Classifying – separating – and assorting solids – Fluid suspension – Liquid
Patent
1980-04-21
1982-05-25
Hill, Ralph J.
Classifying, separating, and assorting solids
Fluid suspension
Liquid
209170, 162 4, B03D 124, D21B 132, D21C 502
Patent
active
043315348
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of and an arrangement for the de-inking of pulp suspensions by means of flotation, wherein the pulp suspension which is laden with air is introduced in a flotation cell, the foam forming on the surface of the pulp suspension is removed together with the impurities and the purified pulp suspension--accept--is drawn off.
The purification of pulp suspensions, as they are generally produced from waste paper, has been the state of the art for a long time. Conventional methods operate in such a way that, in a trough which is equipped with a porous plate in its bottom region, compressed air is applied underneath this plate which compressed air passes through the pulp suspension above the plate in the form of air bubbles, so that the dirt particles can cling to the air bubbles and be carried to the surface of the trough together with the air bubbles. The pulp suspension is continuously conducted through this trough and the foam accumulating at the surface of the trough is paddled, sprayed or blown off. The statistical probability that a dirt particle can deposit on an air bubble in these known units is about 50%, because it is not ensured that the entire pulp suspension flow introduced into the trough is intimately mixed with the rising air bubbles. In order still to obtain a satisfactory purification of the pulp suspension, generally 10 similar cells are connected in series; the pulp suspension must flow through all of these cells before approximately the whiteness of the unprinted raw material is reached.
In order to reduce these significant expenses, in German Offenlegungsschrift No. 27 12 947, a de-inking tower has already been proposed in which the pulp suspension must initially pass through a mixing chamber before it reaches the actual flotation cell. In this mixing chamber, to which compressed air and pulp suspension are admitted, the pulp suspension passes through a controllable gap which is characterized by a porous wall on the one side and an impervious wall on the opposite side. The air flows under pressure through the porous wall into the pulp suspension; this results in an optimum distribution because the gap of the mixing chamber is relatively narrow and, therefore, the liquid film formed by the pulp suspension is very thin. The intimate mixing of air and pulp suspension in connection with the blowing off of the foam, results in an improved efficiency in this unit, so that the number of passages, to wit, the number of stages through which the pulp suspension must be conducted, can be reduced from 10 to 4.
In the flotation cell according to German Offenlegungsschrift No. 27 12 947, the air-laden pulp suspension is supplied to the first cell in the bottom region and the primary accept obtained by the flotation is also removed in the bottom region and the primary accept is fed to the second cell and leaves the cell as secondary accept, etc. Prior to being fed to the next cell, the accept must once again pass through a compulsory mixing chamber in which it is once again charged with air. However, the simultaneous supply and removal of pulp suspension in the bottom region give rise to the great danger that dirt particles, before they can rise toward the top with the air bubbles, are transported through the accept outlet into the next cell where the same danger exists again. Consequently, in spite of the satisfactory air charge of the pulp suspension, this leads to a deterioration of the statistical result, i.e., a plurality of cells must inevitably be connected in series in order to obtain a whiteness of the pulp which approximately corresponds to the original material, because the probability that dirt particles will reach the accept can only be reduced by connecting a plurality of cells in series.
Therefore, the present invention is based on the task of further reducing the number of purification stages required in the past in flotation cells and, if possible, of requiring only a single cell and of essentially preventing the passing of dirt particles through the accept
REFERENCES:
patent: 3428175 (1969-02-01), Hukki
patent: 3870635 (1975-03-01), Clarke-Pounder
patent: 4157952 (1979-06-01), Krofta
patent: 4212730 (1980-07-01), Brooks et al.
E+M Lamort S.A.
Feldmuhle Aktiengesellschaft
Hill Ralph J.
LandOfFree
Method of and arrangement for the de-inking of pulp suspensions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of and arrangement for the de-inking of pulp suspensions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of and arrangement for the de-inking of pulp suspensions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2075750