US 2577247 A
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Description (OCR text may contain errors)
Dec. 4, 1951 E. M. IRWIN METHOD AND APPARATUS FOR EMULSIF'YING FLUIDS Filed Jan. 3, 1948 FIG.. 2.
Patented Dec. 4, 1951 EMULSIFYING FLUID Emmett M. Irwin, San Marino. Calif. Application January 3, 1948, Serial No. 412 14 Claims. (Cl. 9.9-221) My invention relates to the art of producing an emulsion of two liquids such as oil and water, to the art of increasing the permanency of a given emulsion, and finds particular utility in the homogenizing of milk.
The theory of emulsions is complicated and the authorities are in disagreement. It is known, however, that an emulsion of two immiscible liquids separates into its parts. It is also Well known that by passing a mixture of liquids through an emulsifying agency such as a col loidal mill or an homogenizing valve an emulsion can be formed, the permanency of which will vary with the liquids involved. The greater the Aimmiscibility of the liquids the less will be the permanency of the resulting emulsion.
The present invention is useful in emulsifying liquids and in increasing the permanency of liquid emulsions generally. It nds great usefulness in permanently emulsifying milk to prevent the separation of the butter fat and the water, a process known as homogenization.
` Homogenizers currently in use are largely of the valve type making use of tremendous pressures from 1500 to 300() pounds per square inch. The equipment is necessarily bulky and heavy and the cost is too great for the small milk producer. A defect or aw in the valve results in incomplete homogenization which' grows Worse as it continues. Colloidal mills and other forms have the objection that the production rate is low and frequently the process must be repeated several times to effect satisfactory emulsication.
The dispersion of the butter fat particles in the water phase of the milk and the reduction in the particle size by mechanical means as heretofore effected in homogenizing processes is supplemented, according to the present invention, by the effect of electrical charges impressed to change the electrical relationship existing between the particles. Much lower pressurescan be used than heretofore thought possible with resulting savings in costei equipment and in power consumption.
It is a primary object of my invention to provide an emulsifying process in which an electric charge on the fluid particles is positively impressed electrically to provide complete and permanent emulsication. The electrical power involved in imparting the charge directly is very small. For example, I have been able to duplicate the performance of the present day high pressure homogenizers by using a pressure of only 800 pounds to reduce the sizeof the butter fat particles. and by using an electrical energy of less than a watt for the charging current. In general the pressure should be above 500 pounds per square inch and below the pressure necessary to effect permanent emulsiiication. Where milk is the iluid being treated, a pressure range of from 500 to 800 pounds per square inch has been found satisfactory.
It is another object of my invention to provide a fluid emulsifying process and an apparatus operable in accordance therewith in which the particles are charged electrically immediately following the reduction in particle size.
It is another object of my invention to provide a uid emulsiiying process and an apparatus operable in accordance therewith in which the particles are charged electrically simultaneously with the reduction in particle size.
Another object of my invention is to provide a process susceptible of embodiment in an emulsifying apparatus having a unit, the liquid contacting surfaces of which are preferentially wetted by the components ofthe emulsion, one surface being wetted by one component and another surface by the other component, and, in one form, connecting these surfaces to a source of charging current of selected polarity so that the particles have a charge of the proper polarity imparted to them.
Other objects of the invention will be made apparent in the following description and claims.
Referring now to the drawings: A
Figure 1 shows a form of the invention in which a new type of colloidal mill is employed as the device for securing the reduction in size of the particles and simultaneously impressing the electrical charge;
Figure 2 shows another form of the invention in which conventional emulsifying valves are used in connection with a charging unit and which is particularly useful in homogenizing milk; and
Figure 3 shows a special type of homogenizing valve in which 4the charge is imparted to the particle at the same time that it is reduced in size.
The form of the invention shown in Figure l includes a colloidal mill. indicated generally by the numeral I0. This mill may be similar to conventional types and includes a frustro-conical rotor II, and a stator I2 having an inner conical surface which may be brought into closely spaced relationship to the mating surface of the rotor I I.
