WO1999030793A1

WO1999030793A1 - Inlet arrangement

Info

Publication number: WO1999030793A1
Application number: PCT/SE1998/002242
Authority: WO
Inventors: Per-Olof BJÖRK; Bengt Jonsson
Original assignee: Björks Rostfria Ab
Priority date: 1997-12-15
Filing date: 1998-12-08
Publication date: 1999-06-24
Also published as: SE511304C2; SE9704673D0; SE9704673L; AU1895899A

Abstract

The invention relates to an inlet arrangement for a flotation tank (4) comprising a first inflow opening (2) for a first fluid, a second inflow opening (18) for a second fluid and an outflow opening (16) for the first and second fluids. At least one fork (6) downstream of the first inflow opening (2) comprises a first and second branch duct (8, 10).

Description

Inlet arrangement

The present invention relates to an inlet arrangement for a flotation tank, a flotation tank with such an inlet arrangement and also a method of guiding fluids to a flotation tank.

One possible cleaning method for separating particles from liquid is flotation. In flotation, the liquid to be cleaned is introduced into a flotation tank. The liquid is preferably introduced at the bottom of the flotation tank. Air is also supplied at the bottom of the flotation tank, in the form of very small bubbles which rise upwards towards the surface of the liquid in the flotation tank. On the way towards the surface of the liquid, particles present in the liquid adhere to the bubbles which thus carry the particles along with them to the surface. On the surface, a mat of particles is then formed, which is removed at regular intervals.

According to the known art , the air is introduced in the form of bubbles directly into the flotation tank. Alternatively, the air bubbles are introduced in the form of an air-saturated liquid, a so-called dispersion liquid.

One problem that arises in flotation is that of inducing the liquid to be cleaned to flow in a laminar manner in the flotation tank at the same time as the air bubbles rise upwards in this liquid, for the fact is the capacity of the bubbles for carrying the particles up to the surface decreases when the liquid flow is turbulent.

The way the liquid flows in the flotation tank depends to a great extent on how the liquid is introduced into the flotation tank.

One object of the present invention is to provide an inlet arrangement for a flotation tank, which inlet arrangement induces one or more fluids that are introduced into the flotation tank by means of the inlet arrangement to flow in an essentially laminar manner inside the flotation tank.

This is achieved by an inlet arrangement according to Patent Claim 1.

Another object of the invention is to provide a method of inducing one or more fluids to flow in an essentially laminar manner inside a flotation tank.

This is achieved by a method according to Patent Claim 10.

A further object of the invention is to provide a flotation tank in which one or more fluids are induced to flow in an essentially laminar manner on introduction into the flotation tank.

Such an inlet arrangement for a flotation tank leads to a contaminated fluid being cleaned effectively and with very good results because the bubbles introduced into the flotation tank are allowed to adhere to the particles in the fluid flowing in a laminar manner in the flotation tank.

The invention is described in greater detail below with reference to the exemplary embodiments shown in the appended drawings, in which:

Fig. 1 shows an inlet arrangement for a flotation tank according to the present invention, and

Fig. 2 shows a flotation tank with an inlet arrangement according to the present invention.

Fig. 1 shows an inlet arrangement 1 according to the present invention, which inlet arrangement 1 comprises a first inflow opening 2 for a first fluid which is to be cleaned in a flotation tank 4. Downstream of the first inflow opening 2, there is a fork 6 which divides the first fluid into two main flows through a first and second branch duct 8, 10. The first and second branch ducts 8, 10 are of essentially the same length and extend in essentially the same plane.

The first and second branch ducts 8, 10 initially extend away from one another in essentially opposite directions, subsequently to merge with a first bend 12 and a second bend 14 which bring the respective branch ducts 8, 10 to extend in a direction essentially towards one another. The first and second branch ducts 8, 10 thus have a U- shape. It is possible for the first and second branch ducts 8, 10 to extend in different planes which intersect one another.

According to the embodiment shown in Fig. 1, the branch ducts 8, 10 have an essentially circular cross-section, that is to say they are tubular and have essentially the same diameter. The cross-sectional area of the branch ducts 8, 10 may decrease continuously or in a stepped manner, as shown in Fig. 1.

The first and second branch ducts 8, 10 converge or meet at an outflow opening 16 which is orientated in such a manner that the first fluid leaves the outflow opening 16 essentially at right angles in relation to the direction of extension of the first and second branch ducts 8, 10. In other words, a normal to the plane in which the branch ducts 8, 10 extend is parallel to a centre axis of the outflow opening 16.

