Fuel cell membrane humidifier with adjustable off-gas flow

Abstract

The present invention relates to a fuel cell membrane humidifier capable of controlling the flow rate of exhaust gas, which can automatically control the flow rate of exhaust gas according to the temperature of the exhaust gas flowing in from a fuel cell stack. A fuel cell membrane humidifier capable of controlling the flue gas flow rate according to an embodiment of the present invention is, It includes: an exhaust gas inlet through which exhaust gas from a fuel cell stack flows; and an exhaust gas flow rate control unit formed at the exhaust gas inlet and controlling the opening of the exhaust gas inlet according to the temperature of the exhaust gas flowing from the fuel cell stack.

Description

Technology Field

[0001] The present invention relates to a fuel cell membrane humidifier, and more specifically, to a fuel cell membrane humidifier capable of controlling the flow rate of exhaust gas, which can automatically control the flow rate of exhaust gas according to the temperature of the exhaust gas flowing in from a fuel cell stack. Background Technology

[0003] A fuel cell is a power generation type battery that produces electricity by combining hydrogen and oxygen. Unlike general chemical batteries such as dry batteries or storage batteries, fuel cells can continuously produce electricity as long as hydrogen and oxygen are supplied, and they have the advantage of being about twice as efficient as internal combustion engines because there is no heat loss.

[0004] Furthermore, because it directly converts chemical energy generated by the combination of hydrogen and oxygen into electrical energy, it emits fewer pollutants. Therefore, fuel cells have the advantage of not only being environmentally friendly but also alleviating concerns about resource depletion caused by increased energy consumption.

[0005] These fuel cells can be broadly classified into polymer electrolyte membrane fuel cells (PEMFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC), and alkaline fuel cells (AFC) depending on the type of electrolyte used.

[0006] Although each of these fuel cells operates on the fundamentally same principle, they differ in the type of fuel used, operating temperature, catalyst, and electrolyte. Among these, polymer electrolyte fuel cells (PEMFCs) are known to be the most promising for transportation systems as well as small-scale stationary power generation equipment, as they operate at lower temperatures compared to other fuel cells and enable miniaturization due to their high power density.

[0007] One of the most critical factors in improving the performance of Polymer Electrolyte Fuel Cells (PEMFCs) is maintaining the moisture content of the Polymer Electrolyte Membrane (or Proton Exchange Membrane: PEM) within the Membrane Electrode Assembly (MEA) by supplying a certain amount of water. This is because power generation efficiency drops sharply if the polymer electrolyte membrane dries out.

[0008] Methods for humidifying polymer electrolyte membranes include: 1) a bubbler humidification method in which water is filled into a pressure vessel and then the target gas is passed through a diffuser to supply moisture; 2) a direct injection method in which moisture is supplied directly to the gas flow tube through a solenoid valve by calculating the amount of moisture required for the fuel cell reaction; and 3) a humidification membrane method in which moisture is supplied to the fluidized bed of the gas using a polymer membrane.

[0009] Among these, the membrane humidification method, which humidifies the polymer electrolyte membrane by supplying water vapor to the air supplied to the membrane using a membrane that selectively permeates only the water vapor contained in the flue gas, is advantageous in that it allows for the humidification of the humidifier to be made lighter and smaller.

[0010] When forming modules for selective permeability membranes used in membrane humidification methods, hollow fiber membranes with a large permeable surface area per unit volume are preferable. In other words, manufacturing a humidifier using hollow fiber membranes enables high-density integration of the membranes with a large contact surface area, allowing sufficient humidification of the fuel cell even with a small capacity. Furthermore, it offers the advantages of enabling the use of low-cost materials and recovering moisture and heat contained in the off-gas emitted at high temperatures from the fuel cell for reuse through the humidifier.

[0012] Generally, the flow rate of dry gas humidified through a membrane humidifier and supplied to the fuel cell stack is controlled based on the output (power generation demand) of the fuel cell stack. Specifically, as the output increases, the flow rate of dry gas supplied to the fuel cell stack increases. Consequently, the flow rate of exhaust gas (cathode off-gas) discharged from the fuel cell stack and introduced into the membrane humidifier also varies in response to the output.

