DE102008030531A1 - Method and device for removing gas, in particular air from flotation foam and their use - Google Patents

Abstract

The process serves to remove gas, in particular air from flotation foam, e.g. obtained when deinking from a waste paper suspension. For degassing serves a e.g. rotationally symmetrical chamber (5), within which a rotor (3) is arranged and capable of causing the incoming flotation foam (1) in rotation and to the inner wall (2) of the chamber (5) as a rotating liquid ring (13). The degassed flotation foam (1 ') is removed by a vent opening (8) located in the inner wall (2), in the bottom (6) or in the upper wall (7) of the chamber (5). The separated gas can accumulate radially inside the liquid ring (13) and be discharged.

Description

The The invention relates to methods according to the preamble of claim 1 and devices for its implementation.

The Separation of air from flotation foam, the flotation of pulp suspensions, e.g. B. incurred in waste paper processing, is u. a. therefore necessary to continue to treat the flotation foam to be able to. Flotation foam, which in the flotation of a paper fiber-containing suspension is known to be particular difficult to handle as it is difficult to vent or to drain. Such a flotation foam is limited flowable and pumpable and tends to contact the To fix walls.

From the DE 40 09 042 C2 a device for separating air from flotation is known. This device consists essentially of a hydrocyclone, which is indeed well suited for venting liquids and foams, but works as a hydraulic machine in a closed system, which requires appropriate apparatus and requires at least some fluidity of the foam.

From the EP-A2-1 350 887 a device is known in which a winged rotor is surrounded by a non-co-rotating wall. The incoming foam is set in rotation and processed so that a large part of the air can escape. Then he can flow down directly, z. B. in a foam collection tank. This device is simple, compact and reliable.

The DE 35 19 374 A1 describes a mechanical foam destroyer that can be dipped directly into the top foam layer. Such mechanical foam destroyer z. B. be used in a foam collection tank a flotation plant. The Schaumzerstörer capture only the upper, highly air-containing foam layer, suck them and hurl the liquid portion radially away, the liquid drops help secondarily to bring the surface foam bubbles to burst. Deeper foam layers are not detected by this system. In the deeper layers a very heavy, wet foam is created, which is not subjected to forced ventilation. The deaeration of this wet foam happens only by sedimentation, which requires a long residence time. This device is relatively complicated in terms of both its structural design, the space required and the energy consumption.

Of the The invention is therefore based on the object, a corresponding To create a method with no great effort a Separation of air from the outflowing foam allows that at least goes so far as to make the foam pumpable is.

These The object is achieved by that described in the characterizing part of claim 1 Characteristics solved. Suitable degassing devices are described in subclaims.

The inventive method and the used Device with respect to the nature of the flotation foam relatively few claims. The degassing device can used with advantage at the foam collecting channel of a flotation plant be, especially at the discharge opening. There is the horizontal, or slightly sloping Flow direction of the flotation foam in a nearly vertical, downwards deflected. The effect of the rotor is then essentially the outflowing To set foam in rotation, making it a liquid ring forms on the wall surrounding the rotor, wherein the air radially wanders inside. It can then z. B. flow upwards. The deduction of the degassed foam then takes place from this liquid ring out, with advantage by a tangential outlet. By This way of driving can be a relatively high degree of ventilation reach, z. B. a residual air content below 10%.

Perhaps can a pressure build-up, z. B. be used from 0.5 to 0.8 bar, which may be sufficient to remove the foam into the enema to lead a flotation plant. The rotor will be an advantage so driven that an outer peripheral speed between 8 and 25 m / s is achieved. The centrifugal acceleration in the liquid ring corresponds advantageously at least 100 times the gravitational acceleration.

The The invention and its advantages are explained with reference to Drawings. Showing:

1 Sectional view of the degassing device according to the invention;

2 a flotation cell with attached degassing device;

3 Sectional view of another degassing device according to the invention;

4 - 6 each a plan view of a further degassing device according to the invention;

7 - 9 further sketches for the cultivation of the degassing device according to the invention to a flotation cell (variants of 2 ).

