JPS6125889B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to liquefied natural gas cold energy power generation equipment, and in particular, liquefied natural gas (hereinafter abbreviated as LNG) is vaporized and expanded using a heat source such as seawater. It is equipped with a regeneration cycle in which a part of the natural gas expanded by the turbine is cooled and reliquefied by the LNG, and after being pressurized by a pump, it is vaporized together with the LNG again by a heat source such as seawater, and then circulated to the expansion turbine. This relates to the improvement of power generation equipment that utilizes liquefied natural gas cold energy.

[Background of the invention]

Conventionally, LNG was used in power generation equipment that utilized the cold energy of LNG.
There is one based on the direct expansion method. This type of power generation equipment boosts the pressure of LNG with a pump, vaporizes it in a vaporizer using a heat source such as seawater, and then flows it through an expansion turbine, a heater, an expansion turbine, and a heater.
While generating electricity using this repeated cold heat,
LNG is vaporized and supplied. but,
According to this method, the equipment is simple, but the amount of power generated through the use of cold energy is relatively small, so in order to increase the amount of power generated, part of the natural gas expanded in the expansion turbine is cooled with LNG and reliquefied. It has been proposed that the LNG is pressurized using a pump, then mixed with other LNG, vaporized using a heat source such as seawater, and then circulated through the expansion turbine. With this method, the amount of circulating LNG that is reliquefied and revaporized increases the air volume of the expansion turbine, making it possible to increase the amount of power generation.

Figure 1 shows a typical regeneration cycle of this type.
It is a system diagram of a power generation facility using LNG cold energy. In FIG. 1, LNG is pressurized from a conduit 1 to a predetermined pressure by an LNG pump 2, and then enters a reliquefier 4 through a conduit 3. Here, the natural gas from the conduit 5 is reliquefied, and the LNG whose temperature has increased thereby is sent out from the conduit 6. LNG reliquefied in reliquefier 4
passes through conduit 7 and is pressurized by circulation pump 8,
It joins the LNG from the conduit 6 through the automatic valve 9 and the conduit 10, then enters the LNG vaporizer 11, where it is vaporized by a heat source such as seawater, and enters the expansion turbine 13 through the conduit 12, where the expanded natural gas The gas enters the natural gas heater 15 from the conduit 14, is heated by a heat source such as seawater, passes through the conduit 16, enters the expansion turbine 17, and then enters the natural gas heater 18, where the natural gas is heated to room temperature. is conduit 1
9 to the next stage equipment. expansion turbine 1
A portion of the natural gas expanded in step 3 enters the reliquefier 4 as described above via conduit 5, is reliquefied and enters LNG vaporizer 11 together with the LNG from conduit 6,
This cycle is then repeated. Note that the expansion turbine 1
3 and 17 are connected to a generator 20, and the rotation of the expansion turbines 13 and 17 is recovered as electric power.

In such a regeneration cycle, from the viewpoint of safe operation of the circulation pump 8, a control method is adopted in which the reliquefaction temperature in the reliquefier 4 reaches a supercooling state, taking into account various operating conditions and control system responsiveness. We are trying to adopt the following. For example, as shown in FIG. 1, the circulation pump flow rate is controlled by an automatic valve 9 so that the temperature at the inlet conduit 7 of the circulation pump 8 of the LNG leaving the reliquefier 4 reaches a predetermined supercooling temperature. There is. by the way,
Considering the safety of the circulation pump 8, it is preferable to increase the supercooling temperature, but in this case, assuming that the amount of heat exchanged by the reliquefier 4 is constant, in order to increase the supercooling temperature, Since the reliquefaction heat amount per unit flow rate must be increased, the reliquefaction amount (circulation amount) must be reduced. As a result, the turbine air volume decreases and the amount of power generated decreases. Therefore, the key to making the most of the regeneration cycle is to make the circulation pump 8 safe and to increase the amount of circulation. However, the conventional LNG cold energy power generation equipment shown in Figure 1 does not have a configuration that fully satisfies this requirement, and improvements are desired.

[Purpose of the invention]

The present invention has been made in view of the above, and its purpose is to enable safe operation even when the reliquefaction temperature is near the saturation point, and to increase the circulation amount of reliquefied natural gas. The object of the present invention is to provide a power generation facility using liquefied natural gas cold energy that can increase the amount of power generated.

