The present invention relates to a method and to an apparatus for bringing into intimate contact with one another two or more components of which at least one is in liquid form and the remainder of which may be either in solid form, liquid form or gas form, such as to obtain a mixture, an extraction, a solution, a suspen¬ sion, an emulsion, or precipitation.

It is often necessary within, for instance, the field of technical and analytical chemistry, to bring different liquids, or liquids and solids or gaseous substances, into contact with one another as intimately as possible. In the case of liquids which can be dissolved one within the other, the object is to produce the best possible homogenous mixture of liquids and any components that may be dissolved therein. In the case of liquids which cannot be dissolved or which are not readily dissolved in one another, the object is to transfer substances dissolved in one of the liquids to the other liquid, i.e. an extraction process, or to mix the liquids to¬ gether to form an emulsion. It is sometimes also neces¬ sary to mix liquids and solid substances together, or liquids and gaseous substances, in order to leach or dissolve the gas or the solid substance in the liquid, or to obtain a suspension. Another object may be to bring about a reaction between the components, thereby, for instance, dissolving a not-readily dissolved sub- stance in a liquid or causing two or more substances in the components to react- so as to form a new substance

which can be dissolved in one component or with the liquid or liquids can form an emulsion or a suspension, or can precipitate as a deposit.

It is often difficult to bring liquids into sufficiently intimate contact with one another, for instance when the densities of the liquids concerned differ markedly from one another, or when such contact is to be achieved within a short space of time in a process which is continuously in progress. Furthermore, it is necessary in some cases to take separate precautionary measures, such as working in a closed system, for instance when the materials to be mixed are toxic, corrosive, unstable, or not compatiable with air, have high vapour pressures or must be kept sterile. If such circumstanc¬ es exist, those mixing processes available at present cannot be safely applied without causing considerable complications.

Hitherto, liquid components have been mixed in batches with the aid of agitators in large or small vessels, by shaking or vibrating the vessels concerned, or by per¬ mitting the component to flow through a conduit in which fixed vanes are mounted. When using such systems, howev- er, it is difficult to mix the components effectively throughout the whole of the vessel or the conduit con¬ cerned, particularly when a small quantity of a first component shall be mixed with a large quantity of a second component to form an homogenous solution. Fur- thermore, such mixing systems include a large number of mechanical components which are difficult to clean and which may be expensive to replace when new materials are to be mixed together.

The object of the present invention is to overcome the problems that are manifest in earlier methods and

systems intended for achieving intimate contact with liquids, solids and gases.

Accordingly, the invention relates to a method by means of which these problems are avoided and with which a more homogenous mixture of the components concerned is achieved in a shorter time than was previously the case. This is achieved in accordance with the invention by passing the components together through a flexible hose which is arranged and manipulated in a given way. With¬ out throttling or constricting the bore of the hose, the hose is fixed firmly in two mutually spaced hose holders mounted on a support surface, such as to render it impossible for the hose to slide in the direction of its longitudinal axis or to be rotated around its centre axis at its points of attachment. The length of hose which extends between the hose attachment points is greater than the distance between the hose holders and therefore forms a free hose length or loop therebetween, this loop being caused to swing in a circular or ellip¬ tical path whose axis of rotation is a line which ex¬ tends between the two hose attachment points, said rotation or swinging of said hose part being effected with the aid of an external device. Because the hose is unable to twist around its long axis at its attachment points, the circulatory swinging movement of said hose part will be such that a point on the hose wall which at any given moment is located on the outer side of the hose, as seen from the axis of rotation, will lie in- wardly turned towards said axis when the hose has reached a diametrically opposed position of swing. Thus, a cross-section through the hose does not rotate about its own centre during rotation of the hose, but is moved parallel with itself in the circulatory path. The hose is subjected to bending and stretching, but not to rotation about its own axis.

The invention also relates to a system or to apparatus for achieving intimate contact between at least two components in accordance with the invention, said appa¬ ratus including a flexible hose which is fixed between two non-rotatable end pieces which are spaced apart at a distance shorter than the length of the hose contained therebetween, so as to form an intermediate hose loop, one or more connector pipes connected to one end of the hose, the inlet end, or to some other hose inlet part, and an outlet which is connected to the other end of the hose, the outlet end, one or more feed means for feeding the components to be brought into contact with one another to the inlet pipes and through the hose to the hose outlet, and a device for rotating the intermediate hose part in a circular or elliptical path.