In 1 a degassing device according to the invention is shown in section, this drawing contains only the essential functional parts without structural details. The device has a chamber 5 on, which is a substantially rotationally symmetric round inner wall 2 contains and with a floor 6 is completed down. The inner wall 2 the chamber 5 is cylindrical in the example shown here, but it may also be conical and / or have gutters, strips or grooves. The floor 6 prevents the uncontrolled escape of the liquid carried in the chamber down. The chamber may have inside a diameter D between 100 and 1000 mm and an axial extent H between 100 mm and 600 mm. Concentric with the cylindrical inner wall 2 is a rotor 3 arranged, the hydraulically effective part, in particular the rotor blades 4 inside the chamber 5 located. The right rotor wing 4 is only partially drawn. The rotor 3 is powered by a drive 14 set in rotation, preferably so that it rotates outside with a peripheral speed between 8 and 25 m / s.

In the preferred position of use of the device with vertical central axis 11 enters the flotation foam to be degassed 1 from the top into the central area of the chamber 5 one. He is from the rotor blades 4 captured and set in rotation, making it a liquid ring 13 (please refer 2 ) to the inner wall 2 of the container applies. As a result of the centrifugal forces, the gases, in particular the air, migrate radially inwards, resulting in the desired degassing of the flotation foam 1 leads. In general, the gases can escape upwards, with a degassing line 20 , which is here in the center, is helpful, because thereby an unnecessary back mixing of the leaked gases with the incoming flotation foam 1 is avoided. Of course, the gases can also be sucked off, for. B. by a hollow rotor. In the wall of the chamber 5 there is a vent here 8th in the outlet 9 empties. In other cases not shown here, the vented flotation foam 1' also through one or more openings in the ground 6 or in the upper end of the chamber 5 forming wall 7 be derived. In this way, in a liquid layer on the inner wall 2 rotating suspension from the chamber 5 be discharged, so that they are degassed flotation foam 1' the siphon 9 happens.

The peripheral speed of the rotor 3 is suitably chosen so that the centrifugal forces are sufficient to a liquid ring on the inner wall 2 to build. Depending on the diameter of the inner wall 2 That is about 8 to 25 m / s.

To illustrate the applications of the device according to the invention shows 2 in a side sectional view of a flotation device 10 for a waste paper suspension. This contains a substantially closed container, which from above through a mixing device 12 is supplied with the paper fiber-containing suspension S to be floated. In a manner known per se, the suspension S is mixed with air L to form a ventilated suspension S ', from within the flotation device 10 the non-fibrous, hydrophobic ingredients such. B. color particles and stickies in the flotation foam 1 rising up. The accepts 15 at the bottom of the flotation device 10 withdrawn contains most of the paper fibers and water.

The flotation foam 1 flows into the foam collecting channel 16 from and through a z. B. 200 to 600 mm wide downpipe 17 into the already described chamber 5 in which he turns as a rotating liquid ring 13 to the inner wall 2 invests. By this application of the degassing is the greasy strong air-containing flotation foam 1 so far outgassed that he as a flotation foam 1' through the foam outlet nozzle 9 deducted in a centrifugal pump, not shown here can be further transported.

In many cases, the accept again becomes another part of the flotation device 10 or supplied to another flotation, until the cleaning is done so far that the accepts can be further processed. Often, various parts of the flotation device are formed as cells, which are flowed through by the suspension in succession. If such cells are arranged side by side, they can share a common foam collecting channel 16 in which the flotation foam 1 drained, collected and then through a downpipe 17 to the chamber 5 to be led.

The degassing device according to the invention can also be designed so that, unlike in 2 shown the degassing line 20 not central, concentric with the midline 11 is arranged. So is in accordance with 3 outside the downpipe 17 a degassing opening 18 in the chamber closing the chamber upwards 7 , To the degassing openings 18 is a degassing line 19 connected. Due to the radial distance of the degassing opening 18 from the center line 11 of the rotor 3 can its pumping action be used The radially inner regions of the blades 4 can then act as pumping blades for the released gas and its withdrawal from the chamber 5 accelerate.

As a result of the rotation, the liquid ring is formed 13 on the inner wall 2 made with a level height N, preferably between 80 and 120 mm is its smallest point.

