EP4603174A1

EP4603174A1 - A non-ragging static mixer for open channels

Info

Publication number: EP4603174A1
Application number: EP24158353.3A
Authority: EP
Inventors: Eleonora TAFFORA; Mathias Hack; Stefan Leuppi; Marcel Suhner
Original assignee: Sulzer Management AG
Current assignee: Sulzer Management AG
Priority date: 2024-02-19
Filing date: 2024-02-19
Publication date: 2025-08-20
Also published as: WO2025176717A1

Abstract

The present invention relates to a static mixer duct (10) having the form of a channel (11) being open on its top, wherein the static mixer duct comprises an inlet (16) at an upstream end of the channel, an outlet (18) at an opposite downstream end of the channel and at least two blades (22, 22') being arranged at least substantially coplanar within the channel between the inlet and outlet, wherein substantially coplanar means that the blades are inclined with each other with regard to a plane extending through the channel by not more than 10°, wherein each of the blades has an upstream surface (32) being oriented towards the inlet and an opposite downstream surface (34), wherein at least one additive injection opening (44, 44') is provided in, on or above the downstream surface of each of the blades.

Description

The present invention relates to a static mixer and a static mixer duct with an improved additive supply system, to a plant comprising this static mixer (duct) as well as to a method of adding an additive into a fluid and of homogenizing the resulting mixture using this static mixer (duct).
Static mixers and static mixer ducts are of interest for all industries concerned with mixing and dispersing, with gas liquid contacting or with turbulent mixing applications. For instance, static mixers are generally tubular internals that produce desired mixing and dispersion effects as the fluid flows around motionless mixer parts. Static mixers have advantages over other mixing systems, such as dynamic mixers, in that they require only small volumes, low maintenance and they have a simple installation and cleaning as well as excellent reliability.
A typical static mixer is disclosed in EP 0 800 857 A1 and comprise inclined parallel plates providing open narrow passages including a gap region running from wall to wall through the duct axis. Another similar static mixer is disclosed in US 4,758,098 having at least three transversely spaced webs. The webs are spaced transversely from each other to provide gaps through which a fluid may pass during mixing. In addition, each web while being secured to the casing at the upper ends relative to a downward flow has lower terminal ends which are spaced from the casing to provide further gaps through which the liquid may pass during a downward descent. The above-described mixers may often be effective and sufficient provided that enough mixing length is available within the duct as well as sufficient pressure head. However, these mixers do not properly perform in applications with insufficient available length or pressure head.
Other important disadvantages of the known mixer (ducts) are that they do not efficiently and/or rapidly enough homogenize a mixture after dosing another fluid, such as an additive, to a main fluid flowing through the mixer (duct) and that they tend to clog, if the fluid processed therein contains solids. Such an efficient homogenization of a mixture after dosing an additive therein is in particular challenging, when waste water, which often contains solids, fibers, sludge and other components, and which tend to clog a static mixer, has to be mixed with one or more additives, such as a flocculant, a pH-control agent or the like. Traditional static mixer (ducts) clog during such applications after comparable short operational periods.
In view of this, the object underlying the present invention is to provide an improved static mixer and static mixer duct for both mixing of a turbulent flow as well as for dosing an additive into the flow, which rapidly mixes and homogenizes the additive within the fluid, in particular which rapidly homogenizes the additive concentration within the fluid in particular in the case of fluids containing solids, such as of waste water containing solids, fibers, sludge and other components, and, which provides a homogenous distribution of an additive before the fluid/additive mixture reaches the outlet of the static mixer (duct).
In accordance with the present invention, this object is solved by providing a static mixer duct having the form of a channel being open on its top, wherein the static mixer duct comprises an inlet at an upstream end of the channel, an outlet at an opposite downstream end of the channel and at least two blades being arranged at least substantially coplanar within the channel between the inlet and outlet, wherein substantially coplanar means that the blades are inclined with each other with regard to a plane extending through the channel by not more than 10°, wherein each of the blades has an upstream surface being oriented towards the inlet and an opposite downstream surface, wherein at least one additive injection opening is provided in, on or above the downstream surface of each of the blades.
