EP2899408B1

EP2899408B1 - A method for pumping a liquid, a pumping device, as well as an installation

Info

Publication number: EP2899408B1
Application number: EP15151592.1A
Authority: EP
Inventors: Dave van den Bosch
Original assignee: AQUA SAFE BV
Current assignee: AQUA SAFE BV
Priority date: 2014-01-17
Filing date: 2015-01-19
Publication date: 2016-11-30
Anticipated expiration: 2035-01-19
Also published as: NL2012105C2; EP2899408A1; ES2617308T3

Description

The present invention relates to a method for pumping a liquid with a pumping device, which pumping device comprises

a chamber which comprises
- an inlet for the liquid to be pumped, and
- an outlet for pumped liquid;

at least 1 element for controlling the direction of flow through the pumping device;

in a state wherein the inlet for the liquid to be pumped is in liquid connection with liquid to be pumped that is present outside the chamber, by means of the pumping device liquid to be pumped is portion wise introduced into the chamber via the inlet for the liquid to be pumped, and
liquid introduced into the chamber is discharged from the chamber via the outlet for pumped liquid,

a gas conduit, and
the inlet for feeding a gas,

introducing the gas into the chamber that contains the liquid to be pumped,
discharging liquid from the chamber by the gas that is in contact with the liquid to be pumped via the outlet for the liquid to be pumped, and
allowing the liquid to be pumped to flow into the chamber by gravitation and thus allowing the gas introduced into the chamber to flow out of the chamber.

A method according to the preamble is known in the art. In particular for pumping aggressive substances the use of a membrane pump is known. A known application of membrane pumps is in swimming pools where sodium hypochlorite (NaOCl) and an acid, for instance sulphuric acid, are added to the swimming water for the disinfection thereof. With a membrane pump a membrane provides a separation between the driving parts of the membrane pump and the liquid to be pumped.
Despite its simplicity a membrane pump, in particular the membrane, does require maintenance, during which the person carrying out the maintenance and/or the membrane pump is exposed to the aggressive liquid. Or the membrane pump has to be cleaned first, for instance by rinsing it with water. The latter will take time, and will also not work properly when the membrane pump, for instance the membrane itself, is broken. Leakage of the membrane may result in exposure of mechanical and/or electronic parts to the liquid to be pumped, which is undesired, especialy with aggressive liquids.
A method according to the preamble is known from DE 100 17 241 . With the known method the use of a membrane can be avoided. Since gas is merely blown into the chamber, and there is no suction, it can effectively be avoided that liquid to be pumped or pumped liquid reaches mechanical and/or electronic parts used for feeding gas. Maintenance of these parts can take place with increased safety for the mechanic.
The document GR 2007 0100385 is regarded as being the closest prior art and discloses all features of the preamble of claim 1.
The object of the present application is to provide a method which permits faster filling of the chamber with liquid to be pumped.
To this end, a method according to the preamble is characterized in that as the pumping device a pumping device is used wherein

the gas conduit is in connection with a relief outlet for releasing the gas pressure in the gas conduit, and
the chamber has a gas outlet which can be closed off with a passive valve which comprises an element that can open the gas outlet under the influence of gravity.

