Fine particle migration and collection in a wet electrostatic precipitator

Electrostatic precipitation is considered as an effective technology for fine particle removal. A lab-scale wet electrostatic precipitator (ESP) with wire-to-plate configuration was developed to study particle migration and collection. The performance of the wet ESP was evaluated in terms of the corona discharge characteristics, total removal efficiency and fractional removal efficiency. The corona discharge characteristics and particle removal abilities of the wet ESP were investigated and compared with dry ESP. Particle removal efficiency was influenced by discharge electrode type, SO₂ concentration, specific collection area (SCA) and particle/droplet interaction. Results showed that the particle removal efficiency of wet ESP was elevated to 97.86% from 93.75% of dry ESP. Three types of discharge electrodes were investigated. Higher particle removal efficiency and larger migration velocity could be obtained with fishbone electrode. Particle removal efficiency decreased by 2.87% when SO₂ concentration increased from 0 ppm to 43 ppm as a result of the suppression of corona discharge and particle charging. The removal efficiency increased with higher SCA, but it changed by only 0.71% with the SCA increasing from 25.0 m²/(m³/s) to 32.5 m²/(m³/s). Meanwhile, the increasing of particle and droplet concentration was favorable to the particle aggregation and improved particle removal efficiency.

Implications: This work tends to study the particle migration and collection under spraying condition. The performance of a wet electrostatic precipitator (ESP) is evaluated in terms of the corona discharge characteristics, total particle removal efficiency, and fractional particle removal efficiency. The effects of water droplets on particle removal, especially on removal of particles with different sizes, is investigated. The optimization work was done to determine appropriate water consumption, discharge electrode type, and specific collection area, which can provide a basis for wet ESP design and application.     

Energy consumption and energy-saving potential analysis of pollutant abatement systems in a 1000-MW coal-fired power plant

Pollutant abatement systems are widely applied in the coal-fired power sector, and the energy consumption is considered an important part of the auxiliary power. An energy consumption analysis and assessment model of pollutant abatement systems in a power unit was developed based on the dynamic parameters and technology. The energy consumption of pollutant abatement systems in a 1000-MW coal-fired power unit that meets the ultra-low emission limits and the factors of operating parameters, including unit load and inlet concentration of pollutants, on the operating power were analyzed. The results show that the total power consumption of the pollutant abatement systems accounted for 1.27% of the gross power generation during the monitoring period. The wet flue gas desulfurization (WFGD) system consumed 67% of the rate, whereas the selective catalytic reduction (SCR) and electrostatic precipitator (ESP) systems consumed 8.9% and 24.1%, respectively. The power consumption rate of pollutant abatement systems decreased with the increase of unit load and increased with the increase of the inlet concentration of pollutants. The operation adjustment was also an effective method to increase the energy efficiency. For example, the operation adjustment of slurry circulation pumps could promote the energy-saving operation of the WFGD system.

Implications: The application of pollutant abatement technologies increases the internal energy consumption of the power plant, which will lead to an increase of power generation costs. The real-time energy consumption of the different pollutant abatement systems in a typical power unit is analyzed based on the dynamic operating data. Further, the influence of different operating parameters on the operating power of the system and the possible energy-saving potential are analyzed.     

A Federal Tax on Energy

Abstract

In this investigation, the collection efficiency of particulate emission control devices (PECDs), particulate matter (PM) emissions, and PM size distribution were determined experimentally at the inlet and outlet of PECDs at five coal-fired power plants. Different boilers, coals, and PECDs are used in these power plants. Measurement in situ was performed by an electrical low-pressure impactor with a sampling system, which consisted of an isokinetic sampler probe, precut cyclone, and two-stage dilution system with a sample line to the instruments. The size distribution was measured over a range from 0.03 to 10 µm. Before and after all of the PECDs, the particle number size distributions display a bimodal distribution. The PM_2.5 fraction emitted to atmosphere includes a significant amount of the mass from the coarse particle mode. The controlled and uncontrolled emission factors of total PM, inhalable PM (PM₁₀), and fine PM P(M_2.5) were obtained. Electrostatic precipitator (ESP) and baghouse total collection efficiencies are 96.38–99.89% and 99.94%, respectively. The minimum collection efficiency of the ESP and the baghouse both appear in the particle size range of 0.1–1 µm. In this size range, ESP and baghouse collection efficiencies are 85.79–98.6% and 99.54%. Real-time measurement shows that the mass and number concentration of PM₁₀ will be greatly affected by the operating conditions of the PECDs. The number of emitted particles increases with increasing boiler load level because of higher combustion temperature. During test run periods, the data reproducibility is satisfactory.     

