WO2005014155A1 - Stirring device, comprising a combination of dissimilar mixing elements mounted in sequence on a rotating axis - Google Patents

Stirring device, comprising a combination of dissimilar mixing elements mounted in sequence on a rotating axis Download PDF

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Publication number
WO2005014155A1
WO2005014155A1 PCT/EP2004/008826 EP2004008826W WO2005014155A1 WO 2005014155 A1 WO2005014155 A1 WO 2005014155A1 EP 2004008826 W EP2004008826 W EP 2004008826W WO 2005014155 A1 WO2005014155 A1 WO 2005014155A1
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WIPO (PCT)
Prior art keywords
impeller
impellers
shaft
impeller unit
unit
Prior art date
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Ceased
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PCT/EP2004/008826
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French (fr)
Inventor
Francois-Xavier Michel Jean Ricard
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Glaxo Group Ltd
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Glaxo Group Ltd
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Publication of WO2005014155A1 publication Critical patent/WO2005014155A1/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/05—Stirrers
    • B01F27/11—Stirrers characterised by the configuration of the stirrers
    • B01F27/19—Stirrers with two or more mixing elements mounted in sequence on the same axis
    • B01F27/192—Stirrers with two or more mixing elements mounted in sequence on the same axis with dissimilar elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/40—Mixing liquids with liquids; Emulsifying
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/50—Mixing liquids with solids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/05—Stirrers
    • B01F27/11—Stirrers characterised by the configuration of the stirrers
    • B01F27/111—Centrifugal stirrers, i.e. stirrers with radial outlets; Stirrers of the turbine type, e.g. with means to guide the flow
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/05—Stirrers
    • B01F27/11—Stirrers characterised by the configuration of the stirrers
    • B01F27/113—Propeller-shaped stirrers for producing an axial flow, e.g. shaped like a ship or aircraft propeller

Definitions

  • the present invention relates to an impeller unit, in particular for a mixer, especially a conical-vessel mixer, a calorimeter including such a mixer, in particular a conical-vessel reaction calorimeter, and a method of mixing materials.
  • Reaction calorimeters which comprise a mixing vessel and an impeller unit which is rotatably disposed in the mixing vessel to mix materials as introduced thereinto, are used to assess the thermal behaviour of processes.
  • One such reaction calorimeter includes a conical mixing vessel, with the conical vessel design providing for the generation of reliable data at low volume, thus reducing the raw material requirements.
  • the existing impeller unit for conical-vessel reaction calorimeters in particular reaction calorimeters fitted with SV01 conical vessels (as supplied by ettler- Toledo GmbH, Gsammlungsee, Switzerland), has mixing limitations, particularly as to suspending solids, especially heavy slurries, and in mixing viscous solutions. Good mixing performance is essential in reaction calorimeters, as otherwise thermal measurements are skewed by mass or heat transfer limitations, such as encrustation, poor solids suspension, hot/cold spots, etc.
  • Figure 1 illustrates the existing impeller unit 3 (part number 00103599 as supplied by Mettler-Toledo GmbH), where disposed in a frusto-conical mixing vessel 4.
  • the impeller unit 3 comprises a shaft 5, a plurality of first, closely-spaced upper impellers 7a, 7b, 7c, 7d, as pitched-blade turbines, which are disposed to a mid-section of the shaft 5 for the purpose of effecting mixing within the mixing vessel 4, and a second, lower impeller 9, again as a pitched-blade turbine, which is disposed to the lower end of the shaft 5 and disposed adjacent the base of the mixing vessel 4.
  • the impeller unit 3 requires operation at high speed to provide a homogeneous mixture.
  • three zones are developed in the mixing vessel 4, these being a first, dead zone Zl, which is located at the upper region of the mixing vessel 4 above the upper impellers 7a, 7b, 7c, 7d, where no mixing is effected, a second, poorly-mixed zone Z2, which encompasses the main, middle region of the mixing vessel 4 and the upper impellers 7a, 7b, 7c, 7d, where only poor mixing is effected, and a third, well-mixed zone Z3, which is located at the lower region of the mixing vessel 4 beneath the upper impellers 7a, 7b, 7c, 7d and encompasses the lower impeller 9, where good mixing is effected.
  • the present inventors have identified that the upper impellers 7a, 7b, 7c, 7d do not provide a sufficient pumping capacity as to generate a strong circulation loop CL which encompasses the height of the mixing vessel 4; a strong circulation loop CL being necessary, in particular, to lift solids off the base of the mixing vessel 4.
  • the limited pumping capacity of the upper impellers 7a, 7b, 7c, 7d provides only for a restricted circulation loop CL which does not extend much beyond the PB60229 3
  • This limited pumping capacity of the upper impellers 7a, 7b, 7c, 7d apparently arises as a result of a number of factors regarding the configuration of the upper impellers 7a, 7b, 7c, 7d.
