Power Plant Stack Research Articles

Computational fluid dynamics numerical simulation of flue gas emission from stack and tower integration system of coal-fired power plant

ABSTRACT The method of Computational Fluid Dynamics (CFD) simulation has been extensively employed in the stack and tower integration technology (STIT) research; however, a significant number of studies overlooked the impact of thermal buoyancy on the external flow field of cooling tower. In light of this, an improved approach is proposed in this study. A model of a cooling tower and its surrounding flow field was established, and its reliability was confirmed too. Based on our model, the performance of three enhancement strategies under various crosswind speeds and ambient temperatures was simulated. The results indicate that all three enhancement strategies can effectively simulate the effects of thermal buoyancy. In the simulations, the elevation of the flue gases increased from 306 m to either 426 m or 476 m. In the present study, ambient conditions characterized by crosswind speeds below 4 m/s and temperatures below 297.15 K were deemed suitable for the dispersion of stack and tower integration (STI) flue gases. A power function distribution was identified between crosswind speed and the mean height of the plume, while a linear relationship was observed between ambient temperature and the mean height of the plume.

PREDICTION OF STACK PLUME RISE

Plumes can emit from stacks of power plants, refineries and so on. Plume rise depends on multiple factors including stack exit diameter, exhaust gas velocity, effluent temperature, wind speed, lapse rate etc. Increased stack height because of plume rise plays a significant part in reducing ground level concentrations of air pollutants in downwind direction. Various equations have been proposed for prediction of plume rise such as Holland (1953), Rauch (1962), Briggs (1965) etc. In the present paper a plume rise formula was derived from the Rauch (1962) and Lucas-Moore-Spurr (1963) equations. The results revealed that: 1) the derived equation calculated plume rise more accurately than the Stone and Clarke (1967), Lucas-Moore-Spurr (1963) and Csanady (1961) formulas, 2) the derived formula overestimated plume rise by a factor of approximately two and 3) the coefficient of heat emission rate played a key role in calculation of plume rise.

Techno-economic-environmental assessment and AI-enhanced optimization of a gas turbine power plant with hydrogen liquefaction

Most of the power plants in the world are based on gas turbines and many researchers tried to improve their efficiencies. This goal can be attained by the optimum utilization of heat losses. The authors of the present study aim to design, model, and optimize a gas turbine-based multigeneration power plant that uses the maximum possible of input energy to boost the products capacity and improve the efficiency. To decline the hydrogen storage and transportation costs, a hydrogen liquefaction process is applied to liquified the produced hydrogen at the same time. Besides, the power plant stack containing a substantial amount of energy is employed to operate a multi-effect desalination unit. To solve the main functions of the model, a programming code is developed. Then, the objective functions of the model are optimized using a machine learning model coupled with a genetic algorithm. Sensitivity analysis reveals that the fuel mass flow rate plays a pivotal role on total cost rate and hydrogen production rate; however, does not affect the exergy efficiency. Applying such a design for heat recovery, leads to 3.27% improvement in exergy efficiency rather than similar studies. The optimization results indicates that the LCOE is declined by 8.16% and normalized emission of CO2 is mitigated by 5.82 kg/GJ.

14CO2 ACTIVITY IN AIR SAMPLES AND DILUTION FACTOR EVALUATION OF KAKRAPAR GUJARAT SITE, INDIA

ABSTRACT14CO2 activity in air samples collected at Kakrapar Gujarat Site, India, was measured, and site-specific dilution factor for 14CO2 has been evaluated. 14CO2 activity in air samples was monitored for 72 different sampling events at onsite stack of Nuclear Power Plant (NPP) and at ESL meteorology laboratory (at 1.6 km from NPP stack). 14CO2 activity in air at stack of NPP and at ESL meteorology laboratory was observed to 0.10–0.18 TBq (GWe.year)–1, with mean value 0.12 TBq (GWe.year)–1 and ≤0.04–0.13 Bq m–3, with mean value 0.08 Bq m–3 respectively. The results were correlated with meteorological parameters. Site specific dilution factor for 14CO2 in air was evaluated at 1.6 km and was found to be in the range of 4.6E-05 to 21E-05 s m–3. Inter angle (degree) between plume direction and fixed sampling location and rainfall (mm) are found to be the important influencing parameters for dilution factor of 14CO2 in air.

