WO2016120637A1

WO2016120637A1 - Modular photocatalytic reactor

Info

Publication number: WO2016120637A1
Application number: PCT/GB2016/050206
Authority: WO
Inventors: Irene ALLCROFT
Original assignee: Catalysystems Limited
Priority date: 2015-01-30
Filing date: 2016-01-29
Publication date: 2016-08-04
Also published as: GB2543245A; GB201501616D0; CN209061112U; GB2543245B

Abstract

A photocatalytic reactor (110) comprising a plurality of reactor cassettes or modules (111A-E) that can be pieced together to enable such reactors to be easily assembled and subsequently disassembled, for example for repair, replacement or modification. The modular structure may allow significantly increased amounts of catalyst to be disposed within a reactor, or different and differing catalysts to be disposed within a reactor, providing for multiple and/or multi-stage treatment protocols. A reactor cassette or module (111A-E) comprises a bearing surface (118) for a layer of mobile photocatalyst particles, which may be a stator, and an outer wall (123) extending from the bearing surface (118) around the perimeter of the bearing surface (118). These cassettes or modules (111A-E) may be configured, arranged or adapted to stack with adjacent cassettes or modules (111A-E) indefinitely, for limitless applications and treatment volumes.

Description

MODULAR PHOTOCATALYTIC REACTOR

The present invention relates to photocatalytic reactors which use a bed of particulate or granular photocatalyst bodies for the treatment of a fluid, and in particular to an improved reactor for such purposes. In an embodiment of the invention, there is provided a modular reactor comprising a plurality of reactor cassettes or modules. Aspects of the invention relate to reactor cassettes or modules that can be pieced together to construct a photocatalytic reactor or a reaction chamber for a photocatalytic reactor. Background to the invention Catalytic reactors are engineered to maximise the yield of product obtained by the chemical reactions for which they are designed. A catalytic reactor typically has a reaction chamber containing a catalyst and the reactant. The rate of a catalytic reaction may be limited by mass transfer and therefore by the number of reactant molecules brought into

contact with an active site of the catalyst. The volume of the reactor, temperature and mixing of reactants are amongst many parameters that are considered when designing a catalytic reactor, as well as the distribution of the catalyst and the interaction between the reactant and an active site of the catalyst. The Applicant's earlier International Publication Number WO2011/114164, Figure 1A of which is reproduced herein as Figure 1 , discloses a photocatalytic reactor 10 which comprises a flow-through reaction chamber 12. Inside the reaction chamber 12 there is provided an ultraviolet lamp 16, mounted longitudinally and centrally in the reaction chamber 12. Stators 18 surround the ultraviolet lamp 16 and are spatially separated at regular intervals along the longitudinal axis of reaction chamber 12. Each stator 18 provides a bearing surface on which a layer of photocatalyst particles is disposed, and has vanes 28 and slots 30 that are configured to induce turbulent flow in the liquid, such that the liquid leaves the stator 18 with a circular flow pattern. The arrangement and spacing of the stators 18 and ultraviolet lamp 16 is chosen to provide even and complete illumination of the layer of photocatalyst particles disposed on each stator 18. Notwithstanding the improved efficiencies which the Applicant's above-described photocatalytic reactor provides, it is an object of at least one aspect of the present invention to provide a reactor structure that is capable of further improving the