This solution bases on the finding that by arranging at least one additive injection opening in, on or above the downstream surface of each of at least two blades being arranged at least substantially coplanar within the channel between the inlet and outlet, not only a clogging of the static mixer is reliably avoided, but also a rapid mixing and homogenization of the fluid/additive mixture is achieved, even if the fluid is waste water containing solids, fibers, sludge and other components. It is of particular advantage that the additive is added in the static mixer (duct) in accordance with the present invention via one or more additive injection openings being provided in, on or above the downstream surface of each of the blades, i.e. downstream of the static mixer (duct). On account of this reason, the static mixer (duct) in accordance with the present invention does not require any extra additive dosing device, which is contained in the static mixer (ducts) of the prior art typically upstream of the static mixer and acts as obstacle to the flow. The blades of the static mixer (duct) in accordance with the present invention create big counter rotating vortex pairs carrying the additive from the additive injection opening(s) and homogenizes the resulting mixture fast and uniformly over the entire channel cross section. Furthermore, the increased mixing and homogenization efficiency of the static mixer (duct) in accordance with the present invention allows to save additives and provides a high mixing degree at a short mixing time. In addition, the pressure loss in the static mixer (duct) is very low so that the water flow of the mild slope channels is not stopped. Moreover, the static mixer is a ready-to-install solution, which allows a fix installation without need to change or adapt the static mixer depending on the water level within the channel. Finally, the easy geometric design with low complexity of the static mixer (duct) in accordance with the present invention leads to reduced maintenance requirements and to an easy and cost-efficient manufacturing.
The term channel means in accordance with the present invention any hollow space, which is closed at its bottom and at both longitudinal sides, i.e. the sides extending in the longitudinal direction of the channel, for instance by walls, whereas at least a part of the top is open. Longitudinal direction means in this connection the direction along any horizontal line extending between the inlet and the outlet of the channel. Preferably, the whole top surface of the channel is open, whereas the front and rear ends of the channel may be closed, open or at least partially open. For instance, the channel may have the form of a trough with a square, rectangular, u-shaped or v-shaped cross-section.
The upstream end and the downstream end of the channel are related to the flow direction of the fluid during the operation of the channel, i.e. the fluid flows during the operation of the channel from the upstream end to the downstream end of the channel.
Likewise thereto, the upstream and downstream ends of each blade are related to the flow direction of the fluid during the operation of the channel, i.e. the fluid flows during the operation of the channel from the upstream end to the downstream end of the blade.
In accordance with the present invention, the at least two blades are arranged at least substantially coplanar within the channel, wherein substantially coplanar means that the blades are inclined with each other with regard to a plane extending through the channel, such as with regard to a longitudinal plane or the vertical longitudinal section of the channel, by not more than 10°.
In accordance with a one preferred embodiment of the present invention, the blades are inclined with each other with regard to a plane extending through the channel by not more than 5°, more preferably by not more than 2.5°, yet more preferably by not more than 1° and most preferably not at all.
In accordance with an alternatively preferred embodiment of the present invention, the blades are inclined with each other with regard to a plane extending through the channel by more than 0° to not more than 10°, preferably by more than 0° to 10° and more preferably by 1° to 5°. For instance, the blades are slightly tilted by such a small angle with regard to the plane in the same direction, such as, seen in the vertical longitudinal section, in the direction to the upstream end of the channel.
In turn, the term blade means in accordance with the present invention any three-dimensional article. Preferably, each of the blades is a flat article, i.e. an article being significantly smaller in one dimension than in the other two dimensions. For instance, the one dimension is at least 50% smaller than each of the other two dimensions.
More preferably, at least one of the at least two blades and more preferably each of the at least two blades is a flat plate. A flat plate means in accordance with the present invention any plate having a relatively small height or thickness, respectively, compared to its other two dimensions. The flat plate comprises, seen in the plane of the two larger dimensions, preferably two opposite, at least substantially parallel surfaces, wherein at least substantially parallel surfaces means two surfaces, which are inclined with each other by not more than 10°, more preferably by not more than 5°, still more preferably by not more than 1° and most more preferably not at all.
The present invention is not particularly limited concerning the longitudinal sectional form of the flat plate or the form seen in top view, respectively. For instance, the flat plate may have a circular, elliptic, square, rectangular, trapezoidal or polygonal longitudinal sectional form. Thus, in the case of a flat plate having a rectangular, square or trapezoidal longitudinal sectional form, the height or thickness, respectively, of the flat plate is smaller than the length and width of the flat plate, whereas in the case of a flat plate having a circular longitudinal sectional form, the height of the flat plate is smaller than the diameter of the flat plate, and in the case of a flat plate having an elliptic longitudinal sectional form, the height of the flat plate is smaller than the semi axis and the minor axis of the flat plate. Preferably, the height of the flat plate is at most 50%, more preferably at most 30%, still more preferably at most 20%, yet more preferably at most 10%, even more preferably at most 5% and most preferably at most 1% of the other two dimensions.
