Dynamic mixer

Abstract

A dynamic mixer comprising two mixing parts which are rotatable relative to each other about a predetermined axis of rotation, each of said mixing parts having a mixing face, between which is defined a flow path which extends between an inlet and an outlet, each of said mixing faces comprising a series of annular steps centered on the predetermined axis of rotation, having a plurality of offset and overlapping cavities formed therein, such that material moving between the mixing faces of the two mixing parts from the inlet to the outlet is transferable between overlapping cavities.

Claims

1. A stepped conical geometry dynamic mixer comprising: two mixing parts which are rotatable relative to each other about a predetermined axis of rotation, each of said mixing parts having a generally conical mixing face, between which is defined a flow path which extends between an inlet for material to be mixed and an outlet, each of said generally conical mixing faces comprising a series of annular steps centred on the predetermined axis of rotation and defining said generally conical mixing faces, said series of annular steps having a plurality of cavities formed therein, said cavities defining flow passages bridging adjacent steps on each of the two mixing parts, each of said generally conical mixing faces being mutually positionable such that the steps of one mixing part extend towards recesses formed between the steps of the other mixing part, whereby cavities present in one generally conical mixing face are offset relative to, and overlap with, cavities present in the other generally conical mixing face in an axial direction or a transverse direction, such that material moving between the generally conical mixing faces of the two mixing parts from the inlet to the outlet is transferrable between overlapping cavities, wherein at least one step of one of the mixing parts and at least one adjacent step of the other of the mixing parts extends further in the axial direction than in the transverse direction, or vice versa, such that at least one annular mixing zone of substantially uniform volume is provided in between non-overlapping cavities of the two mixing parts, wherein each step is defined by a first surface which is cylindrical and centered on said predetermined axis of rotation and a second surface which is planar and perpendicular to said predetermined axis of rotation, wherein a respective one of said recesses is formed where said first surface meets the second surface of an adjacent step, wherein said first surface extends further in the axial direction than the second surface in the transverse direction or vice versa.

2. The mixer as claimed in claim 1 wherein each step of the series of annular steps comprises a pair of substantially orthogonal surfaces.

3. The mixer as claimed in claim 2 wherein extension of the at least one step of one of the mixing parts and extension of the at least one adjacent step of the other of the mixing parts results in a pair of mutually opposed, continuous, annular surfaces forming the at least one annular mixing zone.

4. The mixer as claimed in claim 3 wherein one of the surfaces extends substantially parallel to the predetermined axis of rotation, and one of the surfaces extends substantially transversely to said axis of rotation.

5. The mixer as claimed in claim 3 wherein the pair of mutually opposed annular surfaces both extend substantially parallel to the predetermined axis of rotation.

6. The mixer as claimed in claim 5 wherein one of the surfaces of the pair of mutually opposed annular surfaces extends at an acute angle to the predetermined axis of rotation.

7. The mixer as claimed in claim 3 wherein the pair of mutually opposed annular surfaces both extend substantially transversely to the predetermined axis of rotation.

8. The mixer as claimed in claim 7 wherein one of the surfaces of the pair of mutually opposed annular surfaces extends at an acute angle transversely to the predetermined axis of rotation.

9. The mixer as claimed in claims 3 wherein at least one of the surfaces of the pair of mutually opposed annular surfaces is provided with a projection which projects towards to the other of the surfaces in the pair.

10. The mixer as claimed in claim 9 wherein the projection is in the form of an annular prism.

11. The mixer as claimed in claim 1 wherein an array of circumferentially spaced cavities is formed in a step of the series of annular steps.

12. The mixer as claimed in claim 11 wherein at least one of the cavities is branched such that a flow of material entering the cavity is divided into separate flow paths, or separate flows of material entering the cavity are combined into a single flow path.

13. The mixer as claimed in claim 11 wherein adjacent steps of the series of annular steps in a mixing part comprise different numbers of cavities.

14. The mixer as claimed in claim 11 wherein adjacent steps of the series of annular steps in a mixing part comprise different sizes of cavities.