Non-nulling protocols for fast, accurate, 3-D velocity measurements in stacks

ABSTRACT The authors present protocols for making fast, accurate, 3D velocity measurements in the stacks of coal-fired power plants. The measurements are traceable to internationally-recognized standards; therefore, they provide a rigorous basis for measuring and/or regulating the emissions from stacks. The authors used novel, five-hole, hemispherical, differential-pressure probes optimized for non-nulling (no-probe rotation) measurements. The probes resist plugging from ash and water droplets. Integrating the differential pressures for only 5 seconds determined the axial velocity V a with an expanded relative uncertainty U r(V a) ≤ 2% of the axial velocity at the probe’s location, the flow’s pitch (α) and yaw (β) angles with expanded uncertainties U(α) = U(β) = 1 °, and the static pressure p s with U r(p s) = 0.1% of the static pressure. This accuracy was achieved 1) by calibrating each probe in a wind tunnel at 130, strategically-chosen values of (V a, α, β) spanning the conditions found in the majority of stacks (|α| ≤ 20 °; |β| ≤ 40 °; 4.5 m/s ≤ V a ≤27 m/s), and 2) by using a long-forgotten definition of the pseudo-dynamic pressure that scales with the dynamic pressure. The resulting calibration functions span the probe-diameter Reynolds number range from 7,600 to 45,000. Implications: The continuous emissions monitoring systems (CEMS) that measure the flue gas flow rate in coal-fired power plant smokestacks are calibrated (at least) annually by a velocity profiling method. The stack axial velocity profile is measured by traversing S-type pitot probes (or one of the other EPA-sanctioned pitot probes) across two orthogonal, diametric chords in the stack cross-section. The average area-weighted axial velocity calculated from the pitot traverse quantifies the accuracy of the CEMS flow monitor. Therefore, the flow measurement accuracy of coal-fired power plants greenhouse gas (GHG) emissions depends on the accuracy of pitot probe velocity measurements. Coal-fired power plants overwhelmingly calibrate CEMS flow monitors using S-type pitot probes. Almost always, stack testers measure the velocity without rotating or nulling the probe (i.e., the non-nulling method). These 1D non-nulling velocity measurements take significantly less time than the corresponding 2D nulling measurements (or 3D nulling measurements for other probe types). However, the accuracy of the 1D non-nulling velocity measurements made using S-type probes depends on the pitch and yaw angles of the flow. Measured axial velocities are accurate at pitch and yaw angles near zero, but the accuracy degrades at larger pitch and yaw angles. The authors developed a 5-hole hemispherical pitot probe that accurately measures the velocity vector in coal-fired smokestacks without needing to rotate or null the probe. This non-nulling, 3D probe is designed with large diameter pressure ports to prevent water droplets (or particulates) from obstructing its pressure ports when applied in stack flow measurement applications. This manuscript presents a wind tunnel calibration procedure to determine the non-nulling calibration curves for 1) dynamic pressure; 2) pitch angle; 3) yaw angle; and 4) static pressure. These calibration curves are used to determine axial velocities from 6 m/s to 27 m/s, yaw angles between ±40°, and pitch angles between ±20°. The uncertainties at the 95% confidence limit for axial velocity, yaw angle, and pitch angle are 2% (or less), 1°, and 1°, respectively. Therefore, in contrast to existing EPA-sanctioned probes, the non-nulling hemispherical probe provides fast, low uncertainty velocity measurements independent of the pitch and yaw angles of the stack flow.

