FLUID MIXING STRUCTURE, CONTINUOUS REACTION UNIT, CONTINUOUS REACTION REACTOR AND METHOD OF USING THE SAME

Abstract

A fluid mixing structure (10) for mixing at least two fluidic components has a flow inlet port and a flow outlet port and comprises a contraction zone (12), an expansion zone (14), and a retention zone (16), arranged in this order in an inflow direction (IFD) of a fluid flow to flow through said fluid mixing structure (10) and being composed of said at least two fluidic components, and a flow splitter (32) arranged In a space (30) formed by said expansion zone (14) and said retention zone (16) to split said fluid flow in a first sub fluid flow and a second sub fluid flow flowing in a first flow path and a second flow path, respectively, formed in the fluid mixing structure, and to mix said first and second sub fluid flows within said space (30) to generate and discharge a homogenized fluid flow, wherein said flow splitter (32) is arranged and configured to let any flow element of each of said first and second sub fluid flows prior to their mixing have a non-zero average flow component in said inflow direction (IFD).

Claims

1. A fluid mixing structure for mixing at least two fluidic components, said fluid mixing structure having a flow inlet port and a flow outlet port and comprising a contraction zone, an expansion zone, and a retention zone, arranged in this order in an inflow direction (IFD) of a fluid flow to flow through said fluid mixing structure and being composed of said at least two fluidic components, and a flow splitter arranged in a space formed by said expansion zone and said retention zone to split said fluid flow in a first sub fluid flow and a second sub fluid flow flowing in a first flow path and a second flow path, respectively, formed in the fluid mixing structure, and to mix said first and second sub fluid flows within said space to generate and discharge a homogenized fluid flow, wherein said flow splitter is arranged and configured to let any flow element of each of said first and second sub fluid flows prior to their mixing have a non-zero average flow component in said inflow direction (IFD).

2. The fluid mixing structure according to claim 1, wherein said at least two flow paths differ in shape and/or length to dephasedly mix the first and second sub fluid flows within said space.

3. The fluid mixing structure according to claim 1, wherein in a longitudinal section of said fluid mixing structure, said flow splitter has a polygonal shape, or a shape homeomorph to that shape.

4. The fluid mixing structure according to claim 3, wherein said polygonal shape has a first side facing towards said contraction zone and acting as a baffle splitting said fluid flow in said first and second sub fluid flows, a second side extending along said first sub fluid flow, and a third side extending along said second sub fluid flow and being connected with said second side to form a tip pointing in a general down-flow direction.

5. The fluid mixing structure according to claim 4, wherein said second and first sides form sides of a triangle.

6. The fluid mixing structure according to claim 5, wherein said triangle is an isosceles triangle.

7. The fluid mixing structure according to claim 5, wherein said triangle is a right angle triangle, with one of said second and third sides forming a cathetus and extending parallel to said inflow direction (IFD), and the other one of said second and third sides forming the hypothenuse.

8. The fluid mixing structure according to claim 4, wherein said first side has an apex pointing in a direction opposite to said inflow direction (IFD), said apex serving as a flow splitting point.

9. The fluid mixing structure according to claim 3, wherein said shape is a parallelogram pointing with one of its acute-angled tips in a general upflow-direction of the fluid flow.

10. Fluid mixing structure according to claim 1, wherein at least one of said at least two fluidic components is a liquid.

11. The fluid mixing structure according to claim 1, wherein at least one of said at least two fluidic components is a gas.

12. The fluid mixing structure according to claim 1, being made at least partly of metal.

13. The fluid mixing structure according to claim 1, wherein said mixing structure is part of a continuous reaction unit having formed therein a process fluid channel system for continuous reaction of a plurality of reactants fed into said continuous reaction unit as feed fluid flows to form at least one product flowing out of said continuous reaction unit as a product fluid flow.

14. A continuous reaction unit having formed therein a process fluid channel system comprising at least one reaction passage formed by at least one fluid mixing structure according to claim 1.

