Solid oxide fuel cell system for mass electricity production

Abstract

The present invention relates to a solid oxide fuel cell system that, unlike conventional methods in which anode off-gas and cathode off-gas are independently used for each individual stack of a solid oxide fuel cell, reduces the total amount of fuel required by the system and decreases the amount of external water used by recycling, in a rear-end stack, anode off-gas from a front-end stack, and reduces the amount of external air required by the system and decreases the electricity consumption of a blower by recycling, in the rear-end stack, cathode off-gas from the front-end stack.

Description

Solid oxide fuel cell systems for mass electricity production

[0001] The present invention relates to a solid oxide fuel cell system for large-scale energy production. The proposed system improves electrical and thermal efficiency, incorporates modularity, incorporates carbon dioxide separation, and minimizes freshwater and air consumption. Ultimately, the invention aims to promote the adoption of SOFC systems as a simpler, more sustainable, and more efficient means of power generation. In particular, the invention focuses on reducing environmental impact through modularity and simplifying the construction of large-scale SOFC systems.

[0002] The world is experiencing a rapid increase in energy demand due to social and economic development, including the growing demand for electricity for domestic, commercial, and industrial activities.

[0003] Conventional fossil fuel-based power generation technologies are causing environmental problems such as greenhouse gas emissions and air pollution, highlighting the need for efficient and clean power generation technologies. Renewable energy sources such as solar and wind are essential, but their intermittent and weather-dependent nature necessitates reliable and efficient backup power sources.

[0004] SOFCs operate at high temperatures (600-850°C) and can achieve high electrical efficiencies of 60-68%. SOFCs also hold promise in combined heat and power (CHP) applications, efficiently supplying both electricity and heat simultaneously. Additionally, SOFC systems can be converted to solid oxide electrolyzer (SOE) mode within 15 minutes, making them advantageous for storing renewable electricity as chemical energy.

[0005] SOFC performance can be degraded by carbon deposition, which can be overcome by mixing additional water vapor into the fuel. However, adding an external water treatment system to produce water vapor can increase the plant's size and cost. Furthermore, improving the efficiency of the entire system is also a critical challenge. Finally, the combustion of unconverted fuel in the burner with air generates CO₂ emissions, which must be separated to reduce the environmental impact.

[0006] Anode off-gas (AOG) recirculation can help improve overall fuel utilization and reduce external moisture requirements, but it must overcome pressure drop issues at high temperatures. Because high-temperature blowers are inefficient, AOG recirculation can reduce the electrical efficiency of the system. Conversely, cathode off-gas (COG) recirculation can reduce fresh air demand and improve heat recovery, but it can also impact stack performance, particularly electrical efficiency.

[0007] Small-scale SOFC systems are generally commercially available. However, for the construction of large-scale SOFC systems, integrating small SOFC modules into power and CHP modes is essential. Achieving high electrical and thermal efficiencies is crucial for large-scale systems.

[0008] Modularization is key to reducing system costs. Manufacturing standard modules can increase production volume and reduce stack costs. Furthermore, scale-up approaches require the use of modules to build large-scale SOFC power and heat generation units, eliminating the need for custom equipment design and plant layout modifications.

[0009] The challenge of the present invention is to maximize the electrical and thermal efficiency of a large-scale SOFC system. To achieve this, the AOG and COG are intelligently utilized to efficiently utilize heat and chemical energy, thereby improving fuel utilization and system performance.

[0010] Another challenge the present invention seeks to address is to propose a method for scaling up to large-scale SOFC systems and simplify the manufacturing process. By standardizing key module production, production volumes can be increased and costs reduced. Furthermore, module design and system assembly can be simplified, enabling modularization and economical construction of large-scale SOFC systems.

[0011] The present invention proposes a solid oxide fuel cell system for mass production of electricity to solve the aforementioned problems.

[0012] An SOFC system of one embodiment comprises: a fuel processing module including a fuel tank, a desulfurizer, and a blower; a steam generation module including a water tank, a pump, and an evaporator; a first air processing module including a blower and a heater; a second air processing module including a blower and a heater; a first stack module group including at least one first stack module including a first reformer and a first stack; and a second stack module group including a plurality of second stack modules including a second reformer and a second stack.

