JPS60206408A - Concentration of stick-water - Google Patents

Abstract

PURPOSE:To highly concentrate stick-water at a high temp. without requiring special pretreatment, by bringing stick-water into contact with a hydrophobic polymer porous membrane while cooling and condensing steam generated from the stick-water and transmitted through the membrane. CONSTITUTION:A membrane tube 2, which transmits steam but transmits no water, comprising a hydrophobic polymer porous membrane made of a fluorocarbon resin is coaxially arranged in an outer tube 1 and a heat transfer pipe 9 is arranged inside the membrane tube 2 to recirculate a cooling medium by an introducing pipe 11 and a discharge pipe 12. The stick-water being the waste solution from a food manufacturing factory is recriculated to a raw solution passage 3 by an introducing pipe 4 and a discharge pipe 5 and replenished from a supply pipe 8. Steam generated from the stick-water transmits the membrane tube 2 to reach a steam space 10 and cooled on the surface of the heat transfer pipe 9 to generate condensed water which is, in turn, flowed down along the surface of the heat transfer pipe 9 and guided out of the system from a condensed water discharge pipe 13. The solid components and valuable solute components in the stick-water and inhibited from permeation by the membrane tube 2 and conc. in the stick-water.

Description

[Detailed description of the invention] The present invention relates to a method for concentrating juice.

Generally, in food manufacturing, various liquid liquids are generated as waste liquids. Such food waste liquid has a high BOD, and discarding it as it is may cause pollution, and the liquid contains a large amount of protein, fat, carbohydrates, etc., so discarding it as it is is a waste of food resources. It is also uneconomical.

Incidentally, the juice after grinding potatoes and separating the starch has a BOD of 10,000 to 40,000 and contains 2 to 3% protein.

To this end, many methods have been proposed in the past in which food juice is treated by membrane separation methods such as reverse osmosis and ultrafiltration to recover proteins and lower the BOD of the juice. However, food juice is generally discharged as high-temperature waste liquid from the food manufacturing process, so when using the membrane separation treatment method described above, it is necessary to cool the juice to around room temperature, which requires extra equipment. In addition to being expensive and expensive, juices generally have a high osmotic pressure and require high pressure for treatment. Therefore, during membrane treatment, a gel layer may form on the membrane surface or the membrane may become clogged, reducing the amount of water permeating through the membrane. Significant decline over time. Furthermore, the water quality of the membrane permeate is not sufficiently clean.

As a result of intensive research in order to solve the above problem, the present inventors utilized the high temperature of the juice discharged from the food manufacturing process, and through membrane processing using this as a driving force,
The present invention was achieved by discovering a method of highly concentrating a juice while maintaining a high concentration efficiency while keeping the temperature high and without performing any pretreatment such as neutralization or filtration.

The present invention is a method for concentrating a juice containing soluble valuables, in which a predetermined high-temperature juice is brought into contact with one side of a hydrophobic polymer porous membrane that allows water vapor to pass through but not water. It is characterized by generating this, passing it through the other side of the porous membrane, cooling and condensing it.

In the method of the present invention, juice refers to waste liquid discharged from the food manufacturing process and containing soluble valuables such as proteins, fats, and carbohydrates.

In the method of the present invention, any of the following methods can be used to cool and condense the water vapor generated from the juice and permeated through the hydrophobic polymer porous membrane.

The first method is to bring a predetermined high temperature liquid into contact with one side of a hydrophobic polymer porous membrane that allows water vapor to pass through but does not allow water to pass through, and then to place the other side of this polymer membrane at an appropriate distance from the membrane surface. A heat transfer wall is provided which is maintained at a predetermined low temperature, and the water vapor generated from the juice and transmitted through the polymer membrane is cooled by the heat transfer wall soil and condensed to obtain condensed water, while the soluble valuable components are Since it does not pass through the membrane, it is concentrated in the juice.

The second method is to bring a predetermined high-temperature liquid into contact with one side of the hydrophobic polymer porous membrane as described above, and bring a predetermined low-temperature cooling medium, such as cooling water, into contact with the other side. The water vapor generated from the sap and permeated through the polymer is directly cooled and condensed in a cooling medium, and is obtained in the cooling medium, while the sap is concentrated in the same manner as described above.