15. The continuous reaction unit according to claim 14, further comprising at least one residence passage.

16. The continuous reaction unit according to claim 15, wherein said at least one reaction passage and said at least one retention passage are alternatingly arranged within said process fluid channel system.

17. The continuous reaction unit according to claim 14, wherein said process fluid channel system is a meander-like structure comprising a plurality of straight passages and curved passages.

18. The continuous reaction unit according to claim 17, wherein each of said at least one reaction passage is arranged within one of said plurality of straight passages.

19. The continuous reaction unit according to claim 14, wherein said continuous reaction unit has the shape of a plane-parallel plate, and a longitudinal section plane of said process fluid channel system is parallel to opposite surfaces of said plane-parallel plate.

20. The continuous reaction unit according to claim 19, wherein said plane-parallel plate comprises two sub-plates connected to each other at their respective connecting surfaces both coinciding with said longitudinal section plane.

21. The continuous reaction unit according to claim 14, wherein said continuous reaction unit is part of a continuous reaction reactor.

22. A continuous reaction reactor comprising at least one continuous reaction unit according to claim 13.

23. The continuous reaction reactor according to claim 22, further comprising at least one heat exchange unit comprising a heat exchange fluid channel system for accommodating and guiding a heat exchange fluid to thermally adjust a temperature of said process fluid channel system.

24. The continuous reaction reactor according to claim 22, wherein said reactor is a micro-reactor.

25. A method for mixing a fluid flow comprising at least two fluidic components using the fluid mixing structure according to claim 1.

26. The method for continuously forming at least one product as a liquid product flow using said continuous reaction unit according to claim 14 from a plurality of reactants each fed into said continuous reaction unit as a fluidic feed flow.

27. The method according to claim 26, wherein said continuous reaction unit is part of said continuous reaction reactor according to claim 22.

Description

[0060] Further objects and advantageous of the present invention will be better understood by the following detailed description of preferred embodiments with reference to the accompanying drawings. In the drawings,

[0061] FIGS. 1A to 1D are various flow regimes obtained using n-butanol as solvent for the alkaline hydrolysis of 4-nitrophenyl acetate with varying flow rates in the SZ, the sickle, and the spade mixing structures;

[0062] FIGS. 2A-2C are variations of a flow splitter in a mixing structure according to first to third embodiments of the present inventions;

[0063] FIGS. 3A-3C are further variations of a flow splitter in a mixing structure according to fourth to sixth embodiments of the present inventions;

[0064] FIGS. 4A-4B are variations of a continuous reaction unit comprising a concatenation of the inventive mixing structures according to a seventh and an eighth embodiment of the present invention;

[0065] FIG. 5 is a perspective view of a reactor published in WO 2007/112945 A1 of the same applicant to which the present invention may be applied;

[0066] FIGS. 6A and 6B each show a comparison between the dependencies of the overall K.sub.ca coefficient on the total flow rate for the above discussed known mixing structures (SZ, space, and sickle) as well as the structure according to the present invention using n-butanol (FIG. 6A) and toluene (FIG. 6B) as organic solvent;

[0067] FIGS. 7A and 7B each show a comparison between the dependencies of the overall K.sub.ca coefficient on the total flow rate for various obstacles (including no obstacle) using n-butanol (FIG. 7A) and toluene (FIG. 7B) as organic solvent; and

[0068] FIG. 8A shows two different obstacles and a structure without obstacle (obstacle-free structure), and FIG. 8B shows a comparison between the dependencies of the overall K.sub.ca coefficient on the total flow rate for two different obstacles and the obstacle-free structure shown in FIG. 8A.

[0069] Firstly, a principle design of a fluid mixing structure 10, having the shape of a plane-parallel plate, according to the present invention that is common to all embodiments of FIGS. 2A to 3C is representatively described with reference to FIG. 2A (all elements defined by reference numerals in FIG. 2A are also found in the other figures). FIGS. 2A to 3C show longitudinal sections of the fluid mixing structure 10.

