Static mixing device

Abstract

A static mixing device (9) for a multiphase flow with a gas phase and a liquid phase comprises a tube (19) and a mixing insert (3', 4') forming the flow channel, which is arranged in the tube (19) and has a plurality of flow-influencing planar elements coated with a catalyst. The mixing insert (3", 4") has a predetermined total length (Lu"+Lb"), wherein, viewed in the insert, the static mixing device (9) has a section (3', 3", 53) of uncoated flow-influencing planar elements over a length (Lu', Lu") upstream (29) of the catalyst-coated flow-influencing planar elements, wherein the uncoated length (Lu', Lu") of this section (3', 3") is between 40% and 95% of the total length (L) of the mixing insert (3, 4).The tube (19) is designed with the section (3', 3") of uncoated flow-influencing planar elements in such a way that in the multiphase flow in the tube (19) a bubble flow is present in which the gas phase is dispersed uniformly in the liquid phase.

Description

TECHNICAL AREA

[0001] The present invention relates to a static mixing device comprising a flow channel with an arbitrary cross-sectional shape, a longitudinal axis, and a hydraulic inner diameter dh, with at least one mixing element arranged in the flow channel and at least one mixing element coated with a catalyst. The uncoated and coated mixing elements preferably have the same geometry, but may also have different geometries and hydraulic diameters dh. STATE OF THE ART

[0002] Static mixers are used today in all areas of chemical engineering. A characteristic feature of static mixers is that only the liquids or gases to be mixed are moved. Unlike dynamic mixing systems, there is no stirring; instead, pumps, blowers, or compressors continuously convey the media to be mixed to the mixing tube, which is equipped with the mixing elements. Static mixers can generally be used in the following applications: Mixing of pumpable liquids; Dispersing and emulsifying of immiscible components; Mixing of reactive liquids; Mixing and homogenizing of polymer melts; Gas-liquid contacting; Mixing of gases; Heat exchange of viscous substances

[0003] A static mixer known from US Patent 3,286,992 A, designated as a helical mixer, features helically curved, blade-like plates or mixing elements arranged in a row with intersecting end faces, which divide the flow of substances to be mixed upon entering each element. The flow channel is uniform in shape and cross-section within each element. The helical mixer is particularly suitable for mixing in turbulent flow regimes. Due to its moderate mixing performance, the helical mixer is only conditionally suitable for use in laminar flow regimes.

[0004] A special family of static mixers are the so-called X-mixers. These consist of intersecting webs or plates. An X-mixer known from AT 330 135 B has at least one mixing element in a pipe, in the form of a pair of plates with webs and slots. The webs of one plate extend through the slots of the other plate, intersecting each other. The plates are inclined relative to each other and to the axis of the pipe. Due to the inclination of the plates, the supplied flow of substances to be mixed is split into partial flows by the webs, with a temporal and spatial offset. In this known mixer, the web bases form significant dead zones, which unnecessarily increase the residence time and can damage critical liquids. Furthermore, the plates must be positioned with numerous welds, which can lead to increased corrosion. Assembling the plates is very time-consuming and therefore costly.This well-known device is particularly suitable for mixing in laminar flow. Its use in turbulent flow is limited due to its high pressure loss.

[0005] The development of the mixer according to CH 642 564 A5 in 1979 represented an improvement in static mixing technology for laminar flowing media. Since then, this mixer has proven its worth and is successfully used in a very wide range of applications, mostly with highly viscous media. Fig. 1 The CH 642 564 A5 shows a mixer with eight web layers, also known as an 8-web mixer, with a UD ratio of 1. The mixer has a very high pressure loss.

[0006] The geometry known as the CSE-X mixer is described in CH 693 560 A5. This patent discloses a device for static mixing, consisting of a tubular housing with at least one mixing insert arranged therein in the form of a plate with ribs and slots, which is bent. Preferably, the plates have projections on the rib edges and elliptical circumferential shapes. Two bent plates, in which the ribs of one plate extend through the slots of the other plate, are attached to the projections. The mixing inserts can be positioned one behind the other in the tubular housing, with the mixing inserts either in direct contact or with gaps between them. With this simple geometry, the device can mix excellently in all flow regimes. The mixing quality is determined solely by the number of mixing inserts and their installation position.The mixed insert became known on the market particularly as a 4-, 6- and 8-rib construction and also exhibits a high pressure loss that increases with the number of ribs.

[0007] WO 2009 / 000642 A1 discloses a mixing device of the type mentioned above, in which – as in EP 0 154 013 A1 – the webs have free spaces between the intersections. The one shown in WO 2009 / 000642 A1 in Fig. 3 The illustrated 5-bar mixer has an L / D ratio of 1. This geometry significantly reduces pressure loss. However, the design is mechanically very weak and difficult to weld professionally. Brazed versions are very complex and generally difficult to achieve gap-free connections.

[0008] US Patent 3,918,688 shows a mixing device in a rectangular channel with corrugated, stacked sheet metal plates. These plates are arranged to create a multitude of inclined, intersecting flow channels. The channels in each layer are at least partially interconnected to allow cross-mixing. Such mixer geometries are particularly suitable for coating applications because of their large surface area.

[0009] In "Static mixers and their application" (MH Pahl, E. Muschelknautz; Chem.-Ing.-Techn. 52 (1980) No. 4, pp. 285 - 291) a large number of static mixers are also described.

[0010] The trade journal CHEMIE TECHNIK No. 5 2004 (33rd year) describes micromacro technology using static mixers. Micromacro mixers are defined as the targeted use of static mixers of various geometries and nominal diameters. Fundamentally, a uniform pre-distribution must first be achieved in the macro mixer, followed by the best possible fine distribution in the micro mixer. CSE-X mixers are typically used as the basis for this process.