A second inflow opening 18 for a second fluid is arranged essentially concentrically in relation to the outflow opening 16. The second inflow opening 18 is thus essentially diametrically located in relation to the outflow opening 16, in the region where the branch ducts 8, 10 meet one another. The geometrical shape of the inlet arrangement 1 leads to the first and second fluids flowing out through the outflow opening 16 in an essentially laminar manner.

As is shown in Fig. 2, an inlet duct 20 in the form of a pipe diverging from the inlet arrangement 1 can be connected to the outflow opening 16 of the inlet arrangement 1. The inlet duct 20 is arranged in the bottom of a flotation tank 4 and extends upwards in the flotation tank 4 to a position below a fluid surface 22 in the flotation tank 4.

The fluid introduced through the first inflow opening 2 may consist of, for example, a contaminated liquid which is to be cleaned in the flotation tank 4. The fluid introduced through the second inflow opening 18 may consist of, for example, an air-saturated liquid, such as a dispersion liquid, which contains a great many air bubbles. When the contaminated liquid and the dispersion liquid together flow in an essentially laminar manner in the inlet duct 20 in the flotation tank 4, the air bubbles from the dispersion liquid adhere to particles in the contaminated liquid. The air bubbles then float up to the surface 22 together with the particles which remain at the surface 22 and form a mat on the surface 22. This mat is removed at regular intervals. Fluid that has been cleaned of particles flows on towards the bottom of the flotation tank 4, where it is drawn off through a draw- off opening 24.

According to the embodiment shown in Fig. 2, the inlet arrangement 1 is located below the flotation tank 4.

The method of guiding the fluids to the flotation tank 4 is implemented in the following manner: the first fluid is made to flow through the first inflow opening 2 of the inlet arrangement 1. The first fluid is then divided into two main flows downstream of the first inflow opening 2. The two main flows are then made to flow in essentially opposite directions in relation to one another, after which the two main flows are, by means of a bend 12, 14 of the inlet arrangement 1 provided for each main flow, made to flow in a direction essentially towards one another. The two main flows then leave the inlet arrangement 1 through a common outflow opening 16. At the same time, a second fluid is made to flow through a second inflow opening 18 of the inlet arrangement 1, after which the second fluid leaves the inlet arrangement 1 through the outflow opening 16. Finally, the first and second fluids are guided together into the flotation tank 4.

Claims

Patent Claims

1. Inlet arrangement for a flotation tank (4) comprising a first inflow opening (2) for a first fluid, a second inflow opening (18) for a second fluid and an outflow opening (16) for the first and second fluids, characterized by at least one fork (6) downstream of the first inflow opening (2) comprising a first and second branch duct (8, 10) .

2. Inlet arrangement according to Claim 1, characterized in that the first and second branch ducts

(8, 10) are of the same length.

3. Inlet arrangement according to one of the preceding claims, characterized in that the first and second branch ducts (8, 10) converge at the outflow opening (16) .

4. Inlet arrangement according to any one of the preceding claims, characterized in that the outflow opening (16) is orientated in such a manner that the first and second fluids leave the outflow opening (16) essentially at right angles in relation to the direction of extension of the first and second branch pipes (8, 10) .

5. Inlet arrangement according to any one of the preceding claims, characterized in that the second inflow opening (18) is arranged essentially concentrically with the outflow opening (16) .

6. Inlet arrangement according to any one of the preceding claims, characterized in that the first and second branch ducts (8, 10) fork in such a manner that the first fluid is divided into two main flows in essentially opposite directions in relation to one another, subsequently to pass through a bend (12, 14) in each branch duct (8, 10), which bends guide the respective main flows in a direction essentially towards one another .

7. Inlet arrangement according to any one of the preceding claims, characterized in that an inlet duct (20) to a flotation tank (4) is arranged at the outflow opening (16) .

8. Inlet arrangement according to Claim 7, characterized in that the inlet duct (20) diverges in the direction away from the outflow opening (16) .

9. Flotation tank comprising an inlet duct (20) for fluids, characterized in that an inlet arrangement (1) according to Claim 1 is arranged at the inlet duct (20) .

10. Method of guiding fluids to a flotation tank according to Patent Claim 9, characterized in that a first fluid is made to flow through a first inflow opening (2) of an inlet arrangement (1) , in that the first fluid is divided into two main flows downstream of the first inflow opening (2) , in that the two main flows are made to flow in essentially opposite directions in relation to one another, in that the two main flows are then, by means of a bend (12, 14) of the inlet arrangement (1) provided for each main flow, made to flow in a direction essentially towards one another, in that the two main flows leave the inlet arrangement (1) through a common outflow opening (16) , in that a second fluid is made to flow through a second inflow opening (18) of the inlet arrangement (1) , in that the second fluid leaves the inlet arrangement (1) through the outflow opening (16) , and in that the first and second fluids are guided together into the flotation tank (4) .