[0013] The first stack module of the first stack module group is:

[0014] A mixture of fuel output from the fuel processing module and steam output from the steam generation module is supplied to the first reformer, hydrogen generated from the first reformer is input to the anode of the first stack, and air output from the first air processing module is input to the cathode of the first stack.

[0015] The second stack module of the second stack module group is,

[0016] In the second reformer, a mixture of fuel output from the fuel processing module and steam output from the steam generation module, and a first stream of anode exhaust gas of the first stack module or a fourth stream of anode exhaust gas of the second stack module located immediately in front are supplied together,

[0017] It is characterized in that the hydrogen generated in the second reformer and the second flow obtained by branching the anode exhaust gas of the first stack module or the fifth flow obtained by branching the anode exhaust gas of the second stack module located immediately in front are input together to the anode of the second stack, and the air output from the second air treatment module is input to the cathode of the second stack.

[0018] Another embodiment of the SOFC system may be configured as follows.

[0019] That is, in the second stack module group, the most advanced second stack module is

[0020] In the second reformer, a mixture of fuel output from the fuel processing module and steam output from the steam generation module and a first stream of anode exhaust gas from the first stack module are supplied together,

[0021] The hydrogen generated in the second reformer and the second flow branched from the anode exhaust gas of the first stack module are input together into the anode of the second stack.

[0022] In addition, in the second stack module group, other second stack modules except the most advanced ones,

[0023] In the second reformer, a mixture of fuel output from the fuel processing module and steam output from the steam generation module and a fourth stream branched from the anode exhaust gas of the second stack module located immediately in front are supplied together,

[0024] At the anode of the second stack, hydrogen generated in the second reformer and a fifth stream branched from the anode exhaust gas of the second stack module located immediately in front are input together.

[0025] In another embodiment, the SOFC system may further include a combustion module having a burner, in which case a third stream of the anode exhaust gas of the first stack module is branched or a sixth stream of the anode exhaust gas of the second stack module is branched and input to the combustion module.

[0026] In another embodiment of the SOFC system, the exhaust gas of the combustion module may be input to a carbon separator.

[0027] In another embodiment, the SOFC system may further include a controller that regulates the amount of at least one of the first to sixth flows depending on operating conditions.

[0028] In another embodiment, the SOFC system may further include a controller that controls the flow of anode exhaust gas and cathode exhaust gas of each stack by varying the operating pressures of each stack included in the first stack module group and the second stack module group according to operating conditions.

[0029] In another embodiment of the SOFC system, the second stack of the second stack module may be configured to input at least a portion of the air from the second air treatment module and the cathode exhaust gas of the first stack module together into the cathode.

[0030] In another embodiment of the SOFC system, the cathode exhaust gas of each second stack module belonging to the second stack module group may be input to an air heat recovery module.

[0031] In another embodiment of the SOFC system, the first stack module may include a heater for preheating hydrogen produced in the first reformer, and the second stack module may not include a heater for preheating hydrogen produced in the second reformer.

[0032] In another embodiment of the SOFC system, a mixture of fuel output from the fuel processing module and steam output from the steam generation module may be supplied to the first reformer after being preheated by a heater, and may be supplied to the second reformer without separate preheating.

[0033] The present invention is an innovative system for large-scale SOFC systems. While conventional methods have employed independent AOG and COG for each stack, the present invention adopts a method of transferring AOG and COG flows from one stack to the next. This utilizes different pressures between stacks to more efficiently utilize heat and fuel, thereby improving system efficiency without the installation of additional blowers.

[0034] Embodiments of the present invention simplify the manufacturing process and promote modularization. By standardizing the size of selected modules, including stacks and auxiliary devices, production volumes can be significantly increased and system costs reduced. Furthermore, by replacing conventional customized equipment and plant layout design approaches, it enables more standardized and simplified construction of large-scale SOFC systems. This can promote cost savings and the diffusion of eco-friendly technologies, and also enables automated carbon (CO₂) separation.