performance of a photocatalytic reactor which adopts or incorporates such a structure. Embodiments of the invention may, for example, allow significantly increased amounts of catalyst to be disposed within a reactor, or different and differing catalysts to be disposed within a reactor, and may enable such reactors to be easily assembled and subsequently disassembled, for example for repair, replacement or modification. Further aims and objects of the invention will become apparent from reading the following description. Summary of the invention According to a first aspect of the invention, there is provided an improved photocatalytic reactor comprising a reaction chamber having a fluid inlet and a fluid outlet displaced in a longitudinal direction of the reaction chamber, wherein the reaction chamber comprises at least one reactor cassette or module comprising a bearing surface for a layer of mobile photocatalyst particles and an outer wall extending from the bearing surface around the perimeter of the bearing surface. The invention provides a photocatalytic reactor with a modular structure which comprises a number of reactor cassettes or modules to enable the reactor to be easily assembled and subsequently disassembled, for example for repair, replacement or modification. Any number of cassettes or modules may be configured, arranged or adapted to stack with adjacent cassettes or modules indefinitely, for limitless applications and treatment volumes. The outer wall of the reactor module or reactor modules may form the housing of the reactor, so dispensing with the need for a separate housing. Most preferably, the wall is integrally formed with the bearing surface. Alternatively, the outer wall is attached to the bearing surface. Preferably, the bearing surface is provided by a stator which comprises one or more channels to allow fluid flow through the bearing surface. Preferably, the one or more channels redirect fluid flow through the bearing surface to create turbulence within a cassette or module treatment volume bounded by the stator and the outer wall. A cassette or module treatment volume may define an individual reaction cell, or a sub- chamber, of the improved photocatalytic reactor. The outer wall of the cassette or module of the reactor may define an outer bound of a reactor treatment volume. Most preferably, the reactor cassette or module is configured to stack with adjacent cassettes or modules. The adjacent cassettes or modules may be like reactor cassettes or modules, or may comprise an inlet cassette or module and/or an outlet cassette or module. Preferably, the outer wall of the reactor cassette or module comprises a first shaped portion at a first end and a second shaped portion at a second end, the second shaped portion shaped and/or sized to receive and/or locate with the first shaped portion of a first end of the outer wall of an adjacent cassette or module. The outer walls of the inlet and/or outlet cassette or module may have a shaped portion which at one end which corresponds to the first or second shaped portions on the outer walls of the reactor cassettes or modules. The shaped portions may be stepped, keyed and/or push- or interference-fit. The shaped portions may further comprise seals. Steps may define shoulders which limit relative movement between adjacent reactor cassettes or modules and/or provide sealing and/or engaging surfaces. A locking mechanism may be provided which may be configured to secure a reactor cassette or module to an adjacent cassette or module. The locking mechanism may comprise one or more latches. The locking mechanism may secure a reactor cassette or module to an adjacent reactor cassette or module, and/or inlet cassette or module, and/or outlet cassette or module. Optionally, the reactor cassette or module comprises an inner wall. One or more inner walls of the reactor may define an inner bound of a reactor treatment volume. The inner walls may also, or alternatively, define an outer bound of a lighting volume which may be shaped and/or sized to receive one or more light sources which may be capable of at least partially illuminating the reactor treatment volume. Preferably the lighting volume extends longitudinally through the reactor. The inner wall may comprise a first shaped portion at a first end and a second shaped portion at a second end, the second shaped portion shaped and/or sized to receive and/or locate with the first shaped portion of an adjacent cassette or module in a manner similar to the first and second shaped portions of the outer wall. Optionally, the reactor comprises at least one light source. The light source may be a UV light source, and may for example comprise one or more UV emitting fluorescent tubes, lamps and/or LEDs. The light source may be located within, around or adjacent the reactor treatment volume. Preferably, the light source is located within the lighting volume. Optionally, the reactor comprises an inlet cassette or module configured to receive and/or locate one of the at least one reactor cassettes or modules. The inlet cassette or module may comprise the fluid inlet, but alternatively may comprise the fluid outlet. Optionally, the reactor comprises an outlet cassette or module configured to be received and/or located on one of the at least one reactor cassettes or modules. The outlet cassette or module may comprise the fluid outlet, but alternatively may comprise the fluid inlet. The inlet cassette or module may be provided with aeration means for aerating fluid within the reactor treatment volume. Preferably, the bearing surface of the reactor cassette or module is circular. Preferably, the outer wall of the reactor cassette or module is cylindrical. If appropriate, preferably the inner wall of the reactor cassette or module is cylindrical. The cassette or module treatment volume may therefore be an annular shape. Optionally, one and/or both (as applicable) of the inner wall and outer wall may comprise a threaded portion. Alternatively, the bearing surface of the reactor cassette or module may be polygonal. For example, the bearing surface of the reactor cassette or module may be