JP2016131929A - Membrane distillation and fractionation unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fractionation unit which has a favorable fractionation efficiency using a membrane distillation apparatus and is capable of efficiently fractionating a treatment objective liquid component simply and inexpensively.SOLUTION: A fractionation system 1 for a treatment objective liquid W is configured by connecting three stages of membrane distillation apparatuses in series. A first membrane distillation apparatus 2 is equipped with a hydrophobic porous membrane 5 to form a first raw water chamber 6 and a first condensation chamber 7 through which the treatment objective liquid W circulates by sandwiching this hydrophobic porous membrane 5. A second membrane distillation apparatus 3 is equipped with a hydrophobic porous membrane 8 to form a second raw water chamber 9 and a second condensation chamber 10 through which a primary distillation liquid W1 circulates by sandwiching this hydrophobic porous membrane 8. A third membrane distillation apparatus 4 is equipped with a hydrophobic porous membrane 11 to form a third raw water chamber 12 and a third condensation chamber 13 through which a secondary distillation liquid W2 circulates by sandwiching this hydrophobic porous membrane 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fractionation unit that has good fractionation efficiency and can efficiently fractionate a liquid component to be treated easily and at low cost, and more particularly to a membrane distillation fractionation unit that uses a vacuum membrane distillation apparatus.

  Conventionally, an oil refining distillation column, for example, a multistage distillation column, is well known as a fractionation technique. A multi-stage distillation column is a type in which a number of horizontal shelves (tray) are installed in the tower and separated, and the shelves are like a stool to allow steam to pass vertically. There are many holes. In such a shelf-type multistage distillation column, the liquid to be treated is supplied to a shelf near the center of the tower. Vapor-liquid equilibrium is established in each shelf, and the more volatile components move to the upper stage in the gas phase, and the less volatile components are notched parts of the shelf (liquid flow From the mouth) to the lower stage in the liquid phase, where gas-liquid equilibrium is again established. In this way, the upper tier is rich in highly volatile components, while the lower tier is rich in less volatile components, and the components are separated according to volatility in each stage.

  In the fractional distillation using the above-described multistage distillation column, it is the stage efficiency that should be noted. The main cause of the drop in stage efficiency is entrainment on the shelf. Droplets due to entrainment not only reduce efficiency because they are richer in higher boiling components than vapor generated on the shelf, but also entrain non-volatile components, thus polluting the tower and distillate. It can also be a cause. The amount of entrained droplets is greatly affected by steam and liquid flow rates, and is particularly large in a vacuum distillation column. For these reasons, in the fractionation technique using a distillation column, a reduction in fractionation efficiency in each shelf due to entrainment of droplets is unavoidable to some extent.

  On the other hand, in addition to desalination from seawater and dehydration from solvents and oils, membrane distillation technology is expected as an energy-saving and space-saving technology for applications that assume concentration in food processes. In particular, interest in vacuum membrane distillation equipment has recently increased.

  This vacuum membrane distillation apparatus has a flow path (raw water chamber) for passing a liquid to be treated at about 60 ° C. to 80 ° C. on one side through a hydrophobic porous membrane (permeating only water vapor) that repels water. The structure in which the water vapor that has passed through the hydrophobic membrane is arranged in a condensing chamber that leads to the condensing part on the opposite side of the liquid to be treated to condense and obtain a distillate is a unit structure, and this unit structure is composed of multiple stages. It is arranged in series. As a result, the concentrated liquid concentrated in the first stage of the unit structure is further concentrated in the second stage arranged in series, and the processed liquid concentrated in the second stage is further concentrated in the third stage, In this way, it is concentrated one after another, and is collected after being concentrated to a desired concentration in the final stage. On the other hand, in the condensing chamber, the water vapor that has passed through the hydrophobic membrane is condensed to obtain a distillate, and therefore, the condensing chamber is at a temperature that is several degrees lower than the liquid to be treated. In this condensing chamber, the water vapor is condensed into a distillate, which is collected separately from the concentrate. As such a vacuum membrane distillation apparatus, techniques as shown in Patent Documents 1 and 2 are known, and a highly porous Teflon (registered trademark) resin film is widely used as the hydrophobic porous film. .

