The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Herek L Clack - One of the best experts on this subject based on the ideXlab platform.
-
particulate carbon emissions from Electrostatic Precipitators used for mercury emissions control operational factors and implications
Air Quality Atmosphere & Health, 2014Co-Authors: Herek L ClackAbstract:Injection of powdered activated carbon (PAC) into the combustion flue gas of a coal-fired boiler is a leading approach to reducing anthropogenic mercury emissions. Small particle size and poor electrical properties are known to make carbonaceous particles more difficult to remove from a gas stream by Electrostatic precipitation, by far the dominant particulate control technology for coal-fired boilers. The present analysis estimates PAC emissions from Electrostatic Precipitators (ESPs) and considers both the operational factors driving such emissions as well as their implications in terms of adsorbed mercury concentrations and their potential to act as a climate forcing agent similar to black carbon. The results of the analysis find the potential for PAC to increase particulate carbon emissions by tens of percent to over 150 % in the worst-case scenario considered. Such emissions could increase the contribution of coal combustion to total anthropogenic emissions of particulate carbon by several percentage points. Elevated levels of mercury on such emissions can translate into gas-phase-equivalent mercury concentrations approaching 1 ppb. The most important uncertainty influencing these results is the removal efficiency within ESPs of PM2.5-activated carbon particles.
-
estimates of increased black carbon emissions from Electrostatic Precipitators during powdered activated carbon injection for mercury emissions control
Environmental Science & Technology, 2012Co-Authors: Herek L ClackAbstract:The behavior of mercury sorbents within Electrostatic Precipitators (ESPs) is not well-understood, despite a decade or more of full-scale testing. Recent laboratory results suggest that powdered activated carbon exhibits somewhat different collection behavior than fly ash in an ESP and particulate filters located at the outlet of ESPs have shown evidence of powdered activated carbon penetration during full-scale tests of sorbent injection for mercury emissions control. The present analysis considers a range of assumed differential ESP collection efficiencies for powdered activated carbon as compared to fly ash. Estimated emission rates of submicrometer powdered activated carbon are compared to estimated emission rates of particulate carbon on submicrometer fly ash, each corresponding to its respective collection efficiency. To the extent that any emitted powdered activated carbon exhibits size and optical characteristics similar to black carbon, such emissions could effectively constitute an increase in b...
-
Electrostatic precipitation of powdered activated carbon and implications for secondary mercury adsorption within Electrostatic Precipitators
Energy & Fuels, 2011Co-Authors: Vinit Prabhu, Herek L ClackAbstract:The injection of powdered sorbents, such as activated carbon, for mercury emissions control at coal-fired power plants has primarily taken place upstream of Electrostatic Precipitators (ESPs), which far outnumber baghouses in the U.S. Although full-scale sorbent injection tests have demonstrated varying degrees of mercury removal efficiency, the actual behavior of powdered activated carbon (PAC) within an ESP has not been well-established, particularly as this behavior relates to adsorbing gas-phase mercury. In the present experimental investigation, results obtained in a lab-scale ESP indicate that the electrical properties of PAC may cause its collection in a full-scale ESP to be significantly different from that of the native fly ash. There appears to be potential for significant collection of PAC on the discharge electrode wires of an ESP. Because these wires are typically not rapped as frequently as collection electrodes in an ESP, over time, such behavior could potentially create a series of cylindr...
