The hydrapulper was created in 1938 by Black Clawson Corporation (B.C.) in the United States. In 1959, B. C Company developed a Vokes Rotor, which could effectively shred waste paper but consumed high electricity. In 1973, B. C Company launched the Power Saver Vokes Rotor, which is still popular worldwide as the P. S type Vokes rotor. This type of rotor can generate strong reflux, resulting in high crushing capacity and low power consumption. Nowadays, various countries have their own hydrapulpers produced, but most of their rotor structures are improved based on the P. S type Vokes rotor.
The Importance of Hydrapulper in Pulp Production
The hydrapulper mainly plays the role of separating fibers in the broken process of waste paper, and also has the preliminary function of separating and removing major impurities. During the broken process, efforts should be made to maintain the original strength of the fibers to separate any debris attached to them. However, excessive broken of debris into fragments should be avoided to facilitate subsequent removal processes. Deinking also starts with the hydrapulper, where a de ink agent is added and matured to fully and dispersedly remove ink from the fiber surface. This is another function of the hydrapulper.
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Classification and Operation of Hydrapulper
Hydrapulper can be classified into vertical and horizontal, continuous and incontinuous, high consistency and low consistency.
The working principle of a hydrapulper is to use the water flow generated by a high-speed rotating rotor (with a circumferential speed of 900-1100m/min) to break down waste paper. Behind (horizontal) or below (vertical) the rotor is a sieve plate, with sieve holes of approximately 4-25mm in size, through which dispersed fibers are discharged. If the pulp is discharged while being crushed, it is called continuous, and if the pulp is discharged in one centralized manner after crushing, it is called intermittent. The winch device in the machine can hook onto impurities such as ropes, rags, iron wires, plastic films, etc. in the waste paper, and pull them out of the (winch) pulp surface to remove them. Coarse and heavy impurities are discharged from the heavy slag discharge outlet, and the volt type horizontal discharge is conducive to continuous slag discharge.
The vertical body has a high height and requires a vertical motor, which is inconvenient for maintenance and has high resistance to pulp discharge. The pulp residue is prone to cold sieving holes, and coarse impurities accumulate at the bottom, causing significant wear on the rotor.
The horizontal and vertical crushing functions are the same, with a low installation height. The horizontal rotor impeller and sieve plate are located on the side, while the slag discharge port is located at the bottom, without interference. From this point of view, the horizontal one is superior.
Intermittent mode can stably and uniformly control the degree of broken, such as when adding a de ink agent, it can ensure uniform and sufficient curing reaction time. If there is no dredging equipment in the subsequent process, the hydrapulper can spend more time further shredding until the fibers are completely separated, but this consumes more electricity. Intermittent operation requires stopping the machine for pulp discharge and cleaning, adding water for feeding, and then restarting the machine. This has a low utilization rate and can easily cause a decrease in fiber strength for fragile waste paper. It is not suitable for installing continuous slag discharge devices and is not very suitable for processing waste paper with excessive impurities.
The situation of continuous type is opposite to intermittent type. Impurities in the waste paper are less likely to be crushed in the machine, but the drawback is that it is not suitable for processing de ink pulp. After adding de ink agent, it cannot guarantee that the pulp of the unit stays in the machine for an equal time, which is not conducive to the stability of the de ink process.
The rotor of the high consistency hydrapulper is in a tower shaped spiral shape, which is an improvement on the basis of the P. S rotor, according to the stability of the upper process of the axial flow pump. The processing concentration has increased by more than twice compared to before. In the rotation of the spiral rotor, the pulp moves from top to bottom along the rotor surface, then is thrown from the lower part of the rotor towards the circumferential wall, and then moves upward along the groove wall. The upward pulp then moves downward again, experiencing the above cycle. During this process, the pulp is subjected to the strong vortex effect of the rotor. When passing through the bottom of the groove, it can generate high-strength turbulence, causing strong friction between fibers, which can shorten the disintegration time, facilitate the separation and dispersion of ink, save power consumption, save de ink chemicals, save heating steam, reduce hydraulic shear, avoid the fragmentation of impurities in the waste paper, and facilitate the removal during purification. Therefore, high concentration means excellent indicators such as high efficiency and low consumption.