In the method of the present invention, the porous polymer membrane is hydrophobic to fluid and does not allow fluid to pass through, but
It is necessary to have the property of permeating water vapor. Therefore, such hydrophobic polymer porous membranes typically have a
It is preferable to have micropores of ~50 μm, preferably 0.1 to 10 μm, and a porosity of 50% or more. In addition, although the film thickness is not particularly limited, it is usually
The thickness is about 1 to 300 μm, preferably about 5 to 50 μm.

] Therefore, in the present invention, as such a polymer membrane, a porous membrane made of a fluororesin such as polytetrafluoroethylene resin is particularly preferably used because it is hydrophobic and has excellent heat resistance. Also, for example,
A porous membrane obtained by extruding a solution or melt of a fluororesin such as vinylidene fluoride resin or ethylene-tetrafluoroethylene copolymer resin is also preferably used.

However, even if a porous membrane is made of a hydrophilic resin such as polysulfone or cellulose resin, when the surface is coated with a water-repellent resin such as a fluororesin or silicone resin to provide a hydrophobic porous surface. Resin films can also be used.

Next, an apparatus suitable for carrying out the method of the present invention will be described based on the drawings.

1 and 2 show an example of an apparatus suitable for carrying out the first method described above.

That is, a membrane tube 2 made of a hydrophobic polymer porous membrane as described above is disposed coaxially within the outer tube 1, and a stock solution for high-temperature juice is placed between the outer tube and the membrane tube. A passage 3 is formed. Therefore, it is preferable that the outer tube has heat retention properties,
For example, it is made of resin. A juice inlet pipe 4 and a juice outlet pipe 5 are connected to the raw liquid passage 3, and the juice, which is heated by a heater 6 provided in these pipes as necessary and maintained at a predetermined temperature, is passed through the pipes 4 and 5. It is circulated and distributed to the stock solution circuit. The juice is appropriately replenished into the stock solution circuit from a juice supply pipe 8 equipped with a valve 7, and a portion of the juice is discharged from the stock solution circuit as necessary through a discharge pipe (not shown).

A heat transfer tube 9 is further disposed coaxially inside the membrane tube 2, and is spaced at an appropriate distance from the membrane tube so as to have a steam space 1o between the tube and the membrane tube. Heat exchanger tubes are made of highly heat conductive materials,
For example, it is a thin-walled tube made of metal. An inlet pipe 11 and an outlet pipe 12 for a cooling medium are connected to the heat exchanger tube, and a cooling medium such as cooling water is circulated through the heat exchanger tube.

Further, a discharge pipe 13 for condensed water that has passed through the membrane tube, been cooled by the heat exchanger tube, and condensed is connected to the steam space.

Note that, since the porous membrane constituting the membrane tube generally has low strength, it is preferably supported on a suitable support (not shown). Such a support only needs to be able to reinforce the polymer membrane and allow water vapor to pass therethrough, and for example, a woven or nonwoven fabric made of polyamide or a porous tube made of ceramic is preferably used.

In the method of the present invention, a liquid-permeable spacer (not shown) is provided in contact with the inner surface of the membrane tube made of the microporous membrane, and a coaxial spacer is further provided in contact with the inner surface of this spacer. Heat exchanger tubes may be installed in the

The spacer must be porous so that the steam that has passed through the membrane tube can pass through to the heat transfer tube, and must also have liquid permeability in at least a predetermined direction for water that has been cooled and condensed by the heat transfer wall. Furthermore, it is preferable that the material has excellent thermal conductivity. In the illustrated apparatus, the spacer needs to have liquid permeability at least in the vertical direction so that the generated condensed water can flow down in the vertical direction.

Of course, the spacer may be bonded in advance to the surface of the microporous membrane or heat exchanger tube.

