Polyaromatic Hydrocarbon Emissions Research Articles

JWST Mid-infrared Spectroscopy Resolves Gas, Dust, and Ice in Young Stellar Objects in the Large Magellanic Cloud

In this work, we present spectra of 11 young stellar objects (YSOs) taken with the Mid-Infrared Instrument / Medium Resolution Spectroscopy (MRS) instrument on board the James Webb Space Telescope (JWST). The YSOs are located in the N79 region of the Large Magellanic Cloud (LMC), an active star-forming region with hundreds of Spitzer- and Herschel-identified YSOs and host to super star cluster (SSC) candidate H72.97-69.39. The three giant molecular clouds in N79 (East, West, and South) have varying star formation rates and stellar populations. MRS follow-up observations of four Spitzer-identified YSOs in N79 East, West, and South have revealed that what seemed to be a single, massive YSO is actually a cluster of YSOs. We discuss the emission and absorption lines of six YSOs that have complete or almost-complete spectral coverage from 4.9–27.9 μm. YSO Y3, located in N79 East, is the youngest source in this study and likely to be less than 10,000 yr old, as inferred from the prominent CH4, NH3, CH3OH, CH3OCHO, and CO2 ice absorption features. The most luminous source is the central ionizing YSO of SSC H72.97-69.39, Y4, which has dozens of fine-structure and H2 emission lines. Unlike the other YSOs in this work, Y4 has no polyaromatic hydrocarbon emission lines, due to the intense ionizing radiation destroying these large carbon-chain molecules. The mass accretion rates based on the H i (7-6) line luminosities of YSOs Y1, Y2, Y4, and Y9 range between 1.22 × 10−4–1.89 × 10−2 M ⊙ yr−1. For the first time in the mid-infrared, we are able to resolve individual high-mass protostars forming in small clusters in an extragalactic environment like the LMC.

Current technologies for plastic waste treatment for energy recovery, it's effects on poly aromatic hydrocarbons emission and recycling strategies

Plastic waste treatment is one of the key challenges faced by many countries. Recycling of the municipal plastic waste for energy recovery is one of the key movements in reduction of plastic waste accumulation. Production of pyrolytic oil and gas products from the plastic waste massive helps to reduce the dependency of fossil fuel. In this review, the exposure of the plastic consumption has been covered. Further, energy recovery methods using the various pyrolysis reactors has been discussed in details. The motive of this review to understand the conversion of plastic waste into value added products such as bio-oil and gas and its consequences in the formation of the polycyclic aromatic hydrocarbons (PAHs) during the handling of municipal plastic waste and e-waste. Besides the impact of PAHs contamination on human health effects also reviewed. Different techniques in converting the plastic waste to energy are discussed in details. Among various pyrolysis methods, microwave assisted pyrolysis possess greater advantage over other process. By varying the type of the feedstock, particle size and temperatures of the reactor, the yield rates can be increased. In addition, by optimizing the reactor temperature their possibility of harmful gaseous products from the plastic waste can be redistricted. Burning of the plastic waste and thermal degradation process releases sixteen types of PAHs compounds to the environment. Inhaling of the PAHs compounds leads to human health effects such as cancer, respiratory diseases and childhood obesity. Thus, an attempt has been made to address the risk of PAHs in the environmental due to the plastic waste handling and its respective human health effects.

Polycyclic aromatic hydrocarbons in citrus fruit irrigated with fresh water under arid conditions: Concentrations, sources, and risk assessment