Thus, when the supply of air to the chamber is stopped, the air pressure in the chamber drops whereby liquid to be pumped is allowed into the chamber under the influence of gravity (communicating vessels). The relief outlet is for instance in the form of a small hole in the gas conduit, via which gas can only escape slowly. Alternatively, also a commercially available discharge vent valve may be used, advantageously an adjustable discharge vent valve. In principle, with the method of the invention also a controlled valve may be used for removing the air pressure in the chamber, but a malfunction in such a controlled valve may lead to an undesired situation and/or to more costs of maintenance. The controlled valve may however be located at a relatively large distance of the pumping device, as a result of which the controller will not be easily exposed to aggressive liquid in case of leakage.
Upon the decrease of the pressure in the chamber the element will, under the influence of gravity, open the passive valve as a result of which air can easily be discharged and liquid can be pumped faster again. The element is for instance formd as a hinging plate which will close in case the difference in air pressure over the valve exceeds a predetermined value.
More comprehensively: The passive valve will open automatically under the influence of gravity when the pressure in the chamber drops. Because of this, gas will be discharged faster from the chamber and thus the liquid will flow faster into the chamber. In other words: the next batch of liquid can be pumped faster (earlier). The passive valve comprises a sealing element such as a ball, the weight of which under the influence of gravity makes sure that the gas outlet is opened before a pressure equilibrium between gas in the gas conduit and the environment is reached. This is because the element will fall when the force exerted upon it by liquid in the chamber is insufficient. The moment of opening can be set by a suitable choice of the weight.
The pumping device is for instance, and preferably, located in a storage tank of the liquid to be pumped, most preferably at the lowest point thereof. In the latter case the inlet for liquid can let as much liquid as possible into the chamber. The gas may be an inert gas, such as nitrogen, but for many uses air will suffice excellently. With the method of the invention the gas is supplied for instance by a compressor, or from a vessel maintained under pressure by a compressor. During pumping, the outlet for pumped liquid is at a lower level than the liquid level and/or lower than the optional upper side of the chamber. In order to control the direction of flow a one way valve may be used. It is also conceivable to use a conduit having a bypass, which bypass is in the form of a loop which with one end branches off in the longitudinal direction of the conduit, via a bend in a loop part that flows out with a transversal component into an upstream part of the conduit. With such a device the flow resistance is higher in one direction than in the other direction. The pumping effiency will decrease, but the number of mechanical parts required for operating the pumping device will also decrease.
An advantageous aspect of the present invention is that a storage tank for liquid to be pumped does not require a through hole below the liquid level. All conduits can be passed into the storage tank from above, whereby the likelihood of leakage is reduced. An additional advantage is that in case the liquid to be pumped gives off vapour or gas easily, a membrane pump will encounter problems because of the presence of the gas, whereas with the present invention this will not cause any problems.
Because of the gas conduit, when the supply of air to the chamber is stopped, the air pressure in the chamber drops as a result of which under the influence of gravity (communicating vessels) liquid to be pumped is allowed into the chamber. The relief outlet is for instance in the form of a small hole in the gas conduit, via which gas can only escape slowly. Alternatively, also a commercially available discharge vent valve may be used, advantageously an adjustable discharge vent valve. In principle, with the method of the invention also a controlled valve may be used for removing the air pressure in the chamber, but a malfunction in this valve may lead to an undesired situation and/or to more costs of maintenance.
With the method according to the invention the chamber can be filled with liquid faster in comparison with the known pump according to the state of the art. Firstly, during filling the chamber with liquid using gravity, the gas is discharged from the chamber via two routes. Secondly, the speed with which the chamber is filled is less dependent on the diameter (flow through cross section) of the gas conduit, which diameter in general preferably is not too large because a larger volume means that a compressor will need more time for building up sufficient pressure, and for filling the chamber more gas has to be discharged. Another advantage is that the pumped amount of a batch can be known more precisely when the volume of the feed conduit is relatively small compared to the volume of the chamber (as long as the liquid level outside the chamber is above the gas outlet opening).
FR2621083A1 describes a method with a pumping device, which pumping device has no separate gas discharge conduit.
According to a favourable embodiment, the feeding of gas to the gas conduit is governed via an electronically controlled valve.
Thus, by leaving the valve open for a desired amount of time, liquid in the chamber can be discharged easily from the chamber. A single compressor can serve more pumping devices, something which is really easy with a controlled valve. A multistage valve may also be used, in which case liquids will be pumped one after another.
According to a favourable embodiment, the gas outlet is in connection with a gas scrubber.
The method according to the invention is particularly suited for pumping liquids which release gases (such as an aqueous hypochlorite solution). The effectiveness of membrane pumps diminishes in the presence of gas in the membrane pump, especially with small flow rates. By using a gas scrubber a gas (including vapour) given off by a liquid can be captured, which is particularly desired if the gas is poisonous, corrosive or otherwise undesired. The gas outlet will normally be connected with the gas scrubber via a conduit.
According to a favourable embodiment, the gas outlet opens up above the liquid to be pumped in a liquid reservoir with the liquid to be pumped, and the liquid reservoir is in connection with the gas scrubber above the liquid to be pumped in the liquid reservoir.
Thus, the amount of air that is passed along the gas scrubber can be limited.
According to a favourable embodiment, the outlet for pumped liquid is connected to an overpressure valve.
Thus, liquid is only pumped at a known pressure difference over the overpressure valve. The overpressure valve will be chosen such that no siphon effect can take place. Thus, the pumping of liquid can be controlled better.
According to a favourable embodiment, the interior cross section of the gas discharge conduit is larger than the interior cross section of the gas conduit.
Thus, gas in the chamber can be discharged faster from the chamber to be filled with liquid by gravity.
According to a favourable embodiment, as the passive valve a valve is applied which as the element comprises an element that can occlude the gas outlet by floating on the liquid to be pumped.
The weight of the element, which is for instance in the form of a ball held captured in a cage and is transported to the opening to be closed when the liquid level in the camber rises, will be chosen depending on the size of the opening that has to be closed off and the gas pressure in the chamber that is used for pumping the liquid out of the chamber.
According to a favourable embodiment, as the passive valve a valve is applied which as the element has an element that has a density of 1 to 2.5 x that of the liquid to be pumped.
As a consequence liquid will flow around the occluding element and will end up in the gas discharge conduit. This will present an extra pressure from the upper side on the occluding element during the pressure release phase, as a result of which the passive valve will be opened faster. The liquid will then flow into the chamber as a result of which the gas discharge conduit is free for quickly discharging gas from the chamber.
This embodiment, for that matter, especially with higher densities of the element, is less suitable for being able to pump with a liquid level outside the chamber that is lower than that of the occluding element. At low densities of the occluding element, air introduced into the chamber can relatively easy carry along the element and block the gas outlet opening, but the advantage of liquid resting on the occluding element is then absent. The density of the occluding element is preferably between 1.1 and 1.8 x.
The present invention also relates to a pumping device for pumping a liquid with a pumping device, which pumping device comprises

