KR810000822B1 - A process and an installation for the elimination by floation of impurities in the form of solid particles contained in a liquid - Google Patents

Abstract

In this air flotation system, before the air/liq. mixt. enters the flotation cell(1-4), a thin layer of liq. is circulated in a mixing chamber(8) while air is blown transversely to the liq. path(7) through the pipe(9). The system pertains to de-inking newspapers, but can be used for other flotation processes. Thus, for a liq. flow rate of 4.23 m/s, the optimum whitening occurs when -0.7 L air is used per L of liquid additional retention time improves the whiteness.

Description

Apparatus for removing impurities contained in the form of solid particles in a liquid by bar wire

1 is a schematic elevation view of a multi-layered installation for removing ink from gripping pulp according to the present invention.

2 is a horizontal cross-sectional view taken along the line A-A of FIG.

3 is a vertical longitudinal section in which the mixing chamber is enlarged.

4 is a cross-sectional view taken along the line B-B in FIG.

5 is an enlarged vertical sectional view showing another structural example of the mixing chamber.

6 is a cross-sectional view taken along the line C-C of FIG.

7 shows the whiteness curve of the pulp.

The present invention relates to an apparatus for removing impurities contained in a liquid in the form of solid particles of the present invention by flotation, and in particular, an air bubble in an air stream in a liquid stream in a float vessel. An apparatus for removing impurities that floats on a liquid surface so as to generate bubbles to lift impurities by injecting them in a state in which air bubbles are dispersed in the liquid and attached to the impurities, and remove the bubbles from the liquid surface. will be.

The flotation method as described above is known as a method for removing the ink from the papermaking pulp produced from the gripping. According to this known method, air is also introduced directly to the bottom of the tank by suction while using a propeller useful for the careful stirring and dispersion of the fiber suspension in the tank.

By introducing air directly into the pulp, it is possible to reliably control the air pressure, and thus to control the diameter of the bubbles depending on the volume of the air. The volume of air can in this case be adjusted within any limits. It is possible to increase the air pressure by increasing the volume of air, and consequently to increase the diameter of the bubbles, while with this known method it is not possible to reduce the diameter of the bubbles while increasing the flow rate of the air.

Such a decrease in the diameter of the bubbles is necessary to separate the impurities in the case of any kind of impurities. Surprisingly, it was found here that the present invention makes it possible to selectively separate impurities by the flotation method by independently controlling the dimensions of the bubbles and the volume of air. Thus, for example, in the case of ink removal of pretreated paper pulp by loosening the grip, it is possible to obtain bubbles having different dimensions, respectively, in order to float the ink, or to fill a filler or fiber such as kaolin, Can be selectively separated.

The present invention aims, in particular, to provide a device capable of adjusting the dimensions of bubbles independently of the volume of air mixed in the water to which impurities are to be removed. For this purpose, the present invention provides that, prior to the introduction of air and liquid into the flotation tank, the liquid circulates in at least one mixing chamber in a thin layer shape, at the same time crossing the passage of the liquid layer and Air is introduced into the liquid layer along a portion of the passageway.

If the liquid is a fibrous suspension, such as paper pulp, the pulp is effectively passed through a narrow room in thin layers to contact air dispensed and dispensed in a direction across the thin liquid-liquid layer containing the suspended fibers. It was found that mutual friction and cleaning took place.

According to one embodiment of the apparatus of the present invention, the thickness of the liquid layer in the mixing chamber and the passage speed of the liquid in the room are controlled. In the case of ink removal of pulp prepared from phage, the volume of air mixed with the pulp and the rate of passage of the pulp in the mixing chamber affects the whiteness of the pulp, and by controlling these factors from 57 ° to 66.5 ° scan. It has been found that various whiteness levels can be obtained.

This control makes it possible to minimize waste and achieve effective purification. In addition, according to one embodiment of the apparatus of the present invention, the length of the passage through which air enters into the liquid is controlled.

Thereby, the amount of air can be proportionally increased and decreased in the liquid layer passing through the mixing chamber. According to another embodiment, air bubbles are guided to the hopper with the air flow and the air is recovered for recirculation.

In the case of performing a barge using a plurality of floats, a mixture of air and liquid from one mixing chamber can be introduced into each tank each time. Therefore, the size of the bubbles can be controlled individually for each set, and impurities can be selectively recovered.

In the case of liquids containing fibers, the cleaning and depletion entering the first sub-tank can be recycled to the liquid in order to minimize the loss of the fibers.