triangular, quadrilateral, pentagonal or hexagonal. The bearing surface of the reactor cassette or module may comprise any shape. The shape of the wall preferably corresponds to the shape of the bearing surface or stator. The reactor cassette or module may therefore comprise an open-top prism. In a preferred embodiment of the invention, the reactor comprises an inlet cassette or module, a plurality of reactor cassettes or modules stacked on top of the inlet cassette or module, and an outlet cassette or module located on top of the plurality of reactor cassettes or modules, the inlet cassette or module comprising the fluid inlet and the outlet cassette or module comprising the fluid outlet, each of the plurality of reactor cassettes or modules comprises a plurality of mobile photocatalyst particles disposed on the bearing surface, and each of the bearing surfaces provided by a stator configured to redirect fluid flow to create turbulence. Fluid passing through the reactor from the inlet to the outlet passes through a plurality of treatment volumes defined by each of the plurality of reactor cassettes or modules, the turbulence created by the stator serving to entrain photocatalyst particles increasing the mobility of the catalyst and thereby increasing the surface area of the catalyst that is able to interact with the fluid and/or be exposed to a UV light source. According to a second aspect of the invention there is provided a photocatalytic reactor cassette or module, which may be for a photocatalytic reactor according to the first aspect, comprising a bearing surface for a layer of mobile photocatalyst particles and an outer wall extending from the bearing surface around the perimeter of the bearing surface, the photocatalytic reactor cassette or module configured, arranged or adapted to stack with adjacent cassettes or modules. The adjacent cassettes or modules may be like photocatalytic reactor cassettes or modules, or may comprise an inlet cassette or module and/or an outlet cassette or module. Most preferably, the outer wall is integrally formed with the bearing surface. Alternatively, the outer wall is attached to the bearing surface. Preferably, the bearing surface is provided by a stator which comprises one or more channels to allow fluid flow through the bearing surface. Preferably, the one or more channels redirect fluid flow through the bearing surface to create turbulence within a cassette or module treatment volume bounded by the stator and the outer wall. A cassette or module treatment volume may define an individual reaction cell, or a sub- chamber, of a photocatalytic reactor in which the reactor cassette or module is comprised. Preferably, the wall of the reactor cassette or module comprises a first shaped portion at a first end and a second shaped portion at a second end, the second shaped portion shaped and/or sized to receive and/or locate with the first shaped portion of an adjacent cassette or module. The shaped portions may be stepped, keyed and/or push- or interference-fit. The shaped portions may further comprise seals. Steps may define shoulders which limit relative movement between adjacent reactor cassettes or modules and/or provide sealing and/or engaging surfaces. Optionally, the reactor cassette or module comprises an inner wall. The inner walls may also, or alternatively, define a lighting volume shaped and/or sized to receive one or more light sources which may be capable of at least partially illuminating the cassette or module treatment volume. Preferably the lighting volume extends longitudinally through the cassette or module. The inner wall may comprise a first shaped portion at a first end and a second shaped portion at a second end, the second shaped portion shaped and/or sized to receive and/or locate with the first shaped portion of an adjacent cassette or module in a manner similar to the first and second shaped portions of the outer wall. Optionally, the reactor cassette or module comprises at least one light source. The light source may be a UV light source, and may for example comprise one or more UV emitting fluorescent tube or lamp or LEDs. The light source may be located within, around or adjacent the reactor treatment volume. Preferably, the light source is located within the lighting volume. Preferably, the bearing surface of the reactor cassette or module is circular. Preferably, the outer wall of the reactor cassette or module is cylindrical. If appropriate, preferably the inner wall of the reactor cassette or module is cylindrical. The cassette or module treatment volume may therefore be an annular shape. Optionally, one and/or both (as applicable) of the inner wall and outer wall comprise a threaded portion. Alternatively, the bearing surface of the reactor cassette or module is polygonal. For example, the bearing surface of the reactor cassette or module may be triangular, quadrilateral, pentagonal or hexagonal. The bearing surface of the reactor cassette or module may comprise any shape. The shape of the wall preferably corresponds to the shape of the bearing surface or stator. The reactor cassette or module may therefore comprise an open-top prism. In a preferred embodiment of the invention, the reactor cassette or module comprises a plurality of mobile photocatalyst particles disposed on the bearing surface, and the bearing surface is provided by a stator configured to redirect fluid flow to create turbulence. When fluid passes through the reactor cassette or module the turbulence created by the stator serves to entrain photocatalyst particles increasing the mobility of the catalyst and thereby increasing the surface area of the catalyst that is able to interact with the fluid and/or be exposed to a UV light source. Embodiments of the second aspect of the invention may comprise features corresponding to the preferred or optional features of the first aspect of the invention or vice versa. According to a further aspect of the invention, there is provided a photocatalytic reactor, a photocatalytic reactor cassette or module, an inlet cassette or module or an outlet cassette or module, substantially as herein described with reference to Figures 2A and 2B.

