Gas / Gas humidifier

Abstract

Gas / gas humidifier (10), with a dry side (11) through which a dry gas to be humidified flows, and with a moist side (12) through which a moist gas as a moisture source flows, with water vapor permeable membranes (14) which separate the moist side (12) from the dry side (11), wherein a liquid separator (16) is integrated in the flow direction of the moist gas after the membranes (13), the membranes (13) are designed as plate-shaped membranes (13), the plate-shaped membranes (13) or mounting plates (19) with the plate-shaped membranes (13) each have a supply opening (20, 22) and a discharge opening (21, 23) for the dry gas and the moist gas, and are stacked with their supply and discharge openings (20, 21, 22, 23) aligned, and the liquid separator (16) is formed by discharge openings (23) which are larger than the supply openings (22) for the moist gas in the plate-shaped membranes (13) or mounting plates (19) with the plate-shaped membranes (13).

Description

[0001] The invention relates to a gas / gas humidifier. The invention also relates to the use of such a humidifier.

[0002] Gas / gas humidifiers with a dry side through which a dry gas to be humidified flows, and with a wet side through which a wet gas flows as the moisture supplier, are known from the general state of the art. They typically have water vapor-permeable membranes that separate the wet side from the dry side and allow only moisture, but not the gases themselves, to pass through. Such humidifiers are used, for example, in fuel cell systems to humidify the supply air for fuel cells using PEM technology in order to prevent the proton exchange membranes in such fuel cells from drying out. For example, reference can be made to US 2006 / 0147773 A1, which shows a combined heat exchanger and humidifier.A comparable solution is known from DE 10 2007 003 144 A1, which describes both the prior art with only one humidifier and a separate charge air cooler and the invention therein with a charge air cooler integrated into the humidifier.

[0003] Particularly in fuel cell systems, it is now often the case that the moist gas serving as a moisture supplier is to be intentionally dried in order to, for example, in a subsequently arranged turbine, as in the last-mentioned prior art, for example in the representations of Fig. 1 and Fig. 2, is to be relaxed. This allows energy to be recovered. However, moisture, which can potentially condense, and especially liquid in the exhaust air flow, is very critical for the turbine, as droplets can damage the turbine due to the high speed of the turbine. Therefore, according to the further general state of the art in such structures, it is provided that not only in front of the humidifier, as in the illustration of the Fig. 1 in the second-mentioned document, but also a further liquid separator is located downstream of the humidifier and especially upstream of the turbine. This second liquid separator, in particular, is crucial for the reliable operation of the turbine.

[0004] Especially for fuel cell systems used in vehicles, installation space is typically very limited. To achieve excellent separation performance and thus keep droplets safely and reliably away from the turbine, a very good liquid separator must be used, which requires a comparatively large installation space. This is essential to protect the turbine from possible damage, so this installation space is generally "sacrificed." However, this represents a significant disadvantage.

[0005] US 6,953,635 B2 discloses a humidifier for a fuel cell comprising a hollow-fiber membrane module in which a hollow-fiber membrane bundle comprising bundled hollow-fiber membranes is housed within a housing. The module includes an inlet header that introduces exhaust gas into the interior of the hollow-fiber membranes, an outlet header that collects exhaust gas that has passed through the hollow-fiber membranes at another end of the hollow-fiber membrane module, and an exhaust outlet that discharges the liquid accumulated in the inlet header. This humidifier can prevent the hollow-fiber membranes from becoming clogged by water.

[0006] Further prior art is disclosed in the documents DE 10 2004 022 312 A1, DE 10 2008 058 072 A1, DE 10 2011 111 742 A1, DE 10 2005 025 643 A1 and DE 10 2009 034 095 A1.

[0007] The object of the present invention is to provide a gas / gas humidifier which avoids the aforementioned disadvantages and which is particularly suitable for use in a fuel cell system, preferably for use in a fuel cell system for providing electrical drive power in a vehicle.

[0008] This object is achieved according to the invention by a gas / gas humidifier having the features of claim 1. Advantageous embodiments and further developments of the gas / gas humidifier according to the invention emerge from the remaining dependent claims.