Modeling and optimization of wet flue gas desulfurization system based on a hybrid modeling method

Sulfur dioxide (SO₂) is one of the main air pollutants from many industries. Most coal-fired power plants in China use wet flue gas desulfurization (WFGD) as the main method for SO₂ removal. Presently, the operating of WFGD lacks accurate modeling method to predict outlet concentration, let alone optimization method. As a result, operating parameters and running status of WFGD are adjusted based on the experience of the experts, which brings about the possibility of material waste and excessive emissions. In this paper, a novel WFGD model combining a mathematical model and an artificial neural network (ANN) was developed to forecast SO₂ emissions. Operation data from a 1000-MW coal-fired unit was collected and divided into two separated sets for model training and validation. The hybrid model consisting a mechanism model and a 9-input ANN had the best performance on both training and validation sets in terms of RMSE (root mean square error) and MRE (mean relative error) and was chosen as the model used in optimization. A comprehensive cost model of WFGD was also constructed to estimate real-time operation cost. Based on the hybrid WFGD model and cost model, a particle swarm optimization (PSO)-based solver was designed to derive the cost-effective set points under different operation conditions. The optimization results demonstrated that the optimized operating parameters could effectively keep the SO₂ emissions within the standard, whereas the SO₂ emissions was decreased by 30.79% with less than 2% increase of total operating cost.

Implications: Sulfur dioxide (SO₂) is one of the main pollutants generated during coal combustion in power plants, and wet flue gas desulfurization (WFGD) is the main facility for SO₂ removal. A hybrid model combining SO₂ removal mathematical model with data-driven model achieves more accurate prediction of outlet concentration. Particle swarm optimization with a penalty function efficiently solves the optimization problem of WFGD subject to operation cost under multiple operation conditions. The proposed model and optimization method is able to direct the optimized operation of WFGD with enhanced emission and economic performance.     

Analysis and discussion on formation and control of primary particulate matter generated from coal-fired power plants

Particulate matter (PM) has been becoming the principal urban pollutant in many major cities in China, and even all over the world. It is reported that the coal combustion process is one of the main sources of PM in the atmosphere. Therefore, an investigation of formation and emission of fine primary PM in coal combustion was conducted. First, the sources and classification of coal-fired primary PM were discussed; then their formation pathways during the coal combustion process were analyzed in detail. Accordingly, the emission control methods for fine particles generated from coal-fired power plants were put forward, and were classified as precombustion control, in-combustion control, and postcombustion control. Precombustion control refers to the processes for improving the coal quality before combustion, such as coal type selection and coal preparation. In-combustion control means to take measures for adjusting the combustion conditions and injection of additives during the combustion process to abate the formation of PM. Postcombustion control is the way that the fine PM are aggregated into larger ones by some agglomeration approaches and subsequently are removed by dust removal devices, or some high-performance modifications of conventional particle emission control devices (PECDs) can be taken for capturing fine particles. Finally, some general management suggestions are given for reducing fine PM emission in coal-fired power plants.

ImplicationsThe analysis and discussions of coal properties and its combustion process are critical to recognizing the formation and emission of the fine primary PM in combustion. The measures of precombustion, in-combustion, and postcombustion control based on the analysis and discussions are favorable for abating the PM emission. Practically, some measures of implementation do need the support of national policies, even needing to sacrifice economy to gain environmental profit, but this is the very time to execute these, and high-performance PECDs, especially novel devices, should be used for removing fine PM in flue gas.     