Examples of the spacer include woven fabrics, non-woven fabrics made of 10 to 1000 meshes of natural or synthetic fibers, such as polyethylene, polyester, polyamide, etc.
Carbon fiber cloth or the like is preferably used. The thickness of the spacer is not particularly limited, but if it is too thick, it will actually reduce the steam condensation efficiency, so it is usually 0.1~
A range of 5 dragons, particularly 0.2 to 3 cranes, is preferred.

Further, as shown in FIG. 3, the device includes a plurality of membrane tubes 2 disposed inside an outer tube l, each membrane tube having a heat transfer tube 9 inside, and a space between the outer tube and each membrane tube. The space may be configured as the stock solution passage 3.

In the first device described above, the liquid juice at a predetermined temperature is introduced into the raw liquid passage 3, and the water vapor generated from the liquid liquid is transferred to the membrane tube 2.
The condensed water passes through the heat exchanger tube 9 and reaches the steam space 10, where it is cooled on the surface of the heat exchanger tube 9 to produce condensed water, which flows down the surface of the heat exchanger tube and is led out of the apparatus through the condensed water outlet tube 13. The solid content and valuable solute components in the stock solution are prevented from permeating through the membrane tube, and fl
Shrunk.

According to this device, the juice can be concentrated and substantially pure water can be obtained as condensed water.

4 and 5 show an example of an apparatus suitable for carrying out the second method described above, in which the same parts as in FIG. 1 are given the same reference numerals.

A membrane tube 2 made of a hydrophobic polymer porous membrane as described above is disposed coaxially within the outer tube l, and a stock solution passage 3 is formed between the outer tube and the membrane tube. A predetermined high temperature liquid is passed through the membrane tube, and a cooling medium such as cooling water is passed through the membrane tube. That is, the juice and the cooling medium are brought into contact through the membrane tube.

An inlet pipe 4 and an outlet pipe 5 for flowing the juice are connected to the raw liquid passage 3, and similarly, an inlet pipe 11 and an outlet pipe 12 for passing the cooling medium are connected to the membrane tube 2.

According to this second device, water vapor generated from the juice and transmitted through the membrane tube wall is immediately cooled and condensed in a cooling medium, for example, cooling water, and is recovered in the cooling water. As described above, the juice is replenished from the juice supply pipe 8 as necessary, heated by the heater 6, and circulated through the stock liquid circuit through the pipes 4 and 5, and the cooling medium is supplied as necessary. Cooling medium accordingly.

The coolant is circulated through the coolant circuit while being cooled to a predetermined temperature by a cooler 14 provided in the circuit, and a portion of the coolant is taken out of the apparatus through a take-out pipe 15 along with the condensed water.

According to this device, the juice at a predetermined temperature and the cooling medium are brought into direct contact through the membrane tube wall, so the water vapor generated from the juice is immediately cooled by the cooling medium, condensed, and collected in the cooling medium. be done. Therefore, not only the vapor permeation rate is high, but also the device can be made smaller than a device with a vapor space between the membrane tube and the heat transfer wall, and the effective membrane area per unit volume is large, which improves the efficiency (sap transfer rate). Concentration can be carried out.

Although not shown, the device may be configured such that a plurality of membrane tubes are housed in an outer tube, a cooling medium is circulated in each membrane tube, and a space outside the membrane tubes is formed in the outer tube to form a stock solution passage.

Incidentally, in the case of any of the above-mentioned devices, the method of the present invention has been described assuming that the liquid liquid is passed through the raw liquid passage 3 between the outer tube and the membrane tube, and the cooling medium is circulated within the membrane tube. Of course, the cooling medium may be passed through the undiluted liquid passage, while the juice may be made to flow through the cooling medium passage.

In addition, when a spacer is provided, both the microporous membrane and the heat transfer wall are in contact with the thin spacer and are arranged in parallel with a certain extremely small interval, and the spacer itself is also a low-temperature conductor. It is cooled by a thermal wall, and since there is no direct contact between the porous membrane and the heat transfer wall, the generation of water vapor from the juice is not hindered, so concentration can be carried out efficiently.

