Cold energy utilization gas turbine power generation system

Abstract

A cold heat utilizing gas turbine power generation system 100 is provided with: an air liquefaction and separation device 10, a gas turbine power generator 20, a bottoming cycle 30, a pressurized oxygen supply line 52, and a pressurized nitrogen supply line 54. The air liquefaction and separation device 10 liquefies air Air by cold heat of liquid hydrogen LH2 to manufacture, in addition to a required amount of hydrogen gas H2, liquid oxygen LO2 and liquid nitrogen LN2. The gas turbine power generator 20 performs oxygen-enriched combustion of the hydrogen gas H2 to generate power. The bottoming cycle 30 has a reheat combustor 32 and a nitrogen cycle 40. The pressurized oxygen supply line 52 pressurizes the liquid oxygen LO2 in a liquid state, and supplies the pressurized liquid oxygen LO2 to the gas turbine combustor 24 as pressurized oxygen gas after heating the same with a nitrogen gas cooler 48. The pressurized nitrogen supply line 54 pressurizes the liquid nitrogen LN2 in a liquid state, and supplies the pressurized liquid nitrogen LN2 to an exit side of a nitrogen gas compressor 42 as pressurized nitrogen gas after heating the same with the nitrogen gas cooler 48.

Description

[Technical Field]

[0001] The present invention relates to a gas turbine power generation system that utilizes the cold energy of liquid hydrogen. [Background technology]

[0002] In 2018, Graz University of Technology announced the Graz Cycle, which uses hydrogen combustion, as a carbon-neutral thermal power generation method that does not emit carbon dioxide, a cause of global warming. In addition, the New Energy and Industrial Technology Development Organization (NEDO) has begun studying a hydrogen-oxygen combustion turbine power generation system based on the Graz Cycle (2020-2022). Hydrogen-oxygen combustion turbine power generation systems are disclosed in, for example, Non-Patent Documents 1-3.

[0003] Non-Patent Document 1 conducts an exergy analysis of the Graz cycle, which utilizes the characteristics of hydrogen-oxygen combustion. The Graz cycle is a semi-closed combined cycle of the Brayton cycle and the Rankine cycle, using only water vapor as the working fluid through hydrogen-oxygen combustion. The exergy loss of combustion in the latest 1600°C-class gas turbine is 26.8%, and the exergy efficiency at the sending end of a gas turbine combined cycle (GTCC) is 56.5%. In contrast, in the Graz cycle, the exergy loss in the combustor with a turbine inlet temperature of 1450°C and a combustion pressure of 13.8 MPa is 16.9%, and the exergy efficiency at the sending end is 61.4%, which is a significant improvement over a 1600°C-class gas turbine. In addition to the calorific value of exergy, liquefied hydrogen also has cold exergy of 13.3 MJ / kg. If this cold energy is used for cryogenic air separation, the exergy efficiency of the Graz cycle at the power plant end can be improved by a further 2.1%.

[0004] Non-Patent Document 2 states that the thermal efficiency of an oxygen-hydrogen combustion power generation cycle is 2-11% higher than that of an air-hydrogen combustion GTCC. However, when oxygen production power is taken into account, the net thermal efficiency is 4-6% lower than the net thermal efficiency. Therefore, it states that the net thermal efficiency is likely to be about the same as that of an air-hydrogen combustion GTCC. Furthermore, Non-Patent Document 2 assumes stoichiometric complete combustion of oxygen and hydrogen, but states that complete combustion is not possible at an equivalence ratio of 1 in reality. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Seiji Yamashita and three others, "Exergy Analysis of Hydrogen-Oxygen Combustion Turbine," Journal of the Gas Turbine Society of Japan, 45-3 (2017), pp. 170-177 [Non-patent document 2] Kotaro Takehanawa and two others, "Exergy and Performance Analysis of Oxygen-Hydrogen Combustion Power Generation Cycle," Journal of Japan Society of Energy and Resources, Vol. 42, No. 5, (2021) [Non-patent document 3] "About the Oxygen-Hydrogen Combustion Turbine Power Generation System," [online], [searched June 20, 2022], Internet,<URL:http: / / www.ghe.iir.titech.ac.jp / japanese / turbine / index.html> Summary of the Invention [Problem to be solved by the invention]

[0006] Fig. 1 is a diagram showing the overall configuration of the hydrogen-oxygen combustion turbine power generation system disclosed in Non-Patent Document 3. In this diagram, A is a cryogenic separation oxygen production plant, and B is a hydrogen-oxygen combustion turbine. Cryogenic separation oxygen production plant A uses two distillation towers (called double columns) with different pressures to cool the air and concentrate the easily evaporating nitrogen into a gas, and the less evaporating oxygen into a liquid, separating the oxygen and nitrogen using the gas-liquid equilibrium of the air. The separated oxygen gas is supplied to the hydrogen-oxygen combustor (hereinafter referred to as the combustor) of hydrogen-oxygen combustion turbine B. Liquid hydrogen is transported by a hydrogen transport ship or the like and stored in a liquefied hydrogen tank, and the hydrogen gas vaporized in a vaporizer is supplied to the combustor. Hydrogen gas, oxygen gas, and water are supplied to the combustor of hydrogen-oxygen combustion turbine B. In the combustor, high-temperature steam is generated by burning hydrogen, which drives the turbine and generates electricity. Part of the steam is extracted from the turbine, compressed by the compressor, and recirculated to the combustor. The remaining steam leaving the turbine is cooled in the condenser to become water (condensed water), some of which is supplied to the combustor by the condensate pump and feedwater pump, and the remainder is discharged to the outside.

