Stack Flue Gas Research Articles

Theoretical and Numerical Analysis of Convective Recuperator for an Oil Fired Water Tube Boiler to Improve the Boiler Performance

Objectives: This paper deals with the theoretical and numerical analysis of a convective recuperator used to recover waste heat from the stack flue gases and use it to pre heat the air before it is fed into the combustion chamber of an oil fired water tube boiler. Methods/Statistical Analysis: Three different tube diameters are considered in the present study. Theoretical analysis is carried out to determine the efficiency and other parameters of the boiler with and without recuperator. To support the theoretically obtained results on improved boiler performance by pre heating the air using recuperator, numerical simulation studies is carried out. Findings: The study showed that 10” inch (0.254 m) pipe diameter arranged in a 3 x 3 array gave a flow velocity of air at around 15 to 25 m/s. The stack flue gas exit temperature decreased from 200oC to 135.50oC whereas the inlet air temperature after pre heating through the recuperator is found to be 85oC with a rise in temperature of around 50oC. After pre heating the air, the efficiency of the boiler improved from 71.90% to 74.60%. The quantity of furnace oil saved per day is 3.76% with respect to its present consumption level. CFD simulations are carried out using ANSYS CFX. A good agreement is found between the data obtained from simulation and theoretical analysis. Payback period by incorporating the recuperator to the existing boiler is estimated to be 60 working days. Application/ Improvements: Optimized performance improvement of existing boiler used in industries is possible without extensive redesign by recovering waste heat leading to energy conservation.

An Assessment of Pollution with Polychlorinated Dibenzodioxins (PCDDs) and Polychlorinated Dibenzofuranes (PCDFs) at Steelmaking

Polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofuranes (PCDFs) are types of persistent organic pollutants (POPs) with a wide range of toxic responses and carcinogenic properties. These pollutants have a negative impact on the steelworkers, environment and population. The aim of this paper is to assess the polychlorinated dibenzodioxins and polychlorinated dibenzofuranes emissions from steelmaking in the electric arc furnace in order to improve the gaseous emissions management. The analyses of polychlorinated dibenzodioxins and polychlorinated dibenzofuranes was performed using a high resolution gas chromatograph/high resolution mass spectrometer (HRGC/HRMS). After evaluating the pollution levels of polychlorinated dibenzodioxins and dibenzofuranes during steelmaking it results that: the total PCDDs and PCDFs concentrations in the stack flue gases was 0.9886 ng/Nm3; in the composition of flue gases predominates the following compounds: tetrachloro dibenzofuran (TCDF) 40.55%, pentachloro dibenzofuran (PeCDF) 19.4%, tetrachloro dibenzo-p-dioxin (TCDD) 12.5%, pentachloro dibenzo-p-dioxin (PeCDD) 10.7% and hexachloro dibenzofuran (HxCDF) 10.5%; the calculated total value of Toxic Equivalent Quantity (Total TEQ) is 0.326482 ng I-TEQ/Nm3; the level of PCDD and PCDF concentrations depends on the plastic (such as polyvinylchloride) content of material input. The reduction of pollution with polychlorinated dibenzodioxins and dibenzofuranes to the steelmaking in the electric arc furnace is possible by charge component selection and by the use of raw materials with reduced plastics content.

An Overview of PCDD/F Inventories and Emission Factors from Stationary and Mobile Sources: What We Know and What is Missing

ABSTRACTThis overview attempts to outline what we currently know about the PCDD/F emission inventories and the source categories therein. Besides the best available control techniques, suggestions are offered on how to reduce the PCDD/F emission factors and emission quantity of some important PCDD/F emission sources. The PCDD/F combustion sources can be classified as either stationary or mobile or minimally/uncontrolled combustion sources. The major stationary sources of PCDD/Fs are metal production processes, waste incineration, heat and power plants, and fly ash treatment plant. Crematories, vehicles, residential boilers and stoves are of key concern due to their proximity to residential areas and their relatively lower lying stacks and exhaust gases, which may result in great impact to their surrounding environment. Moreover, we offered our perspectives on how to improve the quality and representative of the PCDD/F emission factors to attain PCDD/F inventories which correspond more to reality. These points of view include: (1) PCDD/F contributions during start-up procedures of MSWIs should be considered, (2) the sampling times of stack flue gases for EAFs and secondary metal smelters should correspond to whole smelting process stages, (3) longer flue gas sampling time should be executed for power plants, (4) direct exhaust samplings from tailpipes for mobile sources, (5) development of an open burn testing facility that can reflect the real open burning conditions, and (6) long-term sampling techniques like AMESA are suggested to used exclusively for the most contributed PCDD/F stationary sources.

