Some Factors in Minimizing Precipitator Costs

This paper is directed to those individuals involved in design of electrostatic precipitators. The Deutsch-Anderson model is usually employed by industry for the design of electrostatic precipitators. The so-called process design variable in this approach is the total capture area in the precipitator. Unfortunately, little is available on the equipment design of this unit, i.e., the geometric arrangement of the plates that constitute the capture area and the external dimensions of the physical structure that houses the precipitator components. These are important economic considerations, and it is to this subject that this paper is directed. It is relatively easy to predict equipment costs for “off-the-shelf” electrostatic precipitators; it is more difficult to closely predict the cost for a custom-made unit, which is more often the case encountered in practice. Once the capture area is calculated, the total precipitator cost becomes a strong function of the outer casing and outer accessories of the physical system. In this paper, a model is presented that can help minimize precipitator cost. An illustrative example complements the development of the model.     

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.     

BOP Air Cleaning Experiences

The basic oxygen process of steel manufacture evolves a large volume of gas at high temperature during the oxygen blow. This gas contains finely divided oxide particles that are removed in gas-cleaning equipment. Either electrostatic precipitators or water scrubbers are commonly used for the purpose. These devices are quite efficient but breakdowns, usually in the auxiliary equipment, are frequent. Maintenance problems arise primarily from the high temperature of the gases which warps and cracks the plates in the hood that draws the gases to the cleaning device, and from erosion of piping caused by abrasive particles moving at high velocity. This paper presents a number of case histories of BOP gas-cleaning installations, details maintenance problems, and discusses corrective measures that have been adopted. It gives reasons why merely appropriating a large sum of money for cleaning devices does not always guarantee full abatement of air pollution from the basic oxygen process.     

Improvement of Hot–side Precipitator Performance with Sodium Conditioning—An Interim Report

The development of an unexpected, time-dependent degradation of performance of hot-side precipitators collecting ash from certain coals (usually low-sodium, low-sulfur coals) has caused serious problems at a number of major utility installations. A jointly funded research project was developed under the sponsorship of the U.S. Environmental Protection Agency, the Electric Power Research Institute, and Southern Company Services, Inc., to evaluate sodium conditioning as a possible solution to these performance deficiency problems.     

Operating Experience with the Alcoa 398 Process for Fluoride Recovery

During the 1940’s, aluminum smelting installations were increased in size to provide aluminum necessary for World War II. Increased evolution of fluorides made necessary the capture and treatment of pot gases. Following the application of water scrubbers, cyclones, and electrostatic precipitators, Alcoa Research Laboratories at New Kensington, Pa., discovered that small quantities of HF gas would react at low temperature with alumina. Following a series of design efforts, the Alcoa 398 Process was developed, incorporating a fluidizedbed reactor to contact pot gases with incoming feed alumina. Bag filters are used to separate entrained solid materials from pot gases. Ninety-five percent interception of pot gases is reported with 99% recovery of fluorides from gases treated. No significant effect is observed on purity of metal produced.

Installation costs are in the range of $>28-$37 per annual ton for new installations and about 50% more for conversion of old plants. These are somewhat less than the conventional electrostatic precipitators and water scrubbers at today’s prices. Direct operating costs for the Alcoa 398 Process range from $2.90 to $4.70/ton of aluminum and recover $8 worth of fluorine, giving a net credit. This contrasts with $3.93/ton of aluminum to operate existing precipitator scrubber combinations. The Alcoa 398 Process is being rapidly extended throughout the Alcoa system.     

Results of Field Measurements of Industrial Particulate Sources and Electrostatic Precipitator Performance

This paper presents results of source size distribution measurements over the size range from 0.1 μm to 5 μm for six classes of particulate sources and fractional efficiency measurements on five full scale electrostatic precipitators and one pilot scale precipitator. The precipitators all showed moderately high to high particulate collection efficiencies for particles having diameters larger than a few micrometers or smaller than a few hundredths of a micrometer and a minimum in collection efficiency for particles having diameters of a few tenths of a micrometer.     

A State of the Art Report on Industrial Precipitator Control Equipment

Informative report No. 3 has been prepared to provide background information on the origin, purpose, and general theory of operation of automatic power controls for industrial electrostatic precipitators. A comprehensive body of literature describing the process and mechanisms of dust collection in precipitators is readily available to those interested, but information on the control equipment used with the process is widely scattered. This report is intended to provide assistance toward the understanding of manufacturers’ literature describing specific control apparatus, and it may be used as a starting point for more intensive investigation of the subject. To the latter end, a history of the development of these controls and a bibliography of pertinent literature and patents has been included. It is expected that this report will be of particular interest to technical and supervisory personnel concerned with the selection, evaluation, and operation of precipitation equipment.     