Investigation of Kalina Cycle for Power Generation from Heat Dissipation of Tarasht Power Plant

Fuel consumption optimization in thermal power plants is one of the essential topics in the saving energy field in the world. Then; it is necessary to review and provide solutions to increase efficiency. The present manuscript has recovered the heat dissipation from power plant stacks. The Kalina cycle was studied to use exhaust gases to generate power in the Tarasht power plant. Net power output is calculated at about 2080 kW, which increases the total power production of the plant by about 5%. According to environmental analysis, this cycle will cause less damage to the environment due to lowering the temperature of the exhaust gases in the atmosphere and not using additional fossil fuels. Therefore; it is a good solution for using heat dissipation from power plants. The only thing to consider in this solution (based on economic analysis) is the high construction cost compared to other power plant units.

Variability of nitrogen oxide emission fluxes and lifetimes estimated from Sentinel-5P TROPOMI observations

Abstract. Satellite observations of the high-resolution TROPOspheric Monitoring Instrument (TROPOMI) on Sentinel-5 Precursor can be used to observe nitrogen dioxide (NO2) at city scales to quantify short time variability of nitrogen oxide (NOx) emissions and lifetimes on a daily and seasonal basis. In this study, 2 years of TROPOMI tropospheric NO2 columns, having a spatial resolution of up to 3.5 km × 5.5 km, have been analyzed together with wind and ozone data. NOx lifetimes and emission fluxes are estimated for 50 different NOx sources comprising cities, isolated power plants, industrial regions, oil fields, and regions with a mix of sources distributed around the world. The retrieved NOx emissions are in agreement with other TROPOMI-based estimates and reproduce the variability seen in power plant stack measurements but are in general lower than the analyzed stack measurements and emission inventory results. Separation into seasons shows a clear seasonal dependence of NOx emissions with in general the highest emissions during winter, except for isolated power plants and especially sources in hot desert climates, where the opposite is found. The NOx lifetime shows a systematic latitudinal dependence with an increase in lifetime from 2 to 8 h with latitude but only a weak seasonal dependence. For most of the 50 sources including the city of Wuhan in China, a clear weekly pattern of NOx emissions is found, with weekend-to-weekday ratios of up to 0.5 but with a high variability for the different locations. During the Covid-19 lockdown period in 2020, strong reductions in the NOx emissions were observed for New Delhi, Buenos Aires, and Madrid.

Measurement and Analysis of PM10 and PM2.5 from Chimneys of Coal-fired Power Plants Using a Light Scattering Method

Aerial pollutants emitted from the stacks of coal-fired power plants are considered a major source of fine particulate matter released into the atmosphere. To manage such fine particles in the stacks themselves, it is necessary to know the concentration of fine particles emitted in real time; the current system to do so is tedious. In this study, a system for measuring fine particles emitted from the stacks of power plants in real-time was developed, and measurements were performed on six coal-fired power plants. Through these measurements, the mass concentration distribution, according to particle sizes, could be determined. All six stacks showed bimodal distribution, and the count median diameters of each mode were 0.5 µm and 1.1 µm. Additionally, data were compared using the gravimetric measurement method; it was found that the relative accuracies for the measured PM10 amounts were within 20% and that the values obtained using the measuring instrument proposed in this study were reliable. Three power plants were continuously measured for one month, and by comparing PM10 concentration according to the amount of power generated, it was confirmed that PM10 discharged from the stack increased as an exponential function, depending on the amount of power generated.

Review of the Method of Marnoch Heat Engine Recovering Heat from Coal-Fired Power Plants

Heat released from the stacks of coal-fired power plants is a resource that can be harnessed. This paper examines the performance of MHE in recovering useless heat from the main stack in a coal-fired power plant. The MHE units that are installed in the stack have eight (four pairs) shell and tube heat exchangers. The heat recovered by MHE is transferred to electricity and used in the coal-fired power plant. The results show that MHE is utterly useful in recovering heat from coalfired power plant. The MHE units improve the efficiency of the power plant and decrease the amount of CO2 emission, which is beneficial for environmental protection.

