US 3334868 A
Description (OCR text may contain errors)
Aug. 8, 1967 -J. R. LAGE 3,334,353
PROCESS FOR MIXING AND APPARATUS FOR PRACTICING THE PROCESS Filed Sept. 18, 1963 2 Sheets-Sheet 1 I77 ve-rzzm- 677186 Laz ge Atty Aug. 8, 1967 J. R. LAGE 3,334,868
PROCESS FOR MIXING AND APPARATUS FOR PRACTICING THE PROCESS Filed Sept. 18, 1963 2 Sheets-Sheet 2 H alavenzw J2me Large B h United States Patent PROCESS FOR MIXING AND APPARATUS FOR PRACTICING THE PROCESS James Richard Lage, Umiken, Brugg, Switzerland Filed Sept. 18, 1963, Ser. No. 309,662
Claims priority, application Switzerland, Nov. 6, 1962,
12,943/62 11 Claims. (Cl. 259-4) This invention relates to a process for mixing materials at least one of which is capable of flow and apparatus for practising this method.
The mixing process is suitable for example for accelerating dissolution, the production of dispersions, suspensions, emulsions, colloidal solutions, for flotation operations, for homogenising, production and treatment of pastes, the acceleration of chemical, physical and atomic reactions and fermentations, the washing of gases in liquids or the extraction of liquids by means of gases and vapours, for other processes for treating materials in which mixing is necessary or advantageous, and for the washing of solid materials.
In the process according to the invention a current of the material is led laterally out of a container holding the material being mixed and is returned in a jet under pressure into the material in the container, in such a direction that the leading out and return of this current generate respective rotating flow components at right angles to one another, the resultant of which gives rise to a winding positive flow. The best results are obtained if the jet returns the material at least approximately centrally of the cross section of the container. Also it will usually be necessary for the jet to be contracted in relation to the flow cross section of the returning material before it is discharged as a jet in order to attain convenient speeds and pressures in the apparatus used for operating the process.
The process is particularly suitable for continuous operation. The resulting winding flow in the material gives rise to a particularly long and turbulent flow path and to correspondingly eflective mixing.
The apparatus for practising the process according to the invention comprises a container'for the material and is characterised by at least one outlet conduit, an inlet conduit with a mouth directing the material in a jet in the required direction, and a pump the inlet of which is connected to the outlet conduit and the outlet of which is connected to the inlet conduit. The mouth will usually be ulation of the mixing action from zero upwards, and no moving parts in the mixing vessel so that it can be hermetically closed, in connection with which it may be mentioned that hermetically sealed pumps are known.
Examples of the apparatus according to the invention are illustrated in the accompanying diagrammatic drawings. The process according to the invention will be described by way of example with reference to these drawings.
FIG. 1 is a diagrammatic longitudinal section of a mixing apparatus for continuous operation.
3,334,868 Patented Aug. 8, 1967 lCe FIG. 2 is a section on the line II-II in FIG. 1.
FIGS. 3, 4 and 5 show modifications of a part of FIG. 1 in longitudinal section.
FIG. 6 is a diagrammatic longitudinal section of an apparatus for mixing a gas with a liquid.
FIG. 6a is a detail of FIG. 6.
FIGS. 7, 8 and 9 are diagrammatic longitudinal sections of further modifications of FIG. 1. v
The apparatus illustrated in FIGS. 1 and 2 comprises a mixing container 1 having a supply pipe 7 and a discharge pipe 9 for the material. Three supply vessels 8a, 8b, 8c only shown in part communicate through respective flow meters 9a, 9b, 9c and regulating valves 10a, 10b, 10c with the supply pipe 7. A regulating valve 16 is included in the discharge pipe 9.
The container 1 has three outlet conduits 5a, 5b, 50 with respective regulating valves 6a, 6b, 6c. These outlets are connected to a collecting pipe 5 which leads to the inlet of a pump 2. A space for the driving motor of the pump is marked 2a.