Brief description of the drawings There will now be described, by way of example only, various embodiments of the invention with reference to the following drawings (like reference numerals referring to like features) in which: Figure 1 presents a photocatalytic reactor in accordance with the prior art shown in perspective view; Figure 2A presents a photocatalytic reactor in accordance with an embodiment of the present invention shown in a partially-exploded side view; and Figure 2B presents a corresponding partially-exploded perspective view of the photocatalytic reactor illustrated in Figure 2A.

Detailed description of preferred embodiments Note that in the summary of the invention above and in the detailed description which follows, the terms "cassette" and "module" are and may be used interchangeably to refer to various modules which make up the modular structure of the photocatalytic reactor of the present invention. An embodiment of the present invention is illustrated, by way of example only, in Figures 2A and 2B and provides a number of advantages over prior art reactors, specifically by providing a modular structure which aids in construction, maintenance, modification and customisation of photocatalytic reactors which employ such a structure. The photocatalytic reactor 1 10 can be seen to comprise several, in this case five, reactor cassettes or modules 1 11A-E. Reactor cassettes or modules 11 1A and 11 1 B are shown in a stacked arrangement atop an inlet cassette or module 121 , and reactor cassettes or modules 1 11 C-E are shown in a separated arrangement, aligned vertically with one another and with stacked reactor cassettes or modules 11 1 A and 11 1 B. It will be apparent that any number of reactor cassettes or modules may be stacked in this way to achieve a desired size, total treatment volume or effect. Each of the reactor cassettes or modules 11 1 can be seen to comprise an outer cylindrical wall 1 14 which extends around the perimeter of the cassette or module 1 11. A bearing surface or stator 1 18 upon which a layer of mobile photocatalyst particles (not shown) can be deposited is circular and accordingly the walls 114 are cylindrical. In this particular example the height of the walls 114 are such that the distance between stators 1 18 of stacked reactor cassettes or modules (e.g. 11 1 A and 11 1 B) is approximately 50mm. The space between pairs of stators 1 18 defines individual reaction cells or sub-chambers 136, bounded by the respective outer walls 1 14. Of course, the walls 1 14 may be of different and differing heights in order to provide different treatment volumes within individual reaction cells or sub-chambers 136. The individual reaction cells or sub-chambers 136 can be configured for different treatment processes, for example by providing catalysts of different and differing sizes, shapes, material and in different and differing amounts. Accordingly, a single reactor may be configured to effect multiple and/or multi-stage treatment protocols. A further advantage stemming from the modular construction of the reactor is that it may be easily enlarged or reduced in size, and/or individual cassettes or modules or groups of cassettes or modules can be swapped in and/or out as required (for maintenance, repair or replacement, for example). Compared to existing photocatalyst reactor arrangements, the modular structure prevents the transfer of photocatalyst from one reaction cell or sub-chamber 136 to another, as may be possible in arrangements where the stators are housed within a separate, continuous cylindrical housing. The modular structure also prevents untreated or partially treated fluid from bypassing the stator channels and transferring from one reaction cell or sub-chamber to another through gaps between the stators and a separate, continuous cylindrical housing. By travelling through these gaps the fluid may not be properly treated and may have a negative effect on the turbulent fluid flow created by the stators which may reduce the overall efficiency of the reactor. The wall 123 in this example is integrally formed with the stator 1 18 and as such may be formed in a single manufacturing process such as by casting from a mould. Of course, the cassettes or modules 1 11 can be manufactured using any suitable process, including glueing or welding the wall 123 to the stator (for example using cyanoacrylate cement or heat, respectively). Slots 130 and/or vanes 128 in the stator, which may be shaped to create turbulent flow conditions within the reactor treatment volume, can be formed as part of a casting process or can be machined (for example using laser ablation or cutting techniques) subsequently. The reactor cassettes or modules 1 11 A-E are made from poly(methylmethacrylate) (PMMA) which is transparent to visible/natural light, thus allowing the contents and/or processes occurring within the reactor 1 10 to be observed. Alternatively, any other suitable transparent material may be employed, such as quartz glass or borosilicate glass - the method of manufacture of the cassettes or modules tailored accordingly. To assist in stacking and aligning or locating the reactor cassettes or modules 1 11 , the lower end of the wall 114, which in this example protrudes below the stator 118, provides a stepped portion 117 which is sized and shaped to receive a corresponding stepped portion 1 19 at the upper end of the wall 114 of the reactor cassette or module 1 11 below. A shoulder of the stepped portion 1 19 provides a stop to prevent further vertical movement. A seal (not shown) may be provided in the region of this interface, but may be

