Recirculation blower for fuel cell system, and solid oxide fuel cell system comprising same

Abstract

The present invention relates to a recirculation blower for a fuel cell system, and a solid oxide fuel cell system comprising same, the blower comprising: an impeller for suctioning stack off-gas and mixing, compressing, and discharging same; an impeller housing having, therein, a space in which the impeller is accommodated; a motor that provides driving force for rotating the impeller; a rotary shaft for rotating the impeller by means of the driving force of the motor; a coupling provided between the rotary shaft and a motor rotary shaft so as to correct positions thereof and to position the rotary shafts at the center part of the coupling; a cooling chamber provided outside the rotary shaft in order to cool the rotary shaft through the flow of cooling water; and a mechanical seal, which forms a water layer for sealing so that hydrogen is prevented from leaking in the axial direction in the cooling chamber.

Description

Recirculating blower for fuel cell system and solid oxide fuel cell system including same

[0001] The present invention relates to a recirculating blower for a fuel cell system and a solid oxide fuel cell system including the same, and more particularly, to a recirculating blower capable of improving the power generation efficiency of a fuel cell system by recirculating stack off-gas discharged from a fuel cell stack and ensuring stability even in a high-temperature environment, and a solid oxide fuel cell system including the same.

[0002] In general, a fuel cell is a power generator that generates water and electricity through an electrochemical reaction between hydrogen (fuel) and oxygen. The name and operating temperature of each fuel cell are determined by the electrolyte material. In a solid oxide fuel cell (SOFC), oxygen from the cathode passes through a solid electrolyte to the fuel electrode in ion form, typically operating at temperatures between 650 and 900°C.

[0003] In order to improve the efficiency of the system, it is important for high-temperature fuel cells such as SOFC to efficiently utilize the heat and unreacted fuel generated from the electrochemical reaction of the stack. In order to improve the fuel use efficiency, a recirculation blower is provided to recirculate the unreacted fuel discharged from the fuel cell stack back into the fuel cell stack.

[0004] However, recirculating fans installed in high-temperature fuel cells like SOFCs must operate in high-temperature environments of 650-900°C. Therefore, the high-temperature gases flowing within the fan can cause stability issues in components like the rotating shaft. For example, if a metal rotating shaft is exposed to excessive heat from the high-temperature gases, deformation such as warping can occur, potentially preventing normal operation.

[0005] Therefore, a recirculating blower configuration that can secure stability while increasing fuel efficiency in a high-temperature environment is required.

[0006] The present invention has been devised to solve the above problems, and its purpose is to provide a recirculating blower for a fuel cell system having a structure that can improve the power generation efficiency of a fuel cell system by recycling stack off-gas discharged from a fuel cell stack and ensure stability even in a high-temperature environment.

[0007] In addition, in order to prevent deformation of the rotating shaft constituting the recirculating blower, a mechanical seal is applied to a water-cooled cooling structure to block contact between stack off-gas and external air, and a coupling is applied to compensate for the position between the rotating shaft and the motor rotating shaft, thereby providing a recirculating blower for a fuel cell system that can secure long-term stability.

[0008] In addition, the purpose is to provide a solid oxide fuel cell system that can reduce the amount of fuel supplied to the system through fuel recirculation without lowering the temperature through thermal coordination, shortest distance arrangement, integration, etc. of mechanical devices such as heat exchangers, reformers, combustors, and stacks exposed to high temperature areas.

[0009] In order to achieve the above object of the present invention, the present invention provides a recirculation blower for a fuel cell system, which is installed in a fuel line to recirculate stack off-gas discharged from a fuel cell stack, the recirculation blower comprising: an impeller rotatably installed to suck in the stack off-gas, mix and compress it by forming a vortex, and discharge it; an impeller housing having a space therein for accommodating the impeller; a motor providing a driving force for rotating the impeller; a rotational shaft for rotating the impeller through the driving force of the motor; a coupling installed between the rotational shaft and the motor rotational shaft to compensate for position and position the rotational shaft at the center; a cooling chamber installed on the outside of the rotational shaft to cool the rotational shaft through a cooling water flow; and a mechanical seal that forms a water film to seal and block contact between the stack off-gas and the outside air within the cooling chamber and prevent hydrogen from leaking in the axial direction.

[0010] The recirculating blower of the present invention is characterized by having a structure in which a high temperature section installed inside a hot box and a low temperature section installed outside the hot box are separated based on the rotation axis, and the motor is installed outside the hot box and the remaining components are installed inside the hot box, so that the stack off gas continues to circulate within the hot box, thereby maximizing thermal efficiency.