  As shown in FIG. 3, such a membrane distillation apparatus 41 includes a hydrophobic porous membrane 42, and a raw water chamber 43 and a condensing chamber 44 are formed by being partitioned by the hydrophobic porous membrane 42. ing. The raw water chamber 43 is an example of a raw water part that introduces the liquid to be treated w, and the condensing chamber 44 is an example of a condensing part that condenses the vapor S that has passed through the hydrophobic porous membrane 42.

  The hydrophobic porous membrane 42 is an example of means for selectively allowing only the vapor of the liquid to be treated w introduced into the raw water chamber 43 to pass through. As the hydrophobic porous membrane 42, a fluororesin porous membrane can be suitably used because of its excellent heat resistance. This hydrophobic porous membrane 42 allows only the vapor S of the liquid to be treated w to pass through, is hardly affected by the osmotic pressure and viscosity of the liquid to be treated w with respect to the amount of vapor passing through the membrane, and has high vapor permeability. Concentration of suspended components of the treatment liquid w can be performed efficiently.

  A raw water line 45 for introducing the liquid to be treated w is connected to the raw water chamber 43. On the other hand, a vacuum pump 46 is connected to the condensation chamber 44, and a cooling unit 47 is provided on the wall surface of the condensation chamber 44. Then, the raw water chamber 43 is decompressed by the vacuum pump 46 together with the condensing chamber 44 and maintained in a decompressed state, and the cooling unit 47 is cooled by a cooling means (not shown) to a temperature that condenses the vapor S in contact therewith. . Reference numeral 48 denotes a concentrate recovery line for recovering the concentrate w1 from the raw water chamber 43, and 49 denotes a distillate discharge line for recovering the distillate w2 from the condensation chamber 44.

  In the membrane distillation apparatus 41 as described above, first, the liquid w to be treated is brought to a predetermined temperature, for example, less than 100 ° C., preferably 40 ° C. to 90 ° C., particularly about 50 ° C. to 80 ° C. by a heat exchanger (not shown). The temperature is adjusted to be supplied from the raw water line 45. Here, each vacuum membrane distillation apparatus 41 is depressurized by a single vacuum pump 46. For this reason, the liquid to be treated w is sucked into the raw water chamber 43 of the membrane distillation apparatus 41.

  In this case, since the condensing chamber 44 is maintained in a reduced pressure state, it has not only a function of drawing the steam S but also a function of lowering the boiling point of the liquid to be processed w. Thereby, the vapor | steam S which arises from the to-be-processed liquid w becomes remarkable, and the vapor | steam amount which permeate | transmits the hydrophobic porous membrane 42 increases. As a result, the concentrate w1 is obtained in the raw water chamber 43. That is, since much steam S is condensed and removed from the liquid to be processed w and converted into the concentrated liquid w1, the liquid w to be processed in the raw water chamber 43 is efficiently concentrated. Accordingly, a large amount of concentrated liquid w1 is generated from the raw water chamber 43 and recovered from the concentrated liquid recovery line 48. On the other hand, the steam S touches the cooling part 47 of the condensing chamber 44 and condenses to form water droplets L. Thereby, in the cooling part 47, the vapor | steam S condenses and the distillate w2 is discharged | emitted from the distillate discharge line 49. FIG.

JP 2011-173097 A JP 2013-212464 A

  In the vacuum membrane distillation apparatus as described above, the raw water chamber 43 through which the liquid to be treated w circulates and the condensing chamber 44 are completely fractionated via the hydrophobic porous membrane 42 through which only gas passes. Since the droplets of the liquid to be treated w are not entrained in the condensing chamber 44, it is considered to be a technique with high fractional distillation efficiency in each distillation stage, but the membrane distillation apparatus originally concentrates the liquid to be treated w. Therefore, it is difficult to effectively recover each component by fractional distillation. For this reason, the technique of utilizing a membrane distillation apparatus as a fractionation technique has not been proposed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fractionation unit using a membrane distillation apparatus capable of fractionating a liquid component to be treated efficiently and easily at low cost with good fractionation efficiency. And

  In order to solve the above problems, the present invention provides a raw water section and a condensation section partitioned by a hydrophobic porous membrane, a decompression means for maintaining the condensation section in a decompressed state, and a cooling means for cooling the condensation section. The heated liquid to be treated is introduced into the raw water part, and the vapor of the liquid to be treated is permeated through the hydrophobic porous membrane, thereby concentrating the liquid to be treated to produce a concentrated liquid. A fractionation system comprising two or more membrane distillation apparatuses for producing a distillate in the condensing unit, the flow path for introducing the distillate of the previous stage membrane distillation apparatus into the raw water part of the subsequent stage membrane distillation apparatus; Provided is a fractionation system characterized by having a diversion mechanism for collecting a part of the concentrate of the membrane distillation apparatus and refluxing the remainder to the raw water part side of the membrane distillation apparatus (Invention 1). Here, the membrane distillation apparatus preferably includes three or more stages (Invention 2).

