JP2006312135A - Superecritical carbon dioxide sterilizing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supercritical carbon dioxide sterilizing device suitable for sterilizing a liquid easy to foam up. <P>SOLUTION: The supercritical carbon dioxide sterilizing device 1 is provided with a mixing-dissolving means 30 mixing carbon dioxide with the liquid to be sterilized to dissolve, a constant-temperature holding means 40 warming the mixed fluid yielded by the mixing-dissolving means 30 up to the predetermined temperature, and at the same time, holding the mixed fluid warmed up to the predetermined temperature at the predetermined temperature and pressure where the carbon dioxide turns to a supercritical state, to sterilize, a pressure releasing means 52 reducing the pressure of the mixed fluid sterilized by the constant-temperature holding means 40 up to the pressure where the carbon dioxide turns to a gaseous state, and a separating means 60 dividing the mixed fluid pressure-reduced by the pressure releasing means 52 into the carbon dioxide in the gaseous state and the sterilized liquid. In the device, the separating means 60 is to be a cyclone. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for processing a liquid (liquid raw material, product, etc.) and reducing microbial and / or enzymatic activity therein, and more specifically, a sterilizer using carbon dioxide in a supercritical state. About.

  Various sterilizers for improving the preservability of milk, juice, beverages such as soft drinks, mineral water, liquid foods such as soups, alcoholic beverages such as beer, and pre-sterilization of fermentation medium Has been developed. In general, heat sterilization apparatuses are frequently used. However, in heat sterilization, there is a possibility that flavor, tissue, nutritional value will be deteriorated in beverages, etc., and that the function as medium will be reduced in fermentation medium. For this reason, a low temperature heating or a sterilization method not using heating may be required. Non-heated sterilization methods include filtration sterilization, but since it can be applied only to a clear liquid, there is a disadvantage that it cannot be applied to a liquid containing a solid such as a tool. Moreover, although high pressure sterilization is mentioned as a non-heating sterilization method, since high pressure is used, there exists a fault that the cost on an installation or operation is high.

From this point of view, in recent years, a sterilizer using carbon dioxide in a supercritical state (in this specification, sometimes referred to as “supercritical carbon dioxide sterilizer”) is known (for example, Patent Document 1). To 3). In this type of sterilizer, the liquid to be sterilized is brought into contact with carbon dioxide in a supercritical state to sterilize the liquid. Since carbon dioxide has the advantage that it is highly safe and does not remain in the liquid by being vaporized after the sterilization treatment, it is suitable for sterilization of beverages and culture media.
JP 2000-83634 A Japanese Patent Laid-Open No. 7-170965 JP 2004-290081 A

  The supercritical carbon dioxide sterilizer is desired to be applied to sterilization of various liquids. However, in the case of liquids with high viscosity, liquids that easily foam, liquids that contain suspended substances, bubbles are generated when carbon dioxide is vaporized after sterilization, and there is concern that the operation of the apparatus may be hindered. The For example, there is a possibility that bubbles are filled in a tank that stores the sterilized liquid, and that a substantial storage amount is reduced or bubbles are overflowed from the upper part of the tank. In addition, liquid fine particles may be mixed in the vaporized carbon dioxide, so that the amount of recovered liquid that has been sterilized may be reduced, or the recovery or reuse of carbon dioxide may be hindered. In particular, a liquid containing protein is one of the liquids that easily foam. Since protein is denatured by heating, application of a supercritical carbon dioxide sterilizer capable of pasteurization is desired for sterilization of a liquid containing protein.

  It is also conceivable to collect a mixture of the sterilized liquid and supercritical carbon dioxide in a large storage tank and separate gaseous carbon dioxide in the storage tank (for example, the separation described in paragraph 0017 of Patent Document 1). Tank, see separation container described in paragraph 0025 of patent document 2). However, these documents do not particularly describe how to deal with the case where the mixture after treatment becomes foamy, and are not suitable for sterilization of foaming liquid.

  That is, when the mixture after sterilization becomes foamy, the following problems may occur. If the foam-like mixture is simply collected in the storage tank and left to stand, the foam remains for a long time, so that it is difficult to quickly transfer the sterilized liquid to the next step. Further, when sucking with a degassing device, not only gas but also a liquid film of bubbles is sucked, resulting in a problem that the amount of recovered sterilized liquid is reduced. Although it is conceivable to apply known defoaming means and defoaming means, it is difficult to handle sanitary liquids that meet the sanitary standards required. Although the method of adding the antifoamer of a food additive to a liquid beforehand is also considered, addition of an antifoamer may not be preferable depending on the use of a liquid.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the supercritical carbon dioxide sterilizer which can be employ | adopted suitably for sterilization of the liquid which is easy to foam.

