WO2009144770A1

WO2009144770A1 - Immersed membrane separation apparatus

Info

Publication number: WO2009144770A1
Application number: PCT/JP2008/001376
Authority: WO
Inventors: 白岩由紀; 岡島康信; 北野智一
Original assignee: 株式会社クボタ
Priority date: 2008-05-30
Filing date: 2008-05-30
Publication date: 2009-12-03
Also published as: JP5283696B2; JPWO2009144770A1

Abstract

An immersed membrane separation apparatus comprising a wall member surrounding an interior zone extending from an inferior opening to a superior opening and, disposed opposite to the superior opening, a flow straightening part.

Description

Immersion membrane separator

The present invention relates to a submerged membrane separation apparatus used for filtration or concentration in general water treatment such as clean water and wastewater.

As a conventional membrane separator, for example, as shown in FIGS. 15 and 16, a submerged membrane separator 2 in which a plurality of membrane elements 1 are arranged in parallel at an appropriate interval is known. The membrane element 1 is formed by arranging a filtration membrane 4 made of an organic membrane covering a surface of a rectangular flat filter plate 3 as a membrane support, and joining the filtration membrane 4 to the filter plate 3 at the periphery. is there. In addition to the resin filter plate 3, the membrane support includes a nonwoven fabric, a net, and the like. The submerged membrane separation apparatus 2 is used by being immersed in the liquid 6 to be treated in the treatment tank 5, and diffuses aeration gas from the aeration apparatus 7 disposed below the membrane element 1.

The membrane element 1 receives the driving pressure and filters the liquid 6 to be treated with a filtration membrane. Gravity filtration using the head pressure of the treatment tank 5 as a driving pressure or a negative pressure inside the filtration membrane. Used for suction filtration given as driving pressure.

Examples of prior art include those described in Japanese Patent Gazette (Japanese Patent No. 3258858). This is provided with a membrane separation device inside the membrane separation tank, the membrane separation device is provided with a large number of filtration membrane plates arranged in parallel, and the water flow forming device is an upward flow of the liquid to be treated between the filtration membrane plates. Form. A rectifying plate is provided below the water surface above the membrane separation device, the rectifying plate is bent or curved, and the upward flow of the liquid to be treated flowing between the filtration membrane plates is inclined toward the outside of the membrane separation device. Guide upward.

Moreover, the membrane separation apparatus described in Japanese Patent Publication (Patent No. 3290577) is soaked and disposed in a liquid to be treated in a treatment tank, and a plurality of pieces are provided inside a box-shaped case having upper and lower openings. Membrane cartridges are provided in parallel at regular intervals, and an air diffuser is provided below the membrane cartridge. The air diffused from the air diffuser causes an upward flow by the air lift action, and the membrane surface of the membrane cartridge is washed by the upward flow. At the top of the case, a frame-shaped rectification case that guides upward flow that has escaped from the flow path between the membrane cartridges is provided.

Moreover, the membrane separation apparatus described in Japanese Patent Publication (Patent No. 38677481) has a membrane module that is immersed in a liquid to be treated and has a diffuser tube provided below the membrane module. A diffuser induction wall is disposed around the membrane module. The diffuser induction wall has a shape with its upper end folded back outward.

In the submerged membrane separation apparatus 2 described above, an upward flow of the gas-liquid mixed phase is generated by the air lift action of the air, and the flow of the liquid 6 to be processed along the membrane surface of the filtration membrane 4 is formed by the upward flow. The liquid 6 to be treated is supplied in a cross flow with respect to the flow of the permeate that flows through 4. Hereinafter, the flow along the membrane surface of the filtration membrane 4 is referred to as a cross flow. The cross flow flows through the flow path between the membrane surfaces of the opposing filtration membranes 4 and flows upward from the submerged membrane separation device 2 as an upward flow.

However, the cross flow depends on the flow of bubbles, and the flow of bubbles is affected by the shape of the treatment tank 5. For this reason, depending on the shape of the treatment tank 5, the mode of the bubble flow is biased to a part of the membrane surface of the filtration membrane 4, and as a result, the crossflow may not be uniformly formed on the entire membrane surface.