15. The mixer as claimed in claim 1 wherein one mixing face is defined by an inner surface of a hollow outer mixing part and the other mixing face is defined by an outer surface of an inner mixing part.

16. The mixer as claimed in claim 1 wherein the inlet is defined so as to extend substantially parallel to the predetermined axis of rotation, whilst the outlet is defined so as to extend substantially transversely to said axis, or vice versa.

17. The mixer as claimed in claim 1 wherein each of the inlet and outlet are defined so as to extend substantially transversely to the predetermined axis of rotation.

18. The mixer as claimed in claim 1, wherein the cavities are formed on edges of the steps.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To enable a better understanding, the present invention will now be more particularly described, by way of non-limiting example only, with reference to the schematic drawings (not to scale), in which:

(2) FIG. 1 is an axial section through a mixer according to a first embodiment of the present invention;

(3) FIG. 2 is an end view of a mixing part of the mixer of FIG. 1;

(4) FIG. 3 is an axial section through an alternative mixer according to the first embodiment of the present invention;

(5) FIG. 4 is an end view of a mixing part of the mixer of FIG. 3;

(6) FIG. 5 is an axial section through a mixer according to a second embodiment of the present invention;

(7) FIG. 6 is an end view of a mixing part of the mixer of FIG. 5;

(8) FIG. 7 is an axial section through an alternative mixer according to the first embodiment of the present invention;

(9) FIG. 8 is an end view of a mixing part of the mixer of FIG. 7;

(10) FIG. 9 is a partial axial section through a mixer according to a fourth embodiment of the present invention;

(11) FIG. 10 is a partial axial section through a mixer according to a fifth embodiment of the present invention; and

(12) FIG. 11 is an axial section through a mixer according to a sixth embodiment of the invention.

DETAILED DESCRIPTION

(13) Referring to FIG. 1, the illustrated dynamic mixer 10 comprises two mixing parts in the form of an inner rotor 11 and an outer stator 12 which are rotatable relative to each other, in this case rotor 11 being rotatable relative to static stator 12, about a predetermined axis of rotation R. Rotor 11 is mounted on a shaft 13, which is supported in bearings 14 within a housing 15. Stator 12 is mounted on housing 15. Stator 12 defines a mixer inlet 16 and a mixer outlet 17.

(14) A series of four annular steps 18 extend along the generally conical inner mixing surface of stator 12, each step 18 being defined by a first surface 18a which is cylindrical and centred on axis R (thus being an axial surface) and a second surface 18b which is planar and perpendicular to axis R (thus being a transverse surface). A recess 19 is formed where the first surface 18a of one step 18 meets the second surface 18b of the adjacent step 18. Each of first surfaces 18a clearly extends further in the axial direction than in the transverse direction, i.e. the direction in which second surfaces 18b extend.

(15) Rotor 11 similarly supports four annular steps 20 which extend along the generally conical outer mixing surface of rotor 11, each step 20 being defined by a first surface 20a which is cylindrical and centred on axis R (thus being an axial surface) and a second surface 20b which is planar and perpendicular to axis R (thus being a transverse surface). A recess 21 is formed where the first surface 20a of one step 20 meets the second surface 20b of the adjacent step 20. Again each of first surfaces 20a clearly extends further in the axial direction than in the transverse direction, i.e. the direction in which second surfaces 20b extend.

(16) As shown in FIG. 1, with rotor 11 located within the hollow of stator 12, first surfaces 18a of stator are in a closely spaced relationship with first surfaces 20a of rotor, whilst second surfaces 18b of stator are in a closely spaced relationship with second surfaces 20b of rotor, with the closely spaced relationship defining a small gap 22 (for example of the order of 50 m) therebetween. Typically, the higher the viscosity of the material to be processed, the larger the gap between the surfaces will be, and vice versa.