Energy recovery and secondary pollutant emission from the combustion of co-pelletized fuel from municipal sewage sludge and wood sawdust

There are concerns about the boiler efficiency and the secondary pollutants emissions during MSS (municipal sewage sludge) combustion. In the present work, the pellets made from the mixture of MSS and wood sawdust were combusted in a regular boiler. The boiler efficiencies of 10% and 30% (MSS content %) MSS pellet fuels were 76.6% and 75.9%, respectively. The emission, mass balance and distribution characteristics of PCDD/Fs (polychlorinated dibenzo-p-dioxins and dibenzofurans) and heavy metals during the combustion of 10% and 30% MSS pellet fuels were also carried out in a traveling grate boiler. The international toxic equivalency quantities (I-TEQ) of the PCDD/Fs in the stack flue gas from the combustion of 10% and 30% pellet fuels were 0.191 and 0.157 ng I-TEQ Nm−3, respectively. MSS exhibited a remarkable difference in ratios of PCDFs to PCDDs and congener profiles compared with stack flue gas, fly ash and slag. Ratio of PCDFs to PCDDs and congener profiles for slag also differed significantly from those of stack flue gas and fly ash. The emitted pollutants in the traveling grate boiler met the requirement of standards in China (GB 18485 -2001).

Comparing CO2 Emission Factors Estimated Using Stack Flue Gas Measurement Data for Two Types of Ceramic Kiln: A Case Study in Hanoi City, Vietnam

In Vietnam, the ceramic industry is one of the construction material production sectors that has large emission of CO2 - the major greenhouse gas, since it consumes a large amount of fossil fuels. This research aims at preliminarily estimating the CO2 emission factors for two major kiln technologies currently used in ceramic production sector in Vietnam, namely the traditional kiln and tunnel kiln. For this purpose, field measurements of CO2 concentration in stack flue gases of two ceramic factories in Hanoi City, Vietnam were conducted. The results of data analysis have shown that the traditional kiln has higher CO2 emission factors compared to those of tunnel kiln. The low energy efficiency and high energy consumption of the traditional kiln are the major causes for its higher CO2 emission factors.

Comparative Assessment of Co2 Emission Factors Estimated Using Stack Flue Gas Measurement Data for Two Types of Brick Kiln: A Case Study in Phu Tho Province, Vietnam

In Vietnam, the brick production sector is one of the construction material production sectors that has large emission of CO2 – the major greenhouse gas, since it consumes a large amount of fossil fuels. This research aims at preliminarily estimating the CO2 emission factors for two major kiln technologies used in brick production sector in Vietnam, namely tunnel and vertical shaft brick kiln (VSBK). For this purpose, field measurement of CO2 concentration in stack flue gases of two brick factories in Phu Tho province – one of the largest brick production areas in the North of Vietnam were conducted. The results of data analysis have shown that the tunnel kiln has higher CO2 emission factors compared to those of VSBK. The lower specific energy consumption and lower heat losses are the major causes for lower CO2 emission factors of VSBK.

Under-Deposit Caustic Corrosion on Sodium Carbonate Pipeline

Under deposit corrosion (UDC) is defined as a localized corrosion that develop beneath or around deposit on a metal surface. UDC represents an important threat in the integrity matrix of petroleum and petrochemical production and transportation facilities, and has been cited as responsible for high corrosion rates and loss of containment during operations. For a sodium carbonate production process, crude caustic from the caustic plant enters the sodium carbonate storage tanks. When the batch cycle begins, crude caustic is pumped to the top of the carbonation tower. The caustic stream flows down through two packed sections where it contacts boiler's stack flue gas rising up through the tower. The caustic (sodium hydroxide) reacts with the carbon dioxide in the flue gas to form sodium carbonate. A carbon steel pipeline then transports sodium carbonate. This carbon steel pipeline experiences frequent leaks. An investigation was conducted to identify the types and possible causes of the corrosion on the sodium carbonate pipeline. XRF (X-Ray Fluorescence Spectrometry) and carbon/sulfur analyzer and XRD were used to chemically identify the deposited materials in the pipeline and to study the damage morphology. It was concluded the failure of the pipeline is attributed to caustic corrosion aggravated by deposited of process carry-over materials.