unnecessary - for example if an interference or push-fit is provided. The upper end of the wall 1 14 may contact the lower surface of the stator 1 18 of the cassette or module above (where appropriate) as shown with reference to cassettes or modules 11 1 A and 11 1 B. In this exemplary embodiment, a cylindrical inner wall 115 is also provided which defines an inner bound of the individual reaction cells or sub-chambers 136. Furthermore, a continuous bore 1 16 provided through the reaction chamber by virtue of aligned inner walls 115 may receive an ultraviolet light source, such as a UV lamp or array of UV LEDs, to illuminate the interior of the reactor 110. The inner wall 1 15 may be provided with stepped portions, shoulders and the like to assist in stacking and aligning or locating the reactor cassettes or modules 11 1 in a similar manner to the stepped portions 117, 119 provided by the outer wall 1 14. Seals may be provided in this region if necessary. An inlet cassette or module 121 comprising an inlet 122 and an (optional) diffuser 134 for aeration may form the lower end of the reactor 110, and an outlet cassette or module 123 comprising an outlet 124 may form the outlet end of the reactor 110. These cassettes or modules 121 ,123 have corresponding outer and inner walls 114, 115 which stack and align or locate with the reactor cassettes or modules 11 1A, 11 1 E to which they are attached, respectively. Fluid entering the reactor through the inlet 122 travels up through (in this example) five discrete reaction cells or sub-chambers 136 before exiting the reactor through the outlet 124. The modular nature of the inlet cassette or module 121 and/or outlet cassette or module 123 provide benefits corresponding to those of the reactor cassettes or module 1 11 , not least in relation to improved reactor efficiency, ease of construction, repair, maintenance and replacement. Optionally, the reactor cassettes or modules may be made, at least partially, from an opaque material, and/or may be coated with a material which prevents light from entering the reaction chamber. The reactor cassettes or modules may be coated on an internal surface, for example, with a reflective material which serves to internally reflect UV light to enhance illumination of the catalyst material within the reaction chamber assist in the photocatalysis process. Furthermore, while the reactor cassettes or modules are described above as being circular in cross-section, they may of course be elliptical, rectangular or indeed of any cross- section shape provided the other reactor cassettes or modules are able to stack (typically by virtue of being the same cross-section shape). Circular cross-sections of course mean that the engaging surfaces of adjacent reactor cassettes or modules may be threaded for screwing together. They may of course be keyed instead, or be push- or interference-fits with one another. This applies equally to alternative, for example polygonal, or irregular cross-section shapes. A photocatalytic reactor in accordance with the invention may comprise a number of reactor cassettes or modules of different materials, different sizes, different degrees of transparency (ranging from transparent to opaque), and the reactor cassettes or modules may contain catalyst material in different sizes, shapes, materials and amounts. In this way individual reactor cassettes or modules (and the catalyst materials contained therein) can be tailored for specific applications or to remove different kinds of contaminant.

Accordingly, several treatment stages may be accommodated within a single reactor with relative ease, and the treatment stages themselves and/or the order in which the treatment stages take place may be conveniently arranged, re-arranged and altered by virtue of the modular structure of the reactor. In addition, repairs to damaged reactors or reactor components are made far easier than in known reactor systems because a single cassette or module can be removed and (if appropriate) replaced with reduced downtime. Furthermore, the reactor may be extended or enlarged indefinitely as there is no external limit enforced by having to house the reactor system within a housing - the housing is provided by the external/outer walls of the reactor cassettes or modules when joined together. In use, a layer of mobile photocatalyst particles (not shown) will be disposed on the upper surface of each stator 118. The fluid flow through each stator 118 creates turbulence which serves to entrain photocatalyst particles in the fluid flow where they can interact with contaminants as well as being moved across and/or around the surface. Movement of the photocatalyst particles across and/or around the surface of the stator 1 18 may improve mass transfer of contaminants from the fluid to be treated to the surface of the

