WO2004004888A1

WO2004004888A1 - Rotating reactor with spiral element

Info

Publication number: WO2004004888A1
Application number: PCT/GB2003/002757
Authority: WO
Inventors: Colin Ramshaw; Michael Jones; Ian Henderson
Original assignee: Protensive Limited
Priority date: 2002-07-02
Filing date: 2003-06-27
Publication date: 2004-01-15
Also published as: GB2390314A; AU2003246910A1; GB0215245D0

Abstract

A reactor apparatus including at least one support element (4, 5) having a generally spiral configuration with an inner surface (6) and an outer surface (7), the support element (4, 5) being rotatable about an axis of rotation (2) with the inner surface (6) facing the axis of rotation (2), wherein the support element (4, 5) is provided with means (13) for transferring heat to or from the inner surface (6). The means (13) may comprise a conduit (13) for a heat transfer fluid.

Description

ROTATING REACTOR WITH SPIRAL ELEMENT

The present invention relates to a rotating surface of revolution reactor for mass and heat transfer applications, and in particular to such a reactor provided with at least one spiral element.

Rotating reactors for mass and heat transfer applications are known from the present applicant's International patent applications WO00/48731, WO00/48729, WOOO/48732, WO00/48730 and WO00/48728, the full contents of which are hereby incorporated into the present application by reference. Rotating reactors generally comprise a rotating or spinning surface, for example a disc or a cone, onto which one or more fluid reagents are supplied. Centrifugal forces cause the reagents to pass outwardly across the surface (i.e. centrifugal acceleration is aligned with a surface radius vector) in the form of a thin, generally wavy film, the film then being thrown from a circumference of the surface for collection. High turbulence and shear stresses in the film cause excellent mixing and mass transfer, and the low thickness of the film allows for excellent heat transfer to and from the film. However, these known rotating reactors, particularly those with substantially planar surfaces, do not generally allow for a high residence time of the reagents in the reactor due to high radial film velocities, and this can limit their effectiveness for reactions requiring a longer residence time (e.g. where high degrees of conversion are required, such as with some polymerisation reactions and the; like). This problem can be ameliorated by increasing the size/area of the surface of the reactor, but this is often not appropriate, since it is generally desirable in the field of process intensification to keep reactor sizes as small as possible.

One technique whereby residence times can be increased is to provide meshes or other surface extensions on the surface of the reactor, for example as outlined in W OO/48728. This provides a greater wetted area for film drainage and thus reduces the film velocity. However, in order to be effective when significant exotherms are involved, for example, there must be a good thermal connection between the meshes or surface extensions and the surface itself. This becomes more difficult to achieve with greater numbers of mesh layers or surface extensions.

An alternative approach makes use of conical, rather than planar surfaces. By choosing the vertex angle of a conical surface appropriately, it is possible to reduce the resolved component of the centrifugal acceleration along the drainage path and thereby to reduce the liquid velocity. The drainage path length may be increased by increasing the axial length of the conical surface.

It is known, for example from US 4,038,353, to provide a gas-liquid contacting reactor comprised as a spiral band mounted about an axis of rotation with flanges being provided on edges of the band and directed towards the axis. Liquid flows along one face of the spiral band between the flanges from a central part to an outer part of the spiral. Although this arrangement helps to increase a residence time of the liquid in the reactor, there is absolutely no suggestion or disclosure as to how heat transfer may be effectively managed.

According to a first aspect of the present invention, there is provided a reactor apparatus including at least one support element having a generally spiral configuration with an inner surface and an outer surface, the support element being rotatable about an axis of rotation with the inner surface facing the axis of rotation, wherein the support element is provided with means for transferring heat to or from the inner surface.

According to a second aspect of the present invention, there is provided a reactor apparatus including at least one support element having a generally spiral configuration with an inner surface and an outer surface, the support element being rotatable about an axis of rotation with the inner surface facing the axis of rotation, wherein the support element is adapted to transfer heat to or from the inner surface. In operation, at least one reagent fluid (which will generally be a liquid, but may also be in the form of a gas or solid particles having overall fiuidic phase behaviour) is supplied to the inner surface of the spiral support element as it is rotated about the axis. The at least one reagent fluid, which may include one or more species or components, will tend to spread over the inner surface as a thin film, and the film will tend to pass outwardly along the inner surface towards a periphery of the spiral support element from where it is thrown off generally tangentially. The at least one reagent fluid may be supplied to the inner surface at a generally central part of the spiral support element, or at any predetermined position along a spiral length of the inner surface. More than one reagent fluid may be supplied at different positions along the spiral length of the inner surface.

