Dust Deposit Profiles in a High Velocity Pulse-Jet Fabric Filter

Dust deposit profiles in a pilot-scale pulse-jet fabric filter were measured using a beta gauge. Fly ash was collected on polyester needled felt bags, and the dust profiles were measured after the test system was operated to equilibrium at superficial filtration velocities of 50, 75,100,125, and 150 mm/s. The profiles measured show that a large mass of dust is retained on the fabric of a pulse-jet filter when operated at high filtration velocities. This dust mass retention can be caused by two mechanisms: the failure to remove dust from the fabric during a cleaning pulse, and the redeposition of suspended dust onto the fabric after a cleaning pulse. The dust deposit measured at the highest test velocity was found to be much different from the deposits measured at all other velocities. The deposit found at 150 mm/s had almost twice the average areal density and was more evenly distributed than the deposits found at lower velocities.     

The Potential of Pulse-Jet Baghouses for Utility Boilers. Part 2: Performance of Pulse-Jet Fabric Filter Pilot Plants

Pulse-jet fabric filters (PJFFs) are widely used in U.S. industrial boiler applications and in utility and industrial boilers abroad. Their small size and reduced cost relative to more conventional reverse-gas baghouses makes the use of PJFFs appear to be an attractive particulate control option for utility boilers. This paper (Part 2 of a three-part series) summarizes the results of pilot PJFF studies sponsored by the Electric Power Research Institute at different utility sites in the United States. The purpose of these tests is to evaluate PJFF performance for U.S. fossil-fuel-fired applications. These data are also used to corroborate the results of a recent worldwide survey of PJFF user experience, as described in Part 1 of this series. Part 3 will provide a cost comparison of PJFFs to other particulate control options such as electrostatic precipitators and reverse-gas baghouses.     

Performance of a Pulse-Jet Filter at High Filtration Velocity III. Penetration by Fault Processes

Performance data for fabric filters using either woven or felt bags can be better understood when fault processes such as pinhole bypass and seepage are considered. Penetration straight through the dust cake and fabric may not be important by comparison. Observed trends of increased penetration with increased filtration velocity, constant or slightly increased penetration with increasing particle diameter, and constant penetration with additional dust loading can be explained by fault processes. The pulse-jet experimental work described here, done over many filtration and cleaning cycles, shows that penetration increases substantially with increasing filtration velocity and that this increase is due entirely to seepage.     

Survey on the Use of Pulse-Jet Fabric Filters

Pulse-jet fabric filters rely on the filtration of dirty flue gas by the outside surface of the bags, which are then cleaned by a shock wave generated by an air pulse entering each bag from the top. As it travels down the length of the bag, the shock wave flexes the fabric and dislodges the dust cake. Enhancement of the pulse may be achieved by using a venturi, and cleaning may be on-line or off-line. This paper summarizes the results of an exhaustive study conducted for the Electric Power Research Institute to provide a convenient and versatile information base about the use of pulse-jet fabric filters on coal-fired boilers. Predominant features of the many pulse-jet installations identified by vendor survey and literature survey are shown in graphical and tabular form.     

Performance of a Pulse-Jet Filter At High Filtration Velocity II. Filter Cake Redeposition

Pulse-jet filter cleaning is ineffective to the extent that collected dust redeposits rather than falls to the hopper. Dust tracer techniques were used to measure the amount of redeposition in a pilot scale pulse-jet filter. A mathematical model based on experimental results was developed to describe dust transfer from bag to bag, redeposition on the pulsed bag itself, and migration to the dust hopper. Dust redeposition upon the pulsed bag increased markedly with increasing filtration velocity, whereas migration and redeposition on bags adjacent to the pulsed bag decreased. For high velocity pulse-jet filters to operate at lowest possible pressure drop, filter cake redeposition must be minimized.     

