WO2017222376A1

WO2017222376A1 - Spinning disc reactor

Info

Publication number: WO2017222376A1
Application number: PCT/NL2017/050414
Authority: WO
Inventors: Maarten DE JONG; Haske Zadelhoff; Jonathan JANGA; Wessel Frank HENGEVELD
Original assignee: Flowid Holding B.V.
Priority date: 2016-06-23
Filing date: 2017-06-21
Publication date: 2017-12-28
Also published as: NL2017029B1; NL2017029A

Abstract

This invention relates to reactors, more particularly to spinning disc reactors, and to methods to perform reactions using these reactors. These reactors have no mechanical bearings and no dynamic seals. One or more spinning discs provided in the cavities of the reactor are driven from outside the reactor using magnetic forces. These spinning disc reactors can be used for a variety of reactions, including reactions involving aggressive chemicals, with minimal wearing over time.

Description

SPINNING DISC REACTOR

FIELD OF THE INVENTION

The present invention relates to reactors, more particularly to spinning disc reactors, and to methods to perform reactions using these reactors.

BACKGROUND OF THE INVENTION

The chemical and biotechnological industries are continuously working on more efficient and safer production routes. New processes and devices are developed that are more energy efficient, result in less waste products and/or are safer to operate. Major improvements can be realized by developing processes and devices with enhanced mass and heat transfer during the reactions.

Spinning disc reactors are well-known in the art of process intensification. In this respect, reference is made to M. Meeuwse, Rotor-Stator Spinning Disc Reactor, PhD thesis, 2011, Eindhoven University of Technology. This type of reactors is also referred to as rotating disc reactors, spinning disc mixers or rotating disc mixers in the art. The terms can be used interchangeably. The spinning disc reactors according to the present invention are co-current rotor-stator spinning disc reactors that are characterized in that they have a stator housing and one or more rotatable discs inside the housing wherein the housing and the discs are configured such that there is only a small gap between the inner surface of the housing and the discs. Due to the high-velocity gradients which can be generated by the spinning discs in the small gap, large shear forces can be induced in the fluid between the static housing and the rotating surfaces of the discs, enabling improved heat and mass transfer and rapid homogenisation of concentration and temperature variations on the microscopic level. This makes spinning disc reactors attractive devices for e.g. performing exothermic reactions and reactions which are limited by mass transfer rates. Because of the improved heat and mass transfer, the residence time of the reacting material or the total volume of the reacting material in the reactor at a given time can be reduced without compromising reaction yield. Improved heat transfer may decrease energy consumption and the risks and dangers of thermal runaways and thermal ignition frequently encountered in batch reactors due to poor temperature control. Because of these advantages, it is contemplated that spinning disc reactors will strongly influence the manner in which industry carries out fast reactions and/or reactions which are limited by heat or mass transfer rates. W094/21367A1 discloses a method and apparatus for mixing and dispersion of flowable materials such as viscous flowable pastes. The apparatus comprises a stator body and a core member comprising a number of discs. The core member comprises a central shaft having along its length a plurality of uniformly spaced radially outwardly extending discs that can rotate inside the stator body. The core member is driven by a speed-controllable driving means, positioned outside the stator body, via the shaft which extends through the wall of the stator body and which rotates in a mechanical bearing which is sealed and which is positioned in the wall of the stator body. The cavity between the stator body and the core member defines an annular flow passage. During operation, the flowable material to be mixed or dispersed is moved through the passage under pressure so as to maintain the passage full of material while the core member is rotated to induce shear in the moving material.

US2005/0053532A1 discloses a spinning disc reactor with a gap of less than 1 mm between the stator housing and the rotating disc. The rotor disc and rotor shaft are of one part and are driven by a motor, positioned outside of the reactor, via a drive belt. The rotor disc and rotor shaft are able to rotate in a bearing. The bearing ensures that the rotor disc and shaft are correctly positioned in the housing. The gap between the housing and the rotor shaft where the rotor shaft extends through the wall of the housing is closed by a mechanical dynamic seal. During operation, reactants are fed to the surface of the rotating disc such that the reactants spread out on the surface in the form of a thin film.

US2009/0208389A1 discloses spinning tube-in-tube reactors having a reaction passage between the rotor tube exterior surface and the stator tube interior surface, through which reactants pass. The reaction passage is between 50 and 500 μπι wide. The rotor tube is suspended within the stator tube by a flexible connection between a driving motor shaft and the rotor tube and by a thrust bearing which ensures that the rotor tube cannot move vertically.

The spinning disc reactors described in the art are made of metal and/or have a rotor shaft extending through the reactor wall, wherein the rotor shaft is positioned in a mechanical bearing sealed with a mechanical dynamic seal such that the rotor is able to rotate inside the stator housing of the reactor. The mechanical bearings, mechanical dynamic seals and metal are subject to wear due to friction between rotating elements and chemical corrosion due to aggressive chemicals, which may result in leakage of chemicals from the reactor.

It is an object of the invention to provide improved spinning disc reactors and methods of using those spinning disc reactors. It is a further object of the invention to provide spinning disc reactors that can be used for a variety of reactions, including reactions involving aggressive chemicals, with minimal wear over time. SUMMARY OF THE INVENTION

The inventors found that the above objects can be met by avoiding the use of mechanical bearings and dynamic seals and by driving the one or more spinning discs from outside the reactor using magnetic forces.

