Gas turbine cycle equipment, equipment for recovering CO2 from flue gas, and method for recovering exhaust heat from combustion flue gas

By using a combustion flue gas (18) from a power turbine (16), a high-pressure secondary compressed air (12C) is subjected to heat exchange in a first heat exchange unit (19A) of an exhaust heat recovery device (19), and by using resultant heat-exchanged flue gas (18A), a low-pressure primary compressed air (12A) is subjected to heat recovery in a second heat exchange unit (19B) of a saturator (31). Then, a primary compressed air (12B) that has been subjected to heat recovery in the second heat exchange unit (19B) is introduced into a secondary air compressor (22) to increase the pressure of the air, and then the high-pressure air is subjected to heat recovery in the first heat exchange unit (19A), producing a secondary compressed air (12D). The secondary compressed air (12D) is introduced into a combustor (14) and combusted using fuel.

TECHNICAL FIELD

The present invention relates to gas turbine cycle equipment, equipment for recovering CO2from flue gas, and a method for recovering exhaust heat from combustion flue gas that improve cycle efficiency.

BACKGROUND ART

For example, in order to improve gas turbine (G/T) combined cycle efficiency, a heat recovery steam generator for effectively utilizing combustion flue gas from a gas turbine is used. This heat recovery steam generator (HRSG) is an apparatus that generates steam using a high-temperature combustion flue gas discharged from an exhaust heat generation source, such as a gas turbine, and is widely used in, for example, a gas turbine combined cycle (GTCC) power generation plant that supplies steam generated in the heat recovery steam generator to a steam turbine (S/T) and drives a power generator (PTLs 1 and 2).

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, in the related-art heat recovery steam generator, the heat recovery from a high-temperature combustion flue gas is performed at a temperature below a critical pressure using a plurality of stages, for example, high-pressure/medium-pressure/low-pressure individual economizers, an evaporator, a superheater, a reheater, and the like. Thus, heat exchange is performed so as not to reach a temperature falling line and a pinch point of the combustion flue gas. Additionally, there is a problem that reheating in the reheater is also only reheating at a temperature of about 600° C.

Hence, even in a case where a gas turbine inlet temperature is a high pressure/high temperature of, for example, 1500° C. class, the gas turbine efficiency (% LHV) is about 60%. In addition, in a case where the gas turbine inlet temperature is raised to, for example, 1700° C., there is a problem that there are various barriers against a turbine cooling technique, a heat shield coating technique, a heat-resisting material technique, and the like.

Hence, even in gas turbine equipment in which the inlet temperature is, for example, 1500° C. class, the appearance of a system that improves system efficiency is desired.

An object of the invention is to provide gas turbine cycle equipment, equipment for recovering CO2from flue gas, and a method for recovering exhaust heat from combustion flue gas that can improve gas turbine cycle efficiency in view of the above problems.

Solution to Problem

A first invention of the present invention for solving the above problems provides gas turbine cycle equipment including a gas turbine having a combustor that combusts fuel with compressed air and a power turbine that is driven by a high-temperature/high-pressure combustion gas from the combustor; and an exhaust heat recovery device that recovers heat energy from combustion flue gas that has driven the power turbine. The compressed air includes primary compressed air that is compressed by a primary air compressor that compresses air, and secondary compressed air that is compressed by a secondary air compressor that further compresses the primary compressed air. The exhaust heat recovery device includes a first heat exchange unit that performs indirect heat exchange between the combustion flue gas and the secondary compressed air, and a second heat exchange unit that passes through the first heat exchange unit, performs indirect heat exchange between combustion flue gas after first heat exchange, and the primary compressed air and supply water, in a saturator, and entrains steam in the primary compressed air. The primary compressed air, which entrains the steam that has performed heat exchange in the saturator of the second heat exchange unit, is introduced into the secondary air compressor, thereby producing high-pressure/low-temperature secondary compressed air, then heat exchange of the high-pressure/low-temperature secondary compressed air is performed in the first heat exchange unit, thereby producing high-pressure high-temperature secondary compressed air, and then, the high-pressure high-temperature secondary compressed air is introduced into the combustor.

