Classifying – separating – and assorting solids – Treatment subsequent
Patent
1997-09-03
1999-12-07
Nguyen, Tuan N.
Classifying, separating, and assorting solids
Treatment subsequent
209 121, 209 17, 209725, B03B 700
Patent
active
059968060
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a method and apparatus in the treatment of the fiber fraction exiting from treatment of recycled fibers, and/or from vortex cleaning of a paper mill as mill reject, and/or in general a fraction exiting as a mineral-containing reject. As known, sources of recycled fibers include, for example, so-called broke of a paper machine, which may be recycled as raw material, and the actual post-consumer waste paper and board. The present invention especially relates to the treatment of recycled fiber materials of this kind in such a way that the fillers contained in the materials may be recovered as completely as possible and returned to the process as efficiently and economically as possible.
In the short circulation of paper machines manufacturing filler-containing paper grades and especially coated paper grades, a substantial amount of mineral and pigment fraction is discharged nowadays from the process as mill reject of a vortex cleaning plant which as a material could be utilized as raw material for paper but the particle size of this material is too coarse. Another source of mineral-containing rejects in a paper mill are filler and coating pigment manufacturing processes and the flushing waters from the apparatus used in these processes.
In the short circulation of paper machines manufacturing SC grades and other filler-containing grades, the mineral fraction exiting the vortex cleaning as mill reject is the coarse portion of the mineral fraction, i.e. the filler, supplied in the pulp dosing and usually having a particle size of over 10 .mu.m.
In the short circulation of paper machines manufacturing coated paper grades, the mineral fraction exiting the process as mill reject mainly contains non-dispersible coating layer of coated broke. The coating layer has not dispersed in the broke dispersion system to particles fine enough. This fraction of the coating layer, usually having a particle size of over 10 .mu.m, is rejected in the vortex cleaning of the short circulation.
The same applies also to systems for recycled pulp, in which coated magazine paper or like heavily coated raw material for recycled paper is used as the raw material. In the defiberizing system for recycled pulp the coating layer of the coated paper is detached from the fiber layer of the paper itself more of less in sheet-like fractions, which become partially crumbled in the process. The crumbling and dispersion are, however, not complete and thus, these non-dispersed coating pigment particles are discharged from the process as reject of the vortex cleaning in the screening stage of the recycled pulp line. However, in view of their raw material composition, a major part of these particles would be usable in the paper manufacture as filler which may have to be added to the pulp suspension at a later stage in the paper manufacture. The size of these particles, however, will cause problems in the paper machine itself if the particles are not dispersed and thus made usable as filler.
In an arrangement according to the invention, the filler/mineral loss exiting as mill reject from the vortex cleaning process and/or as reject from the manufacture of filler or coating pigment is reduced by treating the fraction having a concentrated mineral content in the vortex cleaning plant in order to disperse the mineral fraction and to return it to the process.
The method and the apparatus of the present invention provide for example the following advantages: possible. Only the useless fraction and the fraction that cannot be processed into a usable form are discharged in a highly concentrated form. suspension; in other words mechanical wear is minimal. carried out with commercial apparatus, repayment period is short. systems by collecting mineral-containing rejects from various sources and by adding in the process, for example, subsequent to the last cleaner step or inside the cleaner plant, a screen to fractionate the mineral fraction and the organic fraction, and a cleaner of a new t
REFERENCES:
patent: 4167438 (1979-09-01), Holz
patent: 4332638 (1982-06-01), Mauer et al.
patent: 5112444 (1992-05-01), Henricson et al.
Ahlstrom Machinery Oy
Nguyen Tuan N.
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