EP0796651B1

EP0796651B1 - Mixing device

Info

Publication number: EP0796651B1
Application number: EP97200806A
Authority: EP
Inventors: Coen Hendrik Decnop
Original assignee: Individual
Current assignee: Typhoon Group BV
Priority date: 1996-03-19
Filing date: 1997-03-19
Publication date: 2004-08-04
Anticipated expiration: 2017-03-19
Also published as: NL1002649C2; DE69730068D1; DE69730068T2; EP0796651A1

Description

The invention relates to a device for mixing a carrier liquid with one or more additives comprising a closed housing with an inlet and an outlet opening for the liquid and an infeed port for the or each additive in addition to a mixing gear accommodated therein.
Such a mixer is applied in many processes wherein use is made of for instance static mixers, i.e. a carrier liquid is transported along a static body together with a pre-admitted additive such that a mixing takes place as a result of the differing flows between additive and carrier liquid. For particular substances as additive this does not work well and use is therefore also often made of active mixers in the form of a fixed quantity of carrier liquid which is mixed with the additive in a vessel by means of stirring apparatus. The drawback here is that a fixed quantity of liquid is mixed at a time, this being disadvantageous for continuous processes.
GB 998329 describes a mixer for two or more liquids comprising a cylindrical mixing chamber with at least two zones separated by an apertured disc around the drive shaft, wherein at least two liquids under pressure are brought into the first zone, and the resulting mixture is constrained to flow through the apertures of the disc to the second zone which is provided with a mixture discharge outlet. This mixer requires dividing of the mixing chamber in zones separated by apertured discs in order to obtain a good mixing of the two or more liquids.
The invention has for its object to provide a device with which a continuous mixing process is realized with a considerably higher efficiency so that a perfect mixing is brought about, also for substances which are difficult to mix.
The device according to the invention is distinguished in that the mixing gear is formed by at least one rotatingly driven blade assembly, the rotation shaft of which is received centrally in the cross sectionally non-round housing, wherein the mixing gear is formed by at least one rotatingly driven blade assembly, the rotation shaft of which is received centrally in the cross sectionally non-round housing, which unround form of the housing causes the main flow between the inlet and the outlet to be situated substantially along the outside of the housing, wherein the inlet opening is situated substantially opposite the mixing gear which is designed for exerting a pushing action on the liquid in the direction toward the inlet opening for creating a counter flow, wherein the vigorous shearing action between the counter flow and main flow results in a good mixing.
Due to the counterflow effect of the stirring apparatus on the carrier liquid there occurs in the mixing housing on the one hand a flow in the main flow direction and on the other a part-flow in opposing direction whereby the additive is mixed vigorously with the carrier liquid. Because of the non-round form of the housing the main flow will be situated along the outside of the housing while the counterflow takes place centrally in the housing. The good mixing of the substances results from the vigorous shearing action between both flows.
The port for the additive is preferably arranged in the side wall of the housing, i.e. it is directly entrained in the main flow which is subsequently fed back into the counterflow in the central part. It is herein also possible to introduce the additive via a guide tube directed from the port toward the central shaft so that this additive directly enters the counterflow.
If the blade assembly is constructed from two groups of blades which are fixed at a mutual distance to the rotation shaft thereof, it is recommended to have the guide tube debouch on the side of at least the leading blade assembly remote from the feed opening for the carrier liquid.
In a further development the leading blade assembly consists of a part which has an axial pushing action and a part which has a radial pushing action. Intensive mixing is hereby improved still further.
Above mentioned and other features of the invention will be further elucidated hereinbelow in the figure description of two embodiments. In the drawing:
fig. 1 shows a perspective view of a first embodiment of the device according to the invention with partly broken away parts of the mixing housing;
fig. 2 shows a view corresponding with fig. 1 of a second embodiment of the device according to the invention;
fig. 3 shows a perspective view of a part of the blade assembly of fig. 2.
Designated in fig. 1 with the numeral 1 is the housing of the device which has a non-round cross section and is embodied here with a rectangular section.
On the right-hand side the rectangular wall connects onto an end flange 2 which can be connected by means of bolts 3 to a connecting flange 4 of a pipe system 5, this such that this latter connects onto the inlet opening 6.
Fixed on the opposite side of the housing by means of bolts 3 via a connecting flange 2' is a connection flange 7 which serves via the bearing 8 as mounting for a rotation shaft 9 extending co-axially in housing 1. Flange 7 bears a plurality of (here four) spacers 10 for fixing a flange 11 of a drive, for instance electric motor 13. This latter is coupled directly to rotation shaft 9 of the mixing gear. The mixing gear consists of a blade assembly formed here by two blade rotors 14, 15 placed at a mutual distance on rotation shaft 9. The blades are adjusted such that when caused to rotate in the direction of arrow P1 a pushing action as according to arrow P2 results, i.e. in the direction of inlet opening 6.
The additives are added to the housing via pipes 16, this being done into the flow P3 of the carrier liquid from inlet opening 6. After the mixing the mix leaves the housing via outlet opening 17 and discharge pipe 18.
The operation of the above described device is as follows. The carrier liquid is fed into housing 1 under pressure through inlet opening 6 via the pipe 5. The additive is simultaneously introduced via the pipes 16 and a first mixing will take place. The main flow will separate into four part-flows which are situated substantially in the corners of the housing. A part of the liquid is fed back in the direction of arrow P2 by the axial pushing action of mixing gear 14, 15. Flows P2 and P3 will be mixed once again wherein a strong turbulent flow is formed. The intensively mixed carrier flow and additives leave the housing via pipes 18.
Fig. 2 shows an alternative embodiment wherein the same elements are however designated with the same reference numerals.
The difference from the embodiment according to fig. 1 is the different embodiment of the mixing gear, consisting here of two rotors 20 and 21 which are placed at a mutual distance and likewise rotated by a rotation shaft 9 in the direction of arrow P1. The left-hand rotor 20 consists of a closed disc on which are placed blades which cause a radial pushing action in the direction of arrow P5.
The right-hand rotor 21 consists of a dish-shaped disc, the outer flange of which is provided with blades 22 (see fig. 3) which cause an axial pushing action in the direction of arrow P2. The outer edge of the dish is provided with a plurality of passage openings 23 placed such that a radial pushing action as according to arrow P6 is created there. Extra turbulent flows are herewith obtained along the corner parts of housing 1 and a stronger shearing action is brought about between these flow parts whereby a highly intensive mixing is obtained.
Another difference from the embodiment according to fig. 1 is that a pipe 24 for an additive is fed through into the housing 1, the outer end of which debouches in the dish-shaped rotor 21. This ensures that the additive first acquires a radial flow path and is subsequently entrained in the axial flow paths.
The invention is not limited to the above described embodiments. The housing does not for instance have to have a square cross-sectional form but may have more than four corners such as a hexagon or octagon. The housing may also have an oval form, this such that within the inventive concept one or more flow spaces are created between the imaginary peripheral cylinder of the rotors of the mixing gear and the inner side of the housing.
The position of the feed pipes 16 in the housing can also be random, wherein an additive may also be already added in the feed pipe 5 for the carrier liquid.

