Plug flow system and method of continuous processing of fluid process materials

Abstract

A continuous flow apparatus for effecting chemical and / or physical change to fluid process materials is disclosed. The continuous flow apparatus comprises: a tube arranged to provide a flow path for the fluid process materials, and a mixing assembly arranged in the tube. The mixing assembly comprises: a stirring mechanism comprising at least one axial stirrer blade configured to generate tangential flow of the fluid; a static baffle assembly arranged to inhibit axial dispersion of fluid in the tube; and one or more rotatable baffles configured to rotate about the longitudinal axis of the tube, and to inhibit axial dispersion of the fluid in the tube.

Description

[0001] PLUG FLOW SYSTEM AND METHOD OF CONTINUOUS PROCESSING OF FLUID PROCESS MATERIALS

[0002] Technical Field The present invention relates to systems for processing of process material, and more particularly to continuous flow apparatuses used to effect chemical or physical change to flowing process materials, and methods of use and manufacture of such apparatus.

[0003] Background

[0004] Batch reactors are stirred vessels used in the process industries for mixing, synthesis, and separation. As such, batch systems process single system volumes at a time. In contrast, continuous flow reactors process multiple volumes without interruption, processing a small fraction of the total lot quantity at any time. Continuous flow systems may thereby process higher volumes per hour per unit volume of system.

[0005] However, many in-process materials are susceptible to degradation and loss of yield through parallel reactions, series reactions or both. Improved control of residence time and temperature in continuous operations contribute to higher quality and yield in such cases.

[0006] Summary of Invention

[0007] Embodiments of the present invention aim to address the above problems and others.

