Technical Bulletin No. 0860: Pulp Mill Process Closure: A Review of Global Technology Developments and Mill Experiences in the 1990s

This report provides a summary of the pollution prevention and effluent minimization (so-called “process closure”) technologies developed and implemented during the 1990s whose impacts have been to reduce the generation and discharge of waste materials from pulp manufacturing operations. It focuses primarily on bleached kraft pulp mills, but includes information on mechanical and sulfite pulping processes. The report includes a description of important technologies and a review of operating experiences of mills that typify the state of the art in one or more areas of process closure. The most notable developments have been the widespread adoption of extended and oxygen delignification, the use of modern washing and screening technologies, and the development and implementation of chlorine alternative bleaching systems. Recovery of a portion of bleaching filtrates at several mills is another significant development, although the substantial costs and impacts on operations attributable to such closure have kept this from becoming mainstream technology. Reducing mill process liquor spills and leaks through improved management and control systems is often noted as a key cost-effective component in minimizing pulp mill wastewater loads.