[0011] WO 2008 / 141472 describes a mixing heat exchanger with crossed multiwall sheets, which also features pipes through the sheets for additional heat exchange. Besides its excellent mixing properties, this mixing element is also capable of tempering liquids at high flow rates. Furthermore, it has a very large surface area.

[0012] Static mixers with catalytically coated surfaces combine two essential functions: Mixing: The static mixer ensures that the liquid and gas (e.g., hydrogen) are thoroughly mixed, generating turbulent flow that optimizes mass transfer between the phases. Catalysis: The catalytic coating on the mixer channels or elements ensures that the chemical reaction takes place directly at the mixer surface. In a hydrogenation process, for example, hydrogen (H₂) is adsorbed onto the catalyst-coated mixer surface, where the reaction with the unsaturated substrate occurs.

[0013] The advantage of such systems lies in the fact that the mass transfer (gas-liquid) and the catalytic reaction are closely coupled both spatially and temporally. This improves the reaction rate and the yield of the desired products.

[0014] WO 2017 / 106916 AI discloses a disclosure relating to catalytic static mixers containing catalytic material. The static mixers can be configured for use with flow reactors, for example, tubular flow reactors for heterogeneous catalytic reactions. This disclosure also relates to methods for manufacturing static mixers and to chemical flow reactors.

[0015] German patent DE 40 02 350 A1 discloses a recirculating reactor where a static mixer is combined downstream with a fixed catalyst structure coated with a catalytic substance. The catalyst consists of fixed-bed pellets or honeycomb structures. Recirculating reactors are widely used in chemical process engineering and are employed in many industrial processes requiring a continuous reaction, particularly reactive processes such as hydrogenation, polymerization, or catalysis. These reactors allow the reaction mixture to be circulated in a closed loop system, thereby optimizing the reaction rate and product quality. However, there are also disadvantages and challenges associated with the use of recirculating reactors. These include: High investment costs and complex infrastructure; high energy demand; risk of byproduct accumulation; difficulties in scaling; hazards due to reaction conditions

[0016] Several publications demonstrate the continuous use of coated static mixers in the laboratory. These include the following publications: "Continuous flow hydrogenations using novel catalytic static mixers inside a tubular reactor" von A. Avril, C. H. Hornung, A. Urban, D. Fraser, M. Horne, J.-P. Veder, J. Tsanaktsidis,T. Rodopoulos, C. Henry and D. R. Gunasegaram, unter DOI: 10.1039 / c6re00188b abrufbar. "Catalytic Static Mixer-Enabled Hydrogenation of a Key Fenebrutinib Intermediate: Realtime Analysis for a Stable and Scalable Process" von René Lebl, Stephan Bachmann, Paolo Tosatti, Joerg Sedelmeier, Kurt Püntener, Jason D. Williams,, C. Oliver Kappe, Center for Continuous Flow Synthesis and Processing (CC FLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria, veröffentlicht in https: / / doi.org / 10.1021 / acs.oprd.1c00258. "Hydrogenation of vinyl acetate using a continuous flow tubular reactor with catalytic static mixers" von X. Nguyen, A. Carafa, C.H.Hornung, CSIRO Manufacturing, Bag 10, Clayton South, Victoria, 3169, Australia, published in "Chemical Engineering and Processing - Process Intensification", Volume 124, February 2018, Pages 215-221. .

[0017] All these publications demonstrate the advantages of a continuous reactor system with fully coated static mixing elements. However, analysis of these laboratory experiments has shown that the static mixers are not operated under the correct process engineering conditions. The flow conditions are mostly in the transition range, and a fine gas droplet dispersion is not guaranteed. This makes it very difficult to achieve the necessary scale-up conditions for a given reaction. Nevertheless, the fully coated static mixers exhibit good properties and performance. PRESENTATION OF THE INVENTION

[0018] The invention is based on the objective of providing a static mixing device with a mixing insert coated with catalyst material, which has an improved dispersion effect without a significant increase in pressure drop and which does not have the aforementioned disadvantages according to the prior art.

[0019] This problem is solved for a static mixing device with the features of claim 1.

[0020] A static mixing device for a multiphase flow with a gas phase and a liquid phase comprises a tube and a mixing insert, which form the flow channel arranged in the tube and have a plurality of flow-modifying planar elements coated with a catalyst. The mixing insert has a predetermined overall length, wherein, viewed in the insert, the static mixing device has a section of uncoated flow-modifying planar elements upstream of the catalyst-coated flow-modifying planar elements over a length of between 40% and 95% of the total length of the mixing insert.The pipe is designed with the section of uncoated, flow-influencing planar elements in such a way that a bubble flow occurs in the multiphase flow in the pipe, in which the gas phase is dispersed uniformly in the liquid phase.

[0021] The liquid phase can consist of a mixture of liquids. In this context, "upstream" refers to the direction opposite to the flow direction of the gas and liquid phases. The longitudinal direction of the pipe, and thus of the mixing device, can be oriented in any direction: vertically upwards, vertically downwards, horizontally, or inclined upwards or downwards.

[0022] The features of the claim achieve the inventive solution to the problem by designing the device such that the gas bubbles in the liquid are small and finely dispersed, that the bubbles are continuously and intensively mixed across the entire cross-section, and that the concentration of dissolved gas in the liquid is sufficiently high to allow the catalyst material to exert its full effect. Furthermore, it is advantageous that the coated static mixer has a large surface area and that the pressure drop is as small as possible, since this directly influences the solubility in the static mixer system. The generally applicable description for the pressure drop is as follows: Δ p = ξ 2 ⋅ ρ ⋅ w 2 ⋅ L D

[0023] ξ The resistance factor of the static mixer is called the ΔF. It depends on the flow regime, i.e., the Reynolds number, and the mixer's geometry. The mixer geometry must be chosen to minimize the resistance factor while simultaneously maximizing the wetted area. Resistance factors generally range from 1 to 5, with a small influence in this case. Changing the mixer's diameter also affects the hydraulic diameter and velocity. This parameter allows for significantly better control of pressure loss.

