JPH0220755B2 - - Google Patents

Abstract

For the purposes of flotation in the deinking of waste paper, a number of flotation cells connected in series inside a compartmentalised, essentially closed, elongate container are provided, which essentially have a mixing pipe for liquid and air dipping into the suspension from above in the centre of the individual cells and where the foam outlet opening is arranged on at least one longitudinal side of the container. In order to improve mixing with air and to provide a low-power device, an injector for the supply of the suspension to be floated in the cell, mixed with air, is added to each mixing pipe. In this way, the mixing pipe in each case ends at a smaller distance from the bottom of each cell than the internal diameter of the mixing pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a plurality of generally closed flotation tanks separated from each other and connected in at least one row, each flotation tank having a fibrous material in the center thereof. The present invention relates to an apparatus for recycling waste paper, in which a mixing tube for liquid and air hangs for immersion in a suspension, and a bubble outlet is provided in the side wall of the flotation tank.

One such device is disclosed in German Patent Publication No. 2726578.

In such known devices, the gas-liquid mixture is mainly supplied with compressed air into an annular chamber defined between the wall of the mixing tube and the wall of a central liquid tube of smaller diameter extending into its interior. It is designed to be transported by a structure that supplies air consisting of.
Although such a device occupies a small space, it has the advantage of taking up a large amount of space inside the tank. However, with such devices, it is not always possible to generate sufficiently fine bubbles that are preferable for flotation separation.

In view of these points, the main object of the present invention is to provide a device that occupies a small space, is simple to manufacture, and has a good floating separation effect.

According to the present invention, the mixing tube of each flotation separation tank is equipped with an injector for mixing air into the suspension in order to float and separate the fibrous suspension. This is achieved by providing a device characterized in that the lower end of the mixing tube is located at a distance from the bottom of the flotation separation tank that is less than the inner diameter of the mixing tube.

According to the device according to the invention, the action of the injector attached to the mixing tube and the flow of the dense suspension exiting from the bottom of the tank are determined by the suitable shape of the tank and the flow of the gas-liquid mixture by the injector. The favorable transfer effect allows, on the one hand, to mix the fibrous suspension well with fine air bubbles and, on the other hand, results in a flotation separation device with low power consumption.

Preferred embodiments of the invention will now be described in detail with reference to the accompanying drawings.

In FIG. 1, the fibrous suspension is introduced into each flotation tank 1 via a feed pipe 4. In FIG. An injector 20 is connected between the supply pipe 4 and the mixing pipe 9.

In this embodiment, this injector 20
consists of a receptacle 5 and a suction pipe 6 protruding toward the center of the receptacle for sucking air.

At the outlet end of the mixing tube 9, an enlarged diameter section 7 forming a generally funnel-shaped diffuser is provided, and a flange plate 8 is fixed to the end edge of the enlarged diameter section 7. The opening 19 at the outlet end of the mixing tube 9 is spaced apart from the bottom of the tank 1 by a distance smaller than the inner diameter of the mixing tube 9.

Thanks to this configuration using the flange portion 8, the flow is strongly deflected, a large shearing force is generated, and fine air bubbles are mixed into the suspension.

In addition, since the baffle plate 10 is used, the flotation separation effect for separating impurities from the fibrous suspension is further promoted. With such a configuration, the bubble stirring device 25 consisting of the adjustable paddle 17 can also be omitted, since the separation of impurities is facilitated. This further reduces power consumption.

The air bubbles are discharged by controlling a weir 15, which is adjustable by a drive mechanism (not shown), via a push rod 16. thus,
The air bubbles pass through the air bubble outlet 12 and are sent to the water spray nozzle 18.
can reach the bubble passageway attached.

On the other hand, the discharge of the fibrous suspension is carried out by the full plate 10.
The liquid is discharged from the liquid discharge port 11 connected between the partition wall 14 and the liquid discharge port 14, and is led to the injector and mixing pipe of the floating separation tank (see FIG. 2) connected to the next stage. For this purpose, a pump not shown can be used.

The flotation separation tank 1 shown in FIG. 1 has a cylindrical shape with a circular cross section so as to obtain the above-mentioned advantages.