  According to such inventions (Inventions 1 and 2), the liquid to be treated has a plurality of components having different volatilization temperatures, but when the liquid to be treated heated by the first-stage membrane distillation apparatus is distilled, the temperature of the liquid to be treated is reduced. While all the components that volatilize volatilize to form a distillate, the components that do not volatilize and the components that cannot be volatilized and recovered become the concentrate, so a part of the concentrate is recovered and the remainder is circulated to the raw water part again. By introducing and repeating the volatilization recovery, the recovery rate of the components that could not be volatilized and recovered can be made desired. Of the volatile components that have permeated through the hydrophobic porous membrane, the volatile components having a high volatilization temperature are liquefied in the condensing part, so a part is recovered as a distillate, and the remaining liquid and the uncondensed gas are the next stage. Supplied to the raw water section of the membrane distillation apparatus. And in the membrane distillation apparatus of the next stage, the temperature of the liquid to be treated is lower than that of the previous stage. The component that could not be volatilized and recovered becomes a concentrated liquid, so that a part of the concentrated liquid is recovered, the remaining part is circulated and reintroduced into the raw water part, and the volatilization recovery is repeated. A high volatile component recovery can be achieved. Of the volatile components that have permeated through the hydrophobic porous membrane, the volatile components with a slightly lower volatilization temperature are liquefied in the condensing part, so some are recovered as distillate, and the remaining liquid and uncondensed gas are the next. Supplied to the raw water section of the stage membrane distillation apparatus. By repeating such an operation in a plurality of stages, particularly three or more stages, it is possible to efficiently fractionate and collect three or more components having different volatilization temperatures.

  In the said invention (invention 1 and 2), it is preferable to provide the adjustment mechanism which can adjust the collection | recovery and circulation ratio of the said concentrate (invention 3).

  According to this invention (invention 3), the fractional distillation efficiency of components having different volatilization temperatures constituting the liquid to be treated can be adjusted to a desired one.

  In the said invention (invention 1-3), it is preferable that the said to-be-processed liquid is a food related solution of fruit juice, liquid sugar, or a honey (invention 4).

  According to this invention (invention 4), these food-related solutions include not only components having a low volatilization temperature but also components having a high volatilization temperature. It is desirable to perform fractional distillation and add the desired components to the concentrate again. However, by applying the method of the present invention, these components having different volatilization temperatures can be efficiently separated and recovered. It can be added to the concentrate.

  According to the fractionation system of the present invention, two or more membrane distillation apparatuses are provided, and the distillation liquid of the previous stage film distillation apparatus is introduced into the raw water part of the subsequent stage membrane distillation apparatus, while a part of the concentrated liquid is recovered. However, since the operation of circulating the remainder and reintroducing it into the raw water portion is repeated in each membrane distillation apparatus, the liquid to be treated has different volatile components depending on the temperature, but the liquid to be treated heated by the membrane distillation apparatus in the first stage When the liquid is distilled, all the components that volatilize at the temperature of the liquid to be treated are volatilized to become a distillate, while the non-volatile components that do not boil and the components that cannot be volatilized and recovered become the concentrate. By recovering a part of the water, circulating the remainder and introducing it into the raw water part and repeating the volatilization recovery, the recovery rate of the components that could not be volatilized and recovered can be made desired. By repeating this, two or more types of components having different volatilization temperatures can be efficiently fractionated and recovered.

It is the schematic which shows the fractionation system which concerns on one Embodiment of this invention. It is the schematic which shows the fractionation system of the comparative example 1. It is the schematic which shows a membrane distillation apparatus.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic view showing a fractionation system according to this embodiment. In FIG. 1, the fractionation system 1 of the liquid W to be treated is connected in series with three stages of the membrane distillation apparatus shown in FIG. 3, that is, the first membrane distillation apparatus 2 at the first stage and the second membrane distillation at the second stage. The apparatus 3 is continuously connected to the third membrane distillation apparatus 4 in the third stage. A heating means (not shown) such as a heat exchanger is disposed on the upstream side of the first membrane distillation apparatus 2.