• PAHs in citrus fruits grown in North of Deir-Alla, Jordan valley were investigated. • Grapefruits showed the highest ∑PAHs concentration (34.857 µg kg −1 ) • The ILCR in the study region indicated a potential cancer risks to population. • PAHs emission sources are biomass burning, vehicular emissions and petrogenic origin. • BCF for ∑16 PAHs was observed in the order of grapefruit > lemon > mandarin > orange. In Jordan, as well as in all the world countries, consumption of citrus fruits is an essential part of the daily diet, so it is important to assess the potential risk of the persistent organic pollutants such as polyaromatic hydrocarbons (PAHs) in these fruits to the human health and identify their sources in order to eliminate or reduce them. This study reports 16 priority PAHs content in four types of peeled citrus fruits grown in Jordan valley. PAHs were detected in all the studied samples in variable quantities depending on the type of citrus fruits. The results showed that the highest PAH level corresponded to acenaphthene (35.018 µg/kg) in grapefruit. Among the carcinogenic PAHs, benzo[a]anthracene (BaA) and benzo(a)pyrene (BaP) were the most representative and found in all the analyzed fruit, soil, and water samples, whereas anthracene (ANT) was not detected at all. The mean ∑16 PAHs for the different fruits were found to be 62.593 µg kg −1 in grapefruit, 24.840 µg kg −1 in lemon, 22.901 µg kg −1 in mandarin, and 5.082 µg kg −1 in orange. The dominance of naphthalene (NAP) and acenaphthene (ACE) in soil under hot climatic conditions indicates the recent and continuous input of these types in the investigated area. The bioconcentration factor (BCF) for ∑16 PAHs was observed in the order of grapefruit > lemon > mandarin > orange. Based on the results of the principal component analysis (PCA), the primary sources of PAHs in agricultural soils mainly originated from biomass burning and vehicular emissions. The incremental lifetime cancer risk (ILCR) indicated that consumption of these four citrus fruits may expose human health to potential cancer risk. The findings of this study call the policymakers and public administrations to the formulation of stringent policies and actions to control biomass burning and vehicular emissions.

The Proof-of-Concept: The Transformation of Naphthalene and Its Derivatives into Decalin and Its Derivatives during Thermochemical Processing of Sewage Sludge

One solution for sewage sludge (SS) management is thermochemical treatment due to torrefaction and pyrolysis with biochar production. SS biochar may contain toxic volatile organic compounds (VOCs) and polyaromatic hydrocarbons (PAHs). This study aimed to determine the process temperature’s influence on the qualitative PAHs emission from SS-biochar and the transformation of PAHs contained in SS. SS was torrefied/pyrolyzed under temperatures 200–600 °C with 1 h residence time. The headspace solid-phase microextraction (SPME) combined with gas chromatography and mass spectrometry (HS-SPME-GC-MS) analytical procedure of VOCs and PAHs emission was applied. The highest abundance of numerous VOCs was found for torrefaction ranges of temperature. The increase of temperatures to the pyrolytic range decreased the presence of VOCs and PAHs in biochar. The most common VOCs emitted from thermally processed SS were acetone, 2-methylfuran, 2-butanone, 3-metylbutanal, benzene, decalin, and acetic acid. The naphthalene present in SS converted to decalin (and other decalin derivatives), which may lead to SS biochar being considered hazardous material.

Comparing emissions of polyaromatic hydrocarbons and metals from marine fuels and scrubbers

• Presenting emission factors to the marine environment from the use of scrubbers. • Scrubber discharge water is enriched with metals and polyaromatic hydrocarbons (PAHs). • Heavy fuel oil combustion with scrubbers increase the relative environmental load. • Scrubbers introduce new contamination sources of chromium to the marine environment. In January 2020, new global regulations were implemented to limit the maximum sulphur content in marine fuels. As an alternative to switch to compliant fuels, the regulations allow for installations of exhaust gas cleaning systems, e.g. scrubbers, that enables a continued use of less expensive heavy fuel oils (HFOs). Characterization of scrubber discharge water shows that the acidified water also becomes enriched with contaminants, and large quantities of metals and polyaromatic hydrocarbons (PAHs) are thus being discharged directly to the marine environment. When emissions of contaminants to the atmosphere and the marine environment are evaluated simultaneously, the results show that HFO, with scrubbers installed, generates higher emission factors of both metals and PAHs compared to MGO. This highlights the importance of including both the marine and the atmospheric perspective when comparing environmental loads and impact of contaminants from shipping.

Public health impact of coal-fired power plants: a critical systematic review of the epidemiological literature

ABSTRACT Coal-based energy production is the most utilized method of electricity production worldwide and releases the highest concentration of gaseous, particulate, and metallic pollutants. Toxicological research has shown that coal combustion by-products are carcinogens, endocrine disruptors, and cardiorespiratory toxins. This article aims to systematically review the epidemiological literature on the impact emissions from coal-based power production has on morbidity and mortality worldwide. Two thousand one hundred and fifty-two articles were retrieved based on search criteria. Word search of abstract and article text filtered the results to 95 articles. Forty articles were included after screening. The literature indicates a significant adverse effect from particulate matter and polyaromatic hydrocarbon emissions on morbidity and mortality. There is a lack of consistency of exposure assessment and inadequate control of significant potential confounders such as social economic status. Future research should focus on improving exposure assessment models, specifically source-apportionment and geographic information system methods to model power plant-specific emissions.

