Study on the Influencing Factors of the Distribution Characteristics of

Nov 17, 2017 - The total mass concentrations of PAHs in condensable PM were quite low (1.05 μg/m3 in stage 1, 0.69 μg/m3 in stage 2, and 1.89 μg/m3...
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Study on the Influencing Factors of the Distribution Characteristics of Polycyclic Aromatic Hydrocarbons in Condensable Particulate Matter Jingwei Li,† Xiaodong Li,*,† Chenyang Zhou,† Min Li,† Shengyong Lu,† Jianhua Yan,† and Zhifu Qi‡ †

State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou 310027, China ‡ Zhejiang Energy Group R&D, Zhejiang Province, Hangzhou 310003, China ABSTRACT: Condensable particulate matter (PM) contributes significantly to the total emissions of particulate matter from stationary sources. The distribution characteristics of polycyclic aromatic hydrocarbons (PAHs) in condensable PM from a coalfired power plant were investigated. The influence of the sulfur content of the burning coal and the wet electrostatic precipitator (WESP) on the PAH distributions in condensable PM was analyzed. The total mass concentrations of PAHs in condensable PM were quite low (1.05 μg/m3 in stage 1, 0.69 μg/m3 in stage 2, and 1.89 μg/m3 in stage 3). 3-ring and 4-ring PAHs were the major PAH compounds in condensable PM. The higher sulfur content in the burning coal led to greater PAH contents and emissions in condensable PM than the lower sulfur content. The sulfur content could promote the formation of PAHs during the coal combustion process. The WESP had good removal efficiency (approximately 63%) of total PAH emissions in condensable PM. The WESP could obviously decrease the total toxic equivalent (TEQ) values of PAHs in condensable PM. The total TEQs of PAHs in condensable PM were mostly contributed by the 3-ring and 5-ring PAHs in this study.

1. INTRODUCTION Polycyclic aromatic hydrocarbons (PAHs) are a series of persistent organic pollutants with two or more fused benzene rings. PAHs are usually formed during incomplete combustion and the pyrolysis of fossil fuels.1,2 Some PAHs are considered to be strongly toxic and carcinogenic and have attracted much attention and been studied for a long time.3,4 Sixteen PAHs specified as priority test compounds by the U.S. EPA are studied in this paper. Ambient PAHs can be transported and deposited over a long time and distance and are a great risk to human health.5 Coal plays a major role in the energy consumption structure in China, and the condition will last for decades. It is necessary to control the pollutant emissions from coal-fired power plants. Coal-fired power plants are one of the main sources of atmospheric PAHs.5,6 Large quantities of PAHs are released from coal-fired power plants, except for particles, NOx, SOx, etc. The study by He et al.7 showed that PAHs associated with fine particulate matter were mainly affected by vehicular exhaust and coal sources. Source identification studies2,8 regarding PAHs indicated that coal-fired power plants are one of the major sources of PAHs in China. Principal component analysis (PCA) associated with diagnostic ratios revealed that coal combustion and vehicle emissions were the major sources for ambient particle-associated PAHs.9 PAHs emitted from coalfired power plants have serious influence on air quality and human health. However, most studies on the control of pollutant emissions focused on the control of PM, NOx, and SOx. It is important to study the emission characteristics and control effects of PAHs from coal-fired power plants. PAHs emitted from coal-fired power plants are composed of gas-phase and particulate-phase PAHs. However, few studies correlate gas-phase PAHs with emissions of particulate matter © XXXX American Chemical Society