[0009] In the gas / gas humidifier according to the invention, the liquid separator is integrated into the gas / gas humidifier downstream of the membranes in the direction of flow of the moist gas. This integration of the liquid separator into the gas / gas humidifier, and in particular into the outlet area for the moist gas from the gas / gas humidifier, enables a very compact design that requires only one common component instead of two individual components. This allows for savings in cable lengths and connection elements, which, in addition to the advantage in terms of installation space, also offers an advantage in terms of assembly. Furthermore, the number of interfaces and thus points where the fundamental risk of leakage exists can be reduced.

[0010] According to an advantageous development of the gas / gas humidifier according to the invention, the liquid separator comprises a knitted fabric. Such a knitted fabric, e.g., in the form of a mesh fabric, a warp-knitted fabric, or the like, in the volume used as a liquid separator, calms the flow of gases therein and allows liquid droplets to rain down or run off the knitted fabric and thus be separated from the gas stream, which entrains the liquid droplets. This design is extremely efficient and requires comparatively little installation space, so that such a liquid separator comprising a knitted fabric can be very easily integrated into the gas / gas humidifier.

[0011] In a very advantageous embodiment of the gas / gas humidifier according to the invention, it is further provided that the moist gas escaping from / between the membranes flows directly into the liquid separator. Such direct inflow of the gas escaping from the membranes or between the membranes into the liquid separator, without any possible conduits, deflections, or the like, enables optimal flow to the liquid separator, since the flow between the membranes is laminar and uniform due to the design of a gas / gas humidifier to ensure the transfer of moisture. Such a laminar and uniform gas flow can thus be maintained at least in the inflow area of ​​the liquid separator with the direct connection to the liquid separator.It ensures very good separation with minimal installation space, especially if there is also a knitted fabric in the area of ​​the liquid separator.

[0012] The gas / gas humidifier according to the invention can thus be implemented simply and compactly together with the liquid separator. It is particularly suitable for use in a fuel cell system, in which very good humidification of the supply air and very good liquid separation from the moist exhaust air must be ensured, especially when a turbine is connected downstream. In particular, the fuel cell system can be used in a vehicle. Since installation space is always extremely limited in such applications, the integration of the liquid separator into the gas / gas humidifier in the manner according to the invention offers not only very efficient separation of liquid droplets but also a welcome space saving.

[0013] Further advantageous embodiments of the gas / gas humidifier according to the invention emerge from the remaining dependent claims and become clear from the exemplary embodiment which is described in more detail below with reference to the figures.

[0014] Showing: Fig. 1 shows a schematically indicated vehicle with a section of a fuel cell system which has a gas / gas humidifier according to the invention; Fig. 2 a sectional view through a possible embodiment of a gas / gas humidifier according to the invention; Fig. 3 a plan view of a section of the gas / gas humidifier according to Fig. 2; and Fig. 4 a sectional view through a possible embodiment according to the invention

[0015] In the presentation of the Fig. 1 shows a fuel cell system 1 in a highly schematic representation. Only the section relevant to the explanation of the invention is shown. The fuel cell system 1 is intended to be located in a vehicle 2, which is indicated in principle, in order to provide electrical drive power there. The core of the fuel cell system 1 is a fuel cell 3, which is intended to be constructed as a stack of PEM fuel cells. Hydrogen is supplied to an anode chamber 4 of the fuel cell 3 from a compressed gas reservoir 5 via a pressure control and metering valve 6. In the embodiment shown here, exhaust gases from the anode chamber 4 are released into the environment. They could just as easily be afterburned via a catalytic burner or recirculated around the anode chamber 4.All of this is known from the general state of the art and is not relevant to the present invention, so it will not be discussed in more detail here.