A second invention is the gas turbine cycle equipment according to the first invention in which the saturator of the second heat exchange unit includes a supply water header that introduces the supply water thereinto, a plurality of heat exchange tubes that communicate with the supply water header at one end and are arranged within the exhaust heat recovery device, a storage header that communicates with the heat exchange tubes at the other end, stores the supply water, and has an introducing part that introduces the primary compressed air into a space of a storage part, and a supply water circulation line along which the supply water is circulated. The primary compressed air is passed through tube spaces for supply water that circulates in the shape of a wet wall along inner wall surfaces of the heat exchange tubes, the primary compressed air is subjected to heat exchange with the combustion flue gas that abuts against outer peripheries of the heat exchange tubes, steam is generated while heating the supply water, and the generated steam is entrained in the primary compressed air subjected to the heat exchange.

A third invention is the gas turbine cycle equipment according to the first or second invention, further including a cooling tower that cools a flue gas after heat exchange discharged from the exhaust heat recovery device; and a supply water supply line along which condensed water is supplied as the supply water to a supply water circulation line along which supply water circulates through the saturator.

A fourth invention is the gas turbine cycle equipment according to any one invention of the first to third inventions in which the exhaust heat recovery device further includes a third heat exchange unit that performs indirect heat exchange between the combustion flue gas after passing through the second heat exchange unit, and the supply water in the supply water supply line.

A fifth invention is equipment for recovering CO2from flue gas including the gas turbine cycle equipment according to any one invention of the first to fourth inventions; and a CO2recovery unit that recovers CO2in flue gas from the cooling tower.

A sixth invention is the equipment for recovering CO2from flue gas according to the fifth invention in which the CO2recovery unit includes a CO2absorption tower that absorbs CO2in flue gas with an absorbing liquid, and an absorbing liquid regeneration tower that regenerates the absorbing liquid which has absorbed CO2, and the absorbing liquid is circulated and reused.

A seventh invention is a method for recovering exhaust heat from combustion flue gas. The method includes using the gas turbine cycle equipment according to the first invention, and subjecting the combustion flue gas from the gas turbine to heat exchange with high-pressure secondary compressed air in the first heat exchange unit of the exhaust heat recovery device, performing heat recovery of low-pressure primary compressed air, using the heat-exchanged flue gas, in the second heat exchange unit of the saturator, introducing the primary compressed air, which has recovered the heat in the second heat exchange unit, into the secondary air compressor, thereby producing high-pressure primary compressed air, then recovering heat in the first heat exchange unit, thereby producing secondary compressed air, and introducing the secondary compressed air into the combustor to combust fuel using the secondary compressed air.

Advantageous Effects of Invention

According to the invention, by using the combustion flue gas from the gas turbine, the high-pressure secondary compressed air is subjected to the heat exchange in the first heat exchange unit of the exhaust heat recovery device, and by using the heat-exchanged flue gas, the low-pressure primary compressed air is subjected to the heat recovery in the second heat exchange unit of the saturator. Then, the primary compressed air that has recovered the heat in the second heat exchange unit is introduced into the secondary air compressor, thereby producing the high-pressure primary compressed air, and then the high-pressure primary compressed air is subjected to the heat recovery in the first heat exchange unit, producing the secondary compressed air. The secondary compressed air is introduced into the combustor and fuel is combusted using the secondary compressed air, and thereby, temperature is increased up to, for example, 1500° C. Accordingly, the exhaust heat recovery efficiency of the exhaust heat recovery device can be made very high. As a result, the gas turbine cycle efficiency can be improved.

DESCRIPTION OF EMBODIMENTS

Preferable examples of the invention will be described below in detail with reference to the accompanying drawings. In addition, the invention is not limited by the examples and includes those configured by combining respective examples in a case where there are a plurality of examples.