a chamber which comprises
an inlet for the liquid to be pumped, and
an outlet for pumped liquid; and
at least 1 element for determining the direction of flow through the pumping device;

the gas conduit is in connection with a relief outlet for releasing the gas pressure in the gas conduit, and
the chamber has a gas outlet which is closeable with a passive valve that comprises an element which can open the gas outlet under the influence of gravity.

Preferred embodiments comprise, in any possible combination, the pumping device with the measures according to the subclaims of the method. Thus, according to a possible embodiment the pumping device comprises for instance a gas scrubber.
According to a favourable embodiment, as the passive valve a valve is applied which as the element has an element that can occlude the gas outlet by floating on the liquid to be pumped.
The weight of the element, which is for instance in the form of a ball held in a cage and is transported to the opening to be closed when the liquid level in the camber rises, will be chosen depending on the size of the opening that has to be closed off and the gas pressure in the chamber that is used for pumping the liquid out of the chamber.
According to a favourable embodiment, the passive valve as the element has an element that has a density of 1 to 2.5 x that of the liquid to be pumped.
As a consequence liquid will flow around the occluding element and will end up in the gas discharge conduit. The density of the occluding element is preferably between 1.1 and 1.8 x.
Finally, the present invention relates to an installation which comprises a pumping device and a storage tank, wherein the pumping device is a pumping device according to one of the pumping device claims.
In particular, the inlet of the pumping device is connected with the interior of the storage tank. Furthermore, there is a discharge channel for discharging liquid, which discharge channel is connected to the outlet for pumped liquid. Preferred embodiments comprise, in any possible combination, the installation with the measures according to the subclaims of the method. Thus, according to a possible embodiment, the installation comprises for instance a gas scrubber. The installation will also comprise a source of gas, such as a gas cylinder or a compressor.
The present invention will now be illustrated with reference to the drawing where

Fig. 1 shows a schematic cross section of the installation according to the invention; and
Fig. 2 shows a schematic cross section through a pumping device according to the invention.

