Method for mixing two fluids and mixing device used therewith

Abstract

 This invention relates to a method and device for mixing two fluids, whereby a fluid is fed into a mixing chamber (1) and the other fluid is injected into this mixing chamber (1), after which the mixture is directed through a tube (19) where the fluids are further mixed with each other. After bringing the fluids together in the mixing chamber (1) and after a first mixing, the fluids are mixed further by directing the mixture in the tube (19) along one side of at least one inner tube (20), which is provided coaxially in the tube and which is provided with axially distributed injection openings (21), and directing it through these injection openings (21) towards the other side of the inner tube (20).

Description

[0001] This invention relates to a method for mixing two fluids, in particular a gas with a liquid, whereby one fluid is brought into a mixing chamber and the other fluid is injected into this mixing chamber, after which the mixture is directed through a tube, where the fluids are further mixed with each other.

[0002] Such methods are applied, for instance, in the beverage industry, such as, for example, in breweries and softdrink factories, for introducing carbon dioxide into beverages.

[0003] Gas under pressure is fed into the chamber, into which the liquid is injected by means of openings in the wall of the chamber. As a consequence, the gas is distributed rather well in the liquid in the form of bubbles, however, still not sufficiently dissolved. This requires a certain period of time, and to this aim the liquid with the gas bubbles is fed into a long tube where the mixing and the dissolving of the gas in the liquid are continued.

[0004] These known methods require a rather long dissolving time.

[0005] It is clear that turbulence stimulates the dissolving, as the gas is distributed better throughout the liquid, and therefore it is known to place partitions into the tube, however, even then the dissolving speed of the gas remains limited.

[0006] Thus, the aim of this invention is to provide for a mixing method which does not have these disadvantages and which thus allows to mix two fluids together entirely in an efficient and fast manner, and, in case of a gas in liquid, allows to mix the gas rapidly and in relatively large quantities with the liquid or, more particularly, to dissolve it in the liquid.

[0007] According to the invention, this aim is achieved in that, after bringing the fluids together in the mixing chamber and after a first mixing, the fluids are mixed further by directing the mixture in the tube along one side of at least one inner tube, which is provided coaxially in the tube and which is provided with axially distributed injection openings, and injecting it through these injection openings towards the other side of the inner tube.

[0008] By the injection, a strong turbulence is obtained.

[0009] Preferably, the mixture is fed between the inner tube and the wall of the tube and injected into the inner tube and discharged through this inner tube.

[0010] Before the mixture of fluids is injected through the injection openings into the inner tube, an additional turbulence can be given to the mixture by altering the passage section in axial direction.

[0011] The invention also relates to a mixing device which is particularly suitable for applying the above-described method according to the invention.

[0012] Thus, the invention relates to a mixing device, which comprises a mixing chamber which is provided with inlets for the fluids to be mixed and with an outlet for the mixture of fluids, the characteristizing feature of which consist in that it also comprises at least one mixing tube, connected to this outlet of the mixing chamber, which mixing tube comprises a tube with therein a coaxially installed inner tube which is provided with axially distributed injection openings and which divides the tube into an inner space and a ring-shaped intermediate space between the inner tube and the wall of the tube, whereby the mixing tube is provided with an inlet which gives out to one of the spaces, and an outlet which connects to the other space.

[0013] Preferably, the inlet connects to the intermediate space and the outlet to the inner space.

[0014] The injection openings preferably are chosen such that they offer sufficient resistance to the mixture in order to obtain that a part thereof still shall reach the injection openings situated most remote in flow direction.

[0015] The injection openings in the inner tube can comprise several groups which are situated in radial planes, whereby the successive groups preferably are situated at regular mutual interspaces.

[0016] Between the successive groups of injection openings, at the side limiting the space for the mixture, the passage section for the mixture is altering in axial direction, in particular diminishing in size in flow direction and then suddenly increasing in size, immediately in front of a group of injection openings.

[0017] Preferably, the outer diameter of the inner tube successively is gradually increasing and subsequently more rapidly decreasing in front of a group of injection openings.

[0018] With the intention of better showing the characteristics of the invention, hereafter, as an example without any limitative character, a preferred form of embodiment of a method for mixing two fluids and of a mixing device used therewith according to the invention is described, with reference to the accompanying drawings, wherein:

figure 1 schematically represents a longitudinal cross-section of a mixing device according to the invention;

figure 2, at a larger scale, represents the part indicated by F2 in figure 1;

figure 3 represents a cross-section according to line III-III in figure 1.

