Long-Term COHPAC Baghouse Performance at Alabama Power Company’s E. C. Gaston Units 2 & 3

Abstract

Following a successful pilot-scale baghouse testing program and after reviewing the performance of Luminant’s COHPAC (EPRI’s patented Compact Hybrid Particulate Collector technology) baghouse installation at its Big Brown Station, Alabama Power Company (APCO) decided to install a COHPAC baghous on Unit 3 at its E. C. Gaston Steam Plant located near Wilsonville, Alabama in late 1996. A second COHPAC baghouse was installed at Gaston Unit 2 in 1999. These baghouse systems were designed with the low pressure/high volume pulse-jet cleaning technology (Hamon Research-Cottrell) that orients the bags in concentric rings and uses rotating pulse manifold arms. Performance of these systems at Plant Gaston Unit 3 and Unit 2 has been excellent during the past eleven and a half and nine years, respectively, Original 3.0 and 2.7 denier Ryton felted fabries have given way to higher permeability 7.0 denier PPS felt bags in both units. Overall flange-to-flange and tubesheet pressure drop performance has improved without compromising particulate collection efficiency. Recent filter drag values of 0.5 in. H₂O/ft/min on Unit 3 and 0.3 in. H₂O/ft/min on Unit 2 have been experienced at air-to-cloth values of 8.0 ft/min. Average pulsing frequencies have ranged from 0.2 pulses per bag per hour for recently installed 7.0 denier PPS felted bags up to 0.7 pulses per bag per hour for older 2.7 denier Ryton felt bags. COHPAC baghouse installation has successfully reduced stack opacity. Comparing the average of the last eleven years of operation (1997–2007) to the average of the two years prior to COHPAC baghouse installation on Unit 3 (1995–1996), the average opacity has been reduced 50% and the number of hours per month that the average opacity has exceeded 20% has been reduced 95%. Similar results have been experienced on Unit 2. Except for early bag failure episodes on each unit caused by bag-to-bag abrasion, bag life has been very good. The original 3.0 denier Ryton felted bags in the rear modules of the Unit 3 baghouse remained in service for five years accumulating over 39,500 hours of exposure to flue gas with few bag failures. Front module bags in Unit 3, however, had much shorter bag lives because of a higher incidence of bag failures. Average service lives for the 3.0 and 2.7 denier filter bags were similar to those of the follow-on 7.0 denier PPS felted fabrics, typically two to three years, 19,000 to 27,000 hours of exposure to flue gas. Evaluation of the performance of various test bags has been ongoing for several years. Early tests compared the performance of 6.0 denier and 7.0 denier PPS felts with traditional 2.7 denier felts. 7.0 denier felted fabries performed very well. More recently, various dual-density felts have been tested. Results after 20,000 hours of flue gas exposure indicate that the Dual Density Torcon- 9058 felt is the best of the four test fabries. The test program is continuing. COHPAC baghouse performance for Alabama Power Company has exceeded expectations and continues to provide an excellent air pollution control benefit.