United States Environmental Protection Agency Air and Energy Engineering Research Laboratory Research Triangle Park NC 27711 Research and Development EPA-600/S9-84-025a Mar. 1985 &ER& Project Summary Fourth Symposium on the Transfer and Utilization of Paniculate Control Technology: Volume I. Fabric Filtration F. P. Venditti, J. A. Armstrong, and M. D. Durham Summarized herein is Volume I of three volumes of proceedings of the Fourth Symposium on the Transfer and Utilization of Particulate Control Tech- nology held in Houston, Texas, October 11-16,1982. Volume I papers discuss theoretical and applied aspects of fabric filtration. Volumes II and III are des- cribed in two separate project sum- maries. This Project Summary was developed by SPA's Air and Energy Engineering Research Laboratory. Research Triangle Park. NC. to announce key findings of the research project that is fully docu- mented in a separate report of the same title (see Project Report ordering infor- mation at back). Introduction The papers in these three volumes of proceedings were presented at the Fourth Symposium on theTransfer and Utilization of Particulate Control Technology in Houston, Texas, October 11-15, 1982, sponsored by the Particulate Technology Branch of the Environmental Research Laboratory of EPA at Research Triangle Park, NC. The symposium brought together re- searchers, manufacturers, users, govern- ment agencies, educators, and students to discuss new technology and provided an effective means for the transfer of this technology out of the laboratories and into the hands of the users. The two major particle control tech- nologies—fabric filters and electrostatic precipitators (ESP's)—were the primary concern of the symposium. These tech- nologies were discussed from perspec- tives of economics, new technical ad- vancements in science and engineering, fundaments, and applications. Several papers dealt with the interaction of sulfur dioxide control and paniculate control. Additional topic areas included mechan- ical collectors, coal characterization, in- halable particulate matter, novel devices, and advanced energy applications for particulate control. The symposium was conducted as a series of parallel sessions, each contain- ing four to six related papers. The sessions were scheduled to avoid conflict due to simultaneous sessions dealing with the same topic. Each series of related ses- sions represented a thread of technology. These parallel threads, extending over the total period of the symposium, pro- vided a highly integrated approach to the total subject of particulate control tech- nology with strands of specialized tech- nologies. These strands of specialized technologies, or perspectives, provided the basis for the division of the papers into three volumes, each volume contain- ing a set of related session topics so as to provide easy access to a unified tech- nology area. Volume I Papers Volume I, summarized here, is a collec- tion of papers describing various aspects of fabric filtration. One section includes papers dealing with the theoretical and fundamental aspects of fabric filtration. Specialized measurement techniques for ------- various aspects of fabric filtration includ- ing pressure drop, dust layer thickness, and bag strength are described in a series of papers. Several papers deal with the application of baghouses to coal-fired boilers. Both pulse jet and reverse air systems are discussed, and data are presented from pilot-scale test devices and full-scale installations. One section deals entirely with results from several research projects on improvements pro- duced through electrostatic enhancement of fabric filtration. Results are presented for enhancement by application of electric fields at the bag surface and by means of precharging the particles. Practical as- pects of fabric filtration are covered in a section dealing with bag cleaning strate- gies, startup procedures, and air flow design. A final section of papers deals with combined 802 and particulate con- trol using spray dryers in combination with fabric filtration. Section A—Fabric Filters: Fundamentals Theory of the Temporal Development of Pressure Drop Across a Fabric Filter During Cake Initiation Eric A. Samuel General Electric Environmental Services, Inc. The time variation of the pressure drop across a fabric filter characteristic of cake initiation in a new fabric as well as in a seasoned fabric is derived on the basis of the Carmen-Kozeny hypothesis, which is well known for its prediction of the linear growth of pressure drop with time char- acteristic of cake filtration. The non-linear growth of pressure drop during cake initiation in a new fabric is associated with the filling of the voids within the fabric prior to cake establishment. The non-linear growth of pressure drop dur- ing cake initiation in a seasoned fabric is associated with non-uniform dust loading on the fabric. The non-uniform loading may either be an initial condition follow- ing cleaning, or be induced by inertia! or external forces. Experimental evidence in support of the theory is presented. Pulse Jet Filtration Theory— A State-of-the-Art Assessment Richard Dennis GCA/Technology Division Louis S. Hovis Air and Energy Engineering Research Laboratory, U.S. Environmental Protection Agency The relevant literature on pulse jet filter theory and applications was assessed to develop coherent guidelines for designing predictive filter models. Observations of several foreign and U.S. researchers not previously subjected to rigorous compar- isons showed that there is a considerable unanimity in technical perspectives when data and theories are viewed from a common baseline. Common misconcep- tions are clarified such as (a) the "air bubble" that descends through the bag during pulsing, (b) dust