(PM) from coal-fired power plants. PM emitted from stationary sources contains filterable PM and condensable PM.10,11 Condensable PM is defined by the U.S. EPA as material that is in the vapor phase under stack conditions but condenses and/or reacts upon cooling and dilution in ambient air to form solid or liquid PM with a diameter less than or equal to 2.5 μm immediately after discharge from the stack.12 Condensable PM has been confirmed to contribute significantly to total PM emissions from stationary sources in previous studies. Corio et al.11 studied the characteristics of condensable PM emissions from several coal-burning boilers using EPA Methods 202 and 201/201A, and the results showed that condensable PM on average comprised approximately 76% of the total PM10 stack emissions. A study13 on the emissions of condensable PM from coal-fired power plants showed that the average condensable PM emission concentration was 21.2 ± 3.5 mg/m3, while the filterable PM emission concentration was 20.6 ± 10.0 mg/m3. In some studies, the organic fraction of condensable PM could account for more than 50% of the total condensable PM emissions.12,14 Notably, the boiling points of the 16 PAHs range from 218 °C (Nap) to 525 °C (BghiP), which are much higher than the ambient temperature. Since gas-phase PAHs could cool and condense while being emitted to the atmosphere, some PAHs may transform to condensable PM. This part of PAHs is very harmful because it turns into condensable PM directly while being emitted to the atmosphere. Research on the correlation between condensable PM and gas-phase PAHs from stationary sources is necessary. Received: July 11, 2017 Revised: November 4, 2017 Published: November 17, 2017 A

DOI: 10.1021/acs.energyfuels.7b01991 Energy Fuels XXXX, XXX, XXX−XXX

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Energy & Fuels

Figure 1. Schematic diagram of the coal-fired utility boiler.

The PAHs and particle emissions from coal-fired power plants can be affected by many factors, such as the coal, boiler load, and the air pollution control devices (APCDs).15,16 This study investigated the emission and distribution characteristics of the PAHs in condensable PM from a coal-fired power plant. The burning coal was set to contain different sulfur contents, and the wet electrostatic precipitator (WESP) operated at different conditions during the study. The filterable PM and condensable PM were collected according to ISO 23210-2009 and EPA Method 202, respectively. The sampled condensable PM was collected and used to study the distribution characteristics of the PAHs. The aims of this paper are to study (1) the distribution characteristics of PAHs in condensable PM, (2) the influence of the sulfur content of the coal on the PAH emissions in condensable PM, and (3) the control effect of the WESP on the emission and distribution characteristics of the PAHs in condensable PM. The results could provide more information on the emission of particleassociated PAHs and the control characteristics of the WESP by investigating the distribution profiles of PAHs and the removal effect of the equipment.

Table 1. Coal Information for the Studied Boiler parameter

basis

FC1

FC2

FC3

moisture, % moisture, % ash, % volatile matter, % fixed carbon, % sulfur, % Qgr, vad MJ/kg Qnet, v MJ/kg

total air dry air dry air dry air dry as received as received as received

13.5 2.75 15.81 31.50 49.94 0.84 26.75 22.73

12.6 4.22 14.10 30.02 51.66 0.48 26.38 23.03

13.0 4.35 14.26 30.25 51.14 0.45 26.27 22.85

and the APCDs kept operating steadily during the test. Stage 2: the feed coal was FC2, and the APCDs kept operating steadily during the test. Stage 3: the feed coal was FC3, and the APCDs, except for the WESP, operated steadily, and the WESP stopped running during the test. 2.2. Sampling Equipment and Methods. Filterable and condensable PM were sampled simultaneously. More than two samples were collected successively in each sampling stage. The filterable PM sampling was conducted according to ISO standard 23210, and the condensable PM sampling was conducted according to U.S. EPA Method 202. The PM sampling equipment contained a sampling tube, a PM sampling train, a pump, a heat controller, and a connector. A schematic of the sampling system is shown in Figure 2. The PM sampling train contained a filterable PM sampling train and a condensable PM sampling train. The main filterable PM sampling device was a Dekati PM10 impactor. The impactor fulfills all requirements of ISO standard 23210. The main condensable PM sampling device was a condensable PM sampling train, which was purchased from Environmental Supply Company, Inc. U.S.A. The CPM sampling train meets the requirements of U.S. EPA Method 202. The sampling tube and filterable PM sampling train were heated to 130 °C during sampling. The elevated temperature could help minimize the influence of moisture in the flue gas. A leak check was conducted during each sampling. In addition, the flue gas parameters (temperature, moisture, and O2 concentration) were measured according to GB/T 16157-199615, China.12 The sampling flow rate was 10 L/min, which could meet the requirement of the Dekati PM10 impactor. The sampling time was 90 min for each sample. The detailed sampling methods and PM sample analysis procedure are shown in a former study.12 The concentrations of PM were converted into standard concentrations (at 6% oxygen, dry

