EP1913994A2

EP1913994A2 - Emulsification apparatus and fine-grain manufacturing apparatus

Info

Publication number: EP1913994A2
Application number: EP07020543A
Authority: EP
Inventors: Hajime Kato; Yuzuro Ito; Hidekazu Tsudome; Yoshishige Endo
Original assignee: Hitachi Plant Technologies Ltd
Current assignee: Hitachi Plant Technologies Ltd
Priority date: 2006-10-20
Filing date: 2007-10-19
Publication date: 2008-04-23
Also published as: CN101219352B; CN101219352A; CN101711961A; EP1913994A3; JP2008100182A

Abstract

A fine-grain manufacturing apparatus 100 has a fluid device including a microscopic channel that has an orifice 203, 204, 205 which brings liquid to a jet 310, a channel wall having a piezoelectric element 206, 207 that actively oscillates liquid, and a unit that measures the diameter of grains floating in a fluid and the number of grains. The piezoelectric element 206, 207 oscillates to skid in the same direction as the flowing direction of a fluid. The fine-grain manufacturing apparatus 100 mass-produces grains having diameters thereof controlled.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus that emulsifies a raw material or a fine-grain manufacturing apparatus that produces fine grains by bringing a raw material to fine grains.

2. Description of the Related Art

An example of a conventional emulsification apparatus is described in Japanese Patent Application Laid-Open Publication No. 2000-210546 . An emulsion manufacturing method described in the publication is intended to quickly and readily bring a rosin system compound to an aqueous emulsion. For this purpose, an emulsifier solution is fed from a high-pressure delivery type emulsification machine to an orifice at a high pressure. The molten rosin system compound is fed to a fast-flow gushing section over another channel, and collided at a mixing temperature within a predetermined temperature range. The mixture is introduced into absorption cells that are inserted in multiple steps, and then discharged from an emulsion discharge section.
An example of a stirring type emulsion manufacturing method that has been widely adopted in the past is described in Japanese Patent Application Laid-Open Publication No. H7-173294 . In the stirring type emulsion manufacturing method described in the publication, 100 weight parts of liquid organopolysiloxane whose viscosity is so high as to fall within a range from ten thousand centistokes (cSt) to one million centistokes at 25°C is added to 1 to 20 weight parts of ionic emulsifier solution, and the mixture is stirred and dispersed. Thereafter, 1 to 50 weight parts of nonionic emulsifier is added to the mixture. The resultant mixture is stirred under a high shearing stress so that it will have a small grain diameter, and finally diluted with water.
Still another emulsion manufacturing method is described in Japanese Patent Application Laid-Open Publication No. 2004-81924 . Described in the publication is a micro-emulsification device that includes a plurality of inlets and one outlet and a plurality of channels which is formed in multiple stages between the inlets and outlet and over which fluids fed through the respective inlets are mixed and introduced to the outlet, and that is intended to produce a high-quality emulsion of a uniform grain diameter with high mass-productivity. The effective sectional area of the channel in each stage, which is a micro-channel, is tapered from the inlet side thereof to the outlet side thereof so that a shearing velocity and its dispersive effect will get higher toward the outlet.
A problem underlying conventional emulsification apparatuses is how to implement a technology, with which production has succeeded in a small-scale laboratory trial, as business in mass-production. In the manufacture of an aqueous emulsion described in Japanese Patent Application Laid-Open Publication No. 2000-210546 , it is necessary to jet a solution under as high a pressure as 250 MPa. Preparation of such a high-pressure facility at an actual plant leads to a massive apparatus and invites an increase in cost. Moreover, only solutions that can withstand a high pressure can be employed, and the types of solutions that can be employed are therefore limited.
In the emulsion manufacturing method described in Japanese Patent Application Laid-Open Publication No. H7-173294 , a first solution of a high viscosity is added to a second solution, and the mixture is stirred. Thereafter, the mixture is stirred under a high shearing stress with a third emulsifier injected. However, in the method described in the publication, solutions that can be employed are limited to special solutions. The method cannot always be applied to emulsification of general oil and a solution.
Further, Japanese Patent Application Laid-Open Publication No. 2004-81924 says that an emulsion that is a mixture of immiscible fluids such as water and oil is realized with a microstructure. According to the method, an emulsion of a uniform grain diameter can be produced. However, since the diameter of droplets is dominated by a flow rate, the flow rate may have to be sacrificed in order to attain a desired droplet diameter. In this case, when an attempt is made to produce a large amount of emulsion, a large-size apparatus has to be adopted or a processing time cannot help being extended. Another method is to utilize shock waves generated with cavitation derived from ultrasonic waves. However, this method can hardly be applied to raw materials containing a biopolymeric material such as protein that is deactivated at high temperature.

