GB2134400A - Improvements in or relating to liquid-dispensing apparatus - Google Patents

Abstract

Apparatus to dispense liquid - for instance a flocculant solution - at a rate proportional to the rate of flow of a fluid such as a polluted stream (25) to which the flocculant is to be added. A tube is coiled around a rotor (7) mounted on a structure (1) floating in the stream, and as the rotor is turned by the stream and tube acts as a coil pump. During each complete revolution of the rotor the inlet (14) of the tube takes in a volume of water as it passes below the surface of the stream, followed by a volume of air as it passes above. The volumes of air are increased in pressure as they pass along the length of the coiled tube, and on emerging from the outlet (19) pass by way of a sealed conduct (28) to a sealed reservoir (29). For each volume of pressurised air that the revervoir receives, a related volume of flocculant (31) is displayed from the reservoir into the stream. <IMAGE>

Description

SPECIFICATION Improvements in or relating to liquid-dispensing apparatus This invention relates to apparatus that will dispense liquid at a rate that is proportional to a flow-related parameter. It relates especially to apparatus that will repeatably dispense equal quantities of a first liquid into a flowing stream of a second liquid, in such a manner that the frequency of the dispensing may be directly related to the flow rate of the second stream and a predetermined concentration of the first liquid within the second downstream of the dispensing point may therefore be achieved.

Simple, robust and relatively maintenance-free apparatus capable of dispensing liquid in this way would find uses in many technical fields, especially that concerned with improving the quality of water.

Thus, for example, such apparatus might be used to help treat the dirty water which runs or is pumped off the tips and other areas at open-cast coal sites. It is customary practice to add flocculants - for instance, aluminium sulphate - to the water as it flows as an open-air stream from such areas into large, open air settlement tanks or ponds. In these ponds suspended solids settle out of the water under gravity, but the addition of the flocculants is necessary if the settlement is to take place rapidly and completely enough for it to be acceptable to release purified water regularly from the ponds into nearby rivers or streams.Hitherto it has been customary to add flocculants by simply placing a lump of the appropriate chemical in solid form in the stream of the dirty water immediatly downstream of the area where it originates, and relying upon the gradual erosion and dissolving of that lump by the stream to create a solution of flocculant in the water that reaches the ponds. The concentration of the solution produced by this crude method obviously tends to vary: for a given rate of flow, a large new lump of solid with high surface area will naturally tend to produce a greater concentration than it will later once it has been worn down and its surface area reduced, and for the same size of lump the concentration produced in a stream of high mass flow will be less than in one with a lower rate.

Dispensing apparatus according to the present invention comprises a rotary flow-responsive device, delivery means mechanically coupled to that device to deliver a predetermined volume of gas of each revolution of the device, a reservoir for liquid to be dispensed, and a connection between the reservoir and the delivery means whereby the delivery of each volume of gas may result in the dispensing of a predetermined volume of liquid from the reservoir.

The apparatus may be adapted to be mounted as a fixed structure standing within a stream of flowing liquid. Alternatively it may be constructed so as to float in a stream of flowing liquid to which the rotary device responds. The rotary device itself may be in the form of a paddle wheel or the like.

In one form of apparatus according to the invention the delivery means may be in the form of a hollow tube having an inlet end and an outlet end, coiled about a horizontal axis and connected to the rotary device so as to be rotated by it: in each revolution of the tube when thus rotated, if the inlet end successively passes through an arc below the liquid surface and an arc above it a pumping action may be set up by which alternate volumes of air and liquid enter the inlet end of the tube, are pumped along its length and are discharged from the outlet end. The delivery means may thus work in a manner similar to that of the known apparatus called a coil pump. The delivery means may be coaxial with the rotary device, and is preferably coiled upon it.For instance, if the device comprises paddles radiating outwardly from the outer face of a hollow rotor, the tube may be coiled around the inner face.