2. MATERIALS AND METHODS 2.1. Facility. The studied coal-fired boiler unit is equipped with a 660 MW supercritical parameters spiral tube direct current furnace, with a corner tangential combustion method. The air pollution control devices (APCDs) consist of a selective catalytic reduction denitration device (SCR), a low-low temperature electrostatic precipitator (LLTESP), a tube type gas−gas heat exchanger (MGGH), a wet flue gas desulphurization (WFGD) device, and a wet electrostatic precipitator (WESP). The WESP has two electric fields. The cooling section of the MGGH is placed in front of the LLT-ESP, and the heating section of the GGH is placed downstream of the WESP. A detailed introduction of the MGGH is reported in a former study.15,16 The overall process of the power plant and sampling site are shown in Figure 1. The sampling site was set between the WESP and the stack. The sampling point was located at the middle of the cross-section of the flue. The boiler was maintained at a 660-MW condition during the sampling of the filterable and condensable PM. The feed coal (FC) included relatively higher sulfur content (0.84%) and relatively lower sulfur content (0.48% and 0.45%), and detailed information is listed in Table 1. The test included three stages. Stage 1: the feed coal was FC1, B

DOI: 10.1021/acs.energyfuels.7b01991 Energy Fuels XXXX, XXX, XXX−XXX

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Table 2. PAH Concentration Distributions in Condensable PM (μg/m3)

Figure 2. Schematic showing of the sampling system. One, isokinetic nozzles; 2, stainless steel sampling probes; 3,6, hoses and hose connector; 4, impactor heater and heater controller; 5, Dekati PM10 impactor; 7, condenser; 8, recirculation pump; 9, water dropout impinger; 10, modified Greenburg−Smith impinger (backup impinger); 11, condensable PM filter; 12, moisture trap; 13, silica gel trap; 14, sampler; 15, water bath; 16 - ice bath standard, standard conditions) according to GB/T 16157-1996 and GB 13223-2011, China. 2.3. Analytical Procedure and Quality Assurance. After the mass analysis of condensable PM samples was conducted, the organic fraction of condensable PM samples was extracted by n-hexane with an ultrasonicator. Extracted samples from the same sampling stage were combined together and preserved for the analysis of PAHs. The PAH analysis process was conducted according to HJ 646-2013 (China). All extracted samples were concentrated to less than 5 mL. A surrogate standard (2-fluorobiphenyl and p-terphenyl-d14) was added to the samples prior to the purification. A silica gel column (each sample, 10 g of silica gel baked at 130 °C for 16 h, with 2 cm Na2SO4 in the upper part) was used for sample purification. The silica gel was rinsed twice with 20−40 mL of dichloromethane and rinsed once with 40 mL of n-hexane. The extracts were transferred to the silica gel column, rinsed with 25 mL of hexane, eluted with 30 mL of hexane/ dichloromethane (2:3, v/v), and collected. The eluted sample containing the PAHs was concentrated to less than 1 mL. Next, 10 μL of internal standards (naphthalene-d8, acenaphthene-d10, phenanthrene-d10, chrysene-d12, and perylene-d12) was added to each sample and used for the quantification of individual PAHs. Every sample was adjusted to a constant volume (1 mL) with the addition of n-hexane. A gas chromatograph/mass spectrometer (GC/MS; JMSQ1050GC, JEOL, Japan) equipped with a DB-5MS column (30 m in length, 0.25 mm ID, 0.25 μm film) used for the determination of PAHs. The temperature program was run from 50 °C (2 min hold) to 200 °C (1 min hold) at a rate of 15 °C min−1 and then to 300 °C (5 min hold) at a rate of 10 °C min−1. The ionization was performed in electron impact mode at 70 eV, and the data were acquired under SIM mode. The PAH concentrations were calculated using a group of six concentration levels from 0.04 to 2 μg/mL. The calibration curves were linear in the concentration ranges, with correlation coefficients (R2) in the range of 0.9943 (BKF) to 0.9993 (Nap). The limits of detection (LOD) of the 16 detected PAHs were determined from the lowest standard in the calibration curve using the area of the peak that had a signal-to-noise ratio of 3, which ranged from 0.04 to 0.35 μg/L. The mean recovery rate of the 16 detected PAHs ranged from 67 to 93%.

