GB2119783A - Improvements in or relating to liquid purifying - Google Patents

Abstract

Apparatus of the coil pump type is used to effect substantial purifying effect upon the pumped liquid. This is achieved by increasing the surface area, within the bore and available for contact by the liquid, to a value substantially above what would be normal practice if the apparatus were being used simply as a pump. The increased surface area may e.g be provided by anchored filaments or by buoyant granules held captive within compartments defined by baffles which restrain the granules but allow liquid to pass. The invention includes arrangements of the inlet and outlet of a coil pump, and arrangements by which both the gaseous and the liquid products of the apparatus may be used to exert a purifying action upon the body of liquid from which the pump is drawing.

Description

SPECIFICATION Improvements in or relating to liquid purifying This invention relates to the purifying of liquid, and in particular to a novel construction of rotating coil pump to perform the operation.

The rotating coil pump has been known, as a pump, for over two hundred years. Essentially it consists of a length of tube wound in a coil, mounted for rotation about the coil axis, and adapted to be arranged relative to a body of liquid so that as the coil is rotated one end of the tube~ which is open and will be referred to as the inlet ~passes alternately beneath and above the surface of the liquid and takes in alternate plugs of liquid and air in so doing. The other end of the tube becomes the outlet and may either be left open or may be connected by way of a sealed rotary joint to a delivery pipe. The ratio of the lengths of the air and liquid plugs taken in alternately by the inlet end is determined by the relative heights of the liquid surface and the tube inlet.With each revolution of the coil, each plug of air and water within the tube passes from one turn of the coil to the next and so moves towards the outlet. Also the air plugs are subjected to increasing pressure as they approach the outlet, so that they shorten while the water plugs remain of constant length. When the expression "coil pump" is used in this specification, it will mean apparatus fulfilling the above essential criteria.

In coil pumps the pressure of the air plugs as they reach the outlet has often been used to lift the plugs of water and discharge them into a header tank. The dimensions of the tube and in particular of the bore of that tube have been dictated by the accepted good practice of the pumping art: in summary, that good practice has called for the cross-section of the bore to be as large relative to the envelope of the tube as is consistent with adequate tube strength, and for the surface area of the bore to be substantially the minimum necessary to define that cross section.

By the envelope of the tube we mean the smallest circle through which the tube will pass.

There is evidence that it has also been appreciated that the operation of such apparatus, involving as it does the continual exposure of surfaces of air and liquid, offers potential for the removal of many organic pollutants from that liquid. When a surface is alternately exposed to air and polluted liquid, a film of organisms tends to build up on the surface which in time interacts with the liquid to reduce the amount of organic matter in it. There has for instance been at least one proposal to purify water by pumping it through a coil pump comprising many coils of plain, small-bore PVC tube all wound concentrically around a single rotatable hub.

The present invention is based upon the appreciation that if apparatus in the form of a coil pump is to operate as an efficient purifier of the liquid that passes through it, then the surface area available for contact by the liquid as it passes through the or each coil must be maximised. If the or each coil is of circular external section, for instance, it is not enough that the interior section is also of circular section but smaller and presents the only solid surface available for contact by the liquid passing through.According to one aspect of the invention liquid is purified by pumping alternate plugs of liquid and air through a coil pump in which the surface area available to be contacted by the liquid at it passes through the interior of the or each coiled tube is enhanced, that is to say is substantially greater than what known coil pump practice would suggest for a tube of equivalent envelope, by which we mean the smallest circle through which the tube would pass.

The surface area available to be contacted by the liquid may be enhanced by forming the inner wall of the tube with ribs or the like, running lengthwise of the tube. Alternatively, and preferably, it is enhanced by partly filling the interior of the tube with a plurality of filaments, which run lengthwise down the bore of the tube.

They may be anchored at their upstream ends, close to the mouth of the tube, and in addition can be anchored at their downstream ends.

As another alternative the,surface area available to be contacted may be enhanced by partly filling the interior of the tube with particulate masses capable of movement within the tube. The tube may be divided into separate compartments along its length by baffles which allow the liquid to pass but confine the masses to the compartment in which they are located and in which they may move back and forth as the coiled tube rotates. Alternatively such masses could simply be present in the bulk of liquid to be purified, so that each plug of liquid entering a coiled tube contains a number of the masses which in time travel the full length of the tube with the liquid and emerge at the other end. The masses may be buoyant, and may for example be of a light material such as expanded polystyrene.

The liquid and/or pressurised air delivered by the pump may be used for further purification of liquid: for instance the pressurised air may be used to aerate liquid. In particular it may be introduced into the body of liquid in which the pump itself is located, so as aerate that liquid. If the pump delivers liquid to an elevated level, that liquid may itself be further purified by descending to its original level through a filtration column, or may be sprayed upon a mass of water at lower level so as to create turbulence within it.