In order to solve the above-mentioned problems, the present invention provides a mixing / dissolving means for mixing and dissolving carbon dioxide in a liquid to be sterilized, a mixed fluid obtained by the mixing / dissolving means being heated to a predetermined temperature, and A constant temperature holding means for sterilizing the mixed fluid heated to a temperature at a predetermined temperature and pressure at which carbon dioxide becomes a supercritical state, and the mixed fluid sterilized by the constant temperature holding means is in a gaseous state. In a supercritical carbon dioxide sterilizer comprising pressure release means for reducing the pressure to a pressure, and separation means for separating the mixed fluid decompressed by the pressure release means into gaseous carbon dioxide and sterilized liquid, A supercritical carbon dioxide sterilizer characterized in that the separation means is a cyclone.
The separating means may be a plurality of cyclones connected in series or in parallel.

  According to the present invention, after a foamable liquid (liquid raw material, product, etc.) is sterilized in a supercritical carbon dioxide sterilization apparatus, bubbles can be efficiently erased, and the sterilized liquid can be recovered with a high yield. Can do. Thereby, the supercritical carbon dioxide sterilizer which can be used conveniently in the field | area of a foodstuff or fermentation can be provided.

The present invention will be described below with reference to the drawings based on the best mode.
FIG. 1 is a schematic configuration diagram showing an example of a supercritical carbon dioxide sterilizer according to the present invention. A supercritical carbon dioxide sterilizer 1 shown in FIG. 1 includes a liquid supply means 10 for supplying a liquid to be sterilized, a carbon dioxide supply means 20 for supplying carbon dioxide, and a liquid to be sterilized by mixing and dissolving carbon dioxide. Mixing and dissolving means 30, and the mixed fluid obtained by the mixing and dissolving means 30 is heated to a predetermined temperature, and the mixed fluid heated to the predetermined temperature has a predetermined temperature at which carbon dioxide becomes a supercritical state. The constant temperature holding means 40 for holding and sterilizing the pressure, the pressure release means 52 for reducing the pressure of the mixed fluid sterilized by the constant temperature holding means 40 until the carbon dioxide is in a gaseous state, and the pressure release means 52 for reducing the pressure. A cyclone is provided as separation means 60 for separating the mixed fluid into gaseous carbon dioxide and sterilized liquid.

  The liquid supply means 10 includes a liquid storage means 11 for storing a liquid to be sterilized, a liquid supply line 12 having one end connected to the liquid storage means 11, and a control valve 13 provided in the middle of the liquid supply line 12. And a pumping pump 14 (metering pump) that pumps the liquid through the liquid supply pipe 12.

  The carbon dioxide supply means 20 includes a carbon dioxide storage means 21 (for example, a liquefied carbon dioxide cylinder) for storing carbon dioxide, a carbon dioxide supply pipe 22 having one end connected to the carbon dioxide storage means 21, and a carbon dioxide supply pipe 22. And a pumping pump 24 (metering pump) for pumping liquid carbon dioxide (liquefied carbon dioxide gas) through. The carbon dioxide supply line 22 is provided with a cooling device (not shown) so that carbon dioxide flowing inside does not boil.

  The mixing and dissolving means 30 mixes and dissolves the liquid to be sterilized and carbon dioxide. In the present invention, a fluid obtained by mixing a liquid to be sterilized and carbon dioxide is referred to as a “mixed fluid”. The mixing / dissolving means 30 includes a pipe connection point 31 where the other end of the liquid supply pipe 12 and the other end of the carbon dioxide supply pipe 22 merge and are connected to each other, and a mixed fluid on the downstream side of the pipe connection point 31. And a mixed fluid conduit 32 through which liquid is passed. The liquid to be sterilized supplied through the liquid supply line 12 and the carbon dioxide supplied through the carbon dioxide supply line 22 are mixed at the pipe connection point 31 and further passed through the mixed fluid line 32. Dissolves with each other to form a mixed fluid.