[0008] Aspects of the disclosure are set out in the independent claims and optional features are set out in the dependent claims. Aspects of the disclosure may be provided in conjunction with each other, and features of one aspect may be applied to other aspects. In an aspect there is provided a continuous flow apparatus for effecting chemical and / or physical change to fluid process materials, wherein the continuous flow apparatus comprises: a tube arranged to provide a flow path for the fluid process materials; a mixing assembly arranged in the tube, the mixing assembly comprising: a stirring mechanism comprising at least one axial stirrer blade configured to generate tangential flow of the fluid; a static baffle assembly arranged to inhibit axial dispersion of f luid in the tube; at least one rotatable radial baffle configured to rotate about the longitudinal axis of the tube, and to inhibit axial dispersion of the fluid in the tube. The at least one axial stirrer blade may have a circular cross-section. The at least one axial stirrer blade may be configured to generate tangential f low in the fluid upon rotation, e.g., rotation about the longitudinal axis of the tube. This may enable processing to be carried out with a reduced system size, which may facilitate higher ratios of heat transfer area to volume and improved mixing characteristics. These factors may in turn contribute to lower capital and operating costs with reduced energy consumption. Other benefits may include improved safety through reduced system size, uniform utilities consumption and less building space used. The tube may provide a conduit for the fluid process materials, e.g. for the fluid to flow from an inlet to an outlet. The tube may be metal, e.g. it may comprise a metal such as stainless steel, and / or Hastelloy. Additionally or alternatively, the tube may be lined with glass, tantalum and / or non-metals, e.g. f luoropolymers. The tube may be sealed and / or rigid. The tube may comprise one or more connections, e.g. f langes, for entry and / or exit of f luid from the tube. The stirring mechanism may comprise a plurality of axial stirrer blades, which may each extend in the longitudinal (axial) direction of the tube. The stirrer blade(s) may preferably be straight in the axial plane. The plurality of stirrer blades may be positioned at the same radial distance from the centre of the tube (e.g. from the longitudinal axis of the tube). The axial stirrer blades may be arranged symmetrically in the tube. The one or more axial stirrer blade(s) may be arranged at or close to the periphery of the tube, and may, upon rotation, cause tangential f low of the fluid in the tube, e.g. rotating / circular f low in the radial plane. The stirring mechanism may be coupled to a drive mechanism to provide rotational movement of the stirring mechanism. The stirring mechanism may further comprise a central shaft coupled to the drive mechanism, and the stirrer blades may be coupled to the central shaft via a stirrer blade support, which may be circular – e.g. a disc having a circular cross section, and may comprise spokes. The static baffle assembly may be arranged radially inwards of the at least one stirrer blade. The static baffle assembly may comprise at least one axial baffle configured to divert tangential f low of the fluid, e.g. to generate radial mixing; and at least one radial baffle configured to inhibit axial dispersion of the fluid across said radial baffle. The static baffle assembly may comprise a plurality of axial baffles, e.g. three or more axial baffles. The static baffle assembly may comprise a plurality of radial baffles. The radial baffles may be disc shaped, e.g. circular. Each of the at least one axial baffle may comprise a slot and each of the at least one radial baffle may comprise a corresponding slot. The radial baffles and axial baffles may be coupled together, e.g. each of the at least one radial baffle may be coupled to each of the at least one axial baffle. The at least one radial baffle slot may overlap with the at least one axial baffle slot, and may together form a rigid 3-dimensional structure, e.g. when pushed together. The radial and axial baffles may be locked in place by alternative methods such as interference fits, bonding, welding, keys, lips, or thermal contraction. Alternatively, they may be formed as a single unit by 3D printing. The at least one stirrer blade may be rotatable to define a swept path, e.g. in the radial plane. The swept path may have an inner diameter and an outer diameter. The swept path of the at least one stirrer blade is within or equal to the radial extent of the at least one rotatable baffle, e.g. between the inner diameter and outer diameter of the rotatable baffle. The at least one rotatable baffle may comprise at least one ring-shaped radial baffle, where each such baffle is configured to rotate about the longitudinal axis of the tube. The at least one ring-shaped radial baffle may be flat. The at least one rotatable baffle may comprise a plurality of such radial baffles. The plurality of rotatable radial baffles may be axially aligned, e.g. to form stages and so as to inhibit axial dispersion between stages. The at least one rotatable baffle may surround the static baffle assembly. The at least one rotatable baffle may be coupled e.g. f ixed to the stirring mechanism, e.g. fixed to the at least one stirrer blade, for example by welding or bonding. The continuous flow apparatus may comprise at least one locking element configured inhibit axial movement of the at least one rotatable baffle relative to the stirrer