JPH09264158A - Gas turbine cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the corrosion of a circulating liquid phase water piping in a water injection regenerating combustion cycle using a cycle internal circulating liquid phase water as heat recovering medium by using a deaerated water as the liquid phase water used as the heat recovering medium. SOLUTION: Air 1 is compressed by a compressor AC1 , cooled through an intermediate cooler R1 using cycle internal circulating liquid phase water 26 as cooling medium, and the liquid phase water 26 is also heated. It is cooled through a feed water preheater R2 using cycle supplying water 24 as cooling medium, and the supplying water 24 is heated. The air leaving the feed water preheater R2 is compressed by a compressor AC2 , cooled through a final stage cooler R3 using cycle internal circulating liquid phase water 33 as cooling medium, and the liquid phase water 33 is also heated. The air 6 leaving the final stage cooler R3 is brought into contact with the liquid phase water 26 in a humidifying tower EXT to provide a mixture. The cycle internal circulating liquid phase water 32 leaving the humidifying tower EXT is deaerated through gas-liquid separators F1 , F2 , and supplied to each cooler R1 , R3 , R4 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water injection regeneration combustion gas turbine cycle using circulating liquid phase water in a cycle as a heat recovery medium.

[Prior art]

Since fuel costs are high in industrialized countries such as Japan, it is essential to efficiently obtain mechanical energy or electric energy from chemical energy in fuel at low cost in order to suppress energy costs. Can be cited as a major development issue. A combustion gas turbine cycle is a system that obtains mechanical or electrical energy from the chemical energy in fuel, including air compressors, combustors,
The simple cycle composed of turbines is the combustion gas turbine cycle with the simplest and lowest thermal efficiency. The thermal efficiency of this simple cycle is 25-35%. It is necessary to improve the thermal efficiency of this combustion gas turbine cycle, and the following improved cycles have been developed.

The intermediate cooling cycle is a simple cycle in which the air compression stage is divided into two stages and compressed, and an air cooler is provided between the low pressure stage compressor and the high pressure stage compressor to introduce the medium temperature low pressure into the high pressure stage compressor. An increase in thermal efficiency is achieved by cooling the air. The feature of the intercooling cycle is to cool the medium-temperature low-pressure air introduced from the low-pressure stage compressor to the high-pressure stage compressor into low-temperature low-pressure air in order to reduce the required mechanical energy in the air compression stage. This is the point that a large amount of air is introduced into the high-pressure stage compressor. From a thermodynamic point of view, by setting the introduction temperature of the high-pressure stage compressor from medium to low, the required mechanical energy in the high-pressure stage compressor is reduced. It is a point. In the intercooling cycle, although there is a difference in contribution to the improvement of thermal efficiency due to the setting of the low-pressure stage pressure and the high-pressure stage pressure, the amount of heat removed in the intercooler, etc. 40%.

The regeneration cycle is a simple cycle in which air introduced into the combustor is used as a heat recovery medium as a method of recovering heat from turbine exhaust gas. The characteristic of the regeneration cycle is that heat is recovered from the turbine exhaust gas of the simple cycle, and the temperature of the turbine exhaust gas of the general simple cycle is a high temperature of about 500 ° C. By using the air introduced into the combustor that is heated by turbine exhaust gas using a heat exchanger (regenerator) with air, the amount of fuel required in the combustor is reduced and the thermal efficiency of the cycle is improved. Is.
The thermal efficiency of the regeneration cycle is 5-10 than that of the simple cycle.
% To 35-40%.

The regeneration water injection cycle is a method of recovering heat from the turbine exhaust gas discharged from the regenerator in the regeneration cycle, in which water is used as a heat recovery medium to generate steam, and the resulting steam is used as a turbine drive medium. It is used as a section. In addition to the features of the regeneration cycle described above, the regeneration water injection cycle is characterized in that heat is further recovered from the turbine exhaust gas coming out of the regenerator, and the recovered heat is used to heat water, which is a heat recovery medium, and to superheat steam. Is used to generate steam and the resulting steam is introduced into the cycle from, for example, a combustor for use as part of the drive medium of the turbine. The introduced steam acts as a turbine drive medium that does not require the compression power (required mechanical energy) by the air compressor in the cycle, the turbine output increases by the amount of introduced steam, and the thermal efficiency of the cycle is improved. That is the point. The thermal efficiency of the regeneration water injection cycle is 10-15% higher than that of the simple cycle.
The improvement is 40 to 45%. Note that in a water injection regenerative combustion gas turbine cycle that uses circulating liquid water in the cycle as a heat recovery medium, the heat recovery of turbine exhaust in a conventional gas turbine cycle is preheating of air, recovery of heat medium steam by a waste heat boiler, Refrigerating energy is recovered by absorption refrigeration, and a method using an air / steam mixture obtained by mixing compressed air with water is also used as a kind of preheating of air.

