CA2283478A1 - Mixer for cohesive powder materials - Google Patents

Mixer for cohesive powder materials Download PDF

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Publication number
CA2283478A1
CA2283478A1 CA002283478A CA2283478A CA2283478A1 CA 2283478 A1 CA2283478 A1 CA 2283478A1 CA 002283478 A CA002283478 A CA 002283478A CA 2283478 A CA2283478 A CA 2283478A CA 2283478 A1 CA2283478 A1 CA 2283478A1
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CA
Canada
Prior art keywords
rubbing
wanes
mixer
rotor
materials
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA002283478A
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French (fr)
Inventor
Geir Nordahl
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of CA2283478A1 publication Critical patent/CA2283478A1/en
Abandoned legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01FMIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/60Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis
    • B01F27/70Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis with paddles, blades or arms
    • B01F27/701Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis with paddles, blades or arms comprising two or more shafts, e.g. in consecutive mixing chambers

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Mixers Of The Rotary Stirring Type (AREA)
  • Detergent Compositions (AREA)
  • Preparation Of Clay, And Manufacture Of Mixtures Containing Clay Or Cement (AREA)
  • Accessories For Mixers (AREA)

Abstract

Method for a mixer for especially cohesive powder materials by rubbing the cohesive materials against the mixer's wall (6, 8) with at least one rubbing vane on each rotor so that the shearing forces are applied to the material during the rubbing process between the rubbing vanes and the wall (6, 8). The mixer comprises two rotors with several vanes (3) spaced along the rotor with at least one rubbing vane (1, 4, 5, 7) provided on each rotor in addition to the mixer's mixing vanes (3), and the rubbing vanes are arranged such that the materials are rubbed between the rubbing vanes and the wall (6, 8) in the mixer's housing.

