JPS6246684B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a gas turbine power generation method using liquid air as a high-pressure air source. Specifically, the present invention relates to a gas turbine power generation method using liquid air as a high-pressure air source. The fuel is expanded to approximately 5 to 50 atmospheres using an expansion turbine to recover power, and then the intermediate pressure air is used to combust fuel and the combustion gas drives a gas turbine.
The present invention relates to a method of generating electricity with extremely high efficiency in combination with the power generated by the expansion turbine. Furthermore, the present invention relates to a gas turbine power generation method that is particularly suitable for use during peak loads, which reduces power generation costs and equipment costs by efficiently utilizing liquid air. Normal gas turbine power generation uses an air compressor to compress the atmosphere to around 5 atmospheres, and uses this compressed air to combust fuel and expand the high-temperature combustion gas obtained by a turbine. about
Since 2/3 of the power is consumed to drive the air compressor, a gas turbine with an output approximately three times the amount of electricity generated is required, which not only increases the price of the gas turbine, but also has a low thermal efficiency of less than 30%. . A gas turbine with a low-temperature suction compressor is a method for reducing the power required for an air compressor in this conventional gas turbine power generation method. In other words, it is a method to reduce the compression power by cooling the intake air of the air compressor using liquid air, liquefied natural gas (LNG, the same applies hereinafter), etc., but it requires a large air compressor. This method is the same as the usual method and has not resulted in a major improvement. By the way, a method has been proposed in which the air compressor is not used during power generation to efficiently generate power. In other words, liquid air is stored by either producing liquid air using the cold temperature of LNG, which is used as a fuel for continuous power generation, or by using surplus electricity during off-peak electricity demand, and then pumping it to produce air. This method converts the air into compressed air and uses it as compressed air for gas turbines. Therefore, since the power required for an air compressor is not required during power generation, power can be generated with an efficiency approximately three times that of a normal case, and is particularly suitable as a peak load power generation method. In this case, liquid air is pressurized to a pressure of 100 atmospheres or more, the fuel is combusted under the same pressure, and at the same time, water is injected to prevent overheating and added to part of the working gas. A method has been considered to generate electricity more efficiently by expanding
However, the combustion generated gas is at 100 atmospheres and over 900 degrees Celsius, and is accompanied by moisture, carbon dioxide, etc., making it difficult and expensive to select materials that can withstand such harsh conditions.
Another drawback is that a large amount of water is used for cooling, which inevitably reduces efficiency. The present invention has been developed in view of the above points, and involves pressurizing liquid air that has been produced and stored in advance to over 100 atmospheres, raising the temperature to over 500 degrees Celsius using exhaust gas from a gas turbine, etc., which will be described later, and then expanding the air. The fuel is introduced into a turbine and expanded to 5 to 50 atmospheres to generate power, and then the exhaust air at intermediate pressure and temperature is used to combust the fuel and exchange heat with the evaporated air of the liquid air to reach a temperature of 900°C or higher. This gas turbine power generation method is characterized in that after the combustion gas is temperature-adjusted, the combustion gas is introduced into a gas turbine to generate power, and a generator is driven together with the power from the air expansion turbine. In other words, liquid air is pressurized to a high pressure by liquid pressurization, which requires less power, and after the temperature is increased, the power is recovered by expanding it.Furthermore, this air can be used to generate gas turbine power without using an air compressor. The equipment cost is reduced by efficient power generation and by using only air in the high-pressure, high-temperature part. The present invention will be explained in detail below with reference to Examples. FIG. 1 shows an example in which an LNG-only combustion thermal power plant is equipped with an air liquefaction separation device that utilizes the cooling of the LNG and a gas turbine power generation device, which is the main part of the present invention. The LNG stored in LNG storage tank 1 is pipe 2
One part is pressurized by LNG pump 3 to 15 atm and -155°C, and then to pipe 4.
is divided into two parts again, and one of the streams is introduced into the air liquefier 8 via the pipe 5. The air introduced from the pipe 6 is compressed by the air compressor 7 and introduced into the air liquefaction separation device 8 at 60 atmospheres and +40°C, where it is cooled by indirect heat exchange with the LNG introduced from the pipe 5, The air is liquefied through a liquefaction process, and is taken out as liquid air through a pipe 9 and stored in a storage tank 10. During this time, air was introduced into the air liquefaction separation device 8 through the pipe 5.
The LNG is heated to near room temperature through heat exchange, and then the pipe 11
It is derived from On the other hand, LNG divided into two from pipe 4
The other flow passes through pipe 12 and enters warmer 13, where it exchanges heat with seawater and is heated to around room temperature.
4, it merges with the flow from the pipe 11, and is supplied as fuel to a thermal power plant 16 through a pipe 15 as natural gas at about 10 atmospheres and about 10°C. The above process is a process in which liquid air is produced and stored using the cold LNG fuel from a thermal power plant, and is a part that is constantly in operation. The next section will be described mainly as reinforcement power generation equipment that will be operated during peak power demand times. Liquid air stored in the storage tank 10 is taken out through a pipe 17, pressurized to 200 atmospheres by a liquid air pump 18, introduced into an evaporator 19, heated by seawater, and raised to near room temperature. This high pressure air is further transferred to heat exchanger 2.
