SK13962000A3 - Filter for removing solids from liquids - Google Patents

Abstract

A filter (10) is disclosed which comprises a casing (18) having an inlet (42) for water to be purified. There is a first stage filter (12, 16, 58) for removing solids from the water. The water flows from the first stage filter to a second stage filter (66) for the purpose of subjecting the water to ultra filtration or micro filtration and/or to reverse osmosis.

Description

Technical field

The present invention relates to filters for removing solids from liquids. The filter is intended separately, but not exclusively, for the removal of solids from water in the purification of drinking water and for other purposes, for example for use as boiler water.

BACKGROUND OF THE INVENTION

There are very few sources of water that can be used for drinking, agricultural or industrial purposes without treatment. The oceans, which are the largest source of water, contain a large amount (30,000 to 40,000 parts per million) of dissolved solids. Depending on the particular geographical area, the water also contains sludge and / or sand in suspension. It must therefore be filtered and desalted before being used for any purpose.

Water from rivers, lakes and underground sources is usually contaminated with dissolved solids and solid material that is suspended or dispersed in water. In addition, this may be a biological material whose removal requires microfiltration or ultrafiltration.

It is an object of the invention to provide a filter which represents an improvement of known filters.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a filter comprising a housing having a water inlet for filtration, a first stage filter inside the housing to remove solid material from the water entering the housing, and a second stage filter inside the housing into which water flows from the first stage filter, wherein the second stage filter comprises reverse osmosis membranes for performing ultrafiltration or microfiltration and / or removing solids that are dissolved in water.

In a preferred embodiment said housing has an elongated shape, wherein said first and second stage filters are adjacent to each other in the length direction of said housing.

According to a further aspect of the present invention there is provided a filter comprising an elongated box delimiting the elongated space, an inlet of purified water into said space, an outlet from said overflow water compartment, an outlet from said brine compartment, a first stage filter in said solids removal compartment. a second stage filter comprising reverse osmosis membranes for performing ultrafiltration or microfiltration and / or removing solids dissolved in the water, wherein the first stage filter, the chamber and the second stage filter; the membranes are positioned so that water flows in the length direction of the housing, passing through said first stage filter into said chamber and through the second stage filter to said outlet from the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and for illustrating the possibility of implementing it, the description of exemplary embodiments refers to the accompanying drawings, in which:

Fig. 1 is a schematic cross-section of a filter according to the invention including a pipe connected to the filter;

Fig. 2 is a front view of the filter disc of FIG. 1, on a larger scale than in FIG. 1;

Fig. 3 is a cross-sectional view of the disc according to line III-ΠΙ in FIG. 2;

Fig. 4 is a rear view of the roll;

Fig. 5 is a larger-scale view than FIG. 2 to 4, for spiral flow;

Fig. 6 is a sectional view, on a larger scale, illustrating the way in which a portion of the filter operates;

Fig. 7 is an illustrative view of a reverse osmosis insert;

Fig. 8 is a cross-sectional view of another embodiment of the invention;

Fig. 9 is an end view of the filter of FIG. 8;

Fig. 10 is an "exploded" schematic view of the filter of FIG. 8 and 9;

Fig. 11 is an illustrative view, on a larger scale, of a portion of the filter of FIG. 8 to 10;

Fig. 12 is a cross-sectional view of another embodiment of a filter;

Fig. 13 is an end view of the filter of FIG. 12 a

Fig. 14 is an "exploded" schematic view of the filter of FIG. 12 and 13.

DETAILED DESCRIPTION OF THE INVENTION

The filter 10 shown in FIG. 1 includes a plurality of porous tubes 12. Each tube 12 has a hairpin bend 14 and the ends of the tubes are connected to a roll 16 which is mounted in a cylindrical housing 18. Between the housing 18 and the roll 16 there are seals (not shown) that are mounted grooves 20 (see especially FIG. 3) formed on the outer periphery of the disc 16.

Opposite ends of the housing are closed by end caps 22 and 24 which are held in place by two-piece locking ring members 26.

The outer ring 28 of each locking annular member 26 is embedded in the wall of the housing 18 when the housing is made of a glass fiber reinforced resin. The inner ring 30 is in the form of a removable split ring whose diameter is reduced before being inserted into the ring 28. The inner rings 30 may be removed by reducing their diameter and pulling out of the housing 18 to release the end caps.

O-rings (not shown) are provided between the end caps 22 and 24 and the housing 18 in grooves 32 and 34 in the end caps 22 and 24.

