KR20240003528A - Solid oxide fuel cell-internal combustion engine hybrid system powered by ammonia - Google Patents

Abstract

This application relates to a solid oxide fuel cell-internal combustion engine hybrid system running on ammonia.

Description

Solid oxide fuel cell-internal combustion engine hybrid system driven by ammonia {SOLID OXIDE FUEL CELL-INTERNAL COMBUSTION ENGINE HYBRID SYSTEM POWERED BY AMMONIA}

This application relates to a solid oxide fuel cell-internal combustion engine hybrid system running on ammonia.

Climate change is becoming more serious with the development of human civilization. According to the International Maritime Organization (IMO), total greenhouse gas (GHG) emissions from ships are more than 100 million tons per year, accounting for 2.9% of global greenhouse gas emissions. IMO aims to reduce annual GHG emissions by 50% by 2050 compared to 2008 to achieve the global _CO2 reduction goal.

Using hydrogen as a fuel can significantly reduce greenhouse gas emissions because it does not produce carbon during the oxidation process. However, because hydrogen is in a gaseous state at most temperatures and pressures, it is not easy to store and transport compared to existing liquid fuels. not.

Ammonia (NH ₃ ) is one of the promising hydrogen carriers, as it can be easily compressed into a liquid at relatively low pressure. Ammonia has no carbon and has three hydrogens per molecule, so a large amount of hydrogen can be stored in a small amount of ammonia. In addition, because ammonia is used to produce fertilizer, large-scale infrastructure investment is not necessary as the infrastructure such as production facilities and transport vehicles are already in place.

Therefore, the use of ammonia with fuel cells is being considered as a future fuel and ship propulsion system for maritime transportation. Currently, proton-exchange membrane fuel cells (PEMFC) are being widely studied, but the operating temperature of PEMFC is only up to 210℃, while ammonia decomposition requires at least 377℃, so PEMFC is not capable of decomposing ammonia. The downside is that it cannot be done. On the other hand, solid oxide fuel cells (SOFC) operate at a temperature higher than the decomposition temperature of ammonia, so SOFC can be used with ammonia and can be used as an eco-friendly marine propulsion system.

Republic of Korea Patent Publication No. 10-2254196.

Our aim is to provide a solid oxide fuel cell-internal combustion engine hybrid system that runs on ammonia.

However, the problem to be solved by the present application is not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

One aspect of the present disclosure is a solid oxide fuel cell including an anode and a cathode; external digester; A solid oxide fuel cell-internal combustion engine hybrid system including an internal combustion engine and a heat exchanger, wherein the external decomposition unit decomposes ammonia into hydrogen and nitrogen and supplies it to the anode of the solid oxide fuel cell, and the internal combustion engine decomposes ammonia into hydrogen and nitrogen and supplies it to the anode of the solid oxide fuel cell. A solid oxide fuel cell-internal combustion engine hybrid system, which is driven by receiving an anode off gas of a fuel cell, is provided.

The solid oxide fuel cell according to embodiments of the present disclosure operates at a temperature higher than the ammonia decomposition temperature and can be used with ammonia.

The solid oxide fuel cell-internal combustion engine hybrid system according to embodiments of the present application can significantly reduce greenhouse gas emissions by using ammonia as a fuel.

The solid oxide fuel cell-internal combustion engine hybrid system according to embodiments of the present disclosure can produce additional power by using the anode off gas of the solid oxide fuel cell as fuel for the internal combustion engine.

By including an internal combustion engine, the solid oxide fuel cell-internal combustion engine hybrid system according to embodiments of the present disclosure can produce additional power equivalent to about 1/3 of the energy that a solid oxide fuel cell stand-alone system can output.

The solid oxide fuel cell-internal combustion engine hybrid system according to embodiments of the present disclosure can improve system efficiency by up to 20% compared to a solid oxide fuel cell stand-alone system.