According to the invention the apparatus comprises a narrow mixing chamber through which at least one thin layer of cleaned and depleted liquid can pass, provided in an upstream side of the subline, in a direction across the liquid layer on the passage of the chamber. Has a means to allow air to flow. According to one embodiment, the mixing chamber is bounded by two parallel walls arranged separately from each other so that the liquid to be purified and depleted can pass therethrough. According to another embodiment, the mixing chamber has means for adjusting the isolation distance of the two walls described above.

Hereinafter, the apparatus showing the features of the present invention will be described in detail again. The device shown represents one suitable example of the present invention for removing the ink of the pulp produced from the waste paper, which merely represents four examples of the present invention.

The illustrated device comprises four sub-ships (1) (2) (3) (4). These squares are annular and are arranged in the axial direction in order to form a four-stage tower having a plurality of bottom surfaces 5. Of course, this tower can also be configured as a multi-stage tower other than four.

Paper pulp in the form of a suspension of decomposed, chemically pretreated fibers contains a blowing agent and first passes through the mixing chamber 8 through the pipe 7 to the inlet of the flotation tank 1 via a pump 6. Is introduced. This mixing chamber 8 has a thin layer shape, and there is a narrow passage through which the suspension of the fiber passes. When passing through this passageway, air is simultaneously introduced in the direction or along a portion of the passageway of the pulp liquid layer. This air is introduced through a pipe 9 via a valve 10, which is connected to the origin of a pressurized hole, not shown. The mixing chamber 8 communicates with the floatation tank 1 via a pipe 11, which is introduced tangentially to the cylindrical wall of the vessel near the bottom surface 5 of the floatation tank 1. The fiber suspension thus turns around the central pipe 12 of the annular bath.

Bubbles generated in the fiber suspension adhere to impurities, and the impurities rise to the surface with bubbles. Bubbles are discharged from the outlet 18 formed in the central pipe 12 to enter the central pipe 12.

The movement of the bubbles is caused in part by the rotational movement of the fiber suspension and in part by the air flow supplied over the suspension. And the vertical plate 50 disposed on the pump liquid level guides the bubbles to the outlet. Bubbles are collected in a hopper 13 arranged to surround the center pipe 12 and accommodated in a waste tank 37 full of water. The air flow for discharging the bubbles to the floater is introduced into the upper portion of the floater through the pipe 14. The pipe 14 is connected to a suction device 15 arranged on the upper side of the axially long columnar pipe 16, and the air for bubble discharge is recycled and used. The conical pipe 16 is arranged concentrically with the central pipe 12 and communicates with all the sub-ships in each stage in common. The foam discharge air enters the tank through the opening 17 and exits the tank through the outlet 18. As it exits the bath, the bubbles that come with the air fall into the hopper 13 by gravity, and the air exits upward through the pipe 16. The pipe 16 extends into a conical portion with a distal end portion facing upwards to the next subline 2, and the portion faces a larger pipe portion.

The pipe part having a large diameter is a pipe part for recirculating the buoy discharge tanks of the adjacent floater tanks 2 and other stages of the floater tanks 3 and 4. One cyclone is formed by the constituent parts of the pipe 16, and the cyclone gives the foam a centrifugal velocity, and air is sucked into the pipe 160 by the action of the suction device 15. It is separated from the foam and returned to the pipe 14 to be reused for the discharge of the foam.

The pulp partially purified in the sub-tank 1 exits the sub-tank 1 via a pipe 19 with a pump 20. The pressure in the pipe 19 can be increased or decreased by the pump 20. The pipe 19 extends to the mixing chamber of the floater 4 located at the end of the tower.

The purification process performed here is the same as the case of the sub-tank of the first stage, and the same purification is performed sequentially in another sub-tank. As a result, pulp, or water containing fibers, gradually increases its purity. During this time, the bubbles collected in the different levels of the buoys are sent to the lower buoys. Bubbles discharged from the buoys of the first and other stages containing the exclusion material may, of course, be recycled or discharged to the outside for treatment by a separate device at each stage. This depends on the type of pulp product intended.

In addition, the apparatus again closes the subsidiary tank 40 of the final stage, a monitoring window 41 for rapid discharge for purification, and a discharge valve 42 for emptying the tub installed for each subsidiary tank with a blank. A flap 46 installed in the air pipe for foam discharge, a floor 43 installed in the pipe 12 to receive the circulated exclusion material, and a pipe for discharging the exclusion material installed in the first sub-ship 1 (44) and pipes (45) for discharging the pulp in the flotation tank (2) for processing the best purified pulp.

3, 4, 5, and 6 show two structural examples of the mixing chamber, respectively. In the case of the structural example shown in FIG. 3 and FIG. 4, the mixing chamber is formed of a rectangular portion consisting of two parallel surface walls 21 and 22 attached in one parallel six-plane body 23. The part forms the groove which communicates with the inlet pipe 7 and the outlet pipe 11.