The outlet of such a coiled tube will also pass through successive arcs above and below the liquid surface, and would normally discharge a volume of air during each arc above the surface and a volume of liquid during each arc below. To reverse this pattern, so that a volume of air is dicharged during each arc that the outlet passes beneath the surface, the length of the tube immediately adjacent the outlet may cross the rotor diametrically before joining the turns of the coil. With such an arrangement of the outlet end of the tube, the connection between the reservoir and the delivery means may comprise en enclosed duct by which the discharged volumes of air may travel to the reservoir, the duct having a downward-facing mouth located within the flowing liquid and vertically over the arc through which the tube outlet passes as it discharges the volumes of air.There may be means to adjust the size of the mouth so as to catch a variable proportion of each air volume as it is discharged. Alternatively the tube outlet may be located on the axis of revolution, as in some conventional coil pumps, and may lead to an enclosed separator vessel from which the pumped air passes to the reservoir and the alternate volumes of pumped liquid are returned to the stream.

In another form of apparatus according to the invention the delivery means may be in the form of a hollow container, closed at one end and open at the other and fixed to the rotary device with the open end pointing in the direction of rotation. During each arc that such a container passes above the liquid surface, liquid pours out of the open mouth as it descends towards the surface and the container becomes full of air. During the succeeding arc beneath the surface that volume of air will escape from the container and may pass to the reservoir by way, for example, of a duct with a downward-facing mouth as already described.

The reservoir may be of enclosed construction, for instance of Marriott-bottle type, which when containing a volume of liquid may operate so that entry to the reservoir of a volume of pressurised gas results in the expulsion from the reservoir of a proportional volume of the liquid.

The invention also includes a method of metering a first liquid into a flowing stream of a second liquid at a rate proportional to the rate of that flow, using apparatus as just described, in which the flowresponsive device and delivery means rotate in the stream of the second liquid and in which the reservoir contains the first liquid and dispenses into the stream downstream of the apparatus.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of an assembly comprising a rotor, coiled tube and associated structure, taken from the front and one side; Figure 2 is a similar view of the rotor and coiled tube only; Figure 3 shows the associated structure in underneath perspective; Figure 4 is an elevation and shows the structure of Figures 1 to 3 in outline, installed and connected to a reservoir; Figure 5 is a diagrammatic axial section through an alternative arrangement of outlet for the coiled tube, and Figure 6 shows an alternative design of flowresponsive device in outline and in elevation.

The assembly shown in Figures 1 to 3 is adapted to float and comprises twin hulls 1, 2 spanned at the bows by a cross-member 3 and at the stern by a cross-member 4. Eyes 5 are attached to member 3, and mooring lines 6 may be attached to these eyes to hold the apparatus floating in a steady position, bows upstream, in flowing water.

A rotary flow-responsive device comprises a rotor 7 having paddle blades 8 mounted on a hollow hub 9, which is itself mounted on a central shaft 10, supported in bearings 11, 12 mounted on hulls 1 and 2. Atube 13 is coiled around the inner wall of hollow hub 9, and the inlet 14 of this tube protrudes through the hub wall at 15. A whole number of turns of the coil separates the inlet 14 from the point on the tube indicated by reference 16 in Figure 2, and from point 16 the tube passes nearly diametrically across the rotor to pass through the hub 9 at 17 and connect with an angled spout 18 terminating in an outlet 19.

As Figure 1 shows best, this outlet projects slightly outside the volume that is swept by the rest of rotor 7 as it rotates in use. A recess 20 is formed in hull 1 to allow clearance for the outlet as it rotates with the hub, and the recess contains a funnel-shaped collector having a downward-facing mouth 21 leading to a neck 22 connected to an angled spout 23.

In ouline, Figure 4 shows the apparatus as so far descibed floating on the surface 24 of a flowing stream 25 bounded by a bed 26, a bank 27 and an opposite bank which is not shown because it lies behind the point from which the Figure is viewed.

