Wallace B. Smith

A mathematical model for calculating electrical conditions in wire‐duct electrostatic precipitation devices

A new method is developed which can be used to calculate electrical conditions in wire‐duct electrostatic precipitation devices. The method, based upon a numerical solution to the governing differential equations under a suitable choice of boundary conditions, accounts for the effect of space charge and is applicable over the entire range of current and voltage before sparkover. The procedure yields voltage‐current characteristics and determines the electric potential and electric field strength as functions of position for each current and applied voltage. Predictions of the theory are compared with existing experimental data and the agreement is excellent.

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.

Experimental investigations of fine particle charging by unipolar ions — A review

Abstract Many theories have been offered in attempts to describe accurately the rate of charge accumulation of fine particles in a unipolar ion field. There has been little experimental data, however, for comparison with these new theories. In this study, the existing experimental data are reviewed and compiled, and additional particle charging experiments done to extend the quantity of data. Before this study was performed the majority of the experimental data which was available for comparison with particle charging theories was contained in a paper by G. Hewitt, published in 1957. Hewitts experiments were carefully done, but the range of experimental variables was limited and his work was never independently verified. The experiments reported here followed Hewitts procedures closely and were designed to extend the quantity of experimental data. There is some overlap between this and Hewitts data, and in these instances, the agreement is good. Experimental results are presented in this paper for the charging rate of particles of 0.109–7 μm dia. at various values of electric field strength, ion density and charging time. A limited amount of data is also given which shows the important effects on the charging rate of variations in the particle dielectric constant and the polarity of the corona ion source.

Cyclone samplers for measuring the concentration of inhalable particles in process streams

Abstract A cyclone precollector for cascade impactors and a dual-cyclone system have been developed and tested. These devices will be used to measure the concentration of inhalable particles in process streams. The sampling flow rates required to achieve 50% collection of 15 μm particles at temperatures of 23, 93 and 150°C were determined empirically. For the precollector, the desired performance was achieved at flow rates of 7,12 and 15 l./min; and for the dual-cyclone system, at 11, 20 and 23 l./min yielding D50s for the second cyclone of 3.1, 2.6 and 2.3 μm respectively.

Fabric filter technology for utility coal-fired power plants. Part III. Performance of full-scale utility baghouses

This is the third in a series of papers discussing the experience of electric utilities in applying baghouse technology for the collection of particulate matter at coal-fired electric power generating plants. The series presents new data obtained in research sponsored by the Electric Power Research Institute (EPRI) on reverse-gas and shake/deflate cleaned baghouses, and specifically addresses a number of unresolved issues in the design and operation of these units. This paper provides an overview of the design and operating characteristics of baghouses now in place in the utility industry. In addition, it discusses three key issues in design and operation: the relationships among dust cake weight and chemical composition, air-to-cloth ratio, and pressure drop; fabric selection; and bag life.

Fabric filter technology for utility coal-fired power plants

This is the third in a series of papers discussing the experience of electric utilities in applying baghouse technology for the collection of particulate matter at coal-fired electric power generating plants. The series presents new data obtained in research sponsored by the Electric Power Research Institute (EPRI) on reverse-gas and shake/deflate cleaned baghouses, and specifically addresses a number of unresolved issues in the design and operation of these units. This paper provides an overview of the design and operating characteristics of baghouses now in place in the utility industry. In addition, it discusses three key issues in design and operation: the relationships among dust cake weight and chemical composition, air-to-cloth ratio, and pressure drop; fabric selection; and bag life.

Fabric Filter Technology for Utility Coal-Fired Power Plants: Part IV: Pilot-Scale and Laboratory Studies of Fabric Filter Technology for Utility Applications

This paper in a series discusses pilot-scale studies of baghouse particulate collection efficiency and opacity, pressure drop interpretation and prediction, and the impacts of startup/shutdown on system performance. It also presents results of laboratory studies of dust cakes.

Calculation of the charging rate of fine particles by unipolar ions

Theories of particle charging based on boundary value solutions to the diffysional equation may not be applicable to electrostatic precipitators where the ion density is rarely more than an order of magnitude greafer than the particle concentration. A new charging equation, based on kinetic theory, is presented which evaluates the charging rate in terms of the probability of collisions between the flust particles and ions. In the presence of an external electric field, the surface of the particle is divided into three charging regions, and separate charging rates are calculated for each region. The total charging rate is the sum of these three individual rates. For large particles and high electric fields, this theory predicts essentially the same charging rate as the classical field charging equation of Rohmann and Pauthenier. For low electric fields, the theory reduces to White’s diffusional charging equation. Agreement is within 25% of Hewitt’s experimental results over the entire range of variables wh...

Preservation of fabric filter dust cake samples

Technique permettant de stabiliser les echantillons en vue de leur etude ulterieure, en particulier de leur microstructure, et consistant a faire diffuser une resine epoxy dans le gâteau de poussiere

Performance of a Steam-Ejector Scrubber

The results of fractional and overall mass efficiency tests of a steam-ejector scrubber are presented. The tests were performed on one of seven modules of a full scale scrubber used for controlling particulate emissions from an open hearth furnace. Total flue gas particulate mass concentrations were determined at the inlet and outlet of the scrubber by conventional (Method 5) techniques. Inlet and outlet particulate concentrations as functions of diameter were determined on a mass basis using cascade impactors for sizes from about 0.3 μm to 5 μm, and on a number basis for diameters smaller than about 1 μm using optical and diffusional methods. Measurements were made under several scrubber operating conditions. The measured efficiencies based on total particulate mass concentrations with the scrubber operating under near optimum conditions ranged from 99.84 to 99.9%. The measured fractional efficiencies ranged from a maximum of 99.99% for particles having diameters of 1 μm to values of 97 and 99.9% for par...