photocatalyst particles. If provided, movement will also improve illumination of the photocatalyst particles by a UV source. An additional benefit may be that the movement of the photocatalyst particles across the surface of the stator 1 18 will have a scrubbing or cleaning effect on the stator 1 18 and other parts of the reactor (for example the outer and inner walls 1 14, 115). Similarly, the resulting collisions between photocatalyst particles will have a scrubbing or cleaning effect on the photocatalyst particles themselves. The invention provides a photocatalytic reactor comprising a plurality of reactor cassettes or modules that can be pieced together to enable such reactors to be easily assembled and subsequently disassembled, for example for repair, replacement or modification. The modular structure may allow significantly increased amounts of catalyst to be disposed within a reactor, or different and differing catalysts to be disposed within a reactor, providing for multiple and/or multi-stage treatment protocols. A reactor cassette or module comprises a bearing surface for a layer of mobile photocatalyst particles, which may be a stator, and an outer wall extending from the bearing surface around the perimeter of the bearing surface. These cassettes or modules may be configured, arranged or adapted to stack with adjacent cassettes or modules indefinitely, for limitless applications and treatment volumes. Throughout the specification, unless the context demands otherwise, the terms 'comprise' or 'include', or variations such as 'comprises' or 'comprising', 'includes' or 'including' will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. Furthermore, relative terms such as "up", "down", "top", "bottom", "upper", "lower", "upward", "downward", "horizontal", "vertical" and the like are used herein to indicate directions and locations as they apply to the appended drawings and will not be construed as limiting the invention and features thereof to particular arrangements or orientations. For example, the reactor and/or reactor cassettes or modules disclosed herein are described and illustrated as being in a vertical orientation with the cassettes or modules stacked one on top of another (i.e. extending in a vertical direction). However, it is also intended and will be readily understood that the reactor and/or reactor cassettes or modules may be oriented horizontally and the cassettes or module may be stacked end on end (i.e. extending in a horizontal direction) in an equivalent manner. Likewise, the term "inlet" shall be construed as being an opening which, dependent on the direction of fluid flow, may also serve as an "outlet", and vice versa. The foregoing description of the invention has been presented for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention as defined by the appended claims.

Claims

Claims 1. A photocatalytic reactor comprising a reaction chamber having a fluid inlet and a fluid outlet displaced in a longitudinal direction of the reaction chamber, wherein the reaction chamber comprises a modular structure, wherein the modular structure comprises at least one reactor module comprising a bearing surface for a layer of mobile photocatalyst particles and an outer wall extending from the bearing surface around the perimeter of the bearing surface, and a housing wherein the housing is provided by the outer wall of the at least one reactor module.

2. The photocatalytic reactor according to any preceding claim, wherein the bearing surface is provided by a stator which comprises one or more channels to allow fluid flow through the bearing surface.

3. The photocatalytic reactor according to claim 2, wherein the one or more channels redirect fluid flow through the bearing surface to create turbulence within a treatment volume bounded by the stator and the outer wall.

4. The photocatalytic reactor according to any preceding claim, wherein the outer wall is integrally formed with the bearing surface.

5. The photocatalytic reactor according to any preceding claim, wherein the outer wall is attached to the bearing surface.

6. The photocatalytic reactor according to any preceding claim, wherein the outer wall of the at least one module of the reactor defines an outer bound of a reactor treatment volume.

7. The photocatalytic reactor according to any preceding claim, wherein the at least one reactor module is configured to stack with adjacent modules of the modular structure.

8. The photocatalytic reactor according to claim 7, wherein the adjacent modules

comprise at least one reactor module.

9. The photocatalytic reactor according to claim 7 or claim 8, wherein the adjacent modules comprise an inlet module which comprises an outer wall corresponding to the outer wall of the at least one reactor module and further comprises the fluid inlet to allow fluid to enter the reactor.

10. The photocatalytic reactor according to any of claims 7 to 9, wherein the adjacent modules comprise an outlet module which comprises an outer wall corresponding to the outer wall of the at least one reactor module and further comprises the fluid outlet to allow fluid to exit the reactor.

1 1. The photocatalytic reactor according to any preceding claim, wherein the outer wall of the at least one reactor module comprises a first shaped portion at a first end and a second shaped portion at a second end, the second shaped portion shaped and/or sized to receive and/or locate with the first shaped portion of a first end of the outer wall of an adjacent module.

