Technical Bulletin No. 0057: An Economic Comparison of Precipitators and Bag Filters for Particulate Emission Control on Kraft Recovery Furnaces (AQTB)

For some time the paper industry has witnessed a steady increase in both installed and operating costs of electrostatic precipitators for kraft recovery furnace particulate emission control. With these cost increases occasioned by use of higher design collection efficiencies it was felt appropriate to determine whether the point had been reached where high efficiency bag filters had become cost competitive with electrostatic precipitators. The attached technical bulletin is based on an engineering report prepared by Rust Engineering Co. for the National Council reviewing and assembling currently available cost information on both emission control approaches. The report found that while considerable narrowing of the cost gap had occurred, capital and operating costs for bag filters were not as yet competitive with those for electrostatic precipitators. The report noted however that (a) current cost estimates for bag filters necessarily reflect the absence of actual field experience in the kraft industry, and the related fact that no competitive market for such equipment has therefore as yet been developed, and (b) other factors might lead to additional precipitator system costs, such as changes in rapping methods, and applications of additional control measures to assure absence of "snowing." Both these findings could therefore be expected to further reduce existing cost differentials. It would appear too that (a) if precipitator design efficiency ratings should continue their upward trend, or (b) if operating experience with high efficiency rated precipitators, and anticipated requirements for maintaining high level performance lead to upward revision in operating and maintenance costs, the reported cost differential may disappear completely. Based on these findings and observations the National Council is currently exploring the possibilities of undertaking pilot scale investigations of bag filtration to determine the necessary design features for insuring successful operation in this new application area, as well as the impact of such design features on bag filter particulate emission control system costs.