This cross flow contributes to the flux by its diffusion action and cleaning action, and contributes to the improvement of filtration efficiency. Here, the diffusion action diffuses the solid substance in the liquid to be treated along the membrane surface, and the cleaning action removes the fouling substance on the membrane surface and prevents the filtration membrane 4 from being clogged. These actions are related to the cross flow velocity, and the larger the flow velocity, the better the diffusing action and the washing action.

Therefore, in order to sufficiently exhibit the diffusion action and the cleaning action, the cross flow is configured to flow uniformly over the entire membrane surface of the filtration membrane 4, and the flow velocity of the cross flow at each part of the membrane surface of the filtration membrane 4 is equal. And it is necessary to be large, and satisfying these conditions contributes to the improvement of filtration efficiency. In order to increase the flow velocity of the cross flow, it is necessary to increase the amount of aeration diffused from the diffuser 7. However, an increase in the amount of aeration is a factor that causes a reduction in device life due to vibration, damage to the membrane, an increase in energy costs, and the like.

Next, the liquid 6 to be treated in the treatment tank 5 flows out from the submerged membrane separation device 2 as an upward flow to the upper region, and then reverses and flows into a side region of the submerged membrane separation device 2 as a downward flow. Then, it flows into the submerged membrane separator 2 again from the lower region, and a circulation flow is formed across the inside and outside of the submerged membrane separator 2.

For this reason, in the submerged membrane separation apparatus 2 in which a plurality of membrane elements 1 are arranged in parallel at a predetermined interval, the cross flow may be unevenly distributed, and is orthogonal to the width direction of the membrane elements 1, that is, the arrangement direction of the membrane elements 1. In the direction, the cross flow that flows through the flow path between the membrane elements 1 tends to increase as the distance from the central portion of the membrane element 1 increases toward the end portion.

On the other hand, when the liquid 6 to be treated flows out as an upward flow from the submerged membrane separation device 2 to the upper region, the liquid 6 is reversed to become a downward flow and flows into the side region of the submerged membrane separation device 2. There is a phenomenon in which some of the contained bubbles are entrained in the downward flow, and the force due to buoyancy acts on the bubbles, causing the bubbles in the downward flow to interfere with the downward flow, resulting in the membrane This hinders the upward flow and cross flow from the separator to the upper region. For this reason, the flow velocity of the cross flow decreases as the amount of bubbles entrained in the downward flow increases.

This phenomenon becomes more prominent as the distance from the wall surface of the treatment tank to the membrane separation apparatus is shorter. Table 1, FIG. 12, and FIG. 13 are analysis results showing changes in crossflow when the distance from the wall surface of the treatment tank to the membrane separation apparatus is different. The conditions of this analysis are: viscosity of liquid 10 mPa · s, bubble diameter of air aerated in liquid 5 mm, aeration rate 2 m ³ / min per unit area below membrane separator, width of membrane separator 0.5 m It is.

In Table 1, FIG. 12, and FIG. 13, the distance from the wall of the treatment tank to the membrane separation device is expressed as “distance from the wall”, and the flow velocity of the cross flow is expressed as “transmembrane liquid flow velocity”. The bubble velocity is expressed as “intermembrane bubble velocity”, and the bubble velocity obtained by subtracting the intermembrane fluid velocity from the intermembrane bubble velocity, that is, the rising velocity of bubbles in a stationary liquid, is denoted as “bubble relative velocity”. ing. However, the intermembrane fluid flow velocity is an average flow velocity at the upper end of the flow path between the membrane elements.

As is apparent from Table 1, FIG. 12 and FIG. 13, until the distance from the wall reaches 2 m, the intermembrane fluid flow rate tends to increase as the distance from the wall increases, and then gradually decreases. Show the trend.

The bubble relative flow velocity almost agrees with the theoretical value of the following formula. However, the case where the distance from the wall is 0.05 m is excluded.

v = 4 / 3Cd · (ρ−ρw) / ρw · g · d
(Where v is the bubble relative flow velocity, Cd is the resistance coefficient, ρ is the bubble density, ρw is the liquid density, g is the gravitational acceleration, and d is the bubble diameter)
From the above results, it can be seen that the closer the distance from the wall of the treatment tank to the membrane separation device, the lower the efficiency of the air lift action and the smaller the cross flow.

