JPS5911077B2 - liquefied natural gas vaporizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing liquefied natural gas (LNG) using an intermediate heat transfer medium.
More specifically, the present invention relates to a vaporizer that can vaporize LNG with high efficiency by preventing overcooling of an intermediate heat medium caused by LNG.

When storing and transporting LNG, it is generally maintained at a low temperature of around -160°C, but when it is used for various purposes, in most cases as fuel for power generation or as city gas, it is usually stored in water or seawater. Natural gas (NG) is heated and vaporized using
is used as.

Regarding the heating and vaporization of such LNG, the applicant has
He developed an invention that could carry out this process with a compact device and with a small amount of water or seawater, and filed a patent application in 1983-36.
Patent applications are pending as No. 401 and No. 53-'36402.

The basic structure of the invention is that LNG is first heated and vaporized to about -20 to -50°C with an intermediate heat medium (e.g., propane, ammonia, fluorinated hydrocarbon such as R-12), and then heated with ordinary water. Alternatively, it is characterized in that seawater is heated to a temperature (usually 0° C. or higher) that can be supplied directly to the source of use, and the intermediate heat medium is heated with the latter used water or seawater. By the way, the intermediate heat medium is condensed in a supercooled state in a heat exchanger with LNG, and if you try to boil and evaporate the supercooled liquid, the boiling heat transfer characteristics will decrease compared to a saturated liquid, and the overall heat transfer efficiency will decrease. There is a problem that the performance decreases. The present invention solves this problem by making it possible to perform cooling and condensation of the intermediate heat medium with LNG at the saturation temperature of the internal operating pressure, thereby improving the efficiency of heating and vaporizing the intermediate heat medium, and further improving the efficiency of heating and vaporizing the intermediate heat medium. This makes it possible to improve the efficiency of warming air. That is, the gist of the present invention is a liquefied natural gas vaporizer that heats and vaporizes liquefied natural gas with an intermediate heat medium and heats and vaporizes a cooled and condensed intermediate heat medium with water or seawater, The present invention resides in a vaporizer characterized in that a filler is disposed at a contact area between cooled condensed droplets and their heated vaporized material to prevent overcooling of the condensed liquid.

In other words, since the intermediate heat medium vapor condenses on the supercooled liquid film dripping on the surface of the filling, the amount of condensation increases, acting as if the heat transfer area had increased. Next, the present invention will be specifically described with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 indicates a portion of the target LNG vaporizer, and propane, which is an intermediate heat medium, is housed in a shell 2 of the LNG vaporizer.

The upper half of this body 2 is composed of a U-shaped tube type heat exchange section 3, and the lower half thereof is composed of a fixed tube plate type heat exchange section 4.
The NG vaporizer, the latter functioning as an extra-tubular liquefied propane (LPG) vaporizer. In the center of the body, which is the boundary between the vaporizer 3 and the evaporator 4, a normal filling material 5 (for example, a mesh wire) is arranged. In the present invention, the vaporizer 3 and the evaporator 4 are not only integrated as described above, but also may be installed separately. In this case, the bottom of the vaporizer 3 is used as an LPG storage section, the filling 5 is placed between this and the upper tube bundle, and the LPG produced in the vaporizer 3 is sent to the evaporator 4, where the LPG is generated. It is only necessary to allow vaporized propane (PG) to come into contact with the filler 5 when it is supplied to the vaporizer 3. In the present invention, an NG warmer 11 may be further combined with the target LNG vaporizer 1 as shown in the drawing.

In the illustrated case, the warmer 11 is constituted by a fixed tube plate heat exchanger, and one end chamber thereof is integrally attached so as to be shared with the end chamber of the evaporator 4. ing. Of course, this warmer 11 may be arranged independently of the LNG vaporizer 1. The vaporizer 1 combined with such a warmer 11 also constitutes a part of the present invention.
In the device having the above configuration, as an example, LNG
(-155℃, 33kg/0111G) is introduced into the tube of the vaporizer 3 from line 12, and the PG outside the tube (-10℃,
2.4kg/CIILG) and heated and vaporized (-3
0° C.), is introduced outside the tube of the warmer 11 via line 13, heated by the seawater inside the tube (5° C.), and taken out of the system via line 14.

On the other hand, seawater (7°C) is introduced into the pipe of the warmer 11 from the line 15, and after warming the NG outside the pipe, is introduced into the shared end chamber 16 (note that some seawater is directly introduced into this end chamber). ), then introduced into the tube of the evaporator 4 to remove the L outside the tube.
The PG is heated and vaporized, and then taken out of the system through line 17. The LPG condensed outside the tube of the vaporizer 3 adheres to the filling 5 during dripping, contacts the rising PG, and reaches a temperature (-
12°C), and then stored outside the tube of the evaporator 4, heated and vaporized by the seawater inside the tube, and supplied and circulated to the vaporizer 3 again. On the other hand, when the filler 5 is not provided in the above device, the LPG condensed outside the tube of the vaporizer 3 is stored as it is outside the tube of the evaporator 4 in a supercooled state,
The temperature of the condensate is -20℃, and the heat transfer characteristics on the outside of the tube decreases when heating and vaporizing it, so the pressure of PG in the evaporator 4 is 2.2kg/DG, and its saturation temperature is -13℃. Therefore, the outlet NG temperature of the vaporizer 3 is -34°C.

If this temperature is set to -30°C, which is the same as the above-mentioned conditions, the amount of LNG vaporized will decrease by about 5%.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a specific example of the device of the present invention,
1 is an LNG vaporizer, 11 is an NG warmer, 3 is an LNG vaporization section, 4 is an LPG evaporation section, and 5 is a filling.

Claims (1)

[Scope of Claims] 1. A liquefied natural gas vaporizer that heats and vaporizes liquefied natural gas with an intermediate heat medium, and heats and vaporizes the cooled and condensed intermediate heat medium with water or seawater; A vaporizer characterized in that a filler is disposed at a contact area between the cooled condensed droplets and the heated vaporized material to prevent overcooling of the condensed liquid. 2. The vaporization according to item 1 above, in which a filling is arranged in the center of the intermediate heat medium storage shell, which has a heat exchange part with the pipe liquefied natural gas in the upper part and a heat exchange part with the pipe water or seawater in the lower part. vessel. 3. A liquefied natural gas vaporizer that heats and vaporizes liquefied natural gas with an intermediate heat medium and heats and vaporizes the cooled and condensed intermediate heat medium with water or seawater, which cools and condenses droplets of the intermediate heat medium and the A filling material is placed at the contact site of the heated vaporized body to prevent supercooling of the condensate, and water or seawater used for further warming the vaporized natural gas is used for heating vaporization of the intermediate heat medium. A vaporizer characterized by being used as a heat source. 4. A filling is placed in the middle of the intermediate heat medium storage shell, which has a heat exchange section with pipe liquefied natural gas in the upper part and a heat exchange part with pipe water or seawater in the lower part, and vaporized natural gas A heat exchange part for further heating the body with water or seawater is integrally attached to the body, and the device is configured to supply water or seawater cooled by the vaporized natural gas into the pipe in the lower part of the body. The vaporizer according to item 3 above.