JPH0827116B2 - Cold water supply device using cold heat of liquefied gas - Google Patents

Description

TECHNICAL FIELD The present invention relates to a chilled water supply device that uses cold heat of liquefied gas such as liquefied natural gas, and can be suitably implemented in, for example, an air separation facility. The present invention relates to a chilled water supply device.

Prior Art A typical prior art is shown in FIG. In the conventional air separation equipment utilizing the cold heat of liquefied natural gas, the air as the raw material from the air intake 1 is compressed in the multistage compressor, and the high pressure air is supplied from the pipe 3 to the refining device 4.
Are supplied as liquid nitrogen from the pipe 5 and as liquid oxygen from the pipe 6. Liquefied natural gas (abbreviation LNG), for which cold heat is to be used, has a temperature of, for example, −150 ° C., is guided from a pipe 7 to a heat exchanger 8 called a cold box, is heated, and in a pipe 9, For example, it becomes vaporized liquefied natural gas at -50 ° C. The liquid nitrogen from the refining device 4 is introduced into the heat exchanger 8 via the conduit 10a, cooled by cooling the liquefied natural gas, and used in the refining device 4.

The heat exchanger 10 is used to raise the temperature of the vaporized liquefied natural gas from the pipe 9, and thus vaporized liquefied natural gas of, for example, 0 ° C. or higher is supplied from the pipe 11. In the heat exchanger 10, cold water of, for example, about 35 ° C. from the intercooler 12 and the final cooler 13 of the multi-stage compressor 2 is cooled in the heat exchanger 10 via the pipe 14, and then from the pipe 15 to a cooling tower.
It is guided to 16 to be cooled, the pressure is raised by a pump 17, and cold water of, for example, 27 ° C. is guided to the intercooler 12 and the final cooler 13 from the pipe 18 and circulated for use.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In such a prior art, the amount of liquefied natural gas used is 0.5 to 3.0 kg per product Nm ³ of liquefied nitrogen, oxygen, and argon in the air separation facility, and the power source thereof is 0.5 to 3.0 kg. The best unit is 0.4kWH / Nm ³ , and the heat exchanger 10
In order to efficiently raise the temperature of the liquefied natural gas and efficiently cool the cold water for the compressor 2, a so-called open rack type heat exchanger or shell and tube type heat exchanger is used. As the heat exchanger 10, a blade fin type heat exchanger using Freon may be used.
There is a problem that the structure of such a heat exchanger 10 is relatively complicated.

Further, in the above-mentioned prior art, the temperature of the circulating water for cooling that is guided from the pipe 18 to the compressor 2 via the pump 17 is 27 ° C., which is relatively high, as described above. It is necessary to design the air intake temperature at around 30 ° C. Therefore, there is a problem that it is necessary to increase the heat transfer area of the intercooler 12 and the final cooler 13, and the pressure loss thereof increases.

FIG. 4 is a graph showing the experimental results of the inventors of the present invention.
This FIG. 4 shows the relationship between the flow rate of liquefied natural gas from the pipe 7 and the basic unit per air-separated product Nm ³ . It can be seen that when the flow rate of liquefied natural gas is increased, the unit consumption per product Nm ^{3 of} air separation is decreased, which is preferable.

FIG. 5 is a graph corresponding to FIG. 4, and shows the relationship between the flow rate of the liquefied natural gas from the pipe 7 and the temperature of the vaporized liquefied natural gas discharged from the outlet of the heat exchanger 8 to the pipe 9. It is a graph which shows. It can be seen that by increasing the flow rate of the liquefied natural gas, the temperature of the vaporized liquefied natural gas at the outlet of the heat exchanger 8 decreases.

Therefore, in an air separation facility that uses the cold heat of liquefied natural gas, it is advantageous to use liquefied natural gas at a flow rate as high as possible in order to improve the production intensity, but doing so makes it possible to use a heat exchanger. The temperature of the vaporized liquefied natural gas at the outlet of 8 has become low, so that in the above-mentioned prior art, it was necessary to install a heat exchanger having a complicated structure as the subsequent heat exchanger 10.

The object of the present invention is, for example, in the air separation installation, with a simple configuration and efficiently, by utilizing the cold heat of the liquefied gas, the cold heat of the liquefied gas can be supplied so that the cold water at a temperature as low as possible can be supplied. It is to provide a chilled water supply device using the same.

Means for Solving the Problems The present invention is provided with a storage tank for storing water, and provided above a liquid level of water stored in the storage tank,
It has multiple nozzles that inject water, a heat transfer tube that is immersed in water in the storage tank, is supplied with low-temperature liquefied gas, and forms ice on the outer peripheral surface, and a pipeline that takes out cold water from the lower part of the storage tank. It is a chilled water supply device that utilizes the cold heat of liquefied gas.

Further, the present invention is characterized in that the cold water from the pipeline is supplied to an intermediate cooler of the multi-stage compressor or a final cooler after leaving the final stage.