  • the pitched, turbine blades of the upper impellers 7a, 7b, 7c, 7d cannot achieve a sufficient axial flow at lower shaft rotation speeds to promote a strong circulation loop CL.
  • This factor together with the factors of the close spacing of the upper impellers 7a, 7b, 7c, 7d and the blades of the upper impellers 7a, 7b, 7c, 7d being narrow, contribute to providing for a limited pumping capacity, and hence the restricted circulation loop CL.
  • the lower impeller 9 in providing for a downward flow and not being encompassed by the restricted circulation loop CL, develops a local mixing loop ML from which material cannot escape.
  • the lower impeller 9 acts to contain the material within the lower region of the mixing vessel 4.
  • the present invention provides an impeller unit, comprising: a shaft about which the impeller unit is in use rotated; a plurality of first impellers disposed in spaced relation along the shaft and being configured to develop a flow towards one, downward end of the shaft on rotation of the PB60229 4
  • impeller unit and a second impeller disposed to the shaft at a position downward of the plurality of first impellers and being configured to develop an outward flow having a principal component in a radial direction on rotation of the impeller unit.
  • the downward flow developed by the plurality of first impellers is such as to extend to the second impeller, whereby a circulation loop is in use generated by the combined action of the plurality of first impellers developing a downward flow to the second impeller, and the second impeller driving the downward flow developed by the plurality of first impellers outwardly to develop an outward flow.
  • the spacing between adjacent ones of the plurality of first impellers is approximately equal to the diametral dimension of the uppermost first impeller.
  • the plurality of first impellers each comprise wide-blade hydrofoils.
  • the second impeller is configured such as to develop substantially no downward flow on rotation of the impeller unit.
  • the second impeller has a smaller diametral dimension than the uppermost first impeller.
  • the spacing between the second impeller and the lowermost first impeller is not more than the maximum spacing between any of adjacent ones of the plurality of first impellers.
  • the impellers are substantially equi-spaced.
  • the second impeller comprises a plurality of blades. PB60229
  • the blades comprise elongate elements extending outwardly and upwardly from the shaft.
  • the blades extend radially from the shaft to provide an outward radial flow.
  • the blades comprise retreating-curve blades.
  • the present invention provides an impeller unit, comprising: a shaft about which the impeller unit is in use rotated; a plurality of first impellers disposed in spaced relation along the shaft and being configured to develop a flow towards one, downward end of the shaft on rotation of the impeller unit, wherein the spacing between adjacent ones of the plurality of first impellers is approximately equal to the diametral dimension of the uppermost first impeller; and a second impeller disposed to the shaft at a position downward of the plurality of first impellers and being configured to develop an outward flow on rotation of the impeller unit.
  • the present invention provides an impeller unit, comprising: a shaft about which the impeller unit is in use rotated; a plurality of first impellers disposed in spaced relation along the shaft and being configured to develop a flow towards one, downward end of the shaft on rotation of the impeller unit; and a second impeller disposed to the shaft at a position downward of the plurality of first impellers and being configured to develop an outward flow on rotation of the impeller unit, wherein the second impeller has a greater diametral dimension than the lowermost first impeller.
  • the present invention provides an impeller unit, comprising: a shaft about which the impeller unit is in use rotated; a plurality of first impellers disposed in spaced relation along the shaft and being PB60229 6
  • the present invention provides an impeller unit, comprising: a shaft about which the impeller unit is in use rotated; a plurality of first impellers disposed in spaced relation along the shaft and being configured to develop a flow towards one, downward end of the shaft on rotation of the impeller unit; and a second impeller disposed to the shaft at a position downward of the plurality of first impellers and being configured to develop an outward flow on rotation of the impeller unit; wherein the impellers are substantially equi-spaced.
  • the present invention also extends to a mixer incorporating the above- described impeller unit.
  • the present invention further extends to a mixer comprising a frusto-conical mixing vessel and the above-described impeller unit disposed in the mixing vessel to mix material as introduced thereinto.
  • the present invention yet further extends to a calorimeter including the above- described mixer.
  • the present invention provides a method of mixing materials, comprising the steps of: providing a mixer comprising: a mixing vessel; and an impeller unit disposed in the mixing vessel to mix materials as introduced thereinto, the impeller unit comprising a shaft, a plurality of first impellers disposed in spaced relation along the shaft and being configured to PB60229 7
  • Figure 1 illustrates a reaction calorimeter incorporating a prior art impeller unit
  • Figure 2 illustrates a reaction calorimeter incorporating an impeller unit in accordance with a preferred embodiment of the present invention
  • Figure 3 illustrates a side view of the impeller unit of Figure 2
  • Figure 4 illustrates in enlarged scale a lower perspective view of one of the first impellers of the impeller unit of Figure 2;
  • Figure 5 illustrates a lower end view (section I-I in Figure 3) of the first impeller of Figure 4; PB60229 8
  • Figure 6 illustrates in enlarged scale a lower perspective view of the second impeller of the impeller unit of Figure 2;
  • Figure 7 illustrates an upper end view (section II-II in Figure 3) of the second impeller of Figure 6.