[0070] The fluid mixing structure 10 of FIG. 2A comprises a contraction zone 12, an expansion zone 14, and a retention zone 16 that are mirror-symmetrically arranged along a symmetry axis SA that coincides with an inflow direction IFD of a fluid flow passing through the mixing structure 10 in a down-up-direction of the figure. The height direction of the fluid mixing structure 10 is perpendicular to the plane of protection. The zones 12, 14, and 16 are formed by bottoms 18, 20, and 22, respectively, respective covers (not shown), and side walls 24, 26, and 28, respectively. As shown in FIG. 2A, the longitudinal sections (top views) of the zones 12, 14, and 16, respectively, essentially form a triangle, a semicircle, and a rectangle, respectively. Arranged within a space 30, that is a combination of the expansion zone 14 and the retention zone 16, is arranged a flow splitter 32 splitting or dividing the flow fluid flowing into the fluid mixing structure 10 immediately after having entered the expansion zone 14. The flow splitter 32 separates the space 30 into a left flow path 34 to the left of the flow splitter 32 in FIG. 2A, and a right flow path 36 to the right of the flow splitter 32. The left and right flow paths (for first and second sub fluid flows, respectively) 34 and 36, respectively, mix to a single flow path behind the flow splitter 32. As shown in FIG. 2A, the flow splitter 32 is a distance d away from the interface between the contraction zone 12 and the expansion zone 14. The distance d depends on the specific shape of the flow splitter 32 to be described later, and parameters of the fluid flow (e. g. flow speed) and the fluid itself (e.g. viscosity), and is usually determined and optimized experimentally. It should be noted that dead zones, that usually occur along flow mixing surfaces 38, 40 of the flow splitter 32 and prevent swirling of the fluid flow, are to be avoided as much as possible.

[0071] FIGS. 2A to 3C show longitudinal sections of the flow splitter 32. That is, the (longitudinal section of the) flow splitter 32 in FIG. 2A is a parallelogram, in FIG. 2B nearly (!) a triangle, in FIG. 2C a rectangle, and in each of FIGS. 3A to 3C a flame-like structure.

[0072] In all variations, there may be defined a diagonal d (for clarity's sake not shown in FIG. 2A) going through a flow-upstream side apex 42 and a flow-downstream side apex 44 of the flow splitter 32. The diagonal d may be inclined with respect to the symmetry axis SA or the inflow direction IFD by an angle α, as shown in FIG. 2B.

[0073] FIG. 2B the flow splitter 32 has the shape of a tetragon as a special case of a polygon, that may be thought of as having been generated from a symmetrically arranged, isosceles triangle whose tip (formed by the two legs of equal length that form its vertex angle) is shifted to the right in FIG. 2B, and whose base (its flow-upstream side acting as a baffle) has formed the kink or apex 42.

[0074] In FIGS. 3A to 3C the flow splitter 32 has the shape of a flame, that can be thought of as having been generated by a homeomorphism, i. e. by continuously deforming a rectangle that circumscribe the “flames” shown in FIGS. 3A to 3C. It is evident from FIGS. 3A to 3C that shape and size of the flow splitter 32 can modified arbitrarily to achieve an optimum flow and mixing characteristics.

[0075] FIGS. 4A and 4B are variations of a continuous reaction unit 46 comprising each a concatenation of the inventive mixing structure 10 forming a process fluid channel system 48 comprising feeding ports 50 for introducing feed fluid flows, and an discharging port 52 for discharging a product fluid flow. Specifically, the process fluid channel system 48 comprises a plurality of reaction passages 54 each composed of a plurality of mixing structures 10, and a plurality of residence passages 56 without mixing structures 10. Specifically, the continuous reaction unit 46 shown in FIG. 4A has only U-turn shaped residence passages 56, while all straight passages of the process fluid channel system 48 are formed by a plurality of mixing structures 10. Specifically, no mixing structures 10 are arranged within the U-turns. In contrast, in the process fluid channel system 48 shown in FIG. 4B, the residence passages 56 are also provided within the straight passages. Similarly to the structure shown in FIG. 4A, no reaction passages 54 are arranged within the U-turns.

