JPS6136679A - Gas liquefier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention uses a high-pressure expansion turbine and a low-pressure expansion turbine using gases with extremely low boiling points such as nitrogen and oxygen separated by an air separation device etc. as a cold generation source. The present invention relates to a gas liquefaction device that liquefies gas using a so-called two-stage expansion turbine.

[Background of the invention]

As a method for efficiently liquefying gases with extremely low boiling points such as oxygen and nitrogen, a two-stage expansion turbine that combines a high-pressure expansion turbine and a low-pressure expansion turbine is used, as shown in Japanese Patent Publication No. 49-40547, for example. The method is known.

In gas liquefaction equipment, when supplying product liquefied gas under high pressure to a storage tank or other equipment, it is necessary to reduce the pressure to a low pressure state. When the pressure is reduced, part of the liquid flashes and gas is generated.

In order to reduce this flabunyuros, it is necessary to supercool the high-pressure product liquefied gas to the saturation temperature after depressurization. Therefore, the gas outlet temperature of the low-pressure expansion turbine must be lowered below the saturation temperature of the liquefied gas after depressurization. need to be lowered. However, if the outlet temperature of the low-pressure expansion turbine is lowered too much, part of the gas will liquefy and mist will be generated. Expansion turbines are generally operated at high-speed rotation (opposite rotation), and if liquid mist is generated in the gas, there is a risk of wear and imbalance resulting in destruction of the turbine. As a protection device for this purpose, a method of controlling the outlet gas temperature of a low-pressure expansion turbine has been employed so far, as disclosed in Japanese Patent Publication No. 49-40547.

On the other hand, in an expansion turbine that generates cold air, based on the principle of thermodynamics, the higher the gas temperature and pressure, the greater the theoretical adiabatic heat drop. This will improve the efficiency of the gas liquefaction equipment.

An example of a gas liquefaction device using a high-pressure expansion turbine and a low-pressure expansion turbine according to the prior art will be described with reference to FIG. 2 as a liquid nitrogen generator.

In Fig. 2, l is a circulation compressor that boosts the pressure of nitrogen gas;
2 is a precooler, 3 is a cooler using Freon or the like as a refrigerant, 4 is a heat exchanger, 5 is a liquefier, 6 is a high pressure expansion turbine, 7 is a low pressure expansion turbine, 8 is a liquefied gas outlet valve, 9 is a heat exchanger A conduit 10 guides a part of the nitrogen gas cooled in the liquefier 4 to the high pressure expansion turbine 6 for generating cold, a conduit 10 leads the remainder to the liquefier 5 as liquefaction gas, and 11 a conduit that leads the nitrogen gas cooled in the liquefier 5 to the high pressure expansion turbine 6. This is a conduit connecting the outlet and the inlet of the low pressure expansion turbine 7.

After increasing the pressure to about 35 Kg/ctIG in the gas nitrogen circulation compressor 1, it was cooled in the precooler 2 and cooler 3, and further cooled to about -]oo"c with low temperature return gas nitrogen in the heat exchanger 4. One of the high-pressure nitrogen gases is introduced into the high-pressure expansion turbine 6 through the conduit 9 and expanded to a pressure of approximately 5Ks+/cIIG to generate a cooling temperature of approximately -160"C. This nitrogen gas is passed through the conduit 11. After recovering the temperature to about -150°C in the liquefier 5, it is introduced into the low pressure expansion turbine 7 and cooled to about -150°C.
A cold temperature of 190"C is generated. The low-pressure, low-temperature nitrogen gas, which has reached a pressure of approximately o3Kp/cal G in the low-pressure expansion turbine 7, is led to the liquefier 5, divided at the outlet of the heat exchanger 4, and sent through the conduit 10. The other high-pressure liquefied nitrogen gas led to the liquefier 5 is liquefied and supercooled at the same time, and the high-pressure nitrogen gas is further cooled in the heat exchanger 4 to recover its temperature, and then the precooler 2
It is returned to the circulation compressor 1 through the. On the other hand, the high-pressure liquefied nitrogen gas liquefied in the liquefier 5 is supercooled to the saturation temperature of the product in the wake of the liquefier 5, and is passed from the conduit to the liquefied gas outlet valve 8.
The product is then stored as liquid nitrogen in storage tanks, or used as a cooling source for rectification towers such as air separation equipment.