compound

TEFs22−24

P1 (stage 1)

P2 (stage 2)

P3 (stage 3)

Nap Acpy Acp Flu Phe Ant Fla Pye BaA Chr BbF BkF BaP DBA IND BghiP Total

0.001 0.001 0.001 0.001 0.001 0.01 0.001 0.001 0.1 0.01 0.1 0.1 1 1 0.1 0.01

0.06 0.01 0.03 0.12 0.03 0.58 0.08 0.09 0.00 0.01 0.01 0.01 0.01 0.00 0.00 0.00 1.05

0.02 0.00 0.01 0.09 0.01 0.42 0.05 0.05 0.00 0.00 0.01 0.01 0.01 0.00 0.00 0.00 0.69

0.10 0.03 0.05 0.27 0.04 1.08 0.14 0.12 0.00 0.01 0.02 0.02 0.02 0.00 0.01 0.00 1.89

PM in this study were quite low compared with the results in previous studies15,17−19 based on stationary sources. The results indicated that a small fraction of gas-phase PAHs could be converted into condensable PM in the emission process. However, the exhaust flow in the studied coal-fired power plant was approximately 2 000 000 N m3/h, which meant that the total amount of PAH emissions was still very high. The total PAH concentration was lower in stages 1 and 2 than in stage 3, and IND (6-ring PAH) was only detected in stage 3. The depth removal effect of the WESP on the PAHs in the flue gas was found in a former study,20 which could explain this result. The PAH distribution characteristics in condensable PM from the three stages were similar. 3- and 4-ring PAHs occupied the main fraction of the total PAHs. Ant had the highest concentration in the three samples. The amount of Nap was relatively low in the three samples, which might be due to the volatility and sublimation of Nap. More stable PAH components tended to appear in the condensable PM, such as Ant, Flu, Fla, and Pye. However, the carcinogenic 5-ring and 6-ring PAHs accounted for a small proportion of the studied PAHs in condensable PM. Previous studies9,21 confirmed that the large molecular weight PAHs (5- and 6-ring) were preferentially found in the particulate phase. Furthermore, this paper tentatively interpreted the low concentration of 5- and 6-ring PAHs as a result of the temperature change of the flue gas in the whole process. The temperature of the flue gas dropped obviously in the LLT-ESP and the WFGD, which led to the condensation and adsorption of gas-phase PAH components. Qi at el.14 studied the removal effect of the LLT-ESP on the condensable PM in flue gas, and the removal efficiencies were quite good (between 77.1% and ∼90.8%). In this study, the high ring PAHs in the flue gas were likely to be mostly eliminated by the APCDs, and few were detected in the condensable PM. 3.2. Influence of S and WESP on PAH Distribution. From Table 1, the difference in the S component distinguished FC1 from FC2 and FC3. During the test, the continuous emission monitoring system (CEMS) showed that the average emission concentration of SO2 was 50 mg/m3 in stage 1, 20 mg/m3 in stage 2, and 19 mg/m3 in stage 3. S also influenced

3. RESULTS AND DISCUSSION 3.1. PAH Distribution in Condensable PM. The average mass concentration of condensable PM was 18.6 mg/m3 in stage 1, 11.9 mg/m3 in stage 2, and 27.1 mg/m3 in stage 3. The average percentage of the organic fraction in condensable PM was 62% in stage 1, 81% in stage 2, and 87% in stage 3. The concentrations of the 16 PAHs analyzed in this study are shown in Table 2. The total mass concentrations of PAHs in condensable PM in stages 1−3 were 1.05, 0.69, and 1.89 μg/ m3, respectively. The total PAH concentrations in condensable C

