KR20230065490A - Combined power generation system and method for generating power using the same - Google Patents

Abstract

The present invention aims to provide a combined power generation system with a high efficiency. The present invention also aims to provide a combined power generation method with the high efficiency by using the system. To this end, the present invention provides a combined power generation system which comprises: a power generation facility discharging high-temperature exhaust gas including moisture; and an inverted Brayton cycle (IBC) facility introducing the high-temperature exhaust gas including moisture discharged from the power generation facility. In addition, the present invention provides a combined power generation method which comprises: a step of acquiring exhaust gas from a power generation facility discharging high-temperature exhaust gas including moisture; and a step of introducing the acquired exhaust gas by the IBC. According to the present invention, power can be generated additionally by introducing high-temperature exhaust gas including moisture discharged from power generation facilities into an IBC facility, and thermal energy can be obtained to greatly improve the process's energy efficiency. In addition, the problem of environmental pollution occurring when high-temperature exhaust gas is emitted to the atmosphere can also be solved.

Description

Combined power generation system and combined power generation method {COMBINED POWER GENERATION SYSTEM AND METHOD FOR GENERATING POWER USING THE SAME}

The present invention relates to a combined power generation system and a combined power generation method using the same.

The use of hydrogen is being considered as one of the ways to respond to the global climate change problem. Hydrogen is an excellent energy storage method and can be used in energy, transportation, and heating fields instead of fossil fuels. In the field of gas turbines, research on engines using hydrogen is in progress, and development of highly efficient power generation systems using hydrogen gas turbines is required.

Currently, the government is applying a method of producing hydrogen from water and natural gas to replace existing fossil fuels in the energy industry to solve the climate change problem. As part of these efforts, development of gas turbines using hydrogen is continuously progressing. Gas turbine combined cycle (GTCCC) is attracting attention as a bridge power source for stable power supply as the proportion of renewable energy increases. This is expected to be

The change in the composition of the exhaust gas due to hydrogen combustion provides new system application possibilities. The Inverted Brayton cycle (IBC), which generates output by additionally expanding the exhaust gas discharged to atmospheric pressure, has not been widely used because the efficiency increase is not large when natural gas is used as fuel. In this case, since the H ₂ O ratio of the exhaust gas is high, the specific heat of the gas is increased as a result, and more power is generated in the same expansion process. Therefore, the model combining IBC with hydrogen GTCC can improve system efficiency by generating additional output by using energy from exhaust gas that is difficult to recover with HRSG.

For example, Korean Patent Publication No. 10-2020-0014754 discloses an apparatus comprising: at least one heat engine that burns fuel and generates exhaust gas containing water as a combustion product; and a reverse Brayton cycle turbine driven by the exhaust gas, and a reverse Brayton cycle compressor driven by the reverse Brayton cycle turbine to receive and compress the exhaust gas from the reverse Brayton cycle turbine. a plurality of heat engines comprising: a condenser positioned in the fluid path of the exhaust gas between the reverse Brayton cycle compressor and the reverse Brayton cycle turbine for condensing at least a portion of the water from the exhaust gas to form condensate; , A steam generating heat exchanger for receiving the condensed water from the condenser and transferring heat to the condensed water to generate steam, the reverse Brayton cycle turbine having a casing according to any one of claims 1 to 19, wherein the The first working fluid comprises the exhaust gas and the second working fluid comprises the steam produced by the steam generating heat exchanger. However, the above document does not mention about obtaining additional energy from high-temperature exhaust gas containing moisture.

In addition, Korean Patent Publication No. 2000-0021120 relates to a cryogenic cooler using a reverse Brayton cycle. Specifically, a power introduction unit into which power is introduced is installed at one end, and the power introduced through the power introduction unit is installed therein. a first device in which a compressor driven by and a small cooling fan are respectively installed; a second device in which a counter flow heat exchanger in which high pressure and low pressure gas exchange heat and an expander for forming a low temperature are respectively installed therein; and a third device for controlling power to a motor driving the compressor between the compressor and the counter flow heat exchanger, wherein the compressor, the expander and the counter flow heat exchanger are manufactured by MEMS technology. are starting However, the above document does not mention the problem that the temperature of the exhaust gas from the power plant is not high enough to efficiently perform the reverse Brayton cycle and the means for solving this problem.

Accordingly, the inventor of the present invention completed the present invention by studying a system and method capable of additionally generating power and obtaining heat energy from high-temperature exhaust gas discharged from power generation facilities.

Republic of Korea Patent Publication No. 10-2020-0014754 Republic of Korea Patent Publication No. 2000-0021120

An object of the present invention is to provide a combined power generation system with high efficiency.