The inventive mixing principle may also be applied for mixing solid phase components in particle form, such as powder form, granular form, or in the form of seeds, grain or chemicals precipitated as crystals, or material which has been ground down to an appropriate particle size.

In this case, the mixing apparatus will preferably be positioned vertically when wishing to pass the compon¬ ents through the device gravitationally. Alternatively, the components may be passed through the system with the aid of compressed air, for instance.

When reaching a given characteristic value of the compo¬ nents passing through the device, the centrifugal force generated by rotation of the hose will cancel out the effect of gravity, when the device is erected vertical¬ ly. The mixing device will then function as a valve and throttle the flow of components through the system. When the mixing device is stationary, i.e. does not

rotate, the components will fall freely through the hose. A desired flow can be achieved between these two extremes, by adapting the rotational speed of the mixer.

When the mixer is erected vertically, the components to be mixed are introduced into respective inlets with the aid of a particular metering device preferred at that time, suitably a funnel, hopper or like device fitted to the inlet. The components may be introduced sequential- ly in separate metered quantities of those components to be mixed, or may be introduced continuously. In the case of sequential feed, the components move generally separately through the hose (in the form of "bands") up to the outermost peak position of loop rotation, from where they then fall further down through the hose, controlled by the speed at which the loop is rotated or swung.

Mixing of the components is achieved by mounting a mixing chamber in the latter part of the hose loop. An advantage is afforded when the mixing chamber is given a non-cylindrical form and is adapted with respect to size so as to accommodate a sufficient number of segments (alternatively sufficient volume) of the components in order to achieve an homogenous mixture. The components are mixed together by forcing said components to eddy or swirl in the mixing chamber as a result of the centrifu¬ gal force generated by rotation.

The invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 is a schematic view of the invention; Figure 2 is a cross-sectional view taken through the line II-II on the inte ediate part of the-hose as it rotates through one half of a revolution;

Figures 3 and 4 illustrate one embodiment of the inven-

tive apparatus; and

Figures 5 and 6 are curves which illustrate the mixing process and which have been obtained when carrying out the inventive method in practice.

The manner in which the inventive method achieves inti¬ mate mixture of two or more components will be described in more detail with reference to Figures 1 and 2.

Figure 1 shows the rotatable hose 1, its inlet end 2 and its outlet end 3. The hose is fixed in hose holders 4 and 5 so that, as before mentioned, the hose is unable to twist about its longitudinal axis at its attachment points and is also unable to slide in the direction of its longitudinal axis, and also such that the bore or throughflow area of the hose is not throttled to any great extent. The free length of the hose extending between the hose attachment points is adapted so as to form an arcuate loop therebetween. Although not shown in the drawings, the free or intermediate length of the hose can be swung by means of an external, mechanical rotary means, attached for instance to the centre of said intermediate hose length, with the line M between the hose attachment points as the axis of rotation.

Figure 2 illustrates the section marked II-II in Figure 1, and illustrates the path travelled by the hose about the rotational axis M, and also illustrates some of the positions through which the hose cross-section passes as it moves through one half of a revolution.

For the sake of simplicity, the following example de¬ scribes how the apparatus functions to mix together solely two liquid components, one of which has the density T and the other of which has the density L, wherein T is greater than L, and which are introduced

into the inlet end 2 of the apparatus and there together form a liquid column.

When the components arrive at that part of the hose which moves in a circulatory path, the component of the highest density T will be urged by centrifugal force towards the periphery of the circulatory path. The component L of lower density will be subjected to a smaller, outwardly acting force and will therefore be located nearer the centre M of the circulatory path than the heavier density component. If the curved part of the hose which moves in a circulatory path were a rigid curved tube, a cross-section of the curved part would also rotate around its own centre m and a diameter through the cross-section, which, when the hose, or tube, is located in a certain position, is directed towards the centre M of the circulatory path, would rotate with this rotary movement and be constantly directed towards the centre line M of the circulatory path. The component of highest density T would then constantly be urged towards the same part of the tubular wall, i.e. that part of the wall which is constantly located distal from the circulatory part. This would result in separation of the heavier component T from the lighter component L.