Establishment of a database of emission factors for atmospheric pollutants from Chinese coal-fired power plants

Field measurements and data investigations were conducted for developing an emission factor database for inventories of atmospheric pollutants from Chinese coal-fired power plants. Gaseous pollutants and particulate matter (PM) of different size fractions were measured using a gas analyzer and an electric low-pressure impactor (ELPI), respectively, for ten units in eight coal-fired power plants across the country. Combining results of field tests and literature surveys, emission factors with 95% confidence intervals (CIs) were calculated by boiler type, fuel quality, and emission control devices using bootstrap and Monte Carlo simulations. The emission factor of uncontrolled SO₂ from pulverized combustion (PC) boilers burning bituminous or anthracite coal was estimated to be 18.0S kg t^?1 (i.e., 18.0 × the percentage sulfur content of coal, S) with a 95% CI of 17.2S–18.5S. NO_X emission factors for pulverized-coal boilers ranged from 4.0 to 11.2 kg t^?1, with uncertainties of 14–45% for different unit types. The emission factors of uncontrolled PM_2.5, PM₁₀, and total PM emitted by PC boilers were estimated to be 0.4A (where A is the percentage ash content of coal), 1.5A and 6.9A kg t^?1, respectively, with 95% CIs of 0.3A–0.5A, 1.1A–1.9A and 5.8A–7.9A. The analogous PM values for emissions with electrostatic precipitator (ESP) controls were 0.032A (95% CI: 0.021A–0.046A), 0.065A (0.039A–0.092A) and 0.094A (0.0656A–0.132A) kg t^?1, and 0.0147A (0.0092–0.0225A), 0.0210A (0.0129A–0.0317A), and 0.0231A (0.0142A–0.0348A) for those with both ESP and wet flue-gas desulfurization (wet-FGD). SO₂ and NO_X emission factors for Chinese power plants were smaller than those of U.S. EPA AP-42 database, due mainly to lower heating values of coals in China. PM emission factors for units with ESP, however, were generally larger than AP-42 values, because of poorer removal efficiencies of Chinese dust collectors. For units with advanced emission control technologies, more field measurements are needed to reduce emission factor uncertainties.     

Evaluation of Catalyzed and Electrically Heated Filters for Removal of Particulate Emissions from Diesel-A- and JP-8-Fueled Engines

Abstract

In-service diesel engines are a significant source of particulate matter (PM) emissions, and they have been subjected to increasingly strict emissions standards. Consequently, the wide-scale use of some type of particulate filter is expected. This study evaluated the effect of an Engelhard catalyzed soot filter (CSF) and a Rypos electrically heated soot filter on the emissions from in-service diesel engines in terms of PM mass, black carbon concentration, particle-bound polycyclic aromatic hydrocarbon concentration, and size distribution. Both filters capture PM. The CSF relies on the engine's exhaust to reach the catalyst regeneration temperature and oxidize soot, whereas the electrically heated filter contains a heating element to oxidize soot. The filters were installed on several military diesel engines. Particle concentrations and compositions were measured before and after installation of the filter and again after several months of operation. Generally, the CSF removed at least 90% of total PM, and the removal efficiency improved or remained constant after several months of operation. In contrast, the electrical filters removed 44-69% of PM mass. In addition to evaluating the soot filters, the sampling team also compared the results of several real-time particle measurement instruments to traditional filter measurements of total mass.     

The role of green innovations,environmental policies and carbon taxes in achieving the sustainable development goals of carbon neutrality

The green innovations, environmental policies, and carbon taxes are the tools to achieve sustainable development goals (SDGs) in the mitigation process. This study is intended to examine the impact of innovation, carbon pricing (CTAX), environmental policies (EP), and energy consumption (ECON) on PM_2.5 and greenhouse gas (GHG) emission for Central-Eastern European countries. The panel effect during 2000–2018 is tested using a dynamic panel data model while the Granger causality approach obtains country-related outcomes. The outcomes reveal that eco-friendly innovations have a more profound effect on carbon mitigation. Environmental policies reduce emissions by 2.7% in the short run and 17.4% in the long run. Similarly, CTAX mitigates GHG emissions by 8.6% in the short-run and PM2.5 by 0.9% and 5.7% in the short and long run. However, urbanization, energy consumption and trade openness are the leading polluters in the region. The main findings remain dominant in the country-specific results and find unidirectional and bidirectional causality evidence among variables. The research concludes that green innovations and strict environmental policy can lead towards achieving sustainable development goals using carbon taxes as a tool on the way.