Description

Mixer for cohesive powder materials The present invention relates to a method and a mixer for mixing of especially cohesive powder materials.
s In various industrial branches, many industrial processes involve the mixing of different materials in one way or another, be it raw materials or intermediate products. Such industrial mixing processes can vary significantly in complexity, from the quite simple process where desired homogeneity in the to mixture is reached with simple means, through the mor difficult processes which put greater demands on the equipment and the process cycles.
Mixing processes can generally be divided into two categories, namely mixing of liquids, gases, solids in liquids is or a combination of such on one hand, and a mixture of parti culate materials, that is powder in dry form or possibly with a moistened content that is lower than the saturation limit. In mixing of powders, there is no motion of particles without the particles being affected, in contrary to fluids, where motion can zo happen by diffusion or also as Hrownian movement. Powder affects in a large degree the mixing process itself by the particles physical properties as size, density, form, surface conditions, and so on. Further, the individual particle in a mass of powder at a size that is several orders of magnitude higher than the Is particles in a fluid.
Many of the problems that arise in mixing processes of various types, are due to differences in the above mentioned properties which are not known, or that have not in sufficient degree been considered in the selection of equipment or mixing 3o cycle. The problems that arise for this reason, result in for example a series of failed attempts to use equipment that is designed for mixing of liquids or the mixing of dry powder materials. Poorly performed mixing processes can result in great losses for the user, losses that can manifest themselves in the 35 form of unnecessary high consumption of raw materials, large production of rejects, problems in the following equipment in the production and dissatisfied costumers and possible loss of market shares.
The primary function in the mixture of one or more WO 98/39087 PCTlN098/00075 -cohesive powders in the same mixture requires a velocity gradient that varies from zero and up to peripheral velocity, and at the same time a shearing force larger than the slip force in the micro plane.
s This slip force is the force that the individual particle must have in order to escape the particle lump or heap or agglomerate, that is a collection of single particles that works as a collected particle, so that it works alone and therefore also so that the entire surface, and not only a small ~o side surface becomes available for the mixture' s ultimate target, which may be the colouring by pigments. This can be better illustrated by considering on one hand that the pigment particles consist of a large ball in a football field, which still will look green. If the ball is divided into particles with for 15 example red colour and with the size of 2 um, the whole field will look red.
I practice the situation is often that the pigment particles work as a collection of particles, consisting of for example ten particles of 2 um, and the colour yield will then ~o only make one half red, because the pigments are lying on the top of each other and not beside each other.
We understand then, that for pigment processes the trick is to convert collections of particles to single particles.
For example, in asphalt production the stone material must show 25 up in their smallest single particles to obtain the desired reactivity with the emulsion. What is important here, is the specific surface because the efficiency of the reactivity relates to the area of the available surface that is exposed to reaction.
It is usual that the filler appears as collections of 1 mm in 3o dimension, it is evident that the end product will be totally different than if the particles appear by themselves in the size of about 10 um. Cohesive particles are particles that because of some internal exchange of forces have tendency to appear as a collection of single particles because the mass is not large 3s enough to dissolve the lump.
In for example medicines, the quantity of filling materials with the present invention might be reduced because less solution is required. The mass is dissolved into single particles so that one can produce much smaller tablets and in fact make the medicines safer and easier to swallow.
Generally speaking, the mixture of powders is more difficult than the mixture of liquids and gases, especially mixture of dry powders. It is often merely impossible to reach theoretically optimum conditions within the frame of the available process techniques, that is use of time, production volume and costs. Choice of proper equipment that could be used for various assignments is essential for an economically favourable result for the users of the mixing equipment. On the ~o other hand, there are many different types of equipment that at first sight seem to be the same, on account of the many problems around mixing processes.
Mixing of solids are carried out by applied diffusion, applied convection or applied shearing force. Most processes and equipment will work with a combination of these mechanisms, but for one base mechanism.
The physical bulk properties of the powder materials change in a significant degree, depending on the size of the particles. If the mass has an average particle size of about 100 zo pm, the powder mass will usually behave as a free flowing mass with a defined slide angle, without tendency to cohesiveness. The mass will not acquire an inner strength after outside pressure, nor will it withstand greater pressure without break down. In order to obtain a successful mixture of such mass, it should be zs diffusive or connective.
If the particle size on the other hand is smaller, that is the main part of particles are substantially less than 100 pm, the powder mass will change character from a free flowing mass to a cohesive mass. It will then get an indefinite, but very 30 large slide angle, which could also be negative, and it will acquire a relatively large strength after outside strain. Changes in the physical properties also show up in the fact that the powder get a significantly greater ability to form agglomerates, that is there will be large lumps that each consists of many ss small particles. The cause of this change in mass properties is that the interparticular forces that contribute to the tying together of the particles will be the dominating forces working in the powder when the particle size is reduced. Interparticular forces could be Van der Waal forces, electrostatic forces, chemical, magnetic or capillary forces. This means that the effects of the force of gravity would be less compared to these forces. As a result, the force of gravity will not by itself be able to break down the powder to single particles, which is necessary in order to obtain a good mixture at microlevels. The powder or agglomerates must thus be exposed to shearing.forces in the form of rubbing or high kinetic energy.