The end cap 22 and the disc 16 define a chamber 36 that includes the tubes 12. The tube 38 extends through the end cap 22 through the chamber 36 and terminates in communication with the central aperture 40 of the disc 16. Through the end cap 22 an aperture 42 opens into the chamber 36. A pump 44 is connected to the opening 42 by a pipe 46, which supplies water for filtration from the source 48 to the chamber 36. The pump 44 is also connected to a reservoir 50 of clean, filtered water. Valves 52, 54 allow the pump 44 to pump either filtered or raw water.

Holes 56 pass through the disc 16, with each end of each tube 12 adjoining a respective aperture 56 and the tubes hanging U-shaped below the disc 16 into the chamber 36. The apertures 56 are not axially arranged but at an angle (see Figs. 2 to 4). so that the water entering the conical vortex chamber 58 formed on the top side of the disc 16 swirls in the chamber 58. As can be seen from FIG. 2 and 4, the openings 56 are arranged in a spiral row.

The spiral flow conduit 60 is integral with or attached to the disc 16. It is located within the vortex chamber 58. The conduit lies within the peripheral skirt 62 that extends from the main body of the disc 16.

The chamber 58 forms one end cap of the space 64 bounded by the disc 16 and the end cap 24.

Inside the space 64 is a hollow envelope 66 comprising two sheets of membrane material through which water can flow. The two sheets are welded or otherwise joined along their perimeter. Any type of membrane material can be used. For example, ultrafiltration membranes, microfiltration membranes or reverse osmosis membranes may be used. The sheets are also welded with two tubes 68 and 70. The tube 68 extends from the envelope 66 through the wall of the housing 18 to the shut-off valve 72. The valve 72 is connected to an air or water source 74 under pressure.

A tube 70 extends through the central opening 76 of the end cap 24 extending from the housing 18 and connected to the valve 78. A plurality of bundles 66 lying side by side may be provided. Spacers 80 within the envelopes 66 and other spacers (not shown) between the envelopes 66 prevent the envelopes from collapsing in normal operation and prevent the envelopes 66 from expanding excessively when overpressure occurs.

The water outlet port 82 containing the last remaining solids passes through the end cap 24. From the port 82 the tube 84 leads to the T-piece 86. The other tubes connected to the T-piece are designated 88 and 90. The tube 88 leads to the valve 92 and the tube 90 to valve 94.

There is a T-piece 96 between valve 94 and pump 44. A valve 98 is connected between the pipe 46 and the tee 96. From the pipe 46, the branch pipe 100 leads to the valve 102. The tube 38 is connected via a pipe 104 to the valve 106.

In operation, the water containing solids to be filtered is withdrawn from source 48 by pump 44 and fed under pressure into chamber 16 via a T-piece 96, valve 98 and tube 46. Tubes 12 filter most solids out of the water as will be described below.

Water that penetrates the walls of the tubes 12 through the pores in the walls enters the interior of the tubes, flows through the internal openings of the tubes 12, enters the openings 56, and then flows into the vortex chamber 58.

The angle at which the openings 56 open into the swirl chamber 58 and the arrangement of the helical conduit 60 promotes the swirling of water in the swirl chamber 58 and a portion of the space 64 immediately above the swirl chamber 58.

The valve 106 is fully open upon actuation and the pressure in the space 64 causes an initial strong outlet of water through the central opening 40 of the tube 38 and the tube 104. This results in a vortex in the center of the chamber 58.

The remainder of the solids not filtered by the tubes 12 enters the aperture 40. It will be appreciated that water entering the aperture 40 flows into the waste. Thus, the flow through the valve 106 is adjusted after start to achieve a minimum water output sufficient to maintain the vortex. By adjusting this flow, it is possible to obtain a flow pattern in which the so-called flow vortex, which normally exists coaxially with the main vortex, is suppressed. Experimental work has shown that the main vortex extends a certain distance above the disc 16 gradually decreasing in strength until finally becoming invisible. Above the main vortex there is an ascending stream of water, but little or no flow vortex capable of entraining particles.

The final stage of the filtration process is carried out as water passes through the membrane material forming the envelopes 66. The solid particles remain on the outside of the envelopes 66 and the water, substantially free of particulates, flows through the tube 70 through the valve 78 and then into the storage tank, water line or place of use.

The pressure at the outlet port 76 of the filter 10 is monitored, and when a pressure loss of sufficient magnitude is detected, an automatic cleaning sequence is initiated.

