JPH06313687A - Liquefied natural gas vaporizer using accumulated cold heat - Google Patents

Abstract

PURPOSE:To effectively utilize cold heat of liquefied natural gas and to simplify a vaporizing facility by heating to vaporize the gas with cold heat accumulator, and providing means for storing the accumulator cooled by absorbing cold heat from the gas to be vaporized. CONSTITUTION:After LNG 2 of an LNG tank 2 is supplied via an LNG line 3 to an LNG vaporizer 4, it is supplied to a demander from an LNG line 5. Brine cold heat accumulator to become a heat source of the vaporizer 4 is fed under pressure by an ambient temperature brine pump 8 from above a cold accumulation vessel 6 via an ambient temperature brine conduit 7, and supplied via another ambient temperature brine conduit 9. Further, the vaporizer 4 subcools brine via LNG 2 to be vaporized, and returns it to a lower part of the vessel 6 via a low temperature brine tube 10. The accumulator of the vessel 6 is fed under pressure by a low temperature brine pump 12 via a low temperature brine tube 11, and then supplied to a cold heat using system 14 via a low temperature brine supply tube 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a raw material for city gas,
The present invention relates to a liquefied natural gas vaporizer utilizing cold storage heat for effectively utilizing the cold heat of liquefied natural gas (hereinafter abbreviated as “LNG”) used for fuel.

[0002]

2. Description of the Related Art Conventionally, natural gas (hereinafter abbreviated as "NG") has been widely used for fuel such as city gas. NG is liquefied for convenience of transportation and storage.
Handled in the G state. When used as a fuel gas, it is necessary to heat and vaporize it. As a heat source for vaporization of LNG, air or industrial tap water is used for a small-scale one. Further, seawater is used when the scale becomes large, and the applicant of the present application also discloses, for example, Japanese Patent Application Laid-Open No. 3-239897 (Japanese Patent Application No.
No. 32736) discloses a vaporizer using seawater.

[0003]

In the conventional LNG vaporizers, heat of vaporization is supplied from air, industrial water, seawater, etc., and cold heat is given to air, industrial water, seawater, etc. To be However, these cold heats are not effectively used, and most of them are discarded in the surrounding environment.

FIG. 5 shows changes in the demand amount of city gas and the like.
And the change in cold energy demand. FIG. 5 (1) shows the time change of the city gas demand amount according to the gas delivery pattern according to the time zone, and FIG. 5 (2) shows the change of the cold heat demand due to the change of the load pattern of the user requiring cooling heat according to the time zone. Indicates.
The gas demand peaks from 17:00 to around 22:00, and is off-peak from 23:00 to around 7:00 the next morning at midnight. On the other hand, the demand for cold heat is almost constant regardless of the time of day, such as oil refining, and in low-temperature warehouses and frozen food manufacturing, the demand is high from 8:00 to 23:00 in the daytime and late at night. The demand is low from the next morning.

In order to effectively use the cold energy of LNG, when LNG is vaporized, the cold energy of LNG is temporarily stored in the form of sensible heat or latent heat of the cold storage heat agent and taken out in accordance with the cold heat demand. A method can be considered. In such a method, a method of exchanging heat between the LNG and the cold storage agent via an intermediate heat medium and a method of directly exchanging heat are considered.
Conventionally, Freon 22 or the like is mainly used as an intermediate heat medium in order to avoid freezing or blocking of seawater in the heat transfer tube. However, due to regulations due to environmental problems, the use of CFC 22 is not preferable in the future, and it is in the stage of being considered to be replaced with another heat medium. In the method of directly exchanging heat between the LNG and the cold storage agent, a heat transfer tube through which LNG with fins or without fins flows is arranged in a container for the cold storage agent, and the cold storage agent around the heat transfer tube is frozen. It has been known. In such a configuration, the heat transfer characteristics of the heat transfer tubes outside the tube regulate the vaporization characteristics of LNG, and it is necessary to provide a large number of heat transfer tubes in a large-scale facility, resulting in high equipment cost. Further, in the cold heat utilization facility, it is necessary to separately provide a heat exchanger or the like for returning the low temperature NG after absorbing the cold heat of LNG to normal temperature.

An object of the present invention is to provide a liquefied natural gas vaporizer utilizing cold storage heat, which can effectively utilize the cold heat possessed by the liquefied natural gas and simplify the liquefied natural gas vaporization equipment.

[0007]

The present invention relates to a liquefied natural gas vaporizer that heats and liquefies liquefied natural gas by performing heat exchange between the liquefied natural gas and a regenerator, and a liquefied natural gas that vaporizes. A cool storage container for storing cold heat storage agent that absorbs cold heat and a cool storage agent is taken out from above the cool storage container,
It is characterized by including a room temperature pump that supplies the liquefied natural gas vaporizer and a low temperature pump that takes out the cold storage agent from the lower side of the cold storage container and returns the cold storage agent heated by using cold heat to the upper side of the cold storage container. It is a liquefied natural gas vaporizer that uses cold storage heat.

