JP2000042378A - Fluid separation element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a practical fluid separation element capable of keeping the concentration polarization near a separation membrane low and drastically reducing the pressure loss of raw liq. due to a passage material. SOLUTION: In this fluid separation element, a membrane unit including a separation membrane, a raw water passage material 4 and a permeated liq. passage material is formed around a water collecting pipe. The raw water passage material 4 consists of a network having a lozenge-shaped mesh and is arranged so that the major axis of the lozenge-shaped mesh may be a flow direction of the raw liq. and also the angle of a net leg 5 to the flow direction is between ±15 to 40 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fluid separation element using a separation membrane such as a reverse osmosis membrane. More specifically, the present invention relates to a fluid separation element that can reduce a pressure loss when a stock solution passes through the fluid separation element.

[0002]

2. Description of the Related Art In recent years, in various fields such as desalination of seawater and desalination of brackish water, production of ultrapure water in the field of semiconductors, concentration of wastewater in various industries, and treatment of wastewater containing valuable substances, the reverse has been developed. Fluid separation using a separation membrane such as an osmosis membrane is performed, and a fluid separation element in which a separation membrane, a permeate flow path material, and a raw liquid flow path material are wound around a water collection pipe is used.

[0003] In order to suppress concentration polarization, a stock solution flow path material is used.
What has a high effect of making the stock solution turbulent is required. Therefore, nets are often used to make the undiluted solution turbulent on the surface of the separation membrane. This net is arranged so that the major axis of the mesh is parallel to the flow direction of the stock solution, and the angle of the mesh legs with respect to the flow direction of the stock solution is ± 45 degrees. However, in such a raw liquid flow path material, the pressure loss of the raw liquid due to the flow path material is large, and in a fresh water generating facility used by filling a plurality of pressure vessels into a pressure vessel, the effective pressure acting on the fluid separation element is reduced. Remarkable. As a result, in order to maintain the quality of the produced water and the amount of produced water, the operating pressure has to be increased, and the power consumption and running cost of the fresh water generating equipment are increased. In addition, a high-pressure pump and piping made of a material having excellent pressure resistance are required as fresh water facilities, which requires a high capital investment.

In order to reduce the pressure loss of the stock solution, Japanese Patent Application Laid-Open No. 5-168869 discloses that the warp yarns are parallel to the flow direction of the stock solution, and the angle of the weft yarn connecting the warps to the stock solution flow direction is 45. Special nets of less than degrees are disclosed. However, the fluid separation element using the raw liquid flow path material has a reduced production water quality and production water volume, and although the effect of reducing the pressure loss is recognized for some time, the fluid separation element is not used in the actual flow velocity range used in the field of fluid separation. The reduction effect is poor and not practical. Furthermore, the mesh is very special as a parallelogram compared to the diamond of the conventional net, and requires advanced net making technology and production technology. As a result, the net becomes an expensive net and lacks practicality.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a practical fluid separation element which suppresses concentration polarization near the separation membrane surface and greatly reduces the pressure loss of the undiluted solution due to the flow path material. And

[0006]

In order to achieve the above object, the present invention provides a separation membrane, a permeate flow path material, and a pressure measured at a flow rate of 0.15 m / s around a water collecting pipe. The pressure loss is 30 when the loss is in the range of 100 to 200 hPa and the flow rate is measured at 0.25 m / s.
It is characterized by a fluid separation element in which a membrane unit including a raw liquid flow path material within a range of 0 to 400 hPa is wound.

Here, a separation membrane module in which the above-mentioned fluid separation element is housed in a pressure vessel is also preferable.

In the present invention, the pressure loss of the stock solution channel material is determined by attaching the stock solution channel material to a parallel plate cell having a channel width of 160 mm and a channel length of 300 mm, and flowing water at 25 ° C. It refers to the measured value.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a fluid separation element according to the present invention includes a membrane unit including a separation membrane 2, a permeate flow path material 3, and a raw liquid flow path material 4 around a water collecting pipe 1. Is a fluid separation element wound. And the stock solution flow path material 4
The mesh is composed of diamond nets, and the major axis of the diamond is arranged in the flow direction of the undiluted solution,
The angle of the legs with respect to the flow direction is ± 15 to 40 degrees.