removal by air flushing rather than mechanical protec- tion from a rapidly decelerating fabric, and (c) failure to recognize that only a small (1-5 percent) fraction of dust dis- lodged by pulse action actually reaches the hopper. Data from several sources suggest that not only the compressed air pressure, but also the rate of pressure rise within a bag and the fabric mobility determine dust removal effectiveness. Unique pairings of pressure intensity and dust dislodgeability (as defined by dust/ fabric adhesive properties) appear es- sential for complete removal of surface dust layers. When air jets are correctly placed for specified pulse jet parameters, the surface dust layer should be com- pletely dislodged. Various investigators also suggest that the residual dust (i.e., the irreversibly embedded dust) is rel- atively constant for fixed dust/fabric combinations. This paper has been reviewed in ac- cordance with the U.S. Environmental Protection Agency's peer and administra- tive review policies and approved for presentation and publication. Laboratory Techniques for Developing Pulse Jet Collectors Robert R. Banks John T. Foster Wheelabrator-Frye Inc., Air Pollution Control Division Technical Center A major factor in the performance of a pulse jet collector is its effectiveness in using compressed air. The manifold con- figuration, venturi design and other fac- tors determine this effectiveness. To expedite the study of these factors over a wide range, two sets of apparatus were built. The first, the impact force tester, meas- ures the momentum of the air pulse from each hole in a manifold and the pressure along the manifold. The momentum o| the jets can be equalized by varying the hold size along the manifold. The second test rig measures the characteristic of the ejector or jet pump formed by the air jet and venturi so that the geometry of this part of the systerr can be optimized. Jet pump curves were found to predict relative performance as measured in a laboratory pilot collector Testing by these methods takes only < fraction of the time required using a pilo collector. Data from tests leading to ar optimum pulse jet cleaning system desigi will be shown. Off-Line Pulse-Jet Cleaning System Thomas C. Sunter C-E Air Preheater, Division of Combustion Engineering, Inc. The paper discusses off-line pulse-jc cleaning systems by formulating a set c simplified mathematical equations t describe the cleaning process. A compu er model is developed from the equatior and manipulated to simulate both tim< based and differential pressure-base control of the pulse-jet system. Practical application of this informatic is discussed as it affects system contrc bag life, energy consumption and syste operation. Section B—Fabric Filter: Measurement Techniques Field Evaluation of the Drag 01 Individual Filter Bags W. T. Grubb R. R. Banks Wheelabrator-Frye Inc. Air Pollution Control Division, Technical Center Evaluation of the performance of filti tion fabrics has heretofore necessitate! full compartment test, as only gene observations could be made using a fi test bags. Compact, inexpensive, readily portal equipment was developed to measure 1 filter drag of a single bag by blowini metered flow of ambient air through 1 bag and measuring the pressure dr The test apparatus is set up in 1 baghouse compartment to minimize c turbance to the bag and its dust cake. Test results show reproducibility i statistically significant differences ami bags made of different cloths and different sites. Evaluation of the per mance of various filter fabrics on ------- lasis of a limited number of trial bags is possible. Selected data will be presented reflecting experience with tests on fiber- glass and synthetic bags in five large utility collectors. A Dual-Detector Beta Particle Backscatter Gauge for Measuring Dust Cake Thickness on Operating Bag Filter and ESP Units Robin P. Gardner Center for Engineering Applications of Radioisotopes R. P. Donovan Process and Chemical Engineering Division, Research Triangle Institute L S. Hovis Utilities and Industrial Process Division Air and Energy Engineering Research Laboratory, U.S. Environmental Protection Agency To avoid the use of moving mechanical parts in the hostile environment of dust collection that is necessary with the dual- beam beta-particle backscatter gauge, an alternative measurement principle has been sought that still allows the measure- ment of dust cake density thickness 'ndependent of distance from the device. It is found that the use of a dual-detector system, in which each detector detects the response of a different part of the backscattered beta-particle spectra from a single radioisotope source, can be used o accomplish this. The system investigated here consists of a Sr-90 source and two thin end- window GM counters, one covered with a iimple paper filter with density thickness of 0.050 g/cm2. The two responses obtained differ significantly with dust :ake density thickness so that models of lach response can be solved simultan- lously for two experimental responses to ive dust cake density thickness inde- >endent of distance from the device. .aboratory results on a prototype device jsing paper samples of known density hickness to simulate dust cake density hickness yield standard errors of 0.0278 nd 0.0151 g/cm2 for bag filter and ESP jnit configurations, respectively. The •ange of distances and simulated dust :ake density thickness investigated were .4 to 7.4 cm and 0 to 0.2133 g/cm2, •espectively. This paper has been reviewed in ac- :ordance with the U.S. Environmental 'rotection Agency's peer and adminis- rative review policies and approved for iresentation and publication. MIT Flex Endurance Tests at Elevated Temperature John T. Foster W. Theron Grubb Wheelabrator-Frye Inc. Air Pollution