blade. The rotatable radial baffle(s) may each comprise at least one hole for receiving a corresponding one of the at least one stirrer blades. The at least one locking element may comprise a ring or sleeve surrounding a portion of the at least one stirrer blade. The at least one locking element may comprise tantalum, e.g. it may consist of or consist essentially of tantalum. Alternatively, the at least one locking element may include a tantalum coating layer. Alternatively the locking element may comprise another metal or metal alloy, coated metal or non-metal. The apparatus may comprise at least two locking elements, for example a locking element may be provided on either side of each rotatable baffle, to hold said baffle in a fixed position in the longitudinal plane. The locking element(s) may be fixedly attached to the stirrer blades without being fixedly attached to the rotatable baffles. The locking element may be fixed to the at least one rotatable baffle, and / or to the at least one stirrer blade. Said fixing may be provided by the locking element being bonded or welded to the stirrer blade. Alternatively, said fixing may be provided by thermal contraction, e.g. thermal contraction of the locking element (e.g. a ring) around a portion of the stirrer blade. The rotatable baffles may be made of metal, coated metal, or non-metal, e.g., they may comprise, consist of, or consist essential of, glass filled Polytetrafluoroethylene (PTFE). The static baffle assembly may comprise a plurality of radial baffles, for example 2 or more radial baffles, for example 4 or more radial baffles, for example 8 or more radial baffles. The apparatus may also comprise a plurality of rotatable radial baffles, for example 2 or more radial baffles, for example 4 or more radial baffles, for example 8 or more radial baffles. A working volume, or “stage” may be provided between each pair of adjacent static and / or rotatable radial baffles in the axial plane, and also between the two end-most static radial baffles and each end of the tube. The radial baffles may reduce axial dispersion between stages, and the axial baffles may deliver effective radial mixing, e.g. under plug flow or approximate plug flow conditions. The continuous flow apparatus may comprise 3 or more stages, preferably 5 or more stages, more preferably 9 or more stages. Without wishing to be bound by theory, it is understood that the greater the number of stages provided, the more closely that the flow of f luid in the apparatus approximates plug flow. The static radial baffle(s) may be aligned with the rotatable radial baffle(s), e.g. axially aligned. Alternatively, the axial position of the static radial baffle may be offset from the rotatable radial baffle, e.g. to provide a channel for the flow. The continuous flow apparatus may further comprise one or more inlet connections for feeding the process material f luid into the tube, and one or more outlet connections for discharging the process material f luid from the tube. The continuous flow apparatus may be configured to provide a continuous chemical reaction. Additionally, or alternatively, the continuous flow apparatus may be configured to provide continuous processing such as chemical, physical or biological changes to process materials including, but not limited to chemical reactions, polymerisation, crystallisation, cell growth, extraction and heating or cooling treatment. The process material may be a flowing liquid comprising one or more components which may include miscible or immiscible liquids, gases and solids. The process materials described herein may be chemicals, foods, other natural products, diluents and catalysts. The continuous flow apparatus may be configured to provide radial mixing of the fluid process material under plug flow conditions. The static baffle assembly and the at least one rotatable baffle (e.g. a plurality of rotatable baffles, and / or the stirrer blades) may be each independently removable from the tube. For example, the static baffle assembly may be removable from a first axial end of the tube, and the at least one rotatable baffle may be removable from a second axial end of the tube, opposite the first end. The continuous flow apparatus may further comprise a sleeve or jacket surrounding the tube. The sleeve or jacket may be configured to heat and / or cool the process fluid. In another aspect there is provided a method of continuous processing of f luid process materials under plug flow conditions, the method comprising: feeding a fluid process material into a tube; mixing the fluid process material; and discharging the fluid process material from the tube; wherein mixing the fluid process material comprises rotating an axial stirrer blade and at least one rotatable baffle inside the tube around a static baffle assembly arranged radially inwards of the stirrer blade and the at least one rotatable baffle. The at least one rotatable baffle may comprise at least one ring- or disc-shaped radial baffle each configured to rotate about the longitudinal axis of the tube. The stirrer blade may be fixed to the at least one rotatable baffle. The axial position of the at least one rotatable baffle may be fixed relative to the stirrer blade. The method of continuous processing may comprise a continuous chemical reaction. Additionally, or alternatively, the processing according may comprise chemical, physical or biological changes to process materials including, but not limited to chemical reactions, polymerisation, crystallisation, cell growth, extraction and heating or cooling treatment. The process material