Even when the fuel utilization factor (UF) of the solid oxide fuel cell is low, the efficiency of the solid oxide fuel cell-internal combustion engine hybrid system according to embodiments of the present disclosure may be maintained or slightly reduced.

The solid oxide fuel cell-internal combustion engine hybrid system according to the embodiments of the present application can be used in a marine propulsion system.

1 is a schematic diagram showing a solid oxide fuel cell-internal combustion engine hybrid system, according to an embodiment of the present application.
Figure 2 is a performance simulation graph of a solid oxide fuel cell using ammonia as fuel, according to an embodiment of the present application.
Figure 3 is a graph showing the pressure within the cylinder of an internal combustion engine according to the crank angle (crack angle degree; CAD) of the internal combustion engine, according to an embodiment of the present application.
FIG. 4 is a graph showing the efficiency of a solid oxide fuel cell-internal combustion engine hybrid system according to the fuel utilization factor (UF) of the solid oxide fuel cell, according to an embodiment of the present application.
FIG. 5 is a graph showing the power of a solid oxide fuel cell-internal combustion engine hybrid system according to fuel utilization rate, according to an embodiment of the present application.
FIG. 6 is a schematic diagram showing a solid oxide fuel cell-internal combustion engine hybrid system that provides heat using an additional heating device without providing heat from an anode off gas to an external decomposer, according to an embodiment of the present application.

Hereinafter, with reference to the attached drawings, implementation examples and embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present application may be implemented in various different forms and is not limited to the implementation examples and examples described herein. In order to clearly explain the present invention in the drawings, parts that are not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout this specification, when a part is said to be “connected” to another part, this includes not only the case where it is “directly connected,” but also the case where it is “electrically connected” with another element in between. do.

Throughout this specification, when a member is said to be located “on” another member, this includes not only the case where the member is in contact with the other member, but also the case where another member exists between the two members.

Throughout the specification of the present application, when a part “includes” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

As used herein, the terms “about,” “substantially,” and the like are used to mean at or close to a numerical value when manufacturing and material tolerances inherent in the stated meaning are presented, and to aid understanding of the present application. It is used to prevent unscrupulous infringers from unfairly exploiting disclosures in which precise or absolute figures are mentioned.

The terms “step of” or “step of” as used throughout the specification herein do not mean “step for.”

Throughout this specification, the term "combination(s) thereof" included in the Markushi format expression means a mixture or combination of one or more selected from the group consisting of the components described in the Markushi format expression, It means containing one or more selected from the group consisting of the above components.

Throughout this specification, description of “A and/or B” means “A or B, or A and B.”

Hereinafter, embodiments of the present application have been described in detail, but the present application may not be limited thereto.

One aspect of the present disclosure is a solid oxide fuel cell including an anode and a cathode; external digester; A solid oxide fuel cell-internal combustion engine hybrid system including an internal combustion engine and a heat exchanger, wherein the external decomposition unit decomposes ammonia into hydrogen and nitrogen and supplies it to the anode of the solid oxide fuel cell, and the internal combustion engine decomposes ammonia into hydrogen and nitrogen and supplies it to the anode of the solid oxide fuel cell. A solid oxide fuel cell-internal combustion engine hybrid system, which is driven by receiving an anode off gas of a fuel cell, is provided.

In one embodiment of the present application, the solid oxide fuel cell-internal combustion engine hybrid system may further include one or more selected from valves, pumps, and blowers.

Typically, a solid oxide fuel cell includes an anode, a cathode, and an electrolyte, and can generate electricity through a chemical reaction of hydrogen and oxygen.

In one embodiment of the present application, the anode of the solid oxide fuel cell may include a commonly used anode material of the solid oxide fuel cell, and as a non-limiting example, nickel and yttria stabilized zirconia (Ni/ YSZ), nickel and gadolinium doped ceria (Ni/GDC), copper and ceria (Cu-Ceria), and may include one or more selected from cermet and perovskite. It may not be limited.