Conventionally, the outlet gas temperature of the low-pressure expansion turbine 7 is adjusted by providing an outlet temperature detector and adjusting the temperature via the liquefied gas outlet valve 8 using a temperature adjusting device M13. In addition, during the reduction operation or when the liquefaction gas cannot be adjusted in time, the method described in Japanese Patent Publication No. 49-40547 mentioned above is also used.

However, in the conventional adjustment method shown in FIG. 2, the inlet temperature of the low-pressure expansion turbine 7, whose temperature is recovered by the liquefier 5, changes depending on the flow rate of the high-pressure liquefaction gas, which is a high-temperature fluid. In other words, in the method of controlling the amount of liquefied gas by the outlet gas temperature of the low-pressure expansion turbine 7, the relationship between the heat transfer areas of the liquefier 5 cannot be changed by a reduction operation other than the design point. The temperature of liquid nitrogen taken out as a product changes greatly due to fluctuations in the amount of liquefied gas due to the outlet temperature priority control of the low-pressure expansion turbine 7. This has the disadvantage that it also affects the inlet temperature of the high-pressure expansion turbine 6.

As the temperature of liquid nitrogen increases, flash loss increases,
Excess nitrogen gas will be discarded, reducing efficiency.

On the other hand, the method disclosed in Japanese Patent Publication No. 49-40547, which bypasses the inlet gas of the high-pressure expansion turbine 6, is effective in protecting the low-pressure expansion turbine 7, but results in a loss of energy, and similarly the efficiency of the liquefaction device is greatly reduced. descend.

[Purpose of the invention]

In order to overcome the drawbacks of the prior art, the present invention adjusts the outlet gas temperature of the low-pressure expansion turbine to the optimum operating condition of the device without affecting the inlet temperature of the high-pressure expansion turbine or the final cooling temperature of the liquefied gas. The object of the present invention is to provide a gas liquefaction device that can be operated together.

[Summary of the invention]

The gist of the present invention is to provide a turbine heat exchanger for adjusting the outlet gas temperature of the low-pressure expansion turbine in the middle of a conduit connecting the high-pressure expansion turbine outlet and the low-pressure expansion turbine inlet, and to provide a high-temperature fluid for temperature adjustment. The liquefied gas is divided into two parts, one of which is passed through a turbine heat exchanger, and the amount of liquefied gas guided to the turbine heat exchanger and the amount of liquefied gas that passes through the liquefier are controlled by control valves depending on the outlet gas temperature of the low-pressure expansion turbine. The temperature is automatically adjusted by detecting the temperature of the product liquefied gas at the liquefier outlet, and automatically adjusting the inlet temperature of the high pressure expansion turbine to the optimum temperature based on the liquefaction temperature.

[Embodiment of the Invention] An embodiment of the present invention will be described below regarding a nitrogen gas liquefaction device.
This will be explained in detail using diagram J1.

In FIG. 1, the same parts as in FIG. 2 are designated by the same reference numerals and explanations will be omitted. 14 is a turbine heat exchanger provided in the middle of the conduit 11 connecting the outlet of the high-pressure expansion turbine 6 and the inlet of the low-pressure expansion turbine 7; 15 is the turbine heat exchanger 1;
4 is an automatic control valve for the liquefied gas flowing through the liquefier 5; 16 is an automatic control valve for the liquefied gas flowing through the middle part of the liquefier 5; 17 is a conduit for introducing the liquefied gas to the turbine heat exchanger 14;
19 is an automatic control valve 1
5.16 A conduit that guides the liquefied gas to the downstream side of the liquefier 5 again, and a set value of the temperature control device 21 that detects the liquefied gas outlet temperature and adjusts the inlet temperature of the high pressure expansion turbine 6. It is an automatic adjustment device that changes the

