Many of the paper machine run-nability problems that are difficult to detect, monitor, and control are caused by hydrophobic particles. These can be, for example, binder-rich particles in coated broke, wood pitch or stickies associated with recycled fiber. The most important characteristic indicating propensity for runnability problems has proven to be the size, or the increase in size, of hydrophobic particles.1,2 The concentration of wood fibers and fillers at the wet-end of a paper machine is typically less than 1%. Hydrophobic particles move freely in diluted water loops but can agglomerate due to hydrodynamic forces. As the agglomeration of these particles proceeds in the wet-end of the paper machine, a critical size of agglomerate is reached. At this point, the larger particles may start to cause deposition on the paper machine.
展开▼
