PAH emissions

Studying the possibility of Identifying the main PAH emission sources In the Sundsvall, Sweden, area and... 

More recently, Duval (15) estimated decay factors for the ambient PAH in Los Angeles using the same data. Following Gordon and co-workers, he assumed that PAH concentrations at a site in downtown Los Angeles were automobile dominated a site near to and downwind from the refineries had both automobile and refinery contributions. Using lead as a tracer for the automobile component at the refinery site, Duval determined the PAH emission profile for the refinery emissions. 

Although there are few chimney sweeps in business today, people are still exposed to considerable amounts of polycyclic aromatic hydrocarbons. Cigarette smoking, for example, is a major source of PAH ( ) coke production also has high PAH emissions (O. 

Levendis, Y. A., Atal, A. Carlson, J. B. 1998a. On the correlation of CO and PAH emissions from the combustion of pulverized coal and waste tires. Environmental Science and Technology, 32, 3767-3777. 

To date, neither PAH emission nor absorption has been detected in the circumstellar envelope around a cool carbon star PAH emission has only been seen in carbon-rich environments where there is substantial energy density of ultraviolet radiation. This correlation could simply be an excitation effect the carbon features are only excited by the presence of ultraviolet radiation. However, it could also be that carbon particles are eroded into PAHs in the environment where ultraviolet penetrates either directly by the ultraviolet radiation or indirectly by shocks that accompany the radiation. 

Fig. 2.6. Annual emission of by-product POPs (PCBs, HCB, and PAHs) Korea 1995 (from MCIE, 1999), Korea 2000 (from KMOE, 2003b) Korea 2001 (from KMOE, 2005a) Other countries 2000 (from UNECE/EMEP, 2002). PAHs emissions were based on 7 PAHs for Korea and 6 PAHs for other countries.

Fig. 2.7. Contribution of each emission source to total emission of by-product POPs in Korea. Dioxins includes PCDDs, PCDFs and coPCBs measured in 2001 (see Table 2.6), and 16-PAHs means the total emission of EPA priority 16 PAHs. PCBs, HCB, and PAHs emissions were quoted from the preliminary estimation study (KMOE, 2003b).

The rank of coal (maturity) is an important factor that affects PAH emissions from residential combustion. PAH emission from various coals is found to have a relationship with their volatile contents, and the complete combustion of coals with a high volatile content is more difficult to achieve. Bituminous and sub-bituminous coals with high volatile content yield more PAHs when burned at low temperatures, such as residential combustion, while anthracite coal containing very little volatile matter can burn more completely and emit PAHs with a mass that is three orders of magnitude lower than bituminous coal. Smoky coal, which is burned as fuel for cooking and heating in unvented homes, produces combustion emissions composed primarily of parent PAHs and alkylated PAHs. 

Because of the enormous differences in economic development, population density, and size of different provinces in China, total emission, emission density, emission intensity, and emission per capita showed geographical variations. In general, the southeastern provinces were characterized by higher emission density, while those in western and northern China featured higher emission intensity and population-normalized emission. The annual PAH emissions at the provincial level ranged from... 

L. Wheatley, Y. A. Levendis, P. Vouros Exploratory-study on the combustion and PAH emissions of selected municipal waste plastics. Environmental Science and Technology, 27(13), 2885-2895 (1993). 

Two different technologies seem to be the most promising alternatives to reduce gaseous PAH emissions catalytic PAH destruction [6, 7] and PAH adsorption on carbonaceous materials [8, 9]. Historically, carbonaceous materials have been used for the removal of vapor phase organic compounds from about 100 ppmv to 10,000 ppmv concentrations in industrial waste gas streams [10]. Recently, it has been shown that dioxins, furans and PAH, at ppbv or lower coneentrations, can be effectively removed from waste incinerator combustion gases by using carbon injection or carbon bed technology [11]. 

Limestone Influence on PAH Emissions from Coal AFBC. Catalytic or/and Adsorption Effect ... 

Limestone incorporation to coal feed during coal atmospheric fluidized bed combustion (AFBC) to control legislated emissions promotes the polyaromatic hydrocarbon (PAH) emissions. This is a fact that has been corroborated working in a laboratory pilot plant at the same eonditions used at the coal FBC power stations. PAH emissions increase one order of magnitude but, is it due to a Ca catalytic effect or is it due to limestone is a porous material ... 

