Vapor pressure gaseous effluents

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. 

Braune and Strassman8 measured the concentration of iodine in gaseous carbon dioxide at pressures up to 50 atm from 32° to 98°C. They passed the carbon dioxide over an excess of solid iodine and analyzed the effluent mixtures. Their pressures were too low to find the saturation vapor pressures or to show whether or not critical end points were formed. 

Extractive Distillation. In extractive distillation a fraction comprising compounds of similar volatility is vaporized and passed countercurrent to a liquid solvent stream in a packed or bubble cap tower. The operating conditions of temperature and pressure are regulated so that one or more of the components of the mixture are dissolved in the entrainer and removed in a liquid phase extract, while the remaining vapor is taken overhead and condensed or discharged as gaseous effluent. 

Water vapor from the evaporator passes to a water-cooled condenser, and the weakly acidic condensate is discharged as liquid effluent. The extractive distillation section of the plant is maintained under slight negative pressure, and the condenser off-gases are scrubbed with water and discharged as gaseous effluent. 

Liquid propylene, gaseous carbon monoxide and hydrogen, and a soluble cobalt catalyst are fed to a high-pressure catalytic reactor. The reactor effluent goes to a flash tank, where all of the solution constituents are vaporized except the catalyst, which is recycled to the reactor. The reaction products are separated from unconsumed reactants in a multiple-unit process, and the product stream, which contains both butyraldehyde and /i-butanol, is subjected to additional hydrogenation with excess hydrogen, converting all of the butyraldehyde to butanol. 

Figure 5.17 Sketch of a heated pneumatic nebuUzer interface for APCI-MS. The LC effluent is nebulized by a fast gas stream and subjected to rapid heating via a heated make-up gas (typically N2 at 120-200 °C, although the heater temperature can be much higher). The vaporized effluent is then introduced into the APCI plasma activated by the corona discharge, all at atmospheric pressure. The gaseous solvated ions are then introduced into the mass spectrometer vacuum via an API interface that must discriminate in favor of ions vs neutrals and also de-solvate the ions (see text). Reproduced from MDS-Sciex literature (The API Book) with permission.

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