DE10336755B4 - Apparatus and method for carbonating drinking water - Google Patents

Abstract

Use of a device with at least one membrane contactor (5) with at least one water inlet (32), at least one inlet (37) for CO2, at least one outlet (41) for enriched water, at least one return (12) from a water outlet to a water inlet, and at least one membrane, on the feed side of CO2 and on the permeate side of which the water to be enriched is led, for the carbonation of drinking water.

Description

The invention relates to an apparatus and a method for the carbonation of drinking water.

Carbonation of drinking water is here and hereafter understood to mean enrichment with CO ₂ .

A variety of methods and apparatus for carbonation of drinking water are known. As a rule, the water is carbonated by cooling, since the solubility of CO _{2 increases} at lower temperatures.

From the WO 94/05407 A1 a device is known for preparing and dispensing soft drinks, in which drinking water is conveyed into a container flooded with CO ₂ . From the over the drinking water gas cushion CO ₂ is then sucked off via a circulation pump and mixed into the water. The container is cooled from the outside via an ice layer produced by cooling coils in order to keep the temperature of the drinking water low. An obvious disadvantage of this device is that the equipment expense is high and therefore expensive, so that it is not suitable for use in the home.

In contrast, the CO ₂ entry in suitable for household, well-known Lanzenkarbonisierungsgeräten accomplished by the CO _{2 is} injected via the lance under pressure in a container containing the drinking water, usually a bottle. The handling of such devices is, however, relatively cumbersome in that the drinking water is to be carbonized in special containers, the drinking water must be previously cooled separately, especially if it is to be enriched with larger amounts of CO ₂ .

From the DE 196 14 754 C1 is also working on the principle injector, developed by the applicant process in addition to apparatus for continuous cooling and carbonation of drinking water known to allow the consumer an easy to use, mug-wise cones of cooled, CO ₂ -containing drinking water and is suitable due to its design in the home. For this purpose, drinking water extracted from the mains network is cooled in a continuous flow system, enriched with CO ₂ in a cooling system connected downstream of the cooling system and withdrawn via a tapping point of a dispensing line, into which the carbonation section passes, wherein the dispensing point has a pressure-controlling function at the end of the dispensing line , In order to improve the CO ₂ input, the drinking water is fed to the carbonation section via a pump with increased pressure. The good functionality is achieved by a technical effort that needs to be reduced.

The invention has for its object to provide a device of the type mentioned, with the retention of the other advantages of the previously discussed device continuous enrichment of water with gas, in particular a carbonization, with little technical effort is possible.

This object is achieved with a device having the features of claim 1 and a method having the features of claim 21.

It has surprisingly been found that membranes, in particular semipermeable membranes, which are generally used in membrane separation processes such as ultrafiltration, reverse osmosis or dialysis, are also outstandingly suitable for the carbonation of drinking water. According to the invention, the membrane serves as a contact surface, wherein the driving forces for mass transfer of the gas through the membrane either a different pressure on both sides of the membrane or the difference in the gas concentration may be on both sides. In this way, an optimal entry of CO ₂ in the water is made possible.

The term permeate side of the membrane is understood here and below to mean always the side on which the water to be enriched is passed, and below the feed side always the side on which the gas is guided, irrespective of the permeability properties of the membrane.

The use of a membrane offers a multitude of advantages. On the one hand, it is possible to dispense with pumps or other motor apparatus for gas enrichment. It has been found that in contrast to the aforementioned, previously developed by the applicant Karbonisierungsvorrichtung to a water pressure that is greater than the Asked about the water supply network, can be dispensed with, so that even a previously required pump can be omitted. This results in a significant simplification of the apparatus engineering, on the other hand, a significant energy savings in the operation of the device, further a much increased operational and reliability as well as a simplification of maintenance. Finally, the noise during operation of the device over prior art devices is considerably lower.

The structure of the membrane in the membrane contactor can be done in various ways, it being important to ensure that for a desired removal amount of gas-enriched water available as the contact surface Surface of the membrane is sufficiently large. Thus, for example, plate membranes, in particular in a multilayer design, in which a plurality of juxtaposed, mutually parallel feed sides and permeate sides are separated by membrane discs come into consideration.