Formation and Dispersion of Nitric Acid Vapor from Stack Flue Gas

Extreme recovery of the thermal energy from the combustion of flue gas may bring about early gas condensation resulting in the increased formation of nitric acid vapor. The behavior of the nitric acid formed inside the stack and in the atmosphere was investigated through a computer-aided simulation in this study. Low temperatures led to high conversion rates of the nitrogen oxide to nitric acid, according to the Arrhenius relationship. Larger acid plumes could be formed with the cooled flue gas at 40℃ than the present exiting gas at 115℃. The acid vapor plume of 0.1 ppm extended to 25 m wide and 200 m high. The wind, which had a seasonal local average of 3 m/s, expanded the influencing area to 170 m along the ground level. Its tail stretched 50 m longer at 40℃ than at 115℃. The emission concentration of the acid vapor in the summer season was a little lower than in the winter. However, a warm atmosphere facilitated the Brownian motion of the discharged flue gas, finally leading to more vigorous dispersion.

Effects of water vapor and temperature upon combustion stability of CeZrO2-modified Pd-Pt/Al2O3 catalyst

Two bimetallic Pd-Pt catalysts were prepared by wash-coating the composites of Pd-Pt/CeZrO2-Al2O3 onto cordierite monolith and they were evaluated in a tubular reactor for stability in combustion of SOFC stack flue gas at GHSV 29,280 h−1 and 1 atm. The Pd-rich catalyst showed better stability than the Pt-rich catalyst for combustion of the wet feed. Water vapor in the stack flue gas affected the catalyst activity adversely via the formation of inactive Pd(OH)2 species at the reaction temperatures of 723 and 823 K, but this effect was eliminated by raising the temperature to 923 K or above. Catalyst properties such as specific surface area, pore size and metal dispersion did not deteriorate significantly after combustion of the wet feed in the temperature range of 723-1,023 K. The presence of CeZrO2 in Al2O3 material was considered to affect the support properties favorably, leading to a kind of metal-support interaction beneficial for the combustion of the wet feed. This interaction helped to enable the Pd-Pt catalysts to maintain good stability for combusting the wet SOFC stack flue gas with the stoichiometric air-to-fuel ratio at 923 K or above.

Characterization and concentrations of polycyclic aromatic hydrocarbons in emissions from different heating systems in Damascus, Syria

Traffic has long been recognized as the major contributor to polycyclic aromatic hydrocarbon (PAH) emissions to the urban atmosphere. Stationary combustion sources, including residential space heating systems, are also a major contributor to PAH emissions. The aim of this study was to determine the profile and concentration of PAHs in stack flue gas emissions from different kinds of space heaters in order to increase the understanding of the scale of the PAH pollution problem caused by this source. This study set out to first assess the characteristics of PAHs and their corresponding benzo[a]pyrene equivalent emissions from a few types of domestic heaters and central heating systems to the urban atmosphere. The study, enabled for the first time, the characterization of PAHs in stationary combustion sources in the city of Damascus, Syria. Nine different types of heating systems were selected with respect to age, design, and type of fuel burned. The concentrations of 15 individual PAH compounds in the stack flue gas were determined in the extracts of the collected samples using high-performance liquid chromatography system (HPLC) equipped with ultraviolet-visible and fluorescence detectors. In general, older domestic wood stoves caused considerably higher PAH emissions than modern domestic heaters burning diesel oil. The average concentration of ΣPAH (sum of 15 compounds) in emissions from all types of studied heating systems ranged between 43 ± 0.4 and 316 ± 1.4μg/m(3). Values of total benzo[a]pyrene equivalent ranged between 0.61 and 15.41μg/m(3).