[0035] Figure 1 shows a list of modules required for a solid oxide fuel cell system according to embodiments of the present invention.

[0036] Figure 2 shows the configuration of modules included in a solid oxide fuel cell system according to one embodiment of the present invention.

[0037] Figure 3 shows a detailed process flow diagram for the embodiment of Figure 2.

[0038] Figure 4 shows a detailed process flow diagram for a modified embodiment of Figure 2.

[0039] Hereinafter, several embodiments of the present invention will be described in detail using drawings. However, this is not intended to limit the present invention to any specific embodiment, and it should be understood that all transformations, equivalents, and substitutions that incorporate the technical spirit of the present invention are included within the scope of the present invention.

[0040] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0041] When a configuration in this specification is described as "having" or "composing" a sub-configuration, it is intended that the configuration may further include other configurations, rather than excluding other configurations, unless otherwise specifically stated.

[0042] The term “connected” in this specification may mean, but is not limited to, that two components are directly connected, and may also mean that the components are connected via one or more other components positioned between the components.

[0043] In this specification, “Module” means a detailed component unit that is independent from the entire system and performs a specific function, and serves as a technical means to maximize the flexibility and efficiency of the system by allowing multiple parts to be designed and assembled independently.

[0044] In embodiments of the present invention, “...module” may mean hardware whose structure, specifications, functions, etc. are designed according to certain standards so as to ensure compatibility and interoperability even in different systems or environments, or may mean a combination of hardware and software.

[0045] Figure 1 shows a list of modules required for a solid oxide fuel cell system according to embodiments of the present invention.

[0046] A fuel cell system according to one embodiment of the present invention includes a fuel processing module (1), a steam generation module (2), a first stack module (stack module 1) (3), a second stack module (stack module 2) (4), a first air processing module (air processing module 1) (5), a second air processing module (air processing module 2) (6), and a heat recovery module (7), and may further include a combustion module (8).

[0047] The fuel treatment module (1) includes a fuel tank (11), a sulfur treatment (12) and a blower (13).

[0048] In this specification, “fuel” means any one of natural gas of the hydrocarbon series such as methane, ethane, and propane; syngas produced by coal gasification, biomass pyrolysis, or waste gasification; and biogas produced from food waste, livestock waste, sewage sludge, etc. However, it is not necessarily limited to the examples listed above, and it should be understood as a general term for raw materials before being converted into hydrogen and carbon monoxide through a reforming process.

[0049] The fuel tank (11) is provided within the fuel processing module (1) and is a temporary storage for fuel connected to an external fuel tank or fuel supply pipe.

[0050] A desulfurizer (12) is a device that removes or neutralizes sulfur components that may exist in the fuel to prevent degradation and deterioration of battery performance. That is, hydrocarbon fuels such as natural gas, biogas, and diesel generally contain sulfur-containing gases such as H₂S and COS. The desulfurizer (12) removes sulfur components before the fuel reaches the SOFC stack, thereby preventing catalyst poisoning, a phenomenon in which sulfur is adsorbed on the nickel surface and interferes with the hydrogen / carbon monoxide oxidation reaction.

[0051] A blower (13) is a device that moves gas using a fan.

[0052] The steam generation module (2) includes a water tank (21), a pump (22), and an evaporator (23).

[0053] The water tank (21) is provided within the steam generation module (2) and is a temporary storage for fresh water connected to an external water tank or supply water pipe, and the pump (22) is a device that moves fluid by pressure caused by the rotation of a motor. The evaporator (23) is a device that vaporizes liquid water into gas, and in particular, generates steam for steam reforming at the later stage.

[0054] The first stack module (3) includes a first reformer (reformer 1) (31) and a first stack (stack 1) (32), and the second stack module (4) includes a second reformer (reformer 2) (41) and a second stack (stack 2) (42).

