JPS6124634B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an apparatus for vaporizing liquefied natural gas (LNG), and more particularly to an apparatus for vaporizing LNG using seawater or heated wastewater as a heat source and further heating it to a temperature suitable for use. LNG whose main component is methane is approximately -160 at normal pressure.
Since it has a boiling point of °C, even if it is vaporized using hot water or steam as a heat source, it is likely to clog the vaporizer due to freezing. LNG vaporizers currently in use that have solved these problems are mainly of the following types. (i) Open rack type vaporizer: In this type of vaporizer, LNG is sent upward through heat transfer tubes.
On the other hand, LNG is vaporized by flowing seawater from above onto the outer surface of the heat transfer tube. However, this type of vaporizer has the drawback that seawater tends to freeze on the surface of the lower portion of the heat transfer tube and impede heat transfer, thus increasing the heat transfer area, which means that the device must be larger and more expensive than necessary. It is. (ii) Intermediate heat medium indirect heating vaporizer: In this type of vaporizer, an intermediate heat medium such as propane or fluorinated hydrocarbon sealed in the vaporizer body is heated with hot water or steam to vaporize it. , LNG is vaporized by the vaporized intermediate heat medium, and the intermediate heat medium that is liquefied again by heat exchange with the LNG is subsequently converted into hot water or steam, and the same operation is repeated. This type of vaporizer is less expensive to construct than an open rack vaporizer, but
The disadvantage is that it requires the use of hot water or steam, which increases operating costs. (iii) Submerged combustion type vaporizer: In this type of vaporizer, combustion gas generated by a burner immersed in water is ejected into the water, and LNG passing through a pipe placed in the water is heated and vaporized. do.
Although this type of vaporizer is relatively inexpensive to construct, the disadvantage is that it requires high heating costs. In view of the current state of the technology as described above, the inventors of the present invention
As a result of various experiments and research, we connected a shell-and-tube countercurrent heat exchanger and an intermediate heat medium heat exchanger in series. The intermediate heat exchanger heats the natural gas by exchanging heat with the vaporized natural gas, while the intermediate heat exchanger is used in a shell-and-tube countercurrent heat exchanger. When a heat medium is heated by water and LNG is vaporized by the heat medium vaporized by the heating, a relatively small amount of seawater or heated We have discovered that LNG can be easily and inexpensively vaporized and heated using wastewater as a heat source. The present invention was completed based on such new knowledge. Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the drawings. In Fig. 1, an intermediate heat medium type indirect heat exchanger 1
and the multi-tubular countercurrent heat exchanger 2 are connected in series. Seawater or heated wastewater as a heat source enters the multi-tubular countercurrent heat exchanger 2 from the supply port 26 via the line 3, where it is countercurrently mixed with the natural gas already vaporized in the intermediate heat medium exchanger 1, which will be described later. Heat exchange is performed to heat the vaporized natural gas to a usable temperature close to that of seawater or heated wastewater. Heat exchange within the shell-and-tube heat exchanger 2 is carried out between liquid (seawater or heated wastewater) and gas (vaporized natural gas), so the heat transfer coefficient on the gas side is small, and also due to the design. The amount of heat exchanged in the shell-and-tube heat exchanger 2 can be made smaller than that in the intermediate heat medium heat exchanger described later. Therefore, the temperature of the water exiting the shell-and-tube heat exchanger 2 can be made lower, for example, by 2 to 3°C, than the temperature of the water entering the shell-and-tube heat exchanger 2. The water used in this multi-tube heat exchanger 2 can be said to have a high enough temperature to serve as a heating source for the intermediate heat medium (or LNG) in the intermediate heat exchanger. From the viewpoint of resource and energy conservation, it can be effectively used again as a heat source as described later. The water that has exited the outlet 2d of the multi-tube heat exchanger 2 passes through the line 4 and enters the lower part 1a of the intermediate heat medium heat exchanger 1 from the supply port 1c. After the intermediate heat medium (refrigerant) at the boiling point is heated and vaporized, it is discharged from the line 5 through the discharge port 1d or is effectively used as low-temperature water. The vaporized intermediate heat medium rises to the upper part 1b of the heat exchanger 1, where it exchanges heat with LNG supplied from the line 6 to the heat transfer tube 7 via the supply port 1e, and is liquefied again. Return to lower part 1a. The natural gas heated and vaporized by the intermediate heat medium in the upper part 1b exits 1f and flows into line 8.
The water then enters the supply port 2a of the multi-tubular heat exchanger 2, is further heated by seawater or heated waste water, and is taken out from the delivery port 2c via the line 9, as described above. In addition, in the intermediate heat medium type heat exchanger 1,
It is advantageous to use LNG and intermediate heat carriers under high pressure. According to the present invention, the following effects are achieved. (i) Since seawater or heated wastewater is effectively used as a heat source for both heat exchangers, only a small amount of seawater or heated wastewater needs to be used. (ii) Therefore, it is possible to downsize the device and the construction cost is significantly reduced. (iii) Since heating fuel is not required and only a small amount of seawater or heated wastewater can be used, operating costs are also significantly reduced. (iv) Blockage of pipes that was difficult to avoid with conventional equipment;
There is no significant decrease in heat transfer efficiency. (v) Low-temperature water discharged from the intermediate heat medium heat exchanger can be effectively used in necessary fields. Examples 1-2 Using seawater as a heat source, LNG was heated under the conditions shown in Table 1 using the apparatus of the present invention shown in FIG. 1, and the results shown in Table 1 were obtained.

[Table] Note that when a conventional open rack type vaporizer having the same LNG vaporization and heating capacity as in Example 1 was used, 5.00 tons/h of seawater was required.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the device of the present invention. 1...Intermediate heat medium indirect heat exchanger, 2...Multiple tube countercurrent exchanger, 3...Seawater or heated wastewater supply line, 4
...Water supply line from multi-tubular countercurrent heat exchanger 2, 5
...Discharge line for used water, 6. LNG supply line, 7. Heat exchanger tube, 8. Supply line for vaporized natural gas, 9. Takeoff line for vaporized and heated natural gas.

Claims (1)

[Claims] 1. Comprising an intermediate heat medium type indirect heat exchanger and a multi-tube type countercurrent heat exchanger, it vaporizes liquefied natural gas as a liquid using seawater or heated wastewater as a heat source to a temperature suitable for use. In the heating device, (i) the upper part 1b houses intermediate heat medium vapor that vaporizes it by exchanging heat with the liquefied natural gas, and the lower part 1a houses the intermediate heat medium vapor that has been liquefied by heat exchange with the liquefied natural gas; a heat exchanger body that accommodates a heat medium;
A supply port 1c for seawater or heated waste water from the multi-tubular heat exchanger 2 described below for exchanging heat with the intermediate heat medium in the lower part 1a and vaporizing it; heat exchange with the liquefied intermediate heat medium has been completed. A discharge port 1d for discharging water out of the system; a supply port 1l for supplying liquefied natural gas to the upper portion 1b of the heat exchanger body; and supplying vaporized natural gas to the multi-tubular heat exchanger 2 described below. (ii) a supply port 2a for the vaporized natural gas sent from the intermediate heat medium indirect heat exchanger 1; Supply port 2 for seawater or heated wastewater to heat it to a temperature suitable for use by countercurrent heat exchange
b; outlet port 2c for the heated vaporized natural gas;
and a multi-tubular countercurrent heat exchanger 2 equipped with an outlet 2d for sending the seawater used for heating vaporized natural gas or heated wastewater to the lower part 1a of the main body of the intermediate heat medium type indirect heat exchanger 1. A liquefied natural gas vaporization and heating device characterized by comprising: