as the solvent. Control of CO2 content in the MEA leaving the stripper is only important for its influence on the equilibrium maintained with the gas leaving the top tray of the absorber-C02 is not lost. Cooling the lean MEA enhances absorption, although its control is not really warranted. In addition, the absorber usually operates at a higher pressure than the skipper. 

The strong inhibiting effect of water during the reduction of well-dispersed iron oxide phases on alumina surfaces is also apparent from the infrared spectrum of carbon monoxide adsorbed onto the reduced catalyst prepared from complex iron cyanides according to the above procedure of Boellaard and co-workers Despite the support, the size of the iron particles, and the loading of iron on the support all being essentially the same, the infrared spectrum of the adsorbed carbon monoxide is completely different. The absorption band at 2155 cm is not seen, which indicates that Fe(II) is not present at the alumina surface when reduced in the presence of low partial pressures of water vapor. Rather than bands with frequencies above about 2000 cm bands at 1806, 1884, and 1984 cm are observed (Fig. 5.9). Even at room temperature, disproportionation of carbon monoxide to carbon dioxide and carbon occurs, which is demonstrated by the presence of carbon dioxide adsorbed onto the alumina support. The infrared bands peaking at 1348 and 1598 cm arise from carbon dioxide adsorbed on alumina. 

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