Homework 3 Handout Problem

For the paper machine (see figure below) a stock suspension of cellulose fibers in water enters the continuous refining system at 4% consistency (4 lb fiber/100 lb mixture) . A dry clay filler is added to the system, and the slurry is then sent to the headbox. The headbox distributes the suspension of fibers and clay evenly over a wire belt to form a thin sheet, which becomes paper after it is dried. In the headbox, the slurry is diluted with a recycle stream of white water that passed through the wire belt during formation of the sheet, to a consistency of 0.5%. It is known that the filler consistency is also 0.5% at this point. The damp sheet leaving the press section and entering the drying section, where water is removed with heat, contains 33.3% solids that consists of 90% fiber and 10% filler. Excess white water not needed in the headbox is discarded.

Assume no fiber loss and calculate:

x The over all % filler retention on the wet sheet

x The % filler retention per pass (on the basis of the total filler that can be retained)