The container 1 has an inlet conduit comprising a pipe 3 one end of which projects into the container and the other end being connected to the outlet of the pump 2. The pipe 3 outside the container passes through a heat exchanger 17 by the aid of which the material flowing in the pipe can be heated -or cooled and at the end projecting into the container has a contracted mouthpiece in the form of a nozzle 4.
A supply pipe 7 and discharge pipe 9 are connected to the container at locations which in relation to the flow in the inlet 3 are opposite one another and in this direction relatively staggered. At the same time the point of connection of the supply pipe 7 advantageously is at a smaller distance from the nozzle 4 than the point of connection of the discharge pipe 9.
The substances at least one of which is a liquid, viscous or pasty fluid and which are intimately mixed for the production of a solution which may be a true solution, or a colloidal solution, or for the production of a dispersion, suspension, emulsion or a paste or for a flotation operation, are supplied to the supply vessels 8a, 8b, 8c and are continuously supplied to the supply pipe 7 and through this to the container 1 in a ratio set by the valves 10a, 10b, 10c and supervised by means of the meters 9a, 9b, 9c. The pump 2 continuously draws out a part of the substances in the container through the outlets 5a, 5b, 5c and pipe 5 and returns this withdrawn portion of the substances under pressure to the container through the pipe 3. By corresponding adjustment of the valves 6a, 6b, 6c this portion of the substances can be taken'from below, in the centre or the top or any determined distribution from these three zones of the container 1. The substance returned to the container 1 undergoes a considerable acceleration of its flow speed at .the nozzle 4. It thus flows at high speed into the substances in the container'l, flow components indicated in FIG. 1 at 11a, 11b thus arising. The flow 11a carries with it substances entering the container 1 through the mouth 13 of the pipe 7 so that these substances take part in the mixing process in the container immediately after their entry. From the flow 11b, part flows 15 are diverted which form the current of substances returned to the container under pressure by the pump 2. As the location on the container of the dischargeconnection 9 is horizontally spaced from the point of connection 13 of the supply pipe 7, and the points of connection of the outlets 5a, 5b, Scare horizontally spaced from the current through the nozzle 4, a horizontal flow also arises in the container. This horizontal flow has flow paths which,
seen in plan (FIG. 2) follow circular arcs marked 12a, 12b and 12c, 12d in FIG. 2. This results in the substances from the mouth 13 of the supply pipe 7 and from the nozzle 4 necessarily reaching the discharge pipe 9 and outlets 5a, 5b, 50 by winding flow, the windings having circular arcuate curved axes. In this way in comparison with the dimensions of the container the streamlines of flow of the substances in the container have a very long path and a correspondingly intensive mixing action is achieved. This mixing action is still further intensfied because the flow path is additionally considerably lengthened in that from the winding flow through the container 1 (from pipe 7 to pipe 9) part currents are diverted before it reaches the discharge pipe 9 and are returned under pressure through the nozzle 4 to the winding flow. In this way the withdrawal of a part of the substances and return thereof not only serves to generate the winding flow as described above which is in itself very advantageous but also to ensure that the substances in part repeatedly follow the winding path. The extent to which this takes place depends on the output of the pump 2 and the rate of flow through the container 1 set by the valve 16. An important advantage is that the radial widening of the current emerging from the nozzle 4 produces intensive eddying which has a correspondingly intensive mixing action.
If the mixing process or some other process to be effected or facilitated by mixing (e.g. dissolving) or some other similar reaction is to be influenced by heating or cooling, the heat exchanger 17 is set in action in the appropriate manner. If the apparatus is also required to carry out any additional action or process such as homogenisation, emulsification, or dispersion, the heat exchanger 17 can be replaced by or combined with a suitable device for the purpose.