Accordingly, in a first aspect a reactor is provided, said reactor comprising:

a) a housing defining a first cavity having an upstream end and a downstream end, said first cavity having at least one fluid inlet at the upstream end for providing fluid into the first cavity and a fluid outlet at the downstream end for withdrawing fluid from the first cavity; b) a circular disc-shaped element provided in the first cavity, said circular disc-shaped element being rotatable within the first cavity around a rotation axis pointing from the downstream end to the upstream end of the first cavity and comprising magnets for driving rotation of the circular disc-shaped element by magnetic forces from outside the housing,

wherein the housing and the circular disc-shaped element define a radial fluid bearing and an axial fluid bearing between the circular disc-shaped element and the wall of the first cavity; and wherein there is a gap having a width of between 1 and 2000 μπι between the wall of the first cavity and the circular disc-shaped element such that the at least one fluid inlet, the gap between the wall of the first cavity and the circular disc-shaped element and the fluid outlet define a fluid pathway through the reactor.

Consequently, the reactor according to the invention has no rotating parts or mechanical bearings extending through the housing of the reactor and no dynamic seals. This overcomes the problems of leakage of chemicals from the reactor. During operation, the circular discshaped element is rotated within the cavity by magnetic forces from outside the housing. The inventors have unexpectedly found that, despite the complex geometry of the reactor, the circular disc-shaped element can be rotated without the use of mechanical bearings inside the reactor. During operation, the fluid flowing through the reactor acts as a lubricant causing fluid bearing of the one or more rotating circular disc-shaped elements in the reactor.

The inventors have further found that when all reactor parts adjacent to the fluid pathway through the reactor are composed of ceramic material, preferably silicon carbide, the reactor can be used for a variety of reactions, including reactions involving aggressive chemicals, with minimal wear over time.

The inventors have established that the above principles also hold true when the reactor comprises multiple cavities and circular disc-shaped elements provided therein. In a second aspect, the invention provides a method for the manufacture of a product in a reactor according to the invention, said method comprising the steps of:

a) supplying two or more fluid reactants to the at least one fluid inlet of the first or the most upstream cavity;

b) forcing the reaction fluid thus formed through the gap between the wall of the one or more cavities and the one or more corresponding circular disc-shaped elements by applying a pressure while the circular disc-shaped elements are rotating to produce a reaction fluid comprising the product;

c) drawing off the reaction fluid comprising the product from the fluid outlet of the most downstream cavity.

DEFINITIONS

The term 'reactant' as used herein is not limited to substances which are intended to undergo chemical reaction but also includes substances which are intended to undergo physical processes such as mixing or heating. As such, the term 'reactant' as used herein encompasses in addition to those components undergoing chemical reaction to form the intended reaction product(s), and eventually by-products, also solvents, co-solvents, dispersants, emulsifiers, catalysts and the like.

The term 'fluid' in 'fluid reactants' may relate to gases, liquids, solids, or combinations thereof. Solids in particulate form may have macroscopic fluid flow properties.

The term 'product' as used herein denotes the intended substance or substances to be manufactured in the reaction fluid which is collected at the downstream end of the reactor.

The term 'fluid bearing' or 'dynamic fluid bearing' as used herein denotes two radially or axially aligned surfaces separated by a fluid forming a lubricating wedge between these two surfaces. In the context of the present invention, one of the surfaces is the inner wall of a cavity and the other surface is the outer surface of a part rotating in said cavity.

BRIEF DESCIPTION OF THE FIGURES

Figure 1 depicts a cross-section of a reactor according to the invention comprising a single circular disc-shaped element.

Figure 2 shows a close-up of Figure 1.

Figure 3 depicts a cross-section of a reactor according to the invention comprising three circular disc-shaped elements. Figure 4 depicts a simplified cross-section of the reactor of Figure 3 wherein some numbering has been omitted.

Figure 5 shows the dependency of flow behaviour on gap ratio G, defined as the gap h between the wall of the cavity and the circular disc-shaped element divided by the radius RD of the circular disc-shaped element, and on rotational Reynolds number RgR, wherein ReR is defined as Regime I in Figure 5 relates to laminar flow (Torsional Couette flow), Regime II to laminar flow (Batchelor flow), Regime III to turbulent flow (Torsional Couette flow) and Regime IV to turbulent flow (Batchelor flow).

Figure 6 shows a diagram from which the flow behaviour on the surface of the circular disc-shaped element at a radius r from the axis of rotation, plug flow or ideally mixed flow, can be inferred from the superimposed dimensionless throughflow rate C_w, defined as

and the rotational Reynolds number ReR, which is defined as

for different values of the gap ratio G, defined as the gap h between the wall of the cavity and the circular disc-shaped element divided by the radius RD of the circular disc-shaped element.

DETAILED DESCRIPTION

Accordingly, in a first aspect of the invention, a reactor is provided, said reactor comprising:

In another embodiment, the housing and the circular disc-shaped element, in operation, define a radial fluid bearing and an axial fluid bearing between the circular disc-shaped element and the wall of the first cavity. The reactor as described herein can be considered a co-current rotor-stator spinning disc reactor wherein the housing is the stator and wherein the circular disc-shaped element constitutes the rotor.