In the present invention, the cold storage agent has a minimum freezing temperature of -40 ° C. or lower, and at least a part of the liquefied natural gas vaporizer is constructed as a vertical double tube type, and the liquefied natural gas is liquefied outside the outer tube. Gas is flowed, natural gas is flowed between the outer pipe and the inner pipe, a heat transfer promoting material is inserted into the inner pipe, and the cold storage heat agent is flowed.

Further, in the present invention, the solidification temperature of the cold storage heat agent is −130 ° C. or lower, and a plurality of inlet / outlet nozzles can be selected in the cold storage container so that the take-out and return positions of the cold storage heat agent can be selected according to the temperature level. Is provided, the liquefied natural gas vaporizer is constituted by a plate fin type heat exchanger, and the liquefied natural gas vaporizer is supplied with cold heat storage agents of a plurality of temperature levels from a cold storage container in accordance with liquefied natural gas vaporization characteristics, It is characterized in that it includes a circulation pump for returning the cooled regenerator from the inflow / outflow nozzle of the corresponding temperature level to the regenerator.

[0010]

According to the present invention, the liquefied natural gas is vaporized by the cold pump supplying the cold storage heat agent from above the cold storage container to the liquefied natural gas vaporizer, and using the cold storage heat agent as a heat source. Cold heat generated during vaporization of liquefied natural gas is absorbed by the cold heat storage agent and returned from below the cold storage container. The cold storage heat agent has a different density depending on the temperature, and the lower the temperature, the higher the density. From the lower part of the cold storage container, a low temperature cold heat storage agent is taken out by a low temperature pump to utilize cold heat. The cold storage agent heated by utilizing the cold heat is returned to the upper side of the cold storage container. Therefore, a relatively high temperature cold storage agent is stored above the cold storage container, and a relatively low temperature cold storage agent is stored below the cold storage container. Since the cold storage heat agent heated by utilizing cold heat is used for vaporizing the liquefied natural gas, sufficient heat of vaporization can be supplied to the liquefied natural gas.

Further, according to the present invention, a cold storage agent having a minimum freezing temperature of −40 ° C. or lower is used, and a liquefied natural gas vaporizer having a vertical double tube structure is used. Although the temperature difference between the cold storage agent and liquefied natural gas increases,
The liquefied natural gas vaporizer is configured as a double pipe type, liquefied natural gas is flowed outside the outer pipe, NG is flowed between the outer pipe and the inner pipe, and a heat transfer promoting material is inserted into the inner pipe to store cold heat. Since the agent is flowed, the heat transfer area can be increased and the flow velocity in the tube can be increased to prevent various adverse effects due to icing.

Further, according to the invention, the solidification temperature of the cold storage heat agent is set to −130 ° C. or lower, and a plate fin type heat exchanger is used as the liquefied natural gas vaporizer. The cold storage heat agents of multiple temperature levels are supplied to the liquefied natural gas vaporizer from the cold storage heat container according to the vaporization characteristics of the liquefied natural gas, and the cold storage heat agents of the corresponding temperature levels are provided in the cold storage container. Since the plate fin type heat exchanger is selectively returned, it is possible to reduce the temperature difference between the liquefied natural gas that directly transfers heat and the cold storage heat agent in the plate fin type heat exchanger. It is possible to prevent thermal cycle fatigue that occurs in the panel.

[0013]

1 shows a schematic system of a cold heat utilization system according to an embodiment of the present invention. The LNG 2 stored in the LNG tank 1 is guided to the LNG vaporizer 4 via the LNG line 3 according to the demand, vaporized, and supplied from the NG line 5 to the demand destination. The cold storage heat agent which is the heat source of the LNG vaporizer 4 is sucked by the room temperature brine pump 8 from above the cool storage container 6 through the room temperature brine pipeline 7, and is supplied through the room temperature brine pipeline 9. The regenerator that can be used is, for example, a brine system that is an aqueous solution of calcium chloride, sodium chloride, ethylene glycol, or the like, and has a concentration such that its minimum solidification temperature is -40 ° C or lower. In this embodiment, an aqueous solution of alcohol of 60 wt% or less is used. In the LNG vaporizer 4, the brine is supercooled to about −50 ° C. by the vaporized LNG 2 and returned to the lower side of the cold storage container 6 via the low temperature brine pipe line 10. The flow rate of the brine is adjusted according to the vaporization flow rate of LNG2. When the demand for LNG2 is high,
The amount of vaporization in the LNG vaporizer 4 also increases, the generated cold heat is absorbed by the cold storage heat agent, and the region of the low temperature cold storage heat agent expands from the lower side to the upper side in the cold storage container 6. The brine used in this example is not a target of dangerous substances as defined by the Fire Service Law and is easy to handle.