Another object of the present invention is to provide a method for performing combined power generation with high efficiency using the same.

To this end, the present invention

Power generation facilities that discharge high-temperature exhaust gas containing moisture; and

An inverted Brayton cycle (IBC) facility into which high-temperature exhaust gas containing moisture discharged from the power generation facility is introduced.

Also, the present invention

obtaining exhaust gas from a power plant that discharges high-temperature exhaust gas containing moisture; and

Introducing the obtained exhaust gas into an inverted Brayton cycle (IBC);

According to the present invention, the high-temperature exhaust gas containing moisture discharged from the power generation facility is introduced into the reverse Brayton cycle facility to additionally generate power and obtain thermal energy, thereby greatly improving the energy efficiency of the process. However, it has the advantage of being able to solve the problem of environmental pollution that occurs when high-temperature exhaust gas is released into the atmosphere.

1 is a process diagram of a combined power generation system according to an embodiment of the present invention,
2 is a process diagram of a combined power generation system according to another embodiment of the present invention;
3 is a process diagram of a reverse Brayton cycle used in the combined power generation system of the present invention;
4 is a graph showing changes in output and water flow rates according to changes in the flow rate of the introduced gas;
5 is a graph showing the change in power and water flow rate according to the temperature change of the introduced gas;
6 is a graph comparing power and efficiency according to fuel and reverse Brayton cycle pressure;
7 is a graph showing a change in efficiency according to the size of a solid oxide fuel cell, and
8 is another graph showing a change in efficiency according to the size of a solid oxide fuel cell.

The present invention provides a combined power generation system. In particular, the present invention provides a combined power generation system capable of additionally generating power from high-temperature exhaust gas discharged from a power generation facility that discharges high-temperature exhaust gas containing moisture.

Specifically, the present invention

Power generation facilities that discharge high-temperature exhaust gas containing moisture; and

An inverted Brayton cycle (IBC) facility into which high-temperature exhaust gas containing moisture discharged from the power generation facility is introduced.

Hereinafter, the combined power generation system of the present invention will be described in detail for each component.

The combined power generation system of the present invention includes a power generation facility that discharges high-temperature exhaust gas containing moisture. A power generation facility is a facility that produces electricity using various raw materials. In the process, exhaust gas is generated. When the exhaust gas generated at this time contains moisture, the specific heat of the exhaust gas is turned on, Within the Layton cycle facility, more power can be generated during the same expansion process.

The combined power generation system of the present invention includes an Inverted Brayton cycle (IBC) facility into which high-temperature exhaust gas containing moisture discharged from the power generation facility is introduced. Since the exhaust gas discharged from the power generation facility is basically of a high temperature higher than room temperature, it not only contains energy in itself, but also pollutes the environment when it is released into the atmosphere as it is. Accordingly, the present invention introduces high-temperature exhaust gas into a reverse Brayton cycle facility, thereby obtaining additional power and heat energy from the exhaust gas, and furthermore, by lowering the temperature of the exhaust gas before releasing it into the atmosphere, it is possible to prevent environmental pollution. there is.

On the other hand, the reverse Brayton cycle additionally expands the exhaust gas discharged to atmospheric pressure to generate additional output, and also obtains additional heat energy using a heat exchanger. Since the temperature of the exhaust gas is lowered in this process, it is possible to solve the problem of polluting the atmospheric environment when discharged to the atmosphere.

The combined power generation system of the present invention preferably further includes a temperature raising facility for increasing the temperature of the exhaust gas before the high-temperature exhaust gas containing moisture is introduced into the reverse Brayton cycle facility. In general, the exhaust gas discharged from the power plant has a high temperature higher than room temperature, but may not be high enough to efficiently operate the later reverse Brayton facility. In particular, when the power generation facility includes a heat recovery boiler (HRSG) for obtaining additional thermal energy from the exhaust gas, the temperature of the exhaust gas discharged may be further lowered, and in this case, the efficiency of the reverse Brayton facility may be lowered. There is a problem with Therefore, the combined power generation system of the present invention further includes a heating facility for raising the temperature of the exhaust gas discharged from the power generation facility before it is introduced into the reverse Brayton cycle facility to raise the temperature of the exhaust gas, and then to the reverse Brayton cycle facility. It is desirable to introduce it considering the efficiency of the reverse Brayton cycle facility.

At this time, various facilities may be used as the temperature raising facility. For example, it may be a power generation facility that discharges exhaust gas at a higher temperature than the exhaust gas of the power generation facility. Specifically, a solid oxide fuel cell (SOFC) may be used. can be used When a facility such as a solid oxide fuel cell is used, since the exhaust gas discharged therefrom is also high-temperature, it can be mixed with the exhaust gas discharged from the power generation facility to raise the temperature, and in this state, the reverse Brayton cycle facility When introduced, there is an advantage of increasing efficiency.