The main part of the cleaning sequence comprises closing the valves 52, 98, 92 and 106 for a short period of time and opening the valves 54, 94 and 102 for a short period of time. As a result, clean water withdrawn from the reservoir 50 is pumped by the pump 44 through the valve 94 to the space 64. The pressure increase in the space 64 results in a proportional increase in the pressure in the tubes 12. Reverse flow through the pores of the tubes 12 cleans the tubes as described below. The cleaning of the tubes 12 is thus carried out by temporarily increasing the internal pressure above their external pressure.

The material ejected from the outer surface of the tubes 12 exits the chamber 36 through the opening 42 of the tube 100 and the valve 102.

The inverted flow of water causes the vortex in the chamber 58 to disappear. When the valves

52, 98, 92 and 106 reopen and the valves 54, 94 and 102 reopen the valve

106 must be fully opened and then the vortex must be restored.

Since pure water is fed into the space 64, the flow of water through the envelopes 66 is not interrupted during the pipe cleaning process.

To clean the envelopes 66, the valve 72 is briefly opened for a second or less, and the envelopes 66 are inflated with air or water under pressure. At the same time, the valve 78 is closed briefly. The external spacers between the envelopes 66 prevent them from blowing and rupture. The sudden expansion of the envelopes ejects the solid material adhered to their exterior, and the total flow from the space 64 to the opening 82 carries the expelled solid material exiting through the valve 92.

It will be appreciated that for each envelope 66, a tube 68 and a tube 70 are provided. The tubes 68 and 70 lead to common manifolds.

The tubes 12 are of rubber, rubber compound or synthetic plastic material having a surface to which the solid material adheres firmly. The type of surface required can be compared to an automobile tire. While the mud is adhered to the tire, the binding is not firm, and if the mud dries, it can easily shake off and, if wet, can easily be rinsed.

Each tube 12 has a plurality of pores that extend from the outer surface of the tube to the inner surface of the tube. One such pore, designated 108, is shown in FIG. 6. A pore 108 i e on the outer surface of the tube wider than on the inner surface of the tube. Preferably, the diameter of the outer pore end is in the range of five micrometers and the inner pore end is of the order of one or two micrometers. The wall thickness of the tube is about 15 mm.

in

The solid material particles designated in FIG. 3, they settle in the pores 108, and for a short period of time after the start (from a few seconds to a few minutes) there is a mass of particles in each pore 108 that acts as a filter to allow water to enter the tube 12 but prevent other solids from passing. Obviously, as the water passes through the particulate filter in each pore 108, a solid material deposited thereon is deposited thereon on the outer surface of the tube 12. This solids accumulation is shown in FIG. 6, designated 112. When the reverse flow through the pores 108 occurs as described, the solids accumulation is flushed.

It was also found that the pressure loss in each 108 score should not be excessive. If the pressure drop is excessive, the particles 110 in the pores 108 and the accumulation 112 of solids are drawn into the pores 108 with such force that expulsion by the accumulation 112 of the material becomes problematic. The pores 108 are thus blocked and the flow through the filter from the tube 46 through the pores 108 in the tubes 12 to the interior of the tubes and thus into the vortex chamber 58 decreases considerably.

The envelopes 66 may be replaced by a spiral wound membrane, for example a reverse osmosis membrane in the form of an insert 114. As shown in FIG. Such a filter will be described in more detail with reference to FIG. 12, 13, 14.

The liner 114 includes a central tube 116 around which assemblies 118 are wrapped, each comprising two polymer sheets 120, 122 and a spacer 124. The tube 116 has openings 126 arranged in rows extending along the tube. The water in the permeate channels 128 enters the pipe 116 through these openings. The salt retention channels are designated 130.

The two sheets 120 and 122 are welded to each other about three of their edges to form each assembly 118. The fourth edges are not welded, but secured by adhesive to the tube 116 on opposite sides of the rows of holes 126 in the tube 116. Thus, each row of holes 126 is in communication with the permeate channel 128 of the assembly.

In FIG. 7, for illustrative purposes, the membrane sheets 120 and 122 of the top assembly 128 are shown separately so that the spacer means 124 is visible. The other assemblies 118 are shown with the welded edges of the sheets 120 and 122 so that the spacer 124 is hidden.

The number of assemblies 118 used depends on the number of rows of apertures 126 because each assembly must be positioned such that its permeate channel 128 is connected to the respective row of apertures.

Once wound onto the tube 116, the diaphragm sheets 120, 122 of each assembly 118 face up in contact with the sheets 120, 122 of the adjacent assembly 118.

After the assemblies 1 18 are adhered to the inner edges of their sheets

120 and 122 to the tube 116. the assemblies are wrapped tightly around the tube 116 and then fixed with tape to prevent them from unwinding. The outer sleeve (not shown) then prevents the sheets 120 and 122 from breaking when water is introduced into the insert 114. The outer sleeve is adapted to be inserted into the housing 18.

