CO2 scrubber

The necessary data required to properly design a CO2 scrubber are separated into three sections, depending upon the CO2 concentration in the feed gas. Corrections... 

Example 11.7 Carbon dioxide is sometimes removed from natural gas by reactive absorption in a tray column. The absorbent, typically an amine, is fed to the top of the column and gas is fed at the bottom. Liquid and gas flow patterns are similar to those in a distillation column with gas rising, liquid falling, and gas-liquid contacting occurring on the trays. Develop a model for a multitray CO2 scrubber assuming that individual trays behave as two-phase, stirred tank reactors. 

Two new technologies have reduced the cost of alkali fuel cells to the point where a European company markets taxis that use them. One is the use of CO2 scrubbers to purify the air supply, making it possible to use atmospheric O2 rather than purified oxygen. The other is the development of ultrathin films of platinum so that a tiny mass of this expensive metal can provide the catalytic surface area needed for efficient fuel-cell operation. 

Li K, Tai MSL, and Teo WK, Design of a CO2 scrubber for self-contained breathing systems using a microporous membrane. Journal of Membrane Science 1994, 86, 119-125. 

A carbon dioxide sensor for monitoring levels in a closed exhalation anesthesia system was developed by Jordan (23). 7,10-dioxa-3,4-diaza-l,5,12,16-hexadecatetrol was prepared by mixing monoethanolamine, often used as a CO2 scrubber, with ethylene gylcol diglycidyl ether in a 2 1 ratio and was used as a coating. The respone was 391 Hz for 10% CO2, exposure time less than 30 sec, and complete recovery in less than 60 sec. No interferences were reported from nitrous oxide, halothane, or oxygen tested at normal anesthesia concentrations. 

An optimum H2/CO ratio in the methanol syngas can in all cases be ensured by a single-stage CO shift conversion unit. However, it will often be more cost-effective to convert only part of the clean gas to CO contents around 3-4 vol. %, while the remaining gas flow bypasses this section (and perhaps also the downstream CO2 scrubber). 

Fig. 5.5. CLL process, (a) Deacidifier, (p) total stripper (c) CO2 scrubber (d) NH3 stripper (e) dryer, (/) NH3 condenser...

To conserve energy, Ground Control ordered the three-man crew to shut down all electrical instruments, to move into the smaller Lunar Module, and to breathe as little as possible. Soon, however. Ground Gontrol realized that the CO2 scrubbers were also turned off and that GOg levels would build up unless something was done. During the process of respiration, COg and water are exhaled. 

CO2 removal agent A CO2 scrubber is used in the purification tube (16) to remove any traces of CO2 from the reference gas. Soda lime and Ascarite (sodium hydroxide coated silica Thomas Scientific Inc., Swedesborough, NJ, USA) are good choices. 

The potassium hydroxide is thus gradually changed to potassium carbonate. The effect of this is that the concentration of OH ions reduces as they are replaced with carbonate COs ions, which greatly affects the performance of the cell. This major difficulty is discussed further in Section 5.6, but one way of at least reducing it is to remove the CO2 from the air as much as possible of, and this is done using a CO2 scrubber in the cathode air supply system. However, it is impossible to remove all the carbon dioxide, so the electrolyte will inevitably deteriorate and require replacing at some point. This mobile system allows that to be done reasonably easily, and of course potassium hydroxide solution is of very low cost. 

The main drawback of the AFC is the absorption of CO2 from the air by the alkaline solution. Carbon dioxide reacts with the hydroxide to form carbonate 2K -1-20H" -H CO2 - K2CO3 -H H2O, which has limited solubility in concentrated alkali, thus leading to deleterious precipitates within the electrode pores. Although there is no absolute solution to this problem, electrolyte replenishment, and upstream CO2 scrubbers provide reasonable compromises. 

Gas entering the primary scrubber contains approximately 0.1 percent oxygen. Dissolved oxygen in water used in CO2 scrubber is the source of this oxygen. 

A critical part of the circle system is the CO2 scrubber (Figure 4.9). Since high partial pressures of CO2 make blood dangerously acidic, it is important to remove it from the circulating air stream. Carbon dioxide is usually removed from the circuit by passing exhaled gas through a container of aqueous alkali or alkaline earth base (typically NaOH, KOH, Ca(OH)2, Ba(OH)2, or mixtures thereof) this... 

Figure 4.9. Picture of a CO2 scrubber used in anesthesia. Reproduced with permission from Morgan et at. (2005).

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