(17) Clearly gap 22 is not linear as it extends from inlet 16 to outlet 17 as it traces the stepped conical shapes of each of rotor 11 and stator 12. Thus material (not shown) passing from inlet 16 to outlet 17 is unable to follow a linear path.

(18) A plurality of cavities 23 is provided in each of the annular steps 18 of stator 12, and a plurality of cavities 24 is provided in each of the annular steps 20 of rotor 11, the configuration of which in rotor 11 is best seen in FIG. 2 which will be described in more detail below. Notwithstanding, the mutual configurations of cavities 23, 24 on each of stator 12 and rotor 11 are such as to be offset but overlapping in the axial direction relative to one another to facilitate movement of material from inlet 16 to outlet 17.

(19) Importantly, in the axial direction between non-overlapping cavities 23 of stator 12 and cavities 24 of rotor 11, annular mixing zones 25 are provided between the axially extended first surfaces 18a, 20a of each of stator 12 and rotor 11 respectively. Gap 22 in the region of annular mixing zones 25 remains constant, thus providing regions of substantially uniform volume in which high extensional and/or shear stressing of the material (not shown) being mixed will be imparted. Of course, it is within the scope of the present invention that gap 22 could be varied in successive annular mixing zones 25.

(20) Referring to FIG. 2, transverse second surfaces 20b of annular steps 20 of rotor 11 are shown. In each of these planar surfaces 20b, an equally spaced array of cavities 24 is provided. In the innermost annular step 20, five cavities 24a are formed. In the next annular step (having a larger diameter in accordance with the generally conical shape of rotor 11), eight cavities 24b are formed. In the next annular step (having a yet larger diameter), eleven cavities 24c are formed. Finally, in the outermost annular step (having the largest diameter), fourteen cavities 24d are formed. Each of the cavities 24 is part-spherical and arranged such that the periphery of each (apart from those located in the innermost annular step) extends across the full width of the surface 20b, but only part way along the width of axial first surfaces 20a, which are extended in the axial direction to provide annular mixing zone 25.

(21) Referring to FIGS. 3 and 4, dynamic mixer 30 is similar to dynamic mixer 10 shown in FIGS. 1 and 2, and for this reason, like reference numerals (however increased by a value of twenty) will be accorded to like features. It may be assumed that the features shown in FIGS. 3 and 4 are configured the same and perform the same purpose as those corresponding features shown in FIGS. 1 and 2, unless modified as described in the following paragraphs.

(22) In the series of four annular steps 38 which extends along the generally conical inner mixing surface of stator 32, each of second surfaces 38b clearly extend further in the transverse direction than in the axial direction, i.e. the direction in which first surfaces 38a extend. Similarly, in the series of four annular steps 40 which extends along the generally conical mixing surface of rotor 31, again each of second surfaces 40b clearly extend further in the transverse direction than in the axial direction, i.e. the direction in which first surfaces 40a extend.

(23) Of the plurality of cavities 43 provided in each of the annular steps 38 of stator 32, and the plurality of cavities 44 provided in each of the annular steps 40 of rotor 31, the mutual configurations of cavities 43, 44 on each of stator 32 and rotor 31 are such as to be offset but overlapping in the transverse direction relative to one another to facilitate movement of material from inlet 36 to outlet 37.

(24) Importantly, in the transverse direction between non-overlapping cavities 43 of stator 32 and cavities 44 of rotor 31, annular mixing zones 45 are provided between the transversely extended second surfaces 38b, 40b of each of stator 32 and rotor 31 respectively. Gap 42 in the region of annular mixing zones 45 remains constant, thus providing regions of substantially uniform volume in which high extensional and/or shear stressing of the material (not shown) being mixed will be imparted.