FIG. 1Ais a schematic view of a gas turbine cycle equipment related to Example 1.FIG. 1Bis a schematic view illustrating an example of the temperature/pressure conditions of the gas turbine cycle equipment related to Example 1.

As illustrated inFIG. 1A, the gas turbine cycle equipment10A related to the present example includes a gas turbine17that has a combustor14that combusts fuel with compressed air and a power turbine16that is driven by a high-temperature/high-pressure combustion gas from the combustor14, and an exhaust heat recovery device19that recovers heat energy from combustion flue gas18that has driven the power turbine16. The compressed air12includes primary compressed air12A that is compressed by a primary air compressor21that compresses air12a, and secondary compressed air12C that is compressed by a secondary air compressor22that further compresses the primary compressed air12A. The exhaust heat recovery device19includes a first heat exchange unit19A that performs indirect heat exchange between the combustion flue gas18and the secondary compressed air12C, and a second heat exchange unit19B that passes through the first heat exchange unit19A, performs indirect heat exchange between combustion flue gas18A after first heat exchange and the primary compressed air12A and the supply water30in an saturator31, and entrain steam38in the primary compressed air12A. The primary compressed air12B, which entrains the steam that has been subjected to heat exchange in the saturator of the second heat exchange unit19B, is introduced into the secondary air compressor22, thereby producing high-pressure secondary compressed air (low temperature)12C, then heat exchange of the high-pressure secondary compressed air (low temperature)12C in the first heat exchange unit19A is performed, thereby producing high-pressure secondary compressed air (high temperature)12D, and then, the high-pressure secondary compressed air (high temperature)12D is introduced into the combustor14as compressed air for combustion.

In the present example, a third heat exchange unit19C that performs heat exchange of the supply water30, using the combustion flue gas18B after being subjected to heat exchange in the second heat exchange unit19B, is further provided on a downstream side of the second heat exchange unit19B of the exhaust heat recovery device19.

Additionally, in the present example, a cooling line L10including a cooling tower41that cools the flue gas40after heat exchange discharged from the exhaust heat recovery device19, and a cooler42that circulates the cooling tower41with a pump P1, and a supply water supply line L11along which condensed water44condensed within the cooling tower41is supplied as the supply water30to the saturator31.

In addition, inFIGS. 1A and 1B, reference sign45represents discharge water,46represents a chimney, G represents a power generator that is coupled to the power turbine16and generates power, L1represents an air introduction line, L2represents a primary compressed air supply line, L3represents a secondary compressed air supply line, L4represents a fuel supply line, L5represents a combustion gas supply line, L6represents a combustion flue gas discharge line, L7represents a flue gas line, L8represents a flue gas discharge line along which the flue gas40is to be discharged to the chimney46, and L12represents a wastewater line.

The gas turbine17includes the primary and secondary air compressors21and22, the combustor14, and the power turbine16. The air12aintroduced from the outside is compressed in the primary and secondary air compressors21and22, and the compressed air12made to have high temperature/high pressure is guided to the combustor14side. In the combustor14, the high-temperature/high-pressure compressed air12, and the fuel13are injected and combusted, and a high-temperature (for example, 1500° C.) combustion gas15is generated. The combustion gas15is injected into the power turbine16, and the heat energy of the high-temperature high-pressure combustion gas15is converted into rotational energy in the power turbine16. The coaxial primary/secondary air compressors21and22are driven with this rotational energy, and the power generator G is driven with the rotational energy remaining after being used to drive this compressor, and generates power.

Next, the combustion flue gas18that has driven the power turbine16is guided to the exhaust heat recovery device19in order to recover the heat energy thereof.

This exhaust heat recovery device19includes the first heat exchange unit19A and the second heat exchange unit19B. In the first heat exchange unit19A, as illustrated inFIG. 1B, the secondary compressed air (a low temperature of 275° C. and a pressure of 21 ata (2.1 MPa))12C is subjected to heat exchanged using the high-temperature (for example, 617° C.) combustion flue gas18discharged from the power turbine16. Additionally, in the second heat exchange unit19B on the downstream side of the first heat exchange unit19A, the primary compressed air (a temperature of 224° C. and a pressure of 6 ata (0.6 MPa))12A is introduced into the saturator31and is subjected to heat exchange.