may be a flowing liquid comprising one or more components which may include miscible or immiscible liquids, gases and solids. The method may further comprise heating and / or cooling the fluid process material. In another aspect there is provided a method of assembling a continuous flow apparatus for effecting chemical and / or physical change to fluid process materials, the method comprising: coupling at least one stirrer blade to a drive system, for rotation of the stirrer blade; mounting a rotatable radial baffle onto the stirrer blade; inserting the rotatable baffle and the stirrer blade into a tube, wherein the tube comprises one or more inlet connections for feeding the process material f luid into the tube, and one or more outlet connections for discharging the process material f luid from the tube. Mounting the rotatable radial baffle onto the stirrer blade may comprise fixing the axial position of the rotatable radial baffle relative to the stirrer blade. For example, the method may comprises fixing a locking element onto the at least one stirrer blade to inhibit the axial movement of the rotatable baffle. The method may comprise mounting one or preferably two locking elements on the stirrer blade, which may surround a portion of the stirrer blade and may be arranged either side of the rotatable baffle. The method may further comprise fixing the locking element to the at least one stirrer blade, e.g. by thermal contraction. Mounting the rotatable radial baffle onto the at least one stirrer blade preferably comprises mounting the rotatable radial baffle onto two or more stirrer blades, as this may fix the position of the rotatable radial baffle in the radial plane. The apparatus and methods described herein may reduce axial dispersion in the flow whilst generating radial mixing of the fluid process materials in the flow. Systems and methods according to the present disclosure may provide a scalable continuous system for single and multiphase materials with mixing and plug flow substantially decoupled from residence time. This may deliver better performance and greater productive capacity than batch for a similar range of applications. Materials pass through the system in the axial direction under plug flow conditions. Mixing and heating or cooling conditions may be applied as required. Chemical, physical, biological or temperature changes occur as materials progress through the system. Materials of different density may travel at different axial velocities or in the opposing axial direction. Intermediate addition and take off points along the system body may also be used. The design principles described here may facilitate the use of baffles fabricated in non- metallic materials tolerant to elevated temperatures and corrosive materials. Standard industrial materials may be used including metals, non-metals, alloys and lined metals. The present disclosure provides a system with rotatable radial baffles which may substantially cover the radial area between the static radial baffles and the tube wall. This may further reduce axial dispersion so that observed residence time is closer to nominal residence time. The rotatable baffles may be mounted on the stirrer blades with locking rings or sleeves. The present invention is concerned with activities within the plug flow length. Non-plug flow sections may also be used. The meanings of certain terms will be understood in the context of the present disclosure. For example, “radial” refers to the plane across the diameter of the system body which is a tube. “Axial” refers to the plane in the longitudinal axis of the tube. A stage refers to the working volume between adjacent static radial baffles in the axial plane and also between static radial baffles and tube ends. Plug flow refers to fluids of the same density flowing at substantially uniform axial velocity through the system, and may be equivalent to a minimum of 3 randomly mixed stages coupled in series with substantially unidirectional f low between stages. Radial mixing refers to mixing in the radial plane. Tangential f low refers to rotational f low in the radial plane. Nominal residence time refers to the system volume divided by volumetric flow rate. Axial dispersion refers to back mixing in axial plane, and is undesirable other than specific cases. Age refers to time material has remained in the system. Residence time distribution refers to age distribution of material leaving the system. Residence time control refers to discharging material having a narrow residence time distribution The plug flow length is the axial length subject to plug flow. Without wishing to be bound by theory, in general, the more stages employed, the closer conditions approach ideal plug flow. Materials of different density such as gases, solids or immiscible liquids may travel at different axial velocities or in the opposing axial direction. Good residence time control is preferred and refers to discharging material having a narrow residence time distribution. Brief Description of Figures Some examples of the present disclosure will now be described with reference to the figures, in which: Figure 1 is an external view of an example continuous flow apparatus; Figure 2 illustrates an example static baffle assembly for use in a continuous flow apparatus; Figure 3 illustrates an example axial stirring mechanism for use in a continuous flow apparatus; Figure 4 illustrates a section of an example rotatable baffle assembly for use in a continuous flow apparatus; Figure 5 illustrates an example rotatable baffle assembly mounted on a drive shaft; Figure 6 is an