[0011] In the present invention, a fixed shaft for stably installing the impeller housing within the hot box may be further installed at the upper and lower portions of the rotating shaft.

[0012] Meanwhile, the mechanical seal may include a fixed sheet positioned inside the cooling chamber body and fixedly installed by being fitted to the rotating shaft, an auxiliary seal sealing between the cooling chamber body and the fixed sheet, a rotary seal sealing between the rotating shaft and the fixed sheet while rotating together with the rotating shaft, an auxiliary seal sealing between the rotating seal and the rotating shaft, and a spring fitted to the rotating shaft and having elastic ends to prevent the contact surface between the fixed sheet and the rotating seal from widening.

[0013] In the present invention, two mechanical seals are installed on both sides of the cooling chamber, and the first mechanical seal installed on the impeller housing side forms a water film in the gap between the rotating seal and the fixed seat to completely separate the fluid from the fluid entering and exiting through the impeller housing, and the second mechanical seal installed on the other side can prevent the cooling water from leaking out of the cooling chamber.

[0014] A baffle may be formed on the inner surface of the outlet side of the impeller housing so that gas / liquid, gas and liquid fluids collide and are mixed, and then discharged through the outlet.

[0015] In addition, the impeller is characterized by comprising a disk in the shape of a circular plate and a plurality of blades arranged radially along the circumference direction on the outer surface of the disk, the blades having the same size for weight balancing of the rotating body, and the blades being joined to the disk by brazing them into grooves formed at regular intervals on the disk.

[0016] In the present invention, the cooling chamber is formed with a cooling water inlet and outlet so that water-cooling is performed, and the cooling water inlet is formed to be located at the lower portion of the rotating shaft, and the cooling water outlet is formed to be located at the upper portion of the rotating shaft, so that the cooling water can be filled from the bottom of the cooling chamber to suppress bubble generation.

[0017] Additionally, at least one bracket may be installed on the lower fixed shaft to have a vibration-resistant structure, and a damper may be installed on the bracket.

[0018] Meanwhile, in order to achieve the above object of the present invention, the present invention comprises a fuel cell stack, a fuel supply unit for supplying fuel to the fuel cell stack, an air supply unit for supplying air to the fuel cell stack, a heat exchanger for increasing the temperature of the fuel supplied from the fuel supply unit through stack fuel off-gas discharged from the fuel cell stack and supplying the fuel off-gas to a multi-functional steam reformer, a multi-functional catalytic combustor for increasing the temperature of the air supplied from the air supply unit and supplying the air to the multi-functional steam reformer by utilizing the heat caused by the combustion reaction of the stack cathode off-gas discharged from the fuel cell stack and the fuel off-gas of a second branch line branched off after passing through the heat exchanger, a multi-functional steam reformer for receiving the heat required for the reforming reaction through a large amount of air whose temperature has been increased by the combustion reaction in the multi-functional catalytic combustor and reforming the fuel supplied from the heat exchanger into hydrogen and supplying it to the fuel cell stack, thereby performing heat exchange using the heat generated from the gas flow of the cathode and the fuel electrode, and a stack fuel off-gas discharged from the fuel cell stack. A solid oxide fuel cell system is provided that includes a recirculation blower installed in a fuel line to continuously recirculate off-gas.

[0019] According to the present invention as described above, the recirculating blower for a fuel cell system of the present invention recirculates stack off-gas discharged from a fuel cell stack, thereby improving the power generation efficiency of the fuel cell system and ensuring stability even in a high-temperature environment.

[0020] In addition, in order to prevent deformation of the rotating shaft constituting the recirculating blower, a mechanical seal is applied to the water-cooled cooling structure to block contact between the stack off-gas and the outside air, and a coupling is applied to compensate for the position between the rotating shaft and the motor rotating shaft, thereby ensuring long-term stability.

[0021] In addition, the recirculating blower is configured as a high-temperature section installed inside the hotbox and a low-temperature section installed outside the hotbox, and the motor is installed outside the hotbox and the remaining components are installed inside the hotbox, so that the stack off-gas continues to circulate inside the hotbox, thereby maximizing thermal efficiency, and through thermal coordination, shortest distance arrangement, integration, etc. of mechanical devices such as a heat exchanger, reformer, combustor, and stack inside the hotbox, there is an effect of reducing the amount of fuel supplied to the system through fuel recirculation without lowering the temperature.

[0022] FIG. 1 is a schematic diagram showing the configuration of a solid oxide fuel cell system including a recirculating blower according to the present invention.

[0023] Figure 2 is a schematic diagram showing the overall flow of fuel and air in a solid oxide fuel cell system according to the present invention.