Study on the representativeness of airborne effluent sampling in the stack of a high-temperature gas-cooled pebble-bed modular reactor

Monitoring the airborne radioactive effluent from the stacks of nuclear power plants is very important. In order to obtain reliable and accurate measurements, the samples acquired from the stack must be representative of the whole. Thus, sampling should be performed at a location where the airflow is well mixed. We studied the transport behavior of airborne radioactive substances in the stack of a high-temperature gas-cooled reactor pebble-bed module (HTR-PM) demonstration power plant using a computational fluid dynamics method. The distributions of effluent flow velocity and concentration have been determined and compared to the mixing uniformity criteria of the ISO-2889 standard, then the source of uniformity is analyzed from vorticity distribution, particle trajectory, cyclone angle and coefficient of variation. We have determined the well-mixed location within the HTR-PM stack where a representative sample can be obtained. We discussed methods for the improvement of flow mixing and analyze the key factors involved.

Using a modified version of Airpacts model for estimating the damage posed by sulfur dioxide emission from power plants to urban and rural building façades (case study: Shahid Rajaee power plant, Qazvin Province, Iran).

This study aimed at upgrading the Air Indicator Report for Public Awareness and Community Tracking (Airpacts) model to evaluate the physical effects of sulfur dioxide (SO2) emissions from Shahid Rajaee power plant on the building façades in Qazvin, Iran in 2018. For this purpose, first, the methodological requirements of the model for the study area, including wind speed, relative humidity, and temperature, were analyzed. Then, the concentration of SO2 emission from the power plant stack was calculated using the Aeroqual Model 200. The obtained data were processed and loaded into the Airpacts model version 1.0. After localization of the costs for reconstruction of 1 m2 of façade, including the costs of purchasing materials, installation, and transport from the power plant, the damage posed by SO2 to the building façades in Qazvin was calculated. Outputs of the modified model suggested that the damage to the building façades included cleansing in contact with SO2 was 494,558,878.12 m2. Based on the calculations, the cost of damage caused by SO2 was estimated to be $0.25 per Megawatt-hour (MWh) electricity generation, reaching an amount of $29,422 annually. Based on the localized results obtained by the modified Airpacts, the external cost of damage to the façades was $0.3 per MWh electricity generation, reaching an amount of $35,720 annually. To overcome the constraints of the original model concerning the constant parameters of mixing height and wind speed in the default model algorithm, the two parameters were considered dynamic variables in the modified model.

Mapping of thermal power plant emitted atmospheric carbon dioxide concentration using AVIRIS-NG data and atmospheric radiative transfer model simulations

Our study demonstrates the potential of Airborne Visible/Infrared Imaging Spectrometer Next Generation (AVIRIS-NG) hyperspectral data and radiative transfer modeling to retrieve the atmospheric carbon dioxide (CO2) concentration from point source emission of one of India’s major coal-fed super thermal power plants at Kota, Rajasthan, India. AVIRIS-NG data with synchronous in situ measurements were collected as a part of the first ISRO-NASA joint airborne hyperspectral science campaign in India. The method utilized in our study includes theoretical simulations of at-sensor radiance in AVIRIS-NG spectral bands through the atmospheric radiative transfer model MODTRAN. Simulations were performed for the specific scene-sensor-atmospheric conditions pertaining to AVIRIS-NG overpass over Kota site. To eliminate the interfering effect of atmospheric water vapor with CO2 concentrations, simulations pertaining to variable water vapor values varying from 0.25 to 4.5 g / cm2 were also carried out, which in turn were utilized to normalize the water vapor effects. Based upon the simulation results pertaining to the specific absorption bands of CO2 in the shortwave infrared spectral range of AVIRIS-NG radiance data, a theoretical model was established between continuum interpolated band ratio (CIBR) and CO2 concentration. The CIBR − CO2 model coefficients for each of the water vapor subranges were then applied to AVIRIS-NG L1 radiance data to obtain the CO2 concentration map of the study area. A distinct CO2 plume could be detected from the coal-fed Kota Super Thermal Power Station with the CO2 concentration (XCO2) of the order of more than 500 ppmv near the power plant stacks. A range of XCO2 from 400 to 550 ppmv was observed within the scene. Our study has provided promising results in mapping the atmospheric CO2 content from the point source using the high-resolution airborne hyperspectral AVIRIS-NG data.