oblique view of a cross-section of continuous flow apparatus; Figure 7 is an exploded view of an example continuous flow apparatus. In the drawings like reference numerals are used to indicate like elements. Specific Description The apparatus and systems described below are configured to provide plug flow within a single containment vessel, e.g. as opposed to stirred tanks coupled in series with interconnecting transfer channels. Process materials may pass through the apparatus described below by the action of pumps or pressure differentials created across the system. Flow rates may be controlled by pumps, flow control valves or system pressure drop. Immiscible materials of different density can be added at opposing ends of the system body for counter current flow. The apparatus is used for continuous operations which require plug flow in combination with radial mixing. The apparatus is scalable and can maintain radial mixing, plug flow and heating or cooling with a large system body diameter, e.g. a diameter greater than 100 millimetres. The uses of the apparatus described include but are not limited to service as a continuous reactor, continuous crystalliser, and continuous extractor. The apparatus may also be used for continuous heating or cooling where controlled residence time is required. Figure 1 is an external view of a continuous flow system, specifically a continuous flow apparatus for effecting chemical and / or physical change to fluid process materials. The system comprises drive system 1 which includes a seal or magnetic coupling configured to rotate the stirrer shaft 11 in one direction. A first end flange 2 seals the system body 3 at one axial end and preferably provides support for the drive system 1. The system body 3 is a sealed rigid tube, preferably circular in profile with a preferred length of between two and ten times the internal diameter. The angle of the system body 3 is oriented according to need. One or more heating / cooling jackets or sleeves 4 may surround the system body with connections to allow the passage of heat transfer fluid. The second end flange 5 seals the system at the opposing axial end of the system body 3 and preferably supports the static assembly. The end flanges 2 and 5 have connections for process materials to flow into or out of the system. Wall penetrations in the tube 3 may also be used. Figure 2 shows a static baffle assembly which may be used in the continuous flow system of Figure 1. One or more static axial baffles 9 lie in the axial plane, and are arranged a shorter radial distance from the central longitudinal axis of the tube 3 than the swept path of the rotating stirrer blades. These baffles 9 promote radial mixing and are preferably straight in the axial plane to minimise unwanted axial f low effects. The static axial baffles 9 extend the plug flow length less clearance needed for stirrer rotation. Two or more static radial baffles 10 break the system into stages and reduce axial dispersion between stages. The radial baffles 10 may minimise the impact of turbulence by limiting turbulence within stage volumes. The static axial and radial baffles may be locked together by thermal contraction and are preferably slide mounted on a static assembly support shaft 8. Other assembly methods may be used. Figure 3 shows an example axial stirrer. The stirrer comprises a central shaft 11 that is coupled to the stirrer drive system / mechanism 1. The stirrer blade support 12 connects the central shaft 11 to the stirrer blades 13. One or more axial stirrer blades 13 are configured rotate at the periphery of the tube, upon actuation of the drive system, to generate tangential f low and extend the plug flow length less clearance needed for rotation. The stirrer blades 13 are preferably straight in axial plane to minimise unwanted axial flow. The preferred cross-sectional profile of the stirrer blade 13 is circular. Figure 4 shows a section of a rotatable baffle assembly. The rotatable baffle assembly comprises two or more radial baffles 14. The rotatable radial baffles 14 are flat ring- shaped and mounted on the stirrer blades 13. The rotatable radial baffles 14 in the tube each extend across a radial distance between the static radial baffles 10 and the system tube wall 3. A radial clearance is provided between each rotating radial baffle 14 and each of the tube wall 3 and the static baffles 10 to allow for rotation and material passage across the baffles (see also Fig. 6). The rotating radial baffles 14 can be fabricated in metal or non-metal. Glass filled PTFE is preferred for the rotating baffles 14 when used with system bodies (tubes) 3 that are lined with glass or fluoropolymers. Different methods can be used to fix the rotating radial baffles. However, sleeves or rings 15 on the stirrer blades 13 are preferred, as are shown in Figure 4. Different f ixing options can be used. Locking by thermal contraction is preferred. Circular rings are preferred. The locking rings can be made from different materials, although tantalum is preferred when used in system bodies that are lined with glass or fluoropolymers. Figure 5 illustrates a rotatable assembly comprising rotatable radial baffles 14, such as that shown in Figure 4, mounted on a drive shaft which forms part of a drive system 1. A stabilising ring 16 can be used to support the stirrer blades 13, and may be mounted on to the stirrer blades 13 by thermal contraction or other methods. Figure 6 shows a cross section of the system body (tube) 3. As shown, the system has an inner clearance 17 between the outer edge of the static radial baffles