[0024] Gas-liquid-solid reactions are widely used in the chemical and petrochemical industries and encompass numerous processes such as oxidation, hydrogenation, synthesis of chemical compounds, exhaust gas purification, and waste treatment. These processes offer high efficiency and flexibility but also place demands on mass transfer, catalyst activity, and process control. Selecting the appropriate reactor design and considering thermodynamic, kinetic, and kinematic aspects are crucial for operating these processes economically and safely.

[0025] As a first step in the design process, the flow conditions in the static mixing system must be described. The VDI Heat Atlas (example: 10th edition 2006), published by Springer-Verlag, ISBN: 978-3-642-19981-3, explains how to calculate the flow conditions. This is a well-known design basis, familiar to experts, and allows for a simplified categorization of the flow into the following categories: Bubble flow, piston bubble flow, chaotic flow or foam flow, ring strand flow, and ring flow.

[0026] The hydrogenation reaction will serve as an example here. However, the device according to the invention is applicable to all gas-liquid-solid reactions. Hydrogenation is a chemical reaction in which hydrogen (H₂) is incorporated into a chemical compound. This reaction is often carried out using a catalyst and is one of the most important reactions in organic chemistry and petrochemistry. It is used in various industrial processes, in particular for the production of saturated compounds from unsaturated precursors.

[0027] Once the flow conditions are defined and bubble flow is present in the system, the foundations are laid for modeling a scalable reactor system. The applicant's micromacro technology can be applied, meaning that various mixer geometries and sizes can be used section by section, coated or uncoated, with different lengths Lm and with the same or different hydraulic inner diameters dh. Alternatively, the reactor system can consist of only one identical mixer geometry, both coated and uncoated, with a single element length Le. In this case, the total length L of the reactor can be calculated from the number of mixing elements Me. L = Me ⋅ Le

[0028] For a system of the applicant, the following applies to the entire length L of the reactor: L = Me n ⋅ Le n ︸ Lm n + Me n + 1 ⋅ Le n + 1 ︸ Lm n + 1 + ..

[0029] Taking as an example a reactor system with a circular channel of diameter Di and identical mixing elements, the mass transfer calculation can be easily represented. The number of sections with uncoated static mixing elements Lm n and with coated static mixing elements Lm n+1 are arbitrarily selectable. Any combination of such an arrangement with length L is called the reactor.

[0030] The fundamentals of the mass transfer process are extensively described in every process engineering textbook and are reduced in this document to the following key figures: the Reynolds number, the Schmidt number, and the Sherwood number

[0031] In summary, the mass transfer during hydrogenation follows a simplified law, whereby the catalytic reaction generally follows a first-order reaction order and must be considered in terms of ks. ks is the mass transfer coefficient from the liquid phase to the solid phase. MTR H 2 = 1 1 k L ⋅ a d 32 + 1 k s ⋅ a k ⋅ p i H i

[0032] The Reynolds number, Re, is a dimensionless number used in fluid mechanics to describe the behavior of a fluid or gas with respect to flow. It indicates whether a flow is laminar or turbulent. The description in this patent applies to Reynolds numbers from 10 to 100,000. Re = ρ ⋅ w ⋅ D η

[0033] The Schmidt number (Sc) is a dimensionless number used in fluid mechanics and thermodynamics to describe the ratio of a substance's molecular diffusion to its viscosity. The Schmidt number is a useful measure for understanding the relationship between diffusion-induced and viscous motion of a substance in a fluid. It is often used to describe mass transfer and flow characteristics in many technical processes. The mixer according to the present invention exhibits Schmidt numbers ranging from 50 to 2000.

[0034] The Sherwood number describes the ratio of advective transport (transport of matter by the flow) to diffusive transport (molecular diffusion) of a substance in a fluid. The Sherwood number is an important parameter for describing mass transport in fluids and helps to quantify the relationship between advective and diffusive transport. It is crucial for the analysis and design of processes involving mass transfer, such as in chemical reactors, air and water treatment systems, and other industrial applications. Sh = c Sh ⋅ Re a ⋅ Sc b

[0035] Typical values ​​for the exponent a in turbulent flows range between 0.33 and 0.67. This value depends on the mixer geometry and the specific flow conditions. A higher exponent indicates a stronger dependence of mass transfer on flow velocity. The exponent b describes the dependence of mass transfer on the Schmidt number, which represents the ratio of the viscosity and diffusion coefficient of the gas in the liquid. The Schmidt number indicates how easily a substance disperses in the liquid. A value for b of approximately 0.33 is typical in many cases where the Schmidt number is within a typical range (e.g., for organic liquids or gas-liquid reactions). c Sh These are values ​​obtained from mass transfer measurements.

[0036] The Sherwood number can be used to determine the mass transfer coefficient. k l Mass transfer coefficients for static mixers are calculated for gas-liquid processes. These coefficients typically range from 10⁻⁶ to 10⁻³ ms⁻¹, depending on the process type and the gas-liquid interaction. These values ​​have been repeatedly confirmed by measurements in the boundary ranges between the Schmidt number (100–2000) and the Reynolds number (200–20,000). k l = Sh ⋅ D d h

[0037] The Sherwood number is also a key parameter for characterizing the mass transfer process between a liquid and a solid. In solid-liquid systems, such as those found in catalytic processes, the Sherwood number describes how effectively reactants are transported from the liquid to the catalyst surface, with both diffusion and convection playing a role. A higher Sherwood number indicates more efficient mass transfer, which is desirable in many industrial processes. The same principle can thus be applied as in gas-liquid mass transfer processes. However, catalytic processes typically also involve a first-order reaction. These fundamentals are well known to those skilled in the art. For mass transfer from a liquid to a solid, the values ​​are often in the range of 10⁻³ to 10⁻² ms⁻¹, as the transfer between liquid and solid is usually more efficient.Comparing the mass transfer processes between gas and liquid and between liquid and solid, differences of a factor of 10 to 10,000 can occur. Therefore, the focus in a gas-liquid-solid process should primarily be on the gas-liquid mass transfer.