The invention includes apparatus to carry out the above methods, including a coil pump in which the surface area available for contact by liquid passing through the tube is enhanced, that is to say is considerably greater than what known coil pump practice would suggest for a tube of equivalent envelope. In particular the invention includes liquid purifying apparatus comprising a coiled tube adapted to be mounted largely above the surface level of the body of liquid to be purified, but in which the inlet to the tube lies at a greater radius from the coil axis than the rest of the coil tube so that the inlet may dip into the liquid once per revolution of the coil whilst the rest of the coil stays clear.In cases where the pump discharges alternate plugs of air and purified liquid direct from the final coil of the tube, without using the generated air pressure to transport the pumped liquid away, means to collect the purified liquid may comprise a trough lying beneath the circle in which the tube outlet rotates, the trough being so placed that as a plug of liquid is released during each revolution of the pump the first part of the plug (which tends to contain most residual impurity) misses the trough, falling back for instance into the body of untreated liquid, while the better-purified remainder of each plug is received by the trough.

The invention is also defined by the claims at the end of this specification and will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a view, partly in side elevation and partly in section, of a coil pump as used in apparatus according to the present invention; Figure 2 is a section on the line A-A in Figure 1; Figure 3 is a section similar to that of Figure 2, but through another design of pump; Figure 4 is a simplified and "unwound" view of the tube of another pump; Figure 5 is a section through one coil of the pump of Figure 4; Figures 6 and 7 are schematic views of two different liquid purifying plants;; Figure 8 is a simplified side elevation of another pump, and Figures 9 and 11 are three views in an axial direction of the outlet end of the pump of Figure 8, taken at successive stages of revolution of the pump.

Figure 1 shows a drum 1 carrying a shaft 2 mounted in bearings 3 and 4 and rotated by a motor shown diagrammatically at 5. A tube 6 of circular cross-section is coiled around the outer surface of drum 1. The inlet 7 of the tube is exposed, while the outlet 8 is connected to bearing 4 which also serves as a rotary joint connecting the outlet 8 to a pipe 9 through which the fluid delivered by the pump passes to a point of use (not shown). The drum 1 is mounted so that the shaft 2 lies slightly above the surface 10 of the body of liquid 11 that is to be purified.As drum 1 is rotated by motor 5, therefore, for part of each revolution inlet 7 lies beneath surface 10 and gathers a "plug" of liquid 11 into tubes 6, while for the remainder of each revolution the inlet moves in air and gathers a plug of air; in the next revolution that air is followed by another plug of liquid, then another plug of air and so on. As the drum rotates, the plugs of water tend to remain in the trough of the coil and are thus transported along the tube by normal rotating coil action towards outlet 8, carrying the intervening plugs of air with them. As they do this, the work done by motor 5 not only gathers the successive plugs of liquid and air but also puts the air plugs under continuously increasing pressure as they approach the outlet, so that they shorten in length relative to the plugs of liquid whose length does not change.

Once the air and water cease to be rotated on reaching the joint 4, the raised pressure of the air plugs can be used to do work upon the liquid in varous ways which will be described.

Were the tubes 6 to be of simple form - for instance, of circular cross-section - and unobstructed, the fact that it is alternately exposed to air and impure liquid would cause a film of organisms to build up on its inner surface.

This film would exercise some degree of purification upon the plugs of liquid as they pass through the tube, by aerobic degradation of organic matter contained in the liquid, but the extent of such purification might not be significant. However by arranging that the surface area available for contact by liquid passing through is much greater than known coil pump practice would suggest for a tube of the same envelope, enough organisms can be accommodated for the extent of purification to become clearly commercially useful. In the apparatus shown in Figures 1 and 2 the surface area is increased by mounting within the tube many filaments 12, of man-made fibre for instance, running lengthwise of the tube anchored at their upstream and downstream ends respectively by rings 13 and 14, the rings being fixed to the inner wall of tube 6.The total crosssection of all the filaments 12 may amount to a considerable proportion of the cross-sectional area of the bore of tube 6 itself, perhaps 50%, but the lengthwise orientation minimises resistance to liquid flow. It also avoids the flattening that the passing plugs of liquid would effect, say, upon short filaments mounted on the inner wall of the tube: such flattening would of course result in upstream filaments masking all but the tips of those immediately downstream, thus restricting the useful area upon which the necessary organisms can build up.

Figure 3 shows an alternative construction in which the surface available for the build-up of organisms within tube 6 is enhanced by filling the tube with a plurality of smaller tubes 1 5. The plugs of liquid and air may move not only through the bores 16 of the smaller tubes but also down the remaining unobstructed parts 1 7 of the bore of tube 6.