Control Division Technical Center The MIT flex endurance test, originally devised for paper, is used to evaluate the fatigue life of woven filtration fabrics. This test is used in predicting the relative life of fiberglass fabric filter bags and in the development of finishes. In the past, MIT flex data has been published only for tests conducted at ambient (room) tem- perature. Fiberglass filter bags, however, are used at operating temperatures up to 550°F. Since the physical properties of the finishes which protect the cloth change with temperature, MIT flex tests conducted at the operating temperature of the cloth should provide more meaning- ful data. An MIT flex tester designed to meet the specifications of ASTM method 02176, and to operate at temperatures as high as 600°F, has been built and tested. A relationship between flex endurance and operating temperature for several com- mercially finished fiberglass fabrics is present. The One-Point In-Situ Calibration Method for Using a Beta-Particle Backscatter Gauge for Continuously Measuring Dust Cake Thickness on Operating Bag Filter and ESP Units Robin P. Gardner Center for Engineering Applications of Radioisotopes R. P. Donovan Process and Chemical Engineering Division, Research Triangle Institute L S. Hovis Utilities and Industrial Processes Division, Air and Energy Engineering Research Laboratory U.S. Environmental Protection Agency An alternative to using the dual-beam beta-particle backscatter gaugeto contin- uously measure dust cake thickness on operating bag filter or electrostatic precip- itator (ESP) units independent of gauge distance from the dust, a one-point in- situ calibration method for using a simple beta-particle backscatter gauge, is de- veloped and demonstrated. The method consists of obtaining a response model for beta-particle backscatter in terms of dust cake density thickness (areal den- sity), distance from the gauge, and either bag filter or collector plate density thick- ness. Then, assuming that the density thickness of the bag filter or the collector plate (on the ESP unit) without dust is either known or (for the ESP) larger than the saturation value for the beta-particle source being used, the initial gauge response before dust is present can be used to establish the gauge distance to the bag filter or collector plate. This approach has been investigated in the laboratory with a system consisting of a Sr-90 beta-particle source and an end- windowGeiger-Mueller(GM) tube detect- or. The ranges of distances and simulated dust cake density thicknesses investi- gated were 3.4 to 7.4 cm and 0 to0.2133 g/cm2, respectively. The accuracies con- tained were quite good. For the bag filter application, dust cake measurement ac- curacies of 0.025 g/cm2 or better were obtained for all distances up to 7.4 cm and dust cake density thicknesses less than 0.05 g/cm2. This assumes counting rate errors of 1 percent and an error in the measurement of the bag filter density thickness of 5 percent. For the ESP application the dust cake measurement accuracies for the equivalent error as- sumptions were even better, ranging from 0.0012 to 0.017 g/cm2 for all distances and dust cake thicknesses investigated. This excellent accuracy for the ESP application is in part due to the basic sensitivity for this case (slope of the calibration curve) and in part because there is no error introduced by variations in the ESP collector plate thickness. The accuracies for both applications have been significantly improved by removing the rotating shield superstructure greatly reducing the background response re- ported for the predecessor dual-beam gauge. This paper has been reviewed in ac- cordance with the U.S. Environmental Protection Agency's peer and administra- tive review policies and approved for presentation and publication. Section C—Fabric Filters: Coal Fired Boilers Pulse-Jet Fabric Filter Experience Using Non-Glass Madias at Air to Cloth Ratios of 5 to 1 on a Pulverized Coal Fired Boiler ------- G. L. Pearson D. D. Capps Adolph Coors Company A 12-module baghouse system using the Carter-Day high temperature module has been in service since November 1979 controlling emissions from the 450,000 Ib/hr Boiler No. 5 unit. Bags were made of felted "Ryton" and cleaning is accomplished via a low pressure-mod- erate volume, pulse-jet technique. Experience to date with this baghouse system will be presented. Data on pres- sure drop, cleaning cycles, cleaning frequency, bag life experience and panic- ulate emissions will be reviewed. Results of on-line evaluation of felted FBI bags will also be presented. Prepared for Presentation at the Fourth Symposium on the Transfer and Utiliza- tion of Particulate Control Technology Sponsored by the U.S. Environmental Protection Agency and held in Houston, Texas, October 11-15, 1982. Start-Up and Operation of a Fabric Filter Controlling Particulate-Emissions from a 250 MW Pulverized Coal-Fired Boiler Charles B. Barrangsr Flakt, Inc. John Saibini Sierra Pacific Power Co. Norm Spence Stone and Webster Summarize and describe the design, construction, start-up and operation of the fabric filter baghouse controlling the particulate emissions from Boiler Unit No. 1 located at Sierra Pacific Power, North Valmy, Nevada. The basic design specification requirements will be des cribed, i.e., fuel type, flue gas, fabric filter type, system arrangement and perfor- mance requirements. Actual pre-start checkout and system start-up procedure will be reviewed in detail. The fabric filter was put on-line in November of 1981. Resulting equipment operating conditions from start-up through date of the paper will be presented. Performance of a 10 MW Fabric Filter Pilot Plant and Comparison to Full-Scale Units Wallace B. Smith Kenneth M. Gushing Southern Research