In a preferred embodiment, the housing of the reactor as defined hereinbefore comprises at least one further cavity and further circular disc-shaped element provided in said further cavity, each further cavity having a fluid inlet at the upstream end of said further cavity for providing fluid into the further cavity, and each further cavity having a fluid outlet at the downstream end of said further cavity for withdrawing fluid from the further cavity, said further circular disc-shaped elements being rotatable within the corresponding further cavities around a rotation axis pointing from the downstream end to the upstream end of the further cavity, wherein the housing and each further circular disc-shaped element define a radial fluid bearing and an axial fluid bearing between the further circular disc-shaped element and the wall of the further cavity; and

wherein there is a gap having a width of between 1 and 2000 μπι between the wall of each further cavity and each further circular disc-shaped element provided therein, and

wherein the fluid outlet of the cavity upstream of each further cavity is connected to the fluid inlet of the further cavity such that the at least one fluid inlet of the most upstream cavity, the gap between the wall of each further cavity and the circular disc-shaped element provided therein and the fluid outlet of the most downstream cavity define a fluid pathway through the reactor, wherein

i) each further circular disc-shaped element comprises magnets for driving rotation of the further disc-shaped element by magnetic forces from outside the housing, or ii) each further circular disc-shaped element is mechanically coupled to a circular discshaped element comprising magnets, or

iii) a combination of i) and ii).

In another embodiment, the housing and each further circular disc-shaped element, in operation, define a radial fluid bearing and an axial fluid bearing between the further circular disc-shaped element and the wall of the further cavity.

In a preferred embodiment, the circular disc-shaped elements are mechanically coupled such that they cannot move independently.

In another preferred embodiment, the reactor as defined hereinbefore comprises two, three, four, five, or more than five further cavities and further circular disc-shaped element provided therein. In still another preferred embodiment, a reactor as defined hereinbefore is provided wherein the housing comprises at least two further cavities and further circular disc-shaped elements provided therein, wherein the reactor comprises different modules that are stackable in axial direction with O-rings in between to make the reactor leak-tight. The number of cavities and circular disc-shaped elements can be easily increased by increasing the number of modules.

The reactor can further comprise one or more heating and/or cooling elements in the body of the housing. Preferably the one or more heating and/or cooling elements are applied adjacent to the fluid pathway through the reactor. In a preferred embodiment, a heating and/or cooling element comprises a cavity adjacent to the fluid pathway through the reactor with a circular disc-shaped element provided in said cavity, said circular disc-shaped element comprising magnets for driving rotation by magnetic forces from outside the housing along the rotation axis as defined hereinbefore.

In a preferred embodiment a reactor as defined hereinbefore is provided wherein the housing comprises at least one further cavity and further circular disc-shaped element provided therein and wherein the rotation axes of all circular disc-shaped elements coincide.

The gap having a width of between 1 and 2000 μπι between the wall of each cavity and the circular disc-shaped element provided therein can also be called 'clearance between rotor and stator' or 'clearance between the wall of the cavity and the circular disc-shaped element provided therein' . In a preferred embodiment, the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements provided therein has a width of between 1 and 1500 μπι, more preferably between 1 and 1000 μπι, even more preferably of between 1 and 500 μπι, still more preferably of between 1 and 400 μπι.

In another preferred embodiment, the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements provided therein has a width of between 3 and 2000 μπι. In still another preferred embodiment, the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements provided therein has a width of between 5 and 2000 μπι. In still another preferred embodiment, the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements provided therein has a width of between 10 and 2000 μπι. In a further preferred embodiment, the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements provided therein has a width of between 15 and 2000 μπι. In a still further preferred embodiment, the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements provided therein has a width of between 20 and 2000 μπι. The gap between the wall of the one or more cavities and the one or more circular discshaped elements provided therein need not have a constant width throughout the fluid pathway through the reactor. The gap between the wall of the one or more cavities and the one or more circular disc-shaped elements is preferably smaller in the axial fluid bearing and in the radial fluid bearing than in the remaining part of the gap in order to optimize lubrication and bearing performance in the fluid bearing and to align the circular disc-shaped elements in their respective cavities during start-up and operation of the reactor. The preferred width of the gap in the axial fluid bearing and in the radial fluid bearing is between 1 and 20 μπι, more preferably between 3 and 15 μπι, still more preferably between 5 and 10 μιη.

In another preferred embodiment, the width of the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements in the axial fluid bearing and in the radial fluid bearing is between 1 and 20 μπι, preferably between 3 and 15 μπι, more preferably between 5 and 10 μπι, while the remaining part of the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements has a width of between 400 and 2000 μπι, more preferably between 500 and 1500 μιη.

In case the gap between the wall of the one or more cavities and the one or more circular disc-shaped element is smaller in the axial fluid bearing and in the radial fluid bearing than in the remaining part of the gap, the cavity wall in the radial fluid bearing preferably comprises two or more grooves in radial direction and/or the axial fluid bearing preferably comprises two or more grooves in axial direction. A groove in axial direction and a groove in radial direction may form a single bigger groove. Without wishing to be bound by theory, it is believed that these grooves improve lubrication of and flow through the fluid bearing and avoid excessive pressure build-up over the fluid bearing during operation of the reactor.

In an embodiment, the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements provided therein is of constant width throughout the fluid pathway through the reactor.