and the inner edge of the rotatable radial baffles. The system also has an outer clearance 18 between the outer edge of the rotatable radial baffles and the inner edge of the tube wall. The inner clearance 17 and outer clearance 18 allow the static and rotatable assemblies to be inserted or removed independently at opposing ends of the system body 3. Passages for axial f low across radial baffles also exist due to the inner 17 and outer 18 clearances in radial plane. Channels can also be provided in the axial plane by offsetting the axial position of the static radial baffle 10 with respect to the rotatable radial baffle 14. Additionally, the radial baffles can be perforated or mesh form. Small channel dimensions may reduce turbulence and may open area across the baffles, contributing to reduced back mixing between stages which is desirable. For practical purposes however, channel clearances may need to take account of stirrer blade movement, solids if present, pressure drop and bi-directional flow where used. The degree of channel oversizing required will be determined by the mechanical design and nature of use. Figure 7 is an exploded view of a continuous flow apparatus such as the apparatus of Fig. 1. The apparatus comprises comprising the static baffle assembly 7 and the rotatable baffle assembly 6 and shows independent insertion or withdrawal of the rotatable assembly 6 and the static assembly 7 from the opposing ends of the system body 3. In this apparatus, the combination of axial stirrer blades with axial baffles minimises unwanted axial flow. The radial baffles may minimise the impact of turbulence by limiting it within stage volumes. The system employs 3 or more stages but 5 or more is preferred with 9 or greater even more preferred. The apparatus includes one or more inlets for entry of the process fluid into the tube 3, proximal to a first end of the tube body 3. The apparatus also includes one or more outlets for discharging of the fluid from the tube 3, proximal to a second end of the tube body 3, as described above with reference to figure 1. For example, inlet and outlet flanges may be provided as described above. With reference to Figures 6 and 7, the system body 3 is a tube inside which are internal axial stirrer blades 13 which are configured to rotate at the periphery of the tube thereby generating tangential f low in the fluid. Static axial baffles 9 lie inside the swept path of the stirrer blades diverting tangential f low to generate radial mixing. Static radial baffles 10 lie inside the swept path of the stirrer blades to break the tube into stages to reduce axial dispersion. Rotatable radial baffles 14 substantially cover the radial area between the static radial baffles and the tube walls to further reduce axial dispersion. Inner clearance 17 and outer clearance 18 allow the rotatable elements and static baffles to be removed independently from opposing ends of the system tube 3. The static axial baffles 9 and static radial baffles 10 may be supported by a static assembly support shaft 8. Rotatable radial baffles 14 may be fixed to the stirrer blades with locking rings 15. Feed materials enter the tube 3 at one end of the axial plane and pass through with plug flow. Processed material discharges at the opposing axial end. One or more external jackets / sleeves (not shown in this figure) are used, e.g. by surrounding the tube, to add or remove heat as required. Intermediate addition or take off points, and instruments can be located in any axial position within the system tube 3 using pipes or probes inserted into the second end flange 5 which pass up through apertures in the static radial baffles. It will be appreciated from the discussion above that the examples shown in the figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein. As will be appreciated by the skilled reader in the context of the present disclosure, each of the examples described herein may be implemented in a variety of different ways. Any feature of any aspects of the disclosure may be combined with any of the other aspects of the disclosure. For example, method aspects may be combined with apparatus aspects, and features described with reference to the operation of particular elements of apparatus may be provided in methods which do not use those particular types of apparatus. In addition, each of the features of each of the examples is intended to be separable from the features which it is described in combination with, unless it is expressly stated that some other feature is essential to its operation. Each of these separable features may of course be combined with any of the other features of the examples in which it is described, or with any of the other features or combination of features of any of the other examples described herein. Furthermore, equivalents and modifications not described above may also be employed without departing from the invention. Certain features of the methods described herein may be implemented in hardware, and one or more functions of the apparatus may be implemented in method steps. It will also be appreciated in the context of the present disclosure that the methods described herein need not be performed in the order in which they are described, nor necessarily in the order in which they are depicted in the drawings. Accordingly, aspects of the disclosure which are described with reference to products or apparatus are also intended to be implemented as methods and vice versa. Other examples and variations of the disclosure will be apparent to the skilled addressee in the context of the present disclosure.