  • Figures 2 to 7 illustrate a conical-vessel reaction calorimeter in accordance with a preferred embodiment of the present invention.
  • the calorimeter comprises a frusto-conical mixing vessel 10, in this embodiment an SVOl reaction vessel having a 1 L capacity (as supplied by Mettler-Toledo GmbH), and an impeller unit 12 which is rotatably disposed at the longitudinal axis of the mixing vessel 10 such as to develop a circulation loop CL over the height of the mixing vessel 10.
  • SVOl reaction vessel having a 1 L capacity (as supplied by Mettler-Toledo GmbH)
  • impeller unit 12 which is rotatably disposed at the longitudinal axis of the mixing vessel 10 such as to develop a circulation loop CL over the height of the mixing vessel 10.
  • impeller unit 12 is formed of glass, but in other embodiments could be formed from other chemically-inert materials, such as plastics or metals, for example, stainless steel or Hastelloy (RTM).
  • the impeller unit 12 comprises a shaft 14, in this embodiment having a length of about 415 mm, a plurality of first, upper impellers 16 which are disposed in spaced relation along a length of the shaft 14 and configured such as to develop a strong downward flow to one, downward end of the shaft 14 which is disposed to the base of the mixing vessel 10, and a second, lower impeller 17 which is disposed to the downward end of the shaft 14 and configured such as to develop an outward flow which drives the downward flow, as developed by the upper impellers 16, radially outwardly.
  • the upper impellers 16a, 16b, 16c can each comprise two or four blades 18.
  • the upper impellers 16a, 16b, 16c are equi-spaced and of decreasing diametral dimension from the uppermost upper impeller 16a to the lowermost upper impeller 16c.
  • the adjacent ones of the upper impellers 16a, 16b, 16c have a spacing of about 45 mm
  • the uppermost upper impeller 16a has a diametral dimension of about 50mm
  • the intermediate upper impeller 16b has a diametral dimension of about 40 mm
  • the lowermost upper impeller 16c has a diametral dimension of about 30 mm.
  • the spacing between adjacent ones of the upper impellers 16a, 16b, 16c is approximately equal to the diametral dimension of the uppermost upper impeller 16a.
  • the blades 18 of the upper impellers 16a, 16b, 16c are wide-blade hydrofoils having an average pitch in the range of from about 30° to about 60°.
  • the blades 18 are petaloid in shape and curved, here as a retreating curve in the sense of rotation, over the height thereof.
  • the lower impeller 17 comprises a plurality of radial-flow blades 22, in this embodiment three radial-flow blades 22 equi-angularly spaced about the shaft 14, for developing an outward, radial flow which drives the downward flow PB60229 10
  • the lower impeller 17 can comprise two or four radial-flow blades 22.
  • the lower impeller 17 is a retreating-curve impeller, where the radial-flow blades 22 comprise radial fins having a retreating curve in the sense of rotation.
  • the radial-flow blades 22 comprise elongate elements which extend outwardly and upwardly from the shaft 14.
  • the lower impeller 17 has a smaller diametral dimension than the uppermost upper impeller 16a. In this embodiment the lower impeller 17 has a diametral dimension of about 45 mm. With this configuration, the lower impeller 17 acts to drive the downward flow, as developed by the upper impellers 16a, 16b, 16c, outwardly such that the upward flow of the circulation loop CL is entrained by the uppermost upper impeller 16a.
  • the spacing between the lower impeller 17 and the lowermost upper impeller 16c is less than the spacing between the adjacent ones of the upper impellers 16a, 16b, 16c. In this embodiment the spacing between the lower impeller 17 and the lowermost upper impeller 16c is about 40 mm.
  • the spacing between the lower impeller 17 and the lowermost upper impeller 16c could be substantially the same as the spacing between the adjacent ones of the upper impellers 16a, 16b, 16c.
  • the impeller unit 12 of the described embodiment of the present invention provides for far improved performance as compared to the prior art impeller unit 3, in that the impeller unit 12 of the described embodiment of the present invention achieves a homogeneous mixture at far lower speeds, especially at higher volume.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Mixers Of The Rotary Stirring Type (AREA)

Abstract

An impeller unit, comprising: a shaft (14) about which the impeller unit is in use rotated; a plurality of first impellers (16a, 16b, 16c) disposed in spaced relation along the shaft (14) and being configured to develop a flow towards one, downward end of the shaft (14) on rotation of the impeller unit; and a second impeller (17) disposed to the shaft (14) at a position downward of the plurality of first impellers (16a, 16b, 16c) and being configured to develop an outward flow having a principal component in a radial direction on rotation of the impeller unit; wherein the downward flow developed by the plurality of first impellers (16a, 16b, 16c) is such as to extend to the second impeller (17), whereby a circulation loop (CL) is in use generated by the combined action of the plurality of first impellers (16a, 16b, 16c) developing a downward flow to the second impeller (17), and the second impeller (17) driving the downward flow developed by the plurality of first impellers (16a, 16b, 16c) outwardly to develop an outward flow.