[0024] Figure 3 is a (a) side cross-sectional view and (b) front cross-sectional view showing the configuration of the recirculating blower of the present invention.

[0025] Figure 4 is an enlarged cross-sectional view showing the main components of the recirculating blower of the present invention.

[0026] Figure 5 is an enlarged cross-sectional view showing the configuration of a mechanical seal in the present invention.

[0027] Figure 6 is a perspective view illustrating a coupling according to the present invention.

[0028] Figure 7 is a drawing showing the structure and principle of a coupling according to the present invention.

[0029] Figure 8 is a schematic diagram showing the cooling water flow of a recirculating blower according to the present invention.

[0030] Figure 9 is a drawing illustrating a vibration-resistant structure according to the present invention.

[0031] Fig. 10 is a drawing showing a disk connection structure in the impeller of the present invention.

[0032] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. First, when assigning reference numerals to components in each drawing, it should be noted that, where possible, identical components are assigned the same numerals even if they are shown in different drawings. In this case, the configuration and operation of the present invention depicted in and described by the drawings are described as at least one embodiment, and the technical concept of the present invention and its core configuration and operation are not limited thereby.

[0033] FIG. 1 is a schematic diagram showing the configuration of a solid oxide fuel cell system including a recirculating blower according to the present invention, and FIG. 2 is a schematic diagram showing the overall configuration of the flow of fuel and the flow of air in the solid oxide fuel cell system according to the present invention.

[0034] The present invention relates to a fuel recirculating solid oxide fuel cell system capable of maximizing thermal efficiency by recirculating fuel, comprising: a fuel cell stack (10); a fuel supply unit (20) for supplying fuel to the fuel cell stack (10); an air supply unit (30) for supplying air to the fuel cell stack (10); a heat exchanger (40) for increasing the temperature of newly supplied fuel by utilizing the heat of stack fuel anode off-gas discharged from the fuel cell stack (10); a multi-functional catalytic combustor (50) for utilizing the stack air anode off-gas discharged from the fuel cell stack (10) and the fuel off-gas that has passed through the heat exchanger as a heat source; a multi-functional steam reformer (60) for reforming fuel, the temperature of which has been increased in the heat exchanger (40), into hydrogen and supplying the reformed fuel to the fuel cell stack (10); and a heat exchanger (40) for supplying the stack fuel anode off-gas discharged from the fuel cell stack (10) to the fuel cell stack (10). It is configured to include a recirculation blower (70) installed in the fuel line to continuously recirculate off-gas.

[0035] The above fuel cell stack (10) is a structure in which a plurality of cells are stacked, and is configured to increase output by connecting each cell in series. It is typically composed of repeatedly used parts such as cells, separators, current collectors, and sealants, a manifold for smoothly supplying gas to the fuel electrode and the air electrode, various types of stack fastening parts, and a busbar for connecting electricity.

[0036] In the fuel cell system of the present invention, the fuel cell stack (10) and BOP (Balance of Plant) are installed in a module form, enabling a stack-customized design, and are characterized by designing an integrated BOP module for optimized heat management.

[0037] That is, in the present invention, the main components of the fuel cell stack (10), heat exchanger (40), multi-functional catalytic combustor (50), multi-functional steam reformer (60), and recirculating blower (70) are installed in a hotbox (80), and as shown in FIG. 1, the fuel cell stack (10) and BOP (Balance of Plant) are installed in a module form so that each module can be separated during maintenance, thereby enabling replacement of the stack (10) when necessary.

[0038] The above BOP (Balance of plant) module is a part related to supporting components and auxiliary systems necessary for power generation, such as transmitting energy, excluding the power generation device, and includes the heat exchanger (40), multi-functional catalytic combustor (50), multi-functional steam reformer (60), and recirculating blower (70) in the present invention.

[0039] The fuel cell system of the present invention has a structure in which a fuel cell stack (10) and a BOP (Balance of Plant) are installed in a hot box (80) and stack fuel electrode off-gas is continuously circulated within the hot box (80) to maximize thermal efficiency.

[0040] That is, in order for the stack fuel off-gas discharged from the stack (10) to be continuously recycled after increasing the temperature of the newly supplied fuel from the heat exchanger (40), in the present invention, a fuel line (107) for fuel recirculation is connected to the heat exchanger (40), and a recirculation blower (70) is installed in the fuel line (107).

[0041] FIG. 3 is a (a) side cross-sectional view and (b) front cross-sectional view showing the configuration of a recirculating blower of the present invention, FIG. 4 is an enlarged cross-sectional view showing the main configuration of the recirculating blower of the present invention, and FIG. 5 is an enlarged cross-sectional view showing the configuration of a mechanical seal in the present invention.

