US3117082A

US3117082A - Flotation system

Info

Publication number: US3117082A
Application number: US756483A
Authority: US
Inventors: John W Schluter
Original assignee: Pfaudler Permutit Inc
Current assignee: Pfaudler Permutit Inc
Priority date: 1958-08-21
Filing date: 1958-08-21
Publication date: 1964-01-07
Anticipated expiration: 1981-01-07

Description

Jan. 7, 1934 J. w. scHLUTER FLOTATION SYSTEM Filed Aug. 21, 1958 llll United States Patent CQ,

3,117,082 Patented Jan. 7, 1964 3,117,082 FLOTA'I'ION SYSTEM .lohn W. Schluter, Maapequa, N .Y., assignor, by mesne assignments, to Pfaudler Permutt, Inc., Rochester, N.Y., a corporation of New York Filed Aug. 21, 1953, Ser. No. 756,483 2 Claims. (Cl. 21h-221) This invention relates to flotation systems such as used for purification of 'liquids and separation of suspended materials from liquids.

Flotation systems are in general well known and 4the general construction and operating characteristics of ota- `tion apparatus and methods to which the present invention may be applied are described, for example, in Schluter application Serial No. 663,105, tiled April 2, 1958, now U.S. Patent 2,994,432, for Control for Flotation Separation Systems, and also Iuell Patent No. 2,330,589, granted September 28, 1943, and Baum Patent No. 2,746,605, granted May 22, 1956. In such systems, .the influent liquid is generally processed from chemicals to precipitate or coagulate dissolved or suspended material which is then separated from the liquid by floating it to the surface as a scum or iioc which is removed as by means of skimming paddles. The aeration of the liquid is generally accomplished after the chemical treatment and after the lloc particles have formed to a considerable extent, and it is found that the aeration of the liquid and more particularly its discharge through the valving employed in introducing it into the flotation chamber cause objectionable shearing of the iioc, reducing the particle size and thus impeding the otation action. It is an object yof the invention to lessen such shearing of partially formed floc.

In prior systems, the inuent liquid generally proceeds through all elements of the apparatus employed in a continuous manner and at the same rate for each element, so that the rate of tlow of material into and out of a lloc forming chamber, an aerating element and the tloation chamber, will all be the same. Under these conditions, it is diiicult to maintain maximum efliciency and it is an object ofthe present invention to permit variation in rate of iiow through one element of the system as compared to another.

In many applications, the concentration of solids in the inuent material may vary quite widely from time to time and the oation eiciency may vary accordingly. It is a further object of the invention to permit regulation of the dilution of the material being treated in the ilotation chamber.

In the apparatus and method according to the present invention, clarified liquid is circulated to and from the dotation chamber at a suitable rate, is preferably aerated during this recirculation, the iniluent stream of liquid to be treated and in which the lloc has been partially formed being mixed with the circulating claried and aerated liquid at an appropriate point and under relatively quiet conditions, thus achieving protection of partially formed iloc from shearing, control over the aeration and flotation steps of the process in a manner not hitherto obtainable.

A system embodying the invention in a preferred form will now be described with reference to the accompanying drawing, and the features forming the invention will then be pointed out in the appended claims.

In the drawings:

FIG. 1 is a schematic diagram of a system embodying the invention in a preferred form; and

FIG. 2 is an enlarged sectional view of the ilotation chamber inlet compartment where the iniiuent stream and recirculated, clarified liquid are mixed.

The elements of the system in general may be conventional and comprise a receiving tank or settling basin 1, to which the inuent liquid is supplied and from which it is 'taken by a pump 2 and delivered through pipe 3 to aoc forming 4tank 4. Supply lines 5 and 6 equipped with rotometers, as indicated, discharge liquid from chemical lfeed tanks 7 and S into the line 3, thus into tank 4. Each of the tanks 7 and 8 is equipped with liquid pump valves and agitator, as indicated, and it will be understood that alum, ferrie sulphate or any other desired :precipitating or coagulating chemical may be mixed with water in these tanks and then supplied at regulated rate by means of pumps and, as indicated, by the rotometers. Tank 4 may be vertically elongated, as indicated, and equipped with a vertical shaft 10 carrying paddles 1-1 which are rotated at a slow rate by motor v12 so as to stir the liquid within the tank but without appreciable agitation or vertical movement, so that the iloc will gradually .form in Vthe liquid as it proceeds from the bottom to the top of tank 4 where it is discharged through supply line 13 leading to the flotation chamber.

