Fractioning in deinking plants - a new path in waste paper preparation

The development of waste paper preparation systems up to todays installations took place in different stages. At the beginning the processed wastepaper was only used for low paper grades. By consistent development of the machines and systems, like screening, dispersing, and in special flotation, the use of the processed waste paper was extended to papers with highest quality demand. Due to the high demands on the final stock, the complexity of the machines increased constantly. Nowadays lines are equipped with several screening and cleaning stages, pre- and post flotation, and up to two dispersing systems with oxidative and reductive bleaching stages to achieve the required final stock properties. This means beside high investment costs also high operating and maintenance costs. Strong competition within the paper industry results in increasing pressure on the equipment suppliers to develop machines and systems with low investment and operating costs but with improved technological features. This challenge has been accepted by Andritz. The fractionation concept, already successfully installed in packaging grade systems, was adjusted, further developed for deinking line applications, and finally integrated in the process. In this case the task is much more complex as in the field of packaging grades. In deinking lines not only the cleanliness of the stock with regard to stickies and cubic impurities is important, especially optical properties like brightness, dirt specks and bleachability of the stock are a big challenge for the de-inking process. This paper describes different operating alternatives in a deinking line with fractionation; the pre-conditions, limitations, and comparisons between investment and operating costs are explained. Furthermore, results of the first installation in a European Paper Mill, which started up successfully in summer 2005, are presented. The excellent results in this mill and the interest of the paper industry prove the importance of this development as a further milestone in the recycling process set by Andritz: fractionation will be used more and more often in future deinking systems.