DOI: 10.1021/acs.energyfuels.7b01991 Energy Fuels XXXX, XXX, XXX−XXX

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promote the formation of PAHs. The formation mechanism of PAHs during pyrolysis might explain the higher content of PAHs in PIO1 in which more PAHs formed when burning the coal with higher sulfur content. From Table 2, when the WESP operated normally, the total PAH value in condensable PM was 0.69 μg/m3, and the total PAH value increased to 1.89 μg/m3 when the WESP stopped. The total emission concentrations of condensable PM were 11.9 mg/m3 in stage 2 and 27.1 mg/m3 in stage 3.Comparing the total PAH values in P2 and P3, it could be concluded that the WESP eliminated approximately 63% of PAHs in condensable PM in the flue gas. The removal effect of the WESP for PAHs in condensable PM was relatively good. The WESP also affected the PAH distributions in condensable PM. The influence of the WESP on individual PAHs in condensable PM was selective. Comparing PIO2 and PIO3, more 2- and 3-ring PAHs in condensable PM were found in PIO3, and 6-ring PAH was detected in PIO3. When the WESP operated, 6-ring PAHs in condensable PM were totally eliminated in this study. When the WESP stopped, the content of 2- and 3-ring PAHs in condensable PM increased obviously. The WESP had obvious remove effect on 2- and 3-ring PAHs. Furthermore, the WESP in this study had a deep removal ability on total PAHs in condensable PM. However, the removal efficiency of the WESP on PAHs in the flue gas was different in previous studies20,30,31 (ranged from 0.254% to 83%), and a detailed understanding of the influence of the WESP on PAHs in flue gas should be investigated further. 3.3. Total Toxic Equivalent (TEQ) of PAHs in Condensable PM. PAHs have adverse effects on human health with carcinogenic and mutagenic properties. Many studies concerned the health risk assessment of inhabitants exposed to PAHs adsorbed in particulate matter in the air.32−35 PAHs in condensable PM emitted from coal-fired power plants have a direct contribution to PAHs in the airborne particulate matter. So this paper evaluated the emission characteristics and the influence factors of the TEQs of PAHs in condensable PM from coal-fired power plants.The toxic equivalency factor (TEF) is the carcinogenic potency estimate of an individual PAH relative to the carcinogenicity of benzo[a]pyrene (BaP), which is commonly used to evaluate the potential carcinogenicity of PAHs.32−35 BaP is the benchmark PAH used in risk assessments because it is a well-characterized carcinogen, and the slope factors are developed for both inhalation and oral routes of exposure.35 The TEFs of the studied PAHs are listed in Table 2. The TEQs for all PAHs in this study were calculated using the following equation:

the emission characteristics of condensable PM significantly. When the boiler burnt FC1, the average percentage of the inorganic fraction of condensable PM in the flue gas was approximately 38%. When the boiler burnt FC2 and FC3, the average percentage of the inorganic fraction of condensable PM dropped to 19% and 13%, respectively. Former studies10−12,25 on condensable PM emitted from stationary sources confirmed that SO4 compounds made up the largest category of inorganic condensable PM. The results in this study validated the previous conclusion and indicated that higher sulfur content in feed coal increased the SO2 and SO42− contents in the flue gas. Comparing the mass concentrations of condensable PM in stages 2 and 3, the WESP also influenced the emission characteristics of condensable PM. When the WESP operated, the mass concentration of condensable PM was much lower in stage 2 than in stage 3. This study analyzed the concentration and distribution characteristics of PAHs in the organic fraction of condensable PM samples (μg/g, Figure 3). The content of PAHs in the

Figure 3. Content of PAHs in the organic fraction of condensable PM (PIO).

