Rotary paper-mill sludge incinerator with a waste heat boiler. Offline pulse-jet (1,176 bags) baghouse used to control particulate emissions. In addition to sludge, other fuel additives consist of polypropylene diapers, corrugated paper, and waste wood at a ratio of 220:5:5:5. Design inlet grain loading is 0.5 gr/acf at 95,000 acfm at 450°F. Gas-to-cloth ratio is 3.69 gross; 4.42 net. 125 mm btu/hr. Bags are nominal six inches in diameter by 14 feet long.
Conventional woven Teflon® B fiberglass fabric filter bags operated at above design particulate emissions (greater than 20 percent opacity) at start-up with a pressure differential of eight inches w.g. versus a design of six inches. The unit operated at 15 inches w.g. in an attempt to build a dust cake to reduce emissions. Precoating was also unsuccessful in controlling bleeding. Dust impingement was found to be responsible for some sewing thread failures. Although this problem was identified, its severity was unknown.
Installed a complete set of GORE® membrane/Teflon B fiberglass fabric filter bags with some inlet-baffle modifications.
The opacity reading (zero percent) dropped below the required limit (20 percent) while the gas flow volume remained at or above design levels with a significant reduction in tubesheet pressure differential (3-4 inches w.g.) with a substantial reduction in compressed-air requirements.
After approximately four weeks of operation, increased opacity readings suggested premature bag failures. The premature bag wear was a result of high velocity dust impingement upon the filter bags.
Since the abrasion problem had previously been recognized, modification steps were expedited. A new set of GORE® membrane/Teflon B fiberglass fabric filters bags were installed.
To date (eight months), the pressure differential operates between three and four inches w.g. (net) at the design gas volume and steam production rate. Emission testing showed the unit operates 7.7 times lower than the required standard.
TEFLON is a registered trademark of E. I. duPont de Nemours & Co., Inc.
Not for use in food, drug, cosmetic or medical device manufacturing, processing, or packaging operations