Memory Effects of Polychlorinated Dibenzo-p-dioxin and Furan Emissions in a Laboratory Waste Incinerator

Laboratory wastes are discharged from experimental, testing, or analysis processes, and contain various toxic chemical compounds with a high heating-value and a high chlorine content (＞ 9%). Elevated PCDD/F (polychlorinated dibenzo-pdioxin and furan) emissions during start-up stages are caused by combustion of waste with high chlorine contents, incomplete combustion, and so called ”memory effects”. Even though the duration of cold start-up is short compared with the hours of continuous steady operation in a waste incinerator, its negative effects with regard to PCDD/F emissions on both human health and the environment cannot be neglected. A full-scale laboratory-waste incinerator which is operated for 10 days in each run and has 15 to 20 runs annually was investigated in this study. Eleven PCDD/F samples of stack flue gas were collected during the cold start-up periods (for 60.5 hrs). The gas temperature of the primary combustion chamber was above 850°C, and was maintained at between 850 and 900°C by injecting diesel fuel without waste feed. For first 1.5-7.5 hours, the PCDD/F concentration in the stack flue gas was as high as 0.656-1.15 ng I-TEQ/Nm^3. Afterward, during hours 10.5-35.5 and 54.5-60.5, this reduced to 0.159-0.459 and 0.218-0.254 ng I-TEQ/Nm^3, respectively. Based on principal component analysis (PCA) and the L/H ratio, the results revealed a higher L/H ratio (1.23) before hour 32, indicating that less chlorinated PCDD/F homologues (tetra and penta) dominated, while after hour 32 more chlorinated PCDD/F homologues (hexa, hepta and Octa) had a higher mass concentration and the L/H ratio fell to 0.42. These results indicate that the PCDD/F emissions during cold start-up were caused by memory effects and thermal desorption. Therefore, in order to reduce the PCDD/F emissions from the stack flue gas of waste incinerators, is highly recommended that a higher amount of activated carbon injection is used in front of the bag filters.

Polychlorinated Dibenzo-p-dioxin and Dibenzofuran (PCDD/F) Emission Behavior during Incineration of Laboratory Waste. Part 1: Emission Profiles Obtained Using Chemical Assay and Bioassay

This study describes polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) behavior during the incineration of laboratory waste, including combustible laboratory solid waste (LSW), laboratory plastic waste (LPW), and organic laboratory liquid waste (LLW). Stack flue gas (SFG), input materials, bottom ash (BTA), first quenching tower ash (FQA), secondary quenching tower ash (SQA), and baghouse ash (BHA) were sampled and analyzed using high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) assay and bioassay. The PCDD/F concentration of SFG met the standard in Taiwan. The Cl levels of LPW and LLW were roughly equivalent to that of municipal solid waste (MSW). Therefore, the SFG concentration, content of fly ash, and distribution behavior of PCDD/Fs are reasonably similar to those of MSW incinerators. The LSW had an extremely high Cl level (11.4%). The emission factor of the whole incineration system was 888 µg I-TEQ/ton-waste, which is 10-fold higher than that of MSW. The PCDD/F was mainly in BTA (31.6 wt.%) and fly ash (63.1 wt.%), resulting in higher PCDD/F level of ashes compared with that of MSW ashes. Both HRGC/HRMS analysis and bioassay results show similar PCDD/F emission characteristics during the incineration of LW. In addition, the linear regression between the values acquired using these two methods show a good relation (R 2 > 0.84), indicating that Ad-DR bioassay is a promising fast-screen method for determining PCDD/F levels.

Polychlorinated Dibenzo-p-dioxin and Dibenzofuran (PCDD/F) Emission Behavior during Incineration of Laboratory Wastes. Part 2: PCDD/F Profiles and Characteristics of Output Materials

This study investigates the polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) profiles of output materials and the influence of Cl content of input materials during the incineration of laboratory waste. The specimens, namely bottom ash (BTA), first quenching tower ash (FQA), secondary quenching tower ash (SQA), baghouse ash (BHA), and stack flue gas (SFG), were sampled and analyzed using high-resolution gas chromatography/high-resolution mass spectrometry, field-emission scanning electron microscopy (FE-SEM), ion chromatography, and X-ray diffraction (XRD). The Cl content was highest in FQA, followed by that in SQA, BHA, and BTA, and most of the Cl existed in soluble form, especially for FQA and SQA. The Cl mass was mainly distributed in FQA and BTA during incineration. The PCDD/F content of ash in each category was highly related to the Cl level in the input materials. The PCDD/Fs of all ashes and the particulate phase of SFG were mainly 7-Cl or 8-Cl PCDD/Fs, but those of the gas phase in SFG were mainly 4-6 Cl PCDD/Fs. In addition, an increase of Cl in the input materials increased the fractions of 7-Cl and 8-Cl PCDD/Fs. The XRD analysis results indicate that the main crystalline phase in fly ashes was NaCl. FE-SEM images show a porous granular morphology, which is consistent with the XRD analysis results.