It will be appreciated that the ducts 130 are open at both axial ends of the wound insert.

The liner is used in conjunction with the two end caps 132 and 134. The end cap 132 includes a disc 136 and a skirt 138 that extends around the periphery of the disc 136. The cap 132 is at the end of the insert from which the brine stream exits. In the disc 136 there is a central aperture 140 that coincides with the pipe 116 and a plurality of apertures 142 through which the brine flows. There is a gap between the end of the liner and the disc 136, for example two to four centimeters. The function of the end cap 132 is to provide back pressure in the immediate vicinity of the outlet ends of the brine channels. The axes of the holes 140, 142 are parallel to the axis of the pipe 116.

The end cap 134 is at the inlet end of the insert. It includes a disc 144 having a central aperture 146 that coincides with the pipe 116 and a plurality of apertures 148 between the aperture 146 and the peripheral skirt 150 that extends around the periphery of the disc 144. The disc 144 may be against the end of the insert or up to four centimeters from the insert.

The axes of the apertures 148 are not parallel to the axis of the tube 116 but are at an angle thereto. This results in discrete water jets that pass through the apertures 148 and impinge on the end of the liner 114 at an angle, not along a path parallel to the pipe 116. The aperture orientation is such that the jets swirl in the same direction as the assemblies are wound.

It will be appreciated that the insert 114 is disposed by an end cap 134 adjacent the disc 16 and an end cap 132 at the other end of the housing 18 adjacent the end cap 24.

Fig. 8 to 11 show a filter 152 which includes a housing 154 in which the diaphragm insert 114 is described with reference to FIGS. 7 and the prefilter 156. The prefilter 156 comprises three rollers 158 having walls of a mesh filter material. The rollers 158 are in the chamber 160. The inlet to the chamber 160 is indicated by 162.

The water flows through the walls of the net rollers 158 to the inside of the rollers and from the inside of the rollers 58 to the next chamber 164 through the openings 166. The chamber 164 is delimited on one side by a disc 168 on which the rollers 158 are mounted. the end cap 134 of the insert 114.

The brine outlet 170 from the liner 114 and the leakage water outlet 172 are in the end cap 174.

The liner 114 and the disc 168 are held in place by the spacer means 176, 178 and 180. The inlet 162 is at the end cap 182. where the ring members 184 and 186 are also in place to hold the end cap 182 and the end cap 174 in place.

A pipe, generally designated 188, connects the interior of the cylinders 158 to the outlet 190 in the end cap 182. The waste pipe 192 extends from the chamber 164 through the end cap 182 to the drain.

During normal operation, entrained solids water enters the filter through an inlet 162. flows through the screen rollers 158 through the chamber 164 and from there into the salt retention channels in the liner 114. The permeate exits through the outlet 172 and the brine exits through the outlet 170.

To clean the filter, pressurized water is fed to outlet 172. water flows from the permeate channels through the membranes to the salt retention channels. From the salt retention channels it enters the chamber 164 and from there a portion of the water flows through the pipe 192 into the drain.

The rest of the water flows through the holes 166 into the rolls 158. A portion of the water entering the rolls 158 flows through the screen and cleans the outer surfaces of the rolls. The remainder of the water flows through line 188 to outlet 190, carrying the solids that have previously passed through the screen of cylinders 158.

The pipe shown in FIG. 1 is modified to allow the liner to be cleaned by removing the tube 68 and connecting the valve 72 and the water source 74 directly to the opening 76. The valve 78 is closed when the membrane is cleaned.

Fig. 12, 13 and 14 show a similar filter to that shown in FIG. 1 but having an insert 114 instead of envelopes 66. Further, it has a structure similar to that of FIG. 8 to 11, but instead of the net rollers 158 has tubes 12 as described by FIG. First

The end cap 134 of FIG. 14 has an aperture arrangement that differs from that shown in FIG. 10. Otherwise, the same reference numerals in FIG. 12, 13 and 14 as in FIG. 8 to 11.

The filter of FIG. 12-14 are cleaned in the same manner as described above with respect to FIGS. 8 to 11.

The filters having the vortex chamber 58 are operated in a vertical position as shown in FIG. 1 and 12. The filter of FIG. 12 to 14 should therefore be operated in a vertical position. The filter of FIG. 8 to 11 may be operated horizontally.

The tubes 12 can remove all solids over 12 microns in size. The filter rollers 158, depending on the screen used, remove all solids above about 20 microns. The type of pre-filter selected depends on the solids loading of the input water and the desired final water quality.