Preferably, the membrane contactor is designed with a multiplicity of waveguides connected in parallel, wherein inside the waveguide optionally the feed side and outside the waveguide is the permeate side or vice versa. Compared to the use of modules with multiple plate membranes here is the constructive advantage that only the inputs and outlets of the waveguide must be connected in parallel, while the space surrounding the waveguide in the membrane contactor requires only one inlet and outlet.

A return is provided between the water outlet of a membrane contactor and its water inlet, so that at least a portion of the enriched water can pass through the enrichment process in the membrane contactor again, so that as a result the concentration of the gas in the water to be enriched is increased overall.

In a preferred embodiment, the waveguides are connected within the membrane contactor via a respective collecting connection piece with the water inlet and with the water outlet. The remaining space in the membrane contactor can then be acted upon via the gas inlet with CO ₂ . By the targeted flow of water through the membrane contactor and its geometric design can be ensured that at the water outlet, the CO ₂ concentration of the desired concentration is consistent.

In this embodiment, it is of considerable advantage if the waveguides have an average diameter of less than 300 μm, in particular less than 250 μm. Already due to the small available space, the formation of even the smallest macroscopic gas bubbles in the waveguide can be substantially prevented. This particularly plays a role for the period in which the water in the waveguides does not flow, but stands, for example, in the event that no enriched water is removed at the outlet of the membrane contactor. At the same time the gas transport over the membrane at standstill of the water comes very quickly to a standstill, since the solubility limit of standing in the waveguide water is reached quickly.

In addition to the possibility of preventing macroscopic gas bubbles forming in the water to be treated due to geometric conditions, macroscopic gas bubbles can also be prevented by having a lower gas pressure on the feed side than the permeate side. Moreover, it is also possible that demolish at the membrane forming gas bubbles early at a suitable flow rate, so that even by choosing a suitable flow rate, the forming gas bubbles remain relatively small.

In particular, when using waveguides with a very small diameter, it is advantageous if more than 5,000, in particular more than 10,000 waveguides are provided to ensure a sufficient flow of water for each application.

A length of the thin waveguides up to 350 mm, in particular a length of about 300 mm, has proven to be advantageous in that the flow resistance for the water flowing through is sufficiently low in each case.

Suitable waveguides in a further preferred embodiment are, in particular, those which are produced from polyamide, in particular polyaryl ether sulfones. Also, membranes made of polypropylene are preferably usable. Other usable membrane materials are, for example, cellulose or cellulose acetate. Especially for drinking water treatment, the materials should be hygienically practical, d. H. meet in particular the necessary criteria for their application in terms of hygiene, microbiological impairment and long-term stability.

In principle, it may be advantageous if the membrane on the permeate side is hydrophobic. In this case, it is possible to lower the pressure on the feed side to a value below the pressure on the permeate side.

Alternatively or in addition to semipermeable membranes used in the membrane contactor, porous technical membranes can also be used, provided that they have a suitable flow resistance for the CO ₂ to be transported through the membrane, in which case overpressure must prevail in operation on the feed side relative to the permeate side.

The device may have at least one cooling unit, which may be downstream of the membrane contactor, but preferably upstream of it, since the solubility of CO _{2 is} substantially increased in the case of cooled water. Instead of or in addition to a cooling unit upstream or downstream of the membrane contactor, a cooling unit may also be interposed in a return line.

In order to exclude an overpressure on the feed side of the membrane contactor or completely to the feed side to vent or vent, a positive pressure or vent valve may be provided on the feed side of the membrane contactor.

According to a further embodiment, the device according to the invention has a manually adjustable control for the gas pressure on the feed side of the membrane contactor and / or the water pressure on the permeate side of the membrane contactor, so that the concentration of the gas in the enriched water can be adjusted.

Also preferably, the device according to the invention has connections for connecting the water inlet to a drinking water supply network, so that it can be used in a simple manner in the home or in other areas in which the enriched water is to be made available in comparatively small portions. Of course, the device can also be supplied via other water sources and adapted ports.

The water outlet of the device according to the invention may be connected to a collecting tank for the treated water, wherein the water outlet may optionally be closed by a valve, which is controlled by a level control in the sump, if necessary. In particular, for the application of the device according to the invention in the household, it may also have a water outlet downstream tapping point with a tap through which the enriched water can be removed in portions.