In the further alternative tube 6 shown in Figure 4, the surface available for the build-up of organisms within the tube is enhanced by dividing the tube into compartments 18 by baffles 19, each baffle being separated from the next by a distance equal to one circumference of drum 1 so that there is one baffle 19 to each coil of tube 6 around the drum. The baffles allow air and liquid to pass as freely as possible but prevent small particulate masses or granules 21, of expanded polystyrene, from leaving the compartment 18 in which they are located. The number of granules in each compartment may be such that if they are lightly packed against one baffle 19 (the most leftward of the three shown in Figure 4) they extend to about the middle of their compartment 18.It is well known that expanded polystyrene has a high surface area relative to its volume, so such granules usefully enhance the area on which organisms can grow within the tube 6. Spherical granules can be effective, but preferably the granules are of some irregular shape (as shown clearly in Figure 4) to help even further enhance surface area relative to volume. While they are less stream-lined in shape than the filaments 12 of Figures 1 and 2, any extra resistance to fluid flow on this account is offset by the fact that the granules are not fixed, but can move back and forth within the compartment 1 8 in which they are located. Figüre 5 is a section through one turn of the coil of tube 6 containing baffles 19 and granules 21.Arrow 22 indicates the direction of rotation of drum 1, and the difference in height between levels 23 and 24 of the plug of liquid 25 shown in this particular coil indicates that it is relatively close to outlet 8: the head difference between the levels indicates the pressure head in the adjacent air plug 26. Were the section to have been taken through a coil close to inlet 7, levels 23 and 24 could, depending on the ambient pressure at the outlet, have been more nearly equal. A baffle 19 is shown which lies to the inlet side of the granules 21 shown in this Figure: this ba#ffle therefore occupies the same position relative to those balls as does the baffle 20 relative to the balls illustrated in full in Figure 4. In Figure 5, the baffle 20 is shown at that moment of revolution of tube 6 when it has just come clear of level 23 of liquid plug 25.As the baffle continues to rotate with the tube it meets the tail end of the group 27 of granules that have descended by gravity through air plug 26 onto liquid level 24. A few of the granules (e.g. those indicated by reference 28) at the base of group 27 may already have become immersed below level 24 sufficiently far to have passed the lowest point 29 of the coil, and to be already rising by reason of their buoyancy through the column of liquid to the other side of it. When baffle 19 meets the tail end of the granules in group 27 it positively sweeps them into liquid plug 25 and past point 29. After this, by reason of buoyancy, all the granules tend to lose contact with the baffle and rise to level 23.

Because this level is close to the crest 30 of the coil some water will flow over 30 and many of the granules overflow over it before they are caught up by baffle 20, and fall through air onto level 24, which, because of the constant movement of the plugs through the tube, will now be the level of the liquid plug next following the plug 25 hitherto referred to. The relative motion between granules and liquid within each revolution develops a hydrodynamic shearing action which enhances the purifying action that will be exerted upon the liquid by maintaining the biological film covering the granules in a thin and active condition. It also helps to diminish any resistance that the granules offer to liquid flow. Of course useful organisms will also tend to grow upon the inner wall of tube 6 itself.

In yet a further alternative application of the invention granules 21 are not held captive within tube 6 as shown' in Figures 4 and 5 but are simply added (as shown at 21 a, in Figure 1) to the bulk 11 of the liquid about to be treated. They may then pass through the tube (probably in practice of plain internal section, without the filaments 21 of Figures 1 and 2) with the liquid, so enhancing the surface area available for contact by that liquid.

Means must be provided at outlet 8 to separate the purified liquid from the granules and to return the latter into the untreated liquid 11 close to the inlet 7.

In Figure 6 coiled tube 6, rotating within a body of water 11 presenting a surface 1 0, delivers through rotary joint 4 to a rising main 9 in which the raised pressure of the air plugs carries the liquid to a header tank 31. Through an outlet 32, located below the water level that forms in the tank, water passes by way of pipe 33 to descend through a column 34 by which it is further purified, for instance by filtration to remove solids of a kind that the organisms within tube 6 to not degrade. Header 31 is located at such height that the air which rises to space 35, above the liquid level, is still at above ambient pressure. This air may be put to use by passing it through a pipe 36 and a valve 37, which can be operated to regulate the pressure, to a diffuser 38 located within liquid 11 and below column 34 so as to aerate liquid and so promote further purification.

Figure 6 shows apparatus by which a finite volume of liquid is continually cycled through the pump and other equipment, but the apparatus could obviously be modified so that some purified liquid drawn off, either continuously or at intervals, and further impure liquid is added to make up for what has been removed. Figure 7 shows a version of the invenion in which drum 1 is mounted in flowing water and a paddle wheel 40 is attached to shaft 2 and drives drum 1 in place of motor 5 of Figure 1. Again the pump delivers to a header tank 31. From this air passes as before by way of pipe 36 to a diffuser 38 located under the surface of the flowing water.The water in header 31, driven by the excess pressure of the air in space 35 above it, passes by way of pipe 33 to a nozzle 41 located closely above the surface of the stream, from which it issues as a pressure jet to strike the surface of the stream and aerate it still further.