[0042] The recirculating blower (70) of the present invention is installed in the fuel line (107) to recirculate the stack off-gas discharged from the fuel cell stack (10), and includes an impeller (710) for sucking the stack off-gas, mixing and compressing it by forming a vortex, and discharging it, an impeller housing (720) having a space therein for accommodating the impeller (710), a motor (730) for providing a driving force for rotating the impeller (710), a rotation shaft (740) for rotating the impeller (710) through the driving force of the motor (730), a coupling (750) installed between the rotation shaft (740) and the motor rotation shaft (732), a cooling chamber (760) installed on the outside of the rotation shaft (740) for cooling the rotation shaft (740) through a coolant flow, and a cooling chamber (760) for cooling the stack off-gas and the outside air within the cooling chamber (760). It is composed of a mechanical seal (770)(790) that forms a water film to seal the body and prevent hydrogen from leaking in the axial direction while blocking contact between the two.

[0043] The recirculating blower (70) of the present invention is configured to be divided into a high temperature section installed inside a hot box (80) based on the rotation shaft (740) and a low temperature section installed outside the hot box (80). Here, the high temperature section is a rotating section for rotating the impeller (710), and the low temperature section is a driving section that provides driving force for rotating the impeller (710).

[0044] That is, the motor (730) is installed outside the hot box (80), and the remaining components except for the motor are installed inside the hot box (80), so that the stack off gas is continuously circulated within the hot box, thereby having a structure that maximizes thermal efficiency.

[0045] Meanwhile, the impeller (710) is installed rotatably within the impeller housing (720) so as to suck in stack off-gas, mix and compress it by forming a vortex, and discharge it again.

[0046] Fig. 10 is a drawing showing a disk connection structure in an impeller of the present invention, wherein the impeller (710) is composed of a disk (712) in the shape of a circular plate and a plurality of blades (714) arranged radially along the circumferential direction on the outer surface of the disk (712).

[0047] The above blades (714) have the same size for weight balancing of the rotating body, and are combined into grooves formed at regular intervals in the disk (712). In the present invention, the same grooves are formed in the disk (712), and the blades (714) are brazed (716) using a brazing sheet to join them to the disk (712).

[0048] The impeller (710) in the present invention may be made of stainless steel (SUS 310S). SUS 310S is a heat-resistant stainless steel used in high-temperature environments, and contains a lot of chromium and nickel among austenitic stainless steels, so it has excellent corrosion resistance and heat resistance.

[0049] Typically, impellers are manufactured by casting, but if the impeller is small, it is difficult to manufacture the impeller using the conventional casting method. Therefore, in the present invention, identical grooves are formed in the disk (712) and the blades (714) are brazed and joined using a brazing sheet, so that all blades (714) radially connected to the disk (712) can have the same shape.

[0050] Meanwhile, the impeller housing (720) is provided with an inlet (722) and an outlet (724) to suck in and then discharge stack off-gas into the gas flow space where the impeller (710) is accommodated.

[0051] Through the above inlet (722), the gaseous / liquid, gaseous, and liquid fluids are supplied into the impeller housing (720) where the impeller (710) is located. Since the impeller (710) continues to rotate, a suction effect is created, so the fluid is sucked in.

[0052] In this case, a baffle (721) may be formed on the inner surface of the outlet (724) side of the impeller housing (720) so that the sucked fluid, i.e., gas / liquid, gas and liquid fluids collide and are mixed, and then discharged through the outlet (724).

[0053] Due to this baffle (721) structure, the fluid hits the baffle (721) and is discharged outside the blower. At this time, a mixing effect is generated when the fluid hits the baffle (721).

[0054] In addition, the impeller (710) of the present invention forms the same groove in the disk (712) and joins the blades (714) by brazing them using a brazing sheet, so that a quantitative supply of fluid is possible due to a certain gap between the blades (714), and a vortex is formed around the blades (714) due to the space between the blades (714) and the rotational movement, so that the fluid can be evenly mixed.

[0055] With regard to the material of the impeller (710) and impeller housing (720) of the present invention, when the recirculating blower of the present invention is applied to a solid oxide fuel cell, it is preferable to apply a high-temperature material such as Inconel, crofer, or STS400 series with a high nickel content, and since it is used at high temperatures, the impeller housing (720) can be manufactured using a welding type.

[0056] Meanwhile, when the recirculating blower of the present invention is applied to a polymer exchange membrane fuel cell, it is possible to apply STS316 and STS316S materials having relatively low nickel content, the flow rate of the cooling chamber can be relatively low, and it is possible to apply at relatively low temperatures, so it is possible to manufacture the impeller housing (720) as a fastening type using bolts.

