JPS5938408B2 - Media recovery method for LNG cold energy power generation equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a medium recovery method for LNG cold energy power generation equipment.

LNG is used as a fuel for city gas, steel manufacturing, chemical factories, etc., and the amount is increasing rapidly every year.

This LNG retains cold energy, so if it were simply vaporized in seawater, the cold energy would be transferred to the seawater and wasted.

For this reason, there is a tendency to install power generation equipment that utilizes the cold energy of LNG as an energy-saving measure.

Methods of power generation using cold energy from LNG include the direct expansion method, in which LNG is pressurized with a pump, vaporized with seawater, and then generated in a turbine, and the other method is the direct expansion method, in which the heat of vaporization of LNG is used to condense a medium (propane gas, fluorocarbon gas, etc.). There is an indirect expansion method (hereinafter referred to as the Rankine cycle) that uses seawater to vaporize the medium after pressurization and generates electricity using a turbine, but in order to increase the amount of power generated, a direct expansion method that combines both methods is preferable. The present invention is suitable for LNG cold energy power generation equipment that uses only a Rankine cycle or a direct expansion type ten Rankine cycle.

When a medium is enclosed in a Rankine cycle, the displaced gas remains.

Generally, when the medium to be sealed is a flammable gas, it is replaced with nitrogen gas, and in other cases, it is replaced with air or the like.

For this reason, if the medium is directly enclosed in the displacement gas remaining in the system, the displacement gas remaining in the medium condenser will stay in the medium condenser when the Rankine cycle is operated, reducing the condensation performance of the medium and causing the cycle The overall heat balance cannot be balanced, causing trouble.

Therefore, as a means for expelling the remaining replacement gas in the Rankine cycle system, a method has been adopted in the past in which the system is evacuated with a vacuum pump and then a medium is enclosed.

However, according to this method, the medium sealed in the Rankine cycle has a considerably high saturation pressure at room temperature, such as propane gas, so it is necessary not only to withstand this pressure but also to have a vacuum-resistant design that takes into account vacuum evacuation. As a result, piping joints, heat exchangers, valves, and instruments were all required to withstand high pressure and vacuum, which had the disadvantage of extremely high equipment costs.

In addition, in order to use a method that does not draw a vacuum, it is necessary to first replace the replacement gas remaining in the Rankine cycle system with the medium gas when filling the medium, and in order to completely expel the residual gas, the medium must be The disadvantage was that a considerable amount of gas was discarded along with the gas, and the expensive medium had to be replenished without losing it.

An object of the present invention is to minimize the loss of medium during filling or recovery of the medium without using a vacuum specification as a Rankine cycle specification.

The present invention is an LNG cold energy power generation facility that uses LNG cold energy power generation equipment that uses the heat of vaporization of LNG to condense the medium, pressurize and degasify it with a pump, and introduce it into a turbine to generate electricity. and medium gas are introduced into a heat exchanger and cooled with LNG, the medium is liquefied and recovered, and the replacement gas is separated and removed, thereby minimizing the amount of medium loss during medium filling or recovery. It is.

Hereinafter, as an embodiment of the present invention, a case where Freon is used as a medium for Rankine cycle will be explained with reference to the drawings.

In the process during normal operation, LNG is sent from the conduit 11, is pressurized to a predetermined pressure by the LNG pump 5, and is transferred to the conduit 11.
2 into LNG vaporizer 1.

Here, the LNG is vaporized by condensing the fluorocarbon gas sent from the fluorocarbon turbine 9, and enters the NG warmer 2 through the conduit 13.

In the NG warmer 2, the seawater supplied from the conduit 27 is heated to around room temperature (0° C. or higher), and then supplied from the conduit 14 as fuel gas.

On the other hand, in the Rankine cycle, fluorocarbons condensed in the LNG vaporizer 1 enter the fluorocarbon pump 6 through conduits 15°16,
After increasing the pressure to a predetermined pressure, it enters the freon evaporator 3 through the conduit 17.

In the Freon evaporator 3, Freon is evaporated by the seawater supplied from the conduit 28, the evaporated Freon gas is expanded by the Freon turbine 9, and the generated power is used to generate electricity in the generator 10.

