Towards Closed-Cycle Kraft; Canadian Mill Case Studies, 1996 Pulping Conference Proceedings

Peter Gleadow

Calvin Hastings

H.A. Simons Ltd.

Brian Richardson

Mike Towers

Vic Uloth

Pulp and Paper Research Institute of Canada

Three case studies were developed for retrofit of closed-cycle designs into existing Canadian bleached kraft mills. These were based on a technical and engineering analysis of four partner mills. These mills presented a range of process and equipment ages, from the 1960s through to late 80s. They involved consideration of both integrated and separate bleach effluent recovery from ECF and TCF bleach plants. Development of these case studies indicated that implementation of closed-cycle operation in “existing” mills may involve substantial capital costs, with the case study estimates at 75 to 90 million 1995 Can$ per mill or $2 16 to $415 per annual ADt. For these case studies, the increase in operating costs was generally that required for servicing the cost of capital, as other operating costs remained similar. Closed-cycle operation appears feasible, although there are still a number of technical issues to resolve. These include issues involving pitch, scales, corrosion and operating dynamics.