Since a flexible hose is used in accordance with the invention, the component T of highest density will wander along the inner surface of the hose so as to constantly lie in that part of the hose which is located furthest away from the centre M of the rotational orbit. Correspondingly, the component L of lower density will wander along the inside of the hose in that part thereof which is nearest the centre M of said circulatory path. The liquid column rotates about its own centre m. This wandering of the two components is illustrated

schematically in Figure 2, which shows the centre part of the hose rotated through one-half revolution. Fric¬ tion generated between the hose and respective liquids has not been taken into account in the Figure 2 illus- tration. Because the hose is fixed so as to be unable to twist about its own axis, as before described, it will instead move parallel with itself around the circulator path described by the hose. This is illus¬ trated in Figure 2 by two dash lines 0 and N, each of which indicates a marking pin firmly anchored to the hose wall. As the hose moves around its circulatory path, the hose moves from position A, through positions B, C and D to the position E, with the marker pin O constantly facing upwards and the marker pin N constant- ly facing downwards.

At the same time as the centrifugal force contributes to movement of each component along the hose wall, this movement is counteracted by the friction generated between the hose wall and respective components, causing a boundary layer to be formed adjacent the hose wall, this boundary layer tailing behind as respective compo¬ nents wander around the hose wall. Consequently, a boundary layer composed of heavier component T will be met in the hose by the lighter component L which moves along the hose wall behind the heavier component T, therewith mixing the two components together. When the hose is rotated at an appropriate speed, eddy currents and turbulence will occur, therewith bringing the components into very intimate contact with one another and effectively mixing said components together.

As a result of the turbulence generated in the compo¬ nents moving through the hose, the various layers will not only be subjected to agitation, as seen through a hose section in the direction of the radius of

rotational movement, but the segments pumped se¬ quentially through t- hose will be mixed intimately with one another, provided that the segments are not excessively long. This longitudinal mixing of the components is also based on the formation of component layers which border on the hose wall as the components advance along the hose.

The hoses used may have a smaller or larger diameter, depending on the nature of the substances to be mixed together. Hoses made of elastomeric material, such as silicone hoses, may be used to advantage. The diameter of the hose may range up to 1 dm or more, for instance up to 3 dm, and down to 0.01 mm, for instance down to 0.1 mm. In the case of a hose having a diameter of 1 dm, the flow rate may, for instance, be between 3 and 300 1/min, whereas the flow rate of a hose having a diameter of 0.1 mm will be, for instance, between 0.12 and 2 ml/min, more particularly between 1 and 2 ml/min. When the components are delivered in segments, or blocks, it is preferred that at least five segments will be located simultaneously in the curved part of the hose. The curved hose part is preferably swung at a speed of between 60 and 400 revolutions per minute, although speeds beneath 60 rpm are also conceivable. A suitable rotational speed is from 100 to 200 rpm.

The components to be mixed together may be introduced into the hose so as to flow together in two or more streams in the inlet end 2 of the hose and/or into an inlet part mounted on the rotary part of the hose. This can be achieved by coupling more than one inlet line to the hose 1. The components may also be delivered in segments or blocks. In this case, a plurality of delivery lines are connected to the hose inlet line in a manner which will enable segments of the different

components to be delivered alternately and in series to the hose inlet line and the hose. In this case, it is necessary to control the size of the individual segments, so as to obtain optimal mixing of the segments in the longitudinal direction.

The present invention thus enables intimate contact to be achieved between the various components, so as to form therewith a homogenous stable mixture, solution, suspension or emulsion, or to produce an unstable mix¬ ture which is then allowed to separate into two liquid layers, a liquid layer and a gas phase or a liquid and a solid sediment. This is achieved without the presence of moveable parts within the vessel, i.e. the hose, where the actual mixing together of the components takes place. This renders the system inexpensive and easy to clean, either by flushing the hose or by simply replac¬ ing the same. The system is also environmentally friendly, since it is a closed system. The system also consumes very little energy.

The inventive mixing apparatus can also be used to mix components together under sterile conditions. This enables the system to be used, for instance, in the preparation of drugs taken in liquid form, or in the hygienic preparation of beverages. The system may also be used at moderate pressures above and beneath the ambient pressure. For instance, the system can be used in the manufacture of paints in which small quantities of concentrated pigment suspensions are to be mixed with very large quantities of a base colour. The inventive system may also be used in the field of analytic chemis¬ try, for instance in the automatic analysis of blood samples or water, where the samples are mixed with different reagents, or for the purpose of homogenizing samples. It will be understood from this that the

inventive system can be used effectively in a large number of fields, since it s possible to mix small substance quantities together with the aid of narrow gauge hoses and also to mix large quantities of differ- ent components together with the aid of hoses of larger gauge and at higher rates of flow.