In a further development of the idea of the present invention, it is suggested that at least one of the at least two blades and more preferably each of the at least two blades is a flat plate having a rectangular longitudinal sectional form. It is preferred in this embodiment that the height of the flat plate is at most 10%, more preferably at most 5% and most preferably at most 1% of the length of the flat plate. Furthermore, it is preferred that the height of the rectangular flat plate is at most 50%, more preferably at most 30% and most preferably at most 20% of the width of the flat plate. Moreover, it is preferred that the quotient of the length divided by the width of the flat plate is 2:1 to 50:1, more preferably 5:1 to 20:1 and most more preferably 7:1 to 14:1, such as about 10:1.
Most preferably, at least one of the at least two blades and more preferably each of the blades is a flat plate having a trapezoidal longitudinal sectional form. Trapezoid means a quadrangle having at least one parallel pair of sides. In this embodiment, each blade comprises, seen in the top view, a front edge, a rear edge and two side edges, wherein each side edge connects one end of the front edge with one edge of the rear edge. While the side edges extend at least substantially in the longitudinal direction of the channel, the front and rear edges extend at least substantially perpendicular to the longitudinal direction of the channel. At least substantially perpendicular means that the angle between the respective front edge and/or rear edge and the longitudinal direction of the channel is 70 to 110°, preferably 80 to 100°, more preferably 85 to 95°, still more preferably 89 to 91° and most preferably 90°, whereas at least substantially in the longitudinal direction of the channel means that the angle between the respective side edge and the longitudinal direction of the channel is -20 to +20°, preferably -10 to +10°, more preferably -5 to +5°, still more preferably -1 to + 1 ° and most preferably 0°. The front edge of the blade is the edge being closer to the inlet than the opposite rear edge, i.e. the front edge of the blade is arranged at the upstream end of the blade, whereas the rear edge of the blade is arranged at the downstream end of the blade. The front and rear edges are parallel to each other, whereas the side edges may or may not be parallel to each other. Preferably, the side edges are not parallel to each other. More preferably, the trapezoid is a right trapezoid, i.e. a trapezoid, in which the angles between one side edge and the front and rear edges are 90°, whereas the angles between the other side edge and the front and rear edges are different from 90°, such as 1 to 45°, preferably 1 to 30° and more preferably 2 to 10°. In this embodiment, preferably the side edge with an angle to the front and rear edges of 90° of the blade is that side edge, which is arranged closer the sidewall of the channel than the other side edge of the blade.
It is particularly preferred that the rear edge of the trapezoid is longer than the front edge. Good results are in particular obtained, when the quotient of the length of the rear edge divided by the length of the front edge is 1.1 to 5, more preferably 1.2 to 3, still more preferably 1.5 to 2.5 and most preferably 1.75 to 2.25, such as about 2. In addition, it is preferred that the quotient of the length of each of the side edges divided by the length of the rear edge is 2 to 25, more preferably 3 to 15, and most preferably 4 to 8.
In principle, the present invention is not particularly restricted concerning the orientation of the at least two blades and preferably the at least two flat plates. Good results are in particular achieved, when at least one of the at least two blades and more preferably each of the at least two blades is, seen in the vertical longitudinal section of the channel from the upstream end to the downstream end of the channel, inclined, wherein the inclination angle of at least one of the at least two blades and more preferably each of the at least two blades and the longitudinal direction of the channel is preferably 10 to 80°, more preferably 20 to 70° and most preferably 30 to 60°. More specifically, the inclination angle is the angle between the upstream surface or downstream surface, respectively, of the blade and the longitudinal direction of the channel, or if the blade is a flat plate, seen two-dimensionally in the vertical longitudinal section, the inclination angle is the angle between the side edge of the blade and the longitudinal direction of the channel.
Good results are in particular obtained, when each of the blades and preferably flat plates is, seen in the vertical longitudinal section of the channel from the upstream end to the downstream end of the channel, inclined downwardly, i.e. when the front edge of each of the blades and preferably flat plates is oriented in the upper portion of the channel, whereas the rear edge is oriented in the lower portion of the channel. In this embodiment, the upstream surface of the blade is the lower side of the blade, whereas the downstream surface of the blade is the upper side of the blade.
In particular in this embodiment, it is preferred that the inclination angle of each of the at least two blades and the longitudinal direction of the channel is as set out above, i.e. 10 to 80°, more preferably 20 to 70° and most preferably 30 to 60°.
In a further development of the idea of the present invention, it is proposed that each of the blades extends, seen in the vertical longitudinal section of the channel, over at least 80%, more preferably over at least 90%, still more preferably over at least 95% and most preferably over 100% of the height of the channel.
In a particular preferred embodiment of the present invention, the static mixer duct comprises exactly two blades being arranged within the channel at least substantially coplanar, i.e. in addition to these two blades no further blade.
Preferably, the blades of the static mixer duct are arranged adjacent, but spaced apart from each other so that a gap is formed between adjacent blades.