(25) Referring to FIG. 4, transverse second surfaces 40b of annular steps 40 of rotor 31 are shown. In each of these planar surfaces 40b, an equally spaced array of cavities 44 is provided. In the innermost annular step 40, four cavities 44a are formed. In the next annular step (having a larger diameter in accordance with the generally conical shape of rotor 31), twelve cavities 44b are formed. In the next annular step (having a yet larger diameter), twenty cavities 44c are formed. Finally, in the outermost annular step (having the largest diameter), twenty eight cavities 44d are formed. Each of the cavities 44 is part-spherical and arranged such that the periphery of each (apart from those located in the innermost annular step) extends across the full width of axial first surfaces 40a, but only part way along the width of transverse second surfaces 40b, which are extended in the transverse direction to provide annular mixing zones 45 which are illustrated in dotted-line outline in FIG. 4.

(26) FIGS. 2 and 4 show the relative disposition of the various cavities 24, 44 in the two rotors 11, 31 respectively. Given that adjacent annular steps 20, 40 define differing numbers of cavities 24, 44, the paths of least resistance through mixer 10, 30 vary continuously as rotor 11, 31 turns within stator 12, 32. Material to be mixed thus follows a complex path which ensures excellent distributive and dispersive mixing, whilst also passing through at least one annular mixing zone 25, 45 where it is subjected to high extensional and/or shear stresses in addition.

(27) Referring to FIGS. 5 and 6, dynamic mixer 50 is similar to dynamic mixer 10 shown in FIGS. 1 and 2, and for this reason, like reference numerals (however increased by a value of forty) will be accorded to like features. It may be assumed that the features shown in FIGS. 5 and 6 are configured the same and perform the same purpose as those corresponding features shown in FIGS. 1 and 2, unless modified as described in the following paragraphs.

(28) In the series of four annular steps 60 which extend along the generally conical inner mixing surface of rotor 51, where each step 60 is defined by a first surface 60a which is cylindrical and centred on axis R (thus being an axial surface) and a second surface 60b which is planar and perpendicular to axis R (thus being a transverse surface), and where each of first surfaces 60a clearly extend further in the axial direction than in the transverse direction, i.e. the direction in which second surfaces 60b extend, an annular projection 66 is provided in the extended portion of each of first surfaces 60a.

(29) Annular projection 66 has, for example in this particular embodiment, a triangular prismatic cross-section (which could also be truncated) which extends from surface 60a towards the extended portion of the corresponding first surface 58a of stator 52. Thus the gap 62 which exists by virtue of the closely spaced relationship between the first surfaces 58a of stator 52 with first surfaces 60a of rotor 51, and between the second surfaces 58b of stator 52 and second surfaces 60b of rotor 51, is reduced (e.g. to 10 m or less) by the nip created between the tip of the triangular prismatic cross section of annular projection 66 and first surface 58a of stator so as to further increase the degree of stress that may be imparted to the material being mixed.

(30) A further difference between the embodiments of the invention shown in FIGS. 1 to 4 and the current embodiment shown in FIGS. 5 and 6 lies in the fact that in the embodiment of FIGS. 1 to 4, the surfaces 18a, 18b and 38a, 38b of stator 12, 32 are mutually perpendicular. As shown in FIG. 5, other arrangements are possible however, for example where the extended portion of first surface 58a of stator 52 which forms annular mixing zone 65 is generally frusto-conical, with the cones being centred on axis R. With such a configuration, relative axial displacement between rotor 51 and stator 52 changes spacing/gap 62 between first surfaces 60a, 58a respectively, as well as the spacing between second surfaces 60b, 58b respectively and, most importantly, between the frusto-conical surface 58a and the tip of projection 66.

(31) Referring to FIGS. 7 and 8, dynamic mixer 70 is similar to dynamic mixer 30 shown in FIGS. 3 and 4, and for this reason, like reference numerals (however increased by a value of forty) will be accorded to like features. It may be assumed that the features shown in FIGS. 7 and 8 are configured the same and perform the same purpose as those corresponding features shown in FIGS. 3 and 4, unless modified as described in the following paragraphs.