In one embodiment of the present application, the cathode of the solid oxide fuel cell may include a commonly used cathode material of the solid oxide fuel cell, and as a non-limiting example, lanthanum strontium cobalt oxide. ; LSC), lanthanum strontium cobalt ferrite (LSCF), and lanthanum strontium manganite (LSM), but may not be limited thereto.

In one embodiment of the present application, the electrolyte of the solid oxide fuel cell may be a commonly used electrolyte of the solid oxide fuel cell, and as a non-limiting example, zirconia (ZrO ₂ )-based oxide, ceria (CeO ₂ )-based electrolyte. oxide, and lanthanum-strontium-gadolinium-magnesium oxide (LSGM) substituted with a rare earth metal oxide. In one embodiment of the present application, the electrolyte of the solid oxide fuel cell is doped with yttria stabilized zirconia (YSZ), scandia (Sc ₂ O ₃ ) stabilized zirconia (ScSZ), and gadolinium (Gd). It may include one or more selected from ceria (gadolinium doped ceria; GDC), but may not be limited thereto.

In one embodiment of the present application, the solid oxide fuel cell may be supplied with high-temperature air from the cathode side and may be supplied with fuel gas containing hydrogen as a main component from the anode side. In one embodiment of the present application, oxygen supplied to the cathode may react with electrons to generate oxygen ions (O ^2- ). The oxygen ions can move to the anode through the electrolyte and react with hydrogen to generate heat, water, and electricity.

In one embodiment of the present application, the external decomposer may be connected to the anode of the solid oxide fuel cell and the internal combustion engine.

In one embodiment of the present application, the external decomposition unit may decompose ammonia into hydrogen and nitrogen using the heat of the anode off gas of the solid oxide fuel cell.

In one embodiment of the present application, the external decomposition unit may additionally decompose ammonia into hydrogen and nitrogen using heat from a separate heating device. In one embodiment of the present application, the separate heating device may produce heat using ammonia and air.

In one embodiment of the present application, the heat exchanger may be connected to the cathode of the solid oxide fuel cell.

In one embodiment of the present application, the heat exchanger may preheat external air using the heat of the cathode off gas of the solid oxide fuel cell.

In one embodiment of the present application, the heat exchanger may discharge exhaust gas of the solid oxide fuel cell-internal combustion engine hybrid system.

In one embodiment of the present application, the internal combustion engine included in the solid oxide fuel cell-internal combustion engine hybrid system may be used without limitation as long as it is applicable to or compatible with the present invention.

In one embodiment of the present application, the internal combustion engine may be driven by receiving anode off gas and air from the solid oxide fuel cell.

In one embodiment of the present application, the anode off gas of the solid oxide fuel cell may be a diluted gas.

In one embodiment of the present application, the combustion method of the internal combustion engine is premixed charge compression ignition (HCCI), reactivity controlled compression ignition (RCCI), and spark-assisted compression ignition. It may include one or more selected from a spark assisted compression ignition (SACI) method, a spark ignition method, and a compression ignition method. In one embodiment of the present application, in order to properly combust the diluted gas, the combustion method of the internal combustion engine is one selected from a premixed compression ignition method, a reactivity-controlled compression ignition method, and a spark-assisted compression ignition method. It may be more than that.

In one embodiment of the present application, the internal combustion engine may produce power by rotating a drive shaft, but may not be limited thereto.

In one embodiment of the present application, the internal combustion engine may include a generator and/or a converter, but may not be limited thereto.