[0016] A cathode chamber 7 is separated from the anode chamber 4 of the fuel cell 3 by proton exchange membranes 8. Air is supplied to the cathode chamber 7 as an oxygen supplier via an air conveyor 9. The supply air is passed through a gas / gas humidifier 10 as dry supply air through a dry side 11 of the humidifier 10 and is humidified in the process. The exhaust air flowing from the cathode chamber 7 serves as the moisture supplier on a wet side 12 of the humidifier 10. This exhaust air is loaded with the product water produced in the fuel cell 3. The moisture can pass from the wet side 12 to the dry side 11 through membranes 13 of the humidifier 10 that are permeable to water vapor. The gases themselves cannot mix with one another due to the membranes 13. After the humidifier 10, the exhaust air reaches the environment via a turbine 14. In the turbine 14, residual energy is recovered from the exhaust air, for example thermal energy and pressure energy.The turbine 14 can be used or used in conjunction with the air conveying device 9. It is mounted together with an electric motor 15 on the same shaft as the air conveying device 9. This design is known from the general state of the art and is also referred to as an electric turbocharger or ETC (Electric Turbo Charger).

[0017] The turbine 14 of the ETC operates at very high speeds. If liquid droplets were to enter the area of ​​the turbine 14, they could cause significant damage. Therefore, in addition to the previously described components, a liquid separator 16 is provided in the gas / gas humidifier 10. This liquid separator 16 is arranged downstream of the membranes 13 in the flow direction of the moist exhaust air stream from the cathode chamber 7 of the fuel cell 3. It ensures that any remaining moisture in the exhaust air stream is safely and reliably separated from the exhaust air stream in the form of liquid droplets before it reaches the area of ​​the turbine 14. The water accumulating in the area of ​​the liquid separator 16 can be drained from time to time or depending on the water level, the electrical energy generated by the fuel cell 3, or the like. For this purpose, a drain line 17 with a drain valve 18 is provided in the illustration of the Fig. 1 indicated.

[0018] This design of the gas / gas humidifier 10 with integrated liquid separator 16 is extremely compact and simple, allowing for very good liquid separation with minimal construction volume. The gas / gas humidifier 10 can preferably be designed as shown below with reference to the Fig. 2 and Fig. 3 is described in more detail.

[0019] In the presentation of the Fig. 2 it can be seen that the membranes 13 of the humidifier 10 are designed as plate-shaped membranes 13 or in fastening plates 19, which in the illustration of the Fig. 3, are accommodated accordingly. The fastening plates 19 and the membranes 13 can be formed in one piece or in several parts. Now, preferably in the area of ​​the fastening plates 19, as shown in the illustration of Fig. 3, a supply opening 20 and a discharge opening 21 are provided for the dry gas flowing from the air conveying device 9 to the cathode chamber 7. In addition, a supply opening 22 and a discharge opening 23 are provided in each of the fastening plates 19 for the moist gas flowing from the cathode chamber 7 to the turbine 14. The supply opening 20 and the discharge opening 21 for the dry gas are in contact with one side of the membrane 13, in the illustration of Fig. 3, for example, with the underside, which is indicated by the dashed arrows. The supply opening 22 and the discharge opening 23 for the moist gas are connected to the other side of the membrane 13, in the example shown in the illustration of the Fig. 3 on the upper side, as indicated by the solid arrows. The dry gas stream is directed cross-flow through the gas / gas humidifier, opposite the moist gas stream.

[0020] If the fastening plates 19 with the membranes 13 are now stacked on top of each other and clamped between an upper end plate 24 and a lower end plate 25, the result is the Fig. 2 shows the basic structure of the gas / gas humidifier 10. In the upper end plate 24, a supply line 26, in this case for the moist gas, can be seen. The moist air now reaches the individual plates via the supply openings 22, which, when stacked one above the other, form a channel running through the entire height of the humidifier 10. It flows between the membranes 13, for example, above the membrane 13 of each of the mounting plates 19, to the discharge openings 23 arranged one above the other. These together also form an area running the entire height of the humidifier 10, which is significantly larger than the area formed by the supply openings 22. This area also serves as the liquid separator 16 and, in the embodiment shown here, is provided with a knitted fabric 27.The flow of the moist gas, which transfers a portion of the moisture through the membranes 13 to the dry gas, which flows transversely thereto, for example, toward the observer. Liquid droplets can then run off or rain down in the liquid separator 16, aided by the knitted fabric 27. This is further facilitated by the fact that the flow between the membranes 13 is laminar and uniform by design. The partial gas flows exiting between the membranes 13 are therefore also laminar and uniform, so that very good separation is achieved in the area of ​​the liquid separator 16, which is integrated into the discharge openings 23 for the moist gas. With minimal installation space, droplets in the gas flow flowing from the humidifier 10 to the turbine 14 are thus virtually eliminated.This is further facilitated by the fact that the humid gas flows out of the humidifier 10 via a discharge line 28 in the upper region, which is the intended use, preferably in the upper end plate 24. Due to this upper discharge, gravity prevents water droplets from being entrained. The water droplets can collect in a liquid reservoir 29, which is preferably integrated into the lower end plate 25, and can be drained via the discharge line 17 and the discharge valve 18, which is preferably also integrated into the lower end plate 25, as needed, from time to time, depending on the fill level or the like.