One wall 21 is movable in parallel with respect to the other wall 22, it is moved by the screw rod (24). The screw rod 24 is guided using the handle 25 in the threaded hole 26 formed in the sleeve 27 attached in the adjacent upper wall of the parallel sixth surface 23, and the two parallel members The distance between the walls 21 and 22 is adjusted, thereby determining the thickness of the liquid layer of the pulp under the action of air jets. The wall 21 is provided with a diaphragm to seal the room. On the other hand, the wall 22 is made of a porous material. In the specific example as shown, a frit glass capable of passing an air jet through the liquid layer of pulp indoors as its porous material is considered. In this case, the plate 28, which can close a part of the surface of the air passage of the frit glass, is again installed in the mixing chamber, thereby controlling the size of the air flow passage surface, which is advantageous.

In the example of the structure shown in FIG. 5 and FIG. 6, the shape of the mixing chamber 8 is conical, and it has the conical walls 29 and 30 parallel to each other in two layers, and between both walls, A passage of pulp liquid is formed in the. The pulp penetrates through the wall 29 of the mixing chamber and is supplied through a nozzle 31 introduced tangentially into the room, and the pulp is pivoted in the room. Air is supplied and injected from an air inlet pipe 32 connected to a compressed air source (not shown) through a plurality of holes 47 formed in the inner wall 30.

The conical inner wall 30 is slidable in the axial direction with respect to the outer wall 29, so that the distance between the inner wall 30 and the outer wall 29 is adjusted. Therefore, as a result of this, the thickness of the pulp liquid layer is adjusted. For this purpose, the rotatable inner wall 30 is applied to the tube 32 so that its position is controlled, the tube 32 being an air supply tube at the same time. In the inner wall 30, a conical obturator 33 is disposed. The obstructions 33 are attached to two rods 34 and 35 that can contact the inside of the cross section of the inner wall 30. If necessary, the obstructions 33 block a portion of the air distribution hole to allow air to flow into the mixing chamber. The passage area can be adjusted. In this way, the adjustment of the air inflow can be performed independently of the flow rate and flow rate of the pulp, so that bubbles can be generated appropriately for the flow of ink, kaolin or fiber in each sub-tank. Separation can be achieved.

Although the present invention has been described in particular with reference to an apparatus for ink removal of paper pulp, the present invention may be used for other purposes, for example for cleaning ore or for purifying white water by the flow of fibers. White curves (48) and (49), plotted against the volume ratio of air to volume obtained from laboratory test results and the pulp velocity in the mixing chamber, are shown in FIG. In the side view, the ratio of the air volume (l) to the pulp volume (l) is indicated on the vertical axis and the pulp whiteness (Scan) on the horizontal axis. Curve 48 shows the pulp color scheme when the flow rate of pulp is 4.23 m / sec, and the other curve 49 shows the pearl whiteness when the flow rate of pulp is 6.35 m / sec.

It can be seen that the difference in whiteness from 57 ° to 66.5 ° Scan can be obtained by adjusting the mixing ratio of air-pulp and the pulp speed in the mixing chamber. As a result of using the above-mentioned holding of the test magazines, a paper containing about 50% of the mechanical pulp whose whiteness of the unprinted margins was 6.65 ° Scan was used.

By applying the apparatus of the present invention, the whiteness of a printing portion containing about 2% of ink can be raised from 46 ° to 66.5 ° Scan with a holding time of 20 minutes. After a holding time of 2.5 minutes, the whiteness has already reached 46 ° to 64.5 ° Scan. In the case of treating by the conventional method using the same phage, even for the best results, only 62.3 ° Scan was achieved after the holding time of 20 minutes, and only about 54 ° Scan whiteness was achieved after 2.5 minutes.

The specific examples and the illustrated apparatus described above are not intended to limit the present invention, but various implementation methods within the scope of the present invention described in the claims are possible.

Claims (1)

Air flow to create at least one substantially cylindrical floatation tank, an inlet for introducing the liquid into the tank, to float and adhere to impurities, and to generate an air bubble in the liquid to form a surface bubble on the liquid in the tank. An apparatus for removing solid impurities contained in a liquid by barges comprising a venting means for supplying, a liquid bubble in the tank, and an outlet for separately discharging the liquid purified from the tank. A bubble discharge means for ejecting and discharging the bubble toward the surface bubble in the exit direction, and a duct means for recirculating the air of the high-flying stream, and an inlet is cut in the direction of the outer wall of the tank The inflow liquid around the axis of the bath provides a substantially circular flow pattern, and the outlet to the bubble is opened at the bottom of the bath, Wherein consisting of axial discharge pipe in the tank group extending to the bubble layer.

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