In one embodiment of the present application, the internal combustion engine may produce power of about 100 kW to about 2,500 kW. In one embodiment of the present application, the internal combustion engine has a power of about 100 kW to about 2,500 kW, about 100 kW to about 2,400 kW, about 100 kW to about 2,300 kW, about 100 kW to about 2,200 kW, about 100 kW to about 2,100 kW, from about 200 kW to about 2,500 kW, from about 200 kW to about 2,400 kW, from about 200 kW to about 2,300 kW, from about 200 kW to about 2,200 kW, from about 200 kW to about 2,100 kW, from about 300 kW to about 2,500 kW, About 300 kW to about 2,400 kW, about 300 kW to about 2,300 kW, about 300 kW to about 2,200 kW, about 300 kW to about 2,100 kW, about 400 kW to about 2,500 kW, about 400 kW to about 2,400 kW, about 400 It may produce power from kW to about 2,300 kW, from about 400 kW to about 2,200 kW, or from about 400 kW to about 2,100 kW.

In one embodiment of the present application, compared to a solid oxide fuel cell stand-alone system, system efficiency may be improved by about 10% or more, about 15% or more, or about 20% or more.

In one embodiment of the present application, the internal combustion engine may produce additional power by additionally supplying ammonia and external air.

In one embodiment of the present application, the solid oxide fuel cell-internal combustion engine hybrid system may be used in a marine propulsion system, but may not be limited thereto.

Hereinafter, the present application will be described in more detail using examples. However, the following examples are merely illustrative to aid understanding of the present application, and the content of the present application is not limited to the following examples.

[Example]

1. Solid oxide fuel cell-internal combustion engine hybrid system (Figure 1)

The solid oxide fuel cell-internal combustion engine hybrid system includes a solid oxide fuel cell (SOFC), an external cracker, a heat exchanger (HEX), and an internal combustion engine (ICE). When explained with reference to FIG. 1, stream 1 is ammonia fuel, which is supplied to an external decomposer and decomposed into N ₂ and H ₂ . The SOFC's anode off gas (stream 3) supplies heat for the decomposition of ammonia in an external digester. After passing through the external digester, stream 2 goes to the anode of the SOFC, and stream 4 goes to the internal combustion engine together with air (stream 5). The H ₂ present in stream 5 is utilized to generate additional power in the internal combustion engine. Outside air (stream 8) passes through a heat exchanger to the cathode of the SOFC. At this time, cathode off gas (stream 10) is supplied to the heat exchanger to preheat the outside air with the heat of the cathode off gas.

In this example, a simulation model was developed using MATLAB and Cantera thermodynamic toolbox, and thermodynamic properties were calculated using the GRI 3.0 mechanism.

2. Solid oxide fuel cell-internal combustion engine hybrid system components

2.1 Solid Oxide Fuel Cell (SOFC)

The 0D SOFC model was developed to determine the composition and power generation of the anode off gas at a given temperature and pressure. An electrochemical model was constructed considering Nernst voltage, activation loss, resistance loss, and concentration loss, and was calculated using Equation 1 below.

[Equation 1]

Referring to Figure 2, in order to confirm that the SOFC model appropriately simulates the performance of SOFC using ammonia fuel, a previous paper 'Cinti, G., Discepoli, G., Sisani, E., & Desideri, U. (2016) ), "SOFC operating with ammonia: Stack test and system analysis", International Journal of Hydrogen Energy, 41(31), 13583-13590.' The model was verified with experimental results. Referring to Figure 2, it can be seen that the experimental results and the model are consistent under pure NH ₃ and H ₂ /N ₂ conditions at various temperatures.

In this example, the operating temperature of the SOFC was assumed to be fixed at 1023.15 K. Table 1 below shows the specifications of the SOFC cell used in this example.

Activated cell area [m ² ] 0.008 Anode thickness [m] 500×10 ^-6 Cathode thickness [m] 50×10 ^-6 Electrolyte thickness [m] 20×10 ^-6 Interconnect thickness [m] 180×10 ^-6 Number of SOFC cells in one stack 80 Number of SOFC stacks 1400

2.2 External cracker

The external decomposer is a countercurrent heat exchanger, and the heat exchanger usefulness was used to calculate the heat exchange amount and ammonia decomposition amount. The usability of the external cracker was set to match the intake gas temperature required for operation of the internal combustion engine, and it was assumed that the SOFC anode inlet gas, which is the outlet stream of the external cracker, was in chemical equilibrium.