[0007] The above-described hydrogen-oxygen combustion turbine power generation system has the following problems. (1) There is a large amount of energy loss in oxygen production plants. In a hydrogen-oxygen combustion turbine, 1 mole of oxygen gas is required for every 2 moles of hydrogen gas for complete combustion. Therefore, in terms of weight ratio, the ratio of hydrogen to oxygen is 1:8 for complete combustion, and more oxygen gas is required for stable combustion. On the other hand, even if air is liquefied and separated using the cold energy of 1 kg of liquefied hydrogen, only about 2 kg of oxygen gas can be obtained. Therefore, oxygen production plants require a power source other than cold energy for the majority of their power, and this results in a large energy loss. In addition, the large amount of nitrogen gas (by-product nitrogen) generated in oxygen production plants does not contribute to power generation. Therefore, there has been a demand for further improvement in the efficiency of power generation, including oxygen production plants. (2) If hydrogen and oxygen are not burned at a stoichiometric ratio, the system will not function properly because non-condensable residual oxygen (or hydrogen) will be mixed in the combustion gas. In fact, complete combustion is not possible at an equivalence ratio of 1. (3) The turbine is essentially a steam turbine, and the final stage is large because it operates at a reduced pressure to recover energy. Furthermore, the steam generated in the hydrogen-oxygen combustor and exiting the turbine must be cooled down to water (condensed water), so the condenser is large and requires a large amount of cooling water. Furthermore, maintenance and management of the water treatment are required. This makes it difficult to install the reactor inland, where large amounts of cooling water cannot be obtained.

[0008] The present invention has been devised to solve the above-mentioned problems. That is, a first object of the present invention is to provide a cold energy gas turbine power generation system that is capable of complete combustion of hydrogen and that can improve power generation efficiency by utilizing the cold energy of liquid hydrogen. A second object of the present invention is to provide a cold energy gas turbine power generation system that can be installed inland where a large amount of cooling water is not available. [Means for solving the problem]

[0009] According to the present invention, there is provided a cryogenic air separation unit that liquefies air using the cold heat of liquid hydrogen to produce a required amount of hydrogen gas as well as liquid oxygen and liquid nitrogen; a gas turbine generator that generates electricity by oxygen-enriching combustion of the hydrogen gas; a supplementary combustion combustor that burns the hydrogen gas with remaining oxygen to heat the exhaust gas of the gas turbine generator; a nitrogen cycle having a nitrogen gas cooler that cools low-pressure nitrogen gas by heat exchange between the liquid oxygen and the liquid nitrogen, and circulating the nitrogen gas to recover power for electricity generation; a pressurized oxygen supply line for pressurizing the liquid oxygen produced in the air separation unit in a liquid state, heating the pressurized liquid oxygen in the nitrogen gas cooler, and supplying the pressurized liquid oxygen as pressurized oxygen gas to the gas turbine generator; and a pressurized nitrogen supply line that pressurizes the liquid nitrogen produced in the air liquefaction separation unit in a liquid state, heats the pressurized liquid nitrogen in the nitrogen gas cooler, and supplies the pressurized liquid nitrogen as pressurized nitrogen gas to the high-pressure nitrogen gas in the nitrogen cycle. [Effects of the Invention]

[0010] According to the configuration of the present invention, the required amount of hydrogen gas is produced by liquefying air using the cold heat of liquid hydrogen in the cryogenic air separation unit, so that energy loss in the cryogenic air separation unit can be minimized.

[0011] The liquid oxygen produced in the air separation unit together with hydrogen gas is less than the amount of oxygen required by the gas turbine generator. However, this liquid oxygen is pressurized in liquid form through the pressurized oxygen supply line, heated in a nitrogen gas cooler, and supplied to the gas turbine generator as pressurized oxygen gas. This reduces the compression power required by the gas turbine generator by an amount equivalent to about five times the amount of compressed oxygen gas. Furthermore, in the gas turbine generator, the hydrogen gas produced in the air separation unit is subjected to oxygen-enriched combustion using compressed air and pressurized oxygen gas, so the hydrogen gas can be stably and completely combusted with a sufficient amount of oxygen.

[0012] In addition, the liquid nitrogen produced in the cryogenic air separation unit is pressurized in a liquid state through a pressurized nitrogen supply line, heated in a nitrogen gas cooler, and added to the high-pressure nitrogen gas in the nitrogen cycle. This reduces the compression power required in the nitrogen cycle and increases the amount of electricity generated by the nitrogen cycle.

[0013] In addition, the hydrogen gas produced in the cryogenic air separation unit is burned with residual oxygen in the reheating combustor to heat the exhaust gas temperature, so that the high-pressure nitrogen gas in the nitrogen cycle can be sufficiently heated with this high-temperature exhaust gas, thereby improving the efficiency of the nitrogen cycle.

[0014] That is, the liquid oxygen produced in the cryogenic air separation unit together with the required amount of hydrogen gas contributes to reducing the power consumption of the gas turbine generator and oxygen-enriched combustion, while the liquid nitrogen contributes to increasing the amount of power generated by the nitrogen cycle.