It is possible to use a disc filter, preferably a self-cleaning disc filter, or any other type of filter that can remove solids to the extent necessary before the water enters the liner 114 or envelopes 66 for ultrafiltration or microfiltration or for dissolving dissolved solids.

When small balls of rubber-like material are placed in the chamber 160, they are displaced by the flowing water and tend to "bounce" in the chamber, keeping the solids in suspension, thus helping to prevent the filter from sticking.

It is also possible to clean the membranes by suddenly closing the valve in the duct

purified water. A shock wave passing in the reverse direction shakes free solids in the salt retention channels. A similar effect can be obtained by introducing pressurized air into the purified water line.

It is also possible to arrange an electrical winding around the insert 114, as described in PCT application WO 98/30501 (PCT / GB98 / 30501), in order to increase the efficiency of the insert. In FIG. 8 and 12, the threads are labeled 194. 196 and 198. They are housed in the walls of the housing during manufacture.

Claims (12)

PATENT CLAIMS A filter comprising a cabinet having a water inlet for filtration, a first stage filter inside the housing to remove solid material from the water entering the housing and a second stage filter inside the housing into which water flows from the first stage filter, the second stage filter comprising: reverse osmosis membranes for performing ultrafiltration or microfiltration and / or removing solids that are dissolved in water. Filter according to claim 1, characterized in that the housing has an elongated shape, wherein said first and second stage filters are adjacent to one another in the length direction of said housing. Filter according to claim 1, characterized in that said housing is vertical, wherein at the lower end of the housing there is an inlet for cleaning water supply to the inlet chamber in the housing, a disc forming part of said first stage filter and representing the upper end of said chamber; a plurality of apertures in said disc, a vortex chamber on top of said disc, the vortex chamber having the shape of an inverted cone, a plurality of apertures passing through said disc and entering said vortex chamber, the apertures being oriented so that water flowing into said vortex chamber from apertures in said vortex chamber, an outlet of said vortex chamber extending downwardly through said disc from the top of said vortex chamber, and in said chamber a plurality of tubes with porous walls, the interior of said tubes being connected to said openings. 4. The filter of claim 3, wherein said openings are open to said vortex chamber in a spiral row. Filter according to claim 3 or 4, characterized in that in said vortex chamber there is a helical conduit for supporting the helical flow of water in the vortex chamber. Filter according to claim 3 or 4, characterized in that each end of each tube is connected to a respective one of said openings, the tubes hanging U-shaped into said inlet chamber. Filter according to claim 1, 2, 3 or 4, characterized in that said first stage filter is formed by a filter comprising a plurality of filter elements which are pressed together and define filter channels therebetween. Filter according to claim 1, 2, 3 or 4, characterized in that said first stage filter comprises a plurality of mesh filter elements through which water flows, wherein the mesh filter elements retain the solid material. The filter of claim 1, wherein said second stage filter comprises a plurality of sealed envelopes of reverse osmosis membranes in a second stage chamber to which water flows from the first stage filter, an outlet of the overflowing water from inside each envelope, means for introducing a fluid under pressure into said envelopes to temporarily pressurize the envelopes, and exit from said second stage chamber for solids water that has been separated from the overflowed water. The filter of claim 1, wherein said second stage filter comprises reverse osmosis membranes wrapped around an overflow water tube, wherein the wrapped membranes are in a second stage chamber into which water flows from the first stage filter, for backwashing. means for supplying pure water under pressure to said permeate tube. 11. The filter of claim 1, wherein said first stage filter comprises a plurality of compartments having walls of mesh material, said compartments being in an inlet filter chamber, a first outlet from each compartment leading to a second stage filter, a second outlet from each compartment. wherein a normally closed valve is provided at said second outlet and means for supplying water through said mesh material from the interior of the compartment to said inlet chamber for cleaning said mesh material and for supplying water through said compartments to said second outlet while the normally closed valve is open. 12. A filter comprising an elongated cabinet bounding an elongated compartment, an inlet of purified water into said compartment, an outlet from said overflow water compartment, an outlet from said brine compartment, a first stage filter in said solids removal compartment entering said water inlet said compartment, a chamber forming part of said compartment, and a second stage filter, the second stage filter comprising reverse osmosis membranes for performing ultrafiltration or microfiltration and / or for removing solids dissolved in water, wherein the first stage filter, chamber and membranes are positioned such that wherein the water flows in the direction of the length of the housing, passing through said first stage filter to said chamber and through the second stage filter to said outlet from the chamber.