Carbon dioxide absorber

Carbon dioxide absorbs infrared energy during bending or stretching motions that are accompanied by a change in dipole moment (from zero). Which of the transitions pictured in Fig. 2b... 

The freshness of roasted coffees can be maintained with packaged oxygen and carbon dioxide absorbents,222-223 or by spraying the coffee beans with a sodium sorbate solution.224... 

Carbon in soil and plant materials can be determined by wet- and dry-combustion methods [7, 8]. In both instances, soil and plant carbon is converted into carbon dioxide, absorbed in alkali and determined either by titration against a standard acid or by weighing. These methods involve large apparatus, are expensive and time consuming, and therefore cannot be adapted to the routine analysis of a large number of samples. 

Fig. 6.IS Methods of packing for water and carbon dioxide absorbers [33]. Reproduced with permission...

The metabolism of enflurane and sevoflurane results in the formation of fluoride ion. However, in contrast to the rarely used volatile anesthetic methoxyflurane, renal fluoride levels do not reach toxic levels under normal circumstances. In addition, sevoflurane is degraded by contact with the carbon dioxide absorbent in anesthesia machines, yielding a vinyl ether called "compound A," which can cause renal damage if high concentrations are absorbed. (See Do We Really Need Another Inhaled Anesthetic ) Seventy percent of the absorbed methoxyflurane is metabolized by the liver, and the released fluoride ions can produce nephrotoxicity. In terms of the extent of hepatic metabolism, the rank order for the inhaled anesthetics is methoxyflurane > halothane > enflurane > sevoflurane > isoflurane > desflurane > nitrous oxide (Table 25-2). Nitrous oxide is not metabolized by human tissues. However, bacteria in the gastrointestinal tract may be able to break down the nitrous oxide molecule. 

Anesthesia is achieved rapidly and smoothly with sevoflurane, and recovery is more rapid than with isoflurane. However, sevoflurane is chemically unstable when exposed to carbon dioxide absorbents in anesthesia machines, degrading to an olefinic compound (fluoromethyl-2,2-difluoro-l-[trifluoromethyl]vinyl ether, also known as compound A) that is potentially nephrotoxic. In addition, sevoflurane is metabolized by the liver to release fluoride ions, raising concerns about potential renal damage. 

Stable to the soda lime or other carbon dioxide absorbents used in closed circuit anesthesia. 

A hydrocarbon fuel such as light oil or natural gas can be burned specifically in order to produce carbon dioxide. The flue gas from this process, which contains less than 0.5% oxygen by volume, is cooled and scrubbed to remove any impurities that may be present. The resultant gas is then passed through an absorbent tower, where it comes into contact with a carbon dioxide absorbing solution. The absorbing solution, now rich in carbon dioxide, is pumped to a stripper tower, where the heat from the combustion of the fuel is used to release the... 

Carbon dioxide molecules get absorbed by plants and are used during a process called photosynthesis. Some of the carbon dioxide absorbed by the plants will contain carbon-12 atoms, while other carbon dioxide molecules will contain carbon-14 atoms. Since humans and animals eat plants, their bodies also contain some carbon-12 and some carbon-14. 

The two linear molecules of most concern to the photochemist are carbon dioxide37 47 and nitrous oxide37. Carbon dioxide absorbs only in the relatively far ultraviolet. The primary dissociation is almost certainly... 

The absorption train is composed of a tube packed with water absorbent, a second tube packed with a carbon dioxide absorbent, and a guard tube packed with equal volumes of the water and carbon dioxide absorbents. Anhydrous magnesium perchlorate (MgC104) is commonly used for the water absorbent, while sodium hydroxide (NaOH) or potassium hydroxide (KOH) impregnated in an inert carrier is used as the carbon dioxide absorber. 