12. The photocatalytic reactor according to claim 1 1 , wherein the outer walls of an inlet and/or an outlet module have a shaped portion which at one end corresponds to the first or second shaped portions on the outer walls of the at least one reactor module.

13. The photocatalytic reactor according to claim 1 1 or claim 12, wherein the shaped portions are stepped, keyed and/or push- or interference-fit.

14. The photocatalytic reactor according to any of claims 1 1 to 13, wherein the shaped portions further comprise seals.

15. The photocatalytic reactor according to any of claims 1 1 to 14, wherein the shaped portion comprises a step defining a shoulder which limits relative movement between the at least one reactor module and an adjacent module.

16. The photocatalytic reactor according to claim 15, wherein the step provides a sealing and/or engaging surface.

17. The photocatalytic reactor according to any preceding claim, further comprising a locking mechanism configured to secure the at least one reactor module to an adjacent module.

18. The photocatalytic reactor according to claim 17, wherein the locking mechanism comprises one or more latches.

19. The photocatalytic reactor according to claim 17 or claim 18, wherein the locking mechanism secures the at least one reactor module to an adjacent reactor module, and/or an inlet module, and/or an outlet module.

20. The photocatalytic reactor according to any preceding claim, wherein the at leasr one reactor module comprises an inner wall.

21. The photocatalytic reactor according to claim 20, wherein the inner wall of the at least one reactor module defines an inner bound of a reactor treatment volume.

22. The photocatalytic reactor according to any preceding claim, wherein an inner wall of the at least one reactor module defines an outer bound of a lighting volume shaped and/or sized to receive one or more light sources which capable of at least partially illuminating a reactor treatment volume.

23. The photocatalytic reactor according to claim 22, wherein the lighting volume

extends longitudinally through the reactor.

24. The photocatalytic reactor according to any of claims 20 to 23, wherein the inner wall comprises a first shaped portion at a first end and a second shaped portion at a second end, the second shaped portion shaped and/or sized to receive and/or locate with a first shaped portion of an adjacent module in a manner similar to first and second shaped portions of the outer wall.

25. The photocatalytic reactor according to any preceding claim, wherein the reactor comprises at least one light source.

26. The photocatalytic reactor according to claim 25, wherein the light source is a UV light source.

27. The photocatalytic reactor according to claim 26, wherein the UV light source

comprises one or more UV emitting fluorescent tubes, lamps and/or LEDs.

28. The photocatalytic reactor according to any of claims 25 to 27, wherein the light source is located within, around or adjacent a reactor treatment volume.

29. The photocatalytic reactor according to claim 28, wherein the light source is located within a lighting volume.

30. The photocatalytic reactor according to any preceding claim, comprising an inlet module configured to receive and/or locate one of the at least one reactor modules.

31. The photocatalytic reactor according to claim 30, wherein the inlet module comprises a fluid inlet.

32. The photocatalytic reactor according to claim 30, wherein the inlet module comprises a fluid outlet.

33. The photocatalytic reactor according to any preceding claim, comprising an outlet module configured to be received and/or located on one of the at least one reactor modules.

34. The photocatalytic reactor according to claim 33, wherein the outlet module

comprises the fluid outlet.

35. The photocatalytic reactor according to claim 33, wherein the outlet module

comprises the fluid inlet.

36. The photocatalytic reactor according to any of claims 30 to 33, wherein the inlet module comprises aeration means for aerating fluid within a reactor treatment volume.

37. The photocatalytic reactor according to any preceding claim, wherein the bearing surface of the reactor module is circular.

38. The photocatalytic reactor according to any preceding claim, wherein the outer wall of the reactor module is cylindrical.

39. The photocatalytic reactor according to any preceding claim, wherein an inner wall of the reactor module is cylindrical.

40. The photocatalytic reactor according to any preceding claim, wherein a treatment volume comprises an annular shape.

41. The photocatalytic reactor according to any preceding claim, wherein the outer wall of the at least one reactor module comprises a threaded portion.

42. The photocatalytic reactor according to any claim 41 , wherein a corresponding inner wall of the at least one reactor module comprises a threaded portion.

43. The photocatalytic reactor according to any of claims 1 to 36, wherein the bearing surface of the at least one reactor module is polygonal.

44. The photocatalytic reactor according to any preceding claim, wherein the shape of the outer wall corresponds to the shape of the bearing surface or stator.