FIG. 14 is a schematic diagram showing the volume fraction of bubbles in the liquid to be treated in the treatment tank when the distance from the wall is 0.35 m, 0.5 m, 1 m, 2 m, and 10 m, respectively. However, the area | region from the center position of the width direction of a membrane separator to the wall surface of a processing tank is shown. In FIG. 14, the wall surface of the treatment tank is indicated by a symbol W, the end of the film surface is indicated by a symbol M, and in the case of 10 m, the wall surface of the treatment tank is omitted.

The display method for indicating the volume fraction is originally performed with a single color shading on the screen, and the shading difference cannot be clearly expressed on paper.

For this reason, in FIG. 14, regions having different volume fractions are schematically and schematically shown, and each region is represented with a different pattern.

In this expression method, FIG. 14 shows that when the distance from the wall surface of the treatment tank to the membrane separation apparatus is 0.35 m, 0.5 m, and 1 m, the amount of bubbles entrained in the downward flow increases. ing.

As the result shown in FIG. 14 and the amount of bubbles entrained in the downward flow increase, the flow velocity of the cross flow decreases, so the distance from the wall of the treatment tank to the membrane separation device is 0.35 m, 0.5 m In the case of 1 m, the flow velocity of the cross flow becomes small. For this reason, it is preferable that the distance from the wall surface of the treatment tank to the membrane separation apparatus is about 2 m or more.

However, when a larger membrane separation apparatus is arranged in a treatment tank having a limited volume, or when more membrane separation apparatuses are arranged, the distance from the wall of the treatment tank to the membrane separation apparatus becomes smaller. Therefore, a solution to the above-described problem is required.

The present invention solves the above-described problems, and the crossflow mode can be made to be close to a state of flowing uniformly over the entire membrane surface of the filtration membrane, and the crossflow in each part of the membrane surface of the filtration membrane. The present invention provides a membrane separation apparatus that can increase the flow rate of the liquid, and further, when a large membrane separation apparatus is disposed in a processing tank having a limited volume or when many membrane separation apparatuses are disposed. However, an object of the present invention is to provide a submerged membrane separation apparatus that can sufficiently exhibit a diffusion action and a cleaning action.

In order to solve the above problems, an immersion type membrane separation apparatus according to the present invention includes a wall surrounding an inner region from a lower opening to an upper opening, a membrane separation means disposed in the inner region, and a lower portion of the membrane separation means. A submerged membrane separation apparatus provided with a diffuser to be disposed, characterized by having a rectifying section extending from an upper end of a wall body or the vicinity thereof and facing the upper opening.

Further, in the submerged membrane separation apparatus of the present invention, the rectifying unit is opposed to a region near the inner edge of the wall body in the upper opening.

Moreover, in the submerged membrane separation apparatus of the present invention, the rectifying unit has a shape protruding toward the inside of the upper region in the vertical direction of the upper opening.

Further, in the submerged membrane separator of the present invention, a plurality of submerged membrane separators are arranged adjacent to each other, and the rectification unit is arranged only at an outer position in the arrangement direction in the plurality of submerged membrane separators in a row. It is characterized by that.

In the submerged membrane separation apparatus of the present invention, the membrane separation means includes a plurality of membrane elements arranged in parallel, and a flow path is formed between the membrane elements, and the membrane elements are disposed on the main surface of the membrane support. A filtration membrane made of a flat membrane is arranged on the surface.

Further, in the submerged membrane separation apparatus of the present invention, the rectification unit is disposed at a position facing each other in a direction orthogonal to the arrangement direction of the membrane elements, and between the rectification units as the distance from the upper opening of the wall body increases. It has a shape with a small distance.

In the submerged membrane separation apparatus according to the present invention, the minimum separation distance between the two rectifying sections is 90% or more with respect to the distance between the wall edges facing each other in the direction orthogonal to the arrangement direction of the membrane elements. % Or less.