Fig. 1 shows an installation 100 according to the invention, which comprises a pumping device 110, a storage tank 120 and a control unit 130.
The control unit 130 comprises a valve 131 and a valve control unit 132 which electronically controls (opens for a desired amount of time) the valve 131. Air under elevated pressure (e.g. 3 Bar) is supplied (for instance from a compressor; not shown). Air is an excellent gas. For specialistic purposes, for instance in the chemical industry, a gas that is suitable for the specific purpose may be chosen, for instance nitrogen when the presence of oxygen is undesirable.
Air transmitted through the valve 131 passes via a gas conduit 101 to the pumping device 110 which is shown in detail in Fig. 2 and will be discussed there.
Liquid that has been ousted with the aid of air fed from the pumping device 110 via the gas conduit 101, is discharged via the liquid discharge conduit 111. The liquid discharge conduit 111 may have an overpressure valve 112 in order to avoid the siphoning of pumped up liquid into the liquid discharge conduit 111. The overpressure valve 112 has a limit value of for instance 0.2 Bar overpressure.
After the valve 131 a relief outlet 133 in the form of a discharge vent valve 133 is provided (EV1/4-360-010, Raminex, Utrecht, The Netherlands), via which air from the gas conduit 101 can gradually escape into the atmosphere. "Gradually" means that the flow rate at a given pressure in the pumping device is smaller than with which air can be fed via the control unit. An actively controlled relief outlet would also be possible, but a passive system requires no control for which reason this is preferred.
The pumping device 110 is connected to a gas discharge conduit 113, via which air introduced into the pumping device 110 can be discharged. With the embodiment shown the gas discharge conduit 113 flows out in the upper part of the storage tank 120. Alternatively, the gas discharge conduit 113 could for instance have been in direct connection with the atmosphere or in connection with the atmosphere via a gas scrubber.
The embodiment of the installation 100 illustrated here also comprises a gas scrubber 190, which is in gas connection with the head space of the storage tank 120. In principle, the pressure in the storage tank 120 will be atmospheric, although it can be operated also under overpressure or underpressure, depending on the desired application.
The storage tank 120 is filled with liquid 121. If this liquid 121 releases poisonous or otherwise undesired vapours, these vapours will be captured by the gas scrubber 190. An example of such a liquid is an aqueous sodiumhypochlorite solution, such as used for the treatment of water in a swimming pool.
Fig. 2 shows a schematic cross section through a pumping device 110. This comprises a chamber 214, an inlet 215 for liquid to be pumped, an outlet 216 for pumped liquid 121 and valves 217, 217' for occluding the inlet 215 and the outlet 216 during pumping liquid from the chamber 214 by introducing air into the chamber 214 via the gas conduit 101 via gas inlet 202. Because of this the liquid level in the chamber 214 will drop. When the valve 131 is closed, the supply of air into the chamber 214 will be stopped. Via the discharge vent valve 133 air will leak away, as a result of which the air pressure in the chamber 214 will drop. As a result the valve 217', which has an element for occluding in the form of a ball, will open and air can be discharged quicker via the air outlet 213 and the gas discharge conduit 113.
When the pressure in the chamber 214 has dropped sufficiently, the element in the form of a ball of valve 217 will be lifted up because of the liquid pressure and new liquid to be pumped will flow into the chamber 214 again for another pumping cycle.