The form of the gap depends on the form of the blades. In the case that the blades are flat plates having a rectangular longitudinal sectional form, the gap will be rectangular. However, in the most preferred case that the blades are flat plates having a trapezoidal longitudinal sectional form with the rear edge being longer than the front edge, the gap will be preferably trapezoidal.
Good results are in particular obtained, when the width of the gap between the rear edges of adjacent blades, i.e. the horizontal distance between the ends of the two rear edges bordering the gap, is 0 to 90% and preferably 0 to 20% of the width of the static mixer duct.
Likewise thereto, it is preferred that the length of the rear edge of a blade is 5% to 50% and preferably 40% to 50%, such as about 45%, of the width of the static mixer duct.
Furthermore, it is preferred that the width of the gap between the front edges of adjacent blades, i.e. the horizontal distance between the ends of the two front edges bordering the gap, is 20 to 100% and preferably 50 to 80% of the width of the static mixer duct.
In addition thereto or alternatively thereto, it is preferred that the the length of the front edge of a blade is 1 to 200% and preferably 10 to 70%, such as about 50%, of the width of the gap between the front edges of adjacent blades.
In a further development of the idea of the present invention, it is suggested that each of the blades comprises at least one side edge and the channel comprises two side walls and a bottom wall, wherein each of the blades is connected with one of its at least one side edge with a side wall of the channel. Connected means in this context that the respective side edge of the blade is permanently fixed to the side wall of the channel. It is particularly preferred that each of the blades is connected with one of its at least one side edge with a side wall of the channel so that substantially no gap or no spacing, respectively, between the respective side edge of the blade and the respective side wall of the channel is present. Substantially no gap or no spacing, respectively, means that at least 70%, preferably at least 80%, more preferably at least 90%, still more preferably at least 95%, yet more preferably at least 99% and most preferably 100% of the length of the respective side edge of the blade is directly connected with the respective side wall of the channel.
In accordance with an alternative particularly preferred embodiment of the present invention, the blades are not connected via their side edges directly to the side wall of the channel, but indirectly, i.e. each of the blades comprises at least one side edge, which is connected with a frame-wall, which extends at least substantially vertical and along the longitudinal direction of the channel, wherein the channel comprises two side walls and a bottom wall, and wherein each of the blades is connected with its frame-wall with a side wall of the channel. Again, connected means in this context that the frame-wall of the blade is permanently fixed to the side wall of the channel. It is particularly preferred that each of the frame-wall is connected with a side wall of the channel so that substantially no gap or no spacing, respectively, between the respective frame-wall of the blade and the respective side wall of the channel is present. Again, substantially no gap or no spacing, respectively, means that the respective frame-wall is directly connected with the respective side wall of the channel along at least 70%, preferably at least 80%, more preferably at least 90%, still more preferably at least 95%, yet more preferably at least 99% and most preferably 100% of the length of the respective frame-wall of the blade.
In dependency of the length and/or height of the blades, it may be advantageous that the static mixer duct further comprises at least one support beam for each blade. For instance, each support beam is arranged below a blade so that it extends vertically between the bottom wall of the channel and a portion of the upstream surface or lower surface, respectively, of the blade.
In accordance with the present invention, at least one additive injection opening is provided in, on or above the downstream surface of each of the blades. The present invention is not particularly limited concerning the kind and arrangement of the at least one additive injection opening.
In accordance with one preferred embodiment of the present invention, at least one blade and preferably each of the blades comprises a cavity and in its downstream surface at least two openings, wherein the cavity is connected with both openings, wherein one of these openings is the additive injection opening, whereas another of these openings is connected via a line with a source of additive.
Preferably, the cavity is arranged fully within the blade.
The cavity may have any cross-sectional form, such as circular, rectangular, square, oval, elliptic or polygonal cross-sectional form, wherein a cavity with a circular cross-sectional form, i.e., seen three-dimensionally, with a cylindrical form is preferred.
In a further development of the idea of the present invention, it is suggested that in the aforementioned embodiment the downstream surface of at least one blade and preferably each of the downstream surfaces of all the blades comprises 1 to 10 and more preferably 1 to 5 additive injection openings. Each of the openings may have any cross-sectional form, such as circular, rectangular, square, oval, elliptic or polygonal cross-sectional form, wherein openings with a circular cross-sectional form are preferred.
Good results are in particular obtained, when the at least additive injection opening is provided, seen from the upstream end to the downstream end of the blade, at a position being located 50 to 99%, preferably 50 to 80% and more preferably 60 to 75% of the length of the downstream surface of the blade. Thus, the at least additive injection opening is arranged in the particular preferred embodiment, in which the blades of the static mixer duct are, seen in the vertical longitudinal section of the channel from the upstream end to the downstream end of the channel, inclined downwardly, in the lower part of the downstream surface of the blade.