BRIEF SUMMARY OF THE INVENTION

The present invention attempts to solve the problems underlying the related art. An object of the present invention is to provide an emulsification apparatus that can readily control the property of an emulsion and can mass-produce the emulsion. Another object of the present invention is to provide a fine-grain manufacturing apparatus that can mass-produce grains having diameters thereof controlled. The present invention is intended to accomplish either of the objects.
In accordance with an aspect of the present invention, an apparatus has a fluid device including a microscopic channel over which liquid is brought to a jet, and a channel wall that actively oscillates liquid. The channel wall that actively oscillates liquid oscillates to skid in the same direction as the flowing direction of the liquid. The channel wall that actively oscillates liquid includes a piezoelectric element. The piezoelectric element has a surface thereof, which comes into contact with the liquid, coated with an insulating material.
In accordance with another aspect of the present invention, an apparatus has a fluid device including a microscopic channel over which liquid is brought to a jet, a channel wall that actively oscillates liquid, and means for measuring the diameter of grains floating in a fluid and the number of grains.
The microscopic channel includes multiple stages of orifices. Preferably, the orifices generate a jet and a swirl. The channel wall that actively oscillates liquid preferably oscillates to skid in the same direction as the flowing direction of the liquid. Moreover, the channel wall that actively oscillates liquid includes a piezoelectric element. The piezoelectric element may have the surface thereof, which comes into contact with liquid, coated with an insulating material. Preferably, the apparatus is either an emulsification apparatus or a fine-grain manufacturing apparatus, and may have a plurality of fluid devices connected in parallel with one another.
According to the present invention, raw materials to be emulsified (a water system raw material and an oil system raw material) are emulsified under a high shearing stress derived from a jet in order to produce an emulsion having a grain diameter that ranges from several tens of micrometers to several hundreds of micrometers. The channel wall is actively oscillated so that an appropriate shearing stress will act on the emulsion. Thus, the emulsion is finely broken to have a desired grain diameter. This makes it easy to control the property of an emulsion in a fine-grain manufacturing apparatus or an emulsification apparatus. Moreover, according to the present invention, channels capable of generating a jet and a shearing stress of an arbitrary intensity are connected in parallel with one another according to a desired throughput. A problem derived from an increase in a scale based on conventional physical analogy can be avoided, and grains having diameters thereof controlled can be mass-produced by a fine-grain manufacturing apparatus or an emulsification apparatus.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and other features, objects and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings wherein:

Fig. 1 is a block diagram of an embodiment of a fine-grain manufacturing apparatus in accordance with the present invention;
Fig. 2, Fig. 3A, and Fig. 3B are explanatory diagrams showing the structure of a channel included in an emulsification device included in the fine-grain manufacturing apparatus shown in Fig. 1; and
Fig. 4A and Fig. 4B are explanatory diagrams concerning production of a double emulsion.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of an emulsification apparatus or a fine-grain manufacturing apparatus in accordance with the present invention will be described in conjunction with the drawings. Fig. 1 is a block diagram showing a fine-grain manufacturing apparatus 100. The fine-grain manufacturing apparatus 100 includes a tank 101 in which a raw material A to be emulsified (disperse phase) is preserved, and a tank 102 in which a raw material B (continuous phase) that disperses the raw material A is preserved. An emulsification device 103 that will be detailed later mixes and emulsifies the raw materials A and B.
A first pump 104 feed a fluid from the tank 101 of the raw material A to the emulsification device 103 over a pipe 107. Likewise, a second pump 105 feeds a fluid from the tank 102 of the raw material B to the emulsification device 103 over a pipe 108. The mixture of the emulsified raw material A and raw material B is fed from the emulsification device 103 to a tank 106 over a pipe 109.
The pipe 109 of the mixture has a bypass 110. The bypass 110 is provided with a grain size distribution meter 111. The grain size distribution meter 111 can online monitor the grain diameter of a disperse phase included in a mixture which is fed out of the emulsification device 103. A piezoelectric element capable of actively oscillating a channel is disposed in a channel in the emulsification device 103. The piezoelectric element is driven by a piezoelectric element drive circuit 112.
The first and second feed pumps 104 and 105, piezoelectric element drive circuit 112, and grain size distribution meter 111 are connected to a user console 113. A user of the fine-grain manufacturing apparatus 100 uses the console 113 to monitor the grain size distribution in the mixture being produced. The ratio between the amounts of the raw material A and raw material B that are fed by the first and second feed pumps 104 and 105 respectively, the amounts of the raw materials to be fed, and the oscillatory intensity attained by the piezoelectric element included in the emulsification device 103 are adjusted in order to produce a desired mixture. The emulsification device 103 and grain size distribution meter 111 constitute an emulsification unit 114.
Fig. 2 shows a longitudinal section of the emulsification device 103 included in the fine-grain manufacturing apparatus 100 shown in Fig. 1. The raw materials fed from the raw material tanks 101 and 102 respectively by the feed pumps 104 and 105 respectively flow, as indicated with arrows 201 and 202, over channels 208a and 208b respectively in the emulsification device 103, and join in a joint channel 208c. The mixture passes through orifices 203, 204, and 205, and passes an enlarged section 208f that has piezoelectric elements 206 and 207 disposed on the wall thereof. The mixture flows out of the device as indicated with an arrow 209 over a channel 208d. The piezoelectric elements 206 and 207 can be, as indicated with a dot line in the drawing, oscillated in thickness sliding oscillatory mode under the external control.
In consideration of the connections of the pipes to the emulsification device 103, that is, in consideration of the connections of the pipes to the channels 208a and 208b, which serve as the inlets for the raw materials A and B, and the channel 208d, which serves as the outlet for an emulsion dispersing fluid, the cross sections of the channels should preferably be circular.
Three kinds of orifice members 203 to 205 are disposed in that order in a flowing direction with a space between adjoining ones between the joint channel 208c and the enlarged section 208f. The first orifice member 203 is located extremely upstream and has an orifice in the center thereof. The opening ratio of the first orifice member is the largest among those of the three orifice members 203 to 205. The second orifice member 204 disposed in the middle has the center of the upstream-side surface thereof dented toward downstream and has the downstream-side surface thereof made perpendicularly to a flowing direction in which a mixture flows over the channel 208d. The opening ratio of the orifice formed in the center of the second orifice member 204 is the smallest among all the orifices of the first to third orifice members 203 to 205.
Moreover, the flow velocity at which a mixture passes the enlarged section 208f, which has the piezoelectric elements formed on the wall surfaces thereof, is decreased in order to prolong a time which the mixture requires to pass the place (enlarged section 208f). Consequently, the sectional area of the enlarged section 208f may be larger than that of the other channels.
Moreover, an oscillatory shearing stress that is as even as possible should preferably be generated in the enlarged section 208f in order to generate fine grains uniformly. Even when the sectional shapes of the other channels are circular, the sectional shape of the enlarged section should preferably be rectangular with two planar piezoelectric elements opposed to each other. The space between the two opposed piezoelectric elements should be as narrow as possible so that an even oscillatory shearing stress can be generated, though it depends on the oscillatory frequency or the viscosities of raw materials.
In the drawings, a gap is created between each of the piezoelectric elements 207 and 208 and the channel wall, on which each piezoelectric element is disposed, for fear skidding oscillation indicated with a dot line may be hindered. When the remnant of liquid concentrate in the gaps poses a sanitary problem, a highly stretchy elastic material may be put in the gaps.
Referring to Fig. 3A and Fig. 3B, a description will be made of the behavior of a fluid mixture in the enlarged section 208f in the emulsification device 103 shown in Fig. 2. Fig. 3A is an explanatory diagram showing a flow through the orifices 203 to 205, and Fig. 3B is an explanatory diagram showing a flow in the enlarged section 208f. As mentioned above, the diameter 307 of the second orifice 204 is smaller than the diameter 306 of the first orifice 203.
When the flow rate of the fluid mixture of the raw materials A and B becomes equal to or larger than a predetermined value, a swirl-like secondary flow 308 is formed in a channel between the first orifice 203 and the second orifice 204. Owing to the secondary flow 308, a disperse phase (raw material A) 302 and a continuous phase (raw material B) 301 that come from upstream to the space between the first and second orifices 203 and 204 are mixed and dispersed into relatively large droplets 309.
Since the diameter 307 of the second orifice 204 is smaller than the diameters of the first and third orifices 203 and 205, a torrential jet 310 is formed toward downstream of the second orifice 204. An intense shearing stress derived from the jet 310 acts on the droplets 309 produced between the first and second orifices 203 and 204. Consequently, the droplets 309 are broken to become fine droplets 311.