The stator is flxedly positioned in a cylindrical housing I3 closed at one end by a wall I4 and at the opposite end by a removable cover plate I5. The stator I2 is preferably mounted upon insulation lpressed into the housing I3, The rotor II, located in the housing I3, is rotated by an exteriorly located motor I8 by being mounted upon shaft 20 which extends through the wall I4. Packing 2| is provided in the wall I4 around the shaft to prevent leakage of liquid from the housing.
A fluid inlet pipe 23, which may connect to a fluid moving pump 24, enters the housing I3 above the rotor and stator. Likewise, an outlet pipe 25 connects to the space in the housing I3 below the mill Ill so that the liquid may be drawn oil? after passage between the apposed faces of the rotor and stator.
In the practice of my invention I impress a potential difference between the rotor II and asma/:.7
the stator I2 so that current flows through the fluid tobe emulsified as it passes between their apposed faces which become electrodes. I accomplish this by connecting a Wire 28 to the stator I2 and extending it through an insulated sealed opening in the housing I3. This wire 26 may be connected in series through an ammeter 21 and rheostat 28 to a current source E, either A. C. or D. C. Another wire 30 from the source E is connected to the frame of the motor I8 which is directly connected electrically through mechanical elements including the shaft 20 to the rotor I I. A circuit is thus established providing a potential difference between the rotor II and the stator I2. As soon as the liquid to be emulsiiled is introduced into the housing I3 and flows between the electrodes comprising the apposed faces of the rotor and the stator this potential will cause a flow of current therethrough which may be regulated by the rheostat 28 and which is indicated by the ammeter 21.
In the operation of this form of apparatus embodying the present invention the liquid to be emulsied is pumped by the pump 24 through the inlet pipe 23 into the housing I3. It then flows downwardly between the rotor II and the stator I2, filling the passage therebetween, and out through the outlet pipe 25. In the passage of the liquid between the rotor and stator a shearing action occurs in the liquid because of the close spacing of the apposed faces, a spacing which is adjustable by raising or lowering the motor I8. By the shearing action the size of the particles is reduced in accordance with well known principles. While passing between the rotor and stator comprising the two electrodes the liquid is under the action of an electric field due to the passage of current therethrough impressed by the potential E. This results in the impressing of electric charges upon the minute uid particles to produce a permanent emulsion. It will thus be evident that in this form of the invention the electric charges are impressed on the particles simultaneously with their reduction in size by the shearing action of the colloidal mill.
In Figure 2'I have shown another form of the invention in which the reduction in size is first accomplished by a pressure reducing valve and the electrical charges are subsequently introduced by passing the liquid through an electrical charging unit connected to the discharge of the valve. IIhe pressure reducing valve, indicated generally by the numeral 35, may be of a conventional type similar to those now employed in the homogenization of milk. It includes a metal body 38 in which is formed a chamber or cavity 31. One side of this cavity communicates through an inlet duct 38 in the body 36 to an inlet pipe 40 connected to a source of liquid under pressure to be emulsied. The entrance of the liquid into the cavity 31 is restricted by a valve disc 42 having a iluted stem 43 formed thereon and extended into the inlet opening 38 to serve as a guide. As the stem 43 is fluted liquid may pass freely along its length. The disc 42, however. makes a seat with the wall of the cavity 31 adjacent the opening 38 so that the liquid is forced to pass therebetween. A spring 44 resiliently holds disc 42 against its seat on the wall of cavity 31, being restrained adjustably by an adjusting screw 48 threaded into an opening 41 in the body 38 in alignment with the axis of the inlet opening 38 seating stem 43. Thus liquid entering the inlet opening 38 passes freely past the stem 83 but is restricted in passage between the disc d2 and its seat on the wall of the cavity 31 by the action of the spring 44. A shearing action on the particles in the liquid thus occurs in accordance with accepted practice in homogenizers and a reduction in particle size occurs as well as dispersion.