The high-temperature gas is introduced into the gas turbine combustion chamber 32, which is introduced into the heat exchanger 22 via the pipe 21, and then led out from the gas turbine combustion chamber 32, which will be described later. The liquid is heated to approximately 560°C by exchanging heat with the liquid and then led out to the conduit 23. In this embodiment, the liquid air is pressurized to 200 atmospheres, but the pressure may be at least the critical pressure, and it is more preferable that it is at least 200 atmospheres. The seawater is then heated by exchanging heat with both the gas turbine exhaust gas or with only the gas turbine exhaust gas. If sufficient temperature cannot be obtained through these processes, the high-temperature gas leaving the gas turbine combustion chamber is heated. The temperature is further increased by exchanging heat with. This raises the temperature of the material of the expansion turbine or the like at the compressed air pressure to the maximum usable temperature, which is usually 500 to 700°C. The high-temperature, high-pressure air of 560℃ and 200 atmospheres thus obtained is pipe 2.
3, the air is introduced into the expansion turbine 24 and expanded to an intermediate pressure of about 20 atmospheres, and the work at that time is done by the shafts 25 and 2.
6 to the generator 27 and recovered as electric power. The intermediate pressure after expansion may be between 5 atm and 50 atm and is not limited to 20 atm. In addition, the expansion at this time is not limited to expansion by a single-stage expansion turbine, but efficiency can be improved by using two or more stages of expansion turbines or by providing a reheating circuit between each expansion turbine. It is possible. On the other hand, LNG is taken out from the storage tank 1 through pipe 2.
The other flow of separated LNG is introduced into the LNG pump 29 via the pipe 28 and pressurized to about 20 atmospheres, and then
In the LNG evaporator 30, the temperature is raised to around room temperature by heat exchange with seawater, and then introduced into the heat exchanger 20, where it exchanges heat with the exhaust gas of the gas turbine, and becomes 20 atmospheres and 230 degrees Celsius, and the pipe 31 It is introduced into the combustion chamber 32 through the. Here, the natural gas at 20 atmospheres and 230°C is led out from the expansion turbine 24 and passed through the pipe 33.
The generated high-temperature combustion gas is mixed with air at an atmospheric pressure of 220°C and combusted, and the generated high-temperature combustion gas is introduced into the heat exchanger 22 through the pipe 34, where it is cooled by exchanging heat with the countercurrent high-pressure air.
It is introduced into the gas turbine 36 through the pipe 35 at an atmospheric pressure of approximately 980°C, and is expanded to near atmospheric pressure.The mechanical work at this time is transmitted to the generator 27 via the shaft 26, and the air expansion turbine 24 It is recovered as electricity in the same way as in the case of electricity. The reason why the high-temperature combustion gas leaving the combustion chamber 32 is introduced into the gas turbine 36 after passing through the heat exchanger 22 is to preheat the high-pressure air. The gas turbine 36 is not limited to one stage, but has two or more stages, or a reheat circuit is set in the middle;
Alternatively, efficiency can be improved by adopting a secondary combustion method by adding fuel again. The temperature of the combustion gas at the inlet of the gas turbine 36 is the maximum usable temperature of the gas turbine material under a pressure of 5 to 50 atmospheres, which is typically 900 DEG C. or higher. The combustion gas expands adiabatically in the gas turbine 36 and reaches a state of 1.2 atmospheres and 430°C. The combustion gas is introduced into the heat exchanger 20 through the pipe 37, where it is cooled by exchanging heat with the high-pressure air, and is heated to an atmospheric pressure of 200°C. The waste gas is discharged from the pipe 38 into the atmosphere. Next, we will discuss an example in which the air expansion turbine has multiple stages and a reheat circuit is provided in the middle, and the gas turbine has multiple stages and a reheat circuit is provided in the middle, and a secondary combustion chamber is provided. Shown in Figure 2. In the figure, high-pressure air at 200 atm and 230°C from the pipe 21 is introduced into the heat exchanger 22, where the temperature becomes 200 atm and 560°C, and then introduced into the first stage 24' of the air expansion turbine where it is expanded. , it generates power and outputs it at 70 atmospheres and 380 degrees Celsius, and is again introduced into the heat exchanger 22 where it is reheated to 70 atmospheres and 560 degrees Celsius and is introduced into the second stage 39 of the air expansion turbine. It expands and generates power.
The generated power drives a generator 27 via shafts 41, 25, 26, and 42. The expanded air is introduced into the combustion chamber 32 through the pipe 40 at 20 atmospheres and at 380°C. The natural gas at 20 atmospheres and 230°C from the pipe 31 is mixed with the air from the pipe 40 in the combustion chamber 32.