Graphical abstract

     

Improving Urban Air Quality in China: Beijing Case Study

Abstract

China is undergoing rapid urbanization because of unprecedented economic growth. As a result, many cities suffer from air pollution. Two-thirds of China’s cities have not attained the ambient air quality standards applicable to urban residential areas (Grade II). Particulate matter (PM), rather than sulfur dioxide (SO₂), is the major pollutant reflecting the shift from coal burning to mixed source pollution. In 2002, 63.2 and 22.4% of the monitored cities have PM and SO₂ concentrations exceeding the Grade II standard, respectively. Nitrogen oxides (NO_x) concentration kept a relatively stable level near the Grade II standard in the last decade and had an increasing potential in recent years because of the rapid motorization. In general, the air pollutants emission did not increase as quickly as the economic growth and energy consumption, and air quality in Chinese cities has improved to some extent. Beijing, a typical representative of rapidly developing cities, is an example to illustrate the possible options for urban air pollution control. Beijing’s case provides hope that the challenges associated with improving air quality can be met during a period of explosive development and motorization.     

Characteristics of inhalable particulate matter concentration and size distribution from power plants in China

In this investigation, the collection efficiency of particulate emission control devices (PECDs), particulate matter (PM) emissions, and PM size distribution were determined experimentally at the inlet and outlet of PECDs at five coal-fired power plants. Different boilers, coals, and PECDs are used in these power plants. Measurement in situ was performed by an electrical low-pressure impactor with a sampling system, which consisted of an isokinetic sampler probe, precut cyclone, and two-stage dilution system with a sample line to the instruments. The size distribution was measured over a range from 0.03 to 10 microm. Before and after all of the PECDs, the particle number size distributions display a bimodal distribution. The PM2.5 fraction emitted to atmosphere includes a significant amount of the mass from the coarse particle mode. The controlled and uncontrolled emission factors of total PM, inhalable PM (PM10), and fine PM P(M2.5) were obtained. Electrostatic precipitator (ESP) and baghouse total collection efficiencies are 96.38-99.89% and 99.94%, respectively. The minimum collection efficiency of the ESP and the baghouse both appear in the particle size range of 0.1-1 microm. In this size range, ESP and baghouse collection efficiencies are 85.79-98.6% and 99.54%. Real-time measurement shows that the mass and number concentration of PM10 will be greatly affected by the operating conditions of the PECDs. The number of emitted particles increases with increasing boiler load level because of higher combustion temperature. During test run periods, the data reproducibility is satisfactory.     

Investigation of aerosol and gas emissions from a coal-fired power plant under various operating conditions

The concentrations of fine particles and selected gas pollutants in the flue gas entering the stack were measured under several common operation modes in an operating coal power plant producing electricity. Particle size distributions in a diameter range from 10 nm to 20 μm were measured by a scanning mobility particle sizer (SMPS), and the flue gas temperature and concentrations of CO₂ and SO₂ were monitored by a continuous emission monitoring system (CEMS). During the test campaign, five plant operating modes were studied: soot blowing, bypass of flue-gas desulfurization (FGD), reheat burner operating at 0% (turned off), 27%, and 42% (normal condition) of its full capacity. For wet and dry aerosols, the measured mode sizes were both around 40 nm, but remarkable differences were observed in the number concentrations (#/cm³, count per square centimeter). A prototype photoionizer enhanced electrostatic precipitator (ESP) showed improved removal efficiency of wet particles at voltages above +11.0 kV. Soot blowing and FGD bypass both increased the total particle number concentration in the flue gas. The temperature was slightly increased by the FGD bypass mode and varied significantly as the rating of reheat burner changed. The variations of CO₂ and SO₂ emissions showed correlations with the trend of total particle number concentration possibly due to the transitions between gas and particle phases. The results are useful in developing coal-fired power plant operation strategies to control fine particle emissions and developing amine-based CO₂ capture technologies without operating and environmental concerns associated with volatile amine emissions.

Implications: The measurement of the fine particle size distributions in the exhaust gas under several common operating conditions of a coal-fired power plant revealed different response relations between aerosol number concentration and the operating condition. A photo-ionizer enhanced ESP was demonstrated to capture fine particles with higher efficiency compared to conventional ESPs, and the removal efficiency increased with the applied voltage. The characteristic information of aerosols and main gaseous pollutants in the exhaust gas is extremely important for developing and deploying CO₂ scrubbers, whose amine emissions and operating effectiveness depends greatly on the upstream concentrations of fine particles, SO₂, from the power plant.     

