TOWARD CLOSED-CYCLE KRAFT - CANADIAN MILL CASE-STUDIES

Three case studies were developed for retrofit of closed-cycle designs into existing Canadian bleached kraft mills. These were based on a te chnical and engineering analysis of four partner mills. These mills pr esented a range of process and equipment ages from the 1960s to the la te 1980s. The case studies consider both integrated and separate bleac h effluent recovery from ECF and TF bleach plants. Development of thes e case studies indicated that, implementation of closed-cycle operatio n in existing mills may involve substantial capital costs, with the ca se study estimates at CAD 15-90 million (in 1995 dollars) per mill or US$ 216-415 per annual air-dried ton. For these case studies, the incr ease in operating costs was generally that required for servicing the cost of capital, asn other operating costs remained similar. Closed-cy cle operation appears feasible, although there are still a number of t echnical issues to resolve. These issues include pitch, scales, corros ion, and operating dynamics.