In the present invention, the long axis refers to the longer one of two mesh points connected to each other, and the angle of the mesh legs with respect to the flow direction of the stock solution means the flow of the stock solution indicated by an arrow in FIG. It is the angle α formed by the direction and the net legs 5 constituting the net.

In the present invention, the mesh of the net is a diamond. A net with a rhombus is easy and inexpensive,
It is a practical net.

Further, in the present invention, if the absolute value of the angle of the mesh legs with respect to the flow direction of the stock solution exceeds 40 degrees, the turbulence effect is increased more than necessary, and the pressure generated when the stock solution passes through the fluid separation element. Losses rise. When the absolute value of the angle is less than 15 degrees, the turbulence effect of the stock solution is excessively reduced, the concentration near the film surface increases, and the concentration polarization increases.
The separation capacity deteriorates and the quality of the produced water deteriorates. Therefore,
In the present invention, the angle of the mesh legs with respect to the flow direction of the stock solution is ± 15 to 40 degrees, preferably ± 20 to 35 degrees.

[0013] The thickness of the net is preferably 0.9 to prevent a decrease in the membrane area and to obtain a sufficient amount of fresh water.
mm or less, more preferably 0.8 mm or less, on the other hand, in order to prevent the flow path width from narrowing and the flow path resistance and pressure loss from significantly increasing, preferably 0.5 mm or more, more preferably 0.6 mm or more. is there.

In the present invention, it is preferable that the major axis length L of the diamond shown in FIG. 2 is in the range of 3.0 to 8.0 mm. By setting the length to 3.0 mm or more, it is possible to suppress the density of the net intersection points per unit area, prevent an increase in liquid flow resistance, and prevent an increase in pressure loss. On the other hand, by setting the length of the major axis to 8.0 mm or less, the unbalanced flow of the undiluted solution is prevented, and the separation performance of only the easy-to-flow portion and the variation in the degree of separation performance with the hard-to-flow portion are prevented. be able to. This major axis length L is more preferably
3.3 to 7.0 mm, more preferably 3.5 to 6.0 mm
mm.

The fluid separation element of the present invention as described above is provided with a plurality of telescope prevention plates 6 shown in FIG. 1 at both ends and connected to each other, and housed in a pressure vessel to form a separation membrane module. Fluid separation is performed using this separation membrane module.

The stock solution is sent through the telescope prevention plate 6 to the stock solution flow path formed by the stock solution flow path material 4, as indicated by the black arrow in FIG. The sent stock solution is separated into a permeate and a concentrate by the separation membrane 2, and the permeate passes through the permeate flow path formed by the permeate flow path material 3 to reach the water collection pipe 1, and is indicated by a white arrow. As described above, it flows downstream through the opposite telescope prevention plate 6. On the other hand, the concentrated water directly flows through the stock solution flow path and the telescope prevention plate 6 to the next separation membrane module, and fluid separation is performed similarly to the upstream side.

In this process, in the separation membrane module using the fluid separation element of the present invention, since the pressure loss due to each fluid separation element is small, it is possible to prevent a decrease in operating pressure acting on the downstream fluid separation element, The pressure difference between the upstream side and the downstream side can be reduced. As a result, the operating pressure on the upstream side can be reduced, and the operating cost is also reduced. Also,
As described above, the pressure loss can be reduced, and the quality of produced water and fresh water performance can be maintained at the conventional levels.

[0018]

Example 1 A polypropylene rhomb net made of polypropylene having a thickness of 0.7 mm, a major axis length of 5 mm, and a net leg angle of ± 33 degrees with respect to the flow direction of the stock solution was used. Parallel plate cell (flow path width 160mm, flow path length 300m) so as to be in the flow direction
m). Then, water at 25 ° C. was flowed, and the relationship between the flow velocity and the pressure loss was measured.

FIG. 3 shows the results.