The CNG acid gas removal process is distinguished from existing AGR processes by three features. The first feature is the use of pure liquid carbon dioxide as absorbent for sulfurous compounds the second feature is the use of triple-point crystallization to separate pure carbon dioxide from sulfurous compounds the third feature is the use of a liquid-solid slurry to absorb carbon dioxide below the triple point temperature of carbon dioxide. Pure liquid carbon dioxide is a uniquely effective absorbent for sulfurous compounds and trace contaminants triple-point crystallization economically produces pure carbon dioxide and concentrated hydrogen sulfide for bulk carbon dioxide absorption the slurry absorbent diminishes absorbent flow and limits the carbon dioxide absorber temperature rise to an acceptable low value. The sequence of gas treatment is shown in Figure 1, an overview of the CNG acid gas removal process. 

The dew point must be warmer than -56.6°C to permit use of liquid carbon dioxide absorbent because pure liquid carbon dioxide cannot exist below the triple point. The carbon dioxide partial pressure, i.e., gas phase CO2 mol fraction times total pressure, of synthesis gas mixtures with -56.6°C dew points is plotted versus synthesis gas pressure in Figure 4. Increasing the H2 CO ratio at fixed total pressure decreases the carbon dioxide partial pressure required for a -56.6°C dew point. Liquid carbon dioxide can be used to absorb sulfur molecules for any combination of gas pressure and carbon dioxide partial pressure which lies above the curves of Figure 4. 

The liquid carbon dioxide absorbent, with sulfurous compounds, other trace contaminants, and perhaps some co-absorbed light hydrocarbons such as methane and ethane, is combined with the contaminated liquid carbon dioxide condensed in precooling to -55°C. The combined carbon dioxide stream, typically 3 to 5 mol % hydrogen sulfide, is stripped of light hydrocarbons if necessary, and sent to the carbon dioxide regenerator. The treated gas, containing less than 1 ppm H2S, leaves the sulfur absorber at essentially -55°C with carbon dioxide the only significant impurity yet to be removed. 

The large effective heat capacity of the liquid-solid slurry absorbent enables relatively small slurry flows to absorb the carbon dioxide heat of condensation with only modest absorber temperature rise. This contrasts with other acid gas removal processes in which solvent flows to the carbon dioxide absorber are considerably larger than flows determined by vapor-liquid equilibrium constraints. Large flows are required to provide sensible heat capacity for the large absorber heat effects. Small slurry absorbent flows permit smaller tower diameters because allowable vapor velocities generally increase with reduced liquid loading (8). 

Carbon dioxide may be removed from commercial carbon monoxide by scrubbing with dry potassium hydroxide or a commercial carbon dioxide absorbent such as Caroxite. A procedure for the preparation and purification of carbon monoxide is given by W. L. Gilliland and A. A. Blanchard.6... 

CS3 A carbon-hydrogen analyzer uses a water absorber (which contains magnesium perchlorate, MgjClO ) and a carbon dioxide absorber (which contains sodium hydroxide, NaOH). The water absorber is always located in front of the carbon dioxide absorber. 

FIG. 14-71 Overall mass transfer coefficients for carbon dioxide absorbed from air by IN caustic solution. Packing = 2-inch metal raschig and pall rings. Air rate = 0.61 kg/s m (450 Ib/hrTt ). To convert from Ib/hrfFto kg/s-m, multiply by 0.00136. To convert from Ib-moles/hr fR atm to kg-moles/s-m atm, multiply by 0.0045. [Eckert et al, Chem. Eng. Progr., 54(1), 70 (1958).]... 

Second, the absorbance capacity of a compound depends on its molecular structure. Certain compounds, such as carbon dioxide absorb strongly in the mid-IR, whereas other compounds, even those of substantial molecular complexity, have less intensive absorbance. 

Baum, J., Sachs, G., Driesch, C., Stanke, H.G. (1995). Carbon monoxide generation in carbon dioxide absorbents. Anesth. Analg. 81 144-6. 

Carbon dioxide absorber. Carbon dioxide is scavenged by calcium hydroxide provided the water content is sufficiently high. This is an irreversible system. Reversible systems are based on absorption on zeolite of active carbon. ... 

LEE DS, SHIN DH, LEE DU, KIM jc and CHEIGH HS, The use of physical carbon dioxide absorbents to control pressure build-up and volume expansion of kimchi packages. Journal of Food Engineering, 48, 183-188. 

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