[0013] Flue gas is introduced into a membrane humidifier to perform moisture exchange with the dry gas flowing inside the hollow fiber membrane. Typically, areas where flue gas does not flow (dead zones) may occur within the membrane humidifier, and minimizing these dead zones can improve humidification efficiency. To this end, various technologies are being studied to control the flow of flue gas introduced from the fuel cell stack into the membrane humidifier.

[0015] FIGS. 1 and FIGS. 2 are drawings illustrating a fuel cell membrane humidifier according to the prior art.

[0016] FIG. 1 is a drawing (Fig. 2) disclosed in Japanese Published Patent No. 2011-089749 (hereinafter, Prior Art 1), and FIG. 2 is a drawing (Fig. 2) disclosed in Japanese Published Patent No. 2010-146810 (hereinafter, Prior Art 2).

[0017] The membrane humidifier of prior art 1 is equipped with an inlet opening / closing mechanism having an upper closed type opening / closing lid (32B, 32C) that receives the driving force of the exhaust gas, and the opening / closing lid (32B, 32C, corresponding to the inlet opening / closing mechanism) is structured to open / close an inlet (24B, 24C) other than the front end side in response to the driving force of the exhaust gas, thereby improving humidification efficiency.

[0018] The membrane humidifier of prior art 2 improves humidification efficiency by using an outlet adjustment device (70) and an inlet adjustment device (80) simultaneously to narrow the opening areas of both the outlet (56) and the inlet (55) when the exhaust gas flow rate is low, thereby increasing the residence time of the exhaust gas, in order to solve the problem that sufficient humidification is not possible in the hollow fiber membrane far from the inlet when the exhaust gas flow rate is low.

[0019] While these conventional fuel cell membrane humidifiers can control the flow of exhaust gas introduced from the fuel cell stack to the membrane humidifier, they have the disadvantages of increased manufacturing costs and larger size due to a complex structure and a large number of parts. Prior art literature

[0021] Prior Art 1: Japanese Published Patent No. 2011-089749 Prior Art 2: Japanese Published Patent No. 2010-146810 The problem to be solved

[0022] The present invention aims to provide a fuel cell membrane humidifier capable of controlling the flow rate of exhaust gas, which can automatically control the flow rate of exhaust gas according to the temperature of the exhaust gas flowing in from the fuel cell stack. means of solving the problem

[0024] A fuel cell membrane humidifier capable of controlling the flue gas flow rate according to an embodiment of the present invention is,

[0025] It includes: an exhaust gas inlet through which exhaust gas from a fuel cell stack flows; and an exhaust gas flow rate control unit formed at the exhaust gas inlet and controlling the opening of the exhaust gas inlet according to the temperature of the exhaust gas flowing from the fuel cell stack.

[0026] In a fuel cell membrane humidifier capable of controlling the flue gas flow rate according to an embodiment of the present invention, the flue gas flow rate control unit may include a negative thermal expansion material that expands in a first temperature range and contracts in a second temperature range greater than the first temperature range.

[0027] In a fuel cell membrane humidifier capable of controlling the flue gas flow rate according to an embodiment of the present invention, the flue gas flow rate control unit may include bismuth (Bi).

[0028] In a fuel cell membrane humidifier capable of controlling the flue gas flow rate according to an embodiment of the present invention, the flue gas flow rate control unit may include oxides of bismuth (Bi), lanthanum (La), and nickel (Ni).

[0029] In a fuel cell membrane humidifier capable of controlling the flue gas flow rate according to an embodiment of the present invention, the flue gas flow rate control unit may include oxides of bismuth (Bi), iron (Fe), and nickel (Ni).

[0030] In a fuel cell membrane humidifier capable of controlling the flue gas flow rate according to an embodiment of the present invention, the flue gas flow rate control unit may be formed in a ring shape on the inner wall of the flue gas inlet.

[0031] In a fuel cell membrane humidifier capable of controlling the flue gas flow rate according to an embodiment of the present invention, the flue gas flow rate controlling part may be inserted in a ring shape into an annular fixing groove formed on the inner wall of the flue gas inlet.

