Pulp & Paper - Paper Mill
Paper Machine Wet End
From the dilution loop at the fan pump, the stock flows to cyclone cleaners and then pressure screens. Mag meters are located on the rejects; this is a noisy application that impacts paper quality.
The cleaners are checked for plugging with our pressure transmitters placed before and after.
From there the stock flows into the head box, which has a specific construction to keep the fibers uniformly mixed without clumping.
The stock flows onto a wire at a specific rate, ratioed to the speed of the wire. Water drains first by gravity, then by foil boxes that create a slight negative pressure.
Vacuum boxes follow, to gently pull the water out as it becomes less “free”. The end of the wire wraps around a couch roll that has a stronger vacuum. At this point the web of paper is transferred to a felt. It transitions smoothly because the felt is rougher than the smooth wire.
The felt moves the paper through the press section, where the water is pressed out. From here the water must be evaporated in the dryer section, on the dry end of the machine.
Under the machine, in the basement, is a whole other process of white water. There is a tremendous amount of water used in this operation, especially considering the stock flow is 99.5% water going onto the wire. It all falls into the wire pit, and is recycled by diluting the thick stock in the basis weight loop.
The save-all system reclaims the fibers for use in the broke system, while the whitewater is used for dilution. The whitewater and save-all systems will include a mag meter application, and our standard mag is fine.