[0076] FIG. 5 is a perspective view of a prior art reactor published in WO 2007/112945 A1 of the same applicant (FIG. 1 thereof), to which the present invention may be applied. In this reactor, reference numerals 1 to 6 refer to “process modules” corresponding to the inventive continuous reaction unit 46, and reference numeral 7 refers to “heat exchange modules” that—similarly to an advantageous embodiment of the present invention—are arranged alternatingly with the process modules. That is, according to the present invention, a plurality of the inventive continuous reaction units 46 can be arranged together with a plurality of heat exchange units (in the terminology of the present invention) comprising a heat exchange fluid channel system assuring an optimum temperature regime for the chemical reactions taking place in the continuous reaction units 46.

EXAMPLES

[0077] In order to evaluate and compare fluid mixing structures in terms of their mixing performance, test reactions have been carried out. A suitable test reaction for mass transfer investigations must be fast enough to be considered not kinetically limited. The conversion of the reactants is then proportional to the mass transfer rate and allows straightforward calculation of the interphase mass transfer coefficient.

[0078] The two-phase alkaline hydrolysis of 4-nitrophenyl acetate:

##STR00001##

[0079] has been used due to its fast intrinsic kinetics and ease of analysis. This fast liquid-liquid reaction allows the direct calculation of the rate of mass transfer and its transport coefficient from the measured conversion. Flow imaging enables identifying the different flow regimes and connecting them to the trends observed in mass transfer.

[0080] The acetate is dissolved in an organic solvent and hydrolyzed by an aqueous alkaline solution. The outlet is quenched in a solution of acetic acid, acetonitrile and water and analyzed by HPLC. By using n-butanol and toluene as the organic solvent, a wide range of phase physical properties are covered and provide a baseline for the fluid mixing structures performance in many systems.

[0081] FIGS. 1A, 1B and 1C demonstrate various flow regimes obtained using n-butanol as solvent for the alkaline hydrolysis of 4-nitrophenyl acetate with varying flow rates in structures termed SZ fluid mixing structure (1A), sickle fluid mixing structure (1B), and spade fluid mixing structure (1C). The SZ fluid mixing structure being a serpentine flow channel (FIG. 1A) is well known in the literature and the sickle fluid mixing structure (FIG. 1B) is a mixer combining a triangular obstacle and a curve, both being developed by the present inventors. The spade fluid mixing structure is similar to that disclosed in WO 2009/009129 A1.

[0082] It is evident from FIGS. 1A, 1B and IC that all these structures produce a parallel flow regime which is disadvantageous in terms of mixing and, therefore, in terms of reaction. In addition for the spade-like structure it has been observed by Woitalka et al. (Chem. Eng. S., 2014) a stratified flow regime at low flow rate (or long residence time) which correspond to a parallel flow regime.

[0083] As shown in FIG. 1D, it is evident that mixing performance according to the present invention (paralleloid or torch mixing structure) does not produce a parallel flow regime, in contrast to the structures discussed above (FIGS. 1A to 1C). Additionally, a fully dispersed flow—defined herein as an indistinguishable emulsion indicative of high mass transfer rates—was obtained by the present invention at total flow rates above only 7 mL/min.

[0084] The mixing performance achieved by present invention is more evidently advantageous in FIGS. 6A and 6B, which compare the overall continuous phase volumetric mass transfer coefficient K.sub.ca for the 4-nitrophenyl acetate hydrolysis as a function of flow rate for the cases of n-butanol (FIG. 6A) and toluene (FIG. 6B) as organic solvent. In FIGS. 6A and 6B, a square refers to the SZ mixing structure, a circle refers to the spade mixing structure, a triangle refers to the sickle mixing structure, and a rhombus refers to the polygonal (inventive) mixing structure. It should be noted that the initiation of the parallel flow regime for the SZ and spade structures is clearly observed when a decrease in mass transfer coefficient (K.sub.ca) is observed with an increase in the flow rate. Also, the domain of the parallel flow is described in FIGS. 1A to 1D.