The combined cycle is designed to improve thermal efficiency by adding a heat recovery cycle for turbine exhaust gas called a bottoming cycle to the simple cycle. The characteristic of this combined cycle is that heat is recovered from the turbine exhaust gas of the simple cycle, and since the temperature of the turbine exhaust gas of a general simple cycle is a high temperature of about 500 ° C., water is extracted from this exhaust gas. By recovering heat as a heat exchange medium to generate steam and driving a steam turbine to generate mechanical energy or electric energy, mechanical energy or electric energy is obtained from the exhaust heat discarded in the simple cycle, and thermal efficiency is obtained. Is the point that has achieved the improvement of. The thermal efficiency of the combined cycle is 45 to 50%, which is 20 to 25% higher than that of the simple cycle, which is the highest thermal efficiency. However, the combined cycle requires a large amount of construction cost as compared with the simple cycle because the bottoming cycle must be added, and in the bottoming cycle, the working medium after steam turbine drive consisting of steam and liquid water is completely liquid phase. There are disadvantages such as the need for a large amount of cooling water to condense water.

[0007]

SUMMARY OF THE INVENTION The inventors of the present invention previously mentioned a water injection method and a heat recovery method in a regenerative water injection cycle using circulating liquid phase water in a cycle by mixing compressed air and water as a heat recovery medium. The air is compressed to a predetermined pressure with a compressor, and the liquid phase water heated as a heat recovery medium in the intermediate cooling stage with the compressed air is passed through an intermediate cooling stage with circulating liquid phase water in the cycle. And a part or all of the compressed air to obtain an air / steam mixture, and the liquid phase water obtained by the contacting operation and in which the compressed air is dissolved is used as a heat recovery medium to recover heat from the turbine exhaust. And liquid phase water, which is used in the intermediate cooling step of the compressor and is subjected to a contact operation with the compressed air, and which is evaporated by the contact operation and transferred to the compressed air as a mixture with air, if necessary. Thermal efficiency is improved by a gas turbine cycle (hereinafter referred to as HAT cycle) which is used as a heat recovery medium in an intermediate cooling stage and is replenished in the liquid phase water used for the contact operation. I found out and filed a patent application first
01-31012). This HAT cycle is 2-5% compared to the combined cycle that has achieved maximum thermal efficiency up to now.
It has been improved to achieve a high thermal efficiency of 50 to 55%.

The recycle water injection cycle using the circulating liquid water in the cycle by mixing compressed air and water as the heat recovery medium such as the HAT cycle achieves a high thermal efficiency of 50 to 55%, but the equipment configuration is simple. The cycle requires an intercooler, a humidification tower, a high-temperature regenerator, a low-temperature regenerator, and auxiliary equipment such as liquid-phase water piping that is a heat recovery medium, and the circulating liquid-phase water in the cycle is compressed in the humidification tower. It is highly corrosive due to its dissolved oxygen due to direct contact with air and its operation at high pressure (15-40ata) and high temperature (90-120 ° C).
In order to operate the power generation equipment stably for a long period of time, it is necessary to use corrosion-resistant materials for the pipes and heat exchangers, so the construction cost is 2.0 to 2.5 times that of the simple cycle. It becomes expensive. An object of the present invention is to maintain stable operation for a long period of time while maintaining high thermal efficiency in a water injection regeneration combustion cycle using circulating liquid phase water in a cycle by mixing compressed air and water as described above as a heat recovery medium. Another object of the present invention is to provide a gas turbine cycle that is capable of reducing the construction cost and obtaining a lower power generation cost.

[0009]

[Means for Solving the Problems] The present inventors diligently studied the above problems in a water injection regeneration combustion cycle using circulating liquid water in a cycle by mixing compressed air and water as a heat recovery medium. As a result, it is possible to prevent corrosion of the circulating liquid-phase water piping in the cycle by degassing the dissolved oxygen in the circulating liquid-phase water from the humidification tower,
The inventors have found that the materials such as piping can be changed from expensive corrosion resistant materials to inexpensive materials, construction costs can be reduced, and cheaper power generation costs can be obtained.

