Mixing apparatus of the CDDM- and/or CTM-type, and its use

Abstract

A distributive and dispersive mixing apparatus comprising two confronting surfaces (1,2) having cavities (3) therein which on relative motion of the surfaces function as a cavity transfer mixer (CTM) or controlled deformation dynamic mixer (CDDM) or both, CHARACTERISED IN THAT the normal separation of the confronting surfaces varies in the direction of bulk flow, so as to define a plurality of regions of successive closer and wider spacing of the confronting surfaces.

Claims

1. A distributive and dispersive mixing apparatus comprising: a material inlet port (4) and a material outlet port (4) having a direction of bulk material flow defined therebetween; and two confronting surfaces (1, 2), each of the confronting surfaces having discrete cavities (3) therein, which on relative motion of the surfaces (1, 2) function as a cavity transfer mixer or controlled deformation dynamic mixer or both, CHARACTERISED IN THAT a normal separation of the two confronting surfaces (1, 2), which is the separation of said surfaces in the absence of said discrete cavities (3), varies in the direction of bulk material flow, so as to define a plurality of regions of successively closer (Y.sup.I, Y.sup.II, Y.sup.III, Y.sup.IV) and wider spacing (X.sup.I, X.sup.II, X.sup.III, X.sup.IV, X.sup.V) of the confronting surfaces (1, 2) in the direction of bulk material flow, the regions of closer spacing (Y.sup.I, Y.sup.II, Y.sup.III, Y.sup.IV) being defined by annular rings and the regions of wider spacing (X.sup.I, X.sup.II, X.sup.III, X.sup.IV, X.sup.V) being defined by annular channels between successive annular rings, wherein a plurality of the discrete cavities (3) are circumferentially disposed in at least one of the annular channels, whereby the separation of said confronting surfaces (1, 2) in the annular channels is greater than the normal separation of the confronting surfaces (1, 2) in adjoining annular rings by a factor of at least 2; and wherein the annular rings are not by passed by flow in and through the discrete cavities (3), such that the apparatus functions as a controlled deformation dynamic mixer.

2. A mixing apparatus according to claim 1 wherein the confronting surfaces (1, 2) comprise generally cylindrical surfaces.

3. A mixing apparatus according to claim 1 wherein the confronting surfaces (1, 2) comprise generally conical surfaces.

4. A mixing apparatus according to claim 1 wherein the confronting surfaces (1, 2) comprise generally disk-like surfaces.

5. A distributive and dispersive mixing apparatus according to claim 1 wherein the separation of the confronting surfaces (1, 2) in the annular channels is greater than the normal separation of the confronting surfaces (1, 2) in adjoining annular rings by a factor of at least 3 to 20.

6. A mixing device apparatus according to claim 1 further comprising at least one cage-like member disposed between the confronting surfaces (1, 2), the surfaces of the cage-like member conforming in profile to the confronting surfaces (1, 2) against which they are respectively disposed.

7. A mixing device apparatus according to claim 1 further comprising regions of axially disposed confronting surfaces (1, 2) which alternate with regions of radially disposed confronting surfaces (1, 2) thereby preventing any leakage flow through the mixer.

Description

(1) In order that the present invention can be better understood it will be described by way of example and with reference to the accompanying figures which relate to devices of modular construction, in which:

(2) FIG. 1: shows an axial section through a relieved rotating cylindrical drum and static co-axial sleeve controlled deformation dynamic mixer (CDDM) according to the invention;

(3) FIG. 2: shows a detailed view of region A in FIG. 1;

(4) FIG. 3: shows an axial section through a relieved rotating cylindrical drum and static co-axial sleeve cavity transfer mixer (CTM) which is according to a less preferred embodiment of the invention;

(5) FIG. 4: shows a detailed view of region A in FIG. 3;

(6) FIG. 5: shows an axial section through a relieved rotating and static disc controlled deformation dynamic mixer (CDDM) according to the invention;

(7) FIG. 6: shows a detailed view of region A in FIG. 5;

(8) FIG. 7: shows an axial section through a relieved rotating and relieved static disc cavity transfer mixer (CTM) according a less preferred embodiment of to the invention;

(9) FIG. 8: shows a detailed view of region A in FIG. 7;

(10) FIG. 9: shows a partial section perspective view of the CDDM of FIG. 1.

