Advanced Process Modeling Saves Money, 2001 Engineering / Finishing & Converting Conference Proceedings

D. Stropky, E. Bibeau, J. Yuan, M. Salcudean--Pulp and Paper process equipment is operationally complex, and design performance depends critically on how gases, liquids, and solids interact. Examples of these interactions include air and black liquor for recovery boilers, white liquor and chips for digesters, gas, oil, or coke and air for lime kilns, pulp fibers and water for headboxes, and biomass and air for power boilers. In these devices, various flow streams are introduced at prescribed velocities, resulting in complex interactions where convection and dissipation forces govern the internal process. Thermal gradients and chemical reactions occur that are dependent on the flow convection and dissipation forces. Processes are three-dimensional, turbulent, and can include heat transfer, combustion, species transport, and multiple phases. Many different designs have been promoted that have not met expectations. The motivation for developing and applying advanced process modeling to such equipment is to reduce the emphasis on trial and error by providing a more rigorous method to achieve sound design and optimized performance, with the end goal of reduced capital and operating costs. Process modeling yields flow, chemistry, and combustion details from which the effects of geometry, operating, and other design parameters can be investigated. This knowledge has been successfully applied to many different types of equipment. Examples include improved combustion air systems, significantly reduced pluggage, reduced down time, reduced environmental emissions, and productive investigations into corrosion mechanisms. Process modeling can also be used to increase a return on investment by better training operators, rapidly providing detailed process analyses various conditions, helping to solve or avoid future operational problems, and reducing the variation in operations between operator shifts. The objective of this paper is to describe what advanced process modeling can and cannot do, how it can be applied in pulp and paper mills, and also to highlight the cost-saving advantages and reductions in capital investment risks.