Liquid after passing through the valve 38 is piped from cavity 31 through an outlet pipe 48 to a charging unit, indicated generally by the numeral 80. Although it is not essential, I prefer to use a tubular construction for the charging unit because of the ease of obtaining tubing and its cheapness of fabrication. The charging unit includes an external tube 8I which functions both as a means for retaining the liquid and also as an electrode, a function to be explained later. The ends of the tube are closed by inlet and outlet end members 82 and 83 which may be threaded thereon. A chamber is thus formed by the tube 8I into which liquid may be conducted by connecting the pipe 48 to a bore 84 through the inlet end member 82. The same liquid, after traversing the length of the tube, .is discharged through an outlet opening 88 in the outlet end 83.
When emulsifying certain liquids. and particularly when homogenizing milk, it may be found that a second valve is desirable. 'Ihis valve 10 may be of the same construction as the valve 35 and is illustrated by the dotted outline in Figure 2. When incorporated, the inlet to this valve 10 is connected to the outlet opening 58 of the charging tube 8l so that the liquid which has been charged in the charging tube is then given a further shearing and blending action by the valve 10. When two valves are used it is usually not necessary to use a greater total pressure, the pressure drop being divided between the two valves.y
In order that the charging unit may function as a charging device for the liquid, I locate inside the tube 5I a cylindrical metallic member 81 held concentrically with respect thereto by the end members 82 and 83 between which it is clamped.
' Cylindrical member 51 is insulated from the supporting end members by insulators 88 which directly seat its ends. Tube or casing 5I and member 81 are thus adapted to form spaced electrodes. Current is conducted to the inner electrode 81 by a conductor 80 which passes through an insulated opening in the inlet end member 82 and connects to the electrode 81. A second conductor 8| connects to the other polarity of the source of power to which wire 80 connects.
Upon passing through the valve 38 in which the particles are greatly reduced in size the liquid in introduced through the inlet opening 84 and passes between the tube 8|' and the member 81 being subjected the while to a flow of electric current. It is this flow of current which supplies the charge to the particles which have been reduced to near micron size by theirl passage through valve 38, and results in the improvement in the emulsion characteristics.
I have found the invention, particularly the form illustrated in Figure 2, tov be particularly useful in the homogenization of milk. When used for this purpose I have used a conventional homogenizer valve as the valve 38. As stated before, such valves ordinarily require a pressure as high as 3000 pounds per square inch to accomplish satisfactory homogenization. By using the identical valve at greatly reduced pressures within the range of 500 to 800 pounds per square inch and following its action by the charging action of the electrical unit I have been able successfully to homogenize milk. In an example in which the ilow rate was gallons per minute the charging tube had a length of approximately 10 inches and an internal diameter of 4` inches. 'I'he inner electrode was 2 inches in diameter. A
` current of 0.15 ampere direct current was used and the voltage drop was approximately 1.25
volts. For example, I have used current densities preciably higher densities are used or if the milk is subjected to the flow of current for too long a period of time the pH of the milk may be changed and other complex results be obtained."
Likewise, if too little current is used the charg ing apparently is incomplete and the etliciency of homogenization' diminishes.
reducing the spacing between the electrodes El' and 5l so that me particles have'a greater opportunity of contacting the charging surface as they pass through the charging tube 50. Still greater eillciency may be obtained by providing stainless steel'baiiles in the space between the electrodes so that the milk must pass through and around these baiiies while passing through the charging tube. Other arrangements should be evident to those skilled in the art.
Referring now to Figure 3, I have shown a special form of valve in which the particle charges are impressed at the time the liquid passes through the valve, thus, as in the embodiment of Figure 1, combining the mechanicall and electrical units into one unit. 'Ihe valve l2 'I'he source of current may be direct or alternating although the results appear somewhat better when direct current is used. In the latter case the4 flow of vcurrent diminishes with the passage of time, a result which can be avoided by impressing an alternating current upon the di- 4rect current of a magnitude suicient to reverse the direction of current now for a minor part of a cycle only.