The low temperature regenerator agent stored in the regenerator 6 is sucked into the low temperature brine pump 12 via the low temperature brine pipe line 11. The brine discharged from the low temperature brine pump 12 is supplied to various cold heat utilization systems 14 via the low temperature brine supply pipe 13. As the cold heat utilization system 14, for example, low temperature aquaculture, low temperature cultivation, district cooling, low temperature drying, a leisure facility artificially manufacturing snow or ice, a low temperature warehouse, or the manufacture of frozen foods is targeted. The brine that has supplied the cold heat to the cold heat utilization system 14 is heated to 5 to 10 ° C., and passes through the brine return pipe 15, the heating system 16 and the room temperature brine pipe line 17,
It is returned from above the cold storage container 6. The heating system 16 heats the brine to 5 to 10 ° C when the temperature of the returned brine is 5 ° C or lower.

FIG. 2 shows a schematic structure of the LNG vaporizer 4 in the embodiment of FIG. The LNG vaporizer 4 has a substantially right-cylindrical barrel 20 having a vertical axis extending vertically. The inside of the body 20 is partitioned from the bottom to the top by a first tube sheet 21, a second tube sheet 22 and a third tube sheet 23. An inlet-side cold storage agent chamber 24 is provided in the lower part of the first tube sheet 21, and an outlet-side cold storage agent chamber 2 is provided in the upper part of the third tube sheet 23.
5 are provided. The inlet-side cold storage agent chamber 24 and the exit-side cold storage agent chamber 25 are connected by an internal heat transfer pipe 26.
A heat transfer promoting material 26 a such as a twist tape is inserted into the inner heat transfer tube 26. The inner heat transfer tube 26 is surrounded by the outer heat transfer tube 27 between the second tube sheet 22 and the third tube sheet 23 at intervals in the radial direction. The outer heat transfer tube 27 is an inner body 28.
Surrounded by A space formed between the inner heat transfer tube 26 and the outer heat transfer tube 27 and a space formed between the outer heat transfer tube 27 and the inner case 28 communicate with each other through a porous plate 29.
Brine near room temperature is supplied to the inlet-side cold storage agent chamber 24 from the cold storage agent inlet 30. Low-temperature brine is taken out from the outlet-side cold storage agent chamber 25 via the cold storage agent outlet 31. In the space formed between the outer heat transfer tube 27 and the inner case 28, for example, LN at −150 ° C. from the LNG inlet 32.
G is supplied, and the NG outlet 33 supplies, for example, NG at room temperature.
Is taken out. Since the heat exchange between the LNG and the brine is performed via the NG flowing between the outer heat transfer tube 27 and the inner heat transfer tube 26, it is possible to prevent freezing or blockage of the brine. Moreover, since the heat storage performance of the regenerator is inferior to that of seawater or water, it is possible to prevent the increase of the required heat transfer area by inserting the heat transfer accelerator 26a.

FIG. 3 shows a schematic system of the present invention. This embodiment is similar to the embodiment shown in FIG. 1, and the corresponding parts are designated by the same reference numerals. It should be noted that the cold storage heat agent having a freezing point of −130 ° C. or lower is used, and the LNG vaporizer 3 is used.
4 is to use a plate fin type heat exchanger. Since NG taken out from the LNG vaporizer 34 has a temperature lower than room temperature, a warmer 35 is provided to heat the room temperature to room temperature. In the cold storage container 36, a cold storage heat agent realized by ethanol / water or an ethanol / methanol mixed system is stored. For example, a mixed system of ethanol 55 wt% / methanol 45 wt% has a solidification temperature of about -143 ° C and can be suitably used. A cool storage heat agent of −10 to 10 ° C. is stored above the cool storage container 36, and a cool storage heat agent of −120 ° C. is stored below the cool storage container 36. Since cold heat at a low temperature of −120 ° C. can be used, the cold heat utilization system 37 can also use cold heat for liquefied carbonic acid production, chemical plant petroleum refining, and the like.

In FIG. 4, in order to effectively store cold heat in the cold storage container 36, the cold heat is divided into a plurality of temperature levels and stored.
The structure for achieving effective use of cold heat according to the vaporization characteristics of G is shown. A plurality of inlet / outlet nozzles 41 to 49 are provided in the cool container 40 at intervals in the vertical direction. The in-and-out nozzles 42 to 48 on the way are, for example, a plurality of selection valves 51 to 54.
And 61-63 are selectively switched, and are circulated between the heat transfer pipe 73 in the LNG vaporizer 34 by the circulating brine pumps 71 and 72 provided for each temperature level. By adjusting the flow rate and mixing the regenerator at each temperature level so that the temperature difference with LNG flowing in the heat transfer tube 74 becomes small, the heat cycle fatigue generated in the panel 75 can be reduced.