Figures 3 and 4 illustrate an exemplifying embodiment of an inventive system. Figure 3 shows the system from one side while Figure 4 is a horizontal sectional view taken on the line IV-IV in Figure 3.

That part of the system in which the mixing process takes place is shown in Figure 4. Similar to the Figure 1 illustration, the rotatable hose is referenced 1, the hose inlet is referenced 2, the hose outlet is refer¬ enced 3, and the hose holders are referenced 4 and 5, wherein the free, intermediate hose part is held fixed against rotation about its own axis by means of suit- able, known clamping devices. The hose holders are fitted to a bottom plate 6.

The free hose part 1 is connected at its midway point to one end of a rod 8 in a manner to prevent the hose from rotating about its own axis. The rod 8 is pivotally attached to peripherally located points 9 and 10 on circular discs 11 and 12 of mutually equal size, as shown in Figures 3 and 4. Each of the two discs 11 and 12 has bolted thereto a gearwheel 13 and 14, which gearwheels are also of mutually equal size. The gearwheels mesh with a further gearwheel 15 positioned centrally between the gearwheels 13,14, said further gearwheel 15, being connected to a motor 17 through its shaft and a coupling 16. All of the shafts of respec- tive gearwheels are journalled in a box-like stand 18.

When the motor is started up, the centre gearwheel 15 meshing with the two outer gearwheels 13 and 14 is rotated via the shaft 16. This results in rotation of respective discs 11 and 12, which rotate at the same speed. The rod 18 pivotally attached to the discs at points 9 and 10 thereon accompanies the rotational movement of the discs while retaining its horizontal position during this movement. The point 7 on the hose 1 at which the rod 8 is connected to the hose is therewith also caused to rotate, thereby moving the midway point of the hose around the intended circulatory path around the axis M. Figure 3 illustrates four different posi¬ tions of the end of the rod 8 and the midway point of the hose.

A number of working examples will now be described with the intention of illustrating how contact is achieved between different components with the aid of the inven¬ tive method and apparatus. The apparatus illustrated in Figures 3 and 4 is used in the examples.

Examples

Example 1

Ethanol and potassium chloride solution were pumped in two streams with the aid of a peristaltic pump, these streams being combined at the hose inlet 2 through a T- coupling. Mounted in the extension of the hose down- stream of the outlet 3 were two platinum wires which could be moved vertically and transversely through the hose. Conductivity was measured in the upper and the lower part of the hose respectively, and the values registerd were recorded on a writer. The result is shown in Figure 5. When the hose was stationary, the liquids pumped through the hose were not mixed to any

appreciable extent. When the hose was swung, the con¬ ductivity measu: i at the bottom of the hose was essen¬ tially the same as that measured at the top of the hose. The two liquids separated immediately into two layers as soon as the hose ceased to rotate.

Example 2

Ethanol was pumped continuously through the apparatus described in Example 1. Short segments of potassium chloride solution were delivered to the ethanol flow. Figure 2 illustrates the variations in concentration when the hose was stationary and also shows how these variations equalized when the hose was rotated.

Example 3

The hose 1 was divided at its midway point and a tank in the form of the volume part of a glass pipette was attached between the separation points. This enabled the components pumped through the hose to be observed.

Water was pumped through the apparatus continuously. When a few chloroform segments were added to the appara- tus during rotation, it was possible to see, with the aid of a tuned stroboscope lamp, that the chloroform segments remained in the tank and rotated therein along its periphery.

Example 4

An aqueous solution coloured with Dithizon was pumped through the apparatus described in Example 3. As the apparatus was rotated, it could be seen how the chloro- form phase extracted the dye from the solution.

Example 5

A diluted caustic solution was pumped through the apparatus used in Example 4. As the apparatus rotated, it could be seen that the dye extracted transferred immediately to the aqueous phase.

Example 6

About one-third of the volume of the tank used in Exam¬ ple 3 was filled with an alkaline aqueous solution coloured with phenolphthalein. As the hose and the tank rotated, air saturated with acetic acid was pumped through the apparatus. The colour of the aqueous solution suddenly disappeared after pumping for a short period of time. No acid reaction in the gas at the hose outlet was observed until the indicator colour had disappeared completely from the tank. The exiting gas was then found to be acid.

This showed that acetic acid was transferred from the gas to the alkaline solution.