Institute Robert C. Carr Electric Power Research Institute This paper provides an update on EPRI's fabric filter research .program currently being conducted by Southern Research Institute of the Arapahoe test facility in Denver, Colorado, and also several full-scale installations. Data are reported which suggest a quantitative relationship between tube-sheet pres- sure drop and air-to-cloth ratio for reverse-gas cleaned baghouses. Typical results show that average tube-sheet pressure drop increases from 4.5 to 8 in. H20 (1.12 to 2.0 kPa) as the air-to-cloth ratio increases from 1..7 to 2.5 acfm/ft2. Large residual dust cakes of up to 1 Ib/ft2 (about 500 mg/cm2) were measured in the bags after cleaning by reverse gas. Current tests indicate that approximately a 20 percent reduction in operating pressure drop could be achieved by increasing the reverse-gas velocity to 6 ft/min (3 cm/sec), although such a high value may be impractical for full-scale units. These results suggest that reverse- gas alone is only marginally effective as a method of cleaning bags in utility appli- cations. Applying intense sonic energy (horns) during reverse-gas cleaning re- sults in much better dust cake removal. Tests now underway indicate that this hybrid bag cleaning mode can reduce the operating pressure drop by more than a factor of two. The Design, Installation, and Initial Operation of the W. H. Sammis Plant Unit 3 Fabric Filter Dennis R. Ross, P.E. Generating Plant Staff Engineer Ohio Edison Company James R. Howard Plant Engineer W. H. Sammis Plant Ohio Edison Company R. Mark Golightley Plant Engineer W. H. Sammis Plant Ohio Edison Company This paper will discuss the design philosophy and preliminary operating experience of the first unit of four units to be retrofitted with fabric filters at the W. H. Sammis Plant. Each unit is 180 MW net. The unit was operational in late August 1982. The paper will identify design criteria initially specified, design enhancements during the course of the project, construc- tion highlights, and preliminary operating] experience. Results from the first months of operation will include pressure drop and opacity. In addition, start-up, shut- down, and maintenance procedures will be discussed. Results from the Fabric Filter Evaluation Program of Coyote Unit#1 H. James Peters Arthur A. Re/singer W. Theron Grubb Wheelabrator-Frye Inc. Air Pollution Control Division and Merrill Lewis Montana Dakota Utilities The fabric filter at Coyote Unit #1 has been in service since May 1981 collecting lignite fly ash and sodium-based sprav dryer product as the second stage of the dry scrubbing system installed by the Wheelabrator-Frye Inc./Rockwell Inter- national joint venture. A program is being conducted to eval- uate the performance of acrylic, polyester Nomex, and fiberglass filtration fabric; and operates at filter ratios of typically 3:1 using combination deflation air an< mechanical shaking as the fabric cleanin; method. This paper highlights the results of thi fabric evaluation program to date includ ing comparisons of the pressure drop throughput, replacement history, filtra tion parameters, and changes in physica properties of the various fabrics over thi first year of operation. Discussion of thi overall performance of the unit am economic and technical consideration: for fabric selection is also covered. Baghouse Performance and Ash Characterization at the Arapahoe Power Station Robert S. Dahlin Southern Research Institute D. Richard Sears U.S. Department of Energy George P. Green Public Service Company of Colorado This paper presents the results of field test conducted in March 1981 onth Unit 3 baghouse of the Arapahoe Static of the Public Service Company of Cole rado. The unit was burning a subbiturr inous coal from Routt County, Coloradi and was retrofitted with a baghouse i 1979. Baghouse performance was four to be excellent with an overall mas efficiency of 99.98 percent. The estimate 4 ------- cumulative collection efficiency of all particles smaller than two microns was 99.92 percent. The average electrical resistivity of the fly ash was found to be 6 x 10" ohm-cm at 266°F. This was consistent with the low level of S03 found in the flue gas (~0.3 ppm). The measured resistivity agreed reasonably well with that predicted by Bickelhaupt's technique using the anal- ysis of the ash obtained by atomic absorp- tion spectrometry. These results suggest that a high SCA and possibly flue gas conditioning would be required to obtain the same collection efficiency from an ESP. A microanalvtical characterization of ash elemental and mineral composition has been performed. Using SEM, detailed major element analyses for —240 indi- vidual ash particles have yielded concen- tration frequency distributions and com- position as a function of particle size, and inter-element concentration correlations. The results have been correlated with coal and ash mineralogy. Suggestions are made concerning possible application of this data to practical problems of fly ash control and disposal. An Evaluation of Full-Scale Fabric Filters on Utility Boilers John W. Richardson John D. McKenna John C. Mycock ETS, Inc. The objective of this EPA-sponsored program was to determine the particulate emission concentrations of a coal-fired electric utility of greater than 100 MW output. Tests were also conducted to determine gaseous constituent concen- trations of the flue gas and particle size via a cascade impactor. Testing was conducted at Southwest- ern Public Service's Harrington Station, Unit 3, between July 6, 1981, and July 11, 1981. A total of three (3) outlet tests and one (1) inlet test were performed. Due to the absence of inlet test ports, inlet testing was done by bypassing the baghouse and testing at the outlet ports of the stack. Emissions