Spout 23 is connected by way of a sealed conduit 28 to a sealed reservoir vessel 29 having a discharge outlet 30 and containing a liquid 31. The joint by which conduit 28 enters reservoir 29 may contain a one-way valve shown diagrammatically at 32. Alternatively, if the run of conduit 28 is rearranged as shown in dotted lines with the crest 33 of the inverted "U"-bend above the level of liquid 31, valve 32 may not be necessary. If a volume of gas under pressure enters vessel 29 from conduit 28, the resulting increase of pressure within vessel 29 forces a related volume of liquid 31 to discharge through spout 30. In practice there may be no need for a non-return valve in spout 30, since balance of pressures may ensure that liquid 31 can only leave vessel 29 in response to the forced entry of a related volume of air into the vessel from conduit 28.

In operation, when the apparatus is moored in a flowing stream of water as shown in Figure 4, the reaction of the flowing water against the paddle wheels 8 rotates the rotor 7, causing the inlet 14 of tube 13to pass successively through an arc under the water surface and then a remaining arc in air in each revolution. During each underwater arc a volume of water enters the tube, and during the arc in air a following volume of air enters. As it continues to rotate, and to be filled with alternate volumes of water and air, the tube 13 acts as a known coil pump and transports the volumes towards outlet 19, compressing and pressurising the air volumes as it does so.The disposition of outlet 19, point 17 and the connecting diametrical length of tube 13 relative to inlet 14 has the consequence that volumes of pumped, compressed air leave outlet 19 at the same time during each revolution as the inlet 14 is passing through its arc in air above water surface 24. The compressed air is therefore released from outlet 19 as that outlet lies within the water and is passing through recess 20, beneath mouth 21. The rotating coiled tube 13 thus acts as a delivery device whereby a proportion of each released volume of compressed air is received by mouth 21 and passes via outlet spout 23 up conduit 28, to enter reservoir 29 through valve 32 and displace a related volume of liquid 31 through outlet 30.By way of example therefore, if the liquid of stream 25 is effluent from a coal washing plant and the liquid 31 in reservoir 29 is a flocculant such as a solution of aluminium sulphate and if the speed of rotation of rotor 7 is directly proportional to the velocity of flow past it, then outlet 30 will dispense a substantially constant volume of flocculant into the stream once per revolution of the rotor, that is to say at a rate proportional to the said rate of flow. The magnitude of each volume dispensed will be proportional to the volume of compressed air that actually enters mouth 21 once per revolutiom of the rotor, and this may of course be varied by the bore of tube 13 or, alternatively and in practice more simply, by altering the arcuate length of mouth 21 or coiling a second tube 13 in parallel with the first. It is of course commonplace to design paddle-wheel rotors so that they rotate at a speed proportional to that of the flowing streams in which they are to be partly immersed, and by appropiate contouring of the bed 26 and the banks 27 it should often in practice be possible to obtain a direct relationship between the frequency and volume of discharge from outlet 30 and the total flow of liquid in the stream, so that a constant concentration of flocculant in the liquid downstream of the apparatus is achieved regardless of changes in the mass flow rate.

In the alternative apparatus shown diagrammatically in Figure 5, one end of shaft 10 is hollowed and the outlet end 34 of coiled tube 13 passes within this hollow interior via a rotary joint 38 into a separator vessel 35 supported by hull 1. From this vessel the separated water passes downwardly by way of conduit 36 to return to stream 25, while the pressurised volumes of air pass upwardly through an outlet 37 to conduit 28 and reservoir 29 as before. In the alternative design of flow-responsive device shown in Figure 6 a hollow cylindrical container 40, closed at one end 41 but with the opposite end 42 open, is attached to the side of the hub 9 of rotor 7 so that the open end 42 points in the direction in which the rotor is turning. When container 40 is descending towards the surface 24 of stream 25, any water inside it pours out and leaves it filled with a volume of air. When end 42 passes beneath the surface that volume is trapped and becomes slightly compressed as the container continues to descend. After further turning of rotor 7 the air starts to escape from the container.