organic fraction of condensable PM (PIO) is determined using the following equation: PIOi = Pi , where i is the sampling OCi stage, 1, 2, or 3; Pi is the mass concentration of the PAH content in condensable PM; and OCi is the mass concentration of the organic fraction in condensable PM. According to the PAH data in Table 2 and Figure 3, it could be concluded that S and the WESP both affected the emission characteristics of PAHs in condensable PM. The total PAH value in P1 was higher than those in P2 and P3. PIO1 was 90 μg/g, PIO2 was 71.2 μg/g, and PIO3 was 79.8 μg/g. The results indicated that the higher sulfur content in the coal led to greater PAH emissions in the flue gas than the lower sulfur content. Few data are available regarding the effect of S on the formation of PAHs during coal combustion. Cheng 26 investigated the emission characteristics of PAHs from coal pyrolysis, and the amount of PAHs produced by the pyrolysis increased with the increase in S content in the coal and reached a maximum value when the S content was 0.8%. The commonly accepted major reaction route of the formation of PAHs in combustion is the hydrogen abstraction−C2H2 addition (HACA) mechanism.27−29 S has a strong effect at removing a H atom from biphenyl aromatic rings, which could

TEQ =

∑ (Ci × TEF)i

where Ci is the measured concentration of individual PAHs, and TEFi is the toxic equivalency factor of the individual PAHs relative to benzo[a]pyrene. The TEQ distribution of the studied PAHs in condensable PM in the flue gas is shown in Figure 4. The total TEQ value was 0.018 μg/m3 for P1, 0.016 μg/m3 for P2, and 0.037 μg/m3 for P3. The total TEQ values of PAHs in condensable PM in this study were lower than the total TEQ values of total PAHs in flue gas in previous studies (0.293 μg/m3,20 0.395−1.439 μg/ m315), and a little higher than some results of the TEQ values of airborne PAHs (0.45−1.12 ng/m3,33 0.30−2.37 ng/m3,34 0.13−0.79 ng/m332). The TEQ studies of PAHs in condensable PM reflected the direct contribution of PAHs TEQs from coalD

DOI: 10.1021/acs.energyfuels.7b01991 Energy Fuels XXXX, XXX, XXX−XXX

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also increased the content of PAHs in condensable PM in the flue gas. The WESP had a good removal effect on PAHs in condensable PM, especially for 2-, 3-, and 6-ring PAHs. The WESP reduced the TEQ values of PAHs in condensable PM. Further studies on the influence of the WESP on PAHs in flue gas should be conducted.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Xiaodong Li: 0000-0002-5331-5968 Zhifu Qi: 0000-0003-3043-2894 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors would like to thank the State Key Laboratory of Clean Energy Utilization and Zhejiang Energy Group R&D. The work is supported by the Major State Basic Research Development Program of China (973 Program, No. 2011CB201500) and the Public Welfare Projects for Environmental Protection (No. 201209022).

Figure 4. TEQ distribution of total PAHs in condensable PM.

fired power plants to the total PAHs TEQs in atmosphere. The potential carcinogenicity assessment of PAHs in this study showed the level of the environmental hazards of PAHs in condensable PM emitted from coal-fired power plants. The 3and 5-ring PAHs (especially Ant and BaP) contributed the most to the total TEQs of PAHs in condensable PM in the three stages in this study. The higher sulfur content in the feed coal led to a higher TEQ value of 3-ring PAHs, as seen by comparing P1 and P2. When the WESP stopped operating, the TEQ values of 3- and 5-ring PAHs increased significantly, especially the 5-ring PAHs. In summary, harmful biological effects are mostly related to Ant and BaP in condensable PM in this study. The WESP showed an remarkable control effect for TEQ values of PAHs in condensable PM in the flue gas, the TEQs decreased about 55% from P3 to P2. However, the sulfur content in feed coal had little effect on the total TEQs of PAHs in condensable PM. It could be concluded that the control effect of APCDs plays an important role in reducing the mutagenicity and carcinogenicity of some PAHs in condensable PM.