Preface to Special Issue - Observation, Control Technologies and Impact Studies of POPs

ABSTRACTPersistent organic pollutants (POPs) include pesticides which are organochlorine compounds, such as aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, alpha and beta hexachlorocyclohexane (also by-products), chlordecone, and lindane. Industrial chemicals such as PCBs, hexachlorobenzene (also a pesticide), hexabromobiphenyl, hexa- and heptabromodiphenyl ether (commercial octabromodiphenyl ether), pentachlorobenzene, perfluorooctane sulfonic acid and its salts perfluorooctane sulfonyl fluoride, tetra- and pentabromodiphenyl ether (commercial pentabromodiphenyl ether), and unintentional by-product compounds, such as polychlorinated dioxins and furans (PCDD/Fs). The international community has repeatedly called for urgent global action to reduce and eventually eliminate the release of these chemicals. However, the emission characteristics, control technologies, atmosphere transport and toxicities of dioxins are not well investigated. This special issue in Aerosol and Air Quality Research features 24 papers submitted by researchers from Australia, Canada, China, Italy, Japan, Malaysia, Norway, Switzerland, Taiwan, Thailand, United Kingdom, USA and Vietnam. In these studies, the characteristics of POPs are investigated in air filters, tree bark, house dust, road dust, ambient air, fugitive nanoparticle, stack flue gas, fly ash, and serum samples.

The PCDD/F Removal Efficiency of a Medical Waste Incinerator Dual-Bag Filter System

This study investigated the polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) removal efficiencies in two medical waste incinerators (MWIs) -MWI-A and MWI-B, with waste burning capacities of 9.12 and 12 tons per day, with dual-and single-bag filter systems, respectively. The PCDD/Fs in the stack flue gas and fly ashes of each air pollution control device (APCD) unit were collected concurrently. Based on mass balance, it was determined that the major PCDD/F removal occurred in the bag filter system with activated carbon injection (ACI). The total PCDD/F emission removal efficiencies for the whole dual-bag filter system, bag filter 1 (BF1), bag filter 2 (BF2) in MWI-A and the single bag filter system (BF) in MWI-B were 99.7%, 84.8%, 98.0%, 99.0% on the mass basis, respectively. The PCDD/F emission ratio (the escaped PCDD/F ratio after all APCDs) with the dual-bag filter system was over four times lower than that with a single bag filter. The results demonstrate a very efficient way to reduce the excess PCDD/F emissions incurred by intermittent operations and irregular waste feeding.

Polychlorinated Dibenzo-P-Dioxins and Dibenzofurans from a Grate-Type Municipal Solid Waste Incinerator in China

The emission characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were evaluated from a grate-type municipal solid waste incinerator (MSWI). The stack flue gas, fly ash and bottom ash samples were sampled and analyzed. Results indicated that the flue gas, fly ash and bottom ash presented their mean dioxin levels of 0.0723 ng I-TEQ/Nm3, 0.614 ng I-TEQ/g and 13.33 ng I-TEQ/kg respectively. The PCDD/Fs congener patterns, in flue gas, fly ash and bottom ash, showed large similarities in both concentration and I-TEQ profiles. The de novo synthesis plays a dominant role in the low-temperature post-combustion zone.

Validation and Characterization of Persistent Organic Pollutant Emissions from Stack Flue Gases of an Electric Arc Furnace by Using a Long-Term Sampling System (AMESA®)