The nozzle 4 can as FIG. 3 shows be brought close to the bottom 1a of the container 1 at a distance 18 which may amount to from 0.2 to 2 times the diameter of the contracted mouth, in order to achieve an intensive radial mixingaction at this region by the impact of the jet on the container bottom. The same thing can be achieved by the provision of a separate impact wall (not shown) arranged in front of the nozzle 4. Such an impact wall is subject to wear (erosion). A similar but increased effect can be achieved without an impact wall subject to wear by use as shown in FIG. 4 of two nozzles 4a and 4b the mouths of which face one another. Both nozzles 4a and 4b are connected to the pipe 3 which in FIG. 4 is perpendicular to the plane of the drawing but is shown dotted turned into the plane of the drawing.
The nozzle 4 (FIG. 1) can have a number of apertures the flow directions of which lie in star formation in a plane or it can have a corresponding angular discharge slit as FIG. 5 shows.
In order to introduce a gas into the substance in the container and distribute it through the substance, the nozzle 4 on the pipe 3 can be constructed as a mixing nozzle and the gas be supplied to this mixing nozzle.
FIG. 6 shows a mixing device for this purpose, of which the. parts 1, 2, 3, 4c and 5 cor-respond to the parts 1, 2, 3, 4 and 5 in FIG. 1. Differing from the nozzle 4 of FIG. 1, the nozzle 4c is a mixing nozzle for example similar to the nozzle of a jet pump. The pipe 3 for the substances and a pipe 23 for the gas are connected to the nozzle 40. This pipe 23 is supplied both through a pipe 22 from a gas holder 20 and through a pipe 21 from the upper gas-containing part 19 of the container 1. The mixing apparatus according to FIG. 6 in addition incorporates a cyclone 25 only indicated symbolically in FIG. 6 but shown diagrammatically in FIG. 6a. This cyclone serves to remove excess gas from the substance in the container 1 which might lead to undesirable foaming. Such an excess of gas can arise for example in fermentation processes. The cyclone 25 is connected by a pipe 26 in which a second pump or blower 2b is included with the upper part of the container 1 and by a branched pipe 28 leading downwardly with the container 1 and with the pipe 5. The branch opening into the pipe 5 is thus under the action of the pump 2. An upwardly directed pipe 27 serves to carry away the excess gas.
To operate the device according to FIG. 6 the container is filled with the fluid to be treated up to a level above the point of connection of the pipe 5 and below the point of connection of the pipe 26, and the holder 20 filled with the gas to be used. The pump 2 is then operated until the liquid has taken up the desired quantity of gas in very fine distribution. By simultaneously operating the pump 2b the foam forming on the surface of the liquid is transferred to the cyclone 25 which separates the liquid and gas from one another by centrifugal action.
The device according to FIG. 6 can be so constructed that the pump 2 also does the duty of the pump 215. Further the device can be constructed to supply gas to a flowing liquid, the liquid being supplied to the container 1 (FIG. 6) at the bottom near the mixing nozzle 4c in the manner above described with reference to FIG. 1 and being led out at the top diametrically opposite the point of supply, while gas is continuously supplied in addition.
If the container in which mixing is to be effected has a longitudinally extended form it is desirable to provide several nozzles distributed along the length of the container as FIGS. 7 and 8 show.
According to FIG. 7 the container 1 is a vessel ar ranged with its axis vertical. The axial length of the vessel is considerably greater than its diameter. A part of the pipe 3 is arranged axially in the vessel 1 and has several nozzles distributed over the height of the vessel. In FIG. 7 four nozzles 4, 17a, 17b and 18 are shown of which the lowermost 4 is directed downwardly, the next above 17a and the uppermost 18 are directed upwardly while the remaining nozzle 17b is arranged in the manner described above with reference to FIG. 5. The substance discharged through the lowermost nozzle 4 impinges at the bottom of the vessel 1 and is redirected thereby upwardly. The outlet conduit consists of a hose 5d of rubber or similar material or made flexible in any other convenient manner, arranged inside the vessel 1 and a pipe 5e outside the vessel connected to the hose and leading to the pump. The outer end 29 of the hose 5d is carried by a float 30 and is thereby always held just beneath the surface 31 of the substances in the vessel 1. In this way independently of how full the vessel 1 is, the substance is always withdrawn from the uppermost layer of the charge. This is important if liquids with very different specific gravities are being treated together and the vessel is not always charged to the same level.
