JP2613212B2 - Liquefied natural gas cold energy utilization system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL APPLICATIONS The present invention utilizes the cold heat during vaporization of liquefied natural gas,
The present invention relates to a low-temperature cooling system for cooling an object to be cooled.

Conventional technology Liquefied natural gas (hereinafter referred to as LNG) is imported from abroad by LNG tankers, stored in LNG tanks at LNG terminals, vaporized and supplied as fuel for power generation, raw material for city gas, etc. Releases large amounts of cold heat upon vaporization.

As an object of utilizing the cold heat during the vaporization of LNG, an air separation system, a cold power generation system, a food refrigeration system, a low-temperature crushing of waste gas, and the like have been proposed, and some of them have been put to practical use.

Conventionally, transport of cold heat has been a technical issue when utilizing cold heat during LNG vaporization.

In other words, conventional brines such as calcium chloride easily coagulate due to the low temperature of LNG, making them unsuitable for transporting cold heat.Freon etc. coagulate, liquefy, and liquefy in a wide temperature range from LNG temperature to room temperature. It was difficult to put into practical use because it involved changes in the three phases of vaporization.

Therefore, in general, liquefied nitrogen is produced by air separation using the cold heat of LNG and transported to cool the target object to the required temperature, or a low-temperature utilization facility is installed in or adjacent to the LNG terminal. Then, LNG is supplied here and cooled directly by LNG.

Conventional problems In the former case, transporting liquefied nitrogen makes it possible to use LNG cryogenic heat at low temperatures in remote locations, but since liquefied nitrogen evaporates and dissipates into consumables, the unit cost of cryogenic heat is low. Are relatively expensive and are often not economically viable.

On the other hand, the latter case has the drawback that not only the construction cost including LNG piping is increased, but also special considerations are required for safety.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the conventional low-temperature utilization system utilizing the heat generated during the vaporization of LNG, and provides a low-cost and safe LNG cold-heat utilization system with improved heat exchange efficiency. The purpose is to propose a cold heat utilization system.

Means for Achieving the Object In order to achieve the above object, the LNG cryogenic low-temperature utilization system according to the present invention cryogenically transports a substance exhibiting a stable liquid state in a temperature range including the required low-temperature temperature and ordinary temperature on the cryogenic utilization system side. A circulation path for circulating the cold heat transport medium between the heat exchange medium flow path of the heat exchanger for vaporizing liquefied natural gas and the cooling bath that directly immerses and cools the object to be cooled on the cold heat utilization system side; And circulating means, and the cooling bath is provided in a plurality of stages corresponding to a plurality of temperatures between the temperature of the cold transport medium in the bath and a temperature lower than or equal to a cooling temperature suitable for cooling the object to be cooled. The cooling / transporting medium is sequentially transferred in each tank from a lower temperature to a higher temperature, and an object to be cooled is sequentially transferred from a tank having a higher temperature to a tank having a lower temperature and is immersed therein.

DESCRIPTION OF THE EMBODIMENTS Hereinafter, embodiments in which the present invention is applied to waste crushing will be described in detail with reference to the drawings.

Low temperature crushing of waste has been proposed as part of the use of cold heat during LNG vaporization. Certain substances become brittle below a certain low temperature and can be crushed with low impact forces. Steel and rubber are examples. Utilizing this phenomenon, waste that is difficult to crush at room temperature, such as waste tires, is cooled to low temperature and crushed, and low-temperature brittle metal, such as steel, and low-temperature non-brittle metal, such as copper, The mixed waste is cooled to below the embrittlement temperature of steel, and is separated and crushed by being crushed by a crusher, whereby each material can be separated and collected.

FIG. 1 shows that the present invention uses the cold heat of LNG vaporization to separate and crush only steel from waste mixed with steel and copper.
It is a figure which shows one Example of the low-temperature crushing system for sorting and collect | recovering steel and copper.

FIG. 2 is a curve diagram showing low-temperature brittleness of carbon steel and copper. As is clear from this figure, when the temperature of carbon steel decreases from around −50 ° C., the Charpy impact value sharply decreases,
It becomes very brittle below -100 ° C. In contrast, in the case of copper, the impact value does not decrease even if the temperature decreases,
As the temperature decreases from 0 ° C to -200 ° C, the impact value becomes about 20ft-
It gradually increases from lb to about 35 ft-lb.