As explained in FIG. 2, the high-pressure nitrogen gas that exits the heat exchanger 4 is divided into two parts, and the nitrogen gas for cold generation is guided through the conduit 9 to the high-pressure expansion turbine 6, where the cold generation nitrogen gas is a turbine heat exchanger 14 installed in the middle of the conduit 11
guided by. On the other hand, the high-pressure nitrogen gas for liquefaction led to the liquefier 5 through the conduit 10 is further divided into two parts, and one of the high-pressure nitrogen gases is led to the turbine heat exchanger 14 through the conduit 17. In the turbine heat exchanger 14 , the cold generation nitrogen gas that has become low temperature in the high-pressure expansion turbine 6 and the liquefied high-pressure nitrogen gas exchange heat, and the cold generation gas is heated to a predetermined temperature and then transferred to the low-pressure expansion turbine 7 . will lead you to the entrance. The high-pressure nitrogen gas for liquefaction is liquefied here, and is divided in the liquefier 5 and joins with the remaining liquefied gas through the automatic control valves 15 and 16 in the conduit 19, and then flows back to the downstream side of the liquefier 5. It is guided and exchanges heat with the cold generated outlet nitrogen gas in the low pressure expansion turbine 7,
Supercooled conduit 12. It passes through the liquefied gas outlet valve 8 and is taken out as a product liquefied gas.

On the other hand, the temperature of the nitrogen gas at the outlet of the low pressure expansion turbine 7 is automatically controlled by the temperature control device 113 via automatic control valves 15 and 16. In addition, the temperature of the product liquefied gas is determined by a temperature sensor installed at the conduit pipe, and an automatic control device that automatically sets the set value of the temperature control device I21 installed at the inlet pipe 9 of the high-pressure expansion turbine 6 is used at the liquefied gas outlet. Automatically controlled via valve 8.

In the above-mentioned embodiment, the automatic control valve 15,16 is activated by detecting the nitrogen gas temperature at the outlet of the low-pressure expansion turbine 7. However, even if the inlet temperature of the low-pressure expansion turbine 70 is detected, the same effect can be achieved indirectly. Effects can be obtained. Furthermore, even if the temperature of the product liquefied gas is detected and directly controlled via the liquefied gas outlet valve 8, the inlet temperature of the high-pressure expansion turbine 6 is automatically controlled to the optimum temperature due to the heat exchange performance of the liquefier 5. However,
In a state where liquefied gas is not generated, such as during startup, the temperature is not fixed, and controllability is poor because the temperature change of liquefied gas is small. According to the present invention, the temperature control device 1i21 of the high-pressure expansion turbine 6 can be provided with a set point limiter at a limit value within the operating range, so problems at startup and controllability are solved.

In addition, instead of the turbine heat exchanger 14 of the present invention, a passage for raising the temperature of high-pressure expansion turbine outlet gas is provided in the conventional liquefier 5, and a pipe is provided directly from the high-pressure expansion turbine outlet to the low-pressure expansion turbine inlet without passing through the liquefier 5. Control similar to the present invention is possible even if a conduit is provided for /f and each valve is operated and controlled by a low-pressure expansion turbine outlet temperature controller.
As the rate of increase in the heat transfer area of the liquefier 5 increases, it becomes economically disadvantageous to provide a control valve in a large-diameter conduit with a large flow rate, and furthermore, the increased pressure loss of the valve causes cooling of the expansion turbine. Since the quantity also decreases, there is a large loss in terms of performance. Further, since the temperature zone of the liquefier changes with changes in operation, the present invention is more effective because it does not affect the change in the temperature zone of the liquefier, which can be considered as the optimum condition.