Description

STIRRING DEVICE , COMPRISING A COMBINATION OF DISSIMILAR MIXING ELEMENTS MOUNTED IN SEQUENCE ON A ROTATING AXIS
Field Of The Invention
The present invention relates to an impeller unit, in particular for a mixer, especially a conical-vessel mixer, a calorimeter including such a mixer, in particular a conical-vessel reaction calorimeter, and a method of mixing materials.
Background Of The Invention
Reaction calorimeters, which comprise a mixing vessel and an impeller unit which is rotatably disposed in the mixing vessel to mix materials as introduced thereinto, are used to assess the thermal behaviour of processes. One such reaction calorimeter includes a conical mixing vessel, with the conical vessel design providing for the generation of reliable data at low volume, thus reducing the raw material requirements.
The existing impeller unit for conical-vessel reaction calorimeters, in particular reaction calorimeters fitted with SV01 conical vessels (as supplied by ettler- Toledo GmbH, Greifensee, Switzerland), has mixing limitations, particularly as to suspending solids, especially heavy slurries, and in mixing viscous solutions. Good mixing performance is essential in reaction calorimeters, as otherwise thermal measurements are skewed by mass or heat transfer limitations, such as encrustation, poor solids suspension, hot/cold spots, etc.
In light of these mixing limitations, alternative impeller constructions have been proposed [1, 2], but these constructions still suffer from mixing limitations. PB60229 2
Figure 1 illustrates the existing impeller unit 3 (part number 00103599 as supplied by Mettler-Toledo GmbH), where disposed in a frusto-conical mixing vessel 4.
The impeller unit 3 comprises a shaft 5, a plurality of first, closely-spaced upper impellers 7a, 7b, 7c, 7d, as pitched-blade turbines, which are disposed to a mid-section of the shaft 5 for the purpose of effecting mixing within the mixing vessel 4, and a second, lower impeller 9, again as a pitched-blade turbine, which is disposed to the lower end of the shaft 5 and disposed adjacent the base of the mixing vessel 4.
In mixing solids suspensions, especially heavy slurries, and viscous solutions, the impeller unit 3 requires operation at high speed to provide a homogeneous mixture. At the lower, usual speeds, three zones are developed in the mixing vessel 4, these being a first, dead zone Zl, which is located at the upper region of the mixing vessel 4 above the upper impellers 7a, 7b, 7c, 7d, where no mixing is effected, a second, poorly-mixed zone Z2, which encompasses the main, middle region of the mixing vessel 4 and the upper impellers 7a, 7b, 7c, 7d, where only poor mixing is effected, and a third, well-mixed zone Z3, which is located at the lower region of the mixing vessel 4 beneath the upper impellers 7a, 7b, 7c, 7d and encompasses the lower impeller 9, where good mixing is effected.
Following investigation, the present inventors have identified that the upper impellers 7a, 7b, 7c, 7d do not provide a sufficient pumping capacity as to generate a strong circulation loop CL which encompasses the height of the mixing vessel 4; a strong circulation loop CL being necessary, in particular, to lift solids off the base of the mixing vessel 4.
The limited pumping capacity of the upper impellers 7a, 7b, 7c, 7d provides only for a restricted circulation loop CL which does not extend much beyond the PB60229 3
extent of the upper impellers 7a, 7b, 7c, 7d, and, furthermore, the mixing effected within the zone encompassed by the restricted circulation loop CL is poor, this being the poorly-mixed zone Z2. As a consequence of the circulation loop CL not extending to the upper or lower regions of the mixing vessel 4, a homogeneous mixture cannot be effected.
This limited pumping capacity of the upper impellers 7a, 7b, 7c, 7d apparently arises as a result of a number of factors regarding the configuration of the upper impellers 7a, 7b, 7c, 7d. In particular, the pitched, turbine blades of the upper impellers 7a, 7b, 7c, 7d cannot achieve a sufficient axial flow at lower shaft rotation speeds to promote a strong circulation loop CL. This factor, together with the factors of the close spacing of the upper impellers 7a, 7b, 7c, 7d and the blades of the upper impellers 7a, 7b, 7c, 7d being narrow, contribute to providing for a limited pumping capacity, and hence the restricted circulation loop CL.
In addition, the lower impeller 9, in providing for a downward flow and not being encompassed by the restricted circulation loop CL, develops a local mixing loop ML from which material cannot escape. The lower impeller 9 acts to contain the material within the lower region of the mixing vessel 4.
In light of this recognition of the shortcomings of the prior art impeller unit 3, the present inventors have developed a new impeller unit which provides for improved performance.