[0015] Therefore, overall, oxygen for combustion can be produced by utilizing the cold energy of the liquid hydrogen, and power generation efficiency can be improved. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is an overall configuration diagram of a hydrogen-oxygen combustion turbine power generation system disclosed in Non-Patent Document 3. [Figure 2] 1 is a diagram showing a first embodiment of a cold energy utilization gas turbine power generation system according to the present invention. [Figure 3] 1 is an overall configuration diagram of a cryogenic air separation unit. [Figure 4] FIG. 1 is an overall configuration diagram of a nitrogen cycle. [Figure 5] FIG. 2 is a diagram showing a second embodiment of a cold energy utilization gas turbine power generation system according to the present invention. [Figure 6] FIG. 1 is an overall configuration diagram of a carbon dioxide gas cycle. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that common parts in the drawings are given the same reference numerals and redundant explanations will be omitted.

[0018] The main specifications of the hydrogen-oxygen combustion turbine power generation system currently under development are as follows: (1) The fuel is pure hydrogen (H2) and the oxidizer is pure oxygen (O2), which are burned in a stoichiometric ratio (i.e., H2 + 1 / 2O2 → H2O, with a molar ratio of H2:O2 = 1:0.5). (2) Hydrogen gas is supplied in the form of liquefied hydrogen, which is compressed and then vaporized for use. (3) Oxygen gas is separated from air using three air separation methods: cryogenic air separation (CAS), pressure swing adsorption (PSA), and high-temperature oxygen separation membrane (OTM). (4) In any of the air separation methods, the purity of oxygen gas cannot be increased to 100%, so stoichiometric combustion is not possible. Therefore, oxygen gas must be added, and the power required to compress the oxygen gas to the combustor pressure is not reflected in the power generation efficiency. (5) The equipment efficiencies used to calculate the power generation efficiency are set as follows: compressor efficiency: 89%, gas turbine efficiency: 92%, steam turbine efficiency: 84% to 89%, mechanical efficiency: 99%, generator efficiency: 99.5%, and liquefied hydrogen compression pump efficiency: 100%. (6) A combined cycle is adopted in which combustion gas (i.e., steam) is expanded in a gas turbine and a steam turbine. (7) Under the above conditions, the power generation efficiency at turbine inlet temperature / pressure: 1550°C / 3.3MPa is estimated to be 62% when using CAS, 63% when using PSA, and 65% when using OTM.

[0019] Hereafter, hydrogen gas will be referred to as H2, liquefied hydrogen as LH2, oxygen gas as O2, liquid oxygen as LO2, nitrogen gas as N2, and liquid nitrogen as LN2.

[0020] (WET type) 2 is a diagram showing a first embodiment of a cold energy utilization gas turbine power generation system 100 according to the present invention. Hereinafter, the system of the first embodiment will be referred to as a WET type. In this figure, a cryogenic gas turbine power generation system 100 includes a cryogenic air separation unit 10 , a gas turbine generator 20 , and a bottoming cycle 30 .

[0021] The cryogenic air separation unit 10 liquefies air (Air) using the cold energy of liquid hydrogen (LH2) to produce the required amount of hydrogen gas (H2), as well as liquid oxygen (LO2) and liquid nitrogen (LN2).

[0022] The gas turbine generator 20 generates electricity by oxygen-enriched combustion of hydrogen gas H2. In this example, the gas turbine generator 20 includes a gas turbine compressor 22 , a gas turbine combustor 24 , and a gas turbine 26 .

[0023] The gas turbine compressor 22 compresses air. That is, the air used as an oxidizer is compressed in the same manner as in the existing GTCC (normal pressure air is compressed by the gas turbine compressor 22 at the pressure ratio of the existing GTCC) and sent to the gas turbine combustor 24. In this example, a pressure ratio of 23 for a 1600°C-class GTCC II is used.

[0024] The gas turbine combustor 24 performs oxygen-enriched combustion of the hydrogen gas H2 vaporized in the air separation unit 10 using compressed air and pressurized oxygen gas (pressurized oxygen gas O2). That is, in the gas turbine combustor 24, the pressurized oxygen gas separated by air liquefaction is mixed with compressed air and used as oxygen-enriched air. The amount of compressed air is adjusted so that the residual oxygen concentration after combustion is 16%, which is the same as that of existing LNG combined cycle plants.

[0025] The gas turbine 26 obtains power generation power from the combustion gas G1 and drives a generator (not shown) to generate electricity. That is, the fuel for the gas turbine generator 20 is hydrogen gas H2, and the oxidizer is air and oxygen gas O2, and combustion is performed in the same manner as the existing GTCC (LNG combined cycle) with an air-fuel ratio of 16% (dry) residual oxygen concentration in the exhaust gas.

[0026] The bottoming cycle 30 recovers power for generating electricity from the exhaust gas G2 of the gas turbine 26. In this figure, the bottoming cycle 30 has a reheating combustor 32, a nitrogen gas turbine cycle (hereinafter referred to as the nitrogen cycle 40), and a steam turbine cycle (hereinafter referred to as the steam cycle 60). That is, in this example, a combined cycle with a two-stage bottoming cycle is adopted, in which a nitrogen cycle 40 using the combustion gas of the additional combustion combustor 32 as a heat source is added between the gas turbine generator 20 and the steam cycle 60.

[0027] The reheating combustor 32 burns hydrogen gas H2 with the remaining oxygen in the exhaust gas from the gas turbine 26, thereby heating the exhaust gas G2 from the gas turbine 26. The heating temperature at the inlet of the bottoming cycle 30 is preferably 650 to 700°C. The amount of additionally heated hydrogen is preferably a small amount equivalent to the amount of heat generated by the nitrogen gas N2 in the nitrogen cycle 40 (approximately 4% of the amount of hydrogen fuel in the gas turbine generator 20).