Use of high kinetic energy, as for example may be obtained by fast rotating knives, is well known and used in many to connections. It is an effective method, but may, however damage the powder material if this is of such a nature that it is easily crushed or in other ways is unable to withstand rough treatment.
Further, other problems may arise, for example pollution of the powder in that the crushing tool itself wears down. If the powder is is of an adhesive nature, the result could easily be that the crushing tool soon be covered by powder and therefore stop functioning satisfactorily.
The present invention supplies a possibility to supply to the powder mass shearing forces without the above mentioned zo draw backs. This is achieved by the method and mixing device according to the invention as they are defined with features set forth in the claims.
The present invention achieves a number of advantages compared to the known art. Segregation properties are signi zs ficantly improved on account of a fine distribution in the micro plane. Environmental improvements are achieved by the fact that the process can be trimmed very precisely so that smaller quantities of harmful materials are being used.
Significant reduction in costs are achieved as a result 3o of small consumption of expensive component. In this connection one could mention pigment processes, such as production of powdered lacquers, in which the present invention can achieve savings in the order of 15~ of the consumption of pigment, which cost significantly more than filler materials. Other effects are 35 increased repetition reliability, simplified and at the same time improved process control, better planning tool and more reliable delivery.
The drawing shows schematically embodiments of the invention, where Fig. 1 shows a cross section of a mixer with two rotors in an embodiment with rubbing wanes, Fig. 2 shows a corresponding partial section with another embodiment of the rubbing wane, s Fig. 3 shows, corresponding to Fig. 2, a third embodi-ment of rubbing wanes, .
Fig. 4 shows a plane view of the mixer in Fig. 1, and Fig. 5 shows an embodiment of a mixer where the rubbing process takes place against the mixer's end wall.
With special rubbing wanes 1, 4, 5 provided between regular wanes 3 which takes care of the transport and blending in the mixer's housing 6, it is achieved that the powder is broken down in several shearing planes, and that it therefore takes place a crushing of agglomerates at the same time as the mixing takes place at the micro plane. Rubbing wanes 1, 4, 5 rub, by rotation by the rotor 2, materials against the bottom wall against the housing 6, and thereby applies sufficient shearing forces that the bonds in the agglomerates are broken . The rubbing process can also be provided by the rubbing of the materials by Zo rubbing wanes 7 against the end wall 8 of the housing 6, as shown in Fig. 5.
Such a mixing process can be performed at low veloci-ties, and therefore it is gentle to the powder mass. The method and the mixer device can be combined with other mixing prin-ciples, so that the three mechanisms for mixing can be utilised at the same time, since the mixing will take place by means of shearing in the micro plane while the entire mass of particles is stirred and mixed by means of diffusion and convection.
A mixer's housing 6 for the embodiment of the method 3o according to the present invention can make use of rubbing wanes 1, 4, 5 mounted on two parallel rotor 2 with opposite rotation direction, where the rubbing wanes press against a part of the powder mass and rub this against the stationary housing 6. This causes, because of the applied stress, that a number of breaks 3s will occur in the powder mass. In the break plane it will, because of the shearing stresses, be a relative motion between each side of the break plane, and because of this motion, it will be a relative mass transport in the break zone itself. Agglo-merates that happen to be in the break zone will therefore be broken down because of the shearing stresses, and the various parts of agglomerates will immediately after the break down be transported away from each other because of the relative motion than happens between the two sides of the shearing plane. This results in a mixing process on micro level that can be performed at low velocity.
The method and mixing devices according to the present invention can be utilized in all processes comprising mixing of fine, cohesive powders where an active medium is to be evenly to distributed in a mass of powder. Such tasks exist within several branches of industry, for example, in production of medicines, for mixing of pigments in raw materials for paint, chemical reactants and catalyzers, flourmixtures, coloured chalk, coal or binders, powders for toners and copying machines, etc.
The method and the mixing device may also advantage-ously be used for mixing of small quantities of liquid in dry powders or for mixing of products in the paste form.
The rubbing wanes can have the shape shown with the rubbing wane 1 in Fig. 1, which consists of a pipe which is bent zo in the form as shown in the Figure. Such bent rubbing wanes 1 in the form of pipes are fastened to the rotors 2, distributed over its length between the mixer's mixing wanes 3.
Fig . 2 shows another embodiment where the rubbing wanes 4 are bent so that the products are rubbed along rubbing wanes zs 4 while they are thrown radially outwardly. Fig. 3 shows on the other hand an embodiment of a rubbing wane 5 that has the form of an elliptic disc, also shaped such that the products will rub against the wall 6.
The width of the rubbing wanes 1, 4, 5, 7 against the so wall 6, 8 are chosen, depending on the materials to be mixed, and otherwise adapted to the special conditions. The rubbing wanes may be produced in the form of plates or pipes.
The present invention has shown to provide specially good results for gentle mixers with low peripheral velocities, 3s for example in the range from 0 to 3 m/s.
~ _.