As is apparent, the operation of the elements justvdescribed may be regulated for optimum iloc formation and economy chemical treatment by the influent liquid. Pipe 13 discharges into the inlet box or compartment 14 of 'the flotation chamber or separator from which liquid iows over a Weir 15 into the ilotation chamber proper. The construction of this chamber may be in general conventional and will be described herein only to the extent necessary for an understanding of the present invention.

Claried water is withdrawn through an outlet 16 and the sludge floating to the top of the liquid is removed by a paddle chain 17, being discharge at 18. The specific construction of the tank element may be selected as desired, structures such as shown and described in the application and patents above mentioned as well as elsewhere being suitable. In addition to being discharged through the outlet 16, clarified liquid is taken from the lower part of the flotation tank or separator through the .pipe 20 controlled by a valve 21 and leading through a gas and liquid mixing -unit 22 to pipe 23 which connects to the intake of circulating -pump 24 which, in turn, discharges through pipe 25 into a retention tank 26 from which recirculated liquid is discharged through valve 27 and pipe 28 to the inlet box or compartment of the flotation tank, where the recirculated stream from pipe 28 lis combined with the influent liquid from pipe 13 as shown most clearly in FIG. 2. As there shown, pipe 13 vterminates in a Vbaffle plate 30 adjacent the bottom 31 of the inlet box flowing radially outward from under this `baffle plate, as indicated by the arrows. Immediately below .pipe 13 is a second and similar baille plate 32 attached by posts 33 to the plate 30, and against which the recirculated clarified liquid from pipe 2S discharges so that this liquid also flows in a radiallyv outward manner between plate 30 and the bottom 31 of the inlet box. As is apparent, the recirculated liquid from pipe 28 and the influent liquid from pipe 13 are thus combined together and mixed thoroughly without appreciable agitation being involved in the mixing process.

The recirculated liquid is aerated by means of a system such as shown in FIG. l. As there shown, part of the discharge of pump 24 is by-passed back through a line 35 which connects two

branches

36 and 37 which are valved, as indicated, and contain air and liquid venturi jet pumps 3S and 39 for mixing air into the recirculated liquid, which is then supplied to the mixer 22 and thus introduced into the stream of recirculating liquid in pipe 23. The

air injectors

38 and 39 are supplied with air through piping 40 equipped with a rotometer and Valve as indicated for controlling the extent of aeration. Normally, only one of the

air injectors

38 or 39 will be used at any given time, the other being shut oit by means of the indicated valves.

The retention tank may be of the type shown in the Baum patent above referred to and will provide for the dissolving in the recirculated liquid of large quantities of air and generally several times the amount of air that can be held in solution at atmospheric pressure. Thereafter, as the recirculated liquid is discharged into the inlet box 14, air commences to go out of solution so that the mixture from

pipes

13 and 28 is thoroughly aerated and without material destruction of any partially formed lloc. The flotation proceeds in the usual manner but with markedly increasing etlciency due to the obtaining and maintaining of floc particles of optimum size.

The method and apparatus of the invention may be used with flotation systems of any known type, as, for example, systems used for clarifying paper mill waste, waste Water from canneries and slaughter houses, waste water from railroad yards or any of a variety of processed liquids such as sugar melts in sugar refineries. The purposes involved may include the recovery of the suspended solids, the purication of the liquid for use or further processing, or the purication of the liquid to permit discharge into a stream or concentration of the solids to permit economical disposal thereof. As is apparent, the process of the invention may be preceded or followed by any desired settling or other operations designed to assist in clarication or separation or perform other operations on the liquids involved.