[0055] The first reformer (31) and the second reformer (41) are devices that convert hydrocarbon fuel into synthesis gas (Syngas) whose main components are hydrogen and carbon monoxide. The first reformer (31) and the second reformer (41) are a type of external reformer in that they reform the fuel in advance and then supply it to the cell. However, they are clearly different from conventional external reformers in that they are packaged together with the first stack (32) or the second stack (42) to form the first stack module (3) or the second stack module (4), respectively.

[0056] The first reformer (31) or the second reformer (41) uses one of steam reforming, partial oxidation, autothermal reforming, and dry reforming. Therefore, if the first reformer (31) or the second reformer (41) uses a reforming method other than steam reforming, the steam generation module (2) may be omitted.

[0057] The first stack (32) and the second stack (42) are important components where electrochemical reactions actually occur and electricity is generated.

[0058] The first stack (32) and the second stack (42) are each composed of a single cell, an interconnector, a gasket, a seal, an insulation material, and a mechanical support. Here, the core component, the single cell, comprises an anode that oxidizes hydrogen (H₂) and carbon monoxide (CO) to emit electrons, and an oxygen ion (O) that does not pass electrons. 2- ) and a cathode that forms oxygen ions from oxygen (O₂) and electrons.

[0059] The first air treatment module (5) includes a blower (51) and a heater (pressure heater) (52), and the second air treatment module (6) includes a blower (61) and a heater (pressure heater) (62).

[0060] Blower (51) and blower (61), like blower (13), are devices that move gas using a fan.

[0061] The air heat recovery module (7) is a heat exchanger for recovering waste heat of the second stack module (4) or the cathode off-gas output from the second stack module (4).

[0062] The SOFC system operates at a high temperature for oxygen ion conduction through a solid electrolyte, and a large amount of high-temperature waste heat is generated during this process. Therefore, if the generated heat is not recovered, it will be released as is, leading to energy loss. Therefore, the air heat recovery module (7) recovers the waste heat of the SOFC system so that the recovered heat is reused in at least one of the fuel preheating heater (H1 in FIG. 3) at the rear of the fuel processing module (1), the air preheating heater (not shown in the drawing) at the rear of the steam generation module (2), the evaporator (23) of the steam generation module (2), the fuel preheating heater (H in FIG. 3) arranged at the rear of the first reformer (31), and the internal reformer of the stack.

[0063] The combustion module (8) includes a burner (81) and a heat recovery unit (82).

[0064] The burner (81) is a device that combusts unreacted fuels such as H2, H3, CH4, and CO, which are used and left over in the first stack module (3) and the second stack module (4), by reacting them with oxygen or air. It is also called an oxy-burner. The burner (81) completely combusts unreacted fuel, thereby preventing safety accidents and reducing wasted energy. In addition, it purifies harmful exhaust gases such as CH4 and CO, while preventing combustible fuel from leaking to the outside.

[0065] The heat recovery device (82) recovers heat from the high-temperature gas generated by combustion of the burner (81), thereby allowing the recovered heat to be reused in at least one of the fuel preheating heater (H1 in FIG. 3) at the rear of the fuel processing module (1), the air preheating heater (not shown in the drawing) at the rear of the steam generation module (2), the evaporator (23) of the steam generation module (2), the fuel preheating heater (H in FIG. 3) arranged at the rear of the first reformer (31), and the internal reformer of the stack.

[0066] Figure 2 shows the configuration of modules of a solid oxide fuel cell system according to one embodiment of the present invention.

[0067] The SOFC system of the present invention enables mass production of electricity by connecting a plurality of stack modules having small production capacities in parallel or series, and grouping stack modules having the same connection relationship.

[0068] As an example, FIG. 2 shows an embodiment of an SOFC system in which the electricity production capacity is scaled up by combining two first stack modules (3) to form a first stack module group and three second stack modules (4) to form a second stack module group.

[0069] In other words, assuming that one stack module has an output of 10 kW, the embodiment of FIG. 2 implements a fuel cell system having an output of 50 kW by configuring one system with a total of five stack modules.