FIG. 2is an enlarged view of main parts ofFIG. 1.FIG. 3is a perspective view of the heat exchange tube, andFIGS. 4 and 5are schematic sectional views of the heat exchange tube.

As illustrated inFIG. 2, the saturator31includes a supply water header32that introduces the supply water condensed in the cooling tower41thereinto, a plurality of heat exchange tubes33that communicate with the supply water header32on one end33aside and are arranged within the exhaust heat recovery device19, a storage header37that communicates with the heat exchange tubes33on the other end33bside, stores the supply water30within a storage part34, and has an introducing part36that introduces the primary compressed air12A into a space35on an upper side of the storage part34, and a supply water circulation line L20along which the supply water30is circulated with a pump P2.

FIGS. 4 and 5are views illustrating an aspect in which supply water is supplied to each heat exchange tube33within the supply water header32.

Referring toFIG. 4, a supply nozzle39provided in the supply water header32is used for the supply of the supply water30, and the supply water30sprayed from the supply nozzle39is dropped while forming a water screen30ain the shape of a wet wall along a wall surface33dwithin the heat exchange tube33.

Referring toFIG. 5, the supply water30is made to overflow from the storage part32aof the supply water header32as the supply of the supply water30, and the overflowed supply water30is dropped while forming the water screen30ain the shape of a wet wall along the wall surface33dwithin the heat exchange tube33.

Then, as illustrated inFIGS. 3, 4, and 5, the primary compressed air12A is passed from a lower side into a tube space33cfor the supply water30dropped and circulated by the water screen30aalong the wall surface33dof each of the plurality of heat exchange tube33. Then, when the primary compressed air12A passes, the primary compressed air is subjected to heat exchange with the combustion flue gas18A that abuts against an outer periphery of each heat exchange tube33. In the case of this heat exchange, the steam38is generated while heating the supply water30that flows down, this generated steam38is entrained in the primary compressed air12A subjected to heat exchange, and is created as the primary compressed air (water steam)12B.

Then, for example, as illustrated inFIG. 4, the supply water30is injected by the supply nozzle39and IS made to flow into the heat exchange tube33. The supply water30that has flowed into the heat exchange tube33is dropped while forming the water screen30ain the shape of a wet wall along the wall surface33dof the heat exchange tube33, and is stored on the storage header37on the downstream side. The stored supply water30is again circulated through the supply water header32by the supply water circulation line L20via the pump P2.

Then, the wet wall-like water screen30athat flows through the inside of the heat exchange tube33is indirectly heated by the heat of the combustion flue gas18A from the outside, and the supply water30becomes the steam38by heat exchange, is entrained in the primary compressed air12A, and becomes the primary compressed air (water steam)12B. The second heat exchange unit19B performs heat exchange using the combustion flue gas18A that has contributed to the heat exchange in the first heat exchange unit19A.

Here, the primary compressed air (a pressure of 6 ata (0.6 MPa))12A introduced into the space35within the storage header37of the saturator31is cooled by the supply water30to be introduced, and the temperature thereof falls from 224° C. to 84° C. within the space35.

The primary compressed air12A made to have this low temperature (84° C.) is indirectly subjected to heat exchange with the combustion flue gas18A after the first heat exchange, in the saturator31of the second heat exchange unit19B, and becomes the primary compressed air (water steam)12B of which the temperature reaches 107° C. (a pressure of 6 ata).

Next, the primary compressed air (water steam)12B is introduced into the secondary air compressor22, is subjected to second compression, and becomes the high-pressure (a pressure of 21 ata (2.1 MPa)) secondary compressed air (low temperature: 275° C.)12C.