“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.     

An Integrated Program to Achieve Maximum Performance of Electrostatic Precipitators

The objective of this paper is to describe the Tennessee Valley Authority's efforts and plans in designing an operating and maintenance program that will ensure maximum performance of the electrostatic precipitators at our power generating stations. Detailed operating and maintenance manuals are being prepared for each plant for the use of plant personnel. These manuals include instructions on operation, maintenance, and testing of the precipitators. Instructions on internal and external equipment inspections to be performed during unit operation, emergency and scheduled outages, and problem diagnostic procedures are included to help the plant personnel solve problem areas. Performance curves are included in the manuals which show the effect of gas volume flow, gas temperature, gas resistivity, coal changes, and loss of transformer-rectifier sets on the precipitator performance. In addition, opacity monitors that record continuous opacity readings are being installed at all our plants to assist the plant in monitoring precipitator performance. Full-time operating and maintenance crews are being organized at the plants to monitor and maintain the precipitator and ash-removal systems. Also, a staff of technical personnel is being organized at the central office to provide technical advice and assistance in design, operation, and maintenance problems and liaison and coordination for all the plants concerning the precipitators. Periodic precipitator field inspections, performance and operating parameter optimization testing, and review of the equipment operating logs are made by the central office technical personnel. Recommendations and technical assistance are then furnished to the plant with regard to the precipitator overall performance and operating characteristics.     

Adhesive Behavior of Dust in Electrostatic Precipitation

In 2-stage precipitators particles are driven to the collecting plates by electrostatic forces but then the electrostatic force reverses and tends to pull the particles off so that dust is held on the collecting electrodes only by adhesion. In Cottrell or single-stage precipitators the corona current can provide a significant force tending to hold the collected dust to the electrode provided that the resistivity of the dust is 10¹⁰ ohm-cm or more. Adhesion is still essential in the collection of lower resistivity dust and is of vital importance in the transfer of dust from the collecting electrodes to the hopper. As the dust falls from the plates to the hopper it must be held in agglomerations or chunks. There are many peculiarities in the adhesive behavior of electrostatically collected dust. A better understanding of this adhesive behavior is essential if we are to improve the transfer of dust from the collecting electrodes to the hopper.     

Factors Affecting Resistivity in Electrostatic Precipitation

The following material is taken from a new book, “The Art of Electrostatic Precipitation,” authored by Mr. Katz and based on his 30 years of field experience with the subject. The book provides practical information on maintaining and upgrading precipitators; chapter titles include fundamentals, operation and maintenance, trouble solving, corrosion factors, methods to improve performance, test evaluation techniques, gas distribution and conditioning, case histories, and optimum designs.     

Information Required for the Selection and Application of Electrostatic Precipitators for the Collection of Dry Particulate Material

This report is a continuation of two prior papers on the selection and application of electrostatic precipitators. The first papers submitted by the TA-5 committee of APCA were primarily concerned with the collection of fly ash from boiler gases. Three other major applications of industrial precipitators include the ferrous, pulp and paper, and cement fields. Other industries utilizing the precipitator but to a lesser degree are: chemical, petroleum, and non-ferrous metals. New application areas in the United States include municipal incinerators and high temperature-high pressure gas cleaning.

While a similarity of theory and equipment is common to all of the above applications, there are sufficient differences both in the processes and types of material collected to make the selection of the Individual precipitator subject to a comprehensive evaluation. In order properly to make this evaluation, it is necessary that a suitable means of communication be established between user and supplier. It is the purpose of this report to recommend ’? terminology, emphasize design factors, and list the information needed by the supplier to make a proper application of his equipment.     

Economic Comparison of Selected Scenarios for Electrostatic Precipitators and Fabric Filters

Compliance with particulate standards for utility boilers burning low sulfur western coal has resulted in the installation and proposed installation of several fabric filter collectors where cold or hot electrostatic precipitators would have traditionally been applied. Recently, SO3 conditioning has been used to improve cold precipitator performance resulting in considerable reduction in specific collection area (SCA). All this suggests that trade-offs exist indicating ranges of SCA, A/C ratio, and power plant size (Mw) where fabric filters become competitive with electrostatic precipitators. Conceptual cost models are presented which indicate total capital investment and annual costs for the control devices. Precipitator costs are correlated with collecting area, gas flow rate, and power input and are presented as functions of SCA and Mw. Fabric filter costs are keyed to gross filter area, pressure drop, and gas flow rate. Fabric filters become competitive when a cold precipitator requires SCAs in excess of 600 to 800 and competitive when a hot precipitator requires equivalent cold precipitator SCAs in excess of 600 to 1000 depending on A/C ratio, Mw, and hot precipitator SCA credit allowance. The S0₃ conditioned precipitator scenario is shown to be economically competitive with fabric filters.     