[0028] The nitrogen cycle 40 circulates nitrogen gas N2 to recover power for generating electricity. In this example, the nitrogen cycle 40 is located immediately downstream of the reheat combustor 32 and includes a nitrogen gas compressor 42 , a nitrogen gas heater 44 , a nitrogen gas turbine 46 , and a nitrogen gas cooler 48 .

[0029] The nitrogen gas compressor 42 compresses low-pressure nitrogen gas (low-pressure nitrogen gas N2). The nitrogen gas heater 44 heats high-pressure nitrogen gas (high-pressure nitrogen gas N2) with high-temperature exhaust gas (high-temperature exhaust gas G2) from the additional combustion combustor 32. The nitrogen gas turbine 46 drives a generator (not shown) and recovers power to generate electricity from the heated high-pressure nitrogen gas.

[0030] The nitrogen gas cooler 48 cools the low-pressure nitrogen gas (intake air cooling) by exchanging heat with the liquid oxygen LO2 and liquid nitrogen LN2 supplied from the cryogenic air separation unit 10. In other words, the nitrogen gas cooler 48 is a heat exchanger that heats the liquid oxygen LO2 and liquid nitrogen LN2 and cools the low-pressure nitrogen gas.

[0031] In FIG. 2, the cold energy recovery gas turbine power generation system 100 further includes a pressurized oxygen supply line 52 and a pressurized nitrogen supply line 54 .

[0032] The pressurized oxygen supply line 52 has a liquid oxygen pump 52a that pressurizes the liquid oxygen LO2 produced in the air separation unit 10 while it is in a liquid state, and the pressurized liquid oxygen LO2 is heated in a nitrogen gas cooler 48 and supplied to the gas turbine combustor 24 as pressurized oxygen gas. The pressurization pressure by the liquid oxygen pump 52 a is set to be equal to or higher than the internal pressure of the gas turbine combustor 24 . The oxygen obtained in the cryogenic air separation unit 10 is liquid oxygen LO2, so by compressing it in a liquefied state, the power required for pressurization up to the combustor inlet pressure is negligibly small.

[0033] The pressurized nitrogen supply line 54 has a liquid nitrogen pump 54a that pressurizes the liquid nitrogen LN2 produced in the air separation unit 10 in a liquid state, and the pressurized liquid nitrogen LN2 is heated in a nitrogen gas cooler 48 and supplied to the outlet side of the nitrogen gas compressor 42 as pressurized nitrogen gas. The pressure applied by the liquid nitrogen pump 54a is set to be equal to or higher than the outlet pressure of the nitrogen gas compressor 42. By compressing the liquid nitrogen LN2 obtained in the cryogenic air separation unit 10 in a liquefied state, the power required for pressurization up to the outlet pressure of the nitrogen gas compressor 42 or higher is negligibly small.

[0034] The steam cycle 60 includes a booster pump 62 , a steam heater 64 , a steam turbine 66 , and a condenser 68 . The booster pump 62 pressurizes the condensed water W1. The steam heater 64 heats the pressurized water W2 with high-temperature exhaust gas from the nitrogen gas heater 44 to generate high-pressure, high-temperature steam (high-pressure, high-temperature steam S). The steam turbine 66 recovers power for generating electricity from the high-pressure, high-temperature steam S. The condenser 68 cools the low-pressure steam S to obtain condensed water W1.

[0035] The nitrogen gas heater 44 and the steam heater 64 are installed in the exhaust path of the additional combustion device 32, and function as a heat recovery heat exchanger (HRHEX) as a whole.

[0036] FIG. 3 is a diagram showing the overall configuration of the cryogenic air separation unit 10. As shown in FIG. Air separation involves pre-treatment using the thermal stoichiometry (TSA) method, followed by liquefaction and separation using heat exchange between LH2 and air. The advantage of this method is that it consumes only half the power of conventional cryogenic air separation methods.

[0037] In FIG. 3, the cryogenic air separation unit 10 includes an air compressor 11 , a nitrogen gas cooler 12 , a helium gas cooler 14 , an expansion valve 15 , a gas-liquid separator 16 , and a gas compressor 17 .

[0038] The air compressor 11 compresses the supply air (air) to a predetermined pressure (for example, 600 kPa).

[0039] The nitrogen gas cooler 12 has a cold / hot heat exchanger 12a and an N2 circulator 12b, and indirectly cools the air by circulating nitrogen gas N2 between liquid hydrogen LH2 and air. The helium gas cooler 14 has a liquefaction heat exchanger 14a and a He circulator 14b, and indirectly cools the air by circulating helium gas He between liquid hydrogen LH2 and the air. The air is cooled to, for example, -176°C by the nitrogen gas cooler 12 and the helium gas cooler 14.

[0040] The expansion valve 15 adiabatically expands the cooled air and further cools it to an extremely low temperature (for example, -194°C). The gas-liquid separator 16 uses, for example, a double column to separate liquid nitrogen LN2 and liquid oxygen LO2. The gas compressor 17 compresses the remaining gas and mixes it with the air compressed by the air compressor 11 .