Claims

A method for pumping a liquid (121) with a pumping device (110), which pumping device (110) comprises
- a chamber (214) which comprises
- an inlet (215) for the liquid to be pumped (121), and

- an outlet (216) for pumped liquid (121);

and
- at least 1 element for controlling the direction of flow through the pumping device (110);
and for pumping the liquid (121)
- in a state wherein the inlet (215) for the liquid to be pumped (121) is in liquid connection with liquid (121) to be pumped that is present outside the chamber, by means of the pumping device (110) liquid (121) to be pumped is portion wise introduced into the chamber (214) via the inlet (215) for the liquid to be pumped (121), and

- liquid (121) introduced into the chamber (214) is discharged from the chamber (214) via the outlet (216) for pumped liquid (121),
wherein
the chamber (214) of the pumping device (110) comprises an inlet (202) for feeding a gas to the chamber (214) wherein the gas is passed to the chamber (214) via
- a gas conduit (101), and

- the inlet (202) for feeding a gas,
and
the pumping device (110) comprises a relief outlet for releasing the gas pressure in the gas conduit (101);
wherein the method comprises the following steps:
- introducing the gas into the chamber (214) that contains the liquid (121) to be pumped,

- discharging liquid (121) from the chamber (214) by the gas that is in contact with the liquid to be pumped (121) via the outlet (216) for the liquid to be pumped (121), and

- allowing the liquid (121) to be pumped to flow into the chamber (214) by gravitation and thus allowing the gas introduced into the chamber (214) to flow out of the chamber (214), the chamber (214) has a gas outlet (213) which can be closed off with a passive valve (217'); characterized in that

- the gas conduit (101) is in connection with a relief outlet (133) for releasing the gas pressure in the gas conduit (101), and

- the passive valve (217') comprises an element that can open the gas outlet (213) under the influence of gravity.
The method according to claim 1, wherein the feeding of gas to the gas conduit (101) is governed via an electronically controlled valve (131).
The method according to claim 1 or 2, wherein the gas outlet is in connection with a gas scrubber (190).
The method according to claim 3, wherein the gas outlet opens up above the liquid to be pumped (121) in a liquid reservoir with the liquid to be pumped (121), and the liquid reservoir is in connection with the gas scrubber (190) above the liquid to be pumped (121) in the liquid reservoir.
The method according to any of the preceding claims, wherein the outlet (216) for pumped liquid (121) is connected to an overpressure valve (112).
The method according to any of the preceding claims, wherein the interior cross section of the gas discharge conduit (113) is larger than the interior cross section of the gas conduit (101).
The method according to any of the preceding claims, wherein as the passive valve (217') a valve (217') is applied which as the element comprises an element that can occlude the gas outlet by floating on the liquid to be pumped (121).
The method according to any of the claims 1 to 6, wherein as the passive valve (217') a valve (217') is applied which as the element has an element that has a density of 1 to 2.5 x that of the liquid to be pumped.
A pumping device (110) for pumping a liquid (121) with a pumping device (110), which pumping device (110) comprises
- a chamber (214) which comprises
- an inlet (215) for the liquid to be pumped (121), and

- an outlet (216) for pumped liquid (121); and

- at least 1 element for determining the direction of flow through the pumping device (110);
wherein
the chamber (214) of the pumping device (110) comprises an inlet (202) for feeding a gas to the chamber (214);
characterized in that
- the gas conduit (101) is in connection with a relief outlet (133) for releasing the gas pressure in the gas conduit (101), and

- the chamber (214) has a gas outlet (213) which is closeable with a passive valve (217') that comprises an element which can open the gas outlet (213) under the influence of gravity.
The pumping device (110) according to claim 9, wherein as the passive valve (217') a valve (217') is applied which as the element has an element that can occlude the gas outlet by floating on the liquid to be pumped (121).
The pumping device (110) according to any of the claims 9 or 10, wherein the passive valve (217') as the element has an element that has a density of 1 to 2.5 x that of the liquid to be pumped.
An installation (100) which comprises a pumping device (110) and a storage tank (120), wherein the pumping device (110) is a pumping device (110) according to one of the pumping device claims.