On the other hand, power generation facilities that discharge high-temperature exhaust gas containing moisture may be various power generation facilities, but may be, for example, a gas turbine combined cycle (GTCC), in particular, hydrogen as a raw material It may be a gas turbine combined cycle power plant used as a The gas turbine combined cycle power plant is attracting attention as a bridge power source for stable power supply and demand according to the increase in the share of renewable energy, and in the case of small gas turbines, it is expected that they will be developed to a level that can operate only with hydrogen in the near future.

In addition, the power generation facility may further include a heat recovery boiler (HRSG) that treats the exhaust gas before discharging the exhaust gas, and through this, there is an advantage in that energy contained in the exhaust gas can be additionally obtained. .

In the combined power generation system according to the present invention, the power generation facility discharging the high-temperature exhaust gas containing moisture may use natural gas or hydrogen as a raw material, and among them, hydrogen is more preferable. When a power generation facility uses hydrogen as a raw material, compared to the case of using other raw materials including natural gas, the moisture content in the exhaust gas increases, and the specific heat of the exhaust gas increases accordingly, so the reverse Brayton cycle facility In a heavy turbine, more output can be generated even during the same expansion process. In addition, when power generation is performed using only hydrogen as a raw material, it is preferable because SOx components are not included in the exhaust gas, and therefore, corrosion problems due to sulfur do not occur in the cooling process of separating water in the reverse Brayton cycle facility. .

The reverse Brayton cycle facility included in the combined power generation system of the present invention can generate power by rotating a turbine using high-temperature exhaust gas and obtain thermal energy using a heat exchanger.

According to the combined power generation system according to the present invention, additional output and thermal energy are obtained from the high-temperature exhaust gas discharged from the power generation facility, thereby increasing the overall power generation efficiency, and also reducing the temperature of the high-temperature exhaust gas during the process. Since it is lowered, there is an advantage of solving the problem of air pollution that may occur when high-temperature exhaust gas is discharged into the atmosphere.

In addition, the present invention provides a combined power generation method, specifically

obtaining exhaust gas from a power plant that discharges high-temperature exhaust gas containing moisture; and

Introducing the obtained exhaust gas into an inverted Brayton cycle (IBC);

Hereinafter, the combined power generation method of the present invention will be described in detail for each step.

The combined power generation method of the present invention includes a step of obtaining exhaust gas from a power generation facility that discharges high-temperature exhaust gas containing moisture. Since the exhaust gas has a high temperature higher than room temperature, additional output and thermal energy can be obtained, and when it is released into the atmosphere as it is, there is a problem of air pollution.

The combined power generation method of the present invention includes introducing the exhaust gas obtained in the above step into an Inverted Brayton cycle (IBC). As described above, the reverse Brayton cycle expands high-temperature exhaust gas to obtain an output, and furthermore, heat energy can be obtained using a heat exchanger. In addition, since the temperature of the exhaust gas is lowered in this process, it is possible to solve the problem of air pollution caused by the high-temperature exhaust gas.

The combined power generation method of the present invention preferably further comprises raising the temperature of the exhaust gas before the obtained high-temperature exhaust gas is introduced into the reverse Brayton cycle. In general, the exhaust gas discharged from the power plant has a high temperature higher than room temperature, but may not be high enough to efficiently operate the later reverse Brayton facility. In particular, when the power generation facility includes a heat recovery boiler (HRSG) for obtaining additional thermal energy from the exhaust gas, the temperature of the exhaust gas discharged may be further lowered, and in this case, the efficiency of the reverse Brayton facility may be lowered. There is a problem with Therefore, the combined power generation method of the present invention further includes raising the temperature of the exhaust gas discharged from the power generation facility before introducing it into the reverse Brayton cycle facility, thereby raising the temperature of the exhaust gas and introducing the exhaust gas into the reverse Brayton cycle facility. It is desirable when considering the efficiency of the reverse Brayton cycle facility.

At this time, the step of raising the temperature of the exhaust gas can be performed in various ways, for example, a method of mixing with the exhaust gas discharged from the power plant that discharges the exhaust gas at a higher temperature than the exhaust gas of the power plant. It may be performed, and specifically, it may be performed by a method of mixing with exhaust gas discharged from a solid oxide fuel cell (SOFC). When a facility such as a solid oxide fuel cell is used, since the exhaust gas discharged therefrom is also high-temperature, it can be mixed with the exhaust gas discharged from the power generation facility to raise the temperature, and in this state, the reverse Brayton cycle facility When introduced, there is an advantage of increasing efficiency.