  The constant temperature holding means 40 has a constant temperature holding pipe 41 through which the mixed fluid passes, and a constant temperature water tank 42 covering the periphery of the constant temperature holding pipe 41. The upstream side of the constant temperature holding pipe 41 is connected to the mixed fluid pipe 32 and forms a continuous flow path continuing from the liquid supply pipe 12 of the liquid supply means 10. Constant temperature water is stored in the constant temperature water tank 42 and maintained at a predetermined temperature. For this reason, the temperature of the mixed fluid that passes through the inside of the constant temperature holding pipe 41 can be kept constant. The mixed fluid that passes through the constant temperature holding pipe 41 is heated to a predetermined temperature by heat exchange with the constant temperature water tank 42, and is further held at a predetermined temperature and pressure at which carbon dioxide in the mixed fluid becomes a supercritical state. The In this way, the liquid to be sterilized in the constant temperature holding pipe 41 comes into contact with the supercritical carbon dioxide, so that the liquid is sterilized. After exiting the constant temperature holding pipe 41, that is, after leaving the constant temperature water tank 42, a discharge pipe 51 is formed through which the mixed fluid having been sterilized by liquid flows. Accordingly, the liquid supply pipe 12, the constant temperature holding pipe 41, and the discharge pipe 51 are connected to each other to form a series of flow paths.

  The discharge pipe 51 is provided with a pressure release means 52 for decompressing the mixed fluid sterilized by the constant temperature holding means 40. The pressure release means 52 releases the pressure and reduces the pressure to a pressure at which carbon dioxide in the mixed fluid becomes a gas state. Therefore, the mixed fluid flowing in the pipe line after the pressure release means 52 is a mixture of the sterilized liquid and the carbon dioxide in a gaseous state. The pressure release means 52 may be configured by one or a plurality of pressure reducing valves. Note that the pressure release means 52 is provided with a heating means for making up for the heat lost as the mixed fluid is depressurized, but is not shown in the drawing.

  The separation means 60 separates the mixed fluid decompressed by the pressure release means 52 into gaseous carbon dioxide and sterilized liquid. The present invention is characterized in that the separating means 60 is constituted by a cyclone.

  An example of the cyclone 60 is shown in FIG. The cyclone 60 has an inflow pipe 61 through which an inflowing mixed fluid passes, a fluid inlet 62 formed at the downstream end of the inflow pipe 61, and a gas-liquid separation in which the downstream end of the inflow pipe 61 is connected. A part 63, a gas discharge pipe 64 through which the gas separated by the gas-liquid separator 63 is discharged, and a liquid outlet 65 through which the sterilized liquid separated by the gas-liquid separator 63 is discharged. The upstream end of the inflow pipe 61 is connected to the discharge pipe 51, and the liquid discharge port 65 is connected to a sterilized liquid storage means (storage tank) 70 in which sterilized liquid is stored. . Although not particularly shown, a terminal for collecting carbon dioxide or a discharge port to the atmosphere is connected to the end of the gas exhaust pipe 64.

  The upper part 63a of the gas-liquid separation part 63 has a cylindrical shape, and a gas discharge pipe 64 passes vertically through the center part of the upper surface. The inflow pipe 61 extends in a tangential direction in a cross section (see FIG. 2C) along the horizontal plane of the gas-liquid separator 63, and communicates with the upper part 63 a of the gas-liquid separator 63 via the fluid inlet 62. ing. The lower part 63b of the gas-liquid separation part 63 is formed in a conical shape that is continuous from the upper part 63a of the gas-liquid separation part 63 and decreases in diameter downward, and a liquid discharge port 65 is formed at the lower end part thereof. Has been. In the cyclone 60, the smaller the inner diameter of the gas-liquid separator 63, the easier it is to obtain a stronger centrifugal force. Therefore, the maximum inner diameter is preferably 50 mm or less, and more preferably the maximum inner diameter is 10 mm or less.

  Next, the operation of the supercritical carbon dioxide sterilizer 1 of this embodiment will be described. Liquid to be sterilized is stored in the liquid storage means 11, and this liquid is transported via the liquid supply pipe 12 by the pressure feed pump 14. At the same time, the liquid state carbon dioxide stored in the carbon dioxide storage means 21 is transported by the pressure pump 24 via the carbon dioxide supply line 22 and mixed with the liquid to be sterilized in the mixing and dissolving means 30. Carbon and each other dissolve.

  The mixed fluid in which the liquid to be sterilized and carbon dioxide are mutually dissolved is maintained at a predetermined temperature and pressure at which carbon dioxide in the mixed fluid is maintained in a supercritical state while flowing through the constant temperature holding pipe 41. The liquid is sterilized by the action of carbon dioxide in the supercritical state. The mixed fluid in which the liquid is sterilized flows through the discharge pipe 51, and is depressurized by the pressure release means 52 to a pressure at which carbon dioxide in the mixed fluid becomes a gas state (for example, normal pressure). By the way, when the liquid to be sterilized is a highly foamable liquid, for example, a liquid with high viscosity, a liquid that easily foams, or a liquid containing suspended solids, when the mixed fluid is decompressed, the sterilized liquid in the mixed fluid has been sterilized. The liquid and the carbon dioxide in the gaseous state may not be smoothly separated and may foam.