2.3 Internal combustion engine

Internal combustion engines are constructed taking into account mass, energy, species balances, heat transfer, and chemical reaction kinetics. For proper combustion of the anode off gas of SOFC, which is a significantly diluted gas, HCCI (homogeneous charge compression ignition), RCCI (reactivity controlled compression ignition), or SACI (spark assisted compression ignition) were used as combustion methods in internal combustion engines. It was assumed that an amount of air was added to make the intake pressure of the internal combustion engine 1 bar.

3. System size

The size of the SOFC-ICE hybrid system was set to a size that can operate a ship. In this example, the marine engine MAN 51/60 was used, and the engine design specifications are shown in Table 2 below.

bore [mm] 510 Stroke [mm] 600 speed [rpm] 500 compression ratio 15 cylinder 6

The size of the SOFC system was determined according to the size of the engine (ICE), and it was assumed that 1,400 SOFC stacks, each consisting of 80 serially connected cells, were used. The number of stacks was determined so that the pressure of the engine intake gas approximates 1 atm. The amount of ammonia entering the system was fixed at 0.421 kg/s, which corresponds to 7.83 MW based on low heating value.

4. Simulation results

4.1 When supplying anode off gas to an external decomposer

Table 3 below shows comparison values between the SOFC-ICE hybrid system and the SOFC stand-alone system at the reference point. The fuel utilization factor (UF) was set at 0.7 and the air utilization factor (UF) was set at 0.4.

SOFC-ICE hybrid system SOFC standalone system System power [kW] 4753 3648 System efficiency [%] 60.59 46.5 SOFC power [kW] 3648 3648 SOFC efficiency [%] 46.5 46.5 ICE power [kW] 1126 - ICE efficiency [%] 41.75 - Decomposer usefulness 0.75 0.85

Referring to Table 3 above, at the baseline, an amount equivalent to about 1/3 of the output of the SOFC was generated by the engine, which significantly improved the efficiency of the system compared to the SOFC-ICE hybrid system compared to the SOFC stand-alone system. Figure 3 shows the pressure within the cylinder according to the crank angle (CAD). Referring to FIG. 3, the engine burns SOFC anode off gas well, and the peak pressure timing was set to 5 CAD after top-dead center.

Table 4 below shows the temperature, pressure, mass flow rate and molar composition of the streams included in the SOFC-ICE hybrid system operating at baseline.

stream One 2 3 4 5 6 7 8 9 10 11 temperature
[K] 298 459 1073 508 298 394 736 298 891 1073 462 enter
[bar] One One One One One One One One One One One mass flow rate
[kg/s] 0.42 0.42 0.84 0.84 1.2 2.03 2.03 6.38 6.38 5.96 5.96 Furtherance NH ₃ One 0.19 0 0 0 0 0 0 0 0 0 N ₂ 0 0.2 0.25 0.25 0.79 0.44 0.5 0.79 0.79 0.84 0.84 H ₂ 0 0.6 0.23 0.23 0 0.15 0.12 0 0 0 0 H ₂ O 0 0 0.52 0.52 0 0.34 0.29 0 0 0 0 O ₂ 0 0 0 0 0.21 0.07 0.09 0.21 0.21 0.16 0.16

Figures 4 and 5 show the power and efficiency of SOFC, ICE and SOFC-ICE hybrid systems at fuel utilization factors (UF) ranging from 0.5 to 0.8. It has been shown that adding an ICE to a SOFC standalone system can produce between 500 kW and 2,000 kW of additional power and improve efficiency by up to 20%. As UF increases, the power of the SOFC increases and the power of the ICE decreases. Therefore, the total system power first increases and then decreases as UF increases. Referring to Figures 4 and 5, it can be seen that system efficiency is highest when UF is 0.6, and that efficiency does not decrease significantly even when UF is low.