Summary Of The Invention
In one aspect the present invention provides an impeller unit, comprising: a shaft about which the impeller unit is in use rotated; a plurality of first impellers disposed in spaced relation along the shaft and being configured to develop a flow towards one, downward end of the shaft on rotation of the PB60229 4
impeller unit; and a second impeller disposed to the shaft at a position downward of the plurality of first impellers and being configured to develop an outward flow having a principal component in a radial direction on rotation of the impeller unit.
Preferably, the downward flow developed by the plurality of first impellers is such as to extend to the second impeller, whereby a circulation loop is in use generated by the combined action of the plurality of first impellers developing a downward flow to the second impeller, and the second impeller driving the downward flow developed by the plurality of first impellers outwardly to develop an outward flow.
In one embodiment the spacing between adjacent ones of the plurality of first impellers is approximately equal to the diametral dimension of the uppermost first impeller.
Preferably, the plurality of first impellers each comprise wide-blade hydrofoils.
Preferably, the second impeller is configured such as to develop substantially no downward flow on rotation of the impeller unit.
Preferably, the second impeller has a smaller diametral dimension than the uppermost first impeller.
In one embodiment the spacing between the second impeller and the lowermost first impeller is not more than the maximum spacing between any of adjacent ones of the plurality of first impellers.
In another embodiment the impellers are substantially equi-spaced.
Preferably, the second impeller comprises a plurality of blades. PB60229
More preferably, the blades comprise elongate elements extending outwardly and upwardly from the shaft.
More preferably, the blades extend radially from the shaft to provide an outward radial flow.
In a preferred embodiment the blades comprise retreating-curve blades.
In another aspect the present invention provides an impeller unit, comprising: a shaft about which the impeller unit is in use rotated; a plurality of first impellers disposed in spaced relation along the shaft and being configured to develop a flow towards one, downward end of the shaft on rotation of the impeller unit, wherein the spacing between adjacent ones of the plurality of first impellers is approximately equal to the diametral dimension of the uppermost first impeller; and a second impeller disposed to the shaft at a position downward of the plurality of first impellers and being configured to develop an outward flow on rotation of the impeller unit.
In a further aspect the present invention provides an impeller unit, comprising: a shaft about which the impeller unit is in use rotated; a plurality of first impellers disposed in spaced relation along the shaft and being configured to develop a flow towards one, downward end of the shaft on rotation of the impeller unit; and a second impeller disposed to the shaft at a position downward of the plurality of first impellers and being configured to develop an outward flow on rotation of the impeller unit, wherein the second impeller has a greater diametral dimension than the lowermost first impeller.
In a yet further aspect the present invention provides an impeller unit, comprising: a shaft about which the impeller unit is in use rotated; a plurality of first impellers disposed in spaced relation along the shaft and being PB60229 6
configured to develop a flow towards one, downward end of the shaft on rotation of the impeller unit; and a second impeller disposed to the shaft at a position downward of the plurality of first impellers and being configured to develop an outward flow on rotation of the impeller unit; wherein the spacing between the second impeller and the lowermost first impeller is less than the spacing between any of adjacent ones of the plurality of first impellers.
In a still further aspect the present invention provides an impeller unit, comprising: a shaft about which the impeller unit is in use rotated; a plurality of first impellers disposed in spaced relation along the shaft and being configured to develop a flow towards one, downward end of the shaft on rotation of the impeller unit; and a second impeller disposed to the shaft at a position downward of the plurality of first impellers and being configured to develop an outward flow on rotation of the impeller unit; wherein the impellers are substantially equi-spaced.
The present invention also extends to a mixer incorporating the above- described impeller unit.
The present invention further extends to a mixer comprising a frusto-conical mixing vessel and the above-described impeller unit disposed in the mixing vessel to mix material as introduced thereinto.
The present invention yet further extends to a calorimeter including the above- described mixer.
In a still yet further aspect the present invention provides a method of mixing materials, comprising the steps of: providing a mixer comprising: a mixing vessel; and an impeller unit disposed in the mixing vessel to mix materials as introduced thereinto, the impeller unit comprising a shaft, a plurality of first impellers disposed in spaced relation along the shaft and being configured to PB60229 7
develop a flow towards one, downward end of the shaft on rotation of the impeller unit, and a second impeller disposed to the shaft at a position downward of the plurality of first impellers and being configured to develop an outward flow having a principal component in a radial direction on rotation of the impeller unit; and rotating the impeller unit such that the plurality of first impellers develop a flow towards one, downward end of the shaft and to the second impeller, and the second impeller develops an outward flow having a principal component in a radial direction, whereby a circulation loop is generated by the combined action of the plurality of first impellers developing a downward flow to the second impeller, and the second impeller driving the downward flow developed by the plurality of first impellers outwardly to develop an outward flow.