The jet 310 produced toward downstream of the second orifice 204 gradually spreads as it goes downstream. Consequently, the mixture cannot pass through the third orifice 205 whose diameter is larger than that of the second orifice 204. Part of the jet is bounced to become a secondary flow 312 that regurgitates upward. The secondary flow 312 is mixed with the fine disperse phase (raw material A) and continuous phase (raw material B), and passes through the third orifice 305 to go downstream.
As mentioned above, the piezoelectric elements 206 and 207 are opposed to each other in the enlarged section 208f formed on the downstream side of the first to third orifices 203 to 205. The piezoelectric elements 206 and 207 cause the channel wall to oscillate to skid, whereby the droplets of the fluid mixture of the raw materials A and B are further broken to be finer. The piezoelectric elements 206 and 207 are, as shown in Fig. 3B, oscillated to have mutually opposite phases. Consequently, oscillatory flow velocity distributions 315 and 316 occur between the two piezoelectric elements 206 and 207. The flow velocity distributions 315 and 316 generate a shearing stress. The shearing stress stretches the spherical droplets, which come from upstream, in a flowing direction so as to produce elongated droplets 317. Finally, the elongated droplets 317 are further broken to become numerous droplets that are nearly spherical. Thus, finer droplets are generated.
The oscillatory flow velocity distributions can be controlled by changing an oscillating velocity 318 in a skidding direction of the piezoelectric elements 206 and 207. Specifically, the number of times by which droplets are torn up is determined with both the time which the droplets 319 require to pass the piezoelectric elements 206 and 207 and the number of oscillations made by the wall surface. Consequently, the number of wall surface oscillations and an oscillatory displacement are adjusted based on the shearing stress needed to break the raw materials A and B and a velocity at which the raw materials A and B flow. Thus, the raw materials A and B can be emulsified while being broken to have a desired grain diameter.
Incidentally, normally, a high voltage is applied to the piezoelectric elements 206 and 207. The surfaces of the piezoelectric elements 206 and 207 coming into contact with the raw materials A and B have to be insulated. In the present embodiment, an insulating resin that is highly stretchy is coated over the surfaces of the piezoelectric elements 206 and 207.
In a description to be made below, the first to third orifices 203 to 205 will be referred to as a passive emulsification section 313, and the enlarged section 208f will be referred to as an active emulsification section 314. In the embodiment, the emulsification device 103 has both the passive emulsification section 313 and active emulsification section 314. The former section 313 is responsible for coarse emulsification, and the latter section 314 produces microscopic fine grains. However, the emulsification device 103 may include either of the emulsification sections according to a requested mixed state.
Moreover, for production of more microscopic grains, a plurality of stages of passive emulsification sections 313 and a plurality of stages of active emulsification sections 314 may be included if necessary. The combination of the emulsification sections 313 and 314 is determined based on the viscosities or densities of the raw materials A and B to be emulsified, the physicality such as the interfacial tension between the raw materials A and B, a target mixed state such as a means grain diameter of fine grains or a grain size distribution.
In Fig. 3B, the piezoelectric elements 206 and 207 are opposed to each other in the enlarged section 208f, and are oscillated to have opposite phases. Alternatively, one of the piezoelectric elements may be included. Even in this case, the emulsification channel 208d should have a sectional area that remains nearly unchanged in a flowing direction. The intensity of a generated shearing stress is smaller than that attained when the two piezoelectric elements 206 and 207 are opposed to each other. However, there are the merits that power to be consumed by the active emulsification section 214 is reduced and that only one drive circuit is needed to drive the piezoelectric element. When the time which droplets require to pass is prolonged by a time equivalent to a decrease in the shearing stress, an advantage nearly identical to the advantage provided when two piezoelectric elements are opposed to each other can be exerted. This is advantageous for processing whose throughput may be relatively small.
Another embodiment of a fine-grain manufacturing apparatus in accordance with the present invention will be described in conjunction with Fig. 4A and Fig. 4B. In the aforesaid embodiment, two raw materials A and B are mixed and then emulsified. In the present embodiment, three or more raw materials A, B, C, etc. are emulsified in order to produce a so-called double emulsion. In Fig. 4A and Fig. 4B, for a better understanding, three raw materials A, B, and C are employed. When three raw materials A, B, and C are employed, one emulsification device 103b is additionally included.
Fig. 4A is a block diagram of a fine-grain manufacturing apparatus 100b that produces a double emulsion. In Fig. 4A, a user console and lines linked to the user console are not shown. An emulsification unit 114b includes two emulsification devices 103 and 103b. The emulsification device 103 produces a fluid mixture 402 of a raw material A (disperse phase) and a raw material B (continuous phase). The additionally included emulsification device 103b introduces a raw material C to the mixture of the raw materials A and B so as to disperse the mixture, and finally produces a double emulsion 404 containing the raw materials A, B, and C. A tank 106 is disposed downstream of the additionally included emulsification device 130b in order to preserve the double emulsion.
Fig. 4B illustratively shows the mixed state of the raw materials A to C in the emulsification unit 114b shown in Fig. 4A. The raw materials A and C are mixed on an upstream side, and the raw material C is mixed in the mixed raw materials A and B on a downstream side. When this procedure is repeated, an emulsion can be produced from four or more kinds of raw materials. At this time, the diameter of fine grains can be varied depending on the diameters of orifices or power to be fed to the piezoelectric elements.
According to the aforesaid embodiments, the grain diameter of an emulsion can be readily controlled, and a multiple structure of an emulsion can be readily produced. For mass-production at a plant, emulsification units are connected in parallel with one another. Although one or several emulsification units are used at a laboratory in order to produce a desired emulsion, when mass-production is launched at a plant, a large number of emulsification units determined with a throughput is connected in parallel with one another. Thus, a problem underlying an increase in a scale based on analogy can be avoided. Examples of the present invention have been described so far. However, the present invention is not limited to the examples.
Features, components and specific details of the structures of the above-described embodiments may be exchanged or combined to form further embodiments optimized for the respective application. As far as those modifications are readily apparent for an expert skilled in the art they shall be disclosed implicitly by the above description without specifying explicitly every possible combination, for the sake of conciseness of the present description.

