Processing of waste paper - using recycled water from paper machine with waste water treatment system

摘要

The process comprises, (a) prefloatation; (b) washing and/or thickening; (c) comminution and detachment of residual unwanted and non-fibrous components; (d) oxidative and/or reductive bleaching in the high-and/or medium- consistency region at elevated temp.; (e) removal of printing ink and other unwanted components by subsequent flotation, washing and/or thickening; (f) purificn. of the washing and/or thickening filtrates by expansion flotation (terms not defined) after adding flocculating agents; and (g) subjecting the washing and/or thickening filtrates from step (f) to further water purificn.. Pref. step (g) is effected by pptn./flocculation, adsorption, microflitration and/or ultrafiltration, opt. followed by reverse osmosis. Step (c) is effected in a dispersing machine. Step (d) is effected with peroxide, Na dithionite or formamidine sulphinic acid (FAS). When FAS is used, the FAS/alkali ratio is sufficient to give a final pH of 6.5-7.5, esp. 6.5