Brief Description Of The Drawings
A preferred embodiment of the present invention will now be described hereinbelow by way of example only with reference to the accompanying drawings, in which:
Figure 1 illustrates a reaction calorimeter incorporating a prior art impeller unit;
Figure 2 illustrates a reaction calorimeter incorporating an impeller unit in accordance with a preferred embodiment of the present invention;
Figure 3 illustrates a side view of the impeller unit of Figure 2;
Figure 4 illustrates in enlarged scale a lower perspective view of one of the first impellers of the impeller unit of Figure 2;
Figure 5 illustrates a lower end view (section I-I in Figure 3) of the first impeller of Figure 4; PB60229 8
Figure 6 illustrates in enlarged scale a lower perspective view of the second impeller of the impeller unit of Figure 2; and
Figure 7 illustrates an upper end view (section II-II in Figure 3) of the second impeller of Figure 6.
Detailed Description Of A Preferred Embodiment
Figures 2 to 7 illustrate a conical-vessel reaction calorimeter in accordance with a preferred embodiment of the present invention.
The calorimeter comprises a frusto-conical mixing vessel 10, in this embodiment an SVOl reaction vessel having a 1 L capacity (as supplied by Mettler-Toledo GmbH), and an impeller unit 12 which is rotatably disposed at the longitudinal axis of the mixing vessel 10 such as to develop a circulation loop CL over the height of the mixing vessel 10.
In this embodiment the impeller unit 12 is formed of glass, but in other embodiments could be formed from other chemically-inert materials, such as plastics or metals, for example, stainless steel or Hastelloy (RTM).
The impeller unit 12 comprises a shaft 14, in this embodiment having a length of about 415 mm, a plurality of first, upper impellers 16 which are disposed in spaced relation along a length of the shaft 14 and configured such as to develop a strong downward flow to one, downward end of the shaft 14 which is disposed to the base of the mixing vessel 10, and a second, lower impeller 17 which is disposed to the downward end of the shaft 14 and configured such as to develop an outward flow which drives the downward flow, as developed by the upper impellers 16, radially outwardly. PB60229 9
The upper impellers 16, in this embodiment first to third upper impellers 16a, 16b, 16c, each comprise a plurality of blades 18, in this embodiment three blades 18 equi-angularly spaced about the shaft 14, which are configured to develop a strong downward flow towards the downward end of the shaft 14, and hence the base of the mixing vessel 10, with the spacing of the upper impellers 16a, 16b, 16c along the length of the shaft 14 being such as to provide that the circulation loop CL extends the full height of the mixing vessel 10. In other preferred embodiments the upper impellers 16a, 16b, 16c can each comprise two or four blades 18.
In this embodiment the upper impellers 16a, 16b, 16c are equi-spaced and of decreasing diametral dimension from the uppermost upper impeller 16a to the lowermost upper impeller 16c. In this embodiment the adjacent ones of the upper impellers 16a, 16b, 16c have a spacing of about 45 mm, the uppermost upper impeller 16a has a diametral dimension of about 50mm, the intermediate upper impeller 16b has a diametral dimension of about 40 mm and the lowermost upper impeller 16c has a diametral dimension of about 30 mm.
In this embodiment the spacing between adjacent ones of the upper impellers 16a, 16b, 16c is approximately equal to the diametral dimension of the uppermost upper impeller 16a.
Referring particularly to Figures 4 and 5, in this embodiment the blades 18 of the upper impellers 16a, 16b, 16c are wide-blade hydrofoils having an average pitch in the range of from about 30° to about 60°. In this embodiment the blades 18 are petaloid in shape and curved, here as a retreating curve in the sense of rotation, over the height thereof.
The lower impeller 17 comprises a plurality of radial-flow blades 22, in this embodiment three radial-flow blades 22 equi-angularly spaced about the shaft 14, for developing an outward, radial flow which drives the downward flow PB60229 10
developed by the upper impellers 16a, 16b, 16c outwardly, and thereby configures the circulation loop CL. In other preferred embodiments the lower impeller 17 can comprise two or four radial-flow blades 22.
Referring particularly to Figures 6 and 7, in this embodiment the lower impeller 17 is a retreating-curve impeller, where the radial-flow blades 22 comprise radial fins having a retreating curve in the sense of rotation. In this embodiment the radial-flow blades 22 comprise elongate elements which extend outwardly and upwardly from the shaft 14. By providing that the lower impeller 17 has principally a radial component, the impeller unit 12 provides for operation at lower speeds, particularly at higher volume.
In this embodiment the lower impeller 17 has a smaller diametral dimension than the uppermost upper impeller 16a. In this embodiment the lower impeller 17 has a diametral dimension of about 45 mm. With this configuration, the lower impeller 17 acts to drive the downward flow, as developed by the upper impellers 16a, 16b, 16c, outwardly such that the upward flow of the circulation loop CL is entrained by the uppermost upper impeller 16a.
In this embodiment the spacing between the lower impeller 17 and the lowermost upper impeller 16c is less than the spacing between the adjacent ones of the upper impellers 16a, 16b, 16c. In this embodiment the spacing between the lower impeller 17 and the lowermost upper impeller 16c is about 40 mm.
In another embodiment the spacing between the lower impeller 17 and the lowermost upper impeller 16c could be substantially the same as the spacing between the adjacent ones of the upper impellers 16a, 16b, 16c.