for Unit 3 are controlled by two (2) baghouse systems, an east and a west, each with its own operating control system and bypass dampers for start- ups, emergency operation and shutdown. Each system incorporates shake/deflate cleaning, and consists of 32 compart- ments with 204 bags per compartment for a total of 6,528 bags. Average outlet concentration resulted in a lower than expected value of 0.007 lbs./106 Btu. The loading of the inlet testing was 2.0 lbs./106 Btu giving a 99.65% collection efficiency for the bag- house. This emission rate is significantly lower than the existing Federal standard of 0.03 lbs./106 Btu. Particle sizing tests indicated that the mass geometric mean diameter for outlet tests 1 through 3 ranged from 7.5 to 13 /urn with an extrapolated inlet mass diameter of 60 yum, and a baghouse collection efficiency of 99.86%. This paper has been reviewed in ac- cordance with the U.S. Environmental Protection Agency's peer and adminis- trative review policies and approved for presentation and publication. Status ofSPS Investigation of Harrington Station Unit 2 Fabric Filter System Richard Chambers Southwestern Public Service Co. Dale Harmon Air and Energy Engineering Research Laboratory U.S. Environmental Protection Agency This paper describes activities during the fourth year of the SPS/EPA fabric filtration study at Harrington Station. The scope of the overall study and its purposes were outlined in earlier papers. During the fourth year of this project, sufficient information was available to make certain comparisons between Har- rington Station's high air-to-cloth ratio (3.4 ft/min) shake/deflate fabric filter system and low air-to-cloth reverse air units. Specifically, comparison of bag life economics and pressure drop perform- ance is addressed. Sizing of reverse air and shake/deflate baghouses is dis- cussed in light of current operating data from Harrington Station and other instal- lations. Operation and maintenance costs are shown for the Harrington Unit 2 fabric filter system, and suggestions for im- proved shaker design are given. Plans to investigate sonic augmentation of bag cleaning are described. This paper has been reviewed in ac- cordance with the U.S. Environmental Protection Agency's peer and adminis- trative review policies and approved for presentation and publication. Update of SPS Pilot Baghouse Operation Richard Chambers Sherry Kunka Southwestern Public Service Co. Date Harmon Air and Energy Engineering Research Laboratory U.S. Environmental Protection Agency An option of the 1977 Environmental Protection Agency (EPA) contract, with Southwestern Public Service Company (SPS) to assess the performance of a large prototype fabric filter system pro- vided for the installation of a pilot bag- house. The pilot unit was placed in service in October 1979. This paper describes the test program being con- ducted in the pilot unit by SPS for the EPA. These test programs to date have primarily involved the evaluation of the filtration characteristics of a number of fabrics in both the shake/deflate and reverse air cleaning modes. This paper has been reviewed in accord- ance with the U.S. Environmental Protec- tion Agency's peer and administrative review policies and approved for presen- tation and publication. The Use of Sonic Air Horns as an Assist to Reverse Air Cleaning of a Fabric Filter Dust Collector Alan R. Menard Ft. Mark Richards Public Service Company of Colorado A detailed summary of the installation, test program, and performance of sonic air horns used as an assist to reverse air cleaning of an operating FFDC is pre- sented. Four sonic air horns were in- stalled and tested on compartment num- ber 11 of Public Service Company of Colorado's Arapahoe Unit #3 FFDC. The overall objective of the test program was to reduce the pressure drop across the tube sheet of the test compartment. Sonic cleaning reduced the compartment tube sheet differential pressure by ap- proximately 27 percent; this was suf- ficient to warrant the purchase and installation of two (2) sonic air horns in each of the 14 baghouse compartments. Section D—Fabric Filters: Electrostatic Enhancement "Electrostatic Stimulation of Reverse-Air-Cleaned Fabric Filters" ------- D. A. Furlong G. P. Greiner ETS, Inc. D. W. Van Osdell Research Triangle Institute L S. Hovis Air and Energy Engineering Research Laboratory U.S. Environmental Protection Agency The concept of electrostatic stimulation of fabric filtration (ESFF) has been invest- igated on a slipstream of a pulverized- coal-fired boiler using reverse-air- cleaned, woven-fiberglass filter bags. Operation was demonstrated using ESFF at a gas-to-cloth ratio (G/C) of 6 ft/min.1 An un-electrified control house was simultaneously operated at a G/C of 3 ft/min. Under these conditions, the ESFF house maintained a pressure drop equal to or less than the control baghouse. In addition to reducing the filter cake pres- sure drop, ESFF was observed to ap- parently have long-term benefits in pre- venting irremovable dust buildup in the fabric. This paper has been reviewed in ac- cordance with the U.S. Environmental Protection Agency's peer and adminis- trative review policies and approved for presentation and publication. Electrical Stimulation of Fabric Filtration: Enhancement by Particle Precharging George E. Lamb Richard I. Jones William B. Lee Textile Research Institute The reductions in pressure drop that accompany the establishment of a strong electric field near a filter fabric appear to be due to three separate mechanisms. One is the formation of a more porous dust cake due to dust capture in the low packing density regions of the fabric. A second mechanism is attraction of part- icles to the bag wall which causes the bag to act like a precipitator. The thickness of dust cake