Application carbon dioxide absorption

As examples of micro-channel process intensification and the respective equipment, in particular gas/liquid micro reactors and their application to toluene and various other fluorinations and also to carbon dioxide absorption can be mentioned [5]. Generally, reactions may be amenable to process intensification, when performed via high-temperature, high-pressure, and high-concentration routes and also when using aggressive reactants [5]. 

The supercritical CO2 absorption bands change in intensity as a function of density but the band shape does not change - at least not at the 8 cm spectral resolution typically used for this application. As a result, it is a simple matter to subtract the supercritical carbon dioxide absorption spectrum from an FT-IR data file collected during an SFC/FT-IR experiment. The subtraction factor is adjusted to exactly compensate for the Fermi resonance absorption. The resulting spectrum will then contain only absorption bands due to other components, if any, entrained in the supercritical fluid. The regions from 3800-3500 cm and from 2500-2200 cm appear as gaps in the spectrum because the supercritical carbon dioxide absorbs all the available infrared radiation in these regions. 

Chemical Sorption Methods. Chemical sorption methods to determine ky a are based on a chemical reaction between the absorbed gas and a chemical that is added to the liquid phase. Four of these methods will be presented here, although many others exist. The sulfite oxidation, hydrazine, and peroxide methods are applicable to systems studying oxygen transport, while the carbon dioxide absorption method, as its name implies, is for measuring dissolved carbon dioxide. 

The absorption of carbon dioxide in water has been shown to be almost entirely liquid-film controlled—presumably because of the relatively low solubility of carbon dioxide. Considerable research has, therefore, been conducted on the CO2-H2O system in connection with both absorption and desorption to determine the liquid-frlm resistance to mass transfer when various packings are used. Some of the data obtained are directly applicable to (he design of commercial installations for carbon dioxide absorption and desorption. 

Chapter 9 deals with developments in the application of MCs and the associated improvements in membrane fabrication to overcome current limitations due to membrane wetting problems, which lower the efficiency of mass transfer and reduce membrane life. There are numerous advantages of MCs over conventional methods for carbon dioxide absorption and stripping technology such as their compacmess and high effective surface area per unit volume. MCs have also been developed for treatment of aqueous systems and they offer a combined membrane separation and absorption process in one physical setting. 

While the carbon dioxide/caiistic test method has become accepted, one should use the results with caution. The chemical reaction masks the effect of physical absorption, and the relative values in the table may not hold for other cases, especially distillation applications where much of the resistance to mass transfer is in the gas phase. Background on this combination of physical and chemical absorption may Be found earher in the present section, under Absorption with Chemical Reaction. ... 

In many applications of mass transfer the solute reacts with the medium as in the case, for example, of the absorption of carbon dioxide in an alkaline solution. The mass transfer rate then decreases in the direction of diffusion as a result of the reaction. Considering the unidirectional molecular diffusion of a component A through a distance Sy over area A. then, neglecting the effects of bulk flow, a material balance for an irreversible reaction of order n gives ... 

Carbon dioxide is absorbed in water from a 25 per cent mixture in nitrogen. How will its absorption rate compare with that from a mixture containing 35 per cent carbon dioxide, 40 per cent hydrogen and 25 per cent nitrogen It may be assumed that the gas-film resistance is controlling, that the partial pressure of carbon dioxide, at the gas-liquid interface is negligible and that the two-lilm theory is applicable, with the gan film thickness the same in the two cases. 

Table A2 (see the appendices) lists briefly the purification methods applicable to many of the solvents listed. It is, however, often advisable to guard solvents, once their bottles have been opened, from the absorption of moisture from the atmosphere, and in the case of basic solvents, also from the absorption of carbon dioxide. If purification is deemed to be necessary and no method is specified in table A2, then usually a method noted for a chemically similar solvent can be employed.

Apart from the aforementioned most frequently used sensor technologies, also selective electrochemical sensor combinations have been commercialised for use in dedicated applications. The combination of electrochemical CO, H2S, SO2 and NH3 sensors was used for quality and freshness control of foods like fish [98] and meat [99]. Combinations of MOSs and MOSFETs supplemented with a selective IR absorption sensor for carbon dioxide and a humidity sensor for measuring relative humidity were also described [100]. 

Existing physical absorption AGR processes are relatively energy inefficient for application in coal gasification they use substantial amounts of steam or stripping gas to regenerate lean solvent and power to pump lean solvent into the AGR absorber. In the treatment of crude gas with substantial carbon dioxide content, work available by expansion of separated carbon dioxide from its partial pressure in the crude gas, typically 100-300 psia, to atmospheric pressure, is not recovered. In theory, an AGR process could recover and utilize this potential energy. 

Reactive absorption is probably the most widely applied type of a reactive separation process. It is used for production purposes in a number of classical bulk-chemical technologies, such as nitric or sulfuric acid. It is also often employed in gas purification processes, e.g., to remove carbon dioxide or hydrogen sulfide. Other interesting areas of application include olefin/paraffin separations, where reactive absorption with reversible chemical complexation appears to be a promising alternative to the cryogenic distillation (62). 

Carbon dioxide removal by reactive absorption in amine solutions is also applied on the commercial scale, for instance, in the treatment of flue gas (see later in this chapter). Another possible application field of the technique is gas desulfurization, in which H2S is removed and converted to sulfur by means of reactive absorption. Aqueous solutions of ferric chelates (160-162) as well as tetramethylene sulfone, pyridine, quinoline, and polyglycol ether solutions of S02 (163,164) have been proposed as solvents. Reactive absorption can also be used for NOx reduction and removal from flue or exhaust gases (165,166). The separation of light olefins and paraffins by means of a reversible chemical com-plexation of olefins with Ag(I) or Cu(I) compounds in aqueous and nonaqueous solutions is another very interesting example of reactive absorption, one that could possibly replace the conventional cryogenic distillation technology (167). 

Two important applications of radiation to determine molecular structure—X-ray crystallography and magnetic resonance—were discussed in Chapters 3 and 5. In this chapter we will discuss a variety of other techniques. Microwave absorption usually forces molecules to rotate more rapidly, and the frequencies of these absorptions provide a direct measure of bond distances. Individual bonds in a molecule can vibrate, as discussed classically in Chapter 3. Here we will do the quantum description, which explains why the greenhouse effect, which overheats the atmosphere of Venus and may be starting to affect the Earth s climate, is a direct result of infrared radiation inducing vibrations in molecules such as carbon dioxide. 

Water, Carbon Dioxide-Free When this type of water is called for, it shall have been boiled vigorously for 5 min or more, and allowed to cool while protected from absorption of carbon dioxide from the atmosphere. Deaerated water is water that has been treated to reduce the content of dissolved air by suitable means, such as by boiling vigorously for 5 min and cooling or by the application of ultrasonic vibration. 

These data also indicate where reasonable care needs to be exercised in the use of supercritical carbon dioxide for cleaning applications. Amorphous materials can show significant uptakes of carbon dioxide depending upon the conditions employed. Secondly, even semicrystalline materials can show property changes that result from the absorption of carbon dioxide that ultimately affects the amount of crystallinity in the polymeric material. 

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