Example PB60229 11
The present invention will now be described hereinbelow with reference to the following non-limiting Example.
In this Example, samples of two volumes, 300 and 600 mL, and having differing solids contents, 1, 5 and 10 %w/w, were mixed in an SVOl reaction vessel (as supplied by Mettler-Toledo GmbH) using the prior art impeller unit 3 and the impeller unit 12 of the described embodiment of the present invention to achieve homogeneous mixtures.
The results of this experimentation are shown in Table 1 hereinbelow. As will be noted, the impeller unit 12 of the described embodiment of the present invention provides for far improved performance as compared to the prior art impeller unit 3, in that the impeller unit 12 of the described embodiment of the present invention achieves a homogeneous mixture at far lower speeds, especially at higher volume.
Figure imgf000013_0001
Table 1 - Experimental Results for Inventive Impeller Unit as Compared to the Prior Art Impeller Unit
Finally, it will be understood that the present invention has been described in its preferred embodiment and can be modified in many different ways without departing from the scope of the invention as defined by the appended claims. PB60229 12
Also, as regards the provision of reference signs in the appended claims, it is to be understood that reference signs are provided only for illustrative purposes and are not intended to confer any limitation to the claimed invention.
The present application claims priority from UK patent application No. 0 318 449.6 filed 6 August 2003, the entire content of which is hereby incorporated herein by reference.
References
[1] Improved Mixing with SVOl, Urs Groth, Mettler-Toledo GmbH, www.rxeforum.com, Tips & Hints, June 1997.
[2] Mixing in the SVOl, Donald J Knoechel, Proceedings of the 6th National RC1 User Forum, San Diego, October 1993.

Claims

PB60229 13CLAIMS
1. An impeller unit, comprising: a shaft (14) about which the impeller unit is in use rotated; a plurality of first impellers (16a, 16b, 16c) disposed in spaced relation along the shaft (14) and being configured to develop a flow towards one, downward end of the shaft (14) on rotation of the impeller unit; and a second impeller (17) disposed to the shaft (14) at a position downward of the plurality of first impellers (16a, 16b, 16c) and being configured to develop an outward flow having a principal component in a radial direction on rotation of the impeller unit.
2. The impeller unit of claim 1, wherein the downward flow developed by the plurality of first impellers (16a, 16b, 16c) is such as to extend to the second impeller (17), whereby a circulation loop (CL) is in use generated by the combined action of the plurality of first impellers (16a, 16b, 16c) developing a downward flow to the second impeller (17), and the second impeller (17) driving the downward flow developed by the plurality of first impellers (16a, 16b, 16c) outwardly to develop an outward flow.
3. The impeller unit of claim 1 or 2, wherein the spacing between adjacent ones of the plurality of first impellers (16a, 16b, 16c) is approximately equal to the diametral dimension of the uppermost first impeller (16a).
4. The impeller unit of any of claims 1 to 3, wherein the plurality of first impellers (16a, 16b, 16c) each comprise hydrofoils.
5. The impeller unit of any of claims 1 to 4, wherein the second impeller (17) is configured such as to develop substantially no downward flow on rotation of the impeller unit. PB60229 14
6. The impeller unit of any of claims 1 to 5, wherein the second impeller (17) has a smaller diametral dimension than the uppermost first impeller (16a).
7. The impeller unit of any of claims 1 to 6, wherein the spacing between the second impeller (17) and the lowermost first impeller (16c) is not more than the maximum spacing between any of adjacent ones of the plurality of first impellers (16a, 16b, 16c).
8. The impeller unit of any of claims 1 to 6, wherein the impellers (16a, 16b, 16c, 17) are substantially equi-spaced.
9. The impeller unit of any of claims 1 to 8, wherein the second impeller (17) comprises a plurality of blades (22).
10. The impeller unit of claim 9, wherein the blades (22) comprise elongate elements extending outwardly and upwardly from the shaft (14).
11. The impeller unit of claim 9 or 10, wherein the blades (22) extend radially from the shaft (14) to provide an outward radial flow.
12. The impeller unit of any of claims 9 to 11, wherein the blades (22) comprise retreating-curve blades.
13. An impeller unit, comprising: a shaft (14) about which the impeller unit is in use rotated; a plurality of first impellers (16a, 16b, 16c) disposed in spaced relation along the shaft (14) and being configured to develop a flow towards one, downward end of the shaft (14) on rotation of the impeller unit, wherein the spacing between adjacent ones of the plurality of first impellers (16a, PB60229 15
16b, 16c) is approximately equal to the diametral dimension of the uppermost first impeller (16a); and a second impeller (17) disposed to the shaft (14) at a position downward of the plurality of first impellers (16a, 16b, 16c) and being configured to develop an outward flow on rotation of the impeller unit.