[0032] A fuel cell membrane humidifier capable of controlling the flue gas flow rate according to an embodiment of the present invention comprises a mid-case, a cap coupled to the mid-case, and a humidification module disposed within the mid-case and accommodating a plurality of hollow fiber membranes, wherein the flue gas inlet may be formed in the mid-case.

[0033] In a fuel cell membrane humidifier capable of controlling the flue gas flow rate according to an embodiment of the present invention, the humidification module may include at least one cartridge comprising an inner case accommodating a plurality of hollow fiber membranes and a potting portion formed at the end of the inner case.

[0035] Specific details of embodiments according to various aspects of the present invention are included in the following detailed description. Effects of the invention

[0037] A fuel cell membrane humidifier according to one embodiment of the present invention has a simple structure with a small number of parts, and the flue gas flow control unit can automatically adjust the opening of the flue gas inlet according to the output condition of the fuel cell stack. Accordingly, the size of the membrane humidifier can be miniaturized and manufacturing costs can be reduced. Brief explanation of the drawing

[0039] FIGS. 1 and FIGS. 2 are drawings illustrating a fuel cell membrane humidifier according to the prior art. FIG. 3 is a drawing showing a fuel cell membrane humidifier according to one embodiment of the present invention. FIG. 4 is an enlarged view of the exhaust gas flow control unit of a fuel cell membrane humidifier according to one embodiment of the present invention. Figure 5 is a diagram showing the operating state of the exhaust gas flow control unit in a low-power environment. Figure 6 is a diagram showing the operating state of the exhaust gas flow control unit in a high-power environment. Specific details for implementing the invention

[0040] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0042] The terms used in this invention are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this invention, terms such as "comprising" or "having" are intended to specify the existence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Hereinafter, a fuel cell membrane humidifier according to an embodiment of the present invention will be described with reference to the drawings.

[0044] FIG. 3 is a drawing showing a fuel cell membrane humidifier according to one embodiment of the present invention.

[0045] As illustrated in FIG. 3, a fuel cell membrane humidifier (100) according to one embodiment of the present invention includes a humidification module (110) that humidifies dry gas supplied from a blower (B) with moisture in the exhaust gas discharged from a fuel cell stack (S). Each of the two ends of the humidification module (110) is coupled with a cap (120: 120a, 120b). The humidification module (110) and the cap (120) may be formed separately or integrally.

[0046] One of the caps (120) (120a) has a dry gas inlet (130) formed therein to supply dry gas supplied from a blower (B) to a humidification module (110), and the other one (120b) has a dry gas outlet (140) formed therein to supply air humidified by the humidification module (110) to a fuel cell stack (S).

[0047] The humidification module (110) is a device in which moisture exchange between the dry gas supplied from the blower (B) and the exhaust gas occurs, and comprises a mid-case (111) having an exhaust gas inlet (111a) and an exhaust gas outlet (111b), and a plurality of hollow fiber membranes (112) within the mid-case (111). Both ends of a bundle of hollow fiber membranes (112) are fixed to a potting section (113).

[0048] Alternatively, the humidification module (110) may include at least one cartridge comprising a plurality of hollow fiber membranes (112) and a potting portion (113) that secures them to one another, in which case the hollow fiber membranes (112) and the potting portion (113) may be formed within a separate cartridge case (inner case). In this case, the hollow fiber membranes (112) may be accommodated within the inner case, and the potting portion (113) may be formed at the end of the inner case. When the humidification module (110) includes a cartridge, a resin layer for securing the cartridge may be formed between both ends of the cartridge and the mid-case (111), or a gasket assembly that provides a hermetic seal through mechanical assembly may be further included.

[0049] The mid-case (111) and the cap (120) may each be independently formed of hard plastic or metal and may have a circular or polygonal cross-section in the width direction. The circular includes elliptical shapes, and the polygon includes polygons with rounded corners. For example, the hard plastic may be polycarbonate, polyamide (PA), polyphthalamide (PPA), polypropylene (PP), etc.

[0050] The hollow fiber membranes (112) may include a polymer membrane formed from polysulfone resin, polyethersulfone resin, sulfonated polysulfone resin, polyvinylidene fluoride (PVDF) resin, polyacrylonitrile (PAN) resin, polyimide resin, polyamideimide resin, polyesterimide resin, or a mixture of at least two of these, and the potting portion (113) may be formed by curing a liquid resin such as liquid polyurethane resin through a casting method such as dip potting or centrifugal potting.

