Increasing the degree of whiteness of fiber suspension obtained from waste paper, comprises dewatering the fiber suspension and partly charging the surface of the solids contained in the filtrate with calcium carbonate in chemical reaction

摘要

The method comprises dewatering (6) a fiber suspension in a worm extruder or a pressure sorting device so that a filtrate (F6) has a mass-related solid content of 1% and partly charging the surface of the solids contained in the filtrate with calcium carbonate in a chemical reaction with carbon dioxide. The filtrate formed during dewatering is treated in a dissolved air flotation plant (9) in such a way that formed thick matter (12) is loaded with calcium carbonate. The carbon dioxide is added in gaseous manner. Before the dewatering, the fiber suspension has a consistency of 0.5-2%. The method comprises dewatering (6) a fiber suspension in a worm extruder or a pressure sorting device so that a filtrate (F6) has a mass-related solid content of 1% and partly charging the surface of the solids contained in the filtrate with calcium carbonate in a chemical reaction with carbon dioxide. The filtrate formed during dewatering is treated in a dissolved air flotation plant (9) in such a way that formed thick matter (12) is loaded with calcium carbonate. The carbon dioxide is added in gaseous manner. Before the dewatering, the fiber suspension has a consistency of 0.5-2% and is cleaned in two successively connected flotation plants by printing ink particles. The thick matter is mixed with the loaded solids (15) and is dispersed and bleached. The solids consist of greater than 50% of fillers.