That is, according to the present invention, a part or all of compressed air obtained by compressing air or a gas mainly composed of air as a combustion-supporting gas, working medium gas, etc. with a compressor and heated as a heat recovery medium. Contact with liquid water
Obtaining a mixture of steam and cooled liquid phase water, heat recovery of the turbine exhaust with the air / steam mixture, and heat recovery of the turbine exhaust using the cooled liquid phase water as a heat recovery medium and an intermediate cooling stage of the compressor. In the gas turbine cycle for performing the above, the liquid phase water used as the heat recovery medium is degassed, and the combustion gas turbine cycle is characterized.

As the combustion-supporting gas / working medium gas, etc., a part or all of compressed air obtained by compressing air or a gas mainly composed of air with a compressor, and liquid-phase water heated as a heat recovery medium A packed tower is the most common apparatus for bringing air / steam mixture and cooled liquid-phase water into contact with each other (hereinafter referred to as "humidification tower"). Conventionally, the circulating liquid phase water in the cycle that comes out of the humidification tower has a high pressure (15 to 40a).
ta), high temperature (90 to 120 ° C.), the dissolved oxygen concentration in the liquid phase water is 100 to 150 ppm, and under this condition, the dissolved oxygen in the liquid phase water causes the corrosion of the pipe, so the pipe is constructed with a corrosion resistant material. It is necessary to use expensive corrosion-resistant materials such as stainless steel for the piping, which makes the piping material cost high. In the present invention, there is no need to use a corrosion resistant material for the piping material by degassing the dissolved oxygen in the circulating liquid in the cycle circulating liquid phase water that exits from the humidification tower that causes corrosion of the liquid phase water piping, Since it becomes possible to use an inexpensive material such as carbon steel, the construction cost can be reduced and a lower power generation cost can be obtained.

There are various methods for degassing liquid phase water used as a heat recovery medium in the present invention, for example, treatment with chemicals, etc., but liquid phase water in which compressed air is dissolved has A method of degassing by reducing the pressure is suitable, and a gas-liquid separator such as a known packed tower is used as the degassing device. Further, in order to avoid the increase in power required for degassing, it is possible to recover the energy in the pressure drop of the liquid water in which the compressed air is dissolved and use it as the power to pressurize the degassed liquid water. .

As a method for degassing the liquid phase water used as the heat recovery medium by lowering the pressure of the liquid phase water in which the compressed air is dissolved, the liquid phase water in which the compressed air is dissolved is vacuumed in one step. Degas by decompressing with an exhaust fan (one-stage degassing method) or use as power to boost degassed liquid-phase water by performing energy for pressure drop of liquid-phase water to atmospheric pressure to a low pressure Then, a method (two-stage degassing method) or the like in which the pressure is made lower than atmospheric pressure by a vacuum exhauster is used. Compared with the one-stage degassing method, this two-stage degassing method requires less power for the vacuum blower, but the energy for lowering the pressure of liquid-phase water also decreases, so the number of equipment used increases and construction costs increase. Therefore, the superiority and inferiority of the two differ depending on the situation.

In the present invention, it is necessary to degas the liquid phase water used as the heat recovery medium, of course, to such an extent that the pipes and devices in the cycle do not become corrosive, and when degassing is performed by lowering the pressure. Is preferably as low as possible. The degassing pressure depends on the material and operating conditions of the piping and equipment in the selected cycle, but when using carbon steel, the dissolved oxygen in the circulating water must be 0.5 ppm or less. Therefore, the pressure is reduced to about 550 to 660 mmHg using a vacuum blower. 2 above
In the step degassing method, the pressure close to the atmospheric pressure is 0.005 to 0.
03 kg / cm ² G and then using a vacuum blower 5
The pressure is reduced to about 50 to 660 mmHg.

The present invention is applied to a water injection regenerative combustion gas turbine cycle which uses circulating liquid water in a cycle by mixing various compressed air and water as a heat recovery medium.
A flow when the two-stage degassing method of the present invention is applied to the AT cycle will be described with reference to FIG. In FIG. 1, the air 1 is compressed to a predetermined pressure by a compressor AC1 and is cooled through an intercooler R1 having the in-cycle circulating liquid phase water 26 as a cooling medium, and at the same time, the circulating liquid phase water in the cycle is a cooling medium.
26 is heated, and then the cycle replenishment water 24 which is the cooling medium is heated while being cooled through the feed water preheater R2 which uses the cycle replenishment water 24 as a cooling medium.