Therefore, by performing low-temperature crushing of waste mixed with steel and copper at a temperature of −100 ° C. or lower, for example, at −120 ° C. with a suitable crusher, only steel in the waste is crushed, and copper Remains without being crushed, so that steel and copper can be selectively recovered.

In the system of the embodiment shown in FIG. 1, 1-propanol (hereinafter, simply referred to as propanol) is used as a cold transport medium for vaporizing LNG. Propanol is one of the lower alcohols and has a melting point of -126.2.
It has a boiling point of + 97.3 ° C at 0 ° C and atmospheric pressure, and is a colorless and transparent liquid at temperatures in between. That is, the liquid has a low rate of evaporation at room temperature and does not have to be coagulated at a low temperature of about -120 ° C., and is therefore a stable liquid between room temperature and a temperature slightly lower than a predetermined low-temperature crushing temperature.

As shown in FIG. 1, a shipping line 3 from an LNG tank 2 in an LNG terminal 1 is provided with, for example, a 30-atm pressure shipping pump 4 and an LNG heat exchanger 5. The propanol flow path is provided as a cold and heat transport medium via the exchange wall, and −1 stored in the LNG tank.
LNG at 62 ° C. is supplied with cold heat to propanol in the heat exchanger 5 to become a gas having a temperature of about 0 ° C. or higher, and is sent to a power plant or a gas holder for city gas.

In a low-temperature crushing plant 6 installed outside the LNG terminal 1, a cooling bath (propanol bath) 8 and a crusher 9 for immersing and cooling an object to be crushed (scrap) 7 are built. A cold storage room 10 is provided. The propanol bath 8 includes a plurality of (four in the illustrated embodiment) buses 8a, 8b,
Consists of 8c and 8d.

Between the heat medium outlet and the inlet of the heat exchanger 5 in the LNG terminal 1 and the cold storage room 10 in the low-temperature crushing plant 6, an insulated pipe 11 and a return pipe 12 for transporting propanol, respectively.
Is plumbed. The return pipe 12 is a heat-insulated pipe or a normal-temperature pipe.

The propanol cooled to −120 ° C. by depriving the LNG of heat from the LNG in the heat exchanger 5 enters the cold storage room 10 via the outgoing pipe 11 and enters the four tanks 8a, 8b, 8 of the propanol bath 8 under atmospheric pressure.
c and 8d are transferred in this order. On the other hand, the scrap 7 is put in a basket made of, for example, stainless steel, and is stored by a lifting / conveying means such as an overhead crane 13 constructed from the cold storage room 10 to the scrap storage yard. The propanol is carried into the cool room 10 from the yard and is sequentially immersed and transferred in the reverse order to the order in which propanol is transferred to the four tanks of the propanol bath 8. As a result, four buses 8a, 8b, 8c, 8
The propanol in d takes heat from the scrap 7 and rises in temperature, and the temperature of propanol in each bath is, for example, −120.
℃, -87.5 ℃, -55 ℃ and -22.5 ℃, the last bus
When exiting from 8d, it is discharged at around room temperature, for example, at 10 ° C. The pipes from each bus to the next bus and the pipes from the last bus to the return pipe 12 are provided with a strainer 14 and a transfer pump 15, respectively. The propanol is removed as much as possible to transfer the propanol to the subsequent stage. In addition,
A buffer tank 16 is provided in the pipe from the last bus to the return pipe 12 in parallel with the transfer pump 15. Return piping 12
A buffer drum 17 and a pump 18 are provided in the piping in the LNG terminal between the heat exchanger 5 and the heat medium inlet of the heat exchanger 5.

Since the low-temperature crushing system is configured as described above, the cold heat of LNG for cooling scrap for low-temperature crushing is transferred from the LNG terminal 1 to the low-temperature crushing plant 6 via the outward heat insulation pipe 11 by propanol as a heat medium. After cooling the scraps sequentially transferred to the plurality of buses 8a, 8b, 8c, and 8d and immersed in the propanol in the buses in the reverse order and transferred, the heat is returned to the heat exchanger 5 of the LNG terminal via the return pipe 12. Return and cycle repeatedly. -12
The scrap 7 cooled to a temperature close to 0 ° C.
In the crusher inside, only the steel of the scrap week is crushed, and the copper remains without crushing. Therefore, by sieving through an appropriate sieve, steel and copper can be selectively collected.