The secondary compressed air12C is low (275° C.) in temperature, is capable of being subjected to heat exchange with the high-temperature (for example, 617° C.) combustion flue gas18in the first heat exchange unit19A of the exhaust heat recovery device19, and becomes the high-pressure secondary compressed air (a high temperature of 565° C.)12D.

In the related art, in a case where one compressor is installed to perform compressing, the primary compressed air (a temperature of 224° C.) compressed by the primary air compressor is introduced into the same secondary air compressor as it is, and is introduced into the combustor as high-pressure (21 ata)/high-temperature (400° C.) compressed air.

In contrast, in the present invention, a total amount of the low-pressure (a pressure of 6 ata) primary compressed air12A, which has passed through the primary air compressor21is introduced into the second heat exchange unit19B of the exhaust heat recovery device19, is subjected to heat exchange with the combustion flue gas18A after being subjected to heat exchange in the first heat exchange unit19A, in the saturator31.

In this case, in the saturator31, the supply water is introduced so as to lower (275° C.→84° C.) the temperature of the low-pressure (a pressure of 6 ata) primary compressed air12A, is subjected to heat exchange with the exhaust heat of the combustion flue gas (a temperature of 336° C.)18A after being subjected to heat exchange in the first heat exchange unit19A, and becomes the low-pressure primary compressed air (water steam)12B of which the temperature has been raised (107° C.). The primary compressed air (water steam) (107° C.)12B is further compressed by the secondary air compressor22next, and becomes the high-pressure (a pressure of 21 ata) secondary compressed air (low temperature: 275° C.)12C. In the case of this secondary compression, the capacity of the compressor can be made small because the temperature falls unlike a case where compression is continuous as in the related art.

Moreover, the high-pressure secondary compressed air (low temperature: 275° C.)12C is introduced into the first heat exchange unit19A of the exhaust heat recovery device19, becomes the high-pressure secondary compressed air (high temperature: 565° C.)12D, and is introduced into the combustor14.

In the present example, since the amount of the steam38to be entrained is small in the case of the heat exchange of the primary compressed air12A in the second heat exchange unit19B, it is possible to raise combustion temperature in the combustor14to a high temperature of, for example, 1500° C.

Additionally, in the present example, the third heat exchange unit19C is installed, and performs heat exchange so as to further improve the exhaust heat recovery efficiency of the combustion flue gas18when condensed water that has condensed moisture in the combustion flue gas18C in the cooling tower41is supplied to the saturator31as the supply water30. That is, since the temperature of the supply water30that is cooled and condensed in the cooling tower41is about 40° C., the supply water30at 40° C. is passed through the third heat exchange unit19C, is subjected to heat exchange with the combustion flue gas (120° C.)18B, and is supplied to the storage header37side as the supply water30at a temperature of 88° C.

In this way, when exhaust heat is recovered by performing heat exchange of the combustion flue gas18, in the exhaust heat recovery device19of the present example, efficient heat exchange is performed in the first heat exchange unit19A, the second heat exchange unit19B, and the third heat exchange unit19C, respectively. Thus, the heat of the high-temperature (617° C.) combustion flue gas18is recovered to a low temperature (95° C.), and the heat recovery efficiency improves.

Additionally, since the amount of the steam38entrained in the primary compressed air (water steam)12B is small, exhaust loss becomes little.

FIG. 6is a relationship view between temperature and enthalpy in a temperature falling line of an combustion flue gas and in a rising line of supply water temperature and compressed air.

As illustrated inFIG. 6, the temperature of the combustion flue gas18falls gradually (the first heat exchange unit19A (617° C.→336° C.), the second heat exchange unit19B (336° C.→120° C.), and the third heat exchange unit19C (120° C.→95° C.)) in the first heat exchange unit19A, the second heat exchange unit19B, and the third heat exchange unit19C.

In contrast, the supply water30rises from 40° C. to 88° C. in the third heat exchange unit19C, and rises from 84° C. to 107° C. because the temperature of the primary compressed air12A falls in the saturator31. Next, the secondary compressed air12C rises from 275° C. to 565° C. in the first heat exchange unit19A.

