Fourdrinier papermachine

This discussion will be eonfined principally to the well-established Fourdrinier papermachine and will only touch upon twin-wire machines that are now common in the industry. 

Figure 13.20. (a). Fourdrinier papermachine. (b) Drainage effects of foils and table rolls. 

Modem papermachines are eomplex items. The greater the eapaeity of the maehine (width and speed), the fewer the grades produced newsprint maehines ran at speeds in exeess of 30 m s The prineiples of papermaking are basieally simple and are illustrated in Figure 13.19 whieh relates to the Fourdrinier papermaehine. 

At the end of the Fourdrinier wire a couch roll removes more water from the web before it is transferred to the press section. At this point the moisture content of the web is about 80% water (20% consistency, 200g/L). The white water from the Fourdrinier is continuously recycled 1000 kg of stock at 0.5% consistency is reduced to a 25 kg mat (5 kg fibre, 20 kg water) by the time it leaves the wire and 975 kg of white water is recycled to the make-up chest and thence back to the headbox. A 500 tonne a day papermachine recycles some 100 000 m of water a day. 

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