[0038] The relationship can be better explained using an example. A hydrogenation process with an organic liquid mixture is carried out at a flow rate of 90 l / h and a pressure of 80 bar. Examples include organic mixtures in which the reactant is diluted with a solvent. For example, the solvents could be ethanol, methanol, or THF. These data correspond to a typical production application in the pharmaceutical industry. The organic liquid mixture has a hydrogen saturation of C*. The higher the pressure, the more hydrogen the liquid is enriched. This is well known to those skilled in the art.

[0039] The chosen example is a Fluitec CSE-X mixer with a nominal diameter of DN15. A reactor length of L = 2000 mm is selected. Under the conditions described above, the CSE-X mixer achieves a bubble flow with bubble sizes of 0.1 to 0.2 mm, corresponding to a specific area of a d 32 = 2324 m 2< m -3< corresponds to this. The mass transfer coefficient is k l = 1.4 x 10⁻⁴ < ms⁻¹ < . These are typical values ​​that can be expected from a static mixer. In comparison, a trickle-bed reactor is approximately 50 to 200 times smaller.

[0040] The k l · a d The 32 value is a measure that quantifies the mass transfer at the gas-liquid interface. Essentially, it indicates k l · a d The 32 value indicates how efficiently a particular substance (e.g., hydrogen) is absorbed by the liquid, or vice versa. Initially, it is k l ·a d 32 = 0.325 s -1< . This decreases with the absorption of gas, as the bubble size decreases over the process.

[0041] The k s · a k The μ-value is a key parameter in the catalysis and mass transfer analysis of solid-liquid systems. It indicates how efficiently reactants are converted into a catalytic reaction and is an important measure for the design and optimization of reactors in the chemical process industry. a k The static mixing device is known to have a volume of 834 m² < m³ < . k s lies in the range of 10⁻³ to 10⁻² < ms⁻¹. Choosing a conservative value of 10⁻³ < ms⁻¹ yields k s · a k = 0.834 s -1< .

[0042] If you compare k l · a d 32 = 0.325 s -1< with the most conservative possible value k s · a k = 0.834 s -1< This shows that the liquid-solid mass transfer process is still at least 2.5 times better at the beginning than the gas-liquid mass transfer. As already mentioned, the catalytic process follows a reaction order and changes over time, or rather, over the length. Thus, over the length L, both the k s · a k -value as well as k l · a d 32 value. Therefore, no statement can be made about how well the mass transfer processes on the gas / liquid and liquid / solid sides take place simultaneously as a function of the mixer's length.

[0043] EP 3 932 531 refers to the principle of segmental analysis for heat transfer. The document describes the temperature profile of reactions with static mixers. Commercially, the product is called the Fluitec calorimeter and sets new standards for the thermal analysis of processes. Since mass transfer processes behave analogously to thermal processes, the principle of segmental analysis is now being applied for the first time. In the mass transfer process, corresponding mass transfer balances are calculated along the length L according to Equation 4, where the length L is virtually divided into, for example, 100 segments for the calculations. With this method, both the instantaneous concentration in the liquid and the consumption of the gas can be represented in the form of the conversion.

[0044] Upstream of the reactor, the gas and liquid phases are combined and directed into the uncoated section at the beginning of the pipe, creating a bubble flow. The uncoated section then takes effect, enriching the liquid phase and dissolving the gas phase as efficiently as possible. Upon reaching the coated section, the catalyst, for example, concentrates and converts the hydrogen content, while simultaneously dissolving additional gas.

[0045] Further embodiments are specified in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Preferred embodiments of the invention are described below with reference to the drawings, which serve only for illustration and are not to be interpreted restrictively. The drawings show: Fig. 1 a schematic representation of the reactor; Fig. 2 a conversion diagram for three reactor arrangements, a fully coated static mixing device according to the prior art, a 50% coated mixing device, and a 12.5% ​​coated mixing device; Fig. 3A a schematic side cross-sectional view of the static mixing device with a mixing insert section coated to 50% of the length of the tube; Fig. 3B a schematic side cross-sectional view of the static mixing device with a mixing insert section coated to 12.5% ​​of the length of the tube; Fig. 4 a schematic side cross-sectional view of the static mixing device in a cascaded arrangement of individual static mixing devices; Fig. 5 a schematic side cross-sectional view of the static mixing device with smaller diameter mixing insert sections arranged as packing in the tube; Fig.6a modified embodiment of the design according to . Fig. 4 , which also after the Fig. 3A oder 3B usable; and Fig. 7 a modified embodiment of the design according to Fig. 5 . DESCRIPTION OF PREFERRED EXECUTION FORMS

[0047] Fig. 1 Figure 9 shows a preferred reactor arrangement with a first static mixing device 3 and a second static mixing device 4, each having a length Lm. The first static mixing device 3 is uncoated, and the second static mixing device 4 is coated. A temperature sensor 5 for monitoring the temperature is integrated into the coated static mixing device 4. Any heating or cooling elements are not shown in the figure. They are arranged around the reactor in a known manner. The reactor 9 has a total length L, which is composed of the two partial lengths Lm and the length of a connecting tube 11 between the two static mixing devices. The partial lengths can be equal, as shown in Figure 1. Fig. 3A shown; however, they can also advantageously have a length ratio of, for example, 8 to 1, as shown in Fig. 3A The diameter of the pipe 19 of the first static mixing device 3 with the uncoated flow-influencing planar elements arranged therein can be larger or smaller than the diameter of the second mixing device 4 with the coated flow-influencing planar elements arranged therein.