Action According to the present invention, water is stored in the storage tank, and a plurality of nozzles are provided above the liquid surface of the water, and the water is jetted from the nozzles. The pressure of the water supplied to the nozzle does not act on the stored water, and therefore, an excessively large pressure does not act on the cold water taken out from the pipe provided at the bottom of the storage tank. In addition, the water falling from this nozzle can be seen from, for example, a viewing window provided in the storage tank, so that it is possible to know that water is being supplied and the flow rate distribution to which the water is supplied. It is possible to estimate the state of ice formed on the surface of the heat transfer tube, as described below, depending on the state of water drop.

A heat transfer tube is immersed in water in the storage tank, and low temperature liquefied gas is supplied to the heat transfer tube. Therefore, ice is formed on the outer peripheral surface of this heat transfer tube and icing occurs. Therefore, the water sprayed from the nozzle and stored is brought into contact with the ice accumulating on the heat transfer tube to be cooled, and reaches, for example, about 0 ° C., and the cold water is supplied from the pipe provided at the bottom of the storage tank. Is taken out as. Therefore, it is possible to reduce the temperature of the cold water taken out from the pipeline to around 0 ° C as described above.

Furthermore, since the heat transfer tubes are iced, when the flow rate of the liquefied gas becomes small, the latent heat of the ice that is iced on the heat transfer tubes is used to cool the water stored in the storage tank. Therefore, even if the flow rate of the liquefied gas fluctuates, it is possible to stably supply cold water having a constant temperature, for example, around 0 ° C., from the pipe line.

Furthermore, such a chilled water supply device has a simple structure and is easy to manufacture.

Instead of liquefied natural gas, liquefied petroleum gas (abbreviated as LPG) or liquefied ethylene may be used.

Embodiment FIG. 1 is a system diagram of an embodiment of the present invention. In this embodiment, a cold water supply device 30 according to the invention is used for the air separation installation. Air serving as a raw material for air separation is supplied from the air intake port 21 to the multi-stage compressor 22, and the air compressed in this way is guided to the refining device 24 from the pipe line 23, and liquid nitrogen is supplied from the pipe line 25. And line L is supplied with liquid oxygen, thus separating the air. The liquefied natural gas for which cold heat should be used is 50 kg / cm ² G,
The temperature is −150 ° C., the temperature is −150 ° C., the temperature is −150 ° C., the temperature is −150 ° C., the temperature is −150 ° C., and the temperature is −150 ° C. The vaporized liquefied natural gas introduced from the outlet of the heat exchanger 28 to the pipe 29 has a temperature of, for example, −60 ° C. to −70 ° C. and is introduced to the cold water supply device 30. The vaporized liquefied natural gas from the chilled water supply device 30 is heated in the heat exchanger 31, and is supplied from the pipe 32 to 0 ° C. or higher,
For example, vaporized liquefied natural gas at room temperature is supplied and used as city gas. The water as a heat source in the heat exchanger 31 may be, for example, seawater, or may be circulating water for cooling in the compressor 22.
Is, for example, a shell and tube type heat exchanger.

Liquid nitrogen separated by air in the purifier 24 is
It is guided from 33 to the heat exchanger 28, serves to raise the temperature of the liquefied natural gas, and is guided to the refining device 24.

An intermediate cooler 34 is provided in the compressor 22, and a final cooler or a rear cooler 35 is provided after leaving the final stage of the compressor 22.

The cooling water from the intermediate cooler 3 and the final cooler 35 is guided to the cold water supply device 30 and cooled in the pipe 36, for example, at 10 ° C. in this embodiment. This cooled water is pressurized from the line 37 by the pump 38, and returned from the line 39 to the intercooler 34 and the final cooler 35 at about 0 ° C. for circulation.

The cold water supply device 30 includes a storage tank 41 having a right cylindrical shape, a plurality of nozzles 42 provided at an upper portion of the storage tank 41, and the storage tank 41.
And a heat transfer tube 43 provided therein. The upper part of the storage tank 41 is covered with a roof 44 and communicates with the atmosphere. The nozzle 42 is arranged above the liquid level of the water 45 stored in the storage tank 41, and the water supplied from the pipe 36 through the header 46 is jetted downward. The nozzle 42 is constructed and arranged so that the nozzle 42 is supplied at a substantially uniform flow rate on a horizontal plane in the storage tank 41.

The heat transfer tube 43 guides the vaporized liquefied natural gas from the conduit 29, is made of a material such as aluminum, and is bent and arranged vertically. This heat transfer tube 43, in the storage tank 41,
They are distributed and arranged with a substantially uniform density in the horizontal plane. This heat transfer tube 43 is immersed in water 45 to be cooled.

FIG. 2 is a horizontal sectional view of a part of the heat transfer tube 43. The heat transfer tube 43 has a fin 48 that protrudes radially outward and contacts the water 45 and extends vertically. On the surfaces of the heat transfer tube 43 and the fin 48, the water 45 is iced as ice 49. A space 50 in which water 45 flows from top to bottom exists between the ice pieces 49 that have landed.
Therefore, the water jetted from the nozzle 42 is stored in the storage tank 41 and cooled by contact with the ice 49, for example, to about 0 ° C., and the water thus cooled is provided in the lower portion of the storage tank 41. It is taken out from the pipe line 37.