Additionally, as shown in Table 1, gas turbine cycle efficiency reaches 66.76% (LHV base) depending on a relationship between input heat and exhaust loss. This made it possible to achieve a significant improvement of about 6.7% or more greater than 60% that is the gas turbine cycle efficiency of a related-art 1500° C. class.

As described above, in a gas turbine combined cycle (GTCC) power generation plant including the related-art exhaust heat recovery steam generator using a high-pressure/medium-pressure/low-pressure boiler, the efficiency (LHV) thereof that is about 60% can be markedly raised.

In the present example, when exhaust heat is recovered by performing heat exchange of the combustion flue gas18, in the exhaust heat recovery device19of the present example, efficient heat exchange is performed in the first heat exchange unit19A, the second heat exchange unit19B, and the third heat exchange unit19C, respectively. However, the third heat exchange unit19C may be omitted as illustrated in the gas turbine cycle equipment10B illustrated inFIG. 7.

In this case, heat of the high-temperature (617° C.) combustion flue gas18is recovered to a low temperature (120° C.). As a result, the heat recovery efficiency becomes slightly lower than that of the gas turbine cycle equipment10A ofFIG. 1. However, the equipment can be simplified.

Next, equipment for recovering CO2from flue gas related to Example 2 of the present invention will be described with reference toFIG. 8.FIG. 8is a schematic view of the equipment for recovering CO2from flue gas related to Example 2. In addition, the same members as those of Example 1 will be designated by the same reference signs, and the description thereof will be omitted. The equipment50for recovering CO2from flue gas related to the present example includes the gas turbine cycle equipment10A of Example 1, and a CO2recovery unit51that recovers CO2in the flue gas40from which the moisture from the cooling tower41has been removed. The CO2recovery unit51includes a CO2absorption tower53that remove CO2in the flue gas40after cooling in the cooling tower41, using an absorbing liquid52, and an absorbing liquid regeneration tower54that regenerates the absorbing liquid52.

Generally, in a case where an amine-based absorbing liquid, for example, is used as the absorbing liquid52, the CO2recovery unit51makes the amine absorbing liquid to absorb and remove CO2contained in the flue gas40within the CO2absorption tower53, and discharges the removed CO2as a treated flue gas55from a top side of the CO2absorption tower53. Additionally, the absorbing liquid52that has absorbed CO2is regenerated by steam stripping using a reboiler59, in the absorbing liquid regeneration tower54, and forms closed-system circulation lines L21and L22to be again reused in the CO2absorption tower53. In addition, within the CO2absorption tower53, the amine-based absorbing liquid is, for example, brought into opposed contact with the flue gas40so as to take CO2into the amine absorbing liquid. Here, on the absorbing liquid regeneration tower54side, the gas56containing CO2removed by the steam stripping is discharged, moisture is removed by a gas-liquid separator, and CO2is recovered as gas.

In the related art, in a case where CO2in flue gas is recovered, a cooling tower is separately provided on a preceding stage side of the CO2recovery unit so as to cool the flue gas. However, in Example 1, the flue gas40is cooled by the cooling tower41for obtaining the supply water30. Thus, it becomes unnecessary to separately install cooling equipment in the equipment50for recovering CO2from flue gas in the present example. Additionally, in ordinary gas turbines, CO2concentration in flue gas is as low as 3.5 to 4.0 Vol. %. However, in the present gas turbine cycle, CO2concentration in flue gas rises as high as 5 to 7 Vol. %. As a result, the amount of the flue gas can be reduced, and the CO2recovery unit can be made compact.

In addition, in the present example, a case including the CO2absorption tower53that absorbs CO2in the flue gas40with the absorbing liquid52, and the absorbing liquid regeneration tower54that regenerates the absorbing liquid52that has absorbed CO2has been described as the CO2recovery unit51. However, the present invention is not limited to this. Arbitrary equipment may be used as long as the equipment can recover CO2in flue gas.

REFERENCE SIGNS LIST