14. An impeller unit, comprising: a shaft (14) about which the impeller unit is in use rotated; a plurality of first impellers (16a, 16b, 16c) disposed in spaced relation along the shaft (14) and being configured to develop a flow towards one, downward end of the shaft (14) on rotation of the impeller unit; and a second impeller (17) disposed to the shaft (14) at a position downward of the plurality of first impellers (16a, 16b, 16c) and being configured to develop an outward flow on rotation of the impeller unit, wherein the second impeller (17) has a smaller diametral dimension than the uppermost first impeller (16a).
15. An impeller unit, comprising: a shaft (14) about which the impeller unit is in use rotated; a plurality of first impellers (16a, 16b, 16c) disposed in spaced relation along the shaft (14) and being configured to develop a flow towards one, downward end of the shaft (14) on rotation of the impeller unit; and a second impeller (17) disposed to the shaft (14) at a position downward of the plurality of first impellers (16a, 16b, 16c) and being configured to develop an outward flow on rotation of the impeller unit; wherein the spacing between the second impeller (17) and the lowermost first impeller (16c) is less than the spacing between any of adjacent ones of the plurality of first impellers (16a, 16b, 16c).
16. An impeller unit, comprising: a shaft (14) about which the impeller unit is in use rotated; PB60229 16 a plurality of first impellers (16a, 16b, 16c) disposed in spaced relation along the shaft (14) and being configured to develop a flow towards one, downward end of the shaft (14) on rotation of the impeller unit; and a second impeller (17) disposed to the shaft (14) at a position downward of the plurality of first impellers (16a, 16b, 16c) and being configured to develop an outward flow on rotation of the impeller unit; wherein the impellers (16a, 16b, 16c, 17) are substantially equi-spaced.
17. A mixer incorporating the impeller unit of any of claims 1 to 16.
18. A mixer comprising a frusto-conical mixing vessel (10) and the impeller unit of any of claims 1 to 16 disposed in the mixing vessel (10) to mix material as introduced thereinto.
19. A calorimeter including the mixer of claim 17 or 18.
20. A method of mixing materials, comprising the steps of: providing a mixer comprising: a mixing vessel (10); and an impeller unit disposed in the mixing vessel (10) to mix materials as introduced thereinto, the impeller unit comprising a shaft (14), a plurality of first impellers (16a, 16b, 16c) disposed in spaced relation along the shaft (14) and being configured to develop a flow towards one, downward end of the shaft (14) on rotation of the impeller unit, and a second impeller (17) disposed to the shaft (14) at a position downward of the plurality of first impellers (16a, 16b, 16c) and being configured to develop an outward flow on rotation of the impeller unit; and rotating the impeller unit such that the plurality of first impellers (16a, 16b, 16c) develop a flow towards one, downward end of the shaft (14) and to the second impeller (17), and the second impeller (17) develops an outward flow, whereby a circulation loop (CL) is generated by the combined action of the plurality of first impellers (16a, 16b, 16c) PB60229 17 developing a downward flow to the second impeller (17), and the second impeller (17) driving the downward flow developed by the plurality of first impellers (16a, 16b, 16c) outwardly to develop an outward flow.
21. An impeller unit substantially as hereinbefore described with reference to any of Figures 2 to 7 of the accompanying drawings.
22. A mixer substantially as hereinbefore described with reference to any of Figures 2 to 7 of the accompanying drawings.
23. A calorimeter substantially as hereinbefore described with reference to any of Figures 2 to 7 of the accompanying drawings.
24. A method of mixing materials substantially as hereinbefore described with reference to any of Figures 2 to 7 of the accompanying drawings.
PCT/EP2004/008826 2003-08-06 2004-08-04 Stirring device, comprising a combination of dissimilar mixing elements mounted in sequence on a rotating axis Ceased WO2005014155A1 (en)

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GBGB0318449.6A GB0318449D0 (en) 2003-08-06 2003-08-06 Impeller unit
GB0318449.6 2003-08-06

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EP2754344A3 (en) * 2013-01-15 2015-02-18 Gottfried Gritzner Flow engine for liquids
US9713799B2 (en) 2013-12-17 2017-07-25 Bayer Cropscience Lp Mixing systems, methods, and devices with extendible impellers
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EP1984104A4 (en) * 2006-02-17 2011-10-19 Outotec Oyj METHOD AND APPARATUS FOR MIXING FOR MIXING GAS TO A PASTE IN A CLOSED REACTOR
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EP2754344A3 (en) * 2013-01-15 2015-02-18 Gottfried Gritzner Flow engine for liquids
US9713799B2 (en) 2013-12-17 2017-07-25 Bayer Cropscience Lp Mixing systems, methods, and devices with extendible impellers
US10350557B2 (en) 2013-12-17 2019-07-16 Bayer Cropscience Lp Mixing systems, methods, and devices with extendible impellers
US20240033696A1 (en) * 2022-07-28 2024-02-01 Newlight Technologies, Inc. Mixing system for allowing the hydrostatic head to remain constant as scale increases

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