RU2302895C2 - Rolled membrane-type filtering member - Google Patents

Abstract

FIELD: equipment for separation of liquid media in reverse osmosis, nanofiltration, ultrafiltration and microfiltration processes.

SUBSTANCE: rolled membrane-type filtering member consists of central tube with radial openings, around which tube one or several membrane-type packets are spirally wound. Membrane-type packet consists of semi-permeable membrane folded inward with its active side and provided with swirling grid inserted therein, and intermediate drain sheets. Membrane packet is sealed within said member by complete sealing-off of both ends with thermoplastic melt or thermosetting glue composition. Solution to be cleaned is introduced in said member through its outer cylindrical surface, and concentrate and filtrate are discharged through central tube. Longitudinal channel of central tube is divided by transverse partition into two isolated portions unequal in length. Longer portion is connected with swirling grids and shorter portion is connected to drain sheets. Membrane packet length to width ratio is from 2 to 5.

EFFECT: increased efficiency and extent of extracting filtrate.

5 dwg, 1 tbl

Description

FIELD OF TECHNOLOGY

The invention relates to the field of construction (device) of a roll-type membrane filter element (hereinafter ME).

ME consists of membrane bags alternating with sheets of drainage material for permeate removal, wound on a perforated perforated filter tube and sealed in a certain way.

MEs are widely used in almost all areas of industry in the processes of reverse osmosis, nano-, ultra-, microfiltration. The most widely used MEs are used for desalination of natural and waste waters of industrial enterprises, for the treatment of technological water for various industries, for the production of drinking water, including for domestic use.

BACKGROUND

Various ME designs are known. MEs differ from each other in general design, manufacturing technology, applied structural materials, and sealing (Japan Patents No. 54-151571, 54-149384, 54-149383, 53-124179; US Patents No. 3966616, 3417870, 4235723, 5538642; Copyright Certificate No. 1205359.1213100, 1595553).

Closest to the claimed design ME is shown in US patent No. 3417870. According to this patent, the ME contains a central tube with holes for draining the filtrate, on which sheets of a membrane with an active layer folded inside the membrane are wound, inside each sheet of which there is a sheet of a mesh-turbulator creating a channel for the solution to be cleaned, the sheets of the folded membrane are separated by a porous material - a channel for removal of the purified liquid filtrate. The sealing of these channels is carried out by applying an adhesive composition to a porous material - drainage on its three sides before winding.

After spiral winding, an ME is formed, which is a cylinder with an axial filtrate outlet tube, inside which channels of the source water and filtrate are formed. Water supply channels are open on both sides (ends) of the ME. The initial liquid is fed into one end of the ME and discharged through the other end. The filtrate is discharged through a filtrate outlet pipe.

This design of the membrane roll element has been developed for a long time and is still widely used by many manufacturers of membrane elements: Filmtec (USA), Hydranautics (USA), Roga (USA), Toray (Japan), Saehan (Korea), Scientific and Production Center "Vladipor" "(Russia), Ecofil LLC (Russia) and others. However, based on many years of experience in the production of membrane elements and their operation, it should be noted certain disadvantages of the above element design:

- when sealing the membrane roll element by applying the adhesive composition on three sides of the perimeter of the drainage sheet, sufficiently wide adhesive seams (30-50 mm) are formed, which significantly reduce the active working area of the membrane in the element, especially in small-sized elements intended for the purification of drinking water in household conditions for offices, for membrane installations of low productivity. For them, the decrease in the active area of the membrane is 20-30%;

- the preparation and application of the adhesive composition, as a rule, is carried out manually by the operator. This process is quite laborious. In addition, it is inevitable that extruding excess adhesive composition on the ends of the membrane element. Therefore, the operation of trimming both ends of the element is necessary to "open" the pressure channels intended for the entrance and exit of the liquid being cleaned;

- to ensure the turbulent flow of the liquid being cleaned in the channels of the membrane roll element, eliminating the occurrence of the concentration polarization effect on the membrane surface, it is necessary to provide a certain linear velocity of its flow, which will determine the conversion coefficient (K) or the degree of filtrate selection - the ratio of the filtrate flow rate (Q _f ) to the flow rate of the initial cleaned liquid (Q _ref ), K = Q _f / Q _ref . Since the total end area of the channels in the above-mentioned design of the membrane element is large enough in comparison with their length, in order to ensure a turbulent flow, the flow rate of the initial cleaned liquid should be large, as a result, the filtrate extraction rate in practice is only 10-15%. For small-sized elements, operated, as a rule, for one element in the installation, more than 90% of the treated water is discharged into the sewer, which is extremely uneconomical.