From FIG. 3, when the flow velocity is 0.15 m / s,
The pressure loss is in the range of 100 to 200 hPa, and when the flow velocity is 0.25 m / s, the pressure loss is 300 to 200 hPa.
It is in the range of 400 hPa, which indicates that the pressure loss of the net is very small. Example 2 A composite reverse osmosis membrane in which an active thin layer of aromatic polyamide was formed on a sheet-like polysulfone porous layer as a separation membrane, and a polyester as a permeate flow path material Were wound around a water collection tube to form a spiral type fluid separation element. The fluid separation element had a diameter of 200 mm, a length of 1 m, and a membrane area of 35 m ² . Six fluid separation elements were arranged in series and housed in a pressure vessel to form a separation membrane module. Pressure loss was measured using a 0.05% aqueous sodium chloride solution as raw water. At this time, the operating pressure was 0.75 MPa, the recovery was 50%, the pH was 6.5, and the temperature was 25 degrees.

The results are shown in Table 1.

Table 1 shows that the pressure loss of the module is very small. Comparative Example 1 The flow velocity and pressure were the same as in Example 1 except that a polypropylene rhombic net having a thickness of 0.7 mm, a major axis length of 4 mm, and a net leg angle of ± 45 degrees with respect to the flow direction of the stock solution was used. The loss relationship was measured.

FIG. 3 shows the result.

Compared to the first embodiment, the flow velocity is 0.15 m
/ S, the pressure loss exceeds 200 hPa, and when the flow velocity is 0.25 m / s, the pressure loss exceeds 400 hPa, and it is recognized that the pressure loss is large. Comparative Example 2 Freshening performance was observed in the same manner as in Example 2, except that the net used in Comparative Example 1 was used as a stock solution flow path material for a fluid separation element.

The results are shown in Table 1.

From Table 1, it can be seen that the above module has a large pressure loss and is inferior to Example 2 in terms of fresh water performance and salt concentration.

[0027]

[Table 1]

[0028]

According to the fluid separation element of the present invention, a separation membrane, a permeated liquid flow path material, and a flow velocity of 0.15 m / s are provided around a water collecting pipe.
Pressure loss when measured as 100 to 200 hPa
, And the membrane unit including the undiluted liquid flow path material having a pressure loss of 300 to 400 hPa when measured at a flow rate of 0.25 m / s is wound. The pressure loss of the element can be kept low.

Further, a net is provided as a stock solution flow path material, and the angle of the net legs with respect to the stock solution flow direction of the net is ± 1.
When it is in the range of 5 to 40 degrees, an appropriate turbulence effect can be provided while suppressing concentration polarization, and the pressure loss can be significantly reduced. In addition, since the net mesh is rhombic, the net can be easily manufactured, becomes an industrially inexpensive stock solution flow path material, and can be manufactured at low cost as a fluid separation element.

Here, the thickness of the net is 0.5 to 0.9 mm.
Within this range, the membrane area is ensured while keeping the pressure loss small, and a sufficient amount of fresh water can be obtained. Further, when the major axis length of the net is 3.0 to 8.0 mm, while preventing the unbalanced flow of the undiluted solution, the pressure loss due to the intersection density of the mesh per unit area is prevented, and the separation performance is prevented from being lowered or varied. Can be.

When the fluid separation element of the present invention is housed in a pressure vessel to form a separation membrane module, a decrease in operating pressure can be prevented due to the above-mentioned effects. However, the same amount of fresh water as before can be obtained, and as a result, the fresh water cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a fluid separation element according to one embodiment of the present invention.

FIG. 2 is a diagram showing a net used in the present invention.

FIG. 3 is a graph showing a relationship between a flow velocity and a pressure loss in Example 1 and Comparative Example 1.

[Explanation of symbols]

 1: Water collecting pipe 2: Separation membrane 3: Permeate flow path material 4: Undiluted liquid flow path material 5: Net leg 6: Telescope prevention plate L: Long axis length α: Angle

Claims (2)

[Claims] 1. A separation membrane, a permeate flow path material, and a pressure loss measured at a flow rate of 0.15 m / s around a water collecting pipe in a range of 100 to 200 hPa. A pressure loss of 30 when measured as 0.25 m / s
A fluid separation element, wherein a membrane unit including a raw liquid flow path material within a range of 0 to 400 hPa is wound. 2. A separation membrane module comprising the fluid separation element according to claim 1 housed in a pressure vessel.