Claims

Claims 1. A continuous flow apparatus for effecting chemical and / or physical change to fluid process materials, wherein the continuous flow apparatus comprises: a tube arranged to provide a flow path for the fluid process materials; a mixing assembly arranged in the tube, the mixing assembly comprising: a stirring mechanism comprising at least one axial stirrer blade configured to generate tangential f low of the fluid; a static baffle assembly arranged to inhibit axial dispersion of f luid in the tube; one or more rotatable baffles configured to rotate about the longitudinal axis of the tube, and to inhibit axial dispersion of the fluid in the tube.

2. The continuous flow apparatus of claim 1, wherein the static baffle assembly is arranged radially inwards of the at least one stirrer blade.

3. The continuous flow apparatus of claim 1 or 2, wherein the at least one stirrer blade is rotatable to define a swept path, wherein the swept path of the at least one stirrer blade is within or equal to the radial extent of the at least one rotatable baffle.

4. The continuous flow apparatus of any preceding claim, wherein the at least one rotatable baffle comprises at least one ring-shaped baffle configured to rotate about the longitudinal axis of the tube.

5. The continuous flow apparatus of any preceding claim, further comprising at least one locking element configured to inhibit axial movement of the at least one rotatable baffle relative to the stirrer blade.

6. The continuous flow apparatus of claim 5, wherein the at least one locking element comprises a ring surrounding a portion of the at least one stirrer blade.

7. The continuous flow apparatus of claim 5 or 6, wherein the at least one locking element comprises tantalum.

8. The continuous flow apparatus of any of claims 5 to 7, wherein the locking element is f ixed to the at least one stirrer blade.

9. The continuous flow apparatus of any of claims 5 to 8, wherein the at least one locking element comprises first and second axially spaced locking elements, wherein the first locking element is arranged adjacent a first side of the at least one rotatable baffle, and the second locking element arranged adjacent a second side of the at least one rotatable baffle, opposite the first side.

10. The continuous flow apparatus of any preceding claim wherein the rotatable baffles are made of glass filled Polytetrafluoroethylene (PTFE).

11. The continuous flow apparatus of any preceding claim, wherein the static baffle assembly comprises: at least one axial baffle configured to divert tangential f low of the fluid; and at least one radial baffle configured to inhibit axial dispersion of the fluid.

12. The continuous flow apparatus of claim 11, wherein the static baffle assembly comprises at least two radial baffles.

13. The continuous flow apparatus of any preceding claim, further comprising an inlet connection for feeding the process material f luid into the tube, and an outlet connection for discharging the process material f luid from the tube.

14. The continuous flow apparatus of any preceding claim, wherein the continuous flow apparatus is configured to provide radial mixing of the fluid process material under plug flow conditions.

15. The continuous flow apparatus of any preceding claim, wherein the static baffle assembly and the at least one rotatable baffle are each independently removable from the tube.

16. The continuous flow apparatus of claim 15, wherein the static baffle assembly is independently removable from a first axial end of the tube, and the at least one rotatablebaffle is independently removable from a second axial end of the tube, opposite the first end.

17. The continuous flow apparatus of any preceding claim, further comprising a sleeve surrounding the tube, wherein the sleeve is configured to heat or cool the process fluid.

18. A method of continuous processing of f luid process materials under plug flow conditions, the method comprising: feeding a fluid process material into a tube; mixing the fluid process material; and discharging the fluid process material from the tube; wherein mixing the fluid process material comprises rotating an axial stirrer blade and at least one rotatable baffle inside the tube around a static baffle assembly that is arranged radially inwards of the stirrer blade and the at least one rotatable baffle.

19. The method of claim 18, wherein the at least one rotatable baffle comprises at least one ring- or disc-shaped radial baffle configured to rotate about the longitudinal axis of the tube.

20. The method of claim 18 or 19, wherein the axial position of the at least one rotatable baffle is f ixed relative to the stirrer blade.

21. The method of any of claims 18 to 20, wherein the method of continuous processing comprises a continuous chemical reaction.

22. A method of assembling a continuous flow apparatus for effecting chemical and / or physical change to fluid process materials, the method comprising: coupling at least one stirrer blade to a drive system, for rotation of the stirrer blade; mounting at least one rotatable radial baffle onto the stirrer blade; inserting the rotatable baffle and the stirrer blade into a tube, wherein the tube comprises an inlet connection for feeding the process material f luid into the tube, and anoutlet connection for discharging the process material f luid from the tube.

23. The method of claim 22 , wherein mounting at least one rotatable radial baffle onto the stirrer blade, comprises mounting a plurality of axially spaced rotatable radial baffles onto the stirrer blade.

24. The method of claim 22 or 23, wherein mounting the rotatable radial baffle onto the stirrer blade comprises fixing the axial position of the rotatable radial baffle relative to the stirrer blade.

25. The method of claim 24, comprising fixing a locking element onto the at least one stirrer blade.

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