A modular design of the device according to the invention is advantageous in that individual elements such as cooling unit, membrane contactor or tapping point can be replaced individually in case of defects. There are also advantages in the production of individual components and their assembly.

The device according to the invention is preferably operated with a flow rate of the drinking water through the membrane contactor of at least 1.2 l / min, in particular of at least 1.5 l / min. Depending on the type of membrane used in the membrane contactor, preferably a permeate-side pressure of 2.5 bar should not be undershot and not exceed 3.5 bar. If a hydrophilic membrane is used, it may be advantageous if a feed-side pressure of 2.9 bar is not undershot and not exceeded by 4.1 bar, the upper limit being determined in particular by the transmembrane pressure of the membrane used. If a hydrophobic membrane is used, it may be advantageous if the minimum pressure on the feed side is 2.5 bar and the maximum pressure is 3.5 bar.

With the device according to the invention and the associated methods are accumulation rates of CO ₂ in water of more than 500 mg _CO2 / l possible, whereby the enrichment preferably in-line, ie to the point at which the drinking water is taken off at the tapping point, takes place ,

In the following the invention with reference to the accompanying drawings, in which preferred embodiments of the device according to the invention is illustrated, explained in more detail. Show it:

1 a flow chart for an embodiment of the device according to the invention;

2 a sectional view of an embodiment of the membrane contactor; and

3 the embodiment 2 in plan view.

The flow chart in 1 illustrated exemplary embodiment is a shut-off valve 1 connected to a drinking water source, not shown, in particular to a drinking water network. In the flow direction indicated by the arrow A follow a backflow preventer 2 and a pressure reducer 3 , which reduces the water pressure to a defined inlet pressure, for example 3 bar. Below is a cooling unit 4 arranged, which may be embodied for example as a compression cooling system or as a Peltier cooling system, wherein a Peltier cooling system has the particular advantage that it is quiet compared to a compression cooling system.

Downstream of the cooling system is a membrane contactor 5 , the input side also with a gas source 6 , For example, a CO ₂ storage container commercial size, via a line 7 connected is. In the line 7 is a pressure reducer 8th provided that relaxes the CO ₂ to, for example, 3.5 bar working pressure. In addition, is in the line 7 between the pressure reducer 8th and the membrane contactor 5 a flow restrictor 9 , For example, a needle valve, arranged with which the amount of gas supplied can be adjusted so that the enriched with CO ₂ water between "quiet" and "sparkling" can be varied, far more than 1000 mg _CO2 / l, with a medium carbonation about 4000 mg _CO2 / l, can be added. On the output side, the membrane contactor closes 5 a tap range 10 with a tap 11 at.

The drinking water is at an in 1 Accordingly, the device according to the invention initially cooled and then in Membrane contactor enriched with CO ₂ . The enrichment takes place in-line, at the exact moment when the tap 8th is opened and water flows from the mains via the cooling system, the membrane contactor and the tap line to the tap.

In principle, the amount of CO _{2 to} be enriched in the water can be influenced by varying the water pressure, the flow rate of the water and the pressure difference between the feed side and the permeate side of the membrane.

Between the water outlet of the membrane contactor 5 and its water inlet is a return 12 provided so that at least a part of the membrane contactor 5 emerging, enriched water again through the enrichment process and thus the concentration of CO ₂ dissolved in the water can be further increased. About a three-way valve 13 the amount of water supplied to the return can be adjusted and thus the degree of enrichment can be varied by the consumer.

In the return 12 is a cooling unit 14 interposed, which is designed here as a second cooling unit. The return can also be performed by a membrane contactor upstream cooling unit, or it can be provided depending on the application, only this one cooling unit in the device according to the invention.

To compensate for the pressure losses caused by a multiple pass of the water through the membrane contactor is between the cooling unit 4 and the membrane contactor 5 a pump 15 provided with the water pressure at the entrance of the diaphragm contactor 5 can be increased if necessary. To control the pump 12 is a pressure switch 13 provided, which turns on the pump when a predetermined minimum pressure in the Zapfstrecke is exceeded, and turns off again when a predetermined maximum pressure in the Zapfstrecke is reached.