In this system, the cold heat of LNG used for cooling on the LNG cold heat utilization system side (low temperature crushing system side in the example in the figure) is supplied to the heat exchanger 5 in the LNG terminal and the cooling bathtub on the LNG cold heat utilization system side (Fig. LN by a cold transport medium (propanol in the figure) circulating between
Since it is transported from G to the object to be cooled (scrap in the figure), there is no need to pass the LNG piping through a low-temperature crushing plant.
The cryogenic crushing plant can be installed at any relatively distant place other than the LNG terminal or adjacent land, and the construction cost is reduced compared to the case where the LNG piping is connected to the cryogenic crushing plant. The above considerations are also reduced.

Since the cold heat transport medium is circulated, the consumption amount is small, and the economic efficiency is improved as compared with the case where liquefied nitrogen gas is used as the heat medium.

In this system, the object to be cooled (scrap in the example shown)
A plurality of cooling tubs for cooling the cooling bath are provided, the low-temperature cold transport medium cooled by LNG is sequentially transferred, and the objects to be cooled are sequentially immersed in the cold transport medium in each cooling bath in the reverse order and transferred. By this, the temperature of the cold transport medium in each cooling bath can be set stepwise, so that the final temperature of the object to be cooled can be close to the temperature of the cold transport medium, and the cooled object and the cold transport medium are directly Because of the immersion contact, heat exchange is performed efficiently.

In the embodiment, in the waste sorting and crushing system,
An application example of the present invention has been shown regarding the use of LNG cold heat,
Other systems for cryogenic crushing of waste, food freezing, etc. are also possible.

In addition, in the embodiment, the crusher is installed in the cold room, but it is also possible to install this outside the cold room, and in this case, the cooled scrap needs to be crushed immediately after cooling. .

Further, the movement of the scrap between the cooling tubs does not necessarily have to be performed by an overhead crane, but may be performed by another means such as a conveyor.

The cold transport medium is not necessarily propanol, and may be any fluid that maintains a stable liquid state in the required cooling temperature and normal temperature range. These include alcohols (such as methyl alcohol and ethyl alcohol) similar to propanol and acetaldehyde.

The cooling tub is in the atmosphere due to the loading and unloading of the object to be cooled.However, for the purpose of disaster prevention, the cooling room is made to have an inert gas atmosphere such as nitrogen gas, or the air from outside the cooling room is applied by applying a slight slight pressure. And the inflow of dust and the like may be prevented.

Also, the LNG heat exchanger on the LNG terminal side may be of a bathtub type like the cooling bathtub.

Effects As described above, according to the present invention, it is possible to obtain the effects of improving the heat exchange efficiency, safety, and economy when cooling the object to be cooled using the cold heat of LNG.

[Brief description of the drawings]

FIG. 1 is a system diagram showing the configuration of an embodiment in which the present invention is applied to a low-temperature crushing system, and FIG. 2 is a curve diagram showing the relationship between the temperature of carbon steel and copper and the Charpy impact value. 1 LNG terminal 2 LNG tank 5 LNG vaporization heat exchanger 6 Low-temperature crushing plant 8,8a, 8b, 8c, 8d Cooling bath 9 Crusher 11,12 Piping ( Circuit)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshimi Ezaki 1 at Chuo Electric Power Co., Inc. General Technology Research Center, No. 20 Odaka-cho, Midori-ku, Nagoya-shi, Aichi Prefecture (72) Inventor Yoshio Furusawa Nagoya, Aichi Prefecture 4-6-15 Sakae Naka-ku Inside Chubu Refrigerating and Heating Co., Ltd. (56) References JP-A-50-139447 (JP, A) JP-A-61-81583 (JP, U) JP-A-59-7679 (JP, Y2)

Claims (1)

(57) [Claims] 1. A cooling system for immersing and cooling an object to be cooled between a heat exchange medium flow path of a heat exchanger for vaporizing liquefied natural gas and a cooling bath for cooling the object to be cooled at room temperature without freezing at the cooling temperature of the object to be cooled. In a low-temperature cooling system that circulates a cold transport medium exhibiting a stable liquid state without vaporization, the cooling tub is configured such that the temperature of the cold transport medium in the tub is between room temperature and a temperature lower than or equal to a cooling temperature suitable for cooling the object to be cooled. Provided in a plurality of stages corresponding to a plurality of temperatures in between, the cold and heat transport medium is sequentially transferred from each tank to the lower one from the lower temperature, and the object to be cooled is sequentially transferred from the tank with the higher temperature to the lower tank. A low-temperature cooling system characterized by being immersed in a different manner.