-
mercury capture within coal fired power plant Electrostatic Precipitators model evaluation
Environmental Science & Technology, 2009Co-Authors: Herek L ClackAbstract:Efforts to reduce anthropogenic mercury emissions worldwide have recently focused on a variety of sources, including mercury emitted during coal combustion. Toward that end, much research has been ongoing seeking to develop new processes for reducing coal combustion mercury emissions. Among air pollution control processes that can be applied to coal-fired boilers, Electrostatic Precipitators (ESPs) are by far the most common, both on a global scale and among the principal countries of India, China, and the U.S. that burn coal for electric power generation. A previously reported theoretical model of in-flight mercury capture within ESPs is herein evaluated against data from a number of full-scale tests of activated carbon injection for mercury emissions control. By using the established particle size distribution of the activated carbon and actual or estimated values of its equilibrium mercury adsorption capacity, the incremental reduction in mercury concentration across each ESP can be predicted and compared to experimental results. Because the model does not incorporate kinetics associated with gas-phase mercury transformation or surface adsorption, the model predictions represent the mass-transfer-limited performance. Comparing field data to model results reveals many facilities performing at or near the predicted mass-transfer-limited maximum, particularly at low rates of sorbent injection. Wheremore » agreement is poor between field data and model predictions, additional chemical or physical phenomena may be responsible for reducing mercury removal efficiencies. 26 refs., 5 figs., 1 tab.« less
-
particle size distribution effects on gas particle mass transfer within Electrostatic Precipitators
Environmental Science & Technology, 2006Co-Authors: Herek L ClackAbstract:Varying degrees of mercury capture and transformation have been reported across Electrostatic Precipitators (ESPs). Previous analyses have shown that the dominant mass transfer mechanism responsible for mercury capture within ESPs is gas-particle mass transfer during particulate collection. Whereas previous analyses assumed dispersions of uniform size, the present analysis reveals the effects of polydispersity on both gas-particle mass transfer and particle collection within an ESP. The analysis reveals that the idealized monodisperse particle size distribution provides the highest gas-particle mass transfer but results in the lowest particle collection efficiency (% mass). As the particle size distribution broadens, gas-particle mass transfer decreases and particle collection efficiency increases. The results suggest that more than just reporting mean particle diameter provided by the sorbent manufacturer, pilot- and field-tests of sorbent injection for mercury emissions control need to experimentally me...
Aibing Yu - One of the best experts on this subject based on the ideXlab platform.
-
process modelling of low temperature Electrostatic Precipitators
Powder Technology, 2017Co-Authors: Ding Yang, Yinbiao Su, Aibing YuAbstract:Abstract Wet type Electrostatic Precipitators (ESPs), or Cold ESPs can effectively remove particulate matters, particularly fine particles (PM2.5), from flue gases. The present paper describes a numerical model for assessing ESPs' performance, considering a series of factors including dust layer resistivity, dewpoint, acid condensation, electric field distribution, particle charging and gas-particle flow. The roles of sulfur trioxide (SO3) in the flue gas and temperature are analysed together with case studies. Without SO3 in flue gas, the collection efficiency of the dry ESP is controlled by the dust layer resistivity. With SO3 present, different physics are involved, which are considered according to the following steps: Firstly, the acid dewpoint and acid condensation are calculated based on mass balance and phasic equilibrium. Then the electric field around a dielectric sphere and the field charging mechanism in relation to wet particles are discussed. An effective electric permittivity for a composite sphere is verified by a sub-particle scale electric field simulation and implemented in a wet particle charging model. The collection efficiencies for ash particles with dielectric constant of 3.9–80 are predicted over a wide range of particle sizes from 0.02 to 25 μm under various conditions. Some questions of industry interest have been clarified by both qualitative and quantitative manners.
-
multi scale simulation of the gas flow through Electrostatic Precipitators
Applied Mathematical Modelling, 2016Co-Authors: Xinglian Ye, Yinbiao Su, Aibing YuAbstract:Abstract The gas flow distribution significantly affects the collecting performance of an Electrostatic Precipitators (ESP) system. Computational Fluid Dynamics (CFD) method is here used to study the gas flow through the ESP system at different scales and in a coupled fashion. Firstly, numerical experiments are conducted at an orifice scale (unit cell study) and ESP unit scale (collection unit study) respectively, to determine the parameters of the perforated plates and ESP unit, such as the pressure drop coefficients. Flow distribution in the large scale ESP system is then simulated and adjusted based on a simplified network model. The simulation results and experiment data match well not only qualitatively but also quantitatively. The study shows that the multi-scale CFD approach is suited to predict the gas flow in ESP systems and the results provide useful guidance for ESP design and control.