[0019] The mixing device represented in the figures is destined for mixing carbon dioxide which is added to a beverage, and substantially consists of a mixing chamber 1 and a mixing tube 2 connected thereto.

[0020] The mixing chamber 1 is a double-walled chamber with an outer cylindrical housing 3, which is provided with a radially directed inlet 4 for the beverage, and an inner, coaxially installed drum 5 which, in its cylindrical mantle, is provided with openings 6 for the beverage, at a first extremity is provided with an axial inlet 7 for the carbon dioxide, and at the opposite extremity is provided with an axial outlet 8 for the mixture of beverage and carbon dioxide.

[0021] The first extremity of the drum 5 is seated in an end piece 9 which, on one hand, comprises a connection 10 for connecting the inlet 7 to a supply conduit for carbon dioxide, and, on the other hand, comprises a flange 11, which radially protrudes out of the drum 5, which flange is fixed by bolts to a flange 12 of the housing 3 and thereby closes off the space 13 between the drum 5 and the mantle 14 of the housing 3 at said extremity.

[0022] The other extremity of the drum 5 also is seated in an end piece 15, which, on one hand, comprises a connection 16 for connecting the outlet 8 to the mixing tube 2, and, on the other hand, comprises a flange 17, which radially protrudes out of the drum 5 and which is fixed to a flange 18 of the housing 3 and thereby closes off the space 13 between the drum 5 and the housing 3 at this other extremity.

[0023] The mixing tube 2 comprises a conduit or tube 19 with therein a coaxially installed inner tube 20, which is provided with axially distributed injection openings 21, and which divides the inner space of the tube 19 into an inner space 22 and a ring-shaped intermediate space 23 between the inner tube 20 and the wall of the tube 19.

[0024] At the side of the mixing chamber 1, the inner tube 20 is closed and seated in an end piece 24 which, by means of bolts, is fixed to a flange 25 at the tube 19 and partially closes off the intermediate space 23, however, by means of an inlet 26 consisting of several openings, connects it to a connection part 27 which is connected, for example, welded, to the connection part 16 of the end piece 15.

[0025] At the opposite side, the inner tube 20 is provided with an outlet 28 and also is seated in an end piece 29 which, by means of bolts, is fixed to a flange 30. This extremity 29 has, at its exterior side, a connection part 31 having the same size as said connection parts 16 and 27, for connecting it to a discharge conduit 32.

[0026] As the connection parts 27 and 31 are of equal size, the mixing tube 2 forms a module. A plurality of such modules can be installed one after the other.

[0027] Opposite to outlet 28, the end piece 29 is provided with an opening 33, such that the inner space 22 gives out to the discharge conduit 32.

[0028] The injection openings 21 in the inner tube 20 are distributed in groups which are situated in the longitudinal direction of the inner tube 20 at regular mutual interspaces, whereby the injection openings 21 of a group are situated in a radial plane and are equally distributed over the circumference of the inner tube 20.

[0029] Whereas the inner tube 20 has a constant inner diameter, the outer diameter thereof is varying in longitudinal direction.

[0030] Starting from a group of injection openings 21, the outer diameter first is gradually increasing and subsequently, immediately in front of a subsequent group of injection openings 21, rapidly diminishes, and is minimum at the height of the group of injection openings 21.

[0031] This means that the passage section in the intermediate space 23 alternatingly decreases and increases.

[0032] The functioning of the mixing installation according to the invention is as follows:

[0033] Through inlet 4, liquid is brought into the space 13, whereas, through connection part 10 and inlet 7, the gas to be mixed with said liquid is injected axially into the drum 5, preferably under pressure.

[0034] The liquid flows from the space 13 through the openings 6 into the drum 5, where it thus is mixed with the gas. It is important that a good distribution of the gas throughout the liquid is obtained.

[0035] The mixture of liquid with gas, which latter to the major part is in the form of bubbles, flows through outlet 8 out of the drum 5 and from there through connection parts 16 and 27 and the inlet 26 into the intermediate space 23 of the mixing tube 2.

[0036] At each group of injection openings 21, a portion of this mixture will be injected through these injection openings 21 into the inner tube 20.

