Sizing and Costing of Electrostatic Precipitators

This is the second of a two-part article that reviews electrostatic precipitation theory, presents size estimating methods, and gives costing procedures for a variety of electrostatic precipitator (ESP) types and sizes. Part I of the article, which appeared in the April 1988 issue of JAPCA, discussed theory and sizing; this part presents costing. Information is given for estimating total capital investment including separate costs for the bare ESP (five types) and auxiliaries. Factors are given for installation and for indirect costs. Direct and indirect annual costs are discussed. An example problem is given.     

Sizing and Costing of fabric Filters Part II: Costing Considerations

This is the second of a two-part article that reviews baghouse filtration theory, presents size estimating methods, and gives costing procedures for a variety of baghouse types and sizes. Part I of the article discussed theory and sizing; this part presents costing. Information is given for estimating total capital investment including separate costs for the bare baghouse (five types), bags, and, where needed, cages and Venturis. Factors are given for installation and for indirect costs. Direct and indirect annual costs are discussed. An example problem is given. The material in this article is taken primarily from the EAB Control Cost Manual.     

The Potential of Pulse-Jet Baghouses for Utility Boilers Part 3: Comparative Economics of Pulse-Jet Baghouse,Precipitators and Reverse-Gas Baghouses

Pulse-jet fabric filters (PJFFs) are widely used in U.S. industrial applications, and in both utility and industrial boilers abroad. Their smaller size and reduced cost relative to more conventional baghouses make PJFFs an attractive particulate control option for utility boilers. This article which is the third in a three-part series, compares the cost of PJFFs with electrostatic precipitators (ESPs) and reverse-gas baghouses (RGBs).

This article presents the capital, operating and maintenance (O&M), and level-ized costs for ESPs, RGBs and PJFFs. The particulate control equipment design and pricing are supplied by manufacturers of the control equipment. A comparison of costs for a base case 250-MW boiler indicates that the PJFF capital cost is 22 percent lower than the cost of an ESP with 400 SCA and 12-inch plate spacing; in addition the PJFF is 35 percent lower than the cost of an RGB. The levelized cost for a PJFF is about equal to the cost of the ESP but 14 percent lower than the cost of the RGB. Overall, the attractiveness of a PJFF versus an ESP depends on the coal type and the outlet emissions limit required. PJFF is favored when low-sulfur coal is fired due to the high-resistivity fly ash. Also, PJFF is favored as more stringent outlet emission rates are required.     

Capital and Operating Costs of Selected Air Pollution Control Systems — I

This is the first installment of a 4-part series which will present capital and operating costs of selected air pollution control systems. The objective of the Series is to identify the individual component costs so that realistic system cost estimates can be determined for any specific application. In Part I, cost estimating procedures and curves are provided to develop the equipment costs for electrostatic pre-cipitators, venturi scrubbers, fabric filters, incinerators, and adsorbers.     

The Smogless Automobile

Demands for high performance and reliability of electrostatic precipitators for collection of fly ash from low sulfur fuels has led to rapid escalation of sizes and uncertainties in sizings of cold-side precipitators. This has led to utilization of the so-called “hot-side” precipitator. The underlying concept of hot-side precipitation is the avoidance of the necessity to operate the precipitator under high resistivity conditions. Data on in-situ measurements of resistivity of low sulfur fuel ash, as well as performance parameters of a number of operating installations, will be reviewed. These data will demonstrate the reduced sensitivity of hot-side precipitator sizing to fuel conditions. Other advantages of hot-side precipitators will be discussed.

Operating experience with hot-side precipitators has focused on structural problems which are peculiar to the larger, higher temperature installations. The nature and solution of these problems will be discussed. General comparative economics of hot-side and cold-side precipitators as they relate to fuel properties will be reviewed.     

Issues and Trends in Electrostatic Precipitation Technology for U.S. Utilities

The pace and direction of electrostatic precipitator (ESP) technology evolution in the United States will be governed by two key forces. The first is new clean air legislation passed by the U.S. Congress and signed by President Bush on November 15,1990. This law requires electric utilities to further reduce SO₂ and NO_x emissions, which may impact particulate controls. In addition, very fine (< 10 micron) participates and potentially toxic trace emissions from utility power plants may be regulated. The second major factor is the expected upsurge in new plant construction beginning in the late 1990s. Together, these forces should define the performance requirements and market for new ESPs.