On the other hand, power generation facilities that discharge high-temperature exhaust gas containing moisture may be various power generation facilities, but may be, for example, a gas turbine combined cycle (GTCC), in particular, hydrogen as a raw material It may be a gas turbine combined cycle power plant used as a The gas turbine combined cycle power plant is attracting attention as a bridge power source for stable power supply and demand according to the increase in the share of renewable energy, and in the case of small gas turbines, it is expected that they will be developed to a level that can operate only with hydrogen in the near future.

In addition, the power generation facility may further include a step of treating the exhaust gas with a heat recovery boiler (HRSG) before discharging the exhaust gas, and through this, the energy contained in the exhaust gas can be additionally obtained. there is

In the combined power generation method according to the present invention, the power generation facility discharging the high-temperature exhaust gas containing moisture may use natural gas or hydrogen as a raw material, and among them, hydrogen is more preferably used. When a power generation facility uses hydrogen as a raw material, compared to the case of using other raw materials including natural gas, the moisture content in the exhaust gas increases, and the specific heat of the exhaust gas increases accordingly, so the reverse Brayton cycle facility In a heavy turbine, more output can be generated even during the same expansion process. In addition, when power generation is performed using only hydrogen as a raw material, it is preferable because SOx components are not included in the exhaust gas, and therefore, corrosion problems due to sulfur do not occur in the cooling process of separating water in the reverse Brayton cycle facility. .

In the reverse Brayton cycle facility used in the combined power generation method of the present invention, power generation is performed by rotating a turbine using high-temperature exhaust gas, and thermal energy can be obtained using a heat exchanger.

According to the combined power generation method according to the present invention, additional output and heat energy are obtained from the high-temperature exhaust gas discharged from the power generation facility, thereby increasing the overall power generation efficiency, and also reducing the temperature of the high-temperature exhaust gas during the process. Since it is lowered, there is an advantage of solving the problem of air pollution that may occur when high-temperature exhaust gas is discharged into the atmosphere.

Hereinafter, the present invention will be described in more detail with reference to process diagrams. The following description is only intended to specifically and exemplarily explain the present invention, and is not intended to be construed as limiting the scope of the claims of the present invention by the contents described below.

Figure 2 shows one embodiment of the combined power generation system of the present invention.

In FIG. 2 , the power generation facility 100 discharging high-temperature exhaust gas rotates the turbine 110 to generate power, and the exhaust gas discharged therefrom passes through the waste heat recovery boiler 120 to recover some of the heat. The exhaust gas that has passed through the heat recovery boiler 120 is mixed with the exhaust gas discharged from the solid oxide fuel cell 200 at the mixing point 300, and the temperature rises, and is introduced into the reverse Brayton cycle facility 400 in an elevated state. In the reverse Brayton cycle facility 400, the turbine 410 is rotated to generate output, and thermal energy is additionally recovered through the heat exchanger 420. Thereafter, moisture in the exhaust gas is removed while passing through the water separator 430, and the expanded exhaust gas is discharged into the atmosphere at atmospheric pressure through the compressor 440.

Hereinafter, the combined power generation system of the present invention will be described in more detail through experimental examples. The following experimental example is a simulation performed using Aspen hysys V10, a commercial software, and the configurations and conditions limited below are exemplary values introduced into the simulation to confirm the effect of the combined power generation system of the present invention, It is not intended that the scope of the rights to be claimed by the present invention be limited and interpreted by the matters described below.

In this experimental example, a combined power generation system in which an inverted Brayton cycle (IBC) is added to a gas turbine combined cycle (GTCC) and a combined power generation system in which SOFC is added to a GTCC + IBC system performance was confirmed. The GTCC system used a 15 MW-class commercial GT, and a single-pressure HRSG.

The configuration of each system is shown in FIGS. 1 and 2 . 2 works with hydrogen (H ₂ ) and natural gas (NG). 3 uses H ₂ as a fuel for the combustor and the anode. Power is produced by GTCC and fuel cell (SOFC). In a gas turbine, combustion gases produce power. H ₂ supplied from the fuel cell reacts with oxygen ions to produce output.

The gas discharged from the anode circulates to supply heat to the input hydrogen, and the remaining gas is supplied to the post combustor together with the exhaust gas of the cathode. The gas emitted from the SOFC is added to the exhaust gas of the GTCC. As described above, the IBC system produces output in the process of expanding the exhaust gas of the GTCC/SOFC below atmospheric pressure, cooling it, and discharging it back to the atmosphere.