Thus, the disadvantages of ME according to US patent No. 3417870 are the large sealing zone of the membrane packages, which reduces the working surface of the ME and its performance, low filtrate selection.

SUMMARY OF THE INVENTION

The aim of the invention is to create a design ME with increased productivity and the degree of selection of the filtrate.

According to the invention, the ME consists of a central tube with radial holes along the length around which one or more membrane packages are spirally wound, each consisting of a semi-permeable membrane folded with its active side inward with a turbulent mesh embedded in it, and intermediate drainage sheets. The ends of the ME are completely sealed by pouring a thermoset adhesive composition or by melt of a thermoplastic material. The longitudinal channel of the central tube is divided by a transverse partition into two isolated sections of unequal length (L1, L2), in the ratio L1: L2 = (1-3) :( 1-6). At the same time, the long section is connected to the turbulence grids, and the short section to the drainage sheets. The ratio of the length L of the membrane package to its width B is from 2 to 5.

The entrance of the liquid to be cleaned into the pressure channel of the ME is organized along the generatrix of the outer surface, then along the spiral channel to the center and the concentrate exits through the axial channel of the central tube from one of the ends of the ME. The filtrate is collected and withdrawn through a spiral drainage channel to the central tube and exit through its channel from the side of the other end of the ME. In the central ME tube, the filtrate and concentrate channels are separated by a transverse baffle.

The authors found that the implementation of the ME design in accordance with the above features allowed to increase its productivity and the degree of filtrate selection. ME according to the invention is characterized by high reproducibility of operational indicators, more technological in manufacturing, its production leads to a significant reduction in solid waste.

To implement the invention, all types of membranes can be used: reverse osmosis, nano-, ultra-, microfiltration.

As a turbulizer mesh, it is preferable to use knotless mesh with a thickness of 0.3 to 2 mm. As a drainage fabric, you can use a knitted fabric soaked in a solution of epoxy resin with its subsequent curing.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a sketch of the claimed ME.

Figure 2 shows a cross section aa of the claimed ME.

Figure 3 shows a transverse section bB of the inventive ME.

Figure 4 shows a sketch of the pressure channel of the inventive ME.

Figure 5 shows a sketch of the drainage channel of the proposed ME.

In the drawings, the positions indicated:

1 - input stream;

2 - turbulatory grid (pressure channel of the element);

3 - membrane;

4 - filtrate;

5 - drainage sheet (channel for filtrate);

6 - tube;

7 - concentrate;

8 - partition,

9 - zone sealing ends ME,

L is the length of the membrane package,

L1 is the length of the portion of the central tube ME connected to the drainage sheets,

L2 is the length of the part of the central ME tube connected to the turbulence grids,

In - the width of the membrane package.

DETAILED DESCRIPTION OF THE INVENTION

The applicant, together with the inventors, made and tested prototype MEs with an external diameter of 45 mm and a length of 300 mm.

The central tube 6 ME has a transverse partition 8 (Fig.1). A folded membrane 3 with a turbulent mesh 2 is spirally wound around the tube (Fig. 2, Fig. 3). The filtrate channel is formed by the drainage sheet 5 (figure 2, figure 3). The ends of the ME are sealed with a melt of a thermoplastic material or thermoset adhesive composition 9 (figure 1).