  The first membrane distillation apparatus 2 includes a hydrophobic porous membrane 5, and a first raw water chamber 6 and a first raw water chamber 6 through which the liquid W to be treated flows with the hydrophobic porous membrane 5 interposed therebetween. A condensation chamber 7 is formed. Thereby, in the 1st film | membrane distillation apparatus 2, while suspending the suspension component and non-volatile component of the to-be-processed liquid W, the primary distillation liquid W1 can be discharged | emitted. Further, the second membrane distillation apparatus 3 is provided with a hydrophobic porous membrane 8, and the second raw water chamber 9 and the second raw water chamber 9 in which the primary distilled liquid W1 flows through the hydrophobic porous membrane 8. The condensing chamber 10 is formed. Thereby, in the 2nd film | membrane distillation apparatus 3, while condensing the volatile component in the primary distillate W1, the secondary distillate W2 can be discharged | emitted. Further, the third membrane distillation apparatus 4 is provided with a hydrophobic porous membrane 11, and the third raw water chamber 12 and the second raw water chamber 12 through which the secondary distilled liquid W2 flows are sandwiched between the hydrophobic porous membrane 11. Three condensing chambers 13 are formed. Thereby, in the 3rd membrane distillation apparatus 4, while condensing the volatile component in the secondary distillation liquid W2, the tertiary distillation liquid W3 can be discharged | emitted.

  In the fractionation system 1 as described above, the inflow path 14 and the discharge path 15 for the liquid W to be treated are connected to the first raw water chamber 6 of the first membrane distillation apparatus 2. And the discharge path 15 is connected, and thereby, a circulation path 16 through which the liquid W to be treated can be circulated is formed, and a recovery path 17 is connected to the circulation path 16. The circulation path 16 and the recovery path 17 function as a diversion mechanism, and are provided with opening / closing valves 18 and 19 as adjustment mechanisms, respectively. The recovered amount and the circulating amount can be adjusted.

  On the other hand, a discharge path 20 is connected to the first condensing chamber 7, and this discharge path 20 communicates with the second raw water chamber 9 of the second membrane distillation apparatus 3 as an inflow path 22. A recovery valve 21 is provided, and by adjusting the opening, the recovery amount of the primary distillate W1 and the secondary distillation amount can be adjusted.

  Similarly, the second raw water chamber 9 of the second membrane distillation apparatus 3 is connected to the inflow path 22 and the discharge path 23 of the primary distilled liquid W1, and the inflow path 22 and the discharge path 23 communicate with each other. Thus, a circulation path 24 through which the primary distillate W1 can be circulated is formed, and a recovery path 25 is connected to the circulation path 24. The circulation path 24 and the recovery path 25 are provided with opening / closing valves 26 and 27 as adjusting mechanisms, respectively, and the amount of the secondary concentrated liquid W5 recovered and circulated by adjusting the respective opening degrees. The amount is adjustable.

  On the other hand, a discharge path 28 is connected to the second condensing chamber 10, and this discharge path 28 communicates as the inflow path 30 of the third raw water chamber 12 of the third membrane distillation apparatus 4. A recovery valve 29 is provided, and by adjusting the opening, the recovery amount of the secondary distillate W2 and the tertiary distillation amount can be adjusted.

  Further, similarly, the third raw water chamber 12 of the third membrane distillation apparatus 4 is connected to the inflow path 30 and the discharge path 31 of the secondary distilled liquid W2, and the inflow path 30 and the discharge path 31 are connected to the third raw water chamber 12. A circulation path 32 through which the secondary distilled liquid W2 can be circulated is formed by communication, and a recovery path 33 is connected to the circulation path 32. The circulation path 32 and the recovery path 33 are provided with open / close valves 34 and 35 as adjusting mechanisms, respectively, and by adjusting their opening degrees, the recovered amount and the circulating amount of the tertiary concentrate W6 are adjusted. And can be adjusted.

  A discharge path 36 is connected to the third condensing chamber 13 so that the tertiary distillate W3 can be discharged.

  Next, regarding the action of the fractionation system 1 of this embodiment formed by connecting the three membrane distillation apparatuses 2, 3 and 4 in series as described above, components A, B and C having different volatilization temperatures (of the volatilization temperature). The case of fractionating the liquid W to be processed which contains the higher volatilization temperature below the heating temperature of the heat exchanger described later will be described in the descending order.