Emission and distribution of PCDD/Fs, chlorobenzenes, chlorophenols, and PAHs from stack gas of a fluidized bed and a stoker waste incinerator in China.

The concentrations, homologue, and congener profiles, as well as the gas/particle distribution of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), chlorobenzenes (CBzs), chlorophenols (CPhs), and polyaromatic hydrocarbons (PAHs) from stack gas of two different municipal solid waste incinerators in China, were characterized. The incinerators were a stoker furnace incinerator equipped with the advanced air pollution control device (APCD) and a common circulating fluidized bed (CFB) furnace. The concentration of PCDD/Fs in the stack gas of the stoker incinerator ranged 0.011-0.109ng international toxic equivalent factor (I-TEQ)/Nm3 and was below the current limit for PCDD/F emissions from the municipal solid waste incinerators (MSWIs) in China (0.1ng I-TEQ/Nm3) in most of the cases. Moreover, the concentration of PCDD/Fs in the stack gas of the stoker incinerator was significantly lower than that of the CFB incinerator (0.734 to 24.6ng I-TEQ/Nm3). In both incinerators, the majority of the total PCDD/F emissions (above 90%) ended up in the gas phase. 2,3,4,7,8-PeCDF, which occupied 24.3-43.6 and 32.5-75.6% of I-TEQ contribution in MSWIs A and B, respectively, was the most abundant congener. However, different types of incinerators and APCDs induced different congener and homologue distributions. The total concentration of CBzs from the stoker incinerator (0.05-3.2μg/Nm3) was also much lower than that formed from the CFB incinerator (10.9-75.2μg/Nm3). The phase distribution of CBzs followed the same pattern as with the PCDD/Fs. Moreover, the emission level of CBz was 100-1000 times higher than that of the PCDD/Fs, which determines the applicability of CBzs as indicators of PCDD/F emissions. High correlations between the emission concentrations of PCDD/Fs, TeCBz, and PCBz in specific ranges were revealed. Furthermore, high concentrations of CPhs (0.6-141.0μg/Nm3) and PAHs (148.6-4986.5μg/Nm3) were detected in the stack gases of MSWI B. In some cases, the concentrations were as high as the concentrations in the fumes exiting the boiler of one foreign stoker without flue gas purification indicating the abundance of CPh and PAH emissions in the stack gas of waste incinerators.

Ethanol, isobutanol, and biohydrocarbons as gasoline components in relation to gaseous emissions and particulate matter.

The exhaust emissions of three cars using different biofuels were explored at a temperature of -7 °C. The biofuels studied contained both low- and high-concentration ethanol blends, isobutanol, and biohydrocarbons. A multipoint fuel injection car (MPFI), direct-injection spark-ignition car (DISI), and flex-fuel car (FFV) represented three different spark-ignition-car technologies. At -7 °C, substantial emissions were observed for the three cars, and differences were found among ethanol, isobutanol, and biohydrocarbons as fuel components. For example, E85 resulted in high acetaldehyde, formaldehyde, ethanol, ethene, and acetylene emissions when compared to E30 or lower ethanol concentrations. Isobutanol-containing fuel showed elevated butyraldehyde, methacrolein, and isobutanol emissions. The highest particulate matter (PM) emissions, associated polyaromatic hydrocarbon (PAH) and indirect mutagenicity emissions were detected with the DISI car. Oxygenated fuels reduced PM emissions and associated priority PAH emissions in the DISI car. PM and PAH emissions from the MPFI and FFV cars were generally low. A combination of 10% ethanol and biohydrocarbon components did not change emissions significantly when compared to ethanol-only-containing E10 gasoline. Therefore, a combination of ethanol or isobutanol with biohydrocarbon components offers an option to reach high gasoline bioenergy content for E10-compatible cars.