2 and 3 show an example of a membrane contactor 20 which can be used in the device according to the invention. The membrane contactor 20 has a container wall forming a hollow cylinder 21 on. The hollow cylinder is down with a foot piece 22 and above with a head piece 23 completed.

Between the foot piece 22 and the head piece 23 is a membrane insert 24 used, the head and foot side with fittings 25 . 26 in designated shots 27 . 28 in the foot piece 22 or in the head piece 23 sitting. The membrane insert 24 has at its head end and at its foot each a Sammelanschlußstück 29 . 30 , over which a variety of waveguides 31 with the head or foot side fittings are in communication. If waveguides constructed from fibers, in particular polyarylethersulfones or another polyamide, cellulose or cellulose acetate, are used, they typically have an inside diameter of about 225 μm and a wall thickness of 30 μm.

In the foot piece 22 is a water intake 32 with a one-way valve 33 receiving valve seat 34 provided that over a bore 35 with the recording 27 for the fitting 25 of the membrane insert 24 connected is. In addition, the foot piece points 23 a gas inlet 37 with a one-way valve 38 receiving valve seat 39 up, over a hole 40 with the membrane insert 24 surrounding cavity is connected in the hollow cylinder.

The head piece 23 has an outlet 41 for the enriched water with a conventional connection fitting 42 to connect the Zapfstrecke, with the recording 28 for the fitting 26 of the membrane insert 24 communicates. Finally, in the head piece is an overpressure or vent valve 43 for the membrane insert 24 surrounding space provided in the hollow cylinder.

A preferably usable membrane insert is offered for example for dialysis purposes under the name Ultrafilter U 8000 S by Gambro Dialysatoren GmbH & Co. KG. This membrane insert has a multilayer ultrafiltration hollow fiber membrane with approximately 18,000 hollow fibers. The hollow fibers are composed of three layers of polyamide with an inner carrier layer, an overlying, foamed intermediate layer and a very thin outer skin lying thereon. The effective membrane surface of the membrane insert is approximately 2.2 square meters ² . The membranes are enclosed by a hollow cylinder, which is closed on the head and foot side with hunt pieces. The feed side of the membrane insert is in the installed state via a lateral bore in one of the hunt connections with the space surrounding the membrane insert within the container wall 21 in connection.

Preferably, this membrane contactor is operated at a water inlet pressure of at least 2.5 bar at a flow rate of at least 1.5 l / min. The pressure difference between the feed and permeate side should preferably be at least 0.4 bar, so that the gas for enrichment of the water is supplied to the waveguides from the outside with a minimum pressure of 2.9 bar. The transmembrane pressure, which is 0.6 bar in this membrane contactor, but should not be exceeded in order to avoid gas cushion in the waveguides, which are formed by an unintentional mass transfer from the feed to the permeate side when the Transmembrandrucks. A corresponding pressure regulation takes place via the pressure reducer 8th ,

Among other things, particular advantages of this membrane contactor are that, because of its use in medical technology, it is generally produced under sterile conditions and the membrane is germ-tight, so that, in particular, no germs can pass from the permeate side to the feed side.

Another example of a membrane contactor which can be used with preference is that offered as an industrial membrane X40 by Membrana GmbH. In this membrane contactor, a hydrophobic, single-layer polypropylene membrane is used. This membrane contactor has about 3,700 capillaries and an effective membrane surface of 0.76 square meters. ²

Due to its hydrophobic membrane, it can be operated with a gas pressure below the water pressure, since no water can get from the permeate side to the feed side. Preferably, this membrane contactor is operated at a drinking water inlet pressure of 2.5 bar to 3.5 bar and a flow rate of 1.2 l / min to 2.0 l / min. The feed side gas pressure should be at least 2.5 bar and a maximum of 3.5 bar.

The particular advantages of this membrane contactor are that it is compact and the gas input into the drinking water is very effective.

Regardless of the type of membrane concentrator, the temperature of the enriched drinking water should be between 5 ° C and 30 ° C, whereby especially carbonated drinking water up to a temperature of 18 ° C is subjectively perceived as refreshing.