In the present invention described above, the submerged membrane separation apparatus is disposed in the treatment tank and is operated in a state in which an upward flow of the liquid to be treated is generated in the treatment tank by the aerated air diffused from the diffuser.

The upward flow flows in the inner region along the membrane surface of the membrane separation means, that is, the membrane element, passes through the rectifying unit from the upper opening, and flows out to the upper region of the treatment tank. And it reverses in the upper area | region of a processing tank, becomes a downward flow, and flows through the side area | region of an immersion type membrane separator.

For this reason, even in the upward flow that flows out from the region near the inner edge of the wall in the upper opening, that is, the region near the both sides of the membrane element, the downward flow does not directly flow from the upper opening. Since it flows down to the upper region of the processing tank and then reverses to become a downward flow, bubbles contained in the upward flow are separated in the upper region of the processing tank, and are released onto the liquid surface of the liquid to be processed. It can suppress that a downward flow entrains a bubble.

At this time, the rectifying portion facing the upper opening acts as a resistance against the upward flow flowing out from the region near the inner edge of the wall in the upper opening, that is, the region near both sides of the membrane element. For this reason, the flow of the upward flow that flows in the region in the vicinity of both sides of the membrane element is suppressed, and as a result, the upward flow is close to a state of flowing evenly over the entire membrane surface of the membrane element.

Therefore, it is possible to make the crossflow mode close to a state where the crossflow flows uniformly over the entire membrane surface of the filtration membrane, and close to the state where the crossflow velocity at each part of the membrane surface of the filtration membrane is equal. be able to. By suppressing the downflow from entraining bubbles, the smooth flow of the downflow is realized by eliminating the factors that hinder the downflow, and as a result, the flow velocity of the crossflow at each part of the membrane surface of the filtration membrane Can be increased.

Therefore, even when a large membrane element is filled in a processing tank having a limited volume, even when a larger number of membrane elements are filled, the diffusing action and the cleaning action can be sufficiently exhibited.

This also means that the same diffusing action and cleaning action can be achieved with a smaller amount of aeration than before.

The perspective view which shows the immersion type membrane separator in embodiment of this invention Sectional view showing the submerged membrane separator Perspective view showing a model of a submerged membrane separator in analysis Sectional view showing a model of a submerged membrane separator in the same analysis Schematic diagram showing rectifying plates in various models of submerged membrane separators in the same analysis Schematic diagram showing rectifying plates in various models of submerged membrane separators in the same analysis Graph showing the flow velocity distribution in the same analysis Graph showing the flow velocity distribution in the same analysis Graph showing the flow velocity distribution in the same analysis The perspective view which shows the other immersion type membrane separator in embodiment of this invention The perspective view which shows the other immersion type membrane separator in embodiment of this invention The graph which shows the flow-velocity distribution in the immersion type membrane separator which concerns on the conventional structure Graph showing the flow velocity distribution in the same configuration Schematic diagram showing the volume fraction of bubbles in the same configuration The perspective view which shows the immersion type membrane separator in the same structure Sectional view showing a submerged membrane separator in the same configuration

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2, the submerged membrane separation device 11 has a plurality of membrane elements 12 arranged in parallel at appropriate intervals as membrane separation means, and a flow path is formed between the membrane elements 12. The membrane separation means is not limited to the membrane element 12 according to the present embodiment, and various types such as a hollow fiber membrane and a ceramic tube membrane can be used.

The membrane element 12 is a filter plate 14 made of an organic membrane covering a surface of a rectangular flat filter plate 13 which is a membrane support, and the filtration membrane 14 is joined to the filter plate 13 at the peripheral edge. is there. In addition to the resin filter plate 13, the membrane support includes a sheet-like nonwoven fabric, a net, and the like. Below the membrane element 12, an air diffuser 15 for diffusing aeration gas is disposed. The submerged membrane separation device 11 is used by being immersed in the liquid 17 to be processed in the processing tank 16.

The membrane element 12 receives the driving pressure and filters the liquid 17 to be treated by the filtration membrane 14. When the head pressure is given as the driving pressure in the tank of the treatment tank 16, or the negative pressure is applied to the inside of the filtration membrane 14. May be given as the driving pressure.