[0057] In the present invention, a fixed shaft (782) (784) may be installed to stably install the impeller housing (720) within the hot box (80). The fixed shaft may be installed at the upper and lower portions of the rotation shaft (740), respectively, and both ends thereof may be supported on the inner surface of the impeller housing (720) and the hot box (80) to serve as a stator.

[0058] Meanwhile, since the recirculating blower (70) of the present invention is installed in a high-temperature fuel cell and must operate in a high-temperature environment of 650 to 900°C, deformation may occur in the rotation shaft (740) due to the high-temperature gas flowing inside the blower.

[0059] That is, since the above-mentioned rotation shaft (740) is made of a metal material (Inconel 600), if it receives a lot of heat from high-temperature gas, deformation such as bending may occur, which may cause a problem in which normal operation is impossible.

[0060] Therefore, to prevent this, a configuration for cooling the rotation shaft (740) is absolutely necessary.

[0061] Accordingly, the present invention provides a cooling chamber (760) for cooling the rotation shaft (740). The cooling chamber (760) is installed outside the rotation shaft (740) and has a water-cooling structure for cooling the rotation shaft (740) through a cooling water flow, and a cooling water inlet (764) and outlet (766) are formed to enable water-cooling.

[0062] In the present invention, it is preferable that the cooling water inlet (764) be formed to be positioned at the lower portion of the rotating shaft (740), and the cooling water outlet (766) be formed to be positioned at the upper portion of the rotating shaft (740). In this case, there is an advantage in that the cooling water is filled from below the cooling chamber (760), thereby suppressing bubble generation.

[0063] FIG. 8 is a schematic diagram showing the flow of cooling water in a recirculating blower according to the present invention, wherein cooling water is supplied to a cooling water inlet (764) of a cooling chamber (760) through a water tank, and the operation and status of the device can be checked through a pressure sensor (PS) and a temperature sensor (TS).

[0064] Meanwhile, a housing may be separately installed outside the cooling chamber (760) for installation of the cooling chamber (760).

[0065] This cooling chamber (760) cools the rotating shaft (740) by allowing cooling water to flow outside the rotating shaft (740), but also forms a water film on the mechanical seal (770) (790) to perform a sealing function.

[0066] As shown in FIG. 4, the above mechanical seals (770)(790) may be installed in two on both sides of the cooling chamber (760). Each mechanical seal may include a fixed seat (772)(792) positioned inside the cooling chamber body (762) and fixedly installed by fitting into the rotation shaft (740), an auxiliary seal (774)(794) sealing between the cooling chamber body (762) and the fixed seat, a rotation seal (776)(796) that is fitted into the rotation shaft (740) and rotates together with the rotation shaft so that the contact surface with the fixed seat (772)(792) is sealed, an auxiliary seal (778)(798) sealing between the rotation seal and the rotation shaft, and a spring (779)(799) that is fitted into the rotation shaft (740) and has both ends elastically supported.

[0067] The mechanical seals (770)(790) are installed in two numbers on both sides of the cooling chamber (760), and are composed of two springs (779)(799) fitted to the rotation shaft (740), and a rotation seal (776a)(796a) fitted to the rotation shaft (740) and rotating together with the rotation shaft can be interposed between the springs.

[0068] In this case, an auxiliary seal may also be installed between the rotary seal (776a)(796a) and the rotary shaft (740), and two springs (779)(799) press the rotary seal (or auxiliary seal) at both ends, thereby sealing by preventing the contact surface between the fixed seat (772)(792) and the rotary seal (776)(796) from widening. Since the rotary shaft, fixed seat (772)(792), and rotary seal (776)(796) are made of metal, an auxiliary seal is used to reduce friction between metals.

[0069] Among the mechanical seals (770)(790), the first mechanical seal (770) installed on the impeller housing (720) side forms a water film in the gap between the rotating seal (776) and the fixed seat (772) to completely separate the fluid entering and exiting through the impeller housing (720), and the second mechanical seal (790) installed on the other side can prevent the cooling water from leaking out of the cooling chamber (760).

[0070] In particular, the first mechanical seal (770) serves to prevent gas from flowing toward the cooling chamber (toward the rotation shaft) from the impeller side by forming a water film in a part where there is a slight gap between the components.

[0071] This is a very important element for high-temperature SOFC operation. Fuel, i.e., hydrogen, flows in the internal space of the impeller housing (720) in which the impeller (710) rotates. However, since the rotation shaft (740) continues to rotate, there may be play. If the fuel flows toward the rotation shaft, a fire may occur. Therefore, there must be no fuel leaking toward the rotation shaft.