[0048] Upstream of reactor 9 are a fluid supply 1 and a gas supply 2. A gas is metered via a gas metering unit, and the liquid via a fluid metering unit 1. Optionally, a Venturi pump 10, shown schematically, can be installed upstream.

[0049] A gas separator 6 is shown schematically behind reactor 9. The separated gas can be removed from the process via gas outlet 7, so that the remaining gas-free liquid can be fed to the next process step.

[0050] In a particularly preferred embodiment, the gas outlet 7 is connected to the gas intake port 8 of the Venturi pump 10, as shown in Fig. 1 This also allows the use of the unreacted gas, for example, hydrogen. It is also possible to provide the gas supply 2 at the gas intake nozzle 8 and to supply these gases together to the liquid via the Venturi pump 10.

[0051] Since a catalyst-coated static mixer 4 is cost-intensive, the use of a reactor 9 with a second static mixing device 4' or 4" (as in Fig. 3A und Fig. 3B shown) with minimal amount of catalyst material is crucial. Fig. 2 shows the conversion and concentration profile of the liquid along reactor 9 over the length L for three different reactor arrangements: with a static mixing device completely coated with catalyst over its length L (state of the art) with a static mixing device coated with 50% catalyst (only the last 50% of the static mixing device is coated with catalyst with respect to its length) (see Fig. 3A ). with a static mixing device coated with 12.5% ​​(only the last 12.5% ​​of the static mixing device is coated with catalyst) (see Fig. 3B ).

[0052] Fig. 2 The diagram shows the measurement results for three different reactor arrangements: one is a fully coated static mixing device, referred to as a 100% catalyst arrangement, designed according to the state of the art; the other is a 50% coated mixing device; and finally, a 12.5% ​​coated mixing device.

[0053] The x-axis (13) shows the length L = 2 m of reactor 9. The y-axis (12) on the left shows the concentration profile, which represents the concentration of the gas in the liquid. A value of 0 on the axis means no enriched gas, while a value of 1 corresponds, for example, to 1 gram of gas dissolved in the liquid per liter. The y-axis (22) on the right shows the conversion from 0 to 1. The conversion indicates how much gas was consumed by the catalyst during the reaction. For example, if the reaction requires 0.3 mol of gas per liter, then 50% conversion would be 0.15 mol per liter.

[0054] Solid line 31 shows the concentration of dissolved gas in the liquid along the length of reactor 9 for a fully (=100%) coated static mixing device. The coarser dashed line 32, starting at 1 m, and the finer dashed line 33, starting at 1.75 m, show the concentration profiles for the partially coated static mixing devices at 50% and 12.5%, respectively. Dotted line 35 shows the concentration profile when no catalyst is used.

[0055] Solid line 41 shows the sales curve of the fully coated static mixing device. Dashed lines 42 and 43 show the static mixing device coated at 50% and 12.5%, respectively. Sales curve 42 for the 50% coated static mixing device begins at a length of 1 m, and sales curve 43 for the 12.5% ​​coated static mixing device begins at a length of 1.75 m. In the first case, 100% sales are achieved, in the second case 98%, and in the third case 69%.

[0056] The coating to 100% means that the surface of the second static mixing device 4 is completely covered with the catalyst over its entire length, as is known from the prior art.

[0057] The design of the sections of the mixing device is better explained in the Fig. 3A und 3B to see. Fig. 3A Figure 1 shows a schematic lateral cross-sectional view of the static mixing device with a mixing insert section 4' coated to 50% of the length of the pipe 19 and the Fig. 3B Figure 1 shows a schematic side cross-sectional view of the static mixing device with a mixing insert section 4 coated to 12.5% ​​of the length of the pipe 19. The static mixing section is shown in cross-section as a box without internal components. These composite rectangles of the Fig. 3A und 3B In cross-section, each would represent a mixing insert that can be inserted into the tube 19. It can then be removed, particularly for the maintenance and regeneration of the catalyst layer.

[0058] The Fig. 3B Figure 1 then shows the 12.5% ​​case, in which the uncoated section 3" has a length Lu" of 1.75 meters, followed by a coated section 4" with a length Lb" of 25 centimeters. The coating in section 4" can also be partial, although complete coverage with catalyst material in this section 4" is preferred.

[0059] The Fig. 4 Figure 1 shows a schematic side cross-sectional view of the static mixing device in a cascaded configuration of two units K1 and K2 consisting of individual static mixing devices 3' / 4'. With a predefined length of tube 19, the mixing device can be cascaded by a sequence of two, or even more, combinations of uncoated and coated sections 3' and 4', respectively. This is particularly advantageous when the catalytic reaction requires 0.6 mol, but the device can only dissolve 0.3 mol. In such cases, cascading is the solution. This is because, with reference to the 50% solution, the concentration curve 32 after the bubble flow passes 1 meter (point 36 in Figure 1) Fig. 2 The flow rate drops sharply from the uncoated section to the coated section and then recovers after a local minimum, as the bubbles passing over the catalyst layer cause the bubble flow to react, resulting in less dissolved gas. Therefore, a further section of uncoated, flow-influencing planar elements is helpful before the bubble flow is again directed past a catalyst layer. The second or subsequent mixing element 4' with coated elements can be shorter (length Lb') than a preceding mixing element 4', particularly in its length Lb' compared to the length Lu' of the uncoated mixing element 3'. In other words, in a cascade, successive cascade elements K2 can each have a shorter overall length than K1, etc., and the length ratio of Lu' to Lb' can also increase, resulting in an increasingly shorter catalyst-coated mixer section.

