Classifying – separating – and assorting solids – Sifting – Feeding
Patent
1990-07-23
1992-06-23
Huppert, Michael S.
Classifying, separating, and assorting solids
Sifting
Feeding
209271, 209380, 210327, 210391, 210797, 210798, B07B 108, B07B 150, D21D 502
Patent
active
051240297
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of fractionating suspensions, preferably containing fibre pulp, the suspension to be fractionated being sprayed in the form of at least one jet against one of the sides of a filter sheet during displacement of the filter sheet and said jet relative to one another, so that the suspension is separated into a fine fraction, which passes through the screen holes of the filter sheet and which contains fine particles, and a coarse fraction, which does not pass through said screen holes and which contains coarse particles and some fine particles. The invention also relates to a device for such a fractionation of suspensions.
In a known method of this kind the filter sheet is circular and is kept fixed in a horizontal position, the suspension being sprayed substantially vertically towards the upper side of the filter sheet during rotation of the jet of the suspension in horizontal direction. The resulting relative displacement between the jet and the filter sheet aims at cleansing the screen holes of the filter sheet, so that these are freed from initial clogging. Such a cleansing effect occurs, but has proved workable only over a limited period of time.
When fractionating it is particularly important that the screen holes are kept free from initial clogging, since these negatively affect the fractionation result. This is so because the sizes of the particles in the coarse and fine fractions are radically changed even with a moderate clogging of the screen holes, so that the intended fractionation cannot be obtained. Therefore, when utilizing the known fractionation method the operation must be stopped regularly for cleansing the screen holes of the filter sheet.
The object of the present invention is to provide a new fractionation method of this general kind, which, during operation efficiently keeps the screen holes clean from initial clogging, whereby stopping to cleanse the screen holes is avoided.
A further object of the present invention is to provide a new fractionation device for accomplishing the new fractionation method.
These objects are obtained by means of a method of the kind initially mentioned, which is characterized primarily by spraying cleansing liquid in the form of at least one jet against the filter sheet, and displacing the filter sheet and said jet of cleansing liquid relative to each other, such that the jet of cleansing liquid hits the screen holes of the filter sheet which have been sprayed upon with suspension.
In this way an advantage is obtained in that the cleansing liquid can be allowed to spray against the filter sheet with a considerably stronger impact pressure than the suspension, since in contrast to the suspension the cleansing liquid is free from relatively coarse particles, which could be pressed into the screen holes of the filter sheet and clog them if the suspension were sprayed at too high a pressure against the filter sheet.
The cleansing liquid is suitably sprayed on the same side of the filter sheet as the suspension if it is primarily required that the liquid concentration of the coarse fraction be kept low. In this case the liquid content of the fine fraction is increased. In the case where the liquid concentration of the coarse fraction is of secondary significance the cleansing liquid is advantageously sprayed on the opposite side of the filter sheet from the suspension, whereby the cleansing effect of the screen holes is further improved.
The cleansing liquid may be sprayed continuously or intermittently against the filter sheet. Intermittent spraying results in a lower dilution of the coarse and fine fractions compared to continuous spraying.
Advantageously, the pressure is kept higher on the coarse fraction side of the filter sheet than on the fine fraction side, whereby the fractionation capacity is increased and the liquid content of the coarse fraction is reduced.
Preferably, the filter sheet is kept substantially vertical and is displaced relative to the jets of suspension and cleansing liquid. In this way, the adva
REFERENCES:
patent: 873390 (1907-12-01), Stevenson et al.
patent: 1041935 (1912-10-01), Worrall
patent: 1155116 (1915-09-01), Westbye
patent: 1675612 (1928-07-01), Laird
patent: 2874840 (1959-02-01), Simpson
patent: 2988223 (1961-06-01), Janson
patent: 3007575 (1961-11-01), Sylvest
patent: 3024911 (1962-03-01), Janson
patent: 3477571 (1969-11-01), Maag
patent: 3490585 (1970-01-01), Gooding et al.
patent: 3542198 (1970-11-01), Borjeson
patent: 3633743 (1972-01-01), Gooding et al.
patent: 3827567 (1974-08-01), Rundqvist
patent: 4889625 (1989-12-01), Nilsson
patent: 4929355 (1990-05-01), Ragnegard et al.
Fjallstrom Roland
Frykhult Rune
Celleco AB
Huppert Michael S.
Wacyra Edward M.
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