Gas Chromatographic Analysis of Ambient Halogenated Compounds

Abstract

Fugitive dust emission from limestone extraction areas is a significant pollution source. The cracking operation in limestone extraction areas easily causes high total suspended particulate (TSP) concentrations in the atmosphere, occasionally exceeding the 1-hr national emission standard of Taiwan (500 μg/m³). The concentration and size distribution were measured at different distances (0.05–15 km) in the extraction areas. The highest hourly concentrations of TSP, PM₁₀ (suspended particulate matter [PM] smaller than 10 μm), and PM_2.5 (suspended PM smaller than 2.5 μm) are 1111, 825, and 236 μg/m³, respectively, during the cracking process. Measurement results obtained from the Micro-Orifice Uniform Deposit Impactor indicated that the mass median aerodynamic diameter is ～0.7 μm, with the geometric standard deviation exceeding 7. In addition, the emission factors are 0.143 and 0.211 kg/t for both vertical well and stair extraction operations, respectively. Experimental results demonstrate that the corresponding TSP control efficiencies for spraying water, planting grass, setting short walls, paving gravel roads, and establishing vertical well transportation are ～55, 50, 44, 22, and 30%, respectively. Furthermore, the PM₁₀ control efficiencies are ～45, 41, 54, 35, and 30%, respectively, whereas the PM_2.5 control efficiencies are roughly 23, 31, 15, 11, and 10%, individually.     

Deriving fuel-based emission factor thresholds to interpret heavy-duty vehicle roadside plume measurements

Remote sensing devices have been used for decades to measure gaseous emissions from individual vehicles at the roadside. Systems have also been developed that entrain diluted exhaust and can also measure particulate matter (PM) emissions. In 2015, the California Air Resources Board (CARB) reported that 8% of in-field diesel particulate filters (DPF) on heavy-duty (HD) vehicles were malfunctioning and emitted about 70% of total diesel PM emissions from the DPF-equipped fleet. A new high-emitter problem in the heavy-duty vehicle fleet had emerged. Roadside exhaust plume measurements reflect a snapshot of real-world operation, typically lasting several seconds. In order to relate roadside plume measurements to laboratory emission tests, we analyzed carbon dioxide (CO₂), oxides of nitrogen (NO_X), and PM emissions collected from four HD vehicles during several driving cycles on a chassis dynamometer. We examined the fuel-based emission factors corresponding to possible exceedances of emission standards as a function of vehicle power. Our analysis suggests that a typical HD vehicle will exceed the model year (MY) 2010 emission standards (of 0.2 g NO_X/bhp-hr and 0.01 g PM/bhp-hr) by three times when fuel-based emission factors are 9.3 g NO_X/kg fuel and 0.11 g PM/kg using the roadside plume measurement approach. Reported limits correspond to 99% confidence levels, which were calculated using the detection uncertainty of emissions analyzers, accuracy of vehicle power calculations, and actual emissions variability of fixed operational parameters. The PM threshold was determined for acceleration events between 0.47 and 1.4 mph/sec only, and the NO_X threshold was derived from measurements where after-treatment temperature was above 200°C. Anticipating a growing interest in real-world driving emissions, widespread implementation of roadside exhaust plume measurements as a compliment to in-use vehicle programs may benefit from expanding this analysis to a larger sample of in-use HD vehicles.

Implications: Regulatory agencies, civil society, and the public at large have a growing interest in vehicle emission compliance in the real world. Leveraging roadside plume measurements to identify vehicles with malfunctioning emission control systems is emerging as a viable new and useful method to assess in-use performance. This work proposes fuel-based emission factor thresholds for PM and NOx that signify exceedances of emission standards on a work-specific basis by analyzing real-time emissions in the laboratory. These thresholds could be used to prescreen vehicles before roadside enforcement inspection or other inquiry, enhance and further develop emission inventories, and potentially develop new requirements for heavy-duty inspection and maintenance (I/M) programs, including but not limited to identifying vehicles for further testing.     

Source Profiles of Particulate Matter Emissions from a Pilot-Scale Boiler Burning North American Coal Blends

ABSTRACT

Recent awareness of suspected adverse health effects from ambient particulate matter (PM) emission has prompted publication of new standards for fine PM with aerodynamic diameter less than 2.5 μm (PM_2.5). However, scientific data on fine PM emissions from various point sources and their characteristics are very limited. Source apportionment methods are applied to identify contributions of individual regional sources to tropospheric particulate concentrations. The existing industrial database developed using traditional source measurement techniques provides total emission rates only, with no details on chemical nature or size characteristics of particulates. This database is inadequate, in current form, to address source-receptor relationships.