(32) In the series of four annular steps 80 which extend along the generally conical inner mixing surface of rotor 71, where each step 80 is defined by a first surface 80a which is cylindrical and centred on axis R (thus being an axial surface) and a second surface 80b which is planar and perpendicular to axis R (thus being a transverse surface), and where each of second surfaces 80b clearly extend further in the transverse direction than in the axial direction, i.e. the direction in which first surfaces 80a extend, an annular projection 86 is provided in the extended portion of each of second surfaces 80b.

(33) Annular projection 86 has, for example in this embodiment, a triangular prismatic cross-section (which could also be truncated) which extends from second surface 80b towards the extended portion of the corresponding second surface 78b of stator 72. Thus the gap 82 which exists by virtue of the closely spaced relationship between the first surfaces 78a of stator 72 with first surfaces 80a of rotor 71, and between the second surfaces 78b of stator 72 and second surfaces 80b of rotor 71, is reduced (e.g. to 10 m or less) by the nip created between the tip of the triangular prismatic cross section of annular projection 86 and second surface 78b of stator so as to further increase the degree of stress that may be imparted to the material being mixed.

(34) Although not shown in FIG. 7, a further possible difference between the embodiments of the invention shown in FIGS. 1 to 4 and the current embodiment shown in FIGS. 7 and 8 would be to provide the extended portion of second surface 78b of stator 72 which forms annular mixing zone 85 in generally frusto-conical form, with the cones being centred on axis R. With such a configuration, relative axial displacement between rotor 71 and stator 72 would change spacing/gap 82 between second surfaces 80b, 78b respectively, as well as the spacing between first surfaces 80a, 78a respectively.

(35) Of course, with regards to the relative locations of annular projections 66, 86 in the embodiments shown in FIGS. 5, 6, 7 and 8, it is possible that said projections could instead, or in addition, be provided on the other mixing part, i.e. if on the rotor, be provided on the stator in addition or in the alternative, or if on the stator, be provided on the rotor in addition or in the alternative.

(36) Turning to the embodiment shown in FIG. 9, dynamic mixer 90 is very similar to dynamic mixer 50 shown in FIGS. 5 and 6, and for this reason, like reference numerals (however increased by a value of forty) will be accorded to like features. It may be assumed that the features shown in FIG. 9 are configured the same and perform the same purpose as those corresponding features shown in FIGS. 5 and 6, unless modified as described in the following paragraphs.

(37) Towards the end of stator 92 in which inlet 96 is provided, but perpendicularly thereto, an additional inlet 107 is provided through which a second or further stream of material to be mixed (not shown) may be incorporated into the material to be mixed (not shown) that has been introduced into mixer 90 via inlet 96. As a consequence, the primary cavities 108 provided in the first annular step 98 of stator 92 and the primary cavities 109 provided in the first annular step 100 of rotor 91 are elongate as compared to the remaining cavities in each; this is done so as to provide an increased volume in which turbulent flow conditions may be achieved when each of cavities 108, 109 overlap, with rotation of rotor 91 within stator 92 causing an initial mixing of materials through inlet 96 and additional inlet 107. By providing additional inlet 107 proximal to inlet 96, the second or further stream of material to be mixed is introduced early in the mixing process, which ensures excellent distributive and dispersive mixing via the turbulent mixing zones created in overlapping cavities 108, 109, prior to flow through mixer 90 to annular mixing zones 105 where high extensional and/or shear stresses are additionally imparted.

(38) Turning to the embodiment shown in FIG. 10, dynamic mixer 120 is very similar to dynamic mixer 90 shown in FIG. 9, and for this reason, like reference numerals (however increased by a value of thirty) will be accorded to like features. It may be assumed that the features shown in FIG. 10 are configured the same and perform the same purpose as those corresponding features shown in FIG. 9, unless modified as described in the following paragraphs.

(39) Towards the end of stator 122 in which inlet 126 is provided, but perpendicularly thereto, a first additional inlet 137 is provided through which a second or further stream of material to be mixed (not shown) may be incorporated into the material to be mixed (not shown) that has been introduced into mixer 120 via inlet 126. As a consequence, the primary cavities 138 provided in the first annular step 128 of stator 122 and the primary cavities 139 provided in the first annular step 130 of rotor 121 are elongate as compared to the remaining cavities in each. Provision of elongate cavities is optional, but more preferred with greater flow rates.