The float 30 is advantageously guided by a guiding device not shown so that it can only move vertically in such a way that the end 29 of the hose is always opposite the supply pipe 7 in relation to the geometrical axis of the pipe 3.
Preferably in the apparatus according to FIG. 7 also, the supply pipe 7 and the mouth of the collecting pipe 5d are located at points of the container which are diametrically opposite in relation to the part of the inlet pipe 3 arranged on the axis of the vessel.
In the embodiment shown in FIG. 8 the container is again an upright vessel 1 the height of which is greater than the diameter. The vessel 1 is divided by several horizontal partitions distributed over its height into chambers. In FIG. 8, two such partitions 16a and 16b are shown which divide the vessel into three chambers. In each of these chambers the mixing process takes place in the manner described above with reference to FIGS. 1 and 2. It is essential to the mode of operation that the inlet and outlet of each chamber are diametrically opposite in relation to the axis of the container on which the nozzles 4 are arranged. Thus the transfer port 240: which forms the outlet from the lowermost chamber and the inlet to the middle chamber is diametrically opposite the inlet (supply pipe) 7 to the lowest chamber and also diametrically opposite the transfer port 24b which forms the outlet from the middle chamber and the inlet to the uppermost chamber and is located diametrically opposite in relation to the outlet (collecting pipe) 5 of the uppermost chamber.
The processes and apparatus above described are suitable for all cases in which it is desired to effect intensive mixing with small expense and in a short time, for example for homogenising, for accelerating dissolution processes, for emulsifying .and dispersing, for the production of suspensions and colloidal solutions, for flotation processes, for accelerating reactions and so forth. If the ap paratus only serves for homogenising it sufi'ices to provide a single supply vessel. If more than three ingredients are to be mixed, the number of supply vessels can be correspondingly increased. It is advantageous, in the diagrammatically illustrated examples to round off the junction of the bottom and top of the container into the side wall in order to avoid dead spaces.
In the apparatus shown in simplified form in FIG. 9, change in the volume of the charge and thus of the position of the surface 31 is taken account of by the outflow pipe 5 to the pump 2 drawing from a separate part In of the container 1. This part is separated from the remainder 1b of the container by means of a separating wall 32 which presents a slit or perforations from top to bottom. This vertically disposed opening or openings in the separating wall enables the medium in the whole container notwithstanding variation in the surface 31 to pass from the part 112 to the part In in accordance with the arrows 33a, 33b and to be drawn through the pipe 5 to the pump 2 and thence directed through the nozzle 4.
The container part 1a can instead be constituted by a slit or perforated pipe disposed within the vessel 1.
For emptying the vessel it would be of advantage if the bottom of this part 1a were arranged at a lower level than that of the part 1b but this is not shown in the drawing.
Various modifications can be made. Thus for example the heat exchanger 17 instead of being traversed by the pipe 3 leadingfrom the outlet pump might be traversed by the pipe 5 leading to the inlet to the pump or there might be two heat exchangers. In apparatus as to FIG. 8 the structure is divided into chambers by partitions communicating from one chamber to the other and there need not be two simple transfer ports but piping arrangements could be provided disposed so that the inlet and outlet of each chamber are in relation to the central inlet conduit diametrically oppositely arranged as Well as being at opposite ends of the chamber.
1. A process of mixing materials, of which at least one is capable of flowing, in a container, said process comprising causing said flowable material to flow along a first predetermined flow path within the body of material in the container to pass out of said container, and returning said flowable material into the container in a jet so as to flow along a second predetermined flow path within the body of material in the container, said first and second flow paths being so predetermined as to generate flow components at right angles to one another the resultant of which gives rise to a winding flow of the flowable material through the material in the container to produce a thorough admixture thereof.