is then greater near the en- trance than at the end of the bag, and this results in a lower pressure drop. The third mechanism involves attraction of parti- cles to the bag electrodes. The dust is then deposited in bands with relatively thin deposits in between. Measurements 'Readers more familiar with metric units may multiply ft/min by 0.305 for the equivalent m/min. and visual inspections of the dust de- posits indicate that the second and third effects are enhanced when the aerosol is charged. A particle charger of new design appears to be particularly suitable for this purpose, and is found to cause major changes in filtration performance. This paper has been reviewed in ac- cordance with the U.S. Environmental Protection Agency's peer and adminis- trative review policies and approved for presentation and publication. ESFF as a Field Effect L. S. Hovis G. H. Ramsey Air and Energy Engineering Research Laboratory U.S. Environmental Protection Agency R. P. Donovan Research Triangle Institute Evidence to suggest that the mechan- ism on which ESFF (electrostatic stimula- tion of fabric filtration) depends is an electric-field-only mechanism (as op- posed to a Coulomb mechanism that depends on both electric field and electric charge) includes: 1. A room-temperature high-humidity factorial experiment in which both external electric field and fly-ash electrical charge were independent variables. 2. Selected experiments carried out at low relative humidity and room temperature. 3. Enhanced filtration measurements made with a 60-Hz ac electric field applied to the bag electrodes. 4. Published precharging data of oth- ers in which enhancement vanish- es at high relative humidity. All of the data collected in EPA/IERL's Research Triangle Park laboratory (items 1 -3, above) refer to experiments in which pulverized coal fly ash was the dust source. Dusts from other sources were used in the experiments of item 4. This paper has been reviewed in ac- cordance with the U.S. Environmental Protection Agency's peer and adminis- trative review policies and approved for presentation and publication. Electrical Enhancement of Fabric Filtration: Precharging Vs. Bag Electrodes R. P. Donovan Research Triangle Institute L. S. Hovis G. H. Ramsey Air and Energy Engineering Research Laboratory U.S. Environmental Protection Agency Two distinct approaches to achieving electrically enhanced fabric filtration are: (1) upstream precharging in a corona discharge; and (2) dust filtration in an external electric field applied by elec- trodes woven into or positioned adjacent to the bag. Both techniques have demon- strated performance enhancement by some measure, but the mechanisms of enhancement may differ; clearly the hardware does. This paper reviews the hardware op- tions and configurations available with each basic approach and summarizes various mechanisms whereby each ap- proach brings about an electrical en- hancement, including those which dom- inate in combined precharge/bag elec- trode systems. From this background, guidelines for matching configurations to source properties are suggested, as well as a hybrid electrostatic precipitator (ESP)/fabric filter design incorporating features that enable it to operate as either an electric-field aided baghouse or a hybrid ESP/baghouse. This paper has been reviewed in accord- ance with the U.S. Environmental Pro- tection Agency's peer and administrative review policies and approved for pre- sentation and publication. Permeability of Dust Cakes Collected Under the Influence of an Electric Field D. W. VanOsdell R. P. Donovan Research Triangle Institute D. A. Furlong ETS, Inc. L. S. Hovis Air and Energy Engineering Research Laboratory U.S. Environmental Protection Agency The reductions in dust cake flow re- sistance and residual pressure drop that, can be achieved by electrostatic stimula- tion of fabric filtration (ESFF) have been documented. The changes in the dust deposition characteristics which cause these improvements are not well under- stood. This paper presents results from three investigations into the nature of dust deposits collected with ESFF. Per- ------- meability data collected at various axial positions along ESFF and conventional bags were the basis of the first study. The second study concerned the deposition patterns of dust collected on a laboratory filter when ESFF was in use, and the third, the resistance to compression of the collected dust with and without an electric field. These investigations gave evidence that ESFF caused the formation of a residual dust deposit which was not axially uni- form (the permeability at the bottom of the bag was half that at the top) and was more easily removed than a conventional dust deposit. In the laboratory, it was shown that ESFF caused newly collected dust to form very nonuniform deposits. The dust tended to collect near the electrodes, in patterns which have not been observed in the pilot units. In the third study, the ESFF electric field was found to improve the resistance to con- solidation of the dust cake collected in a pulse-jet pilot unit. This paper has been reviewed in ac- cordance with the U.S. Environmental Protection Agency's peer and adminis- trative review policies and approved for presentation and publication. Section E—Fabric Filters: Practical Considerations "High Velocity Fabric Filtration for Industrial Coal-Fired Boilers" Gary P. Greiner Shannon Delaney ETS. Inc. Lou S. Hovis U.S. EPA AEERL. MD-61 Two parameters which dramatically affect the technical/economic perform- ance of a fabric filter system are gas/cloth (G/C) ratio (or filtering velocity) and bag life. Under an EPA-sponsored contract, ETS, . Inc. has been conducting a study of state- of-the-art and experimental fabrics and finishes in full-scale baghouses operating on