(40) Furthermore, approximately mid-way along the axial length of stator 122, a second additional inlet 140 is provided through which a third or yet further stream of material to be mixed (not shown) may be incorporated into the material to be mixed that has been introduced into mixer 120 via inlet 126 and optionally also via first additional inlet 137. As a consequence of the presence of second additional inlet 140, the corresponding cavity 141 in stator 122 is made to be elongate (in the same manner as cavity 138) and the corresponding first surface 128a of rotor 121 is yet further extended so as to be co-extensive with elongate cavity 141. Provision of elongate cavity 141 is again done so as to provide an increased volume in which turbulent flow conditions may be achieved on mixing of the third or yet further stream of material through second additional inlet 140 with part-mixed material provided earlier in the flow path via inlet 126 and optionally also first additional inlet 137. By providing second additional inlet 140 approximately mid-way along stator 122 in the axial direction, a further control mechanism is provided to determine the form and timing of introduction of further material into the material flow path.

(41) Turning finally to FIG. 11, the illustrated dynamic mixer 150 comprises two mixing parts in the form of an outer rotor 151 and an inner stator 152 which are rotatable relative to each other, in this case rotor 151 being rotatable relative to static stator 152, about a predetermined axis of rotation R. Rotor 151 is mounted on a shaft 153, which is supported in bearings 154 within a housing 155. Stator 152 is mounted on housing 155. Stator 152 defines a mixer inlet 516 and two mixer outlets 157.

(42) Rotor 151 is substantially symmetrical about axis of rotation R. Rotor 151 is also substantially symmetrical about an axis P that is perpendicular to axis R, resulting in a double-barrelled rotor 151 which effectively corresponds to rotor 31 shown in FIGS. 3 and 4 (labelled A) conjoined to its mirror image (labelled B) about axis R. Stator 152 is configured similarly so as to comprise part C (which effectively corresponds to stator 32 shown in FIG. 3) conjoined to its mirror image (labelled D).

(43) Each of stator parts C and D comprises a series of four annular steps 158 which extend along their generally conical inner mixing surfaces, each step 158 being defined by a first surface 158a which is cylindrical and centred on axis R (thus being an axial surface) and a second surface 158b which is planar and perpendicular to axis R (thus being a transverse surface). A recess 159 is formed where the first surface 158a of one step 158 meets the second surface 158b of the adjacent step 158. Each of second surfaces 158b clearly extends further in the transverse direction than in the axial direction, i.e. the direction in which first surfaces 158a extend.

(44) Each of rotor parts A and B similarly support four annular steps 160 which extend along their generally conical outer mixing surfaces, each step 160 being defined by a first surface 160a which is cylindrical and centred on axis R (thus being an axial surface) and a second surface 160b which is planar and perpendicular to axis R (thus being a transverse surface). A recess 161 is formed where the first surface 160a of one step 160 meets the second surface 160b of the adjacent step 160. Again each of second surfaces 160b clearly extends further in the transverse direction than in the axial direction, i.e. the direction in which first surfaces 160a extend.

(45) As shown in FIG. 1 with stator 152 located within the hollow of double-barrelled rotor 151, first surfaces 158a of stator 152 are in a closely spaced relationship with first surfaces 160a of rotor 151, whilst second surfaces 158b of stator 152 are in a closely spaced relationship with second surfaces 160b of rotor 151, with the closely spaced relationship defining a small gap 162 (for example of the order of 50 m) therebetween.

(46) Clearly gap 162 is not linear as it extends from inlets 156 to outlets 157 as it traces the stepped conical shapes of each of the parts A and B of rotor 151 and corresponding parts C and D of stator 152. Thus material (not shown) passing from inlet 156 to outlets 157 is unable to follow a linear path.