The submerged membrane separation device 11 has a wall 18 surrounding the side surface around the membrane element 12, and forms a flow path from the lower opening 18 a to the upper opening 18 b in the inner region surrounded by the wall 18. The membrane element 12 is arranged in the inner region.

In the present embodiment, the membrane element 12 and the wall body 18 are separate bodies. However, it is also possible to form the wall body 18 on both sides of the membrane element 12 by providing portions forming part of the wall body 18 on both sides of the membrane element 12 and arranging the membrane elements 12.

In the present embodiment, the upper end of the membrane element 12 corresponds to the upper opening 18b and the lower end of the membrane element 12 corresponds to the lower opening 18a in the vertical direction. However, the inner region formed by the wall body 18 can be formed longer than the membrane element 12, the upper opening 18 b is located above the upper end of the membrane element 12, and the lower opening 18 a is below the lower end of the membrane element 12. It is also possible to be located in

A rectifying plate 19 that forms a rectifying portion is provided at the upper end position of the wall body 18, and the shape of the rectifying plate 19 will be described in detail later. The rectifying plates 19 are arranged at positions facing each other in a direction orthogonal to the arrangement direction of the membrane elements 12 and positions facing each other in the arrangement direction of the membrane elements 12.

The mode of providing the rectifying plate 19 is not limited to that provided over the entire circumference of the four sides of the upper opening 18b as shown in FIG. 1, but is opposed to the direction perpendicular to the arrangement direction of the membrane elements 12 as shown in FIG. It is also possible to provide the baffle plate 19 only at the position where it is.

The reason for this is that cross-flow drift occurs mainly in the width direction of the membrane element 12, and rectification is performed only on opposite sides in the width direction of the membrane element 12, that is, in the direction perpendicular to the arrangement direction of the membrane elements 12. The present invention can also be realized by providing the plate 19.

Furthermore, the present embodiment discloses a configuration in which the membrane elements 12 are arranged in one row. However, when the membrane elements 12 are arranged in a plurality of rows, it is possible to arrange the rectifying plates 19 at positions separating the plurality of rows of membrane elements 12.

For example, as shown in FIG. 11, a plurality of submerged membrane separators are arranged adjacent to each other, and the current plate 19 is arranged only at an outer position in the arrangement direction of the plurality of submerged membrane separators in a row. Is also possible. Even in this case, it is possible to provide the rectifying plate 19 only at a position facing each other in the direction orthogonal to the arrangement direction of the membrane elements 12.

The rectifying plate 19 has a shape that protrudes obliquely upward from the upper end position of the wall body 18, that is, toward the inside of the upper region in the vertical direction of the upper opening 18 b, and faces the region near the inner edge of the wall body 18. Opposite the opening 18b. The rectifying plate 19 has a shape in which the distance between the both rectifying plates 19 gradually decreases as the distance from the upper opening of the wall 18 increases, and the tip of both forms a minimum separation portion with a minimum separation distance.

However, the rectifying plate 19 does not have to be an integral structure with the wall body 18, and can be shaped to extend away from the upper end of the wall body 18, that is, from the vicinity of the upper end of the wall body 18, It is also possible to have a shape surrounding the wall 18, and it is also possible to form a minimum separation portion at an intermediate position of the current plate 19. In any case, the rectifying plate 19 protrudes toward the inside of the upper region in the vertical direction of the upper opening 18b.

Further, as shown in FIG. 5, the rectifying plate 19 is not limited to a flat plate surface, but may be a concave surface or a convex surface, and a curved surface or a curved surface may be employed. Furthermore, materials that can be used as the current plate 19 are not limited to members without holes, but include members with holes such as punching metal and members with slits.

The operation of the above configuration will be described below. During the filtration operation, air is aerated from the diffuser 15 into the liquid to be processed, and an upward flow of gas-liquid mixed phase is generated in the liquid to be processed. By this upward flow, the liquid 17 to be treated is supplied along the membrane surface of the membrane element 12 by cross flow, and the membrane surface of the membrane element 12 is washed.

