1、 中文 1973 字 Deinking Primer Pulping Mika Krkk & Ossi Laitinen FIBRE AND PARTICLE ENGINEERING LABORATORY 2008 2 CONTENT 1 Objectives of pulping 3 2 Equipment used 3 2.1 Vat pulpers 4 2.1.1 Low consistency 4 2.1.2 High consistency 4 2.2 Drum pulping 5 3 References 7 3 1 OBJECTIVES OF PULPING Objectives
2、 of pulping can be considered as defibering as well as detaching ink and other impurities of collected papers. Defibering should be as complete as possible i.e. only low amounts of flakes should be in the suspension for avoiding fibre losses during screening. Removal of large particles (plastic back
3、s, cans, etc.) is normally included in a continuous pulping process, while the removal of finer particles is performed in a coarse screening stage to avoid damages in the downstream process. In batch pulping applications large non-fibre material can be purged after the pulper has been emptied. 1 Det
4、achment of ink and other impurities from collected paper should be as complete as possible for making their removal possible in screening and flotation stages. Despite having complete detachment as a goal, at the same time, large ink particles detached from fibres (dirt specks) and adhesive material
5、s (stickies) should be in a size as large as possible for efficient removal during the screening stage. Additionally, care should be taken to avoid excess ink fragmentation, because ink removal in flotation lowers and the probability of ink redeposition increases. 2 EQUIPMENT USED Basically, two dif
6、ferent pulper types (vat and drum type) are used. Vat pulpers are equipped with a rotor in a tank which transfers mechanical energy to pulp suspension. The transferred energy creates shear that defibers, detaches ink and fragments particles. High consistency vat pulpers are typically called helical
7、pulpers due to their rotor shape. The drum pulpers comprise of a rotating vessel equipped with lifters on the inner surface of the drum that raises pulp suspension until the lifter turns upside down (due to rotatory motion) and the pulp falls. Low consistency vat pulpers equipped with a junk trap and drum pulpers can be operated in a continuous mode, while high consistency vat pulpers are normally operated in batch mode (Figure 1). Figure 1. Pulper types available for slushing recycled fibres.2