[0060] Fig. 5 Figure 1 shows a schematic side cross-sectional view of the static mixing device with smaller diameter mixing insert sections 51, arranged as a packing within the tube 19. Advantageously, the mixing insert sections 51 are packed closely together, optionally combined with heating or cooling elements (not shown). Each mixing insert section 51 has a very small diameter compared to the tube diameter, but along its length has two sections 53 and 54 on uncoated and coated, respectively, flow-influencing planar elements. In principle, the elements 3, 3', 3" or 53 can be physically separated from the elements 4, 4', 4" or 54. However, for maintenance reasons, it is preferred to manufacture these elements as a single piece.

[0061] A 50% coating means that the surface of the second static mixing device 4 is completely covered. Of course, alternating covered and uncovered lengths are possible in the length division, as shown in... Fig. 4 It may be shown that such forms are intended, or mixed forms are intended in which the percentage of the surfaces covered with catalyst material also changes over the length, for example in a sawtooth or sine curve around the desired mean value (such as 50% or 12.5%), which corresponds to a cascade.

[0062] In summary, it becomes clear that the higher the gas content of the liquids, the more gas is processed by the coated static mixing device. Therefore, savings can be achieved with the more expensive coated static mixing devices if gas enrichment in the liquid occurs beforehand. It is essential that this first, uncoated static mixing device 3 is designed for the intended gas-liquid combination in such a way that a bubble flow is generated and, in particular, exists and is maintained at the latest at the transition point from an uncoated to a coated section at points 36 or 38.

[0063] The one in Fig. 2 The conversion shown refers to hydrogen consumption. In the examples, the hydrogen requirement for the reaction is 0.3 mol l - 1. 100% conversion is achieved when 0.3 mol of hydrogen in one liter of mixture are completely converted in the reactor. The fully coated mixer achieves this even with the most conservative k s A conversion factor of 10⁻³ < ms⁻¹ < 10⁻³ results in 100% conversion. Surprisingly, it was found that a partially coated, static mixing device, where only the last 50% has a catalyst coating, achieved a conversion rate of 98%. A reactor coated with 12.5% ​​exhibits a surprisingly high conversion rate of 70%. Of course, catalyst coatings between 12.5% ​​and 50% are also possible, e.g., 30% and other intermediate values. In particular, a coating of only 5% can also be used, which, with a pipe length of 2 meters, corresponds to a catalyst coating length Lb of only 10 centimeters.

[0064] The curves showing the concentration profile in the liquid clearly demonstrate that the higher the proportion of gas in the liquid, the more efficiently the reactant is converted in the mixture. This is readily apparent from the slope of the conversion. If the dissolved gas is crucial for mass transport, then the dosed molar fraction of hydrogen must be higher than the requirement for the molecular conversion. This can be illustrated with another example. In the hydrogenation of 5-nitroindole to 5-aminoindole, the chemical formula shows that at least 0.3 mol L⁻¹ of hydrogen is required for 0.1 mol L⁻¹ of reactant.

[0065] However, with a large volumetric flow rate fraction of gas, the static mixer 4 loses efficiency. Furthermore, the residence time in the reactor is reduced. This limit for the volumetric flow rate fraction is approximately 60%. In the worst case, with a volumetric flow rate fraction greater than approximately 60%, depending on the installation orientation (horizontal or vertical), the bubble flow can disappear, which means that mass transfer is no longer guaranteed. Therefore, on the one hand, sufficient hydrogen must be metered so that the reactant can be converted; on the other hand, the flow conditions must be selected such that bubble flow is present in the area of ​​the mixing inserts coated with catalyst material.

[0066] Increasing the pressure allows adjustment of both the gas flow rate and the solvent solubility C*. The pressure can thus be set so that the solvent in the reactor is enriched to such an extent that there is a consistently sufficient amount of hydrogen in the liquid to complete the reaction.

[0067] If the maximum solubility C* is less than the concentration required for the reaction, the system can also be operated in multiple stages. This means that either the gas flow rate is chosen to be sufficiently high and the reactor is first equipped with a section containing uncoated static mixing elements and a section containing coated static mixing elements, and this is repeated as needed until the desired conversion is achieved. Alternatively, the reactor can also be operated in a cascaded manner. This means that if the flow conditions are insufficient for a single dose, gas can be dosed before each new section of the reactor. For example, the reaction might require 0.6 mol of hydrogen per liter. However, the maximum solubility of the liquid is only 0.3 mol per liter. Therefore, the liquid cannot be concentrated above 0.3 mol per liter. If 0.If 6 moles of gas per liter are added to the liquid, the gas will only be enriched if the mixer is coated along its entire length. This results in an expensive design with a very large coated mixer section.

[0068] During operation, special care must be taken to ensure that the coated static mixing elements 3 and 4 do not overheat. If this occurs, reactor 9 must be operated in cascade mode. In this case, the uncoated static mixing elements, in addition to mass transfer, also have the task of cooling the mixture. Therefore, the reactor can be equipped with a double jacket containing a heating or cooling medium. It is also advisable to place at least one temperature sensor in the coated static mixing elements 3 and 4 to monitor the reaction temperature.

[0069] If the volume flow rate is very high, for example 5000 l / h, both the uncoated static mixer 3 and the coated static mixer 4 can be connected in parallel. A particularly preferred embodiment exists when the uncoated mixer has a flow channel and the coated static mixers are connected in parallel. Particularly preferred embodiments are devices according to patents EP 1 067 352 A and WO 2008 / 141472 A. These devices can ensure mass transfer and cool or heat large volume flows. It is also possible to coat such devices.

[0070] Typical coatings include nickel, palladium, platinum, palladium on aluminum oxide, platinum on aluminum oxide, rutenium on aluminum oxide, bimetallic alloys, or carbon. Other coatings can also be chosen.

