Process for recycling waste paper

US5358605A · kind A · utility

Assignee

• J.M. Voith GmbH · DE

Inventors

• Hans-Dieter Dorflinger · Heidenheim, DE
• Michael Schwarz · Klagenfurt, AT

Key dates

• Filing date: Mar 3, 1993
• Grant date: Oct 25, 1994
• Expiry date: Mar 3, 2013

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y02W30/64
• WIPO field: Textile and paper machines
• WIPO sector: Mechanical engineering

Abstract

The invention concerns the recycling of waste paper in a deinking process with flotation with at least one other cleaning stage downstream. According to the invention, selective flotation is performed in multiple stages. After no more than a third flotation stage, the flotation foam collected up to that point is removed and purified by means of flash flotation, which produces sludge, clear water and separated foam that contains the contaminants from the waste paper feed. Subsequently, the sludge is removed from the paper recycling process. Large impurities are removed from the sludge (foam) (except for the foam from up to the three last stages) in up to two washing units (including thickeners) or screen units. The fibers are then separated from the relatively fine contaminants, and these contaminants are primarily removed as sludge from the resulting low-fiber fractions by flash flotation. The fiber-containing fraction and the clear water from flash flotation is recycled to a point prior to the selective flotation system.