[0070] In the embodiment of FIG. 2, it is characteristic that the first stack modules (3) forming the first stack module group are connected in parallel with each other, and the second stack modules (4) forming the second stack module group are connected in series with each other. Here, the “parallel relationship” or “series relationship” does not mean the connection relationship of the electricity output, but rather the connection relationship of the gas input to the anode of each stack.

[0071] In addition, it is preferable that the number of first stack modules (3) forming the first stack module group be equal to or less than the number of second stack modules (4) forming the second stack module group. For example, the first stack module group and the second stack module group may be designed to account for about 40% and about 60%, respectively, of the total power production of the SOFC system.

[0072] FIG. 2 is only one embodiment that can be implemented by the present invention, and the present invention can be modified or extended to various embodiments of an SOFC system including a first stack module group consisting of n first stack modules (where n is an integer greater than or equal to 1) and a second stack module group consisting of m second stack modules (where m is an integer greater than or equal to 2).

[0073] Figure 3 shows a detailed process flow diagram for the embodiment of Figure 2.

[0074] Referring to FIG. 3 below, one embodiment of an SOFC system for mass electricity production is described in detail.

[0075] In the fuel processing module (1), the fuel is desulfurized (11) to remove sulfur components and preheated to a predetermined temperature (e.g., 100°C) by a heater (H1). Then, in the steam generation module (2), fresh water is injected into an evaporator (22) by a pump (21) and converted into steam in the evaporator (22).

[0076] A portion (MX1) of the fuel-steam mixture, in which the fuel and steam are mixed with the sulfur component removed, is input to the first reformer (31) (H5-1, H5-2) of each first stack module (3) belonging to the first stack module group, and after being converted into hydrogen and carbon monoxide in the first reformer (31) (H5-1, H5-2), is input to the anode of each first stack module (3).

[0077] A portion of the above mixture (MX1) may be preheated by a heater (H4) before being fed into the first reformer (31) for smooth reforming, and the hydrogen and carbon monoxide output from the first reformer (31) may be preheated once again by a heater (H) for smooth electrochemical reaction. (For example, it is finally preheated to 600 to 700°C.)

[0078] Another portion (MX2) of the fuel-steam mixture, which is a mixture of fuel and steam from which the sulfur component has been removed, is fed into the second reformer (41) of each second stack module (4) belonging to the second stack module group, and after being converted into hydrogen and carbon monoxide in the second reformer (41), is fed into the anode of each second stack module (4).

[0079] In the first air treatment module (5), external fresh air is injected into the heater (H2) by the blower (51), and the air heated by the heater (H2) is input to the cathode of each first stack module (3) belonging to the first stack module group. In the second air treatment module (6), external fresh air is injected into the heater (H3) by the blower (61), and the air heated by the heater (H3) is input to the cathode of each second stack module (4) belonging to the second stack module group.

[0080] In the embodiments of FIGS. 2 and 3, two first stack modules (3) included in the first stack module group are connected in parallel to each other.

[0081] Specifically, the anode exhaust gas of the first stack (Stack 1) located at the front of the first stack module group is not re-input to the anode of the first stack (Stack 2) located at the rear, but is combined with the anode exhaust gas of the first stack module (Stack 2) at a separate joint point (JT1) and input to the second stack module group. From this perspective, the two first stack modules (3) included in the first stack module group can be viewed as being connected in parallel with each other.

[0082] The anode exhaust gas flow (AOG flow) joined at the above joint point (JT1) is divided into two and input to the second stack (Stack 3) located at the foremost end of the second stack module group.

[0083] Specifically, the branched anode exhaust gas flow 1 (AOG flow 1) is combined with the aforementioned fuel-steam mixture and input to the second reformer (H15) of the second stack module located at the forefront, and another branched anode exhaust gas flow 2 (AOG flow 2) is combined with the output gas of the second reformer (H15) and input to the anode of the second stack (Stack 3) included in the second stack module located at the forefront.

[0084] Additionally, the anode exhaust gas flow (AOG flow) of the second stack (Stack 3) included in the second stack module at the forefront is also divided into two and input to the second stack (Stack 4) of the second stack module located immediately behind it (i.e., at the stop).