4.2 When anode off gas is not supplied to the external decomposer and heat is supplied separately.

Figure 6 shows a SOFC-ICE hybrid system that does not provide heat from the anode off gas to an external decomposer, but provides heat using a separate heating device. Here, the off gas generated at the anode of the SOFC is moved to the internal combustion engine without passing through an external decomposition device. Table 5 below shows data comparing the data of the hybrid system according to the present application that supplies anode off-gas to an external decomposer and the hybrid system that supplies heat using a separate heating device.

Heat supplied by additional heating appliances Anode off-gas supply System efficiency [%] 51.03 60.98 NH ₃ [kg/s] 0.5039 0.4217 External digester [kW] 1528.7 1528.7 SOFC power [kW] 3658.0 3658.0 Internal combustion engine power [kW] 1125.8 1125.8

Referring to Table 5 above, when the heat of the anode off gas is not supplied to an external decomposer but is supplied using a separate heating device, the efficiency of the SOFC-ICE hybrid system according to FIG. 6 compared to the efficiency of the hybrid system according to the present invention is It is lowered by about 10%, and it can be seen that an additional 0.0822 kg/s of ammonia is required.

5. Conclusion

In this example, a SOFC-ICE hybrid system using ammonia as fuel was simulated with 0D models of SOFC and ICE, and both models were verified with experimental data. Additionally, it was confirmed that the SOFC-ICE hybrid system generates a significant amount of additional power compared to the SOFC standalone system at the baseline and can improve system efficiency by up to 20%.

The description of the present application described above is for illustrative purposes, and those skilled in the art will understand that the present application can be easily modified into other specific forms without changing its technical idea or essential features. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, each component described as single may be implemented in a distributed manner, and similarly, components described as distributed may also be implemented in a combined form.

The scope of the present application is indicated by the claims described below rather than the detailed description above, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present application. .

Claims (10)

A solid oxide fuel cell including an anode and a cathode; external digester; Internal combustion engines and heat exchangers
A solid oxide fuel cell-internal combustion engine hybrid system comprising,
The external decomposer decomposes ammonia into hydrogen and nitrogen and supplies it to the anode of the solid oxide fuel cell,
The internal combustion engine is driven by receiving an anode off gas of the solid oxide fuel cell,
Solid oxide fuel cell-internal combustion engine hybrid system.
According to claim 1,
The external decomposer is connected to the anode of the solid oxide fuel cell and the internal combustion engine.
According to claim 1,
The external decomposition unit decomposes ammonia into hydrogen and nitrogen using heat from the anode off gas of the solid oxide fuel cell.
According to claim 1,
A solid oxide fuel cell-internal combustion engine hybrid system, wherein the heat exchanger is connected to the cathode of the solid oxide fuel cell.
According to claim 1,
The heat exchanger is a solid oxide fuel cell-internal combustion engine hybrid system that uses heat from the cathode off gas of the solid oxide fuel cell to preheat external air.
According to claim 1,
The combustion method of the internal combustion engine includes one or more selected from the group consisting of a premixed compression ignition method, a reactivity-controlled compression ignition method, a compression ignition method assisted by a spark, a spark ignition method, and a compression ignition method. -Internal combustion engine hybrid system.
According to claim 1,
A solid oxide fuel cell-internal combustion engine hybrid system in which the internal combustion engine produces power of 100 kW to 2,500 kW.
According to claim 1,
A solid oxide fuel cell-internal combustion engine hybrid system in which system efficiency is improved by more than 10% compared to a solid oxide fuel cell stand-alone system.
According to claim 1,
A solid oxide fuel cell-internal combustion engine hybrid system in which the internal combustion engine produces additional power by additionally supplying ammonia and external air.
According to claim 1,
A solid oxide fuel cell-internal combustion engine hybrid system used in marine propulsion systems.