[0051] The dry gas supplied from the blower (B) flows along the hollows of the hollow fiber membranes (112). The exhaust gas introduced into the mid-case (111) through the exhaust gas inlet (111a) comes into contact with the outer surface of the hollow fiber membranes (112) and is then discharged from the mid-case (111) through the exhaust gas outlet (111b). When the exhaust gas comes into contact with the outer surface of the hollow fiber membranes (112), the moisture contained in the exhaust gas permeates the hollow fiber membranes (112), thereby humidifying the dry gas flowing along the hollows of the hollow fiber membranes (112).

[0052] Meanwhile, the flow rate of the exhaust gas flowing from the fuel cell stack (B) into the exhaust gas inlet (111a) can be controlled by an exhaust gas flow rate control unit (150) that controls the opening of the exhaust gas inlet (111a) according to the temperature of the incoming exhaust gas. The exhaust gas flow rate control unit (150) can automatically determine the degree of opening and closing according to the temperature of the exhaust gas flowing into the exhaust gas inlet (111a) without the need for separate additional parts. Therefore, the number of parts of the membrane humidifier is reduced, allowing for a smaller size and reduced manufacturing costs. This exhaust gas flow rate control unit (150) will be described in detail with reference to FIG. 4.

[0054] FIG. 4 is an enlarged view of the exhaust gas flow control unit of a fuel cell membrane humidifier according to one embodiment of the present invention.

[0055] As shown in FIG. 4, the exhaust gas flow control unit (150) is formed in the exhaust gas inlet (111a) and can control the opening of the exhaust gas inlet (111a) according to the temperature of the exhaust gas flowing in from the fuel cell stack (S).

[0056] The exhaust gas flow control unit (150) may be formed on the inner wall of the exhaust gas inlet (111a). The exhaust gas flow control unit (150) may be formed in a ring shape on the inner wall of the exhaust gas inlet (111a). Alternatively, an annular fixing groove (151) may be formed on the inner wall of the exhaust gas inlet (111a), and the exhaust gas flow control unit (150) may be formed in a ring shape and inserted and fixed into the annular fixing groove (151).

[0057] The flue gas flow control unit (150) may be made of a material that undergoes negative thermal expansion depending on the temperature of the flue gas. The flue gas flow control unit (150) may include a negative thermal expansion material that expands in a first temperature range and contracts in a second temperature range greater than the first temperature range. That is, the flue gas flow control unit (150) may include a negative thermal expansion material that expands at low temperatures and contracts at high temperatures.

[0058] Most materials increase in length or volume due to thermal expansion as temperature rises, but conversely, negative thermal expansion materials have the property of contracting as temperature rises. Such negative thermal expansion materials may be materials containing bismuth (Bi).

[0059] Specifically, negative thermal expansion materials may be materials containing oxides of bismuth (Bi), lanthanum (La), and nickel (Ni). More specifically, Bi 0.95 La 0.05 It can be NiO3 (bismuth-lanthanum nickel oxide). Bi 0.95 La 0.05 NiO3 is 82 parts per million (-82 x 10⁻¹⁰) per 1°C rise in temperature. -6 It represents negative thermal expansion of / ℃.

[0060] Furthermore, specifically, negative thermal expansion materials may be materials containing oxides of bismuth (Bi), iron (Fe), and nickel (Ni). More specifically, BiNi oxide having a structure called 'perovskite'. 1-x Fe x It can be O3 (bismuth-nickel-iron oxide). BiNi 1-x Fe x O3 is 187 parts per million (-187 x 10⁻⁶) per 1°C rise in temperature in the temperature range near room temperature. -6 It exhibits negative thermal expansion ( / ℃). Therefore, Bi 0.95 La 0.05 It can produce substantially the same effect with half the amount compared to NiO3.

[0062] The operating state of the exhaust gas flow rate control unit (150) configured as above will be explained with reference to FIGS. 5 and FIGS. 6.