The quantity of clarified liquid which is recirculated to and from the otation chamber may be varied to suit particular conditions and may be, according to conditions, a fraction or a multiple of the quantity of influent material supplied. For example, where the quantity of solids involved is reasonably constant but the amount of liquid varies so that the inuent is supplied at a lower volumetric rate with a higher concentration of solids at certain times, the recirculation `rate may be comparatively high resulting in a dilution of the influent as it enters the flotation tank, wherever such dilution contributes to eliciency of operation. Since the rate of aeration and the rate of liquid recirculation are independent within reasonable limits, the aeration may also be controlled substantially independently of the recirculation rate. In general, it is possible by controlling the recirculation rate as compared to the rate of inuent supplied and the aeration of the recirculated liquid so as to obtain maximum eiliciency in the air llotation action with minimum shearing or breaking up of the floc which has been formed prior to the influent reaching the inlet box. In the method of the invention, it may be noted that the iniluent after chemical treatment and partial formation of flot: may be brought to the inlet box and discharged therein without any substantial agitation of any kind as, in the example illustrated, by means of a simple gravity flow and thus creating a very desirable condition by comparison with previous systems in which a release of pressure is generally involved resulting in great turbulence and a violent shearing action which tends to destroy the partially formed floc.

What is claimed is:

1. In a flotation separating system, a dotation chamber, means for supplying inlluent liquid containing suspended floatable material to the said chamber, means for removing clarified liquid and floated sludge from the said chamber, and means for withdrawing clarified liquid from the ilotation chamber, aerating it and mixing it with the influent liquid prior to introducing the same into the flotation chamber, in which the last said means comprises pipes for the two liquids having their ends in opposed spaced relation for discharging the respective liquids in opposite directions, a baffle member positioned between the two pipe ends in spaced relation thereto and separating the streams of liquid discharged therefrom, a pair of spaced plates surrounding the discharge ends of the said pipes and forming a ilow passage for liquid discharged by the said pipes against the said baffle, whereby the two streams of liquid are diverted by the baille into the said flow passage and mixed together under relatively quiescent conditions.

2. In a otation separating system, a lloc-forming chamber, a dotation chamber having an inlet box, means for supplying inuent liquid from the Hoc-forming chamber to the inlet box, means for removing clarified liquid and floated sludge from the flotation chamber, and means for withdrawing claried liquid from the flotation chamber, aerating it and mixing it with the influent liquid from the lloc-forming chamber in the said inlet box, in which the last said means comprises pipes for the two liquids having their ends in opposed spaced relation for discharging the respective liquids in opposite directions, a baille member positioned between the two pipe ends in spaced relation thereto and separating the streams of liquid discharged therefrom, a pair of spaced plates surrounding the discharge ends of the said pipes and forming a flow passage for liquid discharged by the said pipes against the said baille, whereby the two streams of liquid are diverted by the baffle into the said ow passage and mixed together under relatively quiescent conditions.

'References Cited in the le of this patent UNITED STATES PATENTS Float-Treat System Bulletin 54-82, by Chain Belt Company, Milwaukee, Wis.; received in Patent Oliice Oct. 1l, 1957.

Claims

1. IN A FLOTATION SEPARATING SYSTEM, A FLOTATION CHAMBER, MEANS FOR SUPPLYING INFLUENT LIQUID CONTAINING SUSPENDED FLOATABLE MATERIAL TO THE SAID CHAMBER, MEANS FOR REMOVING CLARIFIED LIQUID AND FLOATED SLUDGE FROM THE SAID CHAMBER, AND MEANS FOR WITHDRAWING CLARIFIED LIQUID FROM THE FLOTATION CHAMBER, AERATING IT AND MIXING IT WITH THE INFLUENT LIQUID PRIOR TO INTRODUCING THE SAME INTO THE FLOTATION CHAMBER, IN WHICH THE LAST SAID MEANS COMPRISES PIPES FOR THE TWO LIQUIDS HAVING THEIR ENDS IN OPPOSED SPACED RELATION FOR DISCHARGING THE RESPECTIVE LIQUIDS IN OPPOSITE DIRECTIONS, A BAFFLE MEMBER POSITIONED BETWEEN THE TWO PIPE ENDS IN SPACED RELATION THERETO AND SEPARATING THE STREAMS OF LIQUID DISCHARGED THEREFROM, A PAIR OF SPACED PLATES SURROUNDING THE DISCHARGE ENDS OF THE SAID PIPES AND FORMING A FLOW PASSAGE FOR LIQUID DISCHARGED BY THE SAID PIPES AGAINST THE SAID BAFFLE, WHEREBY THE TWO STREAMS OF LIQUID ARE DIVERTED BY THE BAFFLE INTO THE SAID FLOW PASSAGE AND MIXED TOGETHER UNDER RELATIVELY QUIESCENT CONDITIONS.