Particulate acidity

Solid (particulate) emissions are produced from incomplete combustion of fuels, solids, drying operations, crushing and grinding operations, solids handling operations, and so on. The largest volume of emissions is from products of combustion (C02, CO, NOv, SO.v and particulates). Acid... 

Removal of coarse particles from the air stream is desirable for determination of fine particulate acidity because ambient coarse particles may contain basic substances. 

MSC Air-Pollution-Control Systems MSCs generate flue gas that contains particulates, acid gases and trace amounts of organic and volatile metals. Particulates have traditionally been removed Dy use of cyclone separators and electrostatic precipitators. Acid gases require neutralization and removal from the gas stream. This can be accomplished by adding solutions or chemicals to the gas stream and removing the products of the chemical reaction when these materials are mixed together. Two major types of APCs are employed ... 

The organic chemical industry uses and generates both large numbers and large quantities of a wide variety of solvents, metal particulates, acid vapors, and unreacted monomers. These chemicals are released to all media including air, water, and land. The potential sources of pollutant outputs by media are shown below in Table 1.2 [7]. 

Fine particulate matter might be transported and release PH3, whereas particulate acidity decreases and thereby explains why PH3 seems to be ubiquitous in air. Moreover, PH2 probably returns to PH3 via H abstraction from hydrocarbons in the gas phase ... 

In general, the levels of U.S. population exposure to acid aerosols are quite modest in comparison with the levels at which health effects have been demonstrated. The most likely acid sulfate species appears to be NH HSO particle sizes depend on the age of the aerosol but are in the submicron range. Elevated concentrations of acidity are likely to persist at a given location for a few days, at most. Gaseous acidity levels are likely to equal or exceed particulate acidity levels in most locations. 

The main justification for diesel fuel desulfurization is related to particulate emissions which are subject to very strict rules. Part of the sulfur is transformed first into SO3, then into hydrated sulfuric acid on the filter designed to collect the particulates. Figure 5.21 gives an estimate of the variation of the particulate weights as a function of sulfur content of diesel fuel for heavy vehicles. The effect is greater when the test cycle contains more high temperature operating phases which favor the transformation of SO2 to SO3. This is particularly noticeable in the standard cycle used in Europe (ECE R49). 

Anhydride manufactured by acetic acid pyrolysis sometimes contains ketene polymers, eg, acetylacetone, diketene, dehydroacetic acid, and particulate carbon, or soot, is occasionally encountered. Polymers of aHene, or its equilibrium mixture, methylacetylene—aHene, are reactive and refractory impurities, which if exposed to air, slowly autoxidize to dangerous peroxidic compounds. 

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

Gas purification processes fall into three categories the removal of gaseous impurities, the removal of particulate impurities, and ultrafine cleaning. The extra expense of the last process is only justified by the nature of the subsequent operations or the need to produce a pure gas stream. Because there are many variables in gas treating, several factors must be considered (/) the types and concentrations of contaminants in the gas (2) the degree of contaminant removal desired (J) the selectivity of acid gas removal required (4) the temperature, pressure, volume, and composition of the gas to be processed (5) the carbon dioxide-to-hydrogen sulfide ratio in the gas and (6) the desirabiUty of sulfur recovery on account of process economics or environmental issues. 

Particulate Matter Other Phan Systemic Poisons. SUica and asbestos dust produce fibrosis. SUicon carbide, carbon (other than exhaust emissions), and emery are iuert dusts. Many organic dusts, eg, poUen, wood, and resius, cause aUergic reactions. Acids, alkaUes, fluorides, and chromates are irritants. 

The gaseous ammonia is passed through electrostatic precipitators for particulate removal and mixed with the cooled gas stream. The combined stream flows to the ammonia absorber where the ammonia is recovered by reaction with a dilute solution of sulfuric acid to form ammonium sulfate. Ammonium sulfate precipitates as small crystals after the solution becomes saturated and is withdrawn as a slurry. The slurry is further processed in centrifuge faciHties for recovery. Crystal size can be increased by employing one of two processes (99), either low differential controUed crystallization or mechanical size enlargement by continuous compacting and granulation. 

Release agents function by either lessening intermolecular interactions between the two surfaces in contact or preventing such close contact. Thus, they can be low surface-tension materials based on aUphatic hydrocarbon, fluorocarbon groups, or particulate soHds. The principal categories of material used are waxes, fatty acid metal soaps, other long-chain alkyl derivatives, polymers, and fluorinated compounds. 

The quaHty, ie, level of impurities, of the fats and oils used in the manufacture of soap is important in the production of commercial products. Fats and oils are isolated from various animal and vegetable sources and contain different intrinsic impurities. These impurities may include hydrolysis products of the triglyceride, eg, fatty acid and mono/diglycerides proteinaceous materials and particulate dirt, eg, bone meal and various vitamins, pigments, phosphatides, and sterols, ie, cholesterol and tocopherol as weU as less descript odor and color bodies. These impurities affect the physical properties such as odor and color of the fats and oils and can cause additional degradation of the fats and oils upon storage. For commercial soaps, it is desirable to keep these impurities at the absolute minimum for both storage stabiHty and finished product quaHty considerations. 

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