Mathematical Modeling and Simulation of Initial and Mechanical Dewatering of Paper Web in Paper Machine Sections

摘要

In the process of papermaking, the dewatering and drying of the paper web defines significantly the properties and quality of the final product. Modeling and simulation of the process steps involved offer insights into the mechanisms of water removal and sheet construction, which are not available from measurements and experiments. Thus simulation gives new impulses that can directly be used to improve and redesign processes and components. We present a modeling approach of initial dewatering of the paper suspension and mechanical dewatering of the preformed paper web which are essential process steps of papermaking. The chosen approach uses an in-house process simulation library that allows us to simulate complete sections of the paper machine. We follow a modular concept starting from individual flow and material transport modules that are then combined to larger units, e.g. suction boxes or a press nip. To ensure fast and efficient calculations, it is crucial to reduce the level of detail by defining effective parameters describing the important aspects of the materials. These parameters describing the mechanical and the fluid dynamical properties of the fiber web and paper machine clothing are obtained from the evaluation of high-accuracy tomographic imaging in combination with additional lab data using fast and efficient numerical analysis methods. Including also process variables, such as machine speed, press load, or applied vacuum we are able to simulate and optimize the dewatering process as well as the machine performance. Results include, amongst others, the dewatering at the individual elements or the final dryness of the sheet. We will highlight some examples where our modeling tools are used to speed up and to optimize our product development with respect to their area of application. For example, we are able to compare the dewatering performance of different press fabrics in combination with specific press concepts.