ME works as follows (Fig.1-5). The source purified water 1 enters the pressure channel of the ME formed by the turbulence grid 2 and membranes 3. The filtrate 4, penetrating through the membranes 3, moves along the channels of the drainage sheet to the central tube and is discharged from the ME through one end of the tube. The concentrate is discharged through another part of the central tube 7. The channel for output of the filtrate 4 and the channel for output of the concentrate 7 are separated by a longitudinal partition 8 of the central tube 6.

The main design features, starting materials and test results of the prototype ME are shown in the table.

Control tests were carried out:

- nanofiltration elements on a 0.2% solution of MgSO ₄ ,

- microfiltration elements on tap water (Nerlinsky water intake of Vladimir).

Analysis of the test results of experimental samples of elements allows us to draw the following conclusions:

1. Both methods of sealing membrane bags in the elements (see paragraph 4 of the table) are quite reliable.

2. When sealing by pouring ends compared to sealing by applying an adhesive composition on 3 sides of the perimeter of each membrane bag before spiral winding, an increase in the effective (working) area of the membrane in the element is ensured (see section 5.2, for example, samples 1, 2) and, as a result, an increase in its productivity under other identical conditions (see clause 6.1, for example, samples of elements 1 and 2).

3. The use of a partition in the central tube (see clause 2.1, 2.2, samples 2, 5) in combination with the filling of the ends (see clause 4.2) led to an increase in both productivity (see clause 6.1) and the degree of selection ME filtrate (see clause 6.4). The ratio of the length of the membrane package to its width for samples 2, 5 with a transverse septum of the central tube was 3: 1.

Table
The main parameters and test results of prototype ME No. p / p Name of the main parameters and operational Prototype Data Note one 2 3 four 5 one Used membrane web 1.1 Nanofiltration Composite Membrane + + - - - 1.2 Microfiltration membrane (1.0 μm pore size) - - + + + 2 Central filtrate and concentrate discharge tube, bags 2.1 With a transverse septum L1: L2 = 1: 3, the ratio of the length of the membrane channel to its width 3: 1 - + - - + 2.2 Without a partition + - + + - 3 The outer diameter of the sample ME, mm 3.1 45.0 + + + + + four The method of sealing the membrane in the element 4.1 Line application of adhesive composition on 3 sides of the membrane to spiral winding + - + + - according to patent No. 3417870 4.2 Filling of the ends of the element after spiral winding with a thermosetting composition according to this application - + - - + 5 Membrane area in an element 5.1 Total area, m ² 0.36 0.36 0.36 0.36 0.36 5.2 Effective (working) area, m ² 0.23 0.34 0.22 0.23 0.34 It was determined after testing and disassembling the elements 6 ME performance 6.1 Productivity (per filtrate) l / h 37.8 56.3 64.7 65.1 97.5 6.2 Selectivity,%, MgSO ₄ 94.3 94.4 - - - 6.3 Turbidity selectivity (GOST 3351-74) 75.1 74.3 75.8 6.4

The degree of selection of the filtrate

11.7 26.9 14,4 15.0 41.0 7 Test conditions: Pressure, MPa 1,6 1,6 0.15 0.15 0.15 Temperature ° C 20,0 20,0 20,0 20,0 20,0 Mode - Flow Filtration + + + + + 8 Test conditions 8.1 Working environment - an aqueous solution of MgSO ₄ , 0.2% + + - - - - tap water, a fence from the river Nerl of Vladimir - - + + +

Claims (1)

The roll-type membrane filter element, which includes a central tube with radial holes, around which one or more membrane bags are helically wound, each consists of a semi-permeable membrane folded with its active side inward with a turbulence mesh embedded in it, and intermediate drainage sheets, characterized in that a) sealing the membrane package in the element is carried out by completely filling both ends with a melt of a thermoplastic material or a thermoset adhesive composition, with the input of the solution to be cleaned into the element is carried out through its outer cylindrical surface, the output of the concentrate and filtrate through the central tube; b) the longitudinal channel of the central tube is divided by a transverse partition into two isolated sections of unequal length (LI, L2), in the ratio L1: L2 = (1-3) :( 1-6), while the long section is connected to the turbulent grids, and short - with drainage sheets; c) the ratio of the length L of the membrane package to its width B is from 2 to 5.

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