[0041] The above-described configuration of the cryogenic air separation unit 10 uses nitrogen and helium as intermediate media for liquefying the intake air (air), thereby making it possible to avoid direct contact between hydrogen and air and thereby enhance safety. That is, hydrogen gas H2 is supplied in the form of liquid hydrogen LH2. The liquid hydrogen LH2 is first compressed to 5.7 MPa (the same as in existing GTCC), and then the cold heat of vaporization is used to perform air liquefaction separation before being sent to the combustion chamber of the gas turbine combustor 24.

[0042] Table 1 shows the material balance in the cryogenic air separation unit 10. As shown in this table, according to the calculation results, the cold energy of 1 kg / s of liquid hydrogen LH2 can be used to liquefy and separate 3.9 kg / s of liquid nitrogen LN2 and 1.2 kg / s of liquid oxygen LO2.

[0043] [Table 1]

[0044] Table 2 shows the power required for the cryogenic air separation unit 10 when utilizing the cold energy of 1 kg / s of liquid hydrogen LH2. From this table, it can be seen that the power consumed by the air compressor 11, which compresses the intake air (air) to a predetermined pressure (for example, 645 kPa), accounts for 95% or more of the power consumed. It can also be seen that the energy loss is significantly smaller than that of a conventional air separation unit that liquefies the air by adiabatic compression and adiabatic expansion.

[0045] [Table 2]

[0046] 4 is a diagram showing the overall configuration of the nitrogen cycle 40. The nitrogen cycle 40 has a three-stage expansion, and a supercritical nitrogen turbine is used in the high-pressure stage. In this figure, the nitrogen gas heater 44 has a first gas heater 44a, a second gas heater 44b, and a third gas heater 44c, which are located in this order from the upstream side with respect to the high-temperature exhaust gas G2 that has left the post-heating combustor 32. Similarly, the nitrogen gas turbine 46 also has a first expander 46a, a second expander 46b, and a third expander 46c located in this order from the upstream side with respect to the high-temperature exhaust gas G2. The nitrogen gas turbine 46 is preferably a supercritical nitrogen turbine.

[0047] In this example, the nitrogen cycle 40 also has a nitrogen gas heat exchanger 49 at the outlet of the first expander 46a, and a nitrogen gas cooler 48 at the downstream side thereof. The nitrogen gas heat exchanger 49 preheats the inlet gas of the third gas heater 44c with the outlet gas of the first expander 46a to recover heat. The nitrogen gas cooler 48 cools the gas at the inlet of the nitrogen gas compressor 42 in order to reduce the compression power of the compressor 42 .

[0048] Also, in this figure, the nitrogen cycle 40 has a refill port 43 for refilling pressurized nitrogen gas (pressurized nitrogen gas N2) and an extraction port 45 for extracting excess low-pressure nitrogen gas (low-pressure nitrogen gas N2) to the outside. The refill port 43 is provided between the outlet of the nitrogen gas compressor 42 and the inlet of the nitrogen gas heater 44 (in this example, the inlet of the nitrogen gas heat exchanger 49). The extraction port 45 is provided between the outlet of the nitrogen gas turbine 46 (in this example, the outlet of the nitrogen gas heat exchanger 49 ) and the inlet of the nitrogen gas cooler 48 .

[0049] In this example, the nitrogen gas heat exchanger 49 of the nitrogen cycle 40 exchanges heat between the low-temperature (e.g., -12°C) nitrogen gas that joins at the refill port 43 and the medium-temperature (e.g., 10°C) nitrogen gas before being discharged from the extraction port 45.

[0050] As described above, the nitrogen gas cooler 48 of the nitrogen cycle 40 pre-cools the refluxing nitrogen gas N2 by utilizing the cold heat generated by vaporization of the liquid nitrogen LN2 and liquid oxygen LO2 separated from the air by the cryogenic air separation unit 10. The nitrogen cycle 40 is a regenerative semi-closed gas turbine cycle in which vaporized pressurized nitrogen gas is added to the N2 circulation system of the nitrogen cycle 40 through a replenishment port 43, and the same amount of reflux N2 is discharged from an extraction port 45.

[0051] Table 3 shows the main shaft power and power generation output of the nitrogen cycle 40 when 0.22 kg / s of hydrogen gas H2 is burned in the supplementary combustion unit 32. From this table, it can be seen that in the nitrogen cycle 40, the power output obtained by multiplying the difference between the expander shaft power and the compressor shaft power by the generator efficiency and the mechanical efficiency is large. In other words, the expander shaft power / compressor shaft power ratio is approximately 5.7, which is larger than that of a general rotary generator (for example, a gas turbine, which has a ratio of 2.0 or less). In addition, liquid nitrogen LN2 is pressurized in a liquid state, and the pressurized liquid nitrogen LN2 is heated in a nitrogen gas cooler 48 and supplied as pressurized nitrogen gas to the nitrogen cycle 40, thereby achieving high thermal efficiency as described below.

[0052] [Table 3]

[0053] Table 4 shows the calculation conditions and trial calculation results for the cold energy gas turbine power generation system 100 of the first embodiment (WET type). The efficiency of each piece of equipment used to calculate the power generation performance was set as follows: compressor efficiency: 89.5%, gas turbine (GT) efficiency: 91%, steam turbine (ST) efficiency: 90%, mechanical efficiency: 94%, generator efficiency: 98%, LH2 / LO2 / LN2 compression pump efficiency: 70%. Furthermore, in terms of mechanical efficiency, it is necessary to take into account losses from the cooling water pump for the steam condenser, various water quality control devices, lubrication and cooling of various rotating machines, and measurement, control and management devices in an actual plant; in this example, a value of 94%, the same as that of existing GTCC plants, was adopted.