In accordance with another particularly preferred embodiment of the present invention, an additive supply means is arranged on the downstream surface of each of the blades, which comprises at least one additive injection opening.
The present invention is not particularly restricted regarding the form of the additive supply means. For instance, the additive supply means may have a circular, rectangular, square, oval, elliptic or polygonal cross-sectional form, wherein a circular, rectangular or square cross-sectional form is particularly preferred.
Good results are in particular obtained, when the additive supply means is a pipe having a circular, rectangular or square cross-sectional form and being connected with the downstream surface of a blade, wherein the pipe comprises on one of its two front sides at least one additive inlet and on its opposite front side at least one additive injection opening. Preferably, the at least one additive inlet is arranged at the upstream end and is in fluid communication with a source of additive, whereas the at least one additive injection opening is arranged at the downstream end of the pipe.
In a further development of the idea of the present invention, it is proposed that the additive supply means in form of a pipe extends on the downstream surface of the blade, seen from the upstream end to the downstream end of the blade, from a first position being located 1 to 30%, preferably 2 to 20% and more preferably 2 to 10% of the length of the blade to a second position being located 50 to 99%, preferably 50 to 80% and more preferably 60 to 75% of the length of the blade. Preferably, the end of the pipe at the first position comprises at least one additive inlet and the end of the pipe at the second position comprises at least one additive injection opening.
Furthermore, it is preferred that the additive supply means comprises 1 to 10 and more preferably 1 to 5 additive injection openings. Each of the openings may have any cross-sectional form, such as circular, rectangular, square, oval, elliptic or polygonal cross-sectional form, wherein openings with a circular cross-sectional form are preferred.
Good results are in particular obtained, when the static mixer duct does not comprise any further additive supply means in addition to the at least one additive injection opening being connected with the downstream surface of a blade. Thus, the static mixer duct preferably does not contain an additive supply means or additive injection opening, respectively, outside of the at least two blades without being connected with any of the at least two blades. In particular, the static mixer duct preferably does not contain an additive supply pipe being arranged upstream or downstream of the at least two blades.
Both aforementioned particularly preferred embodiments of the present invention may be combined with each other. For instance one of the blades may comprise a cavity being connected with one or more additive injection openings, whereas another of the blades comprises an additive supply means being arranged on the downstream surface thereof, which comprises at least one additive injection opening. Alternatively, each of the blades may comprise a cavity being connected with one or more additive injection openings as well as an additive supply means being arranged on the downstream surface thereof, which comprises at least one additive injection opening. However, preferably each of the blades comprises either a cavity being connected with one or more additive injection openings or an additive supply means being arranged on the downstream surface thereof, which comprises at least one additive injection opening.
In accordance with a further aspect, the present invention relates to a static mixer comprising an inlet at an upstream end, an outlet at an opposite downstream end and at least two blades being arranged at least substantially coplanar, wherein substantially coplanar means that the blades are inclined with each other with regard to a plane extending through the static mixer, such as through the length axis of the static mixer, by not more than 10°, wherein each of the blades has an upstream surface being oriented towards the inlet and an opposite downstream surface, wherein at least one additive injection opening is provided in, on or above the downstream surface of each of the blades.
The features mentioned above as preferred with regard to the static mixer duct are also preferred with regard to the static mixer.
Thus, it is preferred that the blades are inclined with each other with regard to a plane extending through the static mixer by not more than 30°, more preferably by not more than 10°, yet more preferably by not more than 5°, even more preferably by not more than 2.5°, still more preferably by not more than 1° and most preferably not at all. Alternatively, the blades may be inclined with each other with regard to a plane extending through the static mixer by more than 0° to not more than 10°, preferably by more than 0° to 10° and more preferably by 1° to 5°. For instance, the blades are slightly tilted by such a small angle with regard to the plane in the same direction, such as, seen in the vertical longitudinal section, in the direction to the upstream end of the static mixer.
More preferably, at least one of the at least two blades and more preferably each of the at least two blades is a flat plate, which may have a circular, elliptic, square, rectangular, trapezoidal or polygonal longitudinal sectional form. Preferably, the height of the flat plate is at most 50%, more preferably at most 30%, still more preferably at most 20%, yet more preferably at most 10%, even more preferably at most 5% and most preferably at most 1% of the other two dimensions.