[0085] Specifically, the branched anode exhaust gas flow 4 (AOG flow 4) is combined with the aforementioned fuel-steam mixture and input to the second reformer (H25) included in the second stack module of the stop, and another branched anode exhaust gas flow 5 (AOG flow 5) is combined with the output gas of the second reformer (H25) and input to the anode of the second stack (Stack 4) included in the second stack module of the stop.

[0086] Additionally, the anode exhaust gas flow (AOG flow) of the second stack (Stack 4) included in the second stack module of the interruption is also divided into two and input to the second stack (Stack 5) of the second stack module located immediately behind it (i.e., at the end).

[0087] The method and structure of the branched flow of the anode exhaust gas output from the second stack (Stack 4) being input to the second stack (Stack 5) at the end are the same as the method and structure of the anode exhaust gas of the second stack (Stack 3), so a duplicate description is omitted.

[0088] The anode exhaust gas contains unreacted fuel such as H2, H3, CH4, CO, and CO2, as well as water vapor. Therefore, when AOG flow 1 of the first stack module group and AOG flow 4 of the second stack module group are input to the second reformer of the second stack module group as described above, a significant amount of water vapor contained in AOG flow 1 and AOG flow 4 participates in reforming, thereby reducing the amount of external supply water used in the fuel cell system.

[0089] The cathode exhaust gas of each first stack module belonging to the first stack module group is first joined at a joint point (JT2), and the first joined cathode exhaust gas is rejoined with the preheated air from the second air treatment module (6) at a joint point (JT3), and then is branched and individually input to the cathode of each second stack belonging to the second stack module group.

[0090] The air entering the second stack module group is initially preheated by the heater (H3) of the second air treatment module (6), but since it receives additional heat as the high-temperature cathode exhaust gas discharged from the first stack module group joins, a heater (H3) of small capacity may be adopted or even no heater (H3) may be provided. Accordingly, the energy consumed by the system can be reduced and the volume of the system can be further reduced.

[0091] In addition, since the cathode exhaust gas of each first stack module belonging to the first stack module group is input to the second stack module group and recycled, the amount of external air required by the cathode of the second stack module group can be significantly reduced. In addition, such a configuration reduces the power consumption of the blower (61) included in the second air treatment module (6), thereby increasing the electrical efficiency of the entire fuel cell system, and at the same time, the size of the second air treatment module (6) can be reduced as the capacity of the blower (61) is reduced.

[0092] Meanwhile, in the embodiments of FIGS. 2 and 3, three second stack modules (4) included in the second stack module group are connected in series with each other.

[0093] Specifically, the anode exhaust gas of the second stack (Stack 3) located at the forefront of the second stack module group is re-input to the anode of the second stack (Stack 4) located immediately behind it (i.e., at the middle), and the anode exhaust gas of the second stack (Stack 4) located at the middle of the second stack module group is re-input to the anode of the second stack (Stack 5) located immediately behind it (i.e., at the end).

[0094] Although the air joined at the joint point (JT3) is individually input to each of the three second stacks (Stack 3, 4, 5), and the cathode exhaust gas of any one of the second stacks is not re-input to the cathode of the second stack of the subsequent stage but is individually input to the air heat recovery module (7), the three second stack modules (4) included in the second stack module group can be viewed as being connected in series with each other from the perspective that the anode exhaust gas of any one of the second stacks is again input to the anode of the second stack of the next stage.

[0095] The anode exhaust gas of the second stack module located at the end is input to the combustion module (8), where most of the unreacted fuel is burned.

[0096] The cathode exhaust gas output from each second stack module of the second stack module group does not necessarily need to be input to the air heat recovery module (7), and may be input to other components required for efficient operation of the system or environmental requirements, or may be released to the outside as is.

[0097] In addition, the anode exhaust gas of the second stack module located at the end does not necessarily need to be input to the combustion module (8), and may be input to other components required for efficient operation of the system or environmental requirements, or may be released to the outside as is.

[0098] Meanwhile, a carbon separator (9) may be further connected to the rear end of the combustion module (8).