[0054] Table 4 shows that when liquid hydrogen (LH2) of approximately 5.8 kg / s is used, the total power output is approximately 487 MW, and high power generation efficiency is achieved.

[0055] [Table 4]

[0056] (DRY type) 5 is a diagram showing a second embodiment of a cold energy utilization gas turbine power generation system 100 according to the present invention. Hereinafter, the system of the second embodiment will be referred to as a DRY type. In this figure, the bottoming cycle 30 has a carbon dioxide gas cycle 70 instead of the steam cycle 60 downstream of the above-mentioned supplementary combustion device 32 and nitrogen cycle 40.

[0057] The carbon dioxide gas cycle 70 circulates carbon dioxide gas to recover power for generating electricity. In this example, the carbon dioxide cycle 70 includes a carbon dioxide compressor 72 , a carbon dioxide heater 74 , a carbon dioxide expander 76 , and a carbon dioxide cooler 78 . The carbon dioxide compressor 72 compresses carbon dioxide. The carbon dioxide heater 74 heats the pressurized carbon dioxide with high-temperature exhaust gas from the nitrogen gas heater 44 to generate high-pressure, high-temperature carbon dioxide. The carbon dioxide expander 76 drives a generator (not shown) and recovers power to generate electricity from the high-pressure, high-temperature carbon dioxide. The carbon dioxide cooler 78 cools the carbon dioxide at the inlet of the carbon dioxide compressor 72. For cooling the low-pressure carbon dioxide gas in the carbon dioxide gas cooler 78, it is preferable to use a cooling tower 73 which does not require a large amount of cooling water.

[0058] 6 is an overall configuration diagram of the carbon dioxide gas cycle 70. The carbon dioxide gas cycle 70 has three-stage expansion, and a supercritical carbon dioxide gas turbine is applied to the high-pressure stage. In this figure, the carbon dioxide gas heater 74 has a first gas heater 74a, a second gas heater 74b, and a third gas heater 74c, which are located in this order from the upstream side with respect to the high-temperature exhaust gas G2 that has left the nitrogen gas heater 44. Similarly, the carbon dioxide expander 76 has a first expander 76a, a second expander 76b, and a third expander 76c, which are located in this order from the upstream side with respect to the high-temperature exhaust gas G2. The carbon dioxide expander 76 is preferably a supercritical carbon dioxide turbine.

[0059] Furthermore, the carbon dioxide gas compressor 72 has a first gas compressor 72a, a second gas compressor 72b, and a third gas compressor 72c, which are positioned in this order from the low pressure side of the carbon dioxide gas. Similarly, the carbon dioxide gas cooler 78 also has a first cooler 78a, a second cooler 78b, and a third cooler 78c, which are positioned in this order from the low pressure side of the carbon dioxide gas. That is, a carbon dioxide gas cooler 78 using a cooling tower 73 is provided upstream of each of the first gas compressor 72a, the second gas compressor 72b, and the third gas compressor 72c.

[0060] In this example, the carbon dioxide cycle 70 also has a carbon dioxide heat exchanger 79 that exchanges heat between the carbon dioxide expanded in the first expander 76a and the carbon dioxide at the outlet of the third gas compressor 72c. The other configurations are the same as those in the first embodiment.

[0061] Table 5 shows the main shaft power and power generation output of the carbon dioxide gas cycle 70 when the exhaust gas temperature discharged from the nitrogen cycle 40 installed upstream of the carbon dioxide gas cycle 70 is 603°C and the exhaust gas amount is 742 kg / s. From this table, it can be seen that in the carbon dioxide gas cycle 70, the power output obtained by multiplying the difference between the expander shaft power and the compressor shaft power by the generator efficiency and the mechanical efficiency is large. In other words, expander shaft power / compressor shaft power is approximately 2.5, which is larger than that of a general rotary generator (for example, a gas turbine, etc., which has a ratio of 2.0 or less).

[0062] [Table 5]

[0063] Table 6 shows the calculation conditions and trial calculation results for the cold energy gas turbine power generation system 100 of the second embodiment (DRY type). From this table, we can see that when liquid hydrogen LH2 is used at approximately 6.2 kg / s, the total power output is approximately 487 MW, and high power generation efficiency is achieved.

[0064] [Table 6]

[0065] The cold energy utilization gas turbine power generation system 100 of the first and second embodiments described above has the following advantages over a hydrogen-oxygen combustion turbine power generation system.

[0066] (1) In a hydrogen-oxygen combustion turbine power generation system, oxygen gas required for combustion of hydrogen gas must be produced in an oxygen production plant, and the energy loss caused by the oxygen production plant is significant. In contrast, in the cold energy gas turbine power generation system 100, the cryogenic air separation unit 10 uses the cold energy of the liquid hydrogen to produce (separate) only the required amount of hydrogen gas, so the power required by the cryogenic air separation unit 10 is small.

[0067] (2) In a hydrogen-oxygen combustion turbine power generation system, the turbine inlet temperature becomes high when hydrogen and oxygen (pure oxygen) are combusted, so steam or water recirculation is essential, which increases the compressor power and requires larger turbines and condensers. In the cold energy gas turbine power generation system 100, liquid oxygen LO2 produced in the cryogenic air separation unit 10 is pressurized in a liquid state through a pressurized oxygen supply line 52, heated in a nitrogen gas cooler 48, and supplied to the gas turbine combustor 24 as pressurized oxygen gas. Therefore, by simply compressing only the air equivalent to the oxygen shortage in the gas turbine combustor 24 using the gas turbine compressor 22, the turbine inlet temperature can be optimized without recirculating steam or water, and the gas turbine compressor 22 and gas turbine 26 can be made smaller.