It is combusted and becomes high-temperature combustion gas, which is introduced from the pipe 34 through the heat exchanger 22 into the first stage 36' of the gas turbine at 20 atmospheres and 980°C, where it expands adiabatically to generate power, and the expanded gas is led out at 5 atmospheres and 680°C, and introduced into the secondary combustion chamber 44 through the pipe 43.
In the secondary combustion chamber, the fuel branched from the pipe 31 flows into the pipe 4.
5, mixed with combustion gas from pipe 43 that still contains oxygen, re-combusted, heated to 1250°C, enters heat exchanger 22 through pipe 46, and becomes 5 atm and 980°C. The gas is introduced through a pipe 47 into a second stage 48 of the gas turbine. Here again, this high-temperature combustion gas expands adiabatically and generates power, producing a pressure of 1.2 atm.
It is extracted as a gas at 680℃. The power generated in the second stage 48 of the gas turbine is transferred to the air expansion turbines 24', 39 and the first stage 3 of the gas turbine.
The generator 27 is driven via the shaft 42 together with the power generated by the generator 6'. The expanded gas passes through the pipe 49, undergoes heat exchange in the heat exchanger 20, and is then released into the atmosphere. The invention thus provides two advantages: (i) to make maximum use of pre-stored liquid air; and (ii) to operate the high-pressure air expansion turbine and the intermediate-pressure gas turbine at their respective highest possible temperature conditions. As a result, extremely high power generation efficiency can be obtained, thereby providing a power generation method that is extremely suitable for peak power generation. In other words, regarding (i), liquid air is first pressurized to above the critical pressure using a pump, but since it is a liquid, the power required for the pump is extremely small compared to that of a compressor, and the resulting high-pressure air is used as a combustion gas. Alternatively, the heat of the exhaust gas from the gas turbine is used to increase the temperature and the gas is expanded in the turbine to generate power, or the expansion is performed from a high pressure of over critical pressure, preferably over 200 atmospheres, so a large amount of power can be obtained. Regarding (ii), high pressures of 200 atmospheres or more are harsh conditions for turbine materials, and in the case of combustion gas turbines, gas containing carbon dioxide and moisture is
In contrast, in the case of the present invention, the high-pressure turbine expands only air, so the temperature condition is that of gas. Although it is lower than a turbine, it is possible to achieve a temperature of 560℃ and 200 atm, which is close to the upper limit of the possible range. Next, the outlet air of this expansion turbine burns the fuel and operates the gas turbine, but since the pressure here is relatively low, 900
High temperature conditions above ℃ can be selected. As described above, the present invention can achieve high power generation efficiency by organically combining an expansion turbine using high-pressure air and a gas turbine using high-temperature combustion gas, and furthermore, since the energy of high-pressure air is utilized, fuel consumption is significantly reduced. do. The LNG consumption rate and thermal efficiency of power generation determined for the example shown in Figure 1 above are shown in the table below, and are extremely superior to normal gas turbine power generation, indicating that high-output peak power generation is possible. .

[Table] As shown in the table, the present invention enables low-cost power generation by achieving extremely excellent thermal efficiency, but at the same time, by combining a high-pressure air turbine, a similar effect can be achieved with a gas turbine. This makes it possible to keep equipment costs significantly lower than in the case of conventional methods.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the method of the present invention, and FIG. 2 shows another embodiment of the method of the present invention. In the figure, 1 is an LNG storage tank, 3 is an LNG pump, 7 is an air compressor, 8 is an air liquefaction separation device, 1
0 is a liquid air storage tank, 16 is a thermal power plant, 18 is a liquid air pump, 19 is an evaporator, 20 is a heat exchanger,
22 is a heat exchanger, 24 is an air expansion turbine, 27
is a generator, 29 is an LNG pump, 30 is an LNG evaporator, 32 is a combustion chamber, 36 is a gas turbine, 24'
is the first stage of the air expansion turbine, 39 is the second stage of the air expansion turbine, 36' is the first stage of the gas turbine, 48 is the second stage of the gas turbine, and 44 is the secondary combustion chamber. .

Claims (1)

[Claims] 1. Pressurize liquid air that has been produced and stored in advance to 100 atmospheres or more, raise the temperature to about 500°C or more by exhaust gas from a gas turbine described later, etc., and then introduce it into an air expansion turbine. The fuel is expanded to between 30 and 30 atmospheres of pressure to generate power, and then the fuel is combusted with the exhaust air at intermediate pressure and temperature, and the temperature is adjusted to 900°C or higher by exchanging heat with the evaporated air of the liquid air. A gas turbine power generation method characterized by introducing the combustion gas into a gas turbine to generate power and driving a generator together with the power from the air expansion turbine. 2. The gas turbine power generation method according to claim 1, wherein the fuel is liquefied natural gas. 3. The gas turbine power generation method according to claim 1 or 2, wherein the liquid air produced and stored in advance is produced by utilizing the cold of liquefied natural gas. 4. The gas turbine power generation method according to claim 3, wherein the liquefied natural gas that is chilled and used to produce liquid air is a fuel for a thermal power plant.