China's retrofitting measures in coal-fired power plants bring significant mercury-related health benefits

Summary China has implemented retrofitting measures in coal-fired power plants (CFPPs) to reduce air pollution through small unit shutdown, the installation of air pollution control devices (APCDs), and power generation efficiency improvement. The reductions in highly toxic Hg emissions and their related health impacts by these measures remain poorly understood. Here, we evaluated the health benefits of reduced Hg emissions via retrofitting measures during China's 12th Five-Year Plan (2011–2015) by combining plant-level Hg emission inventories with the China Hg Risk-Source-Tracking Model. We found that the measures reduced Hg emissions by 23.5 tons (approximately 1/5 of that from CFPPs in 2010), preventing 30,484.77 total points of intelligence quotient decrement and 114 deaths between 2011 and 2015. These benefits were dominated by CFPP shutdowns and APCD installations, and nearly 50% of provincial health benefits were attributable to Hg reductions in other regions. We suggest that Hg control strategies should consider various factors, such as CFPP location, population density, and trade-offs between reductions in total Hg and in Hg2+.

Polycyclic aromatic hydrocarbons (PAHs) and oxy- and nitro-PAHs in ambient air of the Arctic town Longyearbyen, Svalbard

Abstract. Polycyclic aromatic hydrocarbons (PAHs) are not declining in Arctic air despite reductions in their global emissions. In Svalbard, the Longyearbyen coal-fired power plant is considered to be one of the major local sources of PAHs. Power plant stack emissions and ambient air samples, collected simultaneously at 1 km (UNIS) and 6 km (Adventdalen) transect distance, were analysed (gaseous and particulate phases separately) for 22 nitro-PAHs, 8 oxy-PAHs, and 16 parent PAHs by gas chromatography in combination with single quadrupole electron capture negative ionization mass spectrometry (GC-ECNI-MS) and gas chromatography in combination with triple quadrupole electron ionization mass spectrometry (GC-EI-MS/MS). Results confirm low levels of PAH emissions (∑16 PAHs =1.5 µg kg−1 coal) from the power plant. Phenanthrene, 9,10-anthraquinone, 9-fluorenone, fluorene, fluoranthene, and pyrene accounted for 85 % of the plant emission (not including naphthalene). A dilution effect was observed for the transect ambient air samples: 1.26±0.16 and 0.63±0.14 ng m−3 were the sum of all 47 PAH derivatives for UNIS and Adventdalen, respectively. The PAH profile was homogeneous for these recipient stations with phenanthrene and 9-fluorenone being most abundant. Multivariate statistical analysis confirmed coal combustion and vehicle and marine traffic as the predominant sources of PAHs. Secondary atmospheric formation of 9-nitroanthracene and 2+3-nitrofluoranthene was evaluated and concluded. PAHs partitioning between gaseous and particulate phases showed a strong dependence on ambient temperatures and humidity. The present study contributes important data which can be utilized to eliminate uncertainties in model predictions that aim to assess the extent and impacts of Arctic atmospheric contaminants.

Characterizing Black Carbon Emissions from Gasoline, LPG, and Diesel Vehicles via Transient Chassis-Dynamometer Tests

With global anthropogenic black carbon (BC) emissions increasing, automobiles are significantly contributing as the major source of emissions. However, the appropriate regulations of BC emissions from vehicles are not in place. This study examined BC emissions following fuel types (gasoline, liquefied petroleum gas (LPG), and diesel) and engine combustion (gasoline direct injection (GDI) and multi-port injection (MPI) for gasoline vehicles) with emission regulations. To this end, chassis dynamometer and aethalometer (AE33) were used. Driving modes created by the National Institute of Environmental Research (NIER) and emission certification modes (CVS-75 and NEDC) for vehicles in Korea were used to determine BC emissions for various vehicle speeds. In addition, the contributions of biomass and coal combustion to the data of AE33 were analyzed to determine the possibility of tracking the BC sources. MPI, LPG, and EURO 6 with diesel particulate filter (DPF) vehicles emitted the lowest BC emissions in NIER modes. Among gasoline vehicles, MPI vehicles showed the lower BC content in PM emissions. Also, older vehicles in MPI vehicles emitted the high PM and BC emissions. The BC emissions of EURO 3 vehicles without DPF were the highest as the results of previous studies, and it was found that as emissions regulations were tightened, the level of BC results of diesel vehicles became similar with MPI vehicles. The average absorption Ångström exponent (AAE) from difference emissions sources were biomass combustion (oak wood) > coal combustion (the power plant stack) > automobile emissions (gasoline, LPG, diesel).