-
simulation of the electric field in wire plate type Electrostatic Precipitators
Journal of Electrostatics, 2014Co-Authors: Aibing YuAbstract:Abstract The paper presents a general Control Volume model for electric field simulation in wire-plate type Electrostatic Precipitators, along with a new injection law for charge density. The model is validated against empirical equations and experimental data in the literature when applied to the wire-plate and point-plate configurations. The voltage current characteristics and detailed distribution of field and charge density are characterized, particularly for the case of barbed wire electrode. The effects of geometric variations, such as the sharpness of the tip and the direction of the needles with respect to the plate, are investigated.
Chuenjinn Tsai - One of the best experts on this subject based on the ideXlab platform.
-
numerical modeling of nanoparticle collection efficiency of single stage wire in plate Electrostatic Precipitators
Aerosol Science and Technology, 2010Co-Authors: Chuenjinn TsaiAbstract:The numerical models for predicting the collection efficiency of particles in the size range of 0.3 ∼ 10.0 μm in Electrostatic Precipitators (ESPs) have been well developed. However, for nanoparticles, or particles with the diameter below 100 nm, the existing models can't predict the collection efficiency very well because the electric field and ion concentration distribution were not simulated, or charging models were not adopted appropriately to calculate particle charges. In this study, a 2-D numerical model was developed to predict the nanoparticle collection efficiency in single-stage wire-in-plate ESPs. Laminar flow field was solved by using the Semi-Implicit Method for Pressure-Linked Equation (SIMPLER Method), while electric field strength and ion concentration distribution were solved based on Poisson and diffusion-convection equations, respectively. The charged particle concentration distribution and the particle collection efficiency were then calculated based on the convection-diffusion equati...
D E Stock - One of the best experts on this subject based on the ideXlab platform.
-
interaction of Electrostatic and fluid dynamic fields in wire plate Electrostatic Precipitators
Journal of Fluid Mechanics, 1992Co-Authors: G A Kallio, D E StockAbstract:Gas flow through wire-plate Electrostatic Precipitators is influenced by a secondary flow of electrical origin known as electric wind. This phenomenon arises when significant momentum is transferred from corona-generated ions to the gas. Electric wind can produce turbulence and recirculation. This complex flow field was characterized in a simple, three-wire precipitator by flow visualization, Electrostatic and fluid dynamic numerical modelling, and laser-Doppler anemometry (LDA). Velocity of seeded smoke was measured by two-component LDA. Coulomb effects were regionally eliminated by performing measurements along symmetry axes where the electric field and streamwise velocity component were mutually perpendicular. Coulomb drift velocities were also estimated from field charging theory to allow interpretation of measured transverse velocities. For a low inlet velocity (0.5 m/s), mean flow recirculation was evident and turbulence intensities as high as 50 YO were measured. Higher inlet velocities (1.0, 2.0 m/s) yielded no flow recirculation and lower turbulence levels that were polarity-dependent. Measured profiles of streamwise velocity showed that flow acceleration zones occurred upstream of each wire and also between wires near the collecting plate. The induced turbulence displayed significant inhomogeneity and anisotropy. A combined finite-element, finite-difference Electrostatic model was developed to yield ion density and electric field distributions within the precipitator. These predictions were used to incorporate an electric body force into a two-dimensional, turbulent fluid dynamic model based upon the k+ formulation. The model predicted recirculating mean flow and turbulent diffusivities that were consistent with the smoke flow visualizations and LDA measurements.
L Canadas - One of the best experts on this subject based on the ideXlab platform.