My invention also contemplates the use of different materials for the two electrodes. It is well known that when certain materials are immersed in a liquid mixture' oi', for example, oil and water, the' material will be preferentially wetted by one of the components of the mixture. Most metals, for example, are preferentially wetted by oil. I may make use of this preferential wetting property in the charging unit by making one of the electrodes of a substance preferentially wetted by one of the constituents in the liquid and making the other electrode of a substance preferentially wetted by the other constituent. In the case of an oil and water emulsion I make the outer tube or electrode 5I of a metal such as stainless steel and the inner electrode 5l of carbon. Thus the oil would preferentially wet the outer electrode and the water would preferentially wet the inner. Improved results have been noted from this observance of the wetting characteristics of the electrodes but is is to be understod that it may be ignored.
I also contemplate the use of the proper polarity of electrical potential on the two electrodes so that a charge of the proper polarity will be induced on the particles. Thus in an oil and water emulsion, if it is desired to induce a negative charge on oil particles, the external stainless steel electrode is connected to the negative pole of the battery and theycarbon electrode connected to the positive pole. As'the oil particles are attracted to the metal electrode by the preferential wetting characteristics of this electrode, they will receive a negative charge from it. 'I'he advantages to be gained from the use of preferentially wetted electrodes are evident even in the homogenization of a complex material such as milk. Here I have found that the eillciency of the charging unit can be increased by the use of carbon and stainless steel as the electrodes and by connecting the stainless steel electrode to the negative polarity so that the butter fat particles are given -the negative charge. The efciency of the wetting action can be increased by shown in Figure 3 has severalV parts which are similar to the partsv of valve 35 of the embodiment of Figure 2 Iand therefore bear the same reference characters. In valve l2 the valve disc 42 is electrically insulated from the body 36 as by insulating the disc stem e3 by an insulating tube f 'i3 pressed into an enlarged portion of the inlet opening 38. It is also necessary to insulate the adjusting screw B6 from the valve body 36 and this is accomplished by enlarging the opening 41 in the body 36 and pressing therein an insulating tube 1t. Fixed within the latter is a metallicV sleeve 15 threaded internally to receive the mating threads on the adjusting screw d6 controlling the pressure `on the spring de itself controlling the opening pressure of the valve disc t2. Valve body 36 is connected by a wire 'Il to a source of potential E as is the sleeve l5 by wire 18. As the adjusting screw 46 threads into sleeve 15 wire i8 is ineect connected electrically through the adjusting screw S6 and spring M to the disc 42. With electrical potential applied to the wires il and 'i8 this potential is present between the disc 42 and its mating seat in the body 36 with the disc in open position. a condition which exists when the pressure of the fluid entering through the inlet opening 38 is suillcient to lift the disc. When the disc 42 rises from its seat due to the passage of 'a liquid therebetween, the potential appears and current flows through the liquid. By
thismethod the liquid to be emulsifled is subjected to the charging current simultaneously with its passage through the valve 'l2 where it is given the shearing action to reduce the size of the particles.
While I have discussed the use of direct current for producing the charging current in connection with preferentially wetted electrodes, it should not be inferred that other combinations will not produce homogenization.- I have found that the electrodes can be made of the same material and that either polarity and even alternating current can be used. This is no doubt due to the fact that the flow of current through the liquid is ionic in character and theicharges on these ions are imparted to the particles. .In .the homogenization of milk where ordinances regulate the sterile conditions of the equipment it "may be desirable to make both electrodes out of stainless steel since the carbon would have a tendency to soak up the milk, making it dimcult to maintain sterile conditions. In this case the decrease in efliciency'in the charging tube because preferentially wetted electrodes are not used. can be compensated for by a slight'increase in pressure drop through the v homogenizing valves. Where possible,rit is desirable to use materials giving the greatest elciency in the charging unit so that minimum pressures may be used to produce emulsiflcation.
My invention also contemplates the use of materials for the electrodes such that battery potentials are established by the electrodes in the presence of a liquid to be emulsifled, thus eliminating the need of employing an external battery. For example, it is well known that if the electrodes are made of different materials and the liquid is saline in character, a potential will be established therebetween. This potential will create a flow of current through the liquid if the external wires are connected together or if the insulation is eliminated in the construction of the equipment. In the construction of Figure 3, for example, the disc and the body could be made of stainless steel and white bronze, or vice versa. Controlled charging currents are much easier to obtain, however, when an external source of power is used. i
1. A process for permanently emulsifying immiscible uids comprising treating said fluids mechanically by passing them through a reducing orifice under pressure within a range having a lower limit of 500 pounds per square inch and an upper limit below the pressure necessary to effect permanent emulsiflcation to effect impermanent emulsification and treating said fluids electrically to render the emulsiflcation permanent by passing them between electrodes between which electric current flows at a density Within the range of .1 milliamp and 50 milliamps per square inch at a point midway between said electrodes.