Claims (6)

Claims
1. Method for a mixer for especially cohesive powder materials, CHARACTERIZED IN that the cohesive materials are rubbed against the mixer's wall (6, 8) with at least one rubbing wane on each rotor, so that the materials are exposed to shearing forces during the rubbing process between the rubbing wanes and the wall (6, 8).
2. Mixer for blending of especially cohesive powder materials, including rotors with several wanes (3) provided in a space along the rotor, CHARACTERIZED IN that at least one rubbing wane (1, 4, 5, 7) is provided on each rotor in addition to the mixer's mixing wanes (3), and in that the rubbing wanes are arranged so that the materials are rubbed between the rubbing wanes and the wall (6, 8) in the mixer's housing.
3. Mixer according to claim 2, CHARACTERIZED IN that a number of rubbing wanes (1, 4, 5) are mounted on the rotor (2) between the rotor's mixing wanes (3), and in that the rubbing wanes are shaped radially outward extending rods with preferably a rounded surface against the particles, and in that at least the outer parts of the rubbing wanes are bent to ascertain that the particles are rubbed against the rubbing wanes both against each side of each rubbing wane and against the periphery, so that they provide shearing forces that break down the agglomerates and the particles are mixed.
4. Mixer according to claim 3, CHARACTERIZED IN that the rubbing wanes (5) are radially arranged disks with rounded edges with an axial direction elliptical or similar shape.
5. Mixer according to claims 2-4, CHARACTERIZED IN that the rubbing wanes (1, 4) are pipes that are bent in the radially outer portions.
6. Mixer according to claim 2, CHARACTERIZED IN that each rotor (2) has one rubbing wane (7) at each end, adapted to rub the material against the mixer's end wall (8).
CA002283478A 1997-03-06 1998-03-06 Mixer for cohesive powder materials Abandoned CA2283478A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NO971044A NO306242B1 (en) 1997-03-06 1997-03-06 Blends, especially for cohesive particulate materials
NO971044 1997-03-06
PCT/NO1998/000075 WO1998039087A1 (en) 1997-03-06 1998-03-06 Mixer for cohesive powder materials

Publications (1)

Publication Number Publication Date
CA2283478A1 true CA2283478A1 (en) 1998-09-11

Family

ID=19900468

Family Applications (1)

Application Number Title Priority Date Filing Date
CA002283478A Abandoned CA2283478A1 (en) 1997-03-06 1998-03-06 Mixer for cohesive powder materials

Country Status (11)

Country Link
EP (1) EP1024889A1 (en)
JP (1) JP2001513700A (en)
CN (1) CN1138587C (en)
AU (1) AU6424998A (en)
BR (1) BR9808297A (en)
CA (1) CA2283478A1 (en)
ID (1) ID24467A (en)
NO (1) NO306242B1 (en)
PL (1) PL335511A1 (en)
TR (1) TR199902176T2 (en)
WO (1) WO1998039087A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101492768B (en) * 2008-01-23 2010-12-08 四川龙蟒矿冶有限责任公司 High-efficiency method and equipment for homogeneous mixture of material
ES2732031T3 (en) 2013-05-22 2019-11-20 Waister As Substance fragmentation device

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60202721A (en) * 1984-03-23 1985-10-14 Inoue Seisakusho:Kk Kneading apparatus
AU595556B2 (en) * 1985-11-26 1990-04-05 Lime Industries Pty Ltd Improved storage reservoir for slurries and/or suspensions

Also Published As

Publication number Publication date
AU6424998A (en) 1998-09-22
TR199902176T2 (en) 2000-06-21
CN1249699A (en) 2000-04-05
WO1998039087A1 (en) 1998-09-11
NO971044L (en) 1998-09-07
BR9808297A (en) 2000-05-16
JP2001513700A (en) 2001-09-04
NO971044D0 (en) 1997-03-06
NO306242B1 (en) 1999-10-11
CN1138587C (en) 2004-02-18
ID24467A (en) 2000-07-20
PL335511A1 (en) 2000-04-25
EP1024889A1 (en) 2000-08-09

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Date Code Title Description
FZDE Discontinued