This paper identifies and briefly describes technologies that the Electric Power Research Institute (EPRI) is developing to help U.S. utilities meet these challenges cost-effectively. Among the technologies addressed are: advanced digital voltage controls, flue gas conditioning, intermittent energization, temperature-controlledprecharging (i.e., two-stage ESP), wide plate spacing, positive energization of corona electrodes for hot-side ESPs, and integration of conventional ESPs with pulse-jet baghouses.     

Inhibition and promotion of trace pollutant adsorption within electrostatic precipitators

Among the technologies available for reducing mercury emissions from coal-fired electric utilities is the injection of a powdered sorbent, often some form of activated carbon, into the flue gas upstream of the particulate control device, most commonly an electrostatic precipitator (ESP). Detailed measurements of mercury removal within ESPs are lacking due to the hazardous environment they pose, increasing the importance of analysis and numerical simulation in understanding the mechanisms involved. Our previous analyses revealed that mercury adsorption by particles suspended in the gas and mercury adsorption by particles collected on internal ESP surfaces are not additive removal mechanisms but rather are competitive. The present study expands on this counterintuitive finding. Presented are results from numerical simulations reflecting the complete range of possible mass transfer boundary conditions representing mercury adsorption by the accumulated dust cake covering internal ESP collection electrodes. Using the two mercury removal mechanisms operating concurrently and interdependently always underperforms the sum of the two mechanisms’ individual contributions.

Implications: The dual use of electrostatic precipitators (ESPs) for particulate removal and adsorption of trace gaseous pollutants such as mercury is increasing as mercury regulations become more widespread. Under such circumstances, mercury adsorption by particles suspended in the gas and mercury adsorption by particles collected on internal ESP surfaces are competitive. Together, the two mercury removal mechanisms always underperform the sum of their two independent contributions. These findings can inform strategies sought by electric utilities for reducing the usage costs of mercury sorbents.     

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.     

Polyfunctional Plants for Industrial Waste Disposal—Part II: Economics and Model Evaluation

ABSTRACT

This is the second part of a two-part paper dealing with the preliminary design and costing of polyfunctional waste treatment plants. In this article, we present some criteria for estimating capital investment and annual operating costs of polyfunctional plants for industrial waste treatment. The process and equipment design methods presented in Part I of this article, together with the economic approach proposed here, allow for complete technical/economic analyses. The overall mathematical model appears to be a useful tool in economic feasibility studies. The accuracy of the developed computer mathematical model has been demonstrated, referring to actual cost data from the literature.     

Membrane-based wet electrostatic precipitation

Emissions of fine particulate matter, PM2.5, in both primary and secondary form, are difficult to capture in typical dry electrostatic precipitators (ESPs). Wet (or water-based) ESPs are well suited for collection of acid aerosols and fine particulates because of greater corona power and virtually no re-entrainment. However, field disruptions because of spraying (misting) of water, formation of dry spots (channeling), and collector surface corrosion limit the applicability of current wet ESPs in the control of secondary PM2.5. Researchers at Ohio University have patented novel membrane collection surfaces to address these problems. Water-based cleaning in membrane collectors made of corrosion-resistant fibers is facilitated by capillary action between the fibers, maintaining an even distribution of water. This paper presents collection efficiency results of lab-scale and pilot-scale testing at FirstEnergy's Bruce Mansfield Plant for the membrane-based wet ESP. The data indicate that a membrane wet ESP was more effective at collecting fine particulates, acid aerosols, and oxidized mercury than the metal-plate wet ESP, even with approximately 15% less collecting area.     

Low-resistivity Related ESP Performance Problems in Dry Scrubbing Applications

This paper describes the evaluation of the performance of ESPs operating downstream of spray dryers in high- and medium-sulfur coal flue gas streams. Tests were conducted at the TV A10 MW Spray Dryer/ESP Pilot Plant and the EPRI High Sulfur Test Center. The results of the analysis of particle characteristics, spray dryer operating parameters, and ESP operating variables identify the occurrence of severe particle reentrainment due to the low resistivity (10⁸ ohm-cm and lower) of the sorbent/flyash mixtures at low approach-tosaturation temperatures. The reentrainment has a significant impact on the collection efficiency of ESPs which could represent a fundamental limitation on their ability to adequately perform in this environment. Although this program has been focused on spray dryer applications, because of the similarities of the gas and particle characteristics produced from spray drying and other dry scrubbing processes, the results also have implications to duct slurry injection, dry sorbent injection with humidification, and processes involving furnace sorbent injection with humidification.