The cooled air 4 discharged from the feed water preheater R2 is compressed to a predetermined pressure by the compressor AC2, and is cooled through the final stage cooler R3 using the circulating liquid phase water 33 in the cycle as a cooling medium. The circulating liquid phase water 33, which is a cooling medium, is heated. The cooled air 6 discharged from the final stage cooler R3 is used as a heat recovery medium in the intermediate cooling stage in the humidification tower EXT and is brought into contact with part or all of the heated liquid phase water and the compressed air. Liquid phase water obtained by the contacting operation and having the compressed air dissolved therein is used as a heat recovery medium in the heat recovery stage of the turbine exhaust and the intermediate cooling stage of the compressor and contact with the compressed air Provide for operation.

Compressed air that is humidified and heated by the contact operation
7 is heated by the recovered heat recovered from the turbine exhaust gas 10 through the high temperature regenerator R5, and cools the turbine exhaust gas 10 which is a heating medium. The heated air 8 exiting the high temperature regenerator R5 is introduced into the combustor CC together with the fuel 40 and produces combustion gas 9. The generated combustion gas 9 is introduced into the turbine ET to generate power, and the turbine exhaust gas 10 thereafter passes through the high temperature regenerator R5 and the low temperature regenerator R4 using the in-cycle circulating liquid water 29 as a cooling medium to recover the system. It is discharged to the outside.

In this HAT cycle, the humidifying tower EX
First, the in-cycle circulating liquid phase water 32 leaving T
After depressurizing to a pressure close to atmospheric pressure in 1, it is depressurized to a vacuum pressure in the gas-liquid separator F2, and gas / liquid is separated into dissolved compressed air in the circulating liquid-phase water in the cycle and liquid-phase water. The liquid phase water 2L is pressurized to a predetermined pressure by the boost pump WP and introduced into the intercooler R1, the final stage cooler R3, and the low temperature regenerator R4. In addition, the power recovery turbine B recovers the power by depressurizing the circulating liquid phase water in the cycle and supplies the power to the boost pump WP. Dissolved gas in the circulating liquid water in the cycle is discharged from the gas-liquid separator F1 by the discharge pipe 1V.
And the gas-liquid separator F2 is discharged from the discharge pipe 2V to the outside of the system by the vacuum blower VP. In the case of the one-stage degassing method, the gas-liquid separator F1 is not provided, and the in-cycle circulating liquid phase water is directly introduced from the power recovery turbine B to the gas-liquid separator F2.

[0019]

[Example] In the case of constructing a 90 MW class HAT cycle power generation facility shown in FIG. 1 as an example, liquid phase water used as a heat recovery medium is not deaerated, and circulating liquid phase water in the cycle passes through. When using corrosion resistant material (SUS304) for heat exchanger (intermediate cooler R1, feed water preheater R2, final stage cooler R3, low temperature regenerator R4) and pipes (conventional method)
And various cases in which carbon steel is used for these heat exchangers and pipes by degassing liquid phase water used as a heat recovery medium according to the present invention (1 stage degassing method, 2 stage degassing method) Table 1 shows the results of calculation of performance and power generation cost.

[0020]

[Table 1] Conventional method 1-step degassing method 2-step degassing method (degassing condition) Pressure (ata) 0.875ata (1 step) 1.043ata (2 steps) 0.895ata Liquid water (32A) Temperature (℃) 94.9 93.9 95.0 (Various performances) Transmission end output (MW) 86.05 85.80 85.93 Transmission end thermal efficiency (%, LHV) 51.81 51.73 51.76 Water injection amount (kg / h) 82870 83450 83220 Water discharged from deaerator (kg / h) 1039 377 Net effective amount of water in cycle = − 82411 92843 Amount of air exhausted from deaerator (kg / h) 146 146 Fuel amount (kg / h) 13550 13530 13540 (equipment cost) Power generation facility ¹⁾ (100 million yen) 41.00 40.93 40.97 Heat exchangers ²⁾ (100 million yen) 27.50 22.83 22.90 Piping and others ³⁾ (100 million yen) 31.50 31.58 31.68 Total facility cost (100 million yen) 100.00 95.34 95.55 (Variable cost) Fuel cost (yen / kwh) 3.320 3.325 3.323 Water injection cost (yen / kwh) 0.963 0.973 0.968 Variable cost total (yen / kwh) 4.283 4.298 4.291 Fixed cost total (yen / kwh) 5.306 5.074 5.077 Power generation cost (yen / kwh) 9.589 9.372 9.369 Note 1) Power generation facility ... Gas turbine main body 2) Heat exchangers ... each heat exchanger, humidification tower 3) Piping Other ... each piping equipment, pump, deaerator, power recovery turbine vacuum exhaust fan, electrical and instrumentation equipment, civil engineering and building construction costs, etc.