In another preferred embodiment, each of the one or more circular disc-shaped elements in the reactor as defined hereinbefore comprises a stub axle pointing in upstream direction and a stub axle pointing in downstream direction defining the axial fluid bearing, said stub axles being centred around the axis of rotation. In a more preferred embodiment, the one or more circular disc-shaped elements in the reactor as defined hereinbefore each comprise a stub axle pointing in upstream direction and a stub axle pointing in downstream direction defining the axial fluid bearing, said stub axles being centred around the axis of rotation, and further comprise an edge around each stub axle defining the radial fluid bearing. When these stub axles are present, the circular disc-shaped elements can be mechanically coupled via a stick, made of for example polytetrafluoroethylene (PTFE), positioned in and substantially filling the empty space formed by two opposite grooves applied in adjacent surfaces of the stub axle of a circular disc-shaped element pointing in downstream direction and the stub axle of a circular disc-shaped element pointing in upstream direction, wherein said grooves are centred at the axis of rotation and are applied in the radial direction.

Embodiments wherein the cavity wall, instead of the circular disc-shaped element, comprises a stub axle pointing in upstream direction and a stub axle pointing in downstream direction defining the axial fluid bearing, wherein said stub axles are centred around the axis of rotation, are also envisaged. Likewise, embodiments are envisaged wherein the cavity wall, instead of the circular disc-shaped element, comprises a stub axle pointing in upstream direction and a stub axle pointing in downstream direction defining the axial fluid bearing, said stub axles being centred around the axis of rotation, wherein an edge is provided around each stub axle defining the radial fluid bearing.

Moreover, embodiments are envisaged wherein for each pair of a cavity and a corresponding circular-disc-shaped element one of the stub axles, and preferably one of the edges, is provided on the cavity wall and one of the stub axles, and preferably one of the edges, is provided on the circular disc-shaped element.

Alternatively, the one or more circular disc-shaped elements in the reactor as defined hereinbefore may comprise one or more thickened sections along their outer perimeter such that the radial and axial fluid bearings are defined between the wall of the one or more cavities and the outer perimeter of the one or more circular disc-shaped elements provided in those one or more cavities.

In an embodiment the single cavity, or the most upstream cavity in case the housing comprises more than one cavity, has one fluid inlet. In a more preferred embodiment the single cavity, or the most upstream cavity in case the housing comprises more than one cavity, has two or more fluid inlets. In case the single cavity, or the most upstream cavity in case the housing comprises more than one cavity, has one fluid inlet, this fluid inlet is preferably centred at the axis of rotation of the circular disc-shaped element provided in said cavity. In case the single cavity, or the most upstream cavity in case the housing comprises more than one cavity, has two or more fluid inlets, one of these fluid inlets is preferably centred at the axis of rotation of the circular disc-shaped element provided in said cavity, while the remaining fluid inlets are positioned a distance away from the axis of rotation in radial direction. When such a configuration is used, a second or further reactant fed via the one or more remaining fluid inlets mixes with the bulk of the fluid present between and substantially filling the gap between the cavity wall and the circular disc-shaped element.

In a further embodiment, the one or more cavities have one or more radial fluid openings for providing fluid into the cavity or for withdrawing fluid from the cavity. A radial fluid opening, in the context of the invention, is a fluid opening in radial direction allowing for providing or withdrawing fluid directly from the gap between the wall of the cavity and the circular disc-shaped element provided therein along the outer perimeter of the circular discshaped element. Such openings can for example be used to provide a fluid into the cavity to quench a reaction or to add another reactant in case of a multiple-step synthesis. Hence, if the housing of the reactor as defined hereinbefore comprises at least one further cavity and further circular disc-shaped element provided therein, the most downstream cavity preferably has one or more radial fluid openings for providing fluid into the cavity or for withdrawing fluid from the cavity.

In a still further embodiment the reactor as defined hereinbefore further comprises an external means for driving rotation by magnetic forces of the one or more circular disc-shaped elements provided in the cavities of the housing of the reactor along the axis of rotation. In a preferred embodiment, the external means comprises a motor outside of the housing connected via a driving shaft to a driving disc outside of the housing that can rotate around a rotation axis that coincides with the rotation axis of the one or more circular disc-shaped elements, said driving disc containing one or more magnets. The magnetic forces between the magnets in the driving disc and the magnets in the circular disc-shaped element(s) or mechanically coupled circular disc-shaped elements causes rotation of the circular disc-shaped element(s) in their respective cavities around the axis of rotation.

In another preferred embodiment, the external means comprises electromagnetic coils positioned around the external surface of the housing of the reactor extending in axial direction, said electromagnetic coils being configured to develop an alternating electromagnetic field in the one or more cavities of the reactor causing rotation of the circular disc-shaped element(s) in their respective cavities around the axis of rotation, wherein the electromagnetic coils together with the housing of the reactor define a stator and the one or more circular disc-shaped elements comprising magnets define a rotor.

In still another embodiment, the external means comprises a motor outside of the housing able to rotate magnets positioned around the external surface of the housing of the reactor extending in axial direction. The magnetic forces between the magnets positioned around the external surface of the housing of the reactor extending in axial direction and the magnets in the circular disc-shaped element(s) or mechanically coupled circular disc-shaped elements causes rotation of the circular disc-shaped element(s) in their respective cavities around the axis of rotation.

These preferred examples of external means for driving rotation by magnetic forces are however not intended to limit the scope of the invention.