The inner surface of the spiral support element may be provided with at least one flange at an edge region thereof, the flange being directed inwardly towards the axis of rotation. The at least one flange serves to define a channel or the like in which the at least one reagent fluid is retained during rotation of the spiral support element and helps to prevent spillage of the fluid reagent. For example, where the spiral support element is mounted with a lower edge on a substrate (e.g. a generally planar disc or the like mounted substantially perpendicularly on the axis of rotation), an inwardly directed flange may be provided on an upper edge of the inner surface. Alternatively, where the spiral support element is not mounted on a substrate, inwardly directed flanges may be provided on both the upper and the lower edges of the inner surface.

The spiral support element may be configured as a single spiral or a multi-start spiral (i.e. a plurality of concentric interleaved spirals). A multi-start spiral support element offers a larger total inner surface area than a single spiral support element having the same general size and configuration, and can therefore provide for a higher throughput of reagent fluid.

The spiral support element may be configured so that the inner surface is substantially parallel to the axis of rotation, or so that the inner surface is inclined towards or away from the axis of rotation (either with reference to a substrate on which the support element is mounted or with reference to a predetermined direction along the axis of rotation). The outer surface may be substantially parallel to the inner surface, or may be inclined relative thereto. In other words, the outer surface may also be inclined either towards or away from the axis of rotation, either in the same sense as the inner surface or in an opposite sense.

The spiral support element may be relatively narrow, in that its extent along a length of the axis of rotation is less than a diameter of the spiral support element. Alternatively, the spiral support element may be relatively wide, in that its extent along a length of the axis of rotation is greater than a diameter of the spiral support element.

The means for transferring heat may comprise at least one conduit, channel, pipe or the like (hereinafter referred to simply as the conduit for conciseness) provided on the outer surface of the spiral support element and adapted for passage of a heat transfer fluid. Alternatively or in addition, at least one conduit may be formed between the inner and outer surfaces of the spiral support element, the conduit being adapted for passage of a heat transfer fluid. The conduit may be configured so as to follow the general configuration of the spiral support element, and may be arranged so that the heat transfer fluid flows co-currently with the fluid reagent on the inner surface or counter-current to the fluid reagent. In the latter case, the heat transfer fluid may need to be pumped so as to overcome centrifugal forces caused by rotation of the spiral support element. Alternatively or in addition, the at least one conduit may extend in one or more directions having a resolved component generally parallel to the axis of rotation. For example, where the spiral support element is relatively wide, as defined hereinbefore, and mounted with one edge on a substrate, the at least one conduit may extend from the edge nearest the proximal to the substrate to the edge distal from the substrate, thereby assisting in heat transfer from regions of the inner surface near to the edge distal from the substrate. The heat transfer fluid may be a liquid, a gas or a stream of solid particles displaying fluidic behaviour. The heat transfer fluid may be any appropriate heat transfer fluid known in the art, including aqueous and organic fluids. The heat transfer fluid may be used to absorb heat from the spiral support element or to provide heat to the spiral support element, for example by being cooled or heated to a predetermined temperature either less than or greater than a temperature of the reagent fluid or the spiral support element.

The at least one conduit need not be completely filled with a single phase of a heat transfer fluid. Indeed, in some circumstances it is advantageous for a phase change to occur in the heat transfer fluid, since such a phase change may greatly increase heat transfer by making use of latent heats of evaporation or vaporisation or condensation or latent heats of phase change in general. For example, the heat transfer fluid may be a two phase system with a condensate contacting the conduit at a surface contacting the outer surface of the spiral support element, and with a vapour formed in the remaining volume of the conduit. It will be appreciated that although centrifugal acceleration will tend to cause the condensate of the heat transfer fluid to be thrown outwardly in the conduit away from the outer surface of the spiral support element, the Coanda effect (which causes flowing fluids to follow convex surfaces) will tend to resist this centrifugal acceleration and keep the condensate of the heat transfer fluid in contact with the outer surface or a surface of the conduit that contacts the outer surface. It is envisaged that in some circumstances, the at least one conduit need not be a closed conduit - indeed, the outer surface may itself serve as the at least one conduit with or without specific modification of the shape thereof.

It is preferred that the spiral support element is made of a material or materials having good thermal conductivity, such as metal materials or the like. In this way, heat transfer from the inner surface is facilitated.

However, in some embodiments (for example where the spiral element is relatively narrow or where a heat transfer fluid conduit is provided), the spiral element may be made of an appropriate plastics material, for example a polymer material having suitable characteristics.