The performance characteristics of the ESPs are presented under both baseline and spray dryer conditions. The results are analyzed and the Southern Research Institute ESP Computer Model was used to evaluate the data. Special techniques for measuring particle resistivity at these conditions are described. A theoretical examination of particle reentrainment was undertaken which indicated that at low-resistivity levels the electrostatic forces reverse and tend to pull the particles off the plates with a force proportional to the square of the electric field. This repulsion of particles from the plates at spray dryer conditions was confirmed by laboratory experiments. Chloride content of the coal was found to be an important parameter effecting the performance of the ESP. Implications of the results of this evaluation relative to ESP upgrades are presented.     

Polyfunctional Plants for Industrial Waste Disposal—Part I: Process and Equipment Design

ABSTRACT

This article is the first of two papers dealing with development of a design and costing procedure for polyfunctional waste treatment plants. Part I reviews equipment sizing aspects. Part II defines and validates the cost estimation procedure. In this article, the structure of a general purpose polyfunctional plant for liquid and solid industrial waste treatment is discussed, highlighting the high level of process integration obtainable and the consequent benefits. The plant comprises an incineration section, a section for chemical/physical/biological treatments, and a stabilization/solidification section. Each section is briefly described, and an overview of the sizing procedure for main equipment is presented. Such a procedure forms the basis of a computer model for process and equipment preliminary design to be used in economic feasibility evaluation studies.     

Mass transfer within electrostatic precipitators: trace gas adsorption by sorbent-covered plate electrodes

Varying degrees of mercury (Hg) capture have been reported within the electrostatic precipitators (ESPs) of coal-fired electric utility boilers. There has been some speculation that the adsorption takes place on the particulate-covered plate electrodes. This convective mass transfer analysis of laminar and turbulent channel flows provides the maximum potential for Hg adsorption by the plate electrodes within an ESP under those conditions. Mass transfer calculations, neglecting electrohydrodynamic (EHD) effects, reveal 65% removal of elemental Hg for a laminar flow within a 15-m-long channel of 0.2-m spacing and 42% removal for turbulent flow within a similar configuration. Both configurations represent specific collection areas (SCAs) that are significantly larger than conventional ESPs in use. Results reflecting more representative SCA values generally returned removal efficiencies of <20%. EHD effects, although potentially substantial at low Reynolds numbers, diminish rapidly with increasing Reynolds number and become negligible at typical ESP operating conditions. The present results indicate maximum Hg removal efficiencies for ESPs that are much less than those observed in practice for comparable ESP operating conditions. Considering Hg adsorption kinetics and finite sorbent capacity in addition to the present mass transfer analyses would yield even lower adsorption efficiencies than the present results. In a subsequent paper, the author addresses the mass transfer potential presented by the charged, suspended particulates during their collection within an ESP and the role they potentially play in Hg capture within ESPs.     

Full-scale evaluation of mercury control with sorbent injection and COHPAC at Alabama Power E.C. Gaston

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.     

Novel hybrid composite discharge electrode for electrostatic precipitator

Over the last few decades, electrostatic precipitators (ESPs) have emerged as effective air pollution control devices for treating coal-fired power plant exhausts. Among the components of the ESP, the discharge electrodes are extremely important in determining the collection efficiency of the ESP. Typically, in wet ESPs, the discharge electrodes used must be made of corrosion-resistant alloys, which makes them extremely expensive and heavy. Hybrid composite discharge electrodes have the potential to be lightweight and corrosion-resistant substitute for traditional metal alloy electrodes used in wet ESPs. In this experimental study, a novel hybrid composite electrode (recently patented at Ohio University) is presented as a substitute for traditional metal electrodes in wet ESPs. The samples of hybrid electrodes were fabricated by using carbon fiber composites, combined with metal mesh, in the shape of a long and thin tape. The electrode’s electrical response was evaluated in open atmospheric conditions, while connected to a transformer-rectifier unit to generate a corona current at voltages exceeding 50 kV. Results of these hybrid electrodes were compared with traditional metal electrodes. The hybrid composite discharge electrode produced a uniform corona at comparable power levels to that of metal electrodes, with additional advantages of being compact, lightweight, and highly corrosion resistant. In addition, hybrid composite electrodes exhibited lower corona onset voltage as compared with metal electrodes. The preliminary experimental data are encouraging and show significant potential for this new inexpensive hybrid electrode to replace metal electrodes in wet ESPs, providing comparable (and in some cases exceeding) collection efficiencies with lower ozone generation.