The simulation of GTCC was performed using the commercial software Aspen hysys V10. The target gas turbine is a Titan 130 from Solar turbines. The simulated design performance was compared to reference data and presented in Table 1.

ingredient parameter reference
(Titan 130) simulation compressor pressure ratio 17.1 17.1 input Inlet air temperature (℃) 15 15 input Polytropic efficiency (%) N/A 93 assumed input burner Fuel flow rate (kg/s) N/A 0.86 calculated Fuel LHV (kJ/kg) N/A 49300 assumed input turbine Polytropic efficiency (%) N/A 88.97 assumed input Turbine discharge temperature (℃) 495 495 input Turbine inlet temperature (℃) N/A 1210 assumed input Turbine discharge mass flow (kg/s) 49.96 49.96 input Performance Mechanical Efficiency (%) N/A 97.76 assumed input Gearbox efficiency (%) N/A 97.28 assumed input Generator efficiency (%) N/A 97 assumed input Net Power (MW) 15 15 calculated Net Efficiency (%) 35.2 35.2 calculated

The efficiency of the turbine and compressor was set to a value that satisfies the inlet and outlet temperatures of the turbine and the total output.

The subcycle was modeled using Aspen hysys just like the gas turbine. And the design performance was calculated according to the temperature, flow rate and pressure ratio. The design parameters of the subcycle are listed in Table 2.

ingredient parameter simulation lower cycle condenser pressure (kPa) 4 Steam flow rate (kg/s) 100.13 ST Inlet pressure (kpa) 4150 Inlet temperature (℃) 450 Incenttropic efficiency (%) 89 Pump Incenttropic efficiency (%) 80 Motor Efficiency (%) 95 HRSG Pinch point temperature (℃) 10 Exhaust temperature (℃) 177 GTCC Performance Discharge pressure (kPa) 101.5 Generator efficiency (%) 97 Net Power (MW) 20.8 Net Efficiency (%) 48.8

The incentropic efficiency of the steam turbine (ST) is 89%. The subcycle consists of a single pressure system. The pressure level of the HRSG includes an economizer, an evaporator and a superheater. All heat exchangers were assumed to be of counter flow type.

The IBC system was used in conjunction with GTCC. The IBC system can be seen in FIG. 3 . Exhaust gases from the GTCC pass through the IBC turbine and are expanded below atmospheric pressure. The gas passing through the IBC turbine is cooled to 23°C through a heat exchanger. The cooling water supplied to the heat exchanger is input at 15℃ and discharged at 80℃ or higher. Some H ₂ O is condensed and separated from the gas. The separated H ₂ O is compressed to atmospheric pressure through a pump and discharged. The gas from which H ₂ O is separated is discharged to the atmosphere through a compressor. The polytropic efficiency of IBC's turbine and compressor is 89%. Design specifications can be found in Table 3.

ingredient parameter simulation turbine Polytropic efficiency (%) 89 Discharge pressure (kPa) - compressor Polytropic efficiency (%) 89 Discharge pressure (kPa) 101.325 Performance Generator efficiency (%) 97

The output of each component of the IBC system is determined by the flow rate of the supplied gas and the difference in enthalpy between states.

The total output of the IBC system is calculated as the difference between the output produced by the IBC turbine and the output consumed by the IBC compressor and pump.

When the conditions of the inlet gas are the same, the part that can affect the overall output of the IBC system is the output of the IBC compressor. How much water in the gas can be separated affects the power consumption of the IBC compressor. The expansion ratio of the IBC turbine is determined to separate as much water as possible under given inlet gas conditions.

An increase in the temperature or flow rate of the supplied gas affects the output of the IBC system. That is, when energy is supplied from the outside to the exhaust gas entering the IBC, or when high-temperature exhaust gas discharged from an external power source is supplied, the output of the IBC system may increase.

The reaction of the fuel cell is calculated using the principle of minimizing the Gibbs free energy at a given temperature and pressure. The water gasification reaction generates electricity and heat in fuel cells. Some of the heat generated in the cell stack reaction is used to maintain the operating temperature of the fuel cell stack.

In this experimental example, GTCC exhaust gas is supplied to the IBC system. Therefore, two cases of IBC systems according to the fuel used in GTCC (NG (natural gas), H ₂ ) were compared and analyzed. In the case of using NG as fuel, the gas composition was 75.05% NG, 14.09% O ₂ , 6.83% H ₂ O, 3.14% CO ₂ and 0.89% Ar in terms of molar ratio. When H ₂ was used as fuel, the molar ratio was 73.46% N ₂ , 14.74% O ₂ , 10.89% H ₂ O, 0.04% CO ₂ and 0.87% Ar. The flow rate of the gas supplied to the IBC system was analyzed in the range of 30 kg/s to 80 kg/s and the temperature was in the range of 120 °C to 270 °C. A detailed performance analysis of the components (turbine, compressor, and separated water) of the IBC system was performed. A detailed performance analysis consisted of a process to determine the effect of the temperature and flow rate of the gas supplied to the IBC system on the IBC turbine output, the IBC compressor output, and the separated water flow rate. For the case-by-case comparison of the IBC system, the pressure after expansion of the IBC turbine, which can obtain the optimal performance according to the change in the supplied gas condition, was applied.