Since the water from the pipeline 36 is jetted from the header 46 through the nozzle 42 and falls, the pressure of the water in the pipeline 36 is increased by the storage tank 41.
The water 45 stored in the pipe 37 does not act on the water 45. Therefore, the water from the pipe 37 does not have an excessively high pressure.

A viewing window 51 is provided above the liquid surface of the storage tank 41, and the viewing window 51 is hermetically closed by, for example, a translucent glass plate. By looking at, it is possible to know the state of the water sprayed from the nozzle 42. This makes it possible to know whether or not water is being jetted from the nozzle 42 into the storage tank 41 with a uniform flow distribution in the horizontal plane. By making the distribution of the flow rate of the water jetted from the nozzles 42 uniform, the amount of ice 49 iced on the heat transfer tubes 45 can be made equal in each heat transfer tube 43, and the ice is efficiently transferred. This makes it possible to effectively use the cold heat of liquefied natural gas.

Since ice 49 is formed on the surface of the heat transfer tube 43 and further on the surface of the fin 48 as described above, when the flow rate of liquefied natural gas decreases, the ice 49 melts and the latent heat of the ice 49 is utilized. Then, the water 45 can be cooled. Therefore, the cold water having a stable temperature near 0 ° C. can always be supplied from the pipe 37.

In this way, stable water near 0 ° C. can be taken out from the cold water supply device 30 to the pipe line 37, and such cold water can be fed to the intercooler 34, the final cooler 35, and further to the compressor 22. It can be used in the refining device 24 and the like. Therefore, compared with the prior art of FIG. 1 described above, the logarithmic average temperature difference can be increased, the pressure loss can be reduced as described below, and the suction temperature at each stage of the compressor 22 can be lowered. Therefore, the power required for the compressor 22 can be reduced.

For example, the discharge pressure of the compressor 22 is around 6 kg / cm ² G and is generally boosted in 3 to 4 stages. Since the suction temperature of the intermediate stage can be changed from the conventional 30 ° C. to, for example, 5 ° C. according to the present invention, the power consumption is reduced by about 6.2%. Therefore, in the compressor 22 of 4000 kW, for example, the reduction is 248 kW, and it is understood that the present invention is effective. Also, the logarithmic mean temperature difference of the heat exchange is approximately doubled as the temperature of the circulating water for cooling the compressor 22 is changed from 27 ° C. in the prior art in the pipe 39 to 0 ° C. according to the present invention. While, on the other hand,
The amount of heat exchanged is about 1.8 times, and as a result, the heat transfer area of the intercooler 34 and the final cooler 35 can be reduced by about 10%. In addition, the flow rate of such circulating water can be reduced by about 8%, whereby pressure loss can be reduced by about 16% when the same pipe diameter is used. For example, the total pressure loss in the middle stage of the compressor 22 is typically 0.6 kg / cm.
Since it is about ² , the compressor 22 described above can reduce the power consumption by about 40 kW, which shows that the present invention is effective.

The present invention can be implemented not only in the context of air separation equipment, but also in a wide range of contexts with other equipment utilizing cold water.

EFFECTS OF THE INVENTION As described above, according to the present invention, the water stored in the storage tank is jetted from above the liquid surface by a plurality of nozzles, and liquefied gas is supplied to the water. Since the stored water is immersed in this heat transfer tube, cold water at 0 ° C., for example, can be stably supplied from the pipeline provided in the lower part of the storage tank. The configuration is simple, and it is possible to efficiently and stably supply cold water.

[Brief description of drawings]

FIG. 1 is an overall system diagram of an embodiment of the present invention, FIG. 2 is a horizontal sectional view of a part of a chilled water supply facility 30, FIG. 3 is an overall system diagram of a prior art, and FIG. 4 is air cooling. Fig. 5 is a graph showing the relationship between the flow rate of liquefied natural gas in the facility and the basic unit per product Nm ³ , Fig. 5 shows the flow rate of liquefied natural gas and the temperature of vaporized liquefied natural gas at the outlet of the heat exchanger 8 in Fig. 3. It is a graph which shows a relationship. 22 …… Multi-stage compressor, 24 …… Refining equipment, 28 …… Heat exchanger,
30 ... Cooling supply device, 34 ... Intercooler, 35 ... Final cooler, 37 ... Pipeline, 38 ... Pump, 41 ... Storage tank, 42 ...
… Nozzle, 43… Heat transfer tube, 45… Water, 46… Hezda, 48
...... Fin, 49 ...... Ice ice, 50 ...... Space through which water passes

Claims (2)

[Claims] 1. A storage tank for storing water, a plurality of nozzles provided above the liquid surface of the water stored in the storage tank, for injecting water, and immersed in the water in the storage tank to cool at a low temperature. Liquefied gas is supplied,
A cold water supply device using the cold heat of liquefied gas, comprising a heat transfer pipe on the outer peripheral surface of which ice is formed and a pipe line through which cold water is taken out from a lower portion of a storage tank. 2. The liquefaction according to claim 1, wherein the cold water from the pipe is supplied to an intercooler of the multistage compressor or a final cooler after leaving the final stage. A cold water supply device that uses the cold heat of gas.