2. A process for permanently emulsifying immiscible fluids comprising treating said fluids mechanically by passing them through a reducing orifice under pressure Within a range having a lower limit of 500 pounds per square inch and an upper limit below the pressure necessary to effect permanent emulsiflcatlon to effect impermanent emulsification and treating said fluids electrically to render the emulsiflcation permanent by passing them between electrodes between which direct current flows at a density within the range of .1 milliamp and 50 milliamps per square inch at a point midway between said electrodes.
3. A process for permanently emulsifying immiscible fluids comprising treating said fluids mechanically by passing them through a reducing oriflce under pressure within a range having a lower limit of 500 pounds per square inch and an Aupper limit below the pressure necessary to effect 4nating current flows at a density within the range of .l milliamp and 50 milliamps per square inch at a point midway between said electrodes.
4. A process for permanently emulsifying immiscible fluids comprising treating said fluids mechanically by passing them through a reducing orifice under pressure within a range having a lower limit of 500 pounds per square inch and an upper limit below the pressure necessary to effect permanent emulsiflcation to effect impermanent emulsication and treating said fluids electrically to render the emulsiflcation permanent by passing them between electrodes to effect a flow of direct current with superimposed alternating current therethrough, the current density midway between the electrodes being within the range of' .l milliamp to 50 milliamps per square inch and the strength of the alternating current being sufflcient to reverse the direction of flow of resulting current for a minor part only of a cycle.
5. A process in accordance with claim 1 where- 4 in milk is treated within a pressure range of 500 to 800 pounds per square inch.
` sure necessary to effect permanent emulsiflcation to effect impermanent emulsification and while under said pressure impressing electrical charges upon said particles by flowing electrical current therethrough having a density within the range of .1 milliamp to 50 milliamps per square inch to increase the permanency of the emulsification.
9. An apparatus for permanently emulsifying immiscible fluids comprising an emulsifying unitl including a restricted orifice and means for passing said fluids through the restricted orice at a pressure within a range having a lower limit of 500 pounds per square inch and an Aupper limit below the pressure necessary toefect permanent emulsication whereby impermanent emulsiflcation is effected, and means for impressing on the impermanently emulsied fluid an electrical charge having a current density within the range of .1 milliamp and 50 milliamps per square inch.
10. An apparatus as set forth in claim 9 wherein the means for impressing the electrical charge on the fluids is associated with the emulsifying unit.
11. An apparatus as set forth in claim 9 where- A in the emulsifying unit is provided with a discharge outlet for impermanently emulsified fluids. and the means for impressing the electrical charge is associated with the discharge outlet, whereby the partially emulsifled fluids passing from the emulsifying unit are permanently emulsifled in passing through said charge impressing means.
12. An apparatus as set forth in claim 9 wherein the electrical charge impressing means includes a pair of electrodes one of which is preferentially wetted by one of the fluids and the other by another of the fluids.v
13. An apparatus as set forth in claim 9 wherein the emulsifying unit comprises a colloidal mill including oppositely charged rotor and stator members insulated from one another. 14. An apparatus as set forth in claim 9 wherein the emulsifying unit comprises a pressure redmmg Valve' EMMETT M IRWIN REFERENCES CITED The following references are of record in the le of this patent:
UNITED STATES PATENTS Number Name y Date 1,000,641 Tebbit Aug. l5, 1911 1,200,560 Williams Oct. 10. 1916 1,900,509 Louder Mar. 7, 1933 2,086,324 Feremutsch July 6, 1937 2,122,741 Haddad July 5, 1938 2,243,761 Matzka May 2'7, 1941 2,248,886 McLean July 8, 1941