The present invention relates to a new and improved construction dispersion apparatus for the preparation of waste paper materials or simply referred to herein as waste paper.
Generally speaking, the dispersion apparatus of the present invention is of the type comprising a housing in which there is arranged a rotor which contains teeth arranged in substantially ring-shaped rows disposed concentrically with respect to the axis of rotation of the rotor. Between these teeth there are located tooth gaps. Stationary ring-shaped rows of teeth of a stator engage into the ring-shaped intermediate spaces between the rotatable rows of teeth of the rotor. The stationary ring-shaped rows of teeth of the stator likewise possess tooth gaps. The flow of the processed material or substance is accomplished through the tooth gaps of the rotatable and the stationary rows of teeth.
As is known in the papermaking art such type of dispersion equipment serves to disintegrate the heated waste paper which has been defiberized in upstream arranged devices and concentrated or thickened, for instance, to a 25% to 30% stock density and heated to about 95.degree. C. in a heating worm; and the thus obtained spurious or disturbing substances are comminuted.
With dispersing apparatus of the type upon which the invention is based it was previously conventional practice to flush the dispersed substance or material out of the equipment by spraying water through nozzles into the housing.
This flushing of the housing with water is associated with the following appreciable drawbacks:
On the one hand, there occurs a dilution of the substance or stock, i.e. its consistency, to a degree which is undesired in many instances. For instance, this is unfavorable if a bleaching operation is to subsequently occur, or, if there is required an intermediate storage or stacking of the material.
Furthermore, it can happen that there arises a pronounced bitumenous contamination of the fittings. Under the expression "fittings" or "hardware" as used in the context of this disclosure there is understood in this technology the rotor composed of different concentric rings and provided with teeth and the stator composed of different concentric rings and provided with teeth.
The pronounced bituminous contamination predominantly arises at the outer stator ring. The basis for such bituminous contamination is predictable owing to the cooling of the fittings, especially the outermost fitting ring by the housing flushing water. Part of the bitumen condensates and contaminates or soils the fittings and, on the other hand, can coagulate and form larger lumps or pieces which then can be flushed out of the equipment along with the dispersed substance or material.
A further appreciable drawback of the state-of-the-art equipment resides in the fact that for the removal of the substance or material there is needed additional equipment (i.e. water lines or conduits, regulation devices and nozzles).
Finally, it is further to be here mentioned that an additional danger prevails inasmuch as the nozzles tend to clog during the operation, particularly if, as is typically the case, there is used as the flushing water that water available at the plant which sometimes does not possess the requisite degree of purity. Even with only partial clogging of the nozzles there arises at least a reduced infeed of water which, upon clogging of the housing, can result in combustion of the dispersed substance or material due to the development of heat of friction.