  First, the temperature of the liquid W to be treated is adjusted to a predetermined temperature, for example, less than 100 ° C., preferably about 50 ° C. to 90 ° C. by a heat exchanger (not shown). It is supplied to the first raw water chamber 6. Here, the first condensation chamber 7 of the first membrane distillation apparatus 2 is decompressed by a vacuum pump (not shown). For this reason, not only the function of drawing steam but also the function of lowering the boiling point of the liquid W to be processed are exhibited. As a result, the volatile components A, B, and C of the liquid W to be processed pass through the hydrophobic porous membrane 5 together with the evaporated water. As a result, a primary concentrated liquid W4 from which the volatile components A, B, and C have been removed from the liquid W to be processed at a predetermined ratio is obtained. At this time, a component having a volatilization temperature exceeding the heating temperature by the heat exchanger remains in the primary concentrated liquid W4 without being removed.

  At this time, all of the volatile components A, B, and C are not volatilized, and a part of the volatilization failure remains in the primary concentrated liquid W4. However, in this embodiment, since the circulation path 16 is formed by connecting the inflow path 14 and the discharge path 15, the primary concentrated liquid W4 is circulated. Therefore, by adjusting the opening degree of the open / close valves 18 and 19, the recovery amount of the primary concentrated liquid W4 from the recovery path 17 so that the content of the volatile components A, B and C is reduced to a desired ratio. It is possible to adjust the amount of circulation.

  On the other hand, the water evaporated together with the volatile components A, B, and C comes into contact with the cooling part of the first condensing chamber 7 and condenses to form water droplets containing a large amount of the volatile component A having the highest volatilization temperature. A part of this water droplet is recovered as a primary distillate W1 from the recovery valve 21 of the discharge path 15 (inflow path 22). The remaining primary distillate W1 and a gas containing a large amount of volatile components B and C are supplied to the second raw water chamber 9 of the second membrane distillation apparatus 3 at the next stage.

  In the second membrane distillation apparatus 3, the second condensation chamber 10 is decompressed by a vacuum pump (not shown). At this time, the temperature of the primary distillate W1 is lowered to a temperature lower than the volatilization temperature of the volatile component A and higher than the volatilization temperatures of the volatile components B and C by the treatment in the first membrane distillation apparatus 2. Accordingly, the volatile component A does not pass through the hydrophobic porous membrane 8, but the volatile components B and C pass through the hydrophobic porous membrane 8 together with the evaporated water. As a result, the volatile components B and C are removed from the primary distillate W1 at a predetermined ratio, and a secondary concentrated solution W5 containing abundant volatile components A is obtained. On the other hand, water droplets containing the volatile components B and C are generated by condensing by touching the cooling part of the second condensing chamber 10. Thereby, this water droplet is discharged | emitted from the discharge path 28 as the secondary distilled liquid W2.

  At this time, all of the volatile components B and C do not volatilize, and a part of the volatile components B and C that have failed to volatilize remains in the secondary concentrated liquid W5. However, in this embodiment, since the inflow path 22 and the discharge path 23 are connected to form the circulation path 24, the secondary concentrated solution W5 is circulated. Therefore, the opening amounts of the on-off valves 26 and 27 are adjusted so as to circulate until the content ratios of the volatile components B and C are reduced to a desired ratio, The amount of circulation can be adjusted. As a result, the recovery rate of the volatile component A can be improved.

  On the other hand, the water evaporated together with the volatile components B and C comes into contact with the cooling part of the second condensing chamber 10 and condenses, resulting in water droplets containing a large amount of the volatile component B having the next highest volatilization temperature. This water droplet is recovered as a secondary distillate W2 from the recovery valve 29 of the discharge path 28 (inflow path 30). Further, the remaining secondary distillate W2 and a gas containing a large amount of volatile component C are supplied to the third raw water chamber 12 of the third membrane distillation apparatus 4 at the next stage.

  In the third membrane distillation apparatus 3, the third condensing chamber 13 is decompressed by a vacuum pump (not shown). At this time, the temperature of the secondary distillate W2 is lowered to a temperature lower than the volatilization temperature of the volatile component B and higher than the volatilization temperature of the volatile component C by the treatment in the second membrane distillation apparatus 3. Therefore, the volatile component B does not pass through the hydrophobic porous membrane 11, but the volatile component C passes through the hydrophobic porous membrane 11 together with the evaporated water. As a result, since it is discharged | emitted from the discharge path 28 as the tertiary concentrated liquid W6 containing abundant volatile component B from which the volatile component C was removed from the secondary distilled liquid W2 by the predetermined | prescribed ratio, this can be collect | recovered.

