BAGHOUSE OPTIMIZATION AT A MEDICAL WASTE INCINERATOR

Phoenix Services, Inc., owns and operates the Baltimore Regional Medical Waste Incinerator in Baltimore, Maryland, USA. New regulations for dioxins and furans imposed emission limits considerably below historical emission levels. Therefore, the company had to consider available technologies for dioxin/furan control. After tri- als with different technologies, Phoenix Services, Inc., decided to replace their woven fiberglass filter bags with expanded polytetrafluoroethylene (ePTFE) membrane catalytic filters. This new membrane/catalytic filter system collects fine particulate matter on the surface and destroys dioxins and furans in the gas stream. This catalytic filter system offered several key advantages to Phoenix Services, Inc.: 1) destruction of dioxins and furans instead of adsorption on a catalyst surface; 2) no dioxin-filled residue to dispose of; 3) a passive system requiring minimal operating and maintenance attention; 4) no new capital equipment; and 5) a minimal learning curve. Although Phoenix Services was getting superior PCDD/F reduction with the new membrane/catalytic filters, the supplier of the new filters wanted to optimize the system to make it as cost effective as possible. The system economics were based on an expected filter life of five years, so bags were removed for analysis on a periodic basis to assure this goal would be met. It was also expected that by adjusting the cleaning system, the amount of absorbent material used for acid gas scrubbing would be reduced. While the filter replacement cost represented a significant expenditure at some future date, the scrubbing agent was by far the largest variable expense in the oper- ating budget. After installation of the ePTFE/catalytic filter system in June 1999, and upon recommendation by the supplier, Phoenix Services refurbished the filter bag cleaning system of the baghouse. This was completed in September 1999. It was immediately noted that the membrane filter media operated with different ∆ P characteristics than the glass bags. By October there was a dramatic reduction in scrubbing agent consumption. It became apparent that the reduc- tion was due to decreased filter bag cleaning. The results showed a reduction of more than 20% in adsorbent use. Further analysis was performed to determine the effect of waste composition on these results. Four years of data were investigated to confirm changes in scrubbing agent consumption. Even though the plastic (high chlorine) fraction of waste continued to increase, there was about a 33% reduction in adsorbent cost. The company saved over $100,000 in the first year of operation and reduced PCDD/F emissions by an order of magnitude, well within the new regulatory limits. This paper discusses the actual step-by-step optimization process. The procedures could be useful for process/maintenance/production engineers and/or managers for a Municipal Solid Waste, as well as Medical Waste, Incinerator facility. This paper is aimed at providing actual data from the plant, giving a factual view of new products and their benefits to the plant.