Exhaust odor

N.P.Cemansky, Diesel Exhaust Odor and Irritants A Review, J. Air Pollut. Control Assoc., 33(2), 1983, 97-104. 

Diesel Exhaust Odor and Irritants A Review," Nicholas P. Cernansky, Journal of the Air Pollution Control Association, February 1983... 

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). 

Because PEA is such an important fragrance material this simple, essentially one-step process has been exhaustively studied to optimize reaction conditions and purification procedures. Because of the high reactivity of the iatermediates and the tendency toward polymer formation, critical factors such as throughput, temperature, molar ratios of reactants, addition rates, reactor materials and design, and agitation rate must be carefully balanced to provide an economical product with acceptable odor properties. 

Fuel sulfur is also responsible for a phenomena known as storage and release of sulfur compounds. Sulfur oxides (S02,S02) easily react with ceria, an oxygen storage compound incorporated into most TWC catalysts, and also with alumina. When the air/fuel mixture temporarily goes rich and the catalyst temperature is in a certain range, the stored sulfur is released as H2S yielding a rotten egg odor to the exhaust. A small amount of nickel oxide incorporated into the TWC removes the H2S and releases it later as SO2 (75—79). 

Filter P per Processing. In the fabrication of fuel oil and air filters for vehicles such as motorcycles and diesel locomotives, heat processing of the filter paper is required to cure the resin (usually phenoHc) with which the paper (qv) is impregnated (see Phenolic resins). The cure-oven exhaust, which contains water vapor, alcohols, and dimers and trimers of phenol, produces a typical blue haze aerosol having a pungent odor. The concentration of organic substances in the exhaust is usually rather low. 

Catalysis is utilized in the majority of new paper filter cure ovens as part of the oven recirculation/bumer system which is designed to keep the oven interior free of condensed resins and provide an exhaust without opacity or odor. The apphcation of catalytic fume control to the exhaust of paper-impregnation dryers permits a net fuel saving by oxidation of easy-to-bum methyl or isopropyl alcohol, or both, at adequate concentrations to achieve a 110—220°C exotherm. 

Paint and varnish manufacturing Resin manufacturing closed reaction vessel Varnish cooldng-open or closed vessels Solvent thinning Acrolein, other aldehydes and fatty acids (odors), phthalic anhydride (sublimed) Ketones, fatty acids, formic acids, acetic acid, glycerine, acrolein, other aldehydes, phenols and terpenes from tall oils, hydrogen sulfide, alkyl sulfide, butyl mercaptan, and thiofen (odors) Olefins, branched-chain aromatics and ketones (odors), solvents Exhaust systems with scrubbers and fume burners Exhaust system with scrubbers and fume burners close-fitting hoods required for open kettles Exhaust system with fume burners... 

Rendering plants Feedstock storage and housekeeping Cookers and percolators Grinding Odors SO2, mercaptans, ammonia, odors Particulates (dust) Quick processing, washdown of all concrete surfaces, paving of dirt roads, proper sewer maintenance, enclosure, packed towers Exhaust system, condenser, scrubber, or incinerator Exhaust system and scrubber... 

Other industries of interest are (1) the manufacturing of spices and flavorings, which may use activated carbon filters to remove odors from their exhaust stream (2) the tanning industry, which uses afterburners or activated carbon for odor removal and wet scrubbers for dust removal and (3) glue and rendering plants, which utilize sodium hypochlorite scrubbers or afterburners to control odorous emissions. 

Adequate warning properties This was not included in the final standard. OSHA feels the two major warning properties, odor and irritation, are unreliable or otherwise inappropriate to be used as primary indicators of sorbent exhaustion. 

Less unpleasant odor, particularly in the exhaust gases. 

Aftercondensers operate at atmospheric pressure. They do not affect the steam economy or ejector performance, but they do avoid the nuisance of exhausting steam to the atmosphere, thus, they allow steam to be recovered. They also serve as silencers on the ejectors, and with barometric types they can absorb odors and corrosive apors. 

Where dusts, grits, sawdust or other large particles are being extracted it is normally mandatory to include an air-cleaning device before the air is exhausted. Unless they are toxic or odorous fumes can normally be simply exhausted into the atmosphere at a suitable location well away from anywhere with normal personnel access. 

Occasionally the odor of hydrogen cyanide can be detected during the distillation, even when a trap filled with sodium hydroxide pellets precedes the usual trap cooled in dry ice and acetone to protect the pump. For safety, the vacuum pump should be placed in a hood, or provision should be made for the pump exhaust to be vented into a hood or out-of-doors during the distillation. 

In another college laboratory building, air intake for ventilation and fume hood exhaust ducts were placed too close together on the roof. Under certain wind conditions, unpleasant odors would fill the whole building, causing many caustic comments. 

Installing a hood with its own fan against an outside wall rather than in the roof could result in considerable savings. The exhaust must then go through the wall in a place where it will not be objectionable in the area outside the building. Not all odors are unpleasant, of course, as workers in an industrial laboratory next to a... 

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