Tetra Pak is inserted through a conveyor (pos. 1) to a vertical pulper MCV-20 (pos. 2). In main pulper (pos. 2) fibres are separated from foils; The accept from MCV-20 is pumped by pump N1 to chest B1. The rejects pumped with a special pump to washing pulper pos. 3, from which fibres stock pumped at a low consistency to the chest B1, where is mixed with an accept from the main pulper pos. 2. It will be better if the size of chest B1 was a little more, because in this chest suspension are mixed cyclical at a different consistency and larger volume of chest will better compensate these jumps of consistency.
The pulper is operated in an intermittent mode supervised by a crew. In this control mode there are reached better quality results than in an automated one
The fibres suspension in the chest B1 contains foils and impurities having passed through a pulper screen bored Ø 12mm.
Foils, has not passed through the washing pulper screen (pos. 3) is pumped to Reject thickening node.
Due to the pulping node operation nature there spasmodically appear high water volumes to be accumulated in a suitable vat.
The stock is pumped to HD cleaner pos. 4, where sand and specific coarse impurities are separated. Washing separators pos. 5 with plates screen with boring d-1,8 mm are washed most of the remaining foils. These foils in a periodical mode is pumped to Reject thickening node.
Accept are passed through level-tank to Fine screening node.
The node is operated automatically depending on levels in chests before and after the node.
Pressure screen pos.6 removes on a slotted screen #0,20 mm fine foils and non-pulped fractions; these rejects are pumped to pressure screen pos. 7 with slotted screen #0,20 mm. Accept from Fine screening node is pumped to thickener pos. 9. On the second stage the line will be divided between thickener pos.9 and a belt press pos. 8; during replacement of a pan of the belt press pos. 8 stock, in a small quantity is recirculated through the level tank.
Rejects after last pressure screen pos.7 are pumped to the reject thickening node, where they are dewatered and washed. Dewatered impurities leave to the container. Accept after a last stage of fine screening is pumped back to a chest (level-tank) before a fine screening node for rescreening.
Reject thickening node
Reject thickening node consist of two dewatering drums and one vibrating screen. In each node of stock preparation line is used screen with different diameter of holes and a different type of dewatering equipment. Foils from pulping node are dewatered and washed on the Dewatering drum pos. 10 equipped with a screen with holes Ø8 mm, foils from primary screening are dewatered on vibrating screen pos.12 equipped with a screen with holes Ø2,5 mm and reject from fine screening are dewatered in the drum pos.11 equipped with a screen with holes Ø3 mm. Foils from primary screening may be used and further processed. So it is separated from the reject from the fine screening. If there is no need to separate reject after primary and fine screening, they can be dewatered in one dewatering equipment (usually dewatering drum).