A source dilution system was developed for sampling and characterization of total PM, PM_2.5, and PM₁₀ (i.e., PM with aerodynamic diameter less than 10 μm) from residual oil and coal combustion. This new system has automatic control capabilities for key parameters, such as relative humidity (RH), temperature, and sample dilution. During optimization of the prototype equipment, three North American coal blends were burned using a 0.7-megawatt thermal (MW_t) pulverized coal-fired, pilot-scale boiler. Characteristic emission profiles, including PM_2.5 and total PM soluble acids, and elemental and carbon concentrations for three coal blends are presented.     

PM Emissions Emanating from Limited-Access Highways

ABSTRACT

Motor vehicle contributions to primary particulate matter (PM) emissions include exhaust, tire wear, brake and clutch wear, and resuspended road dust. Relatively few field studies have been conducted to quantify fleetaverage exhaust emissions for actual on-road conditions. Therefore, direct measurements of motor vehicle-related PM emissions are warranted. In this study, PM₁₀ and PM_2.5 mass concentrations were measured near two major highways in the St. Louis area over the period from February–April 1997. Samplers were deployed both upwind and downwind of the roadways to capture the transport and dispersion of PM with distance from the roadway. The observed microscale concentration fields were compared to estimates using the PART5 emission factor model together with the CALINE4 highway dispersion model. Traffic- induced PM mass concentrations observed downwind of the roadway were always less than PART5/CALINE4 predictions; average percent differences for observed traffic-induced mass concentrations compared to predicted values were ?34% for PM_2.5 and -70% for PM₁₀. In most cases, the observed PM concentration decay with increasing distance from the roadway was steeper than predicted by dispersion modeling. Motor vehicle-induced emission factors were reconstructed by fitting CALINE4 to the observed concentration data with the emission factor as the sole adjustable parameter. Reconstructed fleet-average motor vehicle emission factors for the urban interstate highway were 0.03–0.04 g/VMT for both PM_2.5 and PM₁₀, while the fleet-average emission factors for the rural interstate highway were 0.2 and 0.3 g/VMT for PM_2.5 and PM₁₀, respectively.     

PCDDs, PCDFs emission control by dry scrubbing system

Presently, in Japan there are no limitations on the emission of PCDDs or PCDFs, but in order to study the feasibility of dry type air pollution control, a pilot plant was constructed in 1988 and the removal efficiencies for PCDDs, acid gas and heavy metals were measured.At the same time PCDDs concentration was compared with that of a previously installed electrostatic precipitator (ESP) plus wet scrubber line.In this paper, the following two items are reported.

1. (1) The difference in the amounts of PCDDs and PCDFs produced due to differences in gas temperature and retention time in ESP and fabric filter (FF).

2. (2) Removal efficiencies of PCDDs and PCDFs of fabric filter.

PCDDs concentration, generally 100–200 ng/Nm³ at the boiler outlet (ESP inlet and/or Quench Reactor (QR) inlet), increased several times at the ESP outlet, but it showed almost no increase at the QR outlet due to a sudden temperature drop. The temperature was 280–310°C, and the gas retention time was 12 sec. during passage through ESP so that it is thought that PCDD was formed under these conditions.On the other hand, a removal efficiency of approx. 90% was obtained with the fabric filter, and the PCDD at the bag outlet was at a sufficiently low level.     

Particulate Matter Emissions during Transient Locomotive Operation: Preliminary Study

Abstract

Certification testing of locomotive diesel engines is conducted by testing the locomotive in a series of steady-state conditions, or notches. The aim of this work was to determine whether notch changes, which are made on the order of twice per minute during normal locomotive operation, significantly affect emission rates. Particulate matter (PM) measurements recorded by others over 5, 15, and 30 min immediately at notch change were analyzed. By assuming that PM emissions during steady-state conditions were constant, it was possible to determine the amount of PM emitted because of notch change. Certification line-haul and switching duty cycles were modified to include a representative number of notch changes. The results of these calculations suggest that in test cycles in which a representative number of notch changes were included, ~40% of PM emissions occurred because of notch changes.     