Diffuser 38 and nozzle 41 may point towards each other so that the jets from them are aimed at the same target mass of water, which may lie slightly upstream of the inlet 7 of coil tube 6, so that all the water that enters the tube has already been exposed to the aerating action of the jets from both nozzles.

In the embodiments of the invention already described, the compressed air delivered by the pump has always been used to help transport the alternating plugs of liquid away from the outlet of the tube itself. Sometimes however it is useful to collect purified water close to the outlet. This is achieved with the apparatus of Figures 8 to 11.

Here the shaft 2 of drum 1 is located high enough above liquid surface 10 that the entire drum and most of the coils of tube 6 are clear of the liquid at all times. However the coil 42 at the inlet end of the tube 6 is of increased diameter so that inlet 7 passes beneath surface 10 once per revolution.

Instead of being connected by way of joint 4 to a delivery pipe 9, outlet 8 is simply open and a collecting trough 43 is located beneath it. As Figure 9 shows, the end 44 of trough 43 lies less than one radius of the coil from the vertical that passes through shaft 2. The result is that as outlet 8 rotates (in the direction of arrow 22) from the position in which it is shown in Figure 9 to that of Figure 10, the first fraction of water plug 45 that escapes from the outlet will fall back onto the surface 10 of the untreated water and will miss trough 43. As Figure 11 shows, the trough will catch only the latter end of each water plug that is delivered. This may be beneficial, because any impurities remaining in a plug of water after passage through the pump tend to concentrate at the forward end.

Claims (16)

1. Apparatus for purifying liquid comprising a coil pump as hereinbefore described and in which the surface area within the bore available for contact by liquid passing through the tube is considerably greater than what normal pumping practice would suggest for a tube of equivalent envelope.

2. Apparatus according to Claim 1 in which the wall of the bore is formed with ribs or like projecting members, running lengthwise of the tube.

3. Apparatus according to Claim 1 in which the interior of the tube is partly filled with a plurality of filaments, running lengthwise down the bore.

4. Apparatus according to Claim 3 in which the filaments are anchored to the tube at their upstream ends.

5. Apparatus according to Claim 4 in which the filaments are also anchored to the tube at their downstream ends.

6. Apparatus according to Claim 1 in which the increased surface area is provided by partly filling the interior of the tube with particular masses capable of movement within the tube.

7. Apparatus according to Claim 6 in which baffles divide the interior of the tube into separated compartments along its length, and in which the baffles allow the liquid to pass but confine the masses to the compartment in which they are located.

8. Apparatus according to Claim 6 in which the masses are buoyant.

9. Liquid-purifying apparatus comprising a body of liquid to be purified and apparatus according to Claim 1 arranged to take in alternate plugs of liquid and air from that body, and in which there are means to introduce the plugs of air discharged from the coil pump outlet into that body of liquid so as to aerate it.

10. Liquid-purifying apparatus comprising a body of liquid to be purified and apparatus according to Claim 1 arranged to take in alternate plugs of liquid and air from that body, in which there are means to deliver the plugs of liquid discharged from the coil pump outlet to an elevated level, and including a filtration column through which the liquid may then descend under gravity from that elevated level and so be purified further.

11. Liquid-purifying apparatus comprising a body of liquid to be purified and apparatus according to Claim 1 arranged to take in alternate plugs of liquid and air from that body, in which there are means to deliver the plugs of liquid discharged from the coil pump outlet to an elevated level, and including a spray device through which the liquid may descend from the elevated level in spray form.

12. Apparatus according to Claim 1 in which the tube inlet lies at a greater radius from the coil axis than the rest of the coiled tube.

13. Apparatus according to Claim 1 in which the coil pump outlet is open and a trough-like collection device is located adjacent the outlet to collect the purified liquid, the trough being so placed that as a plug of liquid is released from the outlet during each revolution of the coil a first part of the plug misses the trough while the betterpurified remainder of the plug is received by it.

14. A method purifying liquid, using apparatus according to any of the preceding claims.

15. A method according to Claim 14 in which each plug of liquid entering the inlet of the coil pump contains masses which pass through the pump with the liquid to the outlet and contribute surface area for liquid-contacting as they do so.

16. Apparatus for purifying liquid according to Claim 1 and substantially as described with reference to any of the accompanying drawings.

1 7. A method of purifying liquid, according to Claim 14 and substantially as described with reference to any of the accompanying drawings.