-
assessment of plate wire Electrostatic Precipitators based on dimensional and similarity analyses
Fuel, 2011Co-Authors: F Gutierrez J Ortiz, Benito Navarrete, L CanadasAbstract:This paper is focused towards dimensional analysis in ESP model building, showing both the reduction in effort and more effective modeling that can result. Electrostatic Precipitators (ESP) are widely used in industry today and much research has been carried out during the last decades. However, dimensional analysis is still an unsettled matter, in spite of it allows to reduce the number of parameters necessary for defining the ESP performance, provides a reliable scaling-up of the desired operating conditions from the pilot-scale to full-scale plant (based on the invariance of the pi-space) as well as a consistent extrapolation within the range covered by dimensionless numbers, and gives a greater flexibility in choice of parameters. This analysis together with the similarity analysis is presented in this work, in order to obtain a functional dependence between a target number and a set of few dimensionless numbers. The target selected has been the ratio of particle dust concentration at the outlet of the ESP and that at the inlet of the ESP. Thus, after doing these analyses, several quite reduced models have been formulated theoretically and later tested and validated with experimental data obtained in a pilot ESP, in order to show an application of the study. By this way, a non-linear regression model matches well with experimental data from a pilot plant.
-
dimensional analysis for assessing the performance of Electrostatic Precipitators
Fuel Processing Technology, 2010Co-Authors: F Gutierrez J Ortiz, Benito Navarrete, L CanadasAbstract:Abstract Electrostatic Precipitators (ESP) are widely used in industry today and much research has been carried out during the last decades. Dimensional analysis (DA) allows to reduce the number of parameters necessary for defining the ESP performance and provides a reliable scaling-up of the desired operating conditions from the pilot-scale to full-scale plant (based on the invariance of the pi-space). Likewise, DA gives a consistent extrapolation within the range covered by dimensionless number and a greater flexibility in choice of parameters. DA together with similarity analysis is presented in this work in order to obtain a functional dependence between a target number and a set of few dimensionless numbers. The target selected has been the penetration, i.e., the ratio of particle dust concentration at the outlet of the ESP ( C o ) and that at the inlet of the ESP ( C i ). The results can be valuable to assess the data from ESP of different operating characteristics, under geometric, electrical, fluid dynamics and electro-hydrodynamics similarity. Thus, as a consequence of these analyses, several quite reduced models have been formulated theoretically and later tested and validated with experimental data obtained in a pilot ESP in order to show an application of the study. Four models have been fitted by linear regression, resulting unsatisfactory. However, two additional models fitted by non-linear regression predict values of particle removal efficiency that agrees well with the experimental data. Thus, this paper is focused towards dimensional analysis in ESP model building, showing both the reduction in effort and more effective modeling that can result.
-
influence of plate spacing and ash resistivity on the efficiency of Electrostatic Precipitators
Journal of Electrostatics, 1997Co-Authors: Benito Navarrete, L Canadas, L Salvador, V Cortes, J GalindoAbstract:Abstract This paper contributes to the knowledge of the behaviour of Electrostatic Precipitators in pulverized-coal power plants. The information was obtained through real tests carried out on different types of coal with real flue gases in a pilot precipitator installed at a pulverized-coal power plant. In particular, the influence of different plate spacings, the characteristics of the ash generated by each type of coal and the mass load of ash in the gas flow are considered. The tests carried out lead to conclusions with respect to the most advantageous arrangement of the plates for each case. Conclusions with respect to other variables that affect the efficiency, such as gas velocity, can also be drawn.
-
theoretical modelling of Electrostatic Precipitators performance prelec code
Journal of Electrostatics, 1995Co-Authors: L Canadas, Benito Navarrete, L SalvadorAbstract:Abstract This paper presents a model designed to characterize the performance of plate-type Electrostatic Precipitators (ESP). PRELEC is a rigorously Deutschian model, completely theoretically derived, that avoids the use of empirical estimations in its calculations. In the present version, those estimations related with non-ideal effects are not considered. PRELEC calculates electric fields, based on the applied voltage wave, including the effects of ionic and particulate space charge. It is able to simulate two possible types of ESP energization: full-wave rectified current and pulse generation. It also allows the transient evolution of electrical conditions inside the ESP during the rapping intervals to be analysed, taking into account the dust build-up influence. The model predictions show good agreement with experimental measurements taken at two ESPs of Spanish Power Plants under several operational conditions, including different dust characteristics, very high resistivity ashes, operation before and after the installation of a flue gas conditioning plant, and the use of rectified current and pulse energization. PRELEC predictions are also compared with those obtained from Version 3 of EPA/SRI model.