coal-fired boilers at the Kerr Finishing Plant, Travelers Rest, South Carolina. The objective of the study is to operate, test, and evaluate performance at G/C ratios up to 10/1 and screen various fabrics with respect to pressure drop, collection efficiency, and fabric strength charateris- tics necessary for technical/ economic analysis. Included in the program are some revolutionary fabrics which hold promise of technological breakthroughs. This paper will discuss evaluation methodology, performance results, and future program plans. This paper has been reviewed in ac- cordance with the U.S. Environmental Protection Agency's peer and adminis- trative review policies and approved for presentation and publication. Optimizing the Location of Anti-Collapse Rings in Fabric Bags John G. Musgrove Bechtel Power Corporation The number and placement of anti- collapse rings in fabric filter bags are frequently left to the bag manufacturers. Bag manufacturers do not analyze operat- ing requirements for determination of ring location but merely subdivide the bag into sections of approximately equal length. Bags whose section lengths are equal are suspected during reverse air cleaning of having greater collapse (de- flection) in lower sections than in higher sections. An analysis has been developed to predict the amount of collapse (deflection) in all sections of a bag undergoing reverse air cleaning. The methodology uses the catenary principle of a uniformly loaded suspension cable to determine deflection. A computer program utilizing this methodology has been developed to analyze the forces on a warp thread in a bag and to determine the location of anti- collapse rings to assure equal bag col- lapse in all sections. A companion pro- gram has been developed to predict bag section collapse for bags with established ring locations. Pulse Jet On-Line Cleaning Filter for Fly Ash Wayne G. Wellan Carter-Day Company This paper describes the development and performance of on-line cleaning by pulse jet filters with needed felt. This pulse jet filter design is in operation on various types of coal-fired boilers. Con- siderable research and testing was in- volved in finding a fiber that would endure continuous pulsing, high temperatures, and a sulfur environment. Additional research was required to develop the proper filter media in the areas of needling and scrim design. Also, analysis of various types of fly ash was conducted to deter- mine particle size and shape, and what effect it has on the performance of the filter. Top Inlet Versus Bottom Met Baghouse Design Robert M. Jensen Bechtel Power Corporation This paper compares top inlet with bottom inlet baghouse designs for bags that collect on the inside. The comparison includes performance data for top inlet baghouses in service with comparable bottom inlet performance. The paper explains why pressure loss predictions for top inlet may be more reliable than for bottom inlet. Other advantages claimed for top inlet are higher cloth ratio for the same pressure loss as bottom inlet; use of longer bags; better utilization of unreacted reagent after a spray dryer; and more efficient cleaning with the reverse air. The most important advantage of top inlet design may be the apparent ability for all bags to operate at a constant face velocity in contrast to bottom inlet bags in which the face velocity diminishes with time on line after each cleaning. Upgrade of Fly Ash Collection Capability at the Cromby Station T. J. Ingram R. J. Biese Gilbert/Commonwealth R. 0. Jacob Philadelphia Electric Company A description is given of measures to upgrade the dust collection capability of 28-year old Cromby Unit 1 in the interim period before installation of an S02 scrubber. A novel approach was taken to enhance the performance of outdated equipment, resulting in continued usage of existing mechanical collectors, up- graded electrostatic precipitators, and the addition of a sidestream baghouse to accomplish the objective. The equipment was installed and started up within a year of writing specifications, and compliance was attained. The paper discusses some problems experienced, notably bag blind- ing which has resulted in a severe maintenance problem; steps in progress to resolve the problem are discussed. High Sulfur Fuel, Fabric Filter Startup Experience Phil Hanson Power Production Manager City Power and Light Department ------- Larry Adair Project Manager/Senior Engineer Phelps and Phillips Robert N. Roop Product Manager Research-Cottrell, Inc. Robert B. Moyer Manager Fabric Filter Applications Research-Cottrell, Inc. The long-term operation of fabric filters on low sulfur fuels has been, with a few exceptions, well demonstrated. Similar experience on high sulfur coals has not yet been gained. As utilities continue to convert to coal, reliability of fabric filters for high sulfur coal service will be of paramount concern. The City of Independence, Missouri, recently put into service a fabric filter designed for three to five percent sulfur coal flue gases. Details of the design will be discussed. Anticipating the opportun- ity to test in real world conditions, a bag evaluation program was initiated and is in progress. Physical and mechanical properties of the bag fabric are being tested to determine the effects of high sulfur service and a possible relationship to bag life. Results of that bag test program, as obtained to date, and its implications will be presented. Fundamental Strategies for Cleaning Reverse Air Baghouses M. G. Ketchuck M. A. Walsh O. F. Fortune M. L. Miller G. E. Environmental Services, Inc. M. A. Whittlesey Adapco In order to choose among the various cleaning cycle strategies (Batch, Contin- uous, and Distributed) used for utility reverse air cleaned baghouses, it is necessary to understand