As described above, the method of the present invention involves bringing a predetermined high-temperature juice into contact with a hydrophobic polymer porous membrane, and cooling and condensing the water vapor generated from the juice and passing through the membrane.
It condenses the juice and obtains condensed water. Therefore, according to the method of the present invention, it is possible to highly concentrate the high-temperature juice discharged from the fishmeal manufacturing process while maintaining the high temperature and without requiring any pretreatment such as special filtration treatment. can.

In addition, unlike the reverse osmosis method and ultrafiltration method, which use the pressure difference as the driving force, as mentioned above, the driving force is the temperature of the liquid, so no pressurization is required, and a hydrophobic membrane is used. Therefore, there is no clogging of the membrane or concentration polarization, and the juice can be highly concentrated efficiently.

Examples of the present invention are listed below.

Example 1 As shown in Figure 1, a membrane tube with a diameter of 25 mm made of a porous polytetrafluoroethylene membrane lined with a porous polyamide woven fabric was coaxially placed inside a synthetic resin outer tube with a diameter of 40 mm. Furthermore, a stainless steel heat exchanger tube having a diameter of 21 m was disposed within this membrane tube so that the interval between the tube walls was 2 squares, thereby constructing an apparatus. Note that the above porous membrane has an average pore diameter of 0.
．． It had micropores of 2 μm, a porosity of 80%, and an effective membrane area of 240 d in the device.

In this device, cooling water at a temperature of 10°C is passed through a heat transfer tube, and a juice at 40°C after grinding potatoes and separating starch (COD 200' ioo pp
m, electric type conductivity 9750 μs) was circulated to the stock solution passage and concentrated three times. The acquisition rate and properties of condensed water and the properties of concentrated juice are shown in the table. In the table, the concentration ratio l indicates the initial stage of the treatment.

For comparison, a membrane module equipped with a reverse osmosis membrane with a salt removal rate of 95% was used at a temperature of 25°C and a pressure of 40 kg/c+ (,
The same liquid liquid as above was concentrated three times under conditions of a membrane surface flow rate of 1.9 m/sec. The properties of the membrane permeate and concentrate are shown in the table along with the water permeation rate. According to this comparative example, it is understood that the water quality of the membrane-permeated liquid is inferior to that of the method of the present invention, and that the water permeation rate changes significantly over time.

Example 2 In the same apparatus as in Example 1, a 0.5-thick carbon fiber cloth was layered as a spacer on the inner surface of the membrane tube, and the membrane tube and the heat transfer tube were brought into contact with each other via this spacer to construct the apparatus.

In this device, cooling water at a temperature of 10° C. was passed through the heat transfer tube, and the same juice as in Example 1 was heated to 40° C. and circulated and supplied to the stock liquid passage. Is the condensed water acquisition speed initially 0.35n? /ffl·day, 0.0% at the time of 3-fold concentration.
It was 1rd/cd/day.

Example 3 As shown in Fig. 3, a membrane tube with a diameter of 25 mm, which is the same as in Example 1, was coaxially disposed within a synthetic resin outer tube with a diameter of 401 mm, thereby constructing a device with a membrane area of 240 mm. .

In this apparatus, when the same juice as in Example 1 was treated under the same conditions, condensed water having almost the same properties as in Example 1 was obtained.

The condensate acquisition rate is 0.3 tdl at the beginning of the process.
It was rd day.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an example of an apparatus suitable for carrying out the method of the present invention, and FIG. 2 is the same as that of FIG. 1. vIA-
3 is a sectional view taken along line A, FIG. 3 is a sectional view showing another device, FIG. 4 is a sectional view showing yet another device, and FIG. 5 is a sectional view taken along line B-B in FIG. be. 1... Outer tube, 2... Membrane tube, 3... Stock solution passage, 9...
... Heat exchanger tube, 10... Steam space, 13... Condensate outlet pipe. Patent applicant: Nitto Electric Industry Co., Ltd. Patent attorney: Itsube Makino

Claims (1)

[Claims] (1) In a method for concentrating a juice containing soluble valuables, a predetermined high-temperature juice is brought into contact with one side of a hydrophobic polymer porous membrane that allows water vapor to pass through but not water. A method for concentrating a liquid juice, which comprises: generating liquid liquid, passing it through the other side of the porous membrane, cooling and condensing it.