[0071] At the reactor outlet, i.e., after the uncoated and coated arrangement of the static mixing elements, the excess gas, for example hydrogen, should be separated from the liquid. This can be done, for example, by a separator. A separator is a device specifically designed to separate gas and liquid. The most common methods are: Gravity separator: Separation by gravity, simple but slow. Venturi separator: Uses the Venturi effect to accelerate phase separation. Cyclone separator: Separation of gas and liquid occurs through centrifugal force. Filtration or membrane separation: Separation using fine filters, useful for small droplets or solids. Conditioning (cooling): Cooling to separate the phases.

[0072] Preferably, a gravity separator is used. A gravity separator uses gravity to separate the liquid from the gases. This method is cost-effective, requires little maintenance, and is effective at separating phases with significant density differences, which is the case with gas-liquid systems. Once the gas is separated, it can be removed from the process, and the gas-free liquid can be fed into the next process.

[0073] If a Venturi pump is installed upstream of the reactor, i.e., upstream of any uncoated or coated arrangement of static mixing elements, the gas-liquid mass transfer is significantly improved. Furthermore, the system is able to draw in gas.

[0074] A Venturi pump, also called a liquid jet vacuum pump or ejector pump, is a device that utilizes the Venturi effect to pump liquids or gases. The Venturi effect describes the phenomenon where the pressure in a pipe decreases when the flow velocity increases at a narrow point in the pipe. This specific design principle is used in the Venturi pump to draw a liquid or gas into a connected outlet by means of a pressure drop. It is well known to those skilled in the art and extensively documented in the literature.

[0075] Connecting the gas intake of the Venturi pump to the gravity separator creates a gas cycle, for example, a hydrogen cycle, which allows the excess gas exiting the reactor to be reused without an additional pumping device. With precise control, it is now possible to utilize 100% of the hydrogen gas and also ensure that the gas is removed from the liquid stream. However, this is only possible if the pressure drop across the reactor is small. A preferred embodiment is one where the pressure drop across the reactor is < 1 bar, and particularly preferably < 0.5 bar.

[0076] Maintaining pressure downstream of a reactor is crucial for ensuring a smooth and consistent flow. A commonly used system involves installing a pressure regulating valve (PRV) after the reactor. The PRV ensures that the pressure is maintained at a desired level by controlling the flow rate. A throttle valve can also be used to regulate the pressure downstream of the static mixer. These valves operate by reducing the flow within a specific range, thus maintaining the pressure within the desired interval. Pressure regulation downstream of a reactor is well-known to those skilled in the art and will not be described further here.

[0077] The key aspect of pressure maintenance is that by increasing the pressure, the volume flow ratio of the gas phase to the liquid phase can be reduced and, in particular, regulated below a predetermined percentage, for example, a maximum of 60%.

[0078] Fig. 6 shows a modified embodiment of the design according to Fig. 4 , which also according to the explanations as in Fig. 3A oder 3B shown how it can be used. The pipe 19' in the area of ​​the first cascade K1 has a larger diameter. This diameter is reduced to the pipe diameter 19 in a transition area 19". As a rule, the pipes 19 and 19' are, in contrast to the schematic representation in Fig. 6 guided concentrically. The transition area 19" can also be designed differently, for example like the connecting pipe 11 made of Fig. 1 . In other versions, the downstream pipe section of cascade K2 may also have a larger diameter.

[0079] In the version as in Fig. 6 As shown, each pipe section 19 and 19' includes a cascade K1 and K2 respectively with mixing inserts 3' and 4'. In other configurations, the first pipe section 19' may contain only an uncoated mixing insert 3' and the second pipe section 19' only a coated mixing insert 4'.

[0080] Fig. 7 Finally, a modified embodiment of the design according to Fig. 5 The coated mixing insert 54 is as described in Fig. 5 However, the design only affects a mixer package with coated individual pipes. This is a change compared to the Fig. 5 The possibility, but not the necessity, is shown that the pipe diameters of the individual coated mixing inserts are different, here as mixing insert 54' with a larger diameter compared to mixing insert 54.

[0081] The essential difference in execution between Fig. 5 and Fig. 7 The reason lies in the fact that the uncoated mixing insert 53' does not have a package of thinner tubes, but rather, as in Fig. 3A oder Fig. 3B The entire pipe diameter is filled. It is possible that this design is accompanied by a change in the pipe 19, meaning that the uncoated length Lu‴ has a larger or smaller diameter compared to the coated length Lb‴. These adjustments in diameter allow for an adaptation of the bubble flow, particularly at the transition surface 36 or 38 between the uncoated and coated areas. REFERENCE MARK LIST

[0082] 1 Fluid feed 2 Gas feed 3 Uncoated static mixing element (generic) 3' Uncoated static mixing element (50% version) 3" Uncoated static mixing element (12.5% ​​version) 4 Coated static mixing element (generic) 4' Coated static mixing element (50% version) 4" Coated static mixing element (12.5% ​​version) 5 Temperature sensor 6 Gas separator 7 Gas discharge of the separated gas 8 Gas intake port 9 Reactor assembly 10 Venturi pump 11 Connecting pipe 12 Legend of the Y-axis, left, concentrations C 13 X-axis, length of the mixer 19 Pipe 22 Legend of the Y-axis, right, conversion UA ​​29 Flow direction 31 Concentration profile 100% catalyst (state of the art) 32 Concentration profile 50% Catalyst 33 Concentration profile 12.5% catalyst 35 Concentration profile no catalyst (state of the art) 36 Transition from uncoated to coated section, 50% example 37 Drop in concentration profile 38 Transition from uncoated to coated section, 12.5% ​​example 41 Conversion 100% catalyst (state of the art) 42 Conversion 50% catalyst 43 Conversion 12.5% ​​catalyst 51 Static mixing insert with coated and uncoated area 53 Uncoated area 54 Coated area 54' Coated area 58 Intermediate space 59 Inner tube for individual small mixer insert of a package. a d 32 specific surface area a k Specific catalyst surface area C* Hydrogen saturation of the liquid dh Hydraulic diameter Di Inner diameter of the mixer DM Molecular diffusion coefficient of the substance Ks Mass transfer coefficient liquid-solid k l Mass transfer coefficient gas-liquid k s Mass transfer coefficient liquid-solid K1 first cascade K2 second cascade L total length Lm length of a mixing element Lb' length of the coated mixing insert (50% version) Lb" length of the coated mixing insert (12.5% ​​version) Lb‴ length of the coated mixing insert (12.5% ​​version) Pipe package Lu' length of the uncoated mixing insert (50% version) Lu" length of the uncoated mixing insert (12.5% ​​version) Lu‴ length of the uncoated mixing insert (12.5% ​​version) Solid pipe w Speed ​​of flow ρ Density of the liquid or gas η dynamic viscosity