Claims (27)

Use of a device with at least one membrane contactor ( 5 ) with at least one water inlet ( 32 ), at least one inlet ( 37 ) for CO ₂ , at least one outlet ( 41 ) for enriched water, at least one return ( 12 ) from a water outlet to a water inlet, and at least one membrane, on whose feed side CO ₂ and on the permeate side of which the water to be enriched is passed, for the carbonation of drinking water. Device for carbonating drinking water, characterized by at least one membrane contactor ( 5 ) with at least one water inlet ( 32 ), Connections for the supply of water to a drinking water supply network, at least one inlet ( 37 ) for CO ₂ , at least one outlet ( 41 ) for the enriched water, at least one return ( 12 ) from a water outlet to a water inlet, and at least one membrane, on whose feed side CO ₂ and on the permeate side of which the water to be enriched is passed. Apparatus according to claim 2, characterized in that the membrane is a semi-permeable membrane, in particular a membrane suitable for ultrafiltration. Device according to claim 2 or 3, characterized in that the membrane contactor ( 5 ) has at least one plate membrane, in particular a multilayer plate membrane, in which a plurality of juxtaposed, mutually parallel feed sides and permeate sides are separated from each other by membrane discs. Device according to one of claims 2 to 4, characterized in that the membrane contactor ( 5 ) a plurality of parallel waveguides ( 31 ) having. Device according to claim 5, characterized in that the waveguides ( 31 ) within the membrane contactor ( 5 ) via one collecting connector ( 29 . 30 ) with the water inlet ( 32 ) and with the water outlet ( 41 ) and the remaining space in the membrane contactor ( 5 ) via the gas inlet ( 37 ) can be charged with CO ₂ . Device according to claim 5 or 6, characterized in that the waveguides ( 31 ) have an average diameter of less than 300 μm, in particular less than 250 μm. Device according to one of claims 5 to 7, characterized in that more than 5,000, in particular more than 10,000 waveguides ( 31 ) are provided. Device according to one of claims 5 to 8, characterized in that the waveguide ( 31 ) have a length up to 350 mm, in particular of about 300 mm. Device according to one of claims 2 to 9, characterized in that the membranes ( 31 ) are constructed of a polyamide material, in particular of polyarylethersulfones. Device according to one of claims 2 to 9, characterized in that the membranes ( 31 ) are made of a polypropylene material. Apparatus according to claim 3 or any of claims 4 to 11 appended thereto, characterized in that the membrane is hydrophobic on the permeate side. Apparatus according to claim 2, characterized in that the membrane is a porous technical membrane, wherein in operation on the feed side against the permeate side there is an overpressure. Device according to one of claims 2 to 13, characterized by at least one cooling unit ( 4 . 14 ). Apparatus according to claim 14, characterized in that at least one cooling unit ( 4 ) the membrane contactor ( 5 ) upstream in the flow direction of the drinking water. Device according to claim 14 or claim 14, characterized in that at least one cooling unit ( 14 ) in the return ( 12 ) is interposed. Device according to one of claims 2 to 16, characterized by an overpressure or venting valve ( 43 ) on the feed side of the membrane contactor ( 5 ). Device according to one of claims 2 to 17, characterized by a manually adjustable control for the gas pressure on the feed side of the membrane contactor ( 5 ) and / or for the water pressure on the permeate side of the membrane contactor ( 5 ). Device according to one of claims 2 to 18, characterized by a water outlet downstream tapping point ( 11 ). Device according to one of claims 2 to 19, characterized by a modular construction. Method for carbonating drinking water with a device according to one of claims 2 to 20, characterized by a flow rate of the drinking water through the membrane contactor of at least 1.2 l / min, in particular of at least 1.5 l / min and a feed side gas pressure of at least 2 , 5 bar. A method according to claim 21, characterized by a permeate side pressure of at least 2.5 bar. A method according to claim 21 or 22, characterized by a permeate side pressure of at most 3.5 bar. Method according to one of claims 21 to 23, characterized by a feed-side pressure of at least 2.9 bar when using a hydrophilic membrane. Method according to one of claims 21 to 24, characterized by a feed side pressure of at most 4.1 bar when using a hydrophilic membrane and at most 3.5 bar when using a hydrophobic membrane. Method according to one of claims 21 to 25, characterized in that at least 500 mg / l CO _{2 are introduced} into the drinking water. Method according to one of claims 21 to 26, characterized in that the accumulation of CO ₂ in the drinking water takes place in-line.

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