[0018]

As described above, according to the present invention, the cold storage heat agent is circulated from the cold storage container to the liquefied natural gas vaporizer by the normal temperature pump to recover the cold heat at the vaporization of the liquefied natural gas, and the cold storage container is stored by the low temperature pump. Supply the cold heat storage agent to users who need it. Since the normal temperature pump and the low temperature pump can be operated independently, a stable cold heat load can be supplied to a user who needs cold heat. Further, since it is possible to secure a vaporization heat source corresponding to the peak demand of liquefied natural gas in the form of sensible heat or latent heat of the cold storage heat agent, it is possible to simplify the vaporization equipment. Further, since the cold heat possessed by the liquefied natural gas can be effectively used, it is possible to reduce the cost of using city gas or the like.

Further, according to the present invention, the minimum freezing temperature is -4.
By using a cold storage agent having a temperature of 0 ° C. or lower, the cold heat of liquefied natural gas can be effectively used. The cold storage heat agent having a freezing point of −40 ° C. or lower can be realized without containing a large amount of alcohol and the like, and does not correspond to a dangerous substance referred to in the Fire Defense Law, so that the danger in handling can be reduced.

Further, according to the present invention, the cold storage heat agent can be circulated and used at a plurality of temperature levels from the cold storage container via the plurality of inlet / outlet nozzles. Thereby, the cold energy can be efficiently stored by utilizing the temperature distribution of the cold storage agent in one cold storage container. In addition, since the cold storage heat agents of multiple temperature levels are supplied to the liquefied natural gas vaporizer, the temperature difference between the liquefied natural gas and the cold storage agent can be reduced, and the heat cycle fatigue that occurs in the panel or the like that is a medium for heat exchange Can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic system diagram of an embodiment of the present invention.

2 is a schematic cross-sectional view of the LNG vaporizer 4 of the embodiment of FIG.

FIG. 3 is a schematic system diagram of another embodiment of the present invention.

FIG. 4 is a system diagram related to the cold storage container 36 shown in FIG.

FIG. 5 is a graph showing a demand for city gas and a demand for cold heat.

[Explanation of symbols]

 1 LNG tank 2 LNG 4,34 LNG vaporizer 6,36 Cold storage container 8 Room temperature brine pump 12 Low temperature brine pump 14,37 Cold heat utilization system 26 Inner heat transfer tube 26a Heat transfer accelerator 27 External heat transfer tube 41-49 Inlet / outlet nozzle 51-54 , 61-63 Selection valve 71-72 Circulation brine pump

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Koichi Ueno 2-3-1, Niihama, Arai-machi, Takasago, Hyogo Prefecture Kobe Steel Works Takasago Works (72) Inventor Keizo Konishi Takatsukadai, Nishi-ku, Kobe-shi, Hyogo No. 5-5 Inside Kobe Research Institute, Kobe Steel, Ltd.

Claims (3)

[Claims] 1. A liquefied natural gas vaporizer for performing heat exchange between liquefied natural gas and a cold storage heat agent to heat and vaporize the liquefied natural gas, and to cool by absorbing cold heat from the liquefied natural gas to be vaporized. By using the cold storage heat, the cold storage container for storing the cold storage heat agent, the room temperature pump that takes out the cold storage agent from above the cold storage container and supplies it to the liquefied natural gas vaporizer, and the cold storage agent from below the cold storage container A liquefied natural gas vaporizer utilizing cold storage heat, comprising: a low temperature pump for returning the heated cold storage heat agent to above the cold storage container. 2. The minimum solidifying temperature of the cold storage agent is −40 ° C.
Below, at least a part of the liquefied natural gas vaporizer is configured as a vertical double-pipe type, in which liquefied natural gas is flowed outside the outer pipe, natural gas is flowed between the outer pipe and the inner pipe, and inside the inner pipe The liquefied natural gas vaporizer of claim 1, wherein a heat transfer accelerating material is inserted in the cold heat storage agent to flow the cold heat storage agent. 3. The solidification temperature of the cold storage heat agent is −130 ° C. or lower, and the cold storage container is provided with a plurality of inlet / outlet nozzles capable of selecting a take-out position and a return position of the cold storage heat agent according to a temperature level. The liquefied natural gas vaporizer is composed of a plate fin type heat exchanger. The liquefied natural gas vaporizer is supplied with cold heat storage agents having a plurality of temperature levels from a cold storage container according to the vaporization characteristics of the liquefied natural gas and cooled. The liquefied natural gas vaporizer according to claim 1, further comprising a circulation pump for returning the cold storage heat agent to the cold storage container from a corresponding temperature level inlet / outlet nozzle.