JPS592771B2 - Gas turbine that utilizes cold energy from liquefied natural gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas turbine that utilizes the cold energy of liquefied natural gas, which cools the working air of the open cycle gas turbine through heat exchange with liquefied natural gas to increase the thermal efficiency of the gas turbine. More specifically, in open cycle gas turbines, in order to utilize the cold energy of liquefied natural gas,
When exchanging heat between intake air and liquefied natural gas, this eliminates the drawback that moisture contained in the air freezes on the heat transfer surface of the heat exchanger, reducing the heat transfer effect or making cooling impossible. This makes it possible to utilize cold energy during the gasification of liquefied natural gas by cooling the intake air of the gas turbine.

In order to facilitate transportation and storage, natural gas is liquefied at the place where it is produced and then vaporized when it is supplied to the place where it is consumed.

Therefore, in addition to the combustion energy of natural gas, liquefied natural gas (hereinafter abbreviated as LNG) retains part of the energy used in the liquefaction process as a potential at a low temperature of -162℃. ing.

Effective ways to use this energy include directly using it as a low-temperature source, i.e. for producing liquid nitrogen or liquid oxygen, or for freezing, and in thermal power plants to reduce the impact of heated wastewater. It is used for such things.

However, in recent years, from the perspective of energy conservation, cold power generation, which extracts the difference in temperature potential between low temperatures and room temperature as electrical energy, has rapidly attracted attention as a more active form of cold energy utilization.

For cold energy power generation, applications such as the Rankine cycle and the gas turbine cycle are being considered.In the cold energy utilization in gas turbines, the intake air of the gas turbine is cooled by heat exchange with LNG to reduce the compression power, and the This improves the heat recovery effect by exchanging heat between air and exhaust gas.

For example, in the closed cycle gas turbine shown in FIG. 1, LNG 5a in the LNG tank 18 is vaporized via the pump 19 in the vaporizer 7a by heat exchange with nitrogen, which is the working medium of the gas turbine.

The cooled (for example, -140°C) nitrogen 20 is taken into the compressor 3a and pressurized, then preheated in the regenerator 10a by heat exchange with the exhaust gas of the turbine, and further heated in the combustor 11a to power the turbine 2a. drive

The exhaust gas from the turbine 2a passes through the regenerator 10a, reaches the vaporizer 7a, and exchanges heat with the LNG 6a again.

Here, since the nitrogen 20 is cooled by LNG, the compressor power decreases due to the temperature drop, and the gas turbine output increases.

In other words, the increase in thermal efficiency of the gas turbine due to this method is L
This is an NG cold energy utilization effect.

Here, the combustor 11a has nitrogen 20 flowing in a pipe.
is heated from the outside using LNG, etc.
Since the nitrogen 20 in the pipe is heated in a pressurized state, there is a limit to the heating temperature due to the limit of material strength at high temperatures of the pipe, and the turbine inlet temperature is limited to around 700°C.

For this reason, in closed cycle gas turbines,
The limit on turbine inlet temperature also limits the increase in thermal efficiency.

In addition, when looking at the gas turbine plant as a whole, a large combustor made of high quality materials is required, and the equipment cost is high, making it difficult to implement economically.

In the case of LNG cold utilization by an open cycle gas turbine as shown in FIG.
At step b, it is vaporized by heat exchange with the intake air 13b of the gas turbine.

The low-temperature intake air cooled by the vaporizer is compressed by the compressor 3b, and after being preheated by the regenerator 10b, it is heated by the combustor 11b to drive the turbine 2b.The exhaust gas 9b of the turbine 2b is heat exchanged with the regenerator 'IOb. Then exhaust to the outside.

This is because the intake air temperature is lowered by using the cold energy of LNG, which reduces the power required for compression by the compressor 3b, and the inlet temperature of the turbine 2b can be raised to about 1000 degrees Celsius. It has the advantage of higher thermal efficiency than cycle gas turbines.

However, when air is taken in by the compressor 3b, the moisture contained in the intake air freezes on the heat transfer surface of the vaporizer 7b, causing the LNG 6b and the intake air 1 to freeze.
There are still problems that heat exchange with 3b becomes impossible or insufficient, and the intake passage is blocked, so that it cannot be put to practical use as it is.

The present invention is a method that eliminates the drawback that moisture contained in the air freezes on the heat transfer surface of a vaporizer when using cold energy from LNG, and enables the use of cold energy when gasifying liquefied natural gas using an open cycle gas turbine. The purpose is to provide.

In order to achieve this objective, the present invention separately injects low-temperature air cooled by an air cooling device using LNG cold energy into the air taken into the compressor of an open cycle gas turbine, and mixes the intake air. It is characterized by lowering the temperature.

Next, the present invention will be explained in detail with reference to FIG.

In the figure, a generator 1 is driven by a turbine 2.

Further, the compressor 3 is connected to the same shaft as the turbine 2 and driven.

A heat exchanger 10 for exchanging heat between exhaust gas 9 of the turbine 2 and compressed air discharged from the compressor 3 is provided in the discharge pipe line 8 of the compressor 3 leading from the compressor 3 to the turbine 2. The compressed air preheated in the combustor 10 is heated in the combustor 11 and reaches the turbine 2.

A separate air cooling system 1 is installed for the air taken into the compressor 3.
Low-temperature air cooled using the cold energy of LNG in step 2 14
is injected into the mixer 4 and mixed with the intake air 13.

For example, as shown in FIG. 4, a mixer main body 15 is formed in a part of the suction pipe 5 of the compressor 3, and low-temperature air 14 is injected into the mixer main body 15 and mixed with normal-temperature intake air 13. Mouth 16
form.

At this time, it will be more effective if the air 14 is extremely cooled (for example, to about -200° C.) by the air cooling system 12 and turned into liquid air, which is sent to the mixer 4 using a pump or the like.

In this way, the low temperature air 14 is transferred to the injection port 1 of the mixer 4.
6 and mixes with the normal temperature suction air 13, the temperature of the mixed air is lowered to below the freezing point of water.

As a result, the moisture contained in the atmosphere 13 becomes extremely fine ice, which is sucked into the high-pressure compressor 3 in a suspended state in the mixed air.

As described above, according to the present invention, the air whose temperature has decreased using the cold energy of LNG is directly injected and mixed into the suction air of the compressor, thereby cooling the suction air.
Since the cold energy of LNG is used, a heat exchanger (heat transfer type) for heat conversion between the intake air and LNG can be omitted, and it is possible to prevent insufficient or impossible cooling of the intake air due to freezing of the heat transfer surface.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams of a conventional closed-cycle gas turbine and an open-cycle gas turbine that utilize cold energy from LNG.
FIG. 4 is a diagram illustrating the cycle of an open cycle gas turbine that uses G as cold energy, and FIG. 4 is an explanatory diagram of a mixer. 2... Turbine, 3... Compressor, 4... Mixer,
11... Combustor, 12... Air cooling system, 13
... Suction air, 14... Air, 16... Low temperature air injection nozzle.

Claims (1)

[Claims] 1 Compress the air with a compressor and guide it to the combustor,
In a so-called oven cycle gas turbine that drives a turbine as high-temperature gas by burning fuel in the combustor, the air taken into the compressor and a separate air cooling system using liquefied natural gas as a low-temperature source are used. A gas turbine that utilizes cold energy from liquefied natural gas and is configured so that a compressor draws in mixed air with air that has been cooled to an extremely low temperature.