In an embodiment, the reactor according to the invention has no dynamic seals.

In an embodiment, the reactor according to the invention has no rotating parts or mechanical bearings extending through the housing of the reactor.

In another embodiment, the reactor according to the invention has no mechanical bearings inside the housing of the reactor.

In still another embodiment, the reactor according to the invention has neither rotating parts or mechanical bearings extending through the housing of the reactor nor mechanical bearings inside the housing of the reactor, nor dynamic seals.

The skilled person understands that the general concept of the reactor of the invention does not particularly limit the type of materials the circular disc-shaped elements and the wall of the cavity are made of, apart from the requirement that the materials must have sufficient mechanical strength and stiffness. Hence, the circular disc-shaped elements and the wall of the cavity can for example be made of plastics, such as polytetrafluoroethylene (PTFE), metals, such as stainless steel, or ceramics. In a preferred embodiment, the circular disc-shaped elements and the wall of the cavity are made of the same material to avoid excessive wear of only the circular disc-shaped elements or only the cavity wall.

It is actually the type of application of the reactor that determines the preferred type of materials for the circular disc-shaped elements and the wall of the cavity. In a preferred embodiment, the one or more circular disc-shaped elements and the wall of the one or more cavities are composed of ceramic material. Most preferably the ceramic material is silicon carbide (SiC). SiC is known for its good abrasion resistance and heat conductivity and is therefore highly suitable for different types of fluids, aggressive chemicals and reactions that require temperature control.

In a preferred embodiment, the radius RD of the circular disc-shaped elements is between 1 cm and 25 cm, more preferably between 2 and 15 cm, even more preferably between 3 and 10 cm. The radius RD as used throughout the description is calculated from the axis of rotation to the outer perimeter of the circular disc-shaped element.

In another preferred embodiment, the thickness of the rotatable discs, not taking into account stub axles, edges or thickened sections, in axial direction is between 1 mm and 5 cm. In still another preferred embodiment, the gap ratio G of the gap h between the wall of the cavity and the circular disc-shaped element provided therein, not taking into account stub axles, edges or thickened sections, to the radius RD of the circular disc-shaped element, again not taking into account stub axles, edges or thickened sections, is between 4- 10^"6 and 0.03.

The circular disc-shaped elements, not taking into account stub axles, edges or thickened sections, at least have an upstream surface and a downstream surface. Each upstream surface or downstream surface may independently of each other be planar, curved, frilled, corrugated or bent, most preferably planar. In a preferred embodiment, both the upstream and downstream surfaces of the circular disc-shaped elements are planer surfaces radially extending perpendicular to the axis of rotation.

The reactor as defined hereinbefore is preferably used for chemical reaction of different chemical reactants, optionally in the presence of one or more catalysts and optionally in one or more (co-)solvents.

Accordingly, in a second aspect, the invention provides a method for the manufacture of a product in a reactor as defined hereinbefore, said method comprising the steps of:

a) supplying two or more fluid reactants to the at least one fluid inlets of the first or most upstream cavity;

b) forcing the reaction fluid thus formed through the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements by applying a pressure while the circular disc-shaped elements are rotating to produce a reaction fluid comprising the product;

Step b) ensures that during operation the reaction fluid substantially fills the gap between the cavity wall(s) and the circular disc-shaped element(s).

For sufficient heat and mass transfer, it is preferred that the flow of fluid reactants across at least part of the circular disc-shaped element is turbulent. Given the radius RD [m] of the circular disc-shaped element, the gap h [m] between the wall of the cavity and the circular discshaped element and the kinematic viscosity v [m²/s] of the fluid reactants flowing through the reactor, it is within the skills of the artisan to choose the angular velocity ω [rad/s] of the circular disc-shaped elements required for a certain type of flow behaviour across the surface of the circular disc-shaped element. In this respect, reference is made to M. Djaoui et al, Heat transfer in a rotor-stator system with radial inflow, Eur. J. Mech. B. Fluids, 20 (2001), pp 371-398 and to Figure 5. Figure 5 shows a graph of the gap ratio G [-], defined as the gap h [m] between the wall of the cavity and the circular disc-shaped element divided by the radius RD [m] of the circular disc-shaped element, versus -log(RgR), wherein ReR [-] is the rotational Reynolds number which is defined as

Regime I in Figure 5 relates to laminar flow (Torsional Couette flow), Regime II to laminar flow (Batchelor flow), Regime III to turbulent flow (Torsional Couette flow) and Regime IV to turbulent flow (Batchelor flow).

The skilled person can infer from Figure 5 which combination of gap ratio G and rotational Reynolds number ReR leads to laminar or turbulent flow across the circular discshaped elements. The dashed arrow in Figure 5 shows for example the development of flow behaviour for a typical gap ratio of G=0.016 when the angular velocity of the rotating discs is increased, such as during start-up of the reactor. Hence, for a given gap ratio G, kinematic viscosity v and disc radius RD, the angular velocity ω required to obtain turbulent flow can be calculated.

In an embodiment the first cavity, or the most upstream cavity in case the housing comprises more than one cavity, has one fluid inlet. Different reactants may be premixed and provided into the first cavity or into the most upstream cavity through the single fluid inlet.

