Introduction to Simulation: Simulation Uses in Pulp and Paper Industry and Introduction to Building Models, 2000 Engineering Conference Proceedings

A. G. Kirkman--Computer simulation of processes has been available for decision-making in the paper industry for over 25 years. However, the continuing evolution of both the hardware and software for simulation has enhanced the availability and user-friendliness of simulation tools. Thus, there is increased interest in the paper industry in the use of simulation for process analysis and feasibility studies, from the mill-level to the corporate-level. These studies frequently result in an economic evaluation based on capital and operating cost requirements associated with a proposed mill modification. Troubleshooting a process and determining optimum strategies for mill efficiency, and environmental impact, as well as economics, may also be goals in a simulation project.

Most of the process simulation packages available in the paper industry are composed of a collection of unit operation models, which use the principles of transport, kinetics, equilibrium and conservation, etc. to describe mathematically common steps in a process, such as mixing, heating, and washing, etc. The models are put together like building blocks to represent a mill flowsheet. Data from the mill (e.g., production rates, chemical charges, temperatures, and operating efficiencies) are supplied to the models and the system mass and energy balances are calculated. The complexity of most systems, with recycle streams and interconnectivity being common throughout the pulping/bleaching, recovery, and papermaking processes, requires the use of a computer for solution of the material and energy balances. From the results, the user can determine stream flows and characteristics throughout the flowsheet for current mill conditions, and predict the system’s behavior under modified conditions. This quantitative approach allows for a more informed decision-making process to occur.