Implications: The newly invented hybrid composite electrode (HCE) performance was evaluated through experimentation with conventional metal electrodes. The HCE performance was comparable to the metal electrodes. The HCE also exhibited uniform corona fields and steady power while maintaining similar and in some cases superior electrical performance as compared with metal electrodes and thus shows a significant potential to substitute metal electrodes in wet ESP systems.     

粉尘对电除尘器气流分布影响仿真研究

为了更加精确地研究电除尘器入口气流分布特征, 论文采用欧拉-拉格朗日多相流模型,对电除尘器内部气流分布进行了数值仿真。由于在进入除尘器的气流中引入了粉尘粒子,不仅可获得粉尘及粉尘颗粒粒径大小对气流分布均匀性的影响,而且这种模拟更加接近除尘器的气流实际情况。提出的模拟方法为电除尘器的气流分析提供了一条新的途径。     

泛比电阻电除尘器收尘性能实验研究

泛比电阻电除尘器是一种具有辅助电极和交错平板收尘电极的新型电除尘器.通过对其伏安特性及除尘效率的试验研究,并与传统线板式静电除尘器进行比较,结果表明辅助电极对电晕电流具有明显的抑制作用,在相同的外加电压下,泛比电阻电除尘器对高比电阻锅炉飞灰的收尘效率比普通的线板式电除尘器明显要高.     

A Vehicle Emissions System Using a Car Simulator and a Geographical Information System: Part 1—System Description and Testing

Abstract

A methodology for estimating vehicular emissions comprising a car simulator, a basic traffic model, and a geographical information system is capable of estimating vehicle emissions with high time and space resolution. Because of the extent of the work conducted, this article comprises two sections: In Part 1 of this work, we describe the system and its components and use examples for testing it. In Part 2 we will study in more detail the emissions of the sample fleet using the system and will make comparisons with another emission model. The experimental data for the car simulator is obtained using on-board measuring equipment and laboratory Fourier transform IR (FTIR) measurements with a dynamometer following typical driving cycles. The car simulator uses this data to generate emission factors every second. These emission factors, together with information on car activity and velocity profiles of highways and residential and arterial roads in Mexico City in conjunction with a basic traffic model, provide emissions per second of a sample fleet. A geographical information system is used to localize these road emissions.     

“Hot” versus “Enlarged” Electrostatic Precipitation of Fly Ash: A Cost-Effectiveness Study

An article in the February 1974 issue of the Journal of the Air Pollution Control Association entitled “Hot” versus “Enlarged” Electrostatic Precipitation of Fly Ash: A Cost Effectiveness Study,¹ by D. R. Selzler and W. D. Watson, Jr., arrives at the generalized conclusion that “enlarged” precipitation is likely to be a less costly method of attaining high collection efficiencies for low sulfur fly ash. The basis of this conclusion is a multivariate regression analysis of 37 full-scale cold electrostatic precipitators. Using the predictive ability of the resulting equation, modified to include a 95% probability of attaining design efficiency, together with functions describing capital and operating costs, the authors arrived at the above conclusion.

It is our contention that while the overall approach presented is a good attempt to develop a more systematic method of attacking the problem and arriving at a generalized solution, there are many errors in the development which have resulted in incorrect conclusions. Among the more serious errors in this work is the development and acceptance of a regression model based on cold precipitation performance data which is not compatible with the observed performance of cold precipitators. The use of the same equation for hot precipitator sizing can also be shown to be invalid. Additionally, one of the basic parameters used by the authors to distinguish precipitation performance of coals is not meaningful for hot precipitation and of questionable validity for cold precipitation. And, finally, the authors do not appear to recognize that power input to the precipitator (actually power density) is a constrained function which can hardly ever be increased to levels defined by their “optimum” precipitator sizing.