The upward flow flows in the inner region along the membrane surface of the membrane element 12, and flows out from the upper opening 18 b to the upper region of the treatment tank 16 through the minimum separation portion of the rectifying plate 19. And it reverse | inverts in the upper area | region of the processing tank 16, becomes a downward flow, flows through the side area | region of the immersion type membrane separator 11, and forms a circulation flow.

For this reason, even in the upward flow flowing out from the region near the inner edge of the upper opening 18b, that is, the region near both sides of the membrane element 12, there is no direct downward flow from the upper opening 18b. The minimum separation distance of the processing tank 16 passes through the minimum separation portion and flows out to the upper region of the processing tank 16 and then reverses to become a downward flow. Therefore, the bubbles included in the upward flow are separated in the upper region of the processing tank 16 and covered. It is released on the liquid level of the processing liquid, and it is possible to suppress the downward flow from entraining bubbles.

At this time, the rectifying plate 19 facing the upper opening 18b acts as a resistance against the upward flow flowing out from the region near the inner edge of the upper opening 18b, that is, the region near both sides of the membrane element 12. For this reason, the flow of the upward flow that flows in the region in the vicinity of both sides of the membrane element 12 is suppressed, and as a result, the upward flow is close to a state of flowing evenly over the entire membrane surface of the membrane element 12.

Therefore, the upward flow, that is, the cross flow mode can be made to be close to the state of flowing uniformly over the entire membrane surface of the filtration membrane, and the flow velocity of the cross flow in each part of the membrane surface of the filtration membrane is equalized. Can be close.

By suppressing the downward flow from entraining bubbles, the smooth flow of the downward flow is realized without the factor that obstructs the flow of the downward flow. As a result, the cross flow of each part of the membrane surface of the filtration membrane 14 is reduced. The flow rate can be increased.

Accordingly, even when a larger immersion type membrane separation device 11 is arranged in a treatment tank having a limited volume or when more immersion type membrane separation devices 11 are arranged, the diffusion action and the cleaning action are sufficiently exhibited. can do.

Hereinafter, the analysis according to the submerged membrane separation apparatus of the present invention will be described. In FIG. 3, (a) shows the model of the structure of this invention which provided the baffle plate, (b) has shown the model of the conventional structure which does not provide the baffle plate. FIG. 4 partially shows the configuration of the present invention. 3 and 4, the air diffused portion 30 corresponds to the air diffuser 15 in FIGS. 1 and 2, and the other components will be described with reference numerals in FIGS. 1 and 2. On the membrane surface of the membrane element 12, four measurement points, line1, line2, line3, and line4 are set in order from the bottom to the top.

In this analysis, as shown in FIG. 5, eight models are set according to the difference in the shape of the rectifying plate 19, and a model without the rectifying plate 19 is used as a reference standard. Each model will be described below.
Model 1.
As shown in FIG. 5A, the rectifying plate 19 has a flat plate surface, is inclined at 60 ° with respect to the flow path cross section of the upper opening 18b, and the length of the rectifying plate 19 is 200 mm. The separation distance is 300 mm.
Model 2.
As shown in FIG. 5A, the rectifying plate 19 has a flat plate surface, is inclined at 60 ° with respect to the flow path cross section of the upper opening 18b, and the length of the rectifying plate 19 is 100 mm. The separation distance is 400 mm.
Model 3.
As shown in FIG. 5B, the rectifying plate 19 has a flat plate surface, is inclined at 30 ° with respect to the flow path cross section of the upper opening 18b, and the length of the rectifying plate 19 is 200 mm. The separation distance is 154 mm.
Model 4.
As shown in FIG. 5B, the rectifying plate 19 has a flat plate surface, is inclined at 30 ° with respect to the flow path cross section of the upper opening 18b, and the length of the rectifying plate 19 is 100 mm. The separation distance is 327 mm.
Model 5.
As shown in FIG. 5 (c), the rectifying plate 19 has a concave arc shape with respect to the upper opening 18b, the arc chord is inclined at 60 ° with respect to the flow path cross section of the upper opening 18b, and the chord Has a length of 200 mm and a minimum separation distance of 300 mm.
Model 6.
As shown in FIG. 5D, the rectifying plate 19 has a convex arc shape with respect to the upper opening 18b, the chord of the arc is inclined at 60 ° with respect to the flow path cross section of the upper opening 18b, and the string Has a length of 200 mm and a minimum separation distance of 300 mm.
Model 7.
As shown in FIG. 5 (e), the rectifying plate 19 has a bent shape, is composed of a portion parallel to a portion perpendicular to the flow path cross section of the upper opening 18b, and the length of the perpendicular portion is 100 mm. The length of the parallel part is 100 mm, and the minimum separation distance is 300 mm.
Model 8.
As shown in FIG. 5 (f), the rectifying plate 19 has a bent shape, each side is inclined at 45 ° with respect to the flow path cross section of the upper opening 18b, and the length of each side is 141 mm. The minimum separation distance is 300 mm.
Model 9.
As shown in FIG. 5G, the current plate 19 is not provided.
Analysis conditions Analysis software; Fluent ver6.3
Analytical model: 2D, double precision, multi-phase flow (two-fluid Euler-Euler), aeration rate per unit area 2 m ³ / min below the membrane separator, membrane element width 500 mm
Result 1. In all of the models 1 to 8, the circulation flow is formed across the inside and outside of the wall body 18 by performing aeration from the diffused portion 30.