(47) A plurality of cavities 163 is provided in each of the annular steps 158 of stator 152, and a plurality of cavities 164 is provided in each of the annular steps 160 of rotor 151. The mutual configurations of cavities 163, 164 on each of stator 152 and rotor 151 are such as to be offset but overlapping in the transverse direction relative to one another to facilitate movement of material from inlet 156 to outlets 157.

(48) Importantly, in the transverse direction between non-overlapping cavities 163 of stator 152 and cavities 164 of rotor 151, annular mixing zones 165 are provided between the transversely extended second surfaces 158a, 160a of each of stator 152 and rotor 151 respectively. Gap 162 in the region of annular mixing zones 165 remains constant, thus providing regions of substantially uniform volume in which high extensional and/or shear stressing of the material (not shown) being mixed will be imparted.

(49) Furthermore, it should be noted that gap 162 is narrowed from an initial volume in the form of a mixing annulus 166 which opens from inlet 156 to outlets 157. Material to be mixed (not shown) introduced into inlet 156 is rotated around rotor shaft 153 in mixing annulus 166 (which is co-extensive in the axial direction with rotor shaft 153 in its sections between parts A and B) prior to being compelled upwardly and outwardly along the stepped conical paths defined by annular steps 158, 160 to each of outlets 157. The benefit of this configuration is that the axial separating forces that arise in annular mixing zones 165 are balanced about the axis of symmetry P. This reduces or eliminates the resultant axial loads on bearings 154. If so desired, rotor 151 is capable of centring itself axially between stators 152.

(50) Of course, although not shown in the embodiment in FIG. 11, any one or more of the modifications described with respect to any of FIGS. 5 to 10, such as the presence of projections, may be incorporated into the embodiment of FIG. 11 so as to achieve the additional means of control previously described.

(51) Furthermore, geometrical asymmetries (between parts A and C and between parts B and D) about R can produce different flow regimes in the two sides while providing some measure of hydraulic balancing. For instance, narrower gaps between A and C will result in a higher specific mixing energy than that being applied between B and D. Such differences can be exploited to achieve different material properties, such as emulsion droplet size, between the two exiting flow streams: these can then be blended to yield a bimodal particle size distribution from a single machine.

(52) Symmetries may also be achieved in other ways, for instance cavities 163, 164 could be located outboard of the axis of outlets 157.

(53) With all of the embodiments of the invention herein described, each of the rotor and/or the stator may be equipped with fluid passages and/or surfaces for heating and/or cooling.

(54) Specific applications to which a dynamic mixer according to any of the aforementioned embodiments of the invention may be applied include: 1. The formation of oil-water emulsions. For example, within the petrochemical industry, applications include: (i) formation of oil-in-water (O/W) emulsions for the purpose of viscosity reduction of heavy-fraction oils; (ii) water-in-oil (W/O) emulsions for the purposes of cost reduction and improved emission control; and (iii) oil-reagent mixing for the purpose of enhancing reaction rates. 2. The size reduction of solid, semi-solid and/or high-viscosity particles within, and the blending with, low and/or high viscosity fluids. For example, within the food industry, applications include: (i) comminution of sugar crystals; (ii) refining of edible fats; and (iii) comminution of chocolate solids.

(55) Also by way of example, within the polymer industry, applications include the comminution and blending of solid ingredients, such as fillers and reagents, within a base polymer.

(56) The size reduction of solid, semi-solid and/or high-viscosity particles within, and the blending with, low and/or high viscosity fluids may lead to modification of the viscosities of these materials. For example, within the polymer industry, applications include: (i) rupturing of intramolecular linkages, for instance carbon-sulphur bonds; and (ii) solubilisation of previously linked hydrocarbon chains.

(57) Within the food industry, applications include: (i) refining of chocolate; and (ii) conching of chocolate.

(58) Furthermore, the size reduction of solid, semi-solid and/or high-viscosity particles within, and the blending with, low and/or high viscosity fluids may lead to enhancement of reaction rates of materials and material systems.