[0072] Typically, unreacted hydrogen at a temperature of 400-500°C will spontaneously ignite, and if exposed to oxygen in the air, it will react and cause a fire. Therefore, even a small amount of hydrogen must be prevented from leaking in the axial direction, and sealing between the impeller housing (720) and the rotating shaft (740) is very important.

[0073] In the present invention, a water-cooled cooling chamber (760) is installed to cool a rotating shaft (740), and a mechanical seal (770) (790) structure is included inside the cooling chamber, thereby forming a water film through the mechanical seal (770) (790) while cooling the rotating shaft, thereby preventing fuel from leaking toward the rotating shaft.

[0074] Referring to FIG. 5, a slight play may occur at the contact surface (S) between the cooling chamber body (762) and the rotation shaft (740), and between the cooling chamber body (762) and the fixed seat (792) (including the auxiliary seal), and a water film is formed at this part to prevent the fuel, i.e., hydrogen, within the impeller housing (720) from flowing toward the rotation shaft.

[0075] In addition, a water film is formed at the contact surface (F) between the rotating seal (796) and the fixed seat (792), completely separating the fluid flowing in and out through the impeller housing (720), and the second mechanical seal (790) installed on the other side can prevent the cooling water from leaking out of the cooling chamber (760).

[0076] Fig. 6 is a perspective view illustrating a coupling according to the present invention, and Fig. 7 is a drawing illustrating the structure and principle of the coupling according to the present invention.

[0077] In the present invention, a coupling (750) is applied to compensate for the position between the rotation shaft (740) and the motor rotation shaft (732) and to position the rotation shaft (740) at the center.

[0078] The above coupling (750) includes a rotary shaft insertion portion (752) into which a rotary shaft (740) is inserted, a fixing screw (754) for fixing the rotary shaft and the coupling, and a plurality of iron plates (758) for compensating for the position between the rotary shaft (740) and the motor rotary shaft (732) through a variable clearance (756).

[0079] By applying this coupling (750), long-term stability can be secured by compensating the position between the rotation axis (740) and the motor rotation axis (732).

[0080] Figure 9 is a drawing illustrating a vibration-resistant structure according to the present invention.

[0081] In addition, the present invention may have at least one bracket (786) installed on the lower fixed shaft (784) to have a vibration-resistant structure, and a damper (788) may be installed on the bracket (786).

[0082] The above bracket (786) and damper (788) are installed to suppress vibration within the device when the impeller rotates. Since performance may deteriorate when vibration occurs and the rotating shaft is subjected to vibration, such a vibration-resistant structure is required.

[0083] The above damper (788) may be an air damper that injects gas, and at this time, the pressure can be controlled through an EPC (Electronic pressure controller).

[0084] In a solid oxide fuel cell system to which the recirculating blower of the present invention is applied, fuel supplied from the fuel supply unit (20) is introduced into the heat exchanger (40) through the fuel inlet line (102), and a fuel line (106) is connected to the heat exchanger (40) to allow the stack fuel off-gas to be introduced so as to increase the temperature of the fuel newly supplied from the fuel supply unit (20) by utilizing the heat of the stack fuel off-gas discharged from the fuel cell stack (10).

[0085] In order for the fuel off-gas discharged from the stack (10) to be continuously recirculated after raising the temperature of the newly supplied fuel from the heat exchanger (40), a fuel line (107) for fuel recirculation is connected to the heat exchanger (40), and a recirculation blower (70) is installed in the fuel line (107).

[0086] The fuel off-gas suctioned by the above recirculation blower (70) is branched to the fuel inlet line (102) and the multi-functional catalytic combustor (50) to provide recirculated fuel, which is a feature of the present invention.

[0087] That is, the fuel off-gas passing through the recirculating blower (70) is branched into two lines (109) (110), and the first branch line (109) is connected to the fuel inlet line (102) so that it is mixed with new fuel supplied from the fuel supply unit (20) and re-supplied to the stack (10) through the heat exchanger (40), and the second branch line (110) is connected so that the fuel off-gas flows to the multi-functional catalytic combustor (50).

[0088] The fuel off-gas that flows into the fuel inlet line (102) through the first branch line (109) flows into the heat exchanger (40) again, and the fuel off-gas that flows into the multi-functional catalytic combustor (50) through the second branch line (110) meets the air off-gas and is discharged after a combustion reaction, and a large amount of air supplied from the air supply unit receives the heat of combustion by the multi-functional catalytic combustor having a heat exchanger structure, thereby increasing its temperature.