2. In all of the models 1 to 8, the circulation flow tends to be faster as it is closer to the side in the width direction of the membrane element 12, and tends to be slower as it is closer to the center side in the width direction of the membrane element 12. This tendency became more prominent as the flow increased.

FIG. 7 shows changes in the flow velocity in the model 1, and shows the flow velocity of the cross flow at each position of line 1, line 2, line 3, and line 4 on the membrane surface of the membrane element 12. It shows a tendency to become slower as it approaches the center side in the width direction of the membrane element 12 from the membrane end, which is the edge of the membrane element, and this tendency becomes more prominent as the measurement point moves from the lower measurement point to the higher measurement point.

FIG. 8 shows changes in the flow velocity in the model 9 and shows the same tendency as in the model 1. However, as compared with the tendency of the model 1, the tendency to become slower as the distance from the end of the membrane element 12 in the width direction to the center side in the width direction of the membrane element 12 increases.

That is, the presence of the rectifying plate 19 alleviates the uneven distribution of the crossflow velocity on the membrane surface of the membrane element 12.

Tables 2 and 3 show the cross flow velocity in the models 1 to 9, showing the average velocity and the maximum velocity on the entire membrane surface of the membrane element 12, and the average velocity and deviation in the line 4.

As shown in Tables 2 and 3, the average flow velocity tends to be higher in the model in which the rectifying plate 19 is provided than in the model 9 without the rectifying plate 19. However, model 3 is excluded. Further, the deviation also tends to be small in the model in which the current plate 19 is provided.

Especially in Model 1, Model 4, Model 5, and Model 7, both the flow velocity and deviation are improved. In the model 3, the resistance between the rectifying plates 19 is too large, and the average flow velocity is lower than that in the model 9.

FIG. 9 shows the distribution of the average flow velocity in the model 1 and the model 9, and there is a tendency that it becomes slower as it approaches the center side in the width direction of the membrane element 12 from the membrane end that is the end in the width direction of the membrane element 12. Yes, it can be seen that the deviation in the model 1 with the rectifying plate 19 is smaller than the deviation in the model 9 without the rectifying plate 19.

Next, as shown in FIG. 6, ten models having different opening ratios in the minimum separation portion between the rectifying plates 19 were set and analyzed. The opening ratio (%) is the ratio of the minimum separation distance at the minimum separation portion to the apparatus width, and is obtained by the minimum separation distance / apparatus width × 100. The minimum separation distance and the opening ratio of each model are shown in Tables 4 and 5.

In all models 10-19, the device width is 500 mm. In each model 10-14 shown in FIG. 6 (a) and Table 4, the rectifying plate 19 is inclined at 15 ° with respect to the flow path cross section of the upper opening 18b, and each model 15 shown in FIG. 6 (b) and Table 5 is shown. At -19, the rectifying plate 19 is inclined at 60 ° with respect to the flow path cross section of the upper opening 18b.