[Summary of the invention]

The present invention temporarily stores natural gas from an expansion turbine that has been reliquefied in a reliquefier in a receiver tank,
Vaporization in which the supplied liquefied natural gas and the re-liquefied natural gas are vaporized by using a circulation pump to circulate the liquefied natural gas in the receiver tank while keeping the liquid level of the liquefied natural gas in the receiver tank constant. The gas is circulated through the expansion turbine through the tank.

[Embodiments of the invention]

The present invention will be explained in detail below using the embodiment shown in FIG.

FIG. 2 is a system diagram showing an embodiment of the power generation equipment of the present invention. The same parts as in FIG. In FIG. 2, LNG re-liquefied in the re-liquefier 4 is led to the receiver tank 21 through the conduit 7, and the LNG inside the receiver tank 21 is
The LNG is extracted by the circulation pump 8 and pressurized, and this pressurized LNG is transferred to the LNG in the receiver tank 21.
automatic valve 22 that operates according to the liquid level and flow rate;
It is arranged to combine with LNG from the conduit 6 via the conduit 10 and send it to the LNG vaporizer 11.

Here, in order to maintain the LNG in the receiver tank 21 at a saturation temperature, a liquid level regulator 23 is installed, and when the liquid level changes, the liquid level is adjusted to a predetermined value by a liquid level change signal from the liquid level regulator 23. The automatic valve 22 is adjusted with priority over the signal from the flow regulator 24 until the flow returns to . Therefore, for safe operation of the circulation pump 8, even if the LNG in the receiver tank 21 is saturated, the liquid level is controlled to be within a certain range, so the NPSH required by the circulation pump 8 can be maintained. If you plan to your satisfaction, you can secure it without any problems.

In short, according to the embodiment shown in Fig. 2, it is possible to operate in a state where the liquefaction temperature of reliquefied LNG is close to the saturation temperature, and the circulating amount of reliquefied LNG can be increased compared to the conventional case. As a result, the air volume of the expansion turbine 13 can be increased, and the amount of power generated can be increased.

In the embodiment shown in FIG. 2, a part of the natural gas from the expansion turbine 13 is re-liquefied, but it is also possible to re-liquefy a part of the natural gas from the expansion turbine 17. It's okay,
The effect is the same. In addition, the expansion turbine is 13,
17, two natural gas heaters, 15 and 18.
However, the present invention can also be applied to systems in which the number of expansion turbines and heaters is changed depending on the boost pressure of LNG, the delivery temperature of natural gas, the type and characteristics of the expansion turbine, etc. , has the same effect.

〔Effect of the invention〕

As explained above, according to the present invention, stable operation can be performed even when the reliquefaction temperature is near the saturation point, so it is possible to increase the circulation amount of reliquefied LNG and increase the amount of power generation. The effect is that it can be done.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a conventional liquefied natural gas cold energy power generation facility, and FIG. 2 is a system diagram showing an embodiment of the liquefied natural gas cold energy power generation facility of the present invention. 2... LNG pump, 4... Reliquefier, 5,
6, 7, 10... Conduit, 8... Circulation pump, 11
... LNG vaporizer, 13, 17 ... Expansion turbine, 15, 18 ... Natural gas heater, 20 ... Generator, 21 ... Receiver tank, 22 ... Automatic valve, 23 ... Liquid level regulator, 24...Flow rate regulator.

Claims (1)

[Claims] 1. A part of the natural gas obtained by vaporizing liquefied natural gas and expanding it in an expansion turbine is reliquefied in a reliquefaction device using the liquefied natural gas, and this is vaporized together with the liquefied natural gas in a vaporizer to perform the expansion. In a liquefied natural gas cold energy power generation facility equipped with a regeneration cycle for circulating it through a turbine, the natural gas from the expansion turbine that has been reliquefied in the reliquefaction device is temporarily stored in a receiver tank, and the natural gas is liquefied in the receiver tank. The liquefied natural gas cold energy utilization is characterized in that the liquefied natural gas in the receiver tank is circulated to the expansion turbine via the vaporizer using a circulation pump while the liquid level of the natural gas is maintained constant. Power generation equipment.