[0089] In the present invention, the fuel recirculation flow of the fuel line is in the order of fuel cell stack (10) → heat exchanger (40) → recirculation blower (70) → heat exchanger (40) → multi-functional steam reformer (60) → stack (10).

[0090] In addition, the flow in the direction of the multifunctional catalytic combustor (50) of the fuel line can be in the order of the fuel cell stack (10) → heat exchanger (40) → recirculation blower (70) → multifunctional catalytic combustor (50) → exhaust.

[0091] In this way, the fuel whose temperature has increased in the heat exchanger (40) is provided to a multi-functional steam reformer (60) that utilizes the heat of high-temperature air while performing heat exchange to increase the temperature of newly introduced fuel, and the fuel reformed through the multi-functional steam reformer (60) is supplied to a fuel cell stack (10).

[0092] In addition, the stack heat generated by the FC reaction in the fuel cell stack (10), fuel off-gas, and hot steam are first evenly mixed by a recirculating blower and then mixed with NG (city gas) supplied from a fuel supply unit and reformed in a multi-functional steam reformer. By controlling the flow rate of NG (city gas) supplied from the fuel supply unit (20), the external / internal reforming ratio of the fuel cell stack (10) can be adjusted, thereby controlling the temperature of the stack.

[0093] In the present invention, for additional stack temperature control, city gas (NG) is directly supplied separately to the fuel inlet line (105) between the multi-functional steam reformer (60) and the stack (10) to force internal reforming of the stack, thereby controlling the stack temperature.

[0094] Meanwhile, looking at the flow of air in the fuel cell system of the present invention, air is supplied from the air supply unit (30) and introduced into the multifunctional catalytic combustor (50).

[0095] The multifunctional catalytic combustor (50) receives fuel off-gas through the second branch line (110) and at the same time receives high-temperature stack cathode off-gas discharged from the stack, and uses the heat of the stack cathode off-gas to increase the temperature of the newly supplied air.

[0096] Thereafter, the air whose temperature has increased through the multi-functional catalytic combustor (50) is provided to a multi-functional steam reformer (60) that utilizes the heat of the high-temperature air.

[0097] High temperature air is supplied from the multi-functional steam reformer (60) to the fuel cell stack (10).

[0098] The stack air electrode off-gas discharged after the FC reaction in the above stack (10) is introduced into the multifunctional catalytic combustor (50), and the stack air electrode off-gas introduced into the multifunctional catalytic combustor (50) is discharged after undergoing a combustion reaction with the fuel off-gas supplied to the multifunctional catalytic combustor.

[0099] The above description is merely an illustrative description of the technical idea of ​​the present invention, and those skilled in the art can make various modifications and variations without departing from the essential characteristics of the present invention. In addition, the embodiments disclosed in the present invention are not intended to limit the technical idea of ​​the present invention, but rather to explain it, and the scope of the technical idea of ​​the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of the rights of the present invention.

Claims

1. In a recirculation blower installed in a fuel line to recirculate stack off-gas discharged from a fuel cell stack, An impeller rotatably installed to suck in the stack off-gas, mix and compress it by forming a vortex, and discharge it; An impeller housing having a space therein in which the impeller is accommodated; A motor that provides driving force to rotate the impeller; A rotating shaft for rotating the impeller through the driving force of the motor; A coupling installed between the above rotational axis and the motor rotational axis to compensate for position and position the rotational axis at the center; A cooling chamber installed outside the above-mentioned rotating shaft to cool the above-mentioned rotating shaft through a cooling water flow; and A mechanical seal that forms a water film to seal the cooling chamber and prevent hydrogen from leaking in the axial direction while blocking contact between the stack off-gas and the outside air; A recirculating blower for a fuel cell system including:

2. In claim 1, It is divided into a high temperature section installed inside the hot box and a low temperature section installed outside the hot box based on the above rotation axis. A recirculating blower for a fuel cell system having a structure in which the above motor is installed outside the hot box and the remaining components are installed inside the hot box, thereby maximizing thermal efficiency by allowing stack off-gas to continuously circulate within the hot box.

3. In claim 1, A recirculating blower for a fuel cell system, characterized in that a fixed shaft for stably installing the impeller housing within a hot box is further installed at the upper and lower portions of the rotating shaft.