[0021] The according to Fig. The mounting plates 19 formed in FIG. 3 with their membranes 13 can thus be easily and efficiently assembled into the gas / gas humidifier 10 with integrated liquid separator 16 by simply stacking them one above the other and clamping them between the end plates 24, 25, for example via tie rods, clamping straps, a housing that braces the stack, or the like. Optimum liquid separation is ensured with minimal installation space, thus enabling maximum liquid protection for the turbine 14 in the fuel cell system 1.

[0022] In order to prevent the gas flowing along the membranes 13 arranged at the top from flowing through the knitted fabric 27 in the liquid separator too quickly, it can be provided, in addition to or as an alternative to the embodiments described so far, that the knitted fabric 27 also extends into the region of the discharge line 28, in particular within the end plate 24. As an alternative to this embodiment, which is not shown, it would also be possible to displace the discharge line 28 and the liquid reservoir 29 of the liquid separator 16 perpendicular to the stacking direction next to the area of ​​the liquid separator 16 with the knitted fabric 27. This embodiment variant is shown in the illustration of the Fig. 4, which otherwise has a structure analogous to the representation in Fig. 2 shows.

Claims

[1] Gas / gas humidifier (10), with a dry side (11) through which a dry gas to be humidified flows, and with a moist side (12) through which a moist gas as a moisture supplier flows, with water vapor permeable membranes (14) which separate the moist side (12) from the dry side (11), wherein a liquid separator (16) is integrated in the flow direction of the moist gas after the membranes (13), the membranes (13) are designed as plate-shaped membranes (13), the plate-shaped membranes (13) or fastening plates (19) with the plate-shaped membranes (13) each have a supply opening (20, 22) and a discharge opening (21, 23) for the dry gas and the moist gas, and are stacked with the supply and discharge openings (20, 21, 22, 23) aligned, and the liquid separator (16) is formed by discharge openings (23) which are larger than the supply openings (22) for the moist gas in the plate-shaped membranes (13) or fastening plates (19) with the plate-shaped membranes (13). [2] Gas / gas humidifier (10) according to claim 1, characterized by that the liquid separator (16) has a knitted fabric (27). [3] Gas / gas humidifier (10) according to claim 1 or 2, characterized by that the moist gas escaping from / between the membranes (13) flows directly into the liquid separator (16). [4] Gas / gas humidifier (10) according to one of the preceding claims, characterized by that the dry gas and the moist gas are guided in cross flow along the membranes (13). [5] Gas / gas humidifier (10) according to one of the preceding claims, characterized byin that the plate-shaped membranes (13) or fastening plates (19) with the plate-shaped membranes (13) are clamped between end plates (24, 25), wherein the end plates (24, 25) have inlet and outlet lines (26, 28) for the dry gas and the moist gas, wherein the outlet line (28) for the moist gas is arranged at the top during normal use. [6] Gas / gas humidifier (10) according to claim 5, characterized by that the lower end plate (25) in normal use has a liquid reservoir (29) and a drain line (17) for the liquid, and in particular a valve device (18) in the drain line. [7] Use of a gas / gas humidifier (10) according to one of the preceding claims for humidifying supply air flowing to a fuel cell (3) by moist exhaust air from the fuel cell (3). [8] Use according to claim 7, characterized bythat a turbine (14) is arranged downstream of the gas / gas humidifier (10) in the flow direction of the moist exhaust air from the fuel cell (3).

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