(11) FIG. 10: shows a partial section perspective view of the CDDM of FIG. 3.

(12) FIG. 11: shows a perspective view of the static co-axial sleeve of FIG. 1.

(13) FIG. 12: shows a perspective view of the relieved rotating cylindrical drum of FIG. 1.

EXAMPLES

1. Relieved Rotating Cylindrical Drum and Static Co-Axial Sleeve CDDM

(14) FIG. 1 shows a portion of a mixer comprising an inner drum (1) and an outer sleeve (2). Cavities (3) are provided in the drum and the sleeve so that as the drum rotates about its axis (shown dashed), the drum and the sleeve co-operate to form a controlled deformation dynamic mixer (CDDM). Ports (4) are provided for input and output of the process flow. Means for rotating the drum relative to the sleeve and end seals are not shown. Flow of materials within the mixer is from the bottom towards the top.

(15) FIG. 2 provides a more detailed view of the region A in FIG. 1. It can be seen that in regions X.sup.I and X.sup.II the surface of the drum (1) is relieved and the radial spacings of the confronting surfaces of the drum (1) and the sleeve (2) are relatively large as compared with the corresponding radial spacings in regions Y.sup.I and Y.sup.II. In regions X.sup.I and X.sup.II the cavities (3) promote CTM-like distributive mixing while in regions Y.sup.I and Y.sup.II the narrow spacing in the flow path induces extensional flow and CDDM-like dispersive mixing. In this particular embodiment of the mixer the radial spacings in regions X.sup.I and X.sup.II are constant, and the radial spacings in regions Y.sup.I and Y.sup.II are also constant. An important feature of this embodiment is that the gaps at Y.sup.I and Y.sup.II are annular as there is at least some overlap of the wider portion of the drum (1) and the lands between the circumferentially disposed groups of cavities in the sleeve (2). This feature is common to a preferred series of embodiments in which the general configuration is more similar to the CDDM.

(16) The radial spacings in regions X.sup.I and X.sup.II are significantly greater than those in the regions Y.sup.I and Y.sup.II (which can be as close as less than 50 microns and are not drawn to scale in the figures). Hence the torque required to rotate the mixer is significantly reduced, so reducing the energy input and product temperature increase. Further, this reduces the element of dispersive mixing in the regions of CTM-like behaviour, X.sup.I and X.sup.II. By so doing there is greater control of elements of the process history, principal amongst which are thermal homogeneity, temperature rise and shear/extension, each of which can impact on the performance of certain products and intermediates.

2. Relieved Rotating Cylindrical Drum and Static Co-Axial Sleeve CTM

(17) FIG. 3 shows a portion of a mixer comprising an inner drum (1) and an outer sleeve (2). Cavities (3) are provided in the drum and the sleeve so that as the drum rotates about its axis (shown dashed), the drum and the sleeve co-operate to form a cavity transfer mixer. Ports (4) are provided for input and output of the process flow. Means for rotating the drum relative to the sleeve and end seals are not shown. Flow of materials within the mixer is from the bottom towards the top.

(18) FIG. 4 provides a more detailed view of the region A in FIG. 3. It can be seen that in regions X.sup.I, X.sup.II and X.sup.III the surface of the drum (1) is relieved and the radial spacings of the confronting surfaces of the drum (1) and the sleeve (2) are relatively large as compared with the corresponding radial spacings in regions Y.sup.I and Y.sup.II. In regions X.sup.I, X.sup.II and X.sup.III the cavities (3) promote CTM-like distributive mixing while in regions Y.sup.I and Y.sup.II the narrow spacing in the flow path induces an element of extensional flow and CDDM-like dispersive mixing. In this particular embodiment of the mixer the radial spacings in regions X.sup.I, X.sup.II and X.sup.III increase in the direction of flow, while the radial spacings in regions Y.sup.I and Y.sup.II are constant.

(19) The radial spacings in regions X.sup.I, X.sup.II and X.sup.III are significantly greater than those in the regions Y.sup.I and Y.sup.II. Hence the torque required to rotate the mixer is significantly reduced, so reducing the energy input and product temperature increase. Further, this reduces the element of dispersive mixing in the regions of CTM-like behaviour, X.sup.I, X.sup.II and X.sup.III. By so doing there is greater control of elements of the process history, principal amongst which are thermal homogeneity, temperature rise and shear/extension, each of which can impact on the performance of certain products and intermediates.