4. In claim 1, The above mechanical seal is a fixed seat located inside the cooling chamber body and fixedly installed by being fitted to the rotating shaft; An auxiliary seal that seals between the cooling chamber body and the fixed sheet; A rotary seal fitted to the above rotary shaft and rotating together with the above rotary shaft, the contact surface of which is sealed with the above fixed sheet; An auxiliary seal that seals between the above rotary seal and the rotary shaft; and A spring fitted to the above-mentioned rotating shaft and having both ends elastic to prevent the contact surface between the fixed sheet and the rotating seal from widening; A recirculating blower for a fuel cell system, characterized by including:

5. In claim 4, The above mechanical seals are installed in two on both sides of the cooling chamber, The first mechanical seal installed on the impeller housing side forms a water film in the gap between the rotating seal and the fixed seat, completely separating it from the fluid entering and exiting through the impeller housing. A recirculating blower for a fuel cell system, characterized in that a second mechanical seal installed on the other side prevents coolant from leaking outside the cooling chamber.

6. In claim 1, A recirculating blower for a fuel cell system, characterized in that a baffle is formed on the inner surface of the outlet side of the impeller housing so that gas / liquid, gas and liquid fluids collide and are mixed and then discharged through the outlet.

7. In claim 1, The above impeller is composed of a disk in the shape of a circle and a plurality of blades arranged radially along the circumference of the outer surface of the disk. A recirculating blower for a fuel cell system, wherein the blades have the same size for weight balancing of the rotating body and are joined to the disk by brazing the blades into grooves formed at regular intervals on the disk.

8. In claim 1, A recirculating blower for a fuel cell system, characterized in that the cooling chamber is formed with a cooling water inlet and outlet so that water-cooling is performed, the cooling water inlet is formed to be located at the lower portion of the rotating shaft, and the cooling water outlet is formed to be located at the upper portion of the rotating shaft, so that the cooling water is filled from the bottom of the cooling chamber to suppress bubble generation.

9. In claim 1, A recirculating blower for a fuel cell system, characterized in that at least one bracket is installed on a lower fixed shaft to have a vibration-resistant structure, and a damper is installed on the bracket.

10. Fuel cell stack; A fuel supply unit for supplying fuel to the above fuel cell stack; An air supply unit for supplying air to the fuel cell stack; A heat exchanger that increases the temperature of fuel supplied from the fuel supply unit through stack fuel off-gas discharged from the fuel cell stack and supplies the fuel to a multi-functional steam reformer; A multifunctional catalytic combustor that uses the stack air electrode off-gas discharged from the fuel cell stack and the fuel off-gas of the second exhaust line branched off after passing through the heat exchanger as a heat source to increase the temperature of the air supplied from the air supply unit and supply it to a multifunctional steam reformer; A multifunctional steam reformer having a heat exchanger structure that supplies heat required for reforming reaction through a large amount of air whose temperature has increased by combustion reaction in the multifunctional catalytic combustor, reforms fuel supplied from the heat exchanger into hydrogen and supplies it to the fuel cell stack, thereby performing heat exchange using heat from the gas flow of the air electrode and the fuel electrode; and A recirculation blower installed in a fuel line to continuously recirculate stack fuel off-gas discharged from the fuel cell stack; Includes, The above recirculating blower is a rotatably installed impeller that sucks in the stack fuel off-gas, mixes and compresses it by forming a vortex, and discharges it; An impeller housing having a space therein in which the impeller is accommodated; A motor that provides driving force to rotate the impeller; A rotating shaft for rotating the impeller through the driving force of the motor; A coupling installed between the above rotational axis and the motor rotational axis to compensate for position and position the rotational axis at the center; A cooling chamber installed outside the above-mentioned rotating shaft to cool the above-mentioned rotating shaft through a cooling water flow; and A mechanical seal that forms a water film to seal the cooling chamber and prevent hydrogen from leaking in the axial direction while blocking contact between the stack off-gas and the outside air; A solid oxide fuel cell system comprising:

11. In a polymer exchange membrane fuel cell equipped with a recirculation blower for recirculating stack off-gas discharged from a fuel cell stack, The above recirculating blower has an impeller that is rotatably installed to suck in stack off-gas, mix and compress it by forming a vortex, and discharge it; An impeller housing having a space therein in which the impeller is accommodated; A motor that provides driving force to rotate the impeller; A rotating shaft for rotating the impeller through the driving force of the motor; A coupling installed between the above rotational axis and the motor rotational axis to compensate for position and position the rotational axis at the center; A cooling chamber installed outside the above-mentioned rotating shaft to cool the above-mentioned rotating shaft through a cooling water flow; and A mechanical seal that forms a water film to seal the cooling chamber and prevent hydrogen from leaking in the axial direction while blocking contact between the stack off-gas and the outside air; Including, The above impeller and impeller housing are made of STS316 or STS316S material with low nickel content. A polymer exchange membrane fuel cell system characterized in that the impeller housing is manufactured in a bolt-fastened form because the temperature of the gas flowing in the internal space of the impeller housing is relatively low compared to a solid oxide fuel cell.

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