Outdoor cultivation of microalgae in a coal-fired power plant for conversion of flue gas CO2 into microalgal direct combustion fuels

Microalgae have piqued renewed interest as a sustainable biofuel feedstock owing to their high CO2 conversion efficiency. However, the major limitation of microalga-based biofuel production is low productivity. In this study, CO2 in flue gas emitted from the coal-fired power plants was fixed through mass microalgal cultivation using only sunlight as an energy source. To minimize the cost and energy required to supply the flue gas and efficiently utilize the microalgal biomass, a polycarbonate (PC) greenhouse and polymeric photobioreactors were installed near the power plant stack. Four different microalgal strains (Chlamydomonas reinhardtii, Chlorella sorokiniana, Neochloris oleoabundans, and Neochloris oleoabundans #13) were subjected to semi-continuous culturing for 1 month. The maximum biomass productivity was achieved by the N. oleoabundans #13 strain (0.703 g L−1 day−1). Additionally, polymerase chain reaction analysis revealed that the individual microalgal culture was not cross-contaminated with other microalgal cultures in this cultivation system, owing to the structural properties of photobioreactor comprising individual modules. The lipid content and calorific productivity of N. oleoabundans #13 biomass were 45.70% and 3.553 kJ L−1 day−1, respectively, which indicate satisfactory performance of biomass as a direct combustion fuel. The CO2 fixation rate, which was calculated based on the carbon content in the biomass, was 0.309 g CO2 L−1 day−1. Therefore, large amounts of CO2 can be reduced using the large-scale microalgal cultivation system, which enables efficient biological CO2 conversion and maximizes microalgal biomass utilization.

Life cycle greenhouse gas emissions of different CO2 supply options for an algal biorefinery

This paper characterizes the greenhouse gas (GHG) emissions from the provision of CO2 for twelve hours of the day from a range of sources operating on a twenty-four-hour basis. Twelve CO2 supply cases spanning from fossil fuel power plant stack gases to direct air capture (DAC) systems are modeled. The results are compared in a life cycle assessment (LCA) framework. The CO2 supply from the combustion or gasification of biomass has GHG emissions of –1.62 gCO2 eq./g CO2 delivered and is the case with the lowest carbon footprint for supplied CO2. The emissions for all the CO2 supply cases were found to be negative, either because of capturing more CO2 from the atmosphere than is released from the CO2 production process, or because of production of excess electricity that is exported to the grid (replacing emissions from grid electricity). A purpose-built Natural Gas Combined Cycle (NGCC) power plant CO2 source has the highest GHG emissions of −0.40 gCO2 eq./gCO2 delivered of the cases considered because of nighttime emissions and natural gas supply chain losses. The impact of a diurnal cycle can be mitigated by using capture and refrigeration systems as part of the CO2 management system. The results are sensitive to the GHG emissions of the grid electricity, which is imported or exported in different cases. The results provide a benchmark for the comparison of different CO2 supply options for the establishment of a sustainable algal biorefinery.

Single source impacts on secondary pollutants using a Lagrangian reactive puff model: Comparison with photochemical grid models