Assessment of polyaromatic hydrocarbon emissions from laser printers

The potential for polyaromatic hydrocarbon (PAH) emissions from laser printers has been examined using a simulated printing process and a detailed chemical analysis of printer toner. We have analysed the PAH content of both carbon black (a toner constituent) and toner before and after heating and have found measurable evaporation and subsequent condensation of PAHs. Based on our analysis we have estimated a maximum possible PAH emission rate of 82.1 μg min−1 of printing for a 10% page coverage. Our VOC emission results agree well with those of other authors. The concentrations of individual PAHs in the emissions were relatively low, however non-trivial, especially long term.

Emissions from Open Burning of Simulated Military Waste from Forward Operating Bases

Emissions from open burning of simulated military waste from forward operating bases (FOBs) were extensively characterized as an initial step in assessing potential inhalation exposure of FOB personnel and future disposal alternatives. Emissions from two different burning scenarios, so-called "burn piles/pits" and an air curtain burner/"burn box", were compared using simulated FOB waste from municipal and commercial sources. A comprehensive array of emissions was quantified, including CO(2), PM(2.5), volatile organic compounds (VOCs), polyaromatic hydrocarbons (PAHs), polychlorinated dibenzodioxins and -furans (PCDDs/PCDFs), polybrominated dibenzodioxins and -furans (PBDDs/PBDFs), and metals. In general, smoldering conditions in the burn box and the burn pile led to similar emissions. However, when the burn box underwent periodic waste charging to maintain sustained combustion, PM(2.5), VOCs, and PAH emissions dropped considerably compared to smoldering conditions and the overall burn pile results. The PCDD/PCDF and PBDD/PBDF emission factors for the burn piles were 50 times higher than those from the burn box likely due to the dominance of smoldering combustion in the burn piles.

Study of Miller timing on exhaust emissions of a hydrotreated vegetable oil (HVO)-fueled diesel engine

The effect of intake valve closure (IVC) timing by utilizing Miller cycle and start of injection (SOI) on particulate matter (PM), particle number, and nitrogen oxide (NOx) emissions was studied with a hydrotreated vegetable oil (HVO)-fueled nonroad diesel engine. HVO-fueled engine emissions, including aldehyde and polyaromatic hydrocarbon (PAH) emissions, were also compared with those emitted with fossil EN590 diesel fuel. At the engine standard settings, particle number and NOx emissions decreased at all the studied load points (50%, 75%, and 100%) when the fuel was changed from EN590 to HVO. Adjusting IVC timing enabled a substantial decrease in NOx emission and combined with SOI timing adjustment somewhat smaller decrease in both NOx and particle emissions at IVC −50 and −70 °CA points. The HVO fuel decreased PAH emissions mainly due to the absence of aromatics. Aldehyde emissions were lower with the HVO fuel with medium (50%) load. At higher loads (75% and 100%), aldehyde emissions were slightly higher with the HVO fuel. However, the aldehyde emission levels were quite low, so no clear conclusions on the effect of fuel can be made. Overall, the study indicates that paraffinic HVO fuels are suitable for emission reduction with valve and injection timing adjustment and thus provide possibilities for engine manufacturers to meet the strictening emission limits. Implications: NOx and particle emissions are dominant emissions of diesel engines and vehicles. New, biobased paraffinic fuels and modern engine technologies have been reported to lower both of these emissions. In this study, even further reductions were achieved with engine valve adjustment combined with novel hydrotreated vegetable oil (HVO) diesel fuel. This study shows that new paraffinic fuels offer further possibilities to reduce engine exhaust emissions to meet the future emission limits. Supplementary Materials: Supplementary materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for a complete list of analysed PAH compounds.

Semivolatile and Volatile Organic Compound Emissions from Wood-Fired Hydronic Heaters

Emissions including polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), polyaromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs), were sampled from different wood-fired hydronic heater (HH) technologies. Four commercially available HH technologies were studied: a single-stage conventional combustor with natural updraft, a three-stage downdraft combustion system, a bottom-fed pellet burner, and a two-stage heater with both a combustion and gasification chamber. The fuel consisted of three wood types (red oak, white pine, and white ash), one hardwood pellet brand, and one fuel mixture containing 95% red oak and 5% residential refuse by weight. The various HHs and fuel combinations were tested in a realistic homeowner fuel-charging scenario. Differences in emission levels were found between HH technologies and fuel types. PCDD/PCDF emissions ranged from 0.004 to 0.098 ng toxic equivalency/MJ(input) and PAHs from 0.49 to 54 mg/MJ(input). The former was increased by the presence of 5% by weight refuse. The white pine fuel had the highest PAH emission factor, while the bottom fed pellet burner had the lowest. The major VOCs emitted were benzene, acetylene, and propylene. The highest emissions of PAHs, VOCs, and PCDDs/PCDFs were observed with the conventional unit, likely due to the rapid changes in combustion conditions effected by the damper opening and closing.