The degassing opening 18 is then a few millimeters closer to the center (eg 10 to 50 mm), so that no mixing of gas and foam occurs. The rotor 3 dips into the liquid ring 13 one. Its minimum distance to the inner wall 2 is preferably 10 to 40 mm. The distance to the ground 6 as well as to the chamber 5 upwards closing wall 7 is in each case 3 to 50 mm, preferably 10 to 30 mm.

There may be one or more vent lines 19 to be available. With completely symmetrical flow conditions of the foam inflow, they would expediently be distributed uniformly over the circumference. As 4 shows, the degassing lines 19 also inside the downpipe 17 be arranged, wherein they are guided so that they prevent the backmixing of foam and air. It is also conceivable how 5 shows the degassing line 19 ' as radial bulge in the downpipe 17 to design, so that it forms an axially upwardly conveying channel. This radial bulge can be further up in a radial recess 19 '' go over, ie that the air / gas above this transition within the downpipe 17 is continued (s. 6 ). In particular, if the foam is not centrally in the downpipe 17 would be introduced, the degassing line 19 ' be arranged on the foam flow rather opposite side.

Furthermore, the comparison makes the 4 and 5 clearly that the blades 4 of the rotor 3 not only strictly radial, but similar to centrifugal pumps can also be performed bent. The direction of rotation is indicated in these two representations in each case by an arrow. The siphon 9 can z. B. tangential ( 4 ) or radial ( 5 ).

A favorable arrangement of the degassing device according to the invention when connected to a flotation device 10 is already in the 2 been shown. If no central degassing line (such as degassing line 20 in 2 ), but instead variants according to the 3 to 5 , arise also other cultivation situations.

That's how it shows 7 the flotation device 10 with a downpipe 17 for the flotation foam 1 , The degassing line 19 ' is similar to in 5 , as a radial bulge in the downpipe 17 executed and opens up in the gas space of the flotation device 10 , Another option is according to 8th in it, the degassing line 19 (one or more) outside the downpipe 17 from the chamber 5 the degassing directly into the gas space of the flotation device 10 respectively. According to 9 can the vents 18 radially outside the downpipe 17 lie with and in the downpipe 17 lying degassing lines 19 be connected, whereby the device is much more compact.

As a rule, the degassing line, whatever it may be, is advantageously located in the gas space of the flotation device 10 lead. As a result, the release of the gas G, in particular air, immediately sucked back and therefore be reused for flotation. Wind turbines in the environment, moisture loss and air conditioning costs are avoided. Conveniently, the flotation 10 as a closed cell.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4009042 C2 [0003]
• - EP 1350887 A2 [0004]
• - DE 3519374 A1 [0005]

Claims (25)