Claims

Device for mixing a carrier liquid with one or more additives comprising a closed housing (1) with an inlet (6) and an outlet opening (17) for the liquid and an infeed port (16) for the or each additive in addition to a mixing gear accommodated therein, the mixing gear being formed by at least one rotatingly driven blade assembly (14,15), the rotation shaft (9) of which is received centrally in the cross sectionally non-round housing (1), which unround form of the housing causes the main flow between the inlet and the outlet to be situated substantially along the outside of the housing, wherein the inlet opening is situated substantially opposite the mixing gear which is designed for exerting a pushing action on the liquid in the direction toward the inlet opening for creating a counter flow, wherein the vigorous shearing action between the counter flow and main flow results in a good mixing.
Device as claimed in claim 1, characterized in that the port (16) for the additive is arranged in the side wall of the housing.
Device as claimed in claim 2, characterized in that a guide tube (24) directed toward the rotation shaft of the blade assembly connects onto the port for the additive.
Device as claimed in claim 3, characterized in that the guide tube debouches on the side of at least the leading blade assembly remote from the feed opening (6) for the carrier liquid.
Device as claimed in claim 1, characterized in that the leading blade assembly is embodied with a part which has an axial pushing action and a part which has a radial pushing action.
Device as claimed in claim 5, characterized in that the part with the axial pushing action lies concentrically round the part with the radial pushing action.
Device as claimed in any of the foregoing claims, characterized in that the port for the additive is arranged in a wall part of the housing lying closest to the mixing gear.
Device as claimed in any of the foregoing claims, characterized in that the cross section of the housing has a polygonal, preferably square form.