The separation of pulp fibers from foils represents the biggest problem of all and there are only a few paper technologies which more or less succeed in solving this problem. There is usually no problem to get pulp fibers of sufficient purity for their processing in a paper mill, but the foil fraction is usually too impure to use it as a secondary raw material for recycling. This reality is also highlighted by the fact that economic Tetrapak processing has been carried out in relatively high-capacity lines so far, and the lack of it for capacity utilization has been eliminated by adding common waste paper which brings other kinds of impurities into the system leading to complete devaluation of foil fraction.
A unique task
Within its environmental development programme, the corporation ACC in Ukraine, Eastern Europe, asked PAPCEL, specialist paper industry supplier based in the Czech Republic, to help them with a unique task: to create an almost zero waste technology from drinks packaging processing at its paper mill, Kronex Ukraine in Zmiyev. The line output had to be as efficient as possible, consisting of pure pulp fibers intended for further processing at the paper mill and a foil fraction of a maximum impurity of 1 % of the residual pulp fibers. The waste was made up by heavy impurities in raw material and a small amount of water which was biologically cleaned. Task definition was further influenced by the real occurrence of Tetrapak packaging in the Ukraine and was designed for a line capacity of 15 - 20 tpd.
The designed technology was based on long-term experience of both partners with waste paper processing. Firstly it was tested in PAPCEL's plant and then put into practice at the Zmiyev paper mill. The auxiliary machines were provided by the customer while press for fiber dewatering was made by Vanex. The whole line worked in accordance with the flow sheet shown on figure1.
The raw material is pulped in a periodically working pulper (LCV-14) at high consistency. After fiber discharge the remaining foils fraction is washed in the pulper and drained into the dewatering drum (OBN-10), where it is washed and dewatered for the last time. The pulped fraction of cellulose fibres continues through the high density cleaner (SVS-20) into the washing reject screen (VSV-30). This reject screen works in periodical mode and in first cycle it sorts fibres through the screen with holes of diameter of 1.8 mm, then it deflakes the unpulped pieces of cellulose, eventually cleans the remaining fibers stuck on the foils, then it washes this material and finally discharges the remaining foils with water on the vibrating screen.
The dewatered foils together with foils from the dewatering drum continue into the foil container and subsequently into the packing press. The cleaned fibrous fraction goes into the Vanex press (VX-20-VT) connected with the palletizing equipment. All water circulates in several circles and is used for pulping as well as washing according to the content of the impurities. The line runs almost completely automatically (except for manual handling with raw material and products), and is controlled by an AMIT system supplied by Veroz based in the Czech Republic. The operator only gets involved in controlling the pulping process and checks the work quality of the rest of line.
The line produces an average of 15 tonnes/day and fulfils the quality demands of the project. However, line modernization is an ongoing project which includes improvement in the pulp fraction separation by the means of slot-screening and there is a plan to double the capacity of the line in the near future.