[0068] (3) The hydrogen-oxygen combustion turbine power generation system is a combined cycle of the Brayton cycle and the Rankine cycle, and no other bottoming cycle can be applied upstream of the Rankine cycle. In contrast, in the cold energy gas turbine power generation system 100, the bottoming cycle that utilizes the exhaust gas of the gas turbine can be freely set, and in particular, the nitrogen cycle 40 described above can achieve a power generation efficiency of 97% or more.

[0069] (4) As mentioned above, hydrogen-oxygen combustion turbine power generation systems have the drawback that they cannot function unless hydrogen and oxygen are burned at a stoichiometric ratio, because residual oxygen (or hydrogen) remains in the combustion gas. In reality, complete combustion is not possible at an equivalence ratio of 1. In contrast, in the cold energy gas turbine power generation system 100, combustion is performed in the same manner as in the existing GTCC, and stable complete combustion is possible at an air-fuel ratio with a residual oxygen concentration of 16% (dry) in the exhaust gas.

[0070] As described above, according to an embodiment of the present invention, the cryogenic air separation unit 10 liquefies air using the cold energy of liquid hydrogen LH2 to produce the required amount of hydrogen gas H2, thereby minimizing energy loss in the cryogenic air separation unit 10.

[0071] The amount of liquid oxygen LO2 produced in the cryogenic air separation unit 10 together with hydrogen gas H2 is less than the amount of oxygen required by the gas turbine generator 20. However, this liquid oxygen LO2 is pressurized in a liquid state by the pressurized oxygen supply line 52, heated in the nitrogen gas cooler 48, and supplied to the gas turbine generator 20 as pressurized oxygen gas. This makes it possible to reduce the compression power required by the gas turbine generator 20 by an amount equivalent to about five times the amount of compressed oxygen gas out of the amount of air compressed in the gas turbine generator 20. Furthermore, in the gas turbine generator 20, the hydrogen gas H2 produced in the cryogenic air separation unit 10 is subjected to oxygen-enriched combustion using compressed air and pressurized oxygen gas, so that the hydrogen gas H2 can be stably combusted with a sufficient amount of oxygen.

[0072] Furthermore, the liquid nitrogen LN2 produced in the cryogenic air separation unit 10 is pressurized in a liquid state through a pressurized nitrogen supply line 54, heated in a nitrogen gas cooler 48, and supplied as pressurized nitrogen gas to the nitrogen cycle 40. This reduces the compression power required in the nitrogen cycle 40, and increases the amount of electricity generated by the nitrogen cycle 40.

[0073] In addition, the hydrogen gas H2 produced in the cryogenic air separation unit 10 is burned with the remaining oxygen in the reheating combustor 32 to heat the exhaust gas temperature, so that the high-pressure nitrogen gas in the nitrogen cycle 40 can be sufficiently heated with this high-temperature exhaust gas, thereby improving the efficiency of the nitrogen cycle 40.

[0074] In other words, the liquid oxygen LO2 produced in the cryogenic air separation unit 10 together with the required amount of hydrogen gas H2 contributes to reducing the power consumption of the gas turbine generator 20 and oxygen-enriched combustion, and the liquid nitrogen LN2 contributes to increasing the amount of power generated by the nitrogen cycle 40.

[0075] Furthermore, by providing a water vapor cycle 60 or a carbon dioxide cycle 70 downstream of the nitrogen cycle 40, the cold energy of the liquid hydrogen LH2 can be effectively utilized to produce oxygen for combustion and improve power generation efficiency as a whole.

[0076] According to the first embodiment (WET type) of the present invention, the power generation efficiency is estimated to be 70.2% (LHV) under the same turbine inlet temperature / pressure conditions as a 1600°C-class LNG-fired GTCC, which is 5.5 to 8 points higher than the approximately 62% to 65% of a hydrogen-oxygen combustion turbine power generation system.

[0077] Furthermore, the cold energy gas turbine power generation system 100 of the second embodiment (DRY type) does not use a steam turbine, and therefore has the following advantages. (1) There is no need for a water treatment system that is difficult to maintain. (2) The large amount of condensing cooling water required for steam turbines is no longer necessary. (3) It is possible to install the plant inland where cooling water resources such as seawater are scarce, which increases the flexibility of power plant installation. (4) The final stage of the steam turbine is enlarged due to the reduced pressure operation, but the nitrogen cycle 40 and the carbon dioxide cycle 70 of the first embodiment are operated at high pressure, so they can be made smaller.

[0078] Although the power generation efficiency of the second embodiment is 65.6%, which is about 4.6% lower than that of the first embodiment, it is still higher than that of a hydrogen-oxygen combustion turbine power generation system. Therefore, the second embodiment can also be said to be a compact, high-efficiency power generation system that offers a high degree of freedom in power plant installation.