In a further development of the idea of the present invention, it is suggested that at least one of the at least two blades and more preferably each of the at least two blades is a flat plate having a rectangular longitudinal sectional form. It is preferred in this embodiment that the height of the flat plate is at most 10%, more preferably at most 5% and most preferably at most 1% of the length of the flat plate. Furthermore, it is preferred that the height of the rectangular flat plate is at most 50%, more preferably at most 30% and most preferably at most 20% of the width of the flat plate. Moreover, it is preferred that the quotient of the length divided by the width of the flat plate is 2 to 50, more preferably 5 to 20 and most more preferably 7 to 14, such as about 10.
Most preferably, at least one of the at least two blades and more preferably each of the blades is a flat plate having a trapezoidal longitudinal sectional form. Accordingly, each of the blades comprises, seen in the top view, a front edge, a rear edge and two side edges, wherein each side edge connects one end of the front edge with one edge of the rear edge. While the side edges extend at least substantially in the longitudinal direction of the static mixer, the front and rear edges extend at least substantially perpendicular to the longitudinal direction of the static mixer. Preferably, the front and rear edges are parallel to each other, whereas the side edges may or may not be parallel to each other, wherein it is preferred that the side edges are not parallel to each other. More preferably, the trapezoid is a right trapezoid, i.e. a trapezoid, in which the angles between one side edge and the front and rear edges are 90°, whereas the angles between the other side edge and the front and rear edges are different from 90°, such as 1 to 45°, preferably 1 to 30° and more preferably 2 to 10°. In this embodiment, preferably the side edge with an angle to the front and rear edges of 90° of a blade is that side edge, which is arranged, seen in the cross-section of the static mixer, closer to an outer end of the static mixer than the other side edge of the blade.
It is particularly preferred that the rear edge of the trapezoid is longer than the front edge. Good results are in particular obtained, when the quotient of the length of the rear edge divided by the length of the front edge is 1.1 to 5, more preferably 1.2 to 3, still more preferably 1.5 to 2.5 and most preferably 1.75 to 2.25, such as about 2. In addition, it is preferred that the quotient of the length of each of the side edges divided by the length of the rear edge is 2 to 25, more preferably 3 to 15 and most preferably 4 to 8.
Good results are in particular achieved, when at least one of the at least two blades and more preferably each of the at least two blades is, seen in the vertical longitudinal section of the static mixer from the upstream end to the downstream end of the static mixer, inclined, wherein the inclination angle of at least one of the at least two blades and more preferably each of the at least two blades and the longitudinal direction of the static mixer is preferably 10 to 80°, more preferably 20 to 70° and most preferably 30 to 60°, wherein it is most preferred that each of the blades is, seen in the vertical longitudinal section of the static mixer from the upstream end to the downstream end of the static mixer, inclined downwardly.
In a particular preferred embodiment of the present invention, the static mixer comprises exactly two blades being arranged within the static mixer at least substantially coplanar, i.e. in addition to these two blades no further blade.
Preferably, the blades of the static mixer duct are arranged adjacent, but spaced apart from each other so that a gap is formed between adjacent blades.
In accordance with a particularly preferred embodiment of the present invention, each of the blades of the static mixer comprises at least one side edge, which is connected with a frame-wall, which extends at least substantially vertical and along the longitudinal direction of the static mixer.
In a further development of the idea of the present invention, at least one blade and preferably each of the blades comprises i) a cavity and in its downstream surface at least two openings, wherein the cavity is connected with both openings, wherein one of these openings is the additive injection opening, whereas another of these openings is connected via a line with a reservoir of additive, and/or ii) an additive supply means is arranged on the downstream surface of each of the blades, which comprises at least one additive injection opening.
Preferably, the downstream surface and/or the additive supply means of at least one blade and preferably each of the downstream surfaces of all the blades comprises 1 to 10 and more preferably 1 to 5 additive injection openings.
In dependency of the length and/or height of the blades, it may be advantageous that the static mixer further comprises at least one support beam for each blade. For instance, each support beam is arranged below a blade so that it extends vertically between the bottom of the static mixer and a portion of the upstream surface or lower surface, respectively, of the blade.
In yet a further aspect, the present invention relates to a chemical plant, petrochemical plant, refinery or water treatment plant comprising the aforementioned static mixer duct or the aforementioned static mixer.
Preferably, the static mixer duct inlet or mixer inlet is in fluid communication with a source of a liquid flow and the at least one additive injection opening is in fluid communication with a source of additive.
In accordance with still a further aspect, the present invention relates to a method of adding an additive into a fluid and of homogenizing the resulting mixture comprising the steps of:

i) feeding the fluid to the inlet of the aforementioned static mixer duct or into the inlet of the aforementioned static mixer,
ii) leading additive through the at least one additive injection opening and
iii) removing the homogenized mixture at the outlet of the aforementioned static mixer duct or at the outlet of the aforementioned static mixer.

Specific embodiments in accordance with the present invention are subsequently described with reference to the appended drawing.

Fig. 1a: is a partially sectional, perspective view of a static mixer duct in accordance with one embodiment of the present invention.
Fig. 1b: is a longitudinal sectional view of the static mixer duct shown in figure 1a.
Fig. 1c: is a view from the upstream end of the blades of the static mixer duct shown in figures 1a and 1b.

The static mixer duct 10 shown in figure 1a has the form of a channel 11 comprising a bottom wall 12, two side walls 14, 14' (from the second side wall 14' only the upper edge is shown), an inlet 16 and an outlet 18. The top 20 of the channel 11 is open. In addition, two blades 22, 22' being arranged at least substantially coplanar and two support beams 24, 24' are arranged within the static mixer duct 10. The two blades 22, 22' are flat plates having, in top view, a trapezoidal form comprising a front edge 26, a rear edge 28 and two side edges 30, 30', wherein the front edge 26 of the blades 22, 22' is shorter than the rear edge 28. The blades 22, 22' or the side edges 30, 30' of the blades 22, 22', respectively, are inclined, seen in the vertical longitudinal section from the inlet to the outlet of the channel 11, downwardly with an inclination angle α between the upstream surface 32 or downstream surface 34, respectively, of the blade 22, 22' and the longitudinal direction 36 of the channel 11 of about 45°. The lower surface of the blade 22, 22' is the upstream surface 32 of the blade 22, 22', whereas the upper surface is the downstream surface 34 of the blade 22, 22'. Both blades 22, 22' extend, seen in the vertical longitudinal section of the channel 11, over the whole height of the channel 11, wherein both blades 22, 22' are arranged adjacent, but spaced apart from each other so that a gap 38 is formed between both blades 22, 22'. Each of both blades 22, 22' is connected with one of its side edges 30' with a side wall 14' of the static mixer duct 10. Each of the support beams 24, 24' is arranged below a blade 22, 22' and extends vertically between the bottom wall 12 of the channel 11 and a portion of the upstream surface 32 of the blade 22, 22'.
On the downstream surface 34 of each of the two blades 22, 22' one additive supply means 40, 40' is arranged, which extends from slightly below the rear edge 32 over about 65% of the length of the downstream surface 34 of each of the blades 22, 22'. Each of the additive supply means 40, 40' has the form of a square pipe and comprises at its upstream end two additive inlets 42, 42' and on its opposite end two additive injection openings 44, 44'. The additive inlets 42, 42' may be in fluid communication with a source of additive (not shown).
During the operation of the static mixer duct 10, fluid, such as waste water, is fed to the inlet 16 of the static mixer duct 10 and flows from the inlet 16 to the outlet 18 of the static mixer duct 10. Additive is injected via the additive supply means 40, 40' and the additive injection openings 44, 44' at the downstream side of the blades 20, 20' into the fluid. The turbulent flow pattern being generated by the geometry of the blades 20, 20' leads to an efficient mixing of the fluid and additive and to an excellent homogenization of the mixture of fluid and additive.

Reference Numeral List

10: Static mixer duct
11: Channel
12: Bottom wall of channel
14, 14': Side walls of channel
16: Inlet of channel
18: Outlet of channel
20: Top of channel
22 22': Blade
24, 24': Support beam
26: Front edge of blade
28: Rear edge of blade
30: Side edges of blade
32: Upstream surface of blade
34: Downstream surface of blade
36: Longitudinal direction of channel
38: Gap between blades
40: Additive supply means
42: Additive inlets
44: Additive injection openings