[0063] FIG. 5 is a diagram illustrating the operating state of the exhaust gas flow control unit (150) in a low-power environment. When the output of the fuel cell stack (S) is generally less than 40 kW, it can be considered a low-power environment. In a low-power environment, exhaust gas at a relatively low temperature is supplied from the fuel cell stack (S). Here, the low temperature may be a first temperature range of approximately 50°C or less.

[0064] Since the exhaust gas is at a low temperature, the exhaust gas flow control unit (150), which has negative thermal expansion properties, expands, and the opening diameter of the exhaust gas inlet (111a) becomes L1. Accordingly, a relatively small amount of low-temperature exhaust gas is supplied to the humidification module (110).

[0065] FIG. 6 is a diagram illustrating the operating state of the exhaust gas flow control unit (150) in a high-power environment. When the output of the fuel cell stack (S) is generally 40 kW or more, it can be considered a high-power environment. In a high-power environment, exhaust gas at a relatively high temperature is supplied from the fuel cell stack (S). Here, the high temperature may be a second temperature range greater than the first temperature range, approximately in the range of 50 to 150°C.

[0066] Since the exhaust gas is at a high temperature, the exhaust gas flow control unit (150), which has negative thermal expansion properties, contracts, so that the opening diameter of the exhaust gas inlet (111a) becomes L2, which is larger than L1. Accordingly, a relatively larger amount of high-temperature exhaust gas is supplied to the humidification module (110) than in a low-output situation.

[0068] A fuel cell membrane humidifier according to one embodiment of the present invention as described above is configured with a simple structure having a small number of parts, and depending on the output condition of the fuel cell stack (S), the exhaust gas flow control unit (150) can automatically adjust the opening of the exhaust gas inlet (111a), thereby allowing the size of the membrane humidifier to be reduced and manufacturing costs to be reduced.

[0070] Although an embodiment of the present invention has been described above, those skilled in the art may modify and change the present invention in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of the present invention as described in the claims, and such modifications and changes are also to be included within the scope of the rights of the present invention. Explanation of the symbols

[0072] 100: Fuel cell membrane humidifier 110: Humidification module 111a: Flue gas inlet 111b: Flue gas outlet 120 : Cap 150 : Exhaust gas flow control unit B: Blower S: Fuel cell stack

Claims

Claim 1 A fuel cell membrane humidifier capable of controlling the flow of exhaust gas, comprising: an exhaust gas inlet through which exhaust gas from a fuel cell stack is introduced; and an exhaust gas flow control unit formed in the exhaust gas inlet and controlling the opening of the exhaust gas inlet according to the temperature of the exhaust gas introduced from the fuel cell stack, wherein the exhaust gas flow control unit comprises a negative thermal expansion material that expands in a first temperature range and contracts in a second temperature range greater than the first temperature range, and wherein the exhaust gas flow control unit has a ring shape and forms the opening inwardly to the ring shape and is inserted into an annular fixing groove formed on the inner wall of the exhaust gas inlet. Claim 2 delete Claim 3 In claim 1, the exhaust gas flow control unit is a fuel cell membrane humidifier capable of controlling the exhaust gas flow including bismuth (Bi). Claim 4 In claim 1, the flue gas flow control unit comprises an oxide of bismuth (Bi), lanthanum (La), and nickel (Ni), and is a fuel cell membrane humidifier capable of controlling the flue gas flow. Claim 5 In claim 1, the exhaust gas flow control unit comprises an oxide of bismuth (Bi), iron (Fe), and nickel (Ni), and is a fuel cell membrane humidifier capable of controlling the exhaust gas flow. Claim 6 delete Claim 7 delete Claim 8 A fuel cell membrane humidifier capable of controlling the flue gas flow rate, comprising, in any one of claims 1, 3, 4 and 5, a mid-case, a cap coupled to the mid-case, and a humidification module disposed within the mid-case and accommodating a plurality of hollow fiber membranes, wherein the flue gas inlet is formed in the mid-case. Claim 9 A fuel cell membrane humidifier capable of controlling flue gas flow, wherein the humidification module comprises an inner case accommodating a plurality of hollow fiber membranes and at least one cartridge including a potting portion formed at the end of the inner case.

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