Preliminary estimates of performance and cost of mercury control technology applications on electric utility boilers.

Under the Clean Air Act Amendments of 1990, the U.S. Environmental Protection Agency (EPA) determined that regulation of mercury emissions from coal-fired power plants is appropriate and necessary. To aid in this determination, preliminary estimates of the performance and cost of powdered activated carbon (PAC) injection-based mercury control technologies were developed. This paper presents these estimates and develops projections of costs for future applications. Cost estimates were developed using PAC to achieve a minimum of 80% mercury removal at plants using electrostatic precipitators and a minimum of 90% removal at plants using fabric filters. These estimates ranged from 0.305 to 3.783 mills/kWh. However, the higher costs were associated with a minority of plants using hot-side electrostatic precipitators (HESPs). If these costs are excluded, the estimates range from 0.305 to 1.915 mills/kWh. Cost projections developed using a composite lime-PAC sorbent for mercury removal ranged from 0.183 to 2.270 mills/kWh, with the higher costs being associated with a minority of plants that used HESPs.     

Preliminary Estimates of Performance and Cost of Mercury Control Technology Applications on Electric Utility Boilers

ABSTRACT

Under the Clean Air Act Amendments of 1990, the U.S. Environmental Protection Agency (EPA) determined that regulation of mercury emissions from coal-fired power plants is appropriate and necessary. To aid in this determination, preliminary estimates of the performance and cost of powdered activated carbon (PAC) injection-based mercury control technologies were developed. This paper presents these estimates and develops projections of costs for future applications.

Cost estimates were developed using PAC to achieve a minimum of 80% mercury removal at plants using electrostatic precipitators and a minimum of 90% removal at plants using fabric filters. These estimates ranged from 0.305 to 3.783 mills/kWh. However, the higher costs were associated with a minority of plants using hot-side electrostatic precipitators (HESPs). If these costs are excluded, the estimates range from 0.305 to 1.915 mills/kWh. Cost projections developed using a composite lime-PAC sorbent for mercury removal ranged from 0.183 to 2.270 mills/kWh, with the higher costs being associated with a minority of plants that used HESPs.     

Solving Problems in the Electrical Energization of Electrostatic Precipitators

Achieving and maintaining continuous, reliable performance in electrostatic precipitators depends critically upon the proper design, application, operation, and maintenance of the high voltage electrical energization system. Common problems among these factors are discussed, and effects on performance are illustrated from field experience. Practical recommendations for solving problems and for preventing their occurrence in the electrical aspects of precipitation are presented for effective use by designers, operators, and maintenance personnel.     

平煤集团坑口电厂除尘设施的技术改造

平煤集团坑口电厂原有文丘里水膜除尘器不能使排放烟尘达标排放 ,在保留原有两台文丘里水膜除尘器基础上 ,并在其前串联两台单室二电场静电除尘器 ,经改造后 ,电除尘 文丘里水膜除尘串联组合技术总除尘效率达 99 9% ,排放浓度为 10 3mg/Nm3,实现了达标排放     

advances in particle sampling and measurement

Seventeen papers were presented on improved instruments and techniques for measuring the size, number, and composition of particles in process streams. Recent studies on cascade impactors, cyclones, and diffusion batteries were reported. Several papers discussed methods for making in situ particle size or mass determinations through light scattering. Systems that have been developed to determine the collection efficiency of electrostatic precipitators, scrubbers, and bag filters were described.     

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.     

Collection of Fly Ash with High Electrical Resistivity in a Pilot Plant Electrostatic Precipitator Preceded by the EPA/SoRI Precharger

It is well known that dust with high electrical resistivity is difficult to collect in electrostatic precipitators (ESP). The difficulty is primarily due to poor particle charging. This poor particle charging is not because particles having high electrical resistivity are intrinsically difficult to charge, but because back corona (which results from deposition of material on the collection electrode) produces a bipolar ion field. When ions of both positive and negative polarity are present in the charging region, the competing effects of the two, plus low values of electric field, produce low electrical charge on particles.