the fundamen- tals of the cleaning process. This paper describes both analytical and experiment- al investigation of fundamental mechan- ics common to all cleaning strategies. Section F—Dry Scrubbers Design Considerations for Baghouse-Dry SO2 Scrubber Systems Owne F. Fortune Richard L. Miller G. £. Environmental Services, Inc. The combination of a reverse air cleaned baghouse and a dry sulfur dioxide scrubber is attractive because of the ease with which the baghouse can remove over 99.9% of the high solids loading in the gas stream exiting the scrubber, and because sulfur dioxide scrubbing con- tinues to occur in the filter-cake on the bags. However, in order to avoid having gypsum deposits shortening the usable life of the bags, close attention has to be paid to several design considerations. Among them are system response to boiler tube leaks, approach to saturation temperature, reheat system, avoidance of condensation in reverse air cleaning system, plant maintenance problems, changing boiler loads, and changing sulfur dioxide concentrations. Exper- ience-based design strategies to deal with these issues are discussed in this paper. Results of Baghouse and Fabric Testing at Riverside H. W. Spencer III Y. J. Chen M. T. Quach Joy Manufacturing Company Western Precipitation Division This paper presents the results of one year of baghouse and fabric testing at the Riverside Dry FGD Demonstration Facility during 1981. Operating parameters and baghouse performance data are summar- ized. The results of the fabric evaluation test are discussed. Pressure drop meas- urements are reported and pressure drop predictions for various fabric filters based on the experimental data are compared. Pressure drop predictions are compared with overall baghouse pressure drop. Good agreement between the predicted values and the actual measurements are reported. Measurements reported in the paper cover operation with three different coals. Reactivity of Fly Ashes in a Spray Dryer/Fabric Filter FGD Pilot Plant Wayne T. Davis Randal E. Pudelek Gregory D. Reed Department of Civil Engineering The University of Tennessee This paper summarizes the results of a study in which the reactivities of 23 fly ashes were evaluated in a pilot plant spray dryer/fabric filter sulfur dioxide removal system. The primary objective was to determine the ability of each fly ash (including lignite, subbituminous, and bituminous eastern and western ashes) to remove S02 when placed in a water-based slurry and atomized by a spinning disk atomizer into a spray dryer located on a slipstream from a stoker- fired boiler. Data are summarized in both tabular and graphical form including chemical kinetic data as well as S02 removal efficiency indicating the enhancement in efficiency resulting from use of fly ash. The SO2 removal efficiency ranged from 10 to 50% with only fly ash in the slurry. Section G—Plenary Session Fabric Filtration—As It Was, Has Been, Is Now and Shall Be Edward R. Frederick Technical Director Air Pollution Control Association Since the first baghouse patent issued in 1852, commercial filtration technology h,as progressed significantly with ad- vances in both collector design and in the performance capability of filter fiber and fabric. With the resulting extended and expanded service of fabric filters, critical issues have evolved concerning electro- static involvement. Even though the natural charges present on gas entrained particles and on the collecting media interact to play a major role in essentially all filtration operations, more intense interest and study is being devoted to electrical augmentation as a means for optimizing these features and, thereby, all collection parameters. These observa- tions have also stimulated further interest in and the production of new types of electrets, the electrified fibers that retain charges for extended service even under adverse conditions. Although zinc oxide was first suggested as an absorbent for S02 during the last century, more economic reagents now serve with fabric filters to control this emission contaminant commercially by dry and wet/dry scrubbing. Further ad- vances in this technology through the addition of special catalysts/additives and/or with special processing aids, increase SOz removal efficiency and also control NO, effectively. Normal use temperature filter fabrics are being improved and even better, although more exotic, high-temperature products are available. Improved process- ing, finishing and treating practices are in use to offer special value in extending bag ------- life, chemical resistance and cleanability. The major yet unheralded problem of nodule formation deserves special research consideration in view of the check valve effect that these "dingle- berries" have on the filtration process. Corrective measures for this condition and expansion of waste heat/product recovery and utilization will certainly lead to further expansion of fabric filtration technology for S02 as well as particulate matter control. F. Venditti. J. Armstrong, and M. Durham are with Denver Research Institute, Denver, CO 80210 Dale L. Harmon is the EPA Project Officer (see below). ' The complete report, entitled "Fourth Symposium on the Transfer and Utilization of Particulate Control Technology: Volume I. Fabric Filtration," (Order No. PB 85-161891/AS; Cost: $40.00. Set of three volumes PB 85-161883/AS; Cost: $95.50, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Air and Energy Engineering Research Laboratory U.S. Environmental Protection Agency Research Triangle Park, NC 27711 ft U.S. GOVERNMENT PRINTING OFFICE: 1985-55M16/27050 ------- ------- is Is a> I < »•« o <* aez rv> oo < «<, >» 30 »!• GDM-0 f"rn o "» a» -< O J» O CJ ** m o z N>-" * t-~L"T, V o?.-. &2°5 °M ,r3? 1? SS q -;!'g' ^ CO !£ cr •*> ------- |