In case the single cavity, or the most upstream cavity in case the housing comprises more than one cavity, has two or more fluid inlets, one of these fluid inlets is preferably centred at the axis of rotation of the circular disc-shaped element provided in said cavity while the remaining fluid inlets are positioned a distance away from the axis of rotation in radial direction. When such a configuration is used, a second or further reactant fed via the one or more remaining fluid inlets mixes with the bulk of the first reactant already present between and substantially filling the gap between the cavity wall and the circular disc-shaped element. In order to realize optimal mixing of the first and further reactant(s), it may be important that the flow of the first reactant across the circular disc-shaped element at the distance away from the axis of rotation in radial direction where the further inlet of the second reactant is positioned behaves ideally mixed. For a given radius RD [m] of the circular disc-shaped element, gap h [m] between the wall of the cavity and the circular disc-shaped element, angular velocity ω [rad/s] of the one or more circular disc-shaped elements and kinematic viscosity v [m²/s] of the fluid reactants, the skilled person can determine at which radius r from the axis of rotation of the circular disc-shaped elements plug-flow alters into ideally-mixed flow. In this respect, reference is made to figure 4 and paragraph 3.1. of M M. de Beer et al, Single phase fluid-stator heat transfer in a rotor-stator spinning disc reactor, Chem. Eng. Sci., 119 (2014), pp 88-98, and to Figure 6 of the present invention. Figure 6 shows a diagram from which the flow behaviour at a radius TPFR [m] from the axis of rotation of the circular disc-shaped element, plug flow or ideally-mixed flow, can be inferred from the superimposed dimensionless throughflow rate C_w, defined as

wherein Φγ [m³/s] is the volumetric flow rate, and the rotational Reynolds number ReR [-], which is defined as

for different values of the gap ratio G [-], defined as the gap h [m] between the wall of the cavity and the circular disc-shaped element divided by the radius RD [-] of the circular disc-shaped element. At a radius r above TPFR the flow is ideally mixed, while at a radius r below TPFR plug flow takes place.

The angular velocity ω of the one or more circular disc-shaped elements can typically be varied between 0 and 900 rad/s. The preferred angular velocity during operation depends on the radius RD of the circular disc-shaped elements(s). During operation, the angular velocity ω of the one or more circular disc-shaped elements is preferably varied between 100 and 900 rad/s.

The pressure needed to force the fluid reactants through the fluid pathway through the reactor depends on the length of the fluid pathway, the curvature of or obstacles inside the fluid pathway and the viscosity of the reaction fluid. It is within the skills of the artisan to choose the right pump and pumping conditions to obtain a certain residence time of the fluid reactants in the reactor.

If a particular process requires extended residence time, the process may be carried out in a continuous manner with a reactor as defined hereinbefore having a plurality of discs, such as two disc, three discs, four discs, five discs, or more than five discs. Alternatively, at least part of the fluid reactants may be drawn off as product at the one or more outlets of the reactor as defined hereinbefore and at least part of the fluid reactants may be recycled for further conversion with one or more fresh reactants to one or more fluid inlets.

DETAILED DESCRIPTION OF THE FIGURES

Figure 1 depicts a cross-section of a reactor according to the invention comprising a single circular disc-shaped element. The reactor (1) comprises a housing (2), made of SiC, defining a first cavity (3) having an upstream end (4) and a downstream end (5), said first cavity (3) having a fluid inlet (6) at the upstream end (4) for providing fluid into the cavity (3) and a fluid outlet (7) at the downstream end (5) for withdrawing fluid from the first cavity (3). A circular disc-shaped element (8), made of SiC, is provided in the cavity (3), said circular discshaped element (8) being rotatable within the cavity (3) around a rotation axis (9) pointing from the downstream end (5) to the upstream end (4) of the cavity (3) and comprising magnets (10) for driving rotation of the circular disc-shaped element (8) by magnetic forces (11) from outside the housing (2). The reactor (1) further comprises a second fluid inlet (6') positioned a distance away from the axis of rotation in radial direction for providing fluid into the cavity (3).

The circular disc-shaped element (8) comprises a stub axle (12) pointing in upstream direction and a stub axle (12) pointing in downstream direction, both centred around the axis of rotation (9). Moreover, the circular disc-shaped element (8) comprises an edge (13) around both stub axles (12) pointing in upstream direction and in downstream direction. The fluid inlets (6) and (6'), the gap between the wall of the cavity (3) and the circular disc-shaped element (8) and the fluid outlet (7) define a fluid pathway through the reactor.

The housing (2) and the circular disc-shaped element (8), in operation, define an axial fluid bearing (14) and a radial fluid bearing (15) between the circular disc-shaped element (8) and the wall of the cavity (3).

In Figure 1, the gap between the wall of the cavity (3) and the disc-shaped element (8) is smaller in the axial fluid bearing (14) and the radial fluid bearing (15) than in the remaining part of the gap.

Figure 1 further depicts a motor (16) connected via a shaft (17) to a driving disc (18) being rotatable around rotation axis (9). Motor (16), shaft (17) and driving disc (18) are positioned outside of the housing (2). Said driving disc (18) also comprises magnets (19). If the motor (16), during operation, drives rotation of the driving disc (18), the magnetic forces (1 1) between magnets (10) and magnets (19) cause the circular disc-shaped element (8) to rotate around rotation axis (9) in cavity (3).