Claims

An apparatus comprising a fluid device that includes a microscopic channel over which liquid is brought to a jet (310) and a channel wall that actively oscillates liquid,
wherein the channel wall that actively oscillates liquid oscillates to skid in the same direction as the flowing direction of liquid.
The apparatus according to Claim 1,
wherein the channel wall that actively oscillates liquid includes a piezoelectric element (206, 207), and
the piezoelectric element (206, 207) has the surface thereof, which comes into contact with liquid, coated with an insulating material.
An apparatus comprising a fluid device that includes a microscopic channel over which liquid is brought to a jet (310), a channel wall that actively oscillates liquid, and means for measuring the diameter of grains (111) floating in a fluid and the number of grains.
The apparatus according to Claim 3,
wherein the microscopic channel has a plurality of stages of orifices, and the orifices (203, 204, 205) generate a jet (310) and a swirl.
The apparatus according to Claim 3 or 4,
wherein the channel wall that actively oscillates liquid oscillates to skid in the same direction as the flowing direction of liquid.
The apparatus according to Claim 3, 4 or 5,
wherein the channel wall that actively oscillates liquid includes a piezoelectric element (206, 207); and
the piezoelectric element (206, 207) has the surface thereof, which comes into contact with liquid, coated with an insulating material.
The apparatus according to any of Claims 3 to 6,
wherein the apparatus is either an emulsification apparatus or a fine-grain manufacturing apparatus (100).
The apparatus according to Claim 7,
wherein a plurality of fluid devices are connected in parallel with one another.