Once the container passes the lowest point of its underwater arc (where it is shown in chain lines) the remainder of any trapped air will quickly escape. The escaping air may pass to reservoir 29 by way of collector 21 - 22 and conduit 28, arranged as before relative to the rotor 7. Throughput could of course be increased by using a larger container, or mounting more than one container on the rotor.

Claims (17)

1. Dispensing apparatus comprising a rotary flow-responsive device, delivery means mechanically coupled to that device to deliver a predetermined volume of gas for each revolution of the device, a reservoir for liquid to be dispensed, and a connection between the reservoir and the delivery means whereby the delivery of each volume of gas results in the dispensing of a predetermined volume of liquid from the reservoir.

2. Dispensing apparatus according to Claim 1, constructed so as to float in a stream of flowing liquid to which the rotary device responds.

3. Dispensing apparatus according to Claim 1, adapted to be mounted as a fixed structure standing within a stream of flowing liquid.

4. Dispensing apparatus according to Claim 2 or Claim 3, in which the rotary device is in the form of a paddle wheel.

5. Dispensing apparatus according to Claim 2 or Claim 3 in which the delivery means is in the form of a hollow tube having an inlet and an outlet and coiled about a horizontal axis and connected to the rotary device so as to be rotated by it, whereby in each revolution the inlet successively passes below the liquid surface and above it and sets up a pumping action by which alternate volumes of air and liquid enter the inlet, are pumped along the length of the tube and are discharged from the outlet.

6. Dispensing apparatus according to Claim 5 in which the coiled tube and rotary device are coaxial.

7. Dispensing apparatus according to Claim 6 in which the tube is coiled upon the rotary device.

8. Dispensing apparatus according to Claim 7 in which the rotary device comprises paddles radiating outwardly from the outer face of the hollow rotor hub, and in which the tube is coiled around the inner face of the hub.

9. Dispensing apparatus according to Claim 5 in which the outlet passes successively above and below the liquid surface during each revolution, and is arranged to discharge the volumes of air when it is beneath the surface.

10. Dispensing apparatus according to Claim 2 or Claim 3 in which the delivery means is in the form of a container connected to the rotary device and adapted to fill with a volume of air as the device carries it through an arc in air, and then to release that volume during the subsequent arc beneath the surface of the stream.

11. Dispensing apparatus according to Claim 9 in which the connection between the reservoir and the delivery means comprises an enclosed duct by which the discharged volumes of air may travel to the reservoir, the duct having a downward-facing mouth located within the liquid above the arc through which the outlet is passing as it discharges air.

12. Dispensing apparatus according to Claim 11 in which the size of the duct mouth is adjustable, whereby to vary the proportion of each discharged volume of air that enters the mouth.

13. Dispensing appararus according to Claim 5 in which the tube outlet is located substantially on the axis of revolution of the tube and is connected to an enclosed separator vessel from which the discharged volumes of pumped air pass to the reservoir and the alternate volumes of pumped liquid are returned to the body of flowing liquid.

14. Dispensing apparatus according to Claim 1 in which the reservoir is of enclosed construction, for instance of Marriott-bottle type, which when containing a volume of liquid operates so that entry to the reservoir of a volume of gas under pressure results in the expulsion from the reservoir of a proportional volume of the liquid.

15. A method of dispensing a first liquid into a flowing stream of a second liquid at a rate proportional to the rate of flow, using apparatus as claimed in any of the preceding claims, in which the rotary flow-responsive device and coupled delivery means rotate in the stream of the second liquid and in which the reservoir contains the first liquid and dispenses into the stream downstream of the delivery means.

16. Dispensing apparatus according to Claim 1, substantially as described with reference to the accompanying drawings.

17. A method of dispensing liquid, according to Claim 15 and substantially as described with refer ence to the accompanying drawings.