(20) This example illustrates a class of embodiment which is less preferred than that shown in FIGS. 1 and 2. In particular, the region of narrow spacing between the widest part of the drum and the inner surface of the sleeve is now in part crossed by the cavities in the inner wall of the sleeve, which allow some or all of the bulk flow to avoid the regions of high shear Y.sup.I and Y.sup.II.

3. Relieved Rotating Disc and Static Disc CDDM

(21) FIG. 5 shows a portion of a mixer comprising a rotating disc (1) and a static disc (2). Cavities (3) are provided in the rotating disc and static disc so that as the former rotates about its axis (shown dashed), the rotating disc and static disc co-operate to form a controlled deformation dynamic mixer. Ports (4) are provided for input and output of the process flow. Means for rotating the rotating disc relative to the static disc and end seals are not shown. Flow of materials within the mixer is from the centre towards the periphery.

(22) FIG. 6 provides a more detailed view of the region A in FIG. 5. It can be seen that in regions X.sup.I, X.sup.II and X.sup.III the surfaces of the rotating disc (1) are relieved and the axial spacings of the confronting surfaces of the rotating disc (1) and the static disc (2) are relatively large as compared with the corresponding axial spacings in regions Y.sup.I and Y.sup.II. In regions X.sup.I, X.sup.II and X.sup.III the cavities (3) promote CTM-like distributive mixing while in regions Y.sup.I and Y.sup.II the narrow spacing in the flow path induces extensional flow and CDDM-like dispersive mixing. In this particular embodiment of the mixer the axial spacings in regions X.sup.I, X.sup.II and X.sup.III increase in the direction of flow, while the radial spacings in regions Y.sup.I and Y.sup.II are constant.

(23) The axial spacings in regions X.sup.I, X.sup.II and X.sup.III are significantly greater than those in the regions Y.sup.I and Y.sup.II. Hence the torque required to rotate the mixer is significantly reduced, so reducing the energy input and product temperature increase. Further, this reduces the element of dispersive mixing in the regions of CTM-like behaviour, X.sup.I, X.sup.II and X.sup.III. By so doing there is greater control of elements of the process history, principal amongst which are thermal homogeneity, temperature rise and shear/extension, each of which can impact on the performance of certain products and intermediates.

4. Relieved Rotating Disc and Relieved Static Disc CTM

(24) FIG. 7 shows a portion of a mixer comprising a rotating disc (1) and a static disc (2). Cavities (3) are provided in the rotating disc and static disc so that as the former rotates about its axis (shown dashed), the rotating disc and static disc co-operate to form a cavity transfer mixer. Ports (4) are provided for input and output of the process flow. Means for rotating the rotating disc relative to the static disc and end seals are not shown. Flow of materials within the mixer is from the centre towards the periphery.

(25) FIG. 8 provides a more detailed view of the region A in FIG. 7. It can be seen that in regions X.sup.I, X.sup.II, X.sup.III and X.sup.IV the surfaces of the rotating disc (1) and static disc (2) are relieved and the axial spacings of the confronting surfaces of the rotating disc (1) and the static disc (2) are large and significantly increase in the direction of flow. Neither the rotating disc in regions Y.sup.II and Y.sup.IV nor the static disc in regions Y.sup.I and Y.sup.III are relieved, thus limiting the tendency for radial leakage flow induced by such large axial spacings. As with example 2, this is a less preferred embodiment of the invention as it is of the class of embodiments in which the narrower part of the spacing between the confronting surfaces is crossed by the mixing cavities.

(26) By relieving both surfaces, the axial spacings in regions X.sup.I, X.sup.II, X.sup.III and X.sup.IV and Y.sup.I, Y.sup.II, Y.sup.III and Y.sup.IV are significantly increased. Hence the torque required to rotate the mixer is significantly reduced, so reducing the energy input and product temperature increase. This significantly reduces the element of dispersive mixing. By so doing there is greater control of thermal homogeneity and local temperature rise, each of which can impact on the performance of certain products and intermediates.