The aim of this work was to check the role played by limestone and it is concluded that, at the working conditions, the PAH emissions promotion is due to the limestone porosity. No Ca catalytic activity was found at the coal AFBC standard conditions. 

For all combustion processes, the total PAH emitted, as a function of the feed and the bed nature, are shown in Table 2. This Table 2 shows that the total PAH emissions depend on the feed. The PAH total quantity detected in the combustion runs carried out with limestone-coal blend feed are one order of magnitude higher than the detected ones for the corresponding runs carried out just with coal feed. 

It could be thought that the small efficiency differences were relevant on the PAH emissions. However, by comparing the data obtained from LCL runs No 3, 4 and 5, at which the same efficiency value is reached but the emitted PAH amount was different, and those obtained from LCL runs No 2 and No 4, with very close efficiencies but at which the emitted PAH amount were the most extreme values detected, it can be deduced that this influence is negligible and the small differences among the high efficiencies reached in all the runs carried out do not seem to be the only determinant effect on PAH emissions. These results allow inferring the importance of the pyrosynthesis step on the PAH emissions, when a limestone-coal blend is added to the reactor. 

Once formed, the PAH can be emitted as gas or as generating by themselves the smallest particulate matter. These competitive reactions, among the present compounds in the freeboard, will be the ones which determinate the total PAH emissions and will depend on the feed and the bed nature. 

By comparing the experiments carried out at the SC and LCL runs, there are significant differences among the total PAH emissions (Table 2), and among the PAH distribution by traps (Table 3). A possible explanation of these results could be due to species in the reactor and their relationship. In the SC runs, the species involved in the combustion... 

Taking into account that the CO2 concentration at LCL runs is higher than the one at SC runs, on the one side the interactions between the coal released radicals and the available oxygen will be impeded, and so the radicals elimination by oxidation. However, the radical interactions among themselves will be also more difficult, and so the pyrosynthesis process driving to a higher PAH formation and emissions will be hindered. That is to say, a higher CO2 concentration would not imply, in principle, any relevant influence on the total PAH emissions. 

Those facts will justify that, with limestone, not only higher PAH emissions are detected, but the PAH emitted are also trapped on the cyclonee, the condenser and the filter, that is to say, on the solid phase emissions. Moreover PAH emissions were not detected in the XAD-2 resin, gas phase, at LCL runs. However, the PAH solid/gas partitioning results, see Table 3, show that when limestone is not included in the feed, all the PAH emitted are adsorbed in the XAD-2 resin, that is to say, are emitted in the gas phase. 

Therefore, and because of the Ca presence, a possible Ca catal)4ic role could be guessed. The chelating mechanisms reported [10,11] at polymeric pyrolysis can not be applied to coal combustion because the inert-reducing atmosphere at pyrolysis process has not relation to the oxidation conditions at the combustion atmospheres. However, other additional effect in the LCL runs could influence the PAH emission and distribution. This effect would be a possible catalytic role performed by Ca. 

The results obtained (see Tables 2 and 3 and Fig. 1) show that they are closer to the ones obtained with coal as feed than to the ones obtained with coal-limestone feed. Moreover, not only the total PAH emissions are similar to the ones in absence of Ca, but also the PAH solid/gas phase distribution coincide because none PAH was detected in the cyclone and condenser traps, solid emissions. Therefore, all the PAH were emitted on gas phase, as it happens at SC runs. 

These results allow inferring that the Ca catalytic role promoting PAH formation and emissions at coal combustion can be discarded, and that the higher PAH emissions seem to be due to the physical characteristic (porosity) of the limestone. 

These results also allow deducing that despite the limestone increases the PAH emissions, its total performance is positive. Limestone not only abates SO emissions, but also PAH emissions on gas phase are avoided by adsorption, which means that gaseous PAH could be easily controlled by an effective particulate matter trapping system. 

Limestone influence on PAH emissions from coal AFBC. Catalytic or/and adsorption effect ... 

A high combustion efficiency considerably reduces the PAHs emissions. 

The results obtained in this work indicate that this fluorimetric method has a valuable potential for use in on site monitoring of PAHs in river water. Its application is, however, restricted to the determination of PAHs with suitable spectroscopic properties for synchronous fluorimetric detection in mixture. Nevertheless, with the exception of B[a]P and B[k]F, the PAHs that were monitored in the present work, are commonly present in most PAH emission sources and may be considered as suitable environmental markers for PAH contamination of river water. 

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