Alternatively or in addition, where the at least one spiral element is mounted on a substrate, both the substrate and the spiral element are preferably made of a material or materials having good thermal conductivity. In this way, the spiral support element may act in a manner similar to that of a fin of a heat exchanger, with heat being conducted from the inner surface, through the support element and to the substrate. A heat transfer fluid may be supplied to a side of the substrate remote from that of the spiral support element so as to remove or supply heat thereto. It is advantageous for the support element and the substrate to be in good thermal contact. This may be achieved by forming the spiral support element integrally with the substrate or by welding or other joining the spiral support element to the substrate in such a way as to facilitate heat transfer therebetween.

It will be apparent that in configurations where the spiral support element is relatively wide, as defineH hereinbefore, heat transfer by simple thermal conduction across the width of the spiral support element may be insufficient in view of the relatively long thermal path length. Accordingly, provision of a heat transfer fluid conduit as discussed above serves greatly to improve heat transfer to and from the inner surface across its entire width.

The substrate and/or the spiral support element (whether or not mounted on a substrate) may additionally or alternatively be heated or cooled by way of convection, radiation, electric currents, induction, refrigeration or any other appropriate manner. For example, an electrical heating element or refrigeration means may be provided.

For the avoidance of doubt, it is hereby emphasised that embodiments of the present invention may be adapted to effect heat transfer both by cooling and by heating. For example, where an exothermic reaction is taking place in the reagent fluid on the inner surface, it will generally be desirable to remove heat generated thereby by using a relatively cold heat transfer fluid. Conversely, where an endothermic reaction is taking place in the reagent fluid on the inner surface, it will generally be desirable to provide additional heat thereto by using a relatively hot heat transfer fluid.

For a better understanding of the present invention and to show how it may be carried into effect, reference shall now be made by way of example to the accompanying drawings, in which:

FIGURE 1 shows a perspective view of a first embodiment of the present invention;

FIGURE 2 illustrates a typical configuration for a spiral element; and

FIGURE 3 shows a cross-section through a second embodiment of the present invention.

Figure 1 shows a reactor of an embodiment of the present invention comprising a generally disc-shaped substrate 1 mounted on a rotor (not shown) and having an axis of rotation 2. A reagent feed nozzle 3 is provided in a central part of the substrate 1. Two spiral support elements A, 5 are provided on an upper surface of the substrate 1, each spiral support element A, 5 having an inner surface 6 and an outer surface 7 with respect to the axis of rotation 2.

In use, the substrate 1 is rotated (anticlockwise in this case) about the axis of rotation 2 and a fluid reagent (not shown) is supplied by the feed nozzle 3. The fluid reagent spreads out onto the inner surface 6 of each support element 4, 5 and moves centrifugally therealong in the form of a thin film (not shown). The film is thrown from the inner surfaces 6 at a periphery 8 of the reactor. The substrate 1 and the support elements 4, 5 are advantageously each made of a thermally conductive metal and are in good thermal contact with each other so as to facilitate heat transfer to and from the fluid reagent as it passes along the inner surfaces 6. A heat transfer fluid (not shown) may be applied to an underside of the substrate 1 so as to facilitate heat transfer to or from the reagent fluid while on the inner surfaces 6. It is to be appreciated that each support element 4, 5 may extend upwardly (as shown in the diagram) from the substrate 1 significantly more than is shown in Figure 1.

Figure 2 shows a typical configuration for the spiral support elements A, 5 of Figure 1. The support element (indicated here as 4) has a start point A and an end point B and is curved about an origin O through which the axis of rotation 2 passes. The resolved acceleration, at a given point P, of a reagent fluid along an inner surface 6 of the support element 4 as it is rotated about the origin O depends on the angle θ that a local tangent 9 makes with the radius vector r at the point P. The resolved outward acceleration of the reagent fluid is given by the formula (ω²r cosθ), where ω is the angular velocity of the substrate and r is the magnitude of the radius vector. The acceleration can, if necessary, be kept roughly constant at different radial positions by shaping the spiral support element 4 appropriately so that θ changes with r as required. By varying the spiral r/θ characteristics of a support element A, 5 of embodiments of the present invention, a residence time of a fluid reagent can be increased or decreased. This is in addition to altering the residence time by changing the angular velocity ω, the length of the support element A, 5 or the size of the substrate 1.

While any appropriate spiral equation could be employed, it is to be appreciated that in the generic equation:

r = A + Bθ

the resolved component of the radial acceleration along the spiral surface is:

g_τ = ω ²r.(l/r)(dr/dθ) = ω ²B (i.e. it is constant) Since the flow around the spiral channels is also constant, this spiral feature could be advantageous in some reactor applications and may facilitate scale up or other design considerations.