45. The photocatalytic reactor according to any preceding claim, wherein the at least one reactor module comprises an open-top prism.

46. The photocatalytic reactor according to claim 1 , wherein the reactor comprises an inlet module, a plurality of reactor modules stacked on top of the inlet module, and an outlet module located on top of the plurality of reactor modules, the inlet module comprising the fluid inlet and the outlet module comprising the fluid outlet, each of the plurality of reactor modules comprising a plurality of mobile photocatalyst particles disposed on the bearing surface, and each of the bearing surfaces provided by a stator configured to redirect fluid flow to create turbulence.

47. The photocatalytic reactor according to claim 46, wherein a plurality of treatment volumes is defined by the plurality of reactor modules, the turbulence created by the stator of each reactor module serving to entrain photocatalyst particles increasing the mobility of the catalyst and thereby increasing the surface area of the catalyst that is able to interact with the fluid and/or be exposed to a UV light source.

48. A photocatalytic reactor module for a photocatalytic reactor according to any

preceding claim, the reactor module comprising a bearing surface for a layer of mobile photocatalyst particles and an outer wall extending from the bearing surface around the perimeter of the bearing surface, the photocatalytic reactor module configured, arranged or adapted to stack with adjacent modules.

49. The photocatalytic reactor module according to claim 48, wherein the adjacent modules comprise same photocatalytic reactor modules.

50. The photocatalytic reactor module according to claim 48 or claim 49, wherein the adjacent modules comprise an inlet module which comprises a fluid inlet and/or an outlet module which comprises a fluid outlet.

51. The photocatalytic reactor module according to any of claims 48 to 50, wherein the outer wall is integrally formed with the bearing surface.

52. The photocatalytic reactor module according to any of claims 48 to 50, wherein the outer wall is attached to the bearing surface.

53. The photocatalytic reactor module according to any of claims 48 to 52, wherein the bearing surface is provided by a stator which comprises one or more channels to allow fluid flow through the bearing surface.

54. The photocatalytic reactor module according to claim 53, wherein the one or more channels redirect fluid flow through the bearing surface to create turbulence within a module treatment volume bounded by the stator and the outer wall.

55. The photocatalytic reactor module according to any of claims 48 to 54, wherein the outer wall of the reactor module comprises a first shaped portion at a first end and a second shaped portion at a second end, the second shaped portion shaped and/or sized to receive and/or locate with the first shaped portion of an adjacent reactor module.

56. The photocatalytic reactor module according to any of claims 48 to 55, wherein the reactor module comprises an inner wall.

57. The photocatalytic reactor module according to claim 56, wherein the inner wall defines a lighting volume shaped and/or sized to receive one or more light sources capable of at least partially illuminating a module treatment volume.

58. The photocatalytic reactor module according to claim 57, wherein the lighting volume extends longitudinally through the cassette.

59. The photocatalytic reactor module according to any of claims 56 to 58, wherein the inner wall comprises a first shaped portion at a first end and a second shaped portion at a second end, the second shaped portion shaped and/or sized to receive and/or locate with the first shaped portion of an adjacent module in a manner similar to the first and second shaped portions of the outer wall.

60. The photocatalytic reactor module according to any of claims 48 to 59, wherein the reactor module comprises at least one UV light source comprising one or more UV emitting fluorescent tube or lamp or LEDs.

61. The photocatalytic reactor module according to any of claims 48 to 59, wherein the bearing surface of the reactor module is circular.

62. The photocatalytic reactor module according to any of claims 48 to 60, wherein the outer wall of the reactor module is cylindrical.

63. The photocatalytic reactor module according to any of claims 48 to 61 , wherein an inner wall of the reactor module is cylindrical.

64. The photocatalytic reactor cassette according to any of claims 48 to 62, wherein a module treatment volume is an annular shape.

65. The photocatalytic reactor module according to any of claims 48 to 64, wherein the outer wall and/or an inner wall comprise a threaded portion.

66. The photocatalytic reactor module according to claim 48, wherein the reactor module comprises a plurality of mobile photocatalyst particles disposed on the bearing surface, and the bearing surface is provided by a stator configured to redirect fluid flow to create turbulence.

67. A photocatalytic reactor, a photocatalytic reactor module, an inlet module or an outlet module, substantially as herein described with reference to Figures 2A and 2B.