2. A process of mixing according to claim 1 wherein the return jet of flowable material is directed approximately centrally of said container.
3. A process of mixing according to claim 1 wherein a gas is led into the mixture within the container together with the return jet of flowable material.
4. Apparatus for mixing materials at least one of which is capable of'flowing, said apparatus comprising a container, outlet means from said container, inlet means to said container, conduit means connecting said inlet and outlet means, and pump means in said conduit means operable to withdraw flowable material from said container through said outlet means and to return such flow-able material to said container through said inlet means, said inlet means acting to direct the returning material in a free jet into the mixture within said container and said inlet and outlet means being so relatively arranged that when the container is filled with material and the pump means operated, the material withdrawn through said outlet means follows a first predetermined path through the body of material in the container and the jet of material returned through said inlet means follows a second predetermined path through the body of material in the container so selected in relation to said first predetermined path as to generate flow components at right angles to one another the resultant of which gives rise to a winding flow of the flowable material through the body of material in the container.
5. Apparatus for mixing materials according to claim 4, wherein said inlet means is approximately centrally disposed in relation to the cross section of the container.
6. Apparatus for mixing materials according to claim 4, wherein said inlet means comprises an inlet pipe extending vertically into said container and terminating adjacent an impact wall so that material entering said container through said pipe is deflected by said wall and caused to follow a predetermined path extending in a vertical plane and said outlet means is disposed laterally of said container so as to cause outflow of said material along a predetermined path extending in at least one horizontal plane through said container.
7. Apparatus for mixing materials according to claim 4, wherein said inlet means comprises an inlet pipe extending vertically into said container and terminating adjacent an impact wall so that material entering said container through said pipe is deflected by said wall and caused to follow a predetermined path extending in a vertical plane and said outlet means is disposed laterally of said container so as to cause outflow of said material along a predetermined path extending in at least one horizontal plane through said container, and said outlet means comprising a plurality of outlet conduits disposed at different vertically spaced levels so as to cause outflow of material along predetermined paths extending in a plurality of vertically spaced horizontal planes through said container.
8. Apparatus for mixing materials according to claim 4, wherein said inlet means comprises an inlet pipe extending vertically into said container and terminating adjacent an impact will so that material entering said container through said pipe is deflected by said wall and caused to follow a predetermined path extending in a vertical plane and said outlet means is disposed laterally of said container so as to cause outflow of said material along a predetermined path extending in at least one horizontal plane through said container, and said outlet means comprising a plurality of outlet conduits disposed at different vertically spaced levels so as to cause outflow of material along predetermined paths extending in a plurality of vertically spaced horizontal planes through said container, each of said outlet conduits including a flow regulating valve.
9. Apparatus for mixing materials according to claim 4, adapted for continuous operation, including at least one supply conduit for introducing unmixed materials into the container and at least one discharge conduit for withdrawing admixed materials from the container, said supply and discharge conduits being connected to relatively stag- .gered supply and discharge ports in opposite wall surfaces of said container.
10. Apparatus for mixing materials according to claim 4, wherein said inlet means comprises an inlet pipe extending vertically into said container and terminating adjacent an impact wall so that material entering said container through said pipe is deflected by said wall and caused to follow a predetermined path extending in a vertical plane and said outlet means is disposed laterally of said container so as to cause outflow of said material along a predetermined path extending in at least one horizontal plane through said container, the termination of said inlet pipe being arranged a distance from said impact wall Which is from 0.2 to 2 times the diameter of said pipe at its termination.
11. Apparatus for mixing material according to claim 4, including a mixing nozzle arranged at the mouth of said inlet means and a gas supply conduit connected to said mixing nozzle.
References Cited UNITED STATES PATENTS Mobley et al.
Hofimann 259-95 X Auer 2594 Hicks 259-95 X Carver et a1 259-4 X Clark 259-4 10 WALTER A. SCHEEL, Primary Examiner.
J. M. BELL, Assistant Examiner.