Polycyclic Aromatic Hydrocarbon Emission Profiles and Removal Efficiency by Electrostatic Precipitator and Wetfine Scrubber in an Iron Ore Sintering Plant

A monitoring campaign of polychlorinated dibenzo-p-dioxins and dibenzofurans, polyaromatic hydrocarbons (PAHs), and polychlorinated biphenyl was carried out in an Italian iron ore sintering plant by sampling the combustion gases at the electrostatic precipitator (ESP) outlet, at the Wetfine scrubber (WS) outlet, and by collecting the ESP dust. Few data are available on these micropollutants produced in iron ore sintering plants, particularly from Italian plants. This study investigates the PAH emission profiles and the removal efficiency of ESPs and WS. PAHs were determined at the stack, ESP outlet flue gases, and in ESP dust to characterize the emission profiles and the performance of the ESP and the WS for reducing PAH emission. The 11 PAHs monitored are listed in the Italian legislative decree 152/2006. The mean total PAH sum concentration in the stack flue gases is 3.96 μg/N · m3, in ESP outlet flue gases is 9.73 μg/N · m3, and in ESP dust is 0.53 μg/g. Regarding the emission profiles, the most abundant compound is benzo(b)fluoranthene, which has a relative low BaP toxic equivalency factors (TEF) value, followed by dibenzo(a,l)pyrene, which has a very high BaP(TEF) value. The emission profiles in ESP dust and in the flue gases after the ESP show some changes, whereas the fingerprint in ESP and stack flue gases is very similar. The removal efficiency of the ESP and of WS on the total PAH concentration is 5.2 and 59.5%, respectively.

Spitzer Observations of Tidal Dwarf Galaxies

AbstractWe present Spitzer observations of Tidal Dwarf Galaxies (TDGs) in three interacting systems: NGC 5291, Arp 105 & Stephan's Quintet. The spectra show bright emission from polyaromatic hydrocarbons (PAHs), nebular lines and warm molecular hydrogen, characteristic of recent episodes of star formation. The PAH emission that falls in the IRAC 8.0 μm band leads to the TDGs having an extremely red IRAC color, with [4.5] − [8.0] > 3. The emission from PAHs is characterized by a model with mainly neutral 100-C PAH atoms.

Dust and PAH Emission in the Star‐forming Active Nucleus of NGC 1097

The nucleus of the nearby galaxy, NGC 1097, is known to host a young, compact (r < 9 parsec) nuclear star cluster as well as a low-luminosity active galactic nucleus (AGN). It has been suggested both that the nuclear stellar cluster is associated with a dusty torus, and that low-luminosity AGN like NGC 1097 do not have the torus predicted by the unified model of AGN. To investigate these contradictory possibilities we have acquired Gemini/T-ReCS 11.7 micron and 18.3 micron images of the central few hundred parsecs of this galaxy at < 45 parsec angular resolution, in which the nucleus and spectacular, kiloparsec-scale star-forming ring are detected in both bands. The small-scale mid-infrared (mid-IR) luminosity implies thermal emission from warm dust close to the central engine of this galaxy. Fitting of torus models shows that the observed mid-IR emission cannot be accounted for by dust heated by the central engine. Rather, the principal source heating the dust in this object is the nuclear star cluster itself, suggesting that the dust that we detect is not the torus of AGN unified schemes (although it is also possible that the dusty starburst itself could provide the obscuration invoked by the unified model). Comparison of Spitzer/IRS and Gemini/GNIRS spectra shows that, although polyaromatic hydrocarbon emission (PAH) bands are strong in the immediate circumnuclear region of the galaxy, PAH emission is weak or absent in the central 19 parsecs. The lack of PAH emission can probably be explained largely by destruction/ionization of PAH molecules by hard photons from the nuclear star cluster. If NGC 1097 is typical, PAH emission bands may not be a useful tool with which to find very compact nuclear starbursts even in low-luminosity AGN.

Characterization of Polycyclic Aromatic Hydrocarbons from the

Diesel fuels governed by U.S. regulations are based on the index of the total aromatic contents. Three diesel fuels, containing various fractions of light cycle oil (LCO) and various sulfur, total polyaromatic, and total aromatic contents, were used in a heavy-duty diesel engine (HDDE) under transient cycle test to assess the feasibility of using current indices in managing the emissions of polycyclic aromatic hydrocarbons (PAHs) from HDDE. The mean sulfur content in LCO is 20.8 times as much as that of premium diesel fuel (PDF). The mean total polyaromatic content in LCO is 28.7 times as much as that of PDF, and the mean total aromatic content in LCO is 2.53 times as much as that of PDF. The total polyaromatic hydrocarbon emission factors in the exhaust from the diesel engine, as determined using PDF L3.5 (3.5% LCO and 96.5% PDF), L7.5 (7.5% LCO and 92.5% PDF), and L15 (15% LCO and 85% PDF) were 14.3, 25.8, 44, and 101 mg L−1, respectively. The total benzo(a)pyrene equivalent (BaPeq) emission factors in the exhaust from PDF, L3.5, L7.5, and L15 were 0.0402, 0.121, 0.219, and 0.548 mg L−1, respectively. Results indicated that using L3.5 instead of PDF will result in an 80.4% and a 201% increase of emission for total PAHs and total BaPeq, respectively. The relationships between the total polyaromatic hydrocarbon emission factor and the two emission control indices, including fuel polyaromatic content and fuel aromatic content, suggest that both indices could be used feasibly to regulate total PAH emissions. These results strongly suggest that LCO used in the traveling diesel vehicles significantly influences PAH emissions.

Environmental labeling of car tires—toxicity to Daphnia magna can be used as a screening method

Car tires contain several water-soluble compounds that can leach into water and have toxic effects on aquatic organisms. Due to tire wear, 10 000 tonnes of rubber particles end up along the Swedish roads every year. This leads to a diffuse input of emissions of several compounds. Emissions of polyaromatic hydrocarbons (PAHs) are of particular concern. PAHs are ingredients of the high aromatic oil (HA oil) that is used in the rubber as a softener and as a filler. The exclusion of HA oils from car tires has started, and an environmental labeling of tires could make HA oils obsolete. The toxicity to Daphnia magna from 12 randomly selected car tires was tested in this study. Rubber from the tread of the tires was grated into small pieces, to simulate material from tire wear, and the rubber was equilibrated with dilution water for 72 h before addition of test organisms. The 24-h EC 50s of the rubber pieces ranged from 0.29 to 32 g l −1, and the 48-h EC 50s ranged from 0.0625 to 2.41 g l −1. Summer tires were more toxic than winter tires. After the 48-h exposure, the daphnids were exposed to UV-light for 2 h, to determine if the tires contained compounds that were phototoxic. After UV-activation the EC 50s ranged from 0.0625 to 0.38 g l −1. Four of the 12 tires had a very distinct photoactivation, with a toxicity increase of >10 times. This study has shown that the used method for toxicity testing with Daphnia magna according to ISO 6341 could be used as a basis for environmental labeling of car tires.

Combustion of a substitution fuel made of cardboard and polyethylene: influence of the mix characteristics—experimental approach

This article presents an experimental study of the combustion of substitution fuels elaborated from compressed mixes of cardboard and polyethylene (PE). These components are representative of two classical classes of waste materials: materials derived from wood and plastics. The combustion of these fuels has been experimentally characterized in terms of combustion rate, and quantity of PolyAromatic Hydrocarbons (PAH) pollutants emitted. The temperature levels reached within the fuel sample are also reported and discussed. A parametric study has been performed with three characteristics of the fuel as the parameters: (i) the size of the elements before mixing; (ii) the proportion of PE in the mix; (iii) and the apparent density of the ‘bricks’ that were prepared. Experiments were conducted using a standard calorimeter cone. This device leads to a quasi-1D situation, and good repeatability has been observed. A special sample holder and a PAH sampling system were adapted to the system. The samples were irradiated with a flux of 50 kW m −2. No air was blown through the samples, and the ash layer formed at the surface was not removed. It was observed that combustion occurs with two different stages. During the first stage, the fuel is devolatilized, and a flame is formed at the surface. It was observed that the duration of this period was proportional to the fuel density. The mass loss rate (kg s −1 m −2) appeared not to depend upon the brick characteristics. In second stage, the fuel is oxidized. The mass loss rate is again very similar from one brick to another. It is approximately 10 times smaller than during the devolatilization stage. An examination of the temperature levels at three locations inside the bricks indicates that there is not a thin combustion front propagating through the sample. As a consequence of this, despite the large quantity of energy released by the combustion, the temperature reached remains between 700 and 900 °C, which is very close to the surface steady state temperature resulting from the surface irradiation. PAHs are formed during the flame period. The PAH specified here are those formed inside the flame at the brick surface. In the case of an industrial application, it must be emphasized that these PAHs are likely to react downstream depending on the furnace conditions. The density of the fuel and the size of the elements have no impact on these emissions. Our results show that this is the percentage of PE that controls the emissions. We showed that the introduction of more than 30% of PE (expressed in micrograms per gram of PE) leads to very high PAH emissions. Moreover, for mass fractions of PE larger than 30%, heavy PAH, which are more toxic than light PAH, are formed in majority. In conclusion, if PE mass fractions lower than 30% are used, such substitution fuels allows one to recover the available energy of these materials, while solving the environmental and technical problems usually encountered when burning these materials individually.

Polyaromatic Hydrocarbon Emissions in Fly Ashes from an Atmospheric Fluidized Bed Combustor Using Thermal Extraction Coupled with GC/TOF-MS

Over 120 polyaromatic hydrocarbons (PAHs) have been identified in urban pollution, of which 16 have been specified by the United States Environmental Protection Agency (EPA) as priority pollutants. Increased urban concentrations from anthropogenic sources are of particular concern because many of them show carcinogenic and/or mutagenic properties. In this study thermal extraction (TE) coupled with GC/TOF-MS and solvent extraction coupled with GC/MS were utilized to determine the PAH concentrations in fly ash samples collected from a bench-scale 0.1 MWth fluidized bed combustor (FBC). In addition to the evaluation of the analysis procedures including conventional solvent extraction and thermal extraction, a comprehensive study of the effect of operating conditions on PAH emissions in fly ashes samples was conducted. The experimental results indicate the majority of PAHs (two and three fused-ring systems) found in the solid phase (fly ash) are derived from breakdown reactions during the combustion and/or py...

Effects of Limestone on Polycyclic Aromatic Hydrocarbon Emissions during Coal Atmospheric Fluidized Bed Combustion

The aim of this paper is to investigate the effects that the incorporation of limestone to the feed may have on polyaromatic hydrocarbon (PAH) emissions during coal atmospheric fluidized bed combustion (AFBC). The study was performed at a combustion temperature of 850 °C, an oxygen excess percentage of 10%, and a total air velocity of 0.24 m/s (around twice the minimum fluidization velocity of the heaviest solid) in a laboratory scale pilot plant with a fluidized bed reactor (7 cm i.d., 76 cm height). The emissions of 16 PAH's (listed by the US Environmental Protection Agency as priority pollutants) were analyzed considering their feeding and their fluidized bed nature. The samples analyzed were taken from a cyclone, a condenser, a Teflon filter (1-micron pore size), and XAD-2 resin. After sonication extraction with dimethylformamide (DMF) as the solvent, the 16 PAH's were analyzed by fluorescence spectroscopy (FS) in the synchronous mode. The results obtained show that not all the PAH's could be detected and that the highest PAH content was emitted when a limestone bed was used. Wih regard to the PAH gas/solid partitioning emissions, most of them were concentrated on the solid phase when limestone coal blend was added to the reactor, while most of the emissions were produced in the gas phase when only coal was fed. To assess a possible Ca catalytic role, additional combustion experiments were performed through feeding coal (without limestone) to the bed obtained from coal-limestone blend feed. Finally, the influence of the calcite porosity and the Ca presence on PAH formation, emission, and distribution are also reported and discussed.