Figure 2 shows a close-up of the housing (2) and the circular disc-shaped element (8) at the place of the axial (14) and radial (15) fluid bearings. The wall of the housing (2) forming together with the circular disc-shaped element (8) cavity (3) comprises in the fluid bearing four grooves (20) in radial direction and four grooves (20) in axial direction. In Figure 2, every groove in radial direction forms together with a groove in axial direction one bigger groove (20). The close-up on the right-hand side is a close-up in the plane A.

Figure 3 depicts a cross-section of a reactor according to the invention comprising three circular disc-shaped elements. The reactor (1) comprises a housing (2), made of SiC, defining a first cavity (3a) having an upstream end (4a) and a downstream end (5a), said first cavity (3a) having a fluid inlet (6a) at the upstream end (4a) for providing fluid into the first cavity (3a) and a fluid outlet (7a) at the downstream end (5a) for withdrawing fluid from the first cavity (3a). Likewise, the housing (2) comprises a second cavity (3b) and a third cavity (3c). The second and third cavities (3b, 3c) have an upstream end (4b, 4c) and a downstream end (5b, 5c), a fluid inlet (6b, 6c) at the upstream end (4b, 4c) for providing fluid into the cavities (3b, 3c) and a fluid outlet (7b, 7c) at the downstream end (5b, 5c) for withdrawing fluid from the cavities (3b, 3c). The fluid outlet (7a) of cavity (3a) at downstream end (5a) coincides with the fluid inlet (6b) of cavity (3b) at upstream end (4b). Likewise, fluid outlet (7b) of cavity (3b) at downstream end (5b) coincides with the fluid inlet (6c) of cavity (3c) at upstream end (4c).

Circular disc-shaped elements (8a, 8b, 8c), made of SiC, are provided in cavities (3a,

3b, 3c), said circular disc-shaped elements (8a, 8b, 8c) being rotatable within the cavities (3a, 3b, 3c) around a single rotation axis (9) pointing from the downstream end (5c) to the upstream end (4a).

The circular disc-shaped elements (8a, 8b, 8c) comprise a stub axle (12, number not indicated) pointing in upstream direction and a stub axle (12) pointing in downstream direction, both stub axles being centred around the axis of rotation (9), like in Figure 1. Moreover, the circular disc-shaped elements (8a, 8b, 8c) comprise an edge (13, number not indicated) around both stub axles (12) pointing in upstream direction and in downstream direction. The housing (2) and the circular disc-shaped elements (8a, 8b, 8c), in operation, define axial fluid bearings (14, number not indicated) and radial fluid bearings (15, number not indicated) between the circular disc-shaped elements (8a, 8b, 8c) and the wall of the respective cavities (3a, 3b, 3c).

Cavity (3c) comprises a radial fluid opening (7c') for providing fluid into the cavity or for withdrawing fluid from the cavity.

Circular disc-shaped element (8a) comprises magnets (10) for driving rotation of the circular disc-shaped element (8a) by magnetic forces from outside the housing (2). Circular disc-shaped element (8a) is mechanically coupled to circular disc-shaped element (8b) via a stick made of polytetrafluoroethylene (PTFE) (21) positioned in and substantially filling the empty space formed by two opposite grooves applied in adjacent surfaces of the stub axle (12) of circular disc-shaped element (8a) pointing in downstream direction and the stub axle (12) of circular disc-shaped element (8b) pointing in upstream direction. Said grooves are centred at the axis of rotation (9) and are applied in the radial direction. Likewise, circular disc-shaped elements (8b) and (8c) are mechanically coupled via the stub axles and a stick made of PTFE. Hence, the circular disc-shaped elements (8a, 8b, 8c) cannot rotate independently around the axis of rotation (9). If magnetic forces are applied to drive rotation of circular disc-shaped element (8a), this causes circular disc-shaped element (8b) and (8c) to rotate around a rotation axis (9) as well.

Figure 4 depicts a simplified cross-section of the reactor of Figure 3 wherein some numbering has been omitted. The dashed lines show how the reactor can be composed of different modules (22, 23, 24) with O-rings (25) in between to make the reactor leak-tight. The number of cavities and circular disc-shaped elements can be easily increased by increasing the number of modules (23).

Thus, the invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art.

Furthermore, for a proper understanding of this document and its claims, it is to be understood that the verb 'to comprise' and its conjugations are used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. In addition, reference to an element by the indefinite article 'a' or 'an' does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article 'a' or 'an' thus usually means 'at least one'.

All patent and literature references cited in the present specification are hereby incorporated by reference in their entirety.

Claims

Reactor comprising:

a) a housing defining a first cavity having an upstream end and a downstream end, said first cavity having at least one fluid inlet at the upstream end for providing fluid into the first cavity and a fluid outlet at the downstream end for withdrawing fluid from the first cavity;

b) a circular disc-shaped element provided in the first cavity, said circular disc-shaped element being rotatable within the first cavity around a rotation axis pointing from the downstream end to the upstream end of the first cavity and comprising magnets for driving rotation of the circular disc-shaped element by magnetic forces from outside the housing,

wherein the housing and the circular disc-shaped element define a radial fluid bearing and an axial fluid bearing between the circular disc-shaped element and the wall of the first cavity; and

wherein there is a gap having a width of between 1 and 2000 μπι between the wall of the first cavity and the circular disc-shaped element such that the at least one fluid inlet, the gap between the wall of the first cavity and the circular disc-shaped element and the fluid outlet define a fluid pathway through the reactor.