The performance change of the IBC system for the flow rate change was carried out by changing only the gas flow rate at a fixed temperature of 180 °C. When the gas flow rate changes, the optimal operating condition (pressure after expansion) of the IBC system does not change, and the amount of separated water increases as the flow rate increases. Cases using H ₂ as fuel have, on average, 18.4% higher turbine output and 15.9% higher compressor power consumption than cases using NG. Turbine output (a), compressor output (b), and separated water flow rate (c) of the performance of the two cases according to the flow rate change can be confirmed in FIG.

The performance change for temperature change was carried out with only the gas temperature as a variable at a fixed flow rate of 50 kg/s. Unlike the change in flow rate, the optimum operating condition (pressure after expansion) of the IBC system changed according to the change in temperature. As the temperature of the gas increased, the pressure after expansion of the IBC turbine for optimal operation of the IBC system decreased.

Expanding the gas to a lower pressure in the IBC turbine increases the output of the IBC turbine. However, when the pressure of the expanded gas is lowered, the condensation point is lowered and the flow rate of water condensed and separated at 23 ° C is reduced. The more H ₂ O remaining in the gas without being condensed into water, the greater the power consumption of the IBC compressor. In this case, since the power consumption of the IBC compressor is higher than the output of the IBC turbine, there is a limit to the expandable pressure. However, at the same flow rate, if the temperature of the gas supplied to the IBC turbine increases, the lower IBC turbine can expand to a lower pressure.

These characteristics can be clearly seen under the same gas flow condition of 50 kg/s in the case of using H ₂ as fuel. When the input temperature is 120 ° C, the optimum pressure after expansion is 82 kPa, 2.523 kg / s of H ₂ O is separated, and the output of the IBC is 0.073 MWe. It can also expand gas up to 65.38 kPa in the IBC turbine. When the temperature is 270 °C, less H ₂ O is separated at 1.821 kg/s with an optimum pressure of 50 kPa after expansion. However, the output of IBC is 0.89MWe, which is 12.2 times higher than 0.073MWe at 120℃. In this case, the IBC turbine can expand the gas up to 26.51 kPa.

As a result, the change in temperature of the gas supplied to the IBC system leads to a change in the pressure condition for optimal operation and the minimum pressure that can produce additional output in the IBC.

When the temperature of the inlet gas is a variable, the average turbine output of the IBC turbine in the case of using H ₂ as fuel is 22.7% higher than that of the case of using NG, and the compressor power consumption is 20.22% higher. These results can be confirmed in FIG. 5 . 5 shows the performance of the two cases according to temperature change as turbine output (a), compressor output (b), and separated water flow rate (c).

In the case of a system using H ₂ , it can be seen that the overall IBC output is higher than that of the case using NG. This difference was caused by the H ₂ O ratio of the gas supplied to the IBC system. This is because when H ₂ is used as a fuel, the H ₂ O ratio of the gas after combustion increases, and as a result, the specific heat of the gas increases, so more output is generated during the same expansion process. In addition, in the IBC system of a system using H ₂ as a fuel, the increase in power consumption of the IBC compressor is not large because more H ₂ O is separated in the cooling process and then enters the compressor. This trend can be confirmed through the ratio of the output of the compressor to the turbine. In comparison using the flow rate as a variable, the average was 88.5% in the case of using NG and 86.4% in the case of using H ₂ . In comparison using temperature as a variable, the average was 87.34% in the case using NG, but the average was 85.6% in the case using H ₂ .

The performance comparison of the GTCC+IBC system was performed under the design conditions (TIT, PR, temperature conditions) shown in Tables 1 and 2. The performance of GTCC according to fuel can be seen in Table 4.

NG _H2 GT
Performance Fuel flow rate (kg/s) 0.86 0.36 Fuel LHV (kJ/kg) 49300 120000 Combustion temperature (℃) 1177 1177 Discharge temperature (℃) 495 488.5 Turbine exhaust mass flow (kg/s) 49.96 49.46 Net Power (MW) 15 15.4 Net Efficiency (%) 35.2 35.76 GTCC
Performance Exhaust temperature (℃) 177 179.18 Net Power (MW) 20.8 21.1 Net Efficiency (%) 48.8 49

In the GTCC system using NG as fuel under the design conditions, the temperature and flow rate of the gas supplied to the IBC are 177 °C and 49.96 kg/s, respectively, and in the case of using H ₂ as fuel, they are 179.18 °C and 49.46 kg/s.