Abstract Recent updates to U.S. regulatory guidelines for modeling impacts of single sources to secondary pollutants, such as ozone (O3) and fine particulate matter (PM2.5), require the use of established photochemical models with a complete treatment of gas-phase and aerosol chemistry as the preferred method for a Tier 2 demonstration approach. Such models include photochemical grid models (PGMs), as well as Lagrangian puff models with the requisite treatment of processes governing the formation of secondary pollutants from their precursors. SCICHEM is an open source reactive puff model that includes treatments for gas, aerosol, and aqueous-phase chemistry that are comparable to those in PGMs. The dispersion component of SCICHEM is based on the state-of-the-science puff model, SCIPUFF (Second-order Closure Integrated Puff). The model is a valuable tool that requires fewer resources and setup cost to run than PGMs to calculate the impacts of a single source or a small number of sources on downwind ozone and PM2.5. This paper describes a model inter-comparison study of secondary pollutant impacts due to emissions from a hypothetical coal-fired power plant stack. The models compared in this study include SCICHEM and the two most commonly used PGMs, CMAQ and CAMx. Stacks are located in 4 separate regions of the U.S. with distinct differences in chemical environments and geographical features. The key inputs (hypothetical stack parameters and emission rates, meteorology) to the three models are based on a common dataset for consistency. The source impacts calculated by the PGMs are based on zero-out simulations (i.e., with and without the source of interest) as well as the source apportionment tools available in CAMx, while SCICHEM directly predicts source impacts in a single simulation. Annual simulations are conducted to determine the frequency distribution of source impacts over the 4 regions. The comparison of model results shows both similarities and differences in the frequencies and magnitudes of peak impacts predicted by the three models. There is good agreement among all models in their predictions of 98th and 99th percentile impacts.

Continuous measurement of PM10 and PM2.5 concentration in coal-fired power plant stacks using a newly developed diluter and optical particle counter

In this study, concentrations of PM10 and PM2.5 were continuously measured using a newly developed ejector/porous tube diluter with optical particle counter in the stack exhaust of two coal-fired power plants in Chungnam and Gangwon, South Korea. The results were compared with those of EPA Method 201A and the ISO 23,210 gravimetric method, which are standard protocols for fine particle measurement, and relative accuracies of 19.0% and 11.9% were obtained from the two plants, respectively. In addition, the size distribution of fine particles in the stack exhaust could be obtained simultaneously using the diluter. Particle concentrations at both plants exhibited bi-modal distributions with mode diameters of approximately 0.6 and 2.25 μm, but differences in the size distributions of small and large particles due to differences in exhaust gas treatment facilities were evident. In addition, PM10 and PM2.5 concentrations were compared with power generation amounts over more than 30 and 170 h using the diluter and continuous changes in PM10 and PM2.5 concentrations were observed in accordance with increases and decreases in power generation. Finally, we analyzed the composition of fine particles using scanning electron microscopy with energy dispersive spectroscopy and found that the power plant in Chungnam, which has wet desulfurization facilities, released 16.7% more fluorine than the power plant in Gangwon. Application of the system developed in this study may be useful for optimizing the operating conditions of plant treatment facilities in real time to directly control the emissions of PM10 and PM2.5.

Faster, more accurate, stack-flow measurements

ABSTRACTExhaust flows from coal-fired electricity-generating plants are determined by averaging flue gas velocities measured at prescribed points in the stack cross section. These velocity measurements are made using EPA-approved differential pressure probes such as the 2-hole S-probe or the 5-hole spherical probe. Measurements using the more accurate 5-hole spherical probes require a time-consuming rotation (or nulling) of the probe to find the yaw angle. We developed a time-saving non-nulling technique using a spherical probe that measures all 3 components of velocity and therefore provides better accuracy than an S-probe. We compared the non-nulling technique with the EPA Method 2F nulling technique at both high (16 m/s) and low (7 m/s) loads in a coal-fired powerplant smokestack. Their excellent mutual agreement (within 0.3% of the flow) demonstrates that the non-nulling technique accurately measures flue gas flows.Implications: Accurate flow measurements are critical for quantifying the levels of greenhouse gases emitted from coal-fired power plant smokestacks. Flow measurement accuracy derives from the annual calibration of stack flow monitors. Calibrations are performed using EPA sanctioned pitot traverse methods called the flow relative accuracy test audit (RATA). This study demonstrates the viability of a new pitot traverse method, herein called the Non-Nulling Method. Testing in a coal-fired power plant stack showed that the new method is 5 times faster to implement than the most accurate EPA pitot traverse method (i.e., Method 2F), yet gives the same or better accuracy.