Process for removing gas, in particular air, from flotation foam formed in the flotation of a paper-fiber-containing suspension (S) ( 1 ), in which the flotation foam ( 1 ) by at least one driven rotor ( 3 ) is rotated, characterized in that the flotation foam ( 1 ) within one with an inner wall ( 2 ) with a floor ( 6 ) closed chamber ( 5 ) through the rotor ( 3 ) is rotated so that on the inner wall ( 2 ) a liquid ring ( 13 ) and that gas, in particular air, accumulates radially inside this liquid ring and that the at least partially degassed flotation foam ( 1' ) from the liquid ring ( 13 ) is deducted. A method according to claim 1, characterized in that the at least partially degassed flotation foam ( 1' ) by at least one exhaust port ( 8th ) through which the inner wall ( 2 ) is removed through the wall. A method according to claim 1 or 2, characterized in that the at least partially degassed flotation foam ( 1' ) through at least one exhaust opening in the floor ( 6 ) the chamber ( 5 ) or in which the chamber ( 5 ) upwards closing wall ( 7 ) is withdrawn through. Method according to claim 1, 2 or 3, characterized in that the rotor ( 3 ) is driven so that its radially outermost part has a peripheral speed between 6 and 25 m / sec, preferably 7 and 12 m / sec. Method according to claim 1, 2, 3 or 4, characterized in that the liquid ring ( 13 ) over the inner wall ( 2 ) has a level height (N) between 50 and 200 mm, preferably 80 to 120 mm. Method according to one of the preceding claims, characterized in that the centrifugal acceleration in the liquid ring ( 13 ) is at least 100 times the gravitational acceleration. Method according to one of the preceding claims, characterized in that the discharged flotation foam ( 1' ) has an overpressure relative to the ambient pressure of between 0.5 bar and 1.5 bar, preferably 0.5 to 0.8 bar. Method according to one of the preceding claims, characterized in that the flotation foam ( 1 ) is degassed so far that the residual gas content of the partially degassed flotation foam ( 1' ) is at most 10%. Device for carrying out the method according to one of the preceding claims, which comprises a driven rotor ( 3 ) to the flotation foam ( 1 ) in rotation, characterized in that the rotor ( 3 ) within one with an inner wall ( 2 ) ( 5 ) arranged with a floor ( 6 ) is closed at the bottom and in the inner wall ( 2 ) at least one exhaust opening ( 8th ) for discharging the flotation foam ( 1' ) is located. Device according to claim 9, characterized in that the chamber ( 5 ) a cylindrical inner wall ( 2 ) having. Apparatus according to claim 10, characterized in that the inner diameter (D) of the inner wall ( 2 ) between 100 mm and 1200 mm, preferably 300 mm to 800 mm. Apparatus according to claim 10 or 11, characterized in that the inner wall ( 2 ) the chamber ( 5 ) is concentric with the rotor. Apparatus according to claim 10 or 11, characterized in that the inner wall ( 2 ) the chamber ( 5 ) is not concentric with the rotor. Device according to one of claims 9 to 13, characterized in that the axial extent (H) of the chamber ( 5 ) is between 100 mm and 600 mm, preferably 150 to 400 mm. Device according to one of claims 9 to 14, characterized in that the position of use of the device with the vertical center axis ( 11 ). Device according to one of claims 9 to 14, characterized in that the position of use of the device with the horizontal or oblique central axis ( 11 ). Device according to one of claims 9 to 16, characterized in that the rotor ( 3 ) with rotor blades ( 4 ) and that the smallest distance between the rotor blades ( 4 ) and the inner wall ( 2 ) the chamber ( 5 ) a value between 10 mm and the outer diameter of the rotor blades ( 4 ) Has. Device according to one of claims 9 to 17, characterized in that the device via a downpipe ( 17 ) with a flotation device ( 10 ) is connected so that the flotation foam formed therein ( 11 ) into the chamber ( 5 ) can drain. Device according to one of claims 9 to 18, characterized in that for the discharge of the gases from the chamber ( 5 ) at least one not with the rotor ( 3 ) concentric degassing opening ( 18 ) in the wall closing the chamber ( 7 ) is present, which in a degassing line ( 19 ) opens. Apparatus according to claim 18 or 19, characterized in that for the discharge of the gases from the chamber ( 5 ) at least one not with the rotor ( 3 ) concentric degassing line ( 19 ' . 19 '' ) located on or in the downpipe ( 17 ) runs. Device according to one of claims 9 to 18, characterized in that for the discharge of the gases from the chamber ( 5 ) a central degassing line ( 20 ) is available. Device according to one of claims 18, 19, 20 or 21, characterized in that the degassing line ( 19 . 20 ) to a flotation device ( 10 ) and thereby into the gas space of the flotation device ( 10 ) opens. Device according to one of claims 18 and 19, 20 or 21, characterized in that the degassing line ( 19 . 19 ' . 20 ) in the downpipe ( 17 ) opens. Device according to one of claims 9 to 23, characterized in that the rotor ( 3 ) with a drive ( 14 ), which is the radially outer part of the rotor ( 3 ) with a peripheral speed between 8 m / s and 25 m / s can drive. Use of the device according to one of the preceding claims in the degassing of the resulting in the flotation of a paper fiber-containing suspension (S) flotation foam ( 1 in which the flotation serves to remove impurity particles, in particular ink particles, from the suspension (S) and in at least one flotation device ( 10 ) is carried out.