In order to find the optimal operating condition (IBC turbine outlet pressure), both the IBC turbine output and the change in power consumption of the IBC compressor due to water separation must be considered. In the case of using NG, additional output was generated from the pressure of 50 kPa or more in the IBC system combined with GTCC. The highest output and efficiency can be obtained at a pressure of 71 kPa. The output generated by the IBC system is 0.22MWe, and the overall system efficiency increases by 0.5%p. In the case of using H ₂ , output occurred from a pressure of 43.9 kPa or higher in the IBC system. Maximum power and efficiency can be achieved at 66 kPa, resulting in an output of 0.32 MWe. Overall system efficiency rises by 0.7%p. A comparison of the GTCC+IBC system at the optimal point can be found in Table 5.

case NG _H2 system GTCC GTCC+IBC GTCC GTCC+IBC GTCC 20.8 20.8 21.1 21.1 IBC 0.22 0.32 gun 20.8 21.02 21.1 21.42 efficiency 48.8 49.3 49 49.7

At the optimal operating point, the output of the IBC system using _H2 is 45.45% higher than that of NG, and the ratio of compressor to turbine output is 86.59% for _H2 and 88.72% for NG. The output of the IBC system in the case of using H ₂ is 1.5% of the output of GTCC. The GTCC+IBC system using hydrogen has a 1.52% increase in output compared to GTCC. In Figure 6, the performance of the GTCC + IBC system according to fuel and IBC turbine outlet pressure was compared.

The GTCC+IBC system can configure a combined cycle with SOFC that uses H ₂ as fuel and emits 326.7°C exhaust gas. SOFC exhaust is added to the GTCC+IBC system, which feeds GTCC exhaust to the IBC. In the GTCC+SOFC+IBC system, SOFC exhaust gas is added to GTCC exhaust gas and supplied to the IBC. SOFC determines the size of the plant by the number of stacks of cells, and the system efficiency and exhaust gas temperature are constant regardless of the size. In this study, the performance change of the GTCC+SOFC+IBC system according to the size of the SOFC was analyzed, and the system uses H ₂ as fuel. SOFCs ranging in size from 1 MWe to 50 MWe were used.

Since the exhaust gas temperature of SOFC (326.7 °C) is higher than that of GTCC (179.18 °C), the temperature of the inlet gas supplied to the IBC in the GTCC+SOFC+IBC system is higher than that in the GTCC+IBC system. Also, the flow rate of the inlet gas supplied to the IBC increases. The exhaust gas of the GTCC is always constant, but the flow rate of the exhaust gas added varies according to the size of the SOFC. As the SOFC size increases, the temperature and flow rate of the gas introduced into the IBC increase. An increase in the flow rate of the supplied gas affects the increase in output of the IBC system. Increasing the SOFC exhaust gas flow rate increases the temperature of the gas supplied to the IBC system and allows the IBC turbine to expand to a lower pressure. In addition, the optimal operating point pressure of the GTCC+SOFC+IBC system is lowered. This trend can be confirmed in FIG. 7 .

In the five cases according to the SOFC size, the minimum pressure limit for IBC system utilization is all different. The minimum pressure decreased as the size of the SOFC increased. Table 6 summarizes the optimal operating points of the five cases.

H ₂ +SOFC+IBC SOFCs (MW) One 5 15 25 50 GTCC(MW) 21.1 21.1 21.1 21.1 21.1 IBC(MW) 0.4025 0.7199 1.596 2.529 4.801 Net Power (MW) 22.616 26.829 37.726 48.659 76.021 Net Efficiency (%) 50.03 50.95 52.5 53.45 54.65 IBC pressure (kPa) 64 59 54 52 50

It can be seen that the output and efficiency of the entire system increase in proportion to the increase in the size of the SOFC. In FIG. 8, the data in Table 5 was graphically shown. Since SOFC is currently difficult to construct a large-scale plant due to technical limitations, up to 15 MWe, which is the same size as GT, was assumed as the maximum size. The GTCC+SOFC+IBC system composed of SOFC exceeding 15 MWe is marked with a dotted line.

The results of the experiment according to this experimental example are summarized as follows.