The fluorocarbon gas leaving the fluorocarbon turbine 9 returns to the LNG vaporizer 1 via a conduit 19.

A fluorocarbon liquefier 4, a fluorocarbon tank 8, and a fluorocarbon filling pump 7 are installed as accessory equipment.

Regarding the filling method of Freon, since it is necessary to remove moisture in advance in the Rankine cycle, moisture is purged with dry air or nitrogen gas (hereinafter referred to as nitrogen gas).

The purged nitrogen gas needs to be purged out of the system before filling with Freon is completed.

In the procedure for filling the fluorocarbons, the fluorocarbons stored in the fluorocarbon tank 8 are transferred from the conduit 25 to the conduit 2 via the fluorocarbon filling pump 7.
6 to the LNG vaporizer 1.

The filled Freon is transferred to a Freon pump 6, a Freon evaporator 3,
The nitrogen gas flows in the order of the freon turbine 9 and the nitrogen gas remaining in the system is flowed into the LNG vaporizer 1.

The nitrogen gas stagnant in the LNG vaporizer 1 enters the heat exchanger 4 via the conduit 22, where it is converted into LNG supplied from the conduit 20.
The cold energy of G cools nitrogen gas containing fluorocarbon gas.

Therefore, only Freon having a high boiling point is condensed, and nitrogen gas is released from the conduit 23 in gaseous form.

On the other hand, the condensed fluorocarbon is recovered through the conduit 24.

Next, as for the recovery procedure for fluorocarbons, the fluorocarbons in the system are collected through the fluorocarbon pump 6 and into the fluorocarbon tank 8 through conduits 17 and 30. However, if nitrogen gas remains in the fluorocarbon tank 8, the fluorocarbons in the system are recovered through the conduit 31. The fluorocarbon is introduced into the heat exchanger 4, and the fluorocarbon can be separated and recovered from nitrogen gas using -LNG in the same manner as when filling the fluorocarbon.

When replacing the Rankine cycle with nitrogen gas, after the fluorocarbon liquid is transferred to the fluorocarbon tank 8, the remaining fluorocarbon gas is transferred to the fluorocarbon pump 6, the fluorocarbon evaporator 3, the fluorocarbon turbine 9, and the heat exchanger by the nitrogen gas from the conduit 29. Freon gas is sent in the order of vessel 4, liquefied and recovered, and returned to the Freon tank.

Further, even during steady operation, if nitrogen gas accumulates as inert gas in the LNG vaporizer 1, the nitrogen gas can be separated and removed from the conduit 22 by the heat exchanger 4.

As described above, in an LNG cold energy power generation facility having a Rankine cycle, when a medium is charged into or recovered from the Rankine cycle system by using the cold energy of LNG supplied to the heat exchanger, the Rankine cycle system is used. This has the effect of minimizing the amount of media loss without evacuating the media.

Generally speaking, there is a method of using a refrigerator as a cooling source, but there are limitations due to equipment costs and temperature levels.

That is, if LNG is used as a cold heat source for fluorocarbon recovery as a medium, the cooling temperature in the heat exchanger can be reduced to a temperature range that is difficult to cool with a refrigerator because of the extremely low temperature of about -160°C.

This also has the effect of increasing the amount of medium liquefied and increasing the recovery rate of the medium.

[Brief explanation of the drawing]

The drawing is a system diagram showing an embodiment of the medium recovery method for LNG cold energy power generation equipment according to the present invention. 1... LNG vaporizer, 2... NG warmer, 3... Freon evaporator, 4... Heat exchanger, 5... ... LNG pump, 6 ... Freon pump, 7 ... Freon filling pump, 8 ...
... Freon recovery tank, 9... Freon turbine, 10... Generator, 11-31...
·conduit.

Claims (1)

[Claims] I In a power generation facility using LNG cold energy that uses the Rankine cycle, in which the medium is condensed using the heat of vaporization of LNG, the pressure is increased by a pump, and the gas is introduced into the turbine to generate electricity, the replacement gas and medium gas remaining in the Rankine cycle are LNG is introduced into a heat exchanger and cooled by LNG, the medium is liquefied and recovered, and the replacement gas is separated and removed.
Media recovery method for cold energy generation equipment.