Claims

1. Static mixing device (9) for a multiphase flow with a gas phase and a liquid phase, comprising a tube (19) and a mixing insert (3, 4, 51) forming the flow channel which is arranged in the tube (19) and has a plurality of flow-influencing planar elements, wherein the flow-influencing planar elements are coated with a catalyst, characterized by the fact thatThe mixing insert (3, 4, 51) has a predetermined total length (L), wherein the static mixing device (9), viewed in the insert, has a section (3', 3", 53) of uncoated flow-influencing planar elements upstream (29) of the flow-influencing planar elements coated with the catalyst material over a length (Lu', Lu"), wherein the uncoated length (Lu', Lu") of this section (3', 3", 53) is between 30% and 95% of the total length (L) of the mixing insert (3, 4, 51), and that the tube (19) is designed with the section (3', 3", 53) of uncoated flow-influencing planar elements such that a bubble flow is present in the multiphase flow in the tube (19) in which the gas phase is uniformly dispersed in the liquid phase.

2. Static mixing device according to claim 1, wherein for a predetermined gas phase, in particular hydrogen, and a predetermined liquid phase, the tube (19) and the mixing insert (3, 4, 51) are designed such that the Schmidt number of the liquid is 50 to 2000 and the Reynolds number of the liquid is 10 to 100,000.

3. Static mixing device according to claim 1 or 2, wherein the uncoated length (Lu', Lu") of the section (3', 3", 53) of the uncoated flow-influencing planar elements is between 60% and 85% of the total length (L) of the mixing insert (3, 4, 51), preferably between 70% and 80%.

4. Static mixing device according to one of claims 1 to 3, characterized by the fact thatthe pipe (19) has a total length in which several mixing inserts (3, 4, 51), each comprising in the direction of flow (29) a section (3', 3", 53) of uncoated flow-influencing planar elements and a section (4', 4", 54) of coated flow-influencing planar elements, are arranged in cascade one after the other to fill the pipe (19).

5. Static mixing device according to claim 4, characterized by the fact that the total length (K1, K2) of the mixing inserts of the cascade is different from each other and / or that the length of the coated matrix insert (4') differs from the length of the uncoated matrix insert (3') of the different mixing inserts (K1, K2) of the cascade, in particular decreasing in the direction of flow (29).

6. Static mixing device according to one of claims 1 to 5, characterized by the fact thatThe volume flow ratio of the gas phase to the liquid phase is at most 90%, preferably at most 60%, particularly preferably at most 50%.

7. Static mixing device according to claim 6, characterized by the fact that The static mixing device has a pressure control for adjusting, in particular increasing, the pressure in order to control the volume flow ratio of the gas phase to the liquid phase.

8. Static mixing device according to any one of the preceding claims 1 to 7, characterized by the fact that Upon entry into the coated static mixing element (4, 4', 4", 54) the concentration of the gas dissolved in the solvent is at least 20% of the saturation concentration C* of the solvent.

9. Static mixing device according to any one of the preceding claims 1 to 8, characterized by the fact thatA plurality of mixing inserts (51) in associated mixing insert tubes (59) with a smaller diameter than the tube (19) are arranged side by side as a package in the tube (19) of the static mixing device, each of these mixing inserts (51) comprising in the flow direction (29) a section (53) of uncoated flow-influencing planar elements and a section (54) of coated flow-influencing planar elements adjoining this section.

10. Static mixing device according to any one of the preceding claims 1 to 8, characterized by the fact that a section (3') with uncoated flow-influencing planar elements downstream (29) a plurality of mixing inserts (51) with coated flow-influencing planar elements in associated mixing insert tubes (59) with a smaller diameter than the tube (19) are arranged side by side as a package in the tube (19) of the static mixing device.

11. Static mixing device according to any one of the preceding claims 1 to 10, characterized by the fact that the diameter of the mixing inserts (K1 to K2; ) and / or the uncoated and coated mixing inserts (3' to 4'; Lu‴ to Lb‴) and the associated pipes (19 to 19') differs, in particular decreasing and / or increasing in the direction of flow (29).

12. Static mixing device according to any one of the preceding claims 1 to 11, characterized by the fact that a heating element or a cooling element is provided in or on the tube (19, 59) so that the static mixing device can be heated and / or cooled.

13. Static mixing device according to any one of the preceding claims 1 to 12, characterized by the fact that Adjacent to the coated static mixing insert(s) at least one temperature sensor is provided for monitoring the reaction taking place in the pipe (19).

14. Method for operating a static mixing device for a predetermined gas phase and a predetermined liquid phase according to any one of the preceding claims 1 to 13, characterized by the fact that for operation a mixing element is provided in the pipe (19) that the Schmidt number of the liquid is 50 to 2000 and that the Reynolds number of the liquid is 10 to 100,000, and that in the section (3, 3', 3", 53) of the uncoated flow-influencing planar elements the multiphase flow in the pipe (19) is a bubble flow at least at the transition to the section (4, 4', 4", 54) of the catalyst-coated flow-influencing planar elements in which the gas phase is uniformly dispersed in the liquid phase.

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