Absorption, pollutants

STEP TUNABLE LASER - OA ABSORPTION POLLUTION DETECTION... 

Elastomer UV degradation Resistance to water absorption Pollutant Weathering Ozone SO2 NO, H2S... 

Another method to remove pollutants from air is to absorb the pollutants into a nonvolatile liquid such as oil. During absorption, pollutants move from the gas phase to the liquid phase. This movement is an example of mass transfer. To move between phases, the pollutants must cross the liquid-gas interface. Increasing the interfacial area increases the rate of mass transfer. An easy way to increase the interfacial area is to bubble the gas through the liquid. This concept is effective in delivering oxygen to water in fish tanks and it is effective in delivering benzene to oil. 

Allen, H. C. Brauers, T. Finlayson-Pitts, B. J. Illustrating Deviations in the Beer-Lambert Law in an Instrumental Analysis Laboratory Measuring Atmospheric Pollutants by Differential Optical Absorption Spectrometry, /. Chem. 

We are explicitly excluding absorption effects Light-absorbing pollutants modify this description. 

The purpose of such scmbbing operations may be any of the following gas purification (eg, removal of air pollutants from exhaust gases or contaminants from gases that will be further processed), product recovery, or production of solutions of gases for various purposes. Several examples of appHed absorption processes are shown in Table 1. 

The absorption of sulfur dioxide in alkaline (even weakly alkaline) aqueous solutions affords sulfites, bisulfites, and metabisulfites. The chemistry of the interaction of sulfur dioxide with alkaline substances, either in solution, slurry, or soHd form, is also of great technological importance in connection with air pollution control and sulfur recovery (25,227,235—241). Even weak bases such as 2inc oxide absorb sulfur dioxide. A slurry of 2inc oxide in a smelter can be used to remove sulfur dioxide and the resultant product can be recycled to the roaster (242). 

In the early 1970s, air pollution requirements led to the adoption of the double contact or double absorption process, which provides overall conversions of better than 99.7%. The double absorption process employs the principle of intermediate removal of the reaction product, ie, SO, to obtain favorable equiUbria and kinetics in later stages of the reaction. A few single absorption plants are stiU being built in some areas of the world, or where special circumstances exist, but most industriali2ed nations have emission standards that cannot be achieved without utili2ing double absorption or tad-gas scmbbers. A discussion of sulfuric acid plant air emissions, control measures, and emissions calculations can be found in Reference 98. 

Double-Absorption Plants. In the United States, newer sulfuric acid plants ate requited to limit SO2 stack emissions to 2 kg of SO2 per metric ton of 100% acid produced (4 Ib /short ton Ib = pounds mass). This is equivalent to a sulfur dioxide conversion efficiency of 99.7%. Acid plants used as pollution control devices, for example those associated with smelters, have different regulations. This high conversion efficiency is not economically achievable by single absorption plants using available catalysts, but it can be attained in double absorption plants when the catalyst is not seriously degraded. 

Absorption Air pollution Automatic control Biochemical engineering... 

B. B. Crocker, S.M., P.E., Consulting Chemical Engineer Fellow, American Institute of Chemical Engineers Member, Air Pollution Control Association (Section 14, Gas Absorption and Gas-Liquid System Design)... 

In most processes involving the absorption of a gaseous pollutant from an effluent gas stream, the gas stream is the processed fluid hence, its inlet condition (flow rate, composition, and temperature) are usually known. The temperature and composition of the inlet liq-... 

Of the three categories, the packed column is by far the most commonly used for the absorption of gaseous pollutants. Miscellaneous gas-absorption equipment could include acid gas scrubbers that are commonly classified as either wet or diy. In wet scrubber systems, the absorption tower uses a hme-based sorbent liquor that reacts with the acid gases to form a wet/solid by-product. Diy scrubbers can be grouped into three catagories (1) spray diyers (2) circulating spray diyers and (3) dry injection. Each of these systems yields a diy product that can be captured with a fabric filter baghouse downstream and... 

The absorption, distribution, and accumulation of lead in the human body may be represented by a three-part model (6). The first part consists of red blood cells, which move the lead to the other two parts, soft tissue and bone. The blood cells and soft tissue, represented by the liver and kidney, constitute the mobile part of the lead body burden, which can fluctuate depending on the length of exposure to the pollutant. Lead accumulation over a long period of time occurs in the bones, which store up to 95% of the total body burden. However, the lead in soft tissue represents a potentially greater toxicological hazard and is the more important component of the lead body burden. Lead measured in the urine has been found to be a good index of the amount of mobile lead in the body. The majority of lead is eliminated from the body in the urine and feces, with smaller amounts removed by sweat, hair, and nails. 

The extinction coefficient is dependent on the presence of gases and molecules that scatter and absorb light in the atmosphere. The extinction coefficient may be considered as the sum of the air and pollutant scattering and absorption interactions, as shown in Eq. (10-4) ... 

To remove a pollutant from the carrying stream, some property of the pollutant that is different from the carrier must be exploited. The pollutant may have different size, inertia, electrical, or absorption properties. Removal requires that the equipment be designed to apply the scientific principles necessary to perform the separation. 

Absorption of pollutant gases is accomplished by using a selective liquid in a wet scrubber, packed tower, or bubble tower. Pollutant gases commonly controlled by absorption include sulfur dioxide, hydrogen sulfide, hydrogen chloride, chlorine, ammonia, oxides of nitrogen, and low-boiling hydrocarbons. 

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