[0099] The anode exhaust gas flow input to the combustion module (8) is mostly burned except for carbon dioxide (CO2) and steam through an oxidation reaction in the burner (81), so the purity of carbon dioxide and water increases.

[0100] In the embodiment of the present invention, since the anode exhaust gas of each second stack belonging to the second stack module group is recycled as fuel for another second stack connected immediately behind, the overall fuel requirement of the fuel cell system is reduced, and also, since the amount of unreacted fuel included in the anode exhaust gas flowing into the combustion module (8) is reduced, the capacity of the burner (81) required by the combustion module (8) is also reduced accordingly. This allows the combustion module (8) to be made more compact, thereby reducing the size of the overall fuel cell system.

[0101] The high-temperature combustion gas output from the burner (81) is cooled first through a heat recovery device (HX1) and then input into a carbon separator (9).

[0102] A carbon separator (9) is a device that separates carbon dioxide (CO₂) from combustion gas, and depending on the separation method, any one of the following can be used: absorption type based on MEA (Monoethanolamine), adsorption type using pressure swing (PSA) or temperature swing (TSA), membrane separation type using permeability difference, cryogenic separation type that separates CO₂ by cooling it to a low temperature and condensing it into a liquid or solid, chemical conversion type (Chemical Looping, Calcium Looping) that fixes CO₂ as a reactant or induces a conversion reaction using metal oxides or limestone, and electrochemical separation type that selectively moves or decomposes CO₂ through an electrochemical cell.

[0103] When using adsorption carbon separation by temperature swing (TSA) as in the embodiment of Fig. 3, the carbon separator (9) may include a heat recovery device (HX2) and a condenser.

[0104] A portion of the carbon dioxide separated in the carbon separator (9) may be recycled to the burner (81) to control or maintain the temperature of the burner (810) within a set range.

[0105] Figure 4 shows a detailed process flow diagram for a modified embodiment of Figure 2.

[0106] The embodiment of Fig. 4 is identical to the embodiment of Fig. 2 in all other technical configurations, except that the gas input to the combustion module (8) is slightly different from the embodiment of Fig. 2. Therefore, only the parts that are different from the embodiment of Fig. 2 will be described herein.

[0107] In the embodiment of FIG. 4, the anode exhaust gas flow (AOG flow) of the first stack module group, in which the anode exhaust gas of the first stack (Stack 1) and the anode exhaust gas of the first stack (Stack 2) are combined, is further branched into AOG flow 3 in addition to AOG flow 1 and AOG flow 2. And the anode exhaust gas of the second stack (Stack 3) is further branched into AOG flow 6 in addition to AOG flow 4 and AOG flow 5. The anode exhaust gas of the second stack (Stack 4) is also branched in the same way as the anode exhaust gas of the second stack (Stack 3).

[0108] In the embodiment of FIG. 4, the AOG flow 3 of the first stack module group and two AOG flows 6 output from the second stack (Stack 3) and the second stack (Stack 4) of the second stack module group join the anode exhaust gas flow of the second stack (Stack 5) at the joint point (JT4) and are then input to the fuel module (8).

[0109] The solid oxide fuel cell system of the various embodiments described above may further include a controller 1 (not shown in the drawing) that controls the branching amount of at least one of the first to sixth flows according to operating conditions.

[0110] In addition, the SOFC system of another embodiment may further include a controller 2 (not shown in the drawing) that controls the flow of the anode exhaust gas and the cathode exhaust gas of each stack by varying the operating pressures of each stack included in the first stack module group and the second stack module group according to the operating conditions.

[0111] In addition, the solid oxide fuel cell system of the various embodiments described above can apply the Rankine cycle to convert excess heat into electricity, and can also integrate a supercritical CO₂ cycle when necessary, thereby greatly improving the electrical efficiency of the system.

[0112] Furthermore, it is desirable that the types and sizes of the first stack, second stack, first reformer, second reformer, heat recovery unit (heat exchanger), blower, burner, pump, and condenser employed in the embodiments of the present invention be standardized. A simplified design based on standardized equipment not only reduces system construction costs, but also eliminates the need for customized piping and contributes to improving the current practice of applying different customized equipment each time a SOFC system is built, depending on the plant size.