Coarse Particulate Matter Apportionment around a Steel Smelter Plant

Abstract

The results from a study carried out in the urban area of Genoa, Italy, where a large steel smelter recently shut down are presented. We had the opportunity to sample particulate matter (PM) before and after plant closure and, therefore, to measure the changes in concentration and composition of PM₁₀ (atmospheric PM with aerodynamic diameter <10 µm). Elemental concentrations of Na to Pb were obtained through energy dispersive X-ray fluorescence (ED-XRF), and the contributions of specific sources of PM₁₀ were calculated by positive matrix factorization (PMF). The PM₁₀ average concentration turned out to be surprisingly similar before and after closing of the smelter. Nevertheless, the comparison among data collected in the two periods (plant operating and closed), even with the limited information provided by ED-XRF, allowed us to single out two sources of PM related to the smelter activities, to extract their emission profile, and to quantify the impact of the plant on PM₁₀ levels.     

Understanding selected trace elements behavior in a coal-fired power plant in Malaysia for assessment of abatement technologies

The Proposed New Environmental Quality (Clean Air) Regulation 201X (Draft), which replaces the Malaysia Environmental Quality (Clean Air) 1978, specifies limits to additional pollutants from power generation using fossil fuel. The new pollutants include Hg, HCl, and HF with limits of 0.03, 100, and 15 mg/N-m³ at 6% O₂, respectively. These pollutants are normally present in very small concentrations (known as trace elements [TEs]), and hence are often neglected in environmental air quality monitoring in Malaysia. Following the enactment of the new regulation, it is now imperative to understand the TEs behavior and to assess the capability of the existing abatement technologies to comply with the new emission limits. This paper presents the comparison of TEs behavior of the most volatile (Hg, Cl, F) and less volatile (As, Be, Cd, Cr, Ni, Se, Pb) elements in subbituminous and bituminous coal and coal combustion products (CCP) (i.e., fly ash and bottom ash) from separate firing of subbituminous and bituminous coal in a coal-fired power plant in Malaysia. The effect of air pollution control devices configuration in removal of TEs was also investigated to evaluate the effectiveness of abatement technologies used in the plant. This study showed that subbituminous and bituminous coals and their CCPs have different TEs behavior. It is speculated that ash content could be a factor for such diverse behavior. In addition, the type of coal and the concentrations of TEs in feed coal were to some extent influenced by the emission of TEs in flue gas. The electrostatic precipitator (ESP) and seawater flue gas desulfurization (FGD) used in the studied coal-fired power plant were found effective in removing TEs in particulate and vapor form, respectively, as well as complying with the new specified emission limits.

Implications:Coals used by power plants in Peninsular Malaysia come from the same supplier (Tenaga Nasional Berhad Fuel Services), which is a subsidiary of the Malaysia electricity provider (Tenaga Nasional Berhad). Therefore, this study on trace elements behavior in a coal-fired power plant in Malaysia could represent emission from other plants in Peninsular Malaysia. By adhering to the current coal specifications and installation of electrostatic precipitator (ESP) and flue gas desulfurization, the plants could comply with the limits specified in the Malaysian Department of Environment (DOE) Scheduled Waste Guideline for bottom ash and fly ash and the Proposed New Environmental Quality (Clean Air) Regulation 201X (Draft).     

Full-Scale Evaluation of Mercury Control with Sorbent Injection and COHPAC at Alabama Power E.C. Gaston

Abstract

The overall objective of this project was to determine the cost and impacts of Hg control using sorbent injection into a Compact Hybrid Particulate Collector (COHPAC) at Alabama Power’s Gaston Unit 3. This test is part of a program funded by the U.S. Department of Energy’s National Energy Technology Laboratory (NETL) to obtain the necessary information to assess the costs of controlling Hg from coal-fired utility plants that do not have scrubbers for SO₂ control. The economics will be developed based on various levels of Hg control.

Gaston Unit 3 was chosen for testing because COHPAC represents a cost-effective retrofit option for utilities with existing electrostatic precipitators (ESPs). COHPAC is an EPRI-patented concept that places a high air-to-cloth ratio baghouse downstream of an existing ESP to improve overall particulate collection efficiency. Activated carbons were injected upstream of COHPAC and downstream of the ESP to obtain performance and operational data.

Results were very encouraging, with up to 90% removal of Hg for short operating periods using powdered activated carbon (PAC). During the long-term tests, an average Hg removal efficiency of 78% was measured. The PAC injection rate for the long-term tests was chosen to maintain COHPAC cleaning frequency at less than 1.5 pulses/bag/hr.