(1) When gas is supplied to the IBC system after combustion of H ₂ and NG, when the gas flow rate is fixed at 50 kg/s and the temperature is changed between 120℃ and 270℃, the IBC system output of the case using H ₂ is On average, it is 45.23% higher. When the gas temperature is fixed at 180 °C and the flow rate is varied from 30 kg/s to 80 kg/s, the output of the H ₂ -combustion case IBC system is 38.14% higher on average. Based on the calculation results of the IBC system performance according to the fuel type, IBC can be used in a wide range of flow rate and temperature conditions in a system using hydrogen.

(2) The GTCC+IBC system using H ₂ as fuel has 1.52% higher output than the H ₂ -combustion GTCC, and the output and efficiency are improved by 1.9% and 1% compared to the NG-combustion GTCC+IBC system. However, the simple combination of GTCC and IBC does not significantly increase the output and efficiency of the system. When a combined cycle is configured by supplying high-temperature gas discharged from an external power source to the GTCC+IBC system, a higher efficiency system configuration is possible.

(3) When a GTCC+SOFC+IBC system is configured by adding a SOFC that discharges high-temperature gas to the GTCC+IBC system, an effective combined cycle can be created. The high-temperature gas discharged from the SOFC raises the temperature and flow rate of the gas supplied to the IBC system, enabling higher output. The high-efficiency IBC generates synergies of multiple cycles. Whether the combined cycle synergy of SOFC and GTCC is generated by the IBC system can be confirmed in the case where SOFC and GTCC of the same size are combined. The efficiency of 15 MWe SOFC using hydrogen is 52.16% and that of 15 MWe GTCC is 49.3%. A simple combination of GTCC+SOFC without IBC should be between 52.16% and 49.3%, but the efficiency of the GTCC+SOFC+IBC system is 52.5%. That is, it is possible to configure an effective combined cycle of GTCC and other power sources using the IBC system.

100............Power plant
110........... Turbines in power plants
120........... Heat recovery boiler
200............Solid oxide fuel cell
300........mix point
400............... Reverse Brayton Cycle Facility
410 ..................Turbine in a reverse Brayton cycle plant
420...........Heat exchanger
430............ Water Separator
440........Compressor of reverse Brayton cycle plant

Claims (14)

Power generation facilities that discharge high-temperature exhaust gas containing moisture; and
A combined power generation system comprising: an inverted Brayton cycle (IBC) facility into which high-temperature exhaust gas containing moisture discharged from the power generation facility is introduced.
The combined power generation system according to claim 1, wherein the combined power generation system further comprises a temperature raising facility for increasing the temperature of the exhaust gas before the high-temperature exhaust gas containing moisture is introduced into the reverse Brayton cycle facility.
The combined power generation system according to claim 1, wherein the power generation facility discharging high-temperature exhaust gas containing moisture is a gas turbine combined cycle (GTCCC) facility.
The combined power generation system according to claim 1, wherein the power generation facility further comprises a heat recovery boiler (HRSG) that treats the exhaust gas before discharging it.
The combined power generation system according to claim 2, wherein the temperature raising facility is a power generation facility that discharges exhaust gas having a higher temperature than the exhaust gas of the power generation facility.
The combined power generation system according to claim 1, wherein the power generation facility discharging the high-temperature exhaust gas containing moisture uses natural gas or hydrogen as a raw material.
The combined power generation according to claim 1, wherein the inverted Brayton cycle (IBC) facility generates power by rotating a turbine using high-temperature exhaust gas and obtains thermal energy using a heat exchanger. system.
obtaining exhaust gas from a power plant that discharges high-temperature exhaust gas containing moisture; and
A combined power generation method comprising: introducing the obtained exhaust gas into an inverted Brayton cycle (IBC).
The combined power generation method according to claim 8, further comprising raising the temperature of the exhaust gas before the obtained exhaust gas is introduced into the reverse Brayton cycle.
The combined power generation method according to claim 8, wherein the power generation facility discharging the high-temperature exhaust gas containing moisture is a gas turbine combined cycle (GTCCC) facility.
The combined power generation method according to claim 8, wherein the power generation facility includes a step of treating the exhaust gas with a heat recovery boiler (HRSG) before discharging the exhaust gas.
The method of claim 9, wherein the step of raising the temperature of the exhaust gas is performed by mixing the exhaust gas with exhaust gas discharged from a power generation facility that discharges exhaust gas having a higher temperature than that of the exhaust gas of the power generation facility. Characterized by a complex power generation method.
The combined power generation method according to claim 8, wherein the power generation facility discharging the high-temperature exhaust gas containing moisture uses natural gas or hydrogen as a raw material.
The combined power generation according to claim 8, wherein the inverted Brayton cycle (IBC) facility generates power by rotating a turbine using high-temperature exhaust gas and obtains thermal energy using a heat exchanger. method.

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