Reactor according to claim 1, wherein the housing comprises at least one further cavity and further circular disc-shaped element provided in said further cavity, each further cavity having a fluid inlet at the upstream end of said further cavity for providing fluid into the further cavity, and each further cavity having a fluid outlet at the downstream end of said further cavity for withdrawing fluid from the further cavity, said further circular disc-shaped elements being rotatable within the corresponding further cavities around a rotation axis pointing from the downstream end to the upstream end of the further cavity,

wherein the housing and each further circular disc-shaped element define a radial fluid bearing and an axial fluid bearing between the further circular disc-shaped element and the wall of the further cavity, and

wherein there is a gap having a width of between 1 and 2000 μπι between the wall of each further cavity and each further circular disc-shaped element provided therein, and wherein the fluid outlet of the cavity upstream of each further cavity is connected to the fluid inlet of the further cavity such that the at least one fluid inlet of the most upstream cavity, the gap between the wall of each further cavity and the circular disc-shaped element provided therein and the fluid outlet of the most downstream cavity define a fluid pathway through the reactor, wherein

i) each further circular disc-shaped element comprises magnets for driving rotation of the further circular disc-shaped element by magnetic forces from outside the housing, or

ii) each further circular disc-shaped element is mechanically coupled to a circular disc-shaped element comprising magnets, or

iii) a combination of i) and ii).

Reactor according to claim 2, wherein the rotation axes of all circular disc-shaped elements coincide.

Reactor according to claim 2 or 3, wherein the circular disc-shaped elements are mechanically coupled such that they cannot move independently.

Reactor according to any one of claims 1 to 4, wherein each of the one or more circular disc-shaped elements comprises a stub axle pointing in upstream direction and a stub axle pointing in downstream direction defining the axial fluid bearing, said stub axles being centred around the axis of rotation.

Reactor according to claim 5, further comprising an edge around each stub axle defining the radial fluid bearing.

Reactor according to claim 5 or 6, wherein the circular disc-shaped elements are mechanically coupled via a stick positioned in and substantially filling the empty space formed by two opposite grooves applied in adjacent surfaces of the stub axle of a circular disc-shaped element pointing in downstream direction and the stub axle of a circular disc-shaped element pointing in upstream direction, wherein said grooves are centred at the axis of rotation and are applied in the radial direction.

8. Reactor according to any one of claims 1 to 7, wherein the one or more circular discshaped elements and the wall of the one or more cavities are composed of ceramic material.

9. Reactor according to claim 8, wherein the ceramic material is silicon carbide (SiC).

10. Reactor according to any one of claims 1 to 9, wherein the number of fluid inlets of the first cavity or the most upstream cavity is two or more.

11. Reactor according to any one of claims 1 to 10, wherein the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements provided therein has a width of between 1 and 1500 μπι, more preferably of between 1 and 1000 μπι, even more preferably of between 1 and 500 μπι, still more preferably of between 1 and 400 μιη.

12. Reactor according to any one of claims 1 to 11, wherein the width of the gap between the wall of the one or more cavities and the one or more circular disc-shaped elements provided therein in the axial and/or radial fluid bearing is of between 1 and 20 μπι, preferably of between 3 and 15 μπι, more preferably of between 5 and 10 μπι.

13. Reactor according to any one of claims 1 to 12, wherein the gap between the wall of the one or more cavities and the one or more circular disc-shaped element is smaller in the axial fluid bearing and in the radial fluid bearing than in the remaining part of the gap, and wherein the cavity wall in the radial fluid bearing comprises two or more grooves in radial direction and/or the axial fluid bearing comprises two or more grooves in axial direction.

14. Reactor according to any one of claims 1 to 13, wherein the one or more circular discshaped elements are driven by a motor outside of the housing connected via a driving shaft to a driving disc outside of the housing that can rotate around a rotation axis that coincides with the rotation axis of the one or more circular discs, said driving disc containing one or more magnets.

15. Reactor according to any one of claims 2 to 14, wherein the housing comprises at least two further cavities and further circular disc-shaped elements provided therein, and wherein the reactor comprises different modules that are stackable in axial direction with O-rings in between to make the reactor leak-tight.

16. Reactor according to any one of claims 1 to 15, wherein the angular velocity of the one or more circular disc-shaped elements can be varied between 0 and 900 rad/s.

17. Reactor according to any one of claims 1 to 16, further comprising one or more heating and/or cooling elements in the body of the housing.

18. Reactor according to claim 17, wherein a heating and/or cooling element comprises a cavity adjacent to the fluid pathway through the reactor with a circular disc-shaped element provided in said cavity, said circular disc-shaped element comprising magnets for driving rotation by magnetic forces from outside the housing along the rotation axis.

19. Method for the manufacture of a product in a reactor according to any one of claims 1- 18, comprising the steps of:

20. Method according to claim 19, wherein each reactant is supplied to the reactor via a separate inlet.

21. Method according to claim 19 or 20, wherein at least part of the product drawn off from the fluid outlet of the most downstream cavity is recycled for further conversion, optionally with one or more fresh reactants, to a fluid inlet of the most upstream cavity. Method according to any one of claims 19 to 21, wherein the one or more circular discshaped elements are rotating at an angular velocity of between 10 and 900 rad/s.