[0037] The pressure drop of the mixture in the injection openings 21 must be sufficiently high in relation to the pressure drop in the intermediate space 23, in order to obtain that a part of the mixture reaches the extremity of the mixing tube 2 and flows through the injection openings 21 of the last group in front of the outlet 28.

[0038] Due to the varying passage section around the inner tube 20, a large turbulence is created in the intermediate space 23, which turbulence, together with the injection through injection openings 21, guarantees for a good and fast mixing of the liquid and the gas.

[0039] In the inner tube 20, the mixture flows towards the outlet 28, which means that the mixture is injected through the radially directed injection openings 21 and thus arrives in the inner tube 20 directed transverse to the axial flow in this latter, as a result of which a particular mixing effect is obtained.

[0040] The location, the number and the size of the injection openings 21 can be calculated, taking into account the length of the mixing tube 2, the flow rates of the gas and the liquid, and the pressure of the gas, in order to create an optimum mixing, such that, at the outlet 28 of the mixing tube 2, the gas is completely dissolved in the liquid and no bubbles are visible any more.

[0041] If the mixing tube 2 seems to be of insufficient length, then a second tube or even several similar mixing tubes can be attached thereto, whereby then the connection part 27 of a subsequent mixing tube 2 is connected to the connection part 31 of the preceding mixing tube 2.

[0042] The mixing device may, for example, be used for mixing CO₂ with beverages, such as water, lemonade or beer, however, of course other gasses can be mixed with other liquids, too.

[0043] The mixing device also might be used for mixing liquids, for example, for mixing sirup with water or milk.

[0044] The invention is in no way limited to the forms of embodiment described heretofore and represented in the figures, on the contrary may such method for mixing and mixing device be realized in various variants, without leaving the scope of the invention.

Claims

1. Method for mixing two fluids, in particular a gas with a liquid, whereby a fluid is fed into a mixing chamber (1) and the other fluid is injected into this mixing chamber (1), after which the mixture is directed through a tube (19) where the fluids are further mixed with each other, characterized in that, after bringing the fluids together in the mixing chamber (1) and after a first mixing, the fluids are mixed further by directing the mixture in the tube (19) along one side of at least one inner tube (20), which is provided coaxially in the tube and which is provided with axially distributed injection openings (21), and injecting it through these injection openings (21) towards the other side of the inner tube (20).

2. Method according to claim 1, characterized in that the mixture is directed between the inner tube (20) and the wall of the tube (19) and is injected into the inner tube and is discharged through this inner tube (20).

3. Method according to claim 1 or 2, characterized in that, before the mixture of fluids is injected through the injection openings (21) into the inner tube (20), an additional turbulence is given to the mixture by means of an alteration of the passage section in axial direction.

4. Mixing device, comprising a mixing chamber (1) provided with inlets (4,7) for the fluids to be mixed and with an outlet (8) for the mixture of fluids, at least one mixing tube (2) connected to this outlet (8) of the mixing chamber, said mixing tube (2) comprising a tube (19) with therein a coaxially installed inner tube (20), which is provided with axially distributed injection openings (21) and which divides the tube (19) into an inner space (22) and a ring-shaped intermediate space (23) between the inner tube (20) and the wall of the tube (19), whereby the mixing tube (2) is provided with an inlet (26) which gives out to one of the spaces (22,23), and an outlet (28) which connects to the other space (23,22).

5. Mixing device according to claim 4, characterized in that the inlet (26) of the mixing tube (2) connects to the intermediate space (23) and the outlet (28) to the inner space (22).

6. Mixing device according to claim 4 or 5, characterized in that injection openings (21) are chosen such that they offer sufficient resistance to the mixture, in order to obtain that a part thereof reaches the injection openings (21) situated most remote in flow direction.

7. Mixing device according to any of the claims 4 to 6, characterized in that the injection openings (21) in the inner tube (20) comprise several groups which are situated in radial planes, whereby the successive groups preferably are situated at regular mutual interspaces.

8. Mixing device according to any of the claims 4 to 7, characterized in that at the side of the space (22,23) into which the inlet (26) of the inner space (20) gives out, the passage section is varying in longitudinal direction and, for example, successively increases and decreases.

9. Mixing device according to claims 5, 7 and 8, characterized in that between the successive groups of injection openings (21), the outer diameter of the inner tube (20) increases and decreases.

10. Mixing device according to claim 9, characterized in that between two subsequent groups of injection openings (21), the outer diameter of the inner tube (20) first gradually increases and then faster decreases.

Drawing