Effect of Dust Size Distribution on the Collection Efficiency of Pulse-Jet Fabric Filters

Recent advances in vehicle emission control technology have reduced the effectiveness of the conventional tailpipe test used In inspection and maintenance programs. A different approach Is being followed in Harris County, Texas (Houston area), based on identification and correction of misfuellng and tampering. Misfueling Is being identified by using a lead-sensitive test paper to detect lead deposits in the tailpipe that result from using leaded gasoline. Field tests of this procedure demonstrated that it Is reliable and accurate for the Intended purpose. The data also indicated the need to observe certain precautions to avoid contamination and other potential sources of error. This procedure and other emission-related checks have been added to the annual safety inspections. These tests are conducted on vehicles of 1980 model year and later, by approximately 1150 Inspection stations throughout the county that conduct annual safety Inspections. Experience with the first few months of this program has been excellent.     

Extending Fabric Filter Capabilities

It has been amply demonstrated that there are reasons for improving the collection of fine participates. Some areas of research and development which may prove fruitful in extending fabric filter capabilities have been suggested.     

Performance of a Pulse-Jet Filter at High Filtration Velocity I. Particle Collection

The fly ash collection characteristics of a pulse-jet fabric filter have been studied. Fly ash penetration was found to decrease as the dust deposit increased from 0 to 60 micrometers in thickness, to increase as face velocity through the bags increased from 5 to 15 cm/s, and to remain relatively constant for particles from 0.3 to 4.0 µm in diameter. Experiments employing chemically tagged fly ash were performed to investigate three dust penetration mechanisms. On resumption of filtering after cleaning, penetration by straight through dust loss declined rapidly from its maximum, reached a minimum, and then increased. Seepage of dust through the fabric was found to be constant throughout the filtration cycle. Dust lost as pinhole plugs increased after cleaning, passed through a maximum, and then declined. The pinholes appeared to open the way for further penetration by the straight through mechanism.     

Fabric Filter Technology for Utility Coal-Fired Power Plants

This is the fifth 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 describes research to improve reverse-gas cleaning technology, and to characterize reverse-gas sonic assisted and shake/deflate cleaning.     

Types of Fabric Filter Installations

The basis for evaluating fabric filters is examined. Properly applied and maintained fabric filters perform at highly satisfactory efficiency levels.     

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

This is the sixth and last part 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 discusses research, development and demonstration activities now underway or planned to further understand baghouse technology to ensure efficient, economic and reliable service in utility applications. In addition, it summarizes the major findings reported in Parts I through V.     

Third Conference on Fabric Filter Technology for Coal-Fired Power Plants

This paper summarizes information and results presented at the Third Conference on Fabric Filter Technology for Coal-Fired Power Plants held November 19-21, 1985 in Scottsdale, Arizona. Sponsored by the Electric Power Research Institute (EPRI), in cooperation with the Arizona Public Service Co. and Salt River Project, the conference focused on recent technological developments in the design and operation of fabric filters (baghouses) in electric utility settings. Papers were presented by individuals representing utilities, fabric filter manufacturers, research and development organizations, and regulatory agencies. Approximately 200 individuals attended the sessions. Summaries of the first two conferences and results of other fabric Biter research sponsored bv EPRI have been published previously in JAPCA.^1–9     

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.     

Fabric Filter Applications on Coke Oven Pushing Operations

Coke oven pushing emissions containing quantities of tars and dust require new approaches to adapt fabric filter collectors. This paper deals with the Wheelabrator/Taisei precoat filter systems being used on coke oven pushing operations. The Taisei test program and the filter installation at Tokyo Gas are discussed. The variables to be evaluated in the design of a fabric filter emission control system are examined.     

Effect of Ammonia Injection on Fabric Filter Pressure Drop

Experiments have been carried out to assess the effect of ammonia injection upstream of a small-scale fabric filter which collects ash from the burning of coal in Australia. The ammonia injection resulted in an increase in the pressure drop across the filter. This was apparently due to an increase in the cohesivity of the ash, which made dislodgement during cleaning more difficult. There were some indications that the ammonia-conditioned ash formed a more porous dust cake during the filtration cycle.     

Mobile Fabric Filter System: Design and Preliminary Results

In order to study the effects of fabric filter parameters when filtering an actual industrial effluent stream, it is necessary to vary these parameters in the field. A mobile fabric filter system has been designed, fabricated and operated to provide this information. The design characteristics and some preliminary field data collected with this system are summarized.