α: inclination angle

Claims

A static mixer duct having the form of a channel being open on its top,
wherein the static mixer duct comprises an inlet at an upstream end of the channel, an outlet at an opposite downstream end of the channel and at least two blades being arranged at least substantially coplanar within the channel between the inlet and outlet, wherein substantially coplanar means that the blades are inclined with each other with regard to a plane extending through the channel by not more than 10°, wherein each of the blades has an upstream surface being oriented towards the inlet and an opposite downstream surface, wherein at least one additive injection opening is provided in, on or above the downstream surface of each of the blades.
The static mixer duct in accordance with claim 1, wherein each of the blades is a flat plate.
The static mixer duct in accordance with claim 2, wherein each of the blades is a flat plate having a trapezoidal longitudinal sectional form comprising, seen in the top view, a front edge, a rear edge and two side edges, wherein each side edge connects one end of the front edge with one edge of the rear edge, wherein the side edges extend at least substantially in the longitudinal direction of the channel, whereas the front and rear edges extend at least substantially perpendicular to the longitudinal direction of the channel, wherein the front edge is shorter the rear edge, wherein preferably the quotient of the length of the rear edge divided by the length of the front edge is 1.1 to 5, more preferably 1.2 to 3, even more preferably 1.5 to 2.5 and most preferably 1.75 to 2.25.
The static mixer duct in accordance with any of the preceding claims,
wherein each of the blades is, seen in the vertical longitudinal section of the channel from the upstream end to the downstream end of the channel, inclined, wherein the inclination angle of each of the blades and the longitudinal direction of the channel is preferably 10 to 80°, more preferably 20 to 70° and most preferably 30 to 60°, wherein preferably each of the blades is, seen in the vertical longitudinal section of the channel from the upstream end to the downstream end of the channel, inclined downwardly.
The static mixer duct in accordance with any of the preceding claims,
wherein the static mixer duct comprises exactly two blades being arranged within the channel at least substantially coplanar and no further blade in addition thereto.
The static mixer duct in accordance with any of the preceding claims,
wherein the blades are arranged adjacent, but spaced apart from each other so that a gap is formed between adjacent blades.
The static mixer duct in accordance with any of the preceding claims,
wherein each of the blades comprises at least one side edge and the channel comprises two side walls and a bottom wall, and wherein each of the blades is connected with one of its at least one side edge with a side wall of the channel, or wherein each of the blades comprises at least one side edge, which is connected with a frame-wall, which extends at least substantially vertical and along the longitudinal direction of the channel, wherein the channel comprises two side walls and a bottom wall, and wherein each of the blades is connected with its frame-wall with a side wall of the channel.
The static mixer duct in accordance with any of the preceding claims,
wherein at least one blade and preferably each of the blades comprises a cavity and in its downstream surface at least two openings, wherein the cavity is connected with both openings, wherein one of these openings is the additive injection opening, whereas another of these openings is connected via a line with a reservoir of additive.
The static mixer duct in accordance with claim 8, wherein the at least additive injection opening is provided on the downstream surface of the blade, seen from the upstream end to the downstream end of the blade, at a position being located 50 to 99%, preferably 50 to 80% and more preferably 60 to 75% of the length of the downstream surface of the blade.
The static mixer duct in accordance with any of the preceding claims,
wherein an additive supply means is arranged on the downstream surface of each of the blades, which comprises at least one additive injection opening.
The static mixer duct in accordance with claim 10, wherein the additive supply means is a pipe being connected with the downstream surface of a blade, wherein the pipe has on one front side at least one additive inlet and on the opposite side at least one additive injection opening, wherein preferably the pipe extends on the downstream surface of the blade, seen from the upstream end to the downstream end of the blade, from a first position being located 1 to 30%, preferably 2 to 20% and more preferably 2 to 10% of the length of the blade to a second position being located 50 to 99%, preferably 50 to 80% and more preferably 60 to 75% of the length of the blade.
The static mixer duct in accordance with any of the preceding claims,
wherein the static mixer duct does not comprise any further additive supply means in addition to the at least one additive injection opening being connected with the downstream surface of a blade.
A static mixer comprising an inlet at an upstream end, an outlet at an opposite downstream end and at least two blades being arranged at least substantially coplanar, wherein substantially coplanar means that the blades are inclined with each other with regard to a plane extending through the static mixer by not more than 10°, wherein each of the blades has an upstream surface being oriented towards the inlet and an opposite downstream surface, wherein at least one additive injection opening is provided in, on or above the downstream surface of each of the blades.
A chemical plant, petrochemical plant, refinery or water treatment plant comprising the static mixer duct in accordance with any of claims 1 to 12 or the static mixer in accordance with claim 13.
A method of adding an additive into a fluid and of homogenizing the resulting mixture comprising the steps of:
i) feeding the fluid to the inlet of the static mixer duct in accordance with any of claims 1 to 12 or into the inlet of the static mixer in accordance with any of claim 13,

ii) leading additive through the at least one additive injection opening and

iii) removing the homogenized mixture at the outlet of the static mixer duct in accordance with any of claims 1 to 12 or at the outlet of the static mixer in accordance with any of claim 13.