[0079] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0080] Air, G1 combustion gas, G2 exhaust gas, He helium gas, H2 hydrogen gas, LH2 liquid hydrogen, LO2 liquid oxygen, LN2 liquid nitrogen, N2 nitrogen gas, O2 oxygen gas, S water vapor, W1 condensed water, W2 pressurized water, 10 air liquefaction separator, 11 air compressor, 12 nitrogen gas cooler, 12a cold heat exchanger, 12b N2 circulator, 14 helium gas cooler, 14a liquefaction heat exchanger, 14b He circulator, 15 expansion valve, 16 gas-liquid separator, 17 gas compressor, 20 gas turbine generator, 22 gas turbine compressor, 24 gas turbine combustor, 26 gas turbine, 30 bottoming cycle, 32 supplementary combustion combustor, 40 nitrogen cycle, 42 nitrogen gas compressor, 44 nitrogen gas heater, 44a first gas heater, 44b Second gas heater, 44c Third gas heater, 46 Nitrogen gas turbine, 46a First expander, 46b Second expander, 46c Third expander, 48 Nitrogen gas cooler, 52 Pressurized oxygen supply line, 52a Liquid oxygen pump, 54 Pressurized nitrogen supply line, 54a Liquid nitrogen pump, 60 Steam cycle, 62 Pressure pump, 64 Steam heater, 66 Steam turbine, 68 Condenser, 70 Carbon dioxide cycle, 72 Carbon dioxide compressor, 72a First gas compressor, 72b Second gas compressor, 72c Third gas compressor, 73 Cooling tower, 74 Carbon dioxide heater, 74a First gas heater, 74b Second gas heater, 74c Third gas heater, 76 Carbon dioxide expander, 76a First expander, 76b Second expander, 76c Third expander, 78 Carbon dioxide cooler, 78a First cooler, 78b second cooler, 78c third cooler, 79 carbon dioxide heat exchanger, 100 cold energy utilization gas turbine power generation system

Claims

1. an air liquefaction and separation unit that liquefies air using the cold heat of liquid hydrogen to produce a required amount of hydrogen gas as well as liquid oxygen and liquid nitrogen; a gas turbine generator that generates electricity by oxygen-enriching combustion of the hydrogen gas; a supplementary combustion combustor that burns the hydrogen gas with remaining oxygen to heat the exhaust gas of the gas turbine generator; a nitrogen cycle having a nitrogen gas cooler that cools low-pressure nitrogen gas by heat exchange between the liquid oxygen and the liquid nitrogen, and circulating the nitrogen gas to recover power for electricity generation; a pressurized oxygen supply line for pressurizing the liquid oxygen produced in the air separation unit in a liquid state, heating the pressurized liquid oxygen in the nitrogen gas cooler, and supplying the pressurized liquid oxygen as pressurized oxygen gas to the gas turbine generator; a pressurized nitrogen supply line that pressurizes the liquid nitrogen produced in the air separation unit in a liquid state, heats the pressurized liquid nitrogen in the nitrogen gas cooler, and supplies the pressurized liquid nitrogen as pressurized nitrogen gas to the high-pressure nitrogen gas in the nitrogen cycle.

2. 2. The cold energy utilization gas turbine power generation system according to claim 1, further comprising, downstream of the nitrogen cycle, a water vapor cycle that circulates water vapor to recover power for generating electricity from the exhaust gas, or a carbon dioxide cycle that circulates carbon dioxide to recover power for generating electricity from the exhaust gas.

3. The air separation unit is a nitrogen gas cooler that circulates nitrogen gas between the liquid hydrogen and the air to indirectly cool the air; 2. The gas turbine power generation system according to claim 1, further comprising: a helium gas cooler that circulates helium gas between the liquid hydrogen and the air to indirectly cool the air.

4. 3. The cold energy utilization gas turbine power generation system according to claim 2, wherein the nitrogen cycle further comprises a nitrogen gas compressor that compresses low-pressure nitrogen gas, a nitrogen gas heater that heats high-pressure nitrogen gas with high-temperature exhaust gas from the reheat combustor, and a nitrogen gas turbine that recovers power generation power from the heated high-pressure nitrogen gas.

5. The nitrogen cycle is a refill port provided between the outlet of the nitrogen gas compressor and the inlet of the nitrogen gas heater, for refilling the pressurized nitrogen gas; 5. The cold energy utilization gas turbine power generation system according to claim 4, further comprising an extraction port provided between an outlet of the nitrogen gas turbine and an inlet of the nitrogen gas cooler, for extracting excess low-pressure nitrogen gas to the outside.

6. 5. The cold energy utilization gas turbine power generation system according to claim 4, wherein the carbon dioxide cycle comprises a carbon dioxide compressor that compresses carbon dioxide, a carbon dioxide heater that heats the pressurized carbon dioxide with high-temperature exhaust gas from the nitrogen gas heater to generate high-pressure, high-temperature carbon dioxide, a carbon dioxide expander that recovers power generation power from the high-pressure, high-temperature carbon dioxide, and a carbon dioxide cooler that cools the low-pressure carbon dioxide.

7. 5. The cold energy utilization gas turbine power generation system according to claim 4, wherein the steam cycle comprises: a pressure pump that pressurizes condensed water; a steam heater that heats the pressurized water with high-temperature exhaust gas from the nitrogen gas heater to generate high-pressure, high-temperature steam; a steam turbine that recovers power for generating electricity from the high-pressure, high-temperature steam; and a condenser that cools the low-pressure steam to obtain the condensed water.

8. 2. The cold energy utilization gas turbine power generation system according to claim 1, wherein the gas turbine generator comprises: a gas turbine compressor that compresses air; a gas turbine combustor that performs oxygen-enriched combustion of the hydrogen gas with compressed air and pressurized oxygen gas; and a gas turbine that obtains power generation motive power from the combustion gas.

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