[0085] In both cases, it can be noticed that the mixing performance achieved with the structure of the present invention reaches greater mass transfer coefficients at smaller flow rates. This is due to two particular features unique to the proposed fluid mixing structure. Firstly, it relies on a combination of contraction, expansion, and obstacle to dissipate energy, instead curves, such as in the SZ, spade or sickle mixing structures or the spade fluid mixing structure of WO 2009/009129 A1. Curves submit the fluids to centrifugal forces that promote a radial density gradient and the formation of parallel flow which is inadequate in multiphase systems. Secondly, it relies on an asymmetrical obstacle that brakes the dispersed phase and then desynchronizes its fragments, preventing their coalescence after passing the obstacle and overall ending in smaller drops of the dispersed phase.

[0086] Different variations of the proposed invention are displayed on FIG. 7A and further compared on FIGS. 7B and 7C. They depict the overall mass transfer coefficient as a function of flow rate for the mixing structure using an obstacle in the shape of a rhombus (also depicted in FIGS. 6A and 6B), of a triangle, and without an obstacle. The data for the unobstructed structure unambiguously demonstrate how the specially designed asymmetrical obstacle is necessary to produce favorable flow regimes by breaking the dispersed phase in two and subsequently desynchronizing its fragments. At the lowest flow rates, the structures with obstacle are 2 to 3 times greater. Additionally, the blunt face of the triangular obstacle precipitates the formation of a drop flow regime which increases the mass transfer coefficient at lower flow rates compared to the profiled face of the rhombus when using n-butanol.

[0087] FIGS. 7A and 7B again compare the overall continuous phase volumetric mass transfer coefficient K.sub.ca for the 4-nitrophenyl acetate hydrolysis as a function of flow rate for the cases of n-butanol (FIG. 6A) and toluene (FIG. 6B) as organic solvent, in this case for various obstacles of the inventive structure, i. e. with a rhomboid obstacle (rhombi), with a triangular obstacle (triangles), and without obstacle (squares).

[0088] FIG. 8A shows two structures with different obstacles and an obstacle-free structure, and FIG. 8B shows a comparison between the dependencies of the overall K.sub.ca coefficient on the total flow rate for two different obstacles and the obstacle-free structure shown in FIG. 8A. It should be noted that although in the middle structure of FIG. 8A, the short cathetus of the triangle facing in a direction opposite to the flow direction is essentially orthogonal to it, due to a stagnation point in front of the obstacle, the “each of said first and second sub fluid flows prior to their mixing have a non-zero average flow component in said inflow direction” as defined in claim 1.

[0089] The data for the unobstructed structure (squares) unambiguously demonstrate how the specially designed asymmetrical obstacle is necessary to produce favorable flow regimes by breaking the dispersed phase in two and subsequently desynchronizing its fragments. At the lowest flow rates, the structures with obstacle are 2 to 3 times greater. Additionally, the blunt face of the triangular obstacle precipitates the formation of a drop flow regime which increases the mass transfer coefficient at lower flow rates compared to the profiled face of the rhomboid when using n-butanol.

LIST OF REFERENCE NUMERALS

[0090] 10 fluid mixing structure [0091] 12 contraction zone [0092] 14 expansion zone [0093] 16 retention zone [0094] 18 bottom of 12 [0095] 20 bottom of 14 [0096] 22 bottom of 16 [0097] 24 side wall of 12 [0098] 26 side wall of 14 [0099] 28 side wall of 16 [0100] 30 space [0101] 32 flow splitter [0102] 34 left flow path [0103] 36 right flow path [0104] 38 flow mixing surface [0105] 40 flow mixing surface [0106] 42 flow-upstream side apex of 32 [0107] 44 flow-downstream side apex of 32 [0108] 46 continuous reaction unit [0109] 48 process fluid channel system [0110] 50 feeding port [0111] 52 discharge port [0112] 54 reaction passage [0113] 56 residence passage [0114] SA symmetry axis [0115] IFD inflow direction