  In order to cope with the foaming of the mixed fluid, the supercritical carbon dioxide sterilization apparatus 1 according to this embodiment includes a separating unit 60 made of a cyclone on the downstream side of the discharge pipe 51. For this reason, as shown in FIG. 3, the mixed fluid that has flowed into the gas-liquid separator 63 through the inlet pipe 61 and the fluid inlet 62 forms a flow that swirls along the inner surface of the upper part 63 a of the gas-liquid separator 63, Strong centrifugal force is generated by the inflow speed of the mixed fluid. In the gas-liquid separator 63, the gas moves to the center (radially inside) of the gas-liquid separator 63 and the liquid gas-liquid separator 63 due to the difference in specific gravity between the gas and the liquid and the centrifugal force acting on the swirl flow. It moves to the outer peripheral part (outside in the radial direction), and bubbles are destroyed and gas and liquid are separated. The gas (mainly gaseous carbon dioxide) is discharged through the gas discharge pipe 64. The liquid (that is, the sterilized liquid) falls according to gravity and flows into the sterilized liquid storage means 70 from the liquid discharge port 65. As a result, the sterilized liquid is stored in the sterilized liquid storage means 70.

  Thus, in the supercritical carbon dioxide sterilization apparatus of the present invention, a part of the high pressure of the mixed fluid can be used as power for gas-liquid separation with the cyclone 60, and the cyclone 60 does not consume external power, Operates efficiently. In addition, after the sterilization is completed, the inside of the cyclone 60 can be combined with other parts of the supercritical carbon dioxide sterilizer to efficiently perform cleaning, rinsing, drying, and the like.

As mentioned above, although this invention has been demonstrated based on suitable embodiment, this invention is not limited to the above-mentioned example, Various modifications are possible in the range which does not deviate from the summary of this invention.
For example, the supercritical carbon dioxide sterilizer 2 shown in FIG. 4 is the supercritical carbon dioxide sterilizer 1 of the first embodiment described above, except that the separating means 60A is a plurality of cyclones 60, 60 connected in series. It is configured in the same way. That is, the gas discharge pipe 64 of the first-stage cyclone 60 (left side in FIG. 4) is connected to the inflow pipe 61 of the second-stage cyclone 60 (right side in FIG. 4). As a result, even if a part of the sterilized liquid cannot be completely separated by the first-stage cyclone 60 but is mixed in the gas and transferred to the gas discharge pipe 64, it is separated by the second-stage cyclone 60. Thus, the liquid can be collected into the sterilized liquid storage means 70.

  Moreover, the supercritical carbon dioxide sterilizer 3 shown in FIG. 5 is the supercritical carbon dioxide sterilizer 1 of the above-mentioned first embodiment except that the separating means 60B is a plurality of cyclones 60, 60 connected in parallel. It is configured in the same way. That is, a pipe branch point 53 is provided in the downstream portion of the discharge pipe 51, and the branched pipe is connected to the inflow pipe 61 of another cyclone 60. As a result, even if the flow rate of the mixed fluid is an amount that cannot be separated by one cyclone 60, it is possible to efficiently separate the gas and liquid by distributing the processing amount by the plurality of cyclones 60 and 60. become.

  EXAMPLES Next, the present invention will be described with reference to examples. However, the following examples do not particularly limit the present invention.

Example 1
In the supercritical carbon dioxide sterilizer 1 having the configuration shown in FIG. 1, a cyclone 60 having a structure of FIG. 2 having a diameter of 50 mm is installed as the separating means 60 provided downstream of the pressure release means 52. As a test sample, 0.05% inoculation of a supernatant obtained by diluting a commercially available yogurt twice with sterile water and clarified by centrifugation against a 5% solution of whey protein isolate (WPI, ALACEN 895) We used what we did. The number of bacteria in this test sample was 2.2 × 10 ⁵ cfu / ml as a result of measurement using a standard agar medium.