[0113] Although the present invention has been described above with reference to several embodiments thereof, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. Fuel treatment module including fuel tank, desulfurizer and blower; Steam generation module including water tank, pump and evaporator; A first air handling module comprising a blower and a heater; A second air handling module comprising a blower and a heater; A first stack module group comprising at least one first stack module including a first reformer and a first stack; and comprising a second stack module group including a plurality of second stack modules including a second reformer and a second stack; The first stack module of the first stack module group is: A mixture of fuel output from the fuel processing module and steam output from the steam generation module is supplied to the first reformer, hydrogen generated from the first reformer is input to the anode of the first stack, and air output from the first air processing module is input to the cathode of the first stack. The second stack module of the second stack module group is, In the second reformer, a mixture of fuel output from the fuel processing module and steam output from the steam generation module, and a first stream of anode exhaust gas of the first stack module or a fourth stream of anode exhaust gas of the second stack module located immediately in front are supplied together, The hydrogen generated in the second reformer and the second flow of the anode exhaust gas of the first stack module or the fifth flow of the anode exhaust gas of the second stack module located immediately in front are input together to the anode of the second stack, and the air output from the second air treatment module is input to the cathode of the second stack. Solid oxide fuel cell systems for mass electricity production.

2. In paragraph 1, In the above second stack module group, the most advanced second stack module is: In the second reformer, a mixture of fuel output from the fuel processing module and steam output from the steam generation module and a first stream of anode exhaust gas from the first stack module are supplied together, It is characterized in that the hydrogen generated in the second reformer and the second flow branched from the anode exhaust gas of the first stack module are input together into the anode of the second stack, In the above second stack module group, other second stack modules except the most advanced ones, In the second reformer, a mixture of fuel output from the fuel processing module and steam output from the steam generation module and a fourth stream branched from the anode exhaust gas of the second stack module located immediately in front are supplied together, It is characterized in that the hydrogen generated in the second reformer and the fifth flow branched from the anode exhaust gas of the second stack module located immediately in front are input together into the anode of the second stack. Solid oxide fuel cell systems for mass electricity production.

3. In paragraph 1 or 2, Further comprising a combustion module having a burner, Characterized in that the third flow from which the anode exhaust gas of the first stack module is branched or the sixth flow from which the anode exhaust gas of the second stack module is branched is input to the combustion module. Solid oxide fuel cell systems for mass electricity production.

4. In paragraph 3, The exhaust gas of the above combustion module is characterized in that it is input to a carbon separator. Solid oxide fuel cell systems for mass electricity production.

5. In paragraph 3, It is characterized by further including a controller that controls the branching amount of at least one of the first to sixth flows according to the driving conditions. Solid oxide fuel cell systems for mass electricity production.

6. In paragraph 3, It is characterized by further including a controller that controls the flow of anode exhaust gas and cathode exhaust gas of each stack by varying the operating pressures of each stack included in the first stack module group and the second stack module group according to the operating conditions. Solid oxide fuel cell systems for mass electricity production.

7. In paragraph 1, The second stack of the second stack module is characterized in that the air of the second air treatment module and at least a portion of the cathode exhaust gas of the first stack module are input together into the cathode. Solid oxide fuel cell systems for mass electricity production.

8. In paragraph 1 or 2, Characterized in that the cathode exhaust gas of each second stack module belonging to the second stack module group is input to the air heat recovery module. Solid oxide fuel cell systems for mass electricity production.

9. In paragraph 1 or 2, The first stack module includes a heater for preheating hydrogen generated in the first reformer, and the second stack module does not include a heater for preheating hydrogen generated in the second reformer. Solid oxide fuel cell systems for mass electricity production.

10. In paragraph 1 or 2, A mixture of fuel output from the fuel processing module and steam output from the steam generation module is It is characterized in that it is supplied to the first reformer after being preheated by the heater and supplied to the second reformer without separate preheating. Solid oxide fuel cell systems for mass electricity production.

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