Model 10. Minimum separation distance 200 mm, opening ratio 40%, model 11. Minimum separation distance 250 mm, opening ratio 50%, model 12. Minimum separation distance 300 mm, opening ratio 60%, model 13. Minimum separation distance 400 mm, opening ratio 80%, model 14. Minimum separation distance 450 mm, opening ratio 90%, model 15. Minimum separation distance 150 mm, opening ratio 30%, model 16. Minimum separation distance 200 mm, opening ratio 40%, model 17. Minimum separation distance 300 mm, opening ratio 60%, model 18. Minimum separation distance 400 mm, opening ratio 80%, model 19. Minimum separation distance 450mm, opening ratio 90%
Compared to the model 9 without the rectifying plate 19 shown in FIG. 5g and Table 3, the opening ratio is 50% -90% regardless of the inclination angle of the rectifying plate 19, as shown in Tables 4 and 5. Some models 11-14 and 17-19 show a tendency to increase the average flow velocity.

Furthermore, as a preferable result, the model 11, model 12, and model 17 having an opening ratio of 50 to 60% tend to increase the average flow velocity and decrease the deviation.

Based on the above results, the installation of the rectifying plate is effective in improving the liquid flow rate and deviation between the membranes, and the improvement in the liquid flow rate and deviation between the membranes is larger in the opening ratio of the minimum separation part than the shape of the rectifying plate. We were able to confirm that we depended on us. The following factors can be considered as reasons why the rectifying plate 19 is effective in improving the deviation and the average flow velocity in spite of the presence of resistance against the cross flow.

クロス Cross flow relies on bubbly flow, and the cross flow generates a circulating flow throughout the tank. The bubbles themselves move upward due to their buoyancy, and gather on the end of the membrane element 12 in the width direction along the flow of the circulating flow.

When the bubbles are immediately drawn into the downward flow from the upper opening 18b, the bubbles are not the driving force of the upward flow, causing a vortex to occur during the downward flow, and the flow of the downward flow is obstructed, resulting in energy loss.

Due to the phenomenon described above, the flow velocity of the cross flow depending on the bubble flow varies depending on the position of the membrane element 12 on the membrane surface.

However, the flow straightening plate 19 suppresses entrainment of the bubble flow due to the circulation flow, guides the bubble flow upward toward the liquid level of the processing tank, and the bubbles are released onto the liquid level of the processing tank, so Vortex generation can be suppressed and the vortex generation position can be moved away from the submerged membrane separation device. As a result, non-uniformity of the cross flow velocity, that is, deviation is improved, and the average flow velocity is improved. . Further, the present invention can be realized if the opening ratio is 50% -90%.

Claims

A submerged membrane separation apparatus comprising a wall surrounding an inner region from a lower opening to an upper opening, a membrane separation means disposed in the inner region, and an air diffuser disposed below the membrane separation means. A submerged membrane separation apparatus comprising a rectifying section extending from the upper end of the body or the vicinity thereof and facing the upper opening.
2. The submerged membrane separation apparatus according to claim 1, wherein the rectifying unit faces a region near the inner edge of the wall body in the upper opening.
The submerged membrane separation apparatus according to claim 1 or 2, wherein the rectifying unit has a shape protruding toward the inside of the upper region in the vertical direction of the upper opening.
The plurality of submerged membrane separators are arranged adjacent to each other, and the rectifying unit is arranged only at an outer position in the arrangement direction of the plurality of submerged membrane separators in a row. Immersion membrane separator.
The membrane separation means has a plurality of membrane elements arranged in parallel, and a flow path is formed between the membrane elements. The membrane element is formed by arranging a filtration membrane made of a flat membrane on the main surface of the membrane support. The submerged membrane separation apparatus according to claim 1.
The rectifying unit is disposed at a position opposite to each other in a direction orthogonal to the arrangement direction of the membrane elements, and has a shape in which the distance between the both rectifying units decreases as the distance from the upper opening of the wall body increases. The submerged membrane separator according to claim 5.
The minimum separation distance between the two rectifying portions is 50% or more and 90% or less with respect to the distance between the wall edges facing each other in the direction orthogonal to the arrangement direction of the membrane elements. The submerged membrane separation apparatus described in 1.