Dynamic Simulation of Dewatering in High Vacuum Flat Boxes, 1998 Engineering Conference Proceedings
A dynamic simulation model of a flat box was used to interpret data from a series of pilot and commercial trials on the flat box section of the forming wire. The flat box model is based on flow through compressible porous media with constraints due to surface tension forces in the pore structure. Conditions included vacuum, dwell time, speed, basis weight, length and arrangement of slots, temperature and freeness. The pilot data indicated that the ultimate solids leveled off regardless of the dwell time and the sheet dryness increased with increasing vacuum. Increased basis weight slowed drainage but did not reduce the maximum solids. Increased temperature increased final solids by 3.5 % per 100 C. The maximum achievable solids appears to be limited by inability of the vacuum to displace water from the smallest pore due to surface tension forces. The model was validated for the variables in the analysis.
Dynamic Simulation of Dewatering in High Vacuum Flat Boxes, 1998 Engineering Conference Proceedings