A long-term sampling system, called the Adsorption Method for Sampling of Dioxins and Furans (AMESA), was used for long-term sampling (up to 168 hours) of an electric arc furnace (EAF) to obtain the representative flue gas samples. In order to have a comprehensive view of the emissions of persistent organic pollutants (POPs) from EAFs, six POPs, including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polychlorinated diphenyl ethers (PCDEs), polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs), were investigated. Tests showed the breakthroughs of PBDD/Fs and PBDEs are much larger (8.9%–43%), while the others are less than 3%. A significant increase in breakthrough with the increase in halogen numbers is observed, because highly halogen-substituted POPs tend to partition to the particulate-phase. Except for PCBs and PCDEs, whose percentages of the POPs in the rinses to the total POPs collected from the long-term samples (cartridges + rinses) are less than 7%, those of the other POPs are all greater than 30%. Therefore, the solvents from the rinses of the sampling probe and other components need to be combined with an XAD-2 cartridge for analyses. The PCBs and PBDEs are the most abundant pollutants in the stack flue gases of the EAF, and their mass concentrations are one to three orders higher than those of the other POPs. With regard to POPs with dioxin-like toxicity, the percentages of the contributed toxicities by PCDD/Fs, PCBs and PBBD/Fs are 87.1%, 11.7% and 1.2%. The close association that PBDEs and PBDD/Fs have with the concentrations and congener profiles is not present for PCDEs and PCDD/Fs, suggesting the need for further studies of the formation mechanisms of these analogues.

Energy Recovery and Emissions of PBDD/Fs and PBDEs from Co-combustion of Woodchip and Wastewater Sludge in an Industrial Boiler

The emissions of polybrominated dibenzo-pdioxins,dibenzofurans (PBDD/Fs), and polybrominated diphenyl ethers (PBDEs) from trial combustion of 10 wt % dried industrial wastewater-treatment sludge (IWTS) and 90 wt % woodchip in an industrial boiler were investigated and compared to that from woodchip combustion. The PBDD/F toxic equivalent (TEQ) andPBDE emissions increased from 0.121 pg TEQ Nm−3 and 2260 pgNm−3, respectively, of the woodchip combustion to 0.211 pg TEQNm−3 and 4200 pg Nm−3, respectively, of the trial combustion.PBDD/F and PBDE congener profiles of inputs and outputs of the same type of combustion were similar; they also show similarity between woodchip and trial combustions, revealing that the destruction pathway was little affected by the introduction of the IWTS. The fates of PBDD/Fs and PBDEs show that the indigenous pollutants in the feed were effectively depleted (>93.5%). The dominant releasing route of PBDD/F and PBDE shifted from the stack flue gas of woodchip combustion to the ashes of trial combustion. This study demonstrates that co-combustion not only handles the fast growing sludge stream but also yields a saving of 26.3% in the fuel cost and treatment fees of sludge and ashes.

Optimum GHSV for the Catalytic Combustor of an 1.1 kW Solid Oxide Fuel Cell (SOFC) System

The flue gas which resulted from oxidation of the fuel flow in the SOFC stack was burnt off in the catalytic combustor under the operating condition acquired by the process simulation. Conversion of the combustible components in the stack flue gas was experimentally measured at four different GHSVs in a tubular reactor packed with base-metal catalyst pellets. Optimum GHSV of 6,990 hr-1 in the catalytic combustor was determined on the basis of reactor performance including pressure drop, carbon monoxide slip, and conversion of the combustible components.

Emissions of polycyclic aromatic hydrocarbons from coking industries in China

This study set out to assess the characteristics of polycyclic aromatic hydrocarbon (PAH) emission from coking industries, with field samplings conducted at four typical coke plants. For each selected plant, stack flue gas samples were collected during processes that included charging coal into the ovens (CC), pushing coke (PC) and the combustion of coke-oven gas (CG). Sixteen individual PAHs on the US EPA priority list were analyzed by gas chromatography/mass spectrometry (GC/MS). Results showed that the total PAH concentrations in the flue gas ranged from 45.776 to 414.874μg/m3, with the highest emission level for CC (359.545μg/m3). The concentration of PAH emitted from the CC process in CP1 (stamp charging) was lower than that from CP3 and CP4 (top charging). Low-molecular-weight PAHs (i.e., two- to three-ring PAHs) were predominant contributors to the total PAH contents, and Nap, AcPy, Flu, PhA, and AnT were found to be the most abundant ones. Total BaPeq concentrations for CC (2.248μg/m3) were higher than those for PC (1.838μg/m3) and CG (1.082μg/m3), and DbA was an important contributor to carcinogenic risk as BaP in emissions from coking processes. Particulate PAH accounted for more than 20% of the total BaPeq concentrations, which were significantly higher than the corresponding contributions to the total PAH mass concentration (5%). Both particulate and gaseous PAH should be taken into consideration when the potential toxicity risk of PAH pollution during coking processes is assessed. The mean total-PAH emission factors were 346.132 and 93.173μg/kg for CC and PC, respectively.