  At this time, the volatile component C is not completely volatilized, and a part of the volatilized component C remains in the tertiary concentrated liquid W6. However, in this embodiment, since the circulation path 32 is formed by connecting the inflow path 30 and the discharge path 31, the tertiary concentrated liquid W6 is circulated. Therefore, the opening and closing valves 34 and 35 are adjusted so as to circulate until the content of the volatile component C decreases to a desired ratio, and the recovered amount and the circulating amount of the tertiary concentrated liquid W6 from the recovery path 33 Can be adjusted. As a result, the recovery rate of the volatile component B can be improved.

  On the other hand, the water evaporated together with the volatile component C comes into contact with the cooling part of the third condensing chamber 13 and condenses to produce water droplets containing a large amount of the volatile component C having the lowest volatilization temperature. Thereby, the water droplets rich in the volatile component C are discharged from the discharge path 36 as the tertiary distillation liquid W3 and can be collected.

  In addition, as the to-be-processed liquid W used as the said concentration object, the food related solution containing sugars, such as fruit juice, liquid sugar, and honey, is suitable. Here, in the liquid W to be treated, the initial concentration of the target concentrated component such as sugar is 10% or less, particularly about 2 to 7%. It can also be suitably applied to process discharge in industrial processes such as seawater desalination and dehydration from solvents and oils.

  Although the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the configuration of the fractionation system 1 is not limited to three stages, and may be composed of four or more stages according to the number of components to be fractionally collected. Moreover, in this fractionation system 1, the to-be-processed liquid W is applicable not only to food process water but to concentrating the process water of a pharmaceutical or another industrial field.

<Example 1>
When the fruit juice (liquid W to be treated) was fractionated using the fractionation system having the configuration shown in FIG. 1, three types of volatile components could be efficiently fractionated without accompanying entrained droplets.

<Comparative Example 1>
In Comparative Example 1, a fractionation system having the configuration shown in FIG. 2 was used.

  In FIG. 2, the fractionation system 1 of the liquid W to be treated uses the same curtain distillation apparatus as the membrane distillation apparatuses 2, 3, and 4 in the fractionation system 1 shown in FIG. The same reference numerals are given to the components, and detailed description thereof is omitted. A heating means (not shown) such as a heat exchanger is disposed on the upstream side of the first membrane distillation apparatus 2.

  The first membrane distillation apparatus 2 includes a hydrophobic porous membrane 5, and a first raw water chamber 6 and a first raw water chamber 6 through which the liquid W to be treated flows with the hydrophobic porous membrane 5 interposed therebetween. A condensation chamber 7 is formed. Thereby, in the 1st film | membrane distillation apparatus 2, while suspending the suspension component and non-volatile component of the to-be-processed liquid W, the primary distillation liquid W1 can be discharged | emitted. Further, the second membrane distillation apparatus 3 is provided with a hydrophobic porous membrane 8, and the second raw water chamber 9 and the second raw water chamber 9 in which the primary distilled liquid W1 flows through the hydrophobic porous membrane 8. The condensing chamber 10 is formed. Thereby, in the 2nd film | membrane distillation apparatus 3, while being able to concentrate the low volatile component of the primary distillate W1, the secondary distillate W2 can be discharged | emitted. Further, the third membrane distillation apparatus 4 is provided with a hydrophobic porous membrane 11, and the third raw water chamber 12 and the second raw water chamber 12 through which the secondary distilled liquid W2 flows are sandwiched between the hydrophobic porous membrane 11. Three condensing chambers 13 are formed. Thereby, in the 3rd membrane distillation apparatus 4, while concentrating the volatile component in secondary distillation liquid W2, it is possible to discharge | emit tertiary distillation liquid W3.

  In the fractionation system 1 as described above, the first raw water chamber 6 of the first membrane distillation apparatus 2 is connected to the inflow path 14 of the liquid W to be treated and the discharge path 15 of the primary concentrated liquid W4. The discharge path 15 communicates with the inflow path 22 of the second membrane distillation apparatus 3 at the subsequent stage. On the other hand, the first condensing chamber 7 is connected with a discharge path 20 for the primary distillate W1.