Figure 3 shows a cross-section through an alternative embodiment of a reactor according to the present invention. As before, there is provided a disc-shaped substrate 1 mounted on a rotor 10 having an axis of rotation 2, and a fluid reagent feed nozzle 3 mounted centrally on the substrate 1. Fluid reagent is supplied to the feed nozzle 3 by way of a feed pipe (not shown) passing up the rotor shaft 10. Two spiral support elements 4, 5 are mounted on the substrate 1, each support element 4, 5 having an inner surface 6 and an outer surface 7. An edge of each inner surface 6 is provided with an inwardly-directed flange 11. In use, the substrate 1 and the support elements 4, 5 are rotated anticlockwise about the axis of rotation 2 by the rotor 10, and fluid reagent is supplied to the inner surfaces 6 by the feed nozzle 3. The fluid reagent then passes outwardly (with respect to the axis of rotation 2) along the inner surfaces 6 in the form of a thin, wavy film 12, the film 12 being constrained by the flanges 11 and^" the upper surface of the substrate 1. Each support element 4, 5 is provided between its inner 6 and outer 7 surfaces with internal conduits 13 through which a suitable heat transfer fluid is supplied. The heat transfer fluid may be supplied through the rotor shaft 10 to the conduits 13, and may then pass outwardly therealong before being collected at a peripheral part of the reactor. The collected heat transfer fluid may then pass through a heat exchanger before being recycled. Instead of being located between the inner 6 and outer 7 surfaces, the conduits 13 may take the form of pipes (not shown) mounted on the outer surfaces 7.

The preferred features of the invention are applicable to all aspects of the invention and maybe used in any possible combination.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and are not intended to (and do not) exclude other components, integers, moieties, additives or steps.

Claims

CLAIMS:

1. A reactor apparatus including at least one support element having a generally spiral configuration with an inner surface and an outer surface, the support element being rotatable about an axis of rotation with the inner surface facing the axis of rotation, wherein the support element is provided with means for transferring heat to or from the inner surface.

2. A reactor apparatus including at least one support element having a generally spiral configuration with an inner surface and an outer surface, the support element being rotatable about an axis of rotation with the inner surface facing the axis of rotation, wherein the support element is adapted to transfer heat to or from the inner surface.

3. A reactor as claimed in claim 1 or 2, wherein the support element is provided with at least one conduit for passage of a heat transfer fluid.

4. A reactor as claimed in claim 3, wherein the at least one conduit is formed on the outer surface of the support element.

5. A reactor as claimed in claim 3 or A, wherein the at least one conduit is formed between the inner and outer surfaces of the support element.

6. A reactor as claimed in any preceding claim, wherein the support element is disposed on a substrate.

7. A reactor as claimed in claim 6, wherein the substrate has a generally planar disc-shaped configuration.

8. A reactor as claimed in claim 6 or 1, wherein the substrate is provided with means for supplying a heat transfer fluid to a side thereof opposed to the support element.

9. A reactor as claimed in any preceding claim, wherein the support element is provided with an electrical heating element.

10. A reactor as claimed in claim 6 or any claim depending therefrom, wherein the substrate is provided with an electrical heating element.

11. A reactor as claimed in any one of claimed 1 to 8, wherein the support element is provided with refrigeration means.

12. A reactor as claimed in any one of claims 6 to 8 or 11, wherein the substrate is provided with refrigeration means.

13. A reactir as claimed in any preceding claim, wherein at least one edge portion of the inner surface of the support element is provided with a flange directed towards the axis of rotation.

14. A reactor as claimed in any preceding claim, wherein a fluid reagent feed is provided at a central part of the reactor.

15. A reactor as claimed in any preceding claim, wherein the support element is made out of a metallic material with good thermal conductivity.

16. A reactor as claimed in claim 6 or any claim depending therefrom, wherein the substrate is made out of a metallic material with good thermal conductivity.

17. A reactor as claimed in claim 16, wherein the support element and the substrate adapted to allow thermal conduction from one to the other.

18. A reactor as claimed in any preceding claim, wherein the support element extends along the axis of rotation for a distance equal to or greater than a diameter of the support element measured substantially perpendicularly to the axis of rotation.

19. A reactor as claimed in any one of claims 1 to 17, wherein the support element extends along the axis of rotation for a distance equal to or less than a diameter of the support element measured substantially perpendicularly to the axis of rotation.

20. A reactor apparatus substantially as hereinbefore described.

21. A reactor apparatus substantially as hereinbefore described with reference to the accompanying drawings.