Irving Pulp and Paper Recovey Boiler Upgrade: Advanced Design Techniques to Increase Capacity and Improve Cleanabiity, 1997 Engineering Conference Proceedings

The Saint John mill is owned and operated by Irving Pulp and Paper Ltd. In New Brunswick, Canada. Prior to 1996, the recovery boiler was experiencing excessive fouling and plugging of convective surfaces with suspension firing. The owner naturally wanted to improve performance, but at the same time wanted to increase black liquor throughput by 10% to 1580 tonnes of dry solids per day.

A review of other operating units was done to determine the overall design parameters of the air and liquor systems Numerical modeling was used to further improve understanding of unit design and operation, and factors which influence combustion performance and cleanability of the boiler. Several new tertiary air designs were evaluated. Design and operational modifications for air and liquor systems were selected that minimize the potential for fouling and plugging of convective surfaces. Based on combustion and flow modeling results, B&W upgraded the furnace with a new tertiary air system. An arrangement of seven tertiary air ports was installed and a “perimeter firing" strategy using four wedged nozzles was implemented. The modifications were completed and the unit went back online in September 1996. Since then, there has been a significant improvement in the long term cleanability of the boiler, ease of operation and stability of the lower furnace.

This paper describes advanced design techniques used toimprove boiler performance : including numerical modeling results and boiler operating experience before and after changes in design and operation. The modifications have made a significant improvement in the cleanliness of the unit by reduction in the amount of carryover and improved the uniformity of flow and temperature distributions entering the convection pass. Modeling results are generally confirmed by boiler test results and recent operating experience.