〔Effect of the invention〕

As described above, the present invention provides a turbine heat exchanger for adjusting the low-pressure expansion turbine outlet temperature in the middle of the inductor connecting the high-pressure expansion turbine outlet and the low-pressure expansion turbine inlet. Compared to the case where the low-pressure expansion turbine inlet temperature was raised using a liquefier, there is no effect of the low pressure and low-temperature nitrogen gas temperature at the low-pressure expansion turbine outlet, so the low-pressure expansion turbine outlet temperature remains constant under any operating conditions. In addition, by controlling the high-pressure expansion turbine inlet temperature using the liquefied gas outlet temperature, it is possible to easily set the optimum operating conditions for the gas liquefaction equipment that always minimizes energy loss. effective.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a gas liquefaction equipment showing one embodiment of the present invention, and Fig. 2 is a system diagram of a conventional gas liquefaction equipment employing a so-called two-stage expansion turbine using a high-pressure expansion turbine and a low-pressure expansion turbine. It is a diagram. l... Circulating compressor, 2... Precooler, 3
...Cooler, 4...Heat exchanger, 5...
... Liquefier, 6 ... High pressure expansion turbine, 7.
...Low pressure expansion turbine, 8 ... Liquefied gas outlet valve, 9 - 12. 17 - 19 ... Conduit, 13° 4 ... Temperature control device, 14. ...Turbine heat exchanger, = 1-1 diagram'I = 2 diagram

Claims (1)

[Claims] 1. The gas pressurized by the circulation compressor is cooled by low-temperature return gas in a heat exchanger, and then converted into cold generation gas and liquefaction gas.
The cold generation gas of the first divided flow is introduced into the first-stage high-pressure expansion turbine to generate cold, and after recovering the temperature of the gas at the high-pressure expansion turbine outlet, the second-stage low-pressure expansion turbine The low-temperature return gas is passed through a liquefier to liquefy the liquefied gas in the second branch stream, and the temperature is recovered through a heat exchanger, after which the gas is circulated to the circulation compressor. In the liquefaction device, a turbine heat exchanger for increasing the temperature of the high-pressure expansion turbine outlet gas is provided in the middle of a conduit connecting the high-pressure expansion turbine outlet and the low-pressure expansion turbine inlet. is further divided into two parts on the upstream side of the liquefier, and a conduit is provided in which one of the divided gases passes through the turbine heat exchanger and joins with the other divided gas on the downstream side of the liquefier, and the conduit and the other divided gas conduit are connected to each other. A gas liquefaction device characterized in that an automatic control valve is provided to adjust the flow rate, and a temperature control device is provided to detect the inlet or outlet temperature of the low-pressure expansion turbine and operate the automatic control valve. 2. After the gas pressurized by the circulation compressor is cooled by the low-temperature return gas in the heat exchanger, it is divided into cold generation gas and liquefaction gas.
The cold generation gas of the first divided flow is introduced into the first-stage high-pressure expansion turbine to generate cold, and after recovering the temperature of the gas at the high-pressure expansion turbine outlet, the second-stage low-pressure expansion turbine The low-temperature return gas is passed through a liquefier to liquefy the liquefied gas in the second branch stream, and the temperature is recovered through a heat exchanger, after which the gas is circulated to the circulation compressor. In the liquefaction device, a turbine heat exchanger for increasing the temperature of the high-pressure expansion turbine outlet gas is provided in the middle of a conduit connecting the high-pressure expansion turbine outlet and the low-pressure expansion turbine inlet. is further divided into two parts on the upstream side of the liquefier, and a conduit is provided in which one of the divided gases passes through the turbine heat exchanger and joins with the other divided gas on the downstream side of the liquefier, and the conduit and the other divided gas conduit are connected to each other. an automatic control valve for adjusting the flow rate, and a temperature control device for detecting the inlet or outlet temperature of the low-pressure expansion turbine and operating the automatic control valve; Gas liquefaction, characterized in that a turbine inlet gas temperature control device is provided, and a liquefied gas conduit at the liquefier outlet is provided with an automatic control device that detects the product liquefied gas temperature and automatically adjusts the set value of the temperature control device. Device.