  Similarly, the second raw water chamber 9 of the second membrane distillation apparatus 3 is connected to the inflow path 22 of the primary concentrate W4 and the discharge path 23 of the secondary concentrate W2, and this discharge path 23 is connected to the latter stage. The third membrane distillation apparatus 4 communicates with the inflow path 30. On the other hand, the second condensing chamber 10 is connected with a discharge path 28 for the secondary distillate W2.

  Further, similarly, the third raw water chamber 12 of the third membrane distillation apparatus 4 is connected to the inflow path 30 for the secondary concentrated liquid W2 and the discharge path 31 for the tertiary concentrated liquid W3. On the other hand, a discharge path 36 is connected to the third condensing chamber 13.

  In the fractionation system 1 of Comparative Example 1 in which the three membrane distillation apparatuses 2, 3 and 4 as described above are connected in series, the primary concentrated solution W4 concentrated by the first membrane distillation apparatus 2 is used as the first concentrated liquid W4. Further concentration is performed by the second membrane distillation apparatus 3, and the concentrated secondary concentrated solution W5 is further concentrated by the third membrane distillation apparatus 4. Finally, a tertiary concentrated solution W6 is obtained, and the membrane distillation apparatus 2 This is a fractionation system that collects the distillates W1, W2, and W3 in the condensing chambers 7, 10, and 13.

  When the same fruit juice (processed liquid W) as in Example 1 was fractionated by such a fractionation system of Comparative Example 1, the fruit juice was concentrated, but each component could be fractionated with sufficient accuracy. could not. Therefore, as a countermeasure, it may be possible to improve the fractionation accuracy by further installing a similar membrane distillation apparatus in the condensation chambers 7, 10 and 13, but the apparatus becomes large and the equipment cost becomes very high. Not practical.

DESCRIPTION OF SYMBOLS 1 ... Fractionation system 2 ... 1st membrane distillation apparatus 3 ... 2nd membrane distillation apparatus 4 ... 3rd membrane distillation apparatus 5 ... Hydrophobic porous membrane 6 ... 1st raw | natural water chamber 7 ... 1st condensation chamber 8 ... hydrophobic porous membrane 9 ... second raw water chamber 10 ... second condensing chamber 11 ... hydrophobic porous membrane 12 ... third raw water chamber 13 ... third condensing chamber 14 ... inflow passage 15 ... discharge passage 16 ... Circulation path 17 ... Recovery path 18 ... Open / close valve 19 ... Open / close valve 20 ... Discharge path 21 ... Recovery valve 22 ... Inlet path 23 ... Discharge path 24 ... Circulation path 25 ... Recovery path 26 ... Open / close valve 27 ... Open / close valve 28 ... Discharge path 29 ... Recovery valve 30 ... Inlet path 31 ... Discharge path 32 ... Circulation path 33 ... Recovery path 34 ... Open / close valve 35 ... Open / close valve 36 ... Discharge path W ... Liquid to be treated W1 ... Primary distillate W2 ... Secondary distillate W3 ... Tertiary distillate W4 ... Primary concentrate W5 ... Secondary concentrate W6 ... Tertiary concentrate S ... Steam

Claims (4)

Raw water section and condensation section partitioned by a hydrophobic porous membrane;
Pressure reducing means for maintaining the condensing part in a reduced pressure state;
Cooling means for cooling the condensing part,
The heated liquid to be treated is introduced into the raw water part, and the vapor of the liquid to be treated is permeated through the hydrophobic porous membrane, thereby concentrating the liquid to be treated to produce a concentrated liquid and the condensing part. A fractional distillation system comprising two or more membrane distillation devices for producing a distillate at
A flow path for introducing the distillate of the previous stage membrane distillation apparatus into the raw water part of the subsequent stage film distillation apparatus, and recovering a part of the concentrated liquid of the membrane distillation apparatus, while the remainder is the raw water part of the membrane distillation apparatus And a diversion mechanism for refluxing to the side.   The fractionation system according to claim 1, wherein the membrane distillation apparatus includes three or more stages.   The fractionation system according to claim 1, further comprising an adjustment mechanism capable of adjusting a rate of recovery and circulation of the concentrate.   The concentration system according to any one of claims 1 to 3, wherein the liquid to be treated is a food-related solution of fruit juice, liquid sugar, or honey.

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