The calculation conditions for the gas turbine equipment and the like in Table 1 are as follows. 1. Intake air conditions Intake amount 500 Ton / h Intake air temperature 15 ℃ Relative humidity 60% Intake air pressure (atmospheric pressure) 1.033 ata 2, Fuel conditions used Fuel NG (natural gas) temperature 15 ℃ Pressure 1.033 ata True heat value (LHV) 10545 kcal / kg 3, make-up water condition temperature 15 ℃ pressure 1.033 ata 4, compression part condition low pressure stage compressor pressure (outlet) 6.0 ata adiabatic efficiency 88.0% high pressure stage compressor Pressure (outlet) 26.0 ata Adiabatic efficiency 88.0% 5, Humidification tower conditions Pressure (column top) 25.5 ata Pressure loss 0.3 ata 6, Combustion conditions Combustion efficiency 100% 7, Turbine part conditions Intake gas Temperature 1350 ℃ Pressure (Outlet) 1.093 ata Adiabatic efficiency 90.0% 8, Circulating water condition in cycle Pressure 31.0 ata 9, Pressure loss condition Air suction flow Filter 2.23% Humidification tower 1.16% Combustor 4.00% R1 0.83% R2 0.84% R3 0.77% R4 1.88% R5 2.74% 10, various efficiencies Gear loss efficiency 98.0% Generator efficiency 99.99% Distributor loss efficiency 99.99% 11 Various settings for power generation cost estimation Fuel unit price 2.00 yen / 1000kcal Makeup water unit price 100 yen / Ton annual facility operation rate 50% (middle) Class) Fixed cost rate 20%

In the above calculation example, when the liquid phase water is degassed by the method of the present invention, the degassing device discharges a very small amount of steam and air to the outside of the system, and the vacuum blower. The power output at the power transmission end is slightly reduced because the power of the above is required. However, a 90MW class HAT cycle power generation facility will save about 450 million yen in construction costs, resulting in a reduction in annual power generation costs of about 90 million yen.

[0023]

EFFECTS OF THE INVENTION In the gas turbine cycle of the present invention, by degassing the liquid phase water used as a heat recovery medium, the corrosiveness of the circulating liquid phase water in the cycle decreases, so that stable operation can be performed for a longer period of time. become. In addition, it becomes possible to use inexpensive materials for pipes and heat exchangers, thus reducing the construction cost of the power generation facility and the power generation cost.

[Brief description of drawings]

FIG. 1 is a case in which the two-stage degassing method of the present invention is applied to a HAT cycle, which is one of the water injection regeneration combustion cycles using circulating liquid phase water in a cycle by mixing compressed air and water as a heat recovery medium. FIG.

[Explanation of symbols]

 AC1: Low pressure stage compressor AC2: High pressure stage compressor ET: Turbine EXT: Humidification tower R1: Intercooler R2: Water preheater R3: Final stage cooler R4: Low temperature regenerator R5: High temperature regenerator CC: Combustor F1: First-stage gas-liquid separator F2: Second-stage gas-liquid separator VP: Vacuum blower WP: Boost pump B: Power recovery turbine

Claims (4)

[Claims] 1. A part or all of compressed air obtained by compressing air or a gas mainly composed of air as a combustion-supporting gas and working medium gas, and a liquid phase heated as a heat recovery medium. Contact with water to obtain an air / steam mixture and cooled liquid phase water, the air / steam mixture for heat recovery of the turbine exhaust, and the cooled liquid phase water as a heat recovery medium of the turbine exhaust. A combustion gas turbine cycle, wherein liquid phase water used as a heat recovery medium is degassed in a gas turbine cycle that performs heat recovery and an intermediate cooling stage of a compressor. 2. Liquid phase water used as a heat recovery medium,
The combustion gas turbine cycle according to claim 1, wherein the combustion gas turbine cycle is deaerated by lowering the pressure of liquid water in which compressed air is dissolved. 3. The combustion gas turbine cycle according to claim 2, which is configured to recover energy in the pressure drop of the liquid phase water in which the compressed air is dissolved and to provide power for increasing the pressure of the degassed liquid phase water. . 4. The energy for lowering the pressure of the liquid phase water to a low pressure to the atmospheric pressure is recovered so as to be used as power for increasing the pressure of the degassed liquid phase water. The combustion gas turbine cycle according to claim 3, wherein the combustion gas turbine cycle is configured to have a low pressure.