FIG. 3 shows a modified embodiment of the arrangement consisting of an injector and a mixing tube.

In this embodiment, the upper end of the mixing tube 9' is
It forms a suction funnel 23 consisting of a conical opening with an upwardly increasing diameter, towards the inside of which the tapered open end 2 of the supply tube 4' for the fibrous suspension is formed.
1 is rushing in.

Also, a conical body 26 for diverting the flow so as to protrude into the open end 19 of the enlarged diameter portion 7 of the mixing tube 9'.
are appropriately protruded from the bottom of the tank 1.

In the embodiments described above, the tank 1 is used which has an almost perfectly circular cross section, but it may also have an elliptical cross section. Similarly, the part of the tank above the liquid level of the suspension can also consist of a flat lid plate. It is important that the lower region of the tank 1 has a circular cross section. This ensures a suitable structure for obtaining rapid flow diversions.

The distance between the opening 19 at the lower end of the mixing tube and the bottom of the tank may be 10 to 40% of the inner diameter of the mixing tube when air is used without pressurization. for example,
When the inner diameter of the mixing tube is 250 mm, this spacing should be approximately 40 mm. If pressurized air is used, this interval may be reduced by about 10%.

FIG. 4 shows yet another modified embodiment, in which the partition wall of the embodiment of FIG. 1 is not used. The air bubbles pass over the adjustable weir plate 25' and are discharged into the air bubble discharge passage 13, and the cleaned fibrous suspension passes through the liquid outlet provided in the form of a slit just below the weir plate 25'. 11', and is discharged to a liquid passage 42 provided below the bubble discharge passage.

In the embodiments shown in FIGS. 1 to 4, cylindrical tanks with circular cross sections are used.

In the embodiments described above, an almost perfectly cylindrical tank 1 is used, but its cross section may also be oval.

Similarly, the portion of the tank above the liquid level of the suspension may be formed of a flat lid plate. It is important that the lower region of the tank 1 has a circular cross section. This ensures a suitable structure for obtaining sharp flow turns.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view of a flotation tank in a waste paper recycling apparatus based on the present invention. Second
The figure is a side view showing how floating separation tanks are connected in series. FIG. 3 is a partial longitudinal sectional view showing the structure of the mixing tube and injector with some parts omitted. FIG. 4 shows a first embodiment showing yet another embodiment.
It is a figure similar to the figure. DESCRIPTION OF SYMBOLS 1...tank, 4,'4'...supply pipe, 5...injector, 6...intake pipe, 7...diameter enlarged part, 8...flange plate, 9,9'...mixing pipe, 10...buttful plate, 11,
11'...Liquid discharge port, 12...Bubble discharge port, 13...
Air bubble discharge passage, 14... partition wall, 15... weir plate, 16
... Push rod, 17 ... Paddle, 18 ... Water nozzle, 19 ... Open end, 20 ... Injector, 21
...opening end, 22...flange plate, 23...suction funnel,
25... Bubble stirring device, 25'... Weir plate, 26... Cone body.

Claims (1)

[Scope of Claims] 1. A plurality of generally closed flotation tanks separated from each other and connected in at least one row, each flotation tank having a central portion containing a fibrous suspension. An apparatus for recycling waste paper, wherein a mixing tube for liquid and air hangs down for immersion in a liquid and air, and an air bubble outlet is provided in the side wall of the flotation separation tank, comprising: (a) each The mixing pipe 9 of the flotation separation tank 1 is equipped with an injector 20 for mixing air into the suspension in order to float and separate the fibrous suspension, (b) the lower end of the mixing pipe 9 is An apparatus characterized in that the apparatus is located at a distance smaller than the inner diameter of the mixing tube 9 from the bottom of the flotation separation tank. 2. The device according to claim 1, characterized in that the flotation separation tank 1 has a generally cylindrical shape with a generally circular cross section, at least in the vicinity of the surface of the fiber suspension. . 3. The device according to claim 1 or 2, wherein the opening 19 at the lower end of the mixing tube 9 is enlarged in diameter into a generally funnel-like shape and has a flange 8.