JPH0140266B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a liquefaction device having an expansion turbine, and more particularly to improving the efficiency of a liquefaction device using a high-pressure expansion turbine for processing high-pressure process gas.

[Background of the invention]

In an expansion turbine that has a structure in which the amount of gas leaking to the outside from the back surface of the rotor is reduced by a labyrinth seal, the amount of leakage from the labyrinth portion is generally expressed by the following equation.

Q=F・・P・g/R・T…(1) Where, Q: Leakage amount F; Interval area; Flow coefficient g; Gravitational acceleration P; Inlet pressure R; Gas constant T; Inlet temperature (1) As shown in the equation, the amount of leakage increases in proportion to the inlet pressure. For this reason, in a high-pressure expansion turbine that processes high-pressure gas, a large amount of this gas leaks to the outside, which is one of the causes of a decrease in the basic unit (efficiency) of the liquefaction device.

[Purpose of the invention]

An object of the present invention is to reduce the amount of low-temperature gas leaking to the outside from the back surface of a rotor in a liquefier having an expansion turbine.

[Summary of the invention]

Leakage of low-temperature process gas to the outside from the back of the rotor leads to a reduction in the unit consumption of the entire liquefaction equipment that uses this expansion turbine.

Therefore, in order to prevent this, the present invention provides four types of labyrinth seals behind the rotor of the expansion turbine, and a return line that communicates the outlet of the first labyrinth seal closest to the rotor with the outlet of the expansion turbine. , a return line communicating between a second labyrinth seal outlet next closest to the rotor and a heat exchanger for cooling the compressed process gas, and a third labyrinth seal outlet next closest to the rotor and a third labyrinth seal outlet next closest to the rotor. A line for supplying seal gas is provided between the entrance of the labyrinth seal No. 4 and the entrance of the labyrinth seal No. 4.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. First, the function of the gas-cooled liquefier having the expansion turbine shown in FIG. 1 will be explained.

The high-pressure refrigerant gas compressed by the compressor 1 is introduced into the heat exchanger 2. After being cooled by exchanging heat with the returned refrigerant gas in the heat exchanger 2, it passes through a high-pressure expansion turbine 3 and an intermediate-pressure expansion turbine 4 to perform adiabatic expansion work to generate refrigeration. The low-pressure refrigerant cooled through the medium-pressure expansion turbine 4 passes through the heat exchanger 5, exchanges heat with nitrogen gas in the liquefied gas line, and then passes through the heat exchanger 2 and returns to the high-pressure refrigerant gas and the heat exchanger compressor. The nitrogen gas in the liquefaction line cooled by the heat exchanger 5 is introduced into the purification tower 6 and taken out as liquid nitrogen.

Next, the operation and effects of the embodiment of the present invention will be explained.
After gas leaking from the back surface of the rotor of the high-pressure turbine 3 passes through the labyrinth seal 7, a portion thereof passes through a line 11 that returns to the outlet of the high-pressure turbine 3 and is recovered to the outlet. Therefore, the inlet pressure of the labyrinth seal 8 is reduced to the high pressure turbine outlet pressure. A portion of the low-temperature leaked gas that has passed through the labyrinth seal 8 is transferred to the low-temperature return line 12 of the heat exchanger 2.
and is recovered to the heat exchanger 2. Therefore, the inlet pressure of the labyrinth seal 9 is reduced to the pressure of the heat exchanger 2. Furthermore, the low-temperature leaked gas that has passed through the labyrinth seal 9 joins with the sealing gas 13 and increases in temperature, and then passes through the labyrinth seal 10 and is discharged to the outside.

The pressure of the seal gas 13 is controlled by the labyrinth seal 9.
inlet pressure (equal to the low pressure side pressure of heat exchanger 2)
If adjusted slightly higher, the flow of the labyrinth seal 9 will be reversed, and the gas of the seal gas 13 and the low-temperature leaked gas that passed through the labyrinth seal 8 will merge.
It passes through the low pressure return line 12 of the heat exchanger 2 and is recovered to the heat exchanger. At this time, the gas passing through the labyrinth seal 10 is at the temperature of the sealing gas (room temperature), and as is clear from equation (1), the amount of leakage to the outside can be reduced in inverse proportion to the square root of the absolute temperature. Therefore, the sealing gas pressure may be arbitrarily adjusted according to the requirements of the liquefaction device.

〔Effect of the invention〕

According to the present invention, the amount of low-temperature gas leaking from the back of the expansion turbine rotor to the outside of the plant can be reduced to a low pressure, which increases the unit consumption (efficiency) of the plant.
It has the effect of improving.

[Brief explanation of drawings]

FIG. 1 is a drawing showing an embodiment of the present invention. 1... Compressor, 2... Heat exchanger, 3... High pressure expansion turbine, 4... Medium pressure expansion turbine, 5... Heat exchanger, 6... Purification tower, 7... Labyrinth seal, 8... Labyrinth seal, 9... Labyrinth seal, 10... Labyrinth seal, 11... Return line, 12... Return line, 13... Seal gas.

Claims (1)

[Claims] 1 a compressor that compresses process gas; a first heat exchanger that cools the compressed process gas;
A gas cooling liquefaction device including an expansion turbine that expands the process gas that has passed through the heat exchanger to generate a cold process gas, and a second heat exchanger that cools and liquefies the gas to be liquefied with the cold process gas, Four types of labyrinth seals are provided behind the rotor of the expansion turbine, a return line communicating the outlet of the first labyrinth seal closest to the rotor and the outlet of the expansion turbine, and a second labyrinth seal next closest to the rotor. A return line that communicates an outlet of the rotor with the first heat exchanger, and a seal gas is supplied between a third labyrinth seal outlet next closest to the rotor and an inlet of a fourth labyrinth seal next closest to the rotor. A gas cooling liquefaction device characterized by being provided with a line.