Liquid purification or separation – Constituent mixture variation responsive
Patent
1987-02-19
1988-11-15
Hruskoci, Peter
Liquid purification or separation
Constituent mixture variation responsive
210104, 210134, 210199, 2102212, 210520, 210525, 209170, C02F 124
Patent
active
047847646
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an arrangement for flocculating flocculatable substances in suspensions, particularly for the purification of backwater in deinking installations for waste paper processing, wherein air and chemical agents in a quantity necessary for flocculation are fed to the suspension, the formed flocks attached to small air bubbles in a container float to the surface and are separated as flotation scum.
Such an arrangement is in particular required for the purification of the backwater of deinking installations. Such deinking installations are used for separating and removing printing inks from waste paper, so as to produce a cleaner, bright, reusable paper stock as raw material for new paper. The printing inks are separated in the foam by flotation plants and in the filtrate by washing plants. Part of the same is also located in the filtrate of any decker connected downstream. For economic reasons, the water at all these points is wholly or partly recirculated and reused again for fiberizing waste paper.
However, this backwater is contaminated with printing inks, fine fibrous materials and other substances separated from the waste paper during the deinking process. For example, the content of suspended solids can be between 500 and 3,500 mg/l. If this water were used in untreated form for fiberizing waste paper, the waste paper would be additionally contaminated. The backwater therefore must be purified.
PRIOR ART
It is known to carry out this backwater purification by adding chemicals and to flocculate and separate the foreign materials in a container, e.g. in flotation installations. In these flotation installations air is supplied and finely divided in the water. The solids transported to the surface by the air float in the container in the form of scum and can be skimmed from the clarified water using appropriate devices.
The chemicals used can be various cationic agents and/or anionic, as well as non-ionic chemicals, either individually or in combination, for example, alum can be used as a suitable, polymeric cationic agent, for example, polyacrylamide as an additional anionic polymer, for example, high polymeric polyoxy products as non-ionic agents. In order to achieve an optimum purified backwater quality, it is necessary to add each individual chemical as precisely as possible in the quantity necessary for the optimum flocculation of the foreign materials, i.e. the addition of each individual agent must neither be underdosed nor overdosed. This can be achieved by a regulating process, in that the effect is determined at appropriate points by suitable measuring instruments, e.g. turbidimeters and the addition is regulated to an optimum degree of flocculation or turbidity by means of a regulating device connected thereto through the evaluation of the measured degree of turbidity and the mass flow, on the one hand, and the quantity and concentration of the chemical addition, on the other hand. The purification effect can be further improved by successively adding several agents at different infeed points.
However, in the known flotation installations, the purification action in the flotation container, i.e. the floating of the flocculated substances attached to air bubbles and their separation from the clarified water was not of an optimum nature and therefore it was necessary to overdimension the installations to bring about an adequate efficiency per unit of time and an adequate throughput and consequently they operate relatively uneconomically.
SUMMARY OF THE INVENTION
In order to obviate the disadvantages referred to hereinbefore of the prior art, the object of the present invention is to provide an arrangement for flocculating flocculatable substances in suspensions, in particular for the purification of the backwater of deinking installations for waste paper processing, in which the flocculating action and the purification efficiency in the container are improved and an optimum value achieved, in order to permit a higher throughput and an optimum econ
REFERENCES:
patent: 3307701 (1967-03-01), Krofta
patent: 3452869 (1969-07-01), O'Neill
patent: 3552571 (1971-01-01), Neuspiel
patent: 3966598 (1976-06-01), Ettelt
patent: 4022696 (1977-05-01), Krofta
patent: 4173532 (1979-11-01), Keoteklian
patent: 4226714 (1980-10-01), Furness et al.
Bassler Wolfgang
Kahmann Albrecht
Kleinschnittger Hans H.
Siewert Wolfgang
Hruskoci Peter
Kleeman Werner W.
Sulzer-Escher Wyss GmbH
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