The temperature of the constant temperature water tank 42 was set to 30 ° C., the pressure of the constant temperature holding pipe 41 was maintained at 10 MPa, and the mixing ratio of carbon dioxide and the test sample (liquid) was 1: 17.5 to sterilize the test sample. The number of bacteria in the test sample after sterilization was 30 cfu / ml or less as a result of measurement using a standard agar medium. By installing the cyclone 60, most of the sterilized sample can be collected in the storage tank 70 downstream of the cyclone 60, and the amount of liquid transferred to the gas discharge pipe 64 is small. Fine bubbles were observed inside the collected sterilized sample. However, when the sample was allowed to stand for several hours, it floated, and the gas was released and the bubbles disappeared.
The sterilized sample showed a slight decrease in pH value due to dissolution of carbon dioxide. When the aqueous solution of sodium hydroxide was added to return the pH to the original value, it was confirmed that it showed the same physical properties as the raw material solution before sterilization.

(Comparative Example 1)
As shown in FIG. 6, Example 1 is used except that a supercritical carbon dioxide sterilizer 101 in which the discharge pipe 51 is directly connected to the storage tank 70 is used without providing the cyclone 60 downstream of the pressure release means 52. The sterilization test was conducted under the same conditions as above. In this case, the sterilized sample was released in the form of bubbles from the opening of the pipe, and some droplets were scattered. The storage tank 70 was filled with bubbles, and some of the bubbles overflowed from the upper part of the storage tank 70. The sterilized sample was foamy, and it took a whole day and night to return to the liquid state. That is, the sterilized liquid cannot be immediately sent to the next process.

(Example 2)
A sterilization test was performed under the same conditions as in Example 1 using the supercritical carbon dioxide sterilizer 1 having the configuration shown in FIG. 1 except that unsterilized egg white was used as a test sample. The test sample of Example 2 was not inoculated with bacteria. The sterilized sample was separated from carbon dioxide by the cyclone 60 and collected in the storage tank 70. The collected sterilized egg white was a cloudy liquid immediately after flowing into the storage tank 70. When this was left in the refrigerator for a whole day and night, it was confirmed that it returned to the same appearance as before the sterilization test.

  INDUSTRIAL APPLICABILITY The present invention can be used for sterilization of liquids such as beverages, liquid foods, alcoholic beverages, liquid raw materials, fermentation media and the like, and in particular, high-viscosity liquids, liquids that easily foam, liquids containing suspended substances, proteins Suitable for sterilization of highly foamable liquids such as liquids containing

It is a schematic block diagram which shows the 1st example of a supercritical carbon dioxide sterilizer of this invention. It is drawing which shows an example of the cyclone used as the isolation | separation means of this invention, Comprising: (a) is a top view, (b) is a front view, (c) is a cross-sectional view which follows the BB line of (b), (D) is a longitudinal cross-sectional view which follows the AA line of (a). It is drawing explaining the operation | movement principle of the cyclone shown in FIG. 2, Comprising: (a) is a perspective view, (b) is a cross-sectional view which follows the BB line of FIG.2 (b). It is a schematic block diagram which shows the 2nd form example of the supercritical carbon dioxide sterilizer of this invention. It is a schematic block diagram which shows the 3rd form example of the supercritical carbon dioxide sterilizer of this invention. It is a schematic block diagram which shows the supercritical carbon dioxide sterilizer which concerns on a comparative example.

Explanation of symbols

1, 2, 3, ... supercritical carbon dioxide sterilizer, 30 ... mixing and dissolving means, 40 ... constant temperature holding means, 52 ... pressure releasing means, 60 ... cyclone (separation means), 60A ... a plurality of cyclones connected in series (separation) Means), 60B... A plurality of cyclones (separation means) connected in parallel.

Claims (2)

Mixing / dissolving means for mixing and dissolving carbon dioxide in a liquid to be sterilized, and raising the temperature of the mixed fluid obtained by the mixing / dissolving means to a predetermined temperature and increasing the temperature of the mixed fluid to the predetermined temperature to carbon dioxide Constant temperature holding means for holding and sterilizing at a predetermined temperature and pressure at which it becomes a supercritical state, pressure release means for reducing the mixed fluid sterilized by the constant temperature holding means to a pressure at which carbon dioxide is in a gaseous state, and In a supercritical carbon dioxide sterilization apparatus provided with a separation means for separating the mixed fluid decompressed by the pressure release means into gaseous carbon dioxide and sterilized liquid,
The supercritical carbon dioxide sterilizer characterized in that the separation means is a cyclone.   The supercritical carbon dioxide sterilizer according to claim 1, wherein the separating means is a plurality of cyclones connected in series or in parallel.

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