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REFERENCES

(1) Mu, L.; Peng, L.; Cao, J.; He, Q.; Li, F.; Zhang, J.; Liu, X.; Bai, H. Emissions of polycyclic aromatic hydrocarbons from coking industries in China. Particuology 2013, 11 (1), 86−93. (2) Chow, J. C.; Watson, J. G.; Chen, L. A.; Ho, S. S. H.; Koracin, D.; Zielinska, B.; Tang, D.; Perera, F.; Cao, J.; Lee, S. C. Exposure to PM2. 5 and PAHs from the Tong Liang, China epidemiological study. J. Environ. Sci. Health, Part A: Toxic/Hazard. Subst. Environ. Eng. 2006, 41 (4), 517−542. (3) Menzie, C. A.; Potocki, B. B.; Santodonato, J. Exposure to carcinogenic PAHs in the environment. Environ. Sci. Technol. 1992, 26 (7), 1278−1284. (4) Liu, G.; Niu, Z.; Van Niekerk, D.; Xue, J.; Zheng, L. Polycyclic aromatic hydrocarbons (PAHs) from coal combustion: emissions, analysis, and toxicology. In Reviews of environmental contamination and toxicology; Springer: Berlin, 2008; pp 1−28. (5) Zhai, Y.; Li, P.; Zhu, Y.; Xu, B.; Peng, C.; Wang, T.; Li, C.; Zeng, G. Source Apportionment Coupled with Gas/Particle Partitioning Theory and Risk Assessment of Polycyclic Aromatic Hydrocarbons Associated with Size-Segregated Airborne Particulate Matter. Water, Air, Soil Pollut. 2016, 227 (2), 1−15. (6) Teixeira, E. C.; Agudelo-Castañeda, D. M.; Fachel, J. M. G.; Leal, K. A.; Garcia, K. d. O.; Wiegand, F. Source identification and seasonal variation of polycyclic aromatic hydrocarbons associated with atmospheric fine and coarse particles in the Metropolitan Area of Porto Alegre, RS, Brazil. Atmos. Res. 2012, 118, 390−403. (7) He, J.; Fan, S.; Meng, Q.; Sun, Y.; Zhang, J.; Zu, F. Polycyclic aromatic hydrocarbons (PAHs) associated with fine particulate matters in Nanjing, China: Distributions, sources and meteorological influences. Atmos. Environ. 2014, 89 (2), 207−215. (8) Xu, S. S.; Liu, W. X.; Tao, S. Emission of polycyclic aromatic hydrocarbons in China. Environ. Sci. Technol. 2006, 40 (3), 702−708. (9) Kong, S.; Ding, X.; Bai, Z.; Han, B.; Chen, L.; Shi, J.; Li, Z. A seasonal study of polycyclic aromatic hydrocarbons in PM2.5 and PM2.5−10 in five typical cities of Liaoning Province, China. J. Hazard. Mater. 2010, 183 (1−3), 70−80. (10) Yang, H. H., Filterable and Condensable Fine Particulate Emissions from Stationary Sources. Aerosol Air Qual. Res. 2014, 14, 10.4209/aaqr.2014.08.0178 (11) Corio, L. A.; Sherwell, J. In-stack condensible particulate matter measurements and issues. J. Air Waste Manage. Assoc. 2000, 50 (2), 207−218.

4. CONCLUSION This study investigated the emission characteristics of PAHs in condensable PM emitted from a coal-fired power plant. The influence of the S content and the WESP on the PAH distribution was analyzed. The total PAH concentrations in condensable PM were relatively low in this study. A small fraction of gas-phase PAHs in the flue gas could be converted to the compositions of condensable PM. Stable PAH components (Ant, Flu, Fla, and Pye) tended to appear in the condensable PM. 3- and 4-ring PAHs occupied the main part of the PAHs in condensable PM. The temperature drop of the flue gas during the whole process of the boiler unit might lead to the highest molecular weight PAHs appearing in the particulate phase, and very few 5- and 6ring PAHs were detected in condensable PM. The S content in the burning coal affected the emission characteristics of condensable PM and PAHs significantly. A high S content led to a greater inorganic fraction of condensable PM emissions in the flue gas. A high S content E

DOI: 10.1021/acs